CN110546538B

CN110546538B - Circularly polarizing plate and organic EL panel

Info

Publication number: CN110546538B
Application number: CN201880026774.8A
Authority: CN
Inventors: 小岛理; 饭田敏行; 角村浩
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-05-15
Filing date: 2018-01-19
Publication date: 2022-03-01
Anticipated expiration: 2038-01-19
Also published as: WO2018211738A1; KR20200007789A; TW201901201A; CN110546538A; JP2018194606A

Abstract

The invention provides a circularly polarizing plate which can restrain the progress of warping even when used for a curved organic EL panel. The circularly polarizing plate of the present invention comprises a polarizer and a retardation layer directly bonded to the polarizer, and is used for a curved organic EL panel, wherein Re (550) of the in-plane retardation of the retardation layer is 100nm to 180nm, and satisfies the relationship of Re (450) < Re (550), and the absorption axis of the polarizer is adjusted so that the angle formed by the absorption axis of the polarizer and the bending direction of the organic EL panel is 75 DEG to 105 deg.

Description

Circularly polarizing plate and organic EL panel

Technical Field

The present invention relates to a circularly polarizing plate and an organic EL panel.

Background

In recent years, along with the spread of thin displays, displays equipped with organic EL panels have been proposed. Since the organic EL panel has a metal layer having high reflectivity, problems such as reflection of external light and reflection of a background tend to occur. Therefore, it is known to prevent these problems by providing a circularly polarizing plate having a λ/4 plate on the visual confirmation side. However, in a general circularly polarizing plate using a λ/4 plate, the problem of color fading is large. As a means for solving such a problem, it has been proposed to use a λ/4 plate made of a so-called inverse dispersion wavelength material (patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2006 and 171235

Disclosure of Invention

Problems to be solved by the invention

However, when the conventional circularly polarizing plate as described above is used for a curved organic EL panel, the circularly polarizing plate may be warped, and as a result, the optical characteristics of the circularly polarizing plate may be changed.

The present invention has been made to solve the above conventional problems, and a main object thereof is to provide a circularly polarizing plate capable of suppressing the progress of warping even when used for a curved organic EL panel, and an organic EL panel including such a circularly polarizing plate.

Means for solving the problems

The circularly polarizing plate of the present invention comprises a polarizer and a retardation layer directly bonded to the polarizer, and is used for a curved organic EL panel, wherein Re (550) of the in-plane retardation of the retardation layer is 100nm to 180nm, and satisfies the relationship of Re (450) < Re (550), and the absorption axis of the polarizer is adjusted so that the angle formed by the absorption axis and the bending direction of the organic EL panel is 75 DEG to 105 deg.

In one embodiment, the circularly polarizing plate is subjected to corona treatment or plasma treatment on the retardation layer.

In one embodiment, the circularly polarizing plate further includes an easy adhesion layer between the polarizer and the retardation layer.

In one embodiment, the circularly polarizing plate further includes another retardation layer disposed on the side opposite to the polarizer of the retardation layer, and the refractive index characteristics of the other retardation layer satisfy nz > nx ═ ny.

In one embodiment, the circularly polarizing plate has an elongated shape, the angle formed by the elongated direction and the absorption axis of the polarizer is-15 ° to 15 °, and the angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer is 35 ° to 55 °.

In one embodiment, the circularly polarizing plate has a rectangular shape, an angle formed between a long side direction and an absorption axis of the polarizer is 75 ° to 105 °, and an angle formed between the absorption axis of the polarizer and a slow axis of the retardation layer is 35 ° to 55 °.

In one embodiment, the length of the long side of the circularly polarizing plate is 1200mm to 1470 mm.

According to another aspect of the present invention, there is provided an organic EL panel. The organic EL panel includes the circularly polarizing plate.

Effects of the invention

According to the present invention, by adjusting the absorption axis of the polarizer so that the angle formed by the absorption axis and the bending direction of the organic EL panel is 75 ° to 105 °, a circularly polarizing plate capable of suppressing the progress of warping even when used for a bent organic EL panel can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view of a circularly polarizing plate according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a circularly polarizing plate according to another embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(definitions of wording and symbols)

The terms and symbols in the present specification are defined as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index becomes maximum (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is a refractive index in the thickness direction.

(2) In-plane retardation (Re)

"Re (. lamda)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of. lamda.nm. For example, "Re (550)" is an in-plane retardation measured by light having a wavelength of 550nm at 23 ℃. When the thickness of the layer (film) is d (nm), Re (λ) is expressed by the following formula: re is determined as (nx-ny) × d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction measured by light having a wavelength of λ nm at 23 ℃. For example, "Rth (550)" is a phase difference in the thickness direction measured by light having a wavelength of 550nm at 23 ℃. When the thickness of the layer (film) is d (nm), Rth (λ) is expressed by the following formula: and Rth is determined as (nx-nz) × d.

(4) Coefficient of Nz

The Nz coefficient is determined by Nz ═ Rth/Re.

A. Circular polarizing plate

Fig. 1 is a schematic cross-sectional view of a circularly polarizing plate according to an embodiment of the present invention. The circularly polarizing plate 100 of the present embodiment includes a polarizer 10 and a retardation layer 20 directly (i.e., without a protective film) bonded to the polarizer 10. Re (550) of the in-plane retardation of the retardation layer 20 is 100nm to 180nm, and the relationship of Re (450) < Re (550) is satisfied. That is, the retardation layer 20 functions as a λ/4 plate and exhibits wavelength dependence of so-called inverse dispersion. The circularly polarizing plate 100 is typically used for a curved organic EL panel, and is typically used for an organic EL panel that has a rectangular shape and is curved so that the side is concave along the longitudinal direction. The absorption axis of the polarizer 10 is adjusted so that the angle formed by the absorption axis and the bending direction of the organic EL panel is 75 DEG to 105 deg. The retardation layer 20 representatively satisfies the relationship of nx > ny in refractive index characteristic, and has a slow axis. The angle formed by the absorption axis of the polarizer 10 and the slow axis of the phase difference layer 20 is preferably 35 ° to 55 °. The phase difference layer 20 is typically subjected to corona treatment or plasma treatment. The circularly polarizing plate 100 typically further includes an easy-adhesion layer (not shown) between the polarizer 10 and the retardation layer 20. The circularly polarizing plate 100 typically includes a protective film 30 on the side of the polarizer 10 opposite to the retardation layer 20. In recent years, in order to improve the sense of realism and the sense of substitution, a display in which a display screen is curved has been proposed. When a conventional circularly polarizing plate is used for a curved organic EL panel mounted on such a display, the circularly polarizing plate can be exposed to a high temperature environment (for example, 80 ℃) by, for example, continuously lighting the organic EL panel. Particularly, in practical use of the organic EL panel, the circularly polarizing plate may be repeatedly exposed to a high temperature environment. As a result, the circularly polarizing plate is irreversibly warped over time, and the optical characteristics of the circularly polarizing plate change with the warping, which may cause a problem such as a change in the reflected color of the organic EL panel. In contrast, the circularly polarizing plate of the present invention, which is adjusted so that the angle formed by the absorption axis of the polarizer and the bending direction of the organic EL panel is 75 ° to 105 °, can suppress the progress of warping even when used for a bent organic EL panel. Thus, the change of the optical characteristics of the circularly polarizing plate can be suppressed.

Fig. 2 is a schematic cross-sectional view of a circularly polarizing plate according to another embodiment of the present invention. The circularly polarizing plate 101 further includes another retardation layer 40 (hereinafter, may be referred to as a 2 nd retardation layer 40) disposed on the side opposite to the polarizer 10 of the retardation layer 20 (hereinafter, may be referred to as a 1 st retardation layer 20). The refractive index characteristic of the 2 nd retardation layer 40 typically satisfies a relationship of nz > nx ═ ny.

In one embodiment, since the circularly polarizing plate has a long shape, the polarizer 10 and the retardation layer 20 also have long shapes. In this case, the angle formed by the long direction of the circularly polarizing plate (the long direction of the polarizer 10) and the absorption axis of the polarizer 10 is preferably-15 ° to 15 °. In another embodiment, the circularly polarizing plate has a rectangular shape, and therefore, the polarizer 10 and the retardation layer 20 also have a rectangular shape. In this case, the angle formed by the long side direction of the circularly polarizing plate (the long side direction of the polarizer 10) and the absorption axis of the polarizer 10 is preferably 75 ° to 105 °. The length of the long side of the rectangular circularly polarizing plate is typically 1200mm to 1470 mm.

The thickness of the circularly polarizing plate of the present invention varies depending on the structure, and is typically about 40 μm to 300 μm. Hereinafter, each layer constituting the circularly polarizing plate of the present invention will be described.

A-1 polarizer

As described above, the absorption axis of the polarizer is adjusted so that the angle formed by the bending direction of the organic EL panel to which the circularly polarizing plate is applied is 75 ° to 105 °. The angle is preferably 80 ° to 100 °, more preferably 85 ° to 95 °, and particularly preferably about 90 ° (the absorption axis is orthogonal to the bending direction).

When the polarizer is in the form of a long strip, the angle formed by the long direction of the polarizer and the absorption axis of the polarizer is preferably-15 ° to 15 °, more preferably-10 ° to 10 °, still more preferably-5 ° to 5 °, and particularly preferably about 0 ° (the absorption axis is parallel to the long direction) as described above. When the polarizer has a rectangular shape, as described above, the angle formed by the long-side direction of the polarizer and the absorption axis of the polarizer is preferably 75 ° to 105 °, more preferably 80 ° to 100 °, still more preferably 85 ° to 95 °, and particularly preferably about 90 ° (the absorption axis is orthogonal to the long-side direction). By adjusting the angle formed by the absorption axis of the polarizer and the longitudinal direction or the longitudinal direction of the polarizer to be within the above range, the angle formed by the absorption axis of the polarizer and the bending direction can be adjusted to a desired angle when the polarizing plate is used for a bent organic EL panel.

As the polarizer, any suitable polarizer can be used. Specific examples thereof include a polarizer obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film to a dyeing treatment and a stretching treatment with a dichroic substance such as iodine or a dichroic dye, and a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a desalted polyvinyl chloride film. From the viewpoint of excellent optical properties, it is preferable to use a polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching the film.

The dyeing with iodine is performed by, for example, immersing a polyvinyl alcohol film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. In addition, dyeing may be performed after stretching. The polyvinyl alcohol film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the polyvinyl alcohol film in water and washing it with water before dyeing, not only dirt or an antiblocking agent on the surface of the polyvinyl alcohol film can be washed off, but also the polyvinyl alcohol film can be swollen to prevent uneven dyeing and the like.

The monomer transmittance of the polarizer is preferably 42.0% to 47.0%, more preferably 43.0% to 46.5%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

The thickness of the polarizer is typically about 1 μm to 80 μm.

A-2. 1 st phase difference layer

The in-plane retardation Re (550) of the 1 st retardation layer is 100nm to 180nm, more preferably 135nm to 155nm, and the 1 st retardation layer can function as a so-called λ/4 plate.

The 1 st retardation layer exhibits the wavelength dependence of so-called inverse dispersion as described above. Specifically, the in-plane retardation satisfies the relationship Re (450) < Re (550). Re (450)/Re (550) is preferably 0.8 or more and less than 1.0.

The 1 st retardation layer shows any suitable index ellipsoid as long as it has a relationship of nx > ny. It is preferable that the refractive index ellipsoid of the 1 st retardation layer exhibits a relationship of nx > ny ≧ nz. Note that "ny ═ nz" includes not only cases where ny and nz are completely equal but also cases where ny and nz are substantially equal. Therefore, ny < nz may be used as long as the effects of the present invention are not impaired. The Nz coefficient of the 1 st retardation layer is preferably 0.9 to 2.0, more preferably 1.0 to 1.5, and further preferably 1.05 to 1.3. By satisfying such a relationship, when the circularly polarizing plate is used for an organic EL panel, a very excellent reflection hue can be achieved.

The thickness of the 1 st retardation layer is preferably 20 to 100. mu.m, more preferably 30 to 90 μm, and still more preferably 40 to 80 μm.

The 1 st retardation layer may be formed of any appropriate retardation film that can achieve adhesion to the polarizer as described above and satisfy the above optical properties. Such a retardation film can be formed of any suitable resin, and specific examples thereof include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, and the like. Preferred examples thereof include polycarbonate resins and polyvinyl acetal resins. The resins for forming the retardation film may be used alone or in combination according to desired characteristics.

As the polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. In one embodiment, a polycarbonate-based resin including an oligofluorene structural unit may be used. Examples of the polycarbonate-based resin containing an oligofluorene structural unit include resins containing a structural unit represented by the following general formula (1) and/or a structural unit represented by the following general formula (2).

(in the above general formula (1) and the above general formula (2), R₅And R₆Independently represents a directly bonded, substituted or unsubstituted alkylene group having 1 to 4 carbon atoms (preferably an alkylene group having 2 to 3 carbon atoms in the main chain); r₇Is a directly bonded, substituted or unsubstituted alkylene group having 1 to 4 carbon atoms (preferably an alkylene group having 1 to 2 carbon atoms in the main chain); r₈～R₁₃Independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 (preferably 1 to 4, more preferably 1 to 2) carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 (preferably 4 to 8, more preferably 4 to 7) carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 (preferably 1 to 4, more preferably 1 to 2) carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 (preferably 1 to 4, more preferably 1 to 2) carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 (preferably 1 to 4, more preferably 1 to 2) carbon atoms, a substituted or unsubstituted acyloxy group having 1 to 10 (preferably 1 to 4, more preferably 1 to 2) carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 (preferably 1 to 4) carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 (preferably 1 to 4) carbon atoms, a substituted or unsubstituted, A sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, a nitro group or a cyano group. Or R may be₈～R₁₃Wherein at least two adjacent groups are bonded to each other to form a ring)

In one embodiment, the fluorene ring contained in the oligofluorene structural unit has R₈～R₁₃All of (A) are hydrogen atoms, or have R₈And/or R₁₃Is any one selected from the group consisting of a halogen atom, an acyl group, a nitro group, a cyano group and a sulfo group and R₉～R₁₂Is a constituent of a hydrogen atom。

Details of polycarbonate-based resins containing an oligofluorene structural unit are described in, for example, Japanese patent laid-open publication No. 2015-212816 and the like. The description of this publication is incorporated herein by reference.

In another embodiment, a polycarbonate resin comprises: a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from at least one dihydroxy compound selected from the group consisting of alicyclic diol, alicyclic dimethanol, diethylene glycol, triethylene glycol, or polyethylene glycol, and alkylene glycol or spiroglycol. Preferably, the polycarbonate resin comprises: a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from alicyclic dimethanol and/or a structural unit derived from diethylene glycol, triethylene glycol, or polyethylene glycol; further preferably comprises: a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from diethylene glycol, triethylene glycol, or polyethylene glycol. The polycarbonate resin may contain a structural unit derived from another dihydroxy compound, if necessary.

The details of the polycarbonate resin which can be suitably used in the present invention are described in, for example, Japanese patent laid-open Nos. 2017-49574, 2014-10291 and 2014-26266, which are incorporated herein by reference.

The glass transition temperature of the polycarbonate resin is preferably 110 to 250 ℃, more preferably 120 to 230 ℃. If the glass transition temperature is too low, heat resistance tends to be poor, dimensional changes may occur after film formation, and image quality of the obtained organic EL display device may be degraded. If the glass transition temperature is too high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature is determined in accordance with JIS K7121 (1987).

The molecular weight of the polycarbonate resin can be expressed by reduced viscosity. The reduced viscosity was measured at a temperature of 20.0 ℃ C. + -. 0.1 ℃ C. using a Ubbelohde viscometer tube using methylene chloride as a solvent and a polycarbonate concentration precisely adjusted to 0.6 g/dL. The lower limit of the reduced viscosity is usually preferably 0.30dL/g, more preferably 0.35dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.20dL/g, more preferably 1.00dL/g, and still more preferably 0.80 dL/g. If the reduced viscosity is less than the lower limit, there is a problem that the mechanical strength of the molded article may decrease. On the other hand, if the reduced viscosity is higher than the above upper limit, problems such as reduction in flowability at the time of molding, and reduction in productivity and moldability may occur.

The retardation film can be obtained by, for example, stretching a film made of the polycarbonate resin. As a method for forming the film from the polycarbonate-based resin, any appropriate molding method can be employed. Specific examples thereof include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP (Fiber Reinforced Plastics) molding, casting coating (for example, casting), calendering, and hot press. Extrusion or cast coating is preferred. This is because the smoothness of the obtained film can be improved, and good optical uniformity can be obtained. The molding conditions may be appropriately set according to the composition or type of the resin used, the properties desired for the retardation film, and the like.

The thickness of the resin film (unstretched film) may be set to any appropriate value depending on the desired thickness of the obtained retardation film, desired optical properties, stretching conditions described below, and the like. Preferably 50 to 300. mu.m.

The stretching may be performed by any suitable stretching method and stretching conditions (e.g., stretching temperature, stretching ratio, and stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinking, and fixed end shrinking may be used alone, or may be used simultaneously or stepwise. The stretching direction may be performed in various directions or dimensions such as a longitudinal direction, a width direction, a thickness direction, and an oblique direction.

By appropriately selecting the stretching method and the stretching conditions, a retardation film having the desired optical properties (e.g., refractive index properties, in-plane retardation, Nz coefficient) can be obtained.

In one embodiment, the retardation film can be produced by uniaxially stretching the resin film or uniaxially stretching the resin film at a fixed end. As a specific example of the fixed-end uniaxial stretching, a method of stretching the resin film in the width direction (transverse direction) while moving the resin film in the longitudinal direction can be cited. The stretch ratio is preferably 1.1 to 3.5 times.

In another embodiment, the retardation film can be produced by continuously obliquely stretching a long resin film in a direction of a predetermined angle with respect to the longitudinal direction. By employing oblique stretching, a long stretched film having an orientation angle (slow axis in the direction of a predetermined angle) at a predetermined angle with respect to the longitudinal direction of the film can be obtained, and for example, roll-to-roll can be realized in the case of lamination with a polarizer, and the production process can be simplified. The predetermined angle may be an angle formed by an absorption axis of the polarizer and a slow axis of the retardation layer in the optical laminate. As described above, the angle is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, still more preferably 42 ° to 48 °, and particularly preferably about 45 °.

As the stretching machine used for the oblique stretching, for example, a tenter type stretching machine capable of giving a feed force, a stretching force or a pulling force at different speeds in the lateral direction and/or the longitudinal direction is cited. The tenter type stretching machine includes a transverse uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, and any suitable stretching machine can be used as long as it can continuously stretch the long resin film obliquely.

By appropriately controlling the respective speeds in the left and right directions in the stretching machine, a retardation film (substantially long retardation film) having the desired in-plane retardation and a slow axis in the desired direction can be obtained.

Examples of the method of oblique stretching include the methods described in Japanese patent application laid-open Nos. 50-83482, 2-113920, 3-182701, 2000-9912, 2002-86554, and 2002-22944.

The stretching temperature of the film may vary depending on the desired in-plane retardation value and thickness of the retardation film, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature is preferably from Tg-30 ℃ to Tg +30 ℃, more preferably from Tg-15 ℃ to Tg +15 ℃, and most preferably from Tg-10 ℃ to Tg +10 ℃. By stretching at such a temperature, a retardation film having appropriate characteristics in the present invention can be obtained. The Tg is a glass transition temperature of a constituent material of the film.

A commercially available film may also be used as the polycarbonate-based resin film. Specific examples of commercially available products include "PURE-ACE WR-S", "PURE-ACE WR-W", "PURE-ACE WR-M" manufactured by Imperial corporation and "NRF" manufactured by Nindon electric corporation. The commercially available film may be used as it is, or may be subjected to secondary processing (for example, stretching treatment or surface treatment) depending on the purpose.

The details of a retardation film usable as the 1 st retardation layer are described in Japanese patent laid-open No. 2014-10292. The description of this publication is incorporated herein by reference.

A-3. protective film

The protective film is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that becomes the main component of the film include cellulose resins such as triacetyl cellulose (TAC), and transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyether sulfone, polysulfone, polystyrene, polynorbornene, polyolefin, (meth) acrylic, and acetate resins. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone resins, ultraviolet-curable resins, and the like can be mentioned. Further, for example, a glassy polymer such as a siloxane polymer can be cited. Further, the polymer film described in Japanese patent application laid-open No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, there can be used: examples of the resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain include resin compositions having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion-molded product of the above resin composition.

The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ℃ or higher, more preferably 120 ℃ or higher, still more preferably 125 ℃ or higher, and particularly preferably 130 ℃ or higher. This is because the durability can be made excellent. The upper limit of the Tg of the (meth) acrylic resin is not particularly limited, but is preferably 170 ℃ or lower from the viewpoint of moldability and the like.

As the (meth) acrylic resin, any suitable (meth) acrylic resin may be used within a range not impairing the effects of the present invention. Examples thereof include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, methyl methacrylate- (meth) acrylic acid ester copolymers, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymers, methyl (meth) acrylate-styrene copolymers (such as MS resins), and alicyclic hydrocarbon group-containing polymers (such as methyl methacrylate-cyclohexyl methacrylate copolymers and methyl methacrylate- (meth) acrylic acid norbornyl ester copolymers). Preferred examples thereof include a poly (meth) acrylic acid C1-6 alkyl ester such as poly (meth) acrylic acid methyl ester. More preferably, the resin composition comprises a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

Specific examples of the (meth) acrylic resin include ACRYPET VH or ACRYPET VRL20A manufactured by mitsubishi yang corporation, (meth) acrylic resins having a ring structure in the molecule described in jp 2004-a 70296, and high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

The (meth) acrylic resin is particularly preferably a (meth) acrylic resin having a lactone ring structure in view of high heat resistance, high transparency, and high mechanical strength.

Examples of the (meth) acrylic resin having a lactone ring structure include (meth) acrylic resins having a lactone ring structure described in Japanese patent laid-open Nos. 2000-230016, 2001-151814, 2002-120326, 2002-254544 and 2005-146084.

The (meth) acrylic resin having a lactone ring structure preferably has a mass average molecular weight (also referred to as a weight average molecular weight) of 1000 to 2000000, more preferably 5000 to 1000000, still more preferably 10000 to 500000, and particularly preferably 50000 to 500000.

The Tg (glass transition temperature) of the (meth) acrylic resin having a lactone ring structure is preferably 115 ℃ or higher, more preferably 125 ℃ or higher, still more preferably 130 ℃ or higher, particularly preferably 135 ℃ or higher, and most preferably 140 ℃ or higher. This is because the durability can be made excellent. The upper limit of Tg of the (meth) acrylic resin having a lactone ring structure is not particularly limited, but is preferably 170 ℃ or lower from the viewpoint of moldability and the like.

In the present specification, the term "(meth) acrylic" refers to acrylic and/or methacrylic.

The surface of the protective film on the side opposite to the polarizer may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-blocking treatment, and antiglare treatment as needed. The thickness of the protective film is typically 5mm or less, preferably 1mm or less, more preferably 1 μm to 500 μm, and still more preferably 5 μm to 150 μm.

A-4. easy adhesive layer

In one embodiment, an easy adhesion layer (not shown) may be provided between the polarizer and the 1 st retardation layer. In the case of providing the easy adhesion layer, the 1 st retardation layer may or may not be subjected to the surface treatment described above. The 1 st retardation layer is preferably subjected to surface treatment. By combining the easy-adhesion layer with the surface treatment, achievement of a desired adhesion between the polarizer and the 1 st retardation layer can be promoted. The easy adhesion layer preferably contains a silane having a reactive functional group. By providing such an easy adhesion layer, achievement of desired adhesion between the polarizer and the 1 st retardation layer can be promoted.

Specific examples of the silane having a reactive functional group include isocyanate-containing alkoxysilanes such as γ -isocyanatopropyltrimethoxysilane, γ -isocyanatopropyltriethoxysilane, γ -isocyanatopropylmethyldiethoxysilane and γ -isocyanatopropylmethyldimethoxysilane; gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, gamma- (2-aminoethyl) aminopropyltrimethoxysilane, gamma- (2-aminoethyl) aminopropylmethyldimethoxysilane, amino group-containing alkoxysilanes such as γ - (2-aminoethyl) aminopropyltriethoxysilane, γ - (2-aminoethyl) aminopropylmethyldiethoxysilane, γ -ureidopropyltrimethoxysilane, N-phenyl- γ -aminopropyltrimethoxysilane, N-benzyl- γ -aminopropyltrimethoxysilane and N-vinylbenzyl- γ -aminopropyltriethoxysilane; mercapto-containing alkoxysilanes such as γ -mercaptopropyltrimethoxysilane, γ -mercaptopropyltriethoxysilane, γ -mercaptopropylmethyldimethoxysilane, and γ -mercaptopropylmethyldiethoxysilane; epoxy group-containing alkoxysilanes such as γ -glycidoxypropyltrimethoxysilane, γ -glycidoxypropyltriethoxysilane, γ -glycidoxypropylmethyldimethoxysilane, β - (3, 4-epoxycyclohexyl) ethyltrimethoxysilane and β - (3, 4-epoxycyclohexyl) ethyltriethoxysilane; carboxyl group-containing alkoxysilanes such as β -carboxyethyltriethoxysilane, β -carboxyethylphenylbis (2-methoxyethoxy) silane, and N- β - (carboxymethyl) aminoethyl- γ -aminopropyltrimethoxysilane; alkoxysilanes containing an ethylenic unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane, gamma-methacryloxypropylmethyldimethoxysilane, and gamma-acryloxypropylmethyltriethoxysilane; halogen group-containing alkoxysilanes such as gamma-chloropropyltrimethoxysilane; isocyanurategroup-containing alkoxysilanes such as tris (trimethoxysilyl) isocyanurate, amino-modified silyl polymers, silylated amino polymers, unsaturated aminosilane complexes, phenylaminolong-chain alkylsilanes, aminosilylated silicones, silylated polyesters, and derivatives thereof. These may be used alone or in combination of two or more.

The silane may be appropriately selected depending on the kind of the 1 st retardation layer, the kind of the adhesive used for bonding the 1 st retardation layer and the polarizer, and the like. For example, when a PVA-based water-based adhesive is used as the adhesive, amino-containing alkoxysilanes such as γ -aminopropyltrimethoxysilane, γ -aminopropyltriethoxysilane, γ -aminopropylmethyldimethoxysilane, γ -aminopropylmethyldiethoxysilane, γ - (2-aminoethyl) aminopropyltrimethoxysilane, γ - (2-aminoethyl) aminopropylmethyldimethoxysilane, γ - (2-aminoethyl) aminopropyltriethoxysilane, γ - (2-aminoethyl) aminopropylmethyldiethoxysilane, γ -ureidopropyltrimethoxysilane, N-phenyl- γ -aminopropyltrimethoxysilane, N-benzyl- γ -aminopropyltrimethoxysilane and N-vinylbenzyl- γ -aminopropyltriethoxysilane are preferable Silanes. This is because an easy adhesion layer having excellent light transmittance, wettability and adhesion is easily formed. Among them, γ - (2-aminoethyl) aminopropyltriethoxysilane and γ - (2-aminoethyl) aminopropylmethyldiethoxysilane are preferable. This is because an easy-adhesion layer having particularly excellent adhesion is easily formed.

The thickness of the easy adhesion layer is 1nm to 100nm, preferably 1nm to 50nm, and more preferably 10nm to 50 nm. By setting the thickness of the easy-adhesion layer to 100nm or less, discoloration, swelling, unevenness, and streaks do not occur even when the obtained circularly polarizing plate is used under high temperature and high humidity. That is, a circularly polarizing plate having extremely excellent appearance-maintaining performance and optical property-maintaining performance under high temperature and high humidity conditions can be obtained.

A-5. 2 nd phase difference layer

As described above, the 2 nd retardation layer satisfies the relationship of nz > nx ═ ny in the refractive index characteristic, and can function as a so-called positive C plate. The circularly polarizing plate having such a 2 nd retardation layer can suppress variations in reflectance and reflected hue in the case of an organic EL panel used for bending.

The retardation Rth (550) in the thickness direction of the 2 nd retardation layer is preferably from-50 nm to-300 nm, more preferably from-70 nm to-250 nm, still more preferably from-90 nm to-200 nm, and particularly preferably from-100 nm to-180 nm. In this case, "nx ═ ny" includes not only a case where nx and ny are exactly equal but also a case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the 2 nd retardation layer may be less than 10 nm.

The 2 nd retardation layer having a refractive index characteristic of nz > nx ═ ny may be formed of any suitable material. The 2 nd retardation layer may preferably comprise a liquid crystal material fixed to a vertical orientation. The liquid crystal material (liquid crystal compound) which can be vertically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the 2 nd retardation layer include methods for forming a liquid crystal compound and a retardation film described in [0020] to [0028] of Japanese patent laid-open publication No. 2002-333642. In this case, the thickness of the 2 nd retardation layer is preferably 0.5 to 10 μm, more preferably 0.5 to 8 μm, and still more preferably 0.5 to 5 μm.

As another preferable specific example, the 2 nd retardation layer may be composed of a retardation film made of a fumaric diester-based resin as described in Japanese patent laid-open No. 2012-32784. In this case, the thickness is preferably 5 μm to 80 μm, and more preferably 10 μm to 50 μm.

A-6. others

In the lamination of each layer constituting the circularly polarizing plate of the present invention, any suitable adhesive layer or adhesive layer may be used. The adhesive layer is typically formed of an acrylic adhesive. The adhesive layer is typically formed of a polyvinyl alcohol adhesive.

Although not shown, an adhesive layer may be provided on the 1 st retardation layer side (in the case of having a 2 nd retardation layer, the 2 nd retardation layer side) of the circularly polarizing plate. By providing an adhesive layer in advance, the optical member can be easily attached to another optical member. A release film is preferably attached to the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive layer is used.

B. Organic EL panel

The organic EL panel of the present invention includes the circularly polarizing plate on the side of visual confirmation. The circularly polarizing plates are laminated such that the retardation layer thereof is on the organic EL panel side (such that the polarizer is on the visual recognition side). The organic EL panel is typically rectangular, and is curved along the longitudinal direction so that the visible side is concave.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method of each property is as follows. Unless otherwise specified, "parts" and "%" in examples and comparative examples are based on weight.

(1) Thickness of

The measurement was carried out using a dial gauge (manufactured by PEACOCK, product name "DG-205 type pds-2").

(2) Phase difference

The measurement was carried out using an Axoscan manufactured by Axometrics. The measurement wavelength was 450nm and 550nm, and the measurement temperature was 23 ℃. A50 mm. times.50 mm piece of the retardation film was cut out and used as a measurement sample.

(3) Warpage test

The circularly polarizing plates obtained in examples and comparative examples were cut to 250mm × 150mm, and the retardation layer side was laminated on a 250mm × 150mm dummy panel (a panel in which a silver reflective film was attached to an acrylic blackboard (manufactured by clasx, japan) having a thickness of about 1 mm) which simulates an organic EL panel. The state of the organic EL panel used for bending was simulated by fixing both short sides of the laminate of the circularly polarizing plate and the dummy panel with a polyimide adhesive tape having a width of 15mm and bending the laminate so that the polarizer side was concave. The amount of warping of the circularly polarizing plate at this time was measured with a metal ruler, and found to be 30 mm. Next, the polarizing plate was heated in a high-temperature oven at 80 ℃ for a predetermined time, and then the amount of warpage of the circularly polarizing plate was measured to obtain the amount of change (increase) from the initial amount of warpage as an index for progression of warpage in the case of a curved organic EL panel.

(4) Reflectance and reflected hue

The circularly polarizing plates obtained in examples and comparative examples were subjected to diffuse reflection measurement (diffuse reflectance and diffuse reflection hue) using a Konica Minolta spectrophotometer "CM-2600 d". Since the measurement object is bent, the measurement is performed with the measurement unit and the light receiving unit separated by 7 mm. The periphery of the measuring portion is covered with a black tape so as not to leave a gap. Diffuse reflection measurements were performed before and after the warping test in (3) above, and the amounts of change in diffuse reflectance and diffuse reflection hue (Δ R% and Δ xy) due to the warping test were obtained.

(diffuse reflectance)

Δ R < 0.01%. O (good)

Δ R.gtoreq.0.01% × (failure)

(diffuse reflection hue)

Δ xy < 0.01O (good)

Δ xy. gtoreq.0.01X (bad)

(5) Transmittance of monomer

The transmittance of the polarizer was measured using an ultraviolet-visible spectrophotometer (product name "V7100" manufactured by JASCO corporation).

< example 1 >

1. Production of polarizer

A PVA film (VF-PE 6000 manufactured by Kuraray Co.) having a thickness of 60 μm was stretched 2.0 times while being immersed in an aqueous solution at 30 ℃ for 30 seconds (swelling treatment). Then, the PVA film was immersed (dyed) in a dyeing bath at a liquid temperature of 30 ℃ for 3.0 times while adjusting the iodine concentration and the immersion time so that the obtained polarizing plate had a predetermined transmittance. In this example, an aqueous iodine solution containing 0.05 parts by weight of iodine and 0.3 parts by weight of potassium iodide per 100 parts by weight of water was immersed for 60 seconds to dye the fabric. Subsequently, the substrate was immersed in a crosslinking bath (an aqueous boric acid solution prepared by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (crosslinking treatment). Then, while immersing the PVA film in an aqueous boric acid solution (an aqueous solution prepared by adding 4 parts by weight of boric acid and 5 parts by weight of potassium iodide to 100 parts by weight of water) having a liquid temperature of 60 ℃, uniaxial stretching (underwater stretching) was performed so that the total stretching ratio became 6.0 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds. Thereafter, the PVA film was immersed in a washing bath (an aqueous solution prepared by adding 4 parts by weight of potassium iodide to 100 parts by weight of water) having a liquid temperature of 30 ℃ (washing treatment).

Thus, a polarizer having a single transmittance of 43% and a thickness of 22 μm was produced.

2. Production of retardation film constituting retardation layer

(preparation of polycarbonate resin film)

Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl]38.06 parts by weight of methane (0.059mol), 53.73 parts by weight of isosorbide (product name "POLYSORB" manufactured by Roquette freres Co., Ltd.), 9.64 parts by weight of 1, 4-cyclohexanedimethanol (cis-trans mixture manufactured by SK chemical Co., Ltd.) (0.067mol), 81.28 parts by weight of diphenyl carbonate (manufactured by Mitsubishi chemical Co., Ltd.) (0.379mol), and 3.83X 10 parts by weight of calcium acetate monohydrate as a catalyst^-4Parts by weight (2.17X 10)^-6mol) was charged into a reaction vessel, and the inside of the reaction apparatus was replaced with nitrogen under reduced pressure. The raw materials were dissolved while stirring at 150 ℃ for about 10 minutes under a nitrogen atmosphere. As the step of the 1 st stage of the reaction, the temperature was raised to 220 ℃ over 30 minutes, and the reaction was carried out at normal pressure for 60 minutes. Subsequently, the pressure was reduced from normal pressure to 13.3kPa over 90 minutes, and phenol produced by maintaining the pressure at 13.3kPa for 30 minutes was extracted to the outside of the reaction system. Next, as the step of the 2 nd stage of the reaction, the temperature of the heat medium was raised to 240 ℃ over 15 minutes, and the pressure was reduced to 0.10kPa or less over 15 minutes, and the produced phenol was extractedAnd (4) discharging to the outside of the reaction system. After a predetermined stirring torque was reached, the reaction was stopped by repressurizing to normal pressure with nitrogen, the resulting polyester carbonate was extruded into water, and the strand was cut to obtain polycarbonate resin pellets.

(production of retardation film)

The film comprising the polycarbonate resin particles was obliquely stretched to obtain a retardation film (thickness: 50 μm, photoelastic coefficient: 16X 10)^-12Pa, wavelength dispersion characteristic Re (450)/Re (550): 0.83). At this time, the stretching direction was set to 45 ° with respect to the longitudinal direction of the film. The stretching ratio is adjusted to 2 to 3 times so that the retardation film exhibits a retardation of lambda/4. In addition, the stretching temperature was set to 148 ℃ (i.e., Tg +5 ℃ of the unstretched modified polycarbonate film).

3. Manufacture of circular polaroid

One surface of the retardation film obtained above was subjected to corona treatment. In another aspect, with respect to formula: NH (NH)₂CH₂NHCH₂CH₂Si(OC₂H₅)₃The silane compound (product name: APZ6601, manufactured by Nippon Unicar Co.) 100 parts was mixed with isopropanol 67 parts to prepare a 60% silane compound solution. The silane compound solution was applied to the corona-treated surface of the phase difference film, and dried at 120 ℃ for 2 minutes to form an easy-adhesion layer having a thickness of 40nm on the phase difference film.

Next, a retardation film having the easy-adhesion layer formed thereon is bonded to one surface of the polarizer via a PVA adhesive so that the easy-adhesion layer is on the polarizer side. At this time, the retardation film and the polarizer were bonded so that the slow axis of the retardation film and the absorption axis of the polarizer were at an angle of 45 °.

A protective film (70 μm thick, product name: DSG-03HL, manufactured by Dainippon printing Co., Ltd.) was bonded to the other surface of the polarizer via a PVA adhesive.

The laminate was dried at 70 ℃ for 10 minutes and cut into a 250mm × 150mm rectangular shape to obtain a circularly polarizing plate. At this time, the laminate was cut so that the longitudinal direction of the circularly polarizing plate was orthogonal to the absorption axis of the polarizer.

The obtained circularly polarizing plate was subjected to the warping test (3). The results are shown in table 1.

< example 2 >

A circularly polarizing plate was produced in the same manner as in example 1, except that a polarizer having a transmittance of 46.5% as a monomer was produced and the above polarizer was used.

< example 3 >

A circularly polarizing plate was produced in the same manner as in example 2, except that a 2 nd retardation film (manufactured by japan printing company, "MCP-N") was bonded to the side of the retardation film opposite to the polarizer via an adhesive. The refractive index characteristic of the 2 nd retardation film satisfies nz > nx ═ ny, and the retardation in the thickness direction Rth (550) is-135 nm.

< comparative example 1 >

A circularly polarizing plate was obtained in the same manner as in example 1, except that a laminate of a protective film, a polarizer, and a retardation film was cut so that the longitudinal direction of the circularly polarizing plate was parallel to the absorption axis of the polarizer.

< comparative example 2 >

A circularly polarizing plate was produced in the same manner as in comparative example 1 except that a polarizer having a transmittance of 46.5% as a monomer was produced and the above polarizer was used.

< comparative example 3 >

A circularly polarizing plate was produced in the same manner as in comparative example 2, except that a 2 nd retardation film (manufactured by japan printing company, "MCP-N") was bonded to the side opposite to the polarizer via an adhesive.

< comparative example 4 >

A circularly polarizing plate was produced in the same manner as in comparative example 1 except that a polarizer having a transmittance of 47.7% as a monomer was produced and the above polarizer was used.

< comparative example 5 >

A circularly polarizing plate was produced in the same manner as in comparative example 1, except that a cycloolefin resin film (product of Zeon Corporation, "ZD-12") was used as the retardation film.

[ Table 1]

As is clear from table 1, the circularly polarizing plates of comparative examples 1 to 5 were warped by heating in a bent state, and the optical characteristics were changed, but the circularly polarizing plates of examples 1 to 3 were not warped even when heated in a bent state, and the optical characteristics were not changed.

Industrial applicability

The circularly polarizing plate of the present invention is suitably used for a curved organic EL device.

Description of the symbols

10 polarizer

20 st phase difference layer

30 protective film

40 nd 2 nd phase difference layer

100 circular polarizer

101 circular polarizer.

Claims

1. A curved organic EL panel comprising a circularly polarizing plate having a polarizer and a retardation layer directly bonded to the polarizer,

re (550) of the in-plane retardation of the retardation layer is 100nm to 180nm, and the relationship of Re (450) < Re (550) is satisfied,

the absorption axis of the polarizer is adjusted so that the angle formed by the absorption axis and the bending direction of the organic EL panel is 75-105 degrees,

re (450) and Re (550) represent in-plane retardation measured at 23 ℃ at wavelengths of 450nm and 550nm, respectively.

2. The curved organic EL panel having a circularly polarizing plate according to claim 1, wherein the retardation layer is subjected to corona treatment or plasma treatment.

3. The curved organic EL panel provided with a circularly polarizing plate according to claim 1 or 2, further comprising an easy adhesion layer between the polarizer and the retardation layer.

4. The curved organic EL panel having a circularly polarizing plate according to any one of claims 1 to 3, wherein the circularly polarizing plate further has another retardation layer disposed on the side opposite to the polarizer of the retardation layer, and the refractive index characteristic of the other retardation layer satisfies nz > nx ═ ny.

5. The curved organic EL panel provided with a circularly polarizing plate according to any one of claims 1 to 4, wherein the circularly polarizing plate has an elongated shape,

the angle formed by the strip direction and the absorption axis of the polarizer is-15 to 15 degrees,

the angle formed by the absorption axis of the polarizer and the slow axis of the phase difference layer is 35-55 degrees.

6. The curved organic EL panel provided with a circularly polarizing plate according to any one of claims 1 to 4, wherein the circularly polarizing plate has a rectangular shape,

the angle formed by the long side direction and the absorption axis of the polarizer is 75-105 degrees,

7. The curved organic EL panel having a circularly polarizing plate according to claim 6, wherein the length of the long side is 1200mm to 1470 mm.