JP2023075710A - Optical laminate and display device using the same - Google Patents

Abstract

To provide an optical laminate suitable for a display device for on-vehicle use, and a display device using the same.SOLUTION: Provided is an optical laminate that has an antiglare layer and a low refractive index layer on at least one surface of a transparent substrate. The number of protrusions that exist on a surface of the low refractive index layer and whose height is 0.1 μm or more is 600 to 1500 per measurement area 1 mm2. An average inclination angle of the protrusions on the surface of the low refractive index layer is 0.5 to 1.4°.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an optical layered body that suppresses reflection and glare of external light and a display device using the same.

Anti-reflection films such as anti-glare (AG) films and low-reflection (LR) films are used to suppress reflection and reflection of external light on the surface of display devices. The anti-glare film has fine irregularities formed on the surface of the anti-glare layer by incorporating a filler into the anti-glare layer, and the surface irregularities scatter external light. The anti-glare film is suitable for suppressing glare of external light. A low-reflection film has a low-refractive-index layer on the outermost surface, and suppresses reflection by canceling out the light reflected on the surface of the low-refractive-index layer and the light reflected on the surface of the substrate through interference. . A low-reflection film is suitable for displaying images clearly. Also, an antireflection film (AGLR) comprising an antiglare layer and a low refractive index layer, which is a combination of an antiglare film and a low reflection film, is also used.

As an optical layered body having an antiglare layer and a low refractive index layer on a substrate, there is one described in Patent Document 1, for example. In Patent Document 1, by setting the average spacing Sm of the unevenness on the outermost surface of the antiglare layer, the average inclination angle θa of the uneven portion, and the average roughness Rz of the unevenness to predetermined ranges, antiglare properties and glossy black feeling are improved. It is described that a certain black reproducibility, high definition, glare prevention, contrast, and character blur prevention have been achieved.

Japanese Patent No. 5360616

In recent years, display devices for in-vehicle use are increasing. In-vehicle display devices such as a center information display (CID) and a digital meter cluster may display safety-related information. Therefore, an antireflection film used for an in-vehicle display device is required to suppress glare peculiar to an antiglare film, suppress reflection of external light, and have low reflectivity for displaying images clearly. In-vehicle display devices equipped with a touch panel are widely used, but the anti-reflection film used for the display device with a touch panel has good operability of the touch panel and fingerprints attached by touch panel operation. It is required that the wiping property of is good.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical layered body suitable for a display device for in-vehicle use and a display device using the same.

The optical layered body according to the present invention comprises an antiglare layer and a low refractive index layer on at least one surface of a transparent substrate, and convex portions having a height of 0.1 μm or more on the surface of the low refractive index layer. is 600 to 1500 per 1 mm ² of the measured area, and the average inclination angle of the unevenness of the surface of the low refractive index layer is 0.5 to 1.4°.

A display device according to the present invention includes a display panel and the above-described optical laminate provided on the display surface side of the display panel.

ADVANTAGE OF THE INVENTION According to this invention, the optical laminated body suitable for the display apparatus for vehicle-mounted applications, and a display apparatus using the same can be provided.

A cross-sectional view showing a layer structure of an optical layered body according to an embodiment. Schematic cross-sectional view for explaining the surface shape of the optical layered body

FIG. 1 is a cross-sectional view showing the layer structure of an optical layered body according to an embodiment.

The optical layered body 10 is a film that is provided on the outermost surface of the display device and suppresses reflection of external light. The optical laminate 10 includes a transparent substrate 1 and an antiglare layer 2 and a low refractive index layer 3 laminated on one surface of the transparent substrate 1 .

The transparent substrate 1 is a film that serves as a substrate of the optical layered body 10, and is made of a material having excellent visible light transmittance. Materials for forming the transparent substrate 1 include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyacrylates such as polymethyl methacrylate; polyamides such as nylon 6 and nylon 66; Transparent resins such as polyarylate, polycarbonate, triacetyl cellulose, polyacrylate, polyvinyl alcohol, polyvinyl chloride, cycloolefin copolymer, norbornene-containing resin, polyethersulfone, polysulfone, and inorganic glass can be used. Although the thickness of the transparent substrate 1 is not particularly limited, it is preferably 10 to 200 μm.

The surface of the transparent base material 1 may be subjected to a surface modification treatment in order to improve adhesion with the antiglare layer 2 . Examples of surface modification treatment include alkali treatment, corona treatment, plasma treatment, sputtering treatment, application of surfactants, silane coupling agents, and the like, and Si vapor deposition.

The anti-glare layer 2 is an optical function layer that has minute unevenness on the surface and reduces reflection of outside light by scattering outside light with the unevenness. The antiglare layer 2 is formed by applying a coating liquid containing a binder resin and organic fine particles and/or inorganic fine particles to the transparent substrate 1 and curing the coating film.

As the binder resin, an active energy ray-curable resin that is cured by irradiation with ionizing radiation or ultraviolet rays can be used, and for example, a monofunctional, difunctional, trifunctional or higher (meth)acrylate monomer can be used. In this specification, "(meth)acrylate" is a generic term for both acrylate and methacrylate, and "(meth)acryloyl" is a generic term for both acryloyl and methacryloyl.

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 ) 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, phosphoric acid (meth)acrylate, ethylene oxide-modified phosphoric acid (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, methoxypolyethylene 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) acryloyloxy Propyl 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, adamantane derivative mono (meth) acrylate such as adamantyl acrylate having a monovalent mono (meth) acrylate derived from adamantanediol etc.

Examples of bifunctional (meth)acrylate compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth) Acrylates, 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 Di(meth)acrylates such as 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. ) acrylates and the like.

Examples of tri- or higher functional (meth)acrylate compounds include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and tris-2-hydroxyethyl. Tri(meth)acrylates such as isocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, etc.) Functional (meth)acrylate compounds, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate ) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane hexa (meth) acrylate trifunctional or higher polyfunctional (meth) acrylate compounds, and some of these (meth) acrylates are alkyl groups and ε-caprolactone and polyfunctional (meth)acrylate compounds substituted with.

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

Examples of urethane (meth)acrylates include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate. Examples include urethane prepolymers, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymers, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymers.

One type of the active energy ray-curable resin described above may be used, or two or more types may be used in combination. Moreover, the active energy ray-curable resin described above may be a monomer in the coating liquid, or may be a partially polymerized oligomer.

Further, as the active energy ray-curable resin, in addition to the above-described compounds having radically polymerizable functional groups, monomers, oligomers, and prepolymers having cationic polymerizable functional groups such as epoxy groups, vinyl ether groups, and oxetane groups can be used alone. can be used alone or mixed. Monomers include epoxy compounds such as unsaturated polyesters, epoxy acrylates, tetramethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether and various alicyclic epoxies; Oxetane compounds such as ethyl-3-hydroxymethyloxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, and di[1-ethyl(3-oxetanyl)]methyl ether can be exemplified. .

The above-described resin material can be cured by irradiation with ultraviolet light provided that a photopolymerization initiator is added. Photopolymerization initiators include radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, and benzoin methyl ether; cationic polymerization initiators such as aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, and metallocene compounds. Agents can be used alone or in admixture.

The organic fine particles are a material that mainly forms fine unevenness on the surface of the antiglare layer 2 and imparts the function of diffusing external light. As the organic fine particles, translucent resin materials such as acrylic resins, polystyrene resins, styrene-(meth)acrylic acid ester copolymers, polyethylene resins, epoxy resins, silicone resins, polyvinylidene fluoride, and polyethylene fluoride resins are used. Resin particles can be used. The refractive index of the resin particle material is preferably 1.40 to 1.75. In order to adjust the refractive index and the dispersion of the resin particles, two or more kinds of resin particles having different materials (refractive indexes) may be mixed and used.

The average particle size of the organic fine particles is preferably 1.0 to 5.0 μm, more preferably 2.0 to 5.0 μm. When the average particle diameter of the organic fine particles is less than 1.0 μm (lower limit) or when the average particle diameter of the organic fine particles is 5.0 μm (upper limit), the unevenness of the surface of the antiglare layer is adjusted so as to satisfy the conditions described later. It becomes difficult to control it to a desired level, and the desired anti-glare property cannot be obtained. The blending amount of the organic fine particles in the antiglare layer is preferably 10 to 30% by mass, more preferably 10.5 to 26.3% by mass, based on the total solid content constituting the antiglare layer.

The inorganic fine particles are mainly a material for adjusting sedimentation and agglomeration of organic fine particles in the antiglare layer 2 . As the inorganic fine particles, silica fine particles, metal oxide fine particles, various mineral fine particles, and the like can be used. Examples of silica fine particles that can be used include colloidal silica and silica fine particles surface-modified with reactive functional groups such as (meth)acryloyl groups. Examples of metal oxide fine particles that can be used include alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titania, and zirconia. Mineral fine particles include, for example, mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, islarite, kanemite, layered titanate, smectite, synthetic Smectite and the like can be used. Mineral fine particles may be either natural products or synthetic products (including substituted products and derivatives), and a mixture of the two may be used. Among the fine mineral particles, layered organoclays are more preferred. A layered organic clay is a swelling clay in which an organic onium ion is introduced between layers. The organic onium ion is not limited as long as it can be organized by utilizing the cation exchange property of the swelling clay. When layered organoclay minerals are used as fine mineral particles, the synthetic smectites described above can be suitably used. Synthetic smectite has the function of increasing the viscosity of the coating liquid for forming the antiglare layer, suppressing the sedimentation of resin particles and inorganic fine particles, and adjusting the irregular shape of the surface of the optical function layer.

In addition, a leveling agent may be added to the coating liquid for forming the antiglare layer. The leveling agent has the function of orienting on the surface of the coating film during the drying process, equalizing the surface tension of the coating film, and reducing surface defects of the coating film.

Furthermore, an organic solvent may be appropriately added to the resin composition for forming the optical function layer. Examples of organic solvents include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropyl alcohol and isobutanol; ketones such as acetone, methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; and ketone alcohols such as diacetone alcohol. aromatic hydrocarbons such as benzene, toluene and xylene, glycols such as ethylene glycol, propylene glycol and hexylene glycol, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, diethyl carbitol, propylene Glycol ethers such as glycol monomethyl ether Esters such as methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, and amyl acetate Ethers such as dimethyl ether and diethyl ether N-methylpyrrolidone, dimethylformamide, water etc., can be used singly or in combination of two or more.

The low refractive index layer 3 has an optical function of reducing the surface reflection of the optical layered body 10 by canceling the light reflected on the surface of the low refractive index layer 3 by interference with the light reflected on the surface of the transparent substrate 1. layer. The low refractive index layer 3 can be formed by applying a coating liquid containing a binder resin to the surface of the antiglare layer 2 and curing the coating film. The low refractive index layer 3 may contain low refractive index fine particles for adjusting the refractive index.

The binder resin used for forming the low refractive index layer 3 is not particularly limited, and the compounds exemplified as the material for the antiglare layer 2 can be used.

Examples of low refractive index fine particles include fine particles such as LiF, MgF, 3NaF·AlF, or AlF (all of which have a refractive index of 1.4), or Na ₃ AlF ₆ (cryolite, refractive index of 1.33), Silica fine particles having voids inside can be preferably used. Silica fine particles having voids therein are advantageous in lowering the refractive index of the low-refractive-index layer 3 because the void portions can have the refractive index of air (approximately 1). Specifically, porous silica particles and shell-structured silica particles can be used.

Solvents and various additives can be added to the coating liquid for forming the low refractive index layer 3 as necessary. As the solvent, for example, those exemplified as the material of the antiglare layer 2 can be used. Examples of additives include antifoaming agents, leveling agents, antioxidants, ultraviolet absorbers, light stabilizers, polymerization inhibitors, and photosensitizers.

Further, when the coating film of the coating liquid for forming the low refractive index layer is cured by ultraviolet irradiation, a photopolymerization initiator is added to the coating liquid. As the photopolymerization initiator, those exemplified as the material for the antiglare layer 2 can be used.

The refractive index of the low refractive index layer 3 is preferably smaller than the refractive index of the antiglare layer 2 and within the range of 1.25 to 1.50. The lower the refractive index of the refractive index layer is, the closer it is to the refractive index of air (refractive index=1), making it easier to achieve a low reflectance. It may become weaker and more susceptible to scratches. On the other hand, if the refractive index of the low-refractive-index layer exceeds 1.50, the reflectance may increase due to an increase in the difference in refractive index from air.

The film thickness of the low refractive index layer 3 is preferably in the range of 5 nm to 1 μm from the characteristics as an optical interference layer. It is more preferable to design the optical film thickness to be approximately equal to 1/4 of the wavelength of visible light (wavelength to be suppressed) in terms of thinning and suppression of reflectance.

FIG. 2 is a schematic cross-sectional view for explaining the surface shape of the optical layered body. Hereinafter, conditions to be satisfied by the optical layered body 10 according to this embodiment will be described with reference to FIG. 2 .

In the optical laminate 10 according to this embodiment, the surface of the low refractive index layer 3 has a plurality of fine irregularities. In this embodiment, the uneven shape of the surface of the low refractive index layer 3 simultaneously satisfies the following conditions (1) and (2).
(1) Among the plurality of protrusions present on the surface of the low refractive index layer 3, the number of protrusions having a height of 0.1 μm or more is 600 to 1500 per 1 mm ² of the measured area.
(2) The average inclination angle of unevenness existing on the surface of the low refractive index layer 3 is 0.5 to 1.4°.

Here, the number of convex portions is calculated using, for example, the analysis software "VS-Viewer" of the non-contact surface/layer cross-sectional shape measurement system (Vertscan R3300FL-Lite-AC, manufactured by Ryoka Systems Co., Ltd.). can be done. For the number of protrusions, the value of the height threshold was added from the zero height position of the surface height data when the projection analysis was selected as the particle analysis condition of VS-Viewer and the height threshold was set to 0.1 μm. Refers to the number of protruding areas located on the surface.

In addition, when analyzing with VS-Viewer, the height threshold is set to 0.1 μm in the particle analysis conditions, and the height threshold value is added from the zero height position of the surface height data. The projecting region is defined as the projecting portion of the present invention. In addition, the non-projection area located below the surface obtained by adding the height threshold value from the zero height position of the surface height data is not the convex portion of the present invention. Here, the height of the portion defined as the convex portion of the present invention is defined as the height of the unevenness.

Further, in the present invention, average unevenness is generated under the analysis conditions in the cross-sectional profile (multi-line) of VS-Viewer. In the cross-sectional profile (multi-line), the average inclination angle obtained from the cross-section obtained by averaging the cross-sectional profiles of the six set measurement cursors is defined as the uneven average inclination angle of the present invention.

When the number of protrusions having a height of 0.1 μm or more is less than 600 per 1 mm ² of the measured area, as shown in FIG. Therefore, the surface of the low refractive index layer 3 becomes smooth. Therefore, when the optical layered body 10 is touched, the contact area becomes large, and when the optical layered body 10 is used for a display device with a touch panel, the slipperiness of the finger is deteriorated. In addition, since the surface of the low refractive index layer 3 is smooth, dirt tends to spread when wiping off fingerprints, and the wiping-off property of fingerprints deteriorates.

When the number of projections with a height of 0.1 μm or more is 600 or more per 1 mm ² of the measured area, but the average inclination angle is less than 0.5°, as shown in FIG. Since the slope of the convex portion is gentle, the finger tends to touch the side surface near the top of the convex portion when touched. Therefore, when the optical layered body 10 is touched, the contact area is still large, and when the optical layered body 10 is used in a display device with a touch panel, the slipperiness of fingers deteriorates. In addition, since the protrusions have a gentle slope, dirt tends to enter the grooves between the protrusions when wiping off fingerprints, resulting in insufficient fingerprint wiping performance.

When the number of projections with a height of 0.1 μm or more is 600 or more per 1 mm ² of the measured area and the average inclination angle is 0.5° or more, as shown in FIG. The convex shape of the surface of the low refractive index layer 3 becomes sharp, and the contact area of the finger becomes small. Therefore, when the optical layered body 10 is touched, the contact area becomes small, and when the optical layered body 10 is used for a display device with a touch panel, the finger slipperiness is good. In addition, since the convex shape of the surface of the low refractive index layer 3 is sharp and dirt does not spread when wiping off fingerprints, the fingerprint wiping off property is good.

The number of protrusions having a height of 0.1 μm or more is preferably 1400 or more per 1 mm ² of the measurement area. When the number of projections with a height of 0.1 μm or more is 1400 or more per 1 mm ² of the measured area and the average inclination angle is 0.5° or more, as shown in FIG. Sharp convex shapes are densely formed on the surface of the low refractive index layer 3, and the grooves between the convex portions are narrowed, so that the contact area when touched with a finger is reduced. Therefore, the slipperiness of the finger is further improved.

The finger slipperiness is an index of the operability of the display device with a touch panel. If the slipperiness of the finger is poor, resistance makes it difficult to slide or swipe on the touch panel, resulting in poor operability. If the slipperiness of the finger is good and there is no resistance when sliding, the touch panel can be slid or swiped without discomfort, resulting in excellent operability.

In addition, in the optical layered body 10 according to the present embodiment, it is preferable that the surface of the low refractive index layer 3 have an average luminous reflectance (also simply referred to as “luminous reflectance”) of 1.0% or less. If the average luminous reflectance exceeds 1.0%, the surface reflection of the optical layered body 10 increases, which impairs the sharpness of the displayed image, which is not preferable. The average luminous reflectance is obtained by using a spectrophotometer to obtain a spectral reflectance curve by injecting a ray bundle at an incident angle of 5° onto the outermost surface of the optical laminate 10, and calculating the spectrum according to JIS R 3106. It is a value obtained by converting the reflectance curve into the visual average reflectance, and is the Y value in the XYZ color system.

As described above, the optical laminate 10 according to this embodiment includes the antiglare layer 2 and the low refractive index layer 3 on one side of the transparent substrate 1 . Since the antireflection layer of the optical layered body 10 has a layered structure of the antiglare layer 2 and the low refractive index layer 3, when the optical layered body 10 is provided on the viewing side of the display panel to configure a display device, external light is reflected. It is possible to clearly display an image by reducing the reflection while suppressing the reflection. In addition, in the optical layered body 10 according to the present embodiment, the number of protrusions having a height of 0.1 μm or more on the surface of the low refractive index layer 3 is 600 to 1500 per 1 mm ² of the measurement area. and the average inclination angle of the irregularities on the surface of the low refractive index layer 3 is 0.5 to 1.4°. That is, on the surface of the low refractive index layer 3, which is the outermost surface on the viewing side of the optical layered body 10 according to this embodiment, convex portions having sharp shapes are densely arranged. By having such an uneven shape on the surface of the low refractive index layer 3, the slipperiness of a finger and the wiping off of fingerprints are excellent. Therefore, the optical layered body 10 according to the present embodiment is suitable as an antireflection film for an in-vehicle display device, and particularly suitable as an antireflection film for a display device with a touch panel.

Further, when the average luminous reflectance on the surface of the low refractive index layer 3 is 1.0% or less, the reflection on the outermost surface of the optical layered body 10 can be further reduced, and the sharpness of the displayed image can be improved.

EXAMPLES Examples in which the present invention is specifically carried out will be described below.

(Examples 1 to 7, Comparative Examples 3 to 5)
A 40 μm thick triacetyl cellulose (TAC) film was used as a transparent substrate.

Also, a coating solution for forming an antiglare layer containing a polymerizable monomer, a filler, a polymerization initiator, a thickener and a solvent was prepared. Table 1 shows the ratio (% by mass) of the filler to the total solid content (components other than the solvent) of the filler and the coating liquid used in each example and each comparative example.

The coating solution for forming an antiglare layer was applied onto a transparent substrate so that the film thickness after curing was 5 μm, dried, and then the coating film was polymerized and cured by UV irradiation to form an antiglare layer.

A coating liquid for forming a low refractive index layer containing a polymerizable monomer, a hollow silica filler, and a polymerization initiator was applied onto the antiglare layer. As the hollow silica filler, one having an average particle diameter of 75 nm was used, and the content of the hollow silica filler was set to 45.5% by mass based on the total solid content in the low refractive index layer-forming coating liquid. A low refractive index layer-forming coating liquid is applied onto the antiglare layer so that the film thickness after curing is 0.1 μm, dried, and then the coating film is polymerized and cured by ultraviolet irradiation to form a low refractive index layer. formed. As a result, an optical laminate was obtained in which the antiglare layer and the low refractive index layer were laminated in order on the transparent substrate.

(Comparative example 1)
An antiglare layer was formed on a transparent base material in the same manner as in Example 1, and an optical laminate according to Comparative Example 1 was obtained.

(Comparative example 2)
A TAC film with a thickness of 40 μm was used as a transparent substrate. A coating solution for forming a hard coat layer containing a binder resin, a photopolymerization initiator and a solvent is applied onto a transparent substrate so that the film thickness after curing is 5 μm, dried, and then irradiated with ultraviolet rays. The coating film was polymerized and cured to form a hard coat layer. Next, the same coating liquid for forming a low refractive index layer as that used in Example 1 was coated on the hard coat layer so that the film thickness after curing was 0.1 μm, dried, and then irradiated with ultraviolet rays. to polymerize and cure the coating film to form a low refractive index layer. As a result, an optical laminate was obtained in which the hard coat layer and the low refractive index layer were laminated in order on the transparent substrate.

[Surface profile analysis]
The uneven shape of the low refractive index layer surface of the optical laminates according to Examples 1 to 7 and Comparative Examples 1 to 5 was measured by a non-contact surface/layer cross-sectional shape measurement system (measuring device: Vertscan R3300FL-Lite-AC, analysis software : VS-Viewer 6, manufactured by Ryoka System Co., Ltd.) was used for measurement by an optical interference method. Analyzing the measurement data using the particle analysis software of the device, the arithmetic mean roughness Ra of the surface of the low refractive index layer, the maximum height Rz and the surface length Rsm of the curvilinear element, the average inclination angle θa, per 1 mm ² of the measurement area The number of protrusions having a protrusion height of 0.1 μm or more was counted.

In the present invention, average irregularities are generated under the analysis conditions in the cross-sectional profile (multiline) of VS-Viewer. In the cross-sectional profile (multi-line), the arithmetic average roughness Ra, the maximum height Rz, the surface length Rsm of the curvilinear element, and the average inclination angle obtained from the cross section obtained by averaging the cross-sectional profiles of the six set measurement cursors are calculated according to the present invention. is defined as the arithmetic mean roughness Ra, the maximum height Rz, the surface length Rsm and the mean inclination angle of the curvilinear element.

Measurement was performed under the following conditions using the measurement software of the device, and an image file representing the measurement results of the surface unevenness was obtained.
・Optical conditions Camera: Sony HR-50 1/3 inch Objective lens: 10XDI (10x)
Imaging lens (barrel): 0.5x Zoom lens: 1x Light source/wavelength filter: 520nm
ND filter: Not used A-Stop (aperture diaphragm): Not used (fully open)
F-Stop (field diaphragm): Not used (fully open)
・Measurement conditions Measurement device: Piezo Measurement mode: Phase
Scanning speed: 4 μm/sec
Scan range: -10 to 10 μm
Effective pixels: 50%
Measurement area: 704.192 μm×938.923 μm

The acquired image file was analyzed under the following conditions using the analysis software of the device.
・Analysis conditions (VS-Viewer6)
Surface correction: 4th order S filter: automatic L filter: not used, particle analysis conditions (VS-Viewer6)
Analysis type: Projection analysis Image correction: None Height threshold: 0.1 μm
Particle Shaping: None

[How to calculate Ra, Rz, Rsm and θa]
In the acquired image with the surface correction (4th order) and S filter applied, the measurement cursor is placed at 200 μm, 500 μm and 800 μm in the vertical direction (X direction) and at 200 μm, 400 μm and 600 μm in the horizontal direction (Y direction). set. Ra, Rz, Rsm and θa at each cursor position (3 cross sections parallel to the X direction and 3 cross sections parallel to the Y direction, 6 points in total) automatically calculated by the cross-section profile of VS-Viewer. A value was obtained, and the average value (arithmetic mean) of the obtained values was used as the measurement result.

[Method for calculating the number of protrusions]
The number of projections was calculated by performing particle analysis of the obtained image with surface correction (quaternary) and S filter applied using the analysis software of the apparatus. More specifically, the above conditions were set as particle analysis conditions, and the number of projections per 1 mm ² of measurement area identified as projection regions was calculated.

[Fingerprint Wipeability]
A black acrylic plate (Sumipex (registered trademark) 960, manufactured by Sumitomo Chemical Co., Ltd.) was laminated with the optical laminates according to Examples 1 to 7 and Comparative Examples 1 to 5 via a transparent adhesive layer. A 1 cm×1 cm square area on the surface of the low refractive index layer of the optical layered body was coated with sebum, and a wiping test was performed using tissue paper. The state of disappearance of sebum from the surface of the low refractive index layer was visually confirmed and evaluated according to the following evaluation criteria. Interviews were conducted with 20 testers, and the evaluation result was the one with the largest number of evaluations.
◯: Sebum does not spread and is wiped off quickly.
Δ: Sebum spreads and takes time to wipe off.
x: Sebum spreads over a wide area and is difficult to wipe off.

[Slippery]
Optical laminates according to Examples 1 to 7 and Comparative Examples 1 to 5 were laminated to a black acrylic plate (Sumipex (registered trademark) 960, manufactured by Sumitomo Chemical Co., Ltd.) via a transparent adhesive layer. A finger in contact with the surface of the low-refractive-index layer of the optical layered body was slid, and slipperiness (difficulty in getting caught on the finger) was evaluated according to the following evaluation criteria. Interviews were conducted with 20 testers, and the evaluation result was the one with the largest number of evaluations.
⊚: The finger can be slid extremely smoothly without feeling rough.
◯: A finger can be slid smoothly without feeling rough.
Δ: There is a feeling of roughness, and there is a feeling of resistance such that the finger is caught when it is slid.
x: A rough feeling is strong, and there is a strong resistance when the finger is slid.

[Luminous average reflectance]
The spectral reflectance on the surface of the low refractive index layer of the optical laminates according to Examples 1 to 7 and Comparative Examples 1 to 5 was measured using an automatic spectrophotometer (Hitachi U-4100). In the spectral reflectance measurement, the back surface of the optical laminate (the surface of the transparent base material on which the antiglare layer and the low refractive index layer are not formed) is treated with a blackboard for matting to prevent reflection. The incident angle of light was 5°. Based on the obtained spectral reflectance curve, the visual average reflectance (reflection Y value) was calculated according to JIS R 3106.

[Visibility]
The optical laminates according to Examples 1 to 7 and Comparative Examples 1 to 5 were placed in a display device (iPad 3 (3rd generation) manufactured by Apple Inc., "iPad" is a registered trademark such that the transparent substrate faces the display surface side. ), and the visibility of the displayed image on the display device through the optical laminate was visually observed and evaluated according to the following evaluation criteria.
○: Reflection Y value is 1.0% or less ×: Reflection Y value is over 1.0%

Table 2 also shows the above measured values and evaluation results.

In the optical laminates according to Examples 1 to 7, the number of protrusions having a height of 0.1 μm or more on the surface of the low refractive index layer is 600 to 1500 per 1 mm ² of the measurement area, and Since the average inclination angle of the unevenness on the surface of the low refractive index layer was 0.5 to 1.4°, both the fingerprint wiping property and the slip property were good. In addition, the optical laminates according to Examples 1 to 7 also have an average luminous reflectance (reflection Y value) of 1.0% or less, and the reflection of external light is sufficiently suppressed. The visibility of the displayed image was also good when the display was held.

Above all, in the optical layered body according to Example 7, the number of convex portions having a concave-convex height of 0.1 μm or more exceeded 1400/1 mm ² , and sharp convex portions were densely arranged. The finger contact area was further reduced, and the slipperiness was better.

The optical laminate according to Comparative Example 1 is an antiglare film having no low refractive index layer. In the optical layered body according to Comparative Example 1, the number of convex portions having a height of 0.1 μm or more and the average inclination angle of the unevenness present on the outermost surface (surface of the antiglare layer) are approximately the same as those of Example 4. Since there is no low refractive index layer, the visual average reflectance (reflection Y value) is large, and the visibility of the displayed image when used in a display device is poor. In addition, the fingerprint wiping-off property and slipperiness were also poor.

The optical layered body according to Comparative Example 2 has a hard coat layer instead of the antiglare layer. In the optical layered body according to Comparative Example 2, the surface of the low refractive index layer became smooth because the unevenness derived from the antiglare layer was not formed. Therefore, fingerprint wiping-off property and slipperiness were poor.

In the optical laminates according to Comparative Examples 3 and 4, the number of protrusions having a protrusion height of 0.1 μm or more is less than 600/1 mm ² and the average inclination angle θa is less than 0.5°. Wipeability and slipperiness were insufficient.

The optical layered body according to Comparative Example 5 had an average inclination angle θa of less than 0.5°, and therefore had insufficient fingerprint wiping-off property and slipperiness. Moreover, the visual average reflectance (reflection Y value) of the optical layered body according to Comparative Example 5 exceeded 1.0%, and the visibility of the displayed image was poor when used in a display device.

As described above, in the optical laminate having an antireflection layer in which an antiglare layer and a low refractive index layer are laminated on a transparent substrate, the height of the unevenness present on the surface of the low refractive index layer is 0.1 μm or more. The number of parts is 600 to 1500 per 1 mm ² and the average inclination angle of the unevenness of the surface of the low refractive index layer is 0.5 to 1.4°, so that the fingerprint wiping off property and slipperiness are improved. It was confirmed to be good.

The optical laminate according to the present invention can be used as an antireflection film for a display device, and is particularly useful as an antireflection film for a display device with a touch panel for in-vehicle use.

REFERENCE SIGNS LIST 1 transparent substrate 2 antiglare layer 3 low refractive index layer 10 optical laminate

Claims (3)

An antiglare layer and a low refractive index layer on at least one surface of a transparent base material,
The number of projections having a height of 0.1 μm or more on the surface of the low refractive index layer is 600 to 1500 per 1 mm ² of the measurement area,
The optical layered body, wherein the average inclination angle of the irregularities on the surface of the low refractive index layer is 0.5 to 1.4°. 2. The optical laminate according to claim 1, wherein the average luminous reflectance of the surface of the low refractive index layer is 1.0% or less. a display panel;
3. A display device comprising the optical layered body according to claim 1, which is provided on the display surface side of the display panel.

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