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 method comprising: a first lamination step; the method includes a first lamination step in which a first lamination body having a polarizing plate and a first surface protective film and a second lamination body having a first liquid crystal alignment fixing layer and a second surface protective film are laminated via a first adhesive layer so that the polarizing plate and the first liquid crystal alignment fixing layer face each other to produce a first intermediate lamination body; a step for peeling off the second surface protective film from the first intermediate laminate to produce a second intermediate laminate; and a second lamination step in which the second intermediate laminate and a third laminate having a second liquid crystal alignment fixing layer and a third surface protection film are laminated via a second adhesive layer such that the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer face each other.

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 a first laminate having a polarizer and a first surface protective film is laminated with a second laminate having a first liquid crystal orientation fixing layer and a second surface protective film 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 step of peeling the second surface protective film from the first intermediate laminate to produce a second intermediate laminate; and a second lamination step, in which a second intermediate laminate is laminated with a third laminate having a second liquid crystal orientation fixing layer and a third surface protective film 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. At least one of the first surface protection film, the second surface protection film, and the third surface protection film includes a base film and an adhesive layer.

[0010] [2] In the above [1], the method further includes peeling off the first surface protection film and the third surface protection film after the second lamination step.

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

[0012] [4] In any one of [1] to [3] above, at least one of the first surface protection film, the second surface protection film, and the third surface protection film comprises a polyethylene terephthalate-based resin.

[0013] [5] In any one of [1] to [4] above, at least one of the first surface protection film, the second surface protection film, and the third surface protection film has a thickness of 40 μm or more.

[0014] [6] In any one of [1] to [5] above, at least one of the first surface protection film, the second surface protection film, and the third surface protection film has a 90° peel strength of 0.010 N / 15 mm or more.

[0015] [7] In any one of [1] to [6] above, the bending angle of at least one of the first surface protection film, the second surface protection film, and the third surface protection film is less than 45°.

[0016] [8] In any one of [1] to [7] above, the tensile load of at least one of the first surface protection film, the second surface protection film, and the third surface protection film is 20 N or more and 50 N or less.

[0017] Effects of the Invention

[0018] 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

[0019] Figure 1 This is a schematic cross-sectional view of an optical layered body according to one embodiment of the present invention.

[0020] Figure 2A This is a schematic cross-sectional view showing an example of a first laminate in one step of a method for producing an optical laminate according to one embodiment of the present invention.

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

[0022] Figure 2C This is a schematic cross-sectional view showing an example of a first intermediate laminate in one step of a method for producing an optical laminate according to one embodiment of the present invention.

[0023] Figure 2D This is a schematic cross-sectional view showing an example of a second intermediate layered body in one step of a method for producing an optical layered body according to one embodiment of the present invention.

[0024] Figure 2E This is a schematic cross-sectional view showing an example of a third laminate in one step of a method for producing an optical laminate according to one embodiment of the present invention.

[0025] Figure 2F 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.

[0026] Figure 2G It means that the surface protective film is removed from Figure 2F Schematic cross-sectional view of an example of an optical laminate in which the optical laminate shown in FIG. 1 is peeled.

[0027] Explanation of symbols

[0028] 1. First laminate

[0029] 10. 1st surface protective film

[0030] 11. Polarizer

[0031] 111 Polarizer

[0032] 112 protective layer (first protective layer)

[0033] 113 protective layer (second protective layer)

[0034] 12 1st adhesive layer

[0035] 2. Second stack

[0036] 20 Second surface protective film

[0037] 21 First liquid crystal alignment fixing layer

[0038] 221 Base material (first base material)

[0039] 100 1st intermediate laminate

[0040] 200 Second intermediate laminate

[0041] 22 Second adhesive layer

[0042] 3. Third stack

[0043] 30 3rd surface protection film

[0044] 31 Second liquid crystal orientation fixing layer

[0045] 331 Base material (second base material)

[0046] 40 phase difference layer

[0047] 5 Optical laminate

[0048] 50 optical laminate DETAILED DESCRIPTION

[0049] 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".

[0050] (Definition of Terms and Symbols)

[0051] The definitions of terms and symbols in this specification are as follows.

[0052] (1) Refractive index (nx, ny, nz)

[0053] “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.

[0054] (2) In-plane retardation (Re)

[0055] "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.

[0056] (3) Retardation in the thickness direction (Rth)

[0057] "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.

[0058] (4) Nz coefficient

[0059] The Nz coefficient is obtained by Nz=Rth / Re.

[0060] (5) Angle

[0061] 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°.

[0062] A. Method for producing an optical layered body and outline of the optical layered body

[0063] The production method according to the embodiment of the present invention can produce an optical laminate having a polarizing plate and a retardation layer including a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer.

[0064] Figure 11 is a schematic cross-sectional view of an optical laminate that can be produced by the manufacturing method of 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 any suitable first bonding layer 12 (for example, an adhesive layer, an 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 (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 can also be omitted. Therefore, the polarizer can be a so-called two-protection polarizer, a so-called single-protection polarizer, or a polarizer alone. In the optical laminate 5 shown in the figure, surface protective films (a first surface protective film 10 and a third surface protective film 30) are arranged on both sides of the outermost layer, but in the optical laminate, the surface protective film can also be peeled off.

[0065] 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.

[0066] 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 of laminating a first laminate having a polarizer and a first surface protection film with a second laminate having a first liquid crystal alignment fixing layer and a second surface protection film, with the polarizer and the first liquid crystal alignment fixing layer facing each other, via a first adhesive layer to produce a first intermediate laminate; a step of peeling the second surface protection film from the first intermediate laminate to produce a second intermediate laminate; and a second lamination step of laminating the second intermediate laminate with a third laminate having a second liquid crystal alignment fixing layer and a third surface protection film, with the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer facing each other, via a second adhesive layer. At least one of the first surface protection film, the second surface protection film, and the third surface protection film comprises a base film and an adhesive layer.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] In the method for manufacturing an optical laminate according to an embodiment of the present invention, the first laminate and the second laminate stacked in the first lamination process each have a surface protective film (a first surface protective film and a second surface protective film). In addition, the second intermediate laminate and the third laminate stacked in the second lamination process each have a surface protective film (a first surface protective film and a third surface protective film). That is, both sides of the outermost layer of the first intermediate laminate produced in the first lamination process are lined with a surface protective film, and both sides of the outermost layer of the laminate produced in the second lamination process are lined with a surface protective film. In addition, the lined surface protective film (i.e., at least one of the first surface protective film, the second surface protective film, and the third surface protective film) has a base film and an adhesive layer. It is believed that by lining the surface protective film on each of the laminates before lamination (the first laminate and the second laminate and the second intermediate laminate and the third laminate), even if the adhesive layer is cured after lamination, the effect of the curing shrinkage of the adhesive layer is reduced by the surface protective film. That is, it is believed that by lining the surface protective film on each laminate used in lamination, even if the first adhesive layer used in the preparation of the first intermediate laminate is cured and shrinks, the shrinkage of the polarizer (particularly the polarizer) following the curing of the first adhesive layer can be suppressed. Furthermore, even if the second adhesive layer used in the lamination of the second intermediate laminate and the third laminate shrinks during the curing, 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. It is believed that by these, when the adhesive layer is cured, the curing shrinkage of the entire optical laminate (particularly 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 manufacturing method of the optical layered body of the embodiment of the present invention, by suppressing the thickness unevenness between the phase difference layers of the optical layered body, even if the optical layered body is applied to an image display device, the display unevenness (linear unevenness) caused by the interference of light can be suppressed.

[0071] B. Details of the method for producing an optical laminate

[0072] Hereinafter, the method for producing the optical layered body according to the embodiment of the present invention will be described in more detail.

[0073] Figures 2A to 2G This is a schematic cross-sectional view for explaining a method for producing an optical laminate according to one embodiment of the present invention in order of steps. Figures 2A to 2G Each step of the method for producing an optical laminate will be described in detail. Figure 2F and Figure 1 same.

[0074] B-1. First Lamination Step

[0075] The first lamination step is to place the first laminate 1 (see Figure 2A ) and the second laminate 2 (refer to Figure 2B Specifically, in the first lamination step, the first laminate 1 having the polarizer 11 and the first surface protection film 10 and the second laminate 2 having the first liquid crystal orientation fixing layer 21 and the second surface protection film 20 are attached and laminated via the first adhesive layer 22 in such a manner that the polarizer 11 and the first liquid crystal orientation fixing layer 21 face each other. Thus, the first intermediate laminate 100 (see Figure 2C ).exist Figure 2B In the example shown in FIG, the second laminate 2 includes a first substrate 221 for forming the first liquid crystal alignment fixing layer 21. The first substrate 221 is typically ultimately removed by peeling. Specifically, the first substrate 221 can be peeled off simultaneously with or after the second surface protective film is peeled off during the preparation of the second intermediate laminate described below.

[0076] In the first lamination process, it is preferred that the first elongated laminate and the second elongated laminate be conveyed by rollers. More preferably, the first laminate and the second laminate are laminated using lamination rollers. By operating in this manner, a first elongated intermediate laminate can be produced. The first elongated intermediate laminate can be wound in a roll. In this specification, "elongated" refers to an elongated shape having a length that is sufficiently long relative to its width, for example, including an elongated shape having a length that is 10 times or more, preferably 20 times or more, relative to its width.

[0077] B-1-1. Preparation of the first laminate

[0078] like Figure 2A As shown in FIG, a first laminate 1 having a polarizer 11 and a first surface protection film 10 is prepared. The first laminate 1 can be produced, for example, by preparing a polarizer 11 and disposing a surface protection film (first surface protection film 10) on the polarizer 11. Any appropriate method can be used to dispose the first surface protection film on the polarizer.

[0079] B-1-1-1. Polarizing plate

[0080] B-1-1-1-1. Polarizer

[0081] The polarizer 111 is typically formed of a polyvinyl alcohol (PVA) resin film containing a dichroic substance (eg, iodine). Examples of the PVA resin include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0082] 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.

[0083] 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).

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] B-1-1-1-2. Protective layer

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] B-1-1-1-3. Preparation of polarizing film

[0096] The polarizing plate can be produced, for example, as follows.

[0097] 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).

[0098] 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.

[0099] B-1-1-2. First surface protective film

[0100] Next, the first surface protection film 10 is placed on the polarizer 11. The first surface protection film 10 is temporarily attached to the polarizer 11 in a removable manner. Specifically, the first surface protection film 10 includes a base film and an adhesive layer (not shown), and the first surface protection film 10 and the polarizer 11 are attached via the adhesive layer. Thus, a first laminate (see Figure 2A ).

[0101] In the method for producing an optical layered body according to an embodiment of the present invention, the first surface protective film, and the second and third surface protective films described below may be common. Therefore, when describing the surface protective film in this specification, when simply referred to as "surface protective film," it means that the first, second, and third surface protective films are described collectively.

[0102] As the surface protective film, any suitable surface protective film used for the purpose of protecting the surface of an optical film such as a polarizer or a phase difference layer (film) can be adopted. Specifically, in the method for manufacturing an optical laminate of the present embodiment, the surface protective film may include a substrate film and an adhesive layer provided on the substrate film. As a result, in the method for manufacturing an optical laminate of the present embodiment, the surface protective film may have preferred mechanical properties. As a result, it can contribute to the significant effects of the embodiments of the present invention.

[0103] The substrate film can be made of any suitable resin film. As the forming material of the resin film, olefin resins such as polyethylene resins, ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, polyamide resins, polycarbonate resins, their copolymer resins, etc. can be listed. The surface protection film preferably includes polyethylene terephthalate resin as the substrate film. In this case, in the first stacking process, the curing shrinkage of the adhesive layer (the first adhesive layer) when the first stack and the second stack are stacked via the first adhesive layer can be particularly well suppressed. The substrate film, for example, preferably does not substantially have self-adhesiveness.

[0104] The thickness of the base film may preferably be 10 μm to 100 μm, more preferably 20 μm to 50 μm.

[0105] The tensile elastic modulus of the substrate film is preferably 1.0×10 8 Pa~5.0×10 9 Pa, more preferably 2.0×10 8 Pa~3.0×10 9 Pa. The tensile modulus of the substrate film can be measured in accordance with JIS K 7161. Measurement conditions include, for example, room temperature (approximately 23°C ± 5°C) and humidity (50% ± 10%). It should be noted that, in this specification, the tensile modulus of the surface protective film refers to the tensile modulus of the substrate film.

[0106] As the adhesive forming the adhesive layer, any suitable adhesive can be adopted. As the base resin of the adhesive, for example, (meth) acrylic resin, styrene resin, silicone resin can be listed. As the cross-linking agent that can be included in the adhesive, for example, isocyanate compound, epoxy compound, aziridine compound can be listed. The adhesive, for example, can also include a silane coupling agent. The combination formula of the adhesive can be suitably set according to the purpose.

[0107] The thickness of the adhesive layer may be, for example, 1 μm to 60 μm, and preferably 3 μm to 30 μm.

[0108] The thickness of the surface protective film is preferably 35 μm or more, more preferably 40 μm or more, and even more preferably 42 μm or more. The upper limit of the thickness of the surface protective film may be, for example, 100 μm. It should be noted that the thickness of the surface protective film refers to the total thickness of the substrate film and the adhesive layer. If it is within this range, the overall curing shrinkage during the manufacture of the optical laminate can be particularly reduced.

[0109] The 90° peel strength of the surface protective film is preferably 0.010N / 15mm or more, more preferably 0.050N / 15mm or more, and further preferably 0.10N / 15mm or more. If it is within this range, the overall curing shrinkage during the manufacture of the optical laminate can be particularly reduced. The upper limit of the 90° peel strength of the surface protective film is not particularly limited, for example, it can be 0.5N / 15mm. The 90° peel strength of the surface protective film can be measured by the method described in "(2-3) Peel Strength (90° Peel Force)" of the embodiments described later.

[0110] The bending angle of the surface protective film is preferably less than 45°. If it is within this range, the overall curing shrinkage during the manufacture of the optical laminate can be particularly reduced. The bending angle of the surface protective film can be measured as follows. Prepare a sample of a surface protective film having a length of 100 mm, a width of 50 mm, and a thickness of 30 μm to 50 μm. Arrange it on a flat surface such as a table in such a manner that 50% (or 50 mm) of the length of the sample extends into the air. Measure the angle at which the extended portion is bent relative to the vertical direction, and define this angle as the "bending angle of the surface protective film."

[0111] The tensile load of the surface protective film is preferably 20N or more, more preferably 25N or more, and further preferably 30N or more. On the other hand, the tensile load of the surface protective film is preferably 50N or less, more preferably 45N or less. If it is within this range, the overall curing shrinkage during the manufacture of the optical laminate can be particularly reduced. The so-called tensile load of the surface protective film refers to the minimum value of the load required when a certain tensile stress is applied to a surface protective film having a length of 100 mm and a width of 50 mm and the surface protective film is stretched by +50% in the longitudinal direction. Specifically, the tensile load of the surface protective film can be confirmed by applying a prescribed load to a surface protective film having a length of 100 mm and a width of 50 mm using AUTOGRAPH (precision universal testing machine) while stretching it by +50% in the longitudinal direction to measure the tensile stress. The details of the measuring method are as described in the examples below.

[0112] As long as the effects of the present invention are not hindered, the first surface protective film, the second surface protective film, and the third surface protective film may all be the same type of surface protective film, or may be different types of surface protective films, or two may be the same surface protective film and one may be a different surface protective film. Preferably, the first surface protective film, the second surface protective film, and the third surface protective film are all the same surface protective film.

[0113] B-1-2. Preparation of the second laminate

[0114] The second stacked body 2 can be formed, for example, by Figure 2BAs shown in FIG, the second surface protection film 20 is bonded to the first substrate 221 side of the first liquid crystal alignment fixing layer 21. Figure 2C As shown in , the second laminate 2 is used to prepare the first intermediate laminate 100 .

[0115] B-1-2-1. Formation of the first liquid crystal alignment fixing layer

[0116] 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.

[0117] The liquid crystal alignment fixing layer can be formed on any suitable substrate. Figure 2B 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.

[0118] 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).

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] B-1-2-2. Second surface protective film

[0134] The configuration of the second surface protection film 20 on the first liquid crystal orientation fixing layer 21 can be carried out in the same manner as the configuration of the first surface protection film 10 on the polarizing plate 11 in the first stack 1. Specifically, the second surface protection film 20 is temporarily attached to the first liquid crystal orientation fixing layer 21 and the side opposite to the polarizing plate 11 of the first stack 1 (in the example shown, the first substrate 221 side). In this way, the second stack 2 (see Figure 2B ).

[0135] The second surface protection film 20 comprises a base film and an adhesive layer (not shown), and any suitable surface protection film can be used. As described above, the description of the first surface protection film in the above-mentioned B-1-1-2 can be cited for the second surface protection film.

[0136] B-1-3. Formation of the first adhesive layer

[0137] Then, if Figure 2C As shown in FIG, the first laminate 1 and the second laminate 2 are attached 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 placing or applying any appropriate adhesive or pressure-sensitive adhesive.

[0138] 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.

[0139] 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.

[0140] When laminating the first laminate and the second laminate using laminating rollers, it is preferred that the first laminate and the second laminate are respectively conveyed by rollers while supplying an active energy ray-curable adhesive to at least one of the side of the first laminate opposite to the first surface protective film (e.g., the polarizer side) and the side of the second laminate opposite to the second surface protective film (e.g., the first liquid crystal orientation fixing layer side), and then laminating using laminating rollers. In other words, in forming the first adhesive layer, it is preferred that the first laminate and the second laminate are conveyed by rollers while supplying an active energy ray-curable adhesive to the side of the first laminate opposite to the first liquid crystal orientation fixing layer of the second laminate. The supply of the active energy ray-curable adhesive can be provided by any appropriate method. For example, while the first and second laminates are being conveyed, an active energy ray-curable adhesive is applied to the side of the polarizer opposite to the first surface protective film and / or the side of the first liquid crystal alignment fixing layer opposite to the second surface protective film. A second laminate intermediate can also be produced by operating in this manner.

[0141] B-1-4. Curing of the first adhesive layer

[0142] In the case where 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 included after the first lamination step. Specifically, in the first adhesive layer curing step, the first adhesive layer is cured after the first laminate and the second laminate are laminated with the first adhesive layer sandwiched therebetween. It is more preferred to cure the first adhesive layer before peeling off the second surface protective film. In this case, by lining the outermost surface protective films on both sides of the first intermediate laminate (in Figure 2C In the first intermediate laminate 100 shown in the figure, the first surface protective film 10 and the second surface protective film 20 are provided. Thus, even if the first adhesive layer used in the production of the first intermediate laminate undergoes curing shrinkage when curing, the shrinkage of the polarizer (particularly the polarizer) following the curing of the first adhesive layer can be suppressed. Therefore, the curing shrinkage of the entire first intermediate laminate can be suppressed. As a result, if the first intermediate laminate having the lined surface protective film is used for the production of an optical laminate, it can help to better suppress the curing shrinkage of the optical laminate as a whole. Therefore, when the optical laminate is applied to an image display device, the display unevenness (linear unevenness) caused by the interference of light can be significantly suppressed.

[0143] The curing of the first adhesive layer can be cured by any suitable method according to the type and composition of the adhesive agent constituting the first adhesive layer. When 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. It should be noted that the first adhesive layer curing step may not necessarily be after the first lamination step, and for example, it may be cured together with the second adhesive layer after the second lamination step described later. In addition, the first adhesive layer may also be cured in the first lamination step, for example.

[0144] In the curing of the first adhesive layer, it is preferred to bond the long first laminate and the long second laminate by roller conveying while sandwiching the first adhesive layer, and then cure the first adhesive layer by irradiating the first adhesive layer with active energy rays while rolling the bonded first intermediate laminate.

[0145] B-2. Preparation of the Second Intermediate Laminate

[0146] Then, if Figure 2DAs shown in FIG, the second surface protection film 20 is peeled off from the first intermediate layer 100. This produces the second intermediate layer 200. In this case, if the first substrate 221 is present, it is preferred that the first substrate 221 is also peeled off. By peeling the second surface protection film 20 from the first intermediate layer 100, the second intermediate layer 200 is obtained in which the surface of the first liquid crystal alignment fixing layer 21 opposite to the first adhesive layer 12 is exposed. The second intermediate layer 200 can be provided for lamination with the third layer 3.

[0147] B-3. ​​Second Lamination Step

[0148] The second lamination step is to place the second intermediate laminate 200 (see Figure 2D ) and the third laminate 3 (refer to Figure 2E Specifically, in the second lamination step, the second intermediate laminate 200 and the third laminate 3 are attached and laminated via the second adhesive layer 22 in such a manner that the first liquid crystal orientation fixing layer 21 and the second liquid crystal orientation fixing layer 31 are opposite to each other. In this way, a laminated body formed by laminating the second intermediate laminate and the third laminate can be obtained (see Figure 2F ).exist Figure 2E In the example shown in FIG, the third stacked body 3 includes a second substrate 331 for forming the second liquid crystal alignment fixing layer 31. The second substrate 331 can typically be peeled off and removed eventually. Specifically, for example, it can be peeled off during the production of the image display device described later.

[0149] The second lamination step preferably includes conveying the second long intermediate laminate and the second long liquid crystal alignment fixed layer with rollers, and more preferably includes laminating the second intermediate laminate and the second liquid crystal alignment fixed layer with a lamination roller.

[0150] B-3-1. Preparation of the third laminate

[0151] The third stacked body is, for example, Figure 2E As shown in FIG, the third surface protective film 30 can be laminated to the second substrate 331 side of the second liquid crystal alignment fixing layer 31. The third laminate can be produced in the same manner as the second laminate. Therefore, the description of the second laminate in Section B-1-2 can be used for the production of the third laminate.

[0152] B-3-1-1. Second liquid crystal alignment fixing layer

[0153] 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-1-2-1. Hereinafter, an example will be described in which the second liquid crystal alignment fixing layer is a positive C plate.

[0154] 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.

[0155] 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.

[0156] [Chemical Formula 1]

[0157]

[0158] [Chemical Formula 2]

[0159]

[0160] 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 1 is -CO2- or -OCO-. a is an integer of 1 to 6, and b and c are each independently 1 or 2.

[0161] 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).

[0162] [Chemical Formula 3]

[0163]

[0164] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0165] 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.

[0166] 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.

[0167] B-3-1-2. Third surface protective film

[0168] The configuration of the third surface protection film 30 on the second liquid crystal alignment fixing layer 31 can be carried out in the same manner as the configuration of the first surface protection film 10 on the polarizer 11 in the first stack 1. Specifically, the third surface protection film 30 is temporarily attached to the second liquid crystal alignment fixing layer 31 and the side opposite to the first liquid crystal alignment fixing layer 21 of the second intermediate stack 200 (the second substrate 331 side in the example shown). In this way, the third stack 3 (see Figure 2E ).

[0169] The third surface protection film 30 comprises a base film and an adhesive layer (not shown), and any suitable surface protection film can be used. As described above, the description of the first surface protection film in the above-mentioned B-1-1-2 can be cited for the third surface protection film.

[0170] B-3-2. Second adhesive layer

[0171] Then, if Figure 2F As shown in FIG, the second intermediate laminate 200 and the third laminate 3 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.

[0172] 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.

[0173] 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.

[0174] As in the first lamination step, it is also preferred that the second intermediate laminate and the third laminate be conveyed by rollers while an active energy ray-curable adhesive is supplied to at least one of the side of the second intermediate laminate opposite to the first surface protective film (e.g., the first liquid crystal orientation fixing layer side) and the side of the third laminate opposite to the third surface protective film (e.g., the second liquid crystal orientation fixing layer side), and then the laminate is laminated using a lamination roller. In other words, in forming the second adhesive layer, it is preferred that the second intermediate laminate and the third laminate be conveyed by rollers while an active energy ray-curable adhesive is supplied to the side of the second intermediate laminate opposite to the second liquid crystal orientation fixing layer of the third laminate.

[0175] B-4. Curing of the Second Adhesive Layer

[0176] 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 second intermediate laminate 200 and the third laminate 3 are laminated with the second adhesive layer 22 sandwiched between them, and then the second adhesive layer is cured. In this case, the outermost layer of the laminate of the second intermediate laminate and the third laminate is formed by forming a lining surface protective film on both sides (in the Figure 2F In the embodiment, the first surface protective film 10 and the third surface protective film 30 are provided. Thus, even if the second adhesive layer used in the production of the laminate of the second intermediate laminate and the third laminate undergoes curing shrinkage during curing, 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. As a result, if the laminate having the surface protective film as the lining is used for the production of an optical laminate, it can help to better suppress the curing shrinkage of the optical laminate as a whole. Therefore, even if the optical laminate is used in an image display device, the display unevenness (linear unevenness) caused by the interference of light can be significantly suppressed.

[0177] In the curing of the second adhesive layer, it is preferred to bond the elongated second intermediate layer and the elongated third layer together by roller conveying while sandwiching the second adhesive layer, and then cure the bonded layers by irradiating the second adhesive layer with active energy rays while roller conveying the laminated layers.

[0178] By operating in this manner, an optical laminate according to an embodiment of the present invention can be manufactured. Even when the optical laminate manufactured in this manner is used in an image display device, since the laminate (including the intermediate laminate) used in the manufacturing process of the optical laminate has a lined surface protective film, the curing shrinkage of the first adhesive layer and the second adhesive layer, as well as the curing shrinkage of the optical laminate as a whole, can be suppressed, thereby suppressing display unevenness (linear unevenness) caused by light interference in the optical laminate.

[0179] B-5. Surface protection film peeling process

[0180] In a manufacturing method according to one embodiment of the present invention, Figure 2G As shown in , after the second lamination step, the first surface protective film and the third surface protective film may be further peeled off (also referred to as a surface protective film peeling step). After the surface protective film peeling step, the optical laminate 50 can be obtained. When an active energy ray-curable adhesive is used for the second adhesive layer, after the second curing step, the first surface protective film and the third surface protective film may be further peeled off.

[0181] 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 each of the above-mentioned elongated laminates (the first laminate, the second laminate, the third laminate, the first intermediate laminate and the second intermediate laminate) into a specified size and then laminating them together through the above-mentioned steps.

[0182] The obtained optical layered body 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 visual side (specifically, the side after the third surface protective film is peeled off), to produce an image display device.

[0183] Example

[0184] 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.

[0185] (1) Thickness

[0186] The measurement was performed using an interferometer film thickness meter ("MCPD9800" manufactured by Otsuka Electronics Co., Ltd.).

[0187] (2) Physical properties of surface protective film

[0188] (2-1) Thickness

[0189] The measurement was performed in the same manner as in the above-mentioned (1) using an interference film thickness meter ("MCPD9800" manufactured by Otsuka Electronics Co., Ltd.).

[0190] (2-2) Tensile elastic modulus

[0191] Regarding the tensile modulus of the surface protective film, a sample of the surface protective film having a length of 100 mm and a width of 10 mm was prepared (the thickness was the thickness measured by the above (2-1). The same applies to (2-3) to (2-5) below.) The sample was measured in accordance with JIS K 7161 using a tensile testing apparatus (Autograph, a precision universal testing machine manufactured by Shimadzu Corporation) at a temperature of 23°C and a humidity of 50%.

[0192] (2-3) Peel strength (90° peel force)

[0193] First, prepare a sample of a surface protective film with a size of 100 mm in length and 15 mm in width. The sample is pasted on a SUS plate (length 120 mm, width 50 mm, thickness 2.0 mm) via an adhesive tape (double-sided tape). The sample is attached using a hand roller. Then, using a variable angle peeling measuring device, the sample is peeled under the conditions of a peeling angle of 90 °, a peeling speed of 1000 mm / min, and a measuring distance of 80 mm. The measured value thus obtained is set as the peel strength (90 ° peeling force).

[0194] (2-4) Bending angle

[0195] Prepare a surface protection film sample with dimensions of 100 mm in length and 50 mm in width. Place it on a flat table so that 50% of the sample's length (or 50 mm) protrudes into the air. Measure the angle at which the protruding portion bends relative to the vertical direction. The angle obtained is defined as the "surface protection film bend angle."

[0196] (2-5) Tensile load

[0197] Regarding the tensile load of the surface protective film, a sample of the surface protective film having a length of 100 mm and a width of 10 mm was prepared. For the sample, using an AUTOGRAPH (precision universal testing machine), the load when the length in the longitudinal direction becomes 150 mm (the original length of 100 mm stretched in the longitudinal direction by 50%) was measured in sequence, and the lowest load was taken as the tensile load.

[0198] (3) Linear unevenness

[0199] 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.

[0200] 1 (Excellent): No linear unevenness was observed even when observing with a polarizing plate attached under a 3-wavelength fluorescent lamp.

[0201] 2 (good): No linear unevenness was observed in normal observation using a three-wavelength fluorescent lamp.

[0202] 3 (Acceptable): Linear unevenness is slightly observed in normal observation using a 3-wavelength fluorescent lamp.

[0203] 4 (Unacceptable): Linear unevenness that is unacceptable in practice was observed in normal observation using a three-wavelength fluorescent lamp.

[0204] 5 (poor): Linear unevenness is noticeable in normal observation using a 3-wavelength fluorescent lamp

[0205] [Manufacturing Example 1: Preparation of Adhesive A1 Constituting the First Adhesive Layer and the Second Adhesive Layer]

[0206] 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.

[0207] [Example 1]

[0208] 1. Preparation of optical laminates

[0209] 1-1. Preparation of the first laminate

[0210] 1-1-1. Preparation of polarizer

[0211] 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.

[0212] 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).

[0213] 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.

[0214] 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).

[0215] 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).

[0216] 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).

[0217] 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).

[0218] 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.

[0219] 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).

[0220] 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).

[0221] 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."

[0222] 1-1-2. Preparation of Polarizing Plate (PL1)

[0223] 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°.

[0224] 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).

[0225] 1-1-3. Lamination of the first surface protective film

[0226] On the side of the polarizer opposite to the second protective layer, a surface protective film 1 (E-MASKRP109F, manufactured by Nitto Denko Corporation) was releasably laminated as a first surface protective film. The first surface protective film was laminated on the polarizer using a roll-to-roll process. Thus, a first elongated laminate was obtained.

[0227] Table 1 shows the properties of the surface protection film 1.

[0228] In this manner, a first laminate having a structure of first surface protection film / polarizer PL1 is obtained.

[0229] 1-2. Preparation of the Second Laminated Body

[0230] 1-2-1. Preparation of the first liquid crystal alignment fixing layer (LC1)

[0231] 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 having a solid content concentration of 30% by weight. A surfactant ("BYK-360" manufactured by BYK-Chemie) and a photopolymerization initiator ("Omnirad907" 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 photocured by ultraviolet light to obtain a long laminate having a structure of substrate / first liquid crystal alignment fixing layer LC1. The first liquid crystal alignment fixing layer was aligned in the plane and had a thickness of 1.5 μm.

[0232] [Chemical Formula 4]

[0233]

[0234] 1-2-2. Temporary application of the second surface protective film

[0235] On the side of the long strip of laminated body having the structure of substrate / first liquid crystal alignment fixing layer LC1 opposite to the first liquid crystal alignment fixing layer LC1, a surface protection film 1 (E-MASKRP109F, manufactured by Nitto Denko Corporation) was releasably laminated as a second surface protection film. The second surface protection film was laminated using a roll-to-roll process. This resulted in a long strip of the second laminated body having the structure of first liquid crystal alignment fixing layer LC1 / substrate (TAC film) / second surface protection film.

[0236] 1-3. Preparation of the third laminate

[0237] 1-3-1. Preparation of the Second Liquid Crystal Orientation Fixing Layer (LC2)

[0238] A long laminate having a structure of substrate / second liquid crystal alignment fixing layer LC2 was obtained in the same manner as the first liquid crystal alignment fixing layer except that the coating thickness was changed so that Re(550) became 240 nm. The thickness of the second liquid crystal alignment fixing layer was 2.0 μm.

[0239] 1-3-2. Temporary application of the third surface protective film

[0240] On the side of the long strip of laminated body having the second liquid crystal alignment fixing layer LC2 opposite to the second liquid crystal alignment fixing layer LC2, a surface protection film 1 (E-MASKRP109F, manufactured by Nitto Denko Corporation) was releasably laminated as a third surface protection film. The third surface protection film was laminated using a roll-to-roll process. Thus, a long strip of the third laminated body was obtained.

[0241] 1-4. First Lamination Step

[0242] The first and second elongated laminates prepared above were conveyed by rollers while the adhesive A1 of Manufacturing Example 1 was supplied to the second protective layer (TAC film) of the first laminate and the first liquid crystal alignment fixing layer of the second laminate, respectively, so that the thickness of the first adhesive layer after curing was 1.0 μm. The laminates were then laminated using laminating rollers with the polarizer (specifically, the second protective layer on the opposite side of the first surface protective film) and the first liquid crystal alignment fixing layer facing each other via the first adhesive layer. Thus, a first intermediate laminate comprising the first surface protective film / polarizer (first protective layer / polarizer / second protective layer) / first adhesive layer / first liquid crystal alignment fixing layer / substrate / second surface protective film was produced.

[0243] Next, the first intermediate laminate was transported while being irradiated with ultraviolet light (cumulative light intensity 600 mJ / cm 2 ) and perform light curing to cure the first adhesive layer.

[0244] 1-5. Second intermediate laminate

[0245] Next, the second surface protective film is peeled off from the first intermediate laminate after curing the first adhesive layer, producing a long second intermediate laminate having a structure of first surface protective film / polarizer (first protective layer / polarizer / second protective layer) / first adhesive layer / first liquid crystal alignment fixing layer / substrate. Lamination and peeling are performed using a roll-to-roll process.

[0246] 1-6. Second Lamination Step

[0247] First, the substrate (TAC film) of the first liquid crystal orientation fixing layer in the second intermediate layer stack was peeled off. Next, the second intermediate layer stack, from which the substrate was peeled, and the long strip of the third layer stack were conveyed separately by rollers while the adhesive A1 of Manufacturing Example 1 was supplied to the first liquid crystal orientation fixing layer of the second intermediate layer stack and the second liquid crystal orientation fixing layer of the third layer stack, respectively. The adhesive was applied so that the thickness of the cured second adhesive layer became 1.0 μm. The layers were then laminated using a laminating roller so that the first liquid crystal orientation fixing layer and the second liquid crystal orientation fixing layer faced each other, with the second adhesive layer interposed therebetween. Thus, a laminate comprising a first surface protective film / polarizer (first protective layer / polarizer / second protective layer) / first adhesive layer / first liquid crystal orientation fixing layer / second adhesive layer / second liquid crystal orientation fixing layer / substrate / third surface protective film was produced.

[0248] 1-7. Formation and Curing of the Second Adhesive Layer

[0249] Next, the laminate was transported while being irradiated with ultraviolet light (cumulative light intensity 600 mJ / cm 2 ) and photocuring to cure the second adhesive layer. Thus, an optical laminate with a surface protective film was obtained. In the optical laminate with a surface protective film, the first liquid crystal alignment fixing layer was aligned along the surface and had a thickness of 1.5 μm. The slow axis direction of the first liquid crystal alignment fixing layer was 15°. The thickness of the second liquid crystal alignment fixing layer was 2.0 μm. The slow axis direction of the second liquid crystal alignment fixing layer was 75°.

[0250] 2. Fabrication of Image Display Device

[0251] The first surface protection film and the third surface protection film were peeled off from the optical layered body with surface protection films obtained above.

[0252] 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 then 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 in (3). The results are shown in Table 1.

[0253] [Example 2, Comparative Examples 1-2]

[0254] An optical layered body and an image display device were prepared in the same manner as in Example 1, except that the first, second, and third surface protective films were replaced with the protective films listed in Table 1. The resulting image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0255] In addition, the materials shown in the column of "surface protection film" shown in Table 1 are as follows.

[0256] (Surface protection film)

[0257] Surface protection film 1: product name "RP109F" manufactured by Nitto Denko Corporation (film constituent resin: polyethylene terephthalate-based resin. Adhesive layer constituent: acrylic-based resin).

[0258] Surface protection film 2: product name "HP300" manufactured by Nitto Denko Corporation (film constituent resin: polyethylene terephthalate-based resin. Adhesive layer constituent: acrylic-based resin).

[0259] Surface protection film 3: "7832C" manufactured by Toray Industries, Inc. (film constituent resin: polyethylene resin. Self-adhesive).

[0260] Surface protection film 4: product name "A521" manufactured by Toray Industries, Inc. (film constituent resin: polyethylene resin. Self-adhesive).

[0261] Table 1

[0262]

[0263] Industrial applicability

[0264] 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 a first laminate comprising a polarizer and a first surface protective film and a second laminate comprising a first liquid crystal alignment fixing layer and a second surface protective film via a first adhesive layer in a manner such that the polarizer and the first liquid crystal alignment fixing layer face each other, thereby producing a first intermediate laminate; a step of peeling the second surface protection film from the first intermediate laminate to produce a second intermediate laminate; and a second lamination step of laminating the second intermediate laminate and the third laminate having a second liquid crystal alignment fixing layer and a third surface protection film via a second adhesive layer in such a manner that the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer face each other; At least one of the first surface protection film, the second surface protection film, and the third surface protection film includes a base film and an adhesive layer.

2. The method for producing an optical layered body according to claim 1, wherein: After the second lamination step, the method further includes peeling off the first surface protection film and the third surface protection film.

3. The method for producing an optical layered body according to claim 1 or 2, wherein: The first adhesive layer and the second adhesive layer are formed of an active energy ray-curable adhesive.

4. The method for producing an optical layered body according to claim 1 or 2, wherein: At least one of the first surface protection film, the second surface protection film, and the third surface protection film includes a polyethylene terephthalate-based resin.

5. The method for producing an optical layered body according to claim 1 or 2, wherein: At least one of the first surface protection film, the second surface protection film, and the third surface protection film has a thickness of 40 μm or greater.

6. The method for producing an optical layered body according to claim 1 or 2, wherein: At least one of the first surface protection film, the second surface protection film, and the third surface protection film has a 90° peel strength of 0.010 N / 15 mm or more.

7. The method for producing an optical layered body according to claim 1 or 2, wherein: The bending angle of at least one of the first surface protection film, the second surface protection film, and the third surface protection film is less than 45°.

8. The method for producing an optical layered body according to claim 1 or 2, wherein: A tensile load of at least one of the first surface protection film, the second surface protection film, and the third surface protection film is 20 N or more and 50 N or less.

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