Method for manufacturing optical laminate

Abstract

Provided is a method for manufacturing an optical laminate that includes a liquid crystal alignment fixing layer and that can suppress specific display unevenness when applied to an image display device. A method for manufacturing an optical laminate according to an embodiment of the present invention is a method for manufacturing an optical laminate having a polarizing plate and a phase difference layer including a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer. The present invention relates to a method for manufacturing a liquid crystal display panel, the method comprising: a first lamination step for manufacturing a first intermediate laminate by laminating a polarizing plate and a first liquid crystal alignment fixing layer via a first adhesive layer while conveying the polarizing plate and the first liquid crystal alignment fixing layer to face each other; and a second lamination step for producing a second intermediate laminate by laminating the first intermediate laminate and the second liquid crystal alignment fixing layer via a second adhesive layer while conveying the first intermediate laminate and the second liquid crystal alignment fixing layer so that the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer face each other. The conveyance tension after the second lamination step is greater than 700 N and less than 1500 N.

Description

Technical Field

[0001] The present invention relates to a method for producing an optical layered body. Background Art

[0002] In recent years, image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (for example, organic EL display devices, inorganic EL display devices) are rapidly gaining popularity. In image display devices, in most cases, an optical laminate comprising a phase difference film is used (for example, an anti-reflection film formed by integrating a polarizer and a phase difference film). In recent years, with the increasing expectation for thinning of image display devices, the expectation for thinning of optical laminates has also increased. With the thinning of optical laminates as the purpose, progress has been made in thinning the phase difference layer (phase difference film) that contributes greatly to the thickness. As a representative example of a thin phase difference film, a film obtained by orienting a liquid crystal compound and fixing its orientation state can be cited (hereinafter referred to as a liquid crystal film). The liquid crystal compound has a much larger birefringence (Δn) than the resin, so the liquid crystal film can be made to reduce the thickness for obtaining the desired in-plane phase difference compared to the stretched film of the resin film. However, image display devices using an optical laminate including a liquid crystal film may sometimes cause display unevenness (specifically, a phenomenon in which thin, particularly conspicuous pink lines are visually recognized in the absorption axis direction of the polarizer) depending on the viewing environment.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-222282 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present invention has been made to solve the above-mentioned conventional problems, and a main object of the present invention is to provide a method for producing an optical laminate that includes a liquid crystal alignment fixing layer and can suppress specific display unevenness when applied to an image display device.

[0008] Means for solving problems

[0009] [1] The method for manufacturing an optical laminate according to an embodiment of the present invention is a method for manufacturing an optical laminate having a polarizer and a phase difference layer including a first liquid crystal orientation fixing layer and a second liquid crystal orientation fixing layer, the method comprising the following steps: a first lamination step, in which the polarizer and the first liquid crystal orientation fixing layer are conveyed while being laminated via a first adhesive layer in a manner such that the polarizer and the first liquid crystal orientation fixing layer are opposite to each other, thereby producing a first intermediate laminate; a second lamination step, in which the first intermediate laminate and the second liquid crystal orientation fixing layer are conveyed while being laminated via a second adhesive layer in a manner such that the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer are opposite to each other, thereby producing a second intermediate laminate; and the conveying tension after the second lamination step is greater than 700N and less than 1500N.

[0010] [2] In the above [1], the conveying tension after the second lamination step is 800 N or more and 1350 N or less.

[0011] [3] In the above-mentioned [1] or [2], the second adhesive layer is composed of an active energy ray-curable adhesive.

[0012] [4] In any one of [1] to [3] above, the conveying tension until the second lamination step is 100 N or more and 400 N or less.

[0013] [5] In any one of the above [1] to [4], the above-mentioned first lamination process includes: conveying the above-mentioned long-strip polarizer and the above-mentioned long-strip first liquid crystal orientation fixing layer by rollers; and laminating the polarizer and the first liquid crystal orientation fixing layer using a lamination roller, and the above-mentioned second lamination process includes: conveying the above-mentioned long-strip first intermediate layered body and the above-mentioned long-strip second liquid crystal orientation fixing layer by rollers; and laminating the first intermediate layered body and the second liquid crystal orientation fixing layer using a lamination roller.

[0014] Effects of the Invention

[0015] According to the embodiment of the present invention, it is possible to realize an optical laminate that includes a liquid crystal alignment fixing layer and can suppress specific display unevenness when applied to an image display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A This is a schematic perspective view showing an example of a first lamination step in a method for producing an optical layered body according to one embodiment of the present invention.

[0017] Figure 1B This is a schematic cross-sectional view showing an example of a polarizing plate used in the first lamination step of the method for producing an optical layered body according to one embodiment of the present invention.

[0018] Figure 1C This is a schematic cross-sectional view showing an example of a laminate including a first liquid crystal alignment fixing layer used in the first lamination step of the method for producing an optical laminate according to one embodiment of the present invention.

[0019] Figure 1D This is a schematic cross-sectional view showing an example of a first intermediate laminate produced by the first lamination step of the method for producing an optical laminate according to one embodiment of the present invention.

[0020] Figure 2A This is a schematic perspective view showing an example of the second lamination step in the method for producing an optical layered body according to one embodiment of the present invention.

[0021] Figure 2B This is a schematic cross-sectional view showing an example of a laminate including a second liquid crystal alignment fixing layer used in the second lamination step of the method for producing an optical laminate according to one embodiment of the present invention.

[0022] Figure 3A This is a schematic cross-sectional view showing an example of an optical layered body produced by the method for producing an optical layered body according to one embodiment of the present invention.

[0023] Figure 3B This is a schematic cross-sectional view showing an example of an optical layered body produced by a method for producing an optical layered body according to another embodiment of the present invention.

[0024] Explanation of symbols

[0025] 11. Polarizer

[0026] 111 Polarizer

[0027] 112 protective layer (first protective layer)

[0028] 113 protective layer (second protective layer)

[0029] 21 1st liquid crystal alignment fixing layer

[0030] 221 Base material (first base material)

[0031] 100 1st intermediate laminate

[0032] 200 Second intermediate laminate

[0033] 31 Second liquid crystal orientation fixing layer

[0034] 331 Base material (second base material)

[0035] 40 phase difference layer

[0036] 5 Optical laminate

[0037] 50 optical laminate DETAILED DESCRIPTION

[0038] Representative embodiments of the present invention are described below, but the present invention is not limited to these embodiments. In addition, to clarify the description, the drawings sometimes schematically illustrate the width, thickness, shape, etc. of each part compared to the embodiments, but this is ultimately an example and does not limit the interpretation of the present invention. In this specification, "A and / or B" means any of "A", "B", or "A and B".

[0039] (Definition of Terms and Symbols)

[0040] The definitions of terms and symbols in this specification are as follows.

[0041] (1) Refractive index (nx, ny, nz)

[0042] “nx” is the refractive index in the direction where the refractive index in the plane is maximum (ie, the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane (ie, the fast axis direction), and “nz” is the refractive index in the thickness direction.

[0043] (2) In-plane retardation (Re)

[0044] "Re(λ)" is the in-plane retardation of the film measured at 23°C using light of a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation of the film measured at 23°C using light of a wavelength of 550 nm. When the film thickness is d (nm), Re(λ) is calculated using the formula: Re = (nx - ny) × d.

[0045] (3) Retardation in the thickness direction (Rth)

[0046] "Rth(λ)" is the retardation in the thickness direction of the film measured at 23°C using light of a wavelength of λ nm. For example, "Rth(550)" is the retardation in the thickness direction of the film measured at 23°C using light of a wavelength of 550 nm. When the film thickness is d (nm), Rth(λ) is calculated using the formula: Rth = (nx - nz) × d.

[0047] (4) Nz coefficient

[0048] The Nz coefficient is obtained by Nz=Rth / Re.

[0049] (5) Angle

[0050] When referring to an angle in this specification, unless otherwise specified, the angle includes both clockwise and counterclockwise angles. Therefore, for example, "45°" includes ±45°.

[0051] A. Method for producing an optical layered body and outline of the optical layered body

[0052] A method for producing an optical laminate according to an embodiment of the present invention is a method for producing an optical laminate having a polarizer and a phase difference layer including a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer. The method includes the following steps: a first lamination step in which the polarizer and the first liquid crystal alignment fixing layer are conveyed while being laminated with a first adhesive layer interposed therebetween, thereby producing a first intermediate laminate; and a second lamination step in which the first intermediate laminate and the second liquid crystal alignment fixing layer are conveyed while being laminated with a second adhesive layer interposed therebetween, thereby producing a second intermediate laminate. In the method, the conveying tension after the second lamination step is greater than 700 N and less than 1500 N.

[0053] Figure 3A 1 is a schematic cross-sectional view of an optical laminate that can be produced by a method for producing an optical laminate according to one embodiment of the present invention. The optical laminate 5 shown in the figure has a polarizer 11 and a phase difference layer 40. The polarizer 11 and the phase difference layer 40 are laminated via a first bonding layer 12 (for example, an adhesive layer, a pressure-sensitive adhesive layer). The polarizer 11 typically includes a polarizer 111 and protective layers (a first protective layer 112 and a second protective layer 113) arranged on the main surface of the polarizer 111 (on both sides of the main surface in the example shown). Depending on the purpose, the first protective layer 112 and / or the second protective layer 113 may also be omitted. Therefore, the polarizer may be a so-called two-protection polarizer, a so-called single-protection polarizer, or may be composed of a polarizer alone.

[0054] The phase difference layer 40 includes, from the side of the polarizer 11, a first liquid crystal orientation fixing layer 21 and a second liquid crystal orientation fixing layer 31 stacked on the first liquid crystal orientation fixing layer 21 via a second adhesive layer 22. By using a liquid crystal orientation fixing layer as a phase difference layer, the desired in-plane phase difference can be achieved with a thickness that is extremely thin compared to the stretched film of the resin film. As a result, it is possible to seek a significant thinning of the optical laminate. In one embodiment, the phase difference layer 40 has a circular polarization function or an elliptical polarization function as a whole (specifically, as a laminate having a first liquid crystal orientation fixing layer 21 and a second liquid crystal orientation fixing layer 31). In this specification, the description of the phase difference layer, when referred to as a "phase difference layer", refers to the description as a whole of the phase difference layer. In addition, in this specification, a "liquid crystal orientation fixing layer" refers to a layer in which a liquid crystal compound is oriented in a prescribed direction within the layer and the orientation state is fixed. A "liquid crystal orientation fixing layer" is a concept that includes an orientation solidified layer obtained by solidifying a liquid crystal monomer.

[0055] While researching further thinning of optical laminates containing a liquid crystal alignment fixing layer as a phase difference layer, the inventors discovered a new issue: image display devices using optical laminates containing a liquid crystal alignment fixing layer as a phase difference layer sometimes exhibit specific display unevenness depending on the viewing environment. Specifically, they discovered that reflection under a three-wavelength light source can produce a phenomenon (sometimes referred to as linear unevenness) where thin, particularly conspicuous pink lines along the absorption axis of the polarizer can be visually observed throughout the entire device. The inventors conducted in-depth research on suppressing this linear unevenness and discovered that it can be suppressed by suppressing light interference in the optical laminate.

[0056] In addition, the inventors investigated the causes of light interference in the optical laminate and found that the thickness of the phase difference layer including the adhesive layer can be uneven during the manufacturing process. They further found that by suppressing the unevenness of the thickness, the above-mentioned linear unevenness can be significantly suppressed, thereby completing the present invention. That is, the effect of the embodiment of the present invention is to solve the newly discovered problem when studying the further thinning of the optical laminate including the liquid crystal orientation fixing layer as the phase difference layer, which is an unexpected excellent effect. It should be noted that the embodiment of the present invention can of course suppress the display unevenness that has been recognized for a long time.

[0057] The reason why the optical layered body obtained by the manufacturing method of the embodiment of the present invention exhibits the above-mentioned remarkable effects is not necessarily clear, but the following mechanism is speculated. However, the mechanism is ultimately speculation and does not limit the present invention, and the present invention is not restricted by the mechanism.

[0058] In the manufacturing method of the optical laminate of the embodiment of the present invention, in the first lamination process, the polarizer and the first liquid crystal orientation fixing layer are stacked via the first adhesive layer in a manner that the polarizer is opposite to each other, thereby producing a first intermediate laminate. In the second lamination process, the first liquid crystal orientation fixing layer of the first intermediate laminate is stacked via the second adhesive layer in a manner that the second liquid crystal orientation fixing layer of the first intermediate laminate is opposite to each other, thereby producing a second intermediate laminate. It is believed that when the second intermediate laminate stacked in this manner is transported, by setting the transport tension after the second lamination process to a transport tension that is higher than the conventional transport tension of more than 700N and less than 1500N, the curing shrinkage of the second adhesive layer used in the production of the second intermediate laminate during curing can be suppressed. Therefore, it is believed that even when the second adhesive layer is cured, the shrinkage of the polarizer (particularly the polarizer) and the phase difference layer (the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer) following the curing of the second adhesive layer can be suppressed. Therefore, it is believed that when the adhesive layer is cured, the curing shrinkage of the entire optical laminate (especially the entirety including the polarizer and the phase difference layer) can be suppressed, and thickness unevenness can be suppressed. Therefore, it is believed that in the method for manufacturing an optical laminate according to an embodiment of the present invention, by suppressing the thickness unevenness between the phase difference layers of the optical laminate, when the optical laminate is applied to an image display device, display unevenness (linear unevenness) caused by light interference can be suppressed.

[0059] B. Details of the method for producing an optical laminate

[0060] Hereinafter, the method for producing the optical layered body according to the embodiment of the present invention will be described in more detail.

[0061] Figure 1A This is a schematic perspective view for explaining a first lamination step in a method for producing an optical layered body according to one embodiment of the present invention. Figure 1B and Figure 1C Each of them is a schematic cross-sectional view showing an example of a laminate including a polarizing plate and a first liquid crystal alignment fixing layer that can be used in the first lamination step. Figure 1D This is a schematic cross-sectional view showing an example of a first intermediate laminate that can be produced in the first lamination step. Figure 2A This is a schematic perspective view for explaining the second lamination step in the method for producing an optical layered body according to one embodiment of the present invention. Figure 2B This is a schematic cross-sectional view showing an example of a laminate including a second liquid crystal alignment fixing layer that can be used in the second lamination step. Figure 3A This is a schematic cross-sectional view showing an example of an optical layered body produced by the method for producing an optical layered body according to one embodiment of the present invention. Figure 3B This is a schematic cross-sectional view showing an example of an optical laminate produced by a method for producing an optical laminate according to another embodiment of the present invention. Figures 1A to 3B Each step of the method for producing the optical layered body will be described in detail.

[0062] B-1. First Lamination Step

[0063] The first lamination step is to place the polarizing plate 11 (see Figure 1B ) and the first liquid crystal alignment fixing layer 21 (refer to Figure 1C ) stacking process. Specifically, Figure 1A As shown in FIG, in the first lamination step, the polarizing plate 11 and the first liquid crystal orientation fixing layer 21 are conveyed while being bonded and laminated via the first adhesive layer 22 in such a manner that the polarizing plate 11 and the first liquid crystal orientation fixing layer 21 face each other. Thus, the first intermediate laminate 100 (see FIG. Figure 1D ).exist Figure 1C and Figure 1D In the example shown in FIG, a first substrate 221 for forming the first liquid crystal alignment fixing layer 21 is included. The first substrate 221 is typically finally peeled off and removed. Specifically, for example, the first substrate 221 may be peeled off before the second lamination step described later.

[0064] The first lamination step preferably includes conveying the long strip polarizer and the long strip first liquid crystal alignment fixing layer by rollers, and laminating the polarizer and the first liquid crystal alignment fixing layer using a lamination roller. By doing so, a long strip first intermediate laminate can be produced. The long strip first intermediate laminate can be wound in a roll. In this specification, "long strip" refers to an elongated shape that is sufficiently long relative to its width, for example, including an elongated shape that is 10 times or more, preferably 20 times or more, longer than its width.

[0065] The conveying tension before the first lamination process can be adjusted to any suitable tension as long as the effect of the embodiment of the present invention can be obtained. The conveying tension before the first lamination process is preferably more than 100N and less than 400N. The conveying tension before the first lamination process can, for example, be more than 150N and less than 350N, in addition, for example, can also be more than 200N and less than 300N. If the above-mentioned conveying tension is more than 100N, the conveyability of the polarizer and the first liquid crystal orientation fixing layer can be well maintained. If the above-mentioned conveying tension is less than 400N, curling can be well suppressed in the first intermediate laminate produced. In this specification, "conveying tension" is the tension applied to the component when the component (polarizer, phase difference layer, liquid crystal orientation fixing layer, substrate, each laminate, etc.) is conveyed.

[0066] B-1-1. Polarizing plate

[0067] B-1-1-1. Polarizer

[0068] The polarizer 111 is typically formed of a polyvinyl alcohol (PVA) resin film containing a dichroic substance (e.g., iodine). Examples of PVA resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0069] The PVA resin preferably includes an acetoacetyl-modified PVA resin. This configuration allows for a polarizer with desired mechanical strength. The amount of the acetoacetyl-modified PVA resin, relative to 100% by weight of the total PVA resin, is preferably 5% to 20% by weight, more preferably 8% to 12% by weight. This range allows for a polarizer with superior mechanical strength.

[0070] The polarizer preferably contains iodide or sodium chloride (sometimes collectively referred to as halide). Examples of iodide include potassium iodide, sodium iodide, and lithium iodide. The content of halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, relative to 100 parts by weight of PVA resin. The halide can be added to the coating liquid of the PVA resin layer that forms the precursor of the polarizer in the manufacturing method described later, and finally introduced into the polarizer. By introducing the halide into the polarizer, the orientation of the PVA molecules in the polarizer can be improved, thereby realizing a polarizer with excellent optical properties (representatively, a combination of high polarization degree and high monomer transmittance).

[0071] The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single-element transmittance of the polarizer is preferably between 41.0% and 46.0%, more preferably between 42.0% and 45.0%. The polarization degree of the polarizer is preferably at least 97.0%, more preferably at least 99.0%, and even more preferably at least 99.9%. According to embodiments of the present invention, even when the single-element transmittance is within the above-described range, the polarization degree can be maintained within this range.

[0072] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 7 μm or less. Meanwhile, the thickness of the polarizer is, for example, 1 μm or greater, preferably 3 μm or greater. By combining such a thin polarizer with a liquid crystal alignment fixing layer, a significantly thinner optical laminate can be achieved. Furthermore, when the thickness of the polarizer is within the above range, curling during heating can be effectively suppressed.

[0073] The polarizer can be produced by any appropriate method. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0074] Specific examples of polarizers composed of a single-layer resin film include polarizers obtained by dyeing a hydrophilic polymer film such as a PVA film, a partially formalized PVA film, or a partially saponified ethylene-vinyl acetate copolymer film with a dichroic substance such as iodine or a dichroic dye and then stretching it; and polyene-based oriented films such as a dehydrated PVA film or a hydrochloric acid-degraded polyvinyl chloride film. In terms of excellent optical properties, a polarizer obtained by dyeing a PVA film with iodine and then uniaxially stretching it is preferred.

[0075] The dyeing with iodine is performed, for example, by immersing the PVA film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or while dyeing. In addition, dyeing can be performed after stretching. As needed, the PVA film can be subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA film in water and washing it before dyeing, not only can the stains and anti-blocking agent on the surface of the PVA film be washed away, but the PVA film can also be swelled to prevent uneven dyeing.

[0076] As specific examples of polarizers obtained using a laminate, there can be cited polarizers obtained using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by the following method: a PVA-based resin solution is applied to a resin substrate and dried to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to form the PVA-based resin layer into a polarizer. In this embodiment, it is preferred to form a polyvinyl alcohol-based resin layer comprising a halide and a polyvinyl alcohol-based resin on one side of the resin substrate. Stretching typically includes immersing the laminate in a boric acid aqueous solution for stretching. Furthermore, stretching may further include stretching the laminate in the air at a high temperature (e.g., above 95°C) before stretching in the boric acid aqueous solution as needed. Furthermore, in this embodiment, the laminate is preferably subjected to a drying and shrinking treatment by being heated while being transported in the longitudinal direction, thereby shrinking the laminate by at least 2% in the width direction. Typically, the manufacturing method of this embodiment includes sequentially subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying and shrinking treatment. The introduction of the auxiliary stretching treatment improves the crystallinity of the PVA, even when PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by pre-enhancing the orientation of the PVA, problems such as a decrease in orientation and dissolution of the PVA during subsequent immersion in water during the dyeing and stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the orientation disturbance and decrease in orientation of the polyvinyl alcohol molecules can be suppressed compared to a case where the PVA-based resin layer does not contain a halide. This improves the optical properties of the polarizer obtained through treatment steps such as dyeing and underwater stretching, in which the laminate is immersed in a liquid. Furthermore, shrinking the laminate in the width direction during the drying and shrinking treatment can improve optical properties.

[0077] B-1-1-2. Protective layer

[0078] When the polarizing plate includes a protective layer, the protective layer may include a first protective layer and / or a second protective layer. The first protective layer and the second protective layer may have the same structure or different structures.

[0079] The protective layer is made of any suitable resin film. As the material constituting the resin film, representative examples include cellulose resins such as triacetyl cellulose (TAC), cycloolefin resins such as polynorbornene, (meth) acrylic resins, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyolefin resins such as polyethylene, and polycarbonate resins. As a representative example of (meth) acrylic resins, (meth) acrylic resins with a lactone ring structure can be listed. (Meth) acrylic resins with a lactone ring structure are, for example, described in Japanese Patent Application Laid-Open No. 2000-230016 Gazette, Japanese Patent Application Laid-Open No. 2001-151814 Gazette, Japanese Patent Application Laid-Open No. 2002-120326 Gazette, Japanese Patent Application Laid-Open No. 2002-254544 Gazette, and Japanese Patent Application Laid-Open No. 2005-146084 Gazette. These publications are incorporated herein by reference. The material constituting the resin film is preferably a cellulose resin, more preferably TAC. From the viewpoint of obtaining a polarizing plate having low water vapor permeability and excellent durability, a cycloolefin resin and a (meth)acrylic resin are preferred.

[0080] The optical laminate is typically configured on the visual recognition side of the image display device, and the first protective layer 112 is typically configured on its visual recognition side. Therefore, for the first protective layer 112, surface treatment can also be implemented as needed. As surface treatment, for example, hard coating treatment, anti-reflection treatment, anti-adhesion treatment, anti-glare treatment can be listed. And / or, for the first protective layer 112, it is also possible to implement a process (representatively, giving (elliptical) circular polarization function, giving ultra-high phase difference) to improve the visual recognition of the situation of visual recognition through polarized sunglasses as needed. By implementing such a process, even when visually recognizing the display screen through polarized lenses such as polarized sunglasses, excellent visual recognition can be achieved. Therefore, the optical laminate is also suitably applicable to image display devices that can be used outdoors.

[0081] The thickness of the protective layer is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 35 μm. When the first protective layer 112 is surface-treated, the thickness of the first protective layer 112 includes the thickness of the surface-treated layer.

[0082] B-1-1-3. Preparation of polarizing film

[0083] The polarizing plate can be produced, for example, as follows.

[0084] In a polarizer obtained using a single-layer resin film, for example, a polarizing plate can be produced by bonding a protective layer to the polarizer via any appropriate adhesive layer (adhesive layer, pressure-sensitive adhesive layer).

[0085] In the polarizer obtained by using the laminate of resin substrate / polarizer, for example, a polarizer can be made by laminating a protective layer on the polarizer side of the resin substrate / polarizer of the laminate via any suitable bonding layer (adhesive layer, adhesive layer). The resin substrate can be peeled off from the laminate as needed, or another protective layer can be laminated on the surface after the resin substrate is peeled off as needed. Alternatively, for the laminate, the resin substrate can also be directly used as a protective layer to make a polarizer. The details of the manufacturing method of such a polarizer and polarizer are, for example, recorded in Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The overall records of these publications are cited in this specification as a reference.

[0086] B-1-2. Formation of the first liquid crystal alignment fixing layer

[0087] In the method for producing an optical laminate according to an embodiment of the present invention, the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer described later may be common. Therefore, when the liquid crystal alignment fixing layer is simply referred to as the "liquid crystal alignment fixing layer" in this specification, this means that the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer are described together.

[0088] The liquid crystal alignment fixing layer can be formed on any suitable substrate. Figure 1C As shown in , the first liquid crystal orientation fixing layer 21 can be formed on the first substrate 221. Specifically, the first liquid crystal orientation fixing layer 21 can be formed by applying an orientation treatment to the surface of the first substrate 221, applying a coating liquid containing a liquid crystal compound to the surface, aligning the liquid crystal compound in a direction corresponding to the orientation treatment, and fixing the orientation state. In one embodiment, the substrate is any suitable resin film. Preferably, a triacetyl cellulose (TAC) film is used.

[0089] By using a liquid crystal compound, the difference between nx and ny in the resulting liquid crystal alignment fixing layer can be significantly larger than that of a non-liquid crystal material, thereby significantly reducing the thickness of the liquid crystal alignment fixing layer used to achieve the desired in-plane phase difference. As a result, a thinner and lighter optical laminate can be achieved. In this embodiment, the rod-shaped liquid crystal compound is typically aligned along the slow axis of the liquid crystal alignment fixing layer (in-plane alignment).

[0090] As the above-mentioned orientation treatment, any suitable orientation treatment can be adopted. Specifically, mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment can be cited. Specific examples of mechanical orientation treatment include friction treatment and stretching treatment. Specific examples of physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of chemical orientation treatment include oblique evaporation method and optical orientation treatment. The treatment conditions of the various orientation treatments can be any suitable conditions according to the purpose.

[0091] The liquid crystal compound is aligned by treating it at a temperature that exhibits liquid crystallinity, depending on the type of the liquid crystal compound. This temperature treatment causes the liquid crystal compound to assume a liquid crystal state and align in accordance with the alignment treatment direction on the substrate surface.

[0092] In one embodiment, the alignment state is fixed by cooling the aligned liquid crystal compound. If the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the aligned liquid crystal compound to a polymerization treatment or a crosslinking treatment.

[0093] Specific examples of liquid crystal compounds and details of the method for forming the alignment fixing layer are described in Japanese Patent Application Laid-Open No. 2006-163343, the contents of which are incorporated herein by reference.

[0094] When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a cross-linkable monomer. This is because by polymerizing or cross-linking (i.e., curing) the liquid crystal monomer, the orientation state of the liquid crystal monomer can be fixed. After the liquid crystal monomer is oriented, for example, if the liquid crystal monomers are polymerized or cross-linked with each other, the above-mentioned orientation state can be fixed. Here, the polymer is formed by polymerization, and the three-dimensional network structure is formed by cross-linking, but they are non-liquid crystal. Therefore, the formed liquid crystal orientation fixing layer does not cause, for example, the transition to a liquid crystal phase, a glass phase, or a crystalline phase caused by temperature changes that is unique to liquid crystal compounds. As a result, the liquid crystal orientation fixing layer is not affected by temperature changes and has excellent stability.

[0095] As the liquid crystal compound used in the liquid crystal orientation fixing layer, for example, liquid crystal polymers and liquid crystal monomers can be listed. The liquid crystal compound is preferably capable of polymerization (i.e., liquid crystal monomer). If the liquid crystal compound is capable of polymerization, the orientation state of the liquid crystal compound can be fixed by polymerizing the liquid crystal compound after it is oriented. Here, the polymer formed by polymerization is non-liquid crystal. Therefore, the liquid crystal orientation fixing layer formed does not, for example, cause the transition to liquid crystal phase, glass phase, or crystalline phase caused by temperature changes that are unique to liquid crystal compounds. As a result, the liquid crystal orientation fixing layer becomes a phase difference layer with excellent stability that is not affected by temperature changes.

[0096] In one embodiment, the liquid crystal orientation fixing layer can be formed using a composition comprising a liquid crystal compound (polymerizable liquid crystal compound, i.e., liquid crystal monomer) that can be polymerized. The polymerizable liquid crystal compound contained in the composition in this specification refers to a compound having a polymerizable group and having liquid crystal properties. The polymerizable group refers to a group that participates in the polymerization reaction, preferably a photopolymerizable group. Wherein, the photopolymerizable group refers to a group that can participate in the polymerization reaction by an active free radical, acid, etc. produced by a photopolymerization initiator. As a liquid crystal monomer, for example, the polymerizable mesogen compounds described in Japanese Patent Application Publication No. 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171 and GB2280445, etc. can be used. Specific examples of such polymerizable mesogen compounds include LC242 (trade name) from BASF, E7 (trade name) from Merck, and LC-Sillicon-CC3767 (trade name) from Wacker-Chem.

[0097] The liquid crystal compound can exhibit liquid crystallinity through either thermotropic or lyotropic mechanisms. Furthermore, the liquid crystal phase can be either nematic or smectic. From the perspective of ease of production, thermotropic nematic liquid crystals are preferred.

[0098] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

[0099] The birefringence Δn of the liquid crystal alignment fixing layer is preferably 0.06 or greater, more preferably 0.08 or greater, further preferably 0.09 or greater, and particularly preferably 0.10 or greater. The upper limit of Δn can be, for example, 0.13, and further, for example, 0.12. If Δn is within this range, the desired in-plane phase difference can be achieved with a very thin thickness. As a result, the liquid crystal alignment fixing layer and the optical laminate can be further thinned, ultimately contributing to a significant reduction in the thickness of the image display device.

[0100] The liquid crystal alignment fixing layer can exhibit reverse wavelength dispersion characteristics, where the phase difference increases with the wavelength of the measurement light; positive wavelength dispersion characteristics, where the phase difference decreases with the wavelength of the measurement light; or flat wavelength dispersion characteristics, where the phase difference does not change substantially with the wavelength of the measurement light. In one embodiment, the liquid crystal alignment fixing layer exhibits positive wavelength dispersion characteristics. In such cases, the effects achieved by the embodiments of the present invention are significant.

[0101] In one embodiment, the Re(550) of the first liquid crystal orientation fixing layer is preferably 150nm to 300nm, more preferably 200nm to 270nm, and further preferably 220nm to 260nm. In this case, the Re(550) of the second liquid crystal orientation fixing layer described later is preferably 100nm to 200nm, more preferably 110nm to 160nm, and further preferably 110nm to 130nm. In this case, since the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer both have an in-plane phase difference, they exhibit a refractive index characteristic of nx>ny. The first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer typically exhibit a refractive index characteristic of nx>ny=nz (positive A plate). Here, "ny=nz" not only includes the case where ny and nz are strictly equal, but also includes the case where ny and nz are substantially equal. That is, the Nz coefficients of the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer can be 0.9 to 1.1, respectively.

[0102] The thickness of the first liquid crystal orientation fixing layer can be adjusted in a manner to obtain the above-mentioned desired in-plane phase difference. In one embodiment, the thickness of the first liquid crystal orientation fixing layer can be, for example, 1.5 μm to 2.5 μm. As described above, according to an embodiment of the present invention, the thickness of the first liquid crystal orientation fixing layer can be made thinner than before, and linear unevenness can be further suppressed. The thickness of the second liquid crystal orientation fixing layer can also be adjusted in a manner to obtain the above-mentioned desired in-plane phase difference. Specifically, its thickness can be, for example, 0.8 μm to 1.5 μm.

[0103] The angle formed by the slow axis of the first liquid crystal orientation fixing layer and the transmission axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and further preferably 14° to 16°. In this case, the angle formed by the slow axis of the second liquid crystal orientation fixing layer and the transmission axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and further preferably 74° to 76°. The direction of the slow axis of the first liquid crystal orientation fixing layer can be controlled by the above-mentioned orientation treatment. It should be noted that the angle formed by the slow axis of the first liquid crystal orientation fixing layer and the transmission axis of the polarizer and the angle formed by the slow axis of the second liquid crystal orientation fixing layer and the transmission axis of the polarizer can also be opposite.

[0104] B-1-3. Formation of the first adhesive layer

[0105] like Figure 1A As shown in FIG, the polarizing plate 11 and the first liquid crystal alignment fixing layer 21 are bonded and laminated via the first adhesive layer 12. In this way, the first intermediate laminate 100 can be produced. The first adhesive layer can be formed by disposing or applying any appropriate adhesive or pressure-sensitive adhesive.

[0106] Any appropriate structure can be adopted as the first adhesive layer 12. As described above, the adhesive layer may be composed of a binder or an adhesive.

[0107] The first adhesive layer is preferably composed of an adhesive, more preferably composed of an active energy ray-curable adhesive. In this case, the thickness of the adhesive layer is preferably 0.4 μm to 2.0 μm, more preferably 0.6 μm to 1.5 μm.

[0108] In the case where the first adhesive layer is composed of an active energy ray-curing adhesive, it is preferred that when laminating the polarizer and the first liquid crystal orientation fixing layer using a laminating roller, the polarizer and the first liquid crystal orientation fixing layer are respectively conveyed by rollers while the active energy ray-curing adhesive is supplied to at least one side of the polarizer side and the first liquid crystal orientation fixing layer side before laminating. Specifically, in the formation of the first adhesive layer, it is preferred that when laminating the polarizer and the first liquid crystal orientation fixing layer using a roller, the polarizer and the first liquid crystal orientation fixing layer are respectively conveyed by rollers while the active energy ray-curing adhesive is supplied to the side opposite to the first liquid crystal orientation fixing layer, and then the polarizer and the first liquid crystal orientation fixing layer are attached and laminated. The supply of the active energy ray-curing adhesive can be provided by any appropriate method. More specifically, as Figure 1A As shown in FIG, the active energy ray-curable adhesive can be supplied by supplying the active energy ray-curable adhesive (e.g., liquid adhesive 61) that can constitute the first adhesive layer 12 from a supply mechanism 60 that can be disposed between laminating rollers 62. The supply mechanism 60 can have any suitable configuration. By supplying the active energy ray-curable adhesive in this manner, the first adhesive layer 12 can be formed by coating the polarizer 11 and / or the first liquid crystal alignment fixing layer 21 with the active energy ray-curable adhesive. The first intermediate laminate 100 can also be produced by this operation.

[0109] The conveying tension of the first intermediate laminate after the first lamination step can be adjusted to any appropriate tension as long as the effects of the embodiments of the present invention can be achieved. The conveying tension of the first intermediate laminate after the first lamination step can be, for example, 100 N to 400 N, or 150 N to 350 N, or 200 N to 300 N, as before the first lamination step.

[0110] B-1-4. Curing of the first adhesive layer

[0111] When the first adhesive layer is composed of an active energy ray-curable adhesive, a curing step for curing the first adhesive layer (hereinafter sometimes referred to as the "first adhesive layer curing step") may be preferably included after the first lamination step. Specifically, in the first adhesive layer curing step, the polarizer and the first liquid crystal alignment fixing layer are laminated with the first adhesive layer interposed therebetween, and then the first adhesive layer is cured.

[0112] The first adhesive layer can be cured by any appropriate method according to the type and composition of the adhesive constituting the first adhesive layer. In the case where the first adhesive layer is composed of an active energy ray-curable adhesive, the first adhesive layer can preferably be cured by irradiating active energy rays. Any appropriate conditions can be used for the curing of the first adhesive layer. For example, ultraviolet rays can be used as active energy rays. As the cumulative light amount, for example, 500 to 1000 mJ / cm 2 The irradiation direction may be, for example, a direction perpendicular to the transmission axis of the polarizer. It should be noted that the first adhesive layer curing step may not necessarily be performed after the first lamination step. For example, the first adhesive layer may be cured together with the second adhesive layer after the second lamination step described later. Furthermore, the first adhesive layer may also be cured during the first lamination step, for example.

[0113] B-2. Second Lamination Step

[0114] The second lamination step is to place the first intermediate laminate 100 (see Figure 1D ) and the second liquid crystal alignment fixing layer 31 (refer to Figure 2B ) stacking process. Specifically, Figure 2A As shown in FIG, in the second lamination step, while the first intermediate laminate 100 and the second liquid crystal alignment fixing layer 31 are being conveyed, they are bonded and laminated via the second adhesive layer 22 so that the first liquid crystal alignment fixing layer 21 and the second liquid crystal alignment fixing layer 31 face each other. Thus, the second intermediate laminate 200 is produced.

[0115] The second lamination step preferably includes conveying the long strip of the first intermediate laminate and the long strip of the second liquid crystal alignment fixing layer by rollers, and laminating the first intermediate laminate and the second liquid crystal alignment fixing layer using a lamination roller. By doing so, the long strip of the second intermediate laminate can be produced. The long strip of the second intermediate laminate can be wound into a roll.

[0116] The conveying tension before lamination of the first intermediate stack and the second liquid crystal orientation fixing layer (until the second lamination process) can be adjusted to any appropriate tension as long as the effect of the embodiment of the present invention can be obtained. The conveying tension until the second lamination process is preferably greater than 100N and less than 400N. The conveying tension until the second lamination process can also be, for example, greater than 150N and less than 350N, and can also be, for example, greater than 200N and less than 300N. If the above-mentioned conveying tension is greater than 100N, the conveyability of the first intermediate stack and the second liquid crystal orientation fixing layer can be well maintained. If the above-mentioned conveying tension is less than 400N, curling in the produced second intermediate stack can be well suppressed.

[0117] B-2-1. Second liquid crystal alignment fixing layer

[0118] Regarding the second liquid crystal alignment fixing layer, the same configuration as the first liquid crystal alignment fixing layer (positive A plate) can be referred to the description in the above section B-1-2. Hereinafter, an example will be described in which the second liquid crystal alignment fixing layer is a positive C plate.

[0119] For example, the refractive index characteristics of a positive C plate exhibit the relationship nz > nx = ny. The thickness-direction retardation Rth(550) of a positive C plate is preferably -20 nm to -300 nm, more preferably -30 nm to -250 nm, further preferably -40 nm to -200 nm, and particularly preferably -50 nm to -150 nm. Here, "nx = ny" encompasses not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. In other words, the in-plane retardation Re(550) of a positive C plate can be less than 10 nm.

[0120] The positive C plate can be formed using, for example, a composition containing a side chain thermotropic liquid crystal polymer. As the side chain thermotropic liquid crystal polymer, a copolymer having a liquid crystal monomer unit represented by general formula (I) and a non-liquid crystal monomer unit represented by general formula (II) is preferably used.

[0121] [Chemical Formula 1]

[0122]

[0123] [Chemical Formula 2]

[0124]

[0125] In formula (I), R 1 is a hydrogen atom or a methyl group, R 2 is a cyano group, a fluoro group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and X 1is -CO2- or -OCO-. a is an integer of 1 to 6, and b and c are each independently 1 or 2.

[0126] In formula (II), R 3 is a hydrogen atom or a methyl group, R 4 It is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or a group represented by the following general formula (III).

[0127] [Chemical Formula 3]

[0128]

[0129] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0130] A positive C plate is prepared, for example, by preparing a coating liquid containing the aforementioned side-chain thermotropic liquid crystal polymer, applying the coating liquid to a substrate (e.g., a PET substrate) that has been subjected to a homeotropic alignment treatment by any suitable method, and then drying the coating liquid under any suitable heating conditions to align the liquid crystals and form a liquid crystal layer. This liquid crystal layer is then cured by irradiating it with ultraviolet light, thereby producing a laminate having a substrate / second liquid crystal alignment fixing layer (positive C plate) configuration.

[0131] Specific examples of methods for forming a positive C plate include the methods described in

[0020] to

[0028] of Japanese Patent Application Laid-Open No. 2002-333642. In this case, the thickness of the positive C plate is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

[0132] B-2-2. Second adhesive layer

[0133] In the second lamination step, the second intermediate laminate 200 and the second liquid crystal alignment fixing layer 31 are bonded and laminated via the second adhesive layer 22. The second adhesive layer 22 can be formed by disposing or applying any appropriate adhesive or pressure-sensitive adhesive.

[0134] Any appropriate structure can be adopted as the second adhesive layer 22. As described above, the adhesive layer may be composed of a binder or an adhesive.

[0135] The second adhesive layer is preferably composed of an active energy ray-curable adhesive. In embodiments where the second adhesive layer is composed of an active energy ray-curable adhesive, the effects of the embodiments of the present invention become more pronounced. Regarding the composition and method of forming the second adhesive layer, the description regarding the first adhesive layer in Section B-1-3 can be referred to.

[0136] In the case where the second adhesive layer is composed of an active energy ray-curing adhesive, it is preferred that when the first intermediate layer stack and the second liquid crystal orientation fixing layer are stacked using a stacking roller, the first intermediate layer stack and the second liquid crystal orientation fixing layer are respectively conveyed by rollers while the active energy ray-curing adhesive is supplied to at least one side of the first liquid crystal orientation fixing layer side and the second liquid crystal orientation fixing layer side of the first intermediate layer stack before stacking. Specifically, in the formation of the second adhesive layer, it is preferred that when the first intermediate layer stack and the second liquid crystal orientation fixing layer are respectively conveyed by rollers while the active energy ray-curing adhesive is supplied to the side where the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer are opposite to each other, the first intermediate layer stack and the second liquid crystal orientation fixing layer are stacked. The supply of the active energy ray-curing adhesive can be provided by any appropriate method. Specifically, such as Figure 2A As shown in FIG, the active energy ray-curable adhesive can be supplied by supplying an active energy ray-curable adhesive (e.g., a liquid adhesive 61) that can constitute the second adhesive layer 22 from a supply mechanism 60 that can be disposed between laminating rollers 62. The supply mechanism 60 can have any suitable structure. By supplying the active energy ray-curable adhesive in this manner and applying it to the first intermediate laminate 100 (substantially the first liquid crystal alignment fixing layer 21) and / or the second liquid crystal alignment fixing layer 31, the second adhesive layer 22 can be formed. The second intermediate laminate 200 can also be produced by operating in this manner.

[0137] In the manufacturing method of the optical laminate of the embodiment of the present invention, after the first intermediate laminate and the second liquid crystal orientation fixing layer are stacked via the second adhesive layer, that is, after the second lamination process, the conveying tension is more than 700N and less than 1500N. The conveying tension after the second lamination process is preferably more than 750N and less than 1400N, more preferably more than 800N and less than 1350N, and further preferably more than 1000N and less than 1300N. By being within this range, the curing shrinkage of the second adhesive layer can be suppressed. Therefore, even if the second adhesive layer is cured, the shrinkage of the polarizer (especially the polarizer) and the phase difference layer (the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer) following the curing of the second adhesive layer can be suppressed. Therefore, the curing shrinkage of the entire optical laminate (especially the entirety including the polarizer and the phase difference layer) can be suppressed, and the thickness unevenness can be suppressed. As a result, when the optical laminate is applied to an image display device, the linear unevenness caused by the interference of light can be suppressed.

[0138] B-3. ​​Curing of the Second Adhesive Layer (Second Adhesive Layer Curing Step)

[0139] When the second adhesive layer is composed of an active energy ray-curable adhesive, it is preferable to include a curing step for curing the second adhesive layer (hereinafter also referred to as the second adhesive layer curing step). Specifically, in the second adhesive layer curing step, the first intermediate laminate 100 and the second liquid crystal alignment fixing layer 31 are bonded together with the second adhesive layer 22 interposed therebetween, and then the second adhesive layer 22 is cured. The curing conditions in the second adhesive layer curing step can be referred to the description of the first adhesive layer curing step in Section B-1-4.

[0140] During the curing of the second laminate, the first intermediate laminate and the second liquid crystal alignment fixing layer are preferably laminated by roller conveying while sandwiching the second adhesive layer, and then the laminate is irradiated with active energy rays while the laminate is roller conveyed, thereby curing the laminate. In the method for producing an optical laminate according to one embodiment of the present invention, the conveying tension during the curing step of the second adhesive layer can be preferably greater than 700N and less than 1500N, more preferably greater than 800N and less than 1350N, and even more preferably greater than 1000N and less than 1300N.

[0141] In this manner, the optical layered body according to the embodiment of the present invention can be produced (see Figure 3A ). The optical laminate manufactured in this way suppresses the curing shrinkage of the second adhesive layer and / or the first adhesive layer, as well as the curing shrinkage of the optical laminate as a whole, even when it is used in an image display device. Therefore, it is not easy to produce linear unevenness and display unevenness in the optical laminate. It should be noted that the laminate after the first substrate 221 is peeled off from the first intermediate laminate 100 after the above-mentioned first lamination process can also be used for the second lamination process. The peeling of the first substrate 221 from the first intermediate laminate 100 can be carried out by any appropriate method. In addition, the second substrate 331 can also be peeled off from the second intermediate laminate 200 and / or the optical laminate 5 after the above-mentioned second lamination process. The peeling of the second substrate 331 from the second intermediate laminate 200 and / or the optical laminate 5 can also be carried out by any appropriate method in the same way as the first substrate 221. By operating in this way, it is also possible to produce Figure 3B The optical laminate 50 shown in FIG. The obtained optical laminate 50 can be placed in an image display panel or the like with a pressure-sensitive adhesive layer interposed therebetween on the side opposite to the viewing side (specifically, the second liquid crystal alignment fixing layer side) to produce an image display device.

[0142] The obtained optical laminate can be in the form of an elongated strip or a single sheet. The elongated optical laminate can be wound in a roll. The elongated optical laminate can be produced, for example, by the so-called roll-to-roll process as described above. The single sheet optical laminate can be produced by cutting the elongated optical laminate into a specified size (representatively, a size corresponding to the image display device), or by cutting the above-mentioned elongated laminates (polarizer, first intermediate laminate and second intermediate laminate) and liquid crystal orientation fixing layer into specified sizes and then laminating them together through the above-mentioned steps.

[0143] The obtained optical laminate can be arranged in an image display panel or the like on the side opposite to the visual recognition side (specifically, for example, the second liquid crystal alignment fixing layer side) with a pressure-sensitive adhesive layer interposed therebetween, to produce an image display device.

[0144] Example

[0145] The present invention is described in detail below by way of examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are by weight.

[0146] (1) Thickness

[0147] The measurement was performed using an interferometer film thickness meter ("MCPD9800" manufactured by Otsuka Electronics Co., Ltd.).

[0148] (2) Linear unevenness

[0149] The image display devices obtained in Examples and Comparative Examples were visually observed under a three-wavelength fluorescent lamp in a non-lighting state and evaluated based on the following criteria.

[0150] 1 (Excellent): No linear unevenness was observed even when observing with a polarizing plate attached under a 3-wavelength fluorescent lamp.

[0151] 2 (good): No linear unevenness was observed in normal observation using a three-wavelength fluorescent lamp.

[0152] 3 (Acceptable): Linear unevenness is slightly observed in normal observation using a 3-wavelength fluorescent lamp.

[0153] 4 (Unacceptable): Linear unevenness that is unacceptable in practice was observed in normal observation using a three-wavelength fluorescent lamp.

[0154] 5 (poor): Linear unevenness is noticeable in normal observation using a 3-wavelength fluorescent lamp

[0155] [Manufacturing Example 1: Preparation of Adhesive A1 Constituting the First Adhesive Layer and the Second Adhesive Layer]

[0156] 10 parts of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals Co., Ltd.), 4 parts of 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals Co., Ltd.), 60 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 11 parts of tripropylene glycol diacrylate (trade name "ARONIX M-220", manufactured by Toagosei Co., Ltd.), 1 part of 4-vinylphenylboronic acid (manufactured by FUJIFILM Wako Pure Chemical Corporation), 1 part of acrylic oligomer (trade name "ARUFON Adhesive A1 was prepared by stirring 10 parts of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 1 part of diethylthioxanthone (trade name "KAYACUREDETX-S", manufactured by Nippon Kayaku Co., Ltd.) at 50°C for 1 hour.

[0157] [Example 1]

[0158] 1. Preparation of optical laminates

[0159] 1-1. Preparation of polarizer

[0160] As the thermoplastic resin substrate, a long amorphous polyethylene terephthalate copolymer film (thickness: 100 μm) having a Tg of approximately 75° C. was used, and one surface of the resin substrate was subjected to a corona treatment.

[0161] 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol %) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a ratio of 9:1, and the resulting substance was dissolved in water to prepare a PVA aqueous solution (coating liquid).

[0162] The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

[0163] The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130° C. (in-air auxiliary stretching treatment).

[0164] Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilization treatment).

[0165] Next, the film was immersed in a dyeing bath (an iodine aqueous solution prepared by mixing iodine and potassium iodide at a weight ratio of 1:7 per 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single-body transmittance (Ts) of the polarizer obtained finally becomes a desired value (dyeing treatment).

[0166] Next, the film was immersed in a crosslinking bath (boric acid aqueous solution prepared by adding 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment).

[0167] Afterwards, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%) at a liquid temperature of 70°C, and uniaxially stretched (underwater stretching treatment) in the longitudinal direction (length direction) between rollers with different peripheral speeds so that the total stretching ratio became 5.5 times.

[0168] Thereafter, the laminate was immersed in a washing bath (an aqueous solution prepared by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20° C. (washing treatment).

[0169] Thereafter, the sheet was dried in an oven maintained at approximately 90° C. while being brought into contact with a SUS heating roll whose surface temperature was maintained at approximately 75° C. (drying shrinkage treatment).

[0170] In this manner, a polarizer having a thickness of approximately 5 μm was formed on the resin substrate, resulting in a long strip of polarizing plate having a resin substrate / polarizer structure. The polarizer had a single-piece transmittance Ts of 43.3%. The polarizer had an absorption axis in the longitudinal direction. Hereinafter, the absorption axis direction (longitudinal direction) was designated as the "0° direction," and the transmission axis direction (width direction) was designated as the "90° direction."

[0171] 1-2. Preparation of Polarizing Plate (PL1)

[0172] An HC-COP film was bonded to the surface of the resulting polarizer (the surface opposite the resin substrate) via a UV-curable adhesive. The HC-COP film is a film having an HC layer (4 μm thick) formed on a cycloolefin resin (COP) film (25 μm thick), and was bonded so that the COP film faced the polarizer. The Re (550) of the COP film was 100 nm. The HC-COP film was bonded so that the slow axis of the COP film and the absorption axis of the polarizer formed an angle of 45°.

[0173] Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness 20 μm) was bonded to the peeled surface via an ultraviolet curable adhesive. This operation yielded a long polarizing plate PL1 having a structure of HC layer / COP film (first protective layer) / polarizer / TAC film (second protective layer).

[0174] 1-3. Preparation of the First Liquid Crystal Alignment Fixing Layer (LC1)

[0175] A photopolymerizable liquid crystal compound ("Paliocolor LC242" manufactured by BASF, the following chemical formula) showing a nematic liquid crystal phase was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. A surfactant ("BYK-360" manufactured by BYK-Chemie) and a photopolymerization initiator ("Omnirad 907" manufactured by IGM Resins) were added to the solution to prepare a liquid crystal composition solution. The amount of surfactant and polymerization initiator added was set to 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound. As a substrate, a commercially available triacetyl cellulose (TAC) film (manufactured by Fujifilm Corporation, thickness: 80 μm) was prepared. The above-mentioned liquid crystal composition was applied to the substrate using a rod coater in such a manner that Re (550) became 120 nm, and the liquid crystal was oriented by heating at 100°C for 3 minutes. After cooling to room temperature, the film was irradiated with a cumulative light intensity of 400 mJ / cm in a nitrogen atmosphere. 2 The substrate was then photocured with ultraviolet light to obtain a long, strip-shaped laminate having a structure consisting of a substrate and a first liquid crystal alignment fixing layer LC1. The first liquid crystal alignment fixing layer was aligned in the plane, with the slow axis of the first liquid crystal alignment fixing layer oriented at 15°. The thickness of the first liquid crystal alignment fixing layer was 1.5 μm.

[0176] [Chemical Formula 4]

[0177]

[0178] 1-4. Preparation of the Second Liquid Crystal Alignment Fixing Layer (LC2)

[0179] A strip-shaped laminate having a substrate / second liquid crystal alignment fixing layer LC2 structure was obtained by following the same procedures as for the first liquid crystal alignment fixing layer, except that the coating thickness was changed so that Re(550) became 240 nm. The slow axis direction of the second liquid crystal alignment fixing layer was oriented at 75°. The thickness of the second liquid crystal alignment fixing layer was 2.0 μm.

[0180] 1-5. First Lamination Step

[0181] The long polarizer and long first liquid crystal alignment fixing layer prepared above were conveyed by rollers at the conveying tensions shown in the "Conveying Tension Until the Second Lamination Step" in Table 1. Adhesive A1 from Production Example 1 was applied to the second protective layer (TAC film) of the polarizer and the first liquid crystal alignment fixing layer, respectively, so that the thickness of the cured first adhesive layer would be 1.0 μm. The layers were then laminated using laminating rollers with the first adhesive layer interposed therebetween, such that the polarizer and the first liquid crystal alignment fixing layer faced each other. This produced a first intermediate laminate having a structure consisting of polarizer (first protective layer / polarizer / second protective layer) / first adhesive layer / first liquid crystal alignment fixing layer / substrate.

[0182] Next, the first intermediate laminate was irradiated with ultraviolet light (accumulated light amount 600 mJ / cm 2 ) and perform light curing to cure the first adhesive layer.

[0183] 1-6. Second Lamination Step

[0184] Next, the long first intermediate laminate and the laminate comprising the long second liquid crystal alignment fixing layer LC2 and the substrate were conveyed by rollers at the conveying tensions shown in the "Conveying Tension Until the Second Lamination Step" in Table 1. Adhesive A1 from Manufacturing Example 1 was applied to the first liquid crystal alignment fixing layer of the first intermediate laminate and the second liquid crystal alignment fixing layer of the laminate comprising the second liquid crystal alignment fixing layer LC2 and the substrate, respectively. The adhesive was applied so that the thickness of the cured second adhesive layer would be 1.0 μm. The laminate was then laminated using a laminating roller with the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer facing each other via the second adhesive layer. Thus, a second intermediate laminate comprising a polarizer (first protective layer / polarizer / second protective layer) / first adhesive layer / first liquid crystal alignment fixing layer / second adhesive layer / second liquid crystal alignment fixing layer / substrate was produced.

[0185] 1-7. Curing of the Second Adhesive Layer

[0186] Next, the second intermediate laminate was conveyed by rollers at a conveying tension shown in "Conveying tension after the second lamination step" in Table 1 while being irradiated with ultraviolet rays (accumulated light dose 600 mJ / cm 2 ) and photocuring is performed to cure the second adhesive layer. Thus, an optical laminate is obtained.

[0187] 2. Fabrication of Image Display Device

[0188] Next, the cover glass and the optical film on the visual recognition side of a commercially available liquid crystal display device (manufactured by Apple, trade name "iPad (registered trademark)", IPS mode) were removed, and the removed surface was washed. The second liquid crystal alignment fixing layer side of the optical laminate obtained above was bonded to the washed surface via an acrylic adhesive (thickness 10 μm) to obtain an image display device. The obtained image display device was subjected to the evaluation of "linear unevenness" described above (2). The results are shown in Table 1.

[0189] [Examples 2 to 5, Comparative Example 1]

[0190] An optical layered body and an image display device were prepared in the same manner as in Example 1, except that the "conveying tension after the second lamination step" was changed to the conveying tension described in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0191] Table 1

[0192]

[0193] Industrial applicability

[0194] The optical layered body according to the embodiment of the present invention can be suitably used in image display devices (representatively, liquid crystal display devices and organic EL display devices).

Claims

1. A method for producing an optical laminate comprising a polarizing plate and a phase difference layer including a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer, the method comprising the following steps: a first lamination step of laminating the polarizing plate and the first liquid crystal alignment fixing layer with the polarizing plate facing the first liquid crystal alignment fixing layer through a first adhesive layer while conveying the polarizing plate and the first liquid crystal alignment fixing layer to produce a first intermediate laminate; a second lamination step of laminating the first intermediate laminate and the second liquid crystal alignment fixing layer with the second liquid crystal alignment fixing layer facing each other while conveying the first intermediate laminate, thereby producing a second intermediate laminate; The conveying tension after the second lamination step is greater than 700N and less than 1500N.

2. The method for producing an optical layered body according to claim 1, wherein: The conveying tension after the second lamination step is 800 N or more and 1350 N or less.

3. The method for producing an optical layered body according to claim 1, wherein: The second adhesive layer is composed of an active energy ray-curable adhesive.

4. The method for producing an optical layered body according to claim 1, wherein: The conveyance tension until the second lamination step is 100 N or more and 400 N or less.

5. The method for producing an optical layered body according to claim 1, wherein The first lamination step includes: conveying the long-shaped polarizing plate and the long-shaped first liquid crystal alignment fixing layer by rollers; and laminating the polarizing plate and the first liquid crystal alignment fixing layer by using a lamination roller. The second lamination step includes: conveying the long-length first intermediate layer and the long-length second liquid crystal alignment fixing layer with rollers; and laminating the first intermediate layer and the second liquid crystal alignment fixing layer using lamination rollers.

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