CN112748601B

CN112748601B - Image display device

Info

Publication number: CN112748601B
Application number: CN202011167808.0A
Authority: CN
Inventors: 出崎光
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-10-31
Filing date: 2020-10-27
Publication date: 2024-04-26
Anticipated expiration: 2040-10-27
Also published as: CN112748601A

Abstract

The invention provides an image display device capable of further suppressing oblique chromatic aberration. An image display device according to one aspect includes a light-reflective image display layer, a phase difference film, and a polarizing film, wherein an angle between an absorption axis of the polarizing film and an in-plane slow axis of the phase difference film is 45 degrees + -5 degrees, and when an in-plane retardation of the phase difference film is R0, a plane orthogonal to a direction of an inclination angle θ with respect to a thickness direction of the phase difference film is a projection plane, and an in-plane fast axis and an in-plane slow axis of the phase difference film are assumed to be rotation axes, the following formulas (i) to (i) are satisfied when an in-plane retardation of the phase difference film in the projection plane is R (θ) _fast and R (θ) _slow, and an in-plane retardation of the light-reflective image display layer in the projection plane is R (θ) M (iv).α＝R0-{R(θ)_fast+R(θ)M}…(i)β＝R0-{R(θ)_slow-R(θ)M}…(ii)|α(θ)|+|β(θ)|＜10nm…(iii)|R(θ)M|＞0nm…(iv).

Description

Image display device

Technical Field

The present invention relates to an image display device.

Background

In a flat panel display device, an optical laminate in which a retardation film and a polarizing film are laminated is provided for optical compensation of the display device. For example, in both flat panel display devices and organic Electroluminescence (EL) image display devices, such an optical laminate is used in which an internally reflected light reflected from the outside toward the visual recognition side through a light-reflective image display layer incorporated in the inside is reduced, and the light-reflective image display layer is laminated on the visual recognition side. As such an optical laminate, for example, an elliptical polarizing plate as described in patent document 1 is known.

Prior art literature

Patent literature

Patent document 1: JP-A2015-163940

In a flat panel display device, for example, in an organic EL image display device, when a screen is viewed from the front direction and when a screen is viewed from the oblique direction, the reflection color of the internal reflection light which is slightly reflected from the internal reflective image display layer and reaches the visual recognition side is different, and further, a reflection color corresponding to the in-plane angle is generated in the oblique direction. The maximum value of the color difference of the reflected color corresponding to the in-plane angle is referred to as an oblique color difference in the oblique direction. By disposing an optical laminate as described in patent document 1 on an image display surface of a display device, skew color is suppressed. However, in recent years, further suppression of oblique chromatic aberration has been sought.

Disclosure of Invention

The invention aims to provide an image display device capable of further inhibiting oblique chromatic aberration.

An image display device according to one aspect of the present invention includes: a light reflective image display layer; and a retardation film and a polarizing film provided on an image display surface of the light-reflective image display layer, wherein an angle between an absorption axis of the polarizing film and an in-plane slow axis of the retardation film is 45 degrees + -5 degrees, an in-plane retardation of the retardation film is R0, a plane orthogonal to a direction of an inclination angle θ with respect to a thickness direction of the retardation film is a projection plane, an in-plane retardation of the retardation film in the projection plane is R (θ) _fast when an in-plane fast axis of the retardation film is assumed to be a rotation axis, an in-plane retardation of the retardation film in the projection plane is R (θ) _slow when the in-plane slow axis of the retardation film is assumed to be a rotation axis, and an in-plane retardation of the light-reflective image display layer in the projection plane is R (θ) M, and the following formulas (i) to (iv) are satisfied.

α＝R0-{R(θ)_fast+R(θ)M}…(i)

β＝R0-{R(θ)_slow-R(θ)M}…(ii)

|α(θ)|+|β(θ)|＜10nm…(iii)

|R(θ)M|＞0nm…(iv)

In the above-described configuration, the in-plane retardation of the retardation film is considered and the in-plane retardation of the light-reflective image display layer is considered. For this reason, by providing the phase difference film and the polarizing film on the light reflection image display layer, the oblique chromatic aberration can be sufficiently suppressed.

The R0, the R (θ) _fast, the R (θ) _slow, and the R (θ) M may be retardation at a wavelength of 550nm, for example.

The inclination angle θ may be 50 degrees.

An image display device according to another aspect of the present invention includes: a light reflective image display layer; and a retardation film and a polarizing film provided on an image display surface of the light-reflective image display layer, wherein an angle between an absorption axis of the polarizing film and an in-plane slow axis of the retardation film is 45 degrees.+ -.5 degrees, an in-plane retardation of the retardation film is R0, a retardation in a thickness direction of the retardation film is Rth, a plane orthogonal to a direction inclined at 50 degrees with respect to the thickness direction of the retardation film is a projection surface, an in-plane retardation of the light-reflective image display layer in the projection surface is R (50) M, and the Nz and the ρ are represented by the formula (v) and the formula (vi), and when the Nz and the ρ satisfy the formula (vii), the formula (viii) and the formula (ix), or satisfy the formula (vii), the formula (x) and the formula (xi), the R0, the Rth and the R (50) M are retardation with respect to a wavelength of 550 nm.

Nz＝(Rth/R0)+0.5…(v)

ρ＝R(50)M/R0…(vi)

3.5ρ+0.39＜Nz＜3.5ρ+0.65…(vii)

ρ＞0…(viii)

0.5＜Nz≤1.5…(ix)

ρ＜0…(x)

-1.5＜Nz＜0.5…(xi)

In the above structure, the in-plane retardation of the light-reflective image display layer is considered. For this reason, by providing the phase difference film and the polarizing film on the light reflection image display layer, the oblique chromatic aberration can be sufficiently suppressed.

The retardation film may have an a plate and a C plate.

The retardation film and the polarizing film may form a circular polarizing plate.

According to the present invention, an image display device capable of further suppressing oblique chromatic aberration can be provided.

Drawings

Fig. 1 is a schematic diagram showing a schematic configuration of an image display device according to an embodiment.

Fig. 2 is a diagram showing the relationship between the slow axis and the fast axis and the absorption axis of the polarizing film.

Fig. 3 is a drawing for explaining a projection surface.

Fig. 4 is a diagram for explaining a phase difference in oblique view.

Fig. 5 is a diagram depicting the results shown in tables 5 to 7 in the ρ -Nz coordinate system.

Description of the reference numerals:

2 … image display devices;

4 … image display layers (light-reflective image display layers);

12 … phase difference films;

12a … slow axis (in-plane slow axis);

12b … fast axis (in-plane fast axis);

14 … polarizing films;

14a … absorption axis;

18 … a plates;

20 … C plate;

22 … projection plane.

Detailed Description

Embodiments of the present invention are described below with reference to the accompanying drawings. The same reference numerals are given to the same elements, and duplicate descriptions are omitted. The dimensional ratios in the drawings are not necessarily consistent with the description.

Fig. 1 is a schematic diagram showing a schematic configuration of an image display device 2 according to an embodiment. The image display device 2 has an image display layer (light reflective image display layer) 4 and an optical laminate 6. The image display layer 4 and the optical laminate 6 are bonded. In the embodiment shown in fig. 1, the image display layer 4 and the optical laminate 6 are bonded by an adhesive layer 8 a.

The image display layer 4 forms an image inside and displays the image on the image display surface 4a. The image display layer 4 includes an element structure or the like for forming an image. For this reason, the electrode included in the element structure, the wiring connected between the element structures, and the like function as a reflecting portion for reflecting light. For this reason, the image display layer 4 has light reflectivity that reflects light incident on the image display device 2 from the optical laminate 6 side. The thickness of the image display layer 4 is, for example, 0.2mm to 1.0mm.

The image display layer 4 is not limited in its layer structure, material, etc., as long as it is configured to form an image on the image display surface 4 a. The image display layer 4 is, for example, a multilayer body including an electrode and a wiring portion (or layer) using gold, silver, copper, iron, tin, nickel, chromium, molybdenum, titanium, aluminum, indium, or other metals, alloys thereof, oxides thereof, or the like, a resin film, a dielectric portion of a barrier (bank) member, a light emitting element, or the like, and other layers.

The image display layer 4 is, for example, a flat panel display device. Examples of the flat panel display device include a thin (or flat-panel-shaped) organic electroluminescent display device (hereinafter also referred to as an "OLED display device"), and an inorganic electroluminescent device having pixels that emit light independently (hereinafter also referred to as a "micro LED display device"). The display device exemplified as the image display layer 4 is a device in a state in which no member for optical compensation is contained on the image display surface.

In the case where the image display layer 4 is an OLED display device, typically, the electrode included in the OLED display device is the reflective portion. The OLED display device has a thin film structure in which an organic light-emitting material layer is sandwiched between a pair of electrodes facing each other. Electrons are injected from one electrode to the organic light-emitting material layer, and holes are injected from the other electrode to the organic light-emitting material layer, whereby electrons and holes are coupled to each other in the organic light-emitting material layer, and self-luminescence is performed. The electrode on the image display surface 4a side among the 2 electrodes sandwiching the organic light emitting material layer has a function of transmitting light from the organic light emitting material layer, while the other electrode has a function of reflecting light from the organic light emitting material layer toward the image display surface 4 a. Therefore, the other electrode typically functions as a reflecting portion in the OLED display device.

The OLED display device has advantages in that it has a better visibility, is thinner, and can be driven at a low dc voltage than a liquid crystal display device requiring a backlight, or the like.

In the case where the image display layer 4 is a micro LED display device, the light emitting portion including the compound semiconductor, the pixel connection portion, and the electrode portion reflect external light. Therefore, in the micro LED display device, the light emitting portion, the pixel connecting portion, and the electrode portion correspond to the reflecting portion.

[ Adhesive layer ]

The adhesive layer 8a may contain an adhesive composition containing a resin such as a (meth) acrylic, rubber, urethane, ester, silicone, or polyvinyl ether as a main component. Among these, an adhesive composition containing a (meth) acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer is suitable. The adhesive composition may be an active energy ray-curable type or a thermosetting type. The thickness of the adhesive layer 8b is usually 3 to 30. Mu.m, preferably 3 to 25. Mu.m.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, for example, a polymer or copolymer containing one or two or more types of (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate as monomers is suitably used. In the base polymer, the polar monomer is preferably copolymerized. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, acrylamide, N-2-methylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition may contain only the above base polymer, but generally further contains a crosslinking agent. Examples of the crosslinking agent include: a metal ion having a valence of 2 or more which forms a metal carboxylate with a carboxyl group; a polyamine compound forming an amide bond with a carboxyl group; forming an ester-linked polyepoxide, polyol, and carboxyl group; polyisocyanate compounds forming an amide bond with a carboxyl group. Among these, polyisocyanate compounds are preferable.

[ Optical laminate ]

The optical laminate 6 has a polarizing plate 10 and a phase difference film 12. The optical layered body 6 is an optical element for compensating an image displayed on the image display surface 4 a. The polarizing plate 10 and the retardation film 12 are joined. The polarizing plate 10 and the retardation film 12 can be joined by an adhesive layer 8b as shown in fig. 1. The adhesive layer 8b is exemplified as in the case of the adhesive layer 8 a.

[ Polarizing plate ]

The polarizing plate 10 has a polarizing film 14. The polarizing plate 10 may further have two protective films 16. The polarizing plate 10 will be described based on the configuration illustrated in fig. 1.

Polarizing film 14 has linear polarization characteristics. An example of the polarizing film 14 is a film in which a resin film stretched in one axis adsorbs an oriented dichroic dye. The polarizing film 14 is not particularly limited as long as it is a resin film having linear polarization characteristics, and may be a polarizing film used in a known polarizing plate.

Examples of the resin film included in the polarizing film 14 include a polyvinyl alcohol (hereinafter, also referred to as "PVA") based resin film, a polyvinyl acetate resin film, an ethylene/vinyl acetate resin film, a polyamide resin film, and a polyester resin film. A PVA-based resin film, particularly a PVA film, is generally used from the viewpoint of the adsorptivity and orientation of a dichroic dye.

The two protective films 16 sandwich the polarizing film 14 and protect the polarizing film 14. The two protective films 16 are, for example, resin films (for example, triacetyl cellulose (hereinafter also referred to as "TAC") films), glass covers, or glass films, respectively. The materials of the two protective films 16 may be the same or different.

The number of the protective films 16 may be one. For example, the polarizing plate 10 may be free of the protective film 16 on the retardation film 12 side.

The polarizing plate 10 may be manufactured by preparing long members, bonding the members together in a roll-to-roll (roll-to-roll) manner, and then cutting the members into a predetermined shape, or the polarizing plate 10 may be manufactured by bonding the members after cutting the members into a predetermined shape.

[ Retardation film ]

The retardation film 12 has a function of generating a certain retardation of incident light. As shown in fig. 2, the retardation film 12 has a slow axis (in-plane slow axis) 12a and a fast axis (in-plane fast axis) 12b in the film plane. The angle between the slow axis 12a and the fast axis 12b is approximately 90 degrees. The term substantially 90 degrees means 90 degrees ±5 degrees.

The retardation film 12 is arranged such that the slow axis 12a is substantially 45 degrees with respect to the absorption axis 14a of the polarizing film 14 shown by the broken line in fig. 2. The term "substantially 45 degrees" means 45±5 degrees.

Referring back to fig. 1, the retardation film 12 will be further described. The retardation film 12 is bonded to the polarizing plate 10. In the embodiment illustrated in fig. 1, the retardation film 12 is bonded to the polarizing plate 10 via the pressure-sensitive adhesive layer 8 b. The adhesive layer 8b is exemplified as in the case of the adhesive layer 8 a.

The retardation film 12 has an a plate (retardation sublayer) 18 and a C plate (retardation sublayer) 20. The a plate 18 and the C plate 20 are joined. In the form shown in fig. 1, the a plate 18 and the C plate 20 are joined by the adhesive layer 8C. In the present embodiment, the slow axis 12a and the fast axis 12b of the retardation film 12 are slow axes and fast axes in the plane of the a plate 18. In the C plate 20, the in-plane phase difference is substantially 0 (zero), and the slow axis and the fast axis are not present in the plane. In the following, unless otherwise specified, the slow axis 12a and the fast axis 12b shown in fig. 2 are used in the case of describing the refractive index anisotropy in the a plate 18 and the C plate 20.

[ A plate ]

The a plate 18 preferably has characteristics characterized by the following formulas (1) to (3). The A plate 18 can be a positive A plate and can be a lambda/4 plate. The a plate 18 preferably exhibits inverse wavelength dispersion. By providing such an a plate 18, coloring of reflected light can be suppressed. In the present embodiment, the slow axis (slow axis 12 a) of the a plate 18 is arranged at approximately 45 degrees with respect to the absorption axis 14a of the polarizing film 14. The meaning of approximately 45 degrees is as previously described.

0.80＜R0A(450)/R0A(550)＜0.93…(2)

130nm＜R0A(550)＜150nm…(3)

In the formulas (1) to (3), nx denotes a refractive index in the slow axis 12a direction, ny denotes a refractive index in the fast axis 12b direction, and nz denotes a refractive index in the thickness direction (a direction orthogonal to the slow axis 12a and the fast axis 12 b) of the a plate 18. R0A (λ) characterizes the retardation in the wavelength λnm of the a-plate 18. Thus, R0A (450) and R0A (550) in formulas (2) and (3) characterize the retardation at wavelength 450nm and wavelength 550 nm.

In addition to the case where ny and nz are exactly equal, the case where ny and nz are substantially equal is also included. Specifically, as long as the difference between ny and nz is within 0.01, it can be said that ny and nz are substantially equal.

R0A (λ) can be calculated from the refractive index n (λ) at the wavelength λnm and the thickness d1 of the a plate 18 based on the following equation.

R0A(λ)＝〔nx(λ)-ny(λ)〕×d1

R0A (450)/R0A (550) characterizes the wavelength dispersion of the A-plate 18, and is preferably 0.92 or less.

Regarding the retardation R0A (λ) of the a plate 18 at the wavelength λ nm, R0A (450) is preferably 100nm to 135nm, R0A (550) is preferably 137nm to 145nm, and R0A (650) is preferably 137 to 165. R0A (650) characterizes the retardation at a wavelength of 650 nm.

[ C plate ]

The C plate 20 preferably has characteristics characterized by the following formula (4).

The C plate 20 can be a positive C plate 20. By providing such a C plate 20, coloring of reflected light can be suppressed.

In the formula (4), nx denotes a refractive index in a direction of the slow axis 12a, ny denotes a refractive index in a direction of the fast axis 12b, and nz denotes a refractive index in a thickness direction (a direction orthogonal to the slow axis 12a and the fast axis 12 b) of the C plate 20.

In addition to the case where nx and ny are exactly equal, the case where nx and ny are substantially equal is also included. Specifically, nx and ny can be said to be substantially equal as long as the difference between nx and ny is within 0.01.

The retardation in the thickness direction of the C plate 20 is preferably-120 nm or more and 0nm or less, more preferably-110 nm or more and-10 nm or less, and still more preferably-90 nm or more and-20 nm or less at a wavelength of 550nm, although depending on the reflection characteristics of the image display layer 4.

When the retardation of the C plate 20 in the thickness direction with respect to light having a wavelength of λnm is set to RthC (λ), rthC (λ) can be calculated based on the following equation from the refractive index n (λ) at the wavelength of λnm and the thickness d2 of the C plate 20.

RthC(λ)＝{〔nx(λ)+ny(λ)〕/2-nz(λ)}×d2

RthC (450)/RthC (550) characterizes the wavelength dispersion of the C plate 20, preferably 1.5 or less, more preferably 1.1 or less. RthC (450) and RthC (550) are retardation in the thickness direction of the C plate 20 with respect to the wavelength of 450nm and the wavelength of 550nm, respectively.

In the present embodiment, the thickness of the a plate 18 and the C plate 20 can be 0.1 μm or more and 5 μm or less. When the thicknesses of the a plate 18 and the C plate 20 are within this range, sufficient durability can be obtained, and the thickness reduction of the optical laminate 6 can be contributed. Of course, the thicknesses of the a plate 18 and the C plate 20 can be adjusted so that a desired retardation in the thickness direction, such as a layer that imparts a retardation of λ/4, a layer that imparts a retardation of λ/2, a positive a plate, or a positive C plate, can be obtained.

[ Adhesive layer ]

The adhesive layer 8c may contain an adhesive used for a known retardation film. Examples of the adhesive include an aqueous adhesive and an active energy ray-curable adhesive. Instead of the adhesive layer 8c, an adhesive layer similar to the adhesive layer 8b may be used.

[ Method of Forming phase-difference film ]

The a plate 18 and the C plate 20 included in the retardation film 12 may include a composition containing a thermoplastic resin and a polymerizable liquid crystal compound described later. The a-plate 18 and the C-plate 20 preferably comprise a composition comprising a polymerizable liquid crystal compound. As the layer containing the composition containing the polymerizable liquid crystal compound, a cured layer of the polymerizable liquid crystal compound can be given.

The relationship of the formulas (1) to (3) satisfied by the a plate 18 and the relationship of the formula (4) satisfied by the C plate 20 are controlled by, for example, adjusting the types and the formulation ratio of the thermoplastic resin, the polymerizable liquid crystal compound, and the polymerizable liquid crystal compound forming the a plate 18 and the C plate 20, or adjusting the thicknesses of the a plate 18 and the C plate 20.

The layer after curing the polymerizable liquid crystal compound is formed on an alignment film provided on a substrate, for example. The substrate may be a substrate having a function of supporting an alignment film and formed into a long strip. The base material can function as a releasable support and support the phase difference film 12 for transfer. Further, the surface thereof preferably has an adhesive force of such a degree that it can be peeled off. As the base material, a resin film exemplified as a material of the protective film is given.

The thickness of the base material is not particularly limited, and is preferably in the range of 20 μm to 200 μm, for example. When the thickness of the base material is 20 μm or more, strength is imparted. On the other hand, when the thickness is 200 μm or less, the increase of processing scraps and abrasion of the cutting blade can be suppressed every time the substrate is cut to form a single substrate.

The substrate may be subjected to various anti-stick treatments. Examples of the anti-sticking treatment include an easy-to-stick treatment, a treatment for mixing a filler or the like, an embossing treatment (embossing treatment), and the like. By applying such an anti-sticking treatment to the base material, the base materials can be effectively prevented from sticking to each other when the base material is wound, that is, so-called sticking can be effectively prevented, and an optical film can be produced with high productivity.

The layer after curing the polymerizable liquid crystal compound is formed on the substrate via the alignment film. That is, the base material and the alignment film are laminated in this order, and the layer after curing the polymerizable liquid crystal compound is laminated on the alignment film.

The alignment film is not limited to the vertical alignment film, and may be an alignment film in which the molecular axis of the polymerizable liquid crystal compound is aligned horizontally, or an alignment film in which the molecular axis of the polymerizable liquid crystal compound is aligned obliquely. In the case of manufacturing the a plate 18, a horizontal alignment film can be used, and in the case of manufacturing the C plate 20, a vertical alignment film can be used. The alignment film is preferably one having resistance to a solvent which is not dissolved by coating or the like of a composition containing a polymerizable liquid crystal compound described later, and heat resistance in a heat treatment for removing the solvent and aligning the liquid crystal compound. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film, and a groove alignment film having a surface with a concave-convex pattern or a plurality of grooves formed thereon for alignment. The thickness of the alignment film is usually in the range of 10nm to 10000nm, preferably 10nm to 1000nm, more preferably 500nm or less, and still more preferably 10nm to 200 nm.

The resin used for the alignment film is not particularly limited as long as it is a resin used as a material for a known alignment film, and a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth) acrylate monomer with a polymerization initiator can be used. Specifically, examples of the (meth) acrylic acid ester monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and urethane acrylate. The resin may be one of these, or may be a mixture of two or more.

The photo-alignment film can comprise the following composition: comprising a polymer or monomer having a photoreactive group and a solvent. The photoreactive group is a group that generates liquid crystal aligning ability by light irradiation. Specifically, a group involved in a photoreaction that causes the liquid crystal aligning ability to be derived from the alignment initiation or isomerization reaction, dimerization reaction, photocrosslinking reaction, photodecomposition reaction, or the like of a molecule generated by light irradiation can be mentioned. Among these, the group participating in dimerization reaction or photocrosslinking reaction is preferable in that the orientation is excellent. As the photoreactive group, an unsaturated bond is preferable, particularly a group having a double bond, and a group having at least one selected from the group consisting of a carbon-carbon double bond (c=c bond), a carbon-nitrogen double bond (c=n bond), a nitrogen-nitrogen double bond (n=n bond), and a carbon-oxygen double bond (c=o bond) is particularly preferable.

As a photo reactive group with a C=C bond, examples include vinyl, polyene, styrene (スチルべン基), styrene pyridine (スチルバゾリウ厶基), styrene pyridine (スチルバゾリウ厶基), chalcone, and cinnamoyl groups. As a photo reactive group with C=N bonds, groups with aromatic Schiff bases, aromatic hydrazones, and other structures can be identified. As a photo reactive group with N=N bonds, it can provide examples of azophenyl, azonaphthyl, aromatic heterocyclic azo, diazo, methoxy, and groups with oxidized azobenzene structures. As a photo reactive group with C=O bonds, examples include benzoyl, coumarin, anthraquinone, and maleimide groups. These groups can have substituents such as alkyl, alkoxy, aryl, allyloxy, cyano, alkoxycarbonyl, hydroxyl, sulfonic acid, haloalkyl, etc.

Among these, a photoreactive group participating in the photopolymerization reaction is preferable, and a cinnamoyl group and a chalcone group are preferable in that a photoalignment film having relatively small polarization irradiation amount required for photoalignment and excellent thermal stability and stability with time can be easily obtained. As the polymer having a photoreactive group, a polymer having a cinnamoyl group in which the terminal portion of the side chain of the polymer has a cinnamic acid structure is particularly preferable.

The type of polymerizable liquid crystal compound used in the present embodiment is not particularly limited, and can be classified into a rod type (rod-like liquid crystal compound) and a discotic type (discotic liquid crystal compound ) according to the shape thereof. Further, there are a low molecular type and a high molecular type, respectively. The polymer generally means a polymer having a degree of polymerization of 100 or more (refer to "Polymer physics/phase change mechanics, shikon Man, page 2, rock bookstore, 1992").

In this embodiment, any polymerizable liquid crystal compound can be used. Further, two or more kinds of rod-like liquid crystal compounds, two or more kinds of discotic liquid crystal compounds, or a mixture of rod-like liquid crystal compounds and discotic liquid crystal compounds may be used.

As the rod-like liquid crystal compound, for example, the compounds described in paragraphs [0026] to [0098] of claim 1 of JP-A-11-513019 or paragraph [0026] of JP-A-2005-289980 can be used. As the discotic liquid crystal compound, for example, compounds described in paragraphs [0020] to [0067] of JP-A2007-108732 or paragraphs [0013] to [0108] of JP-A2010-244038 are suitably used.

The polymerizable liquid crystal compound may be used in combination of two or more. In this case, at least one kind has two or more polymerizable groups in the molecule. That is, the layer cured with the polymerizable liquid crystal compound is preferably a layer formed by polymerization fixation of a liquid crystal compound having a polymerizable group. In this case, there is no need to show liquid crystallinity already after the layer is formed.

The polymerizable liquid crystal compound has a polymerizable group capable of undergoing a polymerization reaction. Examples of the polymerizable group include a polymerizable ethylenically unsaturated group, a cyclopolymerizable group, and other functional groups capable of undergoing addition polymerization.

More specifically, examples of the polymerizable group include a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among these, (meth) acryl is preferable. The term "(meth) acryl" is a concept including both a methacryl group and an acryl group.

As described later, the layer cured with the polymerizable liquid crystal compound can be formed by, for example, coating a composition containing the polymerizable liquid crystal compound on an alignment film. The composition may contain components other than the polymerizable liquid crystal compound. For example, a polymerization initiator is preferably contained in the composition. The polymerization initiator used corresponds to the form of the polymerization reaction, for example, a thermal polymerization initiator, a photopolymerization initiator is selected. Examples of the photopolymerization initiator include an α -carbonyl compound, an acyloin ether, an α -hydrocarbon-substituted aromatic acyloin compound, a polynuclear quinone compound, a combination of a triarylimidazole dimer and p-aminophenyl ketone, and the like. The amount of the polymerization initiator to be used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content in the coating liquid.

In addition, the composition may contain a polymerizable monomer for uniformity of the coating film and strength points of the film. Examples of the polymerizable monomer include radically polymerizable and cationically polymerizable compounds. Among these, a polyfunctional radical polymerizable monomer is preferable.

The polymerizable monomer is preferably a polymerizable monomer copolymerizable with the polymerizable liquid crystal compound. Specific examples of the polymerizable monomer include those described in paragraphs [0018] to [0020] of JP-A-2002-296423. The amount of the polymerizable monomer to be used is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the polymerizable liquid crystal compound.

In the composition, a surfactant may be included in terms of uniformity of a coating film and strength of the film. As the surfactant, there can be mentioned known compounds. Among these, fluorine compounds are preferred. Specific examples of the surfactant include compounds described in paragraphs [0028] to [0056] of JP-A-2001-330725 and compounds described in paragraphs [0069] to [0126] of JP-A-2005-62673.

In addition, a solvent may be contained in the composition, and an organic solvent is preferably used. Examples of the organic solvent include amides (e.g., N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), haloalkanes (e.g., chloroform, methylene chloride), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), ethers (e.g., tetrahydrofuran, 1, 2-dimethoxyethane)

The composition contains a vertical alignment accelerator such as a polarizing film interface side vertical alignment agent and an air interface side vertical alignment agent, and various alignment agents such as a polarizing film interface side horizontal alignment agent and an air interface side horizontal alignment agent. Further, the composition may further contain an adhesion improver, a plasticizer, a polymer, and the like, in addition to the above-described components.

When the retardation film 12 includes two or more layers of cured polymerizable liquid crystal compounds as the a plate 18 and the C plate 20, the retardation film 12 can be produced by producing the layers of cured polymerizable liquid crystal compounds on the alignment films, respectively, and laminating the two layers with the adhesive layer 8C interposed therebetween, for example. After the two are laminated, the substrate and the alignment film can be peeled off. The thickness of the retardation film 12 is preferably 3 to 30. Mu.m, more preferably 5 to 25. Mu.m.

The retardation film 12 may be produced by preparing long members, cutting the members into a predetermined shape after winding the members in a roll-to-roll manner, or may be produced by cutting the members into a predetermined shape and bonding the members. The C-plate 20 may be obtained by forming the C-plate 20 directly on the a-plate 18. That is, the adhesive layer 8c can be omitted.

[ Modification of retardation film ]

The retardation film 12 may further include 1 or more other layers having a retardation (hereinafter, sometimes referred to as "other retardation sub-layers") in addition to the a plate 18 and the C plate 20. Examples of the other retardation sub-layer include a touch sensor provided to the image display layer 4, a sealing layer for sealing the image display layer 4, and a base film for the image display layer 4. The other retardation sub-layer may be a protective film bonded to the polarizing film 14. The other retardation sub-layer is disposed between the polarizing film 14 and the image display layer 4, preferably between the image display layer 4 and the a plate 18 or the C plate 20 located closest to the image display layer 4.

Other phase difference sublayers may be a plates, but can typically be C plates. Other phase difference sublayers may have characteristics characterized by the following equation (5). That is, the other phase difference sub-layer can be a negative C-plate.

In the formula (5), nx denotes a refractive index in the direction of the slow axis 12a, ny denotes a refractive index in the direction of the fast axis 12b, and nz denotes a refractive index in the thickness direction of the other phase difference sub-layer.

In formula (5)In addition to the case where nx and ny are exactly equal, the case where nx and ny are substantially equal is also included. Specifically, nx and ny can be said to be substantially equal as long as the difference between nx and ny is within 0.01.

The retardation film 12 may include the above-described base material and alignment film, or may include a combination other than the a plate and the C plate. Specifically, two or more a plates may be combined.

The image display device 2 may further include at least one of a front panel and a light shielding pattern (barrier). The front panel and the light shielding pattern are described separately.

< Front Panel >

The front panel may be disposed on the visual recognition side of the polarizing plate 10. The front panel can be laminated on the polarizing plate 10 via an adhesive layer. Examples of the adhesive layer include the adhesive layer 8b and the adhesive layer 8c.

Examples of the front panel include a front panel including a hard coat layer on at least one surface of glass or a resin film. As the glass, for example, a high-transmission glass or a reinforced glass can be used. In the case of using an extremely thin transparent surface material, chemically strengthened glass is preferable. The thickness of the glass can be set to, for example, 100 μm to 5mm.

The front panel including the hard coat layer on at least one surface of the resin film is not as stiff as conventional glass, but can have soft characteristics. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 to 100. Mu.m.

Examples of the resin film include films of cycloolefin derivatives having a unit including a cycloolefin monomer such as norbornene or polycyclic norbornene-based monomer, polymers such as cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl cellulose, propionyl cellulose, butyryl cellulose, and acetyl propionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacrylic acid, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyurethane, and epoxy. The resin film can be an unstretched, 1-axis or 2-axis stretched film. These polymers may be used singly or in combination of two or more kinds. The resin film is preferably a polyamide imide film or a polyimide film excellent in transparency and heat resistance, a 1-axis or 2-axis stretched polyester film, a cycloolefin derivative film excellent in transparency and heat resistance and capable of coping with an increase in film size, a polymethyl methacrylate film, and a triacetyl cellulose and isobutyl cellulose film having no transparency and optical anisotropy. The thickness of the resin film may be 5 to 200. Mu.m, preferably 20 to 100. Mu.m.

< Shading Pattern >

The light shielding pattern (barrier) can also be formed on the image display layer 4 side in the front panel.

The light shielding pattern blocks each wiring of the image display device 2, and can be invisible to the user. The color and/or material of the light shielding pattern is not particularly limited, and may include a resin material having various colors such as black, white, and gold. In one embodiment, the thickness of the light shielding pattern may be in the range of 2 μm to 50 μm, preferably 4 μm to 30 μm, more preferably 6 μm to 15 μm. In addition, in order to suppress the mixing of bubbles due to the step between the light shielding pattern and the display portion and the visual recognition of the boundary portion, a shape can be given to the light shielding pattern.

[ Method for producing optical laminate ]

The optical laminate 6 is produced by laminating the polarizing plate 10 and the retardation film 12 with the pressure-sensitive adhesive layer 8b interposed therebetween. For example, after the polarizing plate 10 is manufactured, the pressure-sensitive adhesive layer 8b formed on the release film is laminated on the protective film 16 facing the retardation film 12. The release film on the pressure-sensitive adhesive layer 8b is peeled off, and the polarizing plate 10 and the retardation film 12 manufactured separately are bonded via the exposed pressure-sensitive adhesive layer 8b. The optical laminate 6 thus obtained can function as a circularly polarizing plate.

[ Method for manufacturing image display device ]

The image display device 2 can be obtained by bonding the retardation film 12 of the optical laminate 6 to the image display layer 4 via the pressure-sensitive adhesive layer 8 a. As shown in fig. 1, the optical laminate 6 is generally attached to the image display layer 4 such that the C-plate 20 is positioned on the image display layer 4 side.

The conditions satisfied by the image display device 2 will be described as embodiment 1 and embodiment 2.

(Embodiment 1)

As shown in fig. 3, a plane perpendicular to a direction of an inclination angle θ with respect to a thickness direction of the image display device 2 (a lamination direction of the image display layer 4 and the optical laminate 6) is referred to as a projection plane 22. The thickness direction corresponds to a direction orthogonal to the slow axis 12a and the fast axis 12 b. When the fast axis 12b of the phase difference film 12 is assumed to be the rotation axis (tilt axis), the retardation of the phase difference film 12 in the projection plane 22 is set to R (θ) _fast, when the slow axis 12a of the phase difference film 12 is assumed to be the rotation axis, the retardation of the phase difference film 12 in the projection plane 22 is set to R (θ) _slow, and the retardation of the image display layer 4 in the projection plane 22 is set to R (θ) M. The term "assume the slow axis 12a (or the fast axis 12 b) as a rotation axis" means that the retardation film 12 is tilted around the slow axis 12a (or the fast axis 12 b). In the present specification, retardation of the retardation film or retardation of the image display layer on the projection surface 22 is retardation of the retardation film or image display layer projected on the projection surface 22.

In the image display device 2, R (θ) _fast、R(θ)_slow and R (θ) M satisfy the following formulas (i) to (iv).

α＝R0-{R(θ)_fast+R(θ)M}…(i)

β＝R0-{R(θ)_slow-R(θ)M}…(ii)

|α(θ)|+|β(θ)|＜10nm…(iii)

|R(θ)M|＞0nm…(iv)

As a result, the reflection color of the screen of the image display device 2 differs between the case of looking in the front direction and the case of looking in the tilt angle θ direction, and a reflection color corresponding to the in-plane angle is generated in the oblique direction. The maximum value of the chromatic aberration of the reflected color corresponding to the in-plane angle in the oblique direction is referred to as oblique chromatic aberration. Further, when the oblique chromatic aberration becomes minimum, the chromatic aberration in the case of looking in the front direction and the case of looking in the oblique angle θ direction becomes minimum. For this reason, even when the image displayed on the image display device 2 is viewed from various angles, the same image as that when viewed from the front direction (the thickness direction) can be observed.

This is further explained. As described above, the image display layer 4 is a light reflective display layer that reflects light incident on the image display device 2 from the optical laminate 6 side. In the following description, therefore, the image display layer 4 is referred to as a light reflection layer RL (refer to fig. 1) based on the above reflection characteristics. In the following description, the optical layered body 6 is a circularly polarizing plate, but the optical layered body 6 is not limited to the circularly polarizing plate.

[ Phase difference of optical electric field ]

The optical electric field vibrates on a plane perpendicular to the propagation direction, and can be decomposed into components of S polarization and P polarization. At this time, the difference in angular frequency, which is the deviation of the electric field oscillation period of the S polarization and the P polarization, is a phase difference. The difference Δδ=δr- δi between the incident light phase difference δi and the reflected light phase difference δr of the light reflection layer RL in the case of not being perpendicular to the incident light (hereinafter, sometimes referred to as "the reflected light phase difference Δδ of the light reflection layer RL") can be calculated from the stokes vector s= (S0, S1, S2, S3) measured using an ellipsometer or a stokes polarimeter.

The polarization azimuth angle ψ, ellipticity angle ε, phase difference δ, ellipticity χ of the optical electric field are represented by the following formulas (6) to (9) using Stokes vectors (refer to "spectroscopic ellipsometer, literature of the Tingyu, pill-like publication, pages 68 to 78, 2011").

[ Math 1]

χ＝tanε…(9)

When the incident light is linearly polarized with the polarization azimuth angle ψ=45° and the ellipticity χ=0, and the stokes vector si= (Si 0, si1, si2, si 3) = (1, 0,1, 0), the phase difference δi becomes 0 by the above formulas (6) to (8).

Similarly, when the light reflection layer RL reflects the incident light, the reflected light is elliptically polarized with the polarization azimuth angle ψ=45° and the ellipticity χ=0.4, and stokes vector sr= (Sr 0, sr1, sr2, sr 3) = (1,1,0.7,0.7), the phase difference δr becomes pi/4 by the above formulas (6) to (8). At this time, the reflection phase difference Δδ of the light reflection layer RL is characterized as pi/4. In the present specification, the ellipticity angle ε > 0 and ellipticity angle ε < 0 are positive and negative respectively in the positive and negative of the reflection phase difference Δδ of the light reflection layer RL for the incident light having the polarization azimuth angle ψ=45° and linearly polarized.

The phase difference Δδ can be converted into a retardation R (nm) by the following equation (10) using the corresponding wavelength λ (nm).

[ Formula 2]

[ Angle dependence of light reflective layer ]

The reflection phase difference Δδ of the light reflection layer RL varies according to the incident angle θr of light to the light reflection layer RL.

The following formula (11) shows a formula in which the boundary conditions of the refractive index of the medium are set and modified in maxwell's equation (see "application engineering I, crane Tian Kuangfu, pill publication, pages 28 to 45, 1990"). The following expression (11) represents a case where the light is obliquely incident on the metal side from the dielectric side, the refractive index of the dielectric is n=n ₁, and the refractive index of the metal is n= -ik using the complex refractive index.

[ Formula 3]

At normal incidence, the reflection phase difference Δb becomes 0, and increases with an increase in the incident angle θr.

In the case where the light reflection layer RL is an OLED display device or a micro LED display device, for example, the light reflection layer RL is a multiple laminate of an electrode, a wiring, a light emitting pixel, a barrier, a plastic film, and the like. In actual measurement, stokes vectors can be measured for each incident angle θr, and the reflection phase difference Δδ of the light reflection layer RL for each incident angle θr can be calculated for theoretical calculation.

The reflection phase difference Δδ of the light reflection layer RL is generated on a reflection surface such as a metal crystal having charge carriers such as free electrons, and is not generated on a reflection surface such as a dielectric such as a resin film having no charge carriers.

In the case where the light reflection layer RL is an OLED display device or a micro LED display device, for example, the reflection phase difference Δδ can take various values depending on the density, shape, and metal species of the electrode and wiring forming the light reflection layer RL. For this reason there is a limited reflected phase difference delta. In many cases, the absolute value of the reflection phase difference Δδ (50) at the projection surface 22 at the tilt angle of 50 degrees is 0.01rad or more in terms of a value of 550nm, and the absolute value of the reflection delay R (50) M is 1.0nm or more in terms of the same value of 550 nm.

The phase difference in oblique view when observing the phase difference film 12 having the slow axis 12a inclined as the rotation axis can be calculated by the following procedure.

As shown in fig. 4, in a rectangular coordinate system in which the front direction is the z axis, if the component parallel to the slow axis 12a (x axis in fig. 4) among the refractive indices of the phase difference film 12 is nx, the component parallel to the fast axis 12b is ny, the component parallel to the front direction is nz, and the angle between the optical field vector propagating through the phase difference film 12 and the z axis isThe angle between the z-axis and the vector of the optical field emitted from the retardation film 12 and propagating in the air is defined asTo use the Snell's rule, the following formula (12) is obtained. /(I)Corresponds to the inclination angle θ in the case where the slow axis 12a is the rotation axis.

[ Math figure 4]

φyz＝arcsin{sin(-φ)/n_x}…(12)

The phase difference of the oblique view with the slow axis 12a as the rotation axis can be obtained from the effective refractive indices Nyz and nx projected from ny and nz onto the projection surface (the plane perpendicular to the straight line connecting the phase difference film 12 and the observer) 22, respectively, as shown in the following formula (13). D in the formula (13) is the thickness of the retardation film 12.

[ Formula 5]

At this time, the effective refractive index Nyz on the projection surface 22 can be obtained by using the refractive index ellipsoid according to the following formula (14) ("the forefront of refractive index control technique of optical material, dui Bian Min line, yujin Ji Hongjian trim, yuzhui, page 14 to page 16, 2009" refer to).

[ Formula 6]

The phase difference of the oblique view field using the fast axis 12b as the rotation axis is also represented by the following formula (15) in the same manner as in formula (13). The following are given in detailCorresponding to the tilt angle θ in the case of using the fast axis 12b as the rotation axis. D in the formula (15) is the same as in the formula (13).

[ Formula 7]

The parameters of the optical elements such as the transmittance in the transmission axis direction (the direction orthogonal to the absorption axis 14 a) of the polarizing film 14, the transmittance in the absorption axis 14a direction, the three-dimensional refractive indices of the a plate 18 and the C plate 20 included in the phase difference film 12, the reflection phase difference of the light reflection layer RL, the transmittance of the adhesive and the front plate can be measured, and the parameters can be substituted into the miller matrix, so that the optical field state in the case where these optical elements transmit or reflect can be calculated with high accuracy.

For example, when calculating the optical field observed by reflecting and transmitting the optical laminate 6 (circular polarizing plate) through the optical laminate 6 (circular polarizing plate) by the light reflection layer RL, the stokes vector of the reflected light Sout is obtained as a solution of the following expression (16).

S_out＝P·A·C·M·C·A·P·S_in…(16)

In the formula (16), P, A, M, S _in is as follows.

P: miller matrix of polarizing film 14

A: a plate 18 Miller matrix

C: miller matrix of C plate 20

M: miller matrix of light reflective layer RL

S _in: stokes vector of incident light

The miller matrix of optical elements is a 4×4 matrix, and for example, polarizing film 14 and retardation film 12 are characterized by the following formulas (17) to (18) ("basis and application of polarization propagation analysis, murray, internal Tian Laohe nursery, pages 57 to 61, 2015" reference).

[ Math figure 8]

T ₁ in the formula (17) is the transmittance in the transmission axis direction in the polarizing film 14, and T ₂ is the transmittance in the absorption axis 14a direction in the polarizing film 14. Δδ (rad) in the formula (17) is the phase difference of the phase difference film 12.

The light reflection layer RL can be captured as a phase difference sub-element that increases in phase difference in proportion to the tilt angle θ, like the C plate 20. For this purpose, the phase difference sub-element and the amplitude reflection element can be defined separately. The retardation subcomponent of the light reflection layer RL defines a miller matrix in the same manner as the retardation film 12.

In calculating the actual circular polarizer structure, it is necessary to reflect the optical axes of the optical elements on the miller matrix. For example, when the slow axis (slow axis 12 a) in the plane of the a plate 18 included in the phase difference film 12 of the formula (18) is defined by rotating by only the angle ζ (rad), the two-side rotation matrix Z (ζ) of the miller matrix is applied as shown in the formula (19).

[ Formula 9]

The reflectance spectrum of the light that is reflected by the optical laminate 6 (circular polarizing plate) at the light reflecting layer RL and is visually recognized again by the optical laminate 6 (circular polarizing plate) can be obtained by obtaining the S0 component of the stokes vector for each wavelength according to the above formula (16). This corresponds to the reflectance of a component that reaches the inside of the optical laminate 6 (circularly polarizing plate) without being reflected at the interface between air and the optical laminate 6 (circularly polarizing plate). On the other hand, the reflectance Rfo at the interface between air and the optical laminate 6 (circularly polarizing plate) varies in proportion to the tilt angle θ and the refractive index ns thereof, and is represented by the following formula (20).

[ Math.10 ]

The interface between the optical laminate 6 (circular polarizing plate) and air is, for example, the interface between the polarizing plate 10 and air when the optical laminate 6 is in contact with the air layer on the surface of the polarizing plate 10. When the optical laminate 6 further includes a front plate on the visual recognition side of the polarizing plate 10 and the front plate is further laminated on the polarizing plate 10 with an adhesive layer interposed therebetween, the interface between the optical laminate 6 (circularly polarizing plate) and air is the interface between the visual recognition side of the front plate and the air layer.

From the above, the total reflectance Rf of the surface reflectance at the interface with air of the optical laminate 6 (circularly polarizing plate) and the internal reflectance that is reflected by the optical laminate 6 (circularly polarizing plate) at the light reflection layer RL and visually recognized again by the optical laminate 6 is obtained by the following formula (21). The interfacial reflection and the multiple reflection between the layers constituting the optical laminate 6 (circularly polarizing plate) are not considered.

Rf＝Rfo+(1-Rfo)×S0

＝Rfo+S0-Rfo×S0…(21)

The optical laminate 6 (circularly polarizing plate) may have an antireflection film at the interface with air.

The antireflection film may have a single-layer structure composed of a low refractive index layer having a low refractive index, or a multilayer structure in which a low refractive index layer having a low refractive index and a high refractive index layer having a high refractive index are laminated in this order. When the antireflection film is provided, for example, the surface reflectance is 2% or less, and further 1% or less, the chromatic aberration of the internal reflection light reflected by the optical laminate 6 (circularly polarizing plate) at the light reflection layer RL and visually recognized again by the optical laminate 6 (circularly polarizing plate) is relatively easy to visually recognize, and therefore the structure of the present invention is more effectively exhibited.

The tristimulus values X _W、Y_W、Z_W of the standard illuminant W (λ) and the tristimulus values X _Rf、Y_Rf、Z_Rf of the reflected light illuminant Rf (λ) ×w (λ) were calculated according to the following formulas (22A) to (22B) using the isochromatic functions X (λ), y (λ), z (λ) (international commission on illumination (CIE) suggestion, 1931) ("reference in color engineering, phylum Tian Bozhi, bingo, north-senson publication, pages 106 to 107", 2007 "). Standard illuminant uses a D65 illuminant (ISO 10526:1999/CIE S005/E-1998).

[ Formula 11]

The reflected light hue value a ^*、b^* and the chroma value C ^* of the L ^*a^*b^* color system are calculated by using the tristimulus values X _W、Y_W、Z_W and X _Rf、Y_Rf、Z_Rf of the standard illuminant W (λ) and the reflected light illuminant Rf (λ) ×w (λ) according to formulas (23) to (25) ("color engineering entrance, Tian Bozhi, rattan-boy co-worker, north-senson publication, page 122, 2007" reference ").

[ Formula 12]

When the slow axis 12a, the x axis, the fast axis 12b, and the y axis of the a-plate 18 are each parallel, a case where the image display device 2 is viewed from a field of view inclined by θ from the z axis (the direction of the inclination θ) (a case where the image display device is viewed from the direction of the open arrow in fig. 2) is referred to as "inclination θ viewing" (refer to fig. 2).

At this time, the saturation C ^* takes the two-degree symmetry of the a-plate 18 along with the change in the xy-plane angle ζ to obtain the two-degree symmetry of the two-degree symmetry C _f ^* and C _s ^*, and the coordinate in the a ^*b^* plane of these two-degree symmetry is represented by the following formula (26) with the distance Δc ^* between the two points being C_f ^*(a_f ^*,b_f ^*)、C_s ^*(a_s ^*,b_s ^*). as the oblique chromatic aberration observed as the oblique angle θ.

[ Formula 13]

When the oblique chromatic aberration under the observation of the oblique angle θ becomes minimum, the color change and the intensity change of the reflected color become minimum when the image display device 2 is observed from all angles, and the optimal image display performance can be obtained.

The characteristics of the polarizing film 14 are not changed, and the following expression (27) may be satisfied in order to adjust the characteristics of the retardation film 12 and the light reflection layer RL to achieve the minimum oblique chromatic aberration.

RthA+RthC+RthM＝0…(27)

In equation (27), rthA is the retardation in the thickness direction of the a plate 18, rthC is the retardation in the thickness direction of the C plate 20, and RthM is the retardation in the thickness direction of the light reflection layer RL.

The retardation in the projection plane 22 in the case where the fast axis 12b is the rotation axis, and the retardation in the projection plane in the case where the slow axis 12a is the rotation axis, among the in-plane retardations of the a-plate 18, is R (θ) a _fast, respectively, is R (θ) a _slow. Similarly, the in-plane retardation of the C plate 20 in the projection surface 22 is R (θ) C, and the in-plane retardation of the light reflection layer RL in the projection surface 22 is R (θ) M.

When the retardation of the a-plate 18 when viewed from the front (when the tilt angle θ=0) is R (0) a, the optimum optical design of the image display device 2 can be described using the following formula (28).

The following expression (28) is simultaneously satisfied when the above expression (27) is satisfied, and the oblique chromatic aberration Δc ^* observed at the oblique angle θ of the expression (26) is optimal.

R(θ)A_fast+{R(θ)C+R(θ)M}

＝R(θ)A_slow-{R(θ)C+R(θ)M}

＝R0A…(28)

When the a plate 18 and the C plate 20 are regarded as one phase difference sublayer, the in-plane retardation R (θ) _fast、R(θ)_slow in the projection plane 22 as viewed at the tilt angle θ is represented by the following formulas (29) and (30).

R(θ)_fast＝R(θ)A_fast+R(θ)C…(29)

R(θ)_slow＝R(θ)A_slow-R(θ)C…(30)

When the expression (28) is rewritten using the expressions (29) and (30), the following expressions (31) and (32) can be obtained.

α＝R0-{R(θ)_fast+R(θ)M}…(31)

β＝R0-{R(θ)_slow-R(θ)M}…(32)

Further, since the light reflection layer RL of the present embodiment has a reflection phase difference, the following expression (33) holds.

|R(θ)M|＞0nm…(33)

Formulas (31) to (33) correspond to formulas (i), (ii) and (iv). Further, the image display device 2 also satisfies the expression (iii). As described above, the expression (i) and the expression (ii) (or the expression (31) and the expression (32)) are expressions in which the reflection phase difference of the light reflection layer RL is taken into consideration.

In the design of an optical compensation member such as a circular polarizing plate, the reflection phase difference of the light reflection layer has not been reflected in the past. However, in practice, the effect of the reflection phase difference of the light reflection layer is generated, and thus, the skew difference cannot be sufficiently (or as designed) suppressed.

In contrast, the image display device 2 satisfies formulas (i) to (iv) in consideration of the reflection phase difference of the light reflection layer RL. For this reason, the image display device 2 has a structure that is optimally designed to minimize the skew difference. As a result, the skew can be sufficiently suppressed (or as designed or in a desired state).

In order to satisfy the formulas (i) to (iv), in manufacturing the image display device 2, for example, the types and the arrangement ratios of the thermoplastic resin and the polymerizable liquid crystal compound forming the a plate 18 and the C plate 20 included in the retardation film 12 may be adjusted, or the thicknesses of the a plate 18 and the C plate 20 may be adjusted.

An OLED display device and a micro LED display device are exemplified as the image display layer 4. However, as other examples of the image display layer 4, there can be mentioned a liquid crystal display device, an electron emission display device (for example, an electric field emission display device (FED), a surface electric field emission display device (SED), an electronic paper (a display device using an electronic ink or an electrophoretic element), a plasma display device, a projection display device (for example, a grating light valve (also referred to as GLV) display device, a display device having a digital micromirror device (also referred to as DMD), a piezoceramic display, or the like.

In particular, in the organic EL display device or the image display device 2 having the inorganic EL display device as the light reflection layer RL, the change in the intensity of the external light reflection light is suppressed, and the stable black display capability which does not change from the front direction even when viewed obliquely can be shown.

(Embodiment 2)

As embodiment 2, the conditions satisfied by the image display device 2 will be described from the standpoint different from embodiment 1. In embodiment 2, as shown in fig. 3, a plane perpendicular to the direction of inclination angle θ with respect to the thickness direction of the image display device 2 (the lamination direction of the image display layer 4 and the optical laminate 6) is defined as a projection plane 22. In embodiment 2, the projection surface 22 is a surface in which θ=50 degrees. Therefore, the retardation of the image display layer 4 on the projection surface 22 is set to R (50) M. The retardation described in embodiment 2 is a retardation for a wavelength of 550nm unless otherwise specified.

The in-plane retardation of the phase difference film 12 is set to R0, and the retardation in the thickness direction of the phase difference film 12 is set to Rth. R0 is the sum of in-plane retardation of the layers constituting the retardation film 12. Rth is the sum of the retardation in the thickness direction of the layers constituting the retardation film 12. As shown in fig. 1, when the retardation film 12 includes a plate a and a plate C, R0 is the total of the in-plane retardation of the plate a and the plate C, and Rth is the total of the retardation of the plate a and the plate C in the thickness direction.

The Nz coefficient of the phase difference film 12 is characterized by equation (v). Further, the ratio of the in-plane retardation R0 of the phase difference film to the in-plane retardation R (50) M of the image display layer 4 in the projection plane 22 is represented by the formula (vi) as ρ -coefficient.

Nz＝(Rth/R0)+0.5…(v)

ρ＝R(50)M/R0…(vi)

The image display device 2 satisfies all of the following formulas (vii), (viii) and (ix), or satisfies formulas (vii), (x) and (xi).

3.5ρ+0.39＜Nz＜3.5ρ+0.65…(vii)

ρ＞0···(viii)

0.5＜Nz≤1.5…(ix)

ρ＜0…(x)

-1.5＜Nz＜0.5…(xi)

In other words, the image display device 2 is a device including the phase difference film 12 and the image display layer 4 which satisfy all of the regions represented by the formula (vii) in the ρ -Nz coordinate system (rectangular coordinate system), the regions of the formulae (viii) and (ix), or the groups of ρ and Nz contained in the regions of the formulae (vii), x, and xi. In addition, instead of the formula (viii), the formula (viii-1) may be used. Instead of formula (ix), formula (ix-1) may be used. Instead of formula (x), formula (x-1) may be used. Instead of the formula (xi), the formula (xi-1) may be used.

0＜ρ＜0.12…(viii-1)

0.5＜Nz≤1.0…(ix-1)

-0.06＜ρ＜0…(x-1)

0.2＜Nz＜0.5…(xi-1)

When ρ is larger than 0 (when the above formula (viii) is satisfied), the following formulas (xii), (xiii) and (xiv) are preferably satisfied.

0.06≤ρ≤0.11…(xii)

Nz≥3.5ρ+0.405…(xiii)

Nz≤3.5ρ+0.61…(xiv)

When ρ is smaller than 0 (when the above formula (x) is satisfied), the following formulas (xv), (xvi) and (xvii) are preferably satisfied.

-0.07≤ρ≤-0.04…(xv)

Nz≥3.5ρ+0.42…(xvi)

Nz≤3.5ρ+0.59…(xvii)

The image display device 2 of embodiment 2 can be manufactured by adjusting the types and the arrangement ratio of the thermoplastic resin and the polymerizable liquid crystal compound forming the a plate 18 and the C plate 20 of the retardation film 12, or by adjusting the thicknesses of the a plate 18 and the C plate 20, for example.

Even in embodiment 2, the image display device 2 satisfies the above condition considering the reflection phase difference of the image display layer 4. For this reason, the image display device 2 has a structure that is optimally designed to minimize the skew difference. As a result, the skew can be sufficiently suppressed (or as desired).

The various embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. A circular polarizing plate is exemplified as an example of the optical laminate 6, but the optical laminate 6 is not limited to the circular polarizing plate.

[ Example ]

The following examples and comparative examples are given to more specifically explain the present invention. The present invention is not limited to the following examples. In the examples, "%" and "parts" refer to% by mass and parts by mass unless otherwise specified. The circular polarizing plate described below corresponds to the optical laminate described in the above embodiment, and the light reflection layer corresponds to the image display layer.

[ Measurement method ]

< Method for measuring film thickness >

The thickness of the film was measured by a contact film thickness meter (MH-15M, counter TC101, MS-5C, manufactured by Nikon Co., ltd.).

< Method for measuring delay >

The retardation in the thickness direction of the A plate and the C plate was measured by using a birefringence evaluation device (KOBRA-WPR manufactured by Ware instruments Co., ltd.).

The retardation of each incident angle of the light reflecting layer was measured using a spectroellipsometer (M-2000 manufactured by j.a. woollam).

< Oblique color difference ΔC ^* observed at oblique angle of 50 degrees >

The oblique chromatic aberration Δc ^* observed at an oblique angle of 50 degrees was measured by the display evaluation system DMS803 made by Instrument SystemsGmbH.

[ Preparation of light reflective layer ]

The following seven light reflecting layers were used.

Light reflecting layer a: the brass plate manufactured by using the metal for a long time is M560.

Light reflecting layer B: commercial Apple Inc. A smart phone iPhone (registered trademark) X equipped with an OLED display device was manufactured and decomposed, and a cover glass and a circularly polarizing plate were taken out for use.

Light reflecting layer C: the glossy surface of "raw foil thickness 50" of aluminum foil manufactured by Kagaku UACJ was used.

Light reflecting layer D: the copper plate was subjected to hard chromium plating (industrial chromium plating JISH 8615).

Light reflecting layer E: eagle XG manufactured by Corning using an alkali-free glass plate.

Light reflection layer F: as the high reflectance reflection plate, MIRO5 5011GP of highly reflective coated aluminum vapor deposited reflection plate manufactured by Alanod was used.

Light reflection layer G: the commercially available tablet pc Galaxy tab S8.4 with an OLED display device mounted thereon was disassembled, and the cover glass and the circularly polarizing plate were taken out for use.

The reflection phase difference Δδ50 (550) and the reflection retardation R50M (550) of the wavelength 550nm at the tilt angle of 50 degrees of each light reflection layer are shown in table 1. In order to measure these under the condition of simulating an actual OLED display device, unstretched cycloolefin polymers were attached to the respective light reflecting layers a to G to perform measurement. The in-plane retardation of the cycloolefin polymer was less than 0.1 at any of wavelengths of 450nm, 550nm and 630 nm.

[ Table 1]

[ Production of circular polarizing plate ]

[ Preparation of composition for Forming horizontal alignment film ]

5 Parts (weight average molecular weight: 30000) of a photo-alignment material having the following structure and 95 parts of cyclopentanone (solvent) were mixed. The resulting mixture was stirred at 80℃for 1 hour to obtain a composition for forming a horizontal alignment film.

[ Chemical formula 1]

[ Preparation of composition for Forming vertical alignment film ]

Use was made of SEI 610, manufactured by Nissan chemical Co., ltd.

[ Preparation of composition for Forming horizontal alignment liquid Crystal cured film ]

The following polymerizable liquid crystal compound a and polymerizable liquid crystal compound B were used to form a horizontally oriented liquid crystal cured film (a plate). The polymerizable liquid crystal compound A is produced by the method described in JP-A2010-31223. The polymerizable liquid crystal compound B was produced by the method described in japanese unexamined patent publication No. 2009-173893. The respective molecular structures are shown below.

[ Polymerizable liquid Crystal Compound A ]

[ Chemical formula 2]

[ Polymerizable liquid Crystal Compound B ]

[ Chemical formula 3]

The polymerizable liquid crystal compound a and the polymerizable liquid crystal compound B were mixed in an amount of 87:13 by mass ratio. To 100 parts of the obtained mixture, 1.0 part of a leveling agent (F-556; DIC Co., ltd.) and 6 parts of 2-dimethylamino-2-biphenyl-1- (4-morpholinophenyl) butan-1-one (Irgacure 369, BASF Japanese Co., ltd.) as a polymerization initiator were added. Further, N-methyl-2-pyrrolidone (NMP) was added so that the solid content became 13%, and the mixture was stirred at 80℃for 1 hour, whereby a composition for forming a horizontally oriented liquid crystal cured film was obtained.

[ Adjustment of composition for Forming vertical alignment liquid Crystal cured film ]

To form a homeotropically oriented liquid crystal cured film (C plate), the compositions were prepared in the following order. To 100 parts of paliocor LC242 (registered trademark of BASF corporation) as a polymerizable liquid crystal compound, 0.1 part of F-556 as a leveling agent and 3 parts of Irgacure369 as a polymerization initiator were added. Cyclopentanone was added so that the solid content concentration became 13%, to obtain a composition for forming a vertical alignment liquid crystal cured film.

[ Production of polarizing plate ]

A polyvinyl alcohol (PVA) film having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was prepared. After immersing the PVA film in pure water at 30 ℃, it was immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30 ℃ to perform iodine dyeing (iodine dyeing step). The PVA film subjected to the iodine dyeing step was immersed in an aqueous solution having a mass ratio of potassium iodide/boric acid/water of 12/5/100 at 56.5℃to carry out boric acid treatment (boric acid treatment step). After the PVA film subjected to the boric acid treatment step was washed with pure water at 8 ℃, it was dried at 65 ℃ to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching of the PVA film is performed in an iodine dyeing process and a boric acid treatment process. The total stretch ratio of the PVA film was 5.3 times. The thickness of the resulting polarizing film was 10. Mu.m.

The polarizing film and a saponified triacetyl cellulose (TAC) film (KC 4UYTAC, manufactured by Konikoku Midada Co., ltd., thickness: 40 μm) were bonded together by a nip roller for an aqueous adhesive. The resulting laminate was dried at 60℃for 2 minutes while maintaining the tension at 430N/m, to obtain a polarizing plate having a TAC film as a protective film on one side. Further, 3 parts of carboxyl group-modified polyvinyl alcohol (made by kohl corporation, "kuku-rao-i KL 318") and 1.5 parts of water-soluble polyamide epoxy resin (made by tattooa chemical industry, inc., "su-i 650", and an aqueous solution having a solid content of 30%) were added to 100 parts of water to prepare an aqueous adhesive.

The obtained polarizing plate was subjected to measurement of optical characteristics. The polarizing film surface of the polarizing plate obtained above was used as an incident surface, and measurement was performed by a spectrophotometer ("V7100", manufactured by japan spectroscopy). The absorption axis of the polarizing plate was identical to the stretching direction of the polyvinyl alcohol, and the obtained polarizing plate had a visibility-compensating monomer transmittance of 42.3%, a visibility-compensating polarization of 99.996%, a monomer hue a of-1.0, and a monomer hue b of 2.7.

[ Production of a horizontal alignment liquid Crystal cured film (A plate) ]

Corona treatment was performed on a cycloolefin resin (COP) film (ZF-14-50) manufactured by ZEON Co., ltd. Corona treatment was performed using TEC-4AX manufactured by Niuwei (USHIO) Motor Co. The corona treatment was carried out 1 time at an output of 0.78kW and a treatment speed of 10 m/min. The composition for forming a horizontal alignment film was applied to a COP film by a bar coater and dried at 80 ℃ for 1 minute. A polarized UV irradiation apparatus ("SPOTCURESP-9", manufactured by Niujiu Co., ltd.) was used to apply polarized UV exposure at an axis angle of Yui at 45℃to the coating film so that the cumulative light amount at a wavelength of 313nm became 100mJ/cm ². The film thickness of the obtained horizontal alignment film was 100nm.

Next, the composition for forming a cured film of a horizontally oriented liquid crystal was applied to the horizontally oriented film using a bar coater, and dried at 120 ℃ for 1 minute. A horizontal alignment liquid crystal cured film was formed BY irradiating the coating film with ultraviolet light (cumulative light amount at a wavelength of 365nm under a nitrogen atmosphere: 500mJ/cm ²) using a high-pressure mercury lamp ("uniQure VB-15201BY-A", manufactured BY Niuwei Motor Co., ltd.). The film thickness of the horizontally oriented liquid crystal cured film was about 1.9 μm.

An adhesive layer is laminated on the horizontally oriented liquid crystal cured film. A film comprising a COP film, an alignment film, and a horizontally aligned liquid crystal cured film is bonded to glass via the adhesive layer. The COP film was peeled off to obtain a sample for measuring retardation.

As a result of measuring the retardation R0A (λ) at each wavelength, the horizontally oriented liquid crystal cured film showed reverse wavelength dispersibility as follows.

R0A(450)＝124nm

R0A(550)＝142nm

R0A(650)＝146nm

R0A(450)/R0A(550)＝0.87

R0A(650)/R0A(550)＝1.03

The horizontal alignment liquid crystal cured film is satisfactoryIs a positive a plate of the relationship. The result of measuring the retardation RthA (λ) at each wavelength is as follows.

RthA(450)＝64nm

RthA(550)＝71nm

RthA(650)＝73nm

[ Production of a vertical alignment liquid Crystal cured film (C plate) ]

Corona treatment was applied to the COP film. The conditions of the corona treatment were the same as described above. The composition for forming a vertical alignment film was applied onto a COP film by a bar coater, and dried at 80 ℃ for 1 minute to obtain a vertical alignment film. The film thickness of the obtained vertical alignment film was 50nm.

The composition for forming a cured film of a homeotropic alignment liquid crystal was applied to the homeotropic alignment film using a bar coater, and dried at 90℃for 120 seconds. A vertical alignment liquid crystal cured film was formed BY irradiating the coating film with ultraviolet light (cumulative light amount at a wavelength of 365nm under a nitrogen atmosphere: 500mJ/cm ²) using a high pressure mercury lamp ("uniQure VB-15201BY-A", manufactured BY Niuwei Motor Co., ltd.). Thus, a film including a COP film, a homeotropic alignment film, and a homeotropic alignment liquid crystal cured film was obtained. The film thickness of the vertically oriented liquid crystal cured film was 0.2. Mu.m.

An adhesive layer is laminated on the vertically oriented liquid crystal cured film. A film comprising a COP film, an alignment film, and a vertical alignment liquid crystal cured film is bonded to glass via the adhesive layer. The COP film was peeled off to obtain a sample for measuring retardation. The result of measuring retardation RthC1 (550) at a wavelength of 550nm is RthC (550) = -20nm.

The vertical alignment liquid crystal cured film satisfiesIs a positive C plate of the relationship.

The COP film, the C plate, and the a plate are laminated in this order by bonding a vertical alignment liquid crystal cured film surface of the vertical alignment liquid crystal cured film (C plate) formed on the COP film and a horizontal alignment liquid crystal cured film surface of the horizontal alignment liquid crystal cured film (a plate) formed on the COP film with an adhesive interposed therebetween, and then peeling the COP film on the a plate side.

Corona treatment was performed on the horizontally oriented liquid crystal cured film (a plate) among the films. The conditions of the corona treatment were the same as described above. The polarizing film 14 and the horizontally oriented liquid crystal cured film (a plate) in the polarizing plate 10 are laminated via an adhesive layer so as to be in contact with each other. At this time, the angle formed by the absorption axis of the polarizing film and the slow axis of the horizontally oriented liquid crystal cured film was 45 °. Thus, a circularly polarizing plate (1) in which the retardation film and the polarizing plate are laminated via the adhesive layer is obtained. The circularly polarizing plate (1) has a layer structure of a TAC film, a polarizing film, an adhesive layer, a horizontally oriented liquid crystal cured film (A plate), an adhesive layer, and a vertically oriented liquid crystal cured film (C plate).

[ Production of circular polarizing plate (2) ]

A circularly polarizing plate (2) was produced in the same manner as the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.3. Mu.m, and RthC (550) = -30 nm.

[ Production of circular polarizing plate (3) ]

A circularly polarizing plate (3) was produced in the same manner as the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.4. Mu.m, and RthC (550) = -40 nm.

[ Production of circular polarizing plate (4) ]

A circularly polarizing plate (4) was produced in the same manner as in the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.5. Mu.m, and RthC (550) = -50 nm.

[ Production of circular polarizing plate (5) ]

A circularly polarizing plate (5) was produced in the same manner as in the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.6. Mu.m, and RthC (550) = -60 nm.

[ Production of circular polarizing plate (6) ]

A circularly polarizing plate (6) was produced in the same manner as in the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.7. Mu.m, and RthC (550) = -70 nm.

[ Production of circular polarizing plate (7) ]

A circularly polarizing plate (7) was produced in the same manner as in the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.8. Mu.m, and RthC (550) = -80 nm.

[ Production of circular polarizing plate (8) ]

A circularly polarizing plate (8) was produced in the same manner as in the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 0.9. Mu.m, and RthC (550) = -90 nm.

[ Production of circular polarizing plate (9) ]

A circularly polarizing plate (9) was produced in the same manner as in the circularly polarizing plate (1), except that the film thickness of the vertically oriented liquid crystal cured film was 1.0. Mu.m, and RthC (550) = -100 nm.

[ Production of circular polarizing plate (10) ]

A circularly polarizing plate (10) was produced in the same manner as the circularly polarizing plate (1) except that the C plate 20 was omitted.

Example 1 ]

In a circularly polarizing plate (1), a COP film is peeled off to expose an adhesive layer is laminated. A circularly polarizing plate (1) and a light reflection layer A are laminated via the adhesive layer to obtain a laminate.

For the obtained laminate, values of an in-plane retardation R0A (550) of the a plate of the circularly polarizing plate (1), an in-plane retardation R50A _fast (550) in the projection plane when viewed at an oblique angle of 50 degrees, an retardation R50A _slow (550) in the thickness direction of the C plate, an in-plane retardation R50C (550) in the projection plane when viewed at an oblique angle of 50 degrees, and a reflection phase difference R50M (550) in the projection plane when viewed at an oblique angle of 50 degrees of the light reflecting layer were measured, respectively.

The resulting laminate was measured for skew color.

Regarding the obtained laminate, the oblique chromatic aberration observed at an oblique angle of 50 degrees was calculated from the above measurement data in the range of 380nm to 780mm in terms of the transmittance T1 in the transmission axis direction, the transmittance T2 in the absorption axis direction, the three-dimensional refractive index nAx, nAy, nAz of the a plate, the in-plane retardation R0A, C of the plate 20 at a wavelength of 550nm, the three-dimensional refractive index nAx, nAy, nAz in the thickness direction at a wavelength of 550nm, the retardation RthC in the light reflection layer, and the reflection retardation R50M of the light reflection layer, using the formulas (6) to (26).

The obtained laminate was visually evaluated for visual recognition of the pattern drawn on the surface of the light reflecting layer. The harder the visual recognition of the pattern is, the smaller the change in the reflected color is, and the more angle-independent good display characteristics can be obtained. The pattern was a Landolt ring having a diameter of 3mm and an opening of 0.5mm, and was drawn with a dark green oil pen, hi-Mckee Bright blue manufactured by ZEBRA. The opening direction is set to be random. The relationship between the optical axis of the horizontally oriented liquid crystal cured film and the position of the observer was changed to observe the film.

Specifically, the observation was visually made from the vicinity of 50 degrees in elevation (tilt angle) at an in-plane angle parallel to the fast axis of the a-plate. Since the hue of the reflected light in this direction is dark green, which is similar to the color of the pattern drawn on the surface of the light reflecting layer, visual recognition becomes relatively difficult. On the other hand, the hue of the reflected light when visually observed from the vicinity of the elevation angle of 50 degrees becomes red at an in-plane angle parallel to the slow axis of the a plate, and the visual recognition of the pattern becomes relatively easy because the color is different from the pattern drawn on the surface of the light reflecting layer. As a result of the whole of the case seen from the slow axis direction and the fast axis direction, the visual recognition of the opening direction of the pattern was clearly judged based on the following criteria 1 to 4.

"1": The opening direction cannot be recognized.

"2": The opening direction can be recognized if looking at the child.

"3": The opening direction can be identified.

"4": The opening direction can be clearly identified.

As a result, it was found that the laminate obtained in example 1 had uniform color of reflected light in any direction, and was capable of performing good black display at a large viewing angle.

Examples 2 to 19, comparative examples 1 to 30 and reference examples 1 to 10

A laminate was produced in the same manner as in example 1, except that the combinations of the circularly polarizing plates (1) to (10) and the light reflecting layers a to G were changed as shown in tables 2 to 4. The resultant laminate was measured for skew color as in example 1. In addition, as in example 1, the obtained laminate was visually examined to evaluate the visibility of the pattern drawn on the surface of the light reflecting layer when the relationship between the optical axis of the horizontally oriented liquid crystal cured film and the position of the observer was changed.

In comparative example 9 using the light reflecting layer B, a commercially available Apple inc. Smart phone iPhone (registered trademark) X equipped with an OLED display device was decomposed, and only a cover slip was taken out to perform measurement of the oblique chromatic aberration Δc ^* and visual recognition evaluation of a figure.

In comparative example 23 using the light reflection layer G, a commercially available tablet computer galaxytabs8.4 having an OLED display device mounted thereon was decomposed, and only a cover glass was removed to measure the oblique chromatic aberration Δc ^* and evaluate the visibility of a figure.

Since the reflection phase difference of the light is 0 as shown in table 1, the oblique chromatic aberration observed at an oblique angle of 50 degrees was calculated by using the simulations of the formulas (6) to (26) for the combination of the light reflection layer E and the circularly polarizing plates (1) to (10). For this reason, the case of using the light reflection layer E was taken as reference examples 1 to 10.

The results of examples 1 to 19, comparative examples 1 to 30 and reference examples 1 to 10 are arranged in the view of embodiment 1. Tables 2 to 4 show the results of examples, reference examples, and comparative examples from the viewpoint of embodiment 1.

In tables 2 to 4, the meanings of the respective item names are as follows.

1: Light reflecting layer used

II: polarizing plate used

III: results of visual evaluation

Δc ^*: measurement of skew

R0: measurement result of retardation in thickness direction of circularly polarizing plate

R50 _fast: measurement result of retardation in the case where the rotation axis is assumed to be the fast axis among in-plane retardation of the circularly polarizing plate in the projection plane at the time of observation at an inclination angle of 50 degrees

R50 _slow: measurement result of retardation in the case where the rotation axis is assumed to be the slow axis among in-plane retardation of the circularly polarizing plate in the projection plane at the time of observation at an inclination angle of 50 degrees

R50M: in-plane retardation of light reflecting layer in projection plane

Alpha: calculation results in the case where R0, R (θ) _fast, and R (θ) M of formula (i) are R0, R50 _fast, and R50M

Beta: calculation results of the cases where R0, R (θ) _slow, and R (θ) M of formula (ii) are R0, R50 _slow, and R50M

|Α|+|β|): based on the calculation results of α and β in tables 2 to 4

In tables 2 to 4, R0, R50 _fast、R50_slow and R50M are delays at a wavelength of 550 nm.

In tables 2 to 4, since reference examples 1 to 10 are simulation results, the column of item name III (visual evaluation result) is set as a blank column.

As shown in tables 2 to 4, comparative examples 1 to 30 and reference examples 1 to 10 do not satisfy any of the above formulas (i) to (iv). The visual evaluation in comparative examples 1 to 30 was 3 or more.

On the other hand, examples 1 to 19 satisfy the above formulas (i) to (iv). At this time, the visual evaluation was 1 or 2. Therefore, in examples 1 to 19, it can be understood that the skew color can be sufficiently suppressed.

The results of examples 1 to 19, comparative examples 1 to 30 and reference examples 1 to 10 were arranged in view of embodiment 2. Tables 5 to 7 are graphs showing the results of examples, reference examples, and comparative examples from the viewpoint of embodiment 2.

In tables 5 to 7, the meanings of the respective item names are as follows. The item names "I", "II", "III", "Δc ^*" and "M50M" are the same as in tables 2 to 4.

R0A: measurement results of in-plane retardation of a horizontally oriented liquid crystal cured film (A plate) possessed by a circularly polarizing plate

RthA: measurement result of retardation in thickness direction of horizontally oriented liquid crystal cured film (A plate) possessed by circularly polarizing plate

RthC: measurement result of retardation in thickness direction of vertical alignment liquid crystal cured film (C plate) possessed by circularly polarizing plate

Nz: calculation results (Nz coefficient) in the case where Rth and R0 in the formula (v) are (RthA +rthc) and R0A, respectively

Ρ: calculation results (ρ coefficients) in the case where R (50) M and R0 in the formula (vi) are R50M and R0

R0, R0A, rthA, rthC and R50M in tables 5 to 7 are delays at a wavelength of 550 nm.

In tables 5 to 7 and fig. 5, since the reference example is a simulation result, the column of item name III (visual evaluation result) is left blank.

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

[ Table 6]

[ Table 7]

Fig. 5 is a drawing in which examples 1 to 19 and comparative examples 1 to 30 described in tables 5 to 7 are drawn on the ρ -Nz plane. The horizontal axis of fig. 5 represents ρ, and the vertical axis represents Nz. The line L1 and the line L2 in fig. 5 are lines characterized by the following expressions, respectively.

L1：Nz＝3.5ρ+0.65

L2：Nz＝3.5ρ+0.39

The hatched areas in ρ > 0 of fig. 5 are areas that all satisfy the formulas (vi), (viii) and (ix). The hatched area in ρ < 0 of fig. 5 is an area satisfying the formula (vi), the formula (x), and the formula (xi).

As shown in fig. 5, all examples are included in the hatched area, and the comparative examples are not included in the hatched area. Further, from tables 5 to 7, the visual evaluation in comparative examples 1 to 30 was 3 or more. On the other hand, the visual evaluation of examples 1 to 19 was 1 or 2. Accordingly, it can be understood that the oblique chromatic aberration can be sufficiently suppressed in examples 1 to 19 contained in the regions (hatched regions in fig. 5) all satisfying the formula (vi), the formula (viii) and the formula (ix) or the regions satisfying the formula (vi), the formula (x) and the formula (xi).

In fig. 5, a region 24 surrounded by a two-dot chain line is a region satisfying the aforementioned formula (xii), formula (xiii), and formula (xiv) in a range where ρ is larger than 0. It can be understood that since the embodiment is included in the region 24, in a range where ρ is larger than 0, the formula (xii), the formula (xiii), and the formula (xiv) are preferably satisfied.

In fig. 5, the region 26 surrounded by the two-dot chain line is a range satisfying the ranges of the foregoing formulas (xv), (xvi) and (xvii) in a range where ρ is smaller than 0. It can be understood that since the embodiment is included in the region 26, in the range where ρ is smaller than 0, the ranges of the formula (xv), the formula (xvi), and the formula (xvii) are preferably satisfied.

Claims

1. An image display device is provided with:

A light reflective image display layer; and

A retardation film and a polarizing film provided on the image display surface of the light-reflective image display layer,

The image display device is characterized in that,

An angle formed between an absorption axis of the polarizing film and an in-plane slow axis of the retardation film is 45 DEG + -5 DEG,

The in-plane retardation of the retardation film was set to R0,

A plane orthogonal to a direction of an inclination angle θ with respect to a thickness direction of the retardation film is set as a projection plane,

Assuming that the in-plane fast axis of the retardation film is a rotation axis, the in-plane retardation of the retardation film in the projection plane is set to R (θ) _fast,

Assuming that the in-plane slow axis of the retardation film is a rotation axis, the in-plane retardation of the retardation film in the projection plane is R (θ) _slow,

The in-plane retardation of the light-reflective image display layer in the projection plane is set to R (θ) M,

In this case, the following formulas (i) to (iv) are satisfied:

α=R0-{R(θ)_fast+R(θ)M}…(i)

β＝R0-{R(θ)_slow-R(θ)M}…(ii)

|α|+|β|＜10nm…(iii)

|R(θ)M|＞0nm…(iv)，

said R0, said R (θ) _fast, said R (θ) _slow, and said R (θ) M are delays at a wavelength of 550nm,

The tilt angle θ is 50 degrees.

2. An image display device is provided with:

A light reflective image display layer; and

The image display device is characterized in that,

The in-plane retardation of the retardation film was set to R0,

In this case, the following formulas (i) to (iv) are satisfied:

α＝R0-{R(θ)_fast+R(θ)M}…(i)

β＝R0-{R(θ)_slow-R(θ)M}…(ii)

|α|+|β|＜10nm…(iii)

|R(θ)M|＞0nm…(iv)，

The absolute value |R (θ) M| of R (θ) M in the formula (iv) is 5.8nm or more,

The tilt angle θ is 50 degrees.

3. The image display device according to claim 1 or 2, wherein,

The phase difference film has an A plate and a C plate.

4. The image display device according to claim 1 or 2, wherein,

The phase difference film and the polarizing film constitute a circular polarizing plate.