CN115244435A

CN115244435A - Method for producing polarizing plate with retardation layer

Info

Publication number: CN115244435A
Application number: CN202180018408.XA
Authority: CN
Inventors: 中西贞裕
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-03-03
Filing date: 2021-02-18
Publication date: 2022-10-25
Also published as: WO2021177046A1; KR20220145332A; JPWO2021177046A1; TW202141087A

Abstract

The invention provides a method for manufacturing a polarizing plate with a phase difference layer, which has small change of optical characteristics even when exposed to a high-temperature environment for a long time and has excellent heating durability. The present invention relates to a method for producing a polarizing plate with a retardation layer, which comprises a protective layer, a polarizer, an adhesive layer, and a retardation layer as an alignment-cured layer of a liquid crystal compound in this order. The manufacturing method comprises the following steps: laminating the polarizer and the retardation layer with an adhesive layer interposed therebetween; and a step of heating the laminate including the polarizer, the retardation layer and the adhesive layer after the lamination step.

Description

Method for producing polarizing plate with retardation layer

Technical Field

The present invention relates to a method for manufacturing a polarizing plate with a retardation layer.

Prior Art

In recent years, image display devices typified by liquid crystal display devices and Electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have rapidly spread. Typically, a polarizing plate and a retardation plate are used in an image display device. In terms of practical use, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, patent document 1).

Further, image display devices such as liquid crystal display devices and organic EL display devices are required to have higher durability. Therefore, an optical member constituting an image display device is required to have small changes in optical characteristics even when exposed to a high-temperature environment for a long time. The alignment liquid crystal film, which is cured by light after aligning liquid crystal molecules, fixes the molecules in an aligned state and does not undergo a phase change even when heated. Therefore, it is considered to have high heating durability and to be used as a retardation layer. However, a polarizing plate with a retardation layer in which a retardation layer formed of an oriented liquid crystal film is laminated via an adhesive layer has a problem that optical characteristics change.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3325560

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made to solve the above-described problems of the conventional art, and a main object of the present invention is to provide a method for producing a polarizing plate with a retardation layer, which has little change in optical characteristics even when exposed to a high-temperature environment for a long time and has excellent heating durability.

Means for solving the problems

In one embodiment, the present invention relates to a method for producing a polarizing plate with a retardation layer, which comprises a protective layer, a polarizer, an adhesive layer, and a retardation layer as an alignment cured layer of a liquid crystal compound in this order. The method for manufacturing the polarizing plate with the phase difference layer comprises the following steps: laminating the polarizer and the retardation layer with an adhesive layer interposed therebetween; and a step of heating the laminate including the polarizer, the retardation layer and the adhesive layer after the lamination step.

In another aspect of the present invention, there is provided a method for producing a polarizing plate with a retardation layer, which comprises a protective layer, a polarizer, a first adhesive layer, a first retardation layer which is an oriented cured layer of a liquid crystal compound, a second adhesive layer, and a second retardation layer in this order. The method for manufacturing the polarizing plate with the phase difference layer comprises the following steps: a step of laminating the first retardation layer and the second retardation layer with a second adhesive layer interposed therebetween; and a step of heating a laminate including the first retardation layer, the second retardation layer, and the second adhesive layer after the laminating step.

In one embodiment, the method for producing a polarizing plate with a retardation layer includes: laminating the polarizer and the first retardation layer with a first adhesive layer interposed therebetween; and a step of heating the laminate including the polarizer, the first retardation layer, and the first adhesive layer after the lamination step.

In one embodiment, the heating time in the step of heating the laminate exceeds 1 hour.

In one embodiment, the heating temperature in the step of heating the laminate is 90 to 110 ℃.

Effects of the invention

According to the present invention, a method for producing a polarizing plate with a retardation layer, which shows little change in optical characteristics even when exposed to a high-temperature environment for a long time and has excellent heat durability, can be provided. The method for producing a polarizing plate with a retardation layer according to the present invention comprises a step of laminating a polarizer and a retardation layer and/or a first retardation layer and a second retardation layer with an adhesive layer interposed therebetween, and a step of heating the laminated body laminated with the adhesive layer interposed therebetween. By producing the polarizing plate with a retardation layer in this order, a polarizing plate with a retardation layer which is excellent in durability to heating and which shows little change in optical characteristics even when left for a long time in a high-temperature environment can be obtained.

Drawings

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

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

Detailed Description

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

(definitions of wording and symbols)

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

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

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

(2) In-plane retardation (Re)

"Re (λ)" is an in-plane phase difference measured at 23 ℃ with light having a wavelength of λ nm. For example, "Re (550)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), re (λ) is obtained by the formula Re (λ) = (nx-ny) × d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of λ nm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23 ℃ by light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), rth (λ) is obtained by the formula Rth (λ) = (nx-nz) × d.

(4) Coefficient of Nz

The Nz coefficient was determined by Nz = Rth/Re.

(5) Angle of rotation

When an angle is referred to in the present specification, the angle includes both a clockwise direction and a counterclockwise direction with respect to a reference direction. Thus, for example, "45" means ± 45 °.

A. Integral constitution of polarizing plate with phase difference layer

Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate with retardation layer 100 of the present embodiment includes a protective layer 10, a polarizer 20, an adhesive layer 30, and a retardation layer 40 (hereinafter, also referred to as a polarizing plate with first retardation layer) as an alignment cured layer of a liquid crystal compound. In one embodiment, the adhesive layer 30 includes an ultraviolet curable adhesive. The phase difference layer 40 may be a single layer of the orientation cured layer, or may have a laminated structure of the first orientation cured layer 21 and the second orientation cured layer 22.

Fig. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. The polarizing plate with retardation layer 101 according to another embodiment includes a protective layer 10, a polarizer 20, a first adhesive layer 31, a first retardation layer 41, a second adhesive layer 32, and a second retardation layer 42 (hereinafter also referred to as a polarizing plate with second retardation layer) in this order. In one embodiment, the first adhesive layer and/or the second adhesive layer includes an ultraviolet curable adhesive. The first retardation layer 41 and the second retardation layer 42 may be single layers of the orientation cured layer, or may have a laminated structure of the first orientation cured layer 21 and the second orientation cured layer 22.

The polarizing plate with a retardation layer according to the embodiment of the present invention may further include another retardation layer. The optical properties (e.g., refractive index properties, in-plane retardation, nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layer can be appropriately set according to the purpose.

The total thickness of the polarizing plate with a retardation layer can be set to any suitable value depending on the constituent elements included. The total thickness of the polarizing plate with the first retardation layer is preferably 10 to 200. Mu.m, more preferably 20 to 150. Mu.m, and still more preferably 30 to 120. Mu.m. The total thickness of the polarizing plate with the second retardation layer is preferably 10 to 200. Mu.m, more preferably 20 to 150 μm, and still more preferably 30 to 120. Mu.m.

A-1 polarizer

As polarizer, any suitable polarizer may be used. Examples of the polarizer include polarizers obtained by uniaxially stretching a dichroic material such as iodine or a dichroic dye adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol (hereinafter, also referred to as PVA) film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film; and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. It is preferable to use a polarizer made of a dichroic material such as a PVA film or iodine.

The polarizer made of a PVA-based film and a dichroic material such as iodine can be obtained by any suitable method. Specifically, the PVA-based film can be produced by immersing the film in an aqueous iodine solution, dyeing the film, and stretching the film to 3 to 7 times the original length. The PVA-based film may be immersed in an aqueous solution of boric acid, potassium iodide, or the like, as necessary. Further, the PVA-based film may be immersed in water and washed with water before dyeing, if necessary. By washing the PVA film with water, the stain and the antiblocking agent on the surface of the PVA film can be washed. Further, unevenness such as uneven dyeing can be prevented by swelling the PVA film. The stretching may be performed after the dyeing with iodine, or may be performed while dyeing, or the PVA-based film subjected to the stretching treatment may be dyed with iodine. Stretching may also be carried out in an aqueous solution such as boric acid or potassium iodide or in a water bath.

The thickness of the polarizer is preferably 2 to 30 μm, more preferably 4 to 20 μm, and still more preferably 5 to 15 μm. When the thickness of the polarizer is in the above range, the optical durability is excellent, the dimensional change in a high-temperature and high-humidity environment is suppressed, and the occurrence of display unevenness can be prevented.

In one embodiment, the thickness of the polarizer is preferably 10 μm or less. The composition (curable resin composition) for forming the adhesive layer described later can be used in combination with a polarizer having a thickness of 10 μm or less, whereby the optical durability of the obtained polarizing plate under severe environments such as high temperature and high humidity can be improved. Polarizers having a thickness of 10 μm or less are relatively more affected by moisture than polarizers having a thickness of more than 10 μm, and thus have insufficient optical durability in an environment under high temperature and high humidity, and are likely to cause an increase in transmittance or a decrease in polarization degree. By laminating the polarizer and the retardation layer via an adhesive layer described later, migration of water to the polarizer in a severe environment of high temperature and high humidity can be suppressed, and deterioration of optical durability such as increase in transmittance and decrease in polarization degree of the polarizing film can be remarkably suppressed. The thickness of the polarizer is more preferably 1 to 7 μm from the viewpoint of thinning. When the thickness of the polarizer is in the above range, a polarizing plate having a small thickness variation and excellent visibility can be obtained. In addition, the size change of the polarizer is small, and the thickness of the polarizer can be thinned.

For example, JP-A-51-069644, JP-A-2000-338329, WO2010/100917, PCT/JP2010/001460, JP-A-2010-269002, and JP-A-2010-263692 describe polarizers having a thickness of 10 μm or less. The entire disclosures of these publications are incorporated herein by reference. These polarizers can be obtained by a production method including a step of stretching a laminate of a PVA-based resin layer and a resin substrate for stretching and a step of dyeing the PVA-based resin layer. By using the laminate of the PVA-based resin layer and the stretching resin base material, even when the PVA-based resin layer is thin, the PVA-based resin layer is supported by the stretching resin base material, and thus stretching can be performed without defects such as breakage due to stretching.

As the polarizer having a thickness of 10 μm or less, it is preferable to use a polarizer obtained by a manufacturing method further including a step of stretching the laminate in an aqueous boric acid solution, because the laminate can be stretched at a high magnification and the polarizing performance can be improved even in a manufacturing method including a step of stretching the laminate in a state of the laminate and a step of dyeing the PVA-based resin layer. Such a production method is disclosed in WO2010/100917 pamphlet, PCT/JP2010/001460 specifications, japanese patent application No. 2010-269002 specifications, and Japanese patent application No. 2010-263692 specifications. All the descriptions of these publications are incorporated herein by reference. More preferably, the polarizer is obtained by a production method including a step of performing in-air stretching in an auxiliary manner before stretching in an aqueous boric acid solution. Such a production method is disclosed in Japanese patent application No. 2010-269002 and Japanese patent application No. 2010-263692. All descriptions of these publications are incorporated herein by reference.

A-2. Phase difference layer

The polarizing plate 100 with a first retardation layer includes a retardation layer 40 as an alignment cured layer of a liquid crystal compound. The polarizing plate 101 with a second retardation layer includes the first retardation layer 41 as an alignment cured layer of a liquid crystal compound. The phase difference layer as an alignment cured layer of the liquid crystal compound can be obtained by: the liquid crystalline composition is applied to a supporting substrate, heated to align the liquid crystalline compound in a predetermined direction, and polymerized or crosslinked by light irradiation. In the polarizing plate 101 with a second retardation layer, the second retardation layer 42 is preferably an alignment cured layer of a liquid crystal compound.

The liquid crystal compound is a thermotropic liquid crystal which exhibits liquid crystallinity by heating. Thermotropic liquid crystals undergo phase changes of a crystal phase, a liquid crystal phase, and an isotropic phase with temperature changes. The liquid crystal compound may be a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal. A chiral agent may be added to the nematic liquid crystal to impart a cholesterol alignment property.

The liquid crystalline composition contains at least 1 photopolymerizable liquid crystal monomer. The photopolymerizable liquid crystal monomer has a mesogenic group and at least 1 photopolymerizable functional group in 1 molecule. The temperature at which the photopolymerizable liquid crystal monomer exhibits liquid crystallinity (liquid crystal phase transition temperature) is preferably 40 to 200 ℃, more preferably 50 to 150 ℃, and still more preferably 55 to 100 ℃.

As the photopolymerizable liquid crystal monomer, any suitable liquid crystal monomer can be used. Examples of the compounds include compounds described in Japanese patent laid-open Nos. 00/37585, 5211877, 4388453, 93/22397, 0261712, 19504224, 4408171, 2280445, 2017-206460, 2014/126113, 2016/114348, 2014/010325, 2015-200877, 2010-31223, 2011/050896, 2011-207765, 2010-31223, 2010-270108, 2008/119427, 2008-107427, 2008-1071077, 2008-2725, 2011/050896, 2011-207765, 2011-31223, 2008-27769, and 27832016-277625. All the descriptions of these publications are incorporated herein by reference. The expression of birefringence and the wavelength dispersion of phase retardation can also be adjusted by selecting the liquid crystal monomer.

The liquid crystalline composition may contain a compound that controls the alignment of the photopolymerizable liquid crystal monomer in a predetermined direction (hereinafter also referred to as an alignment control compound). By including the alignment control compound in the liquid crystalline composition, a liquid crystal layer in which liquid crystal molecules are aligned in a predetermined direction can be formed even when a support substrate not provided with an alignment film is used.

The orientation control compound may be a polymer or a low molecular weight compound. For example, in order to vertically align the liquid crystal monomer, it is preferable to include a side chain type liquid crystal polymer in the liquid crystalline composition. When the polymer has a liquid crystalline segment in a side chain to exhibit liquid crystallinity, the polymer can be promoted to be aligned in a predetermined direction when the liquid crystalline composition is heated to a predetermined temperature.

The liquid crystalline composition may further include a photopolymerization initiator. In order to accelerate photocuring when the liquid crystal monomer is cured by ultraviolet irradiation, the liquid crystalline composition preferably contains a photopolymerization initiator (photo radical generator) that generates radicals by light irradiation. The photo cation generator or photo anion generator may be used according to the kind of the liquid crystal monomer (for example, the kind of the photopolymerizable functional group). The photopolymerization initiator may be used in any suitable amount. The amount of the photopolymerization initiator used is, for example, 0.01 to 10 parts by weight per 100 parts by weight of the liquid crystal monomer. Further, a sensitizer or the like may be used.

The liquid crystalline composition can be prepared by mixing a photopolymerizable liquid crystal monomer, an optional alignment controller, a photopolymerization initiator, and the like, and a solvent. Any suitable solvent may be used as the solvent, and a solvent that can dissolve the photopolymerizable liquid crystal monomer without corroding the substrate or has low corrosiveness may be preferably used. Examples thereof include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and o-dichlorobenzene; phenols such as phenol and p-chlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, and N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as tert-butyl alcohol, glycerol, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; ether solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; ethyl cellosolve, butyl cellosolve, and the like. The solvent may be used alone in 1 kind, or 2 or more kinds may be used in combination.

The solid content concentration of the liquid crystalline composition is usually 5 to 60% by weight. The liquid crystalline composition may further contain other additives such as a surfactant and a leveling agent.

As the supporting substrate to which the liquid crystalline composition is applied, any suitable substrate may be used. Examples thereof include a glass plate, a metal tape, and a resin film substrate. In one embodiment, the support substrate has a first main surface and a second main surface, and the liquid crystal composition is applied to the first main surface.

As the support substrate, a resin film substrate is preferably used. By using the resin film substrate, a series of steps of coating the liquid crystalline composition on the substrate, photocuring the liquid crystal monomer, and heat treatment thereafter can be performed in a roll-to-roll manner, whereby the productivity of the retardation layer can be improved.

As the resin material constituting the resin film substrate, a resin which is insoluble in the solvent used in the liquid crystalline composition and has heat resistance at the time of heating for aligning the liquid crystalline composition is preferably used. Examples thereof include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as norbornene polymers; cellulose polymers such as diacetylcellulose and triacetylcellulose; an acrylic polymer; a styrenic polymer; polycarbonates, polyamides, polyimides, and the like.

The support substrate may have an alignment capability for aligning the liquid crystal molecules in a prescribed direction. For example, by using a stretched film as a support substrate, liquid crystal molecules can be horizontally aligned in the stretching direction thereof. The stretching ratio of the stretched film may be such that the orientation ability is exhibited. For example, to 1.1 to 5 times. In one embodiment, the stretched film may be a biaxially stretched film. Even in the case of a biaxially stretched film, the liquid crystal molecules can be oriented in a direction having a large stretching ratio by using a film having a different stretching ratio between the longitudinal direction and the transverse direction.

The support substrate may have an alignment film on the first main surface. The alignment film may be selected as appropriate depending on the type of the liquid crystal monomer, the material of the substrate, and the like. As the alignment film for horizontally aligning the liquid crystal molecules in a predetermined direction, an alignment film obtained by rubbing an alignment film of a polyimide-based film or a polyvinyl alcohol-based film is preferably used. In addition, a photo alignment film may also be used. The resin film as the support substrate may be subjected to rubbing treatment without providing an alignment film.

In one embodiment, the support substrate may further include an alignment film for vertically aligning the liquid crystal molecules. Examples of the alignment agent for forming a vertically aligned alignment film (vertical alignment film) include lecithin, stearic acid, cetyltrimethylammonium bromide, octadecylamine hydrochloride, chromium monocarboxylate complex, silane coupling agent, organic silane such as siloxane compound, perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene, and the like.

When the liquid crystalline composition contains an alignment controlling compound, a homeotropic alignment liquid crystal film can be formed even when a substrate not provided with an alignment film is used. Since the alignment film is not required to be provided, the versatility of the support substrate can be improved, and the process can be simplified and the manufacturing cost can be reduced.

The retardation layer as an alignment cured layer of a liquid crystal compound is formed by applying a liquid crystal composition on the above-mentioned support substrate and then heating the composition to align the liquid crystal compound in a liquid crystal state. As a method for coating the liquid crystal composition, any suitable method can be used. Examples thereof include spin coating, die coating, contact roll coating, gravure coating, reverse coating, spray coating, meyer bar coating, knife roll coating, and air knife coating. After the solution is applied, the solvent is removed, whereby a liquid crystalline composition layer is formed on the support substrate. The coating thickness may be set to any suitable thickness. The thickness of the liquid crystal composition layer (the thickness of the oriented liquid crystal film) after the solvent is dried and removed can be preferably adjusted to be about 0.1 to 20 μm.

The liquid crystalline compound can be aligned by heating a coating film of the liquid crystal composition coated on the support substrate to bring the coating film into a liquid crystal phase. The heating temperature for aligning the liquid crystalline compound in the predetermined direction may be set to any suitable value depending on the type of the liquid crystalline composition. The heating temperature is usually 40 ℃ to 200 ℃. If the heating temperature is too low, the phase transition into the liquid crystal phase may become insufficient. If the heating temperature is too high, alignment defects may increase. The heating time may be adjusted so that the liquid crystal phase domain grows sufficiently. The heating time is usually 30 seconds to 30 minutes. After alignment by heating, the liquid crystal compound is preferably cooled to a temperature not higher than the glass transition temperature of the liquid crystal compound. As the cooling method, any suitable method may be used. For example, the substrate may be taken out from a heating atmosphere and left at room temperature, or may be forcibly cooled by air cooling or water cooling.

Next, by irradiating the liquid crystal layer with light, the photopolymerizable liquid crystal monomer can be cured in a state having liquid crystal regularity (photocuring). The irradiation light is any suitable irradiation light that can polymerize the photopolymerizable liquid crystal monomer. For example, ultraviolet light or visible light having a wavelength of 250nm to 450nm is used. When the liquid crystalline composition contains a photopolymerization initiator, light having any suitable wavelength may be used depending on the photopolymerization initiator.

As the irradiation Light source, any suitable Light source can be used, and examples thereof include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED (Light-emitting diode), a black Light, and a chemical lamp. In order to promote the photocuring reaction, it is preferable to irradiate light in an inert gas atmosphere such as nitrogen gas.

The irradiation intensity may be set to any suitable value depending on the composition of the liquid crystalline composition, the amount of the photopolymerization initiator added, and the like. The irradiation energy (cumulative irradiation light quantity) is, for example, 20mJ/cm ² ～10000mJ/cm ² Preferably 50mJ/cm ² ～5000mJ/cm ² More preferably 100mJ/cm ² ～800mJ/cm ² . In one embodiment, in order to promote the photo-curing reaction, light irradiation may be performed under heating conditions.

The polymer obtained by photocuring the liquid crystal monomer by light irradiation is non-liquid-crystalline and does not undergo phase transition of a liquid crystal phase, a glass phase, or a crystal phase due to temperature change. Therefore, the liquid crystal layer that is photo-cured in a state in which the liquid crystal monomers are aligned in a predetermined direction is less likely to have a change in molecular alignment due to a change in temperature. In addition, since the oriented liquid crystal film has a large birefringence compared to a film formed of a non-liquid crystal material, the thickness of an optically anisotropic element having a desired phase retardation can be made remarkably small. The thickness of the alignment liquid crystal film (liquid crystal layer) may be set according to the target retardation value, and is, for example, 0.1 to 20 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 7 μm.

A-2-1. First phase difference layer

In the retardation layer of the polarizing plate with the first retardation layer and the first retardation layer of the polarizing plate with the second retardation layer (hereinafter, these are also referred to as the first retardation layer), the refractive index characteristic typically exhibits a relationship of nx > ny = nz. The first retardation layer is typically provided to impart antireflection properties to the polarizing plate, and when the first retardation layer is a single layer of an alignment cured layer, it functions as a λ/4 plate. In this case, the in-plane retardation Re (550) of the first retardation layer is preferably 100nm to 190nm, more preferably 110nm to 170nm, and still more preferably 130nm to 160nm. Here, "ny = nz" includes not only the case where ny and nz are completely equal but also the case where ny and nz are substantially equal. Therefore, ny > nz or ny < nz may be present within a range not impairing the effects of the present invention.

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

The first phase difference layer may also exhibit reverse wavelength dispersion characteristics in which the phase difference value becomes larger according to the wavelength of the measurement light, may also exhibit positive wavelength dispersion characteristics in which the phase difference value becomes smaller according to the wavelength of the measurement light, and may also exhibit smooth wavelength dispersion characteristics in which the phase difference value hardly changes according to the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits reverse wavelength dispersion characteristics. In this case, re (450)/Re (550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection characteristics can be achieved.

The angle θ formed by the slow axis of the first retardation layer and the absorption axis of the polarizer is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and further preferably about 45 °. When the angle θ is in such a range, by setting the first retardation layer to a λ/4 plate as described above, a polarizing plate with a retardation layer having very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) can be obtained.

In another embodiment, the first phase difference layer may have a laminated structure of a first orientation cured layer and a second orientation cured layer. In this case, one of the first orientation cured layer and the second orientation cured layer may function as a λ/4 plate, and the other may function as a λ/2 plate. Therefore, the thicknesses of the first orientation cured layer and the second orientation cured layer can be adjusted so as to obtain the in-plane retardation required for a λ/4 plate or a λ/2 plate. For example, when the first orientation cured layer functions as a λ/2 plate and the second orientation cured layer functions as a λ/4 plate, the thickness of the first orientation cured layer is, for example, 2.0 μm to 3.0 μm, and the thickness of the second orientation cured layer is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re (550) of the first orientation-cured layer is preferably 200nm to 300nm, more preferably 230nm to 290nm, and still more preferably 250nm to 280nm. The in-plane retardation Re (550) of the second orientation-cured layer is as described above in connection with the orientation-cured layer of a single layer. The angle formed by the slow axis of the first orientation cured layer and the absorption axis of the polarizer is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and further preferably about 15 °. The angle of the slow axis of the second oriented cured layer to the absorption axis of the polarizer is preferably from 70 ° to 80 °, more preferably from 72 ° to 78 °, and even more preferably about 75 °. With this configuration, characteristics close to ideal reverse wavelength dispersion characteristics can be obtained, and as a result, very excellent antireflection characteristics can be realized. The liquid crystal compounds constituting the first and second alignment cured layers, the methods for forming the first and second alignment cured layers, the optical properties, and the like are as described above with respect to the single-layer alignment cured layer.

A-2-2. Second phase difference layer

The second retardation layer may be a so-called positive C plate whose refractive index characteristic exhibits a relationship of nz > nx = ny. By using the positive C plate as the second phase difference layer, reflection in an oblique direction can be prevented well, and a wide viewing angle of the antireflection function can be achieved. In this case, the retardation Rth (550) in the thickness direction of the second retardation layer is preferably from-50 nm to-300 nm, more preferably from-70 nm to-250 nm, still more preferably from-90 nm to-200 nm, and particularly preferably from-100 nm to-180 nm. Here, "nx = ny" includes not only a case where nx and ny are strictly equal but also a case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the second retardation layer may be less than 10nm.

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

A-3 protective layer

As the protective layer, any suitable resin film may be used. It is preferable to use a resin film having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Examples of the material for forming the protective layer include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetylcellulose and triacetylcellulose; acrylic polymers such as polymethyl methacrylate; styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin); polycarbonate-based polymers, and the like. Polyolefin polymers such as polyethylene, polypropylene, polyolefin having a cycloolefin structure or a norbornene structure, and ethylene-propylene copolymers; a vinyl chloride polymer; amide polymers such as nylon and aromatic polyamide; an imide polymer; a sulfone-based polymer; a polyether sulfone-based polymer; a polyether ether ketone polymer; polyphenylene sulfide-based polymer; a vinyl alcohol polymer; a vinylidene chloride polymer; a vinyl butyral based polymer; an aryl ester polymer; a polyoxymethylene polymer; epoxy polymers or blends of the above polymers, and the like.

The film forming the protective layer may contain 1 or more of any suitable additive. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. Any suitable amount of these additives may be used.

Examples of the film for forming the protective layer include a polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007), for example, a resin composition containing a thermoplastic resin having a substituted and/or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted and/or unsubstituted phenyl group and a nitrile group in a side chain. Specifically, a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer is exemplified. As the film, a film formed from a mixed extrusion of a resin composition or the like can be used. These films have a small phase difference and a small photoelastic coefficient, and therefore, defects such as unevenness due to deformation of the polarizing film can be eliminated, and moisture permeability is small, and therefore, the films have excellent humidification durability.

The thickness of the protective layer may be set to any suitable value. In view of strength, workability such as workability, and thin layer property, the thickness is preferably 5 μm to 100. Mu.m, more preferably 10 μm to 60 μm, and still more preferably 20 μm to 40 μm.

A-4 adhesive layer

The adhesive layer may be formed using any suitable adhesive. In one embodiment, the adhesive layer preferably contains an ultraviolet-curable adhesive. In one embodiment, the adhesive layer is formed using the following curable resin composition.

A-4-1 curable resin composition

In one embodiment, the adhesive layer is a curable resin composition containing a compound represented by the following general formula (1).

[ chemical Structure 1]

(wherein X is a functional group containing a reactive group, R ¹ And R ² Each independently represents a hydrogen atom, an unsubstituted or substituted aliphatic hydrocarbon group, an aryl group or a heterocyclic group, which may be further bonded to each other to form a ring. )

The above X represents a functional group containing a reactive group. Examples of the reactive group include a hydroxyl group, an amino group, an aldehyde group, a carboxyl group, a vinyl group, a (meth) acryl group, a styryl group, a (meth) acrylamide group, a vinyl ether group, an epoxy group, and an oxetanyl group. When the curable resin composition is used as the active energy ray-curable resin composition, the reactive group contained in X is preferably at least 1 reactive group selected from a vinyl group, (meth) propenyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group and mercapto group. When the curable resin composition is radically polymerizable, the reactive group contained in X is preferably at least 1 reactive group selected from a (meth) acryl group, a styrene group, and a (meth) acrylamide group. When the (meth) acrylamide group is present as a reactive group, the reactivity is high, and when the (meth) acrylamide group is used in combination with an active energy ray-curable resin, the copolymerization rate can be increased. Further, it is also preferable from the viewpoint of high polarity of the (meth) acrylamide group and excellent adhesiveness.

When the curable resin composition is used as the cationic polymerizable resin composition, the reactive group contained in X is preferably at least 1 functional group selected from the group consisting of a hydroxyl group, an amino group, an aldehyde group, a carboxyl group, a vinyl ether group, an epoxy group, an oxetanyl group and a mercapto group, and more preferably an epoxy group. When the epoxy group is contained, the adhesion between the adhesive layer and the adherend can be further improved. When a vinyl ether group is contained as a reactive group, the curability of the curable resin composition can be improved.

In one embodiment, the functional group represented by X is preferably a functional group represented by the following formula.

[ chemical Structure 2]

Z-Y-

(wherein Z represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) propenyl group, a styryl group, (meth) acrylamide group, a vinyl ether group, an epoxy group, an oxetanyl group, a hydroxyl group, an amino group, an aldehyde group and a carboxyl group, and Y represents a phenylene group or an alkylene group).

R is as defined above ¹ And R ² Each independently represents a hydrogen atom, an unsubstituted or substituted aliphatic hydrocarbon group, an aryl group or a heterocyclic group. Examples of the aliphatic hydrocarbon group include an unsubstituted or substituted linear or branched alkyl group having 1 to 20 carbon atoms, an unsubstituted or substituted cyclic alkyl group having 3 to 20 carbon atoms, and an alkenyl group having 2 to 20 carbon atoms. Examples of the aryl group include an unsubstituted or substituted phenyl group having 6 to 20 carbon atoms, an unsubstituted or substituted naphthyl group having 10 to 20 carbon atoms, and the like. Examples of the heterocyclic group include groups having at least one heteroatom and having an unsubstituted or substituted 5-or 6-membered ring. They may also be connected to each other to formAnd (4) a ring. R is ¹ And R ² Preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom.

Specific examples of the compound represented by the general formula (1) include the following compounds.

[ chemical structural formula 3]

In one embodiment, the curable resin composition further comprises at least 1 organometallic compound selected from metal alkoxides and metal chelates. The metal alkoxide is a compound in which at least one alkoxy group as an organic group is bonded to a metal, and the metal chelate is a compound in which an organic group is bonded to or coordinated to a metal through an oxygen atom. As the metal, any suitable metal may be used, preferably titanium, aluminum, zirconium, and more preferably titanium. By using titanium, the adhesion water resistance of the adhesive layer can be further improved.

When the metal alkoxide is contained as the organic metal compound, the number of carbon atoms of the organic group contained in the metal alkoxide is preferably 4 or more, and more preferably 6 or more. When the carbon number is 3 or less, the pot life of the curable resin composition may be shortened and the effect of improving the adhesion water resistance may be reduced. Examples of the organic group having 6 or more carbon atoms include an octyloxy group, and it is preferably used. Examples of the preferable metal alkoxide include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, tert-amyl titanate, tetra-tert-butyl titanate, tetrastearyl titanate, zirconium tetraisopropoxide, zirconium tetran-butoxide, zirconium tetraoctanol, zirconium tetra-tert-butoxide, zirconium tetrapropanol, aluminum sec-butoxide, aluminum ethoxide, aluminum isopropoxide, aluminum butoxide, aluminum di-isopropoxide mono-sec-butoxide, and aluminum di-isopropoxide mono-sec-butoxide. Among them, tetraoctyl titanate is preferable.

When the metal chelate compound is contained as the organometallic compound, the number of carbon atoms of the organic group of the metal chelate compound is preferably 4 or more. When the number of carbon atoms of the organic group is 3 or less, the pot life of the curable resin composition may be shortened, and the effect of improving the adhesion water resistance may be reduced. Examples of the organic group having 4 or more carbon atoms include an acetylacetonato group, an acetoacetoxy group, an isostearate group, and an octanediol ester group. Among them, from the viewpoint of improving the adhesion water resistance of the adhesive layer, an acetylacetonato group or an acetoacetoxyethyl group is preferable as the organic group. Examples of preferred metal chelates include titanium acetylacetonate, titanium octanedioxide, titanium tetraacetylacetonate, titanium ethylacetoacetate, titanium polyhydroxystearate, dipropoxy-bis (acetylacetonate) titanium, dibutoxytitanium-bis (octanedionate), dipropoxytitanium-bis (ethylacetoacetate), titanium lactate, titanium diethanolamine, titanium triethanolamine, dipropoxytitanium-bis (lactate), dipropoxytitanium-bis (triethanolamine), di-n-butoxytitanium-bis (triethanolamine), tri-n-butoxytitanium monostearate, diisopropoxytis-bis (ethylacetoacetate) titanium, diisopropoxytis-bis (acetoacetate) titanium, diisopropoxytris-bis (acetylacetonate) titanium, phosphate, titanium ammonium lactate, titanium-1,3-propanedioxy-bis (ethylacetoacetate), dodecylbenzenesulfonic acid titanium compound, aminoethylaminoethylaminoethylaminoethylaminoethylacetoacetate, zirconium monoacetylacetonate, zirconium bisacetoacetonate, zirconium bisacetoacetate, zirconium tetraacetylacetonate, zirconium tri-n-butoxyacetoacetate, zirconium dibutoxyacetoacetate, zirconium tetraacetoacetate, aluminum tetraacetoacetate, zirconium tetraacetoacetate, aluminum tetraacetoacetate, titanium tetraacetoacetate, zirconium tetraacetoacetate, and titanium tetraacetylacetate, aluminum isopropoxide bis (ethyl acetoacetate), aluminum isopropoxide bis (acetylacetonate), aluminum tris (ethylacetoacetate), aluminum tris (acetylacetonate), aluminum monoacetylacetonate-bis (ethylacetoacetate). Among them, titanium acetylacetonate and titanium ethyl acetoacetate are preferable.

Examples of the organic metal compound include, in addition to the above, zinc chelate compounds such as organic carboxylic acid metal salts such as zinc octylate, zinc laurate, zinc stearate, and tin octylate, zinc acetylacetonate chelate compounds such as zinc benzoylacetonate chelate, zinc dibenzoylmethane chelate, and zinc ethylacetoacetate chelate.

The content of the organometallic compound is preferably 0.05 to 9 parts by weight, more preferably 0.1 to 8 parts by weight, and still more preferably 0.15 to 5 parts by weight, based on 100 parts by weight of the total amount of the active energy ray-curable components. When the amount exceeds 9 parts by weight, the storage stability of the adhesive composition may be deteriorated. Further, the ratio of components for adhesion to the polarizer, retardation layer, protective film, and the like may be relatively insufficient, and the adhesiveness may be lowered. If the amount is less than 0.05 parts by weight, the effect of adhesion and water resistance may not be sufficiently exhibited.

The curable resin composition further contains other curable components. Examples of the curable component include thermosetting resins and active energy ray curable resins. Examples of the thermosetting resin include polyvinyl alcohol resin, epoxy resin, unsaturated polyester, polyurethane resin, acrylic resin, urea resin, melamine resin, phenol resin, and the like, and polyvinyl alcohol resin and epoxy resin are preferably used. The thermosetting resin may be used in combination with a curing agent as required. Examples of the active energy ray-curable resin include an electron beam-curable resin, an ultraviolet-curable resin, and a visible ray-curable resin. In addition, from the viewpoint of the curing form, the resin composition can be classified into a radical polymerization curable resin composition and a cation polymerizable resin composition. The active energy ray-curable resin is preferably used, and the ultraviolet-curable resin is more preferably used. In the present specification, the compound represented by the above formula (1) and the following curable components are also collectively referred to as active energy ray-curable components. In the present specification, active energy rays having a wavelength range of 10nm to 380nm (excluding 380 nm) are referred to as ultraviolet rays, and active energy rays having a wavelength range of 380nm to 800nm are referred to as visible rays.

Examples of the other curable component include a radical polymerizable compound. Examples of the radical polymerizable compound include compounds having a radical polymerizable functional group having a carbon-carbon double bond such as a (meth) acryloyl group or a vinyl group. The curable component may be a monofunctional radical polymerizable compound or a bifunctional or higher polyfunctional radical polymerizable compound. The radical polymerizable compound may be used alone in 1 kind, or 2 or more kinds may be used in combination. As these radical polymerizable compounds, for example, compounds having a (meth) acryloyl group are preferable. In the present specification, a (meth) acryloyl group means an acryloyl group and/or a methacryloyl group, and the same meaning is given below for a "(meth)" group.

The curable resin composition preferably further contains a photopolymerization initiator. As the photopolymerization initiator, any suitable photopolymerization initiator can be used. Examples thereof include benzophenone-based compounds such as benzil, benzophenone, benzoylbenzoic acid, 3,3' -dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α -hydroxy- α, α' dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α -hydroxycyclohexyl phenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1- [4- (methylthio) -phenyl ] -2-morpholinopropane-1; benzoin ether-based compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, and anisoin methyl ether; aromatic ketal compounds such as benzil dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; optically active oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; a halogenated ketone; an acylphosphine oxide; acyl phosphates, and the like.

The amount of the photopolymerization initiator added is, for example, 20% by weight or less based on the total amount of the curable resin composition. The amount of the photopolymerization initiator added is preferably 0.01 to 10% by weight, more preferably 0.1 to 10% by weight, and still more preferably 1 to 10% by weight.

Japanese patent laid-open No. 2016-170412 describes the details of a curable resin composition containing a compound represented by the above general formula (1). The entire disclosure of this publication is incorporated herein by reference.

In one embodiment, a visible ray-curable resin composition is used as the curable resin composition. Examples thereof include a radical polymerizable resin composition and a cation polymerizable curable resin composition. Examples of the curable component contained in the radical polymerization curable resin composition include radical polymerizable compounds used in radical polymerization curable resin compositions. Examples of the radical polymerizable compound include compounds having a radical polymerizable functional group having a carbon-carbon double bond such as a (meth) acryloyl group or a vinyl group. Any of monofunctional radical polymerizable compounds and difunctional or higher polyfunctional radical polymerizable compounds can be used as the curable component. These radical polymerizable compounds may be used alone in 1 kind, or 2 or more kinds may be used in combination. As these radical polymerizable compounds, for example, compounds having a (meth) acryloyl group can be preferably used.

Examples of the monofunctional radical polymerizable compound include compounds represented by the following general formula (2).

[ chemical structural formula 4]

(in the formula, R ³ Is a hydrogen atom or a methyl group, R ⁴ And R ⁵ Each independently represents a hydrogen atom, an alkyl group, a hydroxyalkyl group, an alkoxyalkyl group or a cyclic ether group, R ⁴ And R ⁵ May form a cyclic heterocyclic ring).

The number of carbons in the alkyl portion of the alkyl, hydroxyalkyl and/or alkoxyalkyl groups may be set to any suitable value. For example, those having 1 to 4 carbon atoms can be used. As R ⁴ And R ⁵ Examples of the cyclic heterocyclic ring to be formed include N-acryloylmorpholine.

Specific examples of the compound represented by the general formula (2) include N-alkyl group-containing (meth) acrylamide derivatives such as N-methyl (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, and N-hexyl (meth) acrylamide; n-hydroxyalkyl-containing (meth) acrylamide derivatives such as N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N-methylol-N-propane (meth) acrylamide; and N-alkoxy group-containing (meth) acrylamide derivatives such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide. Examples of the cyclic ether group-containing (meth) acrylamide derivative include a heterocyclic ring-containing (meth) acrylamide derivative in which the nitrogen atom of the (meth) acrylamide group forms a heterocyclic ring. Examples thereof include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine. Among them, N-hydroxyethyl acrylamide and N-acryloyl morpholine are preferably used in terms of excellent reactivity, obtaining a cured product with a high elastic modulus, and excellent adhesiveness.

The curable resin composition may contain, as a curable component, a monofunctional radical polymerizable compound other than the compound represented by the general formula (2). As the monofunctional radical polymerizable compound, for example, there can be used: various (meth) acrylic acid derivatives having a (meth) acryloyloxy group; carboxyl group-containing monomers such as (meth) acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-epsilon-caprolactam, and methyl vinylpyrrolidone; vinyl monomers having a nitrogen-containing heterocycle such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine; and a radically polymerizable compound having an active methylene group.

Examples of the bifunctional or higher polyfunctional radical polymerizable compound include N which is a polyfunctional (meth) acrylamide derivative, N' -methylenebis (meth) acrylamide, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di (meth) acrylate, bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neopentyl glycol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, cyclic trimethylolpropane formal (meth) acrylate, dioxane glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene Oxide (EO) modified diglycerol tetra (meth) acrylate, etc. (3425-phenyl) acrylate, and bis- (2-ethoxyphenyl) acrylate [ 344- (2-phenyl) acrylate Fluorene. As specific examples, ARONIX M-220 (manufactured by Toyo Synthesis Co.), light acrylate1,9ND-A (manufactured by Kyoho chemical Co., ltd.), light acrylate DGE-4A (manufactured by Kyoho chemical Co., ltd.), light acrylate DCP-A (manufactured by Kyoho chemical Co., ltd.), SR-531 (manufactured by Sartomer Co., ltd.), CD-536 (manufactured by Sartomer Co., ltd.) and the like are preferable. Further, various epoxy (meth) acrylates, (meth) acrylic urethanes, polyester (meth) acrylates, various (meth) acrylate monomers, and the like may be mentioned as necessary. The polyfunctional (meth) acrylamide derivative is preferably contained in the curable resin composition because it has a high polymerization rate, excellent productivity, and excellent crosslinkability when the resin composition is cured.

The radical polymerization curable resin composition further contains a photopolymerization initiator. As the photopolymerization initiator, those exemplified above can be used.

The cationic polymerizable compound used in the cationic polymerization curable resin composition can be classified into a monofunctional cationic polymerizable compound having 1 cationic polymerizable functional group in the molecule and a polyfunctional cationic polymerizable compound having 2 or more cationic polymerizable functional groups in the molecule. Since the monofunctional cationic polymerizable compound has a relatively low liquid viscosity, the liquid viscosity of the resin composition can be reduced by including the compound in the resin composition. Further, a monofunctional cationically polymerizable compound often has a functional group which can exhibit various functions, and by including the compound in a resin composition, the resin composition and/or a cured product of the resin composition can exhibit various functions. The polyfunctional cationically polymerizable compound is preferably contained in the resin composition because it can three-dimensionally crosslink a cured product of the resin composition.

Examples of the cationically polymerizable functional group include an epoxy group, an oxetane group, and a vinyl ether group. Examples of the compound having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound. The alicyclic epoxy compound is preferably contained because of excellent curability and adhesiveness. Examples of the alicyclic epoxy compound include 3,4-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexylmethyl ester, 3,4-epoxycyclohexanecarboxylic acid 3,4-caprolactone, trimethylcaprolactone, valerolactone and the like, and specifically include Celloxide 2021, celloxide 2021A, celloxide 2021P, celloxide 2081, celloxide 2083, celloxide2085 (manufactured by Daicel chemical industries, ltd.), cyracure UVR-6105, cyracure UVR-6107, cyracure 30, R-6110 (manufactured by Nippon Dow chemical Co., ltd.), and the like.

By further containing a compound having an oxetanyl group, effects of improving curability and reducing liquid viscosity of the composition can be obtained. Examples of the compound having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [ (3-ethyl-3-oxetanyl) methoxymethyl ] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, bis [ (3-ethyl-3-oxetanyl) methyl ] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, phenol novolak oxetane, and the like, and examples thereof include Aronoxetane OXT-101, aronoxetane OXT-121, aronoxetane OXT-211, aronoxetane OXT-221, and Aronoxetane OXT-212 (manufactured by Toyo Seisaku-Sho Co., ltd.).

By further including a compound having a vinyl ether group, effects of improving curability and reducing the liquid viscosity of the composition can be obtained. Examples of the compound having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, pentaerythritol-type divinyl ether, and the like.

The cationic polymerization curable resin composition further contains a photo cationic polymerization initiator. The photo cation polymerization initiator generates a cation species or lewis acid by irradiation with active energy rays such as visible rays, ultraviolet rays, X-rays, electron beams, and the like, thereby initiating a polymerization reaction of an epoxy group and an oxetanyl group. As the photo cation polymerization initiator, a photoacid generator can be preferably used. In addition, by using a photosensitizer which exhibits a maximum absorption at a wavelength longer than 380nm in combination, it is possible to sense light of a wavelength in the vicinity thereof, promote generation of cationic species or acid from the photo-cationic polymerization initiator.

The curable resin composition may further contain an acrylic oligomer, a photoacid generator, a compound containing an alkoxy group or an epoxy group, a silane coupling agent, a compound having a vinyl ether group, a compound generating keto-enol tautomerism, and the like. In addition, various additives may be contained as other arbitrary components. Examples of the additive include polymers or oligomers such as epoxy resins, polyamides, polyamideimides, polyurethanes, polybutadienes, polychloroprenes, polyethers, polyesters, styrene-butadiene block copolymers, petroleum resins, xylene resins, ketone resins, cellulose resins, fluorine-based oligomers, silicone-based oligomers, and polysulfide-based oligomers; polymerization inhibitors such as phenothiazine and 2,6-di-tert-butyl-4-methylphenol; a polymerization initiation adjuvant; a leveling agent; a wettability modifier; a surfactant; a plasticizer; an ultraviolet absorber; an inorganic filler; a pigment; dyes, and the like.

The details of the radical polymerizable resin composition and the cation polymerizable curable resin composition are described in international publication No. 2017/199978 and japanese patent application laid-open No. 2019-3201. All the descriptions of this publication are incorporated herein by reference.

B. Method for producing polarizing plate with retardation layer

In one embodiment, the method for producing a polarizing plate with a retardation layer includes a step of heating a laminate (a laminate of a polarizer and a retardation layer or a laminate of a polarizer and a first retardation layer and a second retardation layer) laminated via an adhesive layer after a step of laminating a polarizer and a retardation layer and/or a first retardation layer and a second retardation layer via an adhesive layer. By producing the polarizing plate with a retardation layer in this order, a polarizing plate with a retardation layer which is excellent in durability to heating and which shows little change in optical characteristics even when left for a long time in a high-temperature environment can be obtained.

B-1. Laminating step with adhesive layer interposed therebetween

The polarizing plate with the first retardation layer comprises a protective layer, a polarizer, an adhesive layer, and a retardation layer as an alignment cured layer of a liquid crystal compound in this order. The method for producing a polarizing plate with a first retardation layer comprises a step of laminating a polarizer and a retardation layer with an adhesive layer interposed therebetween. The polarizing plate with the second retardation layer comprises a protective layer, a polarizer, a first adhesive layer, a first retardation layer, a second adhesive layer, and a second retardation layer in this order. The method for producing a polarizing plate having a second retardation layer includes a step of laminating a first retardation layer and a second retardation layer. The method for producing a polarizing plate with a second retardation layer preferably further comprises a step of laminating the polarizer and the first retardation layer with an adhesive layer interposed therebetween. In this embodiment, the step of laminating the polarizer and the first retardation layer via the adhesive layer is preferably performed before the heating step described later.

The lamination step via the adhesive layer can be performed by any suitable method. For example, in the polarizing plate with the first retardation layer, the adhesive layer-forming composition (specifically, the curable resin composition) is applied to the polarizer, and then the retardation layer is laminated.

In the polarizing plate with the second retardation layer, the adhesive composition is applied to the polarizing plate with the first retardation layer to form a second adhesive layer, and then the second retardation layer is laminated. In the polarizing plate with a second retardation layer, when the first retardation layer and the polarizer are laminated via the first adhesive layer, a laminate of the first retardation layer and the polarizer may be produced, and then the second retardation layer may be bonded to the surface of the laminate on the side of the first retardation layer via the adhesive layer, or a laminate obtained by laminating the first retardation layer and the second retardation layer via the adhesive layer may be laminated to the polarizer via the adhesive layer. The first adhesive layer and the second adhesive layer may be formed using the same adhesive composition (curable resin composition) or may be formed using different adhesive compositions. As described above, the slow axis of the retardation layer and the absorption axis of the polarizer are laminated at any suitable angle.

As the method for applying the adhesive layer-forming composition, any suitable method can be used. Examples thereof include a reverse coater, a gravure coater (direct, reverse, and offset), a bar reverse coater, a roll coater, a die coater, a bar coater, and a bar coater.

In one embodiment, substantially no solvent is used in the laminating step via the adhesive layer. That is, the laminating step is preferably performed using an adhesive composition substantially free of a solvent. By using the adhesive composition containing substantially no solvent, the adhesive layer can be cured without the steps of drying and heating. In addition, defects (e.g., reduction in heating durability and appearance defects) caused by the remaining solvent can be prevented from occurring. In the present specification, the term "substantially not contained" means that the solvent-derived component is not more than the detection limit value when the obtained adhesive layer is analyzed.

In one embodiment, the adhesive layer is formed by an active energy ray-curable adhesive composition, preferably an ultraviolet-curable adhesive composition. In this embodiment, the adhesive layer can be formed by irradiating the applied adhesive composition with ultraviolet rays to cure the composition. As the irradiation light source, any suitable light source can be used, and examples thereof include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED, a black light, a chemical lamp, and the like.

The irradiation intensity may be set to any appropriate value depending on the adhesive layer-forming composition used. The irradiation energy (cumulative irradiation light quantity) is, for example, 100mJ/cm ² ～5000mJ/cm ² Preferably 200mJ/cm ² ～3000mJ/cm ² More preferably 300mJ/cm ² ～3000mJ/cm ² . In one embodiment, in order to promote the curing reaction, light irradiation may be performed under heating conditions.

B-2. Heating Process

The method for producing the polarizing plate with a retardation layer includes a step of heating a laminate laminated via an adhesive layer. By heating the laminate laminated via the adhesive layer, a polarizing plate with a retardation layer can be obtained which has little change in optical properties even when exposed to a high-temperature environment for a long time and which has excellent heating durability.

The heating of the laminate may be performed by any suitable method. Examples thereof include heating furnaces such as an oven, infrared heaters, and roll heaters.

The heating temperature is preferably 90 to 120 ℃ and more preferably 90 to 110 ℃. The heating time is preferably more than 1 hour, more preferably 2 to 120 hours, and further preferably 6 to 48 hours. By heating the laminate at the above-described temperature or time, a polarizing plate with a retardation layer having little change in optical characteristics even when exposed to a high-temperature environment for a long time can be obtained.

In one embodiment, the polarizing plate with a retardation layer (for example, a polarizing plate with a second retardation layer) includes a laminate in which 2 or more adhesive layers are laminated. In this embodiment, the heating step may be performed in each step of producing a laminate via the adhesive layers, or may be performed after the layers are laminated via the adhesive layers to produce a desired polarizing plate with a retardation layer.

B-3. Other procedures

The method may further include any suitable step other than the laminating step and the heating step with the adhesive layer interposed therebetween. For example, a lamination step of a protective layer and a polarizer can be given. The polarizer and protective layer may be laminated by any suitable method. For example, a method of laminating a protective layer by applying any suitable adhesive or bonding agent to one surface of a polarizer is mentioned.

C. Image display device

The polarizing plate with a retardation layer described above can be suitably used for an image display device. Typical examples of the image display device include a liquid crystal display device and an Electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). In one embodiment, the polarizing plate with a retardation layer may be disposed on a viewing side of an image display device. The polarizing plate with a phase difference layer is laminated such that the phase difference layer is on the image display unit (for example, liquid crystal unit, organic EL unit, or inorganic EL unit) (such that the polarizing film is on the visible side).

[ examples ]

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

< production example 1> preparation of adhesive layer-forming composition 1

An adhesive layer-forming composition (curable resin composition) 1 was obtained by mixing and stirring 1 part by weight of a compound represented by the general formula (1) (3-acrylamidophenylboronic acid, available from pure chemical), 1 part by weight of a metal alkoxide (available from Songyo chemical Co., ltd.; ORGATIX TA-30), 10 parts by weight of hydroxyethylacrylamide (available from Kyoho chemical Co., ltd.; HEAA), 30 parts by weight of acryloylmorpholine (available from Kyoho chemical Co., ltd.; ACMO), 53 parts by weight of 1,9-nonanediol diacrylate (available from Kyoho chemical Co., ltd.; available as "Light acrylate1,9 ND-A"), 3 parts by weight of a polymerization initiator 1 (available from BASF Co., ltd.; available as "IRGACURE 907"), and 2 parts by weight of a polymerization initiator 2 (available from Nippon chemical Co., ltd.; available as "KAYACURE DETX-S") for 1 hour.

< production example 2> preparation of adhesive layer-forming composition 2

An adhesive layer-forming composition (curable resin composition) 2 was obtained, which contained 10 parts by weight of hydroxyethyl acrylamide (manufactured by prospermian corporation), 30 parts by weight of acryloyl morpholine (manufactured by prospermian corporation), 45 parts by weight of 1,9-nonanediol diacrylate (manufactured by honor chemical corporation), 10 parts by weight of ARUFON UP1190 (an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer, manufactured by east asia synthesis corporation), 3 parts by weight of IRGACURE907 (a polymerization initiator, manufactured by BASF corporation), and 2 parts by weight of KAYACURE x-S (a polymerization initiator, manufactured by deta chemical corporation), relative to 100% by weight of the total amount of the curable resin composition.

[ example 1]

1. Production of polarizer laminate

A long amorphous polyethylene terephthalate (A-PET) film (trade name "Novacrea" manufactured by Mitsubishi resin corporation, thickness 100 μm) was prepared as a base material. An aqueous solution of a polyvinyl alcohol (PVA) resin (trade name "Gohsenol (registered trademark) NH-26", manufactured by japan synthetic chemical industries) was applied to one surface of the substrate at 60 ℃, and dried, thereby forming a PVA-based resin layer having a thickness of 7 μm. The laminate thus obtained was immersed in an insolubilization bath having a liquid temperature of 30 ℃ for 30 seconds (insolubilization step). Subsequently, the substrate was immersed in a dyeing bath at a liquid temperature of 30 ℃ for 60 seconds (dyeing step). Subsequently, the resultant film was immersed in a crosslinking bath having a liquid temperature of 30 ℃ for 30 seconds (crosslinking step). Thereafter, the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds while being immersed in an aqueous boric acid solution having a liquid temperature of 60 ℃. The immersion time in the aqueous boric acid solution was 120 seconds and the stretching was continued until the laminate was about to break. Thereafter, the laminate was immersed in a washing bath and then dried with hot air at 60 ℃. In this way, a long-shaped laminate (polarizer laminate) in which a polarizer having a thickness of 5 μm was formed on a base material was obtained.

2. Preparation of polarizing plate

A cycloolefin resin FILM (product name "ZEONOR FILM" of 25 μm thickness, manufactured by japan raptor gmbh) as a protective FILM was bonded to the polarizer-side surface of the laminate via an adhesive, and the substrate was peeled from the polarizer to obtain a polarizing plate.

3. Production of the first retardation layer

A retardation layer (first retardation layer) was produced in the same manner as in example 75 of international publication No. 2017/090418.

The first retardation layer had an in-plane retardation (Re (550)) of 140nm, an Re (450)/Re (550) of 0.85, and an Re (650)/Re (550) of 1.03.

4. Fabrication of second phase difference layer

A liquid crystal coating solution was prepared by dissolving 20 parts by weight of a side chain type liquid crystal polymer represented by the following formula (I), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (product name: paliocolorLC242 manufactured by BASF) and 5 parts by weight of a photopolymerization initiator (product name: irgacure907 manufactured by BASF) in 400 parts by weight of cyclopentanone. Further, the coating liquid was applied to a substrate film (norbornene resin film: product name "ZEONOR" manufactured by Nippon Ralskikai Co., ltd.) by a bar coater, and then heated and dried at 70 ℃ for 4 minutes to align the liquid crystal. The liquid crystal layer is cured by irradiating the liquid crystal layer with ultraviolet rays, thereby forming a liquid crystal cured layer (thickness: 1 μm) serving as a second phase difference layer on the substrate. Re (550) showing the second phase difference layer was 0nm, and Rth (550) was-71 nm (nx: 1.5326, ny:1.5326, nz: 1.6550).

[ chemical structural formula 5]

5. Production of polarizing plate with retardation layer

The retardation film was bonded to the polarizer side of the polarizing plate via the adhesive composition 1 obtained in production example 1 so that the angle formed by the absorption axis of the polarizer and the slow axis of the first retardation layer became 45 °. Next, the second retardation layer was transferred to the surface of the first retardation layer opposite to the polarizer via the adhesive composition 2 obtained in production example 2, thereby obtaining a laminate having a structure of protective layer/polarizer/adhesive layer/first retardation layer/adhesive layer/second retardation layer. The obtained laminate was subjected to a heat treatment in an oven at 90 ℃ for 12 hours, thereby obtaining a polarizing plate with a retardation layer.

[ example 2]

A polarizing plate 2 with a retardation layer was obtained in the same manner as in example 1, except that the heat treatment was performed for 1 hour using an oven at 90 ℃.

[ example 3]

A polarizing plate 3 with a retardation layer was obtained in the same manner as in example 1, except that the heating treatment was performed for 24 hours using an oven at 85 ℃.

Comparative example

A polarizing plate C1 with a retardation layer was obtained in the same manner as in example 1, except that the heat treatment was not performed.

The following evaluations were carried out using the polarizing plates with retardation layers obtained in examples 1 to 3 and comparative example.

< evaluation of reflected color >

The polarizing plates with a retardation layer obtained in examples and comparative examples were measured in SCI using a spectrocolorimeter (CM-2600 d, manufactured by Konika Meinenda Co.) to measure the reflection hues (a, b). An aluminum deposition film (trade name "DMS deposition X-42" manufactured by Toray film processing Co., ltd., thickness: 50 μm) was bonded to a glass plate using an adhesive.

< evaluation of heating durability >

The initial reflection color (a, b) and the reflection color (a, b) after being put into an oven at 85 ℃ for 120 hours and taken out were measured for the polarizing plates with retardation layers obtained in examples and comparative examples, respectively, and the change in reflection color (Δ a, b) was obtained by the following equation.

Δ a × b = SQRT ((a × post-a × pre) ^2+ (b × post-b × pre) ^ 2)

[ Table 1]

	Example 1	Example 2	Example 3	Comparative example
					a front	2.49	-0.01	1.15	-0.10
b front	-1.05	-1.17	-0.89	-1.29
					a back	3.24	2.11	2.89	2.53
b is after	-1.16	-1.23	-1.30	-1.46
					Δab	0.76	2.12	1.74	2.64

In examples 1 to 3 in which the polarizer and the first retardation layer and the first and second retardation layers were laminated via the adhesive layer and then subjected to heat treatment, the change in the reflection hue was suppressed.

Industrial applicability

The polarizing plate with a retardation layer of the present invention is preferably used as a circular polarizing plate for liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

Description of the symbols

10. Protective layer

20. Polarizer

30. Adhesive layer

31. First adhesive layer

32. Second adhesive layer

40. Retardation layer

41. First phase difference layer

42. Second phase difference layer

100. Polarizing plate with phase difference layer

101. Polarizing plate with phase difference layer

Claims

1. A method for producing a polarizing plate with a retardation layer, which comprises a protective layer, a polarizer, an adhesive layer, and a retardation layer as an alignment-cured layer of a liquid crystal compound in this order, the method comprising:

a step of laminating the polarizer and the retardation layer with an adhesive layer interposed therebetween; and

and a step of heating the laminate including the polarizer, the retardation layer and the adhesive layer after the lamination step.

2. A method for producing a polarizing plate with a retardation layer, which comprises a protective layer, a polarizer, a first adhesive layer, a first retardation layer as an oriented cured layer of a liquid crystal compound, a second adhesive layer, and a second retardation layer in this order, the method comprising:

a step of laminating the first retardation layer and the second retardation layer with a second adhesive layer interposed therebetween; and

and a step of heating the laminate including the first retardation layer, the second retardation layer, and the second adhesive layer after the laminating step.

3. The method for producing a polarizing plate with a retardation layer according to claim 2, comprising:

laminating the polarizer and the first retardation layer with a first adhesive layer interposed therebetween; and

and a step of heating the laminate including the polarizer, the first retardation layer, and the first adhesive layer after the lamination step.

4. The method for producing a polarizing plate with a retardation layer according to any one of claims 1 to 3, wherein a heating time in the step of heating the laminate exceeds 1 hour.

5. The method for producing a polarizing plate with a retardation layer according to any one of claims 1 to 4, wherein a heating temperature in the step of heating the laminate is 90 ℃ to 110 ℃.