TWI875989B - Polarizing plate with phase difference layer and adhesive layer, and image display device using the polarizing plate with phase difference layer and adhesive layer - Google Patents

Abstract

The present invention provides a polarizing plate with a phase difference layer and an adhesive layer, which can realize an image display device in which phase difference unevenness can be suppressed in a high temperature environment and color unevenness can be suppressed in a high temperature environment. The polarizing plate with a phase difference layer and an adhesive layer of the present invention has: a polarizing plate, which includes a polarizing element; a phase difference layer, which is bonded to the polarizing plate via a first adhesive layer; and a second adhesive layer, which is arranged as the outermost layer on the side of the phase difference layer opposite to the polarizing plate. The phase difference layer includes a stretched film of a resin film, which satisfies the relationship of Re(450)＜Re(550), and the shrinkage rate in the direction of the retardation axis when heated at 80℃～125℃ for 180 minutes is less than 4%. The paste displacement of the first adhesive layer after the 85°C and 500-hour heating test was more than 300 μm.

Description

Polarizing plate with phase difference layer and adhesive layer, and image display device using the polarizing plate with phase difference layer and adhesive layer

The present invention relates to a polarizing plate with a phase difference layer and an adhesive layer, and an image display device using the polarizing plate with a phase difference layer and an adhesive layer.

In recent years, image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (e.g., organic EL display devices, inorganic EL display devices) have rapidly become popular. Image display devices typically use polarizing plates and phase difference plates. In actual applications, polarizing plates with phase difference layers that integrate polarizing plates and phase difference plates are widely used (e.g., Patent Document 1). However, polarizing plates with phase difference layers will produce uneven phase difference in high temperature environments. As a result, there is a situation where image display devices produce color unevenness in high temperature environments. Prior Art Documents Patent Documents

Patent document 1: Japanese Patent No. 3325560

[The problem the invention is trying to solve]

The present invention is made to solve the above-mentioned previous problems. Its main purpose is to provide a polarizing plate with a phase difference layer and an adhesive layer, which can realize an image display device in which the phase difference unevenness can be suppressed in a high temperature environment and the color unevenness can be suppressed in a high temperature environment. [Technical means to solve the problem]

The polarizing plate with phase difference layer and adhesive layer of the embodiment of the present invention comprises: a polarizing plate including a polarizing element; a phase difference layer attached to the polarizing plate via a first adhesive layer; and a second adhesive layer disposed as an outermost layer on the side of the phase difference layer opposite to the polarizing plate. The phase difference layer comprises a stretched film of a resin film, which satisfies the relationship of Re(450)＜Re(550), and the shrinkage rate in the direction of the retardation axis when heated at 80℃～125℃ for 180 minutes is less than 4%. The paste offset of the first adhesive layer after a heating test at 85℃ and 500 hours is more than 300 μm. Here, Re(450) and Re(550) are the in-plane phase differences measured using light of wavelengths of 450 nm and 550 nm at 23°C, respectively. In one embodiment, Re(550) of the phase difference layer is 100 nm to 200 nm, and the angle between the retardation axis of the phase difference layer and the absorption axis of the polarizing element is 40° to 50° or 130° to 140°. In one embodiment, the thickness of the phase difference layer is 15 μm to 60 μm. In one embodiment, the stretched film constituting the phase difference layer is heat treated at a temperature of 105°C or above for more than 2 minutes. In one embodiment, the polarizing plate with a phase difference layer and an adhesive layer further has another phase difference layer between the phase difference layer and the second adhesive layer, the refractive index characteristic of which shows the relationship of nz>nx=ny. In one embodiment, the phase difference layer comprises: a resin having positive refractive index anisotropy, comprising at least one bonding group selected from the group consisting of carbonate bonds and ester bonds and at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and structural units represented by the following general formula (2); and an acrylic resin; wherein the content of the acrylic resin is 0.5 mass % to 2.0 mass %, the acrylic resin contains more than 70 mass % of structural units derived from methyl methacrylate, and the weight average molecular weight Mw is 10,000 to 200,000. [Chemistry 1] [Chemistry 2] In the general formulae (1) and (2), R ¹ to R ³ are each independently a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴ to R ⁹ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a substituted sulfur atom, a substituted silicon atom, a halogen atom, a nitro group, or a cyano group; wherein R ⁴ to R ⁹ may be the same or different from each other, and R ⁴ At least two adjacent groups in R ⁹ may also be bonded to each other to form a ring. According to another aspect of the present invention, an image display device is provided. The image display device has the above-mentioned polarizing plate with a phase difference layer and an adhesive layer. [Effects of the invention]

According to the implementation method of the present invention, by optimizing the paste offset of the adhesive layer between the polarizing element and the phase difference layer and the heat shrinkage rate of the phase difference layer in the direction of the retardation axis, a polarizing plate with a phase difference layer and an adhesive layer can be realized in which the phase difference unevenness can be suppressed in a high temperature environment. As a result, an image display device can be realized in which the color unevenness can be suppressed in a high temperature environment.

Hereinafter, representative embodiments of the present invention will be described, 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 is the largest (i.e., the direction of the slow axis), “ny” is the refractive index in the direction orthogonal to the slow axis (i.e., the direction of the fast axis), 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 the film measured using light of a wavelength of λ nm at 23°C. For example, “Re(450)” is the in-plane phase difference of the film measured using light of a wavelength of 450 nm at 23°C. Re(λ) is obtained by the formula: Re＝(nx－ny)×d when the thickness of the film is set to d(nm). (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction of the film measured using light of wavelength λ nm at 23°C. For example, "Rth(450)" is the phase difference in the thickness direction of the film measured using light of wavelength 450 nm at 23°C. Rth(λ) is calculated by the formula: Rth = (nx-nz) × d when the thickness of the film is set to d (nm). (4) Nz coefficient The Nz coefficient is calculated by Nz = Rth/Re. (5) Angle In this manual, when an angle is mentioned, unless otherwise specified, the angle includes both clockwise and counterclockwise angles.

A. Overall structure of polarizing plate with phase difference layer and adhesive layer Figure 1 is a schematic cross-sectional view of a polarizing plate with phase difference layer and adhesive layer in one embodiment of the present invention. The polarizing plate with phase difference layer and adhesive layer 100 shown in the figure comprises: a polarizing plate 10; a phase difference layer 30, which is bonded to the polarizing plate 10 via a first adhesive layer 20; and a second adhesive layer 40, which is disposed as the outermost layer on the side of the phase difference layer 30 opposite to the polarizing plate 10. The polarizing plate with phase difference layer and adhesive layer can be bonded to an image display unit via the second adhesive layer 40. The polarizing plate 10 includes a polarizing element 11, a first protective layer 12 disposed on one side of the polarizing element 11, and a second protective layer 13 disposed on the other side of the polarizing element 11. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 can be omitted. For example, the phase difference layer 30 can also function as a protective layer for the polarizing element 11, so the second protective layer 13 can be omitted. The angle between the retardation axis of the phase difference layer 30 and the absorption axis of the polarizing element 11 is preferably 40° to 50°, more preferably 42° to 48°, further preferably 44° to 46°, particularly preferably about 45°, or preferably 130° to 140°, more preferably 132° to 138°, further preferably 134° to 136°, particularly preferably about 135°.

The phase difference layer 30 includes a stretched film of a resin film, which satisfies the relationship of Re(450)＜Re(550), and the shrinkage rate in the direction of the phase axis when heated at 80℃～125℃ for 180 minutes is less than 4%. Re(550) of the phase difference layer 30 is typically 100 nm～200 nm. The paste offset of the first adhesive layer 20 after the heating test at 85℃ and 500 hours is more than 300 μm. The details of each layer constituting the polarizing plate with the phase difference layer and the adhesive layer will be described later.

In one embodiment, the polarizing plate with a phase difference layer and an adhesive layer may further have another phase difference layer (not shown) between the phase difference layer 30 and the second adhesive layer 40. The refractive index characteristics of the other phase difference layer typically show a relationship of nz>nx=ny. By providing such another phase difference layer, reflection in an oblique direction can be well prevented, and a wide viewing angle of the anti-reflection function can be achieved.

In one embodiment, the polarizing plate with a phase difference layer and an adhesive layer may further have a conductive layer or an isotropic substrate with a conductive layer (not shown). When a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate with a phase difference layer and an adhesive layer may be applied to a so-called internal touch panel type input display device in which a touch sensor is assembled between an image display unit (e.g., an organic EL unit) and the polarizing plate. The conductive layer or the isotropic substrate with a conductive layer is typically provided between the phase difference layer 30 and the second adhesive layer 40. When another phase difference layer is provided, the other phase difference layer and the conductive layer or the isotropic substrate with a conductive layer are typically provided in sequence from the phase difference layer 30 side.

The polarizing plate with a phase difference layer and an adhesive layer may have another phase difference layer (not shown). The another phase difference layer may be provided in combination with another phase difference layer, or may be provided alone (i.e., without providing another phase difference layer). The optical properties (e.g., refractive index properties, in-plane phase difference, Nz coefficient, photoelastic coefficient), thickness, configuration position, etc. of the another phase difference layer may be appropriately set according to the purpose.

The polarizing plate with a phase difference layer and an adhesive layer can be in the form of a sheet or a strip. In this specification, the so-called "strip" means a long and thin shape with a very long length relative to the width, for example, including a long and thin shape with a length relative to the width of more than 10 times, preferably more than 20 times. The strip-shaped polarizing plate with a phase difference layer and an adhesive layer can be rolled into a roll.

In actual application, it is preferred to temporarily adhere the release film to the surface of the second adhesive layer 40 until the polarizing plate with the phase difference layer and the adhesive layer is ready for use. By temporarily adhering the release film, the second adhesive layer can be protected, and a roll of the polarizing plate with the phase difference layer and the adhesive layer can be formed.

The following describes the components of the polarizing plate with a phase difference layer and an adhesive layer.

B. Polarizing element Any appropriate polarizing element can be used as the polarizing element 11. For example, the resin film forming the polarizing element can be a single-layer resin film or a laminated body with two or more layers.

Specific examples of polarizing elements including a single-layer resin film include: polyvinyl alcohol (PVA) films, partially formalized PVA films, ethylene-vinyl acetate copolymer partially saponified films, and other hydrophilic polymer films dyed and stretched with dichroic substances such as iodine or dichroic dyes; polyene alignment films such as dehydrated PVA films or dehydrochlorinated polyvinyl chloride films, etc. In terms of excellent optical properties, it is preferred to use a polarizing element obtained by dyeing a PVA film with iodine and uniaxially stretching it.

The dyeing using iodine is performed, for example, by immersing the PVA membrane 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 it can be performed while dyeing. In addition, the dyeing can be performed after the stretching. If necessary, the PVA membrane is subjected to swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc. For example, by immersing the PVA membrane in water and washing it before dyeing, not only can the stains or anti-adhesive agents on the surface of the PVA membrane be washed, but the PVA membrane can also be swelled to prevent uneven dyeing.

Specific examples of polarizing elements 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. A polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by the following method: a PVA-based resin solution is coated on the resin substrate, and the laminate is dried to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and the laminate is stretched and dyed to make the PVA-based resin layer into a polarizing element. In this embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution and stretching it. Furthermore, stretching can further include stretching the laminate in the air at a high temperature (e.g., above 95° C.) before stretching in a boric acid aqueous solution, if necessary. The obtained resin substrate/polarizing element laminate can be used directly (i.e., the resin substrate can be used as a protective layer of the polarizing element), or the resin substrate can be peeled off from the resin substrate/polarizing element laminate, and any appropriate protective layer can be laminated on the peeled surface according to the target laminate. The details of the manufacturing method of such a polarizing element 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 by reference.

The polarizing element preferably includes a single layer of resin film. With such a structure, a polarizing plate with a phase difference layer and an adhesive layer in which phase difference non-uniformity can be suppressed in a high temperature environment can be obtained through the synergistic effect with the optimization of the first adhesive layer and the second adhesive layer.

The thickness of the polarizing element is preferably 15 μm or less, more preferably 1 μm to 12 μm, and further preferably 3 μm to 12 μm. If the thickness of the polarizing element is within this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

The polarizing element preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing element 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 polarizing element 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 a polarizing element. Specific examples of the material as the main component of the film include: cellulose resins such as triacetyl cellulose (TAC); or transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyether sulfone, polysulfone, polystyrene, polybutylene, polyolefin, (meth)acrylic, acetate, etc. In addition, thermosetting resins or ultraviolet curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone can also be cited. In addition, for example, glassy polymers such as siloxane polymers can also be cited. 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 a thermoplastic resin having a substituted or unsubstituted imine group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl and nitrile group in the side chain can be used, for example, a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be cited. The polymer film can be, for example, an extruded product of the above resin composition.

The polarizing plate with a phase difference layer and an adhesive layer is typically arranged on the viewing side of the image display device as described below, and the first protective layer 12 is typically arranged on the viewing side. Therefore, the first protective layer 12 may be subjected to surface treatments such as hard coating, anti-reflection, anti-sticking, and anti-glare as needed. Furthermore/or, the first protective layer 12 may be subjected to treatments to improve 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 when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate with a phase difference layer and an adhesive layer is also suitable for application in image display devices that can be used outdoors.

The thickness of the first protective layer is typically 300 μm or less, preferably 100 μm or less, more preferably 5 μm to 80 μm, and further preferably 10 μm to 60 μm. When surface treatment is applied, 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 that the in-plane phase difference Re(550) is 0 nm to 10 nm, and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm.

C. Phase difference layer C-1. Characteristics of phase difference layer As mentioned above, the in-plane phase difference Re(550) of the phase difference layer is 100 nm to 200 nm, preferably 110 nm to 180 nm, more preferably 120 nm to 160 nm, and further preferably 130 nm to 150 nm. That is, the phase difference layer can function as a so-called λ/4 plate.

The phase difference layer satisfies the relationship of Re(450)＜Re(550) as described above, and preferably further satisfies the relationship of Re(550)＜Re(650). That is, the phase difference layer shows the wavelength dependence of the reverse dispersion in which the phase difference value increases according to the wavelength of the measured light. The Re(450)/Re(550) of the phase difference film is, for example, greater than 0.5 and less than 1.0, preferably 0.7 to 0.95, more preferably 0.75 to 0.92, and further preferably 0.8 to 0.9. The Re(650)/Re(550) is preferably greater than 1.0 and less than 1.15, and more preferably 1.03 to 1.1.

The phase difference layer has an in-plane phase difference as described above, and therefore has a relationship of nx>ny. As long as the phase difference layer has a relationship of nx>ny, it shows any appropriate refractive index characteristics. The refractive index characteristics of the phase difference layer representatively show a relationship of nx>ny≧nz. Furthermore, 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, within the range that does not impair the effect of the present invention, a situation of ny<nz may exist. The Nz coefficient of the phase difference layer is preferably 0.9 to 2.0, more preferably 0.9 to 1.5, and further preferably 0.9 to 1.2. By satisfying this relationship, when the polarizing plate with a phase difference layer and an adhesive 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 in such a way that it can function optimally as a λ/4 plate. In other words, the thickness can be set in such a way that the desired in-plane phase difference can be obtained. Specifically, the thickness is preferably 15 μm to 60 μm, more preferably 20 μm to 55 μm, and most preferably 20 μm to 45 μm. In the embodiment of the present invention, the thickness of the phase difference layer can be significantly reduced compared to a λ/4 plate including a conventional resin film.

In the embodiment of the present invention, the shrinkage rate of the phase difference layer in the direction of the retardation axis when heated at 80°C to 125°C for 180 minutes is 4% or less, preferably 3.5% or less, and more preferably 3% or less. The smaller the shrinkage rate, the better, and its lower limit can be, for example, 0.5%.

The elongation at break of the stretched film constituting the phase difference layer is preferably 200% or more, more preferably 210% or more, further preferably 220% or more, and particularly preferably 245% or more. The upper limit of the elongation at break may be, for example, 500%. In addition to the excellent phase difference performance, the stretched film used in the phase difference layer in the embodiment of the present invention also has such excellent expansibility, so the desired in-plane phase difference can be achieved with a very thin thickness through the synergistic effect. Furthermore, in this specification, the so-called "elongation at break" means the elongation when the film breaks during the fixed-end uniaxial stretching at a specified stretching temperature (e.g., Tg-2°C).

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 polarizing plate with the phase difference layer and the adhesive layer is used in an image display device, display unevenness can be suppressed.

C-2. Constituent materials of phase difference layer The phase difference layer typically contains a resin containing at least one bonding group selected from the group consisting of carbonate bonds and ester bonds. In other words, the phase difference layer contains a polycarbonate resin, a polyester resin or a polyester carbonate resin (hereinafter, these are sometimes collectively referred to as polycarbonate resins, etc.). Polycarbonate resins, etc. contain at least one structural unit selected from the group consisting of structural units represented by the above general formula (1) and/or structural units represented by the above general formula (2). These structural units are structural units derived from divalent oligofluorenes, and are sometimes referred to as oligofluorene structural units hereinafter. Such polycarbonate resins, etc. have positive refractive index anisotropy.

The phase difference layer typically further contains an acrylic resin. The content of the acrylic resin is 0.5 mass % to 1.5 mass %. In this specification, percentages or parts in "mass" are synonymous with percentages or parts in "weight".

C-2-1. Polycarbonate-based resins, etc. <Oligomer fluorene structural unit> The oligomer fluorene structural unit is represented by the above-mentioned general formula (1) or (2). In the general formulae (1) and (2), R ¹ to R ³ are each independently a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴ to R ⁹ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a substituted sulfur atom, a substituted silicon atom, a halogen atom, a nitro group, or a cyano group. Here, R ⁴ to R ⁹ may be the same as or different from each other, and at least two adjacent groups among R ⁴ to R ⁹ may be bonded to each other to form a ring.

The content of the oligofluorene structural unit in the polycarbonate resin is preferably 1% to 40% by mass, more preferably 10% to 35% by mass, further preferably 15% to 30% by mass, and particularly preferably 18% to 25% by mass, relative to the entire resin. When the content of the oligofluorene structural unit is too high, the following problems may occur: too large a photoelastic coefficient, insufficient reliability, and insufficient phase difference expression. Furthermore, since the ratio of the oligofluorene structural unit in the resin becomes higher, the scope of molecular design becomes narrower, and it is difficult to improve when the resin is required to be modified. On the other hand, even if the desired inverse dispersion wavelength dependence is obtained by using a very small amount of oligofluorene structural units, in this case, the optical properties will sensitively change according to the slight deviation of the content of the oligofluorene structural units, so it is difficult to manufacture in a manner that various properties are controlled within a certain range.

The details of the oligofluorene structural unit are described in, for example, International Publication No. 2015/159928, which is incorporated herein by reference.

<Other structural units> Regarding polycarbonate resins, it is typical that, in addition to oligofluorene structural units, other structural units may also be included. In one embodiment, the other structural units are preferably derived from dihydroxy compounds or diester compounds. In order to express the target reverse dispersion wavelength, it is necessary to introduce structural units having positive intrinsic birefringence and oligofluorene structural units having negative intrinsic birefringence into the polymer structure together, so as other monomers to be copolymerized, it is preferably a dihydroxy compound or a diester compound as a raw material of the structural unit having positive birefringence.

As copolymer monomers, there can be cited: compounds into which structural units containing aromatic rings can be introduced, and compounds which do not introduce structural units containing aromatic rings and are composed of aliphatic structures. Specific examples of the above-mentioned compounds composed of aliphatic structures are given below. Dihydroxy compounds of straight-chain aliphatic hydrocarbons such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol; dihydroxy compounds of branched aliphatic hydrocarbons such as neopentyl glycol and hexanediol; 1,2-cyclohexanediol, 1,3-butanediol, 1,2-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol; dihydroxy compounds of branched aliphatic hydrocarbons such as neopentyl glycol and hexanediol; 1,2-cyclohexanediol, 1,3-butanediol, 1,2-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol; Dihydroxy compounds of diols and tertiary alcohols as exemplified alicyclic hydrocarbons such as diol, 1,4-cyclohexanediol, 1,3-dihydroxybutanediol, hydrogenated bisphenol A, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, 2,6-decacyclopentanediol, Dihydroxy compounds as primary alcohols of alicyclic hydrocarbons exemplified by dihydroxy compounds derived from terpene compounds such as hydronaphthalenedimethanol, 1,5-decahydronaphthalenedimethanol, 2,3-decahydronaphthalenedimethanol, 2,3-northane dimethanol, 2,5-northane dimethanol, 1,3-adamantanedimethanol, and limonene; oxyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and polypropylene glycol; diols; dihydroxy compounds with a cyclic ether structure such as isosorbide; dihydroxy compounds with a cyclic acetal structure such as spirodiol and dioxanediol; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. The following are specific examples of the compounds into which the structural unit containing an aromatic ring can be introduced. 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 2,2-bis(4-hydroxy-(3-phenyl)phenyl)propane, 2,2-bis(4-hydroxy-(3,5-diphenyl)phenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl) ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 1,1-bis(4-hydroxyphenyl)decane, bis(4-hydroxy-3-nitrophenyl)methane, 3,3-bis(4-hydroxyphenyl)pentane, 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene, 1,3-bis(2-(4-hydroxyphenyl)- Aromatic bisphenol compounds such as bis(4-hydroxyphenyl)sulfide, bis(4-hydroxy-3-methylphenyl)sulfide, bis(4-hydroxyphenyl)disulfide, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dichlorodiphenyl ether, etc.; 2,2-bis(4-(2-hydroxyethoxy)phenyl)propane, 2,2-bis(4-(2 Dihydroxy compounds having an ether group bonded to an aromatic group, such as 1,3-bis(2-hydroxyethoxy)benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, and bis(4-(2-hydroxyethoxy)phenyl)sulfonate; aromatic dicarboxylic acids, such as terephthalic acid, phthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonate dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Furthermore, the aliphatic dicarboxylic acid and aromatic dicarboxylic acid components listed above can be used as the raw materials of the above polyester carbonates by using the dicarboxylic acid itself, or by using dicarboxylic acid esters such as methyl esters and phenyl esters or dicarboxylic acid derivatives such as dicarboxylic acid halides as the raw materials depending on the production method.

Regarding the comonomer, dihydroxy compounds having a fluorene ring, such as 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, or dicarboxylic acid compounds having a fluorene ring, which are previously known as compounds containing structural units having negative birefringence, can also be used in combination with oligomeric fluorene compounds.

The resin used in the present invention preferably contains a structural unit represented by the following formula (3) as a copolymer component among the structural units that can be introduced by the above-mentioned compound having an alicyclic structure.

As the dihydroxy compound that can be introduced into the structural unit of the above formula (3), spirodiol can be used.

In the resin used in the present invention, the structural unit represented by the above formula (3) is preferably contained in an amount of 5 mass % or more and 90 mass % or less. The upper limit is further preferably 70 mass % or less, and particularly preferably 50 mass % or less. The lower limit is further preferably 10 mass % or more, more preferably 20 mass % or more, and particularly preferably 25 mass % or more. If the content of the structural unit represented by the above formula (3) is above the above lower limit, sufficient mechanical properties or heat resistance and a lower photoelastic coefficient can be obtained. Furthermore, the compatibility with acrylic resins is improved, and the transparency of the obtained resin composition can be further improved. In addition, the polymerization reaction rate of spirodiol is slow, so by suppressing the content to below the above upper limit, the polymerization reaction is easily controlled.

The resin used in the present invention preferably further contains a structural unit represented by the following formula (4) as a copolymer component.

Examples of dihydroxy compounds that can be introduced into the structural unit represented by the above formula (4) include isosorbide (ISB), dehydromannitol, and isoiditol, which are stereoisomers. These can be used alone or in combination of two or more.

In the resin used in the present invention, the structural unit represented by the above formula (4) is preferably contained in an amount of 5 mass % or more and 90 mass % or less. The upper limit is further preferably 70 mass % or less, and particularly preferably 50 mass % or less. The lower limit is further preferably 10 mass % or more, and particularly preferably 15 mass % or more. If the content of the structural unit represented by the above formula (4) is above the above lower limit, sufficient mechanical properties or heat resistance and a lower photoelastic coefficient can be obtained. In addition, the structural unit represented by the above formula (4) has the characteristic of high water absorption. Therefore, if the content of the structural unit represented by the above formula (4) is below the above upper limit, the dimensional change of the molded body caused by water absorption can be suppressed within the allowable range.

The resin used in the present invention may further contain other structural units. Furthermore, the structural unit is sometimes referred to as "other structural unit". As the monomer having other structural units, it is more preferable to use 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, 1,4-cyclohexanedicarboxylic acid (and its derivatives), and 1,4-cyclohexanedimethanol and tricyclodecanedimethanol are particularly preferred. The resin containing structural units derived from these monomers has an excellent balance of optical properties or heat resistance, mechanical properties, etc. In addition, since the polymerization reactivity of the diester compound is relatively low, from the viewpoint of improving the reaction efficiency, it is better not to use a diester compound other than a diester compound containing an oligofluorene structural unit.

The glass transition temperature (Tg) of the resin used in the present invention is preferably not less than 110°C and not more than 160°C. The upper limit is further preferably not more than 155°C, more preferably not more than 150°C, and particularly preferably not more than 145°C. The lower limit is further preferably not less than 120°C, and particularly preferably not less than 130°C. If the glass transition temperature is outside the above range, there is a tendency for heat resistance to deteriorate, which may cause dimensional changes after film formation, or deteriorate the reliability of quality under the conditions of use of the phase difference film. On the other hand, if the glass transition temperature is too high, there is a tendency for uneven film thickness to occur during film formation, or the film becomes brittle and the elongation deteriorates, and there is a tendency for the transparency of the film to be damaged.

The details of the structure and production method of polycarbonate resins are described in, for example, International Publication No. 2015/159928 (mentioned above), which is incorporated herein by reference.

C-2-2. Acrylic resin As the acrylic resin, an acrylic resin which is a thermoplastic resin is used. Examples of monomers that are structural units of acrylic resins include the following compounds: methyl methacrylate, methacrylic acid, methyl acrylate, acrylic acid, benzyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobutyl (meth)acrylate, norbutyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentyl (meth)acrylate, and propylene glycol (meth)acrylate. 2-(meth)acryloyloxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, pentamethylpiperidinyl (meth)acrylate, tetramethylpiperidinyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, cyclopentyl methacrylate, cyclopentyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, cycloheptyl methacrylate, cycloheptyl acrylate, cyclooctyl methacrylate, cyclooctyl acrylate, cyclododecyl methacrylate, cyclododecyl acrylate. These monomers may be used alone or in combination of two or more. Examples of the combination of two or more monomers include copolymerization of two or more monomers, blending of two or more homopolymers of one monomer, and combinations thereof. Furthermore, other monomers copolymerizable with these acrylic monomers (e.g., olefin monomers, vinyl monomers) may be used in combination.

The acrylic resin contains structural units derived from methyl methacrylate. The content of structural units derived from methyl methacrylate in the acrylic resin is preferably 70 mass % or more and 100 mass % or less. The lower limit is more preferably 80 mass % or more, further preferably 90 mass % or more, and particularly preferably 95 mass % or more. Within this range, excellent compatibility with the polycarbonate resin of the present invention can be obtained. As structural units other than methyl methacrylate, methyl acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, and styrene are preferably used. By copolymerizing methyl acrylate, thermal stability can be improved. By using phenyl (meth)acrylate, benzyl (meth)acrylate, and styrene, the refractive index of the acrylic resin can be adjusted, so by adjusting the refractive index of the combined resin, the transparency of the obtained resin composition can be improved. By using this acrylic resin, a reverse dispersion retardation film with excellent expansion and phase difference performance and low haze can be obtained.

The weight average molecular weight Mw of the acrylic resin is greater than 10,000 and less than 200,000. The lower limit is preferably greater than 30,000, and particularly preferably greater than 50,000. The upper limit is preferably less than 180,000, and particularly preferably less than 150,000. If the molecular weight is within this range, compatibility with polycarbonate resins can be obtained, thereby improving the transparency of the final phase difference film (phase difference layer), and the effect of fully improving the expansibility during stretching can be obtained. Furthermore, the above-mentioned weight average molecular weight is a molecular weight converted to polystyrene measured by GPC (Gel Permeation Chromatography). In addition, from the perspective of compatibility, acrylic resins are preferably substantially free of branched structures. The fact that the acrylic resin has no branched structure can be confirmed by the fact that the GPC curve of the acrylic resin is unimodal.

C-2-3. Blending of polycarbonate resins and acrylic resins A method for producing a resin composition for a phase difference film (phase difference layer) by blending polycarbonate resins and acrylic resins (the production method is described in C-3 below). Polycarbonate resins and acrylic resins are preferably blended in a molten state. A representative method for blending in a molten state is melt kneading using an extruder. The kneading temperature (molten resin temperature) is preferably 200°C to 280°C, more preferably 220°C to 270°C, and further preferably 230°C to 260°C. If the kneading temperature is within this range, thermal decomposition can be suppressed, and particles of a resin composition uniformly blended with two resins can be obtained. If the temperature of the molten resin in the extruder exceeds 280°C, there is a possibility of resin coloration and/or thermal decomposition. On the other hand, if the temperature of the molten resin in the extruder is lower than 200°C, the resin viscosity is too high and an excessive load is imposed on the extruder, or the resin is not fully melted. Furthermore, any appropriate structure can be adopted as the structure of the extruder, the structure of the screw, etc. In order to obtain the transparency of the resin that can withstand optical film use, it is preferred to use a double-spindle extruder. Furthermore, regarding the residual low molecular weight components in the resin or the low molecular weight thermally decomposed components in the extrusion mixing, there is a concern that they may contaminate the cooling roll or the conveying roll in the film forming step or the stretching step. Therefore, in order to remove them, it is better to use an extruder equipped with a vacuum vent.

As described above, the content of the acrylic resin in the resin composition (resulting in the phase difference layer) is greater than 0.5 mass % and less than 2.0 mass %. The lower limit is preferably greater than 0.6 mass %. The upper limit is preferably less than 1.5 mass %, more preferably less than 1.0 weight %, further preferably less than 0.9 weight %, and particularly preferably less than 0.8 weight %. In this way, by blending the acrylic resin in a very limited ratio in the polycarbonate resin, the expansibility and phase difference expression can be significantly increased. Furthermore, the haze can be suppressed. This effect is not theoretically clear, but is an unexpectedly excellent effect obtained through repeated tests. Furthermore, if the content of the acrylic resin is too little, there is a situation where the above-mentioned effect cannot be obtained. On the other hand, if the content of the acrylic resin is too high, the haze may increase, and the expansibility and phase difference expression may be insufficient and even lower than those within the above range.

In order to improve mechanical properties and/or solvent resistance, the resin composition may further contain synthetic resins, rubbers, and combinations thereof, such as aromatic polycarbonate, aliphatic polycarbonate, aromatic polyester, aliphatic polyester, polyamide, polystyrene, polyolefin, acrylic acid, amorphous polyolefin, ABS (acrylonitrile-butadiene-styrene), AS (acrylonitrile-styrene), polylactic acid, polybutylene succinate, and the like.

The resin composition may further contain additives. Specific examples of additives include heat stabilizers, antioxidants, catalyst deactivators, ultraviolet absorbers, light stabilizers, mold release agents, dyes/pigments, impact modifiers, antistatic agents, lubricants, lubricants, plasticizers, compatibilizers, nucleating agents, flame retardants, inorganic fillers, and foaming agents. The type, amount, combination, and content of the additives contained in the resin composition may be appropriately set according to the purpose.

C-3. Method for forming phase difference layer The phase difference layer can be obtained by forming a film from the resin composition described in the above C-2, and then stretching the film. As a method for forming a film from a resin composition, any appropriate molding method can be adopted. As specific examples, there can be cited compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP (Fiber Reinforced Plastics) molding, casting coating (such as casting), calendering, hot pressing, etc. Among them, extrusion molding or casting coating, which can improve the smoothness of the obtained film and obtain good optical uniformity, is preferred. The casting coating method may cause problems due to residual solvent, so the extrusion molding method is particularly preferred. Among the extrusion molding methods, the melt extrusion molding method using a T-die is preferred from the perspective of film productivity or ease of subsequent stretching treatment. The molding conditions can be appropriately set according to the composition or type of the resin used, the characteristics required for the phase difference layer, etc. In this way, a resin film including polycarbonate resins and acrylic resins can be obtained.

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

The stretching may be performed by any appropriate stretching method and stretching conditions (e.g., 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. may be used alone, simultaneously, or successively. Regarding the stretching direction, the stretching may be performed in various directions or dimensions such as the length direction, width direction, thickness direction, and oblique direction.

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

In one embodiment, the stretching temperature of the above-mentioned film is a temperature below the glass transition temperature (Tg) of a polycarbonate resin or the like. Usually, when a film of a polycarbonate resin or the like is stretched, the film is in a glassy state at a temperature below Tg, and therefore cannot be stretched substantially. According to the resin film used in the embodiment of the present invention, by blending a small amount of acrylic resin (representatively polymethyl methacrylate), stretching below Tg can be achieved without substantially changing the Tg of the polycarbonate resin or the like. Furthermore, although it is not theoretically clear, by stretching below Tg, a reverse dispersion phase difference film (phase difference layer) with excellent extensibility and phase difference performance and less haze can be achieved. Specifically, the stretching temperature is preferably Tg to Tg-10°C, more preferably Tg to Tg-8°C, and further preferably Tg to Tg-5°C. Furthermore, the film can be properly stretched even at a temperature higher than Tg, such as a maximum of about Tg+5°C or about Tg+2°C.

The stretched film obtained in the above manner is preferably subjected to a heat treatment at a temperature of 105°C or higher for more than 2 minutes. By performing the heat treatment, a phase difference layer having the above-mentioned desired shrinkage rate can be formed. The heating temperature is preferably 105°C to 140°C, more preferably 110°C to 130°C, and further preferably 115°C to 125°C. The heating time is preferably 2 minutes to 150 minutes, more preferably 3 minutes to 120 minutes, and further preferably 5 minutes to 60 minutes.

If necessary, the stretched film can be subjected to a relaxation treatment. In this way, the stress generated by the stretching can be relaxed, and a phase difference layer having the above-mentioned required shrinkage rate can be formed. As a relaxation treatment condition, any appropriate condition can be adopted. For example, the stretched film is shrunk at a prescribed relaxation temperature and a prescribed relaxation rate (shrinkage rate) along the stretching direction. The relaxation temperature is preferably 60°C to 150°C. The relaxation rate is preferably 3% to 6%. In the case of performing a relaxation treatment, the relaxation treatment can typically be performed before the above-mentioned heat treatment.

In the above manner, a phase difference film constituting a phase difference layer can be obtained.

D. First adhesive layer and second adhesive layer D-1. Characteristics of the first adhesive layer and/or the second adhesive layer As described above, the first adhesive layer 20 has a paste offset after a heating test at 85°C for 500 hours of 300 μm or more, preferably 330 μm or more, more preferably 360 μm or more, further preferably 390 μm or more, and particularly preferably 420 μm or more. The upper limit of the paste offset may be, for example, 600 μm. By using an adhesive with a large paste offset to bond the polarizing element to the phase difference layer, the synergistic effect of the effect obtained by controlling the shrinkage rate of the phase difference layer in the direction of the retardation axis and the effect obtained by controlling the creep value of the second adhesive layer described below can be achieved to achieve a polarizing plate with a phase difference layer and an adhesive layer in which the phase difference unevenness can be suppressed in a high temperature environment. Furthermore, in this specification, the so-called "paste offset" refers to the length of the adhesive layer that overflows the most from the end faces of the polarizing element and the phase difference layer after a heating test in the polarizing plate with a phase difference layer and an adhesive layer.

The creep value of the second adhesive layer 40 at 23°C is, for example, 5 μm or more, preferably 20 μm or more, more preferably 30 μm or more, further preferably 60 μm or more, particularly preferably 100 μm or more, and even more preferably 120 μm or more. The upper limit of the creep value may be, for example, 300 μm. In this way, by using an adhesive with a large creep value to adhere the polarizing plate with the phase difference layer and the adhesive layer to the image display unit, the synergistic effect of the effect obtained by controlling the shrinkage rate of the above-mentioned phase difference layer in the direction of the retardation axis and the effect obtained by controlling the paste offset of the above-mentioned first adhesive layer can realize an image display device in which color unevenness is suppressed in a high temperature environment. The creep value can be measured, for example, by the following procedure: a test sample cut from an adhesive sheet is attached to a support plate with a 10 mm × 10 mm joint surface. With the support plate to which the test sample is attached fixed, a load of 500 gf is applied to the lead frame. The deflection from the support plate 1 second after the load is applied and 3600 seconds after the load is applied is measured and set as Cr ₁ and Cr ₃₆₀₀ , respectively. The ΔCr calculated from Cr ₁ and Cr ₃₆₀₀ by the following formula is used as the creep value. In addition, the creep value in this manual is the value when the thickness of the adhesive layer is converted to 20 μm. ΔCr＝Cr ₃₆₀₀ －Cr ₁

The storage modulus of the first adhesive layer and/or the second adhesive layer at 85°C is preferably 1.0×10 ⁴ Pa or more, preferably 2.0×10 ⁴ Pa or more, more preferably 5.0×10 ⁴ Pa or more, and further preferably 1.0×10 ⁵ Pa or more. If the storage modulus is within this range, the above-mentioned required paste deflection amount and/or creep value can be easily achieved. On the other hand, the storage modulus is, for example, 3.0×10 ⁶ Pa or less.

The thickness of the first adhesive layer is preferably 2 μm to 50 μm, more preferably 3 μm to 40 μm. The thickness of the second adhesive layer is preferably 4 μm to 30 μm, more preferably 5 μm to 20 μm. If the thickness of the first adhesive layer and the second adhesive layer is within this range, then through the synergistic effect of controlling the above-mentioned paste offset and creep value, a polarizing plate with a phase difference layer and an adhesive layer in which phase difference unevenness can be suppressed in a high temperature environment can be realized, and an image display device in which color unevenness can be suppressed in a high temperature environment can be realized.

D-2. Constituent materials of the first adhesive layer and the second adhesive layer Regarding the first adhesive layer and the second adhesive layer, any appropriate composition may be adopted as long as the first adhesive layer has the above-mentioned required paste offset amount and the second adhesive layer has the above-mentioned required creep value. The first adhesive layer and the second adhesive layer may contain the same adhesive or different adhesives. In the following, the constituent materials of the first adhesive layer and the second adhesive layer are collectively referred to as adhesive layers. The paste offset and/or creep value can be controlled by adjusting the composition of the adhesive constituting the adhesive layer (e.g., the type of base polymer (polarity, Tg, flexibility), molecular weight), crosslinking structure (e.g., the type of crosslinking agent, the distance between crosslinking points (molecular weight between crosslinking points), crosslinking density), etc.

D-2-1. Base polymer The adhesive layer is typically formed of an adhesive composition containing a (meth)acrylic polymer, a urethane polymer, a silicone polymer or a rubber polymer as a base polymer. When a (meth)acrylic polymer is used as the base polymer, the adhesive layer is formed of an adhesive composition containing a (meth)acrylic polymer (A), for example. The (meth)acrylic polymer (A) contains an alkyl (meth)acrylate as a main component.

<(Meth)acrylic polymer (A)> As described above, the (meth)acrylic polymer (A) contains an alkyl (meth)acrylate as a main component. From the viewpoint of improving the adhesion of the adhesive layer, the alkyl (meth)acrylate is preferably 50% by weight or more of all monomer components forming the (meth)acrylic polymer (A), and the remaining portion of the monomer other than the alkyl (meth)acrylate can be set arbitrarily. In addition, the (meth)acrylate refers to acrylate and/or methacrylate.

As the (meth)acrylic acid alkyl ester constituting the main skeleton of the (meth)acrylic acid polymer (A), there can be mentioned a (meth)acrylic acid alkyl ester having a linear or branched alkyl group with a carbon number of 1 to 18. As the alkyl group, there can be mentioned, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an isooctyl group, a nonyl group, a decyl group, an isodecyl group, a dodecyl group, an isomyristyl group, a lauryl group, a tridecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, and the like. The (meth)acrylic acid alkyl ester can be used alone or in combination. The average carbon number of the alkyl group is preferably 3 to 10.

The (meth)acrylic polymer (A) may contain, in addition to the (meth)acrylic acid alkyl ester as a monomer component, comonomers such as a carboxyl group-containing monomer (a1) and a hydroxyl group-containing monomer (a2) as monomer components. The comonomers may be used alone or in combination.

The carboxyl group-containing monomer (a1) is a compound having a carboxyl group and a polymerizable unsaturated double bond such as a (meth)acrylic acid group or a vinyl group in its structure. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and the like. Among these, acrylic acid is preferred from the viewpoints of copolymerizability, price, and improving the adhesive properties of the adhesive layer.

When the carboxyl group-containing monomer (a1) is used as a monomer component, the content of the carboxyl group-containing monomer (a1) is usually 0.01% by weight or more and 10% by weight or less in all monomer components forming the (meth)acrylic polymer (A).

The monomer (a2) containing a hydroxyl group is a compound containing a hydroxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the monomer containing a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; and (4-hydroxymethylcyclohexyl)methyl acrylate. Among them, from the viewpoint of improving the durability of the adhesive layer, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 4-hydroxybutyl (meth)acrylate is more preferred.

When a hydroxyl group-containing monomer (a2) is used as a monomer component, the content of the hydroxyl group-containing monomer (a2) is usually 0.01% by weight or more and 10% by weight or less in all monomer components forming the (meth)acrylic polymer (A).

The (meth)acrylic polymer (A) preferably contains, as a monomer component, a monomer having an unsaturated carbon double bond whose homopolymer glass transition temperature is 0°C or higher. Examples of the monomer (a3) having an unsaturated carbon double bond whose homopolymer glass transition temperature is 0°C or higher include (meth)acrylic acid alkyl ester monomers and (meth)acrylic acid. The monomer (a3) is preferably a monomer having an unsaturated carbon double bond whose homopolymer glass transition temperature is 20°C or higher, and more preferably a monomer having an unsaturated carbon double bond whose homopolymer glass transition temperature is 40°C or higher.

The content of the monomer (a3) in the (meth)acrylic polymer (A) is not particularly limited. The content is usually 0.1% to 40% by weight, and more preferably 1% to 30% by weight. When two or more monomers (a3) are used in combination, the content is the total content.

Examples of the monomer (a3) include methyl acrylate (Tg: 8°C), methyl methacrylate (Tg: 105°C), ethyl methacrylate (Tg: 65°C), n-propyl acrylate (Tg: 3°C), n-propyl methacrylate (Tg: 35°C), n-pentyl acrylate (Tg: 22°C), n-tetradecyl acrylate (Tg: 24°C), n-hexadecyl acrylate (Tg: 35°C), n-hexadecyl methacrylate (Tg: 15°C), n-octadecyl acrylate (Tg: 30°C), and n-octadecyl methacrylate (Tg: 22°C). g: 38°C) and other linear (meth) alkyl acrylates; branched (meth) alkyl acrylates such as tert-butyl acrylate (Tg: 43°C), tert-butyl methacrylate (Tg: 48°C), isopropyl methacrylate (Tg: 81°C) and isobutyl methacrylate (Tg: 48°C); cyclic (meth) alkyl acrylates such as cyclohexyl acrylate (Tg: 19°C), cyclohexyl methacrylate (Tg: 65°C), isobutyl acrylate (Tg: 94°C) and isobutyl methacrylate (Tg: 180°C); acrylic acid (Tg: 106°C), etc. These can be used alone or in combination.

When the adhesive composition contains the following crosslinking agent, the copolymer monomer becomes a reaction point with the crosslinking agent. Monomers containing carboxyl groups and monomers containing hydroxyl groups are highly reactive with intermolecular crosslinking agents, and therefore can be preferably used to improve the cohesiveness or heat resistance of the obtained adhesive layer. In addition, monomers containing carboxyl groups are better in terms of both durability and secondary processing properties, while monomers containing hydroxyl groups are better in terms of improving secondary processing properties.

As a monomer component, other comonomers (a4) may be further used. Other comonomers (a4) may have polymerizable functional groups having unsaturated double bonds such as (meth)acryl or vinyl. By using other comonomers (a4), the adhesion and heat resistance of the adhesive layer may be improved. Other comonomers (a4) may be used alone or in combination.

By using an amine-containing monomer or an amide-containing monomer as other copolymer monomers (a4), the adhesion of the adhesive layer can be improved. Examples of amine-containing monomers are N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of amide-containing monomers are (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-methyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxymethyl-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide, and N-butyl (meth)acrylamide. Acrylamide monomers such as (methyl)acrylamide, aminoethyl (meth)acrylamide, hydroxymethyl (meth)acrylamide, hydroxyethyl (meth)acrylamide; N-(meth)acryloylpiperidine, N-(meth)acrylpyrrolidine and other N-acryl heterocyclic monomers; N-vinylpyrrolidone, N-vinyl-ε-caprolactam and other N-vinyl lactam monomers.

Other copolymer monomers (a4) may be multifunctional monomers. By using multifunctional monomers, the gel fraction of the adhesive layer can be adjusted or the cohesive force can be controlled. Examples of multifunctional monomers include hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, tetrahydroxymethylmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate and other multifunctional acrylates; and divinylbenzene. The multifunctional acrylate is preferably 1,6-hexanediol diacrylate or dipentaerythritol hexa(meth)acrylate.

As other copolymerizable monomers (a4), in addition to the above, for example, alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate; cyclopolymerizable monomers such as methyl 2-(allyloxymethyl)acrylate; monomers containing an epoxy group such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; ethoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate; Monomers containing sulfonic acid groups, such as sodium olefin sulfonate; Monomers containing phosphate groups; (meth)acrylates having alicyclic hydrocarbon groups, such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobutyl (meth)acrylate; (meth)acrylates having aromatic hydrocarbon groups, such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate; vinyl esters, such as vinyl acetate and vinyl propionate; aromatic vinyl compounds, such as styrene and vinyl toluene; olefins or dienes, such as ethylene, propylene, butadiene, isoprene, and isobutylene; vinyl ethers, such as vinyl alkyl ether; and vinyl chloride.

The content of the other comonomer (a4) in the (meth)acrylic polymer is preferably 20 mass % or less, more preferably 10 mass % or less, further preferably 8 mass % or less, particularly preferably 5 mass % or less.

The weight average molecular weight Mw of the (meth)acrylic polymer (A) is, for example, 200,000 to 3,000,000, preferably 1,000,000 to 2,500,000, and more preferably 1,200,000 to 2,500,000. If the weight average molecular weight Mw is within this range, an adhesive layer having excellent durability (especially heat resistance) can be obtained. If the weight average molecular weight Mw exceeds 3,000,000, the viscosity may increase and/or gelation may occur during polymerization.

D-2-2. Silane coupling agent containing reactive functional groups The adhesive composition may include a silane coupling agent containing reactive functional groups. The reactive functional groups of the silane coupling agent containing reactive functional groups are typically functional groups other than acid anhydride groups. Examples of functional groups other than acid anhydride groups include epoxy groups, hydroxyl groups, amino groups, isocyanate groups, isocyanurate groups, vinyl groups, styryl groups, acetoacetyl groups, urea groups, thiourea groups, (meth)acryl groups, heterocyclic groups, and combinations thereof. The silane coupling agents containing reactive functional groups may be used alone or in combination.

When a silane coupling agent containing a reactive functional group is added to the adhesive composition, the amount of the silane coupling agent containing a reactive functional group is generally 0.001 to 5 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A).

D-2-3. Crosslinking agent The adhesive composition may contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent, a multifunctional metal chelate, etc. may be used. Examples of organic crosslinking agents include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents. A multifunctional metal chelate is a crosslinking agent formed by covalent bonding or coordination bonding of a polyvalent metal and an organic compound. When the adhesive composition is a radiation-curable type, a multifunctional monomer may be used as a crosslinking agent. The crosslinking agent may be used alone or in combination.

When a crosslinking agent is added to the adhesive composition, the amount of the crosslinking agent added is usually 0.01 to 15 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A).

When an isocyanate crosslinking agent is added to the adhesive composition, the amount of the isocyanate crosslinking agent added is generally 0.01 to 15 parts by weight based on 100 parts by weight of the (meth)acrylic polymer.

When a peroxide is added to the adhesive composition, the amount of the peroxide added is usually 0.01 to 2 parts by weight based on 100 parts by weight of the (meth)acrylic polymer. If the amount is within this range, processability and crosslinking stability can be easily adjusted.

D-2-4. Additives The adhesive composition may contain (meth)acrylic oligomers and/or ionic compounds. Furthermore, the adhesive composition may contain additives. Specific examples of additives include: colorants, pigment powders, dyes, surfactants, plasticizers, adhesive agents, surface lubricants, levelers, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foils. Furthermore, within a controllable range, a redox system with a reducing agent added may be used. The type, amount, combination, content, etc. of the additives may be appropriately set according to the purpose. The content of the additive is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and further preferably 1 part by weight or less, based on 100 parts by weight of the (meth)acrylic polymer (A).

E. Image display device The polarizing plate with a phase difference layer and an adhesive layer described in Items A to D above can be applied to an image display device. Therefore, the implementation method of the present invention also includes an image display device using the polarizing plate with a phase difference layer and an adhesive layer. As representative examples of image display devices, liquid crystal display devices and organic EL display devices can be cited. Regarding the image display device of the implementation method of the present invention, it is representative that the polarizing plate with a phase difference layer and an adhesive layer described in Items A to D above is provided on its viewing side. Implementation example

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

(1) Paste offset The polarizing plates with phase difference layers and adhesive layers obtained in the embodiments and comparative examples were cut into specified sizes (M size or T size in Table 1 below) as test samples. The test samples were subjected to a heating test at 85°C for 500 hours, and the amount of the first adhesive layer overflowing from the end faces of the polarizing element and the phase difference layer after the heating test was observed and measured using an objective lens (20 times). The length of the portion of the first adhesive layer with the most overflow was taken as the paste offset. During observation, the transmitted light was adjusted to 0 (zero) and the reflected light was used for observation. (2) Creep value The polarizing plate with phase difference layer and adhesive layer obtained in the embodiment and comparative example was cut into a size of 10 mm × 30 mm as a test sample. The upper end of the test sample was attached to a SUS (Steel Use Stainless Steel) plate with a size of 10 mm × 10 mm via the second adhesive layer, and a load of 500 gf was applied to the lower end of the test sample downward. The displacement between the test sample and the SUS plate was measured 1 second and 3600 seconds after the load was applied, and was set as Cr ₁ and Cr ₃₆₀₀ respectively. The ΔCr calculated by the following formula based on Cr ₁ and Cr ₃₆₀₀ was used as the creep value. ΔCr＝Cr ₃₆₀₀ －Cr ₁ (3) Color unevenness The polarizing plates with phase difference layers and adhesive layers obtained in the examples and comparative examples were cut into a predetermined size (M size or T size in Table 1 below), and attached to a glass plate via a second adhesive layer to serve as test samples. The test samples heated at 85°C for 500 hours were placed on a reflective plate (DMS evaporated film manufactured by Toray Film Processing Co., Ltd.) and the reflected hues a ^* _C and b ^* _C at the center of the sample and a ^* _E and b ^* _E at the edge of the sample were measured using a spectrophotometer (manufactured by Konica Minolta, product name "CM-2600d"). Δab obtained by the following formula was used as an index of color unevenness. The smaller Δab is, the better the color unevenness is. Δab＝{(a ^* _E －a ^* _C ) ^2＋ (b ^* _E －b ^* _C ) ² } ^1/2

[Abbreviations of compounds] The abbreviations of the compounds used in the following production examples are as follows. ・BPFM: Bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane was synthesized by the method described in Japanese Patent Publication No. 2015-25111. [Chemistry 5] ・ISB: Isosorbide [manufactured by Roquette Freres] ・SPG: Spiroglycol [manufactured by Mitsubishi Gas Chemical Co., Ltd.] ・DPC: Diphenyl carbonate [manufactured by Mitsubishi Chemical Co., Ltd.]

[Production Example 1: Production of a phase difference film constituting a phase difference layer] A batch polymerization apparatus including two vertical stirring reactors equipped with stirring blades and a reflux cooler was used for polymerization. 30.31 parts by mass (0.047 mol) of BPFM, 39.94 parts by mass (0.273 mol) of ISB, 30.20 parts by mass (0.099 mol) of SPG, 69.67 parts by mass (0.325 mol) of DPC, and 7.88×10 ^-4 parts by mass (4.47×10 ^-6 mol) of calcium acetate water as a catalyst were added. After the pressure in the reactor was replaced with nitrogen, it was heated with a heat medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature reaches 220°C, and the pressure is reduced while being controlled to maintain the temperature. After reaching 220°C, it takes 90 minutes to make it 13.3 kPa. The phenol vapor produced as a by-product of the polymerization reaction is introduced into a reflux cooler at 110°C, and a certain amount of monomer components contained in the phenol vapor is returned to the reactor. The uncondensed phenol vapor is introduced into a condenser at 45°C and recovered. Nitrogen is introduced into the first reactor, and after temporarily re-pressurizing to atmospheric pressure, the reaction liquid in the first reactor that has been oligomerized is transferred to the second reactor. Subsequently, the temperature and pressure reduction in the second reactor are started, and the internal temperature reaches 240°C and the pressure reaches 20 kPa in 40 minutes. After that, the polymerization is carried out while the pressure is further reduced until the specified stirring power is reached. When the specified power is reached, nitrogen is introduced into the reactor for re-pressurization, and the generated polyester carbonate is extruded into water, and the strands are cut to obtain pellets. This resin is called "PC1". The ratio of the structural units derived from each monomer is BPFM/ISB/SPG/DPC = 21.5/39.4/30.0/9.1 mass %. The reduced viscosity of PC1 is 0.46 dL/g, Mw is 48,000, refractive index n _D is 1.526, melt viscosity is 2480 Pa·s, glass transition temperature is 139℃, photoelastic coefficient is 9×10 ^-12 [m ² /N], and wavelength dispersion Re(450)/Re(550) is 0.85.

Dianal BR80 (manufactured by Mitsubishi Chemical Co., Ltd.) was used as an acrylic resin and extruded and kneaded with the obtained polyester carbonate. The mixture of polycarbonate pellets (99.5 parts by mass) and BR80 powder (0.5 parts by mass) was fed into a double-spindle extruder TEX30HSS manufactured by The Nippon Steel Works Co., Ltd. using a quantitative feeder. The extruder cylinder temperature was set to 250°C, and extrusion was performed at a processing capacity of 12 kg/hr and a screw speed of 120 rpm. In addition, the extruder was equipped with a vacuum vent to extrude the molten resin while depressurizing it to remove volatility. The resin composition pellets thus obtained were vacuum dried at 100°C for more than 6 hours, and then a film-making device equipped with a single-screw extruder (manufactured by Isuzu Kakoki Co., Ltd., screw diameter of 25 mm, cylinder temperature setting: 250°C), a T-die (width of 300 mm, temperature setting: 220°C), a cooling roll (temperature setting: 120-130°C) and a winder was used to make a long unstretched film with a length of 3 m, a width of 200 mm, and a thickness of 100 μm. The long unstretched film was stretched at a stretching temperature Tg and a stretching ratio of 2.4 times. The obtained stretched film was subjected to a relaxation treatment (relaxation temperature: 130° C., relaxation rate: 4.5%), and then subjected to a heat treatment at 125° C. for 2 minutes.

Thus, a phase difference film R1 constituting a phase difference layer was obtained. When the phase difference film R1 was heated at 125°C for 180 minutes, the shrinkage rate in the retardation axis direction was 2.92%. In addition, the phase difference film R1 showed a refractive index characteristic of nx>ny>nz, Re(550) was 145nm, and Re(450)/Re(550) was 0.85.

[Production Example 2: Production of a phase difference film constituting a phase difference layer] A phase difference film R2 was obtained in the same manner as in Production Example 1 except that the relaxation treatment and the heat treatment were not performed. The shrinkage rate of the phase difference film R2 in the direction of the retardation axis when heated at 125°C for 180 minutes was 4.54%. In addition, the phase difference film R2 showed a refractive index characteristic of nx＞ny＞nz, Re(550) was 145 nm, and Re(450)/Re(550) was 0.85.

[Production Example 3: Preparation of Adhesive] (Preparation of Acrylic Polymer A1) A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler. Furthermore, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was added together with 100 parts of ethyl acetate to 100 parts of the monomer mixture. After nitrogen replacement was performed while slowly stirring and introducing nitrogen, the liquid temperature in the flask was maintained at about 55°C, and a polymerization reaction was performed for 8 hours to prepare a solution of acrylic polymer A1 with a weight average molecular weight (Mw) of 1.8 million and Mw/Mn=4.8.

(Preparation of adhesive) With respect to 100 parts of the solid content of the acrylic polymer A1 solution, 0.02 parts of trihydroxymethylpropane/xylylene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "Takenate D110N"), 0.3 parts of peroxide crosslinking agent (manufactured by NOF Corporation, trade name "Nyper BMT"), and 0.2 parts of epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed to obtain adhesive PSA1.

[Production Example 4: Preparation of Adhesive] Except for changing the amount of D110N to 0.1 part, the adhesive PSA2 was obtained in the same manner as in Production Example 3.

[Production Example 5: Preparation of Adhesive] (Preparation of Acrylic Polymer A2) Except for using a monomer mixture containing 94.9 parts of butyl acrylate, 0.1 parts of 2-hydroxyethyl acrylate and 5 parts of acrylic acid, a solution of acrylic polymer A2 with Mw of 2.3 million and Mw/Mn=3.9 was prepared in the same manner as in Production Example 3.

(Preparation of adhesive) With respect to 100 parts of the solid content of the acrylic polymer A2 solution, 0.6 parts of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), 0.2 parts of peroxide crosslinking agent (manufactured by NOF Corporation, trade name "Nyper BMT"), and 0.2 parts of epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed to obtain adhesive PSA3.

[Preparation Example 6: Preparation of Adhesive] (Preparation of Acrylic Polymer A3) Except for using a monomer mixture containing 91 parts of butyl acrylate, 6 parts of N-acryloyl methacrylate, 0.3 parts of 4-hydroxybutyl acrylate and 2.7 parts of acrylic acid, a solution of acrylic polymer A3 with Mw of 2.7 million and Mw/Mn=3.8 was prepared in the same manner as in Preparation Example 3.

(Preparation of adhesive) With respect to 100 parts of the solid content of the acrylic polymer A3 solution, 0.1 parts of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 parts of peroxide crosslinking agent (manufactured by NOF Corporation, trade name "Nyper BMT"), and 0.2 parts of epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed to obtain adhesive PSA4.

[Preparation Example 7: Preparation of Adhesive] (Preparation of Acrylic Polymer A4) Except for using a monomer mixture containing 82.1 parts of butyl acrylate, 13 parts of benzyl acrylate, 0.1 parts of 4-hydroxybutyl acrylate and 4.8 parts of acrylic acid, a solution of acrylic polymer A4 with a Mw of 2.2 million was prepared in the same manner as in Preparation Example 3.

(Preparation of adhesive) Based on 100 parts of the solid content of the acrylic polymer A4 solution, 0.5 parts of a polyether compound having a reactive silyl group (manufactured by Kaneka, trade name "Silyl SAT10"), 0.45 parts of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh, trade name "Coronate L") and 0.1 parts of a peroxide crosslinking agent (benzoyl peroxide) were mixed to obtain an adhesive PSA5.

[Production Example 8: Production of polarizing plate] (Production of polarizing element) A long roll of polyvinyl alcohol (PVA) resin film (manufactured by Kuraray Co., Ltd., product name "PE3000") with a thickness of 30 μm was uniaxially stretched in the length direction by a roller stretching machine so that it became 5.9 times in the length direction, and simultaneously subjected to swelling, dyeing, crosslinking, washing treatment, and finally drying treatment, thereby producing a polarizing element with a thickness of 12 μm. Specifically, the swelling treatment is to stretch it 2.2 times while treating it with pure water at 20°C. Secondly, the dyeing treatment was carried out while stretching 1.4 times in a 30°C aqueous solution with a weight ratio of iodine to potassium iodide of 1:7 and an iodine concentration adjusted so that the monomer transmittance of the obtained polarizing element became 45.0%. Furthermore, the crosslinking treatment adopted a two-stage crosslinking treatment, and the first stage of the crosslinking treatment was carried out while stretching 1.2 times in a 40°C aqueous solution containing boric acid and potassium iodide. The boric acid content of the aqueous solution in the first stage of the crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. The second stage of the crosslinking treatment was carried out while stretching 1.6 times in a 65°C aqueous solution containing boric acid and potassium iodide. The boric acid content of the aqueous solution in the second stage of the crosslinking treatment was 4.3 wt % and the potassium iodide content was 5.0 wt %. In addition, the washing treatment was performed using a potassium iodide aqueous solution at 20° C. The potassium iodide content of the aqueous solution in the washing treatment was set to 2.6 wt %. Finally, the drying treatment was performed at 70° C. for 5 minutes to obtain a polarizing element.

(Preparation of polarizing plate) A triacetyl cellulose film (thickness 40 μm, manufactured by Konica Minolta, trade name "KC4UYW") was bonded to one side of the above polarizing element via a polyvinyl alcohol-based adhesive to obtain a polarizing plate P1 having a protective layer/polarizing element structure.

[Production Example 9: Production of polarizing plate] (Production of polarizing element) As a thermoplastic resin substrate, a long amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) with a Tg of about 75°C was used, and one side of the resin substrate was subjected to a corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gohsefimer") were mixed in a ratio of 9:1, and the resulting mixture was dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm to produce a laminate. The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (length direction) in an oven at 130°C (air-assisted stretching treatment). Then, the laminate was immersed in an insolubilizing bath (a boric acid aqueous 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, while adjusting the concentration so that the monomer transmittance (Ts) of the polarizing element finally obtained becomes the desired value, immerse in a dyeing bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 relative to 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds (dyeing treatment). Then, immerse in a crosslinking bath (an boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid relative to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Thereafter, the laminate was immersed in a boric acid aqueous solution (boric acid concentration of 4 weight percent, potassium iodide concentration of 5 weight percent) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (length direction) between rollers of different circumferential speeds at a total stretching ratio of 5.5 times (underwater stretching treatment). Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by mixing 4 weight parts of potassium iodide with 100 weight parts of water) at a liquid temperature of 20°C (cleaning treatment). Thereafter, it was dried in an oven maintained at approximately 90°C, and contacted with a SUS heating roller maintained at a surface temperature of approximately 75°C (drying shrinkage treatment). In this way, a polarizing element with a thickness of about 5 μm was formed on the resin substrate, and a polarizing plate having a structure of resin substrate/polarizing element was obtained.

(Production of polarizing plate) A cycloolefin film (ZF-12, 23 μm, manufactured by Zeon Co., Ltd., Japan) is bonded to the surface of the obtained polarizing element (the surface opposite to the resin substrate) via a UV-curable adhesive. Specifically, the curable adhesive is applied so that the total thickness becomes about 1.0 μm, and bonding is performed using a roller press. Thereafter, UV rays are irradiated from the cycloolefin film side to cure the adhesive. Subsequently, the resin substrate is peeled off to obtain a polarizing plate P2 having a cycloolefin film (protective layer)/polarizing element structure.

[Examples 1 to 5 and Comparative Examples 1 to 8] A polarizing plate, a phase difference film (phase difference layer), and an adhesive (a first adhesive layer and a second adhesive layer) were combined as shown in Table 1 to produce a polarizing plate with a phase difference layer and an adhesive layer. Here, the polarizing plate and the phase difference layer (phase difference film) were bonded in such a way that the absorption axis of the polarizing element and the retardation axis of the phase difference film formed an angle of 45°. The obtained polarizing plate with a phase difference layer and an adhesive layer was subjected to the above-mentioned color unevenness evaluation. The results are shown in Table 1 together with the paste offset of the first adhesive layer, the shrinkage rate of the phase difference layer, and the creep value of the second adhesive layer. Furthermore, in the "Size" column of Table 1, "M" means 77.4 mm × 162.3 mm, and "T" means 159.5 mm × 244.5 mm.

[Table 1] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Comparison Example 6 Comparison Example 7 Comparative Example 8 Polarizing Plate P1 P1 P1 P1 P1 P2 P1 P1 P1 P1 P1 P1 P1 1st adhesive layer PSA1 PSA1 PSA1 PSA1 PSA1 PSA1 PSA5 PSA5 PSA1 PSA1 PSA1 PSA1 PSA5 Phase difference layer R1 R1 R1 R1 R1 R2 R1 R2 R2 R2 R2 R2 R1 Second adhesive layer PSA4 PSA1 PSA2 PSA3 PSA1 PSA1 PSA2 PSA2 PSA4 PSA1 PSA2 PSA3 PSA2 size M M M M T M M M M M M M T Paste offset 470 427 433 513 448 105 103 115 452 282 342 397 76 Shrinkage rate 2.92 2.92 2.92 2.92 2.92 4.54 2.92 4.54 4.54 4.54 4.54 4.54 2.92 Creep value 30 156 81 41 156 156 81 81 30 156 81 41 81 ∆ab 0.85 0.52 0.88 0.98 0.77 2.3 1.45 2.32 1.12 1.07 1.65 1.46 2.01

[Evaluation] As can be seen from Table 1, by controlling the paste offset of the first adhesive layer, the shrinkage rate of the phase difference layer, and the creep value of the second adhesive layer, a polarizing plate with a phase difference layer and an adhesive layer can be obtained for an image display device that can suppress color unevenness in a high temperature environment. [Industrial Applicability]

The polarizing plate with a phase difference layer and an adhesive layer of the present invention can be suitably used in image display devices (typically, liquid crystal display devices and organic EL display devices).

10: Polarizing plate 11: Polarizing element 12: First protective layer 13: Second protective layer 20: First adhesive layer 30: Phase difference layer 40: Second adhesive layer 100: Polarizing plate with phase difference layer and adhesive layer

FIG. 1 is a schematic cross-sectional view of a polarizing plate with a phase difference layer and an adhesive layer according to an embodiment of the present invention.

10: Polarizing plate

11: Polarizing element

12: 1st protective layer

13: Second protective layer

20: 1st adhesive layer

30: Phase difference layer

40: Second adhesive layer

100: Polarizing plate with phase difference layer and adhesive layer

Claims (7)

A polarizing plate with a phase difference layer and an adhesive layer, comprising: a polarizing plate including a polarizing element; a phase difference layer attached to the polarizing plate via a first adhesive layer; and a second adhesive layer provided as an outermost layer on the side of the phase difference layer opposite to the polarizing plate; and the phase difference layer comprises a stretched film of a resin film, satisfying the relationship of Re(450)<Re(550), and The shrinkage rate in the direction of the retardation axis when heated at 80℃~125℃ for 180 minutes is less than 4%; the paste offset of the first adhesive layer after the heating test at 85℃ and 500 hours is more than 300μm; Here, Re(450) and Re(550) are the in-plane phase differences measured by light with wavelengths of 450nm and 550nm at 23℃, respectively. As in claim 1, the polarizing plate with a phase difference layer and an adhesive layer, wherein the Re (550) of the phase difference layer is 100nm~200nm, and the angle between the phase retardation axis of the phase difference layer and the absorption axis of the polarizing element is 40°~50° or 130°~140°. For example, a polarizing plate with a phase difference layer and an adhesive layer as in claim 1 or 2, wherein the thickness of the phase difference layer is 15μm~60μm. For example, the polarizing plate with a phase difference layer and an adhesive layer as claimed in claim 1 or 2, wherein the stretched film constituting the phase difference layer is subjected to a heat treatment at a temperature above 105°C for more than 2 minutes. The polarizing plate with a phase difference layer and an adhesive layer as claimed in claim 1 or 2 further has another phase difference layer between the phase difference layer and the second adhesive layer, the refractive index characteristics of which show the relationship of nz>nx=ny. A polarizing plate with a phase difference layer and an adhesive layer as claimed in claim 1 or 2, wherein the phase difference layer comprises: a resin having positive refractive index anisotropy, comprising at least one bonding group selected from the group consisting of carbonate bonds and ester bonds and at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and structural units represented by the following general formula (2); and an acrylic resin; wherein the content of the acrylic resin is 0.5 mass % to 2.0 mass %, the acrylic resin contains more than 70 mass % of structural units derived from methyl methacrylate, and the weight average molecular weight Mw thereof is 10,000 to 200,000;

In the general formulae (1) and (2), R ¹ to R ³ are each independently a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴ to R ⁹ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a substituted sulfur atom, a substituted silicon atom, a halogen atom, a nitro group, or a cyano group; wherein R ^{4 to R 9 may be the same or different from each other, and R 4} to R ⁹ may be the same or different from each other, and R ⁴ to R At least two adjacent groups in ⁹ may be bonded to each other to form a ring. An image display device comprises a polarizing plate with a phase difference layer and an adhesive layer as described in any one of claims 1 to 6.