WO2022185802A1

WO2022185802A1 - Circular polarizing plate and image display device using same

Info

Publication number: WO2022185802A1
Application number: PCT/JP2022/003086
Authority: WO
Inventors: 遼太藤野; 寛友久; 洋平山岡; 聡司三田
Original assignee: 日東電工株式会社
Priority date: 2021-03-04
Filing date: 2022-01-27
Publication date: 2022-09-09
Also published as: JP2022134862A; CN116848443A; TW202246818A; KR20230151987A

Abstract

Provided is a thin circular polarizing plate in which phase difference changes in high temperature environments are suppressed, and the phenomenon whereby the reflection hue appears red is suppressed. This circular polarizing plate comprises a polarizing plate, a first liquid crystal orientation fixed layer, a second liquid crystal orientation fixed layer, and a protection layer, in that order from the viewing side, wherein the moisture permeability of the protection layer is 920 (g/m2・ 24 h) or less.

Description

Circularly polarizing plate and image display device using the same

The present invention relates to a circularly polarizing plate and an image display device using the same.

With the spread of thin displays, displays equipped with organic EL panels have been proposed. Since the organic EL panel has a highly reflective metal layer, problems such as reflection of external light and reflection of the background tend to occur. Therefore, it is known to prevent these problems by providing a circularly polarizing plate having a λ/4 retardation film on the viewing side.

In recent years, as displays have become thinner, there has been a demand for thinner circularly polarizing plates. However, such a thin circularly polarizing plate has problems such as that the retardation of the retardation film changes when exposed to a high-temperature environment for a long period of time, and that the reflected hue is visually perceived as red.

Japanese Patent No. 3325560

The present invention has been made to solve the above-described conventional problems, and its main purpose is to suppress the change in phase difference in a high-temperature environment, and to suppress the phenomenon that the reflected hue is viewed as red. An object of the present invention is to provide a circularly polarizing plate.

The circularly polarizing plate of the present invention comprises a polarizing plate, a first liquid crystal alignment fixed layer, a second liquid crystal alignment fixed layer and a protective layer in this order from the viewing side, and the protective layer has a moisture permeability of 920 (g / m ² ·24 hr) or less.
In one embodiment, the in-plane retardation Re (550) of the first liquid crystal alignment fixed layer is 100 nm to 180 nm, and the relationship Re (450) < Re (550) < Re (650) Fulfill.
In one embodiment, the second liquid crystal alignment fixed layer exhibits a refractive index characteristic of nz>nx=ny.
In one embodiment, the protective layer contains an epoxy-based resin or an acrylic-based resin, and the protective layer is a solidified product or a heat-cured product of a coating film of an organic solvent solution of the resin.
In one embodiment, the protective layer has a glass transition temperature of 85° C. or higher, and the resin has a weight average molecular weight Mw of 25,000 or higher.
In one embodiment, the circularly polarizing plate of the present invention comprises at least one additional protective layer between the polarizing plate and the first liquid crystal alignment fixed layer.
In one embodiment, the thickness of the circularly polarizing plate of the present invention is 100 µm or less.
An image display device is provided in another aspect of the present invention. This image display device includes the circularly polarizing plate.

According to the embodiment of the present invention, the polarizing plate, the first liquid crystal alignment fixed layer, the second liquid crystal alignment fixed layer, and the protective layer are provided in this order from the viewing side, and the protective layer has a moisture permeability of 920 (g /m ² ·24 hr) or less, it is possible to obtain a thin circularly polarizing plate in which a change in retardation in a high-temperature environment is suppressed and a phenomenon in which the reflected hue is visually perceived as red is suppressed.

1 is a schematic cross-sectional view of a circular polarizer according to one embodiment of the invention; FIG.

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

(Definition of terms and symbols)
Definitions of terms and symbols used herein are as follows.
(1) refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and "ny" is the in-plane direction orthogonal to the slow axis (i.e., fast axis direction) and "nz" is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re(λ)” is an in-plane retardation measured at 23° C. with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Thickness direction retardation (Rth)
“Rth(λ)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of λ nm. For example, “Rth(550)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is obtained by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to a reference direction. Thus, for example, "45°" means ±45°.

A. Overall Configuration of Circularly Polarizing Plate FIG. 1 is a schematic cross-sectional view of a circularly polarizing plate according to one embodiment of the present invention. The illustrated circularly polarizing plate 100 has a polarizing plate 10, a first liquid crystal alignment fixed layer 20, a second liquid crystal alignment fixed layer 30, and a protective layer 40 in this order from the viewing side. The polarizing plate 10 typically includes a polarizer 11 and a polarizer protective film 12 arranged on the viewing side of the polarizer 11 . Depending on the purpose, another polarizer protective film (not shown) may be provided on the opposite side of the polarizer 11 from the viewing side. The first liquid crystal alignment fixed layer 20 is typically a retardation layer having a circularly polarized light function or an elliptically polarized light function.

In the embodiment of the present invention, the moisture permeability of the protective layer 40 is 920 (g/m ² ·24 hr) or less. When the moisture permeability of the protective layer is within such a range, a thin circularly polarizing plate can be realized in which a change in retardation in a high-temperature environment is suppressed and a phenomenon in which the reflected hue is visually perceived as red is suppressed.

In one embodiment of the present invention, another protective layer may be provided between the polarizing plate and the first liquid crystal alignment fixed layer. As for another protective layer, only one layer may be provided between the polarizing plate and the first liquid crystal alignment fixed layer, or two layers may be provided.

The circularly polarizing plate may further contain other retardation layers. Other optical properties of the retardation layer (for example, refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. can be appropriately set according to the purpose.

Practically, the adhesive layer 50 may be provided as the outermost layer on the surface of the protective layer 40 opposite to the second liquid crystal alignment fixed layer 30 . By providing an adhesive layer, the circularly polarizing plate can be attached to an image display device (substantially, an image display panel). Furthermore, it is preferable that a release film is temporarily attached to the surface of the pressure-sensitive adhesive layer until the circularly polarizing plate is used. Temporarily attaching the release film protects the pressure-sensitive adhesive layer and enables roll formation of the circularly polarizing plate.

The thickness of the circularly polarizing plate is preferably 100 µm or less, more preferably 80 µm or less, even more preferably 70 µm or less, and particularly preferably 60 µm or less. A lower limit for the total thickness can be, for example, 40 μm. The thickness of the circularly polarizing plate means the total thickness from the polarizing plate to the pressure-sensitive adhesive layer. According to embodiments of the present invention, extremely thin circular polarizers can be realized.

The circularly polarizing plate may be sheet-shaped or elongated. As used herein, the term "long shape" means an elongated shape whose length is sufficiently long relative to its width, for example, an elongated shape whose length is 10 times or more, preferably 20 times or more, its width. include. A long circularly polarizing plate can be wound into a roll.

Below, the components of the circularly polarizing plate will be described in more detail. As for the pressure-sensitive adhesive layer, a structure well-known in the industry can be employed, so the detailed structure of the pressure-sensitive adhesive layer is omitted.

B. Polarizing Plate The polarizing plate includes a polarizer and a polarizer protective film disposed on at least one side of the polarizer.

B-1. Polarizer Any appropriate polarizer can be employed as the polarizer. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene/vinyl acetate copolymer films. In addition, oriented polyene films such as those dyed with dichroic substances such as iodine and dichroic dyes and stretched, and dehydrated PVA and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used because of its excellent optical properties.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial drawing is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or may be performed while dyeing. Moreover, you may dye after extending|stretching. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only can dirt and anti-blocking agents on the surface of the PVA-based film be washed away, but also the PVA-based film can be swollen to remove uneven dyeing. can be prevented.

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material is obtained, for example, by applying a PVA-based resin solution to the resin base material and drying the resin base material. forming a PVA-based resin layer thereon to obtain a laminate of a resin substrate and a PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, stretching may further include stretching the laminate in air at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained resin substrate/polarizer laminate may be used as it is (that is, the resin substrate may be used as a polarizer protective film), or the resin substrate may be peeled off from the resin substrate/polarizer laminate. Any suitable polarizer protective film may be laminated on the release surface according to the purpose. Details of such a polarizer manufacturing method are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 (Patent No. 5414738) and Japanese Patent No. 6470455. The publication is incorporated herein by reference in its entirety.

The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm to 22 μm, even more preferably 1 μm to 12 μm, particularly preferably 3 μm to 12 μm. If the thickness of the polarizer is within such a range, it is possible to satisfactorily suppress curling during heating, and obtain excellent durability in appearance during heating.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is 43.0% to 46.0%, preferably 44.5% to 46.0%, as described above. The degree of polarization of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, still more preferably 99.9% or higher.

B-2. Polarizer Protective Film The polarizer protective film is formed of any appropriate film. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based resins. , polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based transparent resins. Thermosetting resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone, or ultraviolet curable resins may also be used. In addition, for example, a glassy polymer such as a siloxane-based polymer can also be used. Further, polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. Materials for this film include, for example, a 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 nitrile group in a side chain. can be used, for example, a resin composition comprising an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extrudate of the resin composition.

As will be described later, the circularly polarizing plate is typically arranged on the viewing side of the image display device, and the polarizer protective film 12 is typically arranged on the viewing side. Therefore, the polarizer protective film 12 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-sticking treatment, anti-glare treatment, etc., if necessary. Further/or, the polarizer protective film may optionally be treated to improve visibility when viewed through polarized sunglasses (typically, imparting an (elliptically) polarizing function, super imparting a high retardation) may be applied. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the circularly polarizing plate can be suitably applied to an image display device that can be used outdoors.

Another polarizer protective film is preferably optically isotropic in one embodiment. As used herein, “optically isotropic” means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is −10 nm to +10 nm. Say. Preferred materials for forming another polarizer protective film include cyclic olefin-based (eg, polynorbornene-based), cellulose-based resins (eg, TAC), and acrylic-based resins.

The thickness of the polarizer protective film is preferably 10 μm to 50 μm, more preferably 10 μm to 30 μm. In addition, when the surface treatment is performed, the thickness of the outer polarizer protective film 12 is the thickness including the thickness of the surface treatment layer.

C. First liquid crystal alignment fixed layer The first liquid crystal alignment fixed layer 20 uses a liquid crystal compound, so that the difference between nx and ny can be significantly increased compared to a non-liquid crystal material. The thickness of the first liquid crystal alignment fixed layer for obtaining retardation can be significantly reduced. As a result, the thickness of the circularly polarizing plate can be further reduced. As used herein, the term “liquid crystal alignment fixed layer” refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. In addition, the "alignment fixed layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer as described later. In the present embodiment, typically, rod-like liquid crystal compounds are aligned in the slow axis direction of the first liquid crystal alignment fixed layer (homogeneous alignment).

The first liquid crystal alignment fixed layer typically exhibits a refractive index characteristic of nx>ny=nz. The first liquid crystal alignment fixed layer is typically provided to impart antireflection properties to the polarizing plate and can function as a λ/4 plate. In this case, the in-plane retardation Re(550) of the first liquid crystal alignment fixed layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, still more preferably 130 nm to 160 nm. Here, "ny=nz" includes not only the case where ny and nz are completely equal but also the case where they are substantially equal. Therefore, ny>nz or ny<nz may be satisfied within a range that does not impair the effects of the present invention.

The Nz coefficient of the first liquid crystal alignment fixed layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained circularly polarizing plate is used in an image display device, a very excellent reflection hue can be achieved.

The first liquid crystal alignment fixed layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. and a flat wavelength dispersion characteristic in which the retardation value hardly changes even with the wavelength of the measurement light. In one embodiment, the first liquid crystal alignment fixed layer preferably exhibits reverse dispersion wavelength characteristics. That is, the first liquid crystal alignment fixed layer preferably satisfies the relationship Re(450)<Re(550)<Re(650). In this case, Re(450)/Re(550) of the first liquid crystal alignment fixed layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection properties can be achieved.

The angle θ between the slow axis of the first liquid crystal alignment fixed layer and the absorption axis of the polarizer 11 is preferably 40° to 50°, more preferably 42° to 48°, and more preferably about 45°. If the angle θ is in such a range, by using the λ/4 plate as the first liquid crystal alignment fixed layer as described above, very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics ) can be obtained.

The thickness of the first liquid crystal alignment fixed layer is preferably 0.5 μm to 7 μm, more preferably 1 μm to 5 μm. By using a liquid crystal compound, it is possible to realize an in-plane retardation equivalent to that of a resin film with a thickness much thinner than that of a resin film.

Liquid crystal compounds include, for example, liquid crystal compounds whose liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. Either lyotropic or thermotropic mechanism may be used to develop the liquid crystallinity of the liquid crystal compound. The liquid crystal polymer and liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (that is, curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, the alignment state can be fixed by polymerizing or cross-linking the liquid crystal monomers. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by cross-linking, but these are non-liquid crystalline. Therefore, the formed first liquid crystal orientation fixed layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to, for example, temperature changes peculiar to liquid crystalline compounds. As a result, the first liquid crystal alignment fixed layer becomes a liquid crystal alignment fixed layer that is not affected by temperature changes and has extremely excellent stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs depending on the type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

Any appropriate liquid crystal monomer can be adopted as the liquid crystal monomer. For example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such polymerizable mesogenic compounds include LC242 (trade name) available from BASF, E7 (trade name) available from Merck, and LC-Sillicon-CC3767 (trade name) available from Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The liquid crystal alignment fixed layer is obtained by subjecting the surface of a predetermined base material to alignment treatment, coating the surface with a coating liquid containing a liquid crystal compound, and orienting the liquid crystal compound in the direction corresponding to the alignment treatment, and It can be formed by fixing the state. In one embodiment, the substrate is any suitable resin film, and the liquid crystal alignment solidified layer formed on the substrate can be transferred to the surface of an adjacent layer (eg, protective layer).

Any appropriate orientation treatment can be adopted as the orientation treatment. Specific examples include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of physical orientation treatment include magnetic orientation treatment and electric field orientation treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photo-alignment treatment. Arbitrary appropriate conditions can be adopted as the processing conditions for various alignment treatments depending on the purpose.

　The alignment of the liquid crystal compound is performed by processing at a temperature that exhibits a liquid crystal phase depending on the type of liquid crystal compound. By performing such a temperature treatment, the liquid crystal compound assumes a liquid crystal state, and the liquid crystal compound is aligned in accordance with the orientation treatment direction of the surface of the base material.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the orientation state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the alignment fixed layer are described in JP-A-2006-163343. The description of the publication is incorporated herein by reference.

D. Second Liquid Crystal Alignment Fixed Layer The second liquid crystal alignment fixed layer can be a so-called positive C plate, which preferably exhibits refractive index characteristics of nz>nx=ny. By using a positive C plate as the second liquid crystal orientation fixed layer, it is possible to satisfactorily prevent reflection in oblique directions and widen the viewing angle of the antireflection function. In this case, the thickness direction retardation Rth (550) of the second liquid crystal alignment fixed layer is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, further preferably −90 nm to −200 nm, particularly preferably is -100 nm to -180 nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the second liquid crystal alignment fixed layer may be less than 10 nm.

The second liquid crystal alignment fixed layer having a refractive index characteristic of nz>nx=ny can be made of any suitable material. The second liquid crystal alignment fixed layer preferably consists of a film containing a liquid crystal material fixed in homeotropic alignment. A liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method for forming the liquid crystal compound and the liquid crystal alignment fixed layer include the liquid crystal compound and the liquid crystal alignment fixed layer described in [0020] to [0028] of JP-A-2002-333642 (Patent No. 4174192). A method for forming the In this case, the thickness of the second liquid crystal alignment fixing layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, still more preferably 0.5 μm to 5 μm.

E. Protective Layer As described above, the protective layer is disposed between the second liquid crystal alignment solidifying layer and the adhesive layer. Furthermore, the moisture permeability of the protective layer is 920 g/m ² ·24 hr or less, preferably 900 g/m ² ·24 hr or less, more preferably 880 g/m ² ·24 hr or less. The lower limit of the moisture permeability of the protective layer can be, for example, 700 g/m ² ·24 hr. The protective layer is arranged between the second liquid crystal alignment solidified layer and the adhesive layer, and the moisture permeability of the protective layer is in such a range, whereby the retardation change in a high temperature environment is suppressed, and , a thin circularly polarizing plate can be obtained in which the phenomenon that the reflected hue is visually perceived as red is suppressed.

The protective layer is a solidified or thermoset coating film of an organic solvent solution of a resin. With such a configuration, the thickness can be made very thin (for example, 10 μm or less). The thickness of the protective layer is preferably 0.01 μm to 5 μm, more preferably 0.02 μm to 3 μm, still more preferably 0.03 μm to 1 μm, and particularly preferably 0.04 μm to 0.6 μm. . Furthermore, with such a configuration, the protective layer can be directly formed on the adjacent layer (for example, the liquid crystal alignment solidifying layer) (that is, without an adhesive layer or a pressure-sensitive adhesive layer). According to the embodiment of the present invention, as described above, the polarizer, the liquid crystal alignment fixing layer and the protective layer are very thin, and the adhesive layer or adhesive layer for laminating the protective layer can be omitted. , the total thickness of the circular polarizer can be made very thin. Furthermore, such a protective layer has the advantage of being excellent in humidification durability because it has lower hygroscopicity and moisture permeability than a solidified aqueous coating film such as an aqueous solution or aqueous dispersion. As a result, it is possible to realize a circularly polarizing plate having excellent durability and capable of maintaining optical properties even in a high-temperature and high-humidity environment. In addition, such a protective layer can suppress adverse effects on the polarizing plate (polarizer) due to ultraviolet irradiation, compared to, for example, a cured product of an ultraviolet curable resin. The protective layer is preferably a solidified product of a coating film of an organic solvent solution of a resin. The solidified product shrinks less during film formation than the cured product, and since it does not contain residual monomers, etc., deterioration of the film itself is suppressed. Adverse effects can be suppressed.

Further, the resin constituting the protective layer has a glass transition temperature (Tg) of 85°C or higher and a weight average molecular weight Mw of 25000 or higher. When the Tg and Mw of the resin are in such ranges, the synergistic effect with the effect of forming the protective layer from the solidified or thermoset coating film of the organic solvent solution of the resin results in a very thin film. Nevertheless, migration of iodine in the polarizer to the image display cell can be remarkably suppressed. The Tg of the resin is more preferably 90° C. or higher, still more preferably 100° C. or higher, particularly preferably 110° C. or higher, and most preferably 120° C. or higher. The upper limit of Tg can be, for example, 200°C. Moreover, Mw of the resin is more preferably 30,000 or more, still more preferably 35,000 or more, and particularly preferably 40,000 or more. The upper limit of Mw can be 150,000, for example.

Furthermore, the protective layer adjacent to the liquid crystal alignment fixed layer may further contain an isocyanate compound in addition to the above resin. Isocyanate compounds include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and derivatives thereof (eg, modified products and adducts). The isocyanate compounds may be used alone or in combination. The content ratio of the resin and the isocyanate compound (resin/isocyanate compound) is 95/5 to 10/90 as described above. The content ratio (resin/isocyanate compound) is, for example, 95/5 to 50/50, for example, 90/10 to 60/40, for example, 85/15 to 70/30, or for example, 85/15 to 75/25. may The content ratio (resin/isocyanate compound) may also be for example from 40/60 to 5/95, also for example from 30/70 to 5/95, also for example from 20/80 to 10/90. With such a configuration, peeling between the protective layer and the liquid crystal alignment fixing layer can be significantly suppressed.

The resin constituting the protective layer is preferably any appropriate thermoplastic as long as it can form a solidified product or a thermoset product of a coating film of an organic solvent solution and has the Tg and Mw as described above. Resins or thermosetting resins can be used. Thermoplastic resins are preferred. Examples of thermoplastic resins include epoxy resins and acrylic resins. An epoxy resin and an acrylic resin may be used in combination. Representative examples of epoxy-based resins and acrylic-based resins that can be used for the protective layer are described below.

<Epoxy resin>
As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. By using an epoxy resin having an aromatic ring as the epoxy resin, adhesion to the polarizer can be improved when the protective layer is arranged adjacent to the polarizer. Furthermore, when the adhesive layer is arranged adjacent to the protective layer, the anchoring force of the adhesive layer can be improved. Examples of epoxy resins having an aromatic ring include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin; phenol novolak epoxy resin, cresol novolak epoxy resin, hydroxybenzaldehyde phenol novolak Novolac type epoxy resins such as epoxy resins; polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, epoxidized polyvinylphenol, naphthol type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin and the like. Bisphenol A type epoxy resin, biphenyl type epoxy resin, and bisphenol F type epoxy resin are preferably used. Epoxy resins may be used alone or in combination of two or more.

<Acrylic resin>
Acrylic resins typically contain, as a main component, repeating units derived from (meth)acrylic acid ester monomers having a linear or branched structure. As used herein, (meth)acryl refers to acryl and/or methacryl. The acrylic resin may contain repeating units derived from any appropriate comonomers depending on the purpose. Examples of copolymerizable monomers (copolymerizable monomers) include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. By appropriately setting the kind, number, combination and copolymerization ratio of the monomer units, an acrylic resin having the predetermined Tg and Mw can be obtained.

<Boron-containing acrylic resin>
In one embodiment, the acrylic resin is more than 50 parts by weight of a (meth)acrylic monomer and more than 0 parts by weight and less than 50 parts by weight of the monomer represented by formula (1) (hereinafter , may be referred to as a copolymer monomer) and a copolymer obtained by polymerizing a monomer mixture (hereinafter sometimes referred to as a boron-containing acrylic resin) including:

(Wherein, X is a vinyl group, a (meth)acryl group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, a hydroxyl group, an amino group, an aldehyde group, and a group consisting of a carboxyl group Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring).

A boron-containing acrylic resin typically has a repeating unit represented by the following formula. By polymerizing a monomer mixture containing a copolymerizable monomer represented by formula (1) and a (meth)acrylic monomer, the boron-containing acrylic resin has a substituent containing boron in the side chain (e.g., repeating unit k in the following formula). Thereby, when the protective layer is arranged adjacent to the polarizer, the adhesion to the polarizer can be improved. The boron-containing substituent may be included continuously (that is, in blocks) in the boron-containing acrylic resin, or may be included randomly.

(Wherein, R6 represents an arbitrary functional group, and j and k represent integers of ¹ or more).

<(Meth) acrylic monomer>
Any appropriate (meth)acrylic monomer can be used as the (meth)acrylic monomer. Examples thereof include (meth)acrylic acid ester-based monomers having a linear or branched structure and (meth)acrylic acid ester-based monomers having a cyclic structure.

Examples of (meth)acrylic ester-based monomers having a linear or branched structure include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and (meth)acrylic acid. isopropyl, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, methyl 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate and the like. . Preferably, methyl (meth)acrylate is used. The (meth)acrylic acid ester-based monomers may be used alone or in combination of two or more.

Examples of (meth)acrylic ester-based monomers having a cyclic structure include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, ( meth)dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, biphenyl (meth)acrylate, o-biphenyloxyethyl (meth)acrylate, o-biphenyloxyethoxy Ethyl (meth)acrylate, m-biphenyloxyethyl acrylate, p-biphenyloxyethyl (meth)acrylate, o-biphenyloxy-2-hydroxypropyl (meth)acrylate, p-biphenyloxy-2-hydroxypropyl (meth)acrylate , m-biphenyloxy-2-hydroxypropyl (meth)acrylate, N-(meth)acryloyloxyethyl-o-biphenyl=carbamate, N-(meth)acryloyloxyethyl-p-biphenyl=carbamate, N-(meth) Acryloyloxyethyl-m-biphenyl=carbamate, biphenyl group-containing monomers such as o-phenylphenol glycidyl ether acrylate, terphenyl (meth)acrylate, o-terphenyloxyethyl (meth)acrylate and the like. Preferably, 1-adamantyl (meth)acrylate and dicyclopentanyl (meth)acrylate are used. A polymer having a high glass transition temperature can be obtained by using these monomers. These monomers may be used alone or in combination of two or more.

A silsesquioxane compound having a (meth)acryloyl group may also be used instead of the (meth)acrylic acid ester-based monomer. By using a silsesquioxane compound, an acrylic polymer having a high glass transition temperature can be obtained. Silsesquioxane compounds are known to have various skeleton structures, such as cage structures, ladder structures, and random structures. The silsesquioxane compound may have only one of these structures, or may have two or more. Silsesquioxane compounds may be used alone or in combination of two or more.

As the silsesquioxane compound containing a (meth)acryloyl group, for example, Toagosei Co., Ltd. SQ series MAC grade and AC grade can be used. MAC grade is a silsesquioxane compound containing a methacryloyl group, and specific examples thereof include MAC-SQ TM-100, MAC-SQ SI-20, MAC-SQ HDM, and the like. AC grade is a silsesquioxane compound containing an acryloyl group, and specific examples thereof include AC-SQ TA-100 and AC-SQ SI-20.

The (meth)acrylic monomer is used in an amount exceeding 50 parts by weight with respect to 100 parts by weight of the monomer mixture.

<Comonomer>
A monomer represented by the above formula (1) is used as the comonomer. By using such a comonomer, a substituent containing boron is introduced into the side chain of the resulting polymer. Comonomers may be used alone or in combination of two or more.

As the aliphatic hydrocarbon group in the above formula (1), a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, 3 to 3 carbon atoms which may have a substituent 20 cyclic alkyl groups and alkenyl groups having 2 to 20 carbon atoms. Examples of the aryl group include an optionally substituted phenyl group having 6 to 20 carbon atoms and a naphthyl group having 10 to 20 carbon atoms which may have a substituent. The heterocyclic group includes a 5- or 6-membered ring group containing at least one optionally substituted heteroatom. R ¹ and R ² may be linked together to form a ring. R ¹ and R ² are preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom.

Reactive groups contained in the functional group represented by X include vinyl group, (meth)acryl group, styryl group, (meth)acrylamide group, vinyl ether group, epoxy group, oxetane group, hydroxyl group, amino group, aldehyde group, and at least one selected from the group consisting of carboxyl groups. Preferably, the reactive groups are (meth)acryl and/or (meth)acrylamide groups. By having these reactive groups, the adhesion to the polarizer can be further improved when the protective layer is arranged adjacent to the polarizer.

In one embodiment, the functional group represented by X is preferably a functional group represented by ZY-. Here, Z is selected from the group consisting of a vinyl group, a (meth)acryl group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, a hydroxyl group, an amino group, an aldehyde group, and a carboxyl group. and Y represents a phenylene group or an alkylene group.

Specifically, the following compounds can be used as the comonomer.

The comonomer is used in a content of more than 0 parts by weight and less than 50 parts by weight with respect to 100 parts by weight of the monomer mixture. It is preferably 0.01 to 50 parts by weight, more preferably 0.05 to 20 parts by weight, even more preferably 0.1 to 10 parts by weight, and particularly preferably 0.1 part by weight to 10 parts by weight. 5 to 5 parts by weight.

<Acrylic resin containing lactone ring, etc.>
In another embodiment, the acrylic resin has a repeating unit containing a ring structure selected from lactone ring units, glutaric anhydride units, glutarimide units, maleic anhydride units and maleimide (N-substituted maleimide) units. . As for the repeating unit containing a ring structure, only one type may be included in the repeating unit of the acrylic resin, or two or more types may be included.

The lactone ring unit is preferably represented by the following general formula (2):

In general formula (2), R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. In addition, the organic residue may contain an oxygen atom. The acrylic resin may contain only a single lactone ring unit, or may contain a plurality of lactone ring units in which R ² , R ³ and R ⁴ in the general formula (2) are different. . An acrylic resin having a lactone ring unit is described, for example, in JP-A-2008-181078, and the description of the publication is incorporated herein by reference.

The glutarimide unit is preferably represented by the following general formula (3):

In general formula (3), R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms; R ¹³ is an alkyl group having 1 to 18 carbon atoms; or an aryl group having 6 to 10 carbon atoms. In general formula (3), preferably R ¹¹ and R ¹² are each independently hydrogen or methyl, and R ¹³ is hydrogen, methyl, butyl or cyclohexyl. More preferably, R ¹¹ is a methyl group, R ¹² is hydrogen and R ¹³ is a methyl group. The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units in which R ¹¹ , R ¹² and R ¹³ in the general formula (3) are different. . Acrylic resins having a glutarimide unit, for example, JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328334, JP-A-2006-337491 (Patent No. 4695439), It is described in JP-A-2006-337492, JP-A-2006-337493 (Japanese Patent No. 4686261), and JP-A-2006-337569, and the descriptions of these publications are incorporated herein by reference. As for the glutaric anhydride unit, the above explanation regarding the glutarimide unit applies, except that the nitrogen atom substituted by R ¹³ in the general formula (3) becomes an oxygen atom.

Regarding the maleic anhydride unit and the maleimide (N-substituted maleimide) unit, the structure is specified from the name, so a specific description is omitted.

The content of repeating units containing a ring structure in the acrylic resin is preferably 1 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, still more preferably 20 mol% to 30 mol%. In addition, acrylic resin contains the repeating unit derived from said (meth)acrylic-type monomer as a main repeating unit.

The protective layer can be formed by applying an organic solvent solution of the resin as described above to form a coating film, and solidifying or thermally curing the coating film. Any appropriate organic solvent that can dissolve or uniformly disperse the acrylic resin can be used as the organic solvent. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed.

The solution may be applied to any appropriate base material, or may be applied to an adjacent layer (eg, liquid crystal alignment and solidification layer). When the solution is applied to the substrate, the solidified product (protective layer) of the coating film formed on the substrate is transferred to the adjacent layer. When the solution is applied to the adjacent layer, the protective layer is directly formed on the adjacent layer by drying (solidifying) the applied film. Preferably, the solution is applied to the adjacent layer to form the protective layer directly on the adjacent layer. With such a configuration, the adhesive layer or adhesive layer required for transfer can be omitted, so the circularly polarizing plate can be made even thinner. Any appropriate method can be adopted as a method of applying the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating, etc.).

A protective layer can be formed by solidifying or thermally curing the coating film of the solution. The heating temperature for solidification or heat curing is preferably 100°C or less, more preferably 50°C to 70°C. If the heating temperature is within this range, it is possible to prevent adverse effects on the polarizer. The heating time can vary depending on the heating temperature. The heating time can be, for example, 1 minute to 10 minutes.

The protective layer (substantially an organic solvent solution of the above resin) may contain any appropriate additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; Reinforcing materials such as carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; inorganic pigments , organic pigments, colorants such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; The type, number, combination, addition amount, etc. of additives can be appropriately set according to the purpose.

F. Image Display Device The circularly polarizing plate described in the above items A to E can be applied to an image display device. Accordingly, embodiments of the present invention include image display devices using such circularly polarizing plates. Typical examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices). An image display device according to an embodiment of the present invention includes the circularly polarizing plate according to the above items A to E on the viewing side thereof. The circularly polarizing plate is laminated so that the liquid crystal alignment fixed layer is on the image display cell (for example, liquid crystal cell, organic EL cell, inorganic EL cell) side (so that the polarizer is on the viewing side). In one embodiment, the image display device has a curved shape (substantially a curved display screen) and/or is foldable or foldable.

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 characteristic is as follows. "Parts" and "%" in Examples and Comparative Examples are by weight unless otherwise specified.

(1) Thickness A thickness of 10 μm or less was measured using an interferometric film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). A thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name “KC-351C”).
(2) Glass transition temperature (Tg)
The glass transition temperature of the resin was measured using a differential scanning calorimeter DSC6220 manufactured by SII Nanotechnology. About 10 mg of a resin sample was placed in an aluminum pan manufactured by the same company, sealed, and heated from 30° C. to 200° C. at a temperature elevation rate of 20° C./min under a nitrogen stream of 50 mL/min. After holding the temperature for 3 minutes, it was cooled to 30°C at a rate of 20°C/min. The temperature was maintained at 30° C. for 3 minutes, and the temperature was again raised to 200° C. at a rate of 20° C./min. From the DSC data obtained in the second temperature increase, a straight line extending the baseline on the low temperature side to the high temperature side and a tangent line drawn at the point where the slope of the curve of the stepwise change part of the glass transition becomes maximum. The extrapolated glass transition start temperature, which is the temperature at the intersection of , was determined and taken as the glass transition temperature (Tg).
(3) Moisture Permeability The protective layers obtained in Examples and Comparative Examples were applied to a triacetyl cellulose (TAC) film, and the permeability was measured using "DELTAPERM" manufactured by Technolox under test conditions of 40°C and 90% RH. Humidity (g/m ² ·24 hr) was measured.
(4) Retardation Value A sample of 50 mm×50 mm was cut out from the retardation film obtained in Examples and Comparative Examples to be used as a measurement sample. The in-plane phase difference of the prepared measurement sample was measured using a phase difference measuring device (product name: "KOBRA21-ADH") manufactured by Oji Scientific Instruments Co., Ltd. The in-plane retardation was measured at a wavelength of 590 nm and at a temperature of 23°C.
(5) The circularly polarizing plate obtained in the heating retardation change Examples and Comparative Examples, to prepare a sample by bonding to the glass via an adhesive layer, retardation in the same manner as in the measurement of the retardation was measured. After the measured sample was placed in an environment of 85° C. for 120 hours, the sample was taken out, the phase difference was measured again, and the rate of change (%) of Re(590) was obtained.
Good: The absolute value of the phase difference change rate (%) is less than 0.9% Poor: The absolute value of the phase difference change rate (%) is 0.9% or more (6) Red discoloration Examples and Comparative Examples The circularly polarizing plate obtained in 1) was attached to a glass plate via an adhesive, and subjected to a heating test at 100°C for 120 hours, and the appearance before and after the heating test was visually observed.
Good: Red discoloration was not observed Poor: Red discoloration was observed

[Production Example 1: Production of boron-containing acrylic resin]
Methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Industries, trade name: methyl methacrylate monomer) 97.0 parts by weight, 3.0 parts by weight of the monomer of general formula (1e), polymerization initiator (Fujifilm Wako Pure 0.2 parts by weight of 2,2′-azobis(isobutyronitrile), manufactured by Yakusha, was dissolved in 200 parts by weight of toluene. Then, a polymerization reaction was carried out for 5.5 hours while heating at 70° C. in a nitrogen atmosphere to obtain Copolymer 1 (solid concentration: 33% by weight). Copolymer 1 had a Tg of 110° C. and a weight average molecular weight of 80,000.

[Production Example 2: Production of polarizing plate A]
1. Production of Polarizer A As a thermoplastic resin substrate, a long amorphous isophthalate-copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of about 75° C. was used. Corona treatment was applied to one side of the resin substrate.
Polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z410") mixed at 9:1: 100 weight of PVA-based resin 13 parts by weight of potassium iodide was added to parts by weight, and dissolved in water to prepare an aqueous PVA solution (coating solution).
The above PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched 2.4 times at the free end in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment).
Then, the finally obtained polarizer is added to a dyeing bath (iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. It was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was 43.0% or more (dyeing treatment).
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 40°C (an aqueous solution of boric acid obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
After that, while immersing the laminate in an aqueous solution of boric acid (boric acid concentration: 4.0% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, the laminate is placed between rolls having different peripheral speeds in the vertical direction (longitudinal direction). Then, the film was uniaxially stretched so that the total draw ratio was 5.5 times (underwater stretching treatment).
After that, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (washing treatment).
After that, while drying in an oven kept at 90° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75° C. for about 2 seconds (drying shrinkage treatment). The shrinkage ratio in the width direction of the laminate due to the drying shrinkage treatment was 5.2%.
Thus, a polarizer A having a thickness of 5 μm was formed on the resin substrate.

2. Preparation of polarizing plate A An HC-TAC film as a polarizer protective film was attached to the surface of the polarizer A obtained above (the surface opposite to the resin substrate) via an ultraviolet curable adhesive. . Specifically, the curable adhesive was applied so as to have a total thickness of 1.0 μm, and was bonded using a roll machine. After that, UV rays were irradiated from the polarizer protective film side to cure the adhesive. The HC-TAC film is a film in which a hard coat (HC) layer (thickness 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness 25 μm), and is attached so that the TAC film faces the polarizer side. Matched. Next, the resin substrate was peeled off to obtain a polarizing plate A having a structure of HC layer/TAC film/adhesive layer/polarizer A.

[Production Example 3: Production of polarizing plate B]
A polarizing plate B was obtained in the same manner as in Production Example 1, except that an HC-COP film was used as the polarizer protective film. The HC-COP film is a film in which a hard coat (HC) layer (2 μm thick) is formed on a cycloolefin (COP) film (manufactured by Zeon Corporation, product name “ZF12”, thickness 25 μm).

[Production Example 4: Production of polarizing plate C]
A polarizing plate C was obtained in the same manner as in Production Example 1 except that the polarizer A obtained in Production Example 1 was used and an acrylic film (thickness: 20 μm) was used as the polarizer protective film.

[Production Example 5: Production of polarizing plate D]
A long roll of polyvinyl alcohol film (manufactured by Kuraray, product name “PE3000”) with a thickness of 30 μm is uniaxially stretched in the long direction by a roll stretching machine so as to be 5.9 times the length in the long direction while simultaneously being swollen and dyed. , cross-linking, washing, and finally drying to obtain a polarizer D having a thickness of 12 μm. An HC-TAC film similar to that of Production Example 1 was attached as a polarizer protective film to the polarizer D via a PVA-based adhesive. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness: 25 μm) was attached to the peeled surface via a PVA-based adhesive to obtain a polarizing plate D.

[Production Example 6: Production of polarizing plate E]
A polarizing plate E was obtained in the same manner as in Production Example 1, except that an HC-TAC film as a polarizer protective film was adhered using a PVA-based adhesive.

[Production Example 7: Production of First Liquid Crystal Alignment Fixed Layer and Second Liquid Crystal Alignment Fixed Layer]
1. Preparation of First Liquid Crystal Alignment Fixed Layer 55 parts of the compound represented by the formula (I), 25 parts of the compound represented by the formula (II), and 20 parts of the compound represented by the formula (III) were mixed with cyclopentanone (CPN). ) after adding to 400 parts, heated to 60 ° C., stirred and dissolved, after confirmation of dissolution, returned to room temperature, 3 parts of Irgacure 907 (manufactured by BASF Japan Co., Ltd.), Megafac F-554 (DIC Co., Ltd.) and 0.1 part of p-methoxyphenol (MEHQ) were added and further stirred to obtain a solution. The solution was clear and homogeneous. The resulting solution was filtered through a 0.20 μm membrane filter to obtain a polymerizable composition. On the other hand, a polyimide solution for an alignment film was applied to a glass substrate having a thickness of 0.7 mm by spin coating, dried at 100° C. for 10 minutes, and then baked at 200° C. for 60 minutes to obtain a coating film. . The resulting coating film was rubbed to form an alignment film. The rubbing treatment was performed using a commercially available rubbing device. The polymerizable composition obtained above was applied to a substrate (substantially an alignment film) by a spin coating method and dried at 100° C. for 2 minutes. After the obtained coating film was cooled to room temperature, it was irradiated with ultraviolet rays for 30 seconds at an intensity of 30 mW/cm ² using a high-pressure mercury lamp to obtain a first liquid crystal alignment fixed layer. The in-plane retardation Re(550) of the first liquid crystal alignment fixed layer was 130 nm. In addition, the Re(450)/Re(550) of the liquid crystal alignment fixed layer was 0.851, showing reverse dispersion wavelength characteristics.

2. Preparation of the second liquid crystal alignment fixed layer Represented by the following chemical formula (I) (numbers 65 and 35 in the formula indicate mol % of the monomer units, and are expressed in block polymer form for convenience: weight average molecular weight 5000) 20 parts by weight of a side chain type liquid crystal polymer, 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242) and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) was dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. Then, after coating the coating solution on a substrate film (norbornene resin film: Nippon Zeon Co., Ltd., trade name “Zeonex”) with a bar coater, the liquid crystal is formed by heating and drying at 80 ° C. for 4 minutes. Oriented. By irradiating this liquid crystal layer with ultraviolet rays and curing the liquid crystal layer, a second liquid crystal alignment fixed layer (thickness: 0.58 μm) was formed on the substrate. This layer had an Re(550) of 0 nm and an Rth(550) of −80 nm, showing refractive index characteristics of nz>nx=ny.

[Example 1]
The boron-containing acrylic resin prepared in Production Example 1 is applied onto the first liquid crystal alignment fixed layer obtained in Production Example 7 so that the thickness after drying is 0.5 μm, forming another protective layer. did. Next, the polarizing plate E obtained in Production Example 6 was laminated on the surface of another protective layer via an acrylic adhesive (thickness: 5 μm). Subsequently, the second liquid crystal alignment fixed layer obtained in Production Example 7 was transferred to the opposite side of the first liquid crystal alignment fixed layer to the polarizer. At this time, they were attached so that the angle formed by the absorption axis of the polarizer and the slow axis of the first liquid crystal alignment fixed layer was +45°. Each transfer (bonding) was performed through the ultraviolet curing adhesive (thickness: 1.0 μm) used in Production Example 2. Thus, the structure of HC layer/TAC film/adhesive layer/polarizer/acrylic pressure-sensitive adhesive layer/another protective layer/first liquid crystal alignment fixed layer/adhesive layer/second liquid crystal alignment fixed layer A laminate having

Copolymer 1 obtained in Production Example 1 (boron-containing acrylic resin) 15 parts (solid content conversion) and thermoplastic epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name "jER (registered trademark) YX6954BH30") 85 parts (solid content conversion) were blended. The resin blend had a Tg of 125°C and a weight average molecular weight of 46,000. This mixture was dissolved in 80 parts of a mixed solvent of ethyl acetate/cyclopentanone (70/30) to obtain a resin solution (20%). This resin solution is applied to the surface of the second liquid crystal alignment fixed layer of the laminate obtained above using a wire bar, the coating film is dried at 60 ° C. for 5 minutes, and the coating film of the resin organic solvent solution is A protective layer (thickness: 0.5 µm) was formed as a solidified product of Next, an adhesive layer (thickness 15 μm) is provided on the surface of the protective layer, and the HC layer/TAC film/adhesive layer/polarizer/acrylic adhesive layer/another protective layer/first liquid crystal alignment solidifying layer/adhesive A circularly polarizing plate having a structure of layer/second liquid crystal alignment fixed layer/protective layer/adhesive layer was obtained. The moisture permeability of the protective layer was 869.8 (g/m ² ·24 hr). The total thickness of the obtained circularly polarizing plate was 65 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 2]
Copolymer 1 obtained in Production Example 1 (boron-containing acrylic resin) 15 parts (solid content conversion) and thermoplastic epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name "jER (registered trademark) YX6954BH30") 85 parts 5 parts of an isocyanate compound (manufactured by Tosoh Corporation, "Coronate L": trimethylolpropane adduct of tolylene diisocyanate) was added to 95 parts of the blend (in terms of solid content). The resin blend had a Tg of 23° C. and a weight average molecular weight of 50,000. A circularly polarizing plate was obtained in the same manner as in Example 1 using this mixture. The protective layer had a moisture permeability of 901.7 (g/m ² ·24 hr), and the total thickness of the resulting circularly polarizing plate was 65 µm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 1]
A circularly polarizing plate was obtained in the same manner as in Example 1, except that no protective layer was provided between the second liquid crystal alignment solidified layer and the adhesive layer. The total thickness of the obtained circularly polarizing plate was 64 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 2]
Implemented except that a trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L") was used for the protective layer between the second liquid crystal alignment solidified layer and the adhesive layer. A circularly polarizing plate was obtained in the same manner as in Example 1. The protective layer had a moisture permeability of 944.6 (g/m ² ·24 hr), and the total thickness of the obtained circularly polarizing plate was 66 µm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 3]
A circularly polarizing plate was obtained in the same manner as in Example 1, except that the polarizing plate B was used as the polarizing plate. The total thickness of the obtained circularly polarizing plate was 61 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 4]
A circularly polarizing plate was obtained in the same manner as in Example 2 except that the polarizing plate B was used as the polarizing plate. The total thickness of the obtained circularly polarizing plate was 61 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 3]
A circularly polarizing plate was obtained in the same manner as in Example 3, except that no protective layer was provided between the second liquid crystal alignment solidified layer and the adhesive layer. The total thickness of the obtained circularly polarizing plate was 60 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 5]
A circularly polarizing plate was obtained in the same manner as in Example 2 except that the polarizing plate C was used as the polarizing plate. The total thickness of the obtained circularly polarizing plate was 54 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 4]
A circularly polarizing plate was obtained in the same manner as in Example 5, except that no protective layer was provided between the second liquid crystal alignment solidified layer and the adhesive layer. The total thickness of the obtained circularly polarizing plate was 53 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 6]
A circularly polarizing plate was obtained in the same manner as in Example 1, except that the polarizing plate D was used as the polarizing plate. The total thickness of the obtained circularly polarizing plate was 96 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 5]
A circularly polarizing plate was obtained in the same manner as in Example 5, except that no protective layer was provided between the second liquid crystal alignment solidified layer and the adhesive layer. The total thickness of the obtained circularly polarizing plate was 95 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 7]
A circularly polarizing plate was obtained in the same manner as in Example 1, except that the polarizing plate A was used as the polarizing plate. The total thickness of the obtained circularly polarizing plate was 65 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 6]
A circularly polarizing plate was obtained in the same manner as in Example 7, except that no protective layer was provided between the second liquid crystal alignment solidified layer and the adhesive layer. The total thickness of the obtained circularly polarizing plate was 64 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Example 8]
A circularly polarizing plate was obtained in the same manner as in Example 1, except that the polarizing plate A was used and the copolymer obtained in Production Example 1 was not applied to the first liquid crystal alignment fixed layer. The total thickness of the obtained circularly polarizing plate was 65 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[Comparative Example 7]
A circularly polarizing plate was obtained in the same manner as in Example 8, except that no protective layer was provided between the second liquid crystal alignment solidified layer and the adhesive layer. The total thickness of the obtained circularly polarizing plate was 64 μm. The resulting circularly polarizing plate was subjected to the above evaluations (4) to (6). Table 1 shows the results.

[evaluation]
As is clear from Table 1, in the circularly polarizing plates of the examples of the present invention, the retardation change in the heating environment is suppressed. Furthermore, it can be seen that the circularly polarizing plate of the example of the present invention is suppressed from red discoloration.

The circularly polarizing plate of the present invention is suitably used as a circularly polarizing plate for liquid crystal display devices, organic EL display devices and inorganic EL display devices.

REFERENCE SIGNS LIST 10 polarizing plate 11 polarizer 12 polarizer protective film 20 first liquid crystal alignment fixed layer 30 second liquid crystal alignment fixed layer 40 protective layer 50 adhesive layer 100 circularly polarizing plate

Claims

A polarizing plate, a first liquid crystal alignment fixed layer, a second liquid crystal alignment fixed layer, and a protective layer are provided in this order from the viewing side, and the moisture permeability of the protective layer is 920 (g/m 2 · 24 hr) or less. , circular polarizer.
The in-plane retardation Re(550) of the first liquid crystal alignment fixed layer is 100 nm to 180 nm, and satisfies the relationship Re(450)<Re(550)<Re(650). circular polarizer.
The circularly polarizing plate according to claim 1 or 2, wherein the second liquid crystal alignment fixed layer exhibits a refractive index characteristic of nz>nx=ny.
4. Any one of claims 1 to 3, wherein the protective layer contains an epoxy-based resin or an acrylic-based resin, and the protective layer is a solidified product or a heat-cured product of a coating film of an organic solvent solution of the resin. Circular polarizer as described.
The circularly polarizing plate according to claim 4, wherein the protective layer has a glass transition temperature of 85°C or higher, and the resin has a weight average molecular weight Mw of 25000 or higher.
The circularly polarizing plate according to any one of claims 1 to 5, comprising at least one other protective layer between said polarizing plate and said first liquid crystal alignment fixed layer.
The circularly polarizing plate according to any one of claims 1 to 6, having a thickness of 100 µm or less.
An image display device comprising the circularly polarizing plate according to any one of claims 1 to 7.