TWI762615B - Retardation film, circular polarizing plate or elliptical polarizing plate, display panel, liquid crystal display panel, organic EL display panel, display device, liquid crystal display device, and organic EL display device - Google Patents

Abstract

The object of the present invention is to provide a retardation film which has good contrast in a wide range of viewing angle and can suppress the change of color with the viewing angle over a wide frequency band. Furthermore, the object is to provide a circularly polarizing plate or an elliptically polarizing plate, a display panel, a liquid crystal display panel, an organic EL display panel, a display device, a liquid crystal display device, and an organic EL display device using the retardation film.

The retardation film of the present invention has: a positive A plate, which has the characteristics of positive A type, when the front retardation at a wavelength of 450 nm is set to Re _A450 , and the front retardation at a wavelength of 550 nm is set to Re _A550 , Re A550 _A450 /Re _A550 is set as _ΔNA ; and positive C plate, which has the characteristics of positive C type, when the thickness direction retardation when the wavelength is 450nm is set as Rth _C450 , the thickness direction retardation when the wavelength is 550nm is set as Rth At _C550 , Rth _C450 /Rth _C550 is set to ΔN _C ; one of ΔN _A and ΔN _C is 1.0 or less, the other is less than 1.0, and |ΔN _A -ΔN _C |≦0.15.

Description

Retardation film, circular polarizing plate or elliptical polarizing plate, display panel, liquid crystal display panel, organic EL display panel, display device, liquid crystal display device, and organic EL display device

The present invention relates to a retardation film, a circularly polarizing plate or an elliptically polarizing plate, a display panel, a liquid crystal display panel, an organic EL display panel, a display device, a liquid crystal display device, and an organic EL display device including the retardation film.

As an optical film applied to an image display device or the like, there is a retardation film which imparts a desired retardation to incident light by a retardation layer. For example, in an organic electroluminescence (organic EL) display device, a λ/4 retardation film is used as a circular polarizer in combination with a linear polarizer to function as an anti-reflection film for external light. Moreover, in liquid crystal display devices such as IPS mode, in order to improve the contrast with respect to the field of view from an oblique direction, a retardation film combining a positive A plate and a positive C plate is used as a part of the optical compensation film.

It is well known that such retardation films do not have the same effect on all wavelengths.

For example, taking the external light reflective film of an organic EL display device as an example, the external light reflective film formed by laminating a λ/4 retardation film and a polarizing element can only make the light with a wavelength of 550 nm into circularly polarized light, but the wavelength is longer and the wavelength is shorter. Its short light becomes elliptically polarized light, and it is difficult to exert complete anti-reflection function of external light.

Also, taking a retardation film used as an optical compensation film in a liquid crystal display device as an example, by using a λ/4 retardation film, the color tone in the frontal direction can be compensated, but it is difficult to adequately compensate for the oblique viewing angle direction. Hue compensation.

For this problem, it has been proposed to use a retardation film having reverse wavelength dispersion properties as a retardation film that functions in a wide wavelength region (broadband) (for example, see Patent Document 1 and Patent Document 2). Here, the reverse wavelength dispersion characteristic refers to the wavelength dispersion characteristic in which the retardation under transmitted light becomes smaller as the wavelength is shorter, and more specifically, the front retardation (Re ₄₅₀ ) at the wavelength of 450 nm and the wavelength at 550 nm The relation of the front retardation (Re ₅₅₀ ) is Re ₄₅₀ <Re ₅₅₀ , and wavelength dispersion characteristics of Re ₄₅₀ /Re ₅₅₀ <1. On the other hand, the wavelength dispersion characteristics in which the retardation in transmitted light is larger on the shorter wavelength side, more specifically, the front retardation (Re ₄₅₀ ) at a wavelength of 450 nm and the front retardation (Re ₅₅₀ ) at a wavelength of 550 nm. ) in the relationship of Re ₄₅₀ >Re ₅₅₀ and the wavelength dispersion characteristics of Re ₄₅₀ /Re ₅₅₀ >1 are called positive wavelength dispersion characteristics.

In addition to wavelength dispersion characteristics, there are also proposed retardation layers (positive A plates) with positive A characteristics, retardation layers with negative A characteristics (negative A plates), and positive C A method of improving various optical properties such as viewing angle characteristics, color tone, etc. by using a retardation layer (positive C plate) with the characteristic of negative C and a retardation layer (negative C plate) with the characteristic of negative C.

Here, the characteristics of positive A refer to those having the following characteristics: when the refractive index in the X-axis direction of the layer is set as Nx, the refractive index in the Y-axis direction along the direction of the layer, which is orthogonal to the X-axis, is set as Nx. For Ny, when the refractive index in the layer thickness direction is Nz, there is a relationship of Nx>Ny≒Nz, and the optical axis is in the Nx direction.

The characteristic of negative A refers to those having the following characteristics: there is a relationship of Nz≒Nx>Ny, and the optical axis is in the Ny direction.

The characteristics of positive C refer to those having the following characteristics: there is a relationship of Nz>Nx≒Ny, and the optical axis is in the Nz direction.

In addition, the characteristic of negative C refers to those having the following characteristics: there is a relationship of Nx≒Ny>Nz, and the optical axis is in the Nz direction.

Furthermore, as described in Patent Document 3, there is known an IPS display device in which one or more negative biaxial retardation films (nx>ny>nz are formed between the polarizing plate and the liquid crystal cell to compensate the viewing angle) ) and one or more +C plates (nx=ny<nz) are arranged so that the negative biaxial retardation film is adjacent to the polarizing plate.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2016-53709

Patent Document 2: Japanese Patent Laid-Open No. 2015-14712

Patent Document 3: Japanese Patent Publication No. 2006-520008

However, even if the previously proposed A plate and C plate are simply used in combination, the viewing angle with good contrast is often narrowed, or the color of the film changes depending on the viewing angle, and improvement is expected.

In addition, in the invention described in Patent Document 3, although the viewing angle contrast is improved, it was found that there is a problem that chromatic aberration occurs at an oblique angle.

In view of the above-mentioned problems, the present invention has an object to provide a retardation film which has good contrast over a wide frequency band and a wide viewing angle range and can suppress the change of color with the viewing angle. Another subject is to provide a circularly polarizing plate or an elliptically polarizing plate, a display panel, a liquid crystal display panel, an organic EL display panel, a display device, a liquid crystal display device, and an organic EL display device using the retardation film.

The inventors of the present invention have repeatedly conducted intensive research on the above-mentioned subject, and as a result, obtained the following insight: not only the wavelength dispersion characteristics of the positive A plate and the positive C plate, but also the relationship between the wavelength dispersion characteristics of the two plates also affects the optical performance, thereby completing the present invention. invention.

The present invention relates to the following [1] to [13].

[1] A retardation film comprising: a positive A plate having the characteristics of a positive A type, when the front retardation when the wavelength is 450 nm is Re _A450 , and the front retardation when the wavelength is 550 nm is Re _A550 , set Re _A450 /Re _A550 as _ΔNA ; and positive C plate, which has the characteristics of positive C type, when the thickness direction retardation when the wavelength is 450nm is set as Rth _C450 , and the thickness direction retardation when the wavelength is 550nm When Rth _C550 is set, Rth _C450 /Rth _C550 is set as ΔN _C ; and one of the above ΔN _A and the above ΔN _C is 1.0 or less, the other is less than 1.0, and |ΔN _A -ΔN _C |≦0.15.

[2] The retardation film according to [1], wherein at least one of the ΔN _A and the above ΔN _C is less than 0.9.

[3] The retardation film according to [1], wherein neither of the above ΔN _A and the above ΔN _C is less than 0.9.

[4] The retardation film according to any one of [1] to [3], wherein any one of the above ΔN _A and the above ΔN _C is 0.75 or more.

[5] The retardation film according to any one of [1] to [4], wherein at least one of the positive A plate and the positive C plate contains a polymerizable rod-shaped liquid crystal material.

[6] A circularly polarizing plate or an elliptically polarizing plate having the retardation film and polarizing element according to any one of [1] to [5].

[7] A display panel including the retardation film according to any one of [1] to [5].

[8] A liquid crystal display panel comprising two polarizing elements, and the retardation film and liquid crystal layer according to any one of [1] to [5] disposed between the two polarizing elements, wherein the liquid crystal The display panel has an optical compensation function.

[9] An organic EL display panel, comprising an organic EL display element; and an anti-reflection film for external light, sequentially comprising any of [1] to [5] disposed on the light-emitting side of the organic EL display element. The retardation film and polarizing element mentioned above.

[10] A display device including the display panel according to any one of [7] to [9].

[11] A liquid crystal display device including the liquid crystal display panel described in [8].

[12] The liquid crystal display device according to [11], wherein the liquid crystal display device is an IPS mode liquid crystal display device.

[13] An organic EL display device including the organic EL display panel described in [9].

According to the present invention, it is possible to provide a retardation film with good contrast and optical compensation over a wide frequency band and a wide viewing angle range, and can also be applied to circular polarizing plates or elliptical polarizing plates, display panels, Liquid crystal display panel, organic EL display panel, display device, liquid crystal display device, and organic EL display device.

10‧‧‧Retardation film

11‧‧‧Substrate

12‧‧‧Alignment film

13‧‧‧Positive C plate

14‧‧‧Positive A board

20‧‧‧Liquid crystal display device

22‧‧‧Backlight

23‧‧‧LCD panel

24‧‧‧Linear polarizer

25‧‧‧Liquid Crystal Cell

26‧‧‧Optical functional laminate

27‧‧‧Polarizing element

28‧‧‧Substrate

30‧‧‧Organic EL Display Panel

33‧‧‧Organic EL display element

36‧‧‧Optical functional laminate

37‧‧‧Polarizing element

38‧‧‧Substrate

FIG. 1 is a diagram showing an example of the layer structure of the retardation film 10 .

FIG. 2 is a diagram for explaining the layer structure of the liquid crystal display device 20 to which the retardation film 10 is applied.

FIG. 3 is a diagram for explaining the layer structure of the organic EL display device 30 to which the retardation film 10 is applied.

FIG. 4 is a diagram for explaining the evaluation of the contrast in the Example.

FIG. 5 is a diagram for explaining the evaluation method of the hue in the examples.

FIG. 6 is a diagram for explaining the evaluation of the hue in the examples.

Hereinafter, the present invention will be described in detail with specific examples. However, the present invention is not limited to the following forms, and various modifications can be made within the scope of not changing the gist of the present invention.

[retardation film]

The retardation film of the present invention has a positive A plate and a positive C plate, the positive A plate has the characteristics of the positive A type, and the positive C plate has the characteristics of the positive C type. In addition, in the positive A plate, when the front retardation when the wavelength is 450 nm is Re _A450 and the front retardation when the wavelength is 550 nm is Re _A550 , Re _A450 /Re _A550 is _ΔNA , and the positive In plate C, when the retardation in the thickness direction at a wavelength of 450 nm is Rth _C450 , and the retardation in the thickness direction at a wavelength of 550 nm is Rth _C550 , Rthc ₄₅₀ /Rth _C550 is denoted as ΔN _C , in this case, the above One of ΔN _A and the aforementioned ΔN _C is 1.0 or less, the other is less than 1.0, and |ΔN _A -ΔN _C |≦0.15.

<Substrate>

1 : is a figure explaining the layer structure of the retardation film 10 of one form of this invention. In this aspect, various optical characteristics can be improved by disposing the retardation film 10 together with various other optical films in a liquid crystal display panel and an organic EL display panel, for example, in an image display device. Examples of the optical properties include anti-reflection of external light, improvement of viewing angle properties, optical compensation related to reduction of oblique light leakage, correction of color tone, and the like.

As can be seen from FIG. 1 , the retardation film 10 of the present embodiment includes a positive C plate 13 and a positive A plate 14 . In FIG. 1 , the retardation film 10 is disposed on the alignment film 12 , and the alignment film 12 is disposed on the substrate 11 .

As the base material 11, a glass base material, a metal foil, a resin base material, etc. are mentioned. Among them, the substrate preferably has transparency, and can be appropriately selected from previously known transparent substrates. In addition, it is not limited to the following examples.

As the transparent substrate, in addition to glass substrates, transparent resin substrates formed using the following resins include: acetyl cellulose-based resins such as triacetyl cellulose; polyethylene terephthalate, polyethylene naphthalate Polyester resins such as diesters, polybutylene terephthalate, and polylactic acid; olefin resins such as polypropylene, polyethylene, and polymethylpentene; (meth)acrylic resins; polyurethane resins; polyethers Polycarbonate resins; Polycarbonate resins; Polyether resins; Polyetherketone resins; imine resin; polyamide; polyimide imide; polyvinyl chloride resin; polyvinylidene chloride resin; polystyrene resin; polyvinyl alcohol resin; polyphenylene sulfide resin; poly Acrylic resin, etc.

The transmittance of the substrate 11 in the visible light region is preferably 80% or more, more preferably 90% or more. Here, the transmittance of the transparent substrate can be measured according to JIS K7361-1:1997 (Test method for total light transmittance of plastics-transparent materials).

Moreover, the haze of the base material 11 is preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less. When the haze of the base material is within the above-mentioned range, the transparency is more excellent, which is preferable. The haze of the base material can be measured according to JIS K 7136:2000 (Method for obtaining the haze of plastics-transparent materials).

Furthermore, when the retardation film is transferred and used, since the base material is not incorporated into the final product as a member, the transmittance and haze of the base material are not particularly limited.

The thickness of the base material 11 is not particularly limited as long as it is within a range that can provide necessary support depending on the application of the retardation film, etc., but is usually 10 μm or more, preferably 25 μm or more, more preferably 30 μm or more, and usually It is 200 micrometers or less, Preferably it is 125 micrometers or less, More preferably, it is 100 micrometers or less. Furthermore, in recent years, the expectation for the thinning of the display device itself is increasing. In this case, the thinner the film, the better. The lower limit is preferably 15 μm or more, more preferably 20 μm or more, and the upper limit is preferably 80 μm or less. It is more preferable that it is 60 micrometers or less, and it is still more preferable that it is 40 micrometers or less. If the thickness is larger than the above-mentioned range, for example, when a long retardation film is formed and a single retardation film is formed by cutting processing, machining chips may increase or the cutting blade may wear faster. Moreover, if it is smaller than the said range, it may become difficult to provide necessary support.

<Alignment film>

In FIG. 1 , the alignment film 12 is a layer for aligning the liquid crystal components contained in the positive C plate 13 in a fixed direction, and is a vertical alignment film. However, the alignment film can be appropriately applied according to the properties of the liquid crystal components of the positive C plate. For example, when the liquid crystal component of the positive C plate itself has vertical alignment, the alignment film may not necessarily have the vertical alignment restraining force. In addition, when the liquid crystal component itself has sufficient self-alignment, it is not always necessary to form an alignment film.

In this form, the vertical alignment film is an alignment film with an alignment restraining force in the vertical direction, and various vertical alignment films known to be used in the production of retardation films for C plates, and various vertical alignment films applied to VA liquid crystal display devices, etc. can be applied. For the alignment film, for example, a polyimide alignment film, an alignment film using a LB film (Langmuir-Blodgett film), and the like can be applied.

Specifically, examples of the constituent materials of the alignment film include lecithin, stearic acid, silane-based surfactants, titanate-based surfactants, pyridinium salt-based polymer surfactants, and chromium zirconium monocarboxylate. compound etc. Moreover, a vertical alignment film can also be formed by the composition for silane coupling-type vertical alignment films, the composition for polyimide-type vertical alignment films, or the like. As a silane-coupling vertical alignment film, the alignment formed by a composition for a silane-coupling vertical alignment film containing a silicon compound having a long-chain alkyl group and an alkoxy group such as n-octadecyltriethoxysilane can be exemplified The film, as a polyimide-based vertical alignment film, includes a soluble polyimide having a long-chain alkyl group or an alicyclic structure in the side chain, a polymer containing a long-chain alkyl group or an alicyclic structure in the side chain. A composition for a polyimide-based vertical alignment film such as polyamic acid. In addition, as the composition for vertical alignment film, polyimide-based vertical alignment film composition "JALS-2021" or "JALS-204" manufactured by JSR Co., Ltd., "JALS-204" manufactured by Nissan Chemical Industry Co., Ltd. can be applied. Commercially available products such as RN-1517", "SE-1211", and "EXPOA-018".

The formation method of the alignment film 12 is not particularly limited. For example, the alignment film can be formed by applying the composition for forming an alignment film on the substrate 11 and imparting an alignment restraining force as necessary. The method of imparting the alignment restricting force to the alignment film can be a conventionally known method.

More specifically, a method of applying the composition for forming an alignment film and drying, a method of applying the composition for forming an alignment film and curing it with ultraviolet rays, etc., and a method of applying the composition for forming an alignment film and drying it can be exemplified. A method of curing it with ultraviolet rays, etc.

The thickness of the alignment film 12 can be appropriately set as long as the liquid crystal components in the positive C plate 13 can be aligned in a fixed direction. The thickness of the alignment film is usually 1 nm or more, preferably 30 nm or more, more preferably 60 nm, more preferably 100 nm or more, and usually 10 μm or less, preferably 5 μm or less, more preferably 1000 nm or less, and more preferably 500nm or less.

<Positive C plate>

The retardation film of the present invention has a positive C plate, and the positive C plate has the characteristics of a positive C type. The positive C plate has the following characteristics: when the refractive index along the X-axis direction of the layer is set as Nx, the refractive index in the Y-axis direction along the direction of the layer, which is orthogonal to the X-axis, is set as Ny, and the layer thickness direction is set as Ny. When the refractive index is set to Nz, there is a relationship of Nz>Nx≒Ny, and the optical axis becomes the Nz direction.

In the present invention, the in-plane retardation value (Re) of the positive C plate is preferably small, preferably 20 nm or less, more preferably 10 nm or less, more preferably 5 nm or less, and still more preferably 1 nm or less.

The positive C plate 13 is a layer that has the above-described positive C properties and has specific wavelength dispersion properties to exhibit an optical function. Furthermore, the positive C plate 13 may be composed of a polymerizable liquid crystal composition containing a liquid crystal material (hereinafter, the "liquid crystal material" is also referred to as a "liquid crystal compound") for producing retardation layers of various optical films. ”), and the liquid crystal compound has a specific wavelength dispersion characteristic. That is, in the positive C plate 13, the liquid crystal compound is homeotropically aligned. In addition, the positive C plate is not limited to this, and may be formed without using a liquid crystal material.

Specifically, the positive C plate 13 has the characteristics of the positive C type. When the retardation in the thickness direction at a wavelength of 450 nm is set to Rth _C450 and the retardation in the thickness direction at a wavelength of 550 nm is set as Rth _C550 , Rthe ₄₅₀ /Rth The ΔN _C obtained by _C550 is less than 1.0 or less than 1.0. More specifically, when ΔN _A described below is 1.0 or less, ΔN _C is less than 1.0, and when ΔN _A is less than 1.0, ΔN _C is 1.0 or less. More preferably, ΔN _C is less than 0.9. In addition, the relationship between this ΔN _C and the ΔN A of the positive _{A plate 14 described below is |ΔN A -ΔN C} |≦0.15.

In the present invention, a retardation film having a positive A plate and a positive C plate is used from the viewpoint of obtaining a good contrast in a wide viewing angle range. However, each of the positive A plate and the positive C plate has wavelength dispersion of retardation. The inventors of the present invention considered that in the retardation film formed by laminating the positive A plate and the positive C plate, the wavelength dispersion characteristics of each are related to the characteristics of the overall retardation film, and as a result, they found that by adding When |ΔN _A -ΔN _C | was set to 0.15 or less, the change in color with the viewing angle (hereinafter, also referred to as "color change") was suppressed.

From the viewpoint of suppressing color variation, the above |ΔN _A -ΔN _C | is 0.15 or less, preferably 0.12 or less, more preferably 0.10 or less, still more preferably 0.08 or less, still more preferably 0.06 or less, and further More preferably, it is 0.04 or less.

From the viewpoint of obtaining a good contrast in a wide viewing angle range and suppressing the change in color with the viewing angle (hereinafter, also referred to as "color variation"), ΔN _C is more preferably 0.87 or less , and more preferably 0.85 or less. Moreover, from the viewpoint of suppressing color variation, ΔN _C is preferably 0.70 or more, more preferably 0.75 or more, still more preferably 0.78 or more, and still more preferably 0.80 or more.

The thickness of the positive C plate 13 is not particularly limited, but when a positive C plate is produced from a liquid crystal material, it is preferably 0.3 μm or more and 3.0 μm or less from the viewpoint of obtaining a desired retardation.

In addition, when a material other than a liquid crystal compound is used, for example, a thermoplastic resin composition containing a styrene-based resin and an acrylic-based resin is produced (refer to Japanese Patent Laid-Open No. 2010-185937, etc.), a desired retardation can be obtained. From a viewpoint, 50 micrometers or more and 150 micrometers or less are preferable.

Furthermore, when the retardation film of the present invention is used in a flexible display device, the retardation film as a whole is preferably thinner, and a positive C plate is preferably made of a liquid crystal material.

The positive C plate is preferably produced from a polymerizable liquid crystal composition containing a liquid crystal material, and the polymerizable liquid crystal composition preferably contains a liquid crystal material that exhibits liquid crystallinity and has a polymerizable functional group in the molecule. As the liquid crystal material, a discotic liquid crystal material and a rod-shaped liquid crystal material are exemplified. In the present invention, the liquid crystal material is preferably a rod-shaped liquid crystal material. The reverse dispersibility is expressed by the difference between the dispersibility of the main chain and the side chain, and thus it is difficult for the discotic liquid crystal material to express the reverse dispersibility. On the other hand, if it is a rod-shaped liquid crystal material, the dispersibility can be controlled by changing a main chain and a side chain, and it is also preferable at the point of easy adjustment of wavelength dispersibility. In addition, in the case of a discotic liquid crystal material, the obtained plate will have the characteristics of Nx≒Ny>Nz, so it is difficult to obtain a positive C plate.

Preferably, at least one of the following positive A plate and positive C plate contains a polymerizable rod-shaped liquid crystal material, and more preferably, either of the positive A plate and the positive C plate contains a polymerizable rod-shaped liquid crystal material. made.

Here, the rod-like liquid crystal material is a general term for liquid crystal materials whose molecular shape is rod-like. Rod-like liquid crystal compound-based liquid crystal material has a positive uniaxial intrinsic birefringence, specifically, a liquid crystal with Nx>Ny≒Nz, or Nz coefficient ((Nx-Nz)/(Nx-Ny))≒1 Material. The rod-like molecular shape means that when the long axis of the molecule is set as a and the short axis of the molecule is set as b, the compound with a/b>1, preferably a/b≧2, preferably a/b ≧3.

As the liquid crystal material, any liquid crystal material known in the past can also be used, and is not particularly limited. As long as it has reverse wavelength dispersion characteristics, for example, the liquid crystal compound etc. which show reverse wavelength dispersion characteristics as described in Japanese Patent Application Laid-Open No. 2010-522892 are mentioned. In addition, the liquid crystal material described in JP 2010-522892 A and the liquid crystal material described in International Publication No. 2013/180217 can also be used.

In addition, as the liquid crystal material, a material exhibiting a liquid crystal phase such as a nematic phase and a smectic phase can be used, and it is more preferable to use a material exhibiting a nematic phase from the viewpoint of being easier to arrange regularly than a liquid crystal material exhibiting other liquid crystal phases. Phase liquid crystal material. As a liquid crystal material exhibiting a nematic phase, a material having a spacer at both ends of a mesogen is preferably used. The liquid crystal material having spacers at both ends of the mesogen group is excellent in flexibility.

Moreover, as described above, the liquid crystal material is preferably a polymerizable liquid crystal material having a polymerizable functional group in the molecule. By having a polymerizable functional group, the liquid crystal material can be polymerized and fixed, so that the alignment stability is excellent, and the time-dependent change of the retardation is not easy to occur. Moreover, it is more preferable that a polymerizable liquid crystal material has two or more polymerizable functional groups in a molecule|numerator. By having two or more polymerizable functional groups, the three-dimensional alignment of the liquid crystal material can be more stable.

As a polymerizable functional group, the thing which polymerizes by the action|action of ion radiation, such as an ultraviolet-ray, an electron beam, or heat, is mentioned, for example. As such a polymerizable functional group, a radically polymerizable functional group is mentioned. Representative examples of the radically polymerizable functional group include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups and acrylates with or without substituents. group (including acrylyl, methacryloyl, acryloxy, methacryloyloxy) and the like.

In addition, as the polymerizable functional group, generally known cationically polymerizable functional groups can also be used, and specific examples thereof include alicyclic ether groups (epoxy groups, oxetanyl groups, etc.), cyclic acetal groups, cyclic A lactone group, a cyclic imino ether group, a cyclic thioether group, a spiro ortho ester group, a vinyloxy group, and the like. Among these, an alicyclic ether group and a vinyloxy group are preferable, and an epoxy group, an oxetanyl group, and a vinyloxy group are more preferable.

Moreover, it is especially preferable that a liquid crystal material has a polymerizable functional group at the terminal. By using such a liquid crystal material, for example, the ends of the liquid crystal material can be polymerized with each other to be in a state of three-dimensional alignment, so that a retardation film having stability and excellent performance of optical properties can be formed.

In addition, a liquid crystal material can be used individually by 1 type or in mixture of 2 or more types.

The rod-shaped liquid crystal material is exemplified below, but the present invention is not limited to these examples.

The content of the liquid crystal material in the polymerizable liquid crystal composition is not particularly limited, but it is preferably contained in the polymerizable liquid crystal composition at a ratio of 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more And the ratio of 30 mass % or less is contained in the polymerizable liquid crystal composition. If the amount of the liquid crystal material is less than 5% by mass, a large amount must be added at the time of production, making it difficult to manufacture, and a large amount of solvent must be removed, so the reliability is likely to deteriorate due to residual solvent. On the other hand, when it exceeds 40 mass %, since the viscosity of this polymerizable liquid crystal composition will become too high, the workability|operativity of the production|production of a layer will worsen.

Moreover, the content of the liquid crystal material with respect to the solid content mass (the mass excluding the solvent) of the polymerizable liquid crystal composition is preferably 75 to 99.9 mass %, more preferably 80 to 99 mass %, and further preferably 85 to 98 mass %. quality%.

The above-mentioned liquid crystal materials are usually dissolved in a solvent. The solvent must be one that can dissolve the above-mentioned liquid crystal material uniformly, and a known solvent can be used. Examples of such solvents include hydrocarbons such as toluene and xylene; ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, and methyl isobutyl ketone; ethers such as tetrahydrofuran; Glycol ethers such as oxy-2-propanol and 1-methoxypropyl-2-acetate; esters such as methyl acetate, ethyl acetate and butyl acetate.

A solvent may be used individually by 1 type, and may use 2 or more types together.

The content of the solvent in the polymerizable liquid crystal composition is preferably 66 parts by mass or more and 1,900 parts by mass or less with respect to 100 parts by mass of the liquid crystal material (liquid crystal compound). If the amount of the solvent is less than 66 parts by mass, the liquid crystal material may not be uniformly dissolved. On the other hand, when it exceeds 1,900 mass parts, a part of a solvent may remain|survive and reliability may fall, and it may not apply|coat uniformly. From this viewpoint, it is more preferably 900 parts by mass or less.

In addition, the polymerizable liquid crystal composition may contain other additives as needed. The other compound is not particularly limited as long as it has compatibility with the liquid crystal material and does not interfere with the arrangement order of the liquid crystal material, and examples include polymerization initiators, polymerizable compounds, plasticizers, surfactants, and silane coupling agents. mixture, etc.

<Positive A board>

The retardation film of the present invention has a positive A plate, and the positive A plate has the characteristics of a positive A type. The positive A plate has the following characteristics: when the refractive index along the X-axis direction of the layer is set as Nx, the refractive index in the Y-axis direction along the direction of the layer, which is orthogonal to the X-axis, is set as Ny, and the layer thickness direction is set as Ny. When the refractive index is Nz, there is a relationship of Nx>Ny≒Nz, and the optical axis becomes the Nx direction. In addition, Ny≒Nz includes those whose refractive index difference between Ny and Nz is 0.03 or less, and Ny≒Nz when |Ny-Nz|≦0.03. Furthermore, when |Ny-Nz|>0, Ny>Nz is preferable.

The positive A plate 14 is a layer which has the characteristic of positive A and has a specific wavelength dispersion characteristic and exhibits an optical function. Furthermore, the positive A plate 14 is preferably composed of a polymerizable liquid crystal composition containing a liquid crystal material for producing a retardation layer of various optical films. That is, the liquid crystal material has a creeping alignment. The plane alignment means a state in which the long axes of the molecules of the liquid crystal material are aligned in the horizontal direction. The positive A plate preferably exhibits a smectic phase. Here, the smectic phase refers to a state in which molecules aligned in one direction have a phase structure. Also, the nematic phase refers to a state in which constituent molecules have an alignment order but not a three-dimensional positional order.

Specifically, the positive A plate 14 has the characteristics of the positive A type. When the front retardation at a wavelength of 450 nm is set as Re _A450 , and the front retardation at a wavelength of 550 nm is set as Re _A550 , the ratio of Re _A450 /Re _A550 is obtained. The _ΔNA is less than 1.0 or less than 1.0. More specifically, when the above-mentioned ΔN _C is 1.0 or less, the ΔN _A is less than 1.0, and when the ΔN _C is less than 1.0, the ΔN _A is 1.0 or less. More preferably, ΔN _A is less than 0.9. In addition, the relationship between this ΔN _A and the ΔN C of the positive C plate 13 is |ΔN _{A -ΔN C |} ≦0.15.

From the viewpoint of obtaining a good contrast in a wide viewing angle range and suppressing the variation of the color with the viewing angle (hereinafter, also referred to as "color variation"), ΔN _A is more preferably 0.87 or less , and more preferably 0.85 or less. Moreover, from the viewpoint of suppressing color variation, ΔN _A is preferably 0.70 or more, more preferably 0.75 or more, still more preferably 0.78 or more, and still more preferably 0.80 or more.

The thickness of the positive A-plate 14 is not particularly limited, but when the positive A-plate is made of a liquid crystal material, it is preferably 0.3 μm or more and 3.0 μm or less from the viewpoint of obtaining a desired retardation.

In addition, when a positive A plate is produced from a material other than a liquid crystal material, for example, a composition containing a polycarbonate-based resin and/or an amorphous cycloolefin-based resin (see Japanese Patent Application Laid-Open No. 2010-185937, Japanese Patent Application Laid-Open No. 2010-185937) From the viewpoint of obtaining a desired retardation, the thickness of the positive A plate is preferably 15 μm or more and 150 μm or less, and more preferably 15 μm or more and 100 μm or less. Further, as the positive A plate, a uniaxially stretched polycarbonate-based resin (uniaxially stretched PC), a uniaxially stretched cycloolefin-based resin (uniaxially stretched COP), and the like can be used.

Furthermore, when the retardation film of the present invention is used in a flexible display device, the retardation film as a whole is preferably thinner, and a positive A-plate is preferably made of a liquid crystal material.

The positive A-plate is preferably produced from a polymerizable liquid crystal composition containing a liquid crystal material, and the polymerizable liquid crystal composition preferably contains a liquid crystal material that exhibits liquid crystallinity and has a polymerizable functional group in the molecule. As the liquid crystal material, a discotic liquid crystal material and a rod-shaped liquid crystal material can be mentioned, and in the present invention, the liquid crystal material is preferably a rod-shaped liquid crystal material. The reverse dispersibility is expressed by the difference between the dispersibility of the main chain and the side chain, and thus it is difficult for the discotic liquid crystal material to express the reverse dispersibility. On the other hand, if it is a rod-shaped liquid crystal material, the dispersibility can be controlled by changing a main chain and a side chain, and it is also preferable at the point of easy adjustment of wavelength dispersibility.

Furthermore, the liquid crystal material is not particularly limited, and it means that all liquid crystal materials included in the composition for forming the positive A plate may be composed of only one type of liquid crystal material, or may be a mixture of two or more types of liquid crystal materials.

As the liquid crystal material, any liquid crystal material known in the past may be used without particular limitation as long as it is a liquid crystal material that exhibits a predetermined wavelength dispersion. For example, the compound represented by the general formula (I) described in Japanese Patent Laid-Open No. 2008-297210, the compound represented by the general formula (1) described in Japanese Patent Application Laid-Open No. 2010-84032, and the Liquid crystal compound A0 and the like described in 2016-53709 publication.

As a polymerizable functional group, the thing which polymerizes by the action|action of ion radiation, such as an ultraviolet-ray, an electron beam, or heat, is mentioned, for example. As such a polymerizable functional group, a radically polymerizable functional group is mentioned. Representative examples of the radically polymerizable functional group include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups and acrylates with or without substituents. group (including acrylyl, methacryloyl, acryloxy, methacryloyloxy) and the like.

In addition, as the polymerizable functional group, generally known cationically polymerizable functional groups can also be used, and specific examples thereof include alicyclic ether groups (epoxy groups, oxetanyl groups, etc.), cyclic acetal groups, cyclic Lactone group, cyclic imino ether group, cyclic thioether group, spirocyclic orthoester group, vinyloxy group, etc. Among these, an alicyclic ether group and a vinyloxy group are preferable, and an epoxy group, an oxetanyl group, and a vinyloxy group are more preferable.

Moreover, it is especially preferable that the liquid crystal material for positive A-plates has a polymerizable functional group at the terminal. By using such a liquid crystal compound, for example, the ends of the liquid crystal material can be polymerized with each other to be in a state of three-dimensional alignment, so that a retardation film having stability and excellent in the expression of optical properties can be formed.

In addition, a liquid crystal material may be used individually by 1 type, and may use 2 or more types together.

The content of the liquid crystal material in the polymerizable liquid crystal composition is not particularly limited, but it is preferably contained in the polymerizable liquid crystal composition at a ratio of 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more And the ratio of 30 mass % or less is contained in the polymerizable liquid crystal composition. If the amount of the liquid crystal material is less than 5% by mass, a large amount must be added during production, making it difficult to manufacture, and a large amount of solvent must be removed, so the reliability is likely to deteriorate due to residual solvent. On the other hand, when it exceeds 40 mass parts, since the viscosity of this polymerizable liquid crystal composition will become too high, the workability|operativity of layer production will worsen.

Moreover, the content of the liquid crystal material with respect to the solid content mass (the mass excluding the solvent) of the polymerizable liquid crystal composition is preferably 75 to 99.9 mass %, more preferably 80 to 99 mass %, and further preferably 85 to 98 mass %. quality%.

The above-mentioned liquid crystal materials are usually dissolved in a solvent. The solvent must be one that can dissolve the above-mentioned liquid crystal material uniformly, and a known solvent can be used. Examples of such solvents include hydrocarbons such as toluene and xylene; ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, and methyl isobutyl ketone; ethers such as tetrahydrofuran; Glycol ethers such as oxy-2-propanol and 1-methoxypropyl-2-acetate; esters such as methyl acetate, ethyl acetate and butyl acetate.

A solvent may be used individually by 1 type, and may use 2 or more types together.

The content of the solvent in the polymerizable liquid crystal composition is preferably 66 parts by mass or more and 1,900 parts by mass or less with respect to 100 parts by mass of the liquid crystal material (liquid crystal compound). If the amount of the solvent is less than 66 parts by mass, the liquid crystal material may not be uniformly dissolved. On the other hand, when it exceeds 1,900 mass parts, a part of a solvent may remain|survive and reliability may fall, and it may not apply|coat uniformly. From this viewpoint, it is more preferably 900 parts by mass or less.

Furthermore, in the polymerizable liquid crystal composition, other additives may be contained as required. The other compound is not particularly limited as long as it has compatibility with the liquid crystal material and does not interfere with the arrangement order of the liquid crystal material, and examples include polymerization initiators, polymerizable compounds, plasticizers, surfactants, and silane coupling agents. mixture, etc.

The retardation film 10 having the above configuration has the following features. That is, when the front retardation when the wavelength of the positive A plate is 450 nm is Re _A450 and the front retardation when the wavelength is 550 nm is Re _A550 , the _ΔNA obtained by Re _A450 /Re _A550 , and when the front retardation when the wavelength is 550 nm is Re A550 When the retardation in the thickness direction of the positive C plate at a wavelength of 450 nm is set as Rth _C450 and the retardation in the thickness direction at a wavelength of 550 nm is set as Rth _C550 , the ΔN _C obtained by Rth _C450 /Rth _C550 has _ΔNA and Δ One of N _C is 1.0 or less, the other is less than 1.0, and the relationship of |ΔN _A -ΔN _C |≦0.15.

As described above, in the present invention, a retardation film having a positive A plate and a positive C plate is used from the viewpoint of obtaining a good contrast in a wide viewing angle range. However, each of the positive A plate and the positive C plate has wavelength dispersion of retardation. The inventors of the present invention considered that, among the retardation films formed by laminating a positive A plate and a positive C plate, the wavelength dispersion characteristics of each are related to the characteristics of the retardation film as a whole, and as a result of investigation, they found that: By setting |ΔN _A -ΔN _C | to be 0.15 or less, the change in color with the viewing angle (hereinafter, also referred to as "color change") is suppressed. In the retardation film in which the positive A plate and the positive C plate are simply laminated, the wavelength dispersion characteristics are not sufficiently studied, and it is difficult to sufficiently suppress the color variation. In the present invention, by laminating the positive A plate and the positive C plate, and further setting the relationship between the wavelength dispersibility of the positive A plate and the positive C plate in a specific range, a retardation film with suppressed color variation can be provided.

By setting |ΔN _A -ΔN _C | to a specific range, the anti-reflection function and optical compensation function, which are the basic functions of the retardation film, can be exerted over a wide wavelength region, and can be spread over a wide field of view Angle improves contrast and suppresses color changes caused by viewing angle.

In this case, at least one of _ΔNA and _ΔNC is preferably less than 0.9. Moreover, it is preferable that at least one of the positive A plate and the positive C plate contains the above-mentioned polymerizable rod-shaped liquid crystal material.

<Manufacturing method of retardation film>

Next, the manufacturing method of the retardation film 10 is demonstrated. For example, the manufacturing method of the retardation film 10 is comprised including the supply process of a base material, the formation process of an alignment film, the formation process of a positive C plate, and the formation process of a positive A plate.

In the supplying step of the substrate, the substrate 11 is supplied by a roller.

Then, in the step of forming the alignment film, the alignment film 12 is formed on one surface of the substrate 11 . The details are as follows.

The base material 11 is pulled out from the supply reel, and the composition constituting the alignment film is laminated on the base material 11 . The method for laminating the composition on the substrate 11 is not particularly limited, and for example, a die coating method, a gravure coating method, a reverse coating method, a blade coating method, a dip coating method, a spray coating method, an air coating method, and a gas coating method can be used. Knife coating method, spin coating method, roll coating method, printing method, dip and pull method, curtain coating method, casting method, bar coating method, extrusion coating method, E-die coating method Wait.

Then, the laminated composition is dried, whereby the alignment film 12 is produced.

In the formation step of the positive C plate, as an example, the composition constituting the positive C plate is laminated on the alignment film 12 in the same manner as in the formation step of the alignment film, and is irradiated with ultraviolet rays, thereby curing the composition to obtain the obtained Positive C plate 13 . As a light source for irradiating ultraviolet rays, low-pressure mercury lamps (bactericidal lamps, fluorescent chemical lamps, black light lamps), high-pressure discharge lamps (high-pressure mercury lamps, metal halide lamps), short arc discharge lamps (ultra-high pressure mercury lamps, xenon lamps, mercury-xenon lamps) can be used lights), etc. Among them, metal halide, xenon lamp, high pressure mercury lamp, etc. can be preferably used. The wavelength of the ultraviolet rays is appropriately set according to the material constituting the composition, etc. Specifically, the wavelengths used are preferably 210 nm or more and 380 nm or less, preferably 230 nm or more and 380 nm or less, and more preferably 250 nm or more and 380 nm or less. the irradiating light. In addition, the irradiation amount (accumulated light amount) of the ultraviolet rays is not particularly limited, but for example, it is preferably within a range of 100 mJ/cm ² or more and 1,500 mJ/cm ² or less, more preferably 100 mJ/cm ² or more and 800 mJ/cm ² within the following range.

In the step of forming the positive A-plate, for example, the composition constituting the positive A-plate is laminated and hardened on the positive C-plate 13 . It can be performed in the same manner as the formation of the positive C plate 13 . At this time, it is preferable to set an alignment film on the A-plate.

However, it is not limited to this, and a positive A plate may be separately produced and transferred and laminated on a positive C plate. Moreover, the retardation film of this invention can also be produced by laminating a positive C plate on a base material having positive A characteristics.

Moreover, a positive C plate may be separately produced, and the positive C plate may be transferred to a positive A plate to produce the retardation film 10 of the present invention.

Next, the optical function laminated body to which the said retardation film 10 is applied is demonstrated. In this optical function laminated body, the retardation film 10 can be arrange|positioned by making one of the structures of various optical function laminated bodies arrange|positioned in an image display panel contain the retardation film 10.

Specifically, the mode in which the retardation film of the present invention is used as an optical compensation film of a liquid crystal display device, or the mode in which it is used together with a linear polarizer as an external light reflection plate of an organic EL display device can be exemplified.

[Circular polarizer or elliptical polarizer]

The circular polarizing plate or the elliptical polarizing plate of the present invention has the retardation film and the polarizing element of the present invention, and is preferably a circular polarizing plate when used as an anti-reflection film for external light.

The circular polarizing plate and the elliptical polarizing plate are arranged on the organic electroluminescence display device or the touch panel to exert the anti-reflection function. The circular polarizing plate and the elliptical polarizing plate are provided with a retardation film on the light source side of the display panel, and a polarizing element is provided on the light incident side to prevent reflection of external light and the like.

<retardation film>

When used for circularly polarizing plates or elliptically polarizing plates, the positive A plate is preferably a 1/2 wavelength retardation plate (hereinafter, also referred to as "λ/2 retardation plate"), a 1/4 wavelength retardation plate (hereinafter, also referred to as "λ/4 retardation plate"), or a combination thereof. In the present invention, when the retardation film is used for the circularly polarizing plate, the positive A plate is preferably a λ/4 retardation plate with reverse dispersion, or a λ/4 retardation plate and a λ/2 retardation plate. layered body.

When the wavelength of the λ/2 retardation plate is 550 nm, the in-plane retardation is preferably 200-300 nm, more preferably 220-280 nm, and more preferably 240-275 nm.

When the wavelength of the λ/4 retardation plate is 550 nm, the in-plane retardation is preferably 100-180 nm, more preferably 110-160 nm, and more preferably 120-150 nm.

<Polarizing element>

In the present invention, the circularly polarizing plate or the elliptically polarizing plate has the retardation film and the polarizing element of the present invention. The polarizing element preferably forms a polarizing plate together with the protective film.

As the polarizer, any of an iodine-based polarizer, a dye-based polarizer using a dichroic dye, or a polyene-based polarizer can be used.

The iodine-based polarizing element and the dye-based polarizing element are usually produced using a polyvinyl alcohol-based film. The absorption axis of the polarizer corresponds to the extending direction of the film. Therefore, the polarizer extending in the longitudinal direction (the conveying direction) has an absorption axis parallel to the longitudinal direction, and the polarizing element extending in the lateral direction (direction perpendicular to the conveying direction) has an absorption axis perpendicular to the longitudinal direction.

The polarizing element usually has a protective film. In the present invention, the following antireflection layer or the above retardation film can function as a protective film of a polarizing element. When the protective film of the polarizing element is laminated separately from the above-mentioned antireflection layer or retardation film, it is preferable to use a cellulose ester film with high optical isotropy as the protective film.

By using a linear polarizing element as a polarizing element and combining with the above-mentioned retardation film, a polarizing element-integrated laminated body that functions as a circular polarizing plate can be produced with high productivity.

[Display panel (liquid crystal display panel, organic EL display panel) and display device (liquid crystal display device, organic EL display device)]

The retardation film of the present invention is preferably used for a display panel. In addition, it is preferably applied to a display device including the display panel. Examples of the display panel include a liquid crystal display panel, an organic electroluminescence display panel (hereinafter, also referred to as an "organic EL display panel"; the same below), a micro light emitting diode display panel (hereinafter referred to as a "micro LED display panel") ), etc., preferably a liquid crystal display panel or an organic EL display panel. In addition, as a display device, a liquid crystal display device including the above-mentioned liquid crystal display panel, an organic EL display device including the above-mentioned organic EL display panel, and a micro-LED display device including the above-mentioned micro-LED display panel can be exemplified, preferably a liquid crystal display device or an organic EL display device. EL display device.

<Liquid crystal display panel and liquid crystal display device>

Usually, the liquid crystal display panel is provided with a liquid crystal cell between two layers of polarizing elements, and a backlight is provided on the incident light side of the liquid crystal display panel. Moreover, as mentioned above, it is preferable that a polarizing element forms a polarizing plate together with a protective film. Furthermore, a reflection plate may be provided on the side opposite to the side where the liquid crystal cells of the backlight are provided.

In the liquid crystal display panel, two layers of polarizers are used, so there are usually four polarizer protective films. The retardation film of the present invention can be used as any one of four polarizer protective films. The retardation film of the present invention is preferably disposed between the liquid crystal cell and the polarizer in the liquid crystal display panel, and can also be used as a protective film disposed between the liquid crystal cell and the polarizer.

Further, the liquid crystal display device is not particularly limited as long as it includes a liquid crystal display panel and a backlight, and preferably includes a liquid crystal display panel and a backlight, a drive control unit electrically connected to the display panel and the backlight, and a device for accommodating the same. case.

As a more specific example, the case where it applies to the liquid crystal display device provided with the retardation film 10 of this invention is demonstrated. FIG. 2 is a diagram showing the layer structure of the liquid crystal display device 20 including the retardation film 10 . In this liquid crystal display device 20 , the optical function layered body 26 is disposed on the output surface side of the liquid crystal display panel 23 . Here, the polarizer 27 for linear polarization and the retardation film 10 are included for optical compensation.

The liquid crystal display device 20 is preferably an IPS liquid crystal display device (In-plane Switching liquid crystal display, IPS-LCD), and a liquid crystal display panel 23 is disposed on the observer side of the backlight 22 .

The liquid crystal display panel 23 is provided with a liquid crystal cell 25 formed of IPS liquid crystal, and a linear polarizer 24 is provided on the back light source 22 side of the liquid crystal cell 25, for example, through a pressure-sensitive adhesive layer (not shown). In addition, the linear polarizing plate 24 is comprised by pinching the polarizing element which functions as a linear polarizing plate between two base materials which consist of a transparent film, for example. Moreover, the retardation film 10 of this invention can also be used as a polarizer protective film (substrate).

The IPS mode (hereinafter also referred to as the IPS mode) is a state in which the liquid crystal material is aligned substantially in parallel during black display, and the liquid crystal molecules are aligned parallel to the substrate surface in a state where no voltage is applied. In the liquid crystal display device of the IPS method provided with the retardation film of the present invention, the color variation due to the oblique viewing angle when viewed from the oblique direction is suppressed.

Furthermore, in FIG. 2 , the retardation film 10 is only provided on the light-emitting side, but the present invention is not limited to this, and the present invention may be further arranged between the linear polarizer 24 and the liquid crystal cell 25 on the incident light side. The retardation film 10 .

In the liquid crystal display device shown in FIG. 2, since the retardation film 10 of the present invention that functions as an optical compensation film is disposed, color variation due to oblique viewing angles is suppressed.

IPS mode liquid crystal display devices can also be used, for example, Japanese Patent Laid-Open No. 2003-15160, Japanese Patent Laid-Open No. 2003-75850, Japanese Patent Laid-Open No. 2003-295171, Japanese Patent Laid-Open No. 2004-12730, JP 2005-106967, JP 2005-134914, JP 2005-241923, JP 2005-284304, JP 2006-189758, JP 2006-194918, JP 2006-194918 No. 2006-220680, JP 2007-140353, JP 2007-178904, JP 2007-293290, JP 2007-328350, JP 2008-3251, JP 2008- Those described in respective gazettes such as JP 2008-40291 A, JP 2008-65196 A, JP 2008-76849 A, and JP 2008-96815 A.

In the liquid crystal display panel 23 shown in FIG. 2 , the optical function laminate 26 is arranged on the output surface of the liquid crystal cell 25 . The optical function layered body 26 includes a retardation film 10 constituting an optical compensation film for optical compensation, a polarizing element 27 , and a substrate (protective film) 28 that is a surface material. A transparent film such as TAC is used as the base material 28, and a polarizing element 27 serving as a linear polarizing element is provided here.

An antireflection layer (low refractive index layer) may be further laminated on the surface (viewable side) of the polarizing element 27 .

In this way, the retardation film 10 constituting the optical function layered body 26 functions as an optical compensation film observed from an oblique field of view in a wide frequency band.

<Organic EL display panel and organic EL display device>

The organic EL display device is a display device in which a light-emitting layer or a multilayer organic compound film including a light-emitting layer is formed between a pair of electrodes of an anode and a cathode, and the organic EL display panel of the present invention is provided on the visible side of the organic EL display device. In addition to the light-emitting layer, the organic compound thin film may have a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, a protective layer, and the like, and each of these layers may have other functions. Each layer of the electrode and the organic compound thin film of the organic EL display device can be formed by well-known materials and methods.

As another concrete example, the case where it is applied to the organic EL display panel provided with the retardation film 10 is demonstrated. FIG. 3 is a diagram showing the layer structure of the organic EL display panel 30 including the retardation film 10 . In the organic EL display panel 30, the optical function laminate 36 is an anti-reflection film for external light disposed on the emitting surface side of the organic EL display element 33. This optical function layered body 36 includes a polarizing element 37 for linear polarization and a retardation film 10, and has a function of preventing reflection of external light as a so-called circular polarizer.

Furthermore, the organic EL display device is not particularly limited as long as it includes the organic EL display panel of the present invention, and preferably includes an organic EL display panel, a drive control unit electrically connected to the organic EL display panel, and a device for accommodating the organic EL display panel. case.

The organic EL display panel 30 is a device for providing image light generated by the organic EL display element 33 self-emission to the observer, and the optical function laminate 36 is arranged on the output surface of the organic EL display element 33 . The optical function layered body 36 functions as a circular polarizer for preventing reflection of external light, and includes a retardation film 10 , a polarizer 37 as a linear polarizer, and a substrate (protective film) 38 as a surface material. In addition, at this time, the positive A plate 14 serving as the retardation film 10 functions as a λ/4 retardation layer, and the positive C plate 13 is laminated thereon.

In this way, the retardation film 10 constituting the optical function layered body 36 functions as an anti-reflection film for external light in a wide frequency band.

Example

In the embodiment, the laminate is modeled according to the liquid crystal display panel 23 shown in FIG. 2 through simulation, and the ΔN A of the positive _A plate and the ΔN of the positive C plate of the retardation film 10 included therein are changed. _C , evaluate the contrast and the hue change at a viewing angle of 60°.

Furthermore, the laminate was modeled according to the organic EL display panel shown in FIG. 3, and the ΔNA of the positive _A plate and the ΔN _C of the positive C plate of the retardation film 10 included therein were changed. The following hue changes were evaluated.

The simulation of the liquid crystal display panel was performed using an LCD-MASTER (SHINTECH Co., Ltd.), and the light source was an LED light source. The layer structure of the model is set to make the absorption axis 90° with respect to the reference from the observer side, the upper polarizer, the positive C plate, the positive A plate with the optical axis parallel to the absorption axis of the upper polarizer, the liquid crystal cell, and the The absorption axis is the lower polarizing plate at 0° with respect to the reference, and it is set as the condition that light is irradiated from the lower polarizing plate side. Furthermore, the contrast ratio of the liquid crystal display panel is calculated by (brightness of white display (ON) ÷ brightness of black display (OFF)). In the simulation of the black display (OFF), the alignment direction of the liquid crystal molecules of the liquid crystal cell is set to 0° with respect to the reference, and the brightness of the black display is calculated. In addition, in the case of white display (ON), the average value when the alignment direction of the liquid crystal molecules of the liquid crystal cell becomes 45° with respect to the reference and when it becomes 135° is set as the brightness of white display.

In addition, the simulation system of the organic EL display panel was similarly performed using LCD-MASTER (SHINTECH Co., Ltd.), and the light source (light incident on the outside of the panel) was a D65 light source. In the layer structure of the model, the angle formed by the absorption axis of the polarizing element and the retardation axis of the positive A plate is set to 45°. In addition, a reflector (100% reflection) is provided on the opposite side of the positive C plate to the side where the positive A plate is provided.

The positive A plate used for the simulation is described below.

Refractive index along the X-axis of the layer (550nm) Nx=1.587

Refractive index (550nm) Ny=1.531 in the Y-axis direction orthogonal to the X-axis in the direction along the layer

Refractive index in layer thickness direction (550nm) Nz=1.531

Re(550nm)=(Nx-Ny)×d=140nm

(Here, d is the thickness (nm) of the positive A plate)

The positive C plate used for the simulation is described below.

Refractive index along the X-axis of the layer (550nm) Nx=1.573

Refractive index (550nm) Ny=1.573 in the Y-axis direction orthogonal to the X-axis in the direction along the layer

Refractive index in layer thickness direction (550nm) Nz=1.629

Rth(550nm)=[{(Nx+Ny)/2}-Nz]×d=-90~-110nm (for liquid crystal display device, adjust appropriately within the above range)

Rth(550nm)=[{(Nx+Ny)/2}-Nz]×d=-70nm (for organic EL display device)

(Here, d is the thickness of the positive C plate (nm))

[Evaluation]

<Contrast>

As shown in an example in Fig. 4(a), the contrast at each viewing angle (circle radius direction) is obtained relative to the center of the screen in all directions (circumferential direction), and the contour of the contrast is obtained (actually in Fig. 4(a) ) Wire).

The line with a polar angle of 60° indicated by the thick dotted circle in Fig. 4(a) is superimposed on this, as shown in Fig. 4(b), and the change in contrast at a polar angle of 60° is investigated, and the curve below the slanted line is obtained. The area of part P. Let this area be the sum of contrast S.

Then, the sum of contrasts at _ΔNA = 1.00 and _ΔNC = 1.00 is set as S ₁ , and the ratio of the sum of contrasts S ₂ to S ₁ in each combination of _ΔNA and _ΔNC is calculated. Therefore, it is S ₂ /S ₁ . Accordingly, it can be said that the larger the value of S ₂ /S ₁ , the better the contrast ratio is relatively compared to when ΔN _A =1.00 and ΔN _C =1.00. The results are shown in Table 1.

<Vision character phase change>

As shown in the schematic diagram in FIG. 5 , the color at a viewing angle inclined at θ=60° with respect to the normal line n extending from the center of the surface of the laminated body to be evaluated was measured. The upper part of Fig. 5 is a plan view of the laminate, and the lower part of Fig. 5 is a side view of the laminate. As can be seen from Figure 5, the viewing angle of θ=60° exists in the form of drawing a circle with O as the center. Therefore, taking T as the starting point and following the arrow K in the way of drawing a circle with O as the center, the circle of each position is obtained. Hue.

As a result, as shown in each example of Fig. 6(a) and Fig. 6(b), the change in color during one revolution is expressed as the xy coordinate of the x-y color system. This makes it possible to evaluate the relationship between the orientation (circumferential position) and the change in color at a viewing angle of 60°. It is preferable that the hue changes less, and it is preferable that it does not span various colors when making a circle at a viewing angle of 60°. Therefore, the thin shape shown by E2 in FIG. 6( b ) can be said to be better with less change in hue compared to the close-to-circle shape shown by E1 in FIG. 6( a ).

That is, when expressed as the xy coordinate of the x-y color system, when a circle is circled at a viewing angle of 60°, as described above, it is preferable that the change of the hue is small, and the distance from white (x=0.33, y=0.33) is small. The sum of the distances is smaller, and preferably the span of the colors without the chromaticity diagram.

For each example, at the above-mentioned 60° viewing angle, a* and b* were acquired every 5° on one rotation (360°). In addition, set a* and b* under a certain angle as a* ₂ and b* ₂ respectively, and set a* and b* under the previous angle (a certain angle -5°) as a* ₁ , b* ₁ . Then, according to the following formula, the color variation value in units of 5° was obtained.

{(a* ₂ -a* ₁ ) ² +(b* ₂ -b* ₁ ) ² } ^0.5

From 0° to 360°, obtain the value of the color variation in units of 5° every 5°, take the sum of all the values, and obtain the sum of the color variation for evaluation. A smaller sum of the color changes means less color change.

<Evaluation by visual inspection of visibility at a viewing angle of 60°>

From the commercially available liquid crystal display device of the IPS method, the layer which exists on the viewing side rather than the liquid crystal cell is peeled off, and the glass part of the liquid crystal cell is exposed. The liquid crystal display device exposed on the glass part of the liquid crystal cell is laminated with an optical laminate to produce a liquid crystal display device. The optical laminate system is formed by laminating a retardation film and a polarizer, and the retardation film is a positive C plate and a positive A plate. Layered.

Further, a portable information terminal, which is a commercially available organic EL display device, was disassembled, the circular polarizing plate was peeled off, and an optical laminate was attached to the organic EL display device after peeling off the circular polarizing plate to produce an organic EL display device. A retardation film and a polarizing plate are laminated, and the retardation film is formed by laminating a positive C plate and a positive A plate.

The produced liquid crystal display device and the organic EL display device were evaluated by making one turn (360°) at a viewing angle of 60° and checking them visually.

The evaluation criteria are as follows.

3 points: The color difference is not obvious.

2 points: there is color difference but no problem

1 point: chromatic aberration but practically acceptable

0 points: The color difference is serious and practically a problem

Evaluation was performed by visual inspection by 20 sensory inspectors, and the average value was used for evaluation.

A: Very good (average 2.5 points or more)

B: Good (average 1.7 points or more and less than 2.5 points)

C: Fair (average 1.0 points or more and less than 1.7 points)

D: Failed (average less than 1.0 points)

The results are shown in Table 4 (liquid crystal display device) and Table 5 (organic EL display device) below.

[result]

In Table 1, the value of S ₂ /S ₁ in contrast evaluation is shown for the liquid crystal display panel. In Table 2, the sum of the color variation of the liquid crystal display panel is shown. In addition, in Table 3, the sum total of the color variation of the organic EL display panel is shown.

In Table 4, the evaluation by visual inspection of the visibility of the liquid crystal display device at a viewing angle of 60° is shown, and in Table 5, the visibility by visual inspection of the organic EL display device at a viewing angle of 60° is shown. Confirm the evaluation made.

As can be seen from Tables 1 to 5, one of the ΔN A of the positive _A plate and the ΔN C of the positive C plate is 1.0 or less, and the other is less than 1.0, and |ΔN _{A -ΔN C |} ≦0.15, a retardation film with good contrast and less color variation due to viewing angle can be obtained.

10‧‧‧Retardation film

11‧‧‧Substrate

12‧‧‧Alignment film

13‧‧‧Positive C plate

14‧‧‧Positive A board

Claims (14)

A retardation film, which has: a positive A plate, which has the characteristics of a positive A type, when the front retardation when the wavelength is 450nm is set as Re _A450 , and the front retardation when the wavelength is 550nm is set as Re _A550 , the Re _A450 /Re _A550 is set as _ΔNA ; and positive C plate, which has the characteristics of positive C type, when the thickness direction retardation when the wavelength is 450nm is set as Rth _C450 , the thickness direction retardation when the wavelength is 550nm is set as Rth At _C550 , Rth _C450 /Rth _C550 is set as ΔN _C ; and one of the above ΔN _A and the above ΔN _C is 1.0 or less, the other is less than 1.0, and |ΔN _A -ΔN _C |≦ 0.15. An alignment film is provided between the above-mentioned positive A plate and the above-mentioned positive C plate, and the above-mentioned positive A plate is obtained by laminating and curing the composition constituting the above-mentioned positive A plate on the above-mentioned positive C plate. The retardation film according to claim 1, wherein at least one of the ΔN _A and the above ΔN _C is less than 0.9. The retardation film according to claim 1, wherein neither of the above ΔN _A and the above ΔN _C is less than 0.9. The retardation film according to any one of claims 1 to 3, wherein any one of the above ΔN _A and the above ΔN _C is 0.75 or more. The retardation film according to any one of claims 1 to 3, wherein at least one of the positive A plate and the positive C plate contains a polymerizable rod-shaped liquid crystal material. The retardation film according to claim 4, wherein at least one of the positive A plate and the positive C plate contains a polymerizable rod-shaped liquid crystal material. A circularly polarizing plate or an elliptically polarizing plate having the retardation film according to any one of claims 1 to 6, and a polarizing element. A display panel comprising the retardation film according to any one of claims 1 to 6. A liquid crystal display panel, comprising: two polarizers; and the retardation film and liquid crystal layer described in any one of claims 1 to 6, which are arranged between the two polarizers; and the liquid crystal display panel With optical compensation function. An organic EL display panel, comprising: an organic EL display element; and an anti-reflection film for external light, sequentially provided with the phase difference according to any one of claims 1 to 6 arranged on the light-emitting side of the organic EL display element film and polarizer. A display device comprising the display panel described in any one of claims 8 to 10. A liquid crystal display device comprising the liquid crystal display panel of claim 9. The liquid crystal display device according to claim 12, wherein the liquid crystal display device is an IPS mode liquid crystal display device. An organic EL display device comprising the organic EL display panel described in claim 10.

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