TWI837452B - Circular polarizing plate with anti-reflection layer and image display device using the circular polarizing plate with anti-reflection layer - Google Patents

Abstract

The topic is: Provide a circular polarizing plate with an anti-reflection layer, which can realize an image display device with suppressed hue unevenness. The solution is: the circular polarizing plate with an anti-reflection layer of the present invention has: a polarizing plate including a polarizer, an anti-reflection layer arranged on one side of the polarizing plate, and a phase difference layer arranged on the other side of the polarizing plate. The refractive index of the anti-reflection layer is 1.29~1.38, the thickness is 70nm~120nm, and in the wavelength range of 380nm~780nm, the wavelength for obtaining the lowest reflectivity exists in the range of 400nm~600nm. The Re(550) of the phase difference layer is 136nm~200nm.

Description

Circular polarizing plate with anti-reflection layer and image display device using the circular polarizing plate with anti-reflection layer

Invention Field

The present invention relates to a circular polarizing plate with an anti-reflection layer and an image display device using the circular polarizing plate with an anti-reflection layer.

Invention background

In recent years, image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (such as organic EL display devices and inorganic EL display devices) are rapidly becoming popular. In image display devices, circular polarizers including polarizers and phase difference plates are sometimes used. However, when circular polarizers are applied to image display devices with low reflectivity (especially organic EL display devices), there is a problem that hue unevenness is easily visible.

Prior art literature

Patent Literature

Patent document 1: Japanese Patent No. 5876441

Patent document 2: Japanese Patent Publication No. 2014-026266

Summary of invention

The present invention is made to solve the above existing problems, and its main purpose is to provide a circular polarizing plate with an anti-reflection layer, which can realize an image display device with suppressed hue unevenness.

The circular polarizing plate with an anti-reflection layer described in the embodiment of the present invention comprises: a polarizer, an anti-reflection layer disposed on one side of the polarizer, and a phase difference layer disposed on the other side of the polarizer. The refractive index of the anti-reflection layer is 1.29-1.38, the thickness is 70nm-120nm, and the wavelength with the lowest reflectivity in the wavelength range of 380nm-780nm exists in the range of 400nm-600nm. The Re (550) of the phase difference layer is 136nm-200nm.

In one embodiment, the reflectivity of the anti-reflection layer is less than 1.5%.

In one embodiment, the angle between the slow axis of the phase difference layer and the absorption axis of the polarizer is 40°~50° or 130°~140°.

In one embodiment, the phase difference layer is composed of a stretched film of a resin film, and Re(450)/Re(550) is 0.97~1.03. Here, Re(450) and Re(550) are the in-plane phase differences measured by light with wavelengths of 450nm and 550nm at 23°C, respectively.

According to another aspect of the present invention, an image display device is provided. The image display device has the circular polarizing plate with the anti-reflection layer on the visual side. The circular polarizing plate with the anti-reflection layer is configured in such a way that the anti-reflection layer becomes the visual side. The reflectivity of the image display device is less than 40%.

In one embodiment, the image display device is an organic electroluminescent display device.

According to the implementation form of the present invention, when a circular polarizer is applied to an image display device, by placing an anti-reflection layer on the side that will become the viewing side, and combining and optimizing the refractive index, thickness and wavelength of the anti-reflection layer that obtains the lowest reflectivity in the visible light region, and then optimizing the in-plane phase difference of the phase difference layer, a circular polarizer with an anti-reflection layer can be obtained, which can realize an image display device with suppressed hue unevenness. Moreover, in addition to the above-mentioned effects, the circular polarizer with an anti-reflection layer can also achieve high transmittance.

10: Polarizing plate

11: Polarizer

12: 1st protective layer

13: Second protective layer

30: Anti-reflective layer

40: Phase difference layer

50: Adhesive layer

100: Circular polarizing plate with anti-reflection layer

FIG1 is a schematic cross-sectional view of a circular polarizing plate with an anti-reflection layer according to an embodiment of the present invention.

Specific implementation methods

The following describes representative embodiments of the present invention, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)

The definitions of terms and symbols in this manual are as follows.

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

"nx" is the refractive index in the direction where the refractive index in the plane reaches the maximum (i.e. the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e. the fast axis direction), and "nz" is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

"Re(λ)" is the in-plane phase difference of a film measured at 23°C by light of wavelength λnm. For example, "Re(450)" is the in-plane phase difference of a film measured at 23°C by light of wavelength 450nm. When the thickness of the film is expressed as d(nm), Re(λ) is calculated by the formula Re=(nx-ny)×d.

(3) Phase difference in thickness direction (Rth)

"Rth(λ)" is the phase difference in the thickness direction of the film measured by light with a wavelength of λnm at 23°C. For example, "Rth(450)" is the phase difference in the thickness direction of the film measured by light with a wavelength of 450nm at 23°C. When the thickness of the film is expressed as d(nm), Rth(λ) is calculated by the formula Rth=(nx-nz)×d.

(4) Nz coefficient

The Nz coefficient is calculated by Nz=Rth/Re.

(5) Angle

When angles are mentioned in this manual, unless otherwise specified, the angles include both clockwise and counterclockwise angles.

A. The overall structure of the circular polarizer with anti-reflection layer

FIG1 is a schematic cross-sectional view of a circular polarizing plate with an anti-reflection layer according to an embodiment of the present invention. The circular polarizing plate with an anti-reflection layer 100 shown in the figure comprises: a polarizing plate 10, an anti-reflection layer 30 disposed on one side of the polarizing plate 10 (for example, the side opposite to the image display unit when applied to an image display device, i.e., the visual recognition side), and a phase difference layer 40 disposed on the other side of the polarizing plate 10 (for example, the image display unit side when applied to an image display device). The anti-reflection layer 30 and the phase difference layer 40 are respectively adhered to the polarizing plate 10 by any appropriate adhesive layer or adhesive layer (not shown). The polarizing plate 10 includes: a polarizer 11, a first protective layer 12 arranged on one side (anti-reflection layer side) of the polarizer 11, and a second protective layer 13 arranged on the other side (phase difference layer side) of the polarizer 11. Depending on the purpose, one or both of the first protective layer 12 and the second protective layer 13 can be omitted. For example, the phase difference layer 40 can also function as a protective layer for the polarizer 11, so the second protective layer 13 can be omitted. In addition, for example, when the anti-reflection layer is representatively formed on a substrate as described later, sometimes the substrate/anti-reflection layer laminate functions as a protective layer. In this case, the first protective layer 12 can be omitted. The substrate/anti-reflection layer laminate can further include a hard coating layer. Therefore, the polarizing plate with an anti-reflection layer may omit two protective layers and have a polarizer 11, an anti-reflection layer 30 disposed on one side of the polarizer 11, and a phase difference layer 40 disposed on the other side of the polarizer 11 (this configuration includes a configuration including a protective layer on one or both sides of the polarizer). In terms of practicality, an arbitrary appropriate adhesive layer 50 is provided as the outermost layer on the side of the phase difference layer 40 opposite to the polarizing plate 10, and the circular polarizing plate with an anti-reflection layer can be attached to the image display unit.

In the embodiment of the present invention, the refractive index of the anti-reflection layer is 1.29-1.38, the thickness is 70nm-120nm, and the wavelength (hereinafter sometimes referred to as the bottom wavelength) that obtains the lowest reflectivity in the wavelength range of 380nm-780nm exists in the range of 400nm-600nm. Thus, by combining and optimizing the refractive index, thickness and bottom wavelength of the anti-reflection layer, an image display device with suppressed hue unevenness can be realized. The details of the anti-reflection layer will be described later in item E.

The phase difference layer 40 is typically formed of a stretched film of a resin film. The Re(550) of the phase difference layer 40 is typically 136nm~200nm. The Re(450)/Re(550) of the phase difference layer is preferably 0.97~1.03. The angle between the slow axis of the phase difference layer and the absorption axis of the polarizer 11 is preferably 40°~50°, more preferably 42°~48°, further preferably 44°~46°, and particularly preferably about 45°; or, preferably 130°~140°, more preferably 132°~138°, further preferably 134°~136°, and particularly preferably about 135°.

In one embodiment, the circular polarizer with an anti-reflection layer may further have another phase difference layer (not shown) between the phase difference layer 40 and the adhesive layer 50. The other phase difference layer typically has a refractive index characteristic showing a relationship of nz>nx=ny. By providing this other phase difference layer, oblique reflection can be well prevented, and a wide viewing angle of the anti-reflection function can be achieved.

In one embodiment, the circular polarizer with an anti-reflection layer may further have a conductive layer or an isotropic substrate with a conductive layer (not shown). In the case where a conductive layer or an isotropic substrate with a conductive layer is provided, the circular polarizer with an anti-reflection layer may be applied to a so-called inner touch panel type input display device of a touch sensor, which is assembled between an image display unit (e.g., an organic EL unit) and a polarizer. The conductive layer or the isotropic substrate with a conductive layer is typically provided between the phase difference layer 40 and the adhesive layer 50. When another phase difference layer is provided, the other phase difference layer and the conductive layer or the isotropic substrate with the conductive layer are typically provided in sequence starting from the phase difference layer 40 side.

The circular polarizer with an anti-reflection layer may have a further phase difference layer (not shown). The further phase difference layer may be provided in combination with other phase difference layers, or may be provided alone (i.e., without providing other phase difference layers). The optical properties (e.g., refractive index properties, in-plane phase difference, Nz coefficient, photoelastic coefficient), thickness, configuration position, etc. of the further phase difference layer may be appropriately set according to the purpose.

The circular polarizer with an anti-reflection layer can be in the form of a single sheet or a strip. In this specification, "strip" refers to a long and narrow shape that is sufficiently long relative to its width, for example, including a long and narrow shape that is more than 10 times, preferably more than 20 times, relative to its width. The long and narrow circular polarizer with an anti-reflection layer can be rolled into a roll.

In practice, it is preferred to temporarily attach a release film to the surface of the adhesive layer 50 until the circular polarizing plate with an anti-reflection layer is ready for use. By temporarily attaching the release film, a roll of the circular polarizing plate with an anti-reflection layer can be formed while protecting the adhesive layer.

The following is an explanation of the components of a circular polarizing plate with an anti-reflection layer.

B. Polarizer

As the polarizer 11, any appropriate polarizer can be used. For example, the resin film forming the polarizer can be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers made of a single layer of resin film include: polarizers obtained by dyeing and stretching hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films using dichroic substances such as iodine and dichroic dyes; polyene-based oriented films such as dehydrated PVA and dehydrogenated polyvinyl chloride. From the perspective of excellent optical properties, it is preferred to use a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it.

The iodine-based dyeing is performed by, for example, immersing the PVA film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching can be performed after the dyeing treatment or while dyeing. In addition, dyeing can be performed after stretching. As needed, the PVA film is subjected to swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc. For example, by immersing the PVA film in water and washing it before dyeing, not only can the dirt and anti-adhesive agent on the surface of the PVA film be washed away, but the PVA film can also be swollen to prevent uneven dyeing.

Specific examples of polarizers 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 laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. The polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be made in the following manner: for example, a PVA-based resin solution is coated on the resin substrate, and the PVA-based resin layer is formed on the resin substrate by drying, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer into a polarizer. In this embodiment, stretching means that the laminate is immersed in a boric acid aqueous solution and stretched. Furthermore, as needed, stretching may also include: before stretching in a boric acid aqueous solution, the laminate is stretched in the air at a high temperature (for example, above 95°C). The obtained resin substrate/polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate/polarizer laminate and any appropriate protective layer corresponding to the purpose can be used on the peeled off area layer. The details of the manufacturing method of this polarizer are described in, for example, Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The descriptions of these patent documents are cited in this specification as reference.

The polarizer is preferably composed of a single layer of resin film. With this structure, a circular polarizer with an anti-reflection layer in which phase difference unevenness is suppressed in a high temperature environment can be obtained through the optimized synergistic effect with the first adhesive layer and the second adhesive layer.

The thickness of the polarizer is preferably about 1μm to 30μm, more preferably about 5μm to 25μm. In particular, in order to obtain a polarizer with a thickness of less than 10μm, Japanese Patent Publication No. 2012-73580, Japanese Patent Publication No. 6470455, etc. can be applied: a method for manufacturing a thin polarizer, which uses the following laminate, that is: a polyvinyl alcohol-based film formed on a thermoplastic resin substrate as the above-mentioned polyvinyl alcohol-based film. If the thickness of the polarizer is within this range, the warping during heating can be well suppressed, and good appearance durability during heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength between 380nm and 780nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

C. Protective layer

The first protective layer 12 and the second protective layer 13 are formed of any appropriate film that can be used as a protective layer of the polarizer. Specific examples of the material as the main component of the film include cellulose resins such as triacetate cellulose (TAC); polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth)acrylic resins, acetate resins and other transparent resins. In addition, thermosetting resins or ultraviolet curing resins such as (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, epoxy resins, and polysilicone resins can also be listed. In addition, glassy polymers such as silicone polymers can also be listed. In addition, the polymer film described in Japanese Patent Publication No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing the following thermoplastic resins can be used: a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl and nitrile group in the side chain, for example, a resin composition having an alternating copolymer formed by isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

The circular polarizing plate with an anti-reflection layer is described below. It is typically arranged on the viewing side of the image display device, and the first protective layer 12 is typically arranged on the viewing side thereof. Therefore, the first protective layer 12 can be subjected to surface treatments such as hard coating, anti-reflection, anti-adhesion, and anti-glare as needed. Furthermore/or, the first protective layer 12 can be subjected to treatments for improving visibility when viewed through polarized sunglasses as needed (representatively, providing (elliptical) circular polarization function and providing ultra-high phase difference). By implementing such treatments, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, circular polarizing plates with anti-reflection layers can also be used in image display devices that can be used outdoors.

The thickness of the first protective layer is typically less than 300 μm, preferably less than 100 μm, more preferably 5 μm to 80 μm, and further preferably 10 μm to 60 μm. In addition, when surface treatment is performed, the thickness of the outer protective layer is the thickness including the thickness of the surface treatment layer.

In one embodiment, the second protective layer 13 is preferably optically isotropic. In this specification, "optically isotropic" means: the in-plane phase difference Re(550) is 0nm~10nm, and the phase difference Rth(550) in the thickness direction is -10nm~+10nm.

D. Phase difference layer

As mentioned above, the in-plane phase difference Re(550) of the phase difference layer is typically 136nm~200nm, preferably 136nm~180nm, more preferably 136nm~160nm, and further preferably 136nm~150nm. That is, the phase difference layer can function as a so-called λ/4 plate. Furthermore, by making the Re(550) of the phase difference layer above 136nm, an image display device with very excellent reflection hue and low visual reflectivity (Y value) can be realized.

The phase difference layer typically exhibits a flat wavelength dependence in which the phase difference value is substantially constant regardless of the wavelength of the measured light. The Re(450)/Re(550) of the phase difference layer is preferably 0.97~1.03, more preferably 0.98~1.02. The Re(650)/Re(550) of the phase difference layer is preferably 0.97~1.03, more preferably 0.98~1.02.

nz的關係。另外，此處的「ny=nz」不僅包括ny與nz完全相等的情況，還包括實質相等的情況。因此，在不損害本發明效果的範圍內，可以存在ny<nz的情況。相位差層的Nz係數優選為0.9~2.0，更優選為0.9~1.5，進一步優選為0.9~1.2。藉由滿足這種關係，在將附抗反射層的圓偏光板用於影像顯示裝置的情況下，能夠實現非常優異的反射色相。 The phase difference layer has an in-plane phase difference as described above, and therefore has a relationship of nx>ny. The phase difference layer can exhibit any appropriate refractive index characteristics as long as it has a relationship of nx>ny. The refractive index characteristics of the phase difference layer typically exhibit nx>ny.

nz. In addition, "ny=nz" here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, within the scope that does not impair the effect of the present invention, there may be a situation where ny<nz. The Nz coefficient of the phase difference layer is preferably 0.9~2.0, more preferably 0.9~1.5, and further preferably 0.9~1.2. By satisfying this relationship, when a circular polarizer with an anti-reflection layer is used in an image display device, a very excellent reflection hue can be achieved.

The thickness of the phase difference layer can be set so that it can function most appropriately as a λ/4 plate. In other words, the thickness can be set so that the desired in-plane phase difference is obtained. Specifically, the thickness is preferably 70μm or less, preferably 45μm to 60μm. If the thickness of the phase difference layer is within this range, the warp during heating can be well suppressed, and the warp during bonding can be well adjusted.

The absolute value of the photoelastic coefficient of the phase difference layer is preferably 20×10 ^-12 (m ² /N) or less, more preferably 1.0×10 ^-12 (m ² /N) to 15×10 ^-12 (m ² /N), and further preferably 2.0×10 ^-12 (m ² /N) to 12×10 ^-12 (m ² /N). If the absolute value of the photoelastic coefficient is within this range, when the circular polarizer with an antireflection layer is applied to an image display device, display unevenness can be suppressed.

The phase difference layer can be composed of any appropriate resin film that can satisfy the above-mentioned characteristics. Representative examples of such resins include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins can be used alone or in combination (e.g., blended or copolymerized). The phase difference layer can be typically composed of a cyclic olefin resin, a polycarbonate resin, or a polyester carbonate resin (hereinafter sometimes referred to as a polycarbonate resin).

As a representative example of the cyclic olefin resin, there can be cited a norbornene resin. A norbornene resin is a resin obtained by polymerizing a norbornene monomer as a polymerizing unit. Examples of the norbornene monomer include norbornene and its alkyl and/or alkylene substituents, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and the like, and their halogen and other polar group-substituted products; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, and the like; dimethyloctahydronaphthalene, its alkyl and/or alkylene substituents, and halogen and other polar group-substituted products; Compounds such as 6-methyl-1,4:5,8-dimethyl-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethyl-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethyl-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethyl-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethyl-1,4,4a,5,6,7,8,8a -octahydronaphthalene, 6-cyano-1,4:5,8-dimethoxy-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethoxy-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethoxy-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; trimers and tetramers of cyclopentadiene, such as 4,9:5,8-dimethoxy-3a, 4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene (4,9: 5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene), 4,11: 5,10: 6,9-trimethyl-bridge-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecanoic-1H-cyclopentanthracene, etc. The above-mentioned norbornene resin can be a copolymer of norbornene monomers and other monomers.

As a polymerized unit in the norbornene resin, other cycloolefins capable of ring-opening polymerization may be used in combination. Specific examples of such cycloolefins include compounds having one reactive double bond, such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

The number average molecular weight (Mn) of the cyclic olefin resin measured by gel permeation chromatography (GPC) using a toluene solvent is preferably 25,000 to 200,000, more preferably 30,000 to 100,000, and most preferably 40,000 to 80,000. If the number average molecular weight is within the above range, the mechanical strength can be excellent, and the solubility, formability, and casting operability can be good.

As the above-mentioned cyclic olefin resin film, commercially available films can be used. Specific examples include: "ZEONEX" and "ZEONOR" manufactured by ZEON Corporation of Japan; "Arton" manufactured by JSR Corporation; "TOPAS" manufactured by TICONA Corporation; and "APEL" manufactured by Mitsui Chemicals Co., Ltd.

The above-mentioned polycarbonate resin typically contains a structural unit derived from a dihydroxy compound having a bonding structure represented by the following formula (I).

The dihydroxy compounds include, for example, the compounds represented by the following formula (II). As such dihydroxy compounds, isosorbide, isomannide, and isoidide, which are in a stereoisomer relationship, can be listed. They can be used alone or in combination of two or more.

The above-mentioned dihydroxy compound can be used in combination with other dihydroxy compounds. As other dihydroxy compounds, for example, alicyclic dihydroxy compounds represented by the following formula (III) can be listed.

HOCH ₂ -R ¹ -CH ₂ OH‧‧‧(III) In formula (III), R ¹ represents a cycloalkylene group having 4 to 20 carbon atoms. The alicyclic dihydroxy compound may be, for example, tricyclic decanedimethanol and pentacyclic pentadecanedimethanol. These include various isomers in which R ¹ in formula (III) is represented by the following formula (IV) (wherein n represents 0 or 1).

In one embodiment, the polycarbonate resin contains a structural unit represented by the following formula (V). That is, the polycarbonate resin can be a copolymer of diphenyl carbonate, isosorbide and tricyclodecanedimethanol.

The details of this polycarbonate resin are described in, for example, Japanese Patent Publication No. 2012-031370, and the description in the publication is cited in this specification as a reference.

The glass transition temperature of the polycarbonate resin is preferably 110°C or higher and 250°C or lower, and more preferably 120°C or higher and 230°C or lower. If the glass transition temperature is too low, the heat resistance tends to deteriorate, and dimensional changes may occur after film forming. If the glass transition temperature is too high, the molding stability during film forming may deteriorate, and the transparency of the film may be impaired. In addition, the glass transition temperature is determined according to JIS K 7121 (1987).

The molecular weight of polycarbonate resins can be expressed by reduced viscosity. The reduced viscosity is measured by using methylene chloride as a solvent, precisely adjusting the resin concentration to 0.6 g/dL, and using an Oodel viscometer at a temperature of 20.0°C ± 0.1°C. The lower limit of the reduced viscosity is usually preferably 0.30 dL/g, and more preferably 0.35 dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.20 dL/g, more preferably 1.00 dL/g, and further preferably 0.80 dL/g. If the reduced viscosity is less than the aforementioned lower limit, the mechanical strength of the molded product may decrease. On the other hand, if the reduced viscosity is greater than the aforementioned upper limit, the fluidity during molding, productivity, and moldability may decrease.

As the polycarbonate resin film, a commercially available film can be used. Specific examples of commercial products include "PUREACE WR-S", "PUREACE WR-W", and "PUREACE WR-M" manufactured by Teijin Co., Ltd. and "NRF" manufactured by Nitto Denko Co., Ltd.

The phase difference layer is obtained by, for example, stretching a film formed from the above-mentioned resin. As a method for forming a resin film, any appropriate molding method can be adopted. As specific examples, there can be listed compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP (Fiber Reinforced Plastics) molding, casting (such as casting), calendering, hot pressing, etc. Extrusion molding or casting is preferred. This is because the smoothness of the obtained film can be improved and good optical uniformity can be obtained. The molding conditions can be appropriately set according to the composition and type of the resin used, the desired properties of the phase difference layer, etc. In addition, as mentioned above, various resin film products are already commercially available, so the commercially available film can also be directly subjected to the stretching treatment.

The thickness of the resin film (unstretched film) can be set to an arbitrary and appropriate value according to the desired thickness of the phase difference layer, the desired optical properties, the stretching conditions described below, etc. It is preferably 50μm~300μm.

The above-mentioned stretching can adopt any and appropriate stretching method and stretching conditions (such as stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinking, fixed end shrinking, etc. can be used alone, or they can be used simultaneously or successively. Regarding the stretching direction, it can also be carried out in various directions and dimensions such as the length direction, width direction, thickness direction, and oblique direction. The stretching temperature is preferably Tg-30℃~Tg+60℃ relative to the glass transition temperature (Tg) of the resin film, and more preferably Tg-10℃~Tg+50℃.

By appropriately selecting the above-mentioned stretching method and stretching conditions, a phase difference film having the above-mentioned desired optical properties (such as refractive index properties, in-plane phase difference, Nz coefficient) can be obtained.

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

In another embodiment, the phase difference film can be produced by continuously stretching a long strip of resin film obliquely along the direction of the above-mentioned angle θ relative to the long side direction. By adopting oblique stretching, a long strip of stretched film with an orientation angle of angle θ relative to the long side direction of the film (having a slow axis in the direction of angle θ) can be obtained. For example, when laminating with a polarizing film, roll-to-roll can be used, which can simplify the manufacturing steps. In addition, the angle θ can be the angle between the absorption axis of the polarizing film in the polarizing plate with a phase difference layer and the slow axis of the phase difference layer. As mentioned above, the angle θ is preferably 40°~50°, more preferably 42°~48°, and further preferably about 45°.

As stretching machines used in oblique stretching, for example, tenter-type stretching machines that can add conveying forces, stretching forces, or pulling forces at different speeds in the horizontal and/or vertical directions can be listed. Tenter-type stretching machines include horizontal unidirectional stretching machines and simultaneous bidirectional stretching machines. Any appropriate stretching machine can be used as long as it can continuously stretch a long strip of resin film in an oblique direction.

By appropriately controlling the left and right speeds in the above-mentioned stretching machine, a phase difference layer (substantially a long strip of phase difference film) having the above-mentioned desired in-plane phase difference and a slow axis in the above-mentioned desired direction can be obtained.

The stretching temperature of the above film can be changed according to the desired in-plane phase difference value and thickness of the phase difference layer, the type of resin used, the thickness of the film used, the stretching ratio, etc. Specifically, the stretching temperature is preferably Tg-30℃~Tg+30℃, further preferably Tg-15℃~Tg+20℃, and most preferably Tg-10℃~Tg+15℃. By stretching at this temperature, a phase difference layer with appropriate characteristics in the present invention can be obtained. In addition, Tg is the glass transition temperature of the constituent material of the film.

E. Anti-reflective layer

The anti-reflection layer 30 is typically a hardened layer of an ionizing radiation hardening resin composition. By providing the anti-reflection layer, a high transmittance that is difficult to achieve with a circular polarizer alone can be achieved.

As mentioned above, the refractive index of the anti-reflection layer is 1.29 to 1.38, preferably 1.30 to 1.37, and more preferably 1.30 to 1.36. If the refractive index of the anti-reflection layer is within this range, an image display device with suppressed hue unevenness can be realized by combining and optimizing the thickness and bottom wavelength.

As mentioned above, the thickness of the anti-reflection layer is 70nm~120nm, preferably 75nm~110nm, and more preferably 75nm~100nm. If the thickness of the anti-reflection layer is within this range, an image display device with suppressed hue unevenness can be realized by combining and optimizing the refractive index and bottom wavelength. If the thickness of the anti-reflection layer is too large, when a circular polarizer with an anti-reflection layer is applied to an image display device, the reflected hue may become too blue and/or the visual reflectivity (Y value) may become too large.

As mentioned above, the bottom wavelength of the anti-reflection layer is in the range of 400nm to 600nm, preferably in the range of 410nm to 580nm, and more preferably in the range of 420nm to 550nm. If the bottom wavelength of the anti-reflection layer is in this range, an image display device with suppressed hue unevenness can be realized by combining and optimizing the thickness and refractive index. If the bottom wavelength deviates from the range, when a circular polarizer with an anti-reflection layer is applied to an image display device, the reflected hue may become too blue and/or the visual reflectivity (Y value) may become too large.

The reflectivity of the anti-reflection layer at the bottom wavelength is preferably 1.5% or less, more preferably 1.3% or less, and further preferably 1.0% or less. The smaller the reflectivity, the better, and its lower limit can be 0.2%, for example. If the reflectivity is within this range, it can prevent the reflection of external light, etc.

The ionizing radiation curable resin composition includes an ionizing radiation curable resin. The ionizing radiation curable resin composition may further include a reactive diluent, an additive containing a fluorine element, hollow particles and/or solid particles according to the purpose.

Representative examples of ionizing radiation curable resins include thermosetting resins, ultraviolet ray curable resins, light (visible light) curable resins, and electron ray curable resins. For example, examples of ionizing radiation curable resins include silicone resins, polyester resins, polyether resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, and polythiol polyene resins. In addition, for example, ionizing radiation curable resins may be curable compounds having acrylate groups and/or methacrylate groups that are cured by heat, light (ultraviolet rays, etc.), or electron rays, etc. As specific examples, oligomers or prepolymers of acrylates and/or methacrylates of multifunctional compounds such as polyols can be cited. Ionizing radiation curable resins can be used alone or in combination of two or more.

The weight average molecular weight of the ionizing radiation curable resin before curing can be, for example, 100 or more, 300 or more, 500 or more, 1000 or more, or 100,000 or less, 70,000 or less, 50,000 or less, 30,000 or less, or 10,000 or less. If the weight average molecular weight before curing is large, the hardness will decrease, but on the other hand, there is a tendency that it is not easy to crack when bent. If the weight average molecular weight before curing is small, there is a tendency that the intermolecular cross-linking density increases and the hardness becomes high.

Reactive diluents typically contain acrylate groups and/or methacrylate groups. As reactive diluents, for example, reactive diluents described in Japanese Patent Publication No. 2008-88309 can be used. As specific examples of reactive diluents, monofunctional acrylates, monofunctional methacrylates, polyfunctional acrylates, and polyfunctional methacrylates can be listed. Trifunctional or higher acrylates and trifunctional or higher methacrylates are preferred. As reactive diluents, for example, butanediol glycerol ether diacrylate, isocyanuric acid acrylate, isocyanuric acid methacrylate, etc. can also be listed. Reactive diluents can be used alone or in combination of two or more.

As an additive containing fluorine elements, any appropriate compound can be used. The additive containing fluorine elements can be, for example, an organic compound or an inorganic compound containing fluorine in the molecule. As an organic compound, for example, fluorine-containing antifouling coating agents, fluorine-containing acrylic compounds, fluorine/silicon-containing acrylic compounds, etc. can be listed. As an organic compound, commercial products can be used. As specific examples, the product name "KY-1203" manufactured by Shin-Etsu Chemical Co., Ltd. and the product name "MEGAFAC" manufactured by DIC Co., Ltd. can be listed. As an inorganic compound, any appropriate fluorine-containing inorganic compound can be used.

The amount of the additive containing the fluorine element may be, for example, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.15 parts by weight or more, 0.20 parts by weight or more, or 0.25 parts by weight or more, or may be 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less, relative to 100 parts by weight of the ionizing radiation curable resin.

As hollow particles, any appropriate hollow particles can be used. As specific examples, silica particles, acrylic particles, and acrylic-styrene copolymer particles can be listed. Commercially available products can be used as hollow particles. As specific examples of commercially available silica particles, the trade names "THRULYA 5320" and "THRULYA 4320" manufactured by HIWA Catalyst Chemicals Co., Ltd. can be listed. The weight-average particle size of the hollow particles can be, for example, greater than 30 nm, greater than 40 nm, greater than 50 nm, greater than 60 nm, or greater than 70 nm, or less than 150 nm, less than 140 nm, less than 130 nm, less than 120 nm, or less than 110 nm. As the shape of the hollow particles, any appropriate shape can be adopted. The shape of the hollow particles can be, for example, a bead-like, roughly spherical shape, or an irregular shape such as a powder. It is preferably roughly spherical, more preferably roughly spherical with an aspect ratio of 1.5 or less, and further preferably substantially spherical. By compounding hollow particles, an anti-reflection layer with a low refractive index and good anti-reflection properties can be obtained. The compounding amount of the hollow particles can be, for example, 30 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, 90 parts by weight or more, or 100 parts by weight or less, or 300 parts by weight or less, 270 parts by weight or less, 250 parts by weight or less, 200 parts by weight or less, or 180 parts by weight or less, relative to 100 parts by weight of the ionizing radiation curable resin. If the compounding amount is within this range, an anti-reflection layer with excellent mechanical properties and a low refractive index can be obtained.

As solid particles, any appropriate solid particles can be used. As specific examples, silica particles, zirconia particles, and titanium particles can be listed. Commercially available solid particles can be used. As specific examples of commercially available silica particles, trade names "MEK-2140Z-AC", "MIBK-ST", and "IPA-ST" manufactured by Nissan Chemical Industries, Ltd. can be listed. The weight-average particle size of the solid particles can be, for example, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 3300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, or 100 nm or less. As the shape of the solid particles, any appropriate shape can be adopted. The shape of the solid particles can be, for example, a bead-like, roughly spherical shape, or an irregular shape such as a powder. It is preferably roughly spherical, more preferably roughly spherical with an aspect ratio of 1.5 or less, and further preferably substantially true spherical. By compounding solid particles, the additive containing fluorine element tends to be concentrated on the surface of the anti-reflection layer, and as a result, an anti-reflection layer with a low refractive index and good anti-reflection properties can be obtained. The compounding amount of solid particles can be, for example, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or less, or 150 parts by weight or less, 120 parts by weight or less, 100 parts by weight or less, or 80 parts by weight or less, relative to 100 parts by weight of the ionizing radiation curable resin. If the compounding amount is within this range, an anti-reflection layer with an excellent balance of mechanical properties, refractive index and transparency can be obtained.

The anti-reflection layer can be typically formed by the following manufacturing method: applying a coating liquid for forming an anti-reflection layer obtained by diluting an ionizing radiation curable resin composition with a diluting solvent; drying the coating film; and curing the dried coating film.

As the diluting solvent, any appropriate solvent may be used according to the ionizing radiation curable resin. Examples of the diluting solvent include alcohols such as methanol, ethanol, isopropyl alcohol, butanol, TBA (tertiary butyl alcohol), and 2-methoxyethanol; ketones such as acetone, methyl ethyl ketone, MIBK (methyl isobutyl ketone), and cyclopentanone; esters such as methyl acetate, ethyl acetate, butyl acetate, and PMA (propylene glycol monomethyl ether acetate); ethers such as diisopropyl ether and propylene glycol monomethyl ether; glycols such as ethylene glycol and propylene glycol; solvents such as ethyl solvent and butyl solvent; aliphatic hydrocarbons such as hexane, heptane, and octane; and aromatic hydrocarbons such as benzene, toluene, and xylene. The diluting solvent may be used alone or in combination of two or more. Polarity can be adjusted by mixing multiple solvents in any suitable ratio corresponding to the purpose.

The diluting solvent may be, for example, a mixed solvent containing MIBK and PMA. The mixing ratio at this time may be appropriately set according to the purpose. Regarding the mixing ratio, PMA may be, for example, 20 parts by weight or more, 50 parts by weight or more, 100 parts by weight or more, 150 parts by weight or more, or 200 parts by weight or less, or 400 parts by weight or less, 350 parts by weight or less, 300 parts by weight or less, or 250 parts by weight or less, relative to 100 parts by weight of MIBK.

The diluting solvent may be, for example, a mixed solvent containing TBA on the basis of MIBK and PMA. The mixing ratio at this time may also be appropriately set according to the purpose. Regarding the mixing ratio, relative to 100 parts by weight of MIBK, PMA may be, for example, more than 10 parts by weight, more than 30 parts by weight, more than 50 parts by weight, more than 80 parts by weight, or more than 100 parts by weight, or less than 200 parts by weight, less than 180 parts by weight, less than 150 parts by weight, less than 130 parts by weight, or less than 110 parts by weight; TBA may be, for example, more than 10 parts by weight, more than 30 parts by weight, more than 50 parts by weight, more than 80 parts by weight, or more than 100 parts by weight, or less than 200 parts by weight, less than 180 parts by weight, less than 150 parts by weight, less than 130 parts by weight, or less than 110 parts by weight.

The solid content concentration of the coating liquid can be set to, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 1.0% by weight or more, or 1.5% by weight or less, or 20% by weight or less, 15% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less. If the solid content concentration is within this range, it can take into account both coating properties (such as wetting and leveling) and prevent poor appearance of the coating film (such as uneven drying and whitening).

A hardener may be added to the coating liquid as needed. As the hardener, any and appropriate polymerization initiator (e.g., thermal polymerization initiator, photopolymerization initiator, etc.) may be used. The amount of the hardener added may be, for example, 0.5 parts by weight or more, 1.0 parts by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, or 2.5 parts by weight or less, or 15 parts by weight or less, 13 parts by weight or less, 10 parts by weight or less, 7 parts by weight or less, or 5 parts by weight or less, relative to 100 parts by weight of the ionizing radiation curable resin.

The anti-reflection layer is typically formed on any appropriate substrate and then laminated on the polarizer or polarizing plate by any appropriate adhesive layer or adhesive layer. First, a coating liquid is applied on the substrate. As a coating method, any appropriate method can be adopted. Specific examples include: fountain coating method, die coating method, spin coating method, spray coating method, gravure coating method, roller coating method, and rod coating method. The coating amount of the coating liquid can be appropriately set according to the thickness of the anti-reflection layer to be formed. The thickness of the formed anti-reflection layer can be, for example, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 1.0 μm or more, or 2.0 μm or less, or 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.

Then, the applied coating liquid is dried to form a coating film. The drying temperature can be appropriately set according to the purpose. The drying temperature can be, for example, above 30°C, above 40°C, above 50°C, above 60°C, above 70°C, above 80°C, above 90°C, or above 100°C, or below 200°C, below 190°C, below 180°C, below 170°C, below 160°C, below 150°C, below 140°C, below 135°C, below 130°C, below 120°C, or below 110°C. In addition, the drying time can also be appropriately set according to the purpose. The drying time can be, for example, above 30 seconds, above 40 seconds, above 50 seconds, or above 60 seconds, or below 150 seconds, below 130 seconds, below 110 seconds, or below 90 seconds.

Next, the coating is cured. Curing can be performed by, for example, heating, light irradiation, etc. The light used for light irradiation can be, for example, ultraviolet rays or visible light. The light source for light irradiation can be, for example, a high-pressure mercury lamp. The irradiation amount of the energy radiation source in ultraviolet curing is preferably 50mJ/ ^cm2 to 500mJ/ ^cm2 in terms of the cumulative exposure amount when the ultraviolet wavelength is 365nm. If the irradiation amount is 50mJ/ ^cm2 or more, it is easy to fully cure, and the hardness of the anti-reflection layer formed is easy to increase. If the irradiation amount is 500mJ/ ^cm2 or less, the anti-reflection layer formed can be prevented from being colored.

F. Image display device

The circular polarizing plate with an anti-reflection layer described in the above items A to E can be applied to an image display device. Therefore, the embodiment of the present invention also includes an image display device using such a circular polarizing plate with an anti-reflection layer. The image display device described in the embodiment of the present invention is typically provided with the circular polarizing plate with an anti-reflection layer described in the above items A to E on its viewing side. The circular polarizing plate with an anti-reflection layer is configured in such a way that the anti-reflection layer becomes the viewing side. The reflectivity of the image display device is preferably 40% or less. In an image display device having such a reflectivity, the effect of the circular polarizing plate with an anti-reflection layer described in the above items A to E becomes significant. Specifically, it is as follows. If the reflectivity of the image display device is low, the reflection of the displayed image can be reduced, and on the other hand, it is easy to visually detect color unevenness. According to the embodiment of the present invention, by optimizing the structure of the circular polarizer with an anti-reflection layer, it is possible to realize an image display device with small reflection of the displayed image and suppressed hue unevenness. Representative examples of image display devices include: liquid crystal display devices and organic electroluminescent (EL) display devices. Organic EL display devices are preferred.

The visual reflectivity of the image display device is preferably 1.5% or less, more preferably 1.2% or less. The visual reflectivity refers to the reflectivity of the Y value of the XYZ color system, and is the reflectivity measured in accordance with JIS Z 8722. The reflection hue b ^* value of the image display device is preferably -15 to -6, and more preferably -14 to -8. The reflection hue b ^* value refers to the b ^* value of the L ^* a ^* b ^* color system, and is measured in accordance with JIS Z 8722:2009 (spectrophotometer). Such visual reflectivity and reflection hue can be achieved by using the circularly polarizing plate with an anti-reflection layer listed in Items A to E above.

Implementation example

The present invention is specifically described below by way of examples, but the present invention is not limited to these examples. In addition, the measurement methods of each characteristic are as follows.

(1) Reflectivity

For the anti-reflection layer used in the embodiment and comparative example, the front reflectance was measured using a spectrophotometer "CM-2600d" manufactured by KONICA MINOLTA. The front reflectance was measured by the SCI method. The wavelength of the measurement light was varied between 380nm and 780nm, and the wavelength at which the lowest reflectance was observed was taken as the bottom wavelength, and the reflectance at the bottom wavelength was taken as the bottom reflectance.

(2)Thickness

The measurement was performed using an interferometer film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000").

(3) Refractive index

The measurement was performed using a prism coupler SPA-4000 (manufactured by Sailun Technology).

(4) In-plane phase difference

The measurement was performed using Axoscan (manufactured by Axometrics). The measurement temperature was 23°C. Furthermore, Re(450)/Re(550) was used as an index of wavelength dispersion characteristics and calculated.

(5) Uneven hue

The circular polarizing plate with anti-reflection layer obtained in the embodiment and comparative example was cut into a specified size and adhered to an alkali-free glass plate via an acrylic adhesive layer to prepare a test sample. The test sample was placed on an organic EL device substitute with the glass plate facing each other, and the color unevenness (stripe unevenness) was visually observed under a fluorescent lamp and evaluated according to the following criteria.

In addition, the organic EL display device substitute is produced as follows. The metal wiring is printed on the acrylic plate in a manner that the reflectivity is specified, and it is used as an organic EL display device substitute. The metal wiring is printed in a manner that the reflectivity of the organic EL display device substitute becomes 21.88% or 40.34%.

A: No hue unevenness was actually confirmed

B: Color unevenness is confirmed, but it is within the acceptable range for practical use

C: The color unevenness is obvious and is unacceptable in practice

(6) b ^* value

The test sample prepared in the same manner as in (5) above was placed on the organic EL device substitute with the glass plate facing each other, and was measured using the spectrophotometer "CM-2600d" manufactured by Konica Minolta.

(7)Y value

The test sample prepared in the same manner as in (5) above was placed on the organic EL device substitute with the glass plate facing each other, and was measured using a spectrophotometer "CM-2600d" manufactured by Konica Minolta using a method based on JIS Z 8722.

[Manufacturing Example 1: Production of polarizer]

A polyvinyl alcohol film with an average degree of polymerization of 2400, a saponification degree of 99.9 mol% and a thickness of 45μm was immersed in warm water at 30°C for 60 seconds to swell. Then, it was immersed in an aqueous solution of iodine/potassium iodide (weight ratio = 1/7) with a concentration of 0.3%, and the film was dyed while being stretched to 2.6 times. After that, it was stretched in a 4 wt% boric acid aqueous solution at 65°C with a total stretch ratio of 6 times. After stretching, it was dried in an oven at 55°C for 1 minute to obtain a PVA-based polarizer. The thickness of the polarizer was 18μm and the moisture content was 15 wt%.

[Manufacturing Example 2: Manufacture of a phase difference film constituting a phase difference layer]

[Manufacturing Example 2-1]

47.19 parts by mass of tricyclodecanedimethanol (hereinafter sometimes abbreviated as "TCDDM"), 175.1 parts by mass of diphenyl carbonate (hereinafter sometimes abbreviated as "DPC") and 0.979 parts by mass of a 0.2% by mass aqueous solution of cesium carbonate as a catalyst were added to a reaction vessel with respect to 81.98 parts by mass of isosorbide (hereinafter sometimes abbreviated as "ISB"), and the temperature of the heating tank was heated to 150°C in a nitrogen gas atmosphere as the first step of the reaction, and the raw materials were dissolved while stirring as necessary (about 15 minutes). Then, the pressure was changed from normal pressure to 13.3 kPa, and the temperature of the heating tank was raised to 190°C over 1 hour, while the generated phenol was discharged out of the reaction vessel. After the entire reaction vessel is maintained at 190°C for 15 minutes, as the second stage, the pressure in the reaction vessel is set to 6.67 kPa, and the temperature of the heating tank is raised to 230°C in 15 minutes to discharge the generated phenol out of the reaction vessel. Since the stirring torque of the stirrer gradually increases, the temperature is raised to 250°C in 8 minutes, and the pressure in the reaction vessel is reduced to below 0.200 kPa in order to remove the generated phenol. After reaching the specified stirring torque, the reaction is terminated, and the generated reactants are extruded into water to obtain pellets of polycarbonate copolymer.

After the obtained pellets were vacuum dried at 80°C for 5 hours, a resin film was prepared using a film-making device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., barrel setting temperature: 250°C), a T-die (width: 200mm, setting temperature: 250°C), a cooling roller (setting temperature: 120~130°C) and a winder. The obtained long strip of resin film was stretched to obtain a phase difference film. By changing the stretching conditions, phase difference films with Re(550) of 135nm, 140nm or 144nm were obtained. The Re(450)/Re(550) of any phase difference film was 1.02.

[Manufacturing Example 2-2]

A commercially available cycloolefin resin film (manufactured by ZEON Corporation of Japan, product name "ZEONORE") was stretched to obtain a phase difference film. By changing the stretching conditions, a phase difference film with Re(550) of 140nm or 144nm was obtained. The Re(450)/Re(550) of any phase difference film was 1.02.

[Manufacturing Example 3: Preparation of anti-reflection layer]

[Manufacturing Example 3-1: Preparation of hard coating]

As the resin included in the hard coating layer, 100 parts by weight of a UV-curing urethane acrylate resin (manufactured by DIC Corporation, trade name "UNIDIC 17-806", solid content 80%) was prepared. 3 parts by weight of a photopolymerization initiator (manufactured by BASF Corporation, trade name "OMNIRAD907") and 0.01 parts by weight of a leveling agent (manufactured by DIC Corporation, trade name "GRANDIC PC4100", solid content 10%) were mixed with 100 parts by weight of the resin solid content of the above resin. The mixture was diluted with a butyl acetate/cyclopentanone mixed solvent (weight ratio of 80/20) to a solid content concentration of 40% to prepare a hard coating layer forming material (coating liquid). The above coating liquid was applied to the surface of a substrate (TAC film with a thickness of 60 μm) using a wire bar. The applied coating liquid was heated at 80°C for 1 minute to dry to form a coating film. The dried coating film was irradiated with ultraviolet light at a cumulative light intensity of 300 mJ/ ^cm2 using a high-pressure mercury lamp to perform a curing treatment to obtain a hard coating thin film (hard coating layer) on the substrate.

[Manufacturing Example 3-2: Preparation of anti-reflection layer]

100 parts by weight of a multifunctional acrylate containing pentaerythritol triacrylate as a main component (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300", solid content: 100% by weight), 100 parts by weight of hollow nano-silica particles (manufactured by Nikko Catalysts & Chemicals Co., Ltd., trade name "THRULYA 5320", solid content: 20% by weight, weight average particle size: 75 nm), 40 parts by weight of solid nano-silica particles (manufactured by Nissan Chemical Industries, Ltd., trade name "MEK-2140Z-AC", solid content: 30% by weight, weight average particle size: 10 nm), 12 parts by weight of an additive containing a fluorine element (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KY-1203", solid content: 20% by weight), and a photopolymerization initiator (IGM Resins 3 parts by weight of "Omnirad907" manufactured by B.V., with a solid content of 100% by weight, were mixed. A mixed solvent obtained by mixing TBA (tert-butyl alcohol), MIBK (methyl isobutyl ketone) and PMA (propylene glycol monomethyl ether acetate) in a weight ratio of 60:25:15 was added to the mixture as a diluent, and the total solid content was 4% by weight, and the coating liquid for forming an anti-reflection layer was prepared by stirring.

The anti-reflection layer-forming coating liquid is applied to the surface of the hard coating layer of the substrate/hard coating layer laminate obtained by Manufacturing Example 3-1 using a wire rod. The applied coating liquid is heated at 80°C for 1 minute and dried to form a coating film. The dried coating film is irradiated with ultraviolet light with a cumulative light amount of 300mJ/ ^cm2 using a high-pressure mercury lamp to perform a hardening treatment to form an anti-reflection layer with a refractive index of 1.36. In this way, a substrate/hard coating (HC) layer/anti-reflection layer laminate is produced.

Furthermore, the amount of hollow nano-silica particles added was changed to form an anti-reflection layer with a refractive index of 1.34 or 1.30. Furthermore, the coating thickness of the coating liquid was changed to change the thickness of the anti-reflection layer formed. An anti-reflection layer having a refractive index and thickness shown in Table 1 below was formed.

[Production Example 4: Preparation of active energy ray-curable adhesive]

A free radical polymerizable compound (a) of 12 parts by weight, a free radical polymerizable compound (b) of 35 parts by weight, a free radical polymerizable compound (c) of 40 parts by weight, an oligomer compound (d) of 10 parts by weight, a photopolymerization initiator (e) of 2 parts by weight and a photosensitizer (f) of 1 part by weight were mixed and stirred at 50° C. for 1 hour to obtain an active energy ray-curable adhesive. In addition, the radical polymerizable compound (a) is HEAA (hydroxyethylacrylamide) (manufactured by KJ Chemicals); the radical polymerizable compound (b) is ACMO (acryloylmorpholine) (manufactured by KJ Chemicals); the radical polymerizable compound (c) is Light Acrylate 1,9ND-A (1,9-nonanediol diacrylate) (manufactured by Kyoeisha Chemicals Co., Ltd.); the oligomer compound (d) is ARUFON UG-4010 (epoxy-modified acrylic oligomer) (manufactured by Toagosei Co., Ltd.); the photopolymerization initiator (e) is Omnirad907 (2-methyl-1-(4-methylthienyl)-2-morpholinylpropane-1-one) (manufactured by IGM Resins B.V.); the photosensitizer (f) is KAYACURE DETX-S (2,4-diethylthioxanthine) (manufactured by Nippon Kayaku Co., Ltd.).

[Implementation Example 1]

Using an MCD coating machine (manufactured by Fuji Machinery Co., Ltd.) (unit shape: honeycomb, number of gravure roll lines: 1000 lines/inch, rotation speed: 140%/relative to line speed), the active energy ray-curable adhesive obtained in Manufacturing Example 4 was coated on the substrate surface of the laminate obtained in Manufacturing Example 3 and one surface of the phase difference film obtained in Manufacturing Example 2-1 in a thickness of 0.7 μm, and then adhered to both sides of the polarizer obtained in Manufacturing Example 1 by roll-to-roll method. Then, after irradiating visible light from both sides using an active energy ray irradiation device to cure the active energy ray-curable adhesive, it was dried with hot air at 70°C for 3 minutes to produce a circular polarizing plate with an antireflection layer having a structure of antireflection layer/HC layer/substrate/polarizer/phase difference layer. In addition, an acrylic adhesive layer (23 μm) is provided on the surface of the phase difference layer of the circular polarizing plate with an anti-reflection layer (the side opposite to the polarizer). The obtained circular polarizing plate with an anti-reflection layer is placed on an organic EL display device substitute having a reflectivity shown in Table 1 and provided for the evaluation of (5) to (7) above. The results are shown in Table 1.

[Examples 2 to 6 and Comparative Examples 1 to 7]

Except that the anti-reflection layer and the phase difference layer are set to the combination shown in Table 1, the same operation as in Example 1 is performed to obtain a circular polarizing plate with an anti-reflection layer. The obtained circular polarizing plate with an anti-reflection layer is placed on an organic EL display device substitute having a reflectivity shown in Table 1 and is provided for the evaluation of (5) to (7) above. The results are shown in Table 1.

[Table 1]

[Evaluation]

It can be clearly seen from Table 1 that the circular polarizer with an anti-reflection layer of the embodiment of the present invention is excellent in hue unevenness, b ^* value and Y value. If any of the bottom wavelength or thickness of the anti-reflection layer, or the Re (550) of the phase difference layer deviates from the range of the embodiment of the present invention, at least one of the hue unevenness, b ^* value and Y value is insufficient. It can be seen that the circular polarizer with an anti-reflection layer of the embodiment of the present invention can realize an image display device with suppressed hue unevenness. It can be further seen that this effect can be obtained in an image display device with a low reflectivity.

Industrial availability

The circular polarizing plate with an anti-reflection layer of the present invention can be suitably used in image display devices (representatively liquid crystal display devices and organic EL display devices).

10: Polarizing plate

11: Polarizer

12: 1st protective layer

13: Second protective layer

30: Anti-reflective layer

40: Phase difference layer

50: Adhesive layer

100: Circular polarizing plate with anti-reflection layer

Claims (5)

A circular polarizing plate with an anti-reflection layer, comprising: a polarizer, an anti-reflection layer disposed on one side of the polarizer, and a phase difference layer disposed on the other side of the polarizer, wherein the refractive index of the anti-reflection layer is 1.29-1.38, the thickness is 70nm-120nm, and within the wavelength range of 380nm-780nm, the wavelength at which the lowest reflectivity is obtained exists within the range of 400nm-600nm, the Re (550) of the phase difference layer is 136nm-200nm, and the angle between the slow axis of the phase difference layer and the absorption axis of the polarizer is 40°-50° or 130°-140°. A circular polarizing plate with an anti-reflection layer as claimed in claim 1, wherein the reflectivity of the anti-reflection layer is less than 1.5%. A circular polarizing plate with an anti-reflection layer as claimed in claim 1 or 2, wherein the phase difference layer is formed of a stretched film of a resin film, and Re(450)/Re(550) is 0.97 to 1.03, wherein Re(450) and Re(550) are the in-plane phase differences measured at 23°C by light of wavelengths of 450nm and 550nm, respectively. An image display device, which has a circular polarizing plate with an anti-reflection layer as in any one of claims 1 to 3 on the viewing side, the anti-reflection layer of the circular polarizing plate with an anti-reflection layer is arranged on the viewing side, and the reflectivity of the image display device is less than 40%. The image display device of claim 4 is an organic electroluminescent display device.