CN114341684A - Phase difference plate, and circularly polarizing plate, liquid crystal display device and organic EL display device having the same - Google Patents

Abstract

The present invention provides a phase difference plate, comprising: a first optically anisotropic layer which is an optically anisotropic layer in which a rod-like liquid crystal compound is aligned with a thickness direction thereof being a helical axis and which has an in-plane phase difference value (Re) of substantially 1/2 wavelengths; and a second optically anisotropic layer, wherein the second optically anisotropic layer,an optically anisotropic layer in which a rod-like liquid crystal compound is aligned with a thickness direction thereof being a helical axis and which has an in-plane phase difference value (Re) of substantially 1/4 wavelengths; wherein a third optically anisotropic layer satisfying the following formula (1) is provided between the first and second optically anisotropic layers, and n_x≒n_y<n_z(1) (in the formula, n_xAnd n_yRepresenting the refractive indices of orthogonal plate plane directions, n_zIndicating the refractive index in the direction perpendicular to the plane direction of the plate).

Description

Phase difference plate, and circularly polarizing plate, liquid crystal display device and organic EL display device having the same

technical field

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, a liquid crystal display device, and an organic EL display device having the retardation plate.

Background technique

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

Conventionally, with regard to image display panels and the like, there has been proposed a method of arranging a circular polarizer on the surface of the image display panel, and reducing reflection of external light by the circular polarizer. This circular polarizing plate is composed of a linear polarizing plate and a 1/4 wavelength retardation plate (hereinafter also referred to as a λ/4 plate). The linear polarizing plate converts the external light toward the display surface of the image display panel into linear polarized light. , and then converted into circularly polarized light through a 1/4 wavelength retardation plate. Here, although the external light from the circularly polarized light is reflected on the surface of the image display panel, etc., the rotation direction of the circularly polarized light is reversed when reflected. As a result, the reflected light is converted into linearly polarized light in the direction opposite to when it arrived and blocked by the quarter-wave retardation plate and the linear polarizer, and then blocked by the linear polarizer, thereby preventing the reflected light from being exposed to the outside.

The retardation plate used in this circularly polarizing plate conventionally has the following problems, for example, due to the wavelength dependence (wavelength dispersion) of the retardation value. The tape did not function as a λ/4 plate, and was colored in a dark state (black screen). The above problems become particularly apparent when viewing the display device with an oblique viewing angle. In order to prevent such a problem, there has been a demand for a retardation plate for a circularly polarizing plate that can function close to a quarter wavelength in a wide wavelength band and can prevent reflection over a wide viewing angle. As the above-mentioned retardation plate, a retardation plate extending uniaxially or biaxially is used. In addition, a method of using one or more twist-aligned nematic liquid crystal layers (twisted nematic liquid crystal layers) is also disclosed.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2014-209220

[Patent Document 2] Japanese Patent Laid-Open No. 2014-224837.

SUMMARY OF THE INVENTION

[Problems to be solved by the invention]

For example, a λ/4 plate obtained by biaxially extending a modified polycarbonate (PC)-based film is known as a retardation plate for widening the angle of view. However, this retardation plate and the retardation plate formed by laminating a λ/4 plate and the same λ/2 plate, which will be described later, show inverse wavelength dispersion with respect to the retardation value corresponding to the visible light wavelength region, but suppress the The effect of coloring when viewed from an oblique direction is not sufficient.

In addition, there is a widening retardation plate obtained by laminating a λ/4 plate obtained by uniaxially extending a cycloolefin (COP)-based film and the same λ/2 plate. However, in this laminated retardation plate, it is necessary to cut each retardation plate so as to have a predetermined optical axis angle with respect to the optical axis of the polarizing plate, and then use an adhesive layer or the like to laminate one by one, which is problematic in terms of productivity. .

In addition, Patent Document 1 describes that by controlling the twist angle and Δnd (the product of the difference in refractive index (Δn) and the thickness (d) of the film), a nematic liquid crystal that undergoes two continuous layers of twist alignment has realized a broadband Compared with the well-known retardation plate with λ/4 plate and λ/2 plate with λ/4 plate, it can convert linearly polarized light of wider wavelength into more complete circularly polarized light. However, regarding the circular polarizing plate using this λ/4 plate, only the results observed from the direction directly above, and the display properties (reproducibility and coloration of black) when viewed from an oblique direction have not been sufficiently discussed.

In addition, in order to improve the above-mentioned display properties when viewed from an oblique direction, it is generally known to add a positive C plate layer having a retardation value in the thickness direction within a predetermined range for the above retardation plate. For example, in Patent Document 2, an attempt is made to improve display properties viewed 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, there is a conventional circular polarizing plate having only "a structure using a nematic liquid crystal layer subjected to double twist alignment and having the functions of a λ/2 plate and a λ/4 plate, respectively" and A broadband λ/4 wavelength retardation plate composed of "stretched films", and also has a positive C plate layer, but this circular polarizer cannot meet the black reproducibility (black brightness (black brightness) of the display device when viewed from an oblique direction. The degree of brightness) and the display properties related to coloring are required to be further improved. In addition, regarding the positive C plate layer, the retardation value (Rth) in the thickness direction and the most preferable arrangement relationship with the retardation plate have not been discussed.

An object of the present application is to provide a broadband retardation plate for a circular polarizer that reduces black luminance in a black screen when viewed from an oblique direction (displays good black), a circular polarizer having the retardation plate, and a circular polarizer having the above-mentioned circular polarizer Panels of liquid crystal display devices and organic EL display devices.

[Means to solve the problem]

The inventors of the present application have conducted detailed studies in order to solve the above-mentioned problems. As a result, by using a positive C plate layer between 2 liquid crystal layers having a twist alignment in the thickness direction, the black luminance in a black screen when viewed from an oblique direction was successfully reduced.

That is, the present invention relates to the following inventions, but is not limited to these.

[Invention 1]

A phase difference plate, comprising:

The first optically anisotropic layer is an optically anisotropic layer in which the rod-like liquid crystal compound is aligned with the thickness direction as the helical axis, and has substantially an in-plane retardation value (Re) of 1/2 wavelength; and

The second optically anisotropic layer is an optically anisotropic layer in which the rod-like liquid crystal compound is aligned with the thickness direction as the helical axis, and has substantially an in-plane retardation value (Re) of 1/4 wavelength; wherein,

Between the first and second optically anisotropic layers, a third optically anisotropic layer satisfying the following formula (1) is provided,

n _x ≒n _y <n _z (1)

(In the formula, n _x and _ny represent the refractive index in the direction perpendicular to the plate plane, and _nz represents the refractive index in the direction perpendicular to the plate plane).

[Invention 2]

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

[Invention 3]

The retardation plate according to Invention 2, wherein the third optically anisotropic layer is a layer having a vertical alignment type liquid crystal compound, and the thickness direction retardation value (Rth) is -150 to -80 nm.

[Invention 4]

A circularly polarizing plate comprising a polarizing element and the retardation plate according to any one of Inventions 1 to 3.

[Invention 5]

The circularly polarizing plate according to Invention 4, wherein the polarizing element comprises a dichroic azo dye whose hue is achromatic color.

[Invention 6]

An organic EL display device including the circular polarizing plate according to Invention 4 or 5.

[Invention 7]

A liquid crystal display device including the circularly polarizing plate according to Invention 4 or 5.

[Effect of invention]

The present application can provide a broadband retardation plate for circularly polarizing plates that reduces black luminance and/or reduces coloration in a black screen when viewed from an oblique direction, a circularly polarizing plate having the retardation plate, and a circularly polarizing plate having the foregoing liquid crystal display device (LCD) and organic electroluminescence (EL) display device (organic light emitting diode (OLED) display device). In one aspect, a display device that displays good blacks in a black screen when viewed from the front can be provided. In one aspect, the present application can provide a thin retardation plate. In one aspect, the present application achieves lower brightness and less tinted black not only in the head-on direction, but also in a broad direction of varying viewing angles, in the black screen of LCD and OLED display devices. In one aspect, the present application can provide a manufacturing method, which does not require complex steps such as sheet-by-sheet lamination or oblique extension, and can manufacture a circular polarizer only by roll-to-roll lamination.

Description of drawings

FIG. 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 aspect example” of the present invention.

4 is a contour diagram of luminance corresponding to polar angles of 0° to 80° and azimuth angles of 0° to 360° in Example 1. FIG.

5 is a contour diagram of luminance corresponding to polar angles of 0° to 80° and azimuth angles of 0° to 360° of Example 2. FIG.

6 is a contour diagram of luminance corresponding to polar angles of 0° to 80° and azimuth angles of 0° to 360° in Example 3. FIG.

7 is a contour diagram of luminance corresponding to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 1. FIG.

8 is a contour diagram of luminance corresponding to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 2. FIG.

9 is a contour diagram of luminance corresponding to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° of Comparative Example 3. FIG.

10 is a contour diagram of luminance corresponding to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 4. FIG.

11 is a contour diagram of luminance corresponding to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 5. FIG.

12 is a contour diagram of luminance corresponding to a polar angle of 0° to 80° and an azimuth angle of 0° to 360° in Comparative Example 6. FIG.

13 shows the experimental results of the circularly polarizing plates of Examples 1 to 3 in a polar angle (tilt angle) of 40° and an azimuth angle of 0 to 360° (in units of 45°).

14 shows the experimental results of the circularly polarizing plates of Examples 1 to 3 in a polar angle (tilt angle) of 50° and an azimuth angle of 0 to 360° (in units of 45°).

15 shows the experimental results of the circularly polarizing plates of Examples 1 to 3 in a polar angle (tilt angle) of 60° and an azimuth angle of 0 to 360° (in units of 45°).

16 shows experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 1 to 3 in a polar angle (tilt angle) of 40° and an azimuth angle of 0 to 360° (in units of 45°).

17 shows experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 1 to 3 in a polar angle (tilt angle) of 50° and an azimuth angle of 0 to 360° (in units of 45°).

18 shows the experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 1 to 3 in a polar angle (tilt angle) of 60° and an azimuth angle of 0 to 360° (in units of 45°).

19 shows the experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 4 to 6 in a polar angle (tilt angle) of 40° and an azimuth angle of 0 to 360° (in units of 45°).

20 shows the experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 4 to 6 in a polar angle (tilt angle) of 50° and an azimuth angle of 0 to 360° (in units of 45°).

21 shows the experimental results of the circularly polarizing plates of Example 1 and Comparative Examples 4 to 6 in a polar angle (tilt angle) of 60° and an azimuth angle of 0 to 360° (in units of 45°).

Detailed ways

Embodiments of the present invention will be described below.

(Phase plate)

A retardation plate (wavelength plate) means an optical element that imparts a predetermined retardation to incident linearly polarized light. The retardation plate of 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, and the first and second optically anisotropic layers are Between the anisotropic layers, a third optically anisotropic layer that suppresses coloration when viewed from an oblique direction is provided. The retardation plate of the present invention is suitable for circular polarizing plates, especially for broadband circular polarizing plates. The manufacturing method of the retardation plate of this invention is not specifically limited, For example, a well-known method, such as roll-to-roll (roll-to-roll), can be manufactured.

Among the retardation plates, the broadband is generally a retardation plate that imparts an almost constant retardation in all wavelengths in the visible light region (380 nm to 780 nm) when linearly polarized light is incident. Therefore, the retardation plate used for the production of the circularly polarizing plate is provided with a phase difference close to 1/4 wavelength in all wavelengths in the visible light region.

(First and second optically anisotropic layers)

The first optically anisotropic layer of the present invention has substantially an in-plane retardation value (Re) of 1/2 wavelength, and functions as a λ/2 plate. As long as the retardation plate of the present invention is applied to a circularly polarizing plate, the above-mentioned Re may not be exactly 1/2 wavelength. For example, a numerical range of ±20%, 15%, 10%, 5%, 2% or 1% is included.

The second optically anisotropic layer of the present invention has an in-plane retardation value (Re) of substantially 1/4 wavelength, and functions as a λ/4 plate. It is the same as above with regard to the use of the word "substantially".

The liquid crystal compounds forming the first and second optically anisotropic layers are generally roughly classified into rod-like (rod-like liquid crystal compounds) and discotic (disc-like liquid crystal compounds) based on their shapes. The present invention preferably uses a rod-like liquid crystal compound to form a twisted nematic (TN) liquid crystal layer. The TN liquid crystal layer is a liquid crystal layer in which nematic liquid crystals in which rod-like elongated molecules are substantially aligned in a fixed direction are continuously changed into a helical liquid crystal layer in which the molecular direction is twisted due to chirality.

The TN liquid crystal layer is preferably a layer formed by fixing a rod-like liquid crystal compound having a polymerizable group or the like by polymerization or the like, and in this case, it is not necessary to exhibit liquid crystallinity after the layer is formed. The type of the polymerizable group contained in the rod-like liquid crystal compound is not particularly limited, but is preferably a functional group capable of an addition polymerization reaction, preferably a polymerizable ethylenically unsaturated group or a cyclic polymerizable group. More specifically, a (meth)acryloyl group, a vinyl group, a styryl group, an allyl group, etc. are preferably mentioned, and a (meth)acryloyl group is more preferable. In the present invention, well-known TN liquid crystal materials can be used. In addition, when forming the TN liquid crystal layer, a desired chiral reagent can also be used together with the above-mentioned liquid crystal compound according to requirements. The chiral agent is added for twist alignment of the liquid crystal compound.

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

The first and second optically anisotropic layers in the retardation plate of the present invention are twist-aligned with the thickness direction as the helical axis. In addition, the twist directions of the two liquid crystal layers are the same. In addition, the in-plane slow axis on the third optically anisotropic layer side of the first optically anisotropic layer is parallel to the in-plane slow axis on the third optically anisotropic layer side 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. The positive and negative (minus:-) of the twist angle are the direction of the counterclockwise rotation from the absorption axis when the direction of the absorption axis of the polarizing element is set to 0° and the polarizing element of the circular polarizer is on the viewing side. And negatively represent the direction of clockwise rotation from the absorption axis.

In one aspect, the twist angle of the first optically anisotropic layer used in the retardation plate of the present invention is substantially 26°. More specifically, it is preferably 26±10°, more preferably 26±7°, still more preferably 26±5°. In this case, the twist angle of the second optically anisotropic layer is substantially 78°. More specifically, it is preferably 78±10°, more preferably 78±7°, still more preferably 78±5°. Or the twist angle of the first optically anisotropic layer is in another aspect substantially -26°. More specifically, it is preferably -26±10°, more preferably -26±7°, still more preferably -26±5°. In this case, the twist angle of the second optically anisotropic layer is substantially -78°. More specifically, it is preferably -78±10°, more preferably -78±7°, still more preferably -78±5°. The above-mentioned twist angle can be 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 product of the refractive index anisotropy Δn1 at a wavelength of 550 nm and the thickness d1 of the liquid crystal layer (Δn1·d1), that is, the surface bond retardation The value (Re) is substantially 275 nm, and more specifically, the aforementioned product (Δn1·d1) is preferably 275±30 nm, more preferably 275±20 nm, and still more preferably 275±10 nm.

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

(Third Optical Anisotropic Layer)

The third optically anisotropic layer included in the retardation plate of the present invention is a type of retardation plate called a positive C plate, and refers to a retardation plate in which xy orthogonal axes are set on the plate plane When the z-axis is set in the direction perpendicular to the plate plane, the refractive indices n _x , _ny , and nz in the respective axis directions are n _x ≒ _ny < _{n z .} In addition, "n _x ≒ _ny " means that n _x and _ny are substantially equal, and the case where they are completely equal is also included. The aforementioned " _nx and _ny are substantially equal", as long as they function as a positive C plate, _nx and _ny may be different. 10%, 5%, 2%, or 1% difference. In addition, the following symbols may be used instead of "≒".

[Number 1]

In the present invention, a well-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-like liquid crystal compound is vertically aligned with respect to the thickness direction (plate plane). The aforementioned vertical, including the alignment angle of the liquid crystal compound, is 90° and almost 90° with respect to the plane of the plate (including differences in such a degree that its influence can be ignored, such as within ±10°, ±5°, ±3°, or ±1°. difference) direction. The third optically anisotropic layer is preferably a layer formed by fixing a rod-like liquid crystal compound having a polymerizable group or the like by polymerization or the like, and in this case, it is not necessary to exhibit liquid crystallinity after it becomes a layer. The type of the polymerizable group contained in the rod-like liquid crystal compound is not particularly limited, but is preferably a functional group capable of an addition polymerization reaction, preferably a polymerizable ethylenically unsaturated group or a cyclic polymerizable group. More specifically, a (meth)acryloyl group, a vinyl group, a styryl group, an allyl group, etc. are preferably mentioned, and a (meth)acryloyl group is more preferable.

In addition, adjustment of the retardation (Rth) in the thickness direction of the liquid crystal layer can be performed by adjusting the film thickness. The film thickness is not particularly limited, but can be set in a range of generally preferably 0.1 μm to 3 μm, more preferably 0.5 μm to 2 μm.

On the other hand, the cellulose-based resin material of Japanese Patent Application Laid-Open No. 2016-108536 can be used. From the viewpoints of thinning and productivity, the aforementioned liquid crystal compounds are preferably used.

The retardation in the thickness direction (Rth) of the third optically anisotropic layer of the present invention is determined according to the Poincare sphere theory. In order to make the locus moving from the coordinates on the equator representing linearly polarized light on the Bonga sphere to the coordinates representing circularly polarized light on the north pole or south pole to be the minimum value, it is preferable to set the range of the most preferable value, specifically, -150 is preferable. to -80 nm, more preferably -132 to -112 nm, still more preferably -126 to -120 nm. In addition, the third optically anisotropic layer is preferably arranged between the above-mentioned first optically anisotropic layer and the second optically anisotropic layer. Accordingly, the circularly polarized light of each wavelength generated by the retardation plate of the present invention will be concentrated on the coordinates representing the circularly polarized light on the north pole or the south pole in the Bonga sphere, thereby forming nearly ideal circularly polarized light in each wavelength. Therefore, in a display device or the like mounted with the circular polarizing plate of the present invention, coloring when viewed from an oblique direction can be suppressed.

(Alignment processing)

The first and second optically anisotropic layers of the present invention are subjected to a treatment for aligning the liquid crystal compound on the substrate, or an alignment film is provided. The liquid crystal alignment is not particularly limited as long as the alignment direction of the aforementioned optically anisotropic layer is appropriately specified and the intended performance of the present invention is not hindered, and alignment techniques well known in the art can be used. Anisotropy can be formed on the surface of the substrate physically using a rubbing roll rotated in a direction of about 0 to 50° with respect to the conveying direction of the substrate. The method of performing the aforementioned rubbing treatment on the resin layer provided on the base material may be a photo-alignment film in which an alignment film having anisotropy due to linearly polarized ultraviolet rays is formed on the polymer film.

(polarizing element)

The polarizing element (sometimes referred to as a polarizer or a polarizing film) used to obtain the circularly polarizing plate, liquid crystal display device, and organic EL display device of the present invention is not particularly limited, and a well-known polarizing element can be appropriately selected according to the application. and use. For example, a polarizing element obtained by uniaxially stretching a polyvinyl alcohol (PVA)-based film obtained by impregnating a dichroic dye such as a water-soluble dichroic dye and/or polyiodide ion in a boric acid warm water bath, A polarizing element obtained by uniaxially extending a polyvinyl alcohol film and then forming a polyene structure through a dehydration reaction, a polarizing element obtained by coating a solution containing a dichroic dye on a base film and aligning the dichroic dye, and a protective film A base material-integrated polarizing element or the like obtained by providing a polyvinyl alcohol layer thereon, and uniaxially extending together with a base film, and then impregnating with a dichroic dye. From the viewpoint of workability and optical properties, typically, a polarizing element obtained by uniaxially extending a PVA-based film and orienting a dichroic dye by adsorption can be preferably used. Examples of commercially available PVA-based films include VF-PS (75 μm in thickness) manufactured by Kuraray. In this case, in general, after aligning a dichroic dye by adsorption, it is uniaxially stretched to a thickness of 25 μm to 35 μm to obtain polarized light. element.

The dichroic dye is preferably an iodide ion or a dichroic dye, both of which can be used to obtain the polarizing element used in the present invention. Examples of dichroic dyes include azo-based dyes, anthraquinone-based dyes, and tetrazine-based dyes. From the viewpoint of hue design and durability against heat, it is preferable to blend 2 to 3 or more kinds of azo-based dyes. dye to use. In addition, in the case of using any of the dichroic dyes, the optical properties of the polarizing element preferably have high transmittance and high degree of polarization from the viewpoint of obtaining antireflection ability and excellent black screen properties in the mounted display device (also referred to as high dichroism), in more detail, the sensitivity-corrected single transmittance (Ys) is preferably 40% to 45%, and the sensitivity-corrected polarization (Py) is preferably 99% or more.

In one aspect of the present invention, it is preferable to have an achromatic hue, that is, it is preferable that the monomer transmittance (Ts) of the polarizing element is almost uniform in the entire visible light region (wavelength 400nm to 700nm, more preferably 380nm to 780nm). The absolute values of the a* and b* values in the L*a*b* colorimetric system are both 1 or less when measured with the polarizer alone. When the polarizers are overlapped and measured, 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 is also preferable as a specific aspect of the achromatic color. According to this, for example, the circularly polarizing plate provided with the broadband retardation plate of the present invention can not only suppress coloring of the reflected light from the display device in the entire visible light region, but also can suppress the coloring of the reflected light originating from the surface of the polarizing element. Shading can be suppressed over the entire visible light region.

Examples of azo dyes having dichroism include C.I.DirectYellow12, C.I.DirectYellow28, C.I.DirectYellow44, C.I.DirectYellow142, C.I.DirectOrange26, C.I.DirectOrange39, C.I.DirectOrange71, C.I.DirectOrange107, C.I.DirectRed2, C.I.DirectRed31, C.I.DirectRed79, DirectRed117, C.I.DirectRed247, C.I.DirectGreen80, C.I.DirectGreen59, C.I.DirectBlue71, C.I.DirectBlue78, C.I.DirectBlue168, C.I.DirectBlue202, C.I.DirectViolet9, C.I.DirectViolet51, C.I.DirectBrown106, C.I.DirectBrown223, etc. Other dyes that can be produced by a well-known method can be used, and examples of the well-known method include the method described in Japanese Patent Laid-Open No. 3-12606, the method described in Japanese Patent Laid-Open No. 59-145255, and the like. In addition, commercially available dyes include KayafectViolet P Liquid, Kayafect Yellow Y, Kayafect Orange G, Kayafect Blue KW and Kayafect Blue Liquid 400 (all manufactured by Nippon Kayaku Co., Ltd.). These azo dyes are used by blending two to three or more types so that their respective transmittances in the visible light region may be uniform. In the polarizing element of the present invention, in order to obtain an achromatic polarizing element having a high transmittance and a high degree of polarization, the methods disclosed in International Publication No. WO2017/146212, International Publication No. WO2019/117131, etc. can be preferably used. Azo dyes with improved dichroism by designing achromatic polarizers.

The polarizing element preferably includes a base material (also referred to as a support or a support film) for protecting the polarizing element. The base material may be arranged only on one side of the polarizing element, or may be arranged on both sides of the polarizing element so that the polarizing element may be sandwiched between two sheets of the same or different base materials. A configuration having a base material in a polarizing element is called a polarizing plate. In the case where the polarizing element includes a substrate to be described later, the substrate disposed between the polarizing element and the display device preferably has an in-plane retardation value (Re) and a thickness-direction retardation (Rth) of 0 or almost 0 (as numerical values) The extent of its influence can be disregarded, eg the range of -5nm to 5nm).

(substrate)

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. The substrate is not particularly limited as long as it has the intended mechanical strength, thermal stability, etc. and does not prevent the present invention from exhibiting the intended performance, and substrates well known in the art can be used. The thickness of the substrate can be appropriately designed, and is preferably 50 to 200 μm, more preferably 10 to 100 μm, and still more preferably 20 to 80 μm.

In addition, 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 are preferably 0 or almost 0. As a commercially available base material which has the said retardation value, a triacetyl cellulose resin film Z-TAC (made by Fuji Film Co., Ltd.), an acrylic resin film OXIS series (made by Okura Kogyo Co., Ltd.), etc. are mentioned, for example.

(adhesive and/or cement)

In the article of the present invention, a layer may be formed by arranging the next layer on a certain layer, or a plurality of layers may be bonded by an adhesive (pressure sensitive adhesive, also referred to as a pressure-sensitive adhesive) and/or an adhesive. layer to form a stack. It is not particularly limited as long as it can function as an adhesive or a bonding agent and does not prevent the present invention from exerting the intended performance, and adhesives or bonding agents well known in the art can be used. Typical examples of the binder include acrylic resins. The thickness can be appropriately designed, but is preferably 1 to 50 μm, and more preferably 5 to 25 μm from the viewpoints of interlayer adhesion and workability 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 photocurable resin, and a method by plasma bonding.

The values of the retardation value and the twist angle of the optically anisotropic layer of the present invention are values that can obtain optically favorable effects. These values are not particularly limited as long as the alignment characteristics and product processability of the actual liquid crystal compound are considered, and may include tolerances or margins.

(circular polarizer)

The circularly polarizing plate of the present invention is a broadband circularly polarizing plate, and includes a polarizing element and the retardation plate of the present invention. Specifically, it includes a polarizing element (or polarizing plate), a first optically anisotropic layer, and a third optical anisotropic layer and second optically anisotropic layer. In addition, in one aspect of each optical axis of the circular polarizer, the absorption axis of the polarizer is located in the direction of 0°, and the twist angle of the first optically anisotropic layer with respect to the absorption axis of the polarizer is substantially 26° ° direction, and from the twist angle of the first optically anisotropic layer, the twist angle of the second optically anisotropic layer is substantially the direction of 78° (that is, 104° with respect to the absorption axis of the aforementioned polarizer direction).

The production method of the circularly polarizing plate of the present invention is not particularly limited. For example, the films or sheets of the above-mentioned layers may be laminated one by one, or the above-mentioned layers formed in a roll shape may be continuously laminated by roll-to-roll. In particular, the circular polarizing plate of the present invention does not need to cut the retardation plate according to a predetermined angle of the optical axis, so that the latter can be easily laminated on a roll-to-roll basis. Therefore, productivity can be improved, for example, compared to the conventional method for producing a broadband circularly polarizing plate in which a uniaxially stretched film such as a COP-based film is laminated.

(Manufacturing method of circularly polarizing plate)

The manufacturing method of the retardation plate and the circularly polarizing plate of this invention can be demonstrated with the following 1st - 2nd aspect examples, but it is not limited to these. In addition, each optically anisotropic layer is formed on the base material from which the liquid crystal layer and the base material can be peeled off after curing, and each base material may be removed to form a circularly polarizing plate in the step of successive lamination described later.

(Example of the first aspect)

As a first step, a liquid crystal compound containing a polymerizable nematic liquid crystal phase, a chiral agent, a photopolymerization initiator, and a A coating composition of a solvent and a diluting solvent, and then the solvent is removed through a drying step, and the coating film is cured by irradiating light to obtain an alignment axis in the 0° direction, a twist angle of 26°, and the retardation value (Re@＠ 550 nm) is the first optically anisotropic layer of 275 nm.

As the second step, a coating composition comprising a composition of a liquid crystal compound exhibiting a polymerizable nematic liquid crystal phase, a photopolymerization initiator, and a diluting solvent is applied on a substrate, followed by a drying step to obtain a The solvent is removed, and the coating film is cured by irradiating light, thereby obtaining a third optically anisotropic layer aligned in a direction perpendicular to the substrate.

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 rubbed surface of the substrate that has been rubbed in the direction of 26° with respect to the conveying direction. , then a drying step is obtained to remove the solvent, and light is applied to harden the coating film, thereby obtaining a second optical element with an alignment axis in the direction of 26°, a twist angle of 78°, and the retardation value (Re@550nm) of 137.5nm. Anisotropic layer.

As the 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 arranged so as to have the optical axis relationship shown in FIG. 3 . The circularly polarizing plate of this invention is obtained by laminating|stacking one by one.

(Example of the second aspect)

In the second step, a coating composition comprising a composition of a liquid crystal compound exhibiting a polymerizable nematic liquid crystal phase, a photopolymerization initiator, and a diluting solvent is applied to the first step obtained in the first step. The liquid crystal surface of an optically anisotropic layer is then dried to remove the solvent and illuminated to harden the coating film, thereby obtaining a third optically anisotropic layer aligned in a direction perpendicular to the liquid crystal surface. Then, the polarizing element (or polarizing plate), the first optically anisotropic layer on which the third optically anisotropic layer is stacked, and the second optically anisotropic layer are sequentially laminated so as to have the optical axis relationship shown in FIG. 3 . It is the same as that of 1st example except that the circularly polarizing plate of this invention was obtained by lamination|stacking.

(display device)

The circularly polarizing plate of the present invention is preferably applied to the viewing side of various display devices such as liquid crystal display devices (LCD) and organic electroluminescence (EL) display devices (organic light emitting diode (OLED) display devices). In addition, the display device can also be configured to include a touch screen, an anti-glare layer or an anti-reflection layer, a light-transmitting cover plate (also referred to as a front panel) and the like according to the design. In addition, the aforementioned light-transmitting cover plate may have a flat shape or a curved shape. The manufacturing method of the display device of the present invention is not particularly limited, and can be manufactured by a well-known method.

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

In addition, in general, since an organic EL display device includes a metal electrode in the display panel portion, an OLED (organic EL display device) itself has a higher reflectance than a liquid crystal panel. This is the reason why displayability is impaired due to the reflection of the external light from the electrodes in the case of use in an environment with a lot of external light, such as outdoors during the day. Therefore, in order to suppress reflection of external light, a circular polarizer is generally attached to the viewing side of the organic EL display device. Therefore, the display characteristics of the organic EL display device also depend on the optical characteristics of the circularly polarizing plate. The circularly polarizing plate of the present invention has a wider viewing angle characteristic than the conventional circularly polarizing plate, so it can be ideally used for an organic EL display device requiring a wide viewing angle.

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

[Example]

The present invention will be specifically described below by means of examples, but the present invention is not limited by these examples.

Assuming that a circular polarizer is attached to an ideal reflector, the following azimuth and inclination angles (polar angles) are used to calculate the black luminance (unit-standardized value) using liquid crystal simulation software LCD master (manufactured by SYMTEC). The configuration and calculation conditions of the circularly polarizing plate are as follows. Table 1 shows a list of the following calculation conditions and the arrangement relationship of the optically anisotropic layers. The in-plane retardation value (Re) and the thickness-direction retardation value (Rth) represent values at a wavelength of 550 nm. In addition, the optically anisotropic layers arranged in Table 1 are shown in the columns of the first layer, the second layer, and the third layer in order from the incident light side.

The structure of the circular polarizer:

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

Example 2: (in order from the incident light side) 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 optically anisotropic layer, third optically anisotropic layer 3, second optically anisotropic layer, reflecting plate

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

Example 5: (in order 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: (in order from incident light side) polarizing element, first optically anisotropic layer, second optically anisotropic layer, third optically anisotropic layer 1, reflecting plate

Comparative Example 2: (in order 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: (in order from the incident light side) polarizing element, first optically anisotropic layer, second optically anisotropic layer, reflecting plate

Comparative Example 4: (in order from the incident light side) polarizing element, general half-wave plate 1, third optically anisotropic layer 6, general quarter-wave plate 1, reflecting plate

Comparative Example 5: (in order from the incident light side) polarizing element, general half-wave plate 2, third optically anisotropic layer 7, general quarter-wave plate 2, reflecting plate

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 optically anisotropic layer 8, reflecting plate

First Optically Anisotropic Layer:

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

The resulting phase difference = 1/2λ

Δn1·d1=275nm

Pre-twist angle = 0°

Torsion 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=137.5nm

Pre-twist angle = -26°

Torsion angle = -78°

Thickness of liquid crystal layer = 1.068 μm

The third optically anisotropic layer:

Liquid crystal layer: polymerizable vertical alignment liquid crystal compound (manufactured by Merck)

n _x = 1.5283

n _y = 1.5283

n _z = 1.6725

Thickness of liquid crystal layer = 0.60 μm to 1.45 μm

Rth: described in the following 1 to 8, respectively

The third optically anisotropic layer 1:

Rth=-120nm

The third optically anisotropic layer 2:

Rth=-115nm

The third optically anisotropic layer 3:

Rth=-130nm

The third optically anisotropic layer 4:

Rth=-80nm

The third optically anisotropic layer 5:

Rth=-150nm

The 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 spectral data with a sensitivity-corrected single-body transmittance Ys=41.5% and a sensitivity-corrected polarization degree Py=99.99%, without a support layer)

Reflective plate:

Material: ideal reflector

General 1/2 wavelength plate (HWP)1:

Material: Cyclic Olefin Polymer (COP)

Nz coefficient = 1.0

General 1/4 wavelength plate (QWP)1:

Material: Cyclic Olefin Polymer (COP)

Nz coefficient = 1.0

General 1/2 wavelength plate (HWP)2:

Material: Cyclic Olefin Polymer (COP)

Nz coefficient = 1.5

General 1/4 wavelength plate (QWP)2:

Material: Cyclic Olefin Polymer (COP)

Nz coefficient = 1.5

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

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

Azimuth Φ=0° to 360° (each in 5° units)

In the above-mentioned test conditions, the nz coefficient is one of the indexes representing the magnitude relationship of the refractive index components _nx , _ny , and _nz , and is a value represented by the following formula (2).

[Number 2]

Among the above calculation conditions, ZLI-4792 (manufactured by Merck) and cycloolefin polymer (COP) were used as standard data attached to LCDmaster. In addition, n _x , _ny and _nz of the third optically anisotropic layer using a polymerizable vertically aligned liquid crystal compound (manufactured by Merck Corporation) were obtained by forming a film of the liquid crystal compound into a film by Abbe refraction. A meter (Abbe's refractometer, manufactured by DR-M2 ATAGO Corporation) was used for measurement.

[Table 1]

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) was shown to be 0.1 or less, and it was confirmed that the light incident from the polarizing element passed through the circular polarizing plate. The reflection from the reflector is sufficiently suppressed. Evaluation was performed based on the black luminance value at this polar angle θ=0°. In addition, this black luminance value is 0 or almost 0, which means that the circularly polarizing plate functions ideally by suppressing the reflection of incident light.

Using the above calculation results, the center is the polar angle θ=0° (head-on), and the azimuth angle Φ=0° corresponding to the range of the polar angle θ=0° to 80° is represented by a contour diagram (contourdiagram) Distribution of black luminance to 360°. At this time, the display black luminance is fixed in the range from the minimum value of 0 to the maximum value of 10. 4 to 6 show Examples 1 to 3, respectively, and FIGS. 7 to 12 show contour plots 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 outer circle end of the diagram) are 1.6 to 1.8, which is less than The value of each comparative example shows that it shows a wider viewing angle. In addition, in the case of Comparative Example 5, the maximum luminance value exceeded 10.

In addition, in order to quantitatively compare the effect of improving the black luminance when viewed from an oblique direction, the black luminance value was extracted under the conditions of the polar angle θ and the azimuth angle Φ described below from the above calculation results. The results of plotting the black luminance value against the azimuth angle Φ at this time are shown in FIGS. 13 to 21 .

Pole angle θ=θ=40°, 50°, 60°

Azimuth Φ=0° to 360° (in units of 45°)

For Examples 1 to 3, the results of plotting under the aforementioned conditions are shown in FIGS. 13 to 15 . In detail, in Examples 1 to 3 in which the Rth of the third optically anisotropic layer was in the range of -130 nm to -115 nm, there was little difference in the black luminance values at the polar angles θ=40°, 50°, and 60°, respectively , the average value (B) of the black luminance at the azimuth angle Φ=0° to 360° (in units of 45°) in the aforementioned respective polar angles is 0.26 to 0.68. From this, it can be estimated that the black brightness will increase by 2.7 times to 7.6 times when viewed obliquely from the polar angles θ=40°, 50° and 60° relative to the polar angle θ=0° (A). . In addition, in the case of Examples 4 and 5 in which the Rth of the third optically anisotropic layer was in the range of -80 nm and -150 nm, the increase in black luminance was 3.2 times to 10.0 times when calculated in the same manner as above. From this, it can be seen that the range of the Rth of the third optically anisotropic layer is preferably -130 nm to -115 nm, whereby the black luminance when viewed from an oblique direction can be further reduced.

For Comparative Examples 1 to 3, graphs were made under the aforementioned conditions, and the results are shown in FIGS. 16 to 18 . The Rth of the third optically anisotropic layer is fixed at -120nm and the third optically anisotropic layer is arranged after the second optically anisotropic layer or before the first optically anisotropic layer or without the third optically anisotropic layer In Comparative Examples 1 to 3 of the optically anisotropic layer, the black luminance values of the respective polar angles θ=40°, 50°, and 60° were larger than those of Examples 1 to 5. value. In addition, the average value (B) of the black luminance of the azimuth angle in each polar angle was obtained in the same manner as described above, and it was 0.59 to 1.72 in Comparative Examples 1 to 2, and 1.27 to 3.88 in Comparative Example 3. From this, it can be estimated that with respect to the polar angle θ=0° (A), the black luminance when viewed obliquely from the polar angle θ=40°, 50°, and 60°, in Comparative Examples 1 to 2 In the comparative example 3, it increased from 6.3 times to 18.2 times, and in Comparative Example 3, it increased from 13.4 times to 41.1 times. From these results, it is shown that the constitutions of Examples 1 to 5 have improved viewing angle characteristics compared with the conventional Comparative Examples 1 to 3.

In Comparative Examples 4 to 6, the third optically anisotropic layer having the following Rth value was used. : -174 nm, Comparative Example 5: -209 nm, and Comparative Example 6: -133 nm). In the same manner as in Examples 1 to 5, the black luminance values of the polar angles θ=40°, 50°, and 60° were obtained and plotted, and the results are shown in FIGS. 19 to 21 . In either condition, the black luminance value showed a large value not only with respect to Examples 1 to 5, but also with respect to Comparative Examples 1 to 3, and Comparative Examples 4 to 6 using conventional COP-based films In the configuration of , even if the third optically anisotropic layer is arranged, widening of the angle cannot be achieved.

[Table 2]

From the above results, in the configuration of the circularly polarizing plate of the present invention, the widening of the bandwidth of the circularly polarizing plate can be achieved not only by the presence or absence of the third optically anisotropic layer and the optimization of its Rth value, but also by By selecting the arrangement of the third optically anisotropic layer with respect to the first optically anisotropic layer and the second optically anisotropic layer, the bandwidth can be further broadened than that of the conventional circularly polarizing plate. Therefore, according to the present invention, for example, in a black screen of an organic EL display device or the like, a black screen with little light leakage when viewed from an oblique direction can be obtained.

In addition, in the retardation plate of the present invention, in order to further reduce the black luminance at the polar angle of 0°, the first and second optical isotropic directions having the most preferable wavelength dispersion characteristics (meaning the wavelength dependence of retardation) may be provided. heterosexual layer. Similarly, in the third optically anisotropic layer, by making this wavelength dispersion characteristic negatively dispersed (inverse wavelength dispersion), the black luminance in a black screen when viewed from an oblique direction can be further reduced.

[Industrial Availability]

The present application can provide a retardation plate that reduces coloration or reflectivity in a black screen when viewed from an oblique direction, a circular polarizing plate having the retardation plate, and a liquid crystal display device and an organic EL display device including the circular polarizing plate. For example, the organic EL display device can provide a wider range of viewing angles, so it can be ideally used for the installation of the display device and the vehicle with a fixed viewing position. Moreover, since the manufacturing method which can manufacture a circular polarizing plate only by roll-to-roll bonding can be provided, it can also respond to manufacture of the circular polarizing plate for large-scale display devices.

Description of reference numerals

101 The retardation plate of the present invention

102 The first optically anisotropic layer

103 Second optically anisotropic layer

104 The third optically anisotropic layer

105 Circular polarizing plate of the present invention

106 Polarizing element (polarizing plate)

107 Twisted Nematic Liquid Crystal

108 Substrate 1 (alignment film)

109 Substrate 2 (alignment film)

201 Absorption axis direction (0°)

202 Friction direction (alignment direction) (0°)

203 Twist angle direction (26°)

204 Friction direction (alignment direction) (26°)

205 Twist angle direction (104°)

206 means parallel to 201.

Claims (7)

1. A phase difference plate, comprising: The first optically anisotropic layer is an optically anisotropic layer in which the rod-like liquid crystal compound is aligned with the thickness direction as the helical axis, and has an in-plane retardation value (Re) of substantially 1/2 wavelength; The second optically anisotropic layer is an optically anisotropic layer in which the rod-like liquid crystal compound is aligned with the thickness direction as the helical axis, and has an in-plane retardation value (Re) of substantially 1/4 wavelength; wherein, A third optically anisotropic layer satisfying the following formula (1) is provided between the first and second optically anisotropic layers, n _x ≒n _y <n _z (1) In the formula, n _x and _ny represent the refractive index in the direction perpendicular to the plate plane, and n _z represent the refractive index in the direction perpendicular to the plate plane. 2 . The retardation plate according to claim 1 , wherein 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 The angle is substantially 78° or substantially -78° from the twist angle of the first optically anisotropic layer. 3. The retardation plate according to claim 1 or 2, wherein the third optically anisotropic layer is a layer having a vertical alignment type liquid crystal compound, and the thickness direction retardation value (Rth) is -150 to -80 nm . 4 . A circularly polarizing plate comprising a polarizing element and the retardation plate according to claim 1 . 5 . The circularly polarizing plate according to claim 4 , wherein the polarizing element comprises a dichroic azo dye whose hue is achromatic. 6 . 6. An organic EL display device comprising the circularly polarizing plate according to claim 4 or 5. 7 . A liquid crystal display device comprising the circularly polarizing plate according to claim 4 .

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