JP6916940B2 - Image display device - Google Patents

Description

The present invention relates to an image display device.

The flat panel display device is provided with an optical laminate in which a retardation film and a polarizing film are laminated for optical compensation of the display device. For example, among flat panel display devices, organic electroluminescence (EL) image display devices reduce internally reflected light that is reflected from the outside toward the viewing side by the light-reflecting image display layer incorporated inside. In order to do so, such an optical laminate is laminated and used on the visual side of the light-reflecting image display layer. Examples of such an optical laminate include an elliptical polarizing plate as described in Patent Document 1.

Japanese Unexamined Patent Publication No. 2015-163940

Among the flat panel display devices, for example, in the organic EL image display device, the screen is slightly reflected from the internal reflective image display layer and reaches the viewing side depending on whether the screen is viewed from the front direction or the oblique direction. The reflected color of the internally reflected light is different, and in the oblique direction, the reflected color is generated according to the in-plane angle. In this diagonal direction, the maximum value of the color difference of the reflected color according to the in-plane angle is called the diagonal color difference. By arranging an optical laminate as described in Patent Document 1 on the image display surface of the display device, the oblique color difference is suppressed. However, in recent years, further suppression of diagonal color difference has been required.

Therefore, an object of the present invention is to provide an image display device capable of further suppressing an oblique color difference.

The image display device according to one aspect of the present invention is an image display device including 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 angle between the absorption axis of the polarizing film and the in-plane slow axis of the retardation film is 45 degrees ± 5 degrees, the in-plane retardation of the retardation film is R0, and the thickness of the retardation film. Assuming that the plane orthogonal to the inclination angle θ direction with respect to the vertical direction is the projection plane and the in-plane advance phase axis of the retardation film is the rotation axis, the in-plane retardation of the retardation film on the projection plane is performed. When R (θ) _{fast is used} and the in-plane slow axis of the retardation film is assumed to be the rotation axis, the in-plane retardation of the retardation film on the projection plane is R (θ) slow, and the projection plane _{is defined as R (θ) slow.} When the in-plane polarization of the light-reflecting image display layer in the above is R (θ) M, the following equations (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 |> 0 nm ... (iv)

In the above configuration, in-plane retardation of the light-reflecting image display layer is taken into consideration as well as in-plane retardation of the retardation film. Therefore, by providing the retardation film and the polarizing film on the light reflection image display layer, the oblique color difference can be sufficiently suppressed.

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

The inclination angle θ may be 50 degrees.

The image display device according to another aspect of the present invention is an image display device including 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. Therefore, the angle formed by the absorption axis of the polarizing film and the in-plane slow axis of the retardation film is 45 degrees ± 5 degrees, the in-plane retardation of the retardation film is R0, and the retardation film is Let Rth be the retardation in the thickness direction, and let the plane orthogonal to the direction in which the inclination angle is 50 degrees with respect to the thickness direction of the retardation film be the projection plane, and the plane of the light-reflecting image display layer on the projection plane. When the internal retardation is R (50) M and the above Nz and the above ρ are expressed by the formulas (v) and the formula (vi), the above Nz and the above ρ are the formulas (vii), the formula (viii) and the formula (ix). ), Or the formula (vii), the formula (x) and the formula (xi) are satisfied, and the above R0, the above Rth and the above R (50) M are retardations for 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)

Also in the above configuration, in-plane retardation of the light-reflecting image display layer is taken into consideration. Therefore, by providing the retardation film and the polarizing film on the light reflection image display layer, the oblique color difference 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, it is possible to provide an image display device capable of further suppressing an oblique color difference.

FIG. 1 is a schematic diagram showing a schematic configuration of an image display device according to an embodiment. FIG. 2 is a drawing showing the relationship between the slow phase axis, the phase advance axis, and the absorption axis of the polarizing film. FIG. 3 is a drawing for explaining a projection plane. FIG. 4 is a drawing for explaining the phase difference in the oblique visual field. FIG. 5 is a chart showing the results of Examples and Comparative Examples based on the viewpoint of the first embodiment. FIG. 6 is a chart showing the results of Examples and Comparative Examples based on the viewpoint of the first embodiment. FIG. 7 is a chart showing the results of Examples and Comparative Examples based on the viewpoint of the first embodiment. FIG. 8 is a chart showing the results of Examples and Comparative Examples based on the viewpoint of the second embodiment. FIG. 9 is a chart showing the results of Examples and Comparative Examples based on the viewpoint of the second embodiment. FIG. 10 is a chart showing the results of Examples and Comparative Examples based on the viewpoint of the second embodiment. FIG. 11 is a drawing in which the results shown in FIGS. 8 to 10 are plotted in the ρ-NZ coordinate system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same elements are designated by the same reference numerals, and duplicate description will be omitted. The dimensional ratios in the drawings do not always match those described.

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 joined. In the form shown in FIG. 1, the image display layer 4 and the optical laminate 6 are bonded by an adhesive layer 8a.

The image display layer 4 forms an image internally and displays the image on the image display surface 4a. The image display layer 4 includes an element structure for forming an image and the like. 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 a 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, 0.2 mm to 1.0 mm.

As long as the image display layer 4 is configured to form an image on the image display surface 4a, the layer structure, materials, and the like are not limited. The image display layer 4 is formed of, for example, metals such as gold, silver, copper, iron, tin, nickel, chromium, molybdenum, titanium, aluminum, and indium, and electrodes and wiring using their alloys and oxides. It can be a part (or layer), a dielectric part such as a resin film, a bank material, a light emitting element, and a multi-layered body such as other layers.

The image display layer 4 is, for example, a flat panel display device. An example of a flat penel display device is a thin (or panel-shaped) organic electroluminescence display device (hereinafter, also referred to as an “OLED display device”, which is also an inorganic electroluminescence 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 a member for optical compensation is not included on the image display surface.

When the image display layer 4 is an OLED display device, the electrode included in the OLED display device is typically the reflection unit. 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 into the organic light emitting material layer from one electrode, and holes are injected from the other electrode, so that the electrons and holes are combined in the organic light emitting material layer to perform self-luminous emission. 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 a function of reflecting toward. Therefore, the other electrode typically functions as a reflector in the OLED display device.

The OLED display device has advantages that it has better visibility than a liquid crystal display device or the like that requires a backlight, can be made thinner, and can be driven by a low DC voltage.

When the image display layer 4 is a micro LED display device, the light emitting portion, the pixel connecting portion, and the electrode portion formed of the compound semiconductor 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 pressure-sensitive adhesive layer 8a can be composed of a pressure-sensitive adhesive composition containing a resin as a main component, such as (meth) acrylic-based, rubber-based, urethane-based, ester-based, silicone-based, and polyvinyl ether-based. Among them, a pressure-sensitive adhesive composition using a (meth) acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer is preferable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type. The thickness of the pressure-sensitive adhesive layer 8b is usually 3 to 30 μm, preferably 3 to 25 μm.

Examples of the (meth) acrylic resin (base polymer) used in the pressure-sensitive adhesive composition include butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2- (meth) acrylate. A polymer or copolymer containing one or more (meth) acrylic acid esters such as ethylhexyl as a monomer is preferably used. It is preferable that the base polymer is copolymerized with a polar monomer. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl (). Examples thereof include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as meta) acrylate.

The pressure-sensitive adhesive composition may contain only the above-mentioned base polymer, but usually further contains a cross-linking agent. The cross-linking agent is a divalent or higher metal ion that forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound that forms an amide bond with a carboxyl group; poly. Epoxy compounds and polyols that form an ester bond with a carboxyl group; polyisocyanate compounds that form an amide bond with a carboxyl group are exemplified. Of these, polyisocyanate compounds are preferable.

[Optical laminate]
The optical laminate 6 includes a polarizing plate 10 and a retardation film 12. The optical laminate 6 is an optical element for compensating for an image displayed on the image display surface 4a. The polarizing plate 10 and the retardation film 12 are bonded to each other. The polarizing plate 10 and the retardation film 12 can be bonded by the pressure-sensitive adhesive layer 8b as shown in FIG. The example of the pressure-sensitive adhesive layer 8b is the same as that of the pressure-sensitive adhesive layer 8a.

[Polarizer]
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 form illustrated in FIG.

The polarizing film 14 has linearly polarized light characteristics. 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 linearly polarizing characteristics, and may be any film used for known polarizing plates.

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

The two protective films 16 sandwich the polarizing film 14 and 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”) -based 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 the protective films 16 may be one. For example, the polarizing plate 10 does not have to have the protective film 16 on the retardation film 12 side.

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

[Phase difference film]
The retardation film 12 has a function of causing a constant retardation in the incident light. As shown in FIG. 2, the retardation film 12 has an in-plane slow phase axis (in-plane slow phase axis) 12a and an in-plane advance phase axis (in-plane advance phase axis) 12b. The angle between the slow-phase axis 12a and the phase-advance axis 12b is approximately 90 degrees. Approximately 90 degrees means 90 degrees ± 5 degrees.

The retardation film 12 is arranged so that the slow phase axis 12a is approximately 45 degrees with respect to the absorption axis 14a of the polarizing film 14 shown by the broken line in FIG. Approximately 45 degrees means 45 ± 5 degrees.

Returning to FIG. 1, the retardation film 12 will be further described. The retardation film 12 is bonded to the polarizing plate 10. In the form illustrated in FIG. 1, the retardation film 12 is bonded to the polarizing plate 10 by the pressure-sensitive adhesive layer 8b. The example of the pressure-sensitive adhesive layer 8b is the same as that of the pressure-sensitive adhesive layer 8a.

The retardation film 12 has an A plate (phase difference layer) 18 and a C plate (phase difference layer) 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-phase shaft 12a and the phase-advancing shaft 12b of the retardation film 12 are the in-plane slow-phase shaft and the phase-advancing shaft of the A plate 18. The in-plane phase difference of the C plate 20 is substantially 0 (zero), and the slow-phase axis and the advance-phase axis do not exist in the in-plane. Hereinafter, unless otherwise specified, the slow phase axis 12a and the phase advance axis 12b shown in FIG. 2 are used when explaining the refractive index anisotropy in the A plate 18 and the C plate 20.

[A plate]
The A plate 18 preferably has the 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 plate. Further, it is preferable that the A plate 18 exhibits anti-wavelength dispersibility. By providing such an A plate 18, it is possible to suppress the coloring of the reflected light. In the present embodiment, the slow-phase axis (slow-phase axis 12a) of the A plate 18 is arranged so as to be approximately 45 degrees with respect to the absorption axis 14a of the polarizing film 14. The meaning of about 45 degrees is as described above.

nx> ny ≒ nz ... (1)
0.80 <R0A (450) / R0A (550) <0.93 ... (2)
130nm <R0A (550) <150nm ... (3)
In the formulas (1) to (3), nx represents the refractive index in the slow axis 12a direction, ny represents the refractive index in the phase advance axis 12b direction, and nz represents the thickness direction of the A plate 18 ( It represents the refractive index of the slow axis 12a and the direction orthogonal to the advance axis 12b). R0A (λ) represents the retardation of the A plate 18 at the wavelength λ nm. Therefore, R0A (450) and R0A (550) in the formulas (2) and (3) represent the retardation having a wavelength of 450 nm and a wavelength of 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 magnitude of 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 λ nm and the thickness d1 of the A plate 18 based on the following formula.
R0A (λ) = [nx (λ) -ny (λ)] × d1
R0A (450) / R0A (550) represents 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 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 preferably 165 or less. R0A (650) represents a retardation with a wavelength of 650 nm.

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

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.

Although it depends on the reflection characteristics of the image display layer 4, specifically, the retardation in the thickness direction of the C plate 20 is preferably −120 nm or more and 0 nm or less, and −110 nm or more and −10 nm or less at a wavelength of 550 nm. More preferably, it is more preferably −90 nm or more and −20 nm or less.

When the retardation of the C plate 20 in the thickness direction with respect to light at the wavelength λ [nm] is RthC (λ), RthC (λ) is the refractive index n (λ) at the wavelength λ nm and the thickness of the C plate 20. It can be calculated from d2 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, and is 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 with respect to a wavelength of 450 nm and a wavelength of 550 nm, 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 thickness of the A plate 18 and the C plate 20 is within this range, sufficient durability can be obtained, which can contribute to the thinning of the optical laminate 6. As a matter of course, the thickness of the A plate 18 and the C plate 20 is the desired retardation such as a layer giving a phase difference of λ / 4, a layer giving a phase difference of λ / 2, a positive A plate, or a positive C plate. , And can be adjusted to obtain thickness retardation.

[Adhesive layer]
The adhesive layer 8c may be formed of the adhesive used in known retardation films. Examples of the adhesive include a water-based adhesive and an active energy ray-curable adhesive. Instead of the adhesive layer 8c, the same adhesive layer as the adhesive layer 8b may be used.

[Method of forming a 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 described later. The A plate 18 and the C plate 20 are preferably formed from a composition containing a polymerizable liquid crystal compound. Examples of the layer formed from the composition containing the polymerizable liquid crystal compound include a layer obtained by curing the polymerizable liquid crystal compound.

The relationship between the formulas (1) to (3) satisfied by the A plate 18 and the relationship (4) satisfied by the C plate 20 is, for example, the relationship between the thermoplastic resin and the 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.

The cured layer of the polymerizable liquid crystal compound is formed on, for example, an alignment film provided on the base material. This base material has a function of supporting the alignment film and may be a long base material. This base material functions as a releasable support and can support the retardation film 12 for transfer. Further, it is preferable that the surface has an adhesive force that can be peeled off. Examples of the base material include the resin film exemplified as the material of the protective film.

The thickness of the base material is not particularly limited, but is preferably in the range of, for example, 20 μm or more and 200 μm or less. 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, when the base material is cut to obtain a single-wafer base material, an increase in processing waste and wear of the cutting blade can be suppressed.

The base material may be subjected to various anti-blocking treatments. Examples of the blocking prevention treatment include an easy-adhesion treatment, a treatment of kneading a filler and the like, an embossing treatment (knurling treatment) and the like. By applying such a blocking prevention treatment to the base material, it is possible to effectively prevent the base materials from sticking to each other when the base material is wound, so-called blocking, and to manufacture an optical film with high productivity. Is possible.

The cured layer of 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 on which the polymerizable liquid crystal compound is cured is laminated on the alignment film.

The alignment film is not limited to the vertical alignment film, and may be an alignment film that horizontally aligns the molecular axis of the polymerizable liquid crystal compound, or may be an alignment film that tilt-aligns the molecular axis of the polymerizable liquid crystal compound. A horizontal alignment film can be used when the A plate 18 is produced, and a vertical alignment film can be used when the C plate 20 is produced. The alignment film has solvent resistance that does not dissolve due to coating of a composition containing a polymerizable liquid crystal compound, which will be described later, and heat resistance in heat treatment for removing the solvent and aligning the liquid crystal compound. preferable. Examples of the alignment film include an alignment film containing an orientation polymer, a photo-alignment film, and a grub alignment film that forms an uneven pattern or a plurality of grooves on the surface and aligns the film. The thickness of the alignment film is usually in the range of 10 nm to 10000 nm, preferably in the range of 10 nm to 1000 nm, more preferably in the range of 500 nm or less, and further preferably in the range of 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, and a conventionally known monofunctional or polyfunctional (meth) acrylate-based monomer is used under a polymerization initiator. A cured product or the like that has been cured can be used. Specifically, examples of the (meth) acrylate-based monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, and trimethyl propantriacrylate. , 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 can be exemplified. The resin may be one of these or a mixture of two or more.

The photoalignment film is formed from a composition containing a polymer or monomer having a photoreactive group and a solvent. A photoreactive group is a group that produces a liquid crystal alignment ability when irradiated with light. Specific examples thereof include groups involved in photoreactions that are the origin of liquid crystal orientation ability such as molecular orientation induction or isomerization reaction, dimerization reaction, photocrosslinking reaction or photodecomposition reaction generated by light irradiation. Of these, groups involved in the dimerization reaction or photocrosslinking reaction are preferable because they are excellent in orientation. As the photoreactive group, an unsaturated bond, particularly a group having a double bond is preferable, and a carbon-carbon double bond (C = C bond), a carbon-nitrogen double bond (C = N bond), and a nitrogen-nitrogen double bond are preferable. A group having at least one selected from the group consisting of a double bond (N = N bond) and a carbon-oxygen double bond (C = O bond) is particularly preferable.

Examples of the photoreactive group having a C = C bond include a vinyl group, a polyene group, a stilbene group, a still bazol group, a still bazolium group, a chalcone group, a cinnamoyl group and the like. Examples of the photoreactive group having a C = N bond include a group having a structure such as an aromatic Schiff base and an aromatic hydrazone. 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. Examples of the photoreactive group having a C = O bond include a benzophenone group, a coumarin group, an anthraquinone group, a maleimide group and the like. These groups may have substituents such as an alkyl group, an alkoxy group, an allyl group, an allyloxy group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, a sulfonic acid group and an alkyl halide group.

Among them, a photoreactive group involved in a photodimerization reaction is preferable, and a photoalignment film having a relatively small amount of polarized light required for photoalignment and excellent thermal stability and stability over time can be easily obtained. , Cinnamoyle group and chalcone group are preferable. As the polymer having a photoreactive group, a polymer having a cinnamoyl group such that the terminal portion of the side chain of the polymer has a cinnamic acid structure is particularly preferable.

The type of the polymerizable liquid crystal compound used in the present embodiment is not particularly limited, but 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. Further, there are a small molecule type and a high molecular type, respectively. The 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").

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

As the rod-shaped liquid crystal compound, for example, those described in claim 1 of JP-A-11-513019 or paragraphs [0026] to [0998] of JP-A-2005-289980 can be preferably used. .. As the disk-shaped 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 preferable. Can be used for.

Two or more kinds 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 cured layer of the polymerizable liquid crystal compound 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.

The polymerizable liquid crystal compound has a polymerizable group capable of carrying out 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 the polymerizable group include a (meth) acryloyl group, a vinyl group, a styryl group, an allyl group and the like. Among them, the (meth) acryloyl group is preferable. The (meth) acryloyl group is a concept that includes both a meta-acryloyl group and an acryloyl group.

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

Further, the composition may contain a polymerizable monomer from the viewpoint of the uniformity of the coating film and the strength of the film. Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Among them, a polyfunctional radically polymerizable monomer is preferable.

The polymerizable monomer is preferably one that can be copolymerized with the above-mentioned polymerizable liquid crystal compound. Specific examples of the polymerizable monomer include those described in paragraphs [0018] to [0020] in 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. Examples of the surfactant include conventionally known compounds. Among them, fluorine-based compounds are particularly preferable. Specific examples of the surfactant include the compounds described in paragraphs [0028] to [0056] in JP 2001-330725, and paragraphs [0069] to [0126] in JP 2005-62673. Examples of the compounds described in.

In addition, the composition may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amide (eg, N, N-dimethylformamide), sulfoxide (eg, dimethyl sulfoxide), heterocyclic compound (eg, pyridine), hydrocarbon (eg, benzene, hexane), alkyl halide (eg, 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 preferable. Further, two or more kinds of organic solvents may be used in combination.

Further, in the composition, a vertical alignment promoter such as a polarizing film interface side vertical alignment agent and an air interface side vertical alignment agent, and a horizontal alignment promotion agent such as a polarizing film interface side horizontal alignment agent and an air interface side horizontal alignment agent are included. Various orienting agents such as agents may be included. Further, the composition may contain an adhesion improver, a plasticizer, a polymer and the like in addition to the above components.

When the retardation film 12 contains two or more layers in which the polymerizable liquid crystal compound is cured as the A plate 18 and the C plate 20, each layer in which the polymerizable liquid crystal compound is cured is prepared on the alignment film, and both are bonded, for example. The retardation film 12 can be produced by laminating through the agent layer 8c. After laminating both, the base material and the alignment film can be peeled off. The thickness of the retardation film 12 is preferably 3 to 30 μm, more preferably 5 to 25 μm.

The retardation film 12 may be manufactured by preparing long members, laminating the members by roll-to-roll, and then cutting the members into a predetermined shape, or forming each member into a predetermined shape. After cutting, they may be pasted together. 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 example of retardation film]
In addition to the A plate 18 and the C plate 20, the retardation film 12 may include one or more other layers having a retardation (hereinafter, may be referred to as “other retarder layers”). Examples of other retarder 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. Further, the other retarder layer may be a protective film attached to the polarizing film 14. The other retarder layer is arranged 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. Placed between.

The other retarder layer may be an A plate, but can usually be a C plate. The other retarder layer may have the characteristics represented by the following formula (5). That is, the other retarder layer can be a negative C plate.
nx ≒ ny> nz… (5)
In the formula (5), nx represents the refractive index in the direction of the slow axis 12a, ny represents the refractive index in the direction of the phase advance axis 12b, and nz represents the refractive index in the thickness direction of the other retarder layers. Represents the refractive index.

In the formula (5), nx≈ny includes not only the case where nx and ny are completely equal to each other but also the case where nx and ny are substantially equal to each other. 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 include the above-mentioned base material and alignment film, and may include a combination 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 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 shading pattern will be described respectively.

<Front plate>
The front plate may be arranged on the visible 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-mentioned adhesive layer 8b and adhesive layer 8c.

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

The front plate, which includes a hard coat layer on at least one surface of the resin film, can have a flexible property rather than being rigid like existing glass. The thickness of the hard coat layer is not particularly limited and may be, for example, 5 to 100 μm.

Examples of the resin film include cycloolefin-based derivatives having a unit of a monomer containing cycloolefin such as norbornene or polycyclic norbornene-based monomer, and cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl ester cellulose). , Propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacrylic, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, Polypropylene, Polymethylpentene, Polyvinyl Chloride, Polyvinylidene Chloride, Polyvinyl Alcohol, Polyvinyl Acetate, Polyether Ketone, Polyether Ether Ketone, Polyether Sulfone, Polymethyl Metalacrylate, Polyethylene Telephthalate, Polybutylene Telephthalate, Polyethylene Naphthalate, Polycarbonate , Polyethylene, epoxy and other polymers may be used. As the resin film, an unstretched uniaxial or biaxially stretched film can be used. Each of these polymers can be used alone or in combination of two or more. As the resin film, a polyamideimide film or a polyimide film having excellent transparency and heat resistance, a uniaxial or biaxially stretched polyester film, a cycloolefin derivative film having excellent transparency and heat resistance and capable of adapting to a large film size. , Polymethylmethacrylate films and triacetylcellulose and isobutylester cellulose films that are transparent and not optically anisotropic are preferred. The thickness of the resin film may be 5 to 200 μm, preferably 20 to 100 μm.

<Shading pattern>
The light-shielding pattern (bezel) can be formed on the image display layer 4 side of the front plate. The shading pattern can hide each wiring of the image display device 2 so that it cannot be seen by the user. The color and / or material of the light-shielding pattern is not particularly limited, and can be formed of a resin substance having various colors such as black, white, and gold. In one embodiment, the thickness of the shading pattern may be 2 μm to 50 μm, preferably 4 μm to 30 μm, and more preferably 6 μm to 15 μm. Further, in order to suppress air bubbles from being mixed in due to a step between the light-shielding pattern and the display unit and visual recognition of the boundary portion, the light-shielding pattern can be given a shape.

[Manufacturing method of optical laminate]
The optical laminate 6 is manufactured by laminating the polarizing plate 10 and the retardation film 12 via the pressure-sensitive adhesive layer 8b. For example, after manufacturing the polarizing plate 10, 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 separately manufactured retardation film 12 are bonded to each other via the exposed pressure-sensitive adhesive layer 8b. The optical laminate 6 thus obtained can function as a circularly polarizing plate.

[Manufacturing method of image display device]
The image display device 2 is obtained by laminating the retardation film 12 of the optical laminate 6 to the image display layer 4 via the pressure-sensitive adhesive layer 8a. Normally, as shown in FIG. 1, the optical laminate 6 is attached to the image display layer 4 so that the C plate 20 is located on the image display layer 4 side.

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

(First Embodiment)
As shown in FIG. 3, a surface orthogonal to the inclination angle θ direction with respect to the thickness direction of the image display device 2 (the stacking direction of the image display layer 4 and the optical laminate 6) is referred to as a projection surface 22. The thickness direction corresponds to a direction orthogonal to the slow phase axis 12a and the phase advance axis 12b. Assuming that the phase advance axis 12b of the retardation film 12 is the rotation axis (tilt axis), the retardation of the retardation film 12 on the projection surface 22 is R (θ) _fast, and the retardation axis 12a of the retardation film 12 is Assuming a rotation axis, the retardation of the retardation film 12 on the projection surface 22 is R (θ) _slow, and the retardation of the image display layer 4 on the projection surface 22 is R (θ) M. Assuming that the slow-phase shaft 12a (or the phase-advancing shaft 12b) is the rotation axis means that the retardation film 12 is tilted around the slow-phase shaft 12a (or the phase-advancing shaft 12b). In the present specification, the retardation of the retardation film or the image display layer on the projection surface 22 is the retardation of the retardation film or the 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 equations (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 |> 0 nm ... (iv)

As a result, the reflected color differs depending on whether the screen of the image display device 2 is viewed from the front direction or the tilt angle θ direction, and the reflected color is generated according to the in-plane angle in the oblique direction. In this diagonal direction, the maximum value of the color difference of the reflected color according to the in-plane angle is called the diagonal color difference. Further, when the oblique color difference is minimized, the color difference when viewed from the front direction and when viewed from the inclination angle θ direction is minimized. Therefore, even when the image displayed on the image display device 2 is viewed from various angles, the same image as when viewed from the front direction (the thickness direction) can be observed.

This point will be further described. As described above, the image display layer 4 is a light-reflecting display layer that reflects light incident on the image display device 2 from the optical laminate 6 side. Therefore, in the following description, the image display layer 4 is referred to as a light reflection layer RL (see FIG. 1) based on the above reflection characteristics. In the following description, the optical laminate 6 is a circularly polarizing plate, but the optical laminate 6 is not limited to the circularly polarizing plate.

[Phase difference of photoelectric field]
The photoelectric field oscillates in a plane perpendicular to the propagation direction and can be decomposed into S-polarized light and P-polarized light components. At this time, the difference in the angular frequency of the deviation of the electric field vibration period between the S-polarized light and the P-polarized light is the phase difference. The difference between the incident light phase difference δi and the reflected light phase difference δr Δδ = δr−δi (hereinafter, may be referred to as “reflection phase difference Δδ of the light reflecting layer RL”) when the light is not vertically incident. , Stokes vector S = (S0, S1, S2, S3) measured using an ellipsometry or a Stokes polarimeter.

The polarization azimuth ψ, ellipticity angle ε, phase difference δ, and ellipticity χ of the photoelectric field are expressed by the following equations (6) to (9) using the Stokes vector ("Spectroscopic ellipsometry, by Hiroyuki Fujiwara". , Maruzen Publishing, pp. 68-78, 2011 ”).

When the incident light is linearly polarized light with a polarization azimuth ψ = 45 ° and an ellipticity χ = 0, and the Stokes vector Si = (Si0, Si1, Si2, Si3) = (1,0,1,0), the above equation From (6) to (8), the phase difference δi becomes 0.

Similarly, the light reflecting layer RL reflects the incident light, and the reflected light is elliptically polarized light having a polarization azimuth ψ = 45 ° and an ellipticity χ = 0.4, and the Stokes vector Sr = (Sr0, Sr1, Sr2, Sr3). ) = (1,1,0.7,0.7), the phase difference δr is π / 4 from the above equations (6) to (8). At this time, the reflection phase difference Δδ of the light reflection layer RL is expressed as π / 4. In the present specification, the positive / negative of the reflection phase difference Δδ of the light reflecting layer RL with respect to the incident light of linearly polarized light with the polarization azimuth ψ = 45 ° is positive when the ellipticity angle ε> 0, and the ellipticity angle ε. The case of <0 is negative.

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

垂直入射で反射位相差Δδは０となり、入射角θrの増加に伴い増加する。 [Angle dependence of light reflecting layer]
The reflection phase difference Δδ of the light reflection layer RL changes depending on the angle of incidence θr of light on the light reflection layer RL. The following equation (11) shows a modified equation by setting the boundary conditions of the refractive index of the medium in Maxwell's equations (see "Applied Engineering I, by Masao Tsuruta, Maruzen Publishing, pp. 28-45, 1990"). .. The following equation (11) represents a case where the dielectric is obliquely incident from the dielectric side to the metal side, the refractive index of the dielectric is n = n ₁ , and the refractive index of the metal is n = − using the complex refractive index. Let it be ik.

The reflection phase difference Δδ becomes 0 in vertical incident, and increases as the incident angle θr increases.

When the light reflecting layer RL is, for example, an OLED display device or a micro LED display device, the light reflecting layer RL is a multi-layered body of electrodes and wiring, light emitting pixels, bank material, plastic film, and the like. In the actual measurement, the Stokes vector can be measured for each incident angle θr, and the reflection phase difference Δδ of the light reflecting layer RL for each incident angle θr can be calculated and used for theoretical calculation.

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

When the light reflecting layer RL is, for example, an OLED display device or a micro LED display device, the reflection phase difference Δδ can take various values depending on the density, shape, and metal type of the electrodes and wirings forming the light reflecting layer RL. .. Therefore, it has a finite reflection phase difference Δδ. In many cases, the absolute value of the reflection phase difference Δδ (50) on the projection surface 22 with an inclination angle of 50 degrees is 0.01 rad or more at a wavelength of 550 nm, and the absolute value of the reflection retardation R (50) M is also at a wavelength of 550 nm. The value is 1.0 nm or more.

The phase difference in the oblique field of view when observing the retardation film 12 tilted with the slow axis 12a as the rotation axis can be calculated by the following procedure.

As shown in FIG. 4, in the Cartesian coordinate system with the front direction as the z-axis, the component parallel to the slow-phase axis 12a (x-axis in FIG. 4) of the refractive index of the retardation film 12 is nx, and the phase-advance axis. The component parallel to 12b is ny, the component parallel to the front direction is nz, the angle formed by the photoelectric field vector propagating in the retardation film 12 and the z-axis is φ, and the component is emitted from the retardation film 12 and propagates in the air. Applying Snell's law with the angle formed by the photoelectric field vector and the z-axis as φyz gives the following equation (12). φyz corresponds to the inclination angle θ when the slow phase axis 12a is used as the rotation axis.

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

At this time, the effective refractive index Nyz on the projection surface 22 can be obtained by the following equation (14) using a refractive index ellipsoid (“Forefront of Refractive Index Control Technology for Optical Materials, Supervised by Toshiyuki Watanabe and Yoshihiro Uozu, Sea”. See MC Publishing, pp. 14-16, 2009 ”).

The phase difference in the oblique visual field with the phase-advancing axis 12b as the rotation axis is also expressed by the following equation (15) in the same manner as in the equation (13). Φxz in the following equation corresponds to the inclination angle θ when the phase advance axis 12b is used as the rotation axis. D in the formula (15) is the same as in the case of the formula (13).

The transmittance of the polarizing film 14 in the transmission axis direction (direction orthogonal to the absorption axis 14a) and the transmittance in the absorption axis 14a direction, the three-dimensional refractive index of the A plate 18 and the C plate 20 of the retardation film 12, and the light reflecting layer. By measuring the parameters of the optical elements such as the reflection phase difference of RL, the transmittance of the adhesive and the front plate, and substituting them into the Muller matrix, the photoelectric field state when these optical elements are transmitted or reflected can be accurately determined. Can be calculated.

For example, when calculating the photoelectric field that passes through the optical laminate 6 (circular polarizing plate), is reflected by the light reflecting layer RL, passes through the optical laminate 6 (circular polarizing plate), and is observed, the reflected light S _out The Stokes vector is obtained as the solution of Eq. (16) below.
S _out = P ・ A ・ C ・ M ・ C ・ A ・ P ・ S _in … (16)
In formula (16), P, A, M, and _Sin are as follows.
P: Muller matrix of polarizing film 14 A: Muller matrix of A plate 18 Muller matrix of C: C plate 20 Muller matrix of light reflecting layer RL S _in : Stokes vector of incident light

式（１７）中のＴ_１は、偏光フィルム１４における透過軸方向の透過率であり、Ｔ_２は、偏光フィルム１４における吸収軸１４ａ方向の透過率である。式（１７）中のΔδ（ｒａｄ）は、位相差フィルム１２の位相差である。 The Muller matrix of optical elements is a 4 × 4 matrix. For example, the polarizing film 14 and the retardation film 12 are represented by the following equations (17) to (18) ("Basics and Applications of Polarized Propagation Analysis, by Koji Ono". , Uchida Old Tsuruno, pp. 57-61, 2015 ”).

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

Similar to the C plate 20, the light reflecting layer RL can be regarded as a retarder whose phase difference increases in proportion to the inclination angle θ. Therefore, the retarder element and the amplitude reflection element can be defined separately. The retarder element of the light reflecting layer RL defined the Muller matrix as in the retardation film 12.

In calculating the actual circularly polarizing plate configuration, it is necessary to reflect the optical axis of the optical element in the Muller matrix. For example, when the in-plane slow axis (slow axis 12a) of the A plate 18 included in the retardation film 12 of the equation (18) is defined by rotating it by an angle ξ (rad), as shown in the equation (19). Let the rotation matrix Z (ξ) act on both sides of the Muller matrix.

The reflectance spectra of light that are reflected by the light reflecting layer RL through the optical laminate 6 (circularly polarized light) and visually recognized through the optical laminate 6 (circularly polarizing plate) are obtained from the above equations (16). It is obtained by finding the S0 component of the Stokes vector of the wavelength. This corresponds to the reflectance of the component that has reached the inside of the optical laminate 6 (circular polarizing plate) without being reflected at the interface between the air and the optical laminate 6 (circular polarizing plate). On the other hand, the reflectance Rfo at the interface between the air and the optical laminate 6 (circular polarizing plate) changes in proportion to the inclination angle θ and the refractive index ns thereof, and is represented by the following equation (20).

なお、光学積層体６（円偏光板）と空気との界面は、例えば光学積層体６が偏光板１０の表面で空気層と接する場合は、偏光板１０と空気との界面である。光学積層体６が偏光板１０の視認側に更に前面板を備え、更に、この前面板が偏光板１０に接着剤層を介して密着して積層されている場合には、光学積層体６（円偏光板）と空気との界面は、この前面板の視認側と空気層との界面である。

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 visible side of the polarizing plate 10, and the front plate is laminated on the polarizing plate 10 in close contact with the polarizing plate 10 via an adhesive layer, the optical laminate 6 ( The interface between the circularly polarizing plate) and the air is the interface between the visible side of the front plate and the air layer.

From the above, the surface reflectance of the optical laminate 6 (circular polarizing plate) at the interface with air, the reflection by the light reflecting layer RL through the optical laminate 6 (circular polarizing plate), and the optical laminate 6 again. The total reflectance Rf with the internal reflectance visually recognized is obtained by the following equation (21). It should be noted that the interfacial reflection and the multiple reflection between the layers constituting the optical laminate 6 (circularly polarized light) are not considered.
Rf = Rfo + (1-Rfo) × S0
= Rfo + S0-Rfo × S0 ・ ・ ・ (21)

The optical laminate 6 (circularly polarized light) may be provided with an antireflection film at the interface with air. The antireflection film may have a single-layer structure composed of only a low refractive index layer having a low refractive index, or a low refractive index layer having a low refractive index and a high refractive index layer having a high refractive index. It may have a multi-layer structure in which the layers are laminated in order. When an antireflection film is provided and the surface reflectance is, for example, 2% or less, further 1% or less, the light is reflected by the light reflecting layer RL through the optical laminate 6 (circular polarizing plate), and the optical laminate is again used. Since the color difference of the internally reflected light visually recognized through 6 (circular polarizing plate) is relatively easy to be visually recognized, the configuration of the present invention is more likely to exert the effect more effectively.

Ｌ^＊ａ^＊ｂ^＊表色系の反射光色相値ａ^＊，ｂ^＊及び彩度値Ｃ^＊は、標準イルミナントＷ（λ）の三刺激値Ｘ_Ｗ，Ｙ_Ｗ，Ｚ_Ｗと反射光イルミナントＲｆ（λ）×Ｗ（λ）の三刺激値Ｘ_Ｒｆ，Ｙ_Ｒｆ，Ｚ_Ｒｆをもちいて式（２３）〜（２５）から算出される（「色彩工学入門、篠田博之・藤枝一郎 共著、森北出版、１２２頁、２００７年」参照）。

_{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) are the tristimulus values, etc. Calculated from the following equations (22A) to (22B) using the color functions x (λ), y (λ), z (λ) (International Commission on Illumination (CIE) recommendation, 1931) ("Introduction to Color Engineering") , Hiroyuki Shinoda and Ichiro Fujieda, Morikita Publishing, pp. 106-107, 2007 ”). A D65 light source (ISO 10526: 1999 / CIE S005 / E-1998) was used as the standard illumination.

L ^* a ^* b ^* The reflected light hue values a ^* , b ^* and the saturation value C ^* _{of the color system are the tristimulus values X W} , Y _W , Z _W and the reflected light illuminant Rf of the standard illuminant W (λ). _{Calculated from equations (23) to (25) using the tristimulus values X Rf} , Y _Rf , and Z _Rf of (λ) × W (λ) (“Introduction to Color Engineering, co-authored by Hiroyuki Shinoda and Ichiro Fujieda, Morikita Publishing) , P. 122, 2007 ”).

When observing the image display device 2 from a field view (inclination angle θ direction) tilted by θ from the z axis when the slow axis 12a and the x axis and the phase advance axis 12b and the y axis of the A plate 18 are parallel to each other ( The case of observing from the direction of the white arrow in FIG. 2) is referred to as “inclination angle θ observation” (see FIG. 2).

^{At this time, the saturation C *} _{takes the bipolar values C f} ^* and C _s ^* due to the double symmetry of the A plate 18 with the change of the xy in-plane angle ξ, and these a ^* b ^* planes. coordinates _{^{C f * (* a f,}} b f *), C s * (a s *, b s *) to. ^{The distance ΔC *} between these two points is expressed by the following equation (26) as an oblique color difference when observing the inclination angle θ.

When the oblique color difference in the tilt angle θ observation is minimized, the color change and intensity change of the reflected color are minimized even when the image display device 2 is observed from all angles, and the best image display performance can be obtained.

In order to make the characteristics of the polarizing film 14 invariant and adjust the characteristics of the retardation film 12 and the light reflecting layer RL to realize the minimum oblique color difference, the following equation (27) may be satisfied.
RthA + RthC + RthM = 0 ... (27)
In the formula (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 reflecting layer RL.

Of the in-plane retardation of the A plate 18, the retardation on the projection surface 22 when the phase advance axis 12b is the rotation axis is R (θ) A _fast , and the retardation on the projection surface when the slow phase axis 12a is the rotation axis is R (θ). ) A _slow . Similarly, the in-plane retardation of the C plate 20 on the projection surface 22 is R (θ) C, and the in-plane retardation of the light reflecting layer RL on the projection surface 22 is R (θ) M.

Assuming that the retardation of the A plate 18 when observed from the front (when the inclination angle θ = 0) is R (0) A, the optimum optical design of the image display device 2 can be described using the following equation (28). The following equation (28) holds at the same time when the above equation (27) is satisfied, and at this time, the oblique color difference ΔC ^{* for} observing the inclination angle θ of the equation (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)

Further, when the A plate 18 and the C plate 20 are regarded as one retardation layer, the in-plane retardation R (θ) _fast and R (θ) _{slow on} the projection surface 22 for observing the inclination angle θ are given by the following equation (29). , (30).
R (θ) _fast = R (θ) A _fast + R (θ) C ... (29)
R (θ) _slow = R (θ) A _slow −R (θ) C ・ ・ ・ (30)

The following equations (31) and (32) can be obtained by rewriting the equation (28) using the equations (29) and (30).
α = R0- {R (θ) _fast + R (θ) M} ・ ・ ・ (31)
β = R0- {R (θ) _slow- R (θ) M} ... (32)

Further, since the light reflecting layer RL of the present embodiment has a reflection phase difference, the following equation (33) is established.
| R (θ) M |> 0 nm ... (33)

Equations (31) to (33) correspond to the equations (i), (ii), and (iv). Further, the image display device 2 also satisfies the formula (iii). Formulas (i) and (ii) (or formulas (31) and (32) are formulas in consideration of the reflection phase difference of the light reflecting layer RL, as described above.

Conventionally, the design of an optical compensation member such as a circularly polarizing plate has not reflected the reflection phase difference of the light reflecting layer. However, in reality, the oblique color difference could not be sufficiently suppressed (or as designed) because of the influence of the reflection phase difference of the light reflecting layer.

On the other hand, the image display device 2 satisfies the equations (i) to (iv) in consideration of the reflection phase difference of the light reflecting layer RL. Therefore, the image display device 2 has a configuration that is optimally designed to minimize the oblique color difference. As a result, the oblique color difference can be sufficiently suppressed (or as designed or in a desired state).

In order to manufacture the image display device 2 so as to satisfy the formulas (i) to (iv), for example, a thermoplastic resin or a polymerizable liquid crystal compound forming the A plate 18 and the C plate 20 of the retardation film 12 can be manufactured. The type and compounding ratio of the above may be adjusted, and the thicknesses of the A plate 18 and the C plate 20 may be adjusted.

As an example of the image display layer 4, an OLED display device and a micro LED display device have been mentioned. However, other examples of the image display layer 4 include 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)), and an electronic paper (electronic ink or an electrophoresis element). Examples thereof include a display device used), a plasma display device, a projection type 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 piezoelectric ceramic display, and the like. The display device includes any of a transmissive liquid crystal display device, a semi-transmissive liquid crystal display device, and the like. The laminate of the present embodiment can be particularly effectively used for an organic EL display device or an inorganic EL display device.

In particular, in the image display device 2 having the organic EL display device or the inorganic EL display device as the light reflection layer RL, the change in the intensity of the external light reflected light is suppressed, and the stability is the same as that in the front direction when viewed from an oblique direction. Can show black display ability.

(Second Embodiment)
As the second embodiment, the conditions satisfied by the image display device 2 will be described from a viewpoint different from that of the first embodiment. Also in the second embodiment, as shown in FIG. 3, a plane orthogonal to the inclination angle θ direction with respect to the thickness direction of the image display device 2 (the stacking direction of the image display layer 4 and the optical laminate 6) is projected. It is called surface 22. In the second embodiment, the projection surface 22 is a surface when θ = 50 degrees. Therefore, the retardation of the image display layer 4 on the projection surface 22 is R (50) M. The retardation described in the second embodiment is a retardation for a wavelength of 550 nm unless otherwise specified.

Let R0 be the in-plane retardation of the retardation film 12, and let Rth be the retardation in the thickness direction of the retardation film 12. R0 is the total in-plane retardation of each layer constituting the retardation film 12. Rth is the sum of the retardations in the thickness direction of each layer constituting the retardation film 12. As shown in FIG. 1, when the retardation film 12 has an A plate and a C plate, R0 is the total in-plane retardation of each of the A plate and the C plate, and Rth is the sum of the in-plane retardations of the A plate and the C plate, respectively. It is the total of the retardation in the thickness direction.

The Nz coefficient of the retardation film 12 is represented by the equation (v). Further, the ratio of the in-plane retardation R0 of the retardation film to the in-plane retardation R (50) M of the image display layer 4 on the projection surface 22 is expressed by the equation (vi) as a 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), formulas (viii) and formulas (ix), or satisfies formulas (vii), formulas (x) and formulas (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, in the ρ-Nz coordinate system (Cartesian coordinate system), the image display device 2 includes all of the formula (vii), the formula (viii), and the formula (ix) in the region represented by the formula (vii). It is an apparatus including a retardation film 12 and an image display layer 4 that satisfy a set of ρ and Nz included in a region to be satisfied or a region to satisfy the formula (vii), the formula (x), and the formula (xi). In addition, instead of the formula (viii), the formula (viii-1) may be used. Instead of the formula (ix), the formula (ix-1) may be used. The formula (x-1) may be used instead of the formula (x). 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), a range satisfying the following formula (xii), formula (xiii) and formula (xiv) is preferable.
0.06 ≤ ρ ≤ 0.11 ... (xii)
Nz ≧ 3.5ρ + 0.405 ・ ・ ・ (xiii)
Nz ≤ 3.5ρ + 0.61 ... (xiv)

When ρ is less than 0 (when the above equation (x) is satisfied), a range satisfying the following equations (xv), equation (xvi) and equation (xvii) is preferable.
-0.07 ≤ ρ ≤ -0.04 ... (xv)
Nz ≧ 3.5ρ + 0.42 ... (xvi)
Nz ≤ 3.5ρ + 0.59 ... (xvii)

The image display device 2 of the second embodiment can adjust, for example, the types and blending ratios 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, and the A plate 18 And can be manufactured by adjusting the thickness of the C plate 20.

Also in the second embodiment, the image display device 2 satisfies the above conditions in consideration of the reflection phase difference of the image display layer 4. Therefore, the image display device 2 has a configuration that is optimally designed to minimize the oblique color difference. As a result, the oblique color difference can be sufficiently suppressed (or as designed or in a desired state).

Although various embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Although a circularly polarizing plate is mentioned as an example of the optical laminate 6, the optical laminate 6 is not limited to the circularly polarizing plate.

Hereinafter, the contents of the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples. In addition, "%" and "part" in an example mean mass% and mass part unless otherwise specified. The circularly polarizing plate described below corresponds to the optical laminate described in the above embodiment, and the light reflecting layer corresponds to the image display layer.

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

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

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

^{<Diagonal color difference ΔC * when} observing an inclination angle of 50 degrees>
^{The oblique color difference ΔC *} observed at an inclination angle of 50 degrees was measured by the display evaluation system DMS803 manufactured by Instrument Systems GmbH.

[Preparation of light reflecting layer]
The following seven types of light reflecting layers were used.
Light-reflecting layer A: M560, which is a brass plate manufactured by Kubo Metal Manufacturing Co., Ltd., was used.
Light-reflecting layer B: Commercially available Apple Inc. The iPhone (registered trademark) X equipped with an OLED display device manufactured by Japan was disassembled, and the cover glass and the circularly polarizing plate were removed before use.
Light-reflecting layer C: A glossy surface of My Foil Thick 50, which is an aluminum foil manufactured by UACJ Corporation, was used.
Light-reflecting layer D: Obtained by subjecting a copper plate to hard chrome plating (industrial chrome plating JIS H8615).
Light-reflecting layer E: Corning's Eagle XG, which is a non-alkali glass plate, was used.
Light-reflecting layer F: MIRO5 5011GP, which is an aluminum vapor-deposited reflector with a high-reflection coating manufactured by Alanod, was used as the high-reflectivity reflector.
Light-reflecting layer G: A commercially available tablet Galaxy tab S 8.4 equipped with an OLED display device manufactured by Samsung Electronics was disassembled, and the cover glass and the circular polarizing plate were removed before use.

The reflection phase difference Δδ50 (550) and the reflection retardation R50M (550) at a wavelength of 550 nm at an inclination angle of 50 degrees of each light reflection layer are as shown in Table 1. These were measured by laminating an unstretched cycloolefin polymer on each of the light reflecting layers A to G in order to measure under conditions simulating an actual OLED display device. The in-plane retardation of the cycloolefin polymer was less than 0.1 at all of the wavelengths of 450 nm, 550 nm and 630 nm.

[Preparation of circularly polarizing plate]
[Preparation of composition for forming horizontal alignment film]
Five parts (weight average molecular weight: 30,000) of a photo-oriented material having the following structure 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]
Sun Ever SE610 manufactured by Nissan Chemical Industries, Ltd. was used.

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

[Polymerizable liquid crystal compound A]

[Polymerizable liquid crystal compound B]

The polymerizable liquid crystal compound A and the polymerizable liquid crystal compound B were mixed at a mass ratio of 87:13. 1.0 part of leveling agent (F-556; manufactured by DIC Corporation) and 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) as a polymerization initiator with respect to 100 parts of the obtained mixture. 6 parts of butane-1-one (Irgacure 369, manufactured by BASF Japan Ltd.) was added. Further, 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 oriented liquid crystal cured film.

[Preparation of composition for forming vertically oriented liquid crystal cured film]
In order to form a vertically oriented liquid crystal cured film (C plate), a composition was prepared by the following procedure. To 100 parts of Pariocolor LC242 (registered trademark of BASF), which is a polymerizable liquid crystal compound, 0.1 part of F-556 was added as a leveling agent, and 3 parts of Irgacure 369 was added as a polymerization initiator. Cyclopentanone was added so that the solid content concentration was 13% to obtain a composition for forming a vertically oriented liquid crystal cured film.

[Preparation of polarizing plate]
A polyvinyl alcohol (PVA) film having an average degree of polymerization of about 2,400, 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 ° C., it was immersed in an aqueous solution having a mass ratio of iodine / potassium iodide / water of 0.02 / 2/100 at 30 ° C. to perform iodine dyeing (iodine dyeing step). .. The PVA film that had undergone 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 ° C. to perform boric acid treatment (boric acid treatment step). .. The PVA film that had undergone the boric acid treatment step was washed with pure water at 8 ° C. and then dried at 65 ° C. to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol. The PVA film was stretched in the iodine dyeing step and the boric acid treatment step. The total draw ratio of the PVA film was 5.3 times. The thickness of the obtained polarizing film was 10 μm.

The polarizing film and the saponified triacetyl cellulose (TAC) film (KC4UYTAC thickness 40 μm manufactured by Konica Minolta Co., Ltd.) were bonded together with a nip roll via an aqueous adhesive. While maintaining the tension of the obtained laminate at 430 N / m, it was dried at 60 ° C. for 2 minutes 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 (Kuraray Co., Ltd., "Kuraray Poval KL318"), and water-soluble polyamide epoxy resin (Taoka Chemical Industry Co., Ltd., "Smiley's Resin 650". , An aqueous solution having a solid content concentration of 30%] was prepared by adding 1.5 parts.

The optical characteristics of the obtained polarizing plate were measured. The measurement was carried out with a spectrophotometer (“V7100”, manufactured by JASCO Corporation) using the polarizing film surface of the polarizing plate obtained above as an incident surface. The absorption axis of the polarizing plate coincides with the stretching direction of polyvinyl alcohol, and the obtained polarizing plate has a luminous efficiency correction single transmittance of 42.3%, a visual sensitivity correction polarization degree of 99.996%, and a single hue a. It was −1.0 and the single hue b was 2.7.

[Preparation of horizontally oriented liquid crystal cured film (A plate)]
Corona treatment was carried out on a cyclic olefin resin (COP) film (ZF-14-50) manufactured by Nippon Zeon Corporation. The 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 processing speed of 10 m / min. The composition for forming a horizontal alignment film was applied to a COP film with a bar coater, and dried at 80 ° C. for 1 minute. The coated film is polarized at an axial angle of 45 ° using a polarized UV irradiator (“SPOT CURE SP-9”, manufactured by Ushio Denki Co., Ltd.) so that the integrated light intensity at a wavelength of 313 nm is 100 mJ / cm2. UV exposure was performed. The film thickness of the obtained horizontal alignment film was 100 nm.

Subsequently, the composition for forming a horizontally oriented liquid crystal cured film was applied to the horizontally oriented film using a bar coater, and dried at 120 ° C. for 1 minute. By irradiating the coating film with ultraviolet rays (in a nitrogen atmosphere, integrated light intensity at a wavelength of 365 nm: 500 mJ / cm2) using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio Denki Co., Ltd.). , A horizontally oriented liquid crystal cured film was formed. The film thickness of the horizontally oriented liquid crystal cured film was about 1.9 μm.

An adhesive layer was laminated on the horizontally oriented liquid crystal cured film. A film composed of a COP film, an alignment film, and a horizontally oriented 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 measuring retardation.

The results of measuring the retardation R0A (λ) at each wavelength are as follows, and the horizontally oriented liquid crystal cured film showed anti-wavelength dispersibility.
R0A (450) = 124 nm
R0A (550) = 142nm
R0A (650) = 146 nm
R0A (450) / R0A (550) = 0.87
R0A (650) / R0A (550) = 1.03

The horizontally oriented liquid crystal cured film was a positive A plate satisfying the relationship of nx> ny≈nz. The results of measuring the retardation RthA (λ) at each wavelength were as follows.
RthA (450) = 64 nm
RthA (550) = 71 nm
RthA (650) = 73 nm

[Preparation of vertically oriented liquid crystal cured film (C plate)]
The COP film was subjected to corona treatment. The conditions for corona treatment were the same as above. The 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 vertically oriented film was 50 nm.

The composition for forming a vertically oriented liquid crystal cured film was applied to the vertically aligned film using a bar coater, and dried at 90 ° C. for 120 seconds. Irradiate the coating film with ultraviolet rays (in a nitrogen atmosphere, integrated light intensity at a wavelength of 365 nm: 500 mJ / cm ² ) using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio Denki Co., Ltd.). To form a vertically oriented liquid crystal cured film. In this way, a film composed of a COP film, a vertically oriented film, and a vertically oriented liquid crystal cured film was obtained. The film thickness of the vertically oriented liquid crystal cured film was 0.2 μm.

An adhesive layer was laminated on the vertically oriented liquid crystal cured film. A film composed of a COP film, an alignment film, and a vertically oriented 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 measuring retardation. As a result of measuring retardation RthC1 (550) at a wavelength of 550 nm,
RthC (550) = −20 nm.
The vertically oriented liquid crystal cured film was a positive C plate satisfying the relationship of nx≈ny <nz.

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

Of this film, the horizontally oriented liquid crystal cured film (A plate) was subjected to corona treatment. The conditions for corona treatment were the same as above. Both were laminated via an adhesive layer so that the polarizing film 14 in the polarizing plate 10 and the horizontally oriented liquid crystal cured film (A plate) were 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 °. In this way, 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 oriented liquid crystal cured film (A plate), an adhesive layer, and a vertically oriented liquid crystal cured film (C plate). ..

[Preparation of circularly 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 μm and RthC (550) = −30 nm.

[Preparation of circularly 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 μm and RthC (550) = −40 nm.

[Preparation of circularly polarizing plate (4)]
A circularly polarizing plate (4) 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 0.5 μm and RthC (550) = −50 nm.

[Preparation of circularly polarizing plate (5)]
A circularly polarizing plate (5) 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 0.6 μm and RthC (550) = −60 nm.

[Preparation of circularly polarizing plate (6)]
A circularly polarizing plate (6) 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 0.7 μm and RthC (550) = −70 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 oriented liquid crystal cured film was 0.8 μm and RthC (550) = −80 nm.

[Preparation of circularly polarizing plate (8)]
A circularly polarizing plate (8) was produced in the same manner as the circularly polarizing plate (1) except that the thickness of the vertically oriented liquid crystal cured film was 0.9 μm and RthC (550) = −90 nm.

[Preparation of circularly polarizing plate (9)]
A circularly polarizing plate (9) 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 1.0 μm and RthC (550) = −100 nm.

[Preparation of circularly 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 not provided.

<Example 1>
An adhesive layer was laminated on the exposed surface of the circularly polarizing plate (1) after the COP film was peeled off. The circularly polarizing plate (1) and the light-reflecting layer A were laminated via this pressure-sensitive adhesive layer to obtain a laminated body.

Regarding the obtained laminate, of the in-plane retardation R0A (550) of the A plate of the circularly polarizing plate (1) and the in-plane retardation on the projection surface when observing at an inclination angle of 50 degrees, the rotation axis is defined as the phase advance axis. Assumed retardation R50A _{fast (550), retardation R50A slow} (550) when the rotation axis is assumed to be the slow axis, retardation RthC (550) in the thickness direction of the C plate, when observing an inclination angle of 50 degrees. The in-plane retardation on the projection surface was measured at R50C (550), and the value of the reflection phase difference R50M (550) on the projection surface when observing the tilt angle of the light reflecting layer at 50 degrees was measured.

The diagonal color difference was measured for the obtained laminate.

Regarding the obtained laminate, the transmittance T1 in the transmission axis direction of the polarizing plate 10, the transmittance T2 in the absorption axis direction, the three-dimensional refractive indexes nAx, nAy, nAz of the A plate, and the in-plane retardation R0A having a wavelength of 550 nm, Equation (6) based on the above measurement data for the three-dimensional refractive indexes nAx, nAy, nAz of the C plate 20, the retardation RthC in the thickness direction at a wavelength of 550 nm, and the reflection retardation R50M of the light reflecting layer in the wavelength range of 380 nm to 780 mm. The oblique color difference for observing a tilt angle of 50 degrees was calculated using Eq. (26).

With respect to the obtained laminated body, the visibility of the figure drawn on the surface of the light reflecting layer was visually evaluated. The more difficult it is to visually recognize a figure, the smaller the change in the reflected color and the better the display characteristics regardless of the angle can be obtained. The figure was a Randold ring with a diameter of 3 mm and an opening of 0.5 mm, and was drawn in Hi-McKee Light Blue made by Zebra, which is a blue-green oil-based pen. The opening direction was random. The observation was performed by changing the relationship between the optical axis of the horizontally oriented liquid crystal cured film and the position of the observer.

Specifically, it was visually observed from an elevation angle (inclination angle) of about 50 degrees at an in-plane angle parallel to the phase advance axis of the A plate. The hue of the reflected light in this direction is bluish green, which is similar to the color of the figure drawn on the surface of the light reflecting layer, so that it is relatively difficult to visually recognize. On the other hand, at an in-plane angle parallel to the slow axis of the A plate, the hue of the reflected light when visually observed from an elevation angle of about 50 degrees is red, which is different from the color of the figure drawn on the surface of the light reflecting layer. Visualization of figures becomes relatively easy. The visibility of the opening direction of the figure was clearly judged by the following criteria 1 to 4 as the overall result when viewed from the slow phase axis direction and the phase advance axis direction.
"1": The opening direction cannot be recognized.
"2": The opening direction can be recognized by squinting.
"3": The opening direction can be recognized.
"4": The opening direction can be clearly recognized.

As a result, it was found that the laminate obtained in Example 1 had a uniform color of reflected light when viewed from any direction, and a good black display could be obtained with a wide viewing angle.

[Examples 2 to 19, Comparative Examples 1 to 30 and Reference Examples 1 to 10]
A laminated body 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 FIGS. 5 to 7. The diagonal color difference of the obtained laminate was measured in the same manner as in Example 1. Further, with respect to the obtained laminated body, as in Example 1, when the relationship between the optical axis of the horizontally oriented liquid crystal cured film and the position of the observer is changed visually, the figure drawn on the surface of the light reflecting layer is visually recognized. Gender was evaluated.

However, in Comparative Example 9 using the light reflecting layer B, commercially available Apple Inc. The iPhone (registered trademark) X equipped with an OLED display device manufactured by OLED was disassembled, only the cover glass was removed, and the oblique color difference ΔC ^* was measured and the visibility of the figure was evaluated.

Further, in Comparative Example 23 using the light reflecting layer G, a commercially available tablet Galaxy tab S 8.4 equipped with an OLED display device manufactured by Samsung Electronics was disassembled, and only the cover glass was removed to ^{measure the oblique color difference ΔC *} and the visibility of the figure. Evaluation was carried out.

As shown in Table 1, the light-reflecting layer E has a reflection phase difference of 0. Therefore, the combinations of the light-reflecting layer E and the circularly polarizing plates (1) to (10) are described in equations (6) to (10). The oblique color difference observed at an inclination angle of 50 degrees was calculated by a simulation using (26). Therefore, the case where the light reflecting layer E is used is referred to 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 summarized from the viewpoint of the first embodiment. 5 to 7 are charts showing the results of Examples, Reference Examples and Comparative Examples based on the viewpoint of the first embodiment.

In FIGS. 5 to 7, the meaning of each item name is as follows.
I: Light-reflecting layer used II: Polarizing plate used III: Visual evaluation result ΔC ^* : Diagonal color difference measurement result R0: Circular polarizing plate thickness direction retardation measurement result R50 _fast : Tilt angle 50 degrees observed Of the in-plane polarization of the circularly polarizing plate on the projection plane, the measurement result of the retardation when the rotation axis is assumed to be the phase-advancing axis R50 _slow : The circularly polarizing plate on the projection plane when the tilt angle is observed at 50 degrees. Of the in-plane polarization, the measurement result of the retardation when the rotation axis is assumed to be the slow axis R50M: In-plane polarization of the light reflecting layer on the projection plane α: R0, R (θ) _fast and R of the equation (i). Calculation result when (θ) M is R0, R50 _fast and R50M β: R0, R (θ), R (θ) _slow and R (θ) M of the _{equation (ii) are R0, R50 slow} and Calculation result when R50M is used | α | + | β |: Calculation result based on α and β in FIGS. 5 to 7

_{R0, R50 fast} , R50 _slow and R50M in FIGS. 5 to 7 were retardations at a wavelength of 550 nm.
Further, in FIGS. 5 to 7, since Reference Examples 1 to 10 are simulation results, the column of item name III (result of visual evaluation) is left blank.

As shown in FIGS. 5 to 7, 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). The visual evaluation at this time was 1 or 2. Therefore, in Examples 1 to 19, it can be understood that the oblique color difference can be sufficiently suppressed.

The results of Examples 1 to 19, Comparative Examples 1 to 30, and Reference Examples 1 to 10 were organized from the viewpoint of the second embodiment. 8 to 10 are charts showing the results of Examples, Reference Examples, and Comparative Examples based on the viewpoint of the second embodiment.

In FIGS. 8 to 10, the meaning of each item name is as follows. The item names "I", "II", "III", "ΔC ^* " and "M50M" are the same as in FIGS. 5 to 7.
R0A: Measurement result of in-plane retardation of the horizontally oriented liquid crystal cured film (A plate) of the circularly polarizing plate RthA: Measurement result of retardation of the horizontally oriented liquid crystal cured film (A plate) of the circularly polarizing plate in the thickness direction RthC: Measurement result of retardation in the thickness direction of the vertically oriented liquid crystal cured film (C plate) of the circularly polarizing plate Nz: Calculation result (Nz coefficient) when Rth and R0 in the formula (v) are set to (RthA + RthC) and R0A, respectively. )
ρ: Calculation result (ρ coefficient) when R (50) M and R0 in the formula (vi) are set to R50M and R0.

R0, R0A, RthA, RthC and R50M in FIGS. 8 to 10 were retardations at a wavelength of 550 nm.
Further, also in FIGS. 8 to 11, since the reference example is a simulation result, the column of item name III (result of visual evaluation) is left blank.

FIG. 11 is a drawing in which Examples 1 to 19 and Comparative Examples 1 to 30 shown in FIGS. 8 to 10 are plotted on a ρ-Nz plane. The horizontal axis of FIG. 11 indicates ρ, and the vertical axis indicates Nz. Lines L1 and L2 in FIG. 11 are lines represented by the following equations, respectively.
L1: Nz = 3.5ρ + 0.65
L2: Nz = 3.5ρ + 0.39

Of ρ> 0 in FIG. 11, the hatched region is a region that satisfies all of the equation (vi), the equation (viii), and the equation (ix). Of ρ <0 in FIG. 11, the hatched region is an region that satisfies the equation (vi), the equation (x), and the equation (xi).

As shown in FIG. 11, all the examples are included in the hatched region, and the comparative example is not included in the hatched region. Further, from FIGS. 8 to 10, 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. Therefore, the first embodiment that satisfies all of the formulas (vi), the formula (viii), and the formula (ix) or is included in the region (hatching region of FIG. 11) that satisfies the formula (vi), the formula (x), and the formula (xi). In ~ 19, it can be understood that the diagonal color difference can be sufficiently suppressed.

In FIG. 11, the region 24 surrounded by the alternate long and short dash line is a range that satisfies the above-mentioned equations (xii), equation (xiii), and equation (xiv) in the range where ρ is larger than 0. Since the region 24 includes examples, it can be understood that it is preferable to satisfy the formula (xii), the formula (xiii), and the formula (xiv) in the range where ρ is larger than 0.
In FIG. 11, the region 26 surrounded by the alternate long and short dash line is a range in which ρ is smaller than 0 and satisfies the above-mentioned equations (xv), equations (xvi) and equations (xvii). Since the region 26 includes the embodiment, it can be understood that it is preferable to satisfy the range satisfying the formula (xv), the formula (xvi) and the formula (xvii) in the range where ρ is smaller than 0.

2 ... Image display device, 4 ... Image display layer (light reflective image display layer), 12 ... Phase difference film, 12a ... Slow phase axis (in-plane slow phase axis), 12b ... Phase advance axis (in-plane advance phase axis) ), 14 ... Polarizing film, 14a ... Absorption shaft, 18 ... A plate, 20 ... C plate, 22 ... Projection plane.

Claims (4)

An image display device including 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 angle formed by the absorption axis of the polarizing film and the in-plane slow phase axis of the retardation film is 45 degrees ± 5 degrees.
The in-plane retardation of the retardation film is set to R0.
The plane orthogonal to the inclination angle θ direction with respect to the thickness direction of the retardation film is defined as the projection plane.
Assuming that the in-plane advancing axis of the retardation film is the rotation axis, the in-plane retardation of the retardation film on the projection plane is R (θ) _fast .
Assuming that the in-plane slow-phase axis of the retardation film is the rotation axis, the in-plane retardation of the retardation film on the projection surface is R (θ) _slow .
When the in-plane retardation of the light-reflecting image display layer on the projection surface is R (θ) M,
The following formula (i) ~ formula (iv) meets,
The R0, the R (θ) _fast , the R (θ) _slow, and the R (θ) M are retardations at a wavelength of 550 nm.
The inclination angle θ is 50 degrees.
Image display device.
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 | ≧ 5.8 nm ・ ・ ・ (iv) An image display device including 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 angle formed by the absorption axis of the polarizing film and the in-plane slow phase axis of the retardation film is 45 degrees ± 5 degrees.
The in-plane retardation of the retardation film is set to R0.
Let Rth be the retardation in the thickness direction of the retardation film.
The plane orthogonal to the direction in which the inclination angle is 50 degrees with respect to the thickness direction of the retardation film is defined as the projection plane, and the in-plane retardation of the light-reflecting image display layer on the projection plane is R (50) M. ,
When Nz and ρ are expressed by the formulas (v) and (vi), the Nz and the ρ satisfy the formulas (a) and (b) , or the formulas (c) and (d) are expressed. Meet,
R0, Rth and R (50) M are retardations for a wavelength of 550 nm.
Image display device.
Nz = (Rth / R0) +0.5 ... (v)
ρ = R (50) M / R0 ... (vi)
0.06 ≤ ρ ≤ 0.11 ... (a)
3.5ρ + 0.405 ≦ Nz ≦ 3.5ρ + 0.61 ・ ・ ・ (b)
-0.07 ≤ ρ ≤ -0.04 ... (c)
3.5ρ + 0.42 ≤ Nz ≤ 3.5ρ + 0.59 ... (d) The retardation film has an A plate and a C plate.
The image display device according to claim 1 or 2. The retardation film and the polarizing film constitute a circular polarizing plate.
The image display device according to any one of claims 1 to 3.

Images