CN117957469A - Optical laminate and image display device - Google Patents

Abstract

The present invention provides an optical laminate capable of functioning as a circular polarizing plate, ensuring sufficiently small reflectance when applied to an image display device, and being less likely to observe slight leakage of internal reflected light due to slight deviation of reflection color tone in the plane of the circular polarizing plate, and an image display device including the optical laminate. An optical laminate comprising, in order, an optical functional layer (A) having a ratio of a reflectance R (450) at a wavelength of 450nm to a reflectance R (550) at a wavelength of 550nm, a linear polarizer, and a retardation layer having inverse wavelength dispersion, and an image display device comprising the optical laminate are provided: r (450)/R (550) is 1.07 or more and 1.55 or less, and the reflectance R (550) is less than 6.0%.

Description

Optical laminate and image display device

Technical Field

The present invention relates to an optical layered body and an image display device.

Background technique

It is known that in image display devices represented by organic electroluminescent (EL) display devices, in order to suppress the reduction of visibility caused by reflection of external light, a circular polarizing plate or the like is used to improve anti-reflection performance [for example, Japanese Patent Publication No. 2020-134934 (Patent Document 1)]. The circular polarizing plate is an optical laminate including a linear polarizing plate and a phase difference layer.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2020-134934

Summary of the invention

Problems to be solved by the invention

The circular polarizing plate is usually arranged on the observation side of an image display element such as an organic EL display element. By configuring the circular polarizing plate in this way, it is possible to suppress the internal reflected light that is incident on the image display element and is reflected by the internal electrodes of the element and emitted to the outside. In particular, it is known that if the circular polarizing plate is a structure including a λ/4 layer with inverse wavelength dispersion, the internal reflected light can be suppressed in a wide visible range, so it is easy to achieve a black display (making the reflection color tone of the circular polarizing plate neutral).

However, there is a problem that as the reflection hue of the circularly polarizing plate becomes more neutral, slight leakage of internal reflected light (hereinafter also referred to as "slight light leakage") caused by slight deviation of the reflection hue within the plane of the circularly polarizing plate becomes more easily observed as unevenness.

An object of the present invention is to provide an optical layered body that can be used as a circular polarizing plate and, when applied to an image display device, ensures a sufficiently low reflectivity while making the above-mentioned slight light leakage less likely to be observed. Another object of the present invention is to provide an image display device including the optical layered body.

Means for solving problems

The present invention provides the following optical layered body and image display device.

[1] An optical laminate comprising, in order, an optical functional layer (A), a linear polarizing plate, and a phase difference layer having reverse wavelength dispersion,

The ratio of the reflectivity R(450)/R(550) of the optical functional layer (A) at a wavelength of 450 nm to the reflectivity R(550) at a wavelength of 550 nm is 1.07 or more and 1.55 or less.

The above-mentioned reflectivity R(550) is less than 6.0%.

[2] The optical layered body according to [1], wherein the optical function layer (A) includes a high refractive index layer having a refractive index of 1.6 or more at a wavelength of 550 nm.

[3] The optical layered body according to [2], wherein the optical functional layer (A) comprises a substrate film and the high refractive index layer laminated thereon.

[4] The optical layered body according to any one of [1] to [3], wherein the ratio of the reflectivity R(450) to the reflectivity R(550): R(450)/R(550) is greater than or equal to 1.07 and less than or equal to 1.35.

[5] The optical layered body according to any one of [1] to [4], wherein the retardation layer includes one or more liquid crystal cured layers.

[6] The optical layered body according to any one of [1] to [5], wherein the optical functional layer (A) further includes a front plate.

[7] The optical layered body according to any one of [1] to [6], further comprising a pressure-sensitive adhesive layer disposed on the opposite side of the retardation layer to the linear polarizing plate.

[8] The optical laminate according to [7], further comprising a separator disposed on the side of the pressure-sensitive adhesive layer opposite to the retardation layer.

[9] The optical layered body according to any one of [1] to [8], further comprising a protective film on the surface of the optical functional layer (A) opposite to the linear polarizer.

[10] An image display device comprising the optical layered body according to any one of [1] to [9].

Effects of the Invention

An optical layered body that can be used as a circular polarizing plate and in which the slight light leakage is not easily observed while ensuring a sufficiently low reflectance when used in an image display device, and an image display device including the optical layered body can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an example of the optical layered body of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the optical layered body of the present invention.

FIG. 3 is a schematic cross-sectional view showing still another example of the optical layered body of the present invention.

FIG. 4 is a schematic cross-sectional view showing still another example of the optical layered body of the present invention.

FIG. 5 is a schematic cross-sectional view showing still another example of the optical layered body of the present invention.

FIG. 6 is a schematic cross-sectional view showing an example of the image display device of the present invention.

Detailed ways

Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. All the following drawings are shown to help understand the present invention, and the size and shape of each component shown in the drawings may not be consistent with the size and shape of the actual component.

＜Optical laminate＞

The optical laminate of the present invention (hereinafter also referred to as "optical laminate") can be used as a circular polarizing plate, and comprises an optical functional layer (A), a linear polarizer, and a phase difference layer having reverse wavelength dispersion in this order. The term "circular polarizing plate" includes an elliptical polarizing plate.

FIG1 is a schematic cross-sectional view showing an example of an optical laminate of the present invention. The optical laminate shown in FIG1 comprises an optical functional layer (A) 1, a linear polarizer 2 and a phase difference layer 3 having reverse wavelength dispersion. The optical functional layer (A) 1 and the linear polarizer 2 can be laminated with the aid of a first laminating layer 10. The linear polarizer 2 and the phase difference layer 3 can be laminated with the aid of a second laminating layer 20. When the optical laminate is applied to an image display device (organic EL display device, etc.), the optical functional layer (A) 1 side of the optical laminate becomes the observation side, that is, the phase difference layer 3 side becomes the image display element (organic EL display element, etc.) side, and is arranged on the observation side of the image display element.

Hereinafter, the components included or which may be included in the optical layered body will be described in detail.

(1) Optical functional layer (A)

The optical function layer (A) is a layer disposed on the observation side of the linear polarizing plate 2 and has the following reflection characteristics.

[a] The ratio of the reflectivity R(450) at a wavelength of 450 nm to the reflectivity R(550) at a wavelength of 550 nm (reflectivity R(450)/reflectivity R(550). Hereinafter, it is also simply referred to as the "reflectivity ratio") is greater than or equal to 1.07 and less than or equal to 1.55.

[b] The reflectivity R(550) is less than 6.0%.

The optical functional layer (A) usually has a laminated structure. When the reflectivity of the first laminating layer 10 is a meaningful value, the laminated structure composed of the optical functional layer (A) 1 and the first laminating layer 10, that is, the laminated structure composed of all layers arranged on the observation side of the linear polarizer 2, is equivalent to the "optical functional layer (A)". On the other hand, when the reflectivity of the first laminating layer 10 is not a meaningful value, that is, when the reflection characteristics of the optical functional layer (A) 1 are substantially equal to the reflection characteristics of the above-mentioned laminated structure, the optical functional layer (A) 1 can be regarded as the optical functional layer (A).

By imparting the optical functional layer (A) 1 having the above-mentioned reflective characteristics to the observation side of the linear polarizer 2, the reflected light reflected on the observation side surface of the optical laminate can be made bluish in color, so that the above-mentioned slight light leakage can be made difficult to be observed. The optical laminate of the present invention has a phase difference layer with reverse wavelength dispersion, which can greatly suppress internal reflection. Therefore, the method of the present invention for controlling the reflected light reflected on the observation side surface of the optical laminate by imparting the optical functional layer (A) 1 is effective in making it difficult to observe slight light leakage. On the other hand, even if the optical functional layer (A) 1 is arranged on the observation side of the linear polarizer 2, it is possible to suppress the transmitted light (white display) from the image display element from changing to a bluish color.

By adjusting the phase difference characteristics of the phase difference layer of the circular polarizing plate, the reflection hue of the circular polarizing plate can also be made into a bluish color. For example, by increasing the wavelength dispersion α, it can be made into a bluish color. However, in this case, other problems arise from the change of the oblique reflection hue. According to the method of imparting the optical functional layer (A) 1 having the above-mentioned reflection characteristics to the observation side of the linear polarizing plate 2, it is possible to make slight light leakage difficult to be observed without causing such problems.

It should be noted that the wavelength dispersion α refers to the ratio of the in-plane phase difference value Re(450) at a wavelength of 450 nm to the in-plane phase difference value Re(550) at a wavelength of 550 nm.

Wavelength dispersion α = in-plane phase difference Re (450) / in-plane phase difference Re (550)

In addition, according to the optical laminate of the present invention, the reflection hue of the optical laminate can be appropriately bluish, thereby giving a high-end feeling to the display of the image display device. The bluish degree of the reflection hue can be controlled by adjusting the reflectivity R(450), the reflectivity R(550) and/or their reflectivity ratio within the above range.

From the viewpoint of not being easy to observe slight light leakage and/or the viewpoint of appropriately reducing the reflectivity Y of the optical laminate, the reflectivity ratio is preferably 1.07 or more and 1.45 or less, more preferably 1.07 or more and 1.35 or less, further preferably 1.10 or more and 1.35 or less, and further preferably 1.12 or more and 1.35 or less. If the reflectivity ratio exceeds 1.55, there is a tendency that the bluish color of the reflection hue of the optical laminate becomes too strong. If the reflectivity ratio is less than 1.07, the effect of not being easy to observe slight light leakage cannot be obtained.

From the viewpoint of appropriately reducing the reflectivity Y of the optical laminate, the reflectivity R (550) is preferably 5.8% or less, more preferably 5.6% or less, and further preferably 5.4% or less. If the reflectivity R (550) is 6.0% or more, the reflectivity Y of the optical laminate becomes too large, and there is a tendency for the visibility of the image display device to decrease. The reflectivity R (550) may be 0.0%, but is usually greater than 0.0%, for example, 0.1% or more, preferably 1.0% or more, more preferably 4.0% or more, and further preferably 4.2% or more.

From the perspective of making it difficult to observe slight light leakage and/or moderately reducing the reflectivity Y of the optical layered body, the reflectivity R(450) is preferably 4.0% to 10.0%, more preferably 4.5% to 9.0%, and further preferably 5.0% to 8.0%.

From the viewpoint of visibility of an image display device, the reflectance Y of the optical layered body is preferably less than 6.0%, more preferably 5.9% or less, further preferably 5.8% or less, and further preferably 5.7% or less. The reflectance Y is usually 4.0% or more.

The reflectance R(450) and the reflectance R(550) of the optical functional layer (A) and the reflectance Y of the optical layered body can be measured by the method described in the section [Examples] described later.

The optical functional layer (A) 1 may include, for example, a high refractive index layer, a pigment layer (for example, a yellow pigment layer), an alternating multilayer of a high refractive index layer and a low refractive index layer, a liquid crystal layer, a fluorescent light-emitting layer, or a combination thereof. The high refractive index layer utilizes interface reflection to realize the above-mentioned reflection characteristics. The pigment layer is, for example, a layer containing a pigment that absorbs yellow light, and is a layer that improves the bluishness of reflected light. The alternating multilayer of the high refractive index layer and the low refractive index layer utilizes interface reflection at the interface of the high refractive index layer and the low refractive index layer to realize the above-mentioned reflection characteristics. The liquid crystal layer utilizes, for example, the reflection of circularly polarized light based on cholesteric liquid crystal to realize the above-mentioned reflection characteristics. Among them, from the viewpoint of the ease of realizing the optical functional layer (A) having the above-mentioned reflection characteristics and the ease of manufacture, the viewpoint of the ease of adjusting the reflection hue of the optical laminate, and the viewpoint of preferably not coloring the transmitted light from the image display element, the optical functional layer (A) 1 preferably includes a high refractive index layer.

As the high refractive index layer, a high refractive index layer of a known structure can be used, preferably a layer in which a refractive index imparting agent is dispersed in a binder resin. As the refractive index imparting agent, for example, particles composed of metal oxides such as zirconium oxide, titanium oxide, tin oxide, zinc oxide, indium tin oxide, indium oxide, aluminum oxide, silicon oxide, yttrium oxide, and antimony oxide can be cited. The average particle size of the particles is, for example, more than 0.01nm and less than 100nm, preferably more than 0.1nm and less than 50nm.

From the viewpoint of the refractive index of high refractive index layer and the film making ease of this layer, in high refractive index layer 100 mass %, the content of the refractive index imparting agent in the high refractive index layer is preferably more than 10 mass % and below 90 mass %, more preferably more than 20 mass % and below 80 mass %, further preferably more than 30 mass % and below 70 mass %, more preferably more than 40 mass % and below 60 mass %.The refractive index of high refractive index layer can be adjusted by the content of the refractive index imparting agent in the high refractive index layer.The more the content of the refractive index imparting agent in the high refractive index layer is, the more the refractive index of the high refractive index layer can be improved.

The binder resin may be a thermoplastic resin or a cured product of a curable resin. The high refractive index layer may have hard coating properties. In this case, the high refractive index layer may be formed by a cured product of a hard coating layer forming composition comprising an active energy ray-curable resin such as an ultraviolet-curable resin and a refractive index imparting agent. As active energy ray-curable resins, for example, (meth) acrylic resins, silicone resins, polyester resins, carbamate resins, amide resins, epoxy resins, etc. may be cited, preferably ultraviolet-curable resins. The ultraviolet-curable resin constituting the binder resin is preferably a (meth) acrylic resin, and from the viewpoint of curability, it is more preferably a (meth) acrylic resin comprising a structural unit from a multifunctional (meth) acrylic monomer.

In addition, in this specification, "(meth)acrylic acid" means that it may be either acrylic acid or methacrylic acid. The "(meth)" of (meth)acrylate etc. has the same meaning.

From the viewpoint of the refractive index of the high refractive index layer and the viewpoint that slight light leakage is not easily observed, the thickness (optical film thickness) of the high refractive index layer is preferably from 10 nm to 1000 nm, more preferably from 10 nm to 500 nm, further preferably from 20 nm to 300 nm, further preferably from 40 nm to 250 nm, and particularly preferably from 100 nm to 200 nm.

The high refractive index layer preferably has a refractive index of 1.6 or more, more preferably 1.62 or more, at a wavelength of 550 nm to prevent slight light leakage from being observed. The refractive index is preferably 1.75 or less, more preferably 1.70 or less, to make the reflection hue of the optical laminate moderately bluish.

The optical functional layer (A) 1 is usually directly laminated on the surface of the linear polarizing plate 2. For example, the high refractive index layer can be directly laminated on the surface of the linear polarizing plate 2 by applying a high refractive index layer-forming composition on the surface of the linear polarizing plate 2 and drying and/or curing the composition as needed.

The optical functional layer (A) 1 may include a substrate film and a high refractive index layer stacked thereon. In this case, the optical functional layer (A) 1 may be stacked on the linear polarizer 2, for example, by means of the first laminating layer 10, in a manner such that its substrate film side is opposed to the linear polarizer 2. By applying a high refractive index layer forming composition on the substrate film, and drying and/or curing it as required, an optical functional layer (A) comprising a substrate film and a high refractive index layer can be formed. Alternatively, a linear polarizing plate may be prepared by laminating the above-mentioned substrate film as a protective film of the linear polarizer 2 on the observation side of the linear polarizer 2, and further laminating the layers constituting the optical functional layer (A) 1 other than the substrate film to the linear polarizer to prepare an optical laminate. In this case, the optical functional layer (A) 1 has layers constituting the optical functional layer (A) 1 other than the substrate film and the substrate film.

As the substrate film, a thermoplastic resin film described later can be used. From the viewpoint of thinning, the thickness of the substrate film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, further preferably 30 μm or less, and usually 5 μm or more, preferably 10 μm or more.

Among them, the substrate film is preferably a cyclic polyolefin-based resin film, a cellulose ester-based resin film, a polyester-based resin film, or a (meth)acrylic resin film.

The optical functional layer (A) 1 may include a thermoplastic resin film other than the above-mentioned substrate film. For example, a linear polarizing plate can be prepared by laminating the thermoplastic resin film as a protective film of the linear polarizing plate 2 on the observation side of the linear polarizing plate 2, and further laminating the layer constituting the optical functional layer (A) 1 other than the thermoplastic resin film to the linear polarizing plate to prepare an optical laminate. In this case, the optical functional layer (A) 1 includes a layer constituting the optical functional layer (A) 1 other than the thermoplastic resin film and a thermoplastic resin film. The details of the thermoplastic resin film will be described later.

When the optical functional layer (A) includes a high refractive index layer and a substrate film, the difference in their refractive index at a wavelength of 550 nm is preferably 0.05 to 0.30, more preferably 0.08 to 0.26, and further preferably 0.10 to 0.24, from the viewpoint that slight light leakage is not easily observed.

When the optical functional layer (A) comprises a high refractive index layer and a substrate film, a resin layer can be sandwiched between the high refractive index layer and the substrate film, or a resin layer can be configured on the side opposite to the substrate film of the high refractive index layer. The example of the resin layer is a hard coat. In addition, the resin layer that can be sandwiched between the high refractive index layer and the substrate film can be a primer. About the hard coat, the record described later is cited.

When the optical functional layer (A) includes a substrate film and a resin layer, a linear polarizing plate can be prepared by laminating the substrate film and the resin layer as a protective film and a hard coating layer of the linear polarizing plate 2 on the viewing side of the linear polarizing plate 2, respectively, and further laminating the substrate film and the layer constituting the optical functional layer (A) 1 other than the resin layer to the linear polarizing plate to prepare an optical laminate. In this case, the optical functional layer (A) 1 includes the layers constituting the optical functional layer (A) 1 other than the substrate film and the resin layer, the substrate film, and the resin layer.

From the viewpoint of making it difficult to observe slight light leakage, when the above-mentioned resin layer is included, the refractive index difference between the resin layer and the high refractive index layer at a wavelength of 550nm is preferably greater than 0.05 and less than 0.30, more preferably greater than 0.08 and less than 0.26, and further preferably greater than 0.10 and less than 0.24.

Optical functional layer (A) 1 can also include 1 or more than 2 layers of the layer that can adjust the reflective characteristics (reflectivity γ, reflection hue) of the optical laminate except comprising high refractive index layer, containing pigment layer (for example containing yellow pigment layer), high refractive index layer and low refractive index layer alternating multilayer, liquid crystal layer, fluorescent luminescent layer or their combination.As such layer, for example, can enumerate above-mentioned resin layer.Resin layer can be configured between high refractive index layer and substrate film or high refractive index layer with the opposite side of substrate film.Resin layer can be adhesive layer.

As another example of a layer capable of adjusting the reflective properties of an optical laminate, there can be mentioned a front panel 90 described later disposed on the side of the high refractive index layer opposite to the substrate film via an adhesive layer (the sixth bonding layer 80 described later). As another example of a layer capable of adjusting the reflective properties of an optical laminate, there can be mentioned a thermoplastic resin film other than the above-mentioned substrate film.

The optical functional layer (A) 1 preferably has high electrical insulation, for example, preferably a layer having a resistance value exceeding 1.0×10 ⁷ Ω/□. In order to improve electrical insulation, it is preferred that the optical functional layer not have a mesh structure such as a metal mesh layer, that is, an optical functional layer that is uniform over the entire surface.

(2) Linear polarizer

The linear polarizer 2 has the function of selectively transmitting linear polarized light in a certain direction from non-polarized light such as natural light. As the linear polarizer, there can be cited a stretched film or stretched layer adsorbed with a dichroic pigment, a cured product containing a polymerizable liquid crystal compound and a liquid crystal cured layer of a dichroic pigment, etc. The optical functional layer (A) 1 and the linear polarizer 2 can be laminated via a first laminating layer 10.

A linear polarizer as a stretched film with adsorbed dichroic dye can generally be manufactured through the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing the polyvinyl alcohol resin film with a dichroic dye such as iodine to adsorb the dichroic dye; a step of treating the polyvinyl alcohol resin film with adsorbed dichroic dye with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The thickness of the stretched film to which the dichroic dye is adsorbed is usually 30 μm or less, preferably 18 μm or less, and more preferably 15 μm or less. The thickness is usually 1 μm or more, for example, 5 μm or more.

The polyvinyl alcohol resin is obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith can be used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acid compounds, olefin compounds, vinyl ether compounds, unsaturated sulfone compounds, and (meth)acrylamide compounds having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and polyvinyl formal, polyvinyl acetal, etc. modified with aldehydes may also be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less.

The linear polarizer as a stretched layer adsorbed with a dichroic dye can usually be manufactured through the following steps: a step of applying a coating liquid containing the above-mentioned polyvinyl alcohol resin on a substrate layer; a step of uniaxially stretching the obtained laminated film; a step of dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb the dichroic dye; a step of treating the film adsorbed with the dichroic dye with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution. The substrate layer can be used as a protective film for the linear polarizer, or it can be peeled off and removed from the linear polarizer. The material and thickness of the substrate layer can be the same as the material and thickness of the thermoplastic resin film described later.

The optical laminate may include a protective film laminated on one or both sides of a linear polarizer as a stretched film or a stretched layer adsorbed with a dichroic pigment. As the protective film, a thermoplastic resin film described later may be used. The linear polarizer and the protective film may be laminated with the aid of a laminating layer described later.

As described above, the thermoplastic resin film (protective film) laminated on the viewing side of the linear polarizing plate is included in the optical functional layer (A). The thermoplastic resin film and the linear polarizing plate may be bonded together via the first bonding layer.

Examples of the thermoplastic resin constituting the thermoplastic resin film include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamide; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having a ring system and a norbornene structure (also referred to as norbornene resins); (meth) acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins, etc. Among them, the thermoplastic resin film is preferably a cyclic polyolefin resin film, a cellulose ester resin film, a polyester resin film, or a (meth) acrylic resin film.

From the viewpoint of thinning, the thickness of the thermoplastic resin film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, further preferably 30 μm or less, and is usually 5 μm or more, preferably 10 μm or more.

A hard coating layer may be formed on the thermoplastic resin film. The hard coating layer may be formed on one side of the thermoplastic resin film or on both sides. By providing the hard coating layer, a thermoplastic resin film having improved hardness and scratch resistance may be produced.

The hard coat layer is, for example, a cured layer of an active energy ray-curable resin, preferably an ultraviolet-curable resin. As ultraviolet-curable resins, for example, (meth) acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, epoxy resins, etc. can be cited. In order to improve the strength, the hard coat layer may contain additives. The additives are not particularly limited, and inorganic microparticles, organic microparticles, or mixtures thereof can be cited.

The polymerizable liquid crystal compound used to form a linear polarizer as a liquid crystal curing layer is a compound having a polymerizable reaction group and showing liquid crystal properties. The polymerizable reaction group is a group that participates in the polymerization reaction, preferably a photopolymerizable reaction group. The photopolymerizable reaction group refers to a group that can participate in the polymerization reaction through active free radicals, acids, etc. generated by a photopolymerization initiator. As a photopolymerizable reaction group, vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, oxirane, oxetane, etc. can be cited. Among them, acryloyloxy, methacryloyloxy, vinyloxy, oxirane and oxetane are preferred, and acryloyloxy is more preferred. The type of polymerizable liquid crystal compound is not particularly limited, and rod-shaped liquid crystal compounds, disc-shaped liquid crystal compounds and mixtures thereof can be used. The liquid crystal properties of the polymerizable liquid crystal compound can be thermotropic liquid crystals or lyotropic liquid crystals. If the thermotropic liquid crystals are classified by order, they can be nematic liquid crystals or smectic liquid crystals.

In the liquid crystal solidification layer, the dichroic pigment is dispersed in the solidified material of the polymerizable liquid crystal compound and oriented. As the dichroic pigment used in the linear polarizer of the liquid crystal solidification layer, it is preferred that the dichroic pigment has a maximum absorption wavelength in the range of more than 300nm and less than 700nm. As such a dichroic pigment, for example, acridine pigment, oxazine pigment, cyanine pigment, naphthalene pigment, azo pigment and anthraquinone pigment, etc. can be mentioned, wherein, preferably azo pigment. As azo pigment, monoazo pigment, disazo pigment, triazo pigment, tetraazo pigment and stilbene azo pigment, etc. can be mentioned, preferably disazo pigment and triazo pigment. The dichroic pigment can be used alone, or two or more can be used in combination, preferably three or more can be used in combination. In particular, more preferably azo compounds of more than three kinds are combined. A part of the dichroic pigment can have a reactive group, and it can also have liquid crystallinity in addition.

The linear polarizer as a liquid crystal solidification layer can be formed, for example, by coating a linear polarizer-forming composition comprising a polymerizable liquid crystal compound and a dichroic pigment on an orientation film formed on a substrate layer, and polymerizing and solidifying the polymerizable liquid crystal compound. It is also possible to form a coating film by coating a linear polarizer-forming composition on a substrate layer, and stretching the coating film together with the substrate layer to form a linear polarizer. The substrate layer for forming a linear polarizer can be used as a protective film for the linear polarizer. The material and thickness of the substrate layer can be the same as the material and thickness of the above-mentioned thermoplastic resin film.

As a composition for forming a linear polarizer including a polymerizable liquid crystal compound and a dichroic pigment, and a method for manufacturing a linear polarizer using the composition, the contents described in Japanese Patent Publication No. 2013-37353, Japanese Patent Publication No. 2013-33249, Japanese Patent Publication No. 2017-83843, etc. can be exemplified. In addition to the polymerizable liquid crystal compound and the dichroic pigment, the composition for forming a linear polarizer may further include additives such as a solvent, a polymerization initiator, a crosslinking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer. These components may be used in one kind only, or in combination of two or more kinds.

The polymerization initiator that the linear polarizer forming composition may contain is a compound that can initiate the polymerization reaction of a polymerizable liquid crystal compound. From the viewpoint of being able to initiate the polymerization reaction under lower temperature conditions, a photopolymerization initiator is preferred. Specifically, a photopolymerization initiator that can generate active free radicals or acids by the action of light can be cited, wherein a photopolymerization initiator that generates free radicals by the action of light is preferred. Relative to the total amount of 100 parts by mass of the polymerizable liquid crystal compound, the content of the polymerization initiator is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 8 parts by mass or less. If within this range, the reaction of the polymerizable group is fully carried out, and it is easy to stabilize the orientation state of the liquid crystal compound.

The thickness of the linear polarizing plate as the liquid crystal solidified layer is usually 10 μm or less, preferably 0.5 μm or more and 8 μm or less, and more preferably 1 μm or more and 5 μm or less.

The optical laminate may include the substrate layer forming a linear polarizer as a liquid crystal solidification layer. The substrate layer may be the thermoplastic resin film or the protective film of the linear polarizer contained in the optical functional layer (A). Alternatively, the substrate layer may be peeled off from the linear polarizer. The optical laminate may or may not have the alignment film.

The linear polarizer as a liquid crystal solidification layer may have an outer coating on one or both sides thereof for the purpose of protecting the linear polarizer, etc. The outer coating may be formed, for example, by applying a composition for forming an outer coating on the linear polarizer. As materials constituting the outer coating, for example, photocurable resins, water-soluble polymers, etc. may be cited, and specifically, (meth) acrylic resins, polyvinyl alcohol resins, etc. may be used.

The visibility-corrected polarization degree Py of the linear polarizer is usually 95% or more, preferably 97% or more, more preferably 98% or more, further preferably 98.7% or more, further preferably 99.0% or more, particularly preferably 99.4% or more, and can be 99.9% or more. The visibility-corrected polarization degree Py of the linear polarizer can be 99.999% or less or 99.99% or less.

The visibility-corrected polarization degree Py can be calculated by performing visibility correction on the obtained polarization degree using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) using a 2-degree field of view (C light source) of "JIS Z 8701".

Increasing the visibility correction polarization degree Py of the linear polarizing plate is advantageous in improving the antireflection function of the optical laminate. If the visibility correction polarization degree Py is less than 95%, the antireflection function may not be exhibited.

The visibility correction single transmittance Ty of the linear polarizer is usually 41% or more, preferably 41.1% or more, more preferably 41.2% or more, and can be 42% or more, or 42.5% or more. The visibility correction single transmittance Ty of the linear polarizer is usually 50% or less, and can be 48% or less, or 46% or less, or 44% or less, or 43% or less. If the visibility correction single transmittance Ty is too high, the visibility correction polarization degree Py becomes too low, and sometimes the anti-reflection function of the optical laminate becomes insufficient.

The visibility-corrected single transmittance Ty can be calculated by performing visibility correction on the obtained transmittance using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) using a 2-degree field of view (C light source) of "JIS Z 8701".

The orthogonal hue a* of the linear polarizer is preferably in the range of -5 to 5, more preferably in the range of -3 to 3. In addition, the orthogonal hue b* is preferably in the range of -10 to 10, more preferably in the range of -5 to 5, and further preferably in the range of -3 to 3. Using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation), the chromaticity a* and b* in the L*a*b* (CIE) colorimetric system are calculated for the obtained transmittance using the colorimetric function of the C light source, thereby obtaining the hue of the linear polarizer monomer (monomer hue), the hue of the linear polarizers arranged in parallel (parallel hue), and the hue of the linear polarizers arranged orthogonally (orthogonal hue).

(3) Phase difference layer

The optical laminate includes a phase difference layer 3 having a first phase difference layer 3a. The linear polarizing plate 2 and the first phase difference layer 3a may be laminated via a second bonding layer 20. When a protective film is laminated on the side opposite to the observation side of the linear polarizing plate 2, the protective film and the first phase difference layer 3a may be laminated via the second bonding layer 20.

The phase difference layer 3 may have only the first phase difference layer 3a, or may have a laminated structure consisting of two or more phase difference layers. That is, the phase difference layer 3 may include one or more phase difference layers different from the first phase difference layer 3a. The phase difference layer 3 may also have an outer coating layer to protect its surface, a substrate layer to support the phase difference layer 3, and the like.

The first phase difference layer 3a is, for example, a λ/4 layer. When the phase difference layer 3 includes two phase difference layers, the combination of the phase difference layers of the layer includes, from the linear polarizing plate 2 side, a combination of a λ/4 layer and a positive C layer, a combination of a λ/2 layer and a λ/4 layer, and a combination of a positive C layer and a λ/4 layer. The lamination of the phase difference layers can use a laminating layer (fifth laminating layer) described later.

The in-plane phase difference value Re(550) of the λ/4 layer at a wavelength of 550nm is usually in the range of 90nm to 220nm, preferably in the range of 100nm to 200nm. The in-plane phase difference value Re(550) of the λ/2 layer at a wavelength of 550nm is preferably in the range of 100nm to 300nm, more preferably in the range of 150nm to 300nm, and further preferably in the range of 200nm to 300nm. In addition, the phase difference value Rth(550) in the thickness direction at a wavelength of 550nm of the positive C layer is usually in the range of -170nm to -10nm, preferably in the range of -150nm to -20nm.

The retardation layer 3 has reverse wavelength dispersion, and the wavelength dispersion α is preferably 0.80 or more and 0.88 or less. This can effectively suppress the above-mentioned internal reflection.

The wavelength dispersion α refers to the ratio of the in-plane phase difference value Re(450) at a wavelength of 450 nm to the in-plane phase difference value Re(550) at a wavelength of 550 nm.

Wavelength dispersion α = in-plane phase difference Re (450) / in-plane phase difference Re (550)

The first phase difference layer 3a and other phase difference layers may be phase difference films formed by stretching the above-mentioned thermoplastic resin film, or may be liquid crystal cured layers. The liquid crystal cured layer is a cured layer formed by polymerizing and curing a polymerizable liquid crystal compound in an oriented state. The phase difference layer 3 may include one or more liquid crystal cured layers, or may include two or more layers.

As the polymerizable liquid crystal compound, a rod-shaped polymerizable liquid crystal compound and a disc-shaped polymerizable liquid crystal compound can be cited. One of them can be used, or a mixture containing both of them can be used. In the case where the rod-shaped polymerizable liquid crystal compound is horizontally oriented or vertically oriented relative to the substrate layer, the optical axis of the polymerizable liquid crystal compound is consistent with the long axis direction of the polymerizable liquid crystal compound. In the case where the disc-shaped polymerizable liquid crystal compound is oriented, the optical axis of the polymerizable liquid crystal compound exists in a direction orthogonal to the disc surface of the polymerizable liquid crystal compound.

In order to make the liquid crystal solidified layer formed by polymerizing the polymerizable liquid crystal compound show an in-plane phase difference, the polymerizable liquid crystal compound can be oriented in a suitable direction. In the case where the polymerizable liquid crystal compound is rod-shaped, the in-plane phase difference is manifested by aligning the optical axis of the polymerizable liquid crystal compound horizontally relative to the plane of the substrate layer, in which case the direction of the optical axis is consistent with the direction of the slow axis. In the case where the polymerizable liquid crystal compound is disc-shaped, the in-plane phase difference is manifested by aligning the optical axis of the polymerizable liquid crystal compound horizontally relative to the plane of the substrate layer, in which case the optical axis is orthogonal to the slow axis. The orientation state of the polymerizable liquid crystal compound can be adjusted by a combination of an orientation layer and a polymerizable liquid crystal compound.

The polymerizable liquid crystal compound is a compound having at least one polymerizable reaction group and having liquid crystal properties. When two or more polymerizable liquid crystal compounds are used in combination, it is preferred that at least one has two or more polymerizable reaction groups in the molecule. The polymerizable reaction group is a group that participates in the polymerization reaction, preferably a photopolymerizable reaction group. The photopolymerizable reaction group refers to a group that can participate in the polymerization reaction through active free radicals, acids, etc. generated by a photopolymerization initiator. Examples of photopolymerizable reaction groups are the same as above. The liquid crystal properties possessed by the polymerizable liquid crystal compound can be thermotropic liquid crystals or lyotropic liquid crystals. If thermotropic liquid crystals are classified by order, they can be nematic liquid crystals or smectic liquid crystals.

The optical laminate may include an alignment layer adjacent to the phase difference layer. The alignment layer has an alignment restriction force that orients the polymerizable liquid crystal compound in a desired direction. The alignment layer may be a vertical alignment layer that orients the molecular axis of the polymerizable liquid crystal compound vertically relative to the substrate layer, a horizontal alignment layer that orients the molecular axis of the polymerizable liquid crystal compound horizontally relative to the substrate layer, or an inclined alignment layer that orients the molecular axis of the polymerizable liquid crystal compound obliquely relative to the substrate layer.

The thickness of the liquid crystal solidified layer may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 2 μm or more, and is preferably 10 μm or less, 8 μm or less, or 5 μm or less.

The liquid crystal solidification layer can be formed by coating a liquid crystal layer-forming composition containing a polymerizable liquid crystal compound on the substrate layer, drying it, and polymerizing the polymerizable liquid crystal compound. The liquid crystal layer-forming composition can be coated on the alignment layer formed on the substrate layer. The material and thickness of the substrate layer can be the same as the material and thickness of the above-mentioned thermoplastic resin film. The substrate layer can be assembled in the optical laminate together with the phase difference layer as the liquid crystal solidification layer, or the substrate layer can be peeled off and only the liquid crystal solidification layer, or the liquid crystal solidification layer and the alignment layer are assembled in the optical laminate.

(4) Adhesive layer

Fig. 2 is a schematic cross-sectional view showing another example of the optical laminate of the present invention. The optical laminate shown in Fig. 2 comprises an optical functional layer (A) 1, a first laminating layer 10, a linear polarizer 2, a second laminating layer 20, a phase difference layer 3 having reverse wavelength dispersion, and an adhesive layer 50. The adhesive layer 50 can be laminated on the surface of the optical laminate opposite to the observation side (optical functional layer (A) 1 side), and can be used for laminating the optical laminate to an image display element such as an organic EL display element.

In the optical laminate shown in FIG2 , the optical functional layer (A) 1 includes, in order from the observation side, a high refractive index layer 1a, a base film 1b, a third laminating layer 30, and a thermoplastic resin film 11. On the side opposite to the observation side of the linear polarizer 2, a protective film 12 is laminated via a fourth laminating layer 40. The third laminating layer 30 and the thermoplastic resin film 11 may be omitted. The fourth laminating layer 40 and the protective film 12 may also be omitted.

In the optical laminate shown in Fig. 2, the retardation layer 3 includes a first retardation layer 3a and a second retardation layer 3b. The first retardation layer 3a and the second retardation layer 3b are bonded together via a fifth bonding layer 3c. However, the fifth bonding layer 3c and the second retardation layer 3b may be omitted.

The thickness of the adhesive layer 50 may be, for example, 250 μm or less, preferably 100 μm or less, more preferably 50 μm or less, and further preferably 40 μm or less from the viewpoint of thinning. From the viewpoint of durability, the lower limit of the thickness of the adhesive layer may be, for example, 1 μm or more, preferably 5 μm or more, and more preferably 10 μm or more.

The adhesive layer 50 may be composed of an adhesive composition mainly composed of (meth) acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, and polyvinyl ether resin. Among them, an adhesive composition based on a (meth) acrylic resin having excellent transparency, weather resistance, heat resistance, etc. is suitable. The adhesive composition may be active energy ray curing type or heat curing type.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, it is suitable to use a polymer or copolymer using one or more of (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate as monomers. It is preferred to copolymerize a polar monomer with the base polymer. As polar monomers, monomers having carboxyl groups, hydroxyl groups, amide groups, amino groups, epoxy groups, etc., such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N,N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate can be cited.

The adhesive composition may only contain the above-mentioned base polymer, but usually also contains a crosslinking agent. As the crosslinking agent, metal ions having a valence of more than two and forming a carboxylic acid metal salt with a carboxyl group, polyamine compounds forming an amide bond with a carboxyl group, polyepoxide compounds or polyols forming an ester bond with a carboxyl group, and polyisocyanate compounds forming an amide bond with a carboxyl group can be cited. Among them, polyisocyanate compounds are preferred.

The adhesive layer 50 may include a light selective absorber. The light selective absorber has a maximum absorption wavelength in the short wavelength region of visible light, i.e., the wavelength region of 390 to 430 nm. Here, in the present embodiment, "visible light" is light with a wavelength in the range of 390 nm to 830 nm. Examples of such light selective absorbers include salicylate compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, triazine compounds, and nickel complex salt compounds.

In addition, a compound having a maximum absorption wavelength in the wavelength region of 390 to 430 nm can be synthesized by a known method and used as a light selective absorber. Such a pigment can use, for example, a compound known as a light selective absorption compound described in Japanese Patent Application Laid-Open No. 2017-120430.

The adhesive layer 50 may be an adhesive layer satisfying the following formula (1).

A(410)≥0.1 (1)

[In formula (1), A(410) represents the absorbance at a wavelength of 410 nm.]

The larger the value of A(410), the higher the light absorption at a wavelength of 410 nm. If the value of A(410) is less than 0.1, the light absorption at a wavelength of 410 nm is low, and it is easy to cause degradation of the organic EL display element and the phase difference layer as a liquid crystal curing layer due to light near 400 nm. The value of A(410) is preferably 0.3 or more, more preferably 0.8 or more, and particularly preferably 1.0 or more. The upper limit is not particularly limited, and is usually 10 or less.

As described above, when the adhesive layer 50 includes a light selective absorber and has a light selective absorption performance, the reflection hue is close to a black display (making the reflection hue of the circular polarizing plate neutral), so it is easy to observe slight light leakage. Therefore, the optical laminate of the present invention having an optical functional layer (A) and being able to make slight light leakage difficult to observe is also advantageous when including a layer with a light selective absorption performance. It should be noted that the light absorption performance can be imparted not only to the adhesive layer, but also to the resin layer or hard coating, laminating layer, etc. The above-mentioned light selective absorber can be contained in a resin layer or hard coating, laminating layer, etc.

The active energy ray-curable adhesive composition has the property of being cured by being irradiated with active energy rays such as ultraviolet rays and electron beams, and has the property of being adhesive before being irradiated with active energy rays and being able to be closely attached to adherends such as films, and being cured by being irradiated with active energy rays so as to adjust the close adhesion. The active energy ray-curable adhesive composition is preferably an ultraviolet curable adhesive composition. In addition to the base polymer and the crosslinking agent, the active energy ray-curable adhesive composition also contains an active energy ray polymerizable compound. It may contain a photopolymerization initiator, a photosensitizer, etc. as needed.

(5) Diaphragm

As shown in FIG3 , the optical laminate may include a diaphragm 60 for protecting the outer surface (the surface opposite to the second phase difference layer 3 b) of the adhesive layer 50. The optical laminate shown in FIG3 has the same layer structure as the optical laminate shown in FIG2 except that it has the diaphragm 60. The diaphragm 60 is usually composed of a thermoplastic resin film subjected to a release treatment using a silicone-based, fluorine-based or other release agent on one side, and the release-treated surface is attached to the adhesive layer 50.

Thermoplastic resin constituting the separator 60 is, for example, polyethylene resin such as polyethylene, polypropylene resin such as polypropylene, polyester resin such as polyethylene terephthalate and polyethylene naphthalate, etc. The separator 60 has a thickness of, for example, 10 μm to 50 μm.

(6) Protective film

As shown in FIG4 , the optical laminate may include a protective film 70 laminated on the surface of the optical functional layer (A) 1 side. The optical laminate shown in FIG4 has the same layer structure as the optical laminate shown in FIG3 except that it has a protective film 70. The protective film 70 is composed of, for example, a substrate film and an adhesive layer laminated thereon. Regarding the adhesive layer, the above description is cited. The resin constituting the substrate film may be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, a polycarbonate resin, or other thermoplastic resin. Polyester resins such as polyethylene terephthalate are preferred.

(7) Front panel

As shown in Figure 5, the optical functional layer (A) 1 may further include a front panel 90. The front panel 90 is usually arranged on the outermost surface of the observation side of the optical laminate. The front panel 90 can be laminated on the surface of the observation side of the high refractive index layer 1a with the help of the sixth bonding layer 80. In this case, the optical functional layer (A) 1 includes the sixth bonding layer 80 and the front panel 90. The optical laminate shown in Figure 5 has the same layer structure as the optical laminate shown in Figure 3 except that it has the sixth bonding layer 80 and the front panel 90.

As long as the front panel 90 is a plate-like body capable of transmitting light, the material and thickness are not limited. The front panel 90 can be composed of only one layer, or can be composed of more than two layers. As the front panel 90, a plate-like body made of resin (such as a resin plate, a resin sheet, a resin film, etc.), a plate-like body made of glass (such as a glass plate, a glass film, etc.), and a laminate of a plate-like body made of resin and a plate-like body made of glass can be cited. The front panel can constitute the outermost surface of the display device.

The thickness of the front panel 90 is, for example, 1000 μm or less, or preferably 800 μm or less. The thickness is usually 10 μm or more, or preferably 20 μm or more.

As the resin constituting the plate-like body of resin, for example, triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, levulinyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly(methyl) acrylic resin (Japanese: ポリ(メタ)アクリル), polyimide, polyether sulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyether sulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, thermoplastic resins such as polyamide-imide can be enumerated. These thermoplastic resins can be used alone or in combination with two or more. From the viewpoint of improving strength and transparency, the plate-like body of resin is preferably a thermoplastic resin film formed by polyimide, polyamide, polyamide-imide, etc.

From the viewpoint of hardness, front panel 90 can be a thermoplastic resin film with hard coating. Hard coating can be formed on one side of thermoplastic resin film, and can also be formed on both sides. By arranging hard coating, hardness and scratch resistance can be improved. About hard coating, quote the above-mentioned record about the hard coating that can be formed on thermoplastic resin film.

When the front panel 90 is a glass plate, the glass plate is preferably tempered glass for display. The thickness of the glass plate can be, for example, 10 μm to 1000 μm, or 10 μm to 800 μm. By using a glass plate, a front panel having excellent mechanical strength and surface hardness can be formed.

The front panel 90 preferably has high rigidity, for example, the Young's modulus is 70GPa or more, and can also be 80GPa or more. The Young's modulus of the front panel 90 is usually less than 100GPa. The Young's modulus can be measured as follows. Use a super cutter to cut out a measurement sample of the front panel 60 with a long side of 110mm×short side of 10mm. Next, use the upper and lower clamps of a tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-Xplus testing machine) to clamp the two ends of the long side direction of the above-mentioned measurement sample in a manner such that the interval between the clamps becomes 5cm. Under an environment of temperature 23°C and relative humidity 55%, stretch along the length direction of the measurement sample at a stretching speed of 4mm/min. According to the slope of the straight line between 20 and 40MPa in the obtained stress-strain curve, the Young's modulus at a temperature of 23°C and a relative humidity of 55% can be calculated.

In the case where the optical functional layer (A) 1 includes a front panel 90 laminated on the observation side of the high refractive index layer 1a via a sixth bonding layer 80, from the viewpoint that slight light leakage is not easily observed, the refractive index of the sixth bonding layer 80 at a wavelength of 550 nm is preferably 1.45 to 1.51, more preferably 1.46 to 1.50, and the refractive index of the front panel 90 at a wavelength of 550 nm is preferably 1.49 to 1.52, more preferably 1.50 to 1.52. The sixth bonding layer 80 is preferably an adhesive layer.

When the optical laminate is applied to an image display device, the front panel 90 not only has the function of protecting the front face (screen) of the image display device (function as a window film), but can also have functions as a touch sensor, a blue light cutoff function, a viewing angle adjustment function, etc.

(8) Lamination layer

The optical laminate may include a laminating layer for joining two layers (or films). As the laminating layer, there may be mentioned a first laminating layer 10 for laminating the optical functional layer (A) 1 to the linear polarizer 2, a second laminating layer 20 for laminating the linear polarizer 2 (or protective film 12) to the phase difference layer 3, a third laminating layer 30 for laminating the substrate film 1b to the thermoplastic resin film 11, a fourth laminating layer 40 for laminating the linear polarizer 2 to the protective film 12, a fifth laminating layer 3c for laminating the first phase difference layer 3a to the second phase difference layer 3b, and a sixth laminating layer 80 for laminating the front panel 90.

The laminating layer is an adhesive layer composed of an adhesive composition or an adhesive layer composed of an adhesive composition. The description of the adhesive composition and the adhesive layer is as described in the above (4) .

As the adhesive composition, for example, water-based adhesives, active energy ray-curable adhesives, etc. can be cited. As the water-based adhesive, for example, polyvinyl alcohol resin aqueous solution, water-based two-component urethane emulsion adhesive, etc. can be cited. Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, and for example, adhesives containing polymerizable compounds and photopolymerization initiators, adhesives containing photoreactive resins, adhesives containing binder resins and photoreactive crosslinking agents can be cited. As the above-mentioned polymerizable compounds, photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth) acrylic monomers, photocurable urethane monomers, and oligomers derived from these monomers can be cited. As the above-mentioned photopolymerization initiator, compounds containing substances that generate active species such as neutral free radicals, anionic free radicals, and cationic free radicals by irradiating active energy rays such as ultraviolet rays can be cited.

The thickness of the bonding layer composed of the adhesive composition may be, for example, 0.1 μm or more, preferably 0.5 μm or more, 1 μm or more or 2 μm or more, and may be 100 μm or less, 50 μm or less, 25 μm or less, 15 μm or less or 5 μm or less.

The two opposing surfaces to be bonded together via the bonding layer may be subjected to surface activation treatment such as corona treatment, plasma treatment, or flame treatment in advance.

＜Image display device＞

The image display device of the present invention comprises the optical laminate of the present invention and an image display element (organic EL display element, etc.). The optical laminate is disposed on the viewing side of the image display element. The optical laminate can be bonded to the image display element using an adhesive layer 50 .

Fig. 6 is a schematic cross-sectional view showing an example of an image display device of the present invention. In Fig. 6, as an example of an optical laminate, the optical laminate shown in Fig. 5 is used. The optical laminate is bonded to the image display element 100 using its adhesive layer 50. On the surface of the optical laminate opposite to the adhesive layer 50 (the outermost surface on the observation side), a front panel 90 is laminated with the sixth bonding layer 80.

The image display device is not particularly limited, and examples thereof include image display devices such as organic electroluminescent (organic EL) display devices, inorganic electroluminescent (inorganic EL) display devices, liquid crystal display devices, and electroluminescent display devices.

Image display devices can be used as mobile devices such as smartphones and tablets, televisions, digital photo frames, electronic billboards, measuring instruments or measuring instruments, office equipment, medical equipment, computer equipment, and the like.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Measurement]

(1) Reflectivity of the optical functional layer

The reflectance R(450) and reflectance R(550) of the optical functional layer were measured using "Cm2600d" manufactured by Konica Minolta Inc. During the measurement, a black acrylic plate ("KANASE LITE 1410" manufactured by KANASE Co., Ltd.) was attached to the surface of the optical functional layer opposite to the surface on which incident light was incident via an adhesive layer.

(2) Refractive index and optical film thickness

The refractive index at a wavelength of 550nm of the film and layer is measured as follows. The spectrophotometer "MPC-2200" made by Shimadzu Corporation is used to measure the reflectivity in the visible light region. During the measurement, a black acrylic plate ("KANASE LITE 1410" made by KANASE Co., Ltd.) is attached to the back side of the measurement surface with the aid of an adhesive layer. For the obtained reflection spectrum, a spectrum fitting is performed to make the reflectivity of the spectrum calculated according to the calculation formula of the thin film interference spectrum, in particular, at a wavelength of 550nm consistent, and the refractive index and optical film thickness at a wavelength of 550nm are calculated. However, with respect to laminate B-1, the refractive index and optical film thickness at a wavelength of 550nm of the high refractive index layer are measured by the following method.

(3) Phase difference characteristics of phase difference layer

The retardation characteristics of the retardation layer were measured using “KOBRA-WPR” manufactured by Oji Scientific Instruments Co., Ltd.

Hereinafter, in the present examples and comparative examples, the optical functional layers in the optical layered bodies obtained from the layered bodies A-1 to A-5, B-1 and B-2 are referred to as optical functional layers A-1' to A-5', B-1' and B-2', respectively.

<Production Example 1: Preparation of Optical Functional Layer>

(1) Preparation of high refractive index layer forming composition

In each of the following examples, the high refractive index layer-forming composition was prepared by the following steps.

A photopolymerization initiator ("Irgacure 184" manufactured by BASF) and a diluent solvent (methyl ethyl ketone/propylene glycol monomethyl ether acetate mass ratio = 5/1) were mixed and stirred. An ultraviolet curable resin ("KAYARAD-DPHA" manufactured by Nippon Kayaku Co., Ltd.) was added and stirred. In addition, a zirconium oxide particle dispersion ("ZRMIBK15WT%-P03" manufactured by CIK-Nano Tek, solid content 15% by mass, average primary particle size 7.8 nm) was added and stirred to prepare a composition for forming a high refractive index layer.

(2) Preparation of Laminated Materials A-1 to A-5

On a triacetylcellulose film (refractive index 1.49 at a wavelength of 550nm, hereinafter also referred to as a "TAC film") having a thickness of 40μm as a substrate film, a high refractive index layer forming composition was applied using a rod coater, dried, and irradiated with ultraviolet light, thereby producing a laminate A-1 consisting of a substrate film and a high refractive index layer having an optical film thickness shown in Table 1. Similarly, a high refractive index layer forming composition was applied to the TAC film, dried, and irradiated with ultraviolet light, thereby producing laminates A-2 to A-5. The refractive index and optical film thickness of the high refractive index layer at a wavelength of 550nm are shown in Table 1.

(3) Preparation of optical functional layers A-1' to A-5'

On the surface of the laminate A-1 opposite to the high refractive index layer (i.e., the surface on the substrate film side), a cyclic polyolefin resin film (HC-COP) with a hard coating layer [in-plane phase difference Re at a wavelength of 590nm: 100nm, thickness of HC layer: 3μm] was bonded via an adhesive layer (refractive index at a wavelength of 550nm: 1.47). In addition, an adhesive layer (refractive index at a wavelength of 550nm: 1.47, haze 0.2%) was laminated on the high refractive index layer of the laminate A-1. An alkali-free glass plate (refractive index at a wavelength of 550nm: 1.51) was bonded to the adhesive layer to obtain an optical functional layer A-1' consisting of glass plate/adhesive layer/high refractive index layer/substrate film/adhesive layer/HC-COP.

An optical function layer A-2' was obtained in the same manner as above except that the laminate A-2 was used.

An optical function layer A-3' was obtained in the same manner as above except that the laminate A-3 was used.

An optical function layer A-4' was obtained in the same manner as above except that the laminate A-4 was used.

An optical function layer A-5' was obtained in the same manner as above except that the laminate A-5 was used.

(4) Preparation of optical functional layers A-2" to A-5"

A cyclic polyolefin resin film (HC-COP) with a hard coating (HC) layer was bonded to the surface of the laminate A-2 opposite to the high refractive index layer (i.e., the surface on the substrate film side) via an adhesive layer (refractive index 1.47 at a wavelength of 550 nm), thereby obtaining an optical functional layer A-2 consisting of high refractive index layer/substrate film/adhesive layer/HC-COP.

An optical function layer A-3" was obtained in the same manner as above except that the laminate A-3 was used.

An optical function layer A-4" was obtained in the same manner as above except that the laminate A-4 was used.

An optical function layer A-5" was obtained in the same manner as above except that the laminate A-5 was used.

(5) Preparation of Optical Functional Layer B-1"

As laminate B-1, "TECHNOLLOY C000" (polycarbonate resin film, total thickness: 75 μm) manufactured by Sumika Acryl Co., Ltd. was used (a single-layer film, for convenience, referred to as laminate B-1). The refractive index and optical film thickness of laminate B-1 at a wavelength of 550 nm are shown in Table 1. The optical film thickness was measured using a contact thickness meter. The refractive index was measured in accordance with JIS K7142.

A cyclic polyolefin resin film (HC-COP) with a hard coating layer was bonded to one side of the laminate B-1 via an adhesive layer (refractive index 1.47 at a wavelength of 550 nm) to obtain an optical functional layer B-1 consisting of laminate B-1/adhesive layer/HC-COP.

(6) Preparation of Optical Functional Layer B-2"

The composition for forming a high refractive index layer was applied on a TAC film (refractive index 1.49 at a wavelength of 550 nm) having a thickness of 40 μm as a substrate film using a bar coater, dried, and irradiated with ultraviolet light to prepare a laminate B-2 consisting of a substrate film and a high refractive index layer having an optical film thickness shown in Table 1. The refractive index and optical film thickness of the high refractive index layer at a wavelength of 550 nm are shown in Table 1.

A cyclic polyolefin resin film (HC-COP) with a hard coating layer was bonded to one side of the laminate B-2 via an adhesive layer (refractive index 1.47 at a wavelength of 550 nm) to obtain an optical functional layer B-2 consisting of laminate B-2/adhesive layer/HC-COP.

[Table 1]

Table 2 shows the reflectivity R(450), reflectivity R(550) and reflectivity R(630) of each optical functional layer, as well as the reflectivity ratio (reflectivity R(450)/reflectivity R(550)).

[Table 2]

<Production Example 2: Preparation of Linear Polarizing Plate>

(1) Fabrication of linear polarizer

A 20 μm thick polyvinyl alcohol resin film (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) was longitudinally uniaxially stretched to about 5 times by dry stretching, and then immersed in pure water at a temperature of 60°C for 1 minute while maintaining the tension state, and then immersed in an aqueous solution at a temperature of 28°C with a mass ratio of iodine/potassium iodide/water of 0.05/5/100 for 60 seconds. Then, it was immersed in an aqueous solution at a temperature of 72°C with a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100 for 300 seconds. Then, after washing with pure water at a temperature of 26°C for 20 seconds, it was dried at a temperature of 65°C to obtain a linear polarizer with a thickness of 8 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol resin film. The obtained linear polarizer had a visibility-corrected single transmittance Ty of 42.5%, a visibility-corrected polarization degree Py of 99.99%, an orthogonal hue a* of 0.1, and an orthogonal hue b* of -0.3.

(2) Preparation of water-based adhesive

A polyvinyl alcohol aqueous solution was prepared by dissolving 3 parts by mass of carboxyl-modified polyvinyl alcohol ("KL-318" manufactured by Kuraray Co., Ltd.) in 100 parts by mass of water. A water-soluble polyamide epoxy resin ("Sumirez Resin 650 (30)" manufactured by Taoka Chemical Industry Co., Ltd., solid content concentration 30% by mass) was mixed in the obtained aqueous solution at a ratio of 1.5 parts by mass to 100 parts by mass of water to obtain a water-based adhesive.

(3) Fabrication of linear polarization plates

The above-obtained water-based adhesive is applied to one side of the above-obtained linear polarizer, and a cyclic polyolefin resin film (HC-COP) with a hard coating (HC) layer is laminated. The above-obtained water-based adhesive is applied to the other side of the linear polarizer, and a TAC film is laminated, and dried at a temperature of 80°C for 5 minutes, thereby obtaining a linear polarizer having protective films on both sides of the linear polarizer. The layer structure of the linear polarizer is HC-COP/water-based adhesive layer/linear polarizer/water-based adhesive layer/TAC film. A protective film having an adhesive layer on a substrate film is laminated on the HC layer of the linear polarizer to obtain a linear polarizer with a protective film (hereinafter also referred to as a "linear polarizer with PF").

In addition, in this linear polarizing plate, the reflectance of the water-based adhesive layer was not measured to a significant value.

<Production Example 3: Preparation of Phase Difference Layer Laminated Body>

(1) Preparation of the first phase difference layer

An orientation layer is formed on a first substrate layer comprising a transparent resin, and a first phase difference layer forming composition comprising a rod-shaped nematic polymerizable liquid crystal compound is applied to prepare a first phase difference layer with a first substrate layer. The first phase difference layer is a λ/4 layer. The thickness of the first phase difference layer is 2 μm. The wavelength dispersion α of the first phase difference layer [in-plane phase difference value Re(450)/in-plane phase difference value Re(550)] is 0.85, and Re(550) is 142 nm (average value at 12 points in the plane).

In addition, the first phase difference layer was cut into 140 mm × 70 mm, and the in-plane phase difference value of the first phase difference layer was measured at 12 locations in the plane. The deviation of the in-plane phase difference value Re (550) was measured and calculated, and the maximum was 143 nm and the minimum was 141 nm. The difference between the maximum and the minimum was 2 nm. The details of the preparation of the first phase difference layer are shown below.

[Preparation of Alignment Layer Forming Composition (X)]

The photo-alignment material (weight average molecular weight: 50000, m:n=50:50) of the following structure was produced according to the method described in Japanese Patent Application Laid-Open No. 2021-196514. 2 parts by mass of the photo-alignment material and 98 parts by mass of cyclopentanone (solvent) were mixed as components, and the obtained mixture was stirred at 80° C. for 1 hour to prepare a composition (X) for forming an alignment layer.

Photo-oriented materials:

[Chemical formula 1]

[Manufacturing of Nematic Polymerizable Liquid Crystal Compound]

A polymerizable liquid crystal compound (A1) and a polymerizable liquid crystal compound (A2) having the structures shown below were prepared respectively. The polymerizable liquid crystal compound (A1) was prepared in the same manner as described in Japanese Patent Application Laid-Open No. 2019-003177. The polymerizable liquid crystal compound (A2) was prepared in the same manner as described in Japanese Patent Application Laid-Open No. 2009-173893.

Polymerizable liquid crystal compound (A1):

[Chemical formula 2]

Polymerizable liquid crystal compound (A2):

[Chemical formula 3]

1 mg of polymerizable liquid crystal compound (A1) was dissolved in 10 mL of chloroform to obtain a solution. The obtained solution was added to a measuring cuvette with an optical path length of 1 cm as a measuring sample, and the measuring sample was set in an ultraviolet visible spectrophotometer ("UV-2450" manufactured by Shimadzu Corporation) to measure the absorption spectrum. The wavelength of the maximum absorbance was read from the obtained absorption spectrum, and the maximum absorption wavelength λmax in the range of 300 to 400 nm was 356 nm.

[Preparation of the first phase difference layer forming composition (Y)]

The polymerizable liquid crystal compound (A1) and the polymerizable liquid crystal compound (A2) were mixed in a mass ratio of 93:7 to obtain a mixture. 0.1 mass parts of a leveling agent "BYK-361N" (manufactured by BM Chemie) and 3 mass parts of "Irgacure OXE-03" (manufactured by BASF Japan Co., Ltd.) as a photopolymerization initiator were added to 100 mass parts of the obtained mixture. In addition, N-methyl-2-pyrrolidone (NMP) was added in such a manner that the solid content concentration became 13 mass%. The mixture was stirred at a temperature of 80°C for 1 hour to prepare a first phase difference layer forming composition (Y).

[Production of the first phase difference layer]

The above-mentioned composition (X) for forming an alignment layer was applied to a biaxially stretched polyethylene terephthalate (PET) film (DIAFOIL manufactured by Mitsubishi Resins Co., Ltd.) as the first substrate layer using a rod coater. The obtained coating film was dried at 120°C for 2 minutes and then cooled to room temperature to form a dry film. Then, a UV irradiation device (SPOT CURE SP-9; manufactured by USHIO Electric Co., Ltd.) was used to irradiate 100mJ (313nm reference) of polarized ultraviolet light to obtain an alignment layer. The film thickness of the alignment layer measured using an ellipsometer M-220 manufactured by JASCO Corporation was 100nm.

The above-mentioned first phase difference layer forming composition (Y) was applied to the obtained orientation layer using a rod coater to form a coating film. The coating film was heated and dried at 120°C for 2 minutes, and then cooled to room temperature to obtain a dry film. Next, a high-pressure mercury lamp ("Unicure VB-15201BY-A" manufactured by USHIO Electric Co., Ltd.) was used to irradiate the above-mentioned dry film with ultraviolet light with an exposure amount of 500mJ/ ^cm2 (365nm reference) under a nitrogen atmosphere, thereby forming a first phase difference layer in which the polymerizable liquid crystal compound was cured in a state of being oriented in a horizontal direction relative to the substrate surface, and a first phase difference layer with a first substrate layer composed of a first substrate layer/orientation layer/first phase difference layer (horizontally oriented liquid crystal cured film) was obtained. The film thickness of the first phase difference layer measured using a laser microscope LEXT OLS4100 manufactured by Olympus Corporation was 2.0μm.

(2) Preparation of the Second Phase Difference Layer

The second retardation layer with the second base layer was produced by the following method.

[Preparation of the second phase difference layer forming composition (Y2)]

100 parts by mass of a polymerizable liquid crystal compound Paliocolor LC242 (manufactured by BASF Japan), 0.1 parts by mass of a leveling agent "BYK-361N" (manufactured by BYK-Chemie) and 2.5 parts by mass of a photopolymerization initiator "Omnirad907" (manufactured by IGM Resin B.V.) were mixed. In addition, 400 parts by mass of propylene glycol 1-monomethyl ether 2-acetate (PGME) was added, and the resulting mixture was stirred at a temperature of 80° C. for 1 hour to prepare a second phase difference layer forming composition (Y2).

Polymerizable liquid crystal compound LC242:

[Chemical formula 4]

[Preparation of Alignment Layer Forming Composition (X2)]

2-Butoxyethanol was added to SUNEVER SE-610 (manufactured by Nissan Chemical Industries, Ltd.), a commercially available aligning polymer, so that the solid content became 1% by mass, to obtain an alignment layer-forming composition (X2).

[Production of the Second Phase Difference Layer]

As the second substrate layer, a cycloolefin polymer (COP) (ZF14 manufactured by ZEON Co., Ltd. of Japan) was used. A corona treatment device (AGF-B10; manufactured by Kasuga Electric Co., Ltd.) was used to perform a corona treatment on one side. The composition for forming an alignment layer (X2) was applied on the surface using a rod coater and dried at 90°C for 1 minute. The film thickness of the obtained alignment layer was measured using a laser microscope, and the result was 30 nm. Next, the composition for forming a second phase difference layer (Y2) was applied on the alignment layer using a rod coater. After drying at 90°C for 1 minute, a high-pressure mercury lamp ("Unicure VB-15201BY-A" manufactured by USHIO Electric Co., Ltd.) was used to irradiate the dried film with ultraviolet light at an exposure amount of 1000 mJ/cm ² (365 nm reference) in a nitrogen atmosphere, thereby obtaining a second phase difference layer with a second substrate layer. The film thickness was measured using a laser microscope, and the film thickness of the second phase difference layer was 450 nm. The in-plane phase difference value was measured using KOBRA-WR manufactured by Oji Instruments Co., Ltd. The results were Re(550)=1nm, Rth(550)=-75nm. Therefore, the second phase difference layer with the second substrate layer has the optical properties shown by nx≈ny＜nz. It should be noted that the phase difference value at a wavelength of 550nm of COP is approximately 0, so it has no effect on the optical properties.

(3) Preparation of UV-curable adhesive

The cationic curable components shown below were mixed to prepare an ultraviolet curable adhesive.

3',4'-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name: CEL2021P, manufactured by Daicel Corporation): 70 parts by mass

Neopentyl glycol diglycidyl ether (trade name: EX-211, manufactured by Nagase ChemteX Corporation): 20 parts by mass

2-Ethylhexyl glycidyl ether (trade name: EX-121, manufactured by Nagase ChemteX Corporation): 10 parts by mass

Cationic polymerization initiator (trade name: CPI-100, 50% solution, manufactured by San-Apro Co., Ltd.): 4.5 parts by mass (substantial solid content: 2.25 parts by mass)

1,4-diethoxynaphthalene: 2.0 parts by mass

(4) Preparation of Phase Difference Layer Laminate

The phase difference layer side of the first phase difference layer with the first substrate layer and the phase difference layer side of the second phase difference layer with the second substrate layer were subjected to corona treatment, respectively. The prepared ultraviolet curable adhesive was applied to one of the corona treated surfaces, and the first phase difference layer with the first substrate layer and the second phase difference layer with the second substrate layer were bonded together. The ultraviolet curable adhesive was cured by irradiating ultraviolet rays from the second substrate layer side to form an adhesive layer. The thickness of the cured ultraviolet curable adhesive layer was 1.5 μm.

<Example 1>

(1) Preparation of optical laminate

An adhesive layer (A(410)=1.10, thickness 15 μm) containing a light selective absorber was bonded to the surface of the TAC film side of the linear polarizing plate obtained in Production Example 2. Next, the first substrate layer of the phase difference laminate obtained in Production Example 3 was peeled off and removed, and the linear polarizing plate was laminated on the exposed orientation layer in such a manner that the adhesive layer containing a light selective absorber was in contact with the linear polarizing plate.

Next, on the HC layer of the linear polarizing plate, the laminate A-1 was laminated in contact with the TAC film side with the aid of an adhesive layer (storage modulus: 25500 Pa, refractive index 1.47 at a wavelength of 550 nm, haze 0.2%, and no light selective absorber). In addition, an adhesive layer (storage modulus: 25500 Pa, refractive index 1.47 at a wavelength of 550 nm, haze 0.2%, and no light selective absorber) was laminated on the high refractive index layer of the laminate A-1. An alkali-free glass plate (refractive index 1.51 at a wavelength of 550 nm) was bonded to the adhesive layer to obtain an optical laminate containing an optical functional layer A-1'.

(2) Measurement and evaluation of reflection characteristics

The reflectivity Y and the reflection hues a* and b* of the optical laminate obtained in (1) above were measured using "Cm2600d" manufactured by Konica Minolta. The results are shown in Table 4. During the measurement, a glass plate (thickness 0.7 mm, "EAGLE XG" manufactured by Corning) was bonded to the surface of the optical laminate opposite to the surface of the incident light (the surface of the optical laminate opposite to the optical functional layer) with the aid of an adhesive layer (storage modulus: 25500 Pa, refractive index 1.47 at a wavelength of 550 nm, haze 0.2%, and no light selective absorber). The optical laminate with the glass plate obtained above was placed on a reflector (reflectivity: 96% or more, diffuse reflectivity: 9% or less) with the optical functional layer facing upward, and the measurement was performed in a state where the layer structure was set to reflector/air/glass plate/optical laminate. The reflectivity Y of the optical laminate was evaluated according to the following criteria. The results are shown in Table 4.

A: The reflectance Y is less than 6.0%.

B: The reflectance Y is 6.0% or more.

(3) Measurement and evaluation of light leakage

The second substrate layer was peeled off from the optical laminate obtained in (1) above, and an aluminum foil ("マイホイル重形50", 20 μm thick, aluminum foil manufactured by UACJ Co., Ltd.) as a reflector was laminated on its non-glossy side on the exposed surface. The state of slight light leakage was visually observed from a point 30 cm upward from the observation side (the side opposite to the aluminum foil) of the optical laminate under a fluorescent lamp, and evaluated according to the following criteria. The results are shown in Table 4.

A: No light leakage was observed.

B: Light leakage was observed.

<Examples 2, 3, 5, 6>

Optical laminates including optical functional layers A-2', A-3', A-4', and A-5' were prepared in the same manner as in Example 1, except that laminates A-2, A-3, A-4, and A-5 were used instead of laminate A-1, respectively, and the reflection characteristics and light leakage were measured and evaluated. The results are shown in Table 4.

<Example 4>

An adhesive layer (A(410)=1.10, thickness 15 μm) containing a light selective absorber was bonded to the surface of the TAC film side of the linear polarizing plate obtained in Production Example 2. Next, the first substrate layer of the phase difference laminate obtained in Production Example 3 was peeled off and removed, and the linear polarizing plate was laminated on the exposed orientation layer in such a manner that the adhesive layer containing a light selective absorber was in contact with the linear polarizing plate.

Next, on the HC layer of the linear polarizing plate, a laminate A-3 was laminated in contact with the TAC film side with the aid of an adhesive layer (storage modulus: 25500 Pa, refractive index at a wavelength of 550 nm: 1.47, haze: 0.2%, and containing no light selective absorber), to obtain an optical laminate containing an optical functional layer A-3″.

<Examples 7 and 8>

Optical laminates including optical functional layers A-4″ and A-2″ were prepared in the same manner as in Example 4 except that laminates A-4 and A-2 were used instead of laminate A-3, and the reflection characteristics and light leakage were measured and evaluated. The results are shown in Table 4.

<Comparative Example 1>

The surface of the linear polarizing plate obtained in Manufacturing Example 2 on the TAC film side was bonded with an adhesive layer containing a light selective absorber (A(410)=1.10, thickness 15 μm). Next, the first substrate layer of the phase difference laminate obtained in Manufacturing Example 3 was peeled off and removed, and the above-mentioned linear polarizing plate was laminated on the exposed orientation layer in a manner that the adhesive layer containing a light selective absorber was in contact with the linear polarizing plate to prepare an optical laminate. The reflection characteristics and light leakage were measured and evaluated in the same manner as in Example 1. The results are shown in Table 4.

<Comparative Example 2>

An alkali-free glass plate (refractive index at a wavelength of 550 nm: 1.51) was laminated on the linear polarizing plate of the optical laminate of Comparative Example 1 via an adhesive layer (storage modulus: 25500 Pa, refractive index at a wavelength of 550 nm: 1.47, haze: 0.2%, and containing no light selective absorber) to prepare an optical laminate, and the reflection characteristics and light leakage were measured and evaluated in the same manner as in Example 1. The results are shown in Table 4.

For the following partial stacking structures contained in the optical stacks of Comparative Examples 1 and 2, the reflectivity R(450), reflectivity R(550) and reflectivity R(630), as well as the reflectivity ratio (reflectivity R(450)/reflectivity R(550)) were measured. The results are shown in Table 3.

Comparative Example 1: HC-COP

Comparative Example 2: Glass plate/adhesive layer/HC-COP

[table 3]

<Comparative Examples 3 to 5>

Optical laminates each including optical functional layers B-1″, B-2″, and A-5″ were prepared in the same manner as in Example 4 except that laminates B-1, B-2, and A-5 were used instead of laminate A-3, and the reflection characteristics and light leakage were measured and evaluated. The results are shown in Table 4.

[Table 4]

Description of Reference Numerals

1: optical functional layer (A), 1a: high refractive index layer, 1b: substrate film, 2: linear polarizer, 3: phase difference layer, 3a: first phase difference layer, 3b: second phase difference layer, 3c: fifth bonding layer, 10: first bonding layer, 11: thermoplastic resin film, 12: protective film, 20: second bonding layer, 30: third bonding layer, 40: fourth bonding layer, 50: adhesive layer, 60: diaphragm, 70: protective film, 80: sixth bonding layer, 90: front panel, 100: image display element.

Claims (10)

1. An optical laminate comprising, in order, an optical functional layer A, a linear polarizer and a retardation layer having inverse wavelength dispersion,

Ratio of reflectance R (450) at wavelength 450nm to reflectance R (550) at wavelength 550nm of the optical functional layer a: r (450)/R (550) is 1.07 or more and 1.55 or less,

The reflectivity R (550) is less than 6.0%.

2. The optical laminate according to claim 1, wherein the optical functional layer a comprises a high refractive index layer having a refractive index of 1.6 or more at a wavelength of 550 nm.

3. The optical laminate according to claim 2, wherein the optical functional layer a comprises a base film and the high refractive index layer laminated on the base film.

4. The optical stack according to claim 1, wherein the ratio of the reflectivity R (450) to the reflectivity R (550): r (450)/R (550) is 1.07 or more and 1.35 or less.

5. The optical laminate according to claim 1, wherein the retardation layer comprises 1 or more cured layers of liquid crystal.

6. The optical laminate according to claim 1, wherein the optical functional layer a further comprises a front panel.

7. The optical laminate according to claim 1, further comprising an adhesive layer disposed on an opposite side of the retardation layer from the linear polarizer.

8. The optical laminate according to claim 7, further comprising a separator disposed on an opposite side of the adhesive layer from the phase difference layer.

9. The optical laminate according to claim 1, further comprising a protective film on a surface of the optical functional layer a opposite to the linear polarizer.

10. An image display device comprising the optical laminate according to any one of claims 1 to 9.