KR20220067538A - A retardation plate, and a circularly polarizing plate provided with the same, a liquid crystal display device, and an organic electroluminescent display device - Google Patents

Abstract

A first optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in the thickness direction in a helical axis and has an in-plane retardation value (Re) of substantially 1/2 wavelength;
A retardation plate comprising a second optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in a helical axis in the thickness direction and has an in-plane retardation value (Re) of substantially 1/4 wavelength,
Between the first and second optically anisotropic layers, the following formula (1):
n _x ≒ n _y < n _z (1)
(Wherein, n _x and n _y are the refractive indices in the orthogonal plate plane direction, and n _z denotes the refractive indices in the perpendicular direction to the plate plane direction)
Retardation plate comprising a third optically anisotropic layer that satisfies

Description

A retardation plate, and a circularly polarizing plate provided with the same, a liquid crystal display device, and an organic electroluminescent 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 circularly polarizing plate having the same, a liquid crystal display device, and an organic EL display device.

The phase difference plate for circularly polarizing plates is used for the wide use of a flat panel display.

Conventionally, regarding an image display panel or the like, there has been proposed a method of arranging a circularly polarizing plate on the surface of the image display panel and reducing the reflection of extraneous light by the circularly polarizing plate. This circularly polarizing plate is composed of a linearly polarizing plate and a quarter-wave retardation plate (hereinafter also referred to as a λ/4 plate), and the extraneous light directed to the display surface of the image display panel is converted into linearly polarized light by the linearly polarizing plate, followed by It is converted into circularly polarized light by a quarter-wave retardation plate. Here, the extraneous light generated by the circularly polarized light is reflected on the surface of the image display panel or the like, but the rotational direction of the circularly polarized light is reversed at the time of this reflection. As a result, the reflected light is converted to linearly polarized light in the direction blocked by the quarter-wave retardation plate and the linear polarizing plate, and then is blocked by the continuous linear polarizing plate, so that exposure of the reflected light to the outside is suppressed do.

The retardation plate used for this circularly polarizing plate is conventionally a λ/4 plate for each wavelength band in the visible region when used for, for example, reflection prevention of an organic EL display device due to the wavelength dependence (wavelength dispersion) of the retardation value. There is a problem in that it does not function as a light source and is colored in a dark state (black display). In particular, the said problem becomes more remarkable when it observes with a viewing angle with respect to a display apparatus. In order to prevent this, a retardation plate for a circularly polarizing plate that functions as almost 1/4 wavelength in a broad wavelength band and can realize reflection prevention at a wide viewing angle is required. The retardation plate uniaxially or biaxially stretched is used for the said retardation plate. Moreover, the method of using one or more layers of twist-aligned nematic liquid crystal layers (twisted nematic liquid crystal layers) is also disclosed.

Japanese Patent Laid-Open No. 2014-209220 Japanese Laid-Open Patent Publication No. 2014-224837

For example, a λ/4 plate obtained by biaxially stretching a modified polycarbonate (PC)-based film is known as a retardation plate for wide viewing angle. However, in the retardation plate and the retardation plate formed by laminating a λ/4 plate and a λ/2 plate to be described later, although the retardation value for the visible light wavelength region exhibits reverse wavelength dispersion, when viewed from an oblique direction, Inhibition of coloration was not sufficient.

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

In addition, in Patent Document 1, a known uniaxial stretching is performed by a nematic liquid crystal that is twisted and oriented in successive two layers in which the twist angle and Δnd (the product of the refractive index difference (Δn) and the thickness (d) of the film) are controlled. It is described to realize a broadband λ/4 plate capable of converting linearly polarized light having a wider wavelength into more complete circularly polarized light than the retardation plates of the λ/4 plate and the λ/2 plate. However, for the circularly polarizing plate using the λ/4 plate, the observation results from the immediately upward direction remain, and display properties (reproducibility and coloration of black) when viewed from an oblique direction are not sufficiently discussed.

It is also known that, with respect to the retardation plate, adding a positive C plate layer having a retardation value in the thickness direction within a predetermined range is generally known to improve the display property from the oblique direction. For example, in Patent Document 2, by adding a positive C plate layer to the material of the λ/2 plate and the λ/4 plate, it is intended to improve display properties from the oblique direction.

As described above, a conventional configuration using two torsionally oriented nematic liquid crystal layers each having a function of a λ/2 plate and a λ/4 plate, or a broadband λ/4 wavelength retardation plate combining a stretched film, Furthermore, in the circularly polarizing plate also provided with the positive C plate layer, the black reproducibility (low black luminance) and color display properties of the display device when viewed from an oblique direction are not satisfactory, and further improvement is required. In addition, the thickness direction retardation value (Rth) of the positive C plate layer or the optimal arrangement relationship with the retardation plate has not yet been discussed.

The present application provides a broadband retardation plate for a circularly polarizing plate that reduces black luminance in black display when viewed from an oblique direction (good black rice is displayed), a circularly polarizing plate having the same, and the circularly polarizing plate An object of the present invention is to provide a liquid crystal display device and an organic EL display device.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined in order to solve the said subject. As a result, by using the positive C plate layer between the two liquid crystal layers having torsional orientation in the thickness direction, it succeeded in reducing the black luminance in the black display when viewed from the oblique direction.

That is, although this invention relates to the following invention, it is not limited to them.

[Invention 1]

A first optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in the thickness direction in a helical axis and has an in-plane retardation value (Re) of substantially 1/2 wavelength;

A retardation plate comprising a second optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in a helical axis in the thickness direction and has an in-plane retardation value (Re) of substantially 1/4 wavelength,

Between the first and second optically anisotropic layers, the following formula (1):

n _x ≒ n _y < n _z (1)

(Wherein, n _x and n _y are the refractive indices in the orthogonal plate plane direction, and n _z denotes the refractive indices in the perpendicular direction to the plate plane direction)

Retardation plate comprising a third optically anisotropic layer that satisfies

[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 substantially 78° or substantially from the twist angle of the first optically anisotropic layer The retardation plate according to invention 1 at -78°.

[Invention 3]

The third optically anisotropic layer is a layer having a vertically aligned liquid crystal compound, and the thickness direction retardation value (Rth) is -150 to -80 nm, the retardation plate according to the first or second invention.

[Invention 4]

A circularly polarizing plate provided with a polarizing element and the retardation plate in any one of Inventions 1-3.

[Invention 5]

The circularly polarizing plate according to invention 4, wherein the polarizing element contains a dichroic azo dye and has an achromatic color.

[Invention 6]

The organic electroluminescent display provided with the circularly polarizing plate of invention 4 or 5.

[Invention 7]

A liquid crystal display device provided with the circularly polarizing plate as described in invention 4 or 5.

The present application provides a broadband retardation plate for a circularly polarizing plate that reduces black luminance and/or reduces coloration in black display when viewed from an oblique direction, a circularly polarizing plate having the same, and a liquid crystal display device including the circularly polarizing plate (LCD) and organic electroluminescence (EL) display devices (organic light emitting diode (OLED) display devices) can be provided. In one aspect, it is possible to provide a display device in which good black rice is displayed in black display when viewed from the front. In one aspect, the present application may provide a thin retarder. In one aspect, the present application achieves a black with significantly reduced coloration and lower luminance in a wider orientation with a viewing angle as well as an orientation of the head-on (front) in black display of LCD and OLED display devices do. One aspect WHEREIN: This application can provide the manufacturing method which makes it possible to produce a circularly polarizing plate only by roll-to-roll bonding without requiring complicated processes, such as single-wafer bonding and diagonal stretching.

1 is a cross-sectional view of a retardation plate according to an embodiment of the present invention.
2 is a cross-sectional view of a circularly polarizing plate according to an embodiment of the present invention.
Fig. 3 is an explanatory diagram of a "first embodiment example" of the present invention.
Fig. 4 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Example 1.
Fig. 5 is an isometric diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Example 2.
Fig. 6 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Example 3.
Fig. 7 is an isometry diagram of luminance in Comparative Example 1 at a polar angle of 0° to 80° and an azimuth angle of 0° to 360°.
Fig. 8 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 2.
9 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 3. FIG.
Fig. 10 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 4.
11 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 5;
Fig. 12 is an isometry diagram of luminance with respect to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 6.
13 is an experimental result of the circularly polarizing plates of Examples 1 to 3 at a polar angle (inclination angle) of 40° and an azimuth angle of 0 to 360° (45° intervals).
14 is an experimental result of the circularly polarizing plates of Examples 1 to 3 at a polar angle (inclination angle) of 50° and an azimuth angle of 0 to 360° (45° intervals).
15 is an experimental result of the circularly polarizing plates of Examples 1 to 3 at a polar angle (inclination angle) of 60° and an azimuth angle of 0 to 360° (45° intervals).
16 is an experimental result of the circularly polarizing plates of Example 1 and Comparative Examples 1 to 3 at a polar angle (inclination angle) of 40° and an azimuth angle of 0 to 360° (45° intervals).
17 is an experimental result of the circularly polarizing plates of Example 1 and Comparative Examples 1 to 3 at a polar angle (inclination angle) of 50° and an azimuth angle of 0 to 360° (45° intervals).
18 is an experimental result of the circularly polarizing plates of Example 1 and Comparative Examples 1 to 3 at a polar angle (inclination angle) of 60° and an azimuth angle of 0 to 360° (45° intervals).
19 is an experimental result of the circularly polarizing plates of Example 1 and Comparative Examples 4 to 6 at a polar angle (inclination angle) of 40° and an azimuth angle of 0 to 360° (45° intervals).
20 is an experimental result of the circularly polarizing plates of Example 1 and Comparative Examples 4 to 6 at a polar angle (inclination angle) of 50° and an azimuth angle of 0 to 360° (45° intervals).
Fig. 21 shows experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 4 to 6 at a polar angle (inclination angle) of 60° and an azimuth angle of 0 to 360° (45° intervals).

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described.

(phase difference plate)

The retardation plate (wave plate) means an optical element that imparts a predetermined retardation to 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 is provided between the first and second optically anisotropic layers. , a third optically anisotropic layer that suppresses coloration when viewed from an oblique direction. The retardation plate according to the present invention is suitable for a circularly polarizing plate, and particularly suitable for a broadband circularly polarizing plate. The manufacturing method of the retardation plate of this invention is not specifically limited, For example, it can produce by well-known methods, such as roll-to-roll.

The broadband in the retardation plate is generally a retardation plate that imparts a substantially constant retardation in all wavelengths of the visible light region (380 nm to 780 nm) when linearly polarized light is incident. Therefore, in the retardation plate used for manufacture of a circularly polarizing plate, in all wavelengths of a visible light region, the phase difference of about 1/4 wavelength is provided.

(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 ?/2 plate. As long as the retardation plate of the present invention is suitable for a circularly polarizing plate, Re may not be completely 1/2 wavelength. For example, numerical ranges of ±20%, 15%, 10%, 5%, 2%, or 1% are included.

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 ?/4 plate. The term &quot;substantially&quot; is the same as above.

Liquid crystal compounds forming the first and second optically anisotropic layers are generally roughly classified into rod-shaped types (rod-shaped liquid crystal compounds) and disk-shaped types (discotic liquid crystal compounds) from their shapes. In this invention, it is preferable to form a twist 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 aligned in a substantially constant direction, continuously change into a spiral shape in which the direction of the molecules is twisted due to chirality.

The TN liquid crystal layer is preferably a layer formed by fixing, for example, a rod-shaped liquid crystal compound having a polymerizable group by polymerization or the like, and in this case, it is not necessary to exhibit liquid crystallinity after forming a layer. The kind of polymerizable group contained in the rod-shaped liquid crystal compound is not particularly limited, and a functional group capable of 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, etc. are mentioned preferably, The (meth)acryloyl group is more preferable. In the present invention, a known TN liquid crystal material can be used. Moreover, when forming a TN liquid crystal layer, you may use a chiral agent as needed with the said liquid crystal compound as needed. A chiral agent is added in order to twist-align a liquid crystal compound.

In addition, by using the polymerizable liquid crystal material as described above for the retardation plate, the thickness is reduced to 5 µm to 20 µm, compared to a film-shaped retardation plate having a film thickness of generally 50 µm to 100 µm. can do.

The first and second optically anisotropic layers in the retardation plate of the present invention are torsionally oriented with the thickness direction as the helical axis. Moreover, the twist direction of both liquid crystal layers is the same. In addition, the in-plane slow axis of the first optically anisotropic layer on the side of the third optically anisotropic layer is parallel to the in-plane slow axis of the third optically-anisotropic layer of the second optically anisotropic layer. That is, the twist angle of the second optically anisotropic layer is arranged based on the twist angle of the first optically anisotropic layer. Positive and negative (minus: -) of the torsion angle indicate that the absorption axis direction of the polarizing element is 0°, and when the polarizing element of the circularly polarizing plate is on the viewing side, a counterclockwise direction from the absorption axis is positive, and the absorption axis The clockwise direction is negative from .

The twist angle of the first optically anisotropic layer used in the retarder 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 still more 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 still more preferable. Alternatively, the twist angle of the first optically anisotropic layer is substantially -26° in another aspect. More specifically, -26±10° is preferable, -26±7° is more preferable, and -26±5° is still more 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 still more preferable. The twist angle is measured using a film inspection apparatus (RETS-1100A, manufactured by Otsuka Electronics Co., Ltd.).

In the first optically anisotropic layer used in the retardation plate of the present invention, the in-plane retardation value Re, 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, is substantially 275 nm, more specifically, 275±30 nm is preferable, as for the said product (Δn1·d1), more preferably 275±20 nm, and still more preferably 275±10 nm.

Further, in the second optically anisotropic layer used in the retardation plate of the present invention, the in-plane retardation value Re, 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, is substantially 137.5 nm, more specifically, the product (Δn2·d2) is preferably 137.5±15 nm, preferably 137.5±10 nm, and still more preferably 137.5±5 nm. The Δn1·d1 and Δn2·d2 are measured using a film inspection apparatus (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 one type of retardation plate called a positive C plate, and when the xy orthogonal axis on the plate plane and the z axis in the direction perpendicular to the plate plane are set, each axial direction The refractive index of n _x , n _y , n _z means a retardation plate such that n _x ≒ n _y < n _z . In addition, "n _x ≒ n _y " represents that n _x and n _y are substantially equivalent, including the case where they are completely equivalent. Said "n _x and n _y are substantially equal" means that as long as it functions as a positive C plate, n _x and n _y may be different, for example, 20%, 15%, 10% of the other when viewed from one side There may be a difference of %, 5%, 2%, or 1%. Also, instead of “≒”

[Equation 1]

You may use symbols such as In the present invention, a known positive C plate can be used. One aspect WHEREIN: The 3rd optically anisotropic layer provided with the retarder of this invention is a liquid crystal layer in which the rod-shaped liquid crystal compound is vertically oriented with respect to the thickness direction (plate plane), for example. The perpendicular means that the alignment angle of the liquid crystal compound is 90° and almost 90° with respect to the plate plane (a difference of negligible influence, for example, ±10°, ±5°, ±3°, or ±1° including the difference within). The third optically anisotropic layer is preferably a layer formed by fixing, for example, a rod-shaped liquid crystal compound having a polymerizable group by polymerization or the like, and in this case, it is not necessary to exhibit liquid crystallinity after forming a layer. The kind of polymerizable group contained in the rod-shaped liquid crystal compound is not particularly limited, and a functional group capable of 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, etc. are mentioned preferably, The (meth)acryloyl group is more preferable.

Moreover, adjustment of the thickness direction retardation (Rth) of the said liquid crystal layer can be performed by adjustment of the said film thickness. Although the said film thickness is not specifically limited, Generally, Preferably it is 0.1 micrometer - 3 micrometers, More preferably, it can form in the range of 0.5 micrometer - 2 micrometers.

In another aspect, the cellulosic resin material of Unexamined-Japanese-Patent No. 2016-108536 can be used. It is preferable to use the liquid crystal compound mentioned above from a viewpoint of thickness reduction and productivity.

The thickness direction retardation (Rth) of the third optically anisotropic layer of the present invention is determined based on the Poincaregu theory. In order to minimize the trajectory of movement from coordinates on the equator representing linearly polarized light to coordinates representing circularly polarized light on the North Pole or South Pole on Poincaregu, it is preferable to form an optimal range of values, specifically -150 to The range of -80 nm is preferable, the range of -132 - -112 nm is more preferable, The range of -126 - -120 nm is still more preferable. Moreover, it is preferable to arrange|position the 3rd optically anisotropic layer between the 1st optically anisotropic layer and 2nd optically anisotropic layer which were mentioned above. Thereby, the circularly polarized light of each wavelength generated by the retarder of the present invention is concentrated on the coordinates indicating the circularly polarized light on the north or south pole in Poincaregu, and circularly polarized light close to the ideal is formed at each wavelength. Therefore, in the display apparatus etc. in which the circularly-polarizing plate of this invention is mounted, coloring when seen from an oblique direction can be suppressed.

(Orientation processing)

The first and second optically anisotropic layers of the present invention form a treatment for orienting a liquid crystal compound on a substrate or an alignment film. Liquid crystal alignment is not particularly limited, as long as the alignment direction of the optically anisotropic layer is appropriately defined and the present invention does not prevent the desired performance from being exhibited, and alignment techniques known in the art can be used. The surface of the substrate may be physically anisotropic by using a rubbing roll that rotates in a direction of about 0 to 50° with respect to the conveying direction of the substrate, and the resin layer formed on the substrate disclosed in Japanese Patent Laid-Open No. 2003-014935 is described above. The method of rubbing may be used, and the photo-alignment film which gives anisotropy by the ultraviolet-ray of linearly polarized light on a polymer film, and forms an alignment film may be sufficient.

(polarizing element)

The polarizing element (also referred to as a polarizer or a polarizing film) used to obtain the circularly polarizing plate, liquid crystal display, and organic EL display device of the present invention is not particularly limited, and a well-known polarizing element is appropriately selected according to the use. can be 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 a polyiodine ion in a hot boric acid bath, or a polyvinyl alcohol film A polarizing element obtained by axial stretching and then forming a polyene structure by dehydration reaction, a polarizing element obtained by applying a solution containing a dichroic dye on a base film to orient the dichroic dye, or poly A base material-integrated polarizing element obtained by forming a vinyl alcohol layer and impregnating a dichroic dye after uniaxial stretching with a base film, etc. are mentioned. From the viewpoint of workability and optical properties, typically, a polarizing element in which a PVA-based film is uniaxially stretched to adsorb and orient a dichroic dye can be preferably used. As a commercially available PVA-based film, for example, VF-PS (thickness 75 µm) manufactured by Kuraray is mentioned, and in this case, generally, when the dichroic dye is adsorbed and orientated to a thickness of 25 µm to 35 µm uniaxial stretching to obtain a polarizing element.

The dichroic dye is preferably an iodine ion or a dichroic dye, and both can be used in order to obtain the polarizing element for this invention. Examples of the dichroic dye include azo dyes, anthraquinone dyes, and tetrazine dyes. desirable. Moreover, when a certain dichroic dye is used, the optical characteristic of a polarizing element is high transmittance and high polarization degree (also called high dichroism) from a viewpoint of obtaining the antireflection ability and the outstanding black display property in the display apparatus to mount. It is preferable to have, and more specifically, it is preferable that the visibility correction|amendment single transmittance|permeability (Ys) is 40 % - 45%, and the visibility correction|amendment polarization degree (Py) is 99 % or more.

In one aspect of the present invention, it is preferable to have an achromatic hue, that is, the single 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 ) is preferably almost uniform across the The absolute values of a* and b* values in the L*a*b* color system are both 1 or less when measured with a single polarizing element, and when measured by overlapping the two polarizing elements so that the absorption axis directions are orthogonal to each other, A hue in which the absolute value of a* value is 4 or less and the absolute value of b* value is 8 or less is also preferable as a specific embodiment of the achromatic color. In this way, for example, by the circularly polarizing plate provided with the broadened retardation plate of the present invention, not only the coloration of the reflected light from the display device is suppressed over the visible region, but also the reflected light derived from the surface of the polarizing element is in the visible region. It is possible to suppress discoloration over the

As azo dyes having dichroism, for example, C.I. Direct Yellow 12, C.I. Direct Yellow 28, C.I. Direct Yellow 44, C.I. Direct Yellow 142, C.I. Direct Orange 26, C.I. Direct Orange 39, C.I. Direct Orange 71, C.I. Direct Orange 107, C.I. Direct Red 2, C.I. Direct Red 31, C.I. Direct Red 79, C.I. Direct Red 81, C.I. Direct Red 117, C.I. Direct Red 247, C.I. Direct Green 80, C.I. Direct Green 59, C.I. Direct Blue 71, C.I. Direct Blue 78, C.I. Direct Blue 168, C.I. Direct Blue 202, C.I. Direct Violet 9, C.I. Direct Violet 51, C.I. Direct Brown 106, C.I. Direct Brown 223 and the like. In addition, a dye that can be produced by a known method may be used, and as a known method, for example, the method described in Japanese Patent Application Laid-Open No. 3-12606 or Japanese Patent Application Laid-Open No. 59-145255 and the method described in the preceding paragraph. Moreover, as a commercially available dye, Kayafect Violet P Liquid, Kayafect Yellow Y, and Kayafect Orange G, Kayafect Blue KW, and Kayafect Blue Liquid 400 (all are made by Nippon Kayaku Co., Ltd.), etc. are mentioned. These azo dyes are used in mixture of 2-3 types or more so that each transmittance|permeability in a visible region may become uniform. In addition, in the polarizing element according to the present invention, in order to obtain an achromatic polarizing element having high transmittance and high polarization degree, International Publication No. WO2017/146212, International Publication No. WO2019/117131, etc. For the design of an achromatic polarizing element, An azo dye with improved dichroism can be preferably used.

It is preferable that a polarizing element contains the base material (it is also mentioned a support body and a support film) for protecting a polarizing element. The base material may be arrange|positioned only on the single side|surface of a polarizing element, and may be arrange|positioned on both surfaces of a polarizing element so that two same or different base materials may pinch a polarizing element. The structure which has a base material in a polarizing element is called a polarizing plate. When the polarizing element is provided with a base material described later, the base material disposed 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 0 (numerically, the influence is negligible) It is preferable that it is possible to the extent possible, for example, in the range of -5 nm to 5 nm).

(write)

The retardation plate and the circularly polarizing plate of the present invention (hereinafter, also referred to as the article of the present invention) may include a base material. There is no restriction|limiting in particular as long as it has desired mechanical strength, thermal stability, etc. as a base material, and this invention does not interfere with desired performance, A base material well-known in this field can be used. Although the thickness of a base material can be designed suitably, 50-200 micrometers is preferable, 10-100 micrometers is more preferable, 20-80 micrometers is still more preferable.

Moreover, when arrange|positioning a base material between a polarizing element and a display device, it is preferable that the in-plane retardation value (Re) and thickness direction retardation value (Rth) of the said base material are 0 or substantially 0. Examples of the commercially available substrate having the retardation value include a triacetyl cellulose-based resin film Z-TAC (manufactured by Fujifilm), an acrylic resin film OXIS series (manufactured by Okura Kogyo), and the like.

(adhesive and/or adhesive)

The article of the present invention WHEREIN: Lamination|stacking may be formed by forming the following layer on a certain layer, and you may form lamination|stacking by bonding several layers together with an adhesive and/or an adhesive agent. There is no particular limitation, as long as it exhibits a function as a pressure-sensitive adhesive or adhesive and does not prevent the present invention from exhibiting the desired performance, and any pressure-sensitive adhesive or adhesive known in the art may be used. As an adhesive, acrylic resin is mentioned typically as an adhesive. Although the said thickness can design suitably, 1-50 micrometers is preferable, and 5-25 micrometers is more preferable from a viewpoint of the adhesiveness between layers, adhesive coating, and lamination processability. Examples of the adhesive include a water-based adhesive containing a PVA-based resin as a main component, an adhesive containing a thermosetting or photocurable resin, and a method by plasma bonding.

The retardation value and twist angle value of the optically anisotropic layer of the present invention are values for obtaining an optically favorable effect. These values are not limited, considering the orientation characteristics and product processability of an actual liquid crystal compound, A tolerance and a margin may be included.

(Circular polarizer)

The circularly polarizing plate of the present invention is a broadband circularly polarizing plate, comprising a polarizing element and the retardation plate of the present invention, specifically, a polarizing element (or polarizing plate), a first optically anisotropic layer, a third optically anisotropic layer, and a second optical Anisotropic layers are provided in this order. Further, in each optical axis of the circularly polarizing plate, in one aspect, the absorption axis of the polarizing element is in the direction of 0°, and the twist angle of the first optically anisotropic layer is substantially 26° with respect to the absorption axis of the polarizing element. and the twist angle of the second optically anisotropic layer is substantially in a direction of 78° from the twist angle of the first optically anisotropic layer (ie, a direction of 104° with respect to the absorption axis of the polarizing element).

The manufacturing method of the circularly polarizing plate of this invention is not specifically limited, For example, you may laminate|stack the film or sheet of each above-mentioned layer for every leaf|leaf, and each of the above-mentioned layers produced in roll shape is roll-to-roll. may be continuously laminated by In particular, in the circularly polarizing plate of the present invention, since the retardation plate does not need to be cut out according to a predetermined optical axis angle, the latter roll-to-roll lamination can be easily performed. Therefore, for example, productivity can be improved compared to the conventional method of manufacturing a broadband circularly polarizing plate in which a uniaxially oriented film such as a COP-based film is laminated.

(Manufacturing method of circularly polarizing plate)

Although the manufacturing method of the retardation plate which concerns on this invention and a circularly-polarizing plate is demonstrated giving examples of 1st - 2nd aspect below, it is not limited to these. Moreover, each optically anisotropic layer is formed on the liquid-crystal layer, the base material, and the base material which can peel after hardening, and in the process of laminating|stacking sequentially mentioned later, you may remove each base material and form a circularly polarizing plate.

(Example 1st Embodiment)

As a first step, a liquid crystal compound exhibiting a polymerizable nematic liquid crystal phase, a chiral agent, a photopolymerization initiator, and a diluent solvent on the rubbing surface of a substrate rubbed in the direction of 0° (transport direction). After the composition is applied, the solvent is removed through a drying step, and the coating film is cured by irradiation with light to have an orientation axis in the 0° direction, a torsion angle of 26°, and the retardation value (Re@550 nm) of 275 nm A first optically anisotropic layer is obtained.

As the second step, a composition for application of a composition comprising a liquid crystal compound exhibiting a polymerizable nematic liquid crystal phase, a photopolymerization initiator, and a diluting solvent is applied to a substrate, followed by a drying step to remove the solvent, and light irradiation and curing the coating film to obtain a third optically anisotropic layer oriented in a direction perpendicular to the substrate.

In the third step, a coating composition containing a TN liquid crystal material, a chiral agent, a photoinitiator, and a diluting solvent is applied to the rubbing surface of the substrate subjected to the rubbing treatment in a direction of 26° with respect to the transport direction, followed by a drying step A second optically anisotropic layer having an orientation axis in a direction of 26°, a twist angle of 78° and a retardation value (Re@550 nm) of 137.5 nm is obtained by removing the solvent through .

As the fourth step, the circularly polarizing plate of the present invention is obtained by sequentially laminating a polarizing element (or a polarizing plate), a first optically anisotropic layer, a third optically anisotropic layer, and a second optically anisotropic layer so that the optical axis relationship shown in FIG. 3 is obtained.

(Example of the second aspect)

In the second step, a composition for coating a composition comprising a liquid crystal compound exhibiting a polymerizable nematic liquid crystal phase, a photopolymerization initiator, and a diluent solvent is applied to the liquid crystal surface of the first optically anisotropic layer obtained in the first step Then, the solvent is removed through a drying step, and the coating film is cured by irradiation with light to obtain a third optically anisotropic layer orientated in a direction perpendicular to the liquid crystal plane. Thereafter, the circularly polarizing plate of the present invention is obtained by sequentially laminating a polarizing element (or polarizing plate), a first optically anisotropic layer on which a third optically anisotropic layer is laminated, and a second optically anisotropic layer so as to have the optical axis relationship shown in FIG. Other than that, it is the same as that of the first embodiment.

(display device)

The circularly polarizing plate of the present invention can be suitably applied to the viewing side of various display devices such as a liquid crystal display (LCD) and an organic electroluminescence (EL) display (organic light emitting diode (OLED) display). have. Further, the display device may have a configuration including a touch panel, an anti-glare layer or an anti-reflection layer, a light-transmitting cover (also referred to as a front plate), and the like depending on the design. Moreover, the said transparent cover may have a planar shape, and may have a curved-surface shape. The manufacturing method of the display device of this invention is not specifically limited, It can produce by a well-known method.

The liquid crystal display device of the present invention may have a configuration including a liquid crystal panel called a transmissive type or a transflective type and a backlight unit, or a configuration including a liquid crystal panel called a reflection type and a reflective layer.

Moreover, since an organic electroluminescence display generally equips the said display panel part with a metal electrode, OLED (organic electroluminescence display) itself has a reflectance higher than a liquid crystal panel. For example, when this is used in an environment with much external light, such as a daytime outdoors, it becomes a cause which impairs display property by external light reflection from the said electrode. Therefore, generally, a circularly polarizing plate is attached to the visual recognition side of an organic electroluminescent display in order to suppress external light reflection. Accordingly, the display characteristics of the organic EL display device also depend on the optical characteristics of the circularly polarizing plate. Since the circularly polarizing plate of this invention has wide viewing angle characteristic than the conventional circularly polarizing plate, it can use suitably for the organic electroluminescent display which requires a wide viewing angle.

Although embodiment of this invention was described so far, this invention is not limited to the above embodiment, Various deformation|transformation and change are possible based on the technical idea of this invention.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

Assuming that a circularly polarizing plate was attached to an ideal reflecting plate, the black luminance (unit is a standardized value) at the following azimuth and inclination angles (polar angles) was calculated using a liquid crystal simulation software LCD master (manufactured by Syntech). . The configuration and calculation conditions of the circular polarizer 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 represent values at a wavelength of 550 nm. In addition, in Table 1, the optically anisotropic layer arrange|positioned is shown in the column of 1st layer, 2nd layer, and 3rd layer in order from the incident light side.

Structure of circular polarizer:

Example 1: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, third optically anisotropic layer 1, second optically anisotropic layer, reflecting plate

Example 2: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, third optically anisotropic layer 2, second optically anisotropic layer, reflecting plate

Example 3: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, third optically anisotropic layer 3, second optically anisotropic layer, reflecting plate

Example 4: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, third optically anisotropic layer 4, second optically anisotropic layer, reflecting plate

Example 5: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, third optically anisotropic layer 5, second optically anisotropic layer, reflecting plate

Comparative Example 1: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, second optically anisotropic layer, third optically anisotropic layer 1, reflecting plate

Comparative Example 2: (Sequentially from the incident light side) Polarizing element, third optically anisotropic layer 1, first optically anisotropic layer, second optically anisotropic layer, reflecting plate

Comparative Example 3: (Sequentially from the incident light side) Polarizing element, first optically anisotropic layer, second optically anisotropic layer, and reflecting plate

Comparative Example 4: (Sequentially from the incident light side) Polarizing element, general 1/2 wave plate 1, third optically anisotropic layer 6, general 1/4 wave plate 1, and reflecting plate

Comparative Example 5: (Sequentially from the incident light side) Polarizing element, general 1/2 wave plate 2, third optically anisotropic layer 7, general 1/4 wave plate 2, reflection plate

Comparative Example 6: (Sequentially from the incident light side) Polarizing element, general 1/2 wave plate 1, general 1/4 wave plate 1, third optically anisotropic layer 8, reflection plate

First optically anisotropic layer:

Liquid crystal layer: ZLI-4792 (manufactured by Merck)

The resulting phase difference = 1/2λ

Δn1·d1 = 275 nm

Pretwist angle = 0°

Twist angle = -26°

Thickness of liquid crystal layer = 2.136 μm

Second optically anisotropic layer:

Liquid crystal layer: ZLI-4792 (manufactured by Merck)

The resulting phase difference = λ/4

Δn2·d2 = 137.5 nm

Pretwist angle = -26°

Twist angle = -78°

Thickness of liquid crystal layer = 1.068 μm

Third optically anisotropic layer:

Liquid crystal layer: polymerizable vertically aligned liquid crystal compound (manufactured by Merck Corporation)

n _x = 1.5283

n _y = 1.5283

n _z = 1.6725

Thickness of liquid crystal layer = 0.60 ㎛ ~ 1.45 ㎛

Rth: Described below in 1 to 8

Third optically anisotropic layer 1:

Rth = -120 nm

Third optically anisotropic layer 2:

Rth = -115 nm

Third optically anisotropic layer 3:

Rth = -130 nm

Third optically anisotropic layer 4:

Rth = -80 nm

Third optically anisotropic layer 5:

Rth = -150 nm

Third optically anisotropic layer 6:

Rth = -174 nm

Third optically anisotropic layer 7:

Rth = -209 nm

Third optically anisotropic layer 8:

Rth = -133 nm

Polarizing element: JET-12 (manufactured by Polar Techno Co., Ltd., using spectral data having a light sensitivity corrected single transmittance Ys = 41.5% and a visibility corrected polarization degree Py = 99.99%, no support layer)

Reflector:

Material: ideal reflector

A typical half-wave plate (HWP) 1:

Material: Cycloolefin Polymer (COP)

Nz coefficient = 1.0

Common Quarter Wave Plate (QWP) 1:

Material: Cycloolefin Polymer (COP)

Nz coefficient = 1.0

Typical half-wave plate (HWP) 2:

Material: Cycloolefin Polymer (COP)

Nz coefficient = 1.5

Common Quarter Wave Plate (QWP) 2:

Material: Cycloolefin Polymer (COP)

Nz coefficient = 1.5

Incident light: natural light (wavelength range: 380 nm to 780 nm)

Inclination angle (polar angle) θ = 40°, 50°, and 60°)

Azimuth Φ = 0° to 360° (each 5° interval)

In the test conditions, the Nz coefficient is one of the indexes indicating the magnitude relationship of the refractive index components n _x , n _y and n _z , and is a value represented by the following formula (2).

[Equation 2]

In the above calculation conditions, standard data attached to LCD master were used for ZLI-4792 (manufactured by Merck Corporation) and cycloolefin polymer (COP). In addition, n _x , n _y , and n _z of the third optically anisotropic layer using a polymerizable vertically aligned liquid crystal compound (manufactured by Merck Corporation) were measured using an Abbe refractometer (DR-M2 ATAGO, Inc.) production) was measured.

Table 2 shows the evaluation result of the black luminance value of Examples 1-5 and Comparative Examples 1-6.

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) was 0.1 or less, and the light incident from the polarizing element was transmitted to the circularly polarizing plate. It was confirmed that the reflection from the reflector was sufficiently suppressed. Evaluation was performed on the basis of the black luminance value at this polar angle θ = 0°. In addition, this black luminance value of 0 or substantially 0 indicates that the circularly polarizing plate suppresses reflection of incident light and is functioning ideally.

Using the above calculation results, the distribution of black luminance at azimuth Φ = 0° to 360° with respect to the polar angle θ = 0° (head-on) at the center and polar angle θ = 0° to 80° It was shown as an isometry diagram (contour diagram). In this case, the black luminance was expressed in a fixed range from a minimum value of 0 to a maximum value of 10. 4-6 are Examples 1-3, and FIGS. 7-12 show the contour diagrams of Comparative Examples 1-6, respectively. In the contour diagrams of Examples 1 to 3, the isoline representing the maximum luminance value when the polar angle θ is shifted from 0° to 80° (from the center of the circle in the figure to the end of the outer circle) is 1.6 to 1.8, which is Since it is a value smaller than the example, it turned out that a wider viewing angle is shown. In addition, in the case of Comparative Example 5, the maximum luminance value exceeded 10.

Further, in order to quantitatively compare the effect of improving black luminance when viewed from the oblique direction, black luminance values were extracted from the above calculation results under the conditions of polar angles θ and azimuth angles Φ described below. 13 to 21 show the results of plotting the black luminance value at this time with respect to the azimuth angle ?.

Polar angle θ = 40°, 50°, 60°

Azimuth Φ = 0° to 360° (45° intervals)

The results plotted under the above conditions for Examples 1 to 3 are shown in Figs. 13 to 15 . Specifically, in Examples 1 to 3 in which the Rth of the third optically anisotropic layer is in the range of -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 black luminance at the azimuth angle ? = 0° to 360° (45° intervals) in each of the polar angles was 0.26 to 0.68. It can be estimated that the black luminance increases by 2.7 to 7.6 times when the black luminance is viewed from the oblique directions of the polar angles θ = 40°, 50°, and 60° with respect to the polar angle θ = 0° (A). there was. Moreover, as a result of performing calculations similarly to the above about the case of Examples 4 and 5 in which the range of Rth of the 3rd optically anisotropic layer is -80 nm and -150 nm, the increase in black luminance was 3.2 times - 10.0 times. From this point, it was found that the black luminance when viewed from the oblique direction can be further reduced by preferably setting the range of Rth of the third optically anisotropic layer to -130 nm to -115 nm.

The results plotted under the above conditions for Comparative Examples 1 to 3 are shown in Figs. 16 to 18 . Rth of the third optically anisotropic layer is fixed to -120 nm, and the arrangement of the third optically anisotropic layer is arranged after the second optically anisotropic layer or before the first optically anisotropic layer, or the third optically anisotropic layer In Comparative Examples 1 to 3 in which there was no Moreover, the average value (B) of the black luminance of the azimuth in each polar angle calculated|required similarly to the above was 0.59 to 1.72 in Comparative Examples 1-2, and 1.27 to 3.88 in Comparative Example 3. This means that the black luminance when viewed from the oblique directions of the polar angles θ = 40°, 50°, and 60° with respect to the polar angle θ = 0° (A) is 6.3 times for Comparative Examples 1 and 2 - 18.2 times, Comparative Example 3 could be estimated to increase by 13.4 times to 41.1 times. As a result, it was shown that the structure of Examples 1-5 improved the viewing angle characteristic rather than the conventional Comparative Examples 1-3.

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

From the above results, in the configuration of the circularly polarizing plate of the present invention, broadening of the circularly polarizing plate is not only the presence or absence of the third optically anisotropic layer and optimization of its Rth value, but also the first optically anisotropic layer and the second optically anisotropic layer for the second optically anisotropic layer. 3 By selecting the arrangement of the optically anisotropic layer, it is possible to increase the bandwidth compared to the conventionally configured circularly polarizing plate. Therefore, according to the present invention, for example, in black display such as an organic EL display device, black display with little light leakage when viewed from an oblique direction can be obtained.

In addition, the retardation plate of the present invention includes first and second optically anisotropic layers having optimum wavelength dispersion characteristics (meaning wavelength dependence of retardation) in order to further reduce black luminance at a polar angle of 0°. You can do it. Similarly, in the third optically anisotropic layer, by setting the wavelength dispersion characteristic to negative dispersion (reverse wavelength dispersion), the black luminance in black display when viewed from the oblique direction can be further reduced.

The present application can provide a retardation plate for reducing coloration or reflectance in black display when viewed from an oblique direction, a circularly polarizing plate provided therewith, and a liquid crystal display and organic EL display including the circularly polarizing plate. For example, since an organic electroluminescent display can give a wider viewing angle, it can use suitably for installation of a display apparatus, vehicle installation in which a viewing place is fixed, etc., for example. Moreover, since the manufacturing method which makes a circularly-polarizing plate producible only by bonding of roll-to-roll can be provided, it can respond also to manufacture of the circularly-polarizing plate for large sized display devices.

101: retardation plate of the present invention
102: first optically anisotropic layer
103: second optically anisotropic layer
104: third optically anisotropic layer
105: circularly polarizing plate of the present invention
106: polarizing element (polarizing plate)
107: torsional nematic liquid crystal
108: substrate 1 (alignment layer)
109: substrate 2 (alignment layer)
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: represents parallel to 201

Claims (7)

A first optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in the thickness direction in a helical axis and has an in-plane retardation value (Re) of substantially 1/2 wavelength;
A retardation plate comprising a second optically anisotropic layer in which the rod-shaped liquid crystal compound is oriented in a helical axis in the thickness direction and has an in-plane retardation value (Re) of substantially 1/4 wavelength,
Between the first and second optically anisotropic layers, the following formula (1):
n _x ≒ n _y < n _z (1)
(Wherein, n _x and n _y are the refractive indices in the orthogonal plate plane direction, and n _z denotes the refractive indices in the perpendicular direction to the plate plane direction)
Retardation plate comprising a third optically anisotropic layer that satisfies The method of claim 1,
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 substantially 78° or substantially from the twist angle of the first optically anisotropic layer At -78°, retarder. 3. The method according to claim 1 or 2,
The third optically anisotropic layer is a layer having a vertically aligned liquid crystal compound, and the thickness direction retardation value (Rth) is -150 to -80 nm. A circularly polarizing plate provided with a polarizing element and the retardation plate in any one of Claims 1-3. 5. The method of claim 4,
The polarizing element includes a dichroic azo dye, the color of which is an achromatic color, a circularly polarizing plate. The organic electroluminescent display provided with the circularly-polarizing plate of Claim 4 or 5. The liquid crystal display device provided with the circularly-polarizing plate of Claim 4 or 5.

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