JP7162037B2 - image display device - Google Patents

Description

The present invention relates to an image display device.

Some flat panel display devices, such as organic EL (electroluminescence) image display devices, have metal electrodes or the like arranged therein. Therefore, when external light is incident on such a flat panel display device, reflection occurs inside. In order to reduce the influence of such internal reflection, a flat panel display device is provided with a circularly polarizing plate in which a retardation film and a polarizing film are laminated. As such a circularly polarizing plate, for example, there is an elliptical polarizing plate as described in Patent Document 1.

JP 2015-163940 A

Even if a circularly polarizing plate for suppressing external light reflection is arranged in the flat panel display device as described above, for example, when the display device is rotated in-plane while viewing the screen from an oblique direction, the external light reflected light There is a problem that the hue tends to change.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image display device in which a change in hue of reflected external light is suppressed when viewed from an oblique direction.

The inventors of the present invention have found that by considering the reflection hue of the image display layer on which the circularly polarizing plate is arranged, it is possible to suppress the change in the hue of the reflected external light when viewed from an oblique direction, and have arrived at the present invention. .

An image display device according to one aspect of the present invention comprises a light-reflective image display layer, and a circularly polarizing plate provided on an image display surface of the light-reflective image display layer, wherein the circularly polarizing plate has When the total retardation in the direction perpendicular to the image display surface between the linear polarizer and the light-reflective image display layer is Rth, the angle of inclination of the light-reflective image display layer with respect to the vertical direction is 50 degrees. with the reflection hue b ^* satisfies the following equation (i).
2.5×b ^* −25 ≦Rth≦2.5×b ^* +40 (i)

With the above configuration, the image display device 2 satisfies the formula (i). That is, Rth, which is the total retardation in the vertical direction between the linear polarizer and the image display layer, depends on the reflection hue b ^* of the image display layer. Therefore, even if the image display device is rotated in-plane while viewing the screen from an oblique direction, the change in the hue of the reflected light can be suppressed.

The circularly polarizing plate may have an A plate arranged on the light reflective image display layer side, and the linear polarizer arranged on the A plate.

In one embodiment, the A plate is, for example, a λ/4 retardation plate.

The circularly polarizing plate may have a C plate arranged on the light reflective image display layer side, and the A plate may be arranged on the C plate.

According to the present invention, it is possible to provide an image display device in which a change in hue of reflected external light is suppressed when viewed from an oblique direction.

FIG. 1 is a schematic diagram showing a schematic configuration of an image display device according to one embodiment. FIG. 2 is a schematic diagram for explaining the tilt angle. FIG. 3 is a schematic diagram showing an example of a hue diagram. FIG. 4 is a drawing showing experimental results.

Embodiments of the present invention will be described below with reference to the drawings. The same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. The dimensional proportions of the drawings do not necessarily match those of the description.

FIG. 1 is a schematic diagram showing a schematic configuration of an image display device 2 according to one embodiment. The image display device 2 has an image display layer (light reflective image display layer) 4 and a circularly polarizing plate 6 . The image display layer 4 and the circularly polarizing plate 6 are bonded together. In the form shown in FIG. 1, the image display layer 4 and the circularly polarizing plate 6 are joined by the adhesive layer 8a.

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 and the like for forming an image. Therefore, the electrodes included in the element structure, the wiring connecting the element structures, and the like function as a reflecting portion that reflects light. Therefore, the image display layer 4 has light reflectivity for reflecting light incident on the image display device 2 from the circularly polarizing plate 6 side. Of the hues a ^* and b ^* of the reflected light in the L ^* a ^* b ^* color system, b ^* in the direction of the inclination angle of 50 degrees of the image display layer 4 in the present embodiment is, for example, −6 or more and 15 or less. . When b ^* is negative, the reflected hue is blue and is inconspicuous, but when b ^* is positive (especially 6 or more), it tends to be warm and conspicuous. The image display layer 4 may have flexibility that allows it to bend, or may have rigidity that it cannot bend. When the image display layer 4 is flexible enough to bend, b ^* is preferably 10-16, more preferably 4-8. When the image display layer 4 has rigidity, b ^* is preferably -8 to -4. The thickness of the image display layer 4 is, for example, 1 mm to 10 mm. Hereinafter, hues a ^* and b ^* in this specification are hues in the L ^* a ^* b ^* color system.

As long as the image display layer 4 is configured to form an image on the image display surface 4a, the layer configuration, material, and the like are not limited. The image display layer 4 is, for example, a portion (or layer) formed from electrodes and wiring using metals such as gold, silver, copper, iron, nickel, chromium, molybdenum, titanium, and aluminum, alloys thereof, etc., resin It can be a multi-layer stack of films, bank materials, dielectric parts such as light emitting elements, and other layers.

The image display layer 4 is, for example, a flat panel display device. An example of a flat panel display is a thin (or panel-like) organic electroluminescent display (hereinafter also referred to as an "OLED display"). The display device exemplified as the image display layer 4 is a device that does not include a member for optical compensation on the image display surface.

When the image display layer 4 is an OLED display device, typically an electrode (for example, a metal electrode) included in the OLED display device is the reflective portion. An OLED display device has a thin film structure in which a layer of organic light emitting material is sandwiched between a pair of electrodes facing each other. Electrons are injected into this organic light emitting material layer from one electrode and holes are injected from the other electrode, so that electrons and holes are combined in the organic light emitting material layer to emit light by themselves. Of the two electrodes sandwiching the organic light emitting material layer, the electrode on the image display surface 4a side has a function of transmitting light from the organic light emitting material layer, while the other electrode transmits light from the organic light emitting material layer to the image display surface 4a. It has the function of reflecting toward Therefore, the other electrode typically functions as a reflector in an OLED display.

OLED display devices have the advantage of having better visibility, being able to be made thinner, and being able to be driven at a low DC voltage, compared to liquid crystal display devices and the like that require a backlight.

[Adhesive layer]
The pressure-sensitive adhesive layer 8a can be composed of a pressure-sensitive adhesive composition whose main component is a (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin. Among them, a pressure-sensitive adhesive composition using a (meth)acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, etc., is preferable. The adhesive composition may be active energy ray-curable or heat-curable. The thickness of the adhesive layer 8b is usually 3 μm to 30 μm, preferably 3 μm to 25 μm.

Examples of the (meth)acrylic resin (base polymer) used in the adhesive composition include butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-(meth)acrylate. Polymers or copolymers containing one or more of (meth)acrylic acid esters such as ethylhexyl as monomers are preferably used. Preferably, the base polymer is copolymerized with a polar monomer. Examples of polar monomers include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, glycidyl ( Monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as meth)acrylates, can be mentioned.

The pressure-sensitive adhesive composition may contain only the above base polymer, but usually further contains a cross-linking agent. The cross-linking agent is a metal ion having a valence of 2 or more, which forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound, which forms an amide bond with a carboxyl group; Examples include epoxy compounds and polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among them, polyisocyanate compounds are preferred.

[Circularly polarizing plate]
The circularly polarizing plate 6 has a polarizing plate 10 and a retardation film 12 . The circularly polarizing plate 6 is an optical element for compensating the image displayed on the image display surface 4a. The polarizing plate 10 and the retardation film 12 are bonded together. The polarizing plate 10 and the retardation film 12 can be bonded with the adhesive layer 8b as shown in FIG. Examples of the adhesive layer 8b are the same as those of the adhesive layer 8a.

[Polarizer]
The polarizing plate 10 has a polarizing film (linear polarizer) 14 . The polarizing plate 10 may further have two protective films 16 . The polarizing plate 10 will be described based on the form illustrated in FIG.

The polarizing film 14 has linear polarization properties. An example of the polarizing film 14 is a film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched resin film. The polarizing film 14 is not particularly limited as long as it is a resin film having linear polarizing properties, and may be one used for known polarizing plates.

Examples of resin films included in the polarizing film 14 include polyvinyl alcohol (hereinafter sometimes referred to as “PVA”) resin films, polyvinyl acetate resin films, ethylene/vinyl acetate resin films, polyamide resin films, and polyester resin films. . PVA-based resin films, particularly PVA films, are usually used from the viewpoint of adsorption and orientation of dichroic dyes.

The two protective films 16 sandwich the polarizing film 14 to protect the polarizing film 14 . Each of the two protective films 16 is, for example, a resin film (for example, a triacetyl cellulose (hereinafter also referred to as “TAC”) film), a glass cover, or a glass film. The materials of the two protective films 16 may be the same or different. The number of protective films 16 may be one. For example, the polarizing plate 10 may not have the protective film 16 on the retardation film 12 side.

The polarizing plate 10 may be manufactured by preparing long members, bonding the respective members together by roll-to-roll, and then cutting them into a predetermined shape, or by cutting each member into a predetermined shape. After that, it can be manufactured by laminating.

[Retardation film]
The retardation film 12 has a function of producing a certain phase difference in incident light. The retardation film 12 has an in-plane slow axis (in-plane slow axis) and a fast axis (in-plane fast axis). The angle between the slow axis and the fast axis is approximately 90 degrees. Approximately 90 degrees means 90 degrees±5 degrees. The retardation film 12 is arranged such that the slow axis is approximately 45 degrees with respect to the absorption axis of the polarizing film 14 . Approximately 45 degrees means 45±5 degrees.

The retardation film 12 is bonded with the polarizing plate 10 . In the form illustrated in FIG. 1, the retardation film 12 is bonded to the polarizing plate 10 by the adhesive layer 8b.

The retardation film 12 has an A plate (retarder layer) 18 and a C plate (retarder layer) 20 . The A plate 18 and C plate 20 are joined together. In the form shown in FIG. 1, the A plate 18 and the C plate 20 are joined by an adhesive layer 8c. In the present embodiment, the slow axis and fast axis of the retardation film 12 are the in-plane slow axis and fast axis of the A plate 18 . Note that the C plate 20 has an in-plane phase difference of substantially 0 (zero), and does not have a slow axis and a fast axis in the plane.

[A plate]
The A plate 18 preferably has characteristics represented by the following formulas (1) to (3). The A-plate 18 can be a positive A-plate and can be a λ/4 retarder. The A plate 18 preferably exhibits reverse wavelength dispersion. By providing such an A plate 18, it is possible to suppress the coloring of the reflected light. In this embodiment, the slow axis of the A plate 18 is arranged at approximately 45 degrees with respect to the absorption axis of the polarizing film 14 . The meaning of approximately 45 degrees is as described above.

nx>ny≈nz (1)
0.80<ROA(450)/ROA(550)<0.93 (2)
130 nm<ROA(550)<150 nm (3)
In formulas (1) to (3), nx represents the refractive index in the slow axis direction, ny represents the refractive index in the fast axis direction, and nz represents the thickness direction of the A plate 18 (slow phase It represents the refractive index in the direction perpendicular to the axis and the fast axis). R0A(λ) represents the retardation of the A plate 18 at the wavelength λnm. Therefore, R0A(450) and R0A(550) in equations (2) and (3) represent retardations at wavelengths of 450 nm and 550 nm.

ny≈nz includes not only the case where ny and nz are completely equal but also the case where ny and nz are substantially equal. Specifically, if 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 according to the following formula.
R0A(λ)=[nx(λ)−ny(λ)]×d1
R0A(450)/R0A(550) represents the wavelength dispersion of the A plate 18, preferably 0.92 or less, preferably 0.83 or more and 0.88 or less.

Regarding the retardation R0A (λ) of the A plate 18 at the wavelength λ nm, R0A (450) is preferably 100 nm or more and 135 nm or less, R0A (550) is preferably 137 nm or more and 145 nm or less, and R0A (650) is 137 It is preferable that it is more than or equal to 165 or less. R0A (650) represents the retardation at a wavelength of 650 nm.

[C plate]
The C-plate 20 preferably has characteristics represented by the following formula (4). C-plate 20 can be a positive C-plate. By providing such a C plate 20, it is possible to suppress the coloring of the reflected light.
nx≈ny<nz (4)
In formula (4), nx represents the refractive index in the direction of the slow axis of the retardation film 12, ny represents the refractive index in the direction of the fast axis of the retardation film 12, and nz represents the C plate 20. represents the refractive index in the thickness direction (the direction orthogonal to the slow axis and the fast axis).

nx≈ny includes not only the case where nx and ny are completely equal but also the case where nx and ny are substantially equal. Specifically, if the magnitude of the difference between nx and ny is within 0.01, it can be said that nx and ny are substantially equal.

When the thickness direction retardation of the C plate 20 with respect to light of wavelength λ [nm] is RthC(λ), RthC(λ) is the refractive index n(λ) at the wavelength λnm and the thickness of the C plate 20 From d2, it can be calculated based on the following formula.
RthC(λ)={[nx(λ)+ny(λ)]/2−nz(λ)}×d2

RthC(450)/RthC(550) represents 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 retardations in the thickness direction of the C-plate 20 for wavelengths of 450 nm and 550 nm, respectively.

In this 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, which can contribute to making the circularly polarizing plate 6 thinner. Of course, the thicknesses of the A-plate 18 and C-plate 20 can be adjusted to the desired retardation, such as a λ/4 retardation layer, a λ/2 retardation layer, a positive A-plate, or a positive C-plate. , and retardation in the thickness direction.

[Adhesive layer]
The adhesive layer 8c may be made of an adhesive used in known retardation films. Examples of adhesives include water-based adhesives and active energy ray-curable adhesives. An adhesive layer similar to the adhesive layer 8b may be used instead of the adhesive layer 8c.

[Method of Forming Retardation Film]
The A plate 18 and the C plate 20 included in the retardation film 12 can be formed from a composition containing a thermoplastic resin or a polymerizable liquid crystal compound to be described later. The A plate 18 and C plate 20 are preferably made of a composition containing a polymerizable liquid crystal compound. A layer formed from a composition containing a polymerizable liquid crystal compound includes a layer in which a polymerizable liquid crystal compound is cured.

The relationship of formulas (1) to (3) satisfied by the A plate 18 and the relation of formula (4) satisfied by the C plate 20 are determined, for example, by the thermoplastic resin or polymerizable liquid crystal compound forming the A plate 18 and the C plate 20. It is controlled by adjusting the type and compounding ratio, and adjusting the thickness of the A plate 18 and the C plate 20 .

A layer in which a polymerizable liquid crystal compound is cured is formed, for example, on an alignment film provided on a substrate. This base material may be a base material that has a function of supporting the alignment film and is formed in an elongated shape. This substrate functions as a release support and can support the retardation film 12 for transfer. Furthermore, it is preferable that the surface has adhesive strength to the extent that it can be peeled off. Examples of the substrate include the resin films exemplified as the material for the protective film.

The thickness of the substrate is not particularly limited, but is preferably in the range of, for example, 20 μm or more and 200 μm or less. Strength is imparted when the thickness of the substrate is 20 μm or more. On the other hand, if the thickness is 200 μm or less, it is possible to suppress an increase in processing waste and wear of the cutting blade when cutting the base material into a sheet base material.

The substrate may be subjected to various antiblocking treatments. Anti-blocking treatments include, for example, easy-adhesion treatments, kneading treatments with fillers and the like, embossing (knurling treatments), and the like. By applying such antiblocking treatment to the base material, it is possible to effectively prevent sticking between the base materials when winding the base material, that is, so-called blocking, and to produce an optical film with high productivity. becomes possible.

A layer in which the polymerizable liquid crystal compound is cured is formed on the substrate via the alignment film. That is, the substrate and the alignment film are laminated in this order, and the layer in which the polymerizable liquid crystal compound is cured is laminated on the alignment film.

The alignment film is not limited to a vertical alignment film, and may be an alignment film that horizontally aligns the molecular axis of the polymerizable liquid crystal compound, or an alignment film that tilts the molecular axis of the polymerizable liquid crystal compound. When fabricating the A plate 18, a horizontal alignment film can be used, and when fabricating the C plate 20, a vertical alignment film can be used. The alignment film has a solvent resistance that does not dissolve when a composition containing a polymerizable liquid crystal compound described later is applied, etc., and also has heat resistance in heat treatment for solvent removal and alignment of the liquid crystal compound. preferable. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film, and a groove alignment film in which an uneven pattern or a plurality of grooves are formed on the surface for alignment. The thickness of the alignment film is usually in the range of 10 nm to 10000 nm, preferably 10 nm to 1000 nm, more preferably 500 nm or less, and still more preferably 10 nm 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. A cured product or the like can be used. Specifically, (meth)acrylate monomers include, for example, 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, urethane acrylate, and the like. In addition, as resin, these 1 types may be sufficient, and the mixture of 2 or more types may be sufficient.

A photo-alignment film is formed from a composition containing a polymer or monomer having a photoreactive group and a solvent. A photoreactive group refers to a group that exhibits liquid crystal alignment ability upon irradiation with light. Specific examples thereof include groups involved in photoreactions, such as orientation induction of molecules caused by light irradiation or isomerization reactions, dimerization reactions, photocrosslinking reactions, photodecomposition reactions, and the like, which are the origin of liquid crystal alignment ability. Among them, a group involved in a dimerization reaction or a photocrosslinking reaction is preferable from the viewpoint of excellent orientation. As the photoreactive group, a group having an unsaturated bond, particularly a double bond is preferable, and a carbon-carbon double bond (C=C bond), a carbon-nitrogen double bond (C=N bond), a nitrogen-nitrogen double bond Groups having at least one selected from the group consisting of a heavy bond (N=N bond) and a carbon-oxygen double bond (C=O bond) are particularly preferred.

Photoreactive groups having a C=C bond include vinyl groups, polyene groups, stilbene groups, stilbazole groups, stilbazolium groups, chalcone groups and cinnamoyl groups. Photoreactive groups having a C═N bond include groups having structures such as aromatic Schiff bases and aromatic hydrazones. Examples of the photoreactive group having an N=N bond include an azobenzene group, an azonaphthalene group, an aromatic heterocyclic azo group, a bisazo group, a formazan group, and a group having an azoxybenzene structure. A benzophenone group, a coumarin group, an anthraquinone group, a maleimide group, etc. are mentioned as a photoreactive group which has a C=O bond. These groups may have substituents such as alkyl groups, alkoxy groups, aryl groups, allyloxy groups, cyano groups, alkoxycarbonyl groups, hydroxyl groups, sulfonic acid groups, and halogenated alkyl groups.

Among them, a photoreactive group that participates in a photodimerization reaction is preferable, since the amount of polarized light irradiation required for photoalignment is relatively small, and a photoalignment film having excellent thermal stability and stability over time can be easily obtained. , cinnamoyl and chalcone groups are preferred. As the polymer having a photoreactive group, a polymer having a cinnamoyl group having a cinnamic acid structure at the end of the polymer side chain is particularly preferred.

Although the type of the polymerizable liquid crystal compound used in the present embodiment is not particularly limited, it is classified into a rod-shaped type (rod-shaped liquid crystal compound) and a disk-shaped type (disk-shaped liquid crystal compound, discotic liquid crystal compound) according to its shape. can. Furthermore, there are low-molecular-weight types and high-molecular-weight types, respectively. The term "polymer" generally refers to a polymer having a degree of polymerization of 100 or more (see "Polymer Physics/Phase Transition Dynamics, Masao Doi, p. 2, Iwanami Shoten, 1992").

Any polymerizable liquid crystal compound can be used in the present embodiment. Furthermore, two or more kinds of rod-like liquid crystal compounds, two or more kinds of discotic liquid crystal compounds, or mixtures of rod-like liquid crystal compounds and discotic liquid crystal compounds may be used.

As the rod-like liquid crystal compound, for example, those described in claim 1 of JP-A-11-513019 or paragraphs [0026] to [0098] of JP-A-2005-289980 can be suitably used. . As the discotic liquid crystal compound, for example, those described in paragraphs [0020] to [0067] of JP-A-2007-108732, or paragraphs [0013] to [0108] of JP-A-2010-244038 are suitable. can be used for

Two or more types of polymerizable liquid crystal compounds may be used in combination. In that case, at least one type has two or more polymerizable groups in the molecule. That is, the layer in which the polymerizable liquid crystal compound is cured is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization. In this case, it is no longer necessary to exhibit liquid crystallinity after forming a layer.

A polymerizable liquid crystal compound has a polymerizable group capable of undergoing a polymerization reaction. As the polymerizable group, for example, a functional group capable of an addition polymerization reaction such as a polymerizable ethylenically unsaturated group or a ring-polymerizable group is preferable. More specifically, examples of polymerizable groups include (meth)acryloyl groups, vinyl groups, styryl groups, and allyl groups. Among them, a (meth)acryloyl group is preferred. In addition, a (meth)acryloyl group is a concept including both a methacryloyl group and an acryloyl group.

A layer in which a polymerizable liquid crystal compound is cured can be formed by coating a composition containing a polymerizable liquid crystal compound, for example, on an alignment film, as described later. The composition may contain components other than the polymerizable liquid crystal compound described above. For example, the composition preferably contains a polymerization initiator. As the polymerization initiator to be used, for example, a thermal polymerization initiator or a photopolymerization initiator is selected according to the type of polymerization reaction. Examples of photopolymerization initiators include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones, and the like. The amount of the polymerization initiator 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.

Moreover, the composition may contain a polymerizable monomer from the viewpoint of the uniformity of the coating film and the strength of the film. Polymerizable monomers include radically polymerizable or cationically polymerizable compounds. Among these, polyfunctional radically polymerizable monomers are preferred.

As the polymerizable monomer, those that can be copolymerized with the polymerizable liquid crystal compound described above are preferred. Specific polymerizable monomers include, for example, those described in paragraphs [0018] to [0020] of JP-A-2002-296423. The amount of the polymerizable monomer 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.

The composition may contain a surfactant from the viewpoint of the uniformity of the coating film and the strength of the film. Surfactants include conventionally known compounds. Among them, fluorine-based compounds are particularly preferable. Specific surfactants include, for example, compounds described in paragraphs [0028] to [0056] in JP-A-2001-330725, and paragraphs [0069] to [0126] in JP-A-2005-62673. and compounds described in.

Moreover, the composition may contain a solvent, and an organic solvent is preferably used. Examples of organic solvents include amides (eg, N,N-dimethylformamide), sulfoxides (eg, dimethylsulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , chloroform, dichloromethane), esters (eg, methyl acetate, ethyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Among them, alkyl halides and ketones are preferred. Moreover, you may use together 2 or more types of organic solvents.

Further, the composition contains a vertical alignment accelerator such as a vertical alignment agent on the polarizing film interface side and a vertical alignment agent on the air interface side, and a horizontal alignment accelerator such as a horizontal alignment agent on the polarizing film interface side and an air interface side horizontal alignment agent. Various alignment agents may also be included. Furthermore, the composition may contain an adhesion improver, a plasticizer, a polymer, etc., in addition to the above components.

When the retardation film 12 includes two or more layers of the cured polymerizable liquid crystal compound as the A plate 18 and the C plate 20, each layer of the cured polymerizable liquid crystal compound is formed on the alignment film, and the two are adhered, for example. The retardation film 12 can be manufactured by laminating via the agent layer 8c. After laminating both, the substrate and the alignment film can be peeled off. The thickness of the retardation film 12 is preferably 3-30 μm, more preferably 5-25 μm.

The retardation film 12 may be manufactured by preparing a long member, bonding the respective members together by roll-to-roll, and then cutting into a predetermined shape, or by cutting each member into a predetermined shape. After cutting, it may be pasted together. C-plate 20 may be obtained by forming C-plate 20 directly on A-plate 18 . That is, the adhesive layer 8c can be omitted.

Hereinafter, in this embodiment, unless otherwise specified, the A plate 18 is a positive A plate that gives a phase difference of λ/4, and the C plate 20 is a positive C plate.

The image display device 2 may further include at least one of a front plate and a light shielding pattern (bezel). The front plate and the light shielding pattern will be explained respectively.

<Front panel>
The front plate may be arranged on the viewing side of the polarizing plate 10 . The front plate can be laminated on the polarizing plate 10 via an adhesive layer. Examples of the adhesive layer include the above-described adhesive layer 8b and adhesive layer 8c.

Examples of the front plate include glass and a resin film having a hard coat layer on at least one surface thereof. As the glass, for example, high transmission glass or tempered glass can be used. Especially when using a thin transparent surface material, chemically strengthened glass is preferable. The thickness of the glass can be, for example, 100 μm to 5 mm.

A front panel comprising a hard coat layer on at least one surface of a resin film can have flexible characteristics, unlike existing glass, which is not rigid. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 to 100 μm.

Examples of resin films include cycloolefin-based derivatives having units of monomers containing cycloolefins such as norbornene or polycyclic norbornene-based monomers, cellulose (diacetylcellulose, triacetylcellulose, acetylcellulose butyrate, isobutyl ester cellulose , propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacryl, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, Polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethylmethacrylate, polyethyleneterephthalate, polybutyleneterephthalate, polyethylenenaphthalate, polycarbonate , polyurethane, epoxy, or other polymer film. Unstretched, uniaxially stretched or biaxially stretched film can be used as the resin film. These polymers can be used alone or in combination of two or more. Resin films include polyamide-imide films or polyimide films with excellent transparency and heat resistance, uniaxially or biaxially oriented polyester films, and cycloolefin derivative films with excellent transparency and heat resistance that can be used for larger films. , polymethyl methacrylate films and transparent and optically non-anisotropic triacetyl cellulose and isobutyl ester cellulose films are preferred. The thickness of the resin film may be 5-200 μm, preferably 20-100 μm.

<Light shielding pattern>
A light shielding pattern (bezel) can be formed on the image display layer 4 side of the front plate. The light-shielding pattern can hide each wiring of the image display device 2 from being visually recognized by the user. The color and/or material of the light-shielding pattern is not particularly limited, and may be formed of resin materials having various colors such as black, white, and gold. In one embodiment, the thickness of the light shielding pattern may range from 2 μm to 50 μm, preferably from 4 μm to 30 μm, more preferably from 6 μm to 15 μm. Further, in order to suppress the inclusion of bubbles due to the difference in level between the light shielding pattern and the display portion and the visibility of the boundary portion, the light shielding pattern can be given a shape.

[Manufacturing method of circularly polarizing plate]
The circularly polarizing plate 6 is manufactured by laminating the polarizing plate 10 and the retardation film 12 via the adhesive layer 8b. For example, after manufacturing the polarizing plate 10 , the adhesive layer 8 b formed on the release film is laminated on the protective film 16 facing the retardation film 12 . The release film on the adhesive layer 8b is peeled off, and the polarizing plate 10 and the separately manufactured retardation film 12 are attached via the exposed adhesive layer 8b. A circularly polarizing plate 6 is thus obtained.

[Method for manufacturing image display device]
The image display device 2 is obtained by bonding the retardation film 12 of the circularly polarizing plate 6 to the image display layer 4 via the adhesive layer 8a. Normally, as shown in FIG. 1, the circularly polarizing plate 6 is attached to the image display layer 4 so that the C plate 20 is located on the image display layer 4 side.

Conditions that the image display device 2 satisfies will be further described. As indicated by the white arrow in FIG. 2, in the image display device 2, when viewed from an inclination angle of 50 degrees (indicated as "50 degrees" in FIG. 2) with respect to the vertical direction N of the image display surface 4a. assume. The vertical direction N is the front direction of the image display device 2, and the tilt angle is the angle toward the image display device 2 when the front direction is 0 degrees. In this case, when the total retardation in the vertical direction N between the polarizing film 14 in the circularly polarizing plate 6 and the image display layer 4 is Rth, Rth is the reflection hue b ^* when the inclination angle is 50 degrees. satisfies the following formula (i). Rth in formula (i) is the retardation for a wavelength of 550 nm.
2.5×b ^* −25 ≦Rth≦2.5×b ^* +40 (i)

In the image display device 2 shown in FIG. 1, the above Rth corresponds to the retardation RthC of the C plate 20 in the thickness direction.

In order to realize the above formula (i), for example, the reflection hue b ^* is measured when the tilt angle of the image display layer 4 is 50 degrees, and the C plate 20 is adjusted so as to satisfy the formula (i). The thickness of the layer may be adjusted, and the types and compounding ratios of the thermoplastic resin and the polymerizable liquid crystal compound may be adjusted.

The effect of the image display device 2 configured to satisfy the formula (i) will be described in comparison with the conventional case.

When the image display layer 4 is, for example, an OLED display device, external light incident on the image display layer 4 is specularly reflected by the metal electrodes or the like, as described above.

In order to prevent such reflection, conventionally, a circularly polarizing plate is arranged on the image display surface side of the image display layer. However, even in a conventional image display device having a circularly polarizing plate, the reflection hue when the image display layer is viewed from an oblique direction is not sufficiently considered. When rotated, the hue of the external light reflected light tended to change.

On the other hand, the image display device 2 satisfies the expression (i). That is, Rth, which is the total retardation in the vertical direction N between the polarizing film 14 and the image display layer 4 , corresponds to the reflection hue b ^* of the image display layer 4 . Therefore, even if the image display device 2 is rotated in-plane while viewing the screen from an oblique direction, the change in the hue of the reflected light can be suppressed.

An experimental example verifying this point will be described below. In the experimental examples, materials and the like will be specifically illustrated, but the present invention is not limited to the following experimental examples. Unless otherwise specified, "%" and "parts" in the description of Experimental Examples mean % by mass and parts by mass. In the following description, a light reflecting layer is used as a model of the image display layer 4. FIG. That is, the light reflecting layer under experiment corresponds to the image display layer 4 .

[Experimental example]
<Method for measuring film thickness>
The thickness of the film was measured using a contact film thickness gauge (MH-15M, counter TC101, MS-5C manufactured by Nikon Corporation).

<Retardation measurement method>
The retardation in the thickness direction and the in-plane retardation of the A plate and the C plate were measured using a birefringence evaluation device (KOBRA-WPR manufactured by Oji Scientific Instruments Co., Ltd.).

The retardation of the light reflecting layer for each incident angle was measured using a spectroscopic ellipsometer (JA Woollam M-2000).

[Preparation of light reflecting layer]
The following four types of light reflecting layers were prepared.
Light reflecting layer A
Light reflecting layer B
Light reflection layer C
Light reflecting layer D
The light reflecting layers A to C were provided on one side of the resin film and were flexible light reflecting layers that could bend together with the resin film. The light reflecting layer D was provided on one surface of the inorganic glass plate and was a rigid light reflecting layer that could not be bent.

The oblique hue b ^* of each of the light-reflecting layers AD was measured. Specifically, the oblique hue (reflection hue) b ^* of the light reflecting layers A to D from the direction of the tilt angle of 50 degrees was measured by a display evaluation system DMS803 (manufactured by Instrument Systems GmbH). The measurement results are shown in Table 1.

[Production of circularly polarizing plate]
[Preparation of Composition for Forming Horizontal Alignment Film]
Five parts of a photo-alignable material having the following structure (weight average molecular weight: 30000) and 95 parts of cyclopentanone (solvent) were mixed. The obtained mixture was stirred at 80° C. for 1 hour to obtain a composition for forming a horizontal alignment film.

[Preparation of composition for forming vertical alignment film]
Sanever SE610 manufactured by Nissan Chemical Industries, Ltd. was used.

[Preparation of composition for forming cured film of horizontally aligned liquid crystal]
In order to form a horizontally aligned liquid crystal cured film (corresponding to the A plate 18), the following polymerizable liquid crystal compound A and polymerizable liquid crystal compound B were used. Polymerizable liquid crystal compound A was produced by the method described in JP-A-2010-31223. Polymerizable liquid crystal compound B was produced according to the method described in JP-A-2009-173893. Each molecular structure is shown below.

[Polymerizable liquid crystal compound A]

[Polymerizable liquid crystal compound B]

Polymerizable liquid crystal compound A and polymerizable liquid crystal compound B were mixed at a mass ratio of 87:13. Per 100 parts of the resulting mixture, 1.0 parts of a leveling agent (F-556; manufactured by DIC Corporation), a polymerization initiator 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl) 6 parts of butan-1-one (Irgacure 369, manufactured by BASF Japan Ltd.) was added. Furthermore, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration was 13%, and the mixture was stirred at 80° C. for 1 hour to obtain a composition for forming a horizontally aligned liquid crystal cured film.

[Adjustment of Composition for Forming Cured Film of Vertically Aligned Liquid Crystal]
In order to form a vertically aligned liquid crystal cured film (corresponding to the C plate 20), a composition was prepared in the following procedure. 0.1 part of F-556 as a leveling agent and 3 parts of Irgacure 369 as a polymerization initiator were added to 100 parts of Paliocolor LC242 (registered trademark of BASF), which is a polymerizable liquid crystal compound. Cyclopentanone was added so that the solid content concentration was 13% to obtain a composition for forming a vertically aligned liquid crystal cured film.

[Preparation of polarizing plate]
A polyvinyl alcohol (PVA) film having an average degree of polymerization of about 2,400, a degree of saponification of 99.9 mol % or more, and a thickness of 75 µm was prepared. After the PVA film was immersed in pure water at 30°C, it was iodine dyed by immersing it in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30°C (iodine dyeing step). . The PVA film that had undergone the iodine dyeing process was subjected to boric acid treatment by immersing it in an aqueous solution having a mass ratio of potassium iodide/boric acid/water of 12/5/100 at 56.5°C (boric acid treatment process). . After the PVA film that had undergone the boric acid treatment step was washed with pure water at 8°C, it was dried at 65°C to obtain a polarizing film in which iodine was adsorbed and oriented in polyvinyl alcohol. The stretching of the PVA film was performed in the iodine dyeing process and the boric acid treatment process. The total draw ratio of the PVA film was 5.3 times. The thickness of the obtained polarizing film was 10 μm.

A polarizing film and a saponified triacetyl cellulose (TAC) film (KC4UYTAC manufactured by Konica Minolta, Inc., thickness 40 μm) were pasted together with a nip roll via a water-based adhesive. The obtained laminate was dried at 60° C. for 2 minutes while maintaining the tension at 430 N/m to obtain a polarizing plate having a TAC film as a protective film on one side. The water-based adhesive is 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., "Kuraray Poval KL318"), and water-soluble polyamide epoxy resin (manufactured by Taoka Chemical Co., Ltd., "Sumireze Resin 650". , an aqueous solution having a solid concentration of 30%] and 1.5 parts.

The optical properties of the obtained polarizing plate were measured. The measurement was performed with a spectrophotometer (“V7100”, manufactured by JASCO Corporation) with the polarizing film surface of the polarizing plate obtained above as the incident surface. The absorption axis of the polarizing plate coincides with the stretching direction of the polyvinyl alcohol. −1.0, and the single hue b was 2.7.

[Preparation of horizontal alignment liquid crystal cured film (A plate)]
Corona treatment was performed on a cyclic olefin resin (COP) film (ZF-14-50) manufactured by Zeon Corporation. Corona treatment was performed using TEC-4AX manufactured by Ushio Inc. The corona treatment was performed once under the conditions of an output of 0.78 kW and a treatment speed of 10 m/min. The composition for forming a horizontal alignment film was applied to the COP film with a bar coater and dried at 80° C. for 1 minute. Using a polarized UV irradiation device (“SPOT CURE SP-9”, manufactured by Ushio Inc.), the coating film was irradiated at an axial angle of 45° so that the integrated light amount at a wavelength of 313 nm was 100 mJ/cm ² . A polarized UV exposure was performed. The film thickness of the obtained horizontal alignment film was 100 nm.

Subsequently, the horizontally aligned liquid crystal cured film-forming composition was applied to the horizontally aligned film using a bar coater and dried at 120° C. for 1 minute. Using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio Inc.), the coating film is irradiated with ultraviolet rays (in a nitrogen atmosphere, integrated light intensity at a wavelength of 365 nm: 500 mJ/cm ² ). Thus, a horizontally aligned liquid crystal cured film (corresponding to the A plate 18) was formed. The film thickness of the horizontally aligned liquid crystal cured film was about 1.9 μm.

An adhesive layer was laminated on the horizontally aligned liquid crystal cured film. A film in which the COP film, the horizontal alignment film, and the horizontal alignment cured film of the horizontal liquid crystal are laminated was bonded to the glass via the pressure-sensitive adhesive layer. The COP film was peeled off to obtain a sample for retardation measurement.

The results of measuring the retardation R0A (λ) at each wavelength are as follows, and the horizontally aligned liquid crystal cured film exhibited reverse wavelength dispersion.
R0A(450) = 121 nm
R0A(550) = 139 nm
R0A(650) = 143 nm
R0A(450)/R0A(550)=0.87
R0A(650)/R0A(550)=1.03

The horizontally aligned liquid crystal cured film was a positive A plate satisfying the relationship nx>ny≈nz. The results of measuring the retardation RthA(λ) in the thickness direction of the horizontally aligned liquid crystal cured film at each wavelength are as follows.
RthA(450) = 67 nm
RthA(550) = 76 nm
RthA(650) = 79 nm

[Preparation of vertically aligned liquid crystal cured film (C plate)]
Corona treatment was performed on the COP film. The corona treatment conditions were the same as above. A composition for forming a vertical alignment film was applied onto the COP film with a bar coater and dried at 80° C. for 1 minute to obtain a vertical alignment film. The film thickness of the obtained vertical alignment film was 50 nm.

A vertically aligned liquid crystal cured film-forming composition was applied to the vertically aligned film using a bar coater and dried at 90° C. for 120 seconds. Using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio Inc.), the coating film is irradiated with ultraviolet rays (in a nitrogen atmosphere, integrated light intensity at a wavelength of 365 nm: 500 mJ/cm ² ). to form a vertically aligned liquid crystal cured film (corresponding to the C plate 20). Thus, a film (retardation film) in which the COP film, the horizontal alignment film, the cured horizontal alignment film, the vertical alignment film, and the cured vertical alignment liquid crystal film were laminated was obtained. The film thickness of the vertically aligned liquid crystal cured film was 0.3 μm.

An adhesive layer was laminated on the vertically aligned liquid crystal cured film. A film composed of a COP film, an alignment film, and a vertically aligned liquid crystal cured film was bonded to glass via the pressure-sensitive adhesive layer. The COP film was peeled off to obtain a sample for retardation measurement. The results of measuring the retardation RthC1 (550) at a wavelength of 550 nm were as follows.
RthC(550) = -30 nm
The vertically aligned liquid crystal cured film was a positive C plate satisfying the relationship nx≈ny<nz.

The vertically aligned liquid crystal cured film surface of the vertically aligned liquid crystal cured film (C plate) and the horizontally aligned film formed on the COP film and the horizontally aligned liquid crystal cured film (A plate) formed on the COP film. Then, the COP film on the A plate side was peeled off to obtain a film in which the COP film, C plate, and A plate were laminated in this order.

Among these films, the horizontally aligned liquid crystal cured film (A plate) was subjected to corona treatment. The corona treatment conditions were the same as above. The polarizing film and the horizontally aligned liquid crystal cured film (A plate) in the polarizing plate were laminated via an adhesive layer so that they were in contact with each other. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the horizontally aligned liquid crystal cured film was 45°. Thus, a circularly polarizing plate (1) in which the retardation film and the polarizing plate were laminated via the pressure-sensitive adhesive layer was obtained. This circularly polarizing plate (1) had a layer structure of a TAC film, a polarizing film, an adhesive layer, a horizontally aligned liquid crystal cured film (A plate), an adhesive layer, and a vertically aligned liquid crystal cured film (C plate). .

[Preparation of circularly polarizing plate (2)]
A circularly polarizing plate (2) was prepared in the same manner as the circularly polarizing plate (1), except that the film thickness of the vertically aligned liquid crystal cured film was set to 0.4 μm and RthC(550)=−40 nm.

[Preparation of circularly polarizing plate (3)]
A circularly polarizing plate (3) was prepared in the same manner as the circularly polarizing plate (1) except that the film thickness of the vertically aligned liquid crystal cured film was set to 0.5 μm and RthC(550)=−50 nm.

[Preparation of circularly polarizing plate (4)]
A circularly polarizing plate (4) was prepared in the same manner as the circularly polarizing plate (1), except that the film thickness of the vertically aligned liquid crystal cured film was set to 0.6 μm and RthC(550)=−60 nm.

[Preparation of circularly polarizing plate (5)]
A circularly polarizing plate (5) was prepared in the same manner as the circularly polarizing plate (1) except that the film thickness of the vertically aligned liquid crystal cured film was set to 0.8 μm and RthC(550)=−80 nm.

[Preparation of circularly polarizing plate (6)]
A circularly polarizing plate (6) was prepared in the same manner as the circularly polarizing plate (1) except that the film thickness of the vertically aligned liquid crystal cured film was set to 0.9 μm and RthC(550)=−90 nm.

[Preparation of circularly polarizing plate (7)]
A circularly polarizing plate (7) was produced in the same manner as the circularly polarizing plate (1) except that the film thickness of the vertically aligned liquid crystal cured film was set to 1.0 μm and RthC(550)=−100 nm.

[Preparation of circularly polarizing plate (8)]
A circularly polarizing plate (8) was prepared in the same manner as the circularly polarizing plate (1) except that the film thickness of the vertically aligned liquid crystal cured film was 1.6 μm and RthC(550)=−160 nm.

[Experimental example 1]
<Preparation of measurement sample (1-1)>
Circularly polarizing plate (1) was attached to an inorganic glass plate (manufactured by Corning, product name: Eagle XG) via an adhesive layer to obtain a circularly polarizing plate-attached glass plate. At this time, the circularly polarizing plate (1) was attached to the inorganic glass plate so that the horizontal alignment film was located on the foam of the inorganic glass plate. In the glass plate with a circularly polarizing plate, ethanol is dropped on the functional surface of the light reflecting layer A (b ^* = 12.18), and the above glass plate with a circularly polarizing plate is left to stand at the place where it was dropped to form a light reflecting layer. A measurement sample (1-1) was obtained in which a glass plate with a circularly polarizing plate was placed on A on the inorganic glass plate side in close contact therewith via ethanol.

The total retardation Rth in the vertical direction between the light reflecting layer A and the polarizing film in the measurement sample (1-1) was 46 nm. The retardation Rth of the measurement sample (1-1) is the thickness direction retardation RthA (550) of the horizontally aligned liquid crystal cured film and the thickness direction retardation of the vertically aligned liquid crystal cured film included in the measurement sample (1-1). It was the sum of RthC(550). The same applies to other measurement samples described below. In this case, the Rth of the measurement sample corresponds to the sum of the retardations in the vertical direction (thickness direction) of the circular polarizer used in the measurement sample, so the Rth of the measurement sample may be referred to as the Rth of the circular polarizer. be.

<Preparation of measurement sample (1-2)>
Measurement sample (1-2) was obtained in the same manner as measurement sample (1-1) except that circular polarizer (2) was used instead of circular polarizer (1).

The total retardation Rth in the vertical direction between the light reflecting layer A and the polarizing film in the measurement sample (1-2) was 36 nm.

<Preparation of measurement sample (1-3)>
A measurement sample (1-3) was obtained in the same manner as the measurement sample (1-1) except that the circular polarizer (3) was used instead of the circular polarizer (1).

Rth, which is the total retardation in the vertical direction between the light reflecting layer A and the polarizing film in the measurement sample (1-3), was 26 nm.

<Preparation of measurement sample (1-4)>
A measurement sample (1-4) was obtained in the same manner as the measurement sample (1-1), except that the circular polarizer (4) was used instead of the circular polarizer (1).

The total retardation Rth in the vertical direction between the light reflecting layer A and the polarizing film in the measurement sample (1-4) was 16 nm.

<Preparation of measurement sample (1-5)>
A measurement sample (1-5) was obtained in the same manner as the measurement sample (1-1) except that the circular polarizer (7) was used instead of the circular polarizer (1).

The total retardation Rth in the vertical direction between the light reflecting layer A and the polarizing film in the measurement sample (1-5) was -24 nm.

Oblique angle color difference was measured for the measurement samples (1-1) to (1-5) produced. Since the measurement method is the same for the measurement samples (1-1) to (1-5), the measurement sample (1-1) will be specifically described as an example.

Reflected hues a ^* and b ^* were measured with a display evaluation system DMS803 (manufactured by Instrument Systems GmbH) from the direction of a tilt angle of 10 degrees (direction of 10 degrees with respect to the thickness direction of the light reflecting layer A) of the measurement sample (1-1). While rotating the measurement sample (1-1) in the sample plane. The resulting reflected hues a ^* and b ^* were plotted on the a ^* -b ^* coordinate system to obtain a hue diagram (color shift). FIG. 3 is a schematic diagram of an example of a hue diagram. The figure 8-shaped solid line in the figure shows the trajectory (hue diagram) of the set of (a ^* , b ^* ) obtained when the measurement sample (1-1) is rotated within the sample plane. By rotating the measurement sample (1-1) by 360 degrees, it returns to the original position (that is, the set of (a ^* , b ^* ) when the rotation angle is 0 degrees). The length of the major axis of the resulting hue diagram (the axis indicated by the dashed line in the figure) was determined and defined as Δa ^* b ^* . Next, reflection hues a ^* and b ^* were similarly measured from directions with tilt angles of 20°, 30°, 40° and 50° to obtain Δa ^* b ^* .

Δa ^* b ^* was similarly obtained for measurement samples (1-2) to (1-5).

The experimental results were as shown in Table 2.

As shown in Table 2, when the tilt angle is 10 degrees, which is almost the front direction, the measurement samples (1-1) to (1-5), that is, the Rth of the circularly polarizing plate is 46, 36, 16, - 24, almost no change in Δa ^* b ^* occurred. On the other hand, as the tilt angle increased, a difference in Δa ^* b ^* occurred between the measurement samples (1-1) to (1-5). At an inclination angle of 50 degrees, Δa ^* b ^* was the smallest for the measurement sample (1-1), that is, when the Rth of the circularly polarizing plate was 46 nm. That is, for the light reflecting layer A, the Rth of the circularly polarizing plate was optimal at 46 nm.

[Experimental example 2]
<Preparation of measurement sample (2-1)>
A measurement sample (2-1) was obtained in the same manner as the measurement sample (1-1) except that the light reflection layer B (b ^* =14.14) was used instead of the light reflection layer A.

Rth, which is the total retardation in the vertical direction between the light reflecting layer B and the polarizing film in the measurement sample (2-1), was 46 nm.

<Preparation of measurement sample (2-2)>
A measurement sample (2-2) was obtained in the same manner as the measurement sample (1-2), except that the light reflection layer B (b ^* =14.14) was used instead of the light reflection layer A.

Rth, which is the total retardation in the vertical direction between the light reflecting layer B and the polarizing film in the measurement sample (2-2), was 36 nm.

<Preparation of measurement sample (2-3)>
A measurement sample (2-3) was obtained in the same manner as the measurement sample (1-3), except that the light reflection layer B (b ^* =14.14) was used instead of the light reflection layer A.

The total retardation Rth in the vertical direction between the light reflecting layer B and the polarizing film in the measurement sample (2-3) was 26 nm.

<Preparation of measurement sample (2-4)>
Measurement sample (2-4) was obtained in the same manner as measurement sample (1-5) except that light reflection layer B (b ^* =14.14) was used instead of light reflection layer A.

The total retardation Rth in the vertical direction between the light reflecting layer B and the polarizing film in the measurement sample (2-4) was -24 nm.

Δa ^* b ^* was obtained in the same manner as in Experimental Example 1 for the prepared measurement samples (2-1) to (2-4). The experimental results were as shown in Table 3.

Also in Experimental Example 2, as shown in Table 3, when the tilt angle is 10 degrees, which is the almost front direction, the measurement samples (2-1) to (2-4), that is, the Rth of the circularly polarizing plate is 46. , 36, 26, and -24, there is almost no change in ^{Δa *} b ^{* .} happened in between. At an inclination angle of 50 degrees, Δa ^* b ^* was the smallest for the measurement sample (2-2), that is, when the Rth of the circularly polarizing plate was 36 nm. That is, for the light reflecting layer B, the Rth of the circularly polarizing plate of 36 nm was optimal.

[Experimental example 3]
<Preparation of measurement sample (3-1)>
A measurement sample (3-1) was obtained in the same manner as the measurement sample (1-1), except that the light reflection layer C (b ^* =6.46) was used instead of the light reflection layer A.

Rth, which is the total retardation in the vertical direction between the light reflecting layer C and the polarizing film in the measurement sample (3-1), was 46 nm.

<Preparation of measurement sample (3-2)>
A measurement sample (3-2) was obtained in the same manner as the measurement sample (1-2), except that the light reflection layer C (b ^* =6.46) was used instead of the light reflection layer A.

Rth, which is the total retardation in the vertical direction between the light reflecting layer C and the polarizing film in the measurement sample (3-2), was 36 nm.

<Preparation of measurement sample (3-3)>
Measurement sample (3-3) was obtained in the same manner as measurement sample (1-3), except that light reflection layer C (b ^* =6.46) was used instead of light reflection layer A.

The total retardation Rth in the vertical direction between the light reflecting layer C and the polarizing film in the measurement sample (3-3) was 26 nm.

<Preparation of measurement sample (3-4)>
A measurement sample (3-4) was obtained in the same manner as the measurement sample (1-4) except that the light reflection layer C (b ^* =6.46) was used instead of the light reflection layer A.

The total retardation Rth in the vertical direction between the light reflecting layer C and the polarizing film in the measurement sample (3-4) was 16 nm.

<Production of measurement sample (3-5)>
A measurement sample (3-5) was obtained in the same manner as the measurement sample (1-5) except that the light reflection layer C (b ^* =6.46) was used instead of the light reflection layer A.

The total retardation Rth between the light reflecting layer C and the polarizing film in the measurement sample (3-5) in the vertical direction was -24 nm.

Δa ^* b ^* was obtained in the same manner as in Experimental Example 1 for the prepared measurement samples (3-1) to (3-5). The experimental results were as shown in Table 4.

Also in Experimental Example 3, as shown in Table 4, when the tilt angle is 10 degrees, which is the almost front direction, the measurement samples (3-1) to (3-5), that is, the Rth of the circularly polarizing plate is 46. , 36, 26, 16, and -24, there is almost no change in ^{Δa *} b ^{* .} 3-5). At an inclination angle of 50 degrees, Δa ^* b ^* was the smallest for the measurement sample (3-3), that is, when the Rth of the circularly polarizing plate was 26 nm. That is, for the light-reflecting layer C, the Rth of the circularly polarizing plate of 26 nm was optimal.

[Experimental example 4]
<Preparation of measurement sample (4-1)>
Measurement sample (4-1) was obtained in the same manner as measurement sample (1-1), except that light reflection layer D (b ^* = -5.59) was used instead of light reflection layer A. .

Rth, which is the total retardation in the vertical direction between the light reflecting layer C and the polarizing film in the measurement sample (3-1), was 46 nm.

<Preparation of measurement sample (4-2)>
^Measurement sample (1 A measurement sample (4-2) was obtained in the same manner as in -1).

The total retardation Rth in the vertical direction between the light reflecting layer D and the polarizing film in the measurement sample (4-2) was -4 nm.

<Preparation of measurement sample (4-3)>
^Measurement sample (1 A measurement sample (4-3) was obtained in the same manner as in the case of -1).

The total retardation Rth in the vertical direction between the light reflecting layer D and the polarizing film in the measurement sample (4-3) was -14 nm.

<Preparation of measurement sample (4-4)>
^Measurement sample (1 A measurement sample (4-4) was obtained in the same manner as in the case of -1).

The total retardation Rth in the vertical direction between the light reflecting layer D and the polarizing film in the measurement sample (4-4) was -24 nm.

<Preparation of measurement sample (4-5)>
^Measurement sample (1 A measurement sample (4-5) was obtained in the same manner as in the case of -1).

The total retardation Rth in the vertical direction between the light reflecting layer D and the polarizing film in the measurement sample (4-5) was -84 nm.

Δa ^* b ^* was obtained in the same manner as in Experimental Example 1 for the prepared measurement samples (4-1) to (4-5). The experimental results were as shown in Table 5.

Also in Experimental Example 4, as shown in Table 5, when the tilt angle is 10 degrees, which is the almost front direction, the measurement samples (4-1) to (4-5), that is, the Rth of the circularly polarizing plate is 46. , −4, −14, −24, and −84, there was almost no change in Δa ^* b ^* . When the tilt angle was 50 degrees, a difference of Δa ^* b ^* occurred between the measurement samples (4-1) to (4-5). At an inclination angle of 50 degrees, Δa ^* b ^* was the smallest for the measurement sample (4-4), that is, when the Rth of the circularly polarizing plate was −24 nm. That is, for the light reflecting layer D, the optimum Rth of the circularly polarizing plate was -24 nm.

From the results of Experimental Examples 1 to 4, the relationship between the reflected hue b ^* of the light reflecting layers A to D and the optimum Rth is as shown in Table 6 at the inclination angle of 50 degrees at which the difference in Δa ^* b ^* appears large. there were.

FIG. 4 is a graph plotting the optimum Rth shown in Table 6 against reflected hue b ^* . The horizontal axis of FIG. 4 indicates the reflected hue b ^* , and the vertical axis indicates the optimum Rth. Lines α and β in the figure are lines represented by the following equations.
α: Rth=2.5×b ^* −25
β: Rth=2.5×b ^* +40

As shown in FIG. 4, the optimal Rth and reflection hue b ^* pairs shown in Table 6 are contained between line α and line β. Therefore, it can be understood that the image display device 2 can suppress a change in the hue of the reflected external light when viewed from an oblique direction by satisfying the expression (i). Region I in FIG. 4 is a region with a reflection hue b ^* of 10-16. Based on Table 6 and FIG. 4, Region I contains the relationship between reflected hue b ^* and optimum Rth for light reflective layer A and light reflective layer B. TABLE 6 FIG. Region II in FIG. 4 is a region where the reflected hue b ^* is 4-8. Based on Table 6 and FIG. 4, Region II contains the relationship between reflected hue b ^* and optimum Rth for light reflective layer C. TABLE 6 FIG. As described above, the light reflecting layer A, the light reflecting layer B and the light reflecting layer C have flexibility. Therefore, it can be seen that the reflection hue b ^* is preferably 4-8 or 10-16 for a flexible light-reflecting layer. Region III in FIG. 4 is a region where the reflection hue b ^* is from −8 to −4. Based on Table 6 and FIG. 4, region III contains the relationship between reflected hue b ^* and optimum Rth for light reflective layer D. TABLE 6 FIG. As mentioned above, the light reflecting layer D is a rigid reflecting layer. Therefore, it can be seen that the reflected hue b ^* is preferably -8 to -4 for a rigid light reflecting layer.

Various embodiments and experimental examples of the present invention have been described above. However, the present invention is not limited to the illustrated various embodiments and experimental examples, and is intended to include the scope indicated by the claims, and the meaning and equivalents of the claims. All changes within scope are intended to be included.

In addition to the A plate 18 and the C plate 20, the retardation film 12 may include one or more layers having a retardation (hereinafter sometimes referred to as "other retardation layers"). Other retardation layers include a touch sensor provided for the image display layer 4, a sealing layer for sealing the image display layer 4, a base film for the image display layer 4, and the like. Another retardation layer may be a protective film attached to the polarizing film 14 . The other retardation layer is disposed between the polarizing film 14 and the image display layer 4, preferably the image display layer 4 and the A plate 18 or C plate 20 closest to the image display layer 4. is placed between

Other retarder layers may be A-plates, but typically can be C-plates. Other retardation layers may have characteristics represented by the following formula (5). That is, the other retarder layer can be a negative C-plate.
nx≈ny>nz (5)
In formula (5), nx represents the refractive index in the slow axis direction, ny represents the refractive index in the fast axis direction, and nz represents the refractive index in the thickness direction of the other retardation layer. .

In addition to the case where nx and ny are completely equal, nx≈ny in Equation (5) also includes the case where nx and ny are substantially equal. Specifically, if the magnitude of the difference between nx and ny is within 0.01, it can be said that nx and ny are substantially equal.

In addition, the retardation film 12 may contain the base material and the alignment film described above, and may contain combinations other than the A plate and the C plate. Specifically, a configuration in which two or more A plates are combined may be used.

The configuration of the circularly polarizing plate is not limited as long as it includes a linear polarizer and functions as a circularly polarizing plate without departing from the scope of the present invention.

Another example of a light-reflective image display layer is an inorganic electroluminescent device (hereinafter also referred to as a "micro LED display") having independently emitting pixels. When the light-reflecting image display layer is a micro LED display device, the light-emitting portion, the pixel connection portion, and the electrode portion formed of a compound semiconductor reflect external light. Still other examples of the light-reflective image display layer include liquid crystal displays, electron emission displays (e.g., field emission displays (FED), surface field emission displays (SED), electronic paper (electronic ink and electrophoretic elements). ), plasma display devices, projection display devices (for example, grating light valve (also referred to as GLV) display devices, display devices having a digital micromirror device (also referred to as DMD), piezoelectric ceramic displays, and the like. Liquid crystal display devices include both transmissive liquid crystal display devices and transflective liquid crystal display devices.

2... Image display device, 4... Image display layer (light reflective image display layer), 12... Retardation film, 14... Polarizing film (linear polarizer), 18... A plate, 20... C plate.

Claims (4)

a light reflective image display layer;
a circularly polarizing plate provided on the image display surface of the light-reflective image display layer;
with
When the total retardation at a wavelength of 550 nm in the direction perpendicular to the image display surface between the linear polarizer of the circularly polarizing plate and the light-reflective image display layer is Rth (nm),
the relationship between the light-reflective image display layer and the reflected hue b ^* at an inclination angle of 50 degrees with respect to the vertical direction satisfies the following formula (i);
the reflected hue b ^* is between 6.46 and 12.18 and the Rth is between 26 nm and 46 nm;
Image display device .
2.5×b ^* −25 ≦Rth≦2.5×b ^* +40 (i) The circularly polarizing plate further has an A plate arranged closer to the light-reflective image display layer than the linear polarizer,
The image display device according to claim 1. The A plate is a λ/4 retardation plate,
3. The image display device according to claim 2. The circularly polarizing plate further has a C plate arranged closer to the light-reflective image display layer than the linear polarizer,
4. The image display device according to claim 2 or 3.

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