WO2021060247A1

WO2021060247A1 - Retardation plate, and circular polarization plate, liquid crystal display device, and organic el display device including retardation plate

Info

Publication number: WO2021060247A1
Application number: PCT/JP2020/035704
Authority: WO
Inventors: 貴大久住; 中村　大輔; べネマ・ヤン・ウィレム
Original assignee: 日本化薬株式会社; デジマテックビー．ブイ．
Priority date: 2019-09-27
Filing date: 2020-09-23
Publication date: 2021-04-01
Also published as: CN114341684A; TW202131031A; JPWO2021060247A1; KR20220067538A

Abstract

This retardation plate comprises a first optically anisotropic layer in which the spiral axis of a stick-shaped liquid crystal compound is aligned with the direction of thickness and which has an in-plane phase difference (Re) of substantially 1/2 wavelength, and a second optically anisotropic layer in which the spiral axis of a stick-shaped liquid crystal compound is aligned with the direction of thickness and which has an in-plane phase difference (Re) of 1/4 wavelength, the retardation plate being characterized by further comprising a third optically anisotropic layer that is disposed between the first optically anisotropic layer and the second optically anisotropic layer and that satisfies equation (1). Equation (1): n_x ≃ n_y < n_z (In the equation, n_x and n_y are refractive indices in the plate planar directions crossing each other at a right angle, and n_z is the refractive index in the direction perpendicular to the plate planar direction.)

Description

A retardation plate, a circular polarizing plate equipped with the retardation plate, a liquid crystal display device, and an organic EL display device.

The present invention relates to a retardation plate useful for a liquid crystal display device and an organic EL display device, and a circular polarizing plate, a liquid crystal display device, and an organic EL display device provided with the retardation plate.

The retardation plate for circular polarizing plates is used in a wide range of applications for flat panel displays.

Conventionally, with respect to an image display panel or the like, a method of arranging a circularly polarizing plate on the surface of the image display panel and reducing the reflection of external light by this circularly polarizing plate has been proposed. This circular polarizing plate is composed of a linear polarizing plate and a 1/4 wavelength retardation plate (hereinafter, also referred to as λ / 4 plate), and the external light directed to the display surface of the image display panel is converted into linearly polarized light by the linear polarizing plate. , Then converted to circularly polarized light by the 1/4 wavelength retardation plate. Here, the external light due to the circular polarization is reflected by the surface of the image display panel or the like, and the rotation direction of the circular polarization is reversed at the time of this reflection. As a result, this reflected light is converted into linearly polarized light in a direction shaded by the 1/4 wavelength retardation plate and the linear polarizing plate, and then shielded by the subsequent linear polarizing plate to the outside, contrary to the time of arrival. The exposure of reflected light is suppressed.

Conventionally, the retardation plate used for this circular polarizing plate is used for each wavelength band in the visible light region when it is used for antireflection of an organic EL display device, for example, due to the wavelength dependence (wavelength dispersion) of the retardation value. On the other hand, it does not function as a λ / 4 plate, and there is a problem that coloring occurs in a dark state (displayed in black). In particular, the above problem becomes more remarkable when the display device is observed with a viewing angle. In order to prevent this, there is a demand for a retardation plate for a circularly polarizing plate that functions as approximately 1/4 wavelength in a wide wavelength band and can realize antireflection with a wide viewing angle. A uniaxially or biaxially stretched retardation plate is used as the retardation plate. Further, a method of using one or more twisted nematic liquid crystal layers (twisted nematic liquid crystal layers) is also disclosed.

Japanese Unexamined Patent Publication No. 2014-209220 Japanese Unexamined Patent Publication No. 2014-224738

For example, a λ / 4 plate obtained by biaxially stretching a modified polycarbonate (PC) film is known as a retardation plate for widening the viewing angle. However, the retardation plate and the retardation plate formed by laminating the λ / 4 plate and the λ / 2 plate described later show inverse wavelength dispersibility with respect to the visible light wavelength region, but in the oblique direction. The suppression of coloring when viewed from the viewpoint was not sufficient.

In addition, there is a retardation plate with a wide viewing angle, which is formed by laminating a λ / 4 plate obtained by uniaxially stretching a cycloolefin (COP) film and a λ / 2 plate of the same type. However, in the laminated retardation plate, each retardation plate must be cut out so as to have a predetermined optical axis angle with respect to the optical axis of the polarizing plate, and then laminated with a single sheet using an adhesive layer or the like. However, there was a problem with productivity.

Further, in Patent Document 1, known uniaxially stretched by a continuous two-layer twist-oriented nematic liquid crystal in which the twist angle and Δnd (the product of the refractive index difference (Δn) and the film thickness (d)) are controlled. It is described to realize a wideband λ / 4 plate capable of converting linearly polarized light having a wider wavelength into more complete circularly polarized light than a retardation plate of λ / 4 plate and λ / 2 plate. However, regarding the circular polarizing plate using the λ / 4 plate, the observation result is limited to the observation result from directly above, and the displayability (black reproducibility and coloring) when viewed from an oblique direction is fully discussed. Not.

Further, with respect to the retardation plate, it is generally known to add a positive C plate layer in which the retardation value in the thickness direction is within a predetermined range in order to improve the displayability from an oblique direction. For example, in Patent Document 2, an attempt is made to improve the displayability from an oblique direction by adding a positive C plate layer to the materials of the λ / 2 plate and the λ / 4 plate.

As described above, a wide-band λ / 4 wavelength retardation plate that is only a combination of a conventional configuration using two twist-oriented nematic liquid crystal layers having the functions of a λ / 2 plate and a λ / 4 plate and a stretched film. Furthermore, with a circular polarizing plate also provided with a positive C plate layer, the black reproducibility (low black brightness) of the display device when viewed from an oblique direction and the displayability regarding coloring are not satisfactory. Further improvement is required. Further, the thickness direction retardation value (Rth) of the positive C plate layer and the optimum arrangement relationship with the retardation plate have not yet been discussed.

In the present application, a broadband retardation plate for a circular polarizing plate that reduces black brightness in a black display when viewed from an oblique direction (a good blackness is displayed), a circular polarizing plate provided thereof, and the circular polarizing plate. It is an object of the present invention to provide a liquid crystal display device and an organic EL display device.

The present inventors have conducted diligent studies in order to solve the above problems. As a result, we succeeded in reducing the black brightness in the black display when viewed from an oblique direction by using a positive C plate layer between the two liquid crystal layers having a twisted orientation in the thickness direction.

That is, the present invention relates to the following inventions, but is not limited thereto.
[Invention 1]
A first optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in the thickness direction along the spiral axis and has an in-plane retardation value (Re) of substantially 1/2 wavelength.
A retardation plate in which a rod-shaped liquid crystal compound is oriented in a spiral axis in the thickness direction and includes a second optically anisotropic layer having an in-plane retardation value (Re) of substantially 1/4 wavelength.
Between the first and second optically anisotropic layers, the following equation (1):

n _x ≈ n _y <n _z (1)

(In the equation, n _x and _ny indicate the refractive index in the plate plane direction orthogonal to each other, and _nz indicates the refractive index in the direction perpendicular to the plate plane direction).
The third optically anisotropic layer satisfying the above is provided.
A retardation plate characterized by that.
[Invention 2]
The twist angle of the first optically anisotropic layer is substantially 26 ° or substantially −26 °, and the twist angle of the second optically anisotropic layer is the twist of the first optically anisotropic layer. The retardation plate according to invention 1, which is substantially 78 ° or substantially −78 ° from an angle.
[Invention 3]
The retardation plate according to Invention 2, wherein the third optically anisotropic layer is a layer having a vertically oriented liquid crystal compound and has a thickness direction retardation value (Rth) of −150 to −80 nm.
[Invention 4]
A circular polarizing plate provided with a polarizing element and a retardation plate according to any one of the inventions 1 to 3.
[Invention 5]
The circular polarizing plate according to Invention 4, wherein the polarizing element contains a dichroic azo dye and its hue is achromatic.
[Invention 6]
An organic EL display device provided with the circular polarizing plate according to the

invention

4 or 5.
[Invention 7]
A liquid crystal display device provided with the circular polarizing plate according to the

invention

4 or 5.

The present application includes a broadband retardation plate for a circular polarizing plate that reduces black brightness in a black display when viewed from an oblique direction and / or reduces coloring, a circular polarizing plate provided with the same, and the circular polarizing plate. A liquid crystal display (LCD) and an organic electroluminescence (EL) display device (organic light emitting diode (OLED) display device) can be provided. In one aspect, it is possible to provide a display device that displays a good blackness in a black display when viewed from the front. In one aspect, the present application can provide a thin retardation plate. In one aspect, the present application provides black with significantly reduced brightness and coloration in the black display of LCD and OLED display devices, not only in the head-on (front) orientation, but also in a wider orientation with a wide viewing angle. Achieve. In one aspect, the present application can provide a manufacturing method capable of producing a circular polarizing plate only by laminating roll-to-roll without requiring complicated steps such as single-wafer laminating and diagonal stretching.

It is sectional drawing of the retardation plate which concerns on one Embodiment of this invention. It is sectional drawing of the circular polarizing plate which concerns on one Embodiment of this invention. It is explanatory drawing of "the first aspect example" of this invention. FIG. 5 is an equivalence diagram of luminance with respect to a polar angle of 0 ° to 80 ° and an azimuth angle of 0 ° to 360 ° according to the first embodiment. FIG. 5 is an equivalence diagram of luminance with respect to a polar angle of 0 ° to 80 ° and an azimuth angle of 0 ° to 360 ° according to the second embodiment. FIG. 5 is an equivalence diagram of luminance with respect to a polar angle of 0 ° to 80 ° and an azimuth angle of 0 ° to 360 ° according to the third embodiment. It is a contour diagram of the luminance with respect to the polar angle 0 ° to 80 ° and the azimuth angle 0 ° to 360 ° of Comparative Example 1. It is a contour diagram of the luminance with respect to the polar angle 0 ° to 80 ° and the azimuth angle 0 ° to 360 ° of Comparative Example 2. It is a contour diagram of the luminance with respect to the polar angle 0 ° to 80 ° and the azimuth angle 0 ° to 360 ° of Comparative Example 3. It is a contour diagram of the luminance with respect to the polar angle 0 ° to 80 ° and the azimuth angle 0 ° to 360 ° of Comparative Example 4. It is a contour diagram of the luminance with respect to the polar angle 0 ° to 80 ° and the azimuth angle 0 ° to 360 ° of Comparative Example 5. It is a contour diagram of the luminance with respect to the polar angle 0 ° to 80 ° and the azimuth angle 0 ° to 360 ° of Comparative Example 6. It is an experimental result of the circularly polarizing plate of Examples 1 to 3 at a polar angle (tilt angle) of 40 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Actual Examples 1 to 3 at a polar angle (tilt angle) of 50 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circularly polarizing plate of Examples 1 to 3 at a polar angle (tilt angle) of 60 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Example 1 and Comparative Examples 1 to 3 at a polar angle (tilt angle) of 40 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Example 1 and Comparative Examples 1 to 3 at a polar angle (tilt angle) of 50 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Example 1 and Comparative Examples 1 to 3 at a polar angle (tilt angle) of 60 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Example 1 and Comparative Examples 4 to 6 at a polar angle (tilt angle) of 40 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Example 1 and Comparative Examples 4 to 6 at a polar angle (tilt angle) of 50 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments). It is an experimental result of the circular polarizing plate of Example 1 and Comparative Examples 4 to 6 at a polar angle (tilt angle) of 60 ° and an azimuth angle of 0 to 360 ° (in 45 ° increments).

Hereinafter, embodiments of the present invention will be described.

(Phase difference plate)
The retardation plate (wave plate) means an optical element that gives a predetermined phase difference to the incident linearly polarized light. The retardation plate according to the present invention is provided with two optically anisotropic layers (first and second optically anisotropic layers) as a λ / 2 plate and a λ / 4 plate, respectively, and further, the first and second optical anisotropic layers are provided. A third optically anisotropic layer that suppresses coloring when viewed from an oblique direction is provided between the square layers. The retardation plate according to the present invention is suitable for a circular polarizing plate, and is particularly suitable for a wideband circular polarizing plate. The method for producing the retardation plate of the present invention is not particularly limited, and the retardation plate can be produced by a known method such as roll-to-roll.
In the retardation plate, the wide band is generally a retardation plate that gives a substantially constant phase difference in all wavelengths in the visible light region (380 nm to 780 nm) when linearly polarized light is incident. Therefore, in the retardation plate used for manufacturing the circular polarizing plate, a phase difference of approximately 1/4 wavelength is provided at all wavelengths in the visible light region.

(First and second optically anisotropic layers)
The first optically anisotropic layer according to the present invention has an in-plane retardation value (Re) of substantially 1/2 wavelength, and functions as a λ / 2 plate. As long as the retardation plate of the present invention is suitable for a circular polarizing plate, the Re does not have to be completely 1/2 wavelength. For example, it includes a numerical range of ± 20%, 15%, 10%, 5%, 2%, or 1%.
The second optically anisotropic layer according to the present invention has an in-plane retardation value (Re) of substantially 1/4 wavelength, and functions as a λ / 4 plate. The term "substantial" is the same as above.

The liquid crystal compounds forming the first and second optically anisotropic layers are generally roughly classified into a rod-shaped type (rod-shaped liquid crystal compound) and a disk-shaped type (discotic liquid crystal compound) according to their shapes. In the present invention, it is preferable to form a twisted nematic (TN) liquid crystal layer using a rod-shaped liquid crystal compound. The TN liquid crystal layer is a liquid crystal layer in which nematic liquid crystals in which rod-shaped elongated molecules are lined up in substantially a certain direction are continuously changed in a spiral shape in which the molecular directions are twisted by chirality.
The TN liquid crystal layer is preferably a layer formed by fixing a rod-shaped liquid crystal compound or the like having a polymerizable group by polymerization or the like, and in this case, it is not necessary to exhibit liquid crystal property after the layer is formed. The type of the polymerizable group contained in the rod-shaped liquid crystal compound is not particularly limited, and a functional group capable of an addition polymerization reaction is preferable, and a polymerizable ethylenically unsaturated group or a ring-polymerizable group is preferable. More specifically, a (meth) acryloyl group, a vinyl group, a styryl group, an allyl group and the like are preferably mentioned, and a (meth) acryloyl group is more preferable. In the present invention, known TN liquid crystal materials can be used. Further, when forming the TN liquid crystal layer, a chiral agent may be used together with the above liquid crystal compound, if necessary. Chiral agents are added to twist the liquid crystal compounds.

Further, by using the above-mentioned polymerizable liquid crystal material for the retardation plate, the thickness is generally reduced to 5 μm to 20 μm as compared with the film-like retardation plate having a film thickness of 50 μm to 100 μm. Can be done.

The first and second optically anisotropic layers in the retardation plate of the present invention are twist-oriented with the spiral axis in the thickness direction. Further, the twisting directions of both liquid crystal layers are the same. The in-plane slow-phase axis of the first optically anisotropic layer on the third optically anisotropic layer side is parallel to the in-plane slow-phase axis of the second optically anisotropic layer on the third optically anisotropic layer side. Is. That is, the twist angle of the second optically anisotropic layer is arranged with reference to the twist angle of the first optically anisotropic layer. For positive and negative (minus:-) twist angles, the absorption axis direction of the polarizing element is 0 °, and when the polarizing element of the circularly polarizing plate is on the visual side, the direction counterclockwise from the absorption axis is positive and negative. The clockwise direction from the absorption axis is shown as negative.

The twist angle of the first optically anisotropic layer used in the retardation plate of the present invention is substantially 26 ° in one aspect. More specifically, 26 ± 10 ° is preferable, 26 ± 7 ° is more preferable, and 26 ± 5 ° is further preferable. In this case, the twist angle of the second optically anisotropic layer is substantially 78 °. More specifically, 78 ± 10 ° is preferable, 78 ± 7 ° is more preferable, and 78 ± 5 ° is further preferable. Alternatively, the twist angle of the first optically anisotropic layer is substantially −26 ° in other embodiments. More specifically, −26 ± 10 ° is preferable, −26 ± 7 ° is more preferable, and −26 ± 5 ° is further preferable. In this case, the twist angle of the second optically anisotropic layer is substantially −78 °. More specifically, −78 ± 10 ° is preferable, −78 ± 7 ° is more preferable, and −78 ± 5 ° is further preferable. The twist angle is measured using a film inspection device (RETS-1100A, manufactured by Otsuka Electronics Co., Ltd.).

In the first optically anisotropic layer used in the retardation plate of the present invention, the face bond retardation value (Δn1 · d1) which is the product (Δn1 · d1) of the refractive index anisotropy Δn1 at a wavelength of 550 nm and the thickness d1 of the liquid crystal layer. Re) is substantially 275 nm, and more specifically, the product (Δn1 · d1) is preferably 275 ± 30 nm, more preferably 275 ± 20 nm, and even more preferably 275 ± 10 nm.

Further, in the second optically anisotropic layer used in the retardation plate of the present invention, the face bond phase difference which is the product (Δn2 · d2) of the refractive index anisotropy Δn2 at a wavelength of 550 nm and the thickness d2 of the liquid crystal layer. The value (Re) is substantially 137.5 nm, and more specifically, the product (Δn2 · d2) is preferably 137.5 ± 15 nm, preferably 137.5 ± 10 nm, and 137.5 ± 5 nm. More preferred. The above Δn1 · d1 and Δn2 · d2 are measured using a film inspection device (RETS-1100A, manufactured by Otsuka Electronics Co., Ltd.).

(Third optically anisotropic layer)
The third optically anisotropic layer included in the retardation plate of the present invention is a kind of retardation plate called a positive C plate, and has an xy orthogonal axis on the plate plane and a z-axis perpendicular to the plate plane. When set, it means a retardation plate in which _{the refractive indexes n x} , n _y , and n _z in each axial direction are n _x ≈ n _y <n _z. In addition, "n _x ≈ n _y " means that n _x and _ny are substantially equal, and includes the case where they are completely equal. The above-mentioned "n _x and _ny _{are substantially equal" means that n x} and _ny may be different as long as they function as a positive C plate. For example, when viewed from one side, the other side is 20%, 15%, and so on. There may be a difference of 10%, 5%, 2%, or 1%. In addition, instead of "≒"

Etc. may be used. In the present invention, a known positive C plate can be used. In one aspect, the third optically anisotropic layer included in the retardation plate of the present invention is, for example, a liquid crystal layer in which a rod-shaped liquid crystal compound is vertically oriented in the thickness direction (plate plane). The vertical means that the orientation angle of the liquid crystal compound is 90 ° and approximately 90 ° with respect to the plate plane (differences to which the influence is negligible, for example, within ± 10 °, ± 5 °, ± 3 °, or ± 1 °). Includes the direction of). The third optically anisotropic layer is preferably a layer formed by fixing a rod-shaped liquid crystal compound or the like having a polymerizable group by polymerization or the like. In this case, it is necessary to exhibit liquid crystallinity after the layer is formed. Absent. The type of the polymerizable group contained in the rod-shaped liquid crystal compound is not particularly limited, and a functional group capable of an addition polymerization reaction is preferable, and a polymerizable ethylenically unsaturated group or a ring-polymerizable group is preferable. More specifically, a (meth) acryloyl group, a vinyl group, a styryl group, an allyl group and the like are preferably mentioned, and a (meth) acryloyl group is more preferable.
Further, the phase difference (Rth) in the thickness direction of the liquid crystal layer can be adjusted by adjusting the film thickness. The film thickness is not particularly limited, but is generally preferably set in the range of 0.1 μm to 3 μm, more preferably 0.5 μm to 2 μm.
In another aspect, the cellulosic resin material described in JP-A-2016-108536 can be used. From the viewpoint of thinning and productivity, it is preferable to use the above-mentioned liquid crystal compound.

The thickness direction retardation (Rth) of the third optically anisotropic layer of the present invention is determined based on Poincare sphere theory. It is preferable to set a range of optimum values in order to minimize the trajectory of movement from the coordinates on the equator showing linearly polarized light to the coordinates showing circularly polarized light on the North Pole or South Pole on the Poancare sphere. The range of 150 to -80 nm is preferable, the range of -132 to -112 nm is more preferable, and the range of -126 to -120 nm is even more preferable. Further, the third optically anisotropic layer is preferably arranged between the above-mentioned first optically anisotropic layer and the second optically anisotropic layer. As a result, the circular polarization of each wavelength generated by the retardation plate of the present invention is aggregated at the coordinates indicating the circular polarization on the north pole or the south pole in the Poancare sphere, and the circular polarization close to the ideal is formed at each wavelength. Become. Therefore, in a display device or the like on which the circular polarizing plate of the present invention is mounted, it is possible to suppress coloring when viewed from an oblique direction.

(Orientation treatment)
The first and second optically anisotropic layers of the present invention are provided with a treatment for aligning a liquid crystal compound or an alignment film on a substrate. The liquid crystal orientation is not particularly limited as long as the orientation direction of the optically anisotropic layer is appropriately defined and the present invention does not prevent the desired performance from being achieved, and an orientation technique known in the art can be used. A rubbing roll that rotates in a direction of about 0 to 50 ° with respect to the transport direction of the base material may be used to physically form anisotropy on the surface of the base material, which is disclosed in Japanese Patent Application Laid-Open No. 2003-014935. The method of rubbing the resin layer provided on the base material may be used, or a photoalignment film may be used in which an anisotropy is formed on the polymer film by linearly polarized ultraviolet rays to form an alignment film.

(Polarizing element)
The polarizing element (sometimes referred to as a polarizer or a polarizing film) used to obtain the circular polarizing plate, the liquid crystal display device, and the organic EL display device of the present invention is not particularly limited and is known depending on the application. The polarizing element can be appropriately selected and used. For example, a polarizing element obtained by uniaxially stretching a polyvinyl alcohol (PVA) -based film impregnated with a water-soluble dichroic dye and / or a dichroic dye such as polyiodine ion in a boric acid warm water bath. Obtained by uniaxially stretching a polyvinyl alcohol film and then applying a solution containing a dichroic dye on a polarizing element obtained by forming a polyene structure by a dehydration reaction or a base film to orient the dichroic dye. Examples thereof include a polarizing element integrated with a base material obtained by providing a polyvinyl alcohol layer on a protective film, uniaxially stretching the base film together with the base material film, and then impregnating with a dichroic dye. From the viewpoint of processability and optical characteristics, a polarizing element obtained by uniaxially stretching a PVA-based film and adsorbing and orienting a dichroic dye can be preferably used. Examples of commercially available PVA-based films include VF-PS (thickness 75 μm) manufactured by Kuraray. In this case, in general, a dichroic dye is adsorbed and oriented, then uniaxially stretched to a thickness of 25 μm to 35 μm and polarized. Get the element.

The dichroic dye is preferably an iodine ion or a dichroic dye, both of which can be used to obtain a polarizing element for the present invention. Examples of the dichroic dye include an azo dye, an anthraquinone dye, and a tetrazine dye. From the viewpoint of hue design and heat durability, two or three or more kinds of azo dyes should be blended and used. Is preferable. Further, when any dichroic dye is used, the optical characteristics of the polarizing element are high transmittance and high polarization degree (high two) from the viewpoint of obtaining antireflection ability and excellent black display property in the display device to be mounted. It is preferable to have chromaticity), and more specifically, the visible sensitivity correction single transmittance (Ys) is 40% to 45%, and the visual sensitivity correction polarization degree (Py) is 99% or more. Is preferable.

In one aspect of the present invention, it is preferable to have an achromatic hue, that is, the simple substance transmittance (Ts) of the polarizing element is in the visible light region (wavelength 400 nm to 700 nm, more preferably 380 nm to 780 nm). It is preferable that the color is substantially uniform. The absolute values of the a * and b * values in the L * a * b * color system are 1 or less when measured by the polarizing element alone, and the absorption axis directions of the two polarizing elements are orthogonal to each other. A hue in which the absolute value of the a * value is 4 or less and the absolute value of the b * value is 8 or less when measured in an overlapping manner is also preferable as a specific embodiment of the achromatic color. As a result, for example, the circularly polarizing plate provided with the widebanded retardation plate of the present invention not only suppresses the coloring of the reflected light from the display device over the visible light region, but also suppresses the coloration of the reflected light derived from the surface of the polarizing element. However, it is possible to suppress coloring over the visible light region.

Examples of the azo dye having dichroism include C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 28, C.I. I. Direct Yellow 44, C.I. I. Direct Yellow 142, C.I. I. Direct Orange 26, C.I. I. Direct Orange 39, C.I. I. Direct Orange 71, C.I. I. Direct Orange 107, C.I. I. Direct Red 2, C.I. I. Direct Red 31, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 117, C.I. I. Direct Red 247, C.I. I. Direct Green 80, C.I. I. Direct Green 59, C.I. I. Direct Blue 71, C.I. I. Direct Blue 78, C.I. I. Direct Blue 168, C.I. I. Direct Blue 202, C.I. I. Direct Violet 9, C.I. I. Direct Violet 51, C.I. I. Direct Brown 106, C.I. I. Direct Brown 223 and the like can be mentioned. In addition, a dye that can be produced by a known method may be used, and examples of the known method include the method described in JP-A No. 3-12606 or the method described in JP-A-59-14255. And so on. Examples of commercially available dyes include Kayafect Violet P Liquid, Kayafect Yellow Y, Kayafect Orange G, Kayafect Blue KW, and Kayafect Blue Liquid 400 (all manufactured by Nippon Kayaku Co., Ltd.). Two or three kinds of these azo dyes are blended and used so that each transmittance in the visible light region becomes uniform. Further, in the polarizing element according to the present invention, in order to obtain an achromatic polarizing element having high transmittance and high degree of polarization, it is disclosed in International Publication WO2017 / 146212, International Publication WO2019 / 117131 and the like. Azo dyes with improved dichroism can be preferably used for the design of achromatic polarizing elements.

The polarizing element preferably contains a base material (also referred to as a support or a support film) for protecting the polarizing element. The base material may be arranged on only one side of the polarizing element, or may be arranged on both sides of the polarizing element so that two identical or different base materials sandwich the polarizing element. A structure in which a polarizing element has a base material is called a polarizing plate. When the polarizing element is provided with a base material described later, the base material arranged between the polarizing element and the display device has an in-plane retardation value (Re) and a thickness direction retardation (Rth) of 0 or almost. It is preferably 0 (a numerical value in which the influence can be ignored, for example, in the range of -5 nm to 5 nm).

(Base material)
The retardation plate and circular polarizing plate of the present invention (hereinafter, also referred to as the article of the present invention) may include a base material. The base material is not particularly limited as long as it has desired mechanical strength, thermal stability, and the like and does not prevent the present invention from exhibiting desired performance, and a base material known in the art can be used. The thickness of the base material can be appropriately designed, but is preferably 50 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 80 μm.

When a base material is arranged between the polarizing element and the display device, the in-plane retardation value (Re) and the thickness direction retardation value (Rth) of the base material may be 0 or almost 0. preferable. Examples of commercially available base materials having the retardation value include triacetyl cellulose-based resin film Z-TAC (manufactured by Fujifilm Co., Ltd.), acrylic resin film OXIS series (manufactured by Okura Industrial Co., Ltd.), and the like.

(Adhesive and / or adhesive)
In the article of the present invention, a laminate may be formed by providing the next layer on a certain layer, or a plurality of layers may be bonded by an adhesive and / or an adhesive to form a laminate. As long as it functions as a pressure-sensitive adhesive or an adhesive and does not prevent the present invention from exhibiting the desired performance, there is no particular limitation, and a pressure-sensitive adhesive or an adhesive known in the art can be used. Acrylic resin is a typical example of the pressure-sensitive adhesive. The thickness can be appropriately designed, but is preferably 1 to 50 μm, and more preferably 5 to 25 μm from the viewpoint of adhesion between layers and processability of adhesive coating and lamination. Examples of the adhesive include a water-based adhesive containing a PVA-based resin as a main component, an adhesive containing a thermosetting or photo-curable resin, and a method using plasma bonding.

The phase difference value and the twist angle value of the optically anisotropic layer of the present invention are values that obtain a good optical effect. These values are not limited in consideration of the orientation characteristics of the actual liquid crystal compound and the product processability, and may include tolerances and margins.

(Circular polarizing plate)
The circular polarizing plate of the present invention is a wideband circular polarizing plate, and includes a polarizing element and a retardation plate of the present invention. A rectangular layer and a second optically anisotropic layer are provided in this order. Further, in one aspect of each optical axis of the circular polarizing plate, the absorption axis of the polarizing element is in the direction of 0 °, and the twist angle of the first optically anisotropic layer is relative to the absorption axis of the polarizing element. It is substantially in the direction of 26 °, and the twist angle of the second optically anisotropic layer is substantially 78 ° from the twist angle of the first optically anisotropic layer (that is, in the absorption axis of the polarizing element. In contrast, the direction is 104 °).

The method for producing the circular polarizing plate of the present invention is not particularly limited, and for example, the films or sheets of the above-mentioned layers may be laminated for each sheet, or the above-mentioned layers produced in a roll shape may be rolled-to-roll. It may be continuously laminated by a roll. In particular, in the circular polarizing plate of the present invention, since it is not necessary to cut out the retardation plate in accordance with a predetermined optical axis angle, the latter roll-to-roll lamination can be easily carried out. Therefore, the productivity can be improved as compared with the conventional method for producing a broadband circular polarizing plate in which a uniaxially stretched film such as a COP-based film is laminated.

(Manufacturing method of circularly polarizing plate)
The method for manufacturing the retardation plate and the circularly polarizing plate according to the present invention will be described below with reference to the first and second embodiments, but the present invention is not limited thereto. Further, each optically anisotropic layer is formed on a base material that can be peeled off from the liquid crystal layer and the base material after curing, and each base material is removed to form a circular polarizing plate in a step of sequentially laminating, which will be described later. You may.

(Example of the first aspect)
As the first step, a liquid crystal compound showing a nematic liquid crystal phase having polymerizable properties, a chiral agent, a photopolymerization initiator, and a diluting solvent are contained on the rubbing surface of the base material rubbed in the direction of 0 ° (transportation direction). The coating composition is applied, then the solvent is removed through a drying step, and the coating film is cured by irradiating with light to have an orientation axis in the 0 ° direction, a twist angle of 26 °, and the retardation value. A first optically anisotropic layer having (Re @ 550 nm) of 275 nm is obtained.
As a second step, a coating composition of a composition containing a liquid crystal compound showing a nematic liquid crystal phase having polymerizable properties, a photopolymerization initiator and a diluting solvent is applied to a base material, and then a drying step is obtained to obtain a solvent. By removing and curing the coating film by irradiating with light, a third optically anisotropic layer oriented in the direction perpendicular to the substrate is obtained.
In the third step, a coating composition containing a TN liquid crystal material, a chiral agent, a photopolymerization initiator, and a diluting solvent is applied to the rubbing surface of the base material that has been rubbed in a direction of 26 ° with respect to the transport direction. After that, a drying step is obtained to remove the solvent, and the coating film is cured by irradiating with light to have an orientation axis in the direction of 26 °, a twist angle of 78 °, and the retardation value (Re @ 550 nm). A second optically anisotropic layer having a thickness of 137.5 nm is obtained.
As a fourth step, the polarizing element (or polarizing plate), the first optically anisotropic layer, the third optically anisotropic layer, and the second optically anisotropic layer are formed so as to have the optical axis relationship shown in FIG. The circular polarizing plate of the present invention is obtained by sequentially laminating.

(Example of the second aspect)
In the second step, a coating composition for a composition containing a liquid crystal compound showing a nematic liquid crystal phase having polymerizable properties, a photopolymerization initiator, and a diluting solvent was obtained in the first step. The third optically anisotropic layer oriented in the direction perpendicular to the liquid crystal surface is formed by applying the layer to the liquid crystal surface, then removing the solvent through a drying step, and irradiating with light to cure the coating film. obtain. After that, the polarizing element (or polarizing plate), the first optically anisotropic layer on which the third optically anisotropic layer is laminated, and the second optically anisotropic layer are formed so as to have the optical axis relationship shown in FIG. It is the same as the first embodiment except that the circular polarizing plate of the present invention is obtained by sequentially laminating.

(Display device)
The circularly polarizing plate of the present invention can be preferably applied to the visual side of various display devices such as a liquid crystal display device (LCD) and an organic electroluminescence (EL) display device (organic light emitting diode (OLED) display device). Further, the display device may be configured to include a touch panel, an antiglare layer, an antireflection layer, a translucent cover (also referred to as a front plate), and the like, depending on the design. Further, the translucent cover may have a planar shape or a curved surface shape. The method for producing the display device of the present invention is not particularly limited, and the display device can be produced by a known method.

The liquid crystal display device of the present invention may be configured to include a liquid crystal panel and a backlight unit referred to as a transmissive type or a transflective type, or may be configured to include a liquid crystal panel and a reflective layer referred to as a reflective type.

Further, since an organic EL display device generally includes a metal electrode on the display panel portion, the OLED (organic EL display device) itself has a higher reflectance than a liquid crystal panel. This causes, for example, when used in an environment with a lot of outside light such as outdoors in the daytime, impairs the displayability due to the reflection of the outside light from the electrode. Therefore, a circularly polarizing plate is generally attached to the visible side of the organic EL display device in order to suppress reflection of external light. Therefore, the display characteristics of the organic EL display device also depend on the optical characteristics of the circular polarizing plate. Since the circular polarizing plate of the present invention has a wider viewing angle characteristic than the conventional circular polarizing plate, it can be suitably used for an organic EL display device that requires a wide viewing angle.

Although the embodiments of the present invention have been described so far, the present invention is not limited to the above embodiments, and various modifications and modifications can be made based on the technical idea of the present invention.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

Assuming that the circular polarizing plate is attached to an ideal reflector, the black brightness (unit is a standardized value) at the following azimuth and inclination angles (polar angles) can be determined by using the liquid crystal simulation software LCDmaster (manufactured by Shintech). The calculation was performed using. The configuration and calculation conditions of the circular polarizing plate are as follows. Table 1 shows a list of the following calculation conditions and the arrangement relationship of the optically anisotropic layer. The in-plane retardation value (Re) and the thickness direction retardation value (Rth) indicate values at a wavelength of 550 nm. Further, in Table 1, the arranged optically anisotropic layers are shown in the columns of the first layer, the second layer, and the third layer in order from the incident light side.
Structure of circularly polarizing plate:
Example 1: Polarizing element (in order from the incident light side), first optically anisotropic layer, third optically anisotropic layer 1, second optically anisotropic layer, reflector Example 2: (from the incident light side) (In order) Polarizing element, first optically anisotropic layer, third optically anisotropic layer 2, second optically anisotropic layer, reflecting plate Example 3: (in order from the incident light side) polarizing element, first optical different Square layer, 3rd optical anisotropic layer 3, 2nd optically anisotropic layer, reflector Example 4: Polarizing element (in order from the incident light side), 1st optically anisotropic layer, 3rd optical heterogeneous Sex layer 4, second optically anisotropic layer, reflector Example 5: Polarizing element, first optically anisotropic layer, third optically anisotropic layer 5, second optical heterogeneity (in order from the incident light side) Sexual layer, reflector Comparative example 1: Polarizing element, first optically anisotropic layer, second optically anisotropic layer, third optically anisotropic layer 1, reflective plate Comparative Example 2: (in order from the incident light side): Polarizing element (in order from the incident light side), third optically anisotropic layer 1, first optically anisotropic layer, second optically anisotropic layer, reflector Comparative Example 3: Polarizing element (in order from the incident light side) , 1st optical anisotropic layer, 2nd optical anisotropic layer, reflector Comparative example 4: (in order from the incident light side) polarizing element, general 1/2 wavelength plate 1, 3rd optical anisotropic layer 6. General 1/4 wavelength plate 1, Reflector Comparative Example 5: Polarizing element (in order from the incident light side), general 1/2 wavelength plate 2, third optically anisotropic layer 7, general 1/4 wavelength plate 2, reflector Comparative example 6: (in order from the incident light side) polarizing element, general 1/2 wavelength plate 1, general 1/4 wavelength plate 1, third optical anisotropic layer 8. Reflector 1st optically anisotropic layer:
Liquid crystal layer: ZLI-4792 (manufactured by Merck & Co., Ltd.)
The resulting phase difference = 1 / 2λ
Δn1 · d1 = 275 nm
Pre-twist angle = 0 °
Twist angle = -26 °
Liquid crystal layer thickness = 2.136 μm
Second optically anisotropic layer:
Liquid crystal layer: ZLI-4792 (manufactured by Merck & Co., Ltd.)
The resulting phase difference = λ / 4
Δn2 · d2 = 137.5 nm
Pre-twist angle = -26 °
Twist angle = -78 °
Liquid crystal layer thickness = 1.068 μm
Third optically anisotropic layer:
Liquid crystal layer: Polymerizable vertically oriented liquid crystal compound (manufactured by Merck & Co., Inc.)
n _x = 1.5283
n _y = 1.5283
n _z = 1.6725
Liquid crystal layer thickness = 0.60 μm to 1.45 μm
Rth: Hereinafter described in the above 1 to 8 Third optically anisotropic layer 1:
Rth = -120nm
Third optically anisotropic layer 2:
Rth = -115nm
Third optically anisotropic layer 3:
Rth = -130nm
Third optically anisotropic layer 4:
Rth = -80nm
Third optically anisotropic layer 5:
Rth = -150nm
Third optically anisotropic layer 6:
Rth = -174nm
Third optically anisotropic layer 7:
Rth = -209nm
Third optically anisotropic layer 8:
Rth = -133nm
Polarizing element: JET-12 (manufactured by Polatechno Co., Ltd., using spectroscopic data with luminous efficiency correction single transmittance Ys = 41.5% and luminous efficiency correction polarization degree Py = 99.99%, no support layer)
reflector:
Material: Ideal reflector General 1/2 wave plate (HWP) 1:
Material: Cycloolefin polymer (COP)
Nz coefficient = 1.0
General 1/4 wave plate (QWP) 1:
Material: Cycloolefin polymer (COP)
Nz coefficient = 1.0
General 1/2 wave plate (HWP) 2:
Material: Cycloolefin polymer (COP)
Nz coefficient = 1.5
General 1/4 wave plate (QWP) 2:
Material: Cycloolefin polymer (COP)
Nz coefficient = 1.5
Incident light: Natural light (wavelength range: 380 nm to 780 nm)
Tilt angle (polar angle) θ = 40 °, 50 °, and 60 °)
Azimuth Φ = 0 ° to 360 ° (in 5 ° increments)

Under the above test conditions, the Nz coefficient is a value represented by the following equation (2) as one of the indexes indicating the magnitude relationship between _{the refractive index components n x} , n _y and n _z.

Under the above calculation conditions, ZLI-4792 (manufactured by Merck & Co., Inc.) and cycloolefin polymer (COP) used the standard data attached to the LCD master. _{Further, n x} , _ny , and n _z of the third optically anisotropic layer using the polymerizable vertically oriented liquid crystal compound (manufactured by Merck Co., Ltd.) are test pieces obtained by forming a film of the liquid crystal compound. It was measured with a refractometer (manufactured by DR-M2 ATAGO).

Table 2 shows the evaluation results of the black luminance values of Examples 1 to 5 and Comparative Examples 1 to 6.
In the calculations of Examples 1 to 5 and Comparative Examples 1 to 6, the black luminance value at the polar angle θ = 0 ° (head-on) is 0.1 or less, and the light incident from the polarizing element is circularly polarized. It was confirmed that the plate sufficiently suppressed the reflection from the reflector. The evaluation was performed based on the black luminance value at this polar angle θ = 0 °. When the black luminance value is 0 or almost 0, it indicates that the circularly polarizing plate suppresses the reflection of the incident light and functions ideally.

Using the above calculation results, the center is set to the polar angle θ = 0 ° (head-on), and the distribution of black brightness with an azimuth angle Φ = 0 ° to 360 ° with respect to the range of the polar angle θ = 0 ° to 80 ° is obtained. It is shown in the contour diagram. At this time, the black brightness is fixedly shown in the range of a minimum value of 0 to a maximum value of 10. 4 to 6 show contour diagrams of Examples 1 to 3, and FIGS. 7 to 12 show contour diagrams of Comparative Examples 1 to 6, respectively. In the contour diagrams of Examples 1 to 3, the contour lines showing the maximum luminance values when the polar angle θ is shifted from 0 ° to 80 ° (from the center of the circle to the end of the outer circle in the figure) are 1.6 to 1. It was .8, which was smaller than that of each comparative example, and thus it was found that the viewing angle was wider. In the case of Comparative Example 5, the maximum luminance value exceeded 10.

Further, in order to quantitatively compare the effect of improving the black brightness when viewed from an oblique direction, the black brightness value was extracted from the above calculation results under the conditions of the polar angle θ and the azimuth angle Φ described below. The results of plotting the black luminance value at this time with respect to the azimuth angle Φ are shown in FIGS. 13 to 21.
Polar angles θ = θ = 40 °, 50 °, 60 °
Azimuth Φ = 0 ° to 360 ° (in 45 ° increments)

The results of plotting Examples 1 to 3 under the above conditions are shown in FIGS. 13 to 15. Specifically, in Examples 1 to 3 in which the Rth range of the third optically anisotropic layer is −130 nm to -115 nm, the black luminance values of the polar angles θ = 40 °, 50 °, and 60 °, respectively. There was almost no difference, and the average value (B) of the black luminance of the azimuth angle Φ = 0 ° to 360 ° (in 45 ° increments) at each of the polar angles was 0.26 to 0.68. This is because the black brightness is 2.7 times to 7. when viewed from the polar angles θ = 40 °, 50 °, and 60 ° diagonally with respect to the polar angle θ = 0 ° (A). It could be estimated that it would increase 6 times. Further, when the same calculation as above was performed for the cases of Examples 4 and 5 in which the Rth range of the third optically anisotropic layer was −80 nm and −150 nm, the increase in black brightness was 3.2 times to 10 times. It was 0.0 times. From this, it was found that the black brightness when viewed from an oblique direction can be further reduced by setting the Rth range of the third optically anisotropic layer to preferably −130 nm to -115 nm.

The results of plotting Comparative Examples 1 to 3 under the above conditions are shown in FIGS. 16 to 18. The Rth of the third optically anisotropic layer is fixed at −120 nm, and the third optically anisotropic layer is arranged after the second optically anisotropic layer or before the first optically anisotropic layer. Or, in Comparative Examples 1 to 3 without the third optically anisotropic layer, the black brightness values at the polar angles θ = 40 °, 50 °, and 60 ° are higher than those in Examples 1 to 5, respectively. Both showed large values. Further, the average value (B) of the black brightness of the azimuth angle at each polar angle obtained in the same manner as described above is 0.59 to 1.72 in Comparative Examples 1 and 2, and 1.27 to 3.88 in Comparative Example 3. Met. This is because the black brightness is the polar angle θ = 0 ° (A), and the black brightness when viewed from the oblique directions of the polar angles θ = 40 °, 50 °, and 60 ° is Comparative Examples 1 and 2. Was estimated to increase from 6.3 times to 18.2 times, and Comparative Example 3 was estimated to increase from 13.4 times to 41.1 times. From this result, it was shown that the configurations of Examples 1 to 5 have improved viewing angle characteristics as compared with the conventional Comparative Examples 1 to 3.

In Comparative Examples 4 to 6, the Rth value when the display body provided with the circular polarizing plate provided with the retardation plate under the relevant conditions has the widest viewing angle (Comparative Example 4: -174 nm, Comparative Example 5: -209 nm, And Comparative Example 6: -133 nm), a third optically anisotropic layer was used. Similar to Examples 1 to 5, black luminance values at polar angles θ = 40 °, 50 °, and 60 ° were obtained and plotted, and the plotted results are shown in FIGS. 19 to 21. Under any condition, the black luminance value shows a large value not only in Examples 1 to 5 but also in Comparative Examples 1 to 3, and in the configuration of Comparative Examples 4 to 6 using the conventional COP-based film, the black luminance value shows a large value. Even if the third optically anisotropic layer was arranged, the wide viewing angle could not be achieved.

From the above results, in the configuration of the circularly polarizing plate of the present invention, widening the bandwidth of the circularly polarizing plate not only optimizes the presence or absence of the third optically anisotropic layer and its Rth value, but also optimizes the first optically anisotropic layer. By selecting the arrangement of the third optically anisotropic layer with respect to the second optically anisotropic layer and the second optically anisotropic layer, it is possible to widen the bandwidth as compared with the conventional circular polarizing plate. Therefore, according to the present invention, for example, in a black display of an organic EL display device or the like, it is possible to obtain a black display with less light leakage when viewed from an oblique direction.

Further, the retardation plate of the present invention has first and second optical anisotropy having optimum wavelength dispersion characteristics (meaning the wavelength dependence of the phase difference) in order to further reduce the black brightness at a polar angle of 0 °. It may have a sex layer. Similarly, in the third optically anisotropic layer, by setting the wavelength dispersion characteristic to negative dispersion (reverse wavelength dispersion), it is possible to further reduce the black brightness in the black display when viewed from an oblique direction. ..

The present application can provide a retardation plate that reduces coloring or reflectance in a black display when viewed from an oblique direction, a circular polarizing plate provided with the retarding plate, and a liquid crystal display device and an organic EL display device provided with the circular polarizing plate. .. For example, since the organic EL display device can provide a wider viewing angle, it can be suitably used in an in-vehicle environment where the display device is installed and the viewing place is fixed. Further, since it is possible to provide a manufacturing method capable of manufacturing a circularly polarizing plate only by laminating roll-to-roll, it is possible to support the manufacturing of a circularly polarizing plate for a large-sized display device.

101 Phase difference plate 102 of the present invention 102 First optically anisotropic layer 103 Second optically anisotropic layer 104 Third optically anisotropic layer 105 Circularly polarizing plate 106 of the present invention Polarizing element (polarizing plate)
107 Twisted nematic liquid crystal 108 Base material 1 (alignment film)
109 Base material 2 (alignment film)
201 Absorption axis direction (0 °)
202 Rubbing direction (orientation direction) (0 °)
203 Twist angle direction (26 °)
204 Rubbing direction (orientation direction) (26 °)
205 Twist angle direction (104 °)
206 Parallel to 201

Claims

A first optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in the thickness direction along the spiral axis and has an in-plane retardation value (Re) of substantially 1/2 wavelength.
A retardation plate in which a rod-shaped liquid crystal compound is oriented in a spiral axis in the thickness direction and includes a second optically anisotropic layer having an in-plane retardation value (Re) of substantially 1/4 wavelength.
Between the first and second optically anisotropic layers, the following equation (1):

n x ≈ n y <n z (1)

(In the equation, n x and ny indicate the refractive index in the plate plane direction orthogonal to each other, and nz indicates the refractive index in the direction perpendicular to the plate plane direction).
The third optically anisotropic layer satisfying the above is provided.
A retardation plate characterized by that.
The twist angle of the first optically anisotropic layer is substantially 26 ° or substantially −26 °, and the twist angle of the second optically anisotropic layer is the twist of the first optically anisotropic layer. The retardation plate according to claim 1, which is substantially 78 ° or substantially −78 ° from an angle.
The retardation plate according to claim 1 or 2, wherein the third optically anisotropic layer is a layer having a vertically oriented liquid crystal compound and has a thickness direction retardation value (Rth) of −150 to −80 nm.
A circular polarizing plate provided with a polarizing element and a retardation plate according to any one of claims 1 to 3.
The circular polarizing plate according to claim 4, wherein the polarizing element contains a dichroic azo dye and its hue is achromatic.
An organic EL display device provided with the circular polarizing plate according to claim 4 or 5.
A liquid crystal display device provided with the circular polarizing plate according to claim 4 or 5.