KR20230052311A - Optical laminate, polarizing plate, and display device - Google Patents

Abstract

An optical laminate capable of suppressing glare while maintaining anti-glare properties and contrast even when applied to a high-definition image display panel is provided. An optical laminate in which at least one optical function layer is laminated on a translucent substrate, wherein at least one surface of the optical function layer has a concavo-convex shape formed, and the optical function layer having the concavo-convex shape comprises at least a resin component and two types of concavo-convex shapes. It contains inorganic fine particles of and resin particles, and the optical layered body has an internal haze X that satisfies the following conditional expressions (1) to (4), and a total haze Y,
Y>X... (One)
Y≤X+17 . (2)
Y≤57 … (3)
19≤X≤40... (4)
When the sharpness of the transmitted image using an optical comb with a width of 0.5 mm is 10 to 50% and the surface concavo-convex shape of the outermost surface of the optical function layer is measured by optical interference method, the area of the portion with the concavo-convex height of 0.4 μm or more is 3.5% of the measurement area. % or less, characterized in that the optical laminate.

Description

Optical laminate, polarizer and display device {OPTICAL LAMINATE, POLARIZING PLATE, AND DISPLAY DEVICE}

The present invention relates to an optical laminate suitable for an anti-glare film, and a polarizing plate and display device using the same.

The anti-glare film exhibits anti-glare properties by scattering external light with a concave-convex structure on its surface. The concavo-convex structure on the surface of the anti-glare film is formed by aggregating particles in the outermost resin layer.

In addition to anti-glare properties, anti-glare properties and functions such as high contrast are required of anti-glare films. Conventionally, the uneven surface structure (external scattering) and internal scattering are optimized by adjusting the shape, particle diameter, refractive index, coating material properties (viscosity), coating process, etc. of the particles (filler), resulting in anti-glare and anti-glare properties. , improvement in high contrast has been attempted. However, anti-glare property, anti-glare property, and high contrast have a contradictory relationship.

The anti-glare property is increased by using a filler having a large particle size, increasing the amount of filler added, and strengthening aggregation of the filler. In this case, the anti-glare property increases as the number of concavities and convexities increases and the size of the concavities and concavities increases, but glare resistance deteriorates due to an increase in the lens effect.

Although glare resistance is improved by use of a filler with a large refractive index difference with resin or increase in internal scattering by increasing the amount of filler added, since diffused light increases, contrast deteriorates. Further, by miniaturizing the surface irregularities, that is, by reducing the average length Sm of the irregularities, the glare resistance is also improved, but the anti-glare property with remarkable whitishness and low quality is obtained.

Contrast is improved by lowering internal scattering, but glare resistance deteriorates. In addition, although the contrast is improved also by forming a low-reflection layer, it becomes disadvantageous in terms of cost because it becomes a multi-layered structure.

Japanese Unexamined Patent Publication No. Hei 10-20103

When anti-glare properties and contrast are maintained as in the prior art with existing anti-glare films due to high-definition of liquid crystal panels in recent years, glare occurs. On the other hand, in order to improve glare resistance, it is necessary to sacrifice anti-glare property and contrast.

Therefore, the present invention is an optical laminate capable of suppressing glare while maintaining anti-glare properties and contrast when applied to an image display panel, in particular, a high-definition image display panel of 200 ppi or more, and a polarizing plate and image using the same It aims to provide a display device.

The present invention relates to an optical laminate formed by laminating at least one or more optical function layers on a translucent substrate. A concavo-convex shape is formed on at least one surface of the optical function layer of the optical laminated body, and the optical function layer having the concavo-convex shape contains at least a resin component, two types of inorganic fine particles, and resin particles, and the optical laminate is formed as follows. Has an internal haze X and a total haze Y that satisfies the conditional expressions (1) to (4) of

Y>X... (One)

Y≤X+17 . (2)

Y≤57 … (3)

19≤X≤40... (4)

When the sharpness of the transmitted image using an optical comb with a width of 0.5 mm is 10 to 50% and the surface concavo-convex shape of the outermost surface of the optical function layer is measured by optical interference method, the area of the portion with the concavo-convex height of 0.4 μm or more is 3.5% of the measurement area. less than %

According to the present invention, even when applied to a high-definition image display panel of 200 ppi or more, an optical laminate capable of suppressing glare while maintaining anti-glare properties and contrast, and a polarizing plate and an image display device using the same can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is the graph which plotted the relationship between the addition amount of the resin particle (organic filler) of Table 1, and the internal haze of the obtained optical laminated body.
Fig. 2 is a graph plotting the added amount of resin particles and the added amount of colloidal silica in Examples 1 to 12 and Comparative Examples 1 to 17 shown in Table 2.
FIG. 3 is a diagram showing concavo-convex shapes on the surface of the optical function layer of the optical laminate according to Example 2. FIG.
4 is a diagram showing concavo-convex shapes on the surface of the optical function layer of the optical laminate according to Comparative Example 6;
5 is a graph showing the distribution of the area ratio of the height of concavo-convex on the surface of the optical function layer according to Example 2 and Comparative Example 6.
Fig. 6 is an enlarged view within the range of the broken line shown in Fig. 5;
7 is a cross-sectional STEM photograph of the optical functional layer of the optical laminate according to Example 2.
8 is a cross-sectional STEM photograph of the optical functional layer of the optical laminate according to Comparative Example 6.
9 is a cross-sectional view showing a schematic configuration of an optical laminate according to an embodiment.
10 is a cross-sectional view showing a schematic configuration of a polarizing plate according to an embodiment.
11 is a cross-sectional view showing a schematic configuration of a display device according to an embodiment.

9 is a cross-sectional view showing a schematic configuration of an optical laminate according to an embodiment. An optical laminate 100 according to an embodiment includes a translucent base 1 and at least one optical functional layer 2 laminated on the translucent base 1 . On the surface of the optical function layer 2, fine irregularities are formed. The optical function layer 2 exhibits anti-glare properties when these irregularities diffusely reflect external light.

As the translucent substrate, polyethylene terephthalate (PET), triacetyl cellulose (TAC), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), polyethylene ( Various resins such as PE), polypropylene (PP), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), cycloolefin copolymer (COC), norbornene-containing resin, polyethersulfone, cellophane, and aromatic polyamide A film can be used suitably.

The total light transmittance (JIS K7105) of the translucent substrate is preferably 80% or more, and more preferably 90% or more. In addition, the thickness of the translucent substrate is preferably 1 to 700 µm, more preferably 25 to 250 µm, in consideration of productivity and handling properties of the optical laminate.

It is preferable to give a surface modification process to the translucent substrate in order to improve adhesiveness with an optical function layer. Examples of the surface modification treatment include alkali treatment, corona treatment, plasma treatment, sputtering treatment, application of a surfactant or silane coupling agent, Si deposition, and the like.

The optical function layer contains a base resin, resin particles (organic filler), and two types of inorganic fine particles. The optical function layer is formed by applying a resin composition, which is a mixture of a base material resin that is cured by irradiation of ionizing radiation or ultraviolet rays, resin particles, and two types of inorganic fine particles, to a translucent base and curing the coating film.

Hereinafter, the structural component of the resin composition used for formation of an optical function layer is demonstrated.

As the base resin, a resin cured by irradiation of ionizing radiation or ultraviolet rays can be used.

Examples of the resin material cured by irradiation of ionizing radiation include radically polymerizable functional groups such as acryloyl, methacryloyl, acryloyloxy, and methacryloyloxy groups, epoxy groups, vinyl ether groups, and oxetane groups. Monomers, oligomers, and prepolymers having a cationically polymerizable functional group may be used alone or in combination. As monomers, methyl acrylate, methyl methacrylate, methoxy polyethylene methacrylate, cyclohexyl methacrylate, phenoxyethyl methacrylate, ethylene glycol dimethacrylate, dipentaerythritol hexaacrylate, trimethylolpropane tri Methacrylate, pentaerythritol triacrylate, etc. can be illustrated. Examples of oligomers and prepolymers include acrylate compounds such as polyester acrylate, polyurethane acrylate, polyfunctional urethane acrylate, epoxy acrylate, polyether acrylate, alkyd acrylate, melamine acrylate and silicone acrylate, and unsaturated poly Epoxy compounds such as esters, tetramethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether and various alicyclic epoxies, 3-ethyl- 3-hydroxymethyloxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, di[1-ethyl(3-oxetanyl)]methyl ether, etc. An oxetane compound can be illustrated.

The resin material described above can be cured by irradiation with ultraviolet rays under the condition of adding a photopolymerization initiator. Examples of the photopolymerization initiator include radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin and benzoin methyl ether, aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, and metallocene compounds. Cationic polymerization initiators may be used alone or in combination.

The resin particles (organic filler) added to the optical function layer aggregate in the base resin to form a fine concavo-convex structure on the surface of the optical function layer. As the resin particles, those containing light-transmitting resin materials such as acrylic resins, polystyrene resins, styrene-acrylic copolymers, polyethylene resins, epoxy resins, silicone resins, polyvinylidene fluoride, and polyethylene fluoride-based resins can be used. The material refractive index of the resin particles is preferably 1.40 to 1.75.

The refractive index n _f of the resin particles and the refractive index n _z of the base resin preferably satisfy the following condition (α), and more preferably satisfy the following condition (β).

|n _z -n _f |≥0.025 … (α)

|n _z -n _f |≥0.035 … (β)

When the refractive index n _z of the resin material serving as the base material and the refractive index n _f of the resin particles do not satisfy the condition (α), it is necessary to increase the addition amount of the resin particles in order to obtain a desired internal haze, resulting in deterioration of image sharpness. do.

It is preferable that it is 0.3-10.0 micrometers, and, as for the average particle diameter of a resin particle, it is more preferable that it is 1.0-7.0 micrometers. When the average particle diameter of the resin particles is less than 0.3 µm, the anti-glare properties decrease. On the other hand, when the average particle diameter of the resin particles exceeds 10.0 μm, the area ratio of the height of concavities and convexities on the surface of the optical function layer cannot be controlled, and the glare resistance deteriorates.

To the base resin of the optical function layer, as two types of inorganic fine particles, a first inorganic fine particle and a second inorganic fine particle are added.

As the first inorganic fine particles, colloidal silica, alumina, and zinc oxide can be used alone or in combination. By adding the first inorganic fine particles, excessive aggregation of the resin particles can be suppressed, and the concavo-convex structure formed on the surface of the optical function layer can be made uniform, that is, the local increase in concavo-convex can be suppressed. By adding the first inorganic fine particles, glare resistance can be improved while maintaining anti-glare properties and high contrast.

The first inorganic fine particles are preferably inorganic nanoparticles having an average particle diameter of 10 to 100 nm. When colloidal silica is used as the first inorganic fine particles, it is more preferable that the average particle diameter is about 20 nm, and when alumina or zinc oxide is used as the first inorganic fine particles, it is more preferable that the average particle diameter is about 40 nm. desirable. The addition amount of the first inorganic fine particles is preferably 0.05 to 10%, and more preferably 0.1 to 5.0% with respect to the total weight of the resin composition for forming an optical function layer. If the amount of addition of the first inorganic fine particles is out of this range, the area ratio of the height of concavities and convexities on the surface of the optical function layer cannot be controlled, and the glare resistance deteriorates.

The second inorganic fine particles are preferably inorganic nanoparticles having an average particle diameter of 10 to 200 nm. The addition amount of the second inorganic fine particles is preferably 0.1 to 5.0%. As the second inorganic fine particles, swelling clay can be used. The swelling clay may be any material that has a cation exchange ability and is swollen by introducing a solvent between the layers of the swelling clay, and may be a natural product or a synthetic product (including substituents and derivatives). It may also be a mixture of a natural product and a synthetic product. As swelling clay, for example, mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, beidelite, saponite, hectorite, stevensite, nontronite, margardiite, islerite, carnemite, layered titanic acid , smectite, synthetic smectite, and the like. 1 type may be used for these swelling clays, and a plurality may be mixed and used.

As the second inorganic fine particles, layered organic clay is more preferable. In the present invention, the layered organic clay refers to one in which organic onium ions are introduced between the layers of swelling clay. The organic onium ion is not limited as long as it can be organically formed by utilizing the cation exchange property of the swelling clay. As the second inorganic fine particles, synthetic smectite (a layered organic clay mineral) can be used, for example. Synthetic smectite functions as a thickener that increases the viscosity of the resin composition for forming an optical function layer. Addition of synthetic smectite as a thickener suppresses sedimentation of the resin particles and the first inorganic fine particles, contributing to formation of a concavo-convex structure on the surface of the optical function layer.

Further, when the first inorganic fine particles and the second inorganic fine particles are used together, the first inorganic fine particles and the second inorganic fine particles form an aggregate in the optical function layer. This aggregation suppresses aggregation of resin particles, and the height of the concavo-convex shape of the concavo-convex shape on the surface of the optical function layer is leveled, thereby making light scattering on the surface of the optical function layer uniform, and glare resistance can be improved.

Moreover, you may add a leveling agent to the resin composition for optical function layer formation. The leveling agent is oriented on the surface of the coating film in the drying process, and has a function of equalizing the surface tension of the coating film and reducing surface defects of the coating film.

Moreover, you may add an organic solvent suitably to the resin composition for optical function layer formation. Examples of organic solvents include alcohols, esters, ketones, ethers, and aromatic hydrocarbons.

It is preferable that it is 1.0-12.0 micrometers, and, as for the film thickness of an optical function layer, it is more preferable that it is 3.0-10.0 micrometers. When the film thickness of the optical function layer is less than 1 μm, curing failure due to oxygen inhibition occurs, and the scratch resistance of the optical function layer tends to decrease. On the other hand, when the film thickness of the optical function layer exceeds 12.0 μm, since curl due to curing shrinkage of the base resin layer becomes strong, it is not preferable.

Moreover, it is preferable that it is 110 to 300% of the average particle diameter of a resin particle, and, as for the film thickness of an optical function layer, it is more preferable that it is 120 to 250%. When the film thickness of the optical function layer is less than 110% of the average particle diameter of the resin particles, whitishness is noticeable and low-quality anti-glare properties are obtained. On the other hand, when the film thickness of the optical function layer exceeds 300% of the average particle diameter of the resin particles, it is not preferable because the anti-glare properties are insufficient.

In the optical layered body according to the present embodiment, the internal haze X and the total haze Y simultaneously satisfy the following conditions (1) to (4).

Y>X... (One)

Y≤X+17 . (2)

Y≤57 … (3)

19≤X≤40... (4)

When the internal haze X does not satisfy the conditional expression (4) and is less than 19%, the glare resistance is insufficient. On the other hand, when the internal haze X does not satisfy conditional expression (4) and exceeds 40%, contrast deteriorates.

It is more preferable that the internal haze X satisfies the following conditional expression (4)'. When the internal haze X satisfies the conditional expression (4)', both of the glare resistance and the contrast can be further improved.

25≤X≤35... (4)'

Moreover, when the total haze Y does not satisfy the conditional expression (3) and exceeds 57%, the irregularities on the surface of the optical function layer are large, and the glare resistance is insufficient.

The transmission image clarity of the optical layered body according to the present embodiment is preferably 10 to 50%, and more preferably 15 to 45% as a measured value measured using an optical comb having a width of 0.5 mm. When the transmitted image clarity is less than 10%, the glare resistance deteriorates. On the other hand, when the transmitted image clarity exceeds 50%, anti-glare properties deteriorate.

When the concavo-convex shape on the surface of the optical function layer according to the present embodiment is measured by an optical interference method, the area of the portion having the concavo-convex height of 0.4 μm or more is 3.5% or less. Among the concavo-convex structures on the surface of the optical function layer, when the area of the portion with the concavo-convex height of 0.4 μm or more exceeds 3.5%, a large portion of the concavo-convex area is locally distributed, so optical lamination as an anti-glare film for an image display device of 200 ppi or more. In the case of using a sieve, glare resistance deteriorates.

Conventionally, in order to suppress excessive filler aggregation, a method of adjusting the paint viscosity, a method of increasing the solid content concentration of the paint during coating, and a method of suppressing convection during drying by using a solvent with a high volatilization rate are employed. However, when employing these methods, there is a problem that planar failure such as coating unevenness is likely to occur. On the other hand, as described in the above embodiment, if the method of adding two types of inorganic fine particles does not affect the physical properties of the paint or the drying speed, it is possible to improve the glare resistance while maintaining the coating suitability.

10 is a cross-sectional view showing a schematic configuration of a polarizing plate according to an embodiment. The polarizing plate 110 includes an optical laminate 100 and a polarizing film 11 . The optical layered body 100 is shown in FIG. 9 , and a polarizing film (polarizing substrate) 11 is provided on the side surface of the translucent substrate 1 on which the optical function layer 2 is not formed. . The polarizing film 11 is obtained by laminating a transparent substrate 3, a polarizing layer 4, and a transparent substrate 5 in this order. The materials of the transparent substrates 3 and 5 and the polarizing layer 4 are not particularly limited, and those normally used for polarizing films can be appropriately used.

11 is a cross-sectional view showing a schematic configuration of a display device according to an embodiment. The display device 120 laminates an optical laminate 100, a polarizing film 11, a liquid crystal cell 13, a polarizing film (polarizing substrate) 12, and a backlight unit 14 in this order. it did The polarizing film 12 is obtained by laminating a transparent substrate 6, a polarizing layer 7, and a transparent substrate 8 in this order. The materials of the transparent substrates 6 and 8 and the polarizing layer 7 are not particularly limited, and those normally used for polarizing films can be appropriately used. The liquid crystal cell 13 includes a liquid crystal panel in which liquid crystal molecules are sealed between a pair of transparent substrates having transparent electrodes, and a color filter, by changing the orientation of the liquid crystal molecules according to a voltage applied between the transparent electrodes, It is a device that forms an image by controlling the light transmittance of a pixel. The backlight unit 14 is a lighting device including a light source and a light diffusing plate (both not shown), uniformly diffusing light emitted from the light source and radiating the light from the emitting surface.

In addition, the display device 120 shown in FIG. 11 may further include a diffusion film, a prism sheet, a brightness enhancing film, a retardation film for compensating for a phase difference between a liquid crystal cell and a polarizing plate, and a touch sensor.

The optical layered body according to the present embodiment may further have at least one layer of a refractive index adjustment layer such as a low refractive index layer, an antistatic layer, and an antifouling layer in addition to the optical function layer that suppresses glare.

The low refractive index layer is formed on the optical function layer that suppresses glare and is a functional layer for reducing the reflectance by lowering the refractive index of the surface. The low refractive index layer is coated with a coating solution containing an ionizing radiation curable material such as a polyester acrylate-based monomer, an epoxy acrylate-based monomer, a urethane acrylate-based monomer, or a polyol acrylate-based monomer and a polymerization initiator, and the coating film is subjected to polymerization. It can be formed by curing. In the low refractive index layer, low refractive index fine particles containing low refractive materials such as LiF, MgF, 3NaF·AlF or AlF (both refractive index 1.4) or Na ₃ AlF ₆ (cryolite, refractive index 1.33) are used as low refractive particles. may be dispersed. Further, as the low refractive index fine particles, particles having voids inside the particles can be suitably used. In particles having voids inside the particles, since the refractive index of air (≒1) can be used for the void portion, low refractive index particles having a very low refractive index can be obtained. Specifically, the refractive index can be lowered by using low refractive index silica particles having voids therein.

The antistatic layer is coated with a coating solution containing an ionizing radiation curable material such as a polyester acrylate-based monomer, an epoxy acrylate-based monomer, a urethane acrylate-based monomer, or a polyol acrylate-based monomer, a polymerization initiator, and an antistatic agent; It can be formed by curing by polymerization. As the antistatic agent, for example, metal oxide fine particles such as antimony-doped tin oxide (ATO) and tin-doped indium oxide (ITO), polymer type conductive compositions, quaternary ammonium salts, and the like can be used. The antistatic layer may be formed on the outermost surface of the optical layered body, or may be formed between the optical function layer that suppresses glare and the translucent substrate.

The antifouling layer is formed on the outermost surface of the optical laminate, and improves antifouling properties by imparting water repellency and/or oil repellency to the optical laminate. The antifouling layer can be formed by dry coating or wet coating of a silicon oxide, a fluorine-containing silane compound, a fluoroalkylsilazane, a fluoroalkylsilane, a fluorine-containing silicon compound, a silane coupling agent containing a perfluoropolyether group, or the like. there is.

In addition to the low refractive index layer, antistatic layer and antifouling layer described above, or in addition to the low refractive index layer, antistatic layer and antifouling layer, at least one layer such as an infrared absorbing layer, an ultraviolet absorbing layer, or a color correction layer may be formed.

Example

Hereinafter, examples in which the optical laminate according to the embodiment is specifically implemented will be described.

(Method of manufacturing optical laminate)

As a translucent base, a triacetyl cellulose film having a thickness of 40 µm was used. The optical function layer was formed by applying the following coating liquid for forming an optical function layer onto the light-transmitting substrate, drying (evaporation of the solvent), and then curing the coating film by polymerization.

[Coating solution for forming optical function layer]

Base resin: UV/EB curable resin light acrylate PE-3A (pentaerythritol triacrylate, manufactured by Kyoeisha Chemical Co., Ltd.), refractive index 1.52

・Resin Filler:

<Examples 1 to 10, Comparative Examples 1 to 17>

Cross-linked styrene monodisperse particles SX350H (manufactured by Soken Chemical Co., Ltd.), average particle diameter 3.5 µm, refractive index 1.595

<Example 11>

Styrene monodisperse filler SSX302ABE (manufactured by Sekisui Kaseihin Co., Ltd.), average particle diameter 2.0 µm, refractive index 1.595

<Example 12>

Cross-linked styrene monodisperse particles SX500H (manufactured by Soken Chemical Co., Ltd.), average particle diameter 5.0 µm, refractive index 1.595

Colloidal silica: organosilica sol MEK-ST (manufactured by Nissan Chemical Industries, Ltd.)

Synthetic smectite: Lucentite SAN (manufactured by Co-op Chemical Co., Ltd.)

Fluorine-based leveling agent: Megapack F-471 (manufactured by DIC Co., Ltd.) 0.1%

・Solvent: Toluene

In addition, the addition amount of the resin particles (organic filler), the first inorganic fine particles (colloidal silica), and the second inorganic fine particles (synthetic smectite) to the coating solution for forming the optical function layer will be described later in the description of Examples and Comparative Examples. . In addition, the addition amount of each component is the ratio (mass %) of the total solid mass of the coating liquid for optical function layer formation. Here, the total solid content of the coating liquid for forming an optical function layer refers to components excluding the solvent. Therefore, the blending ratio (% by mass) of the resin particles, the first inorganic fine particles, and the second inorganic fine particles in the total solid content of the coating liquid for forming the optical function layer, and the resin in the optical function layer, which is a cured film of the coating liquid for forming the optical function layer, The content ratio (% by mass) of the particles, the first inorganic fine particles, and the second inorganic fine particles is the same.

The method for measuring the surface roughness, the clarity of the transmitted image, the haze value, and the film thickness of the optical layered body is as follows.

[Surface Roughness]

The arithmetic average roughness Ra, the maximum height Rz, and the average length RSm of the contour curve elements were measured in accordance with JIS B0601: 2001 using a surface roughness measuring instrument (Surfcoder SE1700α, manufactured by Kosaka Genkyusho Co., Ltd.). The average inclination angle was obtained by obtaining the average inclination measured using the surface roughness meter according to ASEM95, and the average inclination angle was calculated according to the following formula.

average slope angle=arctan(average slope)

[Transmission image clarity]

Transmissive image sharpness was measured according to JIS K7105 with an optical comb width of 0.5 mm using an image quality measuring instrument (ICM-1T, manufactured by Suga Shikenki Co., Ltd.).

[Haze value]

The haze value was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JIS K7105. Here, the haze value of the optical laminated film was made into the total haze. In addition, the value obtained by subtracting the haze value of the transparent sheet with an adhesive from the haze value measured by bonding the transparent sheet with an adhesive to the surface on which the fine concavo-convex shape of the optical laminated film was formed was taken as the internal haze. Further, as a transparent sheet having an adhesive, a polyethylene terephthalate film (thickness: 38 μm) coated with an acrylic adhesive (thickness: 10 μm) was used.

[film thickness]

The film thickness of the optical function layer was measured using a linear gauge (D-10HS, manufactured by Ozaki Seisakusho Co., Ltd.).

(Relationship between resin particles and internal haze)

First, the addition amount of resin particles (organic filler) necessary to obtain an internal haze (19 to 40%) that improves both glare resistance and contrast was investigated. A resin coating solution was prepared in which resin particles and two types of inorganic fine particles were added in the addition amounts shown in Table 1, and an optical laminate was produced according to the above-described production method. The internal haze of the produced optical laminate was determined.

In Table 1, the added amounts of the resin particles and two types of inorganic fine particles and the value of the internal haze of the obtained optical laminate are shown.

BRIEF DESCRIPTION OF THE DRAWINGS It is the graph which plotted the relationship between the addition amount of the resin particle (organic filler) of Table 1, and the internal haze of the obtained optical laminated body. The straight line shown in FIG. 1 is a regression line obtained from the plot.

From the regression line shown in FIG. 1, when the difference in refractive index between the base resin and the resin particles is 0.075, in order to set the value of the internal haze to 19 to 40%, it can be seen that the addition amount of the resin particles is 7 to 15%.

(Examples 1 to 12, Comparative Examples 1 to 17)

Next, optical laminates according to Examples 1 to 12 and Comparative Examples 1 to 17 were prepared using a coating solution for forming an optical function layer in which resin particles and two types of inorganic fine particles were added in the amounts shown in Table 2. .

For each of the manufactured optical laminates according to Examples 1 to 12 and Comparative Examples 1 to 17, haze value, transmission image clarity, and film thickness were measured by the above-described test method.

(Evaluation method and evaluation criteria for glare resistance)

For glare resistance, after bonding the optical laminates of each example and each comparative example to the screen surface of a liquid crystal monitor (iPad3 (3rd generation), manufactured by Apple Inc., 264 ppi) via a transparent adhesive layer, the liquid crystal monitor was set to a green display state, and the presence or absence of glare was evaluated by 100 people at random when viewing the liquid crystal monitor from a place 50 cm vertically away from the center of the screen surface in a dark room. As for the evaluation results, the case where the number of people who did not feel the glare was "○", the case where the number of people who did not feel the flash was "○", the case where the number of people was 30 or more and less than 70 was "Δ", and the case where less than 30 people was made "X".

(Evaluation method and evaluation criteria for anti-glare properties)

The anti-glare property was obtained by bonding the optical laminates of each Example and each Comparative Example to a black acrylic plate (Smipex 960, manufactured by Sumitomo Chemical Co., Ltd.) via a transparent adhesive layer, and then vertically from the center of the black acrylic plate 50 The presence or absence of projection of one's own image (face) on the black acrylic plate when viewed under the condition of illumination of 250 ㏓ from a place away from cm was evaluated by 100 random people's eyes. As for the evaluation results, the case where the number of people who did not feel the projection was "○", the case where the number of people who did not feel the projection was "○", the case where the number of people was 30 or more and less than 70 was set to "Δ", and the case where the number of less than 30 people was set to "X".

(Evaluation method and evaluation standard of luminance ratio)

The luminance ratio was determined by bonding the optical laminate and the translucent substrate of each Example and each Comparative Example to the screen surface of a liquid crystal monitor (iPad3 (3rd generation), manufactured by Apple Inc., 264 ppi) via a transparent adhesive layer. , The luminance was measured with a spectroradiometer (SU-UL1R, manufactured by Topcon Co., Ltd.) at a place 70 cm vertically away from the center of the screen surface in a dark room with the liquid crystal monitor in a white display state. The luminance of the translucent base was 100%, the case of 93% or more was designated as "○", and the case of less than 93% was designated as "x".

In Table 2, the amount of addition of the resin particles and two types of inorganic fine particles, the measured values of the total haze, internal haze, transmission image clarity and film thickness of the obtained optical laminate, and the evaluation results of glare resistance, anti-glare property and luminance ratio indicates

The total haze (Y) and internal haze (X) of the optical laminates according to Examples 1 to 12 satisfy all of the above-described conditional expressions (1) to (4), and the internal haze (X) is 19 to 40%. was within range. In addition, the transmission image clarity was within a more preferable range of 15 to 45%. Therefore, the optical laminates according to Examples 1 to 12 had excellent glare resistance, anti-glare properties, and luminance ratio.

In contrast, in the optical laminates according to Comparative Examples 1 and 2, since the internal haze was less than 19%, the glare resistance was insufficient. Further, in the optical laminate according to Comparative Example 2, since the clarity of the transmitted image exceeded 50%, the anti-glare property was also insufficient.

In the optical laminates according to Comparative Examples 4, 5, 7, and 8 and Comparative Examples 10 to 12, the transmission image sharpness exceeded 50%, and thus the anti-glare properties were insufficient.

In the optical laminates according to Comparative Examples 13 to 17, the internal haze exceeded 40% due to the increase in the addition amount of the resin particles, and all of them had insufficient luminance ratios. In addition to this, in the optical laminates according to Comparative Examples 13 to 16, the total haze exceeded 57%, the surface irregularities were large, and the glare resistance was insufficient. Further, in the optical laminates according to Comparative Examples 13 to 15, glare resistance deteriorated even when the transmission image sharpness became less than 10%.

The optical laminates according to Comparative Examples 3, 6, and 9 in which colloidal silica was not added as the first inorganic fine particles have a high-precision image display device ( 264 ppi), the glare resistance deteriorated. This is because, among the concavo-convex structures formed on the surface of the optical function layer of the optical laminates according to Comparative Examples 3, 6, and 9, the area of adjacent concavo-convex heights of 0.4 μm or more exceeded 3.5%. The detail of this point is mentioned later.

Fig. 2 is a graph plotting the added amount of resin particles and the added amount of colloidal silica in Examples 1 to 12 and Comparative Examples 1 to 17 shown in Table 2. In Fig. 2, Examples 1 to 12 are plotted as -, and Comparative Examples 1 to 17 are plotted as x marks.

As shown in FIG. 2, the plots of the added amount of resin particles and the added amount of colloidal silica in Examples 1 to 12 are the area below the straight line indicated by the solid line in FIG. 2 (except for the horizontal axis), In addition, when the addition amount of the resin particles is within the range of 7 to 15%, even when used as an anti-glare film for a high-definition image display device of 200 ppi or more, excellent performance can be obtained in both glare resistance, anti-glare property and contrast. Confirmed. That is, when the content of the resin particles in the resin composition for forming an optical function layer is set to A (%) and the content of colloidal silica is set to B (%), the following conditional expressions (5) and (6) are simultaneously satisfied: In this case, it was found that both anti-glare, anti-glare and contrast were excellent. The following conditional expression (5) is a straight line passing through both of the plots of the added amount of resin particles and the added amount of colloidal silica in Examples 4 and 10. In addition, the following conditional expression (6) is a necessary condition in order to make the value of internal haze within the range of 19 to 40% in the structure of this Example, as demonstrated with FIG.

0<B≤0.375A-2.44... (5)

7.0≤A≤15.0... (6)

As can be seen from the results of Table 2, when the conditional expressions (5) and (6) are not satisfied at the same time, since any of the glare resistance, anti-glare property, and contrast deteriorates, the anti-glare properties of the high-definition image display device of 200 ppi or more It was not suitable for use as a film.

(Irregular shape of the surface of the optical functional layer)

Here, the concavo-convex shape on the surface of the optical function layer will be described.

Table 3 shows the measured surface roughness values of the optical laminates according to Examples 2 to 4 and Comparative Example 6.

3 is a diagram showing the concavo-convex shape of the surface of the optical function layer of the optical laminate according to Example 2, and FIG. 4 is a diagram showing the concavo-convex shape of the surface of the optical function layer of the optical laminate according to Comparative Example 6. am.

3 and 4 show the optical function by optical interference method using a non-contact surface/layer cross-sectional shape measurement system (measurement device: Vertscan R3300FL-Lite-AC, analysis software: VertScan4, manufactured by Ryoka Systems Co., Ltd.) The concavo-convex shape of the surface of the layer was measured, and the measurement result was output as a three-dimensional image. Table 4 shows the measurement conditions of the measurement system.

As shown in Table 3, the arithmetic average roughness Ra, the maximum height Rz and the average length RSm of the contour curve elements measured according to JIS B0601: 2001, and the average inclination angle measured according to ASEM95 were obtained from Examples 2 to 4 and Comparative Examples. No significant difference was found between 6. However, when the surface concavo-convex shape of the optical function layer of the optical layered body according to Examples 2 to 4 and Comparative Example 6 is measured by optical interference method, there is a difference in the distribution of the concavo-convex shape. In the concavo-convex shape of the surface of the optical function layer according to Example 2 shown in FIG. 3, compared to the concavo-convex shape of the surface of the optical function layer according to Comparative Example 6 shown in FIG. In Fig. 4, the dark-colored portion) is reduced.

FIG. 5 is a graph showing the distribution of the area ratio of the height of concavities and convexities on the surface of the optical function layer in Examples 2 and 3 and Comparative Example 6, and FIG. 6 is an enlarged view within the range of the broken line shown in FIG. 5 .

The graphs shown in FIGS. 5 and 6 were created using the load curve analysis function of the non-contact surface/layer cross-sectional shape measurement system described above. Here, the unevenness height refers to the level difference of the concave part and the convex part in the direction orthogonal to the measuring surface, based on the average level (height 0) of all the uneven heights of the measuring surface. In addition, the area ratio of the height of concavo-convex surfaces refers to the ratio occupied by an area equal to or greater than a predetermined height of concavities and convexities with respect to the measurement area.

5 and 6, in Examples 2 and 3 in which colloidal silica was added as the first inorganic fine particles to the coating liquid for forming the optical function layer, compared to Comparative Example 6 in which no colloidal silica was added, The uneven height is relatively small. Further, when Example 2 and Comparative Example 6 are compared, in the concavo-convex shape of the optical function layer according to Example 2, the area ratio of any concavo-convex height was smaller than the area ratio in Comparative Example 6. In addition, when Example 2 and Comparative Example 6 were compared, a difference was particularly observed in the area ratio of the region having the uneven height of 0.4 µm or more. That is, in Example 2, it is considered that glare resistance was improved by forming the concavo-convex shape on the surface of the optical function layer so that the area ratio of the region having the concavo-convex height of 0.4 μm or more was 3.5% or less. Conversely, in Comparative Example 6, the area ratio of the region having the height of the unevenness of 0.4 μm or more exceeded 3.5%, so that many parts having the relatively high height of the unevenness as shown in FIG. 4 were formed. Therefore, the measured value of general surface roughness Although there is not much difference from Example 2, it is considered that the glare resistance deteriorated.

FIG. 7 is a cross-sectional STEM photograph of the optical function layer of the optical laminate according to Example 2, and FIG. 8 is a cross-sectional STEM photograph of the optical function layer of the optical laminate according to Comparative Example 6.

From the cross-sectional STEM photograph shown in FIG. 7 , it can be confirmed that colloidal silica and synthetic smectite form aggregates in the optical function layer according to Example 2. On the other hand, as shown in FIG. 8, since colloidal silica was not contained in the optical function layer according to Comparative Example 6, the agglomerates shown in FIG. 7 were not formed. Since the aggregate of colloidal silica and synthetic smectite formed in the optical laminate according to Example 2 is larger than the aggregate of synthetic smectite present in the optical function layer according to Comparative Example 6, the effect of suppressing aggregation of resin particles is high. .

As described above, the optical laminates according to Examples 1 to 12 can exhibit excellent performance in both glare resistance, anti-glare and contrast, even when used as an anti-glare film for a high-definition image display device of 200 ppi or higher. Confirmed.

The optical layered body according to the present invention can be used as an anti-glare film used in a high-definition (eg, 200 ppi or higher) image display device.

1: translucent gas
2: optical functional layer
3, 5, 6, 8: transparent substrate
4, 7: polarization layer
11, 12: polarizer
13: liquid crystal cell
14: backlight unit
100: optical laminate
110: polarizer
120: display device

Claims (8)

An optical laminate formed by laminating at least one layer of an optical function layer on a light-transmitting substrate,
A concavo-convex shape is formed on at least one surface of the optical function layer,
The optical function layer having the concavo-convex shape contains at least a resin component, two types of inorganic fine particles, and resin particles,
The two types of inorganic fine particles are first inorganic fine particles having an average particle diameter of 10 to 100 nm and second inorganic fine particles having an average particle diameter of 10 to 200 nm and different from the first inorganic fine particles,
The addition amount of the first inorganic fine particles is 0.5 to 3.0 mass% of the optical function layer, and the addition amount of the second inorganic fine particles is 1.0 to 2.0 mass% of the optical function layer,
The optical layered body has an internal haze X and a total haze Y that satisfy the following conditional expressions (1) to (4),
Y>X... (One)
Y≤X+17 . (2)
Y≤57 … (3)
19≤X≤40... (4)
When the surface concavo-convex shape of the outermost surface of the optical function layer is measured by an optical interference method, the area of a portion having a concavo-convex height of 0.4 μm or more is 3.5% or less of the measurement area. According to claim 1,
An optical laminate characterized in that the two types of inorganic fine particles contained in the optical function layer are inorganic nanoparticles and swelling clay. According to claim 2,
An optical laminate characterized in that the content ratio A (%) of the resin particles and the content ratio B (%) of the inorganic nanoparticles in the optical function layer satisfy the following conditional expressions (5) and (6) sifter.
0<B≤0.375A-2.44... (5)
7.0≤A≤15.0... (6) According to claim 1,
An optical laminate characterized in that the optical function layer contains a radiation curable resin composition as a base resin. According to claim 1,
An optical laminate characterized in that the two types of inorganic fine particles contained in the optical function layer form an aggregate. According to claim 1,
An optical laminate further comprising at least one layer of a refractive index adjustment layer, an antistatic layer, and an antifouling layer. A polarizing plate characterized in that a polarizing substrate is laminated on the translucent substrate constituting the optical layered body according to claim 1. A display device comprising the optical laminate according to claim 1 .

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