Method for manufacturing polarizing plates and method for manufacturing display devices

Abstract

To provide a method for manufacturing a polarizing plate that can appropriately transfer a phase difference layer and has excellent adhesion properties of the phase difference layer.SOLUTION: A polarizing plate has a polarizing element and a composite protection film. The composite protection film has a fist protection film, and a phase difference layer containing a cured product layer of a polymerizable liquid crystal compound in order from the side of the polarizing element. A method for manufacturing a polarizing plate includes: a step (1) of laminating a phase difference layer formed on a base material layer and the first protection film by using an ultraviolet curable adhesive, and obtaining a composite protection film having a base material layer by irradiating the ultraviolet curable adhesive with ultraviolet rays; a step (2) of bonding a side of the first protection film of the composite protection film having a base material layer and the polarizing element by using a first water-based adhesive and obtaining a polarizing plate having a base material layer; and a step (3) of separating the base material layer from the polarizing plate having a base material layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing polarizing plates. [Background technology]

[0002] Liquid crystal display (LCD) displays are widely used not only in LCD televisions but also in personal computers, mobile devices such as cell phones, and in-vehicle applications such as car navigation systems. Typically, an LCD display has a liquid crystal panel in which linear polarizing plates containing polarizing elements are bonded to both sides of a liquid crystal cell, and displays images by controlling the light from the backlight with the liquid crystal panel. In recent years, organic light-emitting diode (OLED) displays have also become widely used in televisions, mobile devices such as cell phones, and in-vehicle applications such as car navigation systems, similar to LCD displays. In OLED displays, a circular polarizing plate (including a polarizing element and a λ / 4 plate) may be placed on the viewing surface of the image display element to prevent ambient light from being reflected by the metal electrode (cathode) and appearing like a mirror.

[0003] Linear and circular polarizers used in display devices are required to achieve good viewing angle characteristics. To improve viewing angle characteristics, it is known that a phase difference layer containing a cured polymerizable liquid crystal compound is used in the display device along with the polarizing element (for example, Patent Document 1).

[0004] As described in Patent Document 1, the cured layer of a polymerizable liquid crystal compound is formed by applying a composition containing the polymerizable liquid crystal compound onto a base film and curing it. The cured layer formed on the base film is then bonded together with the base film to an adherend such as a polarizing element, and then transferred onto the adherend by peeling off the base film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-201510 [Overview of the project] [Problems that the invention aims to solve]

[0006] In linear and circular polarizing plates, when laminating polarizing elements, phase difference layers, and protective films, UV-curing adhesives are sometimes used to bond the layers together. When transferring a cured layer onto a substrate using a UV-curing adhesive, the cured layer on the base film and the substrate are laminated, and after curing the UV-curing adhesive, the base film is peeled off. When peeling off the base film, the cured layer may not be transferred to the substrate and may peel off together with the base film, or the cured layer may be transferred but the adhesion to the substrate may not be sufficient.

[0007] The present invention aims to provide a method for manufacturing a polarizing plate in which, when transferring a phase difference layer containing a cured polymerizable liquid crystal compound layer to a substrate using an ultraviolet-curable adhesive, the phase difference layer adheres closely to the substrate and the phase difference layer can be transferred well. [Means for solving the problem]

[0008] The present invention provides the following method for manufacturing polarizing plates. [1] A method for manufacturing a polarizing plate comprising a polarizing element and a composite protective film, The composite protective film has, in order from the polarizing element side, a first protective film and a phase difference layer including a cured polymerizable liquid crystal compound layer. The aforementioned manufacturing method is Step (1) is to obtain a composite protective film with a base layer by laminating the phase difference layer formed on the base layer and the first protective film using an ultraviolet-curing adhesive and irradiating the ultraviolet-curing adhesive with ultraviolet light, Step (2) is to bond the first protective film side of the composite protective film with the base layer and the polarizing element using a first aqueous adhesive to obtain a polarizing plate with a base layer, A method for manufacturing a polarizing plate, comprising the step (3) of peeling off the base layer from the polarizing plate with the base layer. [2] The method for manufacturing a polarizing plate according to [1], further comprising the step (4) of peeling off the base material layer and forming an adhesive layer on the exposed side. [3] The method for manufacturing a polarizing plate according to [1] or [2], wherein the light transmittance of the first protective film at a wavelength of 365 nm is 80% or more. [4] The method for manufacturing a polarizing plate according to any one of [1] to [3], wherein the first aqueous adhesive contains a polyvinyl alcohol resin. [5] The method for manufacturing a polarizing plate according to any one of [1] to [4], wherein step (2) further includes a step of laminating a second protective film to the side of the polarizing element opposite to the side with the composite protective film. [6] The method for manufacturing a polarizing plate according to [5], wherein the polarizing element and the second protective film are bonded together using a second aqueous adhesive. [7] The method for manufacturing a polarizing plate according to [6], wherein the second aqueous adhesive contains a polyvinyl alcohol-based resin. [8] The method for manufacturing a polarizing plate according to any one of [5] to [7], wherein step (2) involves bonding the polarizing element to the second protective film while bonding the composite protective film with the base layer to the polarizing element. [Effects of the Invention]

[0009] According to the method for manufacturing polarizing plates of the present invention, the phase difference layer can be transferred well, and polarizing plates with excellent adhesion of the phase difference layer can be manufactured. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing a polarizing plate according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view showing a method for manufacturing a polarizing plate according to one embodiment of the present invention. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

[0012] (Polarizing plate) FIG. 1 is a cross-sectional view schematically showing a polarizing plate according to an embodiment of the present invention. The polarizing plate 1 includes a polarizing element 10 and a composite protective film 30, and the composite protective film 30 can be provided on one side of the polarizing element 10. The polarizing plate 1 can include, in this order, a polarizing element 10, a first adhesive layer 21 formed using a first aqueous adhesive, and a composite protective film 30. The first adhesive layer 21 is a layer for bonding the polarizing element 10 and the composite protective film 30, and is in direct contact with the polarizing element 10 and the composite protective film 30. The composite protective film 30 has, in order from the polarizing element 10 side, a first protective film 11, a cured product layer of an ultraviolet curable adhesive (hereinafter sometimes referred to as a "UV adhesive"), that is, a UV adhesive layer 25, and a retardation layer 15. The UV adhesive layer 25 is a layer for bonding the first protective film 11 and the retardation layer 15, and is in direct contact with the first protective film 11 and the retardation layer 15. The retardation layer 15 may include at least one cured product layer of a polymerizable liquid crystal compound and at least one alignment layer having an alignment regulating force for aligning the polymerizable liquid crystal compound in a desired direction. When the retardation layer 15 includes an alignment layer, it is preferable that the alignment layer constitutes the surface of the retardation layer 15 opposite to the UV adhesive layer 25.

[0013] Since the retardation layer 15 and the first protective film 11 are bonded by the UV adhesive layer 25, in the polarizing plate 1, the retardation layer 15 including the cured product layer of the polymerizable liquid crystal compound is supported by the harder UV adhesive layer 25 as compared with an adhesive layer formed by an adhesive. Thereby, deformation of the retardation layer 15 is suppressed, and it is possible to suppress the occurrence of scratches or dents or the like in the retardation layer 15 (particularly, the cured product layer) accompanying the conveyance of the polarizing plate 1.

[0014] The polarizing plate 1 may further have an adhesive layer 28 on the side of the composite protective film 30, and may have a release film for covering and protecting the adhesive layer 28 on the side opposite to the composite protective film 30 side of the adhesive layer 28. The adhesive layer 28 is, for example, a layer for bonding the polarizing plate 1 to an image display element of a display device. The adhesive layer 28 may be provided in direct contact with the composite protective film 30, or may be provided via another layer disposed on the side opposite to the polarizing element 10 side of the composite protective film 30.

[0015] The polarizing plate 1 may further have a second protective film 12 on the side of the polarizing element 10. The polarizing element 10 and the second protective film 12 may be laminated in direct contact with each other, or may be bonded by a second adhesive layer 22 formed using a second aqueous adhesive. When the polarizing element 10 and the second protective film 12 are bonded by the second adhesive layer 22, the second adhesive layer 22 is in direct contact with the polarizing element 10 and the second protective film 12.

[0016] On the side of the second protective film 12 opposite to the polarizing element 10, a surface protective film (protective film) peelable from the second protective film 12 may be laminated on the polarizing plate 1. The surface protective film is for protecting the surface of the second protective film 12.

[0017] The polarizing plate 1 can be laminated and used on an image display element of a display device such as a liquid crystal display device or an organic EL display device.

[0018] (Method for manufacturing a polarizing plate) FIG. 2 is a cross-sectional view schematically showing a method for manufacturing a polarizing plate according to an embodiment of the present invention. The method for manufacturing the polarizing plate 1 is the method for manufacturing the polarizing plate 1 described above, A step (1) of laminating the retardation layer 15 formed on the base material layer 17 and the first protective film 11 using a UV adhesive, and irradiating the UV adhesive with ultraviolet rays (hereinafter sometimes referred to as "UV irradiation") to obtain a composite protective film 31 with a base material layer ((a) and (b) in FIG. 2), Step (2) (Figure 2(c)) involves bonding the first protective film 11 side of the composite protective film 31 with a base layer and the polarizing element 10 using a first aqueous adhesive to obtain a polarizing plate 2 with a base layer, The process includes step (3) (Figure 2(d)) of peeling off the base material layer 17 from the polarizing plate 2 with the base material layer.

[0019] The method for manufacturing the polarizing plate 1 may further include step (4), in which the base layer 17 of the polarizing plate 2 with a base layer is peeled off in step (3) and an adhesive layer 28 is formed on the exposed surface. The adhesive layer 28 may be formed on the surface exposed after peeling off the base layer 17, but it may also be formed on another layer provided on this exposed surface.

[0020] The method for manufacturing the polarizing plate 1 may further include a step in step (2) of laminating a second protective film 12 to the side of the polarizing element 10 opposite to the composite protective film 30 side (Figure 2(c)). In this step, it is preferable to laminate the polarizing element 10 and the second protective film 12 using a second water-based adhesive. In step (2), it is preferable to laminate the polarizing element 10 and the second protective film 12 while laminating the composite protective film 31 with a base layer to the polarizing element 10.

[0021] The cured layer contained in the phase difference layer 15 is usually formed by applying a composition containing a polymerizable liquid crystal compound to the substrate layer 17 or an alignment layer formed on the substrate layer 17, and then polymerizing and curing the polymerizable liquid crystal compound. Therefore, when laminating the phase difference layer 15 containing the above-mentioned cured layer onto the first protective film 11 or another film such as the polarizing element 10, a phase difference film 19 with a substrate layer (Figure 2(a)) is used, in which the phase difference layer 15 is provided on at least one side of the substrate layer 17. When laminating the phase difference layer 15 of the phase difference film 19 with a substrate layer onto an adherend such as the polarizing element 10, a method can be considered in which the phase difference film 19 with a substrate layer is bonded to the adherend, and then the substrate layer 17 is peeled off to transfer the phase difference layer 15 to the adherend. As a method for manufacturing a polarizing plate 1 with the transfer of such a phase difference layer 15, [i] first, a phase difference film 19 with a base layer is attached to a polarizing element with a protective film, which is formed by laminating a polarizing element 10 and a first protective film 11, using a UV adhesive, and [ii] after UV irradiation of the UV adhesive, the base layer 17 is peeled off. The inventors have found that when the base layer 17 is peeled off as in [i] and [ii] above, a transfer failure occurs in which the phase difference layer 15 is not transferred to the polarizing element with a protective film and the phase difference layer 15 peels off together with the base layer 17, or an adhesion failure occurs in which the phase difference layer 15 is transferred but the adhesion between the phase difference layer 15 and the polarizing element with a protective film is not sufficient.

[0022] The reason for poor transfer or poor adhesion of the phase difference layer 15 is presumed to be as follows: The polarizing element 10 and the phase difference layer 15 have absorption in the ultraviolet region (wavelength region of 280-390 nm) and often do not transmit ultraviolet light easily. Therefore, even when a polarizing element with a protective film and a phase difference film with a base layer are laminated via a UV adhesive, and ultraviolet light is irradiated onto the UV adhesive via the polarizing element 10 and / or the phase difference layer 15, the ultraviolet light is absorbed by the polarizing element 10 and / or the phase difference layer 15, making it difficult for the ultraviolet light to reach the UV adhesive, and thus the UV adhesive cannot be sufficiently cured. This is thought to result in poor transfer or poor adhesion of the phase difference layer 15.

[0023] In contrast, according to the manufacturing method of the polarizing plate 1 of this embodiment, first, in step (1) above, UV irradiation is performed on the laminated structure formed by laminating the base layer-attached phase difference film 19 and the first protective film 11 via a UV adhesive. Therefore, by irradiating ultraviolet light from the first protective film 11 side, it is considered that the UV adhesive can be sufficiently cured by the ultraviolet light that has passed through the first protective film 11. As a result, in step (3) above, when peeling off the base layer 17 from the base layer-attached polarizing plate 2 obtained in step (2) above, the occurrence of poor transfer or poor adhesion of the phase difference layer 15 can be suppressed.

[0024] The method for manufacturing the polarizing plate 1 may be carried out using a single sheet or a long sheet. From the viewpoint of continuously producing polarizing plates, it is preferable to use a long sheet. In this case, the layers or films obtained in or during each process can be wound into a roll to form a reel, and the layers or films can be unwound from this reel to carry out the next process. In this specification, a long sheet refers to, for example, a layer or film having a length of 30 to 10,000 m.

[0025] The following describes in detail each step in the manufacturing method of polarizing plate 1. (Process (1)) Step (1) is a step in which the phase difference layer 15 of the phase difference film 19 with a base layer and the first protective film 11 are laminated using a UV adhesive, and the UV adhesive is irradiated with UV light to obtain a composite protective film 31 with a base layer (Figure 2(b)). By irradiating with UV light in step (1), the UV adhesive between the base layer 17 and the phase difference layer 15 is cured to form a UV adhesive layer 25. The composite protective film 31 with a base layer has the base layer 17, the phase difference layer 15, the UV adhesive layer 25, and the first protective film 11 in this order.

[0026] In step (1), the UV adhesive may be applied to the surface of the phase difference layer 15 of the phase difference film 19 with the base layer, or to the surface of the first protective film 11, or to both. It is preferable to perform a surface treatment such as corona treatment, plasma treatment, itro treatment, or saponification treatment on the surfaces of the phase difference layer 15 and the first protective film 11 that come into contact with the UV adhesive, in order to improve the applicability of the UV adhesive and improve adhesion with the UV adhesive.

[0027] Known coating methods such as wire bar coating, gravure coating, doctor blade coating, die coating, and comma coating can be used to apply UV adhesive. Of these, from the viewpoint of applying UV adhesive to a thin film, it is preferable to use either the bar coating method or the gravure coating method.

[0028] The UV adhesive interposed between the phase difference layer 15 of the phase difference film 19 with a base layer and the first protective film 11 can be cured by UV irradiation to form a UV adhesive layer 25. The cured layer of polymerizable liquid crystal compound contained in the phase difference layer 15 tends to have low light transmittance near a wavelength of 365 nm due to its molecular structure. Therefore, from the viewpoint of irradiating the UV adhesive with sufficient ultraviolet light, it is preferable to perform UV irradiation from the side of the first protective film 11. This suppresses the deterioration of the phase difference layer 15 due to UV irradiation and also suppresses the deterioration of the optical properties of the polarizer. From the viewpoint of efficiently curing the UV adhesive, it is preferable that the light transmittance of the first protective film 11 at a wavelength of 365 nm be 80% or more, as will be described later.

[0029] For UV irradiation, light sources with an emission distribution particularly below 400 nm wavelength are preferably used, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps. The UV irradiation intensity to the UV adhesive is determined according to the target composition and is not particularly limited, but for example, an irradiation intensity of 5 to 1000 mW / cm² in the wavelength range effective for activating the photopolymerization initiator (e.g., the UV range with a wavelength of 280 to 390 nm) is preferable. 2 It is preferable to ensure that the UV adhesive is exposed to ultraviolet light in an insufficient amount of light. If the UV adhesive is exposed to ultraviolet light in an insufficient amount of light, the reaction time will be too long. If the UV adhesive is exposed to ultraviolet light in an insufficient amount of light, the heat radiated from the light source and the heat generated during polymerization of the UV adhesive may cause yellowing of the adhesive.

[0030] The UV irradiation time for UV adhesives is controlled according to the composition being cured and is not particularly limited, but the integrated light amount, expressed as the product of UV irradiation intensity and UV irradiation time, is 10 mJ / cm². 2 More than 2,000mJ / cm 2 It is preferable to set the parameters as follows: If the amount of light accumulated on the UV adhesive is too small, the generation of active species derived from the photopolymerization initiator may not be sufficient, and the resulting UV adhesive layer 25 may not be cured properly. If the amount of light accumulated on the UV adhesive is increased, the irradiation time required to cure the UV adhesive becomes very long, which is detrimental to improving the productivity of the polarizing plate 1.

[0031] Step (1) may include a step of preparing a phase difference film 19 with a base layer. The preparation step may include a step of forming a phase difference layer 15 on the base layer 17. The step of forming a phase difference layer 15 on the base layer 17 may include, for example, a step of forming an orientation layer on the base layer 17 that has an orientation restricting force that orients a polymerizable liquid crystal compound in a desired direction, and a step of forming a cured layer of the polymerizable liquid crystal compound on this orientation layer.

[0032] Methods for forming an orientation layer on the substrate layer 17 include forming an orientation polymer layer made of an orientation polymer on the substrate layer 17, forming a photo-orientation polymer layer made of a photo-orientation polymer, and forming a groove orientation layer having an uneven pattern or multiple grooves on the surface of the substrate layer 17. Methods for forming a cured layer of polymerizable liquid crystal compound on the orientation layer include applying a composition containing a polymerizable liquid crystal compound to the orientation layer and polymerizing and curing the polymerizable liquid crystal compound.

[0033] (Process (2)) Step (2) is a step to obtain a polarizing plate 2 with a base layer (Figure 2(c)) by bonding the first protective film 11 side of the composite protective film 31 with a base layer obtained in step (1) to the polarizing element 10 using a first aqueous adhesive. In step (2), the first adhesive layer 21 can be formed by drying the first aqueous adhesive between the composite protective film 31 with a base layer and the polarizing element 10. The polarizing plate 2 with a base layer has the base layer 17, the phase difference layer 15, the UV adhesive layer 25, the first protective film 11, the first adhesive layer 21, and the polarizing element 10 in this order.

[0034] Step (2) may further include a step of laminating the second protective film 12 to the side of the polarizing element 10 opposite to the composite protective film 31 with the base layer, and may also include a step of laminating the polarizing element 10 and the second protective film 12 using a second aqueous adhesive. The second adhesive layer 22 can be formed by drying the second aqueous adhesive between the polarizing element 10 and the second protective film 12. The polarizing plate 2 with a base layer having the second protective film 12 has the base layer 17, the phase difference layer 15, the UV adhesive layer 25, the first protective film 11, the first adhesive layer 21, the polarizing element 10, the second adhesive layer 22, and the second protective film 12 in this order. The second protective film 12 may have a surface protective film laminated on the side opposite to the polarizing element 10.

[0035] In step (2), it is preferable to bond the polarizing element 10 to the second protective film 12 while bonding the composite protective film 31 with the base layer to the polarizing element 10. This bonding can be achieved, for example, by overlapping the composite protective film 31 with the base layer, the polarizing element 10, and the second protective film 12 and passing them between a pair of bonding rolls and applying pressure. Between the pair of bonding rolls, the composite protective film 31 with the base layer, the polarizing element 10, and the second protective film 12 are arranged such that the first protective film 11 side of the composite protective film 31 with the base layer faces the polarizing element 10 via the first aqueous adhesive, and the second protective film 12 faces the other side of the polarizing element 10 via the second aqueous adhesive. If the polarizing plate 1 does not have a second protective film 12, the composite protective film 31 with the base layer and the polarizing element 10 may be arranged between the pair of bonding rolls so that they face each other via the first aqueous adhesive.

[0036] It is preferable to inject the first water-based adhesive between the composite protective film 31 with a base layer and the polarizing element 10 using an adhesive injection device before passing it between a pair of laminating rolls. It is preferable to inject the second water-based adhesive between the polarizing element 10 and the second protective film 12 using an adhesive injection device before passing it between a pair of laminating rolls.

[0037] The first aqueous adhesive may be applied to the first protective film 11 side of the composite protective film 31 with a base layer, applied to the polarizing element 10, or applied to both, instead of using an adhesive injection device. Similarly, the second aqueous adhesive may be applied to the polarizing element 10, applied to the second protective film 12, or applied to both. When applying the first aqueous adhesive to the composite protective film 31 with a base layer and / or the polarizing element 10, the application method can be selected according to the viscosity of the first or second aqueous adhesive, and can be carried out by, for example, the doctor blade method, wire bar coater method, die coater method, comma coater method, gravure coater method, dip coater method, casting method, etc.

[0038] It is preferable to perform surface treatments such as corona treatment, plasma treatment, itro treatment, or saponification treatment on the surface of the composite protective film 31 with a base layer and the polarizing element 10 that comes into contact with the first aqueous adhesive, in order to improve the applicability of the first aqueous adhesive and improve adhesion with the first aqueous adhesive. It is also preferable to perform the same surface treatment on the surface of the polarizing element 10 and the second protective film 12 that comes into contact with the second aqueous adhesive for the same reasons.

[0039] The first aqueous adhesive interposed between the composite protective film 30 and the polarizing element 10, and the second aqueous adhesive interposed between the polarizing element 10 and the second protective film 12, become the first adhesive layer 21 and the second adhesive layer 22, respectively, by heat drying or the like. The heat drying method can be any known method, such as heat drying with hot air or heat drying with a far-infrared heater.

[0040] The heating and drying temperature is preferably 30°C to 90°C. If it is below 30°C, the drying time will be longer, reducing productivity and making it unfavorable for improving productivity. If the heating and drying temperature exceeds 90°C, the polarization performance of the polarizing element 10 may deteriorate due to the heat. The heating and drying time can be approximately 10 seconds to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 seconds to 750 seconds, and more preferably 150 seconds to 600 seconds.

[0041] After heating and drying the first water-based adhesive, or the first water-based adhesive and the second water-based adhesive, the composite protective film 30 and the polarizing element 10, or the composite protective film 30, the polarizing element 10, and the second protective film 12 may be cured (stored) at a temperature above room temperature for half a day or more, preferably several days or more. The curing temperature is more preferably 30°C to 50°C, and even more preferably 35°C to 45°C. The humidity during curing is not particularly limited, but it is preferably in the range of 0%RH to 70%RH relative humidity. The curing time is usually about 1 to 10 days, preferably about 2 to 7 days.

[0042] (Step (3)) Step (3) is the step of peeling the base layer 17 from the polarizing plate 2 with the base layer. The peeling of the base layer 17 may be done by peeling off the base layer 17, or the orientation layer may be peeled off together with the base layer 17.

[0043] (Step (4)) Step (4) is a step of forming an adhesive layer 28 on the side of the polarizing plate 2 with a base layer that has been peeled off and exposed (hereinafter sometimes referred to as the "exposed surface"). The adhesive layer 28 may be formed directly on the exposed surface, or if another layer is formed on the exposed surface, it may be formed on this other layer. Methods for forming the adhesive layer 28 include bonding the exposed surface or other layer to the adhesive layer 28 formed on the release film, and applying an adhesive to the exposed surface or other layer. Prior to bonding the exposed surface or other layer to the adhesive layer 28, it is preferable to perform surface treatment such as corona treatment, plasma treatment, or Itro treatment on the surface of the exposed surface or other layer and the surface of the adhesive layer 28 on the side in contact with the exposed surface or other layer.

[0044] The following describes the details of the layers and films that make up polarizing plate 1. (Polarizing element) A polarizing element is an absorbing polarizing film that has the property of absorbing linearly polarized light with a vibration plane parallel to its absorption axis and transmitting linearly polarized light with a vibration plane perpendicular to the absorption axis (parallel to the transmission axis).

[0045] The polarizing element is a polyvinyl alcohol-based resin layer (hereinafter sometimes referred to as "PVA-based resin layer") on which a dichroic dye is adsorbed and oriented. Known polarizing elements can be used. Examples of polarizing elements include a stretched film obtained by dyeing a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as "PVA-based resin film") with a dichroic dye and uniaxially stretching it, and a stretched layer obtained by using a laminated film having a coated layer formed by applying a coating solution containing polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") to a base film, dyeing the coated layer with a dichroic dye, and uniaxially stretching the laminated film. Stretching may be performed after dyeing with the dichroic dye, stretching while dyeing, or dyeing after stretching.

[0046] PVA-based resins are obtained by saponifying polyvinyl acetate-based resins. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers copolymerizable thereto. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0047] The degree of saponification of the PVA resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and even more preferably about 99 mol% or more and 100 mol% or less. The degree of polymerization of the PVA resin is, for example, 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The PVA resin may be modified, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc., modified with aldehydes.

[0048] Examples of dichroic dyes adsorbed and oriented on the PVA resin layer include iodine or dichroic dyes. Iodine is preferred as the dichroic dye. Examples of dichroic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc.

[0049] The thickness of the polarizing element is preferably 3 μm to 35 μm, more preferably 4 μm to 30 μm, and even more preferably 5 μm to 25 μm. A polarizing element thickness of 35 μm or less suppresses the effect of polyene formation of the PVA resin on the degradation of optical properties, for example, under high-temperature environments. A polarizing element thickness of 3 μm or more facilitates the creation of a configuration that achieves desired optical properties.

[0050] (Manufacturing method for polarizing elements) The method for manufacturing polarizing elements is not particularly limited, but typical methods include a method in which a PVA-based resin film, which has been pre-wound into a roll, is fed out and stretched, dyed, crosslinked, etc. (hereinafter referred to as "manufacturing method 1"), and a method in which a coating solution containing PVA-based resin is applied to a base film to form a PVA-based resin layer which is a coating layer, and the resulting laminate is stretched (hereinafter referred to as "manufacturing method 2").

[0051] Manufacturing method 1 can be produced by following the steps of: uniaxial stretching of a PVA-based resin film; dyeing the PVA-based resin film with a dichroic dye such as iodine and adsorbing the dichroic dye; treating the PVA-based resin film on which the dichroic dye has been adsorbed with a boric acid aqueous solution; and washing with water after treatment with the boric acid aqueous solution.

[0052] The swelling process is a treatment process in which the PVA resin film is immersed in a swelling bath. The swelling process can remove dirt and blocking agents from the surface of the PVA resin film, and can also suppress uneven dyeing by swelling the PVA resin film. Typically, a water-based medium such as water, distilled water, or pure water is used as the swelling bath. The swelling bath may also have surfactants, alcohol, etc., added as appropriate according to conventional methods. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide may be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less.

[0053] The temperature of the swelling bath is preferably between 10°C and 60°C, more preferably between 15°C and 45°C, and even more preferably between 18°C ​​and 30°C. The immersion time in the swelling bath cannot be determined definitively because the degree of swelling of the PVA resin film is affected by the temperature of the swelling bath, but it is preferably between 5 seconds and 300 seconds, more preferably between 10 seconds and 200 seconds, and even more preferably between 20 seconds and 100 seconds. The swelling process may be performed only once, or multiple times as needed.

[0054] The dyeing process involves immersing a PVA-based resin film in a treatment bath (dyeing bath) containing a dichroic dye, which allows the PVA-based resin film to adsorb and orient a dichroic dye such as iodine. The dyeing bath is a dyeing solution containing a dichroic dye, and is preferably an iodine solution. The iodine solution is preferably an aqueous iodine solution and preferably contains iodine and an iodide as a solubilizing agent. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred from the viewpoint of controlling the potassium content in the polarizing element.

[0055] The concentration of iodine in the iodine solution is preferably between 0.01% by mass and 1% by mass, and more preferably between 0.02% by mass and 0.5% by mass. The concentration of iodide in the iodine solution is preferably between 0.01% by mass and 10% by mass, more preferably between 0.05% by mass and 5% by mass, and even more preferably between 0.1% by mass and 3% by mass.

[0056] The temperature of the dyeing bath is preferably between 10°C and 50°C, more preferably between 15°C and 45°C, and even more preferably between 18°C ​​and 30°C. The immersion time in the dyeing bath cannot be determined definitively because the degree of dyeing of the PVA resin film is affected by the temperature of the dyeing bath, but it is preferably between 10 seconds and 300 seconds, and more preferably between 20 seconds and 240 seconds. The dyeing process may be performed only once, or multiple times as needed.

[0057] The crosslinking process involves immersing the PVA resin film, dyed in the dyeing process, in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the PVA resin film, allowing iodine molecules or dye molecules to be adsorbed onto the crosslinked structure. Examples of boron compounds include boric acid, borates, and borax. The crosslinking bath is generally an aqueous solution, but it may also be a mixed solution of a water-miscible organic solvent and water. From the viewpoint of controlling the potassium content in the polarizing element, the crosslinking bath preferably contains potassium iodide.

[0058] In the crosslinking bath, the concentration of the boron compound is preferably about 1% by mass or more and 15% by mass or less, more preferably about 1.5% by mass or more and 10% by mass or less, and even more preferably about 2% by mass or more and 5% by mass or less. When potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1% by mass or more and 15% by mass or less, more preferably about 1.5% by mass or more and 10% by mass or less, and even more preferably about 2% by mass or more and 5% by mass or less.

[0059] The temperature of the crosslinking bath is preferably between 20°C and 70°C, and more preferably between 30°C and 60°C. The immersion time in the crosslinking bath cannot be determined definitively because the degree of crosslinking of the PVA resin film is affected by the temperature of the crosslinking bath, but it is preferably between 5 seconds and 300 seconds, and more preferably between 10 seconds and 200 seconds. The crosslinking process may be performed only once, or multiple times as necessary.

[0060] The stretching process is a process in which a PVA-based resin film is stretched to a predetermined magnification in at least one direction. Generally, the PVA-based resin film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either wet stretching or dry stretching can be used. The stretching process may be performed only once, or multiple times as needed. The stretching process may be performed at any stage in the manufacturing of the polarizing element.

[0061] In the wet stretching method, the treatment bath (stretching bath) can usually be a solvent such as water or a mixed solution of a water-miscible organic solvent and water. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1% by mass or more and 15% by mass or less, more preferably about 2% by mass or more and 10% by mass or less, and more preferably about 3% by mass or more and 6% by mass or less. The treatment bath (stretching bath) may contain a boron compound from the viewpoint of suppressing film breakage during stretching. When a boron compound is included, the concentration of the boron compound in the stretching bath is preferably about 1% by mass or more and 15% by mass or less, more preferably about 1.5% by mass or more and 10% by mass or less, and more preferably about 2% by mass or more and 5% by mass or less.

[0062] The temperature of the stretching bath is preferably 25°C to 80°C, more preferably 40°C to 80°C, even more preferably 50°C to 75°C, and particularly preferably 65°C to 75°C. The immersion time in the stretching bath cannot be determined definitively because the degree of stretching of the PVA resin film is affected by the temperature of the stretching bath, but it is preferably about 10 seconds to 800 seconds, and more preferably about 30 seconds to 500 seconds. The stretching treatment in the wet stretching method may be performed together with one or more of the following treatment steps: swelling, dyeing, crosslinking, and washing.

[0063] Examples of dry stretching methods include the inter-roll stretching method, the heated roll stretching method, and the compression stretching method. The dry stretching method may also be performed in conjunction with the drying process.

[0064] The total stretching ratio (cumulative stretching ratio) applied to the PVA resin film can be set appropriately depending on the purpose, but it is preferably between 2 and 7 times, more preferably between 3 and 6.8 times, and even more preferably between 3.5 and 6.5 times.

[0065] The cleaning process involves immersing the PVA resin film in a cleaning bath, which removes any foreign matter remaining on the surface of the PVA resin film. The cleaning bath typically uses a water-based medium such as water, distilled water, or pure water. Furthermore, from the viewpoint of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably 1% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 4% by mass or less, and even more preferably 1.8% by mass or more and 3.8% by mass or less.

[0066] The temperature of the washing bath is preferably between 5°C and 50°C, more preferably between 10°C and 40°C, and even more preferably between 15°C and 30°C. The immersion time in the washing bath cannot be determined definitively because the degree of cleaning of the PVA resin film is affected by the temperature of the washing bath, but it is preferably between 1 second and 100 seconds, more preferably between 2 seconds and 50 seconds, and even more preferably between 3 seconds and 20 seconds. The washing process may be performed only once, or multiple times as needed.

[0067] Furthermore, it is preferable to have a metal ion treatment step as one of the above-described steps or as a separate step. The metal ion treatment step can be carried out by immersing the PVA-based resin film in a metal salt solution containing a metal salt of a metal ion. The metal salt solution is preferably an aqueous solution containing a metal salt. The metal ion treatment step allows metal ions to be incorporated into the PVA-based resin film.

[0068] The metal ions are not limited to potassium ions, but are preferably ions of metals other than alkali metals, and are particularly preferably at least one transition metal ion such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, or iron, from the viewpoint of color adjustment and imparting durability. Among these metal ions, zinc ions are preferred from the viewpoint of color adjustment and imparting heat resistance. Examples of zinc salts include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate.

[0069] The metal ion treatment process involves immersing a PVA-based resin film in a zinc salt aqueous solution, which is a zinc-containing solution. The concentration of zinc ions in the zinc salt aqueous solution is in the range of approximately 0.1% by mass to 10% by mass, preferably 0.3% by mass to 7% by mass. From the viewpoint of facilitating the impregnation of zinc ions into the PVA-based resin film, the zinc salt aqueous solution is preferably an aqueous solution containing potassium ions and iodide ions using potassium iodide or the like. The concentration of potassium iodide in the zinc salt aqueous solution is preferably approximately 0.1% by mass to 10% by mass, and more preferably 0.2% by mass to 5% by mass.

[0070] When immersing the PVA resin film in an aqueous zinc salt solution, the temperature of the aqueous zinc salt solution is usually between 15°C and 85°C, preferably between 25°C and 70°C. The immersion time is usually between 1 second and 120 seconds, preferably between 3 seconds and 90 seconds. When immersing the PVA resin film in an aqueous zinc salt solution, the zinc content in the PVA resin film is adjusted to the above range by adjusting conditions such as the concentration of the aqueous zinc salt solution, the immersion temperature of the PVA resin film in the aqueous zinc salt solution, and the immersion time. There are no particular restrictions on the timing of the immersion treatment in the aqueous zinc salt solution. The immersion treatment in the aqueous zinc salt solution may be performed alone, or the zinc salt may be present in the dyeing bath, crosslinking bath, or stretching bath and performed simultaneously with at least one of the dyeing, crosslinking, or stretching processes.

[0071] The drying process involves drying the PVA-based resin film, which has been cleaned in the washing process, to obtain a polarizing element. Drying can be carried out by any suitable method, such as natural drying, forced-air drying, or heat drying.

[0072] Manufacturing method 2 can be carried out by the steps of applying a coating solution containing a PVA resin onto a base film, uniaxially stretching the obtained laminated film, staining the PVA resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb it and form a polarizing element, treating the film on which the dichroic dye has been adsorbed with an aqueous boric acid solution, and washing with water after treatment with the aqueous boric acid solution. The base film used to form the polarizing element may also be used as a second protective film for the polarizing element. If necessary, the base film may be peeled off from the polarizing element.

[0073] (phase contrast layer) The phase difference layer may include at least one cured layer of polymerizable liquid crystal compound. The phase difference layer includes a cured layer of polymerizable liquid crystal compound and may also include at least one alignment layer for aligning the polymerizable liquid crystal compound. Preferably, the phase difference value of the phase difference layer has inverse wavelength dispersion. Since the cured layer forming the inverse wavelength dispersion phase difference layer tends to have low light transmittance in the ultraviolet region, it is preferable to employ the above-described method for manufacturing polarizing plates when producing polarizing plates with excellent transferability and adhesion of the phase difference layer.

[0074] Examples of materials constituting the phase difference layer include: Patent No. 5463666, JP 2010-031223, JP 2010-030979, JP 2009-173893, JP 2009-227667, JP 2010-241919, JP 2010-024438, JP 2011-162678, JP 2011-207765, JP 2010-270108, JP 20 Suitable materials include polymerizable liquid crystal compounds and materials for forming alignment layers (alignment films) as described in 11-246381, JP 2012-021068, JP 2016-121339, JP 2018-087152, JP 2017-179367, JP 2017-210601, JP 2019-151763, Patent 6700468, JP 2020-074021, etc.

[0075] The phase difference layer is preferably formed by applying a composition containing a polymerizable liquid crystal compound to a substrate layer or an alignment layer provided on the substrate layer, and polymerizing and curing the polymerizable liquid crystal compound. This allows for the formation of a cured layer of polymerizable liquid crystal compound with a thickness of 0.1 μm to 10 μm. Since the substrate layer used to form the phase difference layer can be peeled off during the polarizing plate manufacturing process, a thin phase difference layer can be formed, and furthermore, the polarizing plate can be made thinner.

[0076] The phase difference layer can be used as a viewing angle compensation film for optical compensation of a liquid crystal cell (IPS mode liquid crystal cell) that has a liquid crystal layer containing liquid crystal molecules oriented in a homogeneous arrangement in the absence of an electric field. The phase difference layer used as a viewing angle compensation film may have a first optical compensation layer and a second optical compensation layer in order from the polarizing element 10 side, with the second optical compensation layer being located on the liquid crystal cell side. Preferably, at least one of the first optical compensation layer and the second optical compensation layer is a cured product layer of a polymerizable liquid crystal compound, and more preferably, both are cured product layers from the viewpoint of thinning the polarizing plate.

[0077] The viewing angle compensation film and the polarizing element are typically laminated such that the slow axis of the second optical compensation layer and the absorption axis of the polarizing element are substantially parallel. In this specification, substantially parallel includes not only perfectly parallel but also substantially parallel, and the angle is generally within ±2°, preferably within ±1°, and more preferably within ±0.5°. In this specification, substantially orthogonal includes not only perfectly orthogonal but also substantially orthogonal, and the angle is generally in the range of 90±2°, preferably within 90±1°, and more preferably within 90±0.5°.

[0078] The first optical compensation layer and the second optical compensation layer may be directly laminated together or laminated together via an adhesive layer. The adhesive can be a water-based adhesive or a UV adhesive, as described later.

[0079] The thicknesses of the first optical compensation layer and the second optical compensation layer are not particularly limited, but can be typically 0.1 μm or more and 10 μm or less, independently of each other.

[0080] The first optical compensation layer and the second optical compensation layer can satisfy the following equations (1) and (2). nz1 > nx1 = ny1 (1) nx2 > ny2 ≥ nz2 (2) [In equations (1) and (2), nx1 represents the refractive index in the slow axis direction within the plane of the first optical compensation layer. nx2 represents the refractive index in the slow axis direction within the plane of the second optical compensation layer. ny1 represents the refractive index in the phase-advancing axis direction within the plane of the first optical compensation layer. ny2 represents the refractive index in the phase-advancing axis direction within the plane of the second optical compensation layer. nz1 represents the refractive index in the thickness direction of the first optical compensation layer. nz2 represents the refractive index in the thickness direction of the second optical compensation layer. The refractive indices in equation (1) above are values ​​measured at the same wavelength, and the refractive indices in equation (2) above are values ​​measured at the same wavelength.

[0081] The first optical compensation layer and the second optical compensation layer may be composed of the same material or different materials. Known polymerizable liquid crystal compounds can be used for the first and second optical compensation layers. The wavelength dispersion characteristics of the phase difference values ​​of the first and second optical compensation layers are not particularly limited and can suitably range from positive wavelength dispersion to negative wavelength dispersion.

[0082] It is preferable that both the first optical compensation layer and the second optical compensation layer have inverse wavelength dispersion characteristics that satisfy the following equations (3) to (6). Rth1(450) / Rth1(550)≦1.00 (3) 1.00≦Rth1(650) / Rth1(550) (4) Re2(450) / Re2(550)≦1.00 (5) 1.00 ≤ Re2(650) / Re2(550) (6)

[0083] In equations (3) to (6), Rth1(λ)={(nx1+ny1) / 2-nz1}×d1 Re2(λ)=(nx2-ny2)×d2 [In the above formula, d1 represents the thickness of the first optical compensation layer, d2 represents the thickness of the second optical compensation layer, and λ represents the measurement wavelength.]

[0084] The optical properties of the first optical compensation layer and the second optical compensation layer preferably satisfy the following equations (7) to (10). 0nm ≤ Re1(550) ≤ 5nm (7) -200nm≦Rth1(550)≦-20nm (8) 110nm ≤ Re2(550) ≤ 150nm (9) 35nm ≤ Rth2(550) ≤ 105nm (10)

[0085] The optical properties of the first optical compensation layer and the second optical compensation layer are more preferably satisfied by the following equations (7a) to (10a). 0nm ≤ Re1(550) ≤ 5nm (7a) -120nm≦Rth1(550)≦-50nm (8a) 120nm ≤ Re2(550) ≤ 140nm (9a) 50nm ≤ Rth2(550) ≤ 80nm (10a)

[0086] In equations (7) to (10) and (7a) to (10a) above, Rth1(λ)={(nx1+ny1) / 2-nz1}×d1 Rth2(λ)={(nx2+ny2) / 2-nz2}×d2 Re1(λ)=(nx1-ny1)×d1 Re2(λ)=(nx2-ny2)×d2 [In the above formula, d1 represents the thickness of the first optical compensation layer, d2 represents the thickness of the second optical compensation layer, and λ represents the measurement wavelength.]

[0087] (base material layer) The base layer can be used to form the phase difference layer as described above. The base layer can be a resin film, and may be an optically transparent resin film. The resin film may be a single-layer film or a multilayer film having two or more layers. Examples of resin materials constituting the resin film include the resin materials constituting the first protective film described later.

[0088] From the viewpoint of optical properties, a thin substrate layer is preferable, but if it is too thin, the strength decreases and the processability is poor. An appropriate thickness is 5 μm to 100 μm, preferably 10 μm to 80 μm, and more preferably 15 μm to 70 μm.

[0089] (First protective film) The first protective film is preferably an optically transparent resin film. The light transmittance of the first protective film at a wavelength of 365 nm is preferably 80% or more, may be 85% or more, may be 90% or more, or may be 92% or more. The light transmittance can be measured by the method described in the examples below. The first protective film may be a single-layer film or a multilayer film having two or more layers.

[0090] The thickness of the first protective film is preferably thin from the viewpoint of optical properties, but if it is too thin, its strength will decrease and its processability will be poor. An appropriate thickness is 5 μm to 100 μm, preferably 10 μm to 80 μm, and more preferably 15 μm to 70 μm.

[0091] The first protective film is preferably one that has excellent transparency, mechanical strength, thermal stability, and moisture shielding properties, and is less prone to optical unevenness due to distortion. A resin film is preferably used as the first protective film.

[0092] Examples of resin materials constituting the first protective film include polycarbonate resins, polyvinyl alcohol resins, cellulose resins, polyester resins, polyarylate resins, polyimide resins, cyclic polyolefin resins, polysulfone resins, polyethersulfone resins, polyolefin resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Thermosetting resins such as urethane, acrylic urethane, epoxy, and silicone resins, or UV-curable resins, can also be used as the resin material constituting the first protective film. The first protective film may contain one or more suitable additives.

[0093] The cellulose resin constituting the first protective film is preferably a cellulose ester resin, which is a fatty acid ester of cellulose. Specific examples of cellulose ester resins include triacetylcellulose, diacetylcellulose, cellulose acylate, trippropionylcellulose, and dipropionylcellulose. Among these, triacetylcellulose is particularly preferred. Many products of triacetylcellulose are commercially available, offering advantages in terms of availability and cost. While many triacetylcellulose products exhibit a thickness-direction retardation (Rth) exceeding 10 nm, a cellulose resin film with low regression in both the frontal and thickness directions can be obtained by using additives that counteract this retardation or by adjusting the film-forming method. Examples of the above film-forming methods include laminating a base film such as polyethylene terephthalate, polypropylene, or stainless steel coated with a solvent such as cyclopentanone or methyl ethyl ketone onto a general cellulose-based film, heating and drying (for example, at 80-150°C for 3-10 minutes), and then peeling off the base film; or coating a general cellulose-based resin film with a solution of norbornene-based resin, (meth)acrylic resin, etc., dissolved in a solvent such as cyclopentanone or methyl ethyl ketone, and then heating and drying (for example, at 80-150°C for 3-10 minutes), and then peeling off the coated film. "(Meth)acrylic" refers to at least one of acrylic and methacrylic.

[0094] As a cellulose resin film with low retardation in the thickness direction (Rth), a fatty acid cellulose resin film with controlled fat substitution can be used. In commonly used triacetylcellulose, the degree of acetic acid substitution is about 2.8, but preferably, the Rth can be reduced by controlling the degree of acetic acid substitution to 1.8 to 2.7. The Rth can be controlled to be small by adding plasticizers such as dibutyl phthalate, p-toluenesulfonanilide, and acetyltriethyl citrate to the fatty acid substituted cellulose resin. The amount of plasticizer added is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and even more preferably 1 to 15 parts by weight, per 100 parts by weight of the fatty acid cellulose resin.

[0095] As the first protective film, A polymer film containing a resin composition comprising a thermoplastic resin having substituted and / or unsubstituted imide groups in its side chains, as described in Japanese Patent Publication No. 2001-343529 (WO01 / 37007), etc., and a thermoplastic resin having substituted and / or unsubstituted phenyl and nitrile groups in its side chains; Polymer films containing acrylic resins having a lactone ring structure as described in Japanese Patent Publication No. 2000-230016, Japanese Patent Publication No. 2001-151814, Japanese Patent Publication No. 2002-120326, Japanese Patent Publication No. 2002-254544, Japanese Patent Publication No. 2005-146084, Japanese Patent Publication No. 2006-171464, etc., Japanese Patent Publication No. 2004-70290, Japanese Patent Publication No. 2004-70296, Japanese Patent Publication No. 2004-163924, Japanese Patent Publication No. 2004-29 Polymer films containing (meth)acrylic resin having structural units of unsaturated alkyl carboxylates and glutaric acid anhydride as described in Japanese Patent Publication No. 2812, Japanese Patent Publication No. 2005-314534, Japanese Patent Publication No. 2006-131898, Japanese Patent Publication No. 2006-206881, Japanese Patent Publication No. 2006-265532, Japanese Patent Publication No. 2006-283013, Japanese Patent Publication No. 2006-299005, Japanese Patent Publication No. 2006-335902, etc.; Films containing thermoplastic resins having a glutarimide structure as described in Japanese Patent Publication No. 2006-309033, Japanese Patent Publication No. 2006-317560, Japanese Patent Publication No. 2006-328329, Japanese Patent Publication No. 2006-328334, Japanese Patent Publication No. 2006-337491, Japanese Patent Publication No. 2006-337492, Japanese Patent Publication No. 2006-337493, Japanese Patent Publication No. 2006-337569, etc., can also be used. These films are preferable because they exhibit low frontal and thickness-direction retardation, as well as a low photoelastic coefficient. Therefore, even if the polarizing plate is distorted by heating or other factors, defects such as unevenness are less likely to occur. Furthermore, their low moisture permeability makes them excellent in terms of humidification resistance.

[0096] It is also preferable to use a cyclic polyolefin resin as the resin material constituting the first protective film. Specifically, norbornene resins are preferred as the cyclic polyolefin resin. Cyclic polyolefin resins are a general term for resins polymerized using cyclic olefins as polymerization units, and examples include resins described in Japanese Patent Publication No. 1-240517, Japanese Patent Publication No. 3-14882, Japanese Patent Publication No. 3-122137, etc. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with α-olefins such as ethylene and propylene and their copolymers (typically random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and their hydrides. Norbornene monomers are a specific example of cyclic olefins.

[0097] Various cyclic polyolefin resins are commercially available. Specific examples include "Zeonor" manufactured by Nippon Zeon Corporation, "Arton" manufactured by JSR Corporation, "Topas" manufactured by TICONA, and "Appel" manufactured by Mitsui Chemicals, Inc.

[0098] The first protective film is preferably an optically isotropic film having optical isotropy. An optically isotropic film is one that satisfies the following formulas (11) and (12). 0 nm ≤ |Re3(590)| ≤ 20 nm (11) 0 nm ≤ |Rth3(590)| ≤ 20 nm (12)

[0099] In Expressions (11) and (12), Rth3(λ) = {(nx3 + ny3) / 2 - nz3} × d3 Re3(λ) = (nx3 - ny3) × d3 [In the above expressions, nx3 represents the refractive index in the direction of the slow axis in the plane of the optically isotropic film, ny3 represents the refractive index in the direction of the fast axis in the plane of the optically isotropic film, d3 represents the thickness of the optically isotropic film, λ represents the measurement wavelength.]] represents.

[0100] The material, manufacturing method, etc. of the optically isotropic film are not particularly limited as long as they satisfy the above optical characteristics, and the above-described resin materials can be used. The optically isotropic film may be an optical film having a single-layer structure or an optical film having a multilayer structure of two or more layers. Preferably, the optically isotropic film is a film having a single-layer structure. This is because it can reduce the shrinkage stress of the polarizing element, the generation of birefringence due to the heat of the light source, and unevenness, and can make the liquid crystal panel thinner.

[0101] The absolute value of the photoelastic coefficient of the optically isotropic film is preferably 1.0×10 -10 m 2 / N or less, more preferably 5.0×10 -11 m 2 / N or less, still more preferably 1.0×10 -11 m 2 / N or less, and most preferably 5.0×10 -12 m 2It is particularly preferable that the value of the photoelastic coefficient be less than or equal to / N. By setting the value of the photoelastic coefficient within the above range, when a polarizing plate is applied to a display device, it is possible to obtain a display device that has excellent optical uniformity, exhibits little change in optical properties even in environments such as high temperature and high humidity, and has excellent durability. Furthermore, there is no particular limit to the lower limit of the photoelastic coefficient, but it is generally 5.0 × 10 -13 m 2 It is greater than or equal to / N.

[0102] (UV-curing adhesive) The UV adhesive can be a known UV adhesive, preferably containing at least one of a cationically polymerizable curable compound and a radically polymerizable curable compound. The UV adhesive can be, for example, a mixture of a radically polymerizable (meth)acrylic compound and a photo-radical polymerization initiator, or a mixture of a cationically polymerizable epoxy compound and a photo-cationic polymerization initiator. The UV adhesive can also be a mixture of a cationically polymerizable epoxy compound and a photo-radical polymerizable (meth)acrylic compound, with a photo-cationic polymerization initiator and a photo-radical polymerization initiator used as initiators.

[0103] (UV adhesive layer) The UV adhesive layer 25 is a cured layer of UV adhesive, and it bonds the phase difference layer 15 and the first protective film 11. As described above, since the phase difference layer 15 is supported by the UV adhesive layer 25, it is possible to suppress the occurrence of scratches or dents in the cured layer of polymerizable liquid crystal compound contained in the phase difference layer 15 when transporting the polarizing plate 1, etc.

[0104] The thickness of the UV adhesive layer 25 on the polarizing plate 1 can be set arbitrarily, but is preferably 0.1 μm to 7 μm, more preferably 0.2 μm to 5 μm, even more preferably 0.3 μm to 4 μm, and most preferably 0.4 μm to 3 μm.

[0105] (Water-based adhesive No. 1, Water-based adhesive No. 2) The first water-based adhesive and the second water-based adhesive (hereinafter, both may be collectively referred to as "water-based adhesives") can be known water-based adhesives, and the first water-based adhesive and the second water-based adhesive may have the same composition or different compositions. As the water-based adhesive, a water-based adhesive containing a PVA resin (hereinafter, sometimes referred to as "PVA-based adhesive") is preferably used. From the viewpoint of adhesiveness, the average degree of polymerization of the PVA resin contained in the water-based adhesive is preferably about 100 to 5500, and more preferably about 1000 to 4500. From the viewpoint of adhesiveness, the average degree of saponification of the PVA resin is preferably about 85 mol% to 100 mol%, and more preferably about 90 mol% to 100 mol%.

[0106] The PVA resin contained in the PVA adhesive is preferably one that contains acetoacetyl groups. This is because it provides excellent adhesion between the PVA resin layer constituting the polarizing element and the first or second protective film, and also provides excellent durability. The PVA resin containing acetoacetyl groups can be obtained, for example, by reacting a PVA resin with diketene in any way. The degree of modification of the acetoacetyl groups in the PVA resin containing acetoacetyl groups is typically 0.1 mol% or more, and preferably around 0.1 mol% to 20 mol%.

[0107] The concentration of the PVA resin in the PVA adhesive is preferably 0.1% to 15% by weight, and more preferably 0.5% to 10% by weight.

[0108] When the PVA resin contains an acetoacetyl group, the PVA adhesive preferably contains one or more of glyoxal, glyoxylate, and methylolmelamine as a crosslinking agent, preferably at least one of glyoxal and glyoxylate, and particularly preferably glyoxal.

[0109] PVA-based adhesives may contain organic solvents. In this case, since they are miscible with water, alcohols are preferred as the organic solvent, and among alcohols, methanol or ethanol is preferred.

[0110] From the viewpoint of improving heat resistance, PVA-based adhesives may further contain urea compounds such as urea, urea derivatives, thiourea, and thiourea derivatives; reducing agents such as ascorbic acid, erythorbic acid, thiosulfate, and sulfite; dicarboxylic acids such as maleic acid and phthalic acid; ammonium compounds such as ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride; dextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin; blocked isocyanate compounds in which isocyanate compounds are blocked by a blocking agent; nitroxyl radicals such as N-oxyl compounds; and compounds having a nitroxide group.

[0111] (First adhesive layer, second adhesive layer) The first adhesive layer 21 can be formed by heating and drying the first water-based adhesive, and it bonds the polarizing element 10 to the composite protective film 30. The second adhesive layer 22 can be formed by heating and drying the second water-based adhesive, and it bonds the polarizing element 10 to the second protective film 12.

[0112] The thicknesses of the first adhesive layer 21 and the second adhesive layer 22 can be set arbitrarily, but each is preferably 0.01 μm to 7 μm, more preferably 0.01 μm to 5 μm, even more preferably 0.01 μm to 2 μm, and most preferably 0.01 μm to 1 μm.

[0113] (Second protective film) The second protective film is preferably an optically transparent resin film. The second protective film can be a film of the thickness and material described for the first protective film. When the composite protective film including the first protective film, the polarizing element, and the second protective film are bonded together using a water-based adhesive, it is preferable that at least one of the first and second protective films is a cellulose resin film or a polymer film containing (meth)acrylic resin. The second protective film is preferably a cellulose acylate film.

[0114] The second protective film may have a surface functional layer such as a hard coat layer, an anti-reflective layer, an anti-sticking layer, an anti-glare layer, or a diffusion layer on one side of the resin film. Preferably, the surface functional layer is provided on the side of the resin film opposite to the polarizing element side.

[0115] (Adhesive layer) The adhesive layer is used to bond a polarizing plate to an image display element or the like of a display device. The adhesive layer may consist of one or more layers, but preferably one layer. The thickness of the adhesive layer is preferably 1 to 100 μm, more preferably 2 to 80 μm, even more preferably 2 to 50 μm, and particularly preferably 3 to 30 μm.

[0116] The adhesive layer is a layer formed using an adhesive composition. The adhesive composition exhibits adhesion by being attached to the substrate itself, and is a so-called pressure-sensitive adhesive. The adhesive composition can have (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin as its main component (base polymer). Among these, an adhesive composition using (meth)acrylic resin as the base polymer, which has excellent transparency, weather resistance, and heat resistance, is preferred. The adhesive composition may be of the active energy ray curing type or thermosetting type.

[0117] As a base polymer used in adhesive compositions, polymers or copolymers of (meth)acrylic resins using one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, are preferably used. It is preferable to copolymerize polar monomers into the base polymer. Examples of polar monomers include monomers having carboxyl groups, hydroxyl groups, amide groups, amino groups, epoxy groups, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0118] The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylate salts with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0119] (Release film) The release film is provided so as to be removable from the adhesive layer 28 and covers and protects the surface of the adhesive layer 28. The release film comprises a base film and a release treatment layer. The base film may be a resin film. The resin film can be formed, for example, from a resin material used to form the first protective film described above. The release treatment layer may be any known release treatment layer, for example, a layer formed by coating the base film with a release agent such as a fluorine compound or a silicone compound.

[0120] (Surface protective film) The surface protection film (protective film) is provided so as to be removable from the second protective film 12. The surface protection film may include a base film and an adhesive layer, or it may be a self-adhesive film. The base film may be a resin film, and the base film can be formed from, for example, the resin material used to form the first protective film described above. The surface protection film preferably uses a film in which an adhesive layer is provided on one side of a base film made of a polyester resin such as polyethylene terephthalate and polyethylene naphthalate. Examples of thermoplastic resins that constitute a self-adhesive film include polypropylene resins and polyethylene resins. [Examples]

[0121] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0122] <Fabrication of polarizing elements> A 30 μm thick polyvinyl alcohol (PVA) resin film was immersed in pure water at 21.5°C for 80 seconds (swelling treatment), then immersed for 55 seconds in an aqueous solution at 23°C with a potassium iodide / boric acid / water mass ratio of 2 / 2 / 100 and containing 1.0 mM iodine (dyeing process). Subsequently, it was immersed for 76 seconds in an aqueous solution at 63°C with a potassium iodide / boric acid / water mass ratio of 2.5 / 4 / 100 (first crosslinking process). Subsequently, it was immersed for 10 seconds in an aqueous solution at 45°C with a potassium iodide / boric acid / zinc chloride / water mass ratio of 3 / 5.5 / 0.6 / 100 (second crosslinking process, metal ion treatment process). After that, it was washed by immersion in a washing bath (washing process) and dried at 38°C (drying process) to obtain a 12 μm thick polarizing element with iodine adsorbed and oriented on the PVA resin film. Stretching was mainly carried out during the dyeing process and the first crosslinking process, and the total stretching ratio was 5.85 times.

[0123] <Preparation of water-based adhesives> 50 g of a modified polyvinyl alcohol resin containing acetoacetyl groups (Mitsubishi Chemical Corporation: Gosenex Z-410) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain a PVA solution. This PVA solution, pure water, and methanol were mixed so that the concentration of the polyvinyl alcohol resin was 3.0% by weight, the concentration of the methanol was 35% by weight, and the concentration of the urea was 0.5% by weight to obtain a water-based adhesive, which is a PVA-based adhesive.

[0124] [Example 1] (Fabrication of composite protective film with substrate layer) A phase difference film with a substrate layer was prepared, in which a phase difference layer containing a cured polymerizable liquid crystal compound was formed on the substrate layer. The phase difference layer had inverse wavelength dispersion properties.

[0125] A UV-curing adhesive (UV adhesive) ("ADEKA Arclus KR-75T", manufactured by ADEKA Corporation) was applied to the first protective film ("KC2CT1W" (20 μm thick triacetylcellulose (TAC) film), manufactured by Konica Minolta, Inc.) using a bar coater to a thickness of 1.5 μm. The first protective film and the phase difference film with the base layer prepared above were laminated together via the applied UV adhesive, with the phase difference layer side being the bonding surface. Subsequently, from the first protective film side of this laminated structure, an integrated amount of light (UVA) transmitted through the first protective film was applied to the first protective film, with an integrated light intensity (UVA) of 400 mJ / cm². 2 The UV adhesive was cured by irradiating it with ultraviolet light to form a UV adhesive layer, and a composite protective film with a substrate layer was obtained. The layer structure of the composite protective film with a substrate layer was first protective film / UV adhesive layer / phase difference layer / substrate layer.

[0126] The light transmittance of the first protective film used above at a wavelength of 365 nm was measured using a U-4100 ultraviolet-visible spectrophotometer manufactured by Hitachi High-Tech Science Co., Ltd. The measurement involved first measuring the transmittance of light at a wavelength of 365 nm at an arbitrary sample angle, then rotating the sample by 90° and measuring the transmittance of light at 365 nm again, and calculating the average value of these measurements as the light transmittance at a wavelength of 365 nm. As a result, the light transmittance of the first protective film at a wavelength of 365 nm was 80% or higher.

[0127] When the first protective film used above was irradiated with ultraviolet light, ultraviolet light in the wavelength range of 280-390 nm was sufficiently transmitted through the first protective film. From this, it can be concluded that the UV adhesive layer of the composite protective film with a substrate layer was sufficiently cured.

[0128] (Saponification treatment) The composite protective film with a base layer prepared as described above, and the second protective film ("TJ40UL" (40 μm thick cellulose acylate film, manufactured by Fujifilm Corporation)) were immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes and then washed with water. Subsequently, each film was immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water bath under running water for 30 seconds to neutralize each film. After that, the films were drained three times using an air knife. After draining, each film was left in a drying zone at 70°C for 15 seconds to dry, obtaining a saponified composite protective film with a base layer and a saponified second protective film.

[0129] (Fabrication of polarizing plate with substrate layer (1)) A composite protective film with a saponified substrate layer and a saponified second protective film were laminated to both sides of the polarizing element prepared as described above, via the water-based adhesive prepared as described above. The composite protective film with a substrate layer was laminated to the polarizing element so that the side with the first protective film was the bonding surface. This laminated structure was heated and dried to form a first adhesive layer and a second adhesive layer between the composite film with a substrate layer and the polarizing element, and between the polarizing element and the second protective film, respectively, thereby obtaining a polarizing plate with a substrate layer (1). The layer structure of the polarizing plate with a substrate layer (1) was second protective film / second adhesive layer / polarizing element / first adhesive layer / first protective film / UV adhesive layer / phase difference layer / substrate layer.

[0130] (Fabrication of polarizing plates) A polarizing plate (1) was obtained by peeling off the base layer from a polarizing plate (1) with a base layer. In the polarizing plate (1) with a base layer, the phase difference layer was in close contact with the first protective film side, and the base layer could be peeled off well and the phase difference layer transferred to the first protective film side.

[0131] [Comparative Example 1] (Saponification treatment) The first protective film and the second protective film were subjected to saponification treatment using the same procedure as in Example 1. The first protective film and the second protective film were the same films used in Example 1.

[0132] (Fabrication of polarizing plate (2) with substrate layer) A saponified first protective film and a saponified second protective film were laminated onto both sides of the polarizing element prepared above, via the water-based adhesive prepared above, and then heated and dried to obtain a polarizing element with a protective film having a layer structure of second protective film / second adhesive layer / polarizing element / first adhesive layer / first protective film.

[0133] A UV adhesive was applied to the first protective film side of the protective film polarizing element using a bar coater to a thickness of 1.5 μm. The protective film polarizing element and the phase difference film with a base layer were laminated together via the applied UV adhesive, with the phase difference layer side of the phase difference film with a base layer being the bonding surface. Subsequently, ultraviolet light was irradiated from the second protective film side (protective film polarizing element side) of this laminated structure under the same conditions as in Example 1 (conditions in which the UV intensity of the light source and irradiation time were the same) to obtain a polarizing plate with a base layer (2). The UV adhesive and the phase difference film with a base layer were the same as those used in Example 1.

[0134] The layer structure of the polarizing plate with a base layer (2) was the same as that of the polarizing plate with a base layer (1), but the curing of the UV adhesive in the UV adhesive layer is considered to be insufficient for the following reason. When ultraviolet light was irradiated onto the laminate of the second protective film and polarizing element used above, ultraviolet light in the wavelength range of 280 to 390 nm hardly penetrated this laminate. From this, it is considered that the curing of the UV adhesive layer of the polarizing plate with a base layer (2) is insufficient compared to the UV adhesive layer of the polarizing plate with a base layer (1).

[0135] When the substrate layer was peeled off from the polarizing plate with the substrate layer (2), the phase difference layer was not in close contact with the first protective film side, and the phase difference layer peeled off together with the substrate layer. As a result, the phase difference layer could not be transferred to the first protective film side, and a polarizing plate could not be obtained.

[0136] [Comparative Example 2] A polarizing plate (3) with a substrate layer was obtained using the same procedure as in Comparative Example 1, except that ultraviolet light was irradiated from the substrate layer side (the phase difference film side with the substrate layer) instead of from the second protective film side.

[0137] The polarizing plate with a substrate layer (3) had the same layer structure as the polarizing plate with a substrate layer (1), but the curing of the UV adhesive in the UV adhesive layer is considered to be insufficient for the following reason. When ultraviolet light was irradiated onto the phase difference film with a substrate layer used above, ultraviolet light in the wavelength range of 280 to 390 nm was hardly transmitted through the phase difference film with a substrate layer. From this, it is considered that the curing of the UV adhesive in the polarizing plate with a substrate layer (3) is insufficient compared to the UV adhesive in the polarizing plate with a substrate layer (1).

[0138] A polarizing plate (3) was obtained by peeling off the base layer from the polarizing plate (3) with the base layer. The base layer was peeled off from the polarizing plate (3) with the base layer and the phase difference layer was transferred to the first protective film side, but the phase difference layer did not adhere sufficiently to the first protective film side.

[0139] [Scratch resistance test] The polarizing plate with a base layer (1) obtained in Example 1 and the polarizing plate with a base layer (3) obtained in Comparative Example 2 were bonded to a glass plate via an acrylic adhesive layer, and then the base layer was peeled off. The phase difference layer exposed after peeling off the base layer was subjected to a scratch resistance test using the friction and abrasion testing machine "Tribogear" (manufactured by Shinto Kagaku Co., Ltd.). The scratch resistance test was performed by setting steel wool #0000 on a contact terminal with a diameter of 25 mm, applying a load of 100 g, moving at a speed of 6000 mm / min, and performing 10 reciprocals over a distance of 60 mm. The surface condition of the phase difference layer after the scratch resistance test was visually checked to confirm whether or not deep scratches had occurred. The results are shown in Table 1. Note that the polarizing plate with a base layer (2) obtained in Comparative Example 1 could not be subjected to the scratch resistance test because the phase difference layer peeled off together with the base layer.

[0140] [Table 1] [Explanation of Symbols]

[0141] 1 Polarizing plate, 2 Polarizing plate with base layer, 10 Polarizing element, 11 First protective film, 12 Second protective film, 15 Phase difference layer, 17 Base layer, 19 Phase difference film with base layer, 21 First adhesive layer, 22 Second adhesive layer, 25 UV adhesive layer, 28 Adhesive layer, 30 Composite protective film, 31 Composite protective film with base layer.

Claims

1. A method for manufacturing a polarizing plate comprising a polarizing element and a composite protective film, The composite protective film has, in order from the polarizing element side, a first protective film and a phase difference layer including a cured polymerizable liquid crystal compound layer. The aforementioned manufacturing method is Step (1) is to obtain a composite protective film with a base layer by laminating the phase difference layer formed on the base layer and the first protective film using an ultraviolet-curing adhesive and irradiating the ultraviolet-curing adhesive with ultraviolet light, Step (2) is to bond the first protective film side of the composite protective film with the base layer and the polarizing element using a first aqueous adhesive to obtain a polarizing plate with a base layer, The process (3) involves peeling the substrate layer from the polarizing plate with the substrate layer, A method for manufacturing a polarizing plate, comprising the step (4) of peeling off the base material layer and forming an adhesive layer on the exposed surface.

2. The method for manufacturing a polarizing plate according to claim 1, wherein the light transmittance of the first protective film at a wavelength of 365 nm is 80% or more.

3. The method for producing a polarizing plate according to claim 1 or 2, wherein the first aqueous adhesive comprises a polyvinyl alcohol-based resin.

4. The method for manufacturing a polarizing plate according to any one of claims 1 to 3, wherein step (2) further includes a step of laminating a second protective film to the side of the polarizing element opposite to the side of the composite protective film.

5. A method for manufacturing a polarizing plate according to claim 4, wherein the polarizing element and the second protective film are bonded together using a second aqueous adhesive.

6. The method for manufacturing a polarizing plate according to claim 5, wherein the second aqueous adhesive comprises a polyvinyl alcohol-based resin.

7. The method for manufacturing a polarizing plate according to any one of claims 4 to 6, wherein step (2) involves bonding the polarizing element to the second protective film while bonding the composite protective film with the base layer to the polarizing element.

8. A polarizing plate is manufactured by the polarizing plate manufacturing method described in any one of Claims 1 to 7, A method for manufacturing a display device, comprising bonding the adhesive layer of the polarizing plate to an image display element of the display device.

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