Optical laminate and display member using the same

Abstract

To provide an optical laminate enabling efficient manufacturing while suppressing yellowness, 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, and a pigment configured to absorb light having a wavelength of 550-650 nm. A yellowness index YI is 2.5 or lower, measured in accordance with JIS K 7373:2006.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 inherent in glass, a hard coat film in which a hard coat layer is laminated on a transparent base material made of a resin film is widely used. As the transparent base material of the hard coat film used for a foldable display device, a transparent polyimide (CPI) film having 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 made of a composition for forming a hard coat layer containing an acrylate compound is formed 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] Therefore, an object of the present invention is to provide an optical laminate capable of efficiently manufacturing while suppressing the yellowness index, and a display member using the same.

Means for Solving the Problems

[0007] 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, and a dye that absorbs light having a wavelength of 550 to 650 nm, and the yellowness index YI measured in accordance with JIS K 7373:2006 is 2.5 or less.

[0008] The display member according to the present invention includes the above optical laminate and is foldable.

Effects of the Invention

[0009] The present invention can provide an optical laminate capable of efficiently manufacturing while suppressing the yellowness index, and a display member using the same.

Brief Description of the Drawings

[0010]

Figure 1

Modes for Carrying Out the Invention

[0011] FIG. 1 is a cross-sectional view schematically showing an optical laminate according to an embodiment.

[0012] 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.

[0013] (Transparent Substrate) The transparent substrate 1 is a film serving 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.

[0014] 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, sputter treatment, application of a surfactant or a silane coupling agent, and Si deposition.

[0015] (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 hard coat layer-forming composition containing a (meth)acrylate compound, an organic compound having a thiol group, and a dye that absorbs light having a wavelength of 550 to 650 nm (hereinafter, also simply referred to as "dye"). The thickness of the hard coat layer 2 can be appropriately set according to the surface hardness and the overall thickness required for the optical laminate 10, and is not particularly limited. For example, it is preferably 2 to 10 μm. When the thickness of the hard coat layer 2 is less than 2 μm, the hardness of the hard coat layer may be insufficient. When the thickness of the hard coat layer 2 exceeds 10 μm, it is not preferable because it is disadvantageous for thinning the optical laminate 10.

[0016] ((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, difunctional, 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.

[0017] 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.

[0018] 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, etc.

[0019] 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 some of these (meth)acrylates are substituted with an alkyl group or ε-caprolactone; and acrylic polymers having a weight average molecular weight of 20,000 to 30,000 with a plurality of (meth)acryloyl groups and hydroxyl groups introduced into the main chain, etc.

[0020] 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.

[0021] 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.

[0022] The above-mentioned active energy ray-curable resin may be used alone or in combination of two or more. Also, the above-mentioned active energy ray-curable resin may be a monomer or a partially polymerized oligomer in the composition for forming the hard coat layer.

[0023] 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.).

[0024] (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 introducing a sulfide bond into the resin matrix by the organic compound having a thiol group, the flexibility of the hard coat layer 2 can be improved and curl can be reduced.

[0025] The blending amount of the organic compound having a thiol group is preferably 0.5 to 9.0% by mass of all components other than the solvent of the hard coat layer-forming composition. 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 curl reduction 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.

[0026] 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.).

[0027] (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% by mass of all components other than the solvent of the hard coat layer-forming composition, preferably 0.001 to 0.100% by mass, and more preferably 0.001 to 0.030% by mass. When the blending amount of the dye is less than 0.001% by mass, 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% by mass, the blueness of the optical laminate 10 becomes too strong, damaging the color tone of the display image.

[0028] (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. Compounds that can be used as the leveling agent are 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).

[0029] (UV absorber) In addition, in order to suppress the deterioration of the dye and improve the light resistance of the optical laminate 10, a UV absorber may be blended in the composition for forming the hard coat layer. As the UV absorber, for example, compounds of benzophenone type, benzotriazole type, triazine type, oxalic acid anilide type, and cyanoacrylate type can be used. Since the UV absorber is blended to suppress the deterioration of the dye, a UV absorber having absorbability to light in the wavelength range that contributes to the deterioration of the dye in the UV region is used. However, when curing the composition containing the UV absorber, if the amount of UV absorption by the UV 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 a UV absorber whose absorption wavelength range in the UV region is different from the absorption wavelength range of the photoinitiator in the UV region. The blending ratio of the UV 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. Compounds that can be used as the UV 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).

[0030] (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 into 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).

[0031] In addition, a solvent may be added to the composition for forming the hard coat layer for viscosity adjustment. 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, and ketones such as acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, and methylcyclohexanone, and 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 further cellosolves such as methyl cellosolve, cellosolve, butyl cellosolve, and cellosolve acetate. These may be used alone or in combination of two or more.

[0032] In addition, the composition for forming the hard coat layer may contain metal oxide fine particles for the purpose of refractive index adjustment and hardness imparting. 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.

[0033] 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 that imparts water repellency and / or oil repellency and enhances antifouling properties.

[0034] 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.

[0035] 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, etc.

[0036] (Yellowness index) The yellowness index 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 index YI is a value measured in accordance with JIS K 7373:2006. As a method for reducing the yellowness index YI of the optical laminate, a method of providing a blue coloring layer in addition to the transparent base material and the hard coat layer, or a method of coloring the polyimide film itself blue can be considered. However, when a blue coloring layer is provided in addition to the transparent base material 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. In addition, 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 index, a coloring layer other than the transparent base material 1 and the hard coat layer 2 is unnecessary, and a polyimide film used as the transparent base material 1 can be selected from existing products.

[0037] (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.

[0038] (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 a pressure of

[0039] (Flexural resistance) After the 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 the 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.

[0040] 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 colored 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 configuration in which a hard coat layer 2 having a resin matrix mainly composed of (meth)acrylate and a thiol compound is laminated on a transparent substrate 1 made of a polyimide film having excellent mechanical properties. Therefore, it is suitable for use as a protective film provided on the outermost surface of a foldable display device because it is excellent in surface hardness, scratch resistance, and flexural resistance.

[0041] The optical laminate 10 according to the present embodiment can be used to form a display member by laminating it with 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 the present embodiment can be used to form an electronic device including a foldable display device.

Example

[0042] Hereinafter, examples of specific implementation of the present invention will be described.

[0043] The materials shown below were mixed at the ratios shown in Table 1 to prepare compositions for forming a hard coat layer according to Combinations 1 to 6. The unit of the blending 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: Kalenz MT (registered trademark) PE1 (manufactured by Showa Denko K.K.) · Dye 1-hydroxy-4-toluidinoanthraquinone (manufactured by Tokyo Chemical Industry 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)

[0044]

Table 1

[0045] (Examples 1 to 8, Comparative Example 2) 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 shown in Table 2, dried, and then irradiated with ultraviolet rays to form a hard coat layer.

[0046] (Comparative Example 1) The same clear polyimide film as that used in Example 1 was used as the film according to Comparative Example 1.

[0047] (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 side of a clear polyimide film with 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 side 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) · 72.5% by mass of dimethylol dicyclopentane diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) · 24.2% by mass of 3-(acryloyloxy)-2-hydroxypropyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) · 0.1% by mass of 1-hydroxy-4-toluidinoanthraquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), · 3.0% by mass of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by Tokyo Chemical Industry Co., Ltd.), · 0.2% by mass of PC4300 (manufactured by DIC Corporation)

[0048] (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.

[0049] (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.

[0050] (Adhesion) Based on the cross-cut test specified in the old JIS K 5400 General Test Methods for Paints, 1 mm was applied to each hard coat layer. 2One hundred meshes were formed. An adhesive tape (CT405AP-24, manufactured by Nichiban Co., Ltd.) was attached to the formed meshes and uniformly pressed using a spatula. After that, the adhesive tape was peeled off in the 90° direction, and the number of hard coat layers remaining without peeling was visually confirmed.

[0051] (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 hard coat layer surface was measured under the conditions of a load of 750 g and a scratching speed of 0.5 mm / sec. Repeated tests were conducted 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.

[0052] (Scratch resistance) The prepared film was set in a Kagaku-Shinbun type friction fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.), and a scratch resistance test was conducted by contacting steel wool (Bonstar #0000) 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 check for 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.

[0053] (Flexural resistance) Samples were prepared by cutting out the prepared film into a width of 30 mm. These samples were set in a clam shell type bending tester (DR11MR-CS-t, manufactured by Yuasa System Devices Co., Ltd.) with the hard coat layer on the inside, and a bending test of 200,000 times was conducted at 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. Also, samples prepared in the same way were set in the tester with the hard coat layer on the outside, and after a bending test of 200,000 times at a radius of 2.5 mm, the surface of the hard coat layer was visually observed to evaluate the presence or absence of cracks.

[0054] Table 2 shows the configurations and evaluation results of each example and each comparative example.

[0055]

Table 2

[0056] For the hard coat films according to Examples 1 to 8, the yellowness index YI was suppressed to 2.5% or less, and all of the scratch resistance, flex resistance, and surface hardness were excellent, and the adhesion of the hard coat layer to the transparent substrate was also good.

[0057] 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.

[0058] For the hard coat film according to Comparative Example 3, the layer containing the dye was provided separately from the transparent substrate and the hard coat layer, and since it was 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 increased, which was disadvantageous in terms of manufacturing efficiency.

Industrial Applicability

[0059] The present invention can be used as a hard coat film for a display device, and in particular, it is suitable as a protective film for a foldable display device.

Explanation of Signs

[0060] 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, wherein 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, and a dye that absorbs light having a wavelength of 550 to 650 nm, An optical laminate having a yellowness index YI of 2.5 or less measured in accordance with JIS K 7373:2006.

2. The optical laminate according to claim 1, wherein the blending amount of the dye is 0.001 to 0.200% by mass of all components other than the solvent of the composition.

3. The pencil hardness of the surface of the hard coat layer is 4H or more, and 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 damage to the hard coat layer, and the pure water contact angle on the surface of the hard coat layer is 100° or more. no cracks occur in the hard coat layer after a bending test of bending 200,000 times with a radius of 1.5 mm so that the hard coat layer is on the inside, and after a bending test of bending 200,000 times with a radius of 2.5 mm so that the hard coat layer is on the outside. The optical laminate according to claim 1.

4. A foldable display member including the optical laminate according to any one of claims 1 to 3.

Images