Method for manufacturing optical laminates

Abstract

To provide a method for manufacturing an optical laminate, an optical laminate, and an image display device that can smoothly manufacture an optical laminate that can suppress the occurrence of optical defects. [Solution] A method for manufacturing an optical laminate according to an embodiment of the present invention includes a first preparation step, a second preparation step, a first bonding step, a first delamination step, and a second delamination step. In the first preparation step, a first laminate is prepared. The first laminate comprises a polarizer located on a first substrate. In the second preparation step, a second laminate is prepared. The second laminate comprises a phase difference layer located on a second substrate. The phase difference layer includes an orientation solidification layer of a liquid crystal compound. In the first bonding step, the polarizer of the first laminate and the phase difference layer of the second laminate are bonded together. The first and second delamination steps are performed after the first bonding step to delaminate the first substrate from the polarizer and the second substrate from the phase difference layer.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an optical laminate, an optical laminate, and an image display device. [Background technology]

[0002] Image display devices, such as liquid crystal displays and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), are rapidly becoming widespread. These image display devices sometimes utilize optical laminates containing polarizers and orientation-solidified layers of liquid crystal compounds. As a method for manufacturing such optical laminates, for example, a method has been proposed in which a polarizer is formed on a resin substrate, a protective layer is attached to the surface of the polarizer opposite to the resin substrate, and then the resin substrate is peeled off from the polarizer, and an orientation solidified layer of liquid crystal compound is attached to the polarizer (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-68282 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When an optical laminate manufactured by the method described in Patent Document 1 is applied to an image display device, optical defects such as anisotropic reflection defects (hereinafter sometimes referred to as reflection defects) may occur. The main objective of the present invention is to provide a method for manufacturing an optical laminate, an optical laminate, and an image display device that can smoothly manufacture an optical laminate that can suppress the occurrence of optical defects. [Means for solving the problem]

[0005] [1] A method for manufacturing an optical laminate according to an embodiment of the present invention includes a first preparation step, a second preparation step, a first bonding step, a first delamination step, and a second delamination step. In the first preparation step, a first laminate is prepared. The first laminate comprises a first substrate and a polarizer located on the first substrate. In the second preparation step, a second laminate is prepared. The second laminate comprises a second substrate and a phase difference layer located on the second substrate. The phase difference layer includes an orientation solidification layer of a liquid crystal compound. In the first bonding step, the polarizer of the first laminate and the phase difference layer of the second laminate are bonded together. The first delamination step and the second delamination step are performed after the first bonding step. In the first delamination step, the first substrate is peeled off from the polarizer. In the second peeling step, the second substrate is peeled off from the phase difference layer. [2] In the method for manufacturing an optical laminate described in [1] above, the first peeling step may be performed before the second peeling step. [3] In the method for manufacturing an optical laminate described in [1] or [2] above, the phase difference layer may have a single-layer structure consisting of an orientation solidified layer of the first liquid crystal compound. [4] The method for manufacturing the optical laminate described in [3] above may include a third preparation step, a second bonding step, and a third peeling step. In the third preparation step, the third laminate is prepared. The third laminate comprises a third substrate and an orientation solidified layer of a second liquid crystal compound located on the third substrate. The second bonding step is performed after the second peeling step. In the second bonding step, the orientation solidified layer of the first liquid crystal compound is bonded to the orientation solidified layer of the second liquid crystal compound. The third peeling step is performed after the second bonding step. In the third peeling step, the third substrate is peeled from the orientation solidified layer of the second liquid crystal compound. The first peeling step may be performed after the second bonding step. [5] In the method for manufacturing an optical laminate described in [4] above, the first peeling step may be performed before the third peeling step. [6] In the method for manufacturing an optical laminate according to any one of [1] to [5] above, the second preparation step includes: forming an orientation solidified layer of a first liquid crystal compound on the second substrate; forming an orientation solidified layer of a second liquid crystal compound on a third substrate; bonding the orientation solidified layer of the first liquid crystal compound to the orientation solidified layer of the second liquid crystal compound; and, after the step of bonding the orientation solidified layer of the first liquid crystal compound to the orientation solidified layer of the second liquid crystal compound, peeling the third substrate from the orientation solidified layer of the second liquid crystal compound. In the first bonding step, the polarizer and the orientation solidified layer of the second liquid crystal compound are bonded together. [7] In the method for manufacturing an optical laminate described in any of [1] to [6] above, the first peeling step may be performed before the second peeling step. [8] The method for manufacturing an optical laminate described in any of [1] to [7] above may further include a protection step, which is performed after the first peeling step, in which a protective layer is attached to the polarizer. [9] In the method for manufacturing an optical laminate described in any of [1] to [8] above, the thickness of the polarizer may be 3 μm to 7 μm.

[10] In the method for manufacturing an optical laminate according to any of [1] to [9] above, the first preparation step may include: applying a coating solution containing a polyvinyl alcohol-based resin to the first substrate to obtain a resin layer support comprising a polyvinyl alcohol-based resin layer and the first substrate; dyeing the polyvinyl alcohol-based resin layer with a dichroic substance; and stretching the resin layer support.

[11] The method for manufacturing an optical laminate described in any of [1] to

[10] above may further include an adhesive layer formation step and a temporary bonding step. The adhesive layer formation step is performed after the second peeling step. In the adhesive layer formation step, an adhesive layer is formed on the surface of the phase difference layer. In the temporary bonding step, a peeling liner is attached to the adhesive layer.

[12] In the method for manufacturing an optical laminate described in any of [1] to

[11] above, the phase difference layer may function as a λ / 4 plate.

[13] An optical laminate according to another aspect of the present invention comprises a polarizer and a phase difference layer. The phase difference layer is located on one side of the polarizer in the thickness direction. The phase difference layer contains an orientation solidified layer of a liquid crystal compound. The polarizer has a first surface and a second surface in the thickness direction. The first surface is located on the side of the phase difference layer. The second surface is located on the opposite side of the phase difference layer from the first surface. The second surface is smoother than the first surface.

[14] In the optical laminate described in

[13] above, the number of reflection defects per unit area on the second surface of the polarizer may be less than the number of reflection defects per unit area on the first surface of the polarizer.

[15] An image display device according to another aspect of the present invention comprises an image display panel and an optical laminate as described in

[13] or

[14] above. The optical laminate is positioned on the viewing side of the image display panel. The polarizer is positioned on the opposite side of the image display panel from the phase difference layer. [Effects of the Invention]

[0006] According to embodiments of the present invention, optical laminates that can suppress the occurrence of optical defects can be manufactured smoothly. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram illustrating the first and second preparation steps included in a method for manufacturing an optical laminate according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram illustrating the first bonding process, which follows the first and second preparation processes shown in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 4] Figure 4 is a schematic cross-sectional view of the second laminate prepared in the second preparation step of Figure 1. [Figure 5] Figure 5 is a schematic diagram illustrating the second preparation step for preparing the second laminate shown in Figure 4. [Figure 6]FIG. 6 is a schematic cross-sectional view of the first intermediate laminate obtained in the first bonding step of FIG. 2. [Figure 7] FIG. 7 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention. [Figure 8] FIG. 8 is a schematic explanatory view for explaining a third preparation step included in a method for manufacturing an optical laminate according to another embodiment of the present invention. [Figure 9] FIG. 9 is a schematic explanatory view for explaining a second bonding step following the third preparation step of FIG. 8.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments. Also, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) “nx” is the refractive index in the direction where the in-plane refractive index is maximum (i.e., the slow axis direction), “ny” is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction. In the equation of the ellipse (x 2 / a 2 )+(y 2 / b 2 ) = 1, a is nx, b is ny, x and y are the refractive indices in the x-direction and y-direction at an angle θ on the ellipse, and by solving the simultaneous equations from y = x(tanθ) and the above nx and ny, the “refractive index in the transmission axis direction” is obtained by √(x 2 +y 2 ). The “average refractive index” is obtained by (nx + ny + nz) / 3. (2) In-Plane Phase Difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23°C. Re(λ) can be calculated using the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Phase difference in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. Rth(λ) can be calculated using the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re. (5)Angle In this specification, when an angle is referred to, it encompasses both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, "45°" means ±45°. (6) substantially parallel or orthogonal The expressions "substantially parallel" and "approximately parallel" include cases where the angle between the two directions is within 0°±3°. Furthermore, the expressions "substantially orthogonal" and "approximately orthogonal" include cases where the angle between the two directions is 90°±3°.

[0010] A. Overview of the manufacturing method for optical laminates A method for manufacturing an optical laminate according to one embodiment of the present invention includes a first preparation step, a second preparation step, a first bonding step, a first peeling step, and a second peeling step. As shown in Figure 1, the first preparation step involves preparing the first laminate 1. The first laminate 1 comprises a first substrate 11 and a polarizer 12. The polarizer 12 is located on the first substrate 11. The polarizer 12 has a first surface 12a and a second surface 12b in the thickness direction of the polarizer 12 (hereinafter sometimes simply referred to as the thickness direction). The first surface 12a of the polarizer 12 is located on the opposite side from the first substrate 11. The second surface 12b of the polarizer 12 is located on the side of the first substrate 11. In the illustrated example, the second surface 12b of the polarizer 12 is in contact with the surface of the first substrate 11 in the thickness direction. In the second preparation step, the second laminate 2 is prepared. The second laminate 2 comprises a second substrate 21 and a phase difference layer 22. The phase difference layer 22 is located on the second substrate 21. The phase difference layer 22 contains an orientation-solidified layer of liquid crystal compounds. In this specification, "orientation-solidified layer of liquid crystal compounds" refers to a layer in which liquid crystal compounds are oriented in a predetermined direction within the layer, and this orientation state is fixed. Note that "orientation-solidified layer" is a concept that includes orientation-hardened layers obtained by hardening liquid crystal monomers, as described later. Hereafter, the orientation-solidified layer of liquid crystal compounds may be referred to as the liquid crystal orientation-solidified layer. As shown in Figure 2, in the first bonding step, the polarizer 12 of the first laminate 1 and the phase difference layer 22 of the second laminate 2 are bonded together. The first delamination process and the second delamination process are performed after the first bonding process. In the first delamination process, the first substrate 11 is peeled off from the polarizer 12. In the second delamination process, the second substrate 21 is peeled off from the phase difference layer 22. The inventors of this invention have discovered that optical defects (typically reflection defects) that occur when an optical laminate comprising a polarizer and an orientation-solidified layer of liquid crystal compound is applied to an image display device are due to the surface shape of the polarizer. Therefore, the inventors diligently investigated the relationship between optical defects and the surface shape of the polarizer and found that by positioning the relatively smooth surface of the polarizer further away from the orientation solidification layer of the liquid crystal compound than the relatively rough surface of the polarizer, optical defects (typically reflection defects) in the image display device can be reduced. In one embodiment of the first laminate 1, the second surface 12b of the polarizer 12 is located on the first substrate 11 side (see Figure 1). Therefore, since the second surface 12b of the polarizer 12 is held (or fixed or protected) by the first substrate 11, even if deformation such as thickness variations, waviness, scratches, or dents occurs during the manufacturing process of the polarizer 12, it is formed more smoothly than the first surface 12a. In the first bonding step described above, the polarizer 12 and the phase difference layer 22 are bonded together such that the first surface 12a of the polarizer 12 faces the phase difference layer 22. In other words, the relatively smooth second surface 12b is located on the opposite side of the phase difference layer 22, which contains the orientation solidification layer of the liquid crystal compound, from the relatively rough first surface 12a. Therefore, when an optical laminate 100 (see Figure 3) manufactured by this method is applied to an image display device, the smoother surface of the polarizer 12 can be directed towards the viewing side of the image display device, and as a result, the occurrence of optical defects (typically reflection defects) can be suppressed. Furthermore, in the first lamination process described above, the second surface 12b of the polarizer 12 is held (or fixed) by the first substrate 11 in the first laminate 1, so that unevenness in optical path length is less likely to occur in the lamination process. In other words, even if shrinkage occurs in the adhesive layer due to polymerization reaction (or condensation reaction, or solvent drying), waviness is less likely to occur in the first laminate 1 or the adhesive layer. This characteristic is less likely to occur the more the first substrate 11 is a coating substrate for the polarizer 12. In addition, it is less likely to occur the more the first substrate 11 is a stretched film, preferably a stretched film stretched in the transport direction of the first lamination process, more preferably a stretched film stretched in the same direction as the orientation direction of the polarizer 12, and even more preferably a stretched film stretched simultaneously with the polarizer 12 in the manufacturing process (first preparation process) of the polarizer 12. An optical laminate 100 that is less prone to unevenness in optical path length in this way is less prone to appearance defects due to interference. Therefore, applying an optical laminate 100 manufactured by this method to an image display device can reduce optical defects (typically linear streaks) in the image display device.

[0011] As shown in Figure 3, in one embodiment, the method for manufacturing the optical laminate further includes a protection step. The protection step is performed after the first peeling step. In the protection step, a protective layer 13 is attached to the polarizer 12. More specifically, the protective layer 13 is attached to the second surface 12b of the polarizer 12. This protects the second surface of the polarizer, thereby preventing damage to the second surface and stably suppressing the occurrence of optical defects in the image display device to which the optical laminate is applied.

[0012] In one embodiment, the method for manufacturing the optical laminate further includes an adhesive layer formation step. The adhesive layer formation step is performed after the second peeling step. In the adhesive layer formation step, an adhesive layer 5 is formed on the surface of the phase difference layer 22. More specifically, the adhesive layer 5 is formed on the surface of the phase difference layer 22 opposite to the polarizer 12. This makes it possible to manufacture an optical laminate having an adhesive layer. Thus, the optical laminate can be attached by the adhesive layer to any suitable substrate (typically an image display panel) of an image display device.

[0013] The method for manufacturing the optical laminate may further include a temporary bonding step. In the temporary bonding step, a release liner 6 is attached to the adhesive layer 5. More specifically, the release liner 6 is attached to the surface of the adhesive layer 5 opposite to the phase difference layer 22. Typically, the release liner 6 is temporarily attached to the adhesive layer 5 until the optical laminate is attached to the substrate, and is peeled off from the adhesive layer 5 when the optical laminate is attached.

[0014] B. Details of the manufacturing method for optical laminates Next, with reference to Figures 1 to 7, the details of a method for manufacturing an optical laminate according to one embodiment will be described. In one embodiment, the method for manufacturing an optical laminate includes the above-described first preparation step, the above-described second preparation step, the above-described first bonding step, the above-described first peeling step, the above-described second peeling step, the above-described protection step, the above-described adhesive layer forming step, and the above-described temporary bonding step.

[0015] B-1.First preparation process As shown in Figure 1, in the first preparation step, a first laminate 1 comprising a first substrate 11 and a polarizer 12 is prepared. In the first preparation step, any suitable method capable of preparing the first laminate 1 is employed. In one embodiment, the first preparation step includes a coating step, a dyeing step, and a stretching step.

[0016] B-1-1.Coating process In the coating process, first, a first substrate is prepared, and a coating solution containing a polyvinyl alcohol-based resin (hereinafter referred to as PVA-based resin) is applied to the first substrate. In other words, in one embodiment, the first substrate is a coating substrate for a polarizer. This prepares a resin layer support comprising a PVA-based resin layer and the first substrate.

[0017] The first substrate contains any suitable resin material. The first substrate is typically a polyethylene terephthalate film. Examples of constituent materials for the first substrate include amorphous (non-crystallized) polyethylene terephthalate resins, and preferably amorphous (difficult to crystallize) polyethylene terephthalate resins. Specific examples of amorphous polyethylene terephthalate resins include copolymers further containing isophthalic acid as a dicarboxylic acid, and copolymers further containing cyclohexanedimethanol as a glycol.

[0018] The glass transition temperature (Tg) of the first substrate is, for example, 170°C or lower, preferably 120°C or lower. Having such a Tg in the first substrate can suppress crystallization of the PVA resin and allow the stretching process to be carried out smoothly. On the other hand, the lower limit of the glass transition temperature (Tg) of the first substrate is typically 60°C. This makes it possible to suppress thermal deformation of the first substrate (e.g., the occurrence of unevenness, sagging, and wrinkles). The glass transition temperature (Tg) is measured according to, for example, JIS K 7121.

[0019] The thickness of the first substrate before the stretching process is, for example, 20 μm to 300 μm, preferably 50 μm to 200 μm.

[0020] The surface of the first substrate may be subjected to any appropriate surface treatment (e.g., corona treatment), and an easy-adhesion layer may be formed thereon.

[0021] The coating solution typically contains a solvent and a PVA-based resin. The solvent can dissolve the PVA resin. Examples of solvents include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide N-methylpyrrolidone, glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. Solvents can be used alone or in combination. Among the solvents, water is preferred.

[0022] Any suitable resin can be used for the PVA-based resin. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. The degree of saponification of PVA-based resins is typically 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%, and even more preferably 99.0 mol% to 99.5 mol%. The degree of saponification is measured according to, for example, JIS K 6726-1994.

[0023] The average degree of polymerization of the PVA resin can be appropriately selected depending on the purpose. For example, the average degree of polymerization of the PVA resin is 1000 or more, preferably 1500 or more, more preferably 2000 or more, and even more preferably 3000 or more. On the other hand, the average degree of polymerization of the PVA resin is 10000 or less, preferably 6000 or less, and more preferably 4300 or less. The average degree of polymerization is measured according to, for example, JIS K 6726-1994.

[0024] In one embodiment, the PVA-based resin includes acetoacetyl-modified PVA. The content of acetoacetyl-modified PVA in PVA-based resins is, for example, 5% by mass or more, preferably 8% by mass or more. On the other hand, the content of acetoacetyl-modified PVA in PVA-based resins is, for example, 20% by mass or less, preferably 12% by mass or less. If the PVA-based resin contains acetoacetyl-modified PVA, the mechanical strength of the polarizer can be improved.

[0025] The PVA-based resin content in the coating solution is, for example, 3 to 20 parts by mass per 100 parts by mass of solvent. With such a resin concentration, a uniform coating film that adheres closely to the first substrate can be formed.

[0026] The coating solution preferably further contains a halide. The presence of a halide in the coating solution allows the PVA-based resin layer formed from the coating solution to also contain the halide. Therefore, even when the PVA-based resin layer is immersed in the liquid, disruption of the orientation of PVA molecules and a decrease in orientation can be suppressed. As a result, the optical properties of the polarizer produced in the first preparation step can be improved.

[0027] Examples of halides include iodides and sodium chloride. In one embodiment, the coating solution contains iodide. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide, with potassium iodide being preferred. Halides can be used individually or in combination. The halogen content in the coating solution is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, per 100 parts by mass of PVA resin. On the other hand, the halogen content in the coating solution is, for example, 20 parts by mass or less, preferably 15 parts by mass or less. When the halogen content is within this range, the clouding of the final polarizer can be suppressed.

[0028] The coating solution may further contain any suitable additives. Examples of additives include plasticizers and surfactants.

[0029] Such a coating solution is applied to one side of the first substrate in the thickness direction by any suitable method. This prepares a resin layer support comprising a PVA-based resin layer and the first substrate. Subsequently, the PVA-based resin layer of the resin layer support is dried as needed. The thickness of the PVA-based resin layer before the stretching process is, for example, 3 μm to 40 μm, preferably 5 μm to 30 μm.

[0030] B-1-2. Dyeing process In the dyeing process, the PVA-based resin layer is dyed with a dichroic substance. More specifically, the dyeing solution is brought into contact with the PVA-based resin layer to adsorb the dichroic substance.

[0031] The staining solution contains a dichroic substance. This dichroic substance can form complexes with PVA-based resins. Examples of dichroic substances include iodine and organic dyes, with iodine being preferred. Dichroic substances can be used alone or in combination. The staining solution is typically an iodine aqueous solution. The iodine content in the staining solution is, for example, 0.05 to 3 parts by mass, preferably 0.5 to 3 parts by mass, per 100 parts by mass of water.

[0032] In one embodiment, the staining solution further contains an iodine compound. This can improve the solubility of iodine in water. Examples of iodine compounds include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide, with potassium iodide being preferred. Iodine compounds can be used alone or in combination. The mass ratio of iodine to iodine compound in the dyeing solution (iodine:iodine compound) is, for example, 1:5 to 1:20, preferably 1:5 to 1:10. This can impart excellent optical properties to the polarizer.

[0033] The temperature of the staining bath is, for example, 10°C or higher, preferably 20°C or higher. On the other hand, the temperature of the staining bath is, for example, 50°C or lower, preferably 40°C or lower. The time required for the dyeing process (dyeing time) is, for example, 5 seconds or more, preferably 30 seconds or more. On the other hand, the dyeing time is, for example, 300 seconds or less, preferably 90 seconds or less, and more preferably 60 seconds or less.

[0034] In one embodiment, the resin layer support is immersed in a dyeing solution. However, the method of adsorbing the dichroic substance in the dyeing process is not limited to the immersion described above. For example, the dyeing solution may be coated onto the PVA-based resin layer, or the dyeing solution may be sprayed onto the PVA-based resin layer. As a result, the PVA-based resin layer of the resin support is stained with a dichroic substance.

[0035] B-1-3. Stretching process In the stretching process, the resin layer support is stretched. The stretching process may be carried out in one step or in two or more steps. The stretching ratio in the stretching process is arbitrarily and appropriately adjusted according to the application of the polarizer. For example, the stretching ratio in the stretching process is 3.0 to 8.0 times, or 4.0 to 7 times, or 5.0 to 6.5 times. If the stretching process is carried out in multiple stages, the stretching ratio in the stretching process is the product of the stretching ratios at each stage.

[0036] The stretching process typically includes a water stretching process that is carried out after the dyeing process. In the underwater stretching process, the resin layer support, which includes a dyed PVA-based resin layer, is stretched in a stretching bath (stretching solution) in a predetermined direction.

[0037] The stretching solution is typically an aqueous solution of boric acid. The boric acid content in the stretching solution is, for example, 1 part by mass or more, preferably 3 parts by mass or more, per 100 parts by mass of water. On the other hand, the boric acid content in the stretching solution is, for example, 10 parts by mass or less, preferably 8 parts by mass or less, per 100 parts by mass of water.

[0038] In one embodiment, the stretching solution further contains the iodine compound described above. The presence of an iodine compound in the stretching solution can suppress the elution of iodine adsorbed onto the PVA-based resin layer. The iodine compound content in the stretching solution is, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, per 100 parts by mass of water. On the other hand, the iodine compound content in the stretching solution is, for example, 10 parts by mass or less, preferably 6 parts by mass or less, per 100 parts by mass of water. The mass ratio of boric acid to iodine compound (boric acid:iodine compound) in the stretching solution is, for example, 1:0.5 to 1:1.2, and preferably 1:0.6 to 1:1.

[0039] The temperature of the stretching bath is, for example, 40°C or higher, preferably 60°C or higher. On the other hand, the temperature of the stretching bath is, for example, 85°C or lower, preferably 80°C or lower. The duration of the underwater stretching process is, for example, 15 to 300 seconds.

[0040] In one embodiment, the stretching process includes an air stretching process performed before the dyeing process, in addition to the underwater stretching process. In the air stretching process, the resin layer support, which has a PVA-based resin layer before dyeing, is stretched in a predetermined direction. If the stretching process includes an air stretching process, the orientation of PVA molecules in the PVA resin layer can be improved before the dyeing process. Therefore, a decrease in the orientation of PVA molecules and dissolution of PVA can be suppressed during the dyeing process and / or the water stretching process, thereby improving the optical properties of the polarizer.

[0041] The stretching temperature in the air stretching process is typically above the glass transition temperature (Tg) of the PVA resin. The stretching temperature in the air stretching process is, for example, 95°C to 150°C, preferably 120°C to 140°C. The stretching ratio in the air stretching process is, for example, 2.1 times or more, preferably 2.3 times or more. On the other hand, the upper limit of the stretching ratio in the air stretching process is typically 4 times. This can improve the orientation of the PVA resin and suppress the dissolution of the PVA resin layer in the dyeing solution. If the stretching process includes both an underwater stretching process and an air stretching process, the stretching ratio in the underwater stretching process is, for example, 1.5 to 4.0 times, preferably 1.5 to 3 times.

[0042] B-1-4. Drying shrinkage process In one embodiment, the first preparation step further includes a drying shrinkage step. In the drying shrinkage process, typically, the resin layer support following the underwater stretching process is heated while being transported in the longitudinal direction.

[0043] The drying shrinkage process is carried out by any suitable heating and drying apparatus. The heating and drying apparatus may be a zone heating system in which the entire interior of the apparatus is heated, or a heated roll drying system in which the conveying rolls are heated. Preferably, the heating and drying apparatus performs both.

[0044] The internal temperature of the heating and drying apparatus is, for example, 70°C or higher, preferably 80°C or higher. On the other hand, the internal temperature of the heating and drying apparatus is, for example, 120°C or lower, preferably 100°C or lower. The surface temperature of the heating roll is, for example, 60°C or higher, preferably 70°C or higher. On the other hand, the surface temperature of the heating roll is, for example, 100°C or lower, preferably 80°C or lower. By drying using a heated roll, the heat curl of the resin layer support can be efficiently suppressed, enabling the efficient production of polarizers with superior appearance. Furthermore, during the drying shrinkage process, the resin layer support shrinks in the width direction perpendicular to the length direction by contact with the heated roll. The shrinkage rate in the width direction of the resin layer support during the drying shrinkage process is, for example, 2% or more, preferably 4% or more. When the resin layer support shrinks in this manner during the drying shrinkage process, the orientation of PVA and PVA / dichroic substance complex (iodine complex) can be improved, and the optical properties of the polarizer can be further improved. On the other hand, the shrinkage rate in the width direction of the resin layer support is, for example, 10% or less, preferably 8% or less, and more preferably 6% or less. By adjusting the shrinkage rate in the width direction in this way, it is possible to suppress the occurrence of appearance defects such as wrinkles in the polarizer.

[0045] B-1-5. Immobilization process, crosslinking process The first preparation step may further include an immobilization step and / or a crosslinking step. The immobilization step is typically performed before the dyeing step. In one embodiment, the immobilization step is performed after the air stretching step and before the dyeing step. In the immobilization process, the resin layer support is typically immersed in an aqueous boric acid solution, which serves as the immobilization solution. The boric acid content in the immobilization solution is, for example, 1 to 10 parts by mass per 100 parts by mass of water. The temperature of the insolubilizing solution is, for example, 10°C or higher, preferably 20°C or higher. On the other hand, the temperature of the insolubilizing solution is, for example, 60°C or lower, preferably 50°C or lower. The duration of the immobilization process is, for example, 10 seconds or more, preferably 20 seconds or more. On the other hand, the duration of the immobilization process is, for example, 200 seconds or less, preferably 60 seconds or less.

[0046] The crosslinking process is typically performed after the dyeing process. In one embodiment, the crosslinking process is performed after the dyeing process and before the underwater stretching process. In the crosslinking process, typically, the PVA resin layer is brought into contact with an aqueous boric acid solution, which serves as the crosslinking solution. When the PVA resin layer is brought into contact with the aqueous boric acid solution, the boric acid can bond with the PVA resin to form crosslinks. Examples of crosslinking include crosslinking by the formation of tetrahydroxyborate anions in the aqueous solution, which then form hydrogen bonds with the PVA resin, and crosslinking by the dehydration condensation of boric acid with the hydroxyl groups of the PVA resin to form boric acid esters. This can suppress the elution of the PVA resin and dichroic substances (preferably iodine). The range of boric acid content in the crosslinking solution is similar to, for example, the range of boric acid content in the insolubilization solution. In one embodiment, the crosslinking solution further contains the iodine compound described above. When the crosslinking solution contains the iodine compound, the elution of iodine adsorbed on the PVA resin can be stably suppressed. The content of the iodine compound in the crosslinking solution is, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, per 100 parts by mass of water. On the other hand, the content of the iodine compound in the crosslinking solution is, for example, 8 parts by mass or less, preferably 5 parts by mass or less, per 100 parts by mass of water. The mass ratio of the iodine compound to boric acid in the crosslinking solution (iodine compound:boric acid) is, for example, 1:1 to 1:3, and preferably 1:1.5 to 1:2. The temperature of the crosslinking bath is, for example, 20°C or higher, preferably 30°C or higher. On the other hand, the temperature of the crosslinking bath is, for example, 60°C or lower, preferably 50°C or lower. The duration of the crosslinking process is, for example, 5 seconds or more, preferably 10 seconds or more. On the other hand, the duration of the crosslinking process is, for example, 200 seconds or less, preferably 60 seconds or less.

[0047] B-1-6. Details of the first layer The first laminate 1 is thus prepared. As shown in Figure 1, the first laminate 1 comprises a first substrate 11 and a polarizer 12.

[0048] The first substrate 11 is detachable from the polarizer 12 (see Figure 2). In one embodiment, the first substrate 11 is a stretched film stretched together with the PVA resin layer in the stretching process described above. When the first substrate is a stretched film, it is possible to suppress shrinkage of the first substrate in the direction perpendicular to the stretching direction (TD direction) during the first lamination process. Therefore, it is possible to stably suppress the occurrence of interference unevenness in the optical laminate.

[0049] The thickness of the first substrate 11 is, for example, 10 μm to 60 μm, preferably 20 μm to 50 μm, and more preferably 20 μm to 40 μm.

[0050] The thickness of the polarizer 12 is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, and even more preferably 3 μm to 7 μm. Having the polarizer thickness within this range allows for a thinner optical laminate.

[0051] Polarizer 12 typically exhibits absorption dichroism at wavelengths between 380 nm and 780 nm. The transmittance of the polarizer 12 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of the polarizer 12 is, for example, 50.0% or more, preferably 60.0% or more, more preferably 90.0% or more, even more preferably 97.0% or more, and particularly preferably 99.0% or more.

[0052] The average refractive index of the polarizer 12 at a wavelength of 550 nm is, for example, 1.40 to 1.65, preferably 1.45 to 1.60, and more preferably 1.50 to 1.60.

[0053] The polarizer 12 of the first laminate 1 has, in the thickness direction, a first surface 12a opposite to the first substrate 11 and a second surface 12b on the side of the first substrate 11. In the first laminate 1, the first surface 12a of the polarizer 12 is an air surface and is exposed.

[0054] In the first laminate 1, the second surface 12b of the polarizer 12 is smoother than the first surface 12a of the polarizer 12. The smoothness of the surface of the polarizer 12 can be evaluated, for example, by measuring the number of reflection defects per unit area. The smaller the number of reflection defects per unit area, the better the smoothness. The number of reflection defects per unit area on the second surface 12b of the polarizer 12 is smaller than the number of reflection defects per unit area on the first surface 12a of the polarizer 12. The number of reflection defects per unit area on the second surface 12b of the polarizer 12 is, for example, 2 per m 2 or less, preferably 1 per m 2 or less, more preferably 0 per m 2 or less. The number of reflection defects per unit area on the first surface 12a of the polarizer 12 is, for example, 3 per m 2 or more. On the other hand, the number of reflection defects per unit area on the first surface 12a of the polarizer 12 is, for example, 20 per m 2 or less, preferably 10 per m 2 or less, more preferably 5 per m 2 or less. Incidentally, the number of reflection defects per unit area is measured, for example, by visually evaluating the polarizer by reflection (polar angle 50°, azimuth angle one full turn, distance between the polarizer and the light source is 30 cm, distance between the polarizer and the evaluator is 30 cm) and counting the reflection defects having anisotropy depending on the azimuth angle. At this time, for reflection defects with extremely weak visibility, an acrylic adhesive may be laminated on the surface, and only those that are still visible may be counted.

[0055] B-2. Second Preparation Step In the second preparation step, a second laminate 2 including a retardation layer 22 and a second base material 21 is prepared. The retardation layer 22 may have in-plane retardation or retardation in the thickness direction, and preferably has in-plane retardation. The refractive index of the retardation layer 22 shows a relationship of, for example, nx > ny = nz. Note that "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where they are substantially equal. Therefore, within a range that does not impair the effects of the present invention, ny > nz or ny < nz may occur. The in-plane retardation Re(550) of the retardation layer 22 is, for example, 100 nm to 300 nm. The Nz coefficient of the retardation layer 22 is, for example, 0.9 to 1.5, preferably 0.9 to 1.3. The retardation layer 22 may function as a λ / 2 plate, or may function as a λ / 3 plate, λ / 4 plate, λ / 5 plate, or C-Plate. In the illustrated example, the retardation layer 22 functions as a λ / 4 plate. When the retardation layer 22 functions as a λ / 4 plate, the in-plane retardation Re(550) of the retardation layer 22 is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm. The thickness of the retardation layer 22 is arbitrarily and appropriately adjusted so as to obtain a desired in-plane retardation.

[0056] The retardation layer 22 has any suitable configuration including a liquid crystal alignment cured layer. The retardation layer 22 may have a single-layer structure composed of a liquid crystal alignment cured layer, or may have a laminated structure including other layers in addition to the liquid crystal alignment cured layer. In the embodiment shown in FIG. 1, the retardation layer 22 has a single-layer structure composed of a liquid crystal alignment cured layer 23. Hereinafter, in items B-2-1 to B-2-4, after explaining the case where the retardation layer 22 has a single-layer structure, in item B-2-5, the case where the retardation layer 22 has a laminated structure will be explained.

[0057] B-2-1. Second Substrate In one embodiment, in the second preparation step, first, the second substrate 21 is prepared. The second substrate 21 is configured to support the retardation layer 22. The second substrate 21 has any suitable configuration. The second substrate 21 typically contains a resin material. Examples of resin materials include polyester resins such as polyethylene terephthalate (PET); polyolefin resins such as polyethylene and polypropylene; cycloolefin (COP) resins such as polynorbornene; cellulose resins such as triacetylcellulose (TAC); polycarbonate (PC) resins; and (meth)acrylic resins. Note that "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins. Resin materials can be used alone or in combination. Among the resin materials, polyester resins and cellulose resins are preferred.

[0058] In one embodiment, the second substrate 21 is a coating substrate for the liquid crystal alignment solidification layer 23. One surface of the second substrate 21 in the thickness direction is subjected to an alignment treatment. The alignment-treated surface of the second substrate 21 is configured to align the liquid crystal compound, which will be described later. Orientation treatments include, for example, mechanical orientation treatments, physical orientation treatments, and chemical orientation treatments.

[0059] B-2-2. Liquid crystal composition Next, the liquid crystal composition is coated onto the second substrate 21. The liquid crystal composition typically contains an organic solvent and a rod-shaped liquid crystal compound.

[0060] Organic solvents can dissolve liquid crystal compounds. Examples of organic solvents include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenols such as phenol and parachlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, and N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; ether solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; and ethyl cellsolve and butyl cellsolve. Solvents can be used alone or in combination. Among the solvents, toluene and butyl acetate are preferred.

[0061] Examples of liquid crystal compounds include liquid crystal compounds in which the liquid crystal phase is a nematic phase (nematic liquid crystals). Examples of such liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. Liquid crystal polymers and liquid crystal monomers may be used individually or in combination. The mechanism by which liquid crystalline properties are expressed in liquid crystal compounds may be lyotropic or thermotropic.

[0062] When a liquid crystal compound contains a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinkable monomer. The orientation of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer.

[0063] Any suitable liquid crystal monomer can be used. Examples of liquid crystal monomers include polymerizable mesogenic compounds described in Japanese Patent Publication No. 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Specific examples of such polymerizable mesogenic compounds include BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767.

[0064] When the liquid crystal compound is a polymerizable monomer, the liquid crystal composition preferably further comprises a photopolymerization initiator (photoradical generator). The photopolymerization initiator is optionally and appropriately selected depending on the type of liquid crystal monomer. Examples of photopolymerization initiators include photocation generators and photoanion generators. The content ratio of the photopolymerization initiator is, for example, 0.01 to 10 parts by mass per 100 parts by mass of liquid crystal monomer.

[0065] The liquid crystal composition may further contain any suitable additives as needed. Examples of additives include sensitizers, surfactants, and leveling agents. The solid content concentration in the liquid crystal composition is, for example, 5% to 60% by mass.

[0066] B-2-3. Details of the method for forming the liquid crystal alignment solidification layer In one embodiment, the above-described liquid crystal composition is coated onto the orientation-treated surface of the second substrate 21 by any suitable coating method (typically a bar coater). This causes the rod-shaped liquid crystal compounds to be aligned in a predetermined direction (homogenous orientation).

[0067] Subsequently, the liquid crystal composition coating film formed on the second substrate 21 is heated, and then irradiated with ultraviolet light as necessary. The heating temperature is, for example, 60°C to 150°C, preferably 90°C to 110°C. The heating time is, for example, 30 to 180 seconds, preferably 60 to 120 seconds. As a result, the liquid crystal compound solidifies (hardens) in an oriented state, forming a liquid crystal oriented solidified layer 23 on the second substrate 21 (see Figure 2). More specifically, when a liquid crystal compound contains polymerizable liquid crystal monomers, their orientation is fixed by polymerization or crosslinking of the liquid crystal monomers. Here, polymerization forms a polymer, and crosslinking forms a three-dimensional network structure, but these are non-liquid crystal. Therefore, the formed liquid crystal orientation solidified layer does not undergo transitions to liquid crystal phase, glass phase, or crystalline phase due to temperature changes, which is characteristic of liquid crystal compounds. As a result, the liquid crystal orientation solidified layer can have extremely excellent stability that is unaffected by temperature changes. Specific examples of liquid crystal compounds and details of the method for forming the orientation solidification layer are described in Japanese Patent Publication No. 2006-163343. The description in said publication is incorporated herein by reference.

[0068] B-2-4. Details of the second layer The second layer 2 is thus prepared. As shown in Figure 2, in one embodiment, the second laminate 2 comprises a second substrate 21 and a liquid crystal alignment solidification layer 23.

[0069] The second substrate 21 is peelable from the liquid crystal alignment solidification layer 23. The thickness of the second substrate 21 is, for example, 5 μm to 100 μm, preferably 20 μm to 80 μm.

[0070] The liquid crystal alignment solidification layer 23 may function as a λ / 2 plate, or as a λ / 3 plate, λ / 4 plate, λ / 5 plate, or C-Plate. In the illustrated example, the liquid crystal alignment solidification layer 23 functions as a λ / 4 plate.

[0071] The thickness of the liquid crystal alignment solidification layer 23 is, for example, 5 μm or less, preferably 3 μm or less, and more preferably 2 μm or less. On the other hand, the lower limit of the thickness of the liquid crystal alignment solidification layer 23 is typically 0.5 μm.

[0072] The average refractive index of the liquid crystal alignment solidification layer 23 at a wavelength of 550 nm is, for example, 1.45 to 1.65, preferably 1.50 to 1.65, and more preferably 1.55 to 1.65.

[0073] B-2-5. Modified example of the second layer As shown in Figure 4, in another embodiment, the phase difference layer 22 may have a laminated structure that includes other layers in addition to the liquid crystal alignment solidification layer. Examples of other layers include a stretched polymer film and an alignment solidification layer of another liquid crystal compound. In one embodiment, the phase difference layer 22 comprises a first liquid crystal alignment solidification layer 24 and a second liquid crystal alignment solidification layer 25.

[0074] The second laminate 2, which includes a phase difference layer 22 having such a laminated structure, is prepared by any suitable method. As shown in Figure 5, in one embodiment, a first liquid crystal alignment solidification layer 24 (first liquid crystal alignment solidification layer 24) is formed on the second substrate 21. The first liquid crystal alignment solidification layer 24 will be described in the same manner as the liquid crystal alignment solidification layer 23 described above. Therefore, the description of the first liquid crystal alignment solidification layer 24 will be omitted.

[0075] Furthermore, a second liquid crystal alignment solidification layer 25 is formed on the third substrate 27. The third substrate 27 will be described in the same manner as the second substrate 21 described above. Therefore, the description of the third substrate 27 will be omitted. The second liquid crystal alignment solidification layer 25 is described in the same manner as the liquid crystal alignment solidification layer 23 described above. Therefore, the description of the second liquid crystal alignment solidification layer 25 will be omitted as appropriate. In the illustrated example, the second liquid crystal alignment solidification layer 25 functions as a λ / 2 plate. In other words, in one embodiment, the first liquid crystal alignment solidification layer 24 functions as a λ / 4 plate, and the second liquid crystal alignment solidification layer 25 functions as a λ / 2 plate. With such a configuration, the wavelength dispersion characteristics of the manufactured optical laminate can be brought closer to ideal inverse wavelength dispersion characteristics. Therefore, the optical laminate can be given excellent anti-reflective properties. Furthermore, the second liquid crystal alignment solidification layer 25 may function as a λ / 4 plate, and the first liquid crystal alignment solidification layer 24 may function as a λ / 2 plate.

[0076] Next, as shown in Figure 4, the first liquid crystal alignment solidification layer 24 on the second substrate 21 and the second liquid crystal alignment solidification layer 25 on the third substrate 27 are bonded together. More specifically, the first liquid crystal alignment solidification layer 24 and the second liquid crystal alignment solidification layer 25 are bonded together via an adhesive layer 26.

[0077] The adhesive layer 26 may be an adhesive layer or a tack layer. In one embodiment, the adhesive layer 26 is an adhesive layer. The adhesive layer 26 is typically composed of a curing adhesive.

[0078] Curing adhesives typically contain a curing component and a polymerization initiator. Each of the curing component and polymerization initiator is selected arbitrarily and appropriately depending on the type of curing adhesive. Examples of curing adhesives include thermosetting adhesives, moisture-curing adhesives, and active energy ray-curing adhesives, with active energy ray-curing adhesives being preferred. Specific examples of active energy ray-curing adhesives include visible light-curing adhesives, electron beam-curing adhesives, and ultraviolet-curing adhesives. These curing adhesives can be used individually or in combination.

[0079] In one embodiment, the curable adhesive includes an active energy ray curable adhesive. Active energy ray curing adhesives typically contain a radical polymerizable compound as a curing component and a radical generator as a polymerization initiator. The types, combinations, and proportions of radical polymerizable compounds and radical generators can be adjusted arbitrarily and appropriately.

[0080] Radical polymerizable compounds typically contain monofunctional and polyfunctional components. Typical monofunctional components include higher alkyl esters of (meth)acrylic acid and their modified forms. Specific examples of monofunctional components include isostearyl acrylate, lauryl acrylate, acryloyl morpholine, and unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone. When radical polymerizable compounds contain such monofunctional components, the curing shrinkage rate of curable adhesives can be reduced. Typical examples of polyfunctional components include monomers and / or oligomers having two or more functional groups such as (meth)acrylate groups and (meth)acrylamide groups. Specific examples of polyfunctional components include polyethylene glycol diacrylate, trimethylpropane triacrylate, and glycerin triacrylate. Specific examples of radical polymerizable compounds other than those listed above include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecanedimethanol diacrylate, phenoxydiethylene glycol acrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO-modified diglycerin tetraacrylate, γ-butyrolactone acrylate, N-methylpyrrolidone, hydroxyethyl acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, 9-vinylcarbazole, 4-vinylphenylboronic acid, and fluorene-based acrylates.

[0081] In one embodiment, the radical polymerizable compound has a ring structure. Examples of radical polymerizable compounds having a ring structure include acryloylmorpholine, γ-butyrolactone acrylate, unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone, N-methylpyrrolidone, 9-vinylcarbazole, and fluorene-based acrylates. The radical polymerizable compound preferably includes acryloylmorpholine, unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone, and a fluorene-based acrylate. If the radical polymerizable compound has a ring structure, the free volume of the radical polymerizable compound can be reduced (the density can be increased), and the curing shrinkage rate of the curable adhesive can be further reduced. These radical polymerizable compounds can be used individually or in combination.

[0082] The content of radical polymerizable compounds in the active energy ray curing adhesive is, for example, 80% to 99% by mass, preferably 85% to 95% by mass. Among the radical polymerizable compounds, the proportion of radical polymerizable compounds having a ring structure is, for example, 80% to 100% by mass, preferably 90% to 100% by mass.

[0083] Examples of radical generators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, and diethylthioxanthone. Radical generators can be used alone or in combination. The content ratio of the radical generator is, for example, 1.0 to 10.0 parts by mass, preferably 3.0 to 8.0 parts by mass, per 100 parts by mass of the radical polymerizable compound.

[0084] The active energy ray-curable adhesive may optionally further contain an acrylic polymer. The molecular weight of the acrylic polymer can be appropriately set depending on the purpose. If the active energy ray-curable adhesive contains an acrylic polymer that does not form further bonds, the curing shrinkage rate of the curable adhesive can be further reduced. The content of the acrylic polymer is, for example, 1.0 to 10.0 parts by mass, preferably 3.0 to 8.0 parts by mass, per 100 parts by mass of the radical polymerizable compound.

[0085] The active energy ray curing adhesive may further contain, if necessary, cationic polymerizable compounds, plasticizers (e.g., oligomeric components), crosslinking agents, diluents, etc. Commercially available products may be used for each of the above components. Details of the active energy ray curing adhesive are described, for example, in Japanese Patent Publication No. 2018-017996. The description in said publication is incorporated herein by reference.

[0086] To bond the first liquid crystal alignment solidification layer 24 and the second liquid crystal alignment solidification layer 25 using a curable adhesive, the curable adhesive is applied to at least one of the first liquid crystal alignment solidification layer 24 and the second liquid crystal alignment solidification layer 25, and then the curable adhesive is cured while the first liquid crystal alignment solidification layer 24 and the second liquid crystal alignment solidification layer 25 are in contact with the coating. This forms an adhesive layer 26 composed of the cured product of the curable adhesive. The thickness of the adhesive layer 26 is, for example, 1 μm to 10 μm.

[0087] As described above, a second laminate 2 is prepared, comprising the third substrate 27, the second liquid crystal alignment solidification layer 25, the adhesive layer 26, the first liquid crystal alignment solidification layer 24, and the second substrate 21 in this order. Subsequently, if necessary, the third substrate 27 is peeled off from the second liquid crystal alignment solidification layer 25.

[0088] B-3. ​​First lamination process As shown in Figure 6, in the first bonding step, the first laminate 1 prepared in the first preparation step and the second laminate 2 prepared in the second preparation step are bonded together. More specifically, the polarizer 12 of the first laminate 1 and the phase difference layer 22 of the second laminate 2 are bonded together via an adhesive layer 4. Typically, the adhesive layer 4 is in contact with the first surface 12a of the polarizer 12 and the surface of the phase difference layer 22 opposite to the second substrate 21. In the embodiment shown in Figure 2, the adhesive layer 4 is in contact with the liquid crystal alignment solidification layer 23, bonding the polarizer 12 and the liquid crystal alignment solidification layer 23 together. Furthermore, in the embodiment shown in Figure 6, the adhesive layer 4 is in contact with the second liquid crystal alignment solidification layer 25, bonding the polarizer 12 and the second liquid crystal alignment solidification layer 25 together.

[0089] The adhesive layer 4 is typically composed of a curing adhesive. Examples of curable adhesives that constitute the adhesive layer 4 include those similar to the curable adhesive that constitutes the adhesive layer 26 described above.

[0090] To bond the polarizer 12 and the phase difference layer 22, a curable adhesive is applied to at least one of the first surface 12a of the polarizer 12 and the surface of the phase difference layer 22, and then the curable adhesive is cured while the polarizer 12 and the phase difference layer 22 are in contact with the coating. This forms an adhesive layer 4 composed of the cured product of the curable adhesive. The thickness of the adhesive layer 4 is, for example, 1 μm to 10 μm.

[0091] As described above, a first intermediate laminate 7 is prepared, comprising the first substrate 11, the polarizer 12, the adhesive layer 4, the phase difference layer 22, and the second substrate 21 in this order. When the phase difference layer 22 comprises a first liquid crystal alignment solidification layer 24 and a second liquid crystal alignment solidification layer 25 (see Figure 5), the angle between the absorption axis direction of the polarizer 12 and the slow phase axis direction of the first liquid crystal alignment solidification layer 24 is, for example, 70° to 80°, preferably 72° to 78°, and more preferably 74° to 76°. Also, the angle between the absorption axis direction of the polarizer 12 and the slow phase axis direction of the second liquid crystal alignment solidification layer 25 is, for example, 10° to 20°, preferably 12° to 18°, and more preferably 14° to 16°. With this configuration, the wavelength dispersion characteristics of the manufactured optical laminate can be brought closer to ideal inverse wavelength dispersion characteristics. Therefore, excellent anti-reflective properties can be stably imparted to the optical laminate. Furthermore, the range of angles between the absorption axis direction of the polarizer and the slow axis direction of the first liquid crystal alignment solidification layer may be reversed from the range of angles between the absorption axis direction of the polarizer and the slow axis direction of the second liquid crystal alignment solidification layer.

[0092] B-4. First peeling process and second peeling process Next, a first peeling process and a second peeling process are carried out. The first peeling process may be carried out before the second peeling process or after the second peeling process. In one embodiment, the first peeling step is performed before the second peeling step. In other words, the first substrate 11 is peeled from the second surface 12b of the polarizer 12 before the second substrate 21 is peeled from the phase difference layer 22. In the case of a laminate having peelable substrates on both sides in the thickness direction, when peeling off one substrate, a defect may occur in which the other substrate lifts locally. That is, when peeling off the first substrate 11 from the first laminate 1, the optical laminate 100 may have a defect in appearance at the location where the second substrate 21 lifts locally. Also, when peeling off the first substrate 11 from the first laminate 1, the phase difference layer 22 and polarizer 12 may break at the location where the second substrate 21 lifts locally, and a defect may occur in which the second substrate 21 peels off from the first laminate 1 instead of the first substrate 11. To suppress such defects, the peeling angle can be adjusted to further reduce the peeling force of the first substrate 11 from the first laminate 1. Preferably, when peeling off the first substrate 11 from the first laminate 1, the polarizer 12 is transported at an acute angle to the first laminate 1 and the first substrate 11 is transported at an obtuse angle. More preferably, the transport direction of the polarizer 12 after the first substrate 11 has been peeled off is opposed to the transport direction of the first laminate 1. Even more preferably, the first substrate 11 after peeling off is transported in an extended position without changing its angle relative to the transport direction of the first laminate 1. Even more preferably, the transport tension of the polarizer 12 after the first substrate 11 has been peeled off is increased relative to the first substrate 11 after peeling off. In addition, after peeling off the first substrate 11, the peeling of the second substrate 21 may be performed without including a winding step.

[0093] B-5.Protection process As shown in Figure 7, the protection process is typically performed after the first peeling process and before the second peeling process. In other words, the protection process is performed on the first intermediate laminate 7 from which the first substrate 11 has been peeled off (i.e., the first intermediate laminate 7 comprising the polarizer 12, adhesive layer 4, phase difference layer 22, and second substrate 21 in that order).

[0094] In one embodiment, during the protection step, a resin film is attached to the second surface 12b of the polarizer 12 to form a protective layer 13. The protective layer 13 contains any suitable transparent resin. Examples of transparent resins include cycloolefin (COP) resins such as polynorbornene-based resins; polyester resins such as polyethylene terephthalate (PET)-based resins; cellulose resins such as triacetylcellulose (TAC); polycarbonate (PC) resins; (meth)acrylic resins; polyvinyl alcohol-based resins; polyamide resins; polyimide resins; polyethersulfone resins; polysulfone resins; polystyrene resins; polyolefin resins; and acetate resins. Thermosetting resins or UV-curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone resins can also be used. In addition, glassy polymers such as siloxane polymers can also be used. Polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As a material for the protective layer, for example, a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in its side chains, and a thermoplastic resin having substituted or unsubstituted phenyl groups and nitrile groups in its side chains can be used. Examples include a resin composition having an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above resin composition. The protective layer materials can be used individually or in combination.

[0095] The thickness of the protective layer 13 is, for example, 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm.

[0096] Furthermore, a surface treatment layer may be provided on the surface of the protective layer 13 as needed. Examples of surface treatment layers include a hard coat layer, an anti-reflective layer, an anti-sticking layer, and an anti-glare treatment layer. Preferably, the surface treatment layer is provided on the surface of the protective layer 13 opposite to the polarizer 12.

[0097] Such a protective layer 13 is attached to the second surface 12b of the polarizer 12 with any suitable adhesive. Examples of adhesives include the curing adhesives described above.

[0098] B-6.Adhesive layer formation process In one embodiment, the adhesive layer formation step is performed after the second peeling step and after the protection step. That is, the adhesive layer formation step is performed after the second substrate 21 has been peeled off from the phase difference layer 22 and the protective layer 13 has been attached to the polarizer 12.

[0099] In the adhesive layer formation process, an appropriate adhesive is applied to the surface of the phase difference layer 22 opposite to the polarizer 12 to form the adhesive layer 5. Examples of adhesives include (meth)acrylic adhesives, urethane adhesives, and silicone adhesives. The adhesives can be used alone or in combination. Among the adhesives, (meth)acrylic adhesives are preferred.

[0100] The thickness of the adhesive layer 5 is, for example, 3 μm or more, preferably 5 μm or more, and preferably 10 μm or more. On the other hand, the thickness of the adhesive layer 5 is, for example, 50 μm or less, and preferably 30 μm or less.

[0101] B-7. Temporary Attachment Process As described above, the temporary bonding process is carried out after the adhesive layer formation process. In the temporary bonding process, the release liner 6 is temporarily bonded to the surface of the adhesive layer 5 opposite to the phase difference layer 22. The peel-off liner 6 contains any suitable resin material. Examples of the resin material include the resin material contained in the first substrate 11, and preferably polyethylene terephthalate (PET), polyethylene, and polypropylene. Resin materials can be used alone or in combination.

[0102] In one embodiment, a release treatment layer is provided on the contact surface of the release liner 6 with the adhesive layer 5. The release layer typically contains a release agent. Examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents, with silicone-based release agents being preferred, and vinyl group-containing addition-type silicones being even more preferred. Release agents can be used alone or in combination. The thickness of the release layer is, for example, 50 nm to 400 nm.

[0103] As described above, an optical laminate 100 comprising a polarizer 12 and a phase difference layer 22 is manufactured. The phase difference layer 22 is located on one side in the thickness direction of the polarizer 12. As described above, the phase difference layer 22 of the optical laminate 100 shown in Figure 3 has a single-layer structure consisting of a liquid crystal alignment solidification layer 23. As described above, the phase difference layer 22 of the optical laminate 100 shown in Figure 7 has a laminated structure including a first liquid crystal alignment solidification layer 24 and a second liquid crystal alignment solidification layer 25. In the illustrated example, the phase difference layer 22 comprises the first liquid crystal alignment solidification layer 24, the adhesive layer 26, and the second liquid crystal alignment solidification layer 25 in this order.

[0104] C. Another Embodiment As shown in Figures 5 to 7, in the above-described embodiment, in the second preparation step, a second laminate 2 comprising a phase difference layer 22 including a first liquid crystal alignment solidification layer 24 and a second liquid crystal alignment solidification layer 25 is prepared, and an optical laminate 100 having a phase difference layer 22 with a laminated structure is manufactured. The method for manufacturing the optical laminate 100, which includes a phase difference layer 22 having a layered structure, is not limited thereto. As shown in Figures 8 and 9, in one embodiment, the method for manufacturing an optical laminate further includes a third preparation step, a second bonding step, and a third peeling step. In this embodiment, typically, in the second preparation step, a second laminate 2 is prepared which includes a phase difference layer 22 having a single-layer structure consisting of a liquid crystal alignment solidification layer 23 (see Figure 2). In the following, the liquid crystal alignment solidification layer 23 of the laminate 2 may be referred to as the first liquid crystal alignment solidification layer 23 for convenience. In this embodiment, the first liquid crystal alignment solidification layer 23 preferably functions as a λ / 2 plate.

[0105] C-1.Third preparation process As shown in Figure 8, the third preparation step involves preparing the third laminate 3. The third laminate 3 comprises a third substrate 27 and a second liquid crystal alignment solidification layer 25. The second liquid crystal alignment solidification layer 25 is located on the third substrate 27. In the third preparation step, typically, the second liquid crystal alignment solidification layer 25 is formed on the third substrate 31 in the same manner as described in "B-2-5. Modified Examples of the Second Laminate" above. In this embodiment, the second liquid crystal alignment solidification layer 25 preferably functions as a λ / 4 plate.

[0106] C-2.Second lamination process As shown in Figure 9, the second bonding step is performed after the first bonding step described above and after the second peeling step described above. In other words, it is performed on the first intermediate laminate 7 (see Figure 2) from which the second substrate 21 has been peeled off. In the second bonding step, the first liquid crystal alignment solidification layer 23 of the first intermediate laminate 7 and the second liquid crystal alignment solidification layer 25 of the third laminate 3 are bonded together. More specifically, the first liquid crystal alignment solidification layer 24 and the second liquid crystal alignment solidification layer 25 are bonded together via the adhesive layer 26 described above.

[0107] In the illustrated example, a second intermediate laminate 8 is prepared by a second bonding step, comprising a first substrate 11, a polarizer 12, an adhesive layer 4, a first liquid crystal alignment solidification layer 23, an adhesive layer 26, a second liquid crystal alignment solidification layer 25, and a third substrate 27 in that order. In the second intermediate laminate 8, the angle between the absorption axis direction of the polarizer 12 and the slow phase axis direction of the first liquid crystal alignment solidification layer 23 is, for example, 10° to 20°, preferably 12° to 18°, and more preferably 14° to 16°. The angle between the absorption axis direction of the polarizer 12 and the slow phase axis direction of the second liquid crystal alignment solidification layer 25 is, for example, 70° to 80°, preferably 72° to 78°, and more preferably 74° to 76°.

[0108] In this embodiment, the first peeling step described above is performed after the second bonding step, and preferably before the third peeling step. That is, in one embodiment, after the second bonding step and before the third peeling step, the first substrate 11 of the second intermediate laminate 8 is peeled off from the polarizer 12. Thereafter, the protection step described above is performed as necessary.

[0109] C-3. Third peeling process The third peeling step is performed after the second bonding step described above. In the third peeling step, the third substrate 27 is peeled off from the second liquid crystal alignment solidification layer 25. Thereafter, the adhesive layer formation step and temporary bonding step described above are performed as needed.

[0110] This also makes it possible to manufacture an optical laminate 100 having a phase difference layer 22 having a laminated structure. However, the method for manufacturing an optical laminate described in sections A and B above can stably manufacture an optical laminate with suppressed optical defects more effectively than the method for manufacturing an optical laminate described in section C.

[0111] D. Optical Laminates As shown in Figure 7, according to the manufacturing method of the optical laminate described in sections A to C above, an optical laminate 100 comprising a polarizer 12 and a phase difference layer 22 can be smoothly manufactured. In such an optical laminate 100, the first surface 12a of the polarizer 12 is located on the phase difference layer 22 side, and the second surface 12b of the polarizer 12 is located on the opposite side of the phase difference layer 22 from the first surface 12a. In the optical laminate 100 as well, the second surface 12b of the polarizer 12 is smoother than the first surface 12a of the polarizer 12, as described above. Therefore, by applying the optical laminate 100 to an image display device such that the first surface 12a of the polarizer 12 faces the viewing side, the occurrence of optical defects (typically reflection defects) in the image display device can be suppressed.

[0112] Furthermore, the refractive index of the phase difference layer 22 in the transmission axis direction of the polarizer (hereinafter sometimes simply referred to as the transmission axis direction) is, for example, 1.55 or higher, preferably 1.60 or higher. On the other hand, the upper limit of the refractive index of the phase difference layer 22 in the transmission axis direction is typically 1.65. Furthermore, when the optical laminate 100 consists of two liquid crystal alignment solidification layers having a front phase difference, such as when it includes a liquid crystal alignment solidification layer that functions as a λ / 2 plate and a liquid crystal alignment solidification layer that functions as a λ / 4 plate, the refractive index in the transmission axis direction of each liquid crystal alignment solidification layer is, for example, 1.40 or more and 1.70 or less, preferably 1.50 or more and less than 1.65, and more preferably 1.55 or more and less than 1.65.

[0113] E. Image display device The optical laminate described in Section D above can be applied to any suitable image display device. Therefore, one embodiment of the present invention also includes an image display device using such an optical laminate. Examples of image display devices include liquid crystal displays and organic light-emitting diodes (EL displays). An image display device according to an embodiment of the present invention comprises an image display panel and the optical laminate 100 described above. The image display panel typically includes an image display cell. The optical laminate 100 is positioned on the viewing side of the image display panel. In the optical laminate 100, the polarizer 12 is located on the opposite side of the image display panel from the phase difference layer 22. Therefore, the relatively smooth second surface 12b of the polarizer 12 is located on the viewing side. This makes it possible to stably suppress the occurrence of optical defects (typically reflection defects) in the image display device. [Examples]

[0114] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows.

[0115] (1) Measurement of the number of reflection defects on the surface of a polarizer The first laminate used in the examples and comparative examples was prepared separately. In the first laminate, the polarizer had a first surface which was the air surface and a second surface which was the first substrate side. Next, the first substrate was peeled off from the second surface of the polarizer, and the number of reflection defects on the first and second surfaces of the polarizer was measured. More specifically, the polarizer surface was observed for reflection using an LED light source in a darkroom. The polar angle was set to 50°, and the azimuth angle was varied from 0° to 360°. Observations were performed with a distance of 30cm between the polarizer and the light source, and a distance of 30cm between the polarizer and the evaluator, and the number of anisotropic reflection defects was counted. In this case, for reflection defects that were extremely difficult to see, an acrylic adhesive was applied to the surface, and only those that remained visible afterward were counted. As a result, the number of reflection defects on the first surface of the polarizer is 3 defects / m 2 Therefore, the number of reflection defects on the second plane of the polarizer is 0 defects / m 2 That was the case.

[0116] <<Preparation Example 1: Preparation of UV-Curing Adhesive>> 60 parts by mass of fluorene-based acrylate (product name: Ogusol EA-F5710, manufactured by Osaka Gas Chemical Co., Ltd.), 10 parts by mass of caprolactone-modified acrylate (product name: Praxel FA1DDM, manufactured by Daicel Corporation), 20 parts by mass of acryloylmorpholine (product name: ACMO, manufactured by KJ Chemicals Co., Ltd.), 5 parts by mass of acrylic polymer (product name: ARFON UP-1190, manufactured by Toagosei Co., Ltd.), 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (photopolymerization initiator, product name: Omnirad 819, manufactured by IGM Resins BV), 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (photopolymerization initiator, product name: Omnirad 184, manufactured by IGM Resins BV), and diethylthioxanthone (photopolymerization initiator, product name: KAYACURE Two parts by mass of DETX-S (manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare an ultraviolet-curable adhesive. The refractive index nAD of the ultraviolet-curable adhesive at a wavelength of 550 nm was 1.56.

[0117] <<Preparation example 2: 1st preparation step>> As a thermoplastic resin substrate, an amorphous isophthalic copolymer polyethylene terephthalate film (thickness: 100 μm) in a long length with a Tg of approximately 75°C was used, and one side of the film was subjected to corona treatment. This yielded the first substrate. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by mass of a PVA-based resin, which was prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosephymer") in a 9:1 ratio, with 13 parts by mass of potassium iodide. A PVA aqueous solution was applied to the corona-treated surface of the first substrate and dried at 60°C to form a 13 μm thick PVA-based resin layer on the first substrate. This obtained a resin layer support. The resulting resin layer support was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (air-assisted stretching). Next, the resin layer support was immersed for 30 seconds in an insolubilization bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 4 parts by mass of boric acid with 100 parts by mass of water) (insolubilization treatment). Next, the resin layer support was immersed for 60 seconds in a dyeing bath at a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by mass of water) while adjusting the concentration so that the final transmittance (Ts) of the polarizer obtained would be the desired value (dyeing treatment). Next, the resin layer support was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with 100 parts by mass of water) (crosslinking treatment). Subsequently, the resin layer support was immersed in a boric acid aqueous solution (boric acid concentration 4% by weight, potassium iodide concentration 5% by weight) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to achieve a total stretch ratio of 5.5 times (underwater stretching treatment). Subsequently, the resin layer support was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by mass of potassium iodide with 100 parts by mass of water) (washing treatment). Subsequently, the resin layer support was dried in an oven maintained at approximately 90°C while being brought into contact with a SUS heated roll whose surface temperature was maintained at approximately 75°C (drying shrinkage treatment). In this way, a polarizer with a thickness of approximately 5 μm was formed on the first substrate, and a first laminate having the configuration of first substrate / polarizer was obtained.

[0118] <<Preparation example 3: 2nd preparation step>> A liquid crystal composition (coating solution) was prepared by dissolving 10 parts by mass of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (BASF: trade name "Paliocolor LC242", represented by the following formula) and 3 parts by mass of a photopolymerization initiator for the polymerizable liquid crystal compound (BASF: trade name "Irgacure 907") in 40 parts by mass of toluene. [ka] The surface of a polyethylene terephthalate (PET) film (38 μm thick) was rubbed using a rubbing cloth and subjected to orientation treatment. The direction of the orientation treatment was set so that, when laminated to an optical film (described later), it would be at a 45° angle to the absorption axis of the polarizer when viewed from the viewing side. The liquid crystal coating solution was applied to this orientation-treated surface using a bar coater, and the liquid crystal compound was oriented by heating and drying at 90°C for 2 minutes. In the liquid crystal layer formed in this manner, a metal halide lamp is used to apply 1 mJ / cm³ of liquid crystal. 2 A liquid crystal alignment solidification layer was formed on the PET film by irradiating it with light and curing the liquid crystal layer. The thickness of the liquid crystal alignment solidification layer was 1 μm. The liquid crystal alignment solidified layer had a refractive index of nx > ny = nz. The in-plane phase difference Re(550) of the liquid crystal alignment solidified layer obtained in Preparation Example 3 was 140 nm. In other words, the liquid crystal alignment solidified layer can function as a λ / 4 plate. The average refractive index of the liquid crystal alignment solidified layer was 1.59, and the refractive index of the liquid crystal alignment solidified layer in the transmission axis direction was 1.59. This allowed us to prepare a second laminate comprising a liquid crystal alignment solidification layer (phase difference layer) and a PET film (second substrate).

[0119] <<Preparation example 4: 2nd preparation step>> A first liquid crystal alignment solidification layer (λ / 4 plate) was formed on a PET film (second substrate) in the same manner as in Preparation Example 3, except that the orientation processing direction was changed to a 75° direction relative to the absorption axis axis of the polarizer when viewed from the viewing side. The average refractive index of the first liquid crystal alignment solidification layer was 1.59, and the refractive index of the first liquid crystal alignment solidification layer in the transmission axis direction was 1.64. Furthermore, a second liquid crystal alignment solidification layer (λ / 2 plate) was formed on a PET film (third substrate) in the same manner as in Preparation Example 3, except that the coating thickness was changed and the orientation treatment direction was changed to a 15° direction relative to the absorption axis axis of the polarizer when viewed from the viewing side. The in-plane phase difference Re(550) of the second liquid crystal alignment solidification layer was 270 nm. This means that the second liquid crystal alignment solidification layer can function as a λ / 2 plate. The average refractive index of the second liquid crystal alignment solidification layer was 1.59, and the refractive index in the transmission axis direction of the second liquid crystal alignment solidification layer was 1.54. Next, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer were bonded together using the ultraviolet-curable adhesive obtained in Preparation Example 1. More specifically, the ultraviolet-curable adhesive was applied to the surface of the first liquid crystal alignment solidified layer to form a first coating film. Then, the ultraviolet-curable adhesive was applied to the surface of the second liquid crystal alignment solidified layer to form a second coating film. After that, the first coating film and the second coating film were brought into contact, and the coating films were irradiated with ultraviolet light to cure the ultraviolet-curable adhesive. Next, the PET film (third substrate) was peeled off from the second liquid crystal alignment solidification layer. This allowed us to prepare a second laminate comprising a phase difference layer containing a first liquid crystal alignment solidification layer (λ / 4 plate) and a second liquid crystal alignment solidification layer (λ / 2 plate), and a PET film (second substrate).

[0120] <<Preparation example 5: 2nd preparation step>> A second laminate comprising a first liquid crystal alignment solidification layer and a PET film (second substrate) was prepared in the same manner as in Preparation Example 3, except that the coating thickness was changed and the orientation treatment direction was changed to a 15° direction relative to the absorption axis axis of the polarizer when viewed from the viewing side. The thickness of the first liquid crystal alignment solidification layer was 2 μm. The in-plane phase difference Re(550) of the first liquid crystal alignment solidified layer obtained in Preparation Example 5 was 270 nm. In other words, the first liquid crystal alignment solidified layer can function as a λ / 2 plate. The average refractive index of the first liquid crystal alignment solidified layer was 1.59, and the refractive index in the transmission axis direction of the first liquid crystal alignment solidified layer was 1.54.

[0121] <<Preparation Example 6: Third Preparation Step>> A third laminate comprising a second liquid crystal alignment solidification layer (λ / 4 plate) and a PET film (third substrate) was prepared in the same manner as in Preparation Example 3, except that the orientation processing direction was changed to a 75° direction relative to the absorption axis axis of the polarizer when viewed from the viewing side. The average refractive index of the second liquid crystal alignment solidification layer was 1.59, and the refractive index of the second liquid crystal alignment solidification layer in the transmission axis direction was 1.64.

[0122] [Example 1] The first laminate obtained in Preparation Example 2 and the second laminate obtained in Preparation Example 3 were bonded together using an ultraviolet-curing adhesive (first bonding step). More specifically, a first coating film was formed by applying an ultraviolet-curing adhesive to the surface of the polarizer of the first laminate. A second coating film was then formed by applying an ultraviolet-curing adhesive to the surface of the liquid crystal alignment solidification layer (λ / 4 plate) of the second laminate. Next, the first and second coating films were brought into contact. Afterward, the coating films were irradiated with ultraviolet light to cure the ultraviolet-curing adhesive. As a result, an intermediate laminate comprising a first substrate, a polarizer, a liquid crystal alignment solidification layer (λ / 4 plate), and a second substrate in this order was prepared. In the intermediate laminate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the liquid crystal alignment solidification layer (λ / 4 plate) was 45°. Next, the first substrate was peeled off and removed from the polarizer (first peeling step). Subsequently, a norbornene resin film (25 μm thick) was applied as a protective layer to the surface of the polarizer opposite to the liquid crystal alignment solidification layer via an ultraviolet-curing adhesive (protection step). Next, the second substrate was peeled off and removed from the liquid crystal alignment solidification layer (λ / 4 plate) (second peeling step). Subsequently, a (meth)acrylic adhesive was applied to the surface of the liquid crystal alignment solidification layer (λ / 4 plate) opposite to the polarizer to form an adhesive layer with a thickness of 15 μm (adhesive layer formation step). This resulted in the preparation of an optical laminate comprising a protective layer, a polarizer, a liquid crystal alignment solidification layer (λ / 4 plate), and an adhesive layer in that order. In the optical laminate of Example 1, the second surface of the polarizer, which has a relatively small number of reflection defects, was located on the opposite side of the liquid crystal alignment solidification layer (i.e., the viewing side) from the first surface, which has a relatively large number of reflection defects.

[0123] [Example 2] The first laminate obtained in Preparation Example 2 and the second laminate obtained in Preparation Example 4 were bonded together using an ultraviolet-curing adhesive (first bonding step). More specifically, a first coating was formed by applying an ultraviolet-curing adhesive to the surface of the polarizer of the first laminate. A second coating was then formed by applying an ultraviolet-curing adhesive to the surface of the second liquid crystal alignment solidification layer (λ / 2 plate) of the second laminate. Next, the first and second coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the ultraviolet-curing adhesive. As a result, an intermediate laminate comprising a first substrate, a polarizer, a second liquid crystal alignment solidification layer (λ / 2 plate), another first liquid crystal alignment solidification layer (λ / 2 plate), and the second substrate in this order was prepared. In the intermediate laminate, the angle between the polarizer's absorption axis and the slow phase axis of the second liquid crystal alignment solidification layer (λ / 2 plate) was 15°, and the angle between the polarizer's absorption axis and the slow phase axis of the first liquid crystal alignment solidification layer (λ / 4 plate) was 75°. Next, the first substrate was peeled off and removed from the polarizer (first peeling step). Subsequently, a norbornene resin film (25 μm thick) was applied as a protective layer to the surface of the polarizer opposite to the second liquid crystal alignment solidification layer via an ultraviolet-curing adhesive (protection step). Next, the second substrate was peeled off and removed from the first liquid crystal alignment solidification layer (λ / 4 plate) (second peeling step). Subsequently, a (meth)acrylic adhesive was applied to the surface of the first liquid crystal alignment solidification layer (λ / 4 plate) opposite to the second liquid crystal alignment solidification layer (λ / 2 plate) to form an adhesive layer with a thickness of 15 μm (adhesive layer formation step). This resulted in the preparation of an optical laminate comprising a protective layer, a polarizer, a second liquid crystal alignment solidification layer (λ / 2 plate), a first liquid crystal alignment solidification layer (λ / 4 plate), and an adhesive layer in that order. In the optical laminate of Example 2, the second surface of the polarizer, which has a relatively small number of reflection defects, was located on the opposite side (i.e., the viewing side) from the second liquid crystal alignment solidification layer, relative to the first surface, which has a relatively large number of reflection defects.

[0124] [Example 3] The first laminate obtained in Preparation Example 2 and the second laminate obtained in Preparation Example 5 were bonded together using an ultraviolet-curing adhesive (first bonding step). More specifically, a first coating was formed by applying an ultraviolet-curing adhesive to the surface of the polarizer of the first laminate. A second coating was then formed by applying an ultraviolet-curing adhesive to the surface of the first liquid crystal alignment solidification layer (λ / 2 plate) of the second laminate. Next, the first and second coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the ultraviolet-curing adhesive. As a result, a first intermediate laminate comprising a first substrate, a polarizer, a first liquid crystal alignment solidification layer (λ / 2 plate), and a second substrate in this order was prepared. In the first intermediate laminate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the first liquid crystal alignment solidification layer (λ / 2 plate) was 15°. Next, the second substrate was peeled off and removed from the first liquid crystal alignment solidification layer (λ / 2 plate) (second peeling step). Subsequently, the first intermediate laminate, from which the second substrate had been removed, and the third laminate obtained in Preparation Example 6 were bonded together using the ultraviolet-curing adhesive obtained in Preparation Example 1 (second bonding step). More specifically, a UV-curable adhesive was applied to the surface of the first liquid crystal alignment solidification layer (λ / 2 plate) opposite the polarizer to form a third coating. Furthermore, a UV-curable adhesive was applied to the surface of the second liquid crystal alignment solidification layer (λ / 4 plate) of the third laminate to form a fourth coating. Next, the third and fourth coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the UV-curable adhesive. As a result, a second intermediate laminate was prepared, comprising a first substrate, a polarizer, a first liquid crystal alignment solidification layer (λ / 2 plate), a second liquid crystal alignment solidification layer (λ / 4 plate), and a third substrate in that order. In the second intermediate laminate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the second liquid crystal alignment solidification layer (λ / 4 plate) was 75°. Next, the first substrate was peeled off and removed from the polarizer (first peeling step). Subsequently, a norbornene resin film (25 μm thick) was applied as a protective layer to the surface of the polarizer opposite to the first liquid crystal alignment solidification layer via an ultraviolet-curing adhesive (protection step). Next, the third substrate was peeled off and removed from the second liquid crystal alignment solidification layer (λ / 4 plate) (third peeling step). Subsequently, a (meth)acrylic adhesive was applied to the surface of the second liquid crystal alignment solidification layer (λ / 4 plate) opposite to the first liquid crystal alignment solidification layer (λ / 2 plate) to form an adhesive layer with a thickness of 15 μm (adhesive layer formation step). This resulted in the preparation of an optical laminate comprising a protective layer, a polarizer, a first liquid crystal alignment solidification layer (λ / 2 plate), a first liquid crystal alignment solidification layer (λ / 4 plate), and an adhesive layer in that order. In the optical laminate of Example 3, the second surface of the polarizer, which has a relatively small number of reflection defects, was located on the opposite side (i.e., the viewing side) from the first liquid crystal alignment solidification layer, relative to the first surface, which has a relatively large number of reflection defects.

[0125] [Comparative Example 1] A norbornene resin film (25 μm thick) was applied as a protective layer to the first surface of the polarizer of the first laminate obtained in Preparation Example 2 via an ultraviolet-curing adhesive (protection step). Next, the first substrate was peeled off and removed from the polarizer (first peeling step). Subsequently, the second laminate obtained in Preparation Example 3 was attached to the surface of the polarizer opposite to the protective layer using an ultraviolet-curing adhesive (first bonding step). More specifically, a first coating was formed by applying an ultraviolet-curing adhesive to the surface of the polarizer. A second coating was then formed by applying an ultraviolet-curing adhesive to the surface of the liquid crystal alignment solidification layer (λ / 4 plate) of the second laminate. Next, the first and second coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the ultraviolet-curing adhesive. This resulted in the preparation of an intermediate laminate comprising a protective layer, a polarizer, a liquid crystal alignment solidification layer (λ / 4 plate), and a second substrate in that order. In the intermediate laminate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the liquid crystal alignment solidification layer (λ / 4 plate) was 45°. Next, the second substrate was peeled off and removed from the liquid crystal alignment solidification layer (λ / 4 plate) (second peeling step). Subsequently, a (meth)acrylic adhesive was applied to the surface of the liquid crystal alignment solidification layer (λ / 4 plate) opposite to the polarizer to form an adhesive layer with a thickness of 15 μm (adhesive layer formation step). This resulted in the preparation of an optical laminate comprising a protective layer, a polarizer, a liquid crystal alignment solidification layer (λ / 4 plate), and an adhesive layer in that order. In the optical laminate in Comparative Example 1, the first surface of the polarizer, which had a relatively small number of reflection defects, was located on the liquid crystal alignment solidification layer side (i.e., the side opposite to the viewing side).

[0126] [Comparative Example 2] A norbornene resin film (25 μm thick) was applied as a protective layer to the first surface of the polarizer of the first laminate obtained in Preparation Example 2 via an ultraviolet-curing adhesive (protection step). Next, the first substrate was peeled off and removed from the polarizer (first peeling step). Subsequently, the second laminate obtained in Preparation Example 4 was attached to the surface of the polarizer opposite to the protective layer using an ultraviolet-curing adhesive (first bonding step). More specifically, a first coating was formed by applying an ultraviolet-curing adhesive to the surface of the polarizer of the first laminate. A second coating was then formed by applying an ultraviolet-curing adhesive to the surface of the second liquid crystal alignment solidification layer (λ / 2 plate) of the second laminate. Next, the first and second coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the ultraviolet-curing adhesive. This resulted in the preparation of a first intermediate laminate comprising a protective layer, a polarizer, a second liquid crystal alignment solidification layer (λ / 2 plate), a first liquid crystal alignment solidification layer (λ / 2 plate), and a second substrate in that order. In the first intermediate laminate, the angle between the polarizer's absorption axis and the slow phase axis of the second liquid crystal alignment solidification layer (λ / 2 plate) was 15°, and the angle between the polarizer's absorption axis and the slow phase axis of the first liquid crystal alignment solidification layer (λ / 4 plate) was 75°. Next, the second substrate was peeled off and removed from the first liquid crystal alignment solidification layer (λ / 4 plate) (second peeling step). Subsequently, a (meth)acrylic adhesive was applied to the surface of the first liquid crystal alignment solidification layer (λ / 4 plate) opposite to the second liquid crystal alignment solidification layer (λ / 2 plate) to form an adhesive layer with a thickness of 15 μm (adhesive layer formation step). This resulted in the preparation of an optical laminate comprising a protective layer, a polarizer, a second liquid crystal alignment solidification layer (λ / 2 plate), a first liquid crystal alignment solidification layer (λ / 4 plate), and an adhesive layer in that order. In the optical laminate in Comparative Example 2, the first surface of the polarizer, which had a relatively small number of reflection defects, was located on the side of the second liquid crystal alignment solidification layer (i.e., the side opposite to the viewing side).

[0127] [Comparative Example 3] A norbornene resin film (25 μm thick) was applied as a protective layer to the first surface of the polarizer of the first laminate obtained in Preparation Example 2 via an ultraviolet-curing adhesive (protection step). Next, the first substrate was peeled off and removed from the polarizer (first peeling step). Subsequently, the second laminate obtained in Preparation Example 5 was attached to the surface of the polarizer opposite to the protective layer using an ultraviolet-curing adhesive (first bonding step). More specifically, a first coating was formed by applying an ultraviolet-curing adhesive to the surface of the polarizer. A second coating was then formed by applying an ultraviolet-curing adhesive to the surface of the first liquid crystal alignment solidification layer (λ / 2 plate) of the second laminate. Next, the first and second coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the ultraviolet-curing adhesive. This resulted in the preparation of a first intermediate laminate comprising a protective layer, a polarizer, a first liquid crystal alignment solidification layer (λ / 2 plate), and a second substrate in that order. In the first intermediate laminate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the first liquid crystal alignment solidification layer (λ / 2 plate) was 15°. Next, the second substrate was peeled off and removed from the first liquid crystal alignment solidification layer (λ / 2 plate) (second peeling step). Subsequently, the first intermediate laminate, from which the second substrate had been removed, and the third laminate obtained in Preparation Example 6 were bonded together using the ultraviolet-curing adhesive obtained in Preparation Example 1 (second bonding step). More specifically, a UV-curable adhesive was applied to the surface of the first liquid crystal alignment solidification layer (λ / 2 plate) opposite the polarizer to form a third coating. Furthermore, a UV-curable adhesive was applied to the surface of the second liquid crystal alignment solidification layer (λ / 4 plate) of the third laminate to form a fourth coating. Next, the third and fourth coatings were brought into contact. Afterward, the coatings were irradiated with ultraviolet light to cure the UV-curable adhesive. This resulted in the preparation of a second intermediate laminate comprising a protective layer, a polarizer, a first liquid crystal alignment solidification layer (λ / 2 plate), a second liquid crystal alignment solidification layer (λ / 4 plate), and a third substrate in that order. In the second intermediate laminate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the second liquid crystal alignment solidification layer (λ / 4 plate) was 75°. Next, the third substrate was peeled off and removed from the second liquid crystal alignment solidification layer (λ / 4 plate) (third peeling step). Subsequently, a (meth)acrylic adhesive was applied to the surface of the second liquid crystal alignment solidification layer (λ / 4 plate) opposite to the first liquid crystal alignment solidification layer (λ / 2 plate) to form an adhesive layer with a thickness of 15 μm (adhesive layer formation step). This resulted in the preparation of an optical laminate comprising a protective layer, a polarizer, a first liquid crystal alignment solidification layer (λ / 2 plate), a first liquid crystal alignment solidification layer (λ / 4 plate), and an adhesive layer in that order. In the optical laminate in Comparative Example 3, the first surface of the polarizer, which had a relatively small number of reflection defects, was located on the side of the first liquid crystal alignment solidification layer (i.e., the side opposite to the viewing side).

[0128] [Table 1]

[0129] [Reflection defect evaluation] The optical laminates obtained in each example and comparison were observed for reflection using an LED light source in a darkroom. The protective layer side was set facing the evaluator, the polar angle was set to 50°, and the azimuth angle was varied from 0° to 360°. Observations were performed with a distance of 30 cm between the polarizer and the light source, and a distance of 30 cm between the polarizer and the evaluator, and the number of anisotropic reflection defects was counted. The results are shown in Table 1. [Interference unevenness evaluation] The optical laminates obtained in each example and comparison were attached to a black board with an adhesive layer to serve as test samples. The obtained test samples were placed under a three-wavelength fluorescent lamp, and the interference uniformity was evaluated visually under two conditions: a first embodiment in which a polarizing plate was placed between the test sample and the observer, and a second embodiment in which no polarizing plate was placed between the test sample and the observer, according to the following criteria. The results are shown in Table 1. A: In both the first and second embodiments, no interference unevenness extending in the MD direction (the transmission axis direction of the polarizer) is visible. B: In the second embodiment, interference unevenness is not visible, but in the first embodiment, interference unevenness is visible. C: In both the first and second embodiments, interference irregularities are visible. As is clear from Table 1, when the second face of the polarizer, which has a relatively small number of reflection defects, is located on the viewing side (Example), reflection defects are suppressed compared to when the first face of the polarizer, which has a relatively large number of reflection defects, is located on the viewing side (Comparative Example). Furthermore, interference unevenness is also suppressed. [Industrial applicability]

[0130] The optical laminate manufactured according to the embodiments of the present invention can be suitably used in image display devices (typically liquid crystal display devices and organic EL display devices). [Explanation of Symbols]

[0131] 1. First layer 11 First base material 12 polarizers 12a 1st page 12b Side 2 13 Protective layer 2. Second Laminate 21 Second base material 22 Retardation layer 23 Liquid crystal alignment solidification layer 24. First liquid crystal alignment solidification layer 25. Second liquid crystal alignment solidification layer 27 Third base material 3. Third layer 5. Adhesive layer 6. Release Liner 7. First Intermediate Laminate 8. Second Intermediate Laminate

Claims

1. A first preparation step of preparing a first laminate comprising a first substrate and a polarizer located on the first substrate, A second preparation step involves preparing a second laminate comprising a second substrate and a phase difference layer located on the second substrate. A first bonding step of bonding the polarizer provided in the first laminate and the phase difference layer provided in the second laminate, After the first bonding step, a first peeling step is performed to peel the first substrate from the polarizer, The process includes, after the first bonding step, a second peeling step of peeling the second substrate from the phase difference layer, A method for manufacturing an optical laminate, wherein the phase difference layer includes an orientation solidification layer of a liquid crystal compound.

2. The method for manufacturing an optical laminate according to claim 1, wherein the first peeling step is performed before the second peeling step.

3. The method for manufacturing an optical laminate according to claim 1, wherein the phase difference layer has a single-layer structure consisting of an orientation solidified layer of the first liquid crystal compound.

4. A third preparation step to prepare a third laminate comprising a third substrate and an orientation solidified layer of a second liquid crystal compound located on the third substrate, A second bonding step is performed after the second peeling step, in which the orientation solidified layer of the first liquid crystal compound and the orientation solidified layer of the second liquid crystal compound are bonded together. The process further includes a third peeling step, which involves peeling the third substrate from the orientation-solidified layer of the second liquid crystal compound after the second bonding step, The method for manufacturing an optical laminate according to claim 3, wherein the first peeling step is performed after the second bonding step.

5. The method for manufacturing an optical laminate according to claim 4, wherein the first peeling step is performed before the third peeling step.

6. The second preparation step is, A step of forming an orientation solidified layer of the first liquid crystal compound on the second substrate, A step of forming an orientation solidified layer of a second liquid crystal compound on a third substrate, A step of bonding the first liquid crystal compound orientation solidification layer and the second liquid crystal compound orientation solidification layer, The process includes a step of bonding the first liquid crystal compound orientation solidification layer and the second liquid crystal compound orientation solidification layer together, followed by a step of peeling the third substrate from the second liquid crystal compound orientation solidification layer. A method for manufacturing an optical laminate according to claim 1, wherein in the first bonding step, the polarizer and the orientation solidification layer of the second liquid crystal compound are bonded together.

7. The method for manufacturing an optical laminate according to claim 6, wherein the first peeling step is performed before the second peeling step.

8. A method for manufacturing an optical laminate according to any one of claims 1 to 7, further comprising the step of attaching a protective layer to the polarizer after the first peeling step.

9. The method for manufacturing an optical laminate according to any one of claims 1 to 7, wherein the thickness of the polarizer is 3 μm to 7 μm.

10. The first preparation step is, A step of applying a coating solution containing a polyvinyl alcohol-based resin to the first substrate to obtain a resin layer support comprising a polyvinyl alcohol-based resin layer and the first substrate, The process involves dyeing the polyvinyl alcohol-based resin layer with a dichroic substance, A method for manufacturing an optical laminate according to any one of claims 1 to 7, comprising the steps of stretching the resin layer support in this order.

11. The process involves forming an adhesive layer on the surface of the phase difference layer after the second peeling step, A method for manufacturing an optical laminate according to any one of claims 1 to 7, further comprising the step of attaching a release liner to the adhesive layer.

12. The method for manufacturing an optical laminate according to any one of claims 1 to 7, wherein the phase difference layer functions as a λ / 4 plate.

13. Polarizer and, A phase difference layer located on one side in the thickness direction of the polarizer, comprising a phase difference layer including an orientation solidification layer of a liquid crystal compound, The polarizer has, in the thickness direction, a first surface on the phase difference layer side and a second surface located on the opposite side of the phase difference layer from the first surface. An optical laminate in which the second surface of the polarizer is smoother than the first surface of the polarizer.

14. The optical laminate according to claim 13, wherein the number of reflection defects per unit area on the first surface of the polarizer is less than the number of reflection defects per unit area on the second surface of the polarizer.

15. Image display panel, An optical laminate according to claim 13 or 14, comprising an optical laminate disposed on the viewing side of the image display panel, An image display device wherein the polarizer is located on the opposite side of the phase difference layer from the image display panel.

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