WO2025243974A1 - Optical laminate and article - Google Patents

Abstract

In the present invention, an antireflection film is provided with a film base material and an optically functional layer. The optically functional layer comprises, sequentially from the film base material side, a first high-refractive index layer having an optical thickness of 25-43 nm, a first low-refractive index layer having an optical thickness of 54-69 nm, a second high-refractive index layer having an optical thickness of 278-308 nm, and a second low-refractive index layer having an optical thickness of 131-141 nm. The antireflection film exhibits a transmission rate of not less than 86% with respect to light having a wavelength of 940 nm, and a visibility reflectance Y of not more than 1.0%. The a^* value and the b^* value expressed in the CIE-LAB color system for total reflection light obtained when light having a wavelength of 380-780 nm generated by a standard light source D65 is caused to enter the antireflection film satisfy -4.0<a^*<4.0 and -15.0<b^*<0.0, respectively.

Description

Optical laminates and articles

The present invention relates to optical laminates and articles.
This application claims priority based on Japanese Patent Application No. 2024-082905, filed on May 21, 2024, the contents of which are incorporated herein by reference.

Anti-reflection films, such as those disclosed in Patent Documents 1 to 3, are used in a variety of devices to prevent surface reflection. For example, they are used in in-vehicle films such as head-up displays, and in display devices such as smartphone touch panels. When attached to a display device, optical laminates such as anti-reflection films are desirably less likely to color the light reflected by the display device. In other words, it is desirable that color unevenness is not visible even when the user changes the viewing angle of the display device. In response to this demand, development is underway on optical laminates that minimize color unevenness when the viewing angle changes (for example, Patent Document 1).

Furthermore, the optical laminate in Patent Document 2 is said to comprise a laminate in which layers of low refractive index material and layers of high refractive index material are alternately stacked on a glass substrate. The optical laminate in Patent Document 2 is formed by sputtering an optical functional layer onto the glass substrate.

Furthermore, an infrared sensor (IR sensor) that responds to infrared rays may be installed on the front surface of a display device, etc. For this reason, optical laminates such as anti-reflection films installed on the front surface of a display device, etc., that have high infrared transmittance are desired, and development is underway (for example, Patent Document 3).

Furthermore, in recent years, curved display devices have become popular from the perspective of improved functionality and design, which reduce strain on the user's eyes while also enhancing the sense of immersion, taking into account the distance from the user's eyes.

Patent No. 6956909 Patent No. 6881172 Patent No. 7121070

However, optical laminates such as those described in Patent Document 1 do not take into consideration the installation of an infrared sensor in a display device, and have low infrared transmittance. As a result, in display devices formed with the optical laminate described in Patent Document 1, the IR sensor may not function.

Furthermore, the optical laminate of Patent Document 2 has an optical functional layer formed on a chemically strengthened glass substrate with a thickness of approximately 2 mm, which, combined with the low flexibility of glass substrates, makes it unsuitable for curved display devices. If a curved display device were to be manufactured using a glass substrate with the above thickness, the glass substrate would need to be bent before the optical functional layer is deposited. If the glass substrate were bent, the distance from the deposition target to the glass substrate would be uneven at each position when the optical functional layer is formed on the substrate by sputtering. This raises concerns that the in-plane uniformity of the formed optical functional layer may be reduced. If the in-plane uniformity of the optical functional layer is reduced, it is thought that the optical properties of the optical laminate, such as infrared transmittance and hue when the viewing angle changes, would vary in the in-plane direction.

Furthermore, optical laminates such as those described in Patent Document 3 may not have good total reflection hue, and color unevenness may be visible depending on the viewing angle.

No optical laminate is known that has high infrared transmittance, good total reflection hue, and is applicable to curved display devices. In optical laminates, the overall characteristics are determined by the mutual influence of the configuration of each layer, and there is a need to develop an optical laminate with a new configuration that can achieve both of the above characteristics.

The present invention was made in consideration of the above circumstances, and aims to provide an optical laminate that has high infrared transmittance, good total reflection hue, and is applicable to curved display devices, as well as an article provided with such an optical laminate.

To solve the above problems, the inventors provide the following means.

(1) An optical laminate according to one aspect of the present invention is an antireflection film including a film substrate and an optical functional layer formed on the film substrate,
The optical functional layer is, in order from the film substrate side,
a first high refractive index layer having an optical thickness of 25 nm or more and 43 nm or less;
a first low refractive index layer having an optical thickness of 54 nm or more and 69 nm or less;
a second high refractive index layer having an optical thickness of 276 nm or more and 308 nm or less;
a second low refractive index layer having an optical thickness of 128 nm or more and 141 nm or less,
The transmittance of light at a wavelength of 940 nm is 86% or more,
The luminous reflectance Y is 1.0% or less,
When light having a wavelength of 380 nm to 780 nm is incident using standard light source D65, the a ^* value of the total reflected light in the CIE-LAB color system is −4.0<a ^* <4.0 and the b ^* value is −15.0<b ^* <0.0.

(2) In the optical laminate of (1) above, when light having a wavelength of 380 nm to 780 nm by standard light source D65 is incident on the surface at an incident angle of 5° to 50°, the a ^* value in the CIE-LAB color system of the specular reflected light may be −4.0<a ^* <4.0 and the b ^* value may be −15.0<b ^* <6.0.

(3) In the optical laminate of (1) or (2) above, when light of a wavelength of 380 nm to 780 nm by standard light source D65 is incident on the surface at an incident angle of 30° to 40°, the a ^* value of the specular reflected light in the CIE-LAB color system may be −4.0<a ^* <4.0 and the b ^* value may be −4.0<b ^* <4.0.

(4) In the optical laminates of (1) to (3) above, the film substrate is made of an organic material, and may further include a hard coat layer in contact with the film substrate and an adhesive layer in contact with the hard coat layer and the optical functional layer between the film substrate and the optical functional layer, and may further include an antifouling layer disposed on the opposite side of the second low refractive index layer from the second high refractive index layer.

(5) In the optical laminates according to any one of (1) to (4) above, the antifouling layer may have an optical thickness of 3 nm or more and 13 nm or less.
(6) In the optical laminate of any one of (1) to (5) above, the transmittance of light at a wavelength of 940 nm may be 90% or more.
(7) In the optical laminate of any one of (1) to (6) above, the physical thickness of the optical functional layer may be 290 nm or less, and the difference in refractive index between the high refractive index layer and the low refractive index layer included in the optical functional layer may be 0.70 or more and 1.10 or less.
(8) In the optical laminate of (1) to (7) above, the first high refractive index layer and the second high refractive index layer may contain Nb ₂ O ₅ as a main component, and the first low refractive index layer and the second low refractive index layer may contain SiO ₂ as a main component.
(9) In the optical laminate of (1) to (8) above, the optical function layer may be composed of four layers: the first high refractive index layer, the first low refractive index layer, the second high refractive index layer, and the second low refractive index layer.

(10) An article comprising any one of the optical laminates described above in (1) to (9).

(11) In the article of (10) above, the anti-reflection film may be provided on the surface of an image display device.

The present invention provides an optical laminate that has high infrared transmittance, good total reflection hue, and is applicable to curved display devices. Furthermore, according to (2) and (3) above, it is possible to provide an optical laminate that is less susceptible to visible color unevenness even when the viewing angle changes.

1 is a cross-sectional view showing an example of a configuration of an optical laminate according to one embodiment of the present invention. 1 is a schematic diagram showing an example of the configuration of a manufacturing apparatus that can be used in a method for manufacturing an optical laminate according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the configuration of an optical laminate according to a modified example of FIG. 1 . 4 is a schematic diagram showing a state in which the optical laminate of FIG. 3 is bonded to a bonding surface of an object.

Hereinafter, this embodiment will be described in detail with reference to the drawings as appropriate.
The drawings used in the following description may show characteristic portions enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them and can be implemented with appropriate changes within the scope of the effects.

[Optical laminate]
FIG. 1 is a cross-sectional view showing an example of the configuration of an optical laminate according to one embodiment of the present invention. The optical laminate 100 shown in FIG. 1 includes a film substrate 10, a hard coat layer 20, an adhesive layer 30, and an optical functional layer 40, in this order. This optical laminate 100 functions as an anti-reflection film. The optical laminate 100 further includes, for example, an antifouling layer 50 on the optical functional layer 40. The optical functional layer 40 includes, in order from the film substrate 10 side, a first high refractive index layer 41a having an optical thickness of 25 nm to 43 nm, a first low refractive index layer 42a having an optical thickness of 54 nm to 69 nm, a second high refractive index layer 41b having an optical thickness of 278 nm to 308 nm, and a second low refractive index layer 42b having an optical thickness of 131 nm to 141 nm. In this embodiment, the "optical thickness" is the product of the physical thickness and the refractive index. The "refractive index" is measured in accordance with JIS K7105 at a temperature of 25°C and a wavelength of 550 nm. The "physical thickness" can be determined by, for example, measuring the thickness at 20 points on a cross-sectional image taken using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), and averaging the values at the 20 points.

The optical laminate 100 has a light transmittance at a wavelength of 940 nm (total transmittance of light at a wavelength of 940 nm) of 86% or more. The optical laminate 100 has a luminous reflectance Y (SCI) of 1.0% or less. When light having a wavelength of 380 nm to 780 nm (380 nm or more and 780 nm or less) is incident on the optical laminate 100 using standard illuminant D65, the a ^* value of total reflected light in the CIE-LAB color system is -4.0<a ^* <4.0 and the b ^* value is -15.0<b ^* <0.0.

<Film substrate>
The film substrate 10 is, for example, a plastic film. Examples of materials constituting the plastic film include polyester-based resins, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyarylate-based resins, and polyphenylene sulfide-based resins. As described above, the film substrate 10 may be made of an organic material, or may be an inorganic substrate such as a glass film. The film substrate 10 is formed from a transparent material capable of transmitting visible light and infrared light. A triacetyl cellulose (TAC) substrate is preferred as the film substrate 10. When a TAC substrate is used as the film substrate 10 and a hard coat layer 20 is formed on one surface thereof, a permeation layer is formed in which some of the components constituting the hard coat layer 20 have permeated into the TAC substrate. As a result, the adhesion between the film substrate 10 and the hard coat layer 20 is improved, and the occurrence of interference fringes due to the difference in refractive index between the layers is suppressed.

In addition, in this embodiment, "(meth)acrylic" means methacrylic and acrylic.

The film substrate 10 may contain a reinforcing material as long as the optical properties are not significantly impaired. Examples of reinforcing materials include cellulose nanofiber and nanosilica. In particular, polyester-based resins, acetate-based resins, polycarbonate-based resins, and polyolefin-based resins are preferably used as reinforcing materials.

The film substrate 10 may be a film that has been given either or both optical and physical functions. Examples of films that have either or both optical and physical functions include polarizing plates, phase difference compensation films, heat-blocking films, transparent conductive films, brightness-enhancing films, and barrier-enhancing films.

The thickness of the film substrate 10 is 1000 μm or less, for example, 25 μm or more, preferably 40 μm or more and 500 μm or less, and preferably 200 μm or less or 150 μm or less. When the thickness of the film substrate 10 is 25 μm or more, wrinkles are less likely to occur even when stress is applied to the optical laminate 100. Furthermore, when the thickness of the film substrate 10 is 25 μm or more, wrinkles are less likely to occur even when the hard coat layer 20 is continuously formed on the film substrate 10, reducing manufacturing concerns. When the thickness of the film substrate 10 is 40 μm or more, wrinkles are even less likely to occur. Furthermore, a film substrate 10 having the above thickness can be attached to a curved attachment surface, as will be described in detail below with reference to Figure 4, and is applicable to display devices with curved surfaces.

When manufacturing is performed using a roll, it is preferable that the thickness of the film substrate 10 is thin. This is because the optical laminate 100 during manufacturing and the optical laminate 100 after manufacturing can be easily wound into a roll, allowing the optical laminate 100 to be manufactured efficiently. Furthermore, when the thickness of the film substrate 10 is within the above range, it can be easily applied to curved surfaces.

The surface of the film substrate 10 may be previously subjected to an etching treatment such as sputtering, corona discharge, ultraviolet irradiation, electron beam irradiation, chemical conversion, or oxidation, and/or a primer treatment. By previously performing these treatments, adhesion to the hard coat layer 20 formed on the film substrate 10 can be improved. Furthermore, before forming the hard coat layer 20 on the film substrate 10, it is also preferable to remove dust and clean the surface of the film substrate 10, as necessary, by subjecting the surface of the film substrate 10 to solvent washing, ultrasonic cleaning, or the like. By configuring the film substrate 10 as described above, the optical laminate 100 including the film substrate 10 can also be laminated to a curved surface.

<Hard Coat Layer>
For example, a hard coat layer 20 and an adhesive layer 30 are formed between the film substrate 10 and the optical functional layer 40. The hard coat layer 20 is a layer that contacts the film substrate 10. The hard coat layer 20 is not particularly limited, and a known hard coat layer can be used. The hard coat layer 20 may contain, for example, a binder resin and a filler. In addition, the hard coat layer 20 may contain a leveling agent.

The binder resin is preferably transparent, and is, for example, an ionizing radiation curable resin that is cured by ultraviolet light or electron beams, a thermoplastic resin, or a thermosetting resin.

Examples of ionizing radiation curable resins that serve as binder resins include ethyl (meth)acrylate, ethylhexyl (meth)acrylate, styrene, methylstyrene, and N-vinylpyrrolidone. The ionizing radiation curable resin may also be a compound having two or more unsaturated bonds. Examples of ionizing radiation curable resins having two or more unsaturated bonds include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and dipentaerythritol tetra(meth)acrylate. and polyfunctional compounds such as tetrapentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate. Among these, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), and pentaerythritol tetraacrylate (PETTA) are preferably used as the binder resin. Note that "(meth)acrylate" refers to methacrylate and acrylate. Furthermore, the ionizing radiation curable resin may be one obtained by modifying the above-mentioned compounds with PO (propylene oxide), EO (ethylene oxide), CL (caprolactone), or the like. The ionizing radiation curable resin is preferably an acrylic ultraviolet curable resin composition.

Examples of thermoplastic resins that can be used as binder resins include styrene-based resins, (meth)acrylic resins, vinyl acetate-based resins, vinyl ether-based resins, halogen-containing resins, alicyclic olefin-based resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, cellulose derivatives, silicone-based resins, and rubber or elastomers. The above-mentioned thermoplastic resins are amorphous and soluble in organic solvents (particularly common solvents that can dissolve multiple polymers and curable compounds). In particular, from the standpoints of transparency and weather resistance, binder resins such as styrene-based resins, (meth)acrylic resins, alicyclic olefin-based resins, polyester-based resins, and cellulose derivatives (such as cellulose esters) are preferred.

Thermosetting resins used as binder resins may be, for example, phenolic resins, urea resins, diallyl phthalate resins, melamine resins, guanamine resins, unsaturated polyester resins, polyurethane resins, epoxy resins, aminoalkyd resins, melamine-urea co-condensation resins, silicon resins, polysiloxane resins (including cage-shaped, ladder-shaped, and other so-called silsesquioxanes), etc.

The hard coat layer 20 may contain a translucent organic resin and an inorganic material, or may contain an organic-inorganic hybrid material, to provide anti-glare properties. These particles are intended to provide the hard coat layer 20 with a light-diffusing function and an anti-glare function through the formation of surface irregularities. The translucent resin microparticles can be formed from resins including styrene-acrylic monomer copolymer resin (styrene-acrylic copolymer resin), (meth)acrylic resin, polystyrene resin, polyethylene resin, polycarbonate resin, vinyl chloride resin, etc.

The filler may be made of an organic substance, an inorganic substance, or a mixture of organic and inorganic substances. Various fillers can be selected for the hard coat layer 20 depending on the intended use of the optical laminate 100, from the standpoints of anti-glare properties, adhesion to the optical functional layer 40 (described below), anti-blocking properties, etc. Specifically, known fillers such as silica (oxide of silicon) particles, alumina (aluminum oxide) particles, and organic fine particles can be used.

When the filler contained in the hard coat layer is one or both of silica particles and alumina particles, the average particle diameter of the filler is, for example, 800 nm or less, preferably 100 nm or less, and more preferably 10 nm or more and 70 nm or less. When the filler contained in the hard coat layer is organic fine particles, the average particle diameter of the organic fine particles is, for example, 10 μm or less, preferably 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less.

The thickness of the hard coat layer 20 is, for example, 0.5 μm or more and 100 μm or less, and preferably 1 μm or more and 20 μm or less. If the thickness of the hard coat layer 20 is 1 μm or more, scratches are less likely to occur during manufacturing. Furthermore, if the thickness of the hard coat layer 20 is 20 μm or less, the optical laminate 100 can be made thinner and lighter. Furthermore, if the thickness of the hard coat layer 20 is 20 μm or less, microcracks in the hard coat layer 20 that occur when the optical laminate 100 is bent during manufacturing are less likely to occur, improving productivity.

<Adhesion layer>
The adhesion layer 30 is formed to improve adhesion between the hard coat layer 20, which is an organic film, and the optical function layer 50A, which is an inorganic film. The adhesion layer 30 is preferably made of an oxygen-deficient metal oxide or metal. An oxygen-deficient metal oxide refers to a metal oxide in which the number of oxygen atoms is deficient compared to the stoichiometric composition. Examples of oxygen-deficient metal oxides include SiOx, AlOx, TiOx, ZrOx, CeOx, MgOx, ZnOx, TaOx, SbOx, SnOx, and MnOx. Examples of metals include Si, Al, Ti, Zr, Ce, Mg, Zn, Ta, Sb, Sn, Mn, and In. The adhesion layer 30 may be, for example, SiOx, where x is greater than 0 and less than 2.0. The adhesion layer may also be formed from a mixture of multiple metals or metal oxides.

From the viewpoint of maintaining adhesion between the hard coat layer 20 and the optical function layer 40 and obtaining good optical properties, the thickness of the adhesion layer 30 is preferably more than 0 nm and less than 20 nm, and particularly preferably 1 nm or more and 10 nm or less.

<Optical functional layer>
The optical function layer 40 is formed on the film substrate 10. In this embodiment, "formed on" includes a configuration in which the layer is in direct contact with the film substrate 10 and a configuration in which the layer is formed via another layer. The optical function layer 40 is a layer that exhibits an optical function. The optical function is a function that controls the properties of light, such as reflection, transmission, and refraction, and examples thereof include an anti-reflection function, a selective reflection function, an anti-glare function, and a lens function.

The optical functional layer 40 is, for example, a laminate film in which high refractive index layers and low refractive index layers are alternately stacked in this order from the film substrate 10 side. The high refractive index layers have a higher refractive index than the low refractive index layers. The reflection wavelength and reflectance of the optical laminate 100 can be adjusted, for example, by the optical thickness of the high refractive index layers and low refractive index layers, the total number of high refractive index layers and low refractive index layers, and the refractive index difference between the high refractive index layers and low refractive index layers. In this embodiment, the optical functional layer 40 is composed of high refractive index layers and low refractive index layers. Of the optical functional layers, the layer formed closest to the film substrate is, for example, the high refractive index layer. The number of high refractive index layers and the number of low refractive index layers are typically the same.

From the viewpoint of flexibility of the optical laminate, the total number of high refractive index layers and low refractive index layers in the optical laminate is preferably 4 or 6. From the viewpoint of flexibility, the thickness of the optical function layer 40 is preferably a physical thickness of 300 nm or less, more preferably a physical thickness of 290 nm or less, and even more preferably a physical thickness of 270 nm or less.

In the optical laminate 100, the optical function layer 40 is made up of a first high refractive index layer 41a, a first low refractive index layer 42a, a second high refractive index layer 41b, and a second low refractive index layer 42b.
The optical thickness of the first high refractive index layer 41a is 25 nm or more and 43 nm or less, preferably 27 nm or more and 35 nm or less, and more preferably 27 nm or more and 32 nm or less.
The optical thickness of the first low refractive index layer 42a is 54 nm or more and 69 nm or less, and preferably 57 nm or more and 67 nm or less. The first low refractive index layer 42a is provided in contact with the first high refractive index layer 41a.
The second high-refractive index layer 41b has an optical thickness of 276 nm to 308 nm, preferably 278 nm to 293 nm, and more preferably 278 nm to 283 nm. The second high-refractive index layer 41b is provided in contact with the first low-refractive index layer 42a.
The optical thickness of the second low refractive index layer 42b is 128 nm or more and 141 nm or less, and preferably 129 nm or more and 136 nm or less. The second low refractive index layer 42b is provided in contact with the second high refractive index layer 41b.

The refractive index of the high-refractive-index layer is preferably 2.00 or more and 2.60 or less, more preferably 2.10 or more and 2.45 or less. Examples of the main component of such a high-refractive-index layer include niobium pentoxide (Nb ₂ O ₅ , refractive index 2.33), titanium oxide (TiO ₂ , refractive index 2.33 to 2.55), tungsten oxide (WO ₃ , refractive index 2.2), cerium oxide (CeO ₂ , refractive index 2.2), tantalum pentoxide (Ta ₂ O ₅ , refractive index 2.16), zinc oxide (ZnO, refractive index 2.1), indium oxide (InO ₂ ), tin oxide (SnO ₂ ), aluminum oxide (AlO ₂ ), and composite oxides thereof. Examples of composite oxides include ITO (indium tin oxide) and IZO (indium oxide-zinc oxide). The main component of the first high-refractive-index layer 41a and the second high-refractive-index layer 41b is preferably niobium pentoxide. In this specification, the term "main component" refers to the component with the highest content, and means, for example, a component with a content of 80% by mass or more, preferably 90% by mass or more, and more preferably 99% by mass or more.

The refractive index of the low-refractive-index layer is preferably 1.20 or more and 1.60 or less, more preferably 1.30 or more and 1.50 or less. Examples of the main component of such a low-refractive-index layer include silicon dioxide (SiO ₂ , refractive index 1.46), calcium fluoride (CaF ₂ , refractive index 1.42), and magnesium fluoride (MgF ₂ , refractive index 1.38). The main component of the first low-refractive-index layer 42 a and the second low-refractive-index layer 42 b is preferably silicon dioxide. Furthermore, when the refractive index of the low-refractive-index layer falls within the above range, other elements may be contained. Specifically, adding approximately 10% zirconium in elemental ratio can improve chemical resistance. As another example, N ₂ gas may be introduced during film formation to improve hardness. Furthermore, a metal element such as Al may be added to improve the optical properties.

The difference in refractive index between the high refractive index layer and the low refractive index layer is preferably 0.40 or more and 1.40 or less, more preferably 0.70 or more and 1.10 or less, and even more preferably 0.80 or more and 0.90 or less. Examples of such combinations of high refractive index layer and low refractive index layer include _Nb2O5 and _SiO2 , _TiO2 and _SiO2 , _etc. In the optical laminate 100, it is preferable that the difference in refractive index between adjacent high refractive index layer and low refractive index layer is within the above range, and that the differences in refractive index between the high refractive index layer and the low refractive index layer included in the optical function layer 40 are both within the above numerical range.

In the optical function layer 40, when the first high-refractive index layer _41a is primarily composed of _Nb2O5 , the physical thickness is preferably 11 nm to 18 nm, more preferably 12 nm to 15 nm, and even more preferably 12 nm to 14 nm. When the first low-refractive index layer 42a is primarily composed of _SiO2 , the physical thickness is preferably 37 nm to 47 nm, and more preferably 39 _nm to 46 nm. When the second high-refractive index layer 41b is primarily composed of _Nb2O5 , the physical thickness is preferably 118 nm to 132 nm, more preferably 119 nm to 126 nm, and even more preferably 119 nm to 122 nm. When the second low-refractive index layer 42b is primarily composed of _SiO2 , the physical thickness is preferably 88 nm to 97 nm, and even more preferably 87 nm to 93 nm.

<Anti-fouling layer>
The antifouling layer 50 is formed on the outermost surface of the optical function layer 40 and prevents contamination of the optical function layer 40. Furthermore, when the antifouling layer 50 is applied to a touch panel or the like, it suppresses wear of the optical function layer 40 due to its abrasion resistance.
The antifouling layer 50 of this embodiment is made of, for example, a vapor-deposited film formed by vapor-depositing an antifouling material. In this embodiment, the antifouling layer 50 is formed by vacuum-depositing a fluorine-based organic compound as the antifouling material on the upper layer when provided on the optical function layer 40, i.e., on one surface of the second low refractive index layer 42b in the optical laminate 100 shown in FIG. 1. In this embodiment, since the antifouling material contains a fluorine-based organic compound, the optical laminate 100 has even better abrasion resistance and alkali resistance.

The fluorine-based organic compound that constitutes the anti-fouling layer 50 is preferably a compound consisting of a fluorine-modified organic group and a reactive silyl group (e.g., alkoxysilane). Commercially available products include Optool DSX (manufactured by Daikin Corporation) and the KY-100 series (manufactured by Shin-Etsu Chemical Co., Ltd.).

When a compound consisting of a fluorine-modified organic group and a reactive silyl group (e.g., alkoxysilane) is used as the fluorine-based organic compound constituting the antifouling layer 50 and a layer consisting of SiO2 is used as the second low refractive index layer 42b located on the outermost surface of the optical function layer 40 in contact with the antifouling layer ₅₀ , a siloxane bond is formed between the silanol group, which is the skeleton of the fluorine-based organic compound, and the _SiO2 . This results in good adhesion between the optical function layer 40 and the antifouling layer 50, which is preferable.

The optical thickness of the anti-fouling layer 50 is, for example, in the range of 1 nm to 20 nm, and preferably in the range of 3 nm to 13 nm. If the optical thickness of the anti-fouling layer 50 is 1 nm or more, sufficient abrasion resistance can be ensured when the optical laminate 100 is used for touch panels, etc. Furthermore, if the optical thickness of the anti-fouling layer 50 is 3 nm or more, the liquid resistance, etc. of the optical laminate 100 is improved. Furthermore, if the optical thickness of the anti-fouling layer 50 is 13 nm or less, the time required for vapor deposition can be shortened, allowing for efficient production.

By including the optical functional layer 40 as described above, the optical laminate 100 according to this embodiment can achieve high infrared transmittance. Specifically, the optical laminate 100 has a total transmittance of 86% or more, preferably 88% or more, more preferably 90% or more, and even more preferably 91% or more at a wavelength of 940 nm. The optical laminate 100 has a specular transmittance of 82% or more, preferably 84% or more, at an incident angle of 5° to 40°. The specular transmittance of 83% or more, preferably 85% or more, at an incident angle of 5° to 30° at a wavelength of 940 nm. The optical laminate 100 has a total reflectance of 10% or less, more preferably 8% or less, at a wavelength of 940 nm.

The optical laminate 100 according to this embodiment has the above-described configuration, and therefore exhibits excellent flexibility, making it suitable for foldable displays and rollable displays. In particular, by using Nb ₂ O ₅ as the main component of the high refractive index layer and SiO ₂ as the main component of the low refractive index layer, and by ensuring that the total physical thickness of each layer is 300 nm or less, excellent flexibility can be obtained, and by ensuring that the total physical thickness of each layer is 290 nm or less, particularly excellent flexibility can be obtained. Specifically, the optical laminate 100 according to this embodiment preferably has a mandrel diameter of 10 mm or less at which no cracks occur in a bending test using a cylindrical mandrel method (in accordance with JIS K5600-5-1), from the perspective of compatibility with foldable displays and rollable displays. That is, in a bending test using a cylindrical mandrel method, it is preferable that the mandrel diameter at which cracks first occur is 10 mm or less. In this embodiment, an optical laminate that exhibits such test results in a bending test using a cylindrical mandrel method may be referred to as a flexible optical laminate.

The optical laminate 100 according to this embodiment has a luminous reflectance Y of 1.0% or less, preferably 0.8% or less, and more preferably 0.6% or less. Furthermore, the optical laminate 100 according to this embodiment has Nb ₂ O ₅ as the main component of the high refractive index layer and SiO ₂ as the main component of the low refractive index layer, thereby achieving high production stability, higher infrared transmittance, and a neutral color tone for the reflected light. The luminous reflectance is the reflectance according to the SCI method (including specular reflection).

In the optical laminate 100 according to this embodiment, the a ^* value in the CIE-LAB color system of the total reflected light when light of a wavelength of 380 nm to 780 nm by standard illuminant D65 is incident is -4.0 < a ^* < 4.0, preferably -3.0 < a ^* < 3.5, more preferably -2.5 < a ^* < 3.0, and even more preferably -2.2 < a ^* ≦ 2.8, and the b ^* value is -15.0 < b ^* < 0.0, preferably -13.0 < b ^* < 0.0, and may be -12.0 < b ^* < -5.0 or -11.5 < b ^* < -7.0. In the optical laminate 100 according to this embodiment, each layer constituting the optical functional layer 40 is selected so as to satisfy the optical thickness as described above, and thereby the optical laminate 100 exhibits such a hue, and the infrared transmittance and luminous reflectance satisfy specific configurations.

Furthermore, by having the above-described configuration, the optical laminate 100 according to this embodiment can be said to have a good total reflection hue. Furthermore, it is preferable that the optical laminate according to this embodiment has color unevenness that is less visible even when the viewing angle changes. The optical laminate 100 according to this embodiment has a CIE-LAB color system a ^* value of specularly reflected light when light having a wavelength of 380 nm to 780 nm from a standard illuminant D65 is incident on the surface at an angle of incidence within a range of 5° to 50°, and the a* value is preferably -4.0 < a ^* < 4.0, more preferably -3.0 < a ^* < 3.8, and even more preferably -2.5 < a ^* ≦ 3.7, and the b ^* value is preferably -15.0 < b ^* < 6.0, more preferably -13.0 < b ^* < 5.9, and even more preferably -11.0 < b ^* < 5.9.

In particular, the optical laminate 100 according to this embodiment has a CIE-LAB color system a* value of specularly reflected light when light having a wavelength of 380 nm to 780 nm by standard light source D65 is incident on the surface at an angle of incidence in the range of ³⁰ ° to 40°, preferably -4.0 < a ^* < 4.0, more preferably -2.5 < a ^* < 3.6, even more preferably -1.0 < a ^* ≦ 3.3, and particularly preferably -0.5 < a ^* ≦ 3.2, and a ^{b *} value of specularly reflected light when light is incident on the surface ^{at an} angle of incidence of 30° ^to 40°. The closer to neutral the reflected light is when light is incident on the surface at an angle of incidence of 30° to 40°, for example, when a display device provided with the optical laminate 100 is used in the center console of an automobile, the less coloring can be perceived when viewed from the driver's seat.

[Method of manufacturing optical laminate]
Next, a method for manufacturing the optical laminate 100 according to the embodiment will be described using an example of a method for manufacturing the optical laminate 100 according to the embodiment. In this embodiment, as an example of a method for manufacturing an optical laminate, a case in which the optical laminate 100 is manufactured using a film substrate 10 wound in a roll shape will be described. First, the film substrate 10 wound in a roll shape is unwound.

(Hard Coat Layer Forming Step)
Then, a material containing a material for the hard coat layer 20 is applied to the film substrate 10 by a known method, and cured by a known method corresponding to the material for the hard coat layer 20. This forms the hard coat layer 20 on the film substrate 10 (hard coat layer formation process). The material used may contain one or more additives, such as a polymerization initiator and a leveling agent, as necessary. Examples of the polymerization initiator include a photopolymerization initiator. For example, a UV-curable resin composition containing metal oxide particles, a urethane (meth)acrylate oligomer, a trifunctional or higher functional (meth)acrylate monomer, a bifunctional (meth)acrylate monomer, and a photopolymerization initiator is uniformly mixed and prepared using a stirrer such as a disper according to a conventional method.

Next, the UV-curable resin composition is applied to the substrate. There are no particular limitations on the application method, and any known method can be used. Known application methods include, for example, microgravure coating, wire bar coating, direct gravure coating, die coating, dipping, spray coating, reverse roll coating, curtain coating, comma coating, knife coating, and spin coating.

Next, the UV-curable resin composition on the substrate is dried and photo-cured to form a hard coat layer 20. There are no particular limitations on the drying conditions, and natural drying or artificial drying, in which the drying humidity and drying time are adjusted, may be used. However, if wind is blown onto the paint surface during drying, it is preferable to avoid wind ripples on the coating surface. This is because wind ripples will deteriorate the appearance of the coating and cause uneven thickness on the surface. In addition to UV light, energy rays such as gamma rays, alpha rays, and electron beams can also be used as light to cure the UV-curable resin composition.

Here, it is preferable to etch the surface of the hard coat layer 20 to protrude the metal oxide particles. The method for protruding the metal oxide particles is not particularly limited as long as it is possible to selectively etch the resin of the hard coat layer 20, and examples that can be used include glow discharge treatment, plasma treatment, ion etching, and alkali treatment. Among these, it is preferable to use glow discharge treatment, which allows for large-area treatment. Thereafter, the film substrate 10 with the hard coat layer 20 formed on its surface is wound into a roll by a known method.

Next, an adhesion layer forming process is performed to form an adhesion layer 30 on the hard coat layer 20, and an optical function layer forming process is performed to form an optical function layer 40. After that, an antifouling layer forming process is performed to form an antifouling layer 50 on the optical function layer 40. In this embodiment, it is preferable to perform a first surface treatment process to treat the surface of the hard coat layer 20 before the optical function layer forming process, and then perform the adhesion layer forming process and the optical function layer forming process. Also, in this embodiment, it is preferable to perform a second surface treatment process to treat the surface of the optical function layer 40 after the optical function layer forming process, and then perform the antifouling layer forming process.

(Adhesion layer forming step)
An adhesion layer made of an oxygen-deficient metal oxide is formed on the surface of the hard coat layer 20. Sputtering using a target is preferably used as a method for forming the adhesion layer. For example, when forming a SiOx film, it is preferable to use a silicon target and reactive sputtering in a mixed gas atmosphere of oxygen gas and argon gas. Furthermore, the anti-reflection layer formed on the adhesion layer can also be formed by sputtering, thereby improving productivity.

(Optical functional layer formation process)
As will be described in detail later, the optical functional layer is formed by alternately forming high refractive index layers made of a dielectric material and low refractive index layers made of a dielectric material having a refractive index lower than that of the high refractive index layers by sputtering. The optical functional layer can be formed using, for example, a thin film forming apparatus described in JP 2014-034701 A.

(Anti-fouling layer forming process)
The antifouling layer can be formed by a method such as physical vapor deposition, chemical vapor deposition, wet coating, etc., depending on the material to be formed. For example, the antifouling layer can be formed by vacuum-depositing a fluorine-based compound as an antifouling material.

In the method for manufacturing the optical laminate 100 of this embodiment, it is preferable that the first surface treatment process, adhesion layer formation process, optical functional layer formation process, second surface treatment process, and antifouling layer formation process be carried out consecutively while the optical laminate being manufactured is maintained under reduced pressure.

Specific examples of manufacturing equipment that can be used in the method for manufacturing an optical laminate of this embodiment include manufacturing equipment 200 shown in Figure 2.

The manufacturing apparatus 200 shown in Figure 2 is equipped with a roll unwinding device 4, preprocessing device 2A, thin film forming device 1, preprocessing device 2B, vapor deposition device 3, and roll winding device 5. As shown in Figure 2, these devices 4, 2A, 1, 2B, 3, and 5 are connected in this order. The manufacturing apparatus 200 shown in Figure 2 is a roll-to-roll type manufacturing apparatus that continuously forms multiple layers on a substrate by unwinding the substrate from a roll, passing it through the connected devices in succession (preprocessing device 2A, thin film forming device 1, preprocessing device 2B, and vapor deposition device 3 in Figure 2), and then winding it up.

When manufacturing the optical laminate 100 using a roll-to-roll manufacturing device, the conveying speed (line speed) of the optical laminate 100 during manufacturing can be set as appropriate. The conveying speed is preferably, for example, 0.5 to 20 m/min, and more preferably 0.5 to 10 m/min.

<Roll unwinding device>
The roll unwinding device 4 shown in Fig. 2 has a chamber 34 the inside of which is kept at a predetermined reduced pressure, one or more vacuum pumps 21 (one in Fig. 2) that exhaust gas from the chamber 34 to create a reduced pressure atmosphere, and an unwinding roll 23 and a guide roll 22 installed in the chamber 34. As shown in Fig. 2, the chamber 34 is connected to the chamber 31 of the thin film forming apparatus 1 via the pretreatment device 2A.
The film substrate 10 having the hard coat layer 20 formed on its surface is wound around the unwinding roll 23. The unwinding roll 23 supplies the film substrate 10 having the hard coat layer 20 formed on its surface to the pretreatment device 2A at a predetermined transport speed.

<Pretreatment device 2A>
The pretreatment device 2A shown in Fig. 2 has a chamber 32, the interior of which is kept at a predetermined reduced pressure, a can roll 26, a plurality of guide rolls 22 (two in Fig. 2), and a plasma discharge device 44. As shown in Fig. 2, the can roll 26, the guide rolls 22, and the plasma discharge device 44 are installed in the chamber 32. As shown in Fig. 2, the chamber 32 is connected to the chamber 31 of the thin film forming device 1.

The can roll 26 and guide roll 22 transport the transparent substrate 11 on which the hard coat layer 20 has been formed, sent from the roll unwinding device 4, at a predetermined transport speed, and send the transparent substrate 11 with the surface of the hard coat layer 20 treated to the thin film forming device 1.

As shown in Figure 2, the plasma discharge device 44 is positioned opposite the outer circumferential surface of the can roll 26 at a predetermined distance. The plasma discharge device 44 ionizes the gas by glow discharge. The gas is preferably inexpensive, inert, and does not affect the optical properties; for example, argon gas, oxygen gas, nitrogen gas, helium gas, etc. can be used. In this embodiment, argon gas or oxygen gas is preferably used as the gas.

<Thin film forming device>
The thin film forming apparatus 1 shown in Fig. 2 includes a chamber 31 having a predetermined reduced pressure atmosphere inside, one or more vacuum pumps 21 (two in Fig. 2) that exhaust gas from the chamber 31 to create a reduced pressure atmosphere, a film forming roll 25, a plurality of guide rolls 22 (two in Fig. 2), a plurality of film forming sections (sputtering chambers) 45 (four in the example shown in Fig. 2), and a plurality of optical monitors 81 to 84 (four in the example shown in Fig. 2). As shown in Fig. 2, the film forming roll 25, the guide roll 22, and the film forming section 45 are installed in the chamber 31. As shown in Fig. 2, the chamber 31 is connected to a chamber 32 of the pretreatment device 2B.

The film-forming roll 25 and guide roll 22 transport the film substrate 10 with the surface-treated hard coat layer 20 formed thereon, sent from the pre-treatment device 2A, at a predetermined transport speed, and supply the film substrate 10 with the adhesion layer 30 and optical function layer 40 formed on the hard coat layer 20 to the pre-treatment device 2B.

In the thin film forming apparatus 1 shown in Figure 2, an adhesion layer 30 is laminated by sputtering on the hard coat layer 20 of the film substrate 10 running on the film forming roll 25, and high refractive index layers (first high refractive index layer 41a, second high refractive index layer 41b, etc.) and low refractive index layers (first low refractive index layer 42a, second low refractive index layer 42b, etc.) are alternately laminated on top of that to form the optical function layer 40.

As shown in FIG. 2, multiple film forming units 45 are arranged facing the outer circumferential surface of the film forming roll 25 at a predetermined distance, surrounding the film forming roll 25. The number of film forming units 45 is determined based on the total number of laminated layers of the adhesive layer 30 and the high and low refractive index layers that make up the optical functional layer 40. If the total number of laminated layers of the high and low refractive index layers that make up the adhesive layer 30 and the optical functional layer 40 is large and it is difficult to ensure sufficient distance between adjacent film forming units 45, multiple film forming rolls 25 may be provided in the chamber 31, and a film forming unit 45 may be arranged around each film forming roll 25. When multiple film forming rolls 25 are provided, additional guide rolls 22 may be installed as necessary. Multiple chambers 31 each equipped with a film forming roll 25 and a film forming unit 45 may be connected. Furthermore, the diameter of the film forming roll 25 may be appropriately changed to make it easier to ensure sufficient distance between adjacent film forming units 45.

Each film forming unit 45 has a predetermined target (not shown) placed on an electrode (not shown). A voltage is applied to the target using a known structure. In this embodiment, a gas supply unit (not shown) that supplies a predetermined reactive gas and carrier gas to the target at a predetermined flow rate, and a known magnetic field generating source (not shown) that forms a magnetic field on the surface of the target are provided near the target.

The target material and the type and flow rate of the reactive gas are appropriately determined depending on the composition of the adhesion layer 30, first high refractive index layer 41a, second high refractive index layer 41b, first low refractive index layer 42a, and second low refractive index layer 42b formed on the film substrate 10 by passing between the film-forming unit 45 and the film _- forming roll 25. For example, when forming a layer made of _SiO2 , Si is used as the target and _O2 is used as the reactive gas. Furthermore, when forming a layer made of _Nb2O5 , Nb is used as the target and _O2 is used as the reactive gas. The first low refractive index layer 42a and the second low refractive index layer 42b are preferably formed at a vacuum level of less than 0.5 Pa, and the first high refractive index layer 41a and the second high refractive index layer 41b are preferably formed at a vacuum level of less than 1.0 Pa. Forming these layers at the above vacuum levels results in a denser optical function layer 40, a lower water vapor permeability, and improved durability.

In this embodiment, it is preferable to use magnetron sputtering as the sputtering method from the viewpoint of increasing the film formation speed.
The sputtering method is not limited to magnetron sputtering, and may be a two-pole sputtering method that uses plasma generated by DC glow discharge or high frequency, or a three-pole sputtering method that adds a hot cathode.

In the optical function layer forming section, the target of the film forming section 45 for forming the optical function layer 40 is preferably positioned perpendicular to the film substrate 10 on which the hard coat layer 20 and adhesive layer 30 are formed. This configuration allows a uniform optical function layer 40 to be formed on the adhesive layer 30. If the film substrate 10 on which the hard coat layer 20 and adhesive layer 30 are formed is positioned curved relative to a target with a flat surface, the distance from the target will vary depending on the position on the film on which the thin film is to be formed, which could result in reduced in-plane uniformity of the formed optical function layer. If the in-plane uniformity of the optical function layer 40 is reduced, it is thought that the optical properties of the optical laminate, such as infrared transmittance and hue as the viewing angle changes, will vary in-plane. For this reason, it is preferable to form the optical function layer 40 by sputtering perpendicular to the film, as shown in Figure 2.

The thin film forming apparatus 1 is equipped with, for example, an optical monitor 80, which is a measurement unit that measures optical properties after film formation. In a thin film forming apparatus equipped with multiple chambers, the optical monitor 80 is preferably installed in each chamber. The optical monitor 80 measures the optical properties in the width direction of the adhesion layer 30 and optical function layer 40 formed on the hard coat layer 20 using an optical head that can scan in the width direction. This optical monitor 80 can measure, for example, the peak wavelength of reflectance as an optical property and convert it to optical thickness to obtain the optical thickness distribution in the width direction. This makes it possible to confirm the quality of the layers formed by each film forming unit 45.

A thin film forming apparatus configured as described above can form a multi-layer optical function layer 40 by forming a thin film on the film unwound from the guide roll 22. Here, the optical monitor 80 measures the optical characteristics of the thin film formed on the film in the width direction, and by adjusting the sputtering conditions in real time, such as the flow rate of reactive gas from the gas supply unit in each film forming unit 45 arranged in the width direction, based on the optical characteristics, it is possible to form a thin film of uniform thickness in the longitudinal and width directions. Note that the above example is not limiting, and additional film forming units or cathodes may be added, or a planar or rotary cathode system may be used to increase productivity.

<Pretreatment device>
The pretreatment device 2B shown in Fig. 2 has a chamber 32, the interior of which is kept at a predetermined reduced pressure, a can roll 26, a plurality of guide rolls 22 (two in Fig. 2), and a plasma discharge device 44. As shown in Fig. 2, the can roll 26, the guide rolls 22, and the plasma discharge device 44 are installed in the chamber 32. As shown in Fig. 2, the chamber 32 is connected to a chamber 33 of the vapor deposition device 3.

The can roll 26 and the guide roll 22 transport the film substrate 10, on which each layer up to the optical functional layer 40 has been formed, sent from the thin film forming device 1, at a predetermined transport speed, and send the film substrate 10, on which the surface of the optical functional layer 40 has been treated, to the vapor deposition device 3.
The plasma discharge device 44 may be, for example, the same as the pretreatment device 2A.

<Vapor deposition equipment>
The vapor deposition apparatus 3 shown in Fig. 2 includes a chamber 33 having a predetermined reduced pressure atmosphere inside, one or more vacuum pumps 21 (one in Fig. 2 ) that exhaust gas from the chamber 33 to create a reduced pressure atmosphere, multiple guide rolls 22 (four in Fig. 2 ), a vapor deposition source 43, and a heating device 53. As shown in Fig. 2 , the guide rolls 22 and the vapor deposition source 43 are installed in the chamber 33. The chamber 33 is connected to a chamber 35 of the roll winding device 5.

The vapor deposition source 43 is disposed opposite the film substrate 10 having the treated surface of the optical function layer 40, which is being transported substantially horizontally between two adjacent guide rolls 22. The vapor deposition source 43 supplies evaporated gas made of a material that will become the antifouling layer 50 onto the optical function layer 40. The orientation of the vapor deposition source 43 can be set as desired.
The heating device 53 heats the material that will become the antifouling layer 50 to the vapor pressure temperature. The heating device 53 can be one that uses a resistance heating method, a heater heating method, an induction heating method, an electron beam heating method, or the like. In the resistance heating method, a container that contains the antifouling material that will become the antifouling layer 50 is heated by passing electricity through it as a resistor. In the heater heating method, the container is heated by a heater arranged around the periphery of the container. In the induction heating method, the container or the antifouling material is heated by electromagnetic induction from an externally installed induction coil.

The vapor deposition device 3 shown in FIG. 2 includes a guide plate (not shown) for guiding the vapor deposition material evaporated by the vapor deposition source 43 to a predetermined position, a film thickness meter (not shown) for observing the thickness of the antifouling layer 50 formed by vapor deposition, a vacuum pressure meter (not shown) for measuring the pressure inside the chamber 33, and a power supply unit (not shown).
The guide plate may have any shape as long as it can guide the evaporated deposition material to a desired position. If the guide plate is not necessary, it does not have to be provided.
As the vacuum pressure gauge, for example, an ion gauge can be used.
The power supply device may be, for example, a high frequency power supply.

<Roll winding device>
The roll winding device 5 shown in Figure 2 has a chamber 35 inside which a predetermined reduced pressure atmosphere is maintained, one or more vacuum pumps 21 (one in Figure 2) that exhaust gas from the chamber 35 to create a reduced pressure atmosphere, and a winding roll 24 and a guide roll 22 installed in the chamber 35.
The film substrate 10 (optical laminate 100) having each layer formed on its surface up to the antifouling layer 50 is wound around the winding roll 24. The winding roll 24 and the guide roll 22 wind up the optical laminate 100 at a predetermined winding speed.
If necessary, a carrier film may also be used.

The vacuum pump 21 provided in the manufacturing apparatus 200 shown in FIG. 2 can be, for example, a dry pump, oil rotary pump, turbomolecular pump, oil diffusion pump, cryopump, sputter ion pump, or getter pump. The vacuum pump 21 can be selected appropriately or used in combination to create the desired reduced pressure state in each of the chambers 31, 32, 33, 34, and 35.

The vacuum pump 21 may be installed in any position or number in the manufacturing apparatus 200 as long as it can maintain both the chamber 31 of the thin film forming apparatus 1 and the chamber 33 of the vapor deposition apparatus 3 at the desired reduced pressure. In addition, in the manufacturing apparatus 200 shown in FIG. 2, the roll unwinding device 4, pre-processing device 2A, thin film forming apparatus 1, pre-processing device 2B, vapor deposition apparatus 3, and roll winding device 5 are connected. Therefore, the vacuum pump 21 may be installed in each of the chambers 31, 32, 33, 34, and 35, or may be installed in only some of the chambers 31, 32, 33, 34, and 35, as long as it can maintain both the chamber 31 of the thin film forming apparatus 1 and the chamber 33 of the vapor deposition apparatus 3 at the desired reduced pressure.

Using this method, the optical laminate 100 according to the above embodiment can be manufactured. The optical laminate 100 according to the above embodiment has high infrared transmittance, exhibits hue stability such that color unevenness is not easily visible even when the viewing angle changes, and exhibits high flexibility that makes it applicable to curved display devices that use the film substrate 10.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various omissions, substitutions, modifications, and alterations are possible within the spirit and scope of the invention as set forth in the claims. These embodiments and their modifications are included within the scope of the invention as set forth in the claims and their equivalents, as well as within the scope and spirit of the invention.

For example, the optical laminate according to this embodiment may have a configuration as shown in FIG. 3. FIG. 3 is a cross-sectional view showing an example of the configuration of an optical laminate according to a modified example of FIG. 1. In addition to the configuration of the optical laminate 100 shown in FIG. 1, the optical laminate 101 shown in FIG. 3 has an adhesive layer 60 and a release layer 70 on the surface of the film substrate 10 opposite the side on which the optical functional layer 40 is formed.

The release layer 70 is a layer that protects the adhesive layer 60. The release layer 70 is peeled off at the time of lamination, and the adhesive layer 60 exposed by peeling off the release layer 70 adheres to the film substrate 10. The release layer 70 is, for example, paper or film coated with a release agent. The thickness of the release layer 70 is, for example, 70 μm or more and 80 μm or less.

The adhesive layer 60 is a layer that is adhered to the film substrate 10. The adhesive layer 60 includes, for example, an acrylic adhesive, a silicone adhesive, or a urethane adhesive. The thickness of the adhesive layer 60 is, for example, 10 μm or more and 50 μm or less, and preferably 20 μm or more and 30 μm or less.

Figure 4 is a schematic diagram showing how the optical laminate of Figure 3 is bonded to a substrate. As shown in Figure 4, the optical laminate 101 is bonded to the bonding surface 301 of the object 300 with the release layer 70 peeled off. The object 300 may be a display device. The size of the optical laminate 101 in the in-plane direction is preferably slightly larger than the bonding surface 301 of the object 300 to which it is bonded. If the size of the optical laminate 101 in the in-plane direction is larger than the bonding surface 301 of the object 300, an excess portion of the optical laminate will protrude from the periphery of the object 300. This excess portion is cut off after the optical laminate is bonded. Cutting can be performed, for example, using a cutting tool (not shown) while the optical laminate is bonded to the object 300.

Figure 4 shows an example in which the bonding surface 301 of the object 300 is curved, but the bonding surface 301 may also be flat. The optical laminate 101 of this embodiment can be bonded to curved surfaces due to the high flexibility provided by the use of the film substrate 10. Furthermore, the optical laminate of this embodiment does not have an optical functional layer formed on a curved member. Instead, the film substrate 10 on which the hard coat layer 20 and the adhesive layer 30 are formed is flat and the optical functional layer 40 is formed. This results in high film thickness precision and uniform optical properties in the in-plane direction. Furthermore, after fabrication, the optical laminate of this embodiment can be bonded to devices with a variety of designs, allowing for a high degree of structural freedom. Furthermore, because the optical laminate of this embodiment has high film thickness precision for each layer, even when bonded to a curved surface, it has high infrared transmittance and suppresses changes in hue when the viewing angle is changed.

[Goods]
The article of this embodiment is, for example, a liquid crystal display panel, an organic EL display panel, or the like, in which the above-described optical laminate is provided on the display surface of an image display unit. Furthermore, the article is not limited to image display devices, and may be, for example, a window glass or goggles on which the optical laminate of this embodiment is provided, the light-receiving surface of a solar cell, a smartphone screen or personal computer display, an information input terminal, a tablet terminal, an AR (augmented reality) device, a VR (virtual reality) device, an electronic display board, a glass table surface, a gaming machine, a navigation support device for an aircraft or train, a navigation system, an instrument panel, or the surface of an optical sensor, or any other object to which the optical laminate can be applied. For example, the optical laminate may be attached to the curved surface of an article having a curved surface.

In addition, the upper and/or lower limit values of the numerical ranges described in this specification can be arbitrarily combined to define a preferred range. For example, the upper and lower limit values of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limit values of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limit values of the numerical ranges can be arbitrarily combined to define a preferred range.

Furthermore, although the drawings only show an optical laminate in which the hard coat layer 20 and adhesive layer 30 are formed, this embodiment is not limited to this example, and the hard coat layer 20 and adhesive layer 30 may be omitted. For example, when an inorganic material such as a glass film is used as the film substrate 10, these layers may be omitted.

The following describes examples of the present invention. The optical laminates in the following examples are examples of optical laminates that function as anti-reflection films, and the present invention is not limited to these examples.

[Example 1]
In Example 1, an optical laminate was produced, and the luminous reflectance Y, reflection hue, total reflectance and total transmittance of infrared light with a wavelength of 940 nm, and flexibility were evaluated.

First, an 80 μm thick TAC substrate was used, and a 5 μm thick hard coat layer made of an acrylic resin layer was formed on the TAC. The hard coat layer was formed by photopolymerizing a UV-curable resin containing a urethane (meth)acrylate oligomer, a trifunctional or higher (meth)acrylate monomer, a bifunctional (meth)acrylate monomer, and a photopolymerization initiator. Next, a 3 nm thick adhesion layer made of SiOx was formed on the hard coat layer by sputtering.

Next, using a thin film forming apparatus, an optical functional layer was formed on the adhesive layer by alternately laminating high refractive index layers and low refractive index layers. Here, in the optical laminate of Example 1, the optical functional layer was configured from four layers: a first high refractive index layer, a first low refractive index layer, a second high refractive index layer, and a second low refractive index layer from the adhesive layer side. Furthermore, an anti-fouling layer with an optical thickness of 5 nm made of an alkoxysilane compound having a perfluoropolyether group was formed on the optical functional layer, thereby producing the anti-reflection film of Example 1. The optical laminate was produced using the above procedure by a roll-to-roll method using a manufacturing apparatus such as the one shown in Figure 2.

[Examples 2 to 4]
An optical laminate was produced in the same manner as in Example 1, except that the optical thickness and haze value of each of the high refractive index layers and low refractive index layers constituting the optical functional layer were changed.

[Comparative Examples 1 to 4]
An optical laminate was produced in the same manner as in Example 1, except that the optical thickness of each of the high refractive index layers and the low refractive index layers constituting the optical functional layer was changed.
Here, Comparative Examples 2 to 4 have configurations that fall within the scope of disclosure in Japanese Patent No. 7121070.

<Evaluation>
(Infrared transmittance)
The spectral transmittance was measured using a spectrophotometer (manufactured by Hitachi High-Tech Science Corporation, product name: UH4150) in the direction in which incident light was transmitted from the film substrate surface of the optical laminate, and the total transmittance at 940 nm was determined. In addition, the spectrophotometer (manufactured by JASCO Corporation, product name: V-770) was used to measure the regular transmittance at a wavelength of 940 nm for Example 1 and Comparative Example 1 when the incident angle was changed from 5° to 40°.
Here, the specular transmittance is the transmittance when only transmitted light (specular transmitted light) coaxial with the incident angle is detected, and the total transmittance is the transmittance when detected as the sum of the specular transmitted light component and the diffuse transmitted light component using an integrating sphere.

(Total reflectance)
The optical laminate was cut into 50 mm square pieces to prepare evaluation samples. The film substrate surface of the evaluation sample was attached to the surface of a black acrylic plate via a transparent acrylic adhesive, eliminating backside reflection and allowing measurement of only the surface reflection. The luminous reflectance Y was measured using a spectrophotometer (Hitachi High-Tech Science Corporation, product name: UH4150) to measure the spectral reflectance of total reflected light (measurement wavelength: 380 nm to 780 nm, incident angle: 8°, 2-degree field of view). Using the measured spectral reflectance and the relative spectral distribution of CIE standard illuminant D65 (standard illuminant D65), the luminous reflectance Y (tristimulus value Y, luminous reflectance Y (SCI)) of the object color due to reflection in the XYZ color system specified in JIS Z8701 was calculated.
Here, the total reflected light is the sum of the specular reflected light component and the diffuse reflected light component, and is extracted by an integrating sphere in the spectrophotometer.
The reflectance at a wavelength of 940 nm was measured using the same test specimen, and the spectral reflectance of total reflected light (measurement wavelength: 940 nm) was measured using a spectrophotometer (manufactured by Hitachi High-Tech Science Corporation, product name: UH4150) for the test specimen.

(reflection hue)
The reflection hue of the total reflected light was calculated based on the XYZ color system obtained in the process of calculating the luminous reflectance Y, and the chromaticities a ^* and b ^* in the CIE-Lab color system were calculated by conversion using the following formula: The a ^* and b ^* values of the specular reflection hue at incident angles (5°, 10°, 20°, 30°, 40°, 50°) were determined using the same test specimen as for the total reflected light. The specular reflectance (measurement wavelength: 380 nm to 780 nm) of the test specimen at each incident angle was measured using a spectrophotometer (manufactured by JASCO Corporation, product name: V-770), and the chromaticities (chromanetics indexes) a ^* and b ^* in the CIE-Lab color system were then calculated using the same procedure as for the reflection hue of the total reflected light. In the following formula (1), X, Y, and Z are the tristimulus values of the sample in the XYZ color system, and _Xn , _Yn , and _Zn are the tristimulus values of the perfect diffuse reflection surface.

(Hayes)
The haze value of the produced optical laminate was measured using a haze measuring device (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH800SP) according to the method of JIS-K-7136.

(Flexibility test)
A bending test (based on JIS-K5600-5-1) using a cylindrical mandrel method in which a test piece of an antireflection film is bent with the antireflection layer side facing outward was performed using a mandrel bending tester (manufactured by COTEC). Specifically, the optical laminate was first placed in a bending tester set to a predetermined diameter so that the surface on which the antifouling layer was formed was bent inward. The optical laminate was then bent 180° by bending the test device over 2 seconds and held for 10 seconds. The presence or absence of cracks in the antifouling layer was then confirmed visually and under an optical microscope. The above procedure was repeated, with the mandrel diameter being replaced with a smaller one every 1 mm, until an abnormality such as a crack was observed visually and under an optical microscope on the surface of the antifouling layer side of the optical laminate. The test was continued until the first crack was discovered.

Table 1 summarizes the physical thickness and optical thickness of each layer constituting the optical functional layer in the optical laminates of Examples 1 to 4, the optical thickness of the antifouling layer, and the properties measured by the above-mentioned methods. Table 2 also summarizes the physical thickness and optical thickness of each layer constituting the optical functional layer in the optical laminates of Comparative Examples 1 to 4, the optical thickness of the antifouling layer, and the properties.

The "OK" and "NG" ratings in Tables 1 and 2 were based on the following criteria, with good results being rated as "OK" and poor results being rated as "NG".
Infrared transmittance at a wavelength of 940 nm (total transmittance): 86% or more (good if 86% or more)
Total reflection hue: Whether the chromaticity a ^* value is -4.0<a ^* <4.0 and the b ^* value is -15.0<b ^* <0.0 (if the chromaticity a ^* value and b ^* value are within the above numerical ranges, it is considered good)
Color unevenness due to angle change: When light with a wavelength of 380 nm to 780 nm using standard light source D65 is incident on the surface at an angle of incidence of 5° to 50°, the chromaticity a ^* value of the specular reflected light does not satisfy -4.0 < a ^* < 4.0 and the b ^* value does not satisfy -15.0 < b ^* < 6.0 (it is considered good if the chromaticity a ^* value and b ^* value are within the above numerical ranges at all angles of incidence).
Flexibility test: whether cracks occurred with a mandrel diameter of more than 10 mm (good if no cracks occurred with a mandrel diameter of more than 10 mm)

As shown in Tables 1 and 2, the optical laminates of Examples 1 to 4 according to this embodiment had high infrared transmittance (total transmittance at a wavelength of 940 nm of 86% or more), low luminous reflectance of 1% or less, and good total reflection hue. It was confirmed that the hue changed little even when the viewing angle was changed. On the other hand, it was confirmed that Comparative Example 1, in which the optical thicknesses of the first low refractive index layer, second high refractive index layer, and second low refractive index layer were small, had low infrared transmittance. Furthermore, Comparative Examples 2 to 4, in which the optical thickness of the first low refractive index layer was small, had high infrared transmittance but exhibited significant color unevenness when the viewing angle was changed. Furthermore, in Comparative Examples 2, 3, and 4, the color of the reflected light was not neutral. Thus, the comparative examples did not achieve satisfactory results in terms of total reflection hue and suppression of color unevenness when the viewing angle was changed. In the comparative examples, it was confirmed that the thick first high-refractive index layer caused a large shift in the positive direction (+) for both a ^* and b ^* of the hue when the angle was changed, and that the thick optical thickness of the first low-refractive index layer caused a shift in the positive direction (+) for the hue a ^* when the angle was changed. The difference between the maximum and minimum values of a ^* at incident angles of 5° to 50° was 4.5 or less in Examples 1 to 4, and 3.0 or less in Examples 1, 3, and 4. Similarly, the difference between the maximum and minimum values of b ^* at incident angles of 5° to 50° was 16.7 or less in Examples 1 to 4, 15.0 or less in Examples 1, 2, and 4, and 12.5 or less in Examples 1 and 2. Furthermore, as shown in Table 3, it was confirmed that at least in Example 1, a certain level of transmittance was maintained even when infrared light was incident at an angle. In Examples 1 to 4, the physical thickness of the entire optical laminate was in the range of 300 nm to 400 nm, or 330 nm to 365 nm.

10: Film substrate, 20: Hard coat layer, 30: Adhesion layer, 40: Optical functional layer, 41a: First high refractive index layer, 41b: Second high refractive index layer, 42a: First low refractive index layer, 42b: Second low refractive index layer, 50: Antifouling layer, 100, 101: Optical laminate, 300: Object, 301: Bonding surface

Claims (11)

An anti-reflection film comprising a film substrate and an optically functional layer formed on the film substrate,
The optical functional layer is, in order from the film substrate side,
a first high refractive index layer having an optical thickness of 25 nm or more and 43 nm or less;
a first low refractive index layer having an optical thickness of 54 nm or more and 69 nm or less;
a second high refractive index layer having an optical thickness of 276 nm or more and 308 nm or less;
a second low refractive index layer having an optical thickness of 128 nm or more and 141 nm or less,
The transmittance of light at a wavelength of 940 nm is 86% or more,
The luminous reflectance Y is 1.0% or less,
An optical laminate in which the a ^* value of total reflected light in the CIE-LAB color system when light having a wavelength of 380 nm to 780 nm by standard light source D65 is incident is -4.0<a ^* <4.0 and the b ^* value is -15.0<b ^* <0.0. When light having a wavelength of 380 nm to 780 nm by a standard light source D65 is incident on the surface at an incident angle of 5° to 50°, the a ^* value of the specular reflected light in the CIE-LAB color system is −4.0<a ^* <4.0,
the b ^* value is −15.0<b ^* <6.0;
The optical laminate according to claim 1 . When light having a wavelength of 380 nm to 780 nm by a standard light source D65 is incident on the surface at an incident angle of 30° to 40°, the a ^* value of the specular reflected light in the CIE-LAB color system is −4.0<a ^* <4.0,
the b ^* value is −4.0<b ^* <4.0;
The optical laminate according to claim 1 . the film substrate is made of an organic material,
The optical functional layer further includes a hard coat layer between the film substrate and the optical functional layer, the hard coat layer being in contact with the film substrate, and an adhesive layer being in contact with the hard coat layer and the optical functional layer,
The optical laminate according to claim 1 , further comprising an antifouling layer disposed on the second low refractive index layer opposite to the second high refractive index layer. The optical laminate described in claim 4, wherein the optical thickness of the anti-fouling layer is 3 nm or more and 13 nm or less. The optical laminate of claim 1, having a light transmittance of 90% or more at a wavelength of 940 nm. The physical thickness of the optical functional layer is 290 nm or less,
2. The optical laminate according to claim 1, wherein the difference in refractive index between the high refractive index layer and the low refractive index layer included in the optical functional layer is 0.70 or more and 1.10 or less. the first high refractive index layer and the second high refractive index layer contain Nb ₂ O ₅ as a main component,
The optical laminate according to claim 7 , wherein the first low refractive index layer and the second low refractive index layer contain SiO ₂ as a main component. The optical laminate described in claim 7, wherein the optical functional layer consists of four layers: the first high refractive index layer, the first low refractive index layer, the second high refractive index layer, and the second low refractive index layer. An article comprising the optical laminate described in any one of claims 1 to 9. The article described in claim 10, wherein the optical laminate is provided on the surface of an image display device.