Substrate laminates, optical laminates, manufacturing methods of substrate laminates, and manufacturing methods of polarizing plates.

Abstract

This invention provides a substrate laminate whose end pieces can be easily removed during the manufacturing process of an optical laminate. The substrate laminate A of this invention comprises a substrate layer 2 and a surface treatment layer 3 directly deposited on the surface of the substrate layer 2. The substrate laminate A includes a pair of opposing ends AE in a direction substantially parallel to the surface of the substrate layer 2, and a central portion AC located between the pair of ends AE. The peel strength of the substrate layer 2 at at least one end AE of the substrate laminate A to the surface treatment layer 3 is expressed as Ie. The peel strength of the substrate layer 2 at the central portion AC of the substrate laminate A to the surface treatment layer 3 is expressed as Ic. Ie is higher than Ic.

Description

Technical Field

[0001] This invention relates to a substrate laminate, an optical laminate, a method for manufacturing a substrate laminate, and a method for manufacturing a polarizing plate. Prior Technology

[0002] Polarizing plates are used in image display devices (liquid crystal displays or organic EL (electroluminescence) displays, such as the surface panels of televisions, computers, smartphones, smartwatches, portable game consoles, or vehicles. Polarizing plates are manufactured by laminating multiple layers such as a protective layer (protective film), a polarizing element layer, an adhesive layer, and a phase retardation layer (see Patent Documents 1-4 below). [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-028133 [Patent Document 2] Japanese Patent Application Publication No. 2017-83843 [Patent Document 3] International Publication No. 2020 / 122117 [Patent Document 4] International Publication No. 2020 / 179864 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] A method for manufacturing a polarizing plate includes, for example, the following steps: directly depositing a surface treatment layer (hard coating, etc.) onto a substrate layer (PET (polyethylene terephthalate) film, etc.) to obtain a substrate laminate; directly or indirectly depositing a polarizing element layer onto the surface treatment layer contained in the substrate laminate; and directly or indirectly depositing other resin layers (phase retardation layers, etc.) onto the polarizing element layer via an adhesive layer. An optical laminate is manufactured by at least these steps. Furthermore, a polarizing plate can be obtained by peeling the substrate layer from the optical laminate.

[0006] Ideally, the adhesive layer should cover the entire surface of the substrate layer (e.g., polarizing element layer, outer cover layer of polarizing element layer, or retardation layer) directly laminated to which the adhesive layer is applied. However, the ends of the substrate layer surface tend to be difficult to be coated with the adhesive layer. The portion of the substrate layer surface that is not coated with the adhesive layer is referred to as the "uncoated portion". The portions that indirectly overlap with the uncoated portions at the ends of the multiple layers laminated between the adhesive layer and the substrate layer (e.g., surface treatment layer and polarizing element layer) together with the uncoated portions constitute "end pieces". In other words, the end piece is the portion of the optical laminate fabricated during the manufacturing process of the polarizing plate that is not directly or indirectly fixed by the adhesive layer. Because the end piece is not fixed by the adhesive layer, it is easy to detach from the optical laminate during the manufacturing process of the polarizing plate. Compared to the previous polarizing element layer (extended film) containing polyvinyl alcohol, the polarizing element layer containing polymeric liquid crystal compounds and dichroic pigments is thinner and more easily damaged. Therefore, when the polarizing element layer in the optical stack contains polymeric liquid crystal compounds and dichroic pigments, the end pieces are prone to detaching from the optical stack. These detached end pieces contaminate the polarizing plate production line. As a result, the end pieces easily become foreign matter mixed into the polarizing plate, leading to a decrease in polarizing plate quality. Removing the ends of the optical stack before peeling off the substrate layer allows for the removal of the end pieces. However, removing the ends of the optical stack increases the number of steps required to manufacture the polarizing plate, thus reducing the productivity of the polarizing plate. Furthermore, when removing the ends of the optical stack, it is easy to accidentally remove normal ends that do not need to be removed along with the end pieces, resulting in waste of the material constituting the ends of the optical stack. As a result, the productivity of polarizing plates decreased.

[0007] One objective of this invention is to provide a substrate laminate, an optical laminate, a method for manufacturing a substrate laminate, and a method for manufacturing a polarizing plate. The substrate laminate can be easily removed from the end piece of the optical laminate produced during the manufacturing process of the polarizing plate. [Technical means to solve the problem]

[0008] One embodiment of the present invention comprises a substrate laminate including a substrate layer and a surface treatment layer directly laminated on the surface of the substrate layer. The substrate laminate includes a pair of opposite ends in a direction substantially parallel to the surface of the substrate layer, and a central portion located between the pair of ends. The peel strength of the substrate layer at at least one end of the substrate laminate to the surface treatment layer is denoted as Ie. The peel strength of the substrate layer at the central portion of the substrate laminate to the surface treatment layer is denoted as Ic. Ie is higher than Ic.

[0009] Ie is higher than Ic and can be above 0.40 N / 25 mm. Ic is lower than Ie and can be below 0.55 N / 25 mm.

[0010] One embodiment of the optical laminate of the present invention comprises the aforementioned substrate laminate and a polarizing element layer. The polarizing element layer is deposited directly or indirectly on the surface of the surface treatment layer included in the substrate laminate. The polarizing element layer comprises a polymer of a polymeric liquid crystal compound and a dichroic pigment.

[0011] In a direction substantially parallel to the surface of the surface treatment layer, at least one end of the substrate laminate may be located outside the area surrounded by the outer periphery of the polarizing element layer.

[0012] One embodiment of the optical laminate of the present invention may include an adhesive layer and other resin layers. The adhesive layer may be deposited directly or indirectly on the surface of the polarizing element layer. Other resin layers may be deposited directly on the surface of the adhesive layer.

[0013] In one embodiment of the optical laminate of the present invention, the other resin layers may be phase retardation layers.

[0014] In a direction parallel to the surface of the surface treatment layer, at least one end of the substrate laminate may be located outside the area surrounded by the outer periphery of the adhesive layer.

[0015] In a direction that is substantially parallel to the surface of the surface treatment layer and substantially perpendicular to the outer periphery of the adhesive layer, the width of at least one end of the substrate laminate may be 0.1 mm or more but less than 55 mm.

[0016] In a direction parallel to the surface of the surface treatment layer, at least one end of the polarizing element layer may be located outside the area surrounded by the outer periphery of the adhesive layer.

[0017] The method for manufacturing a substrate laminate of the present invention is a method for manufacturing the above-mentioned substrate laminate, and includes the following steps: a step of directly depositing a surface treatment layer onto the surface of a substrate layer to obtain a laminate; a step of winding the laminate to obtain a roll; and a step of heating at least one of a pair of opposite end faces of the roll.

[0018] Another embodiment of the present invention is a method for manufacturing the above-mentioned substrate laminate, and includes the following steps: performing corona treatment on at least one end of a pair of opposing ends of the substrate layer; and after the corona treatment, directly depositing a surface treatment layer on the surface of the substrate layer.

[0019] The method for manufacturing a polarizing plate of one state of the present invention includes the step of peeling off a substrate layer from the above-mentioned optical laminate.

[0020] Another embodiment of the present invention provides a method for manufacturing a polarizing plate comprising the following steps: directly depositing a surface treatment layer onto the surface of a substrate layer; directly or indirectly depositing a polarizing element layer onto the surface of the surface treatment layer; directly or indirectly depositing other resin layers onto the surface of the polarizing element layer via an adhesive layer; after depositing other resin layers directly or indirectly onto the surface of the polarizing element layer via an adhesive layer, simultaneously heating the ends of both the substrate layer and the surface treatment layer; and after simultaneously heating the ends of both the substrate layer and the surface treatment layer, peeling off the substrate layer. By simultaneously heating the ends of both the substrate layer and the surface treatment layer, the peel strength of the ends of the substrate layer to the ends of the surface treatment layer is improved. The polarizing element layer comprises a polymer of a polymeric liquid crystal compound and a dichroic pigment.

[0021] In another embodiment of the present invention, the method for manufacturing a polarizing plate may be a phase retardation layer. [Effects of the Invention]

[0022] According to one aspect of the present invention, a substrate laminate, an optical laminate, a method for manufacturing the substrate laminate, and a method for manufacturing a polarizing plate are provided. The substrate laminate can be easily removed from the end piece of the optical laminate produced during the manufacturing process of the polarizing plate. Simple Explanation of the Diagram

[0023] Figure 1 shows a cross-section of a substrate laminate according to one embodiment of the present invention. The cross-section is substantially parallel to the lamination direction of the substrate laminate and substantially perpendicular to the surface of the substrate layer contained in the substrate laminate. Figure 2 shows a cross-section of an optical laminate according to one embodiment of the present invention. The cross-section is substantially parallel to the stacking direction of the optical laminate and substantially perpendicular to the surface of the surface treatment layer contained in the optical laminate. Figure 3 shows the surface of the surface treatment layer, the outer periphery of the polarizing element layer overlapping the surface of the surface treatment layer, and the outer periphery of the bonding layer overlapping the surface of the surface treatment layer in an optical laminate according to one embodiment of the present invention. Figure 4 shows a cross-section of a polarizing plate obtained by peeling a substrate layer from an optical laminate according to one embodiment of the present invention. The cross-section is generally parallel to the stacking direction of the optical laminate and the polarizing plate, and generally perpendicular to the surface of the surface treatment layer contained in the optical laminate and the polarizing plate. Implementation

[0024] The preferred embodiment of the present invention (first embodiment) is described below with reference to the drawings. In the drawings, the same symbols are used to denote the same constituent elements. The present invention is not limited to the following embodiments. X, Y, and Z in each figure represent three mutually orthogonal coordinate axes. The directions indicated by the X, Y, and Z coordinate axes in each figure are common to all figures. The X-axis direction can be referred to as the width direction of each layer contained in the substrate laminate, optical laminate, and polarizing plate. The Y-axis direction can be referred to as the length direction or conveying direction of each layer contained in the substrate laminate, optical laminate, and polarizing plate. The Z-axis direction can be referred to as the lamination direction of each of the substrate laminate, optical laminate, and polarizing plate. The substrate laminate, optical laminate, and polarizing plate can be elongated.

[0025] (Substrate laminates, optical laminates, polarizing plates, and manufacturing methods of polarizing plates) As shown in Figure 1, the substrate laminate A of the first embodiment includes at least a substrate layer 2 and a surface treatment layer 3 directly laminated on the surface of the substrate layer 2. The substrate layer 2 and the surface treatment layer 3 may each be a layer containing a resin (polymer compound). The surface treatment layer 3 may be referred to as a first protective layer or a hard coating. The surface treatment layer 3 may cover the entire surface of the substrate layer 2. A substrate protective layer 1 (substrate protective film) may be directly laminated on the surface of the substrate layer 2 on the back side of the surface where the surface treatment layer 3 is laminated. The substrate laminate A includes a pair of opposing ends AE in a direction substantially parallel to the surface of the substrate layer 2 (X-axis direction) and a central portion AC located between the pair of ends AE. The central portion AC may be referred to as the portion located between the pair of ends AE in a cross-section of the substrate laminate A substantially perpendicular to the surface of the substrate layer 2. The peel strength of the substrate layer 2 at at least one end AE of the substrate laminate A to the surface treatment layer 3 is expressed as Ie. The peel strength of the substrate layer 2 at each of the two ends AE of the substrate laminate A to the surface treatment layer 3 can be expressed as Ie. The peel strength of the substrate layer 2 at the central part AC of the substrate laminate A to the surface treatment layer 3 can be expressed as Ic. Ie is higher than Ic. The peel strength of the substrate layer 2 at one end AE of the substrate laminate A to the surface treatment layer 3 can be equal to the peel strength of the substrate layer 2 at the other end AE of the substrate laminate A to the surface treatment layer 3. The peel strength of the substrate layer 2 at one end AE of the substrate laminate A to the surface treatment layer 3 can also be different from the peel strength of the substrate layer 2 at the other end AE of the substrate laminate A to the surface treatment layer 3. The unit of peel strength is N / 25 mm. For example, peel strength can be determined by a 180-degree peel test according to Japanese Industrial Standard (JIS Z 0237). The substrate layer 2 can be easily peeled from the surface treatment layer 3 located at the central part AC of the substrate laminate A. The surface treatment layer 3 located in the central part AC of the substrate laminate A is not easily damaged when the substrate layer 2 is peeled off.

[0026] The optical laminate of the first embodiment includes at least a substrate laminate A and a polarizing element layer. The polarizing element layer is deposited directly or indirectly on the surface of the surface treatment layer included in the substrate laminate. The polarizing element layer includes a polymer of a polymeric liquid crystal compound and a dichroic pigment.

[0027] In addition to the substrate laminate A and the polarizing element layer, the optical laminate may further include an adhesive layer and other resin layers. The adhesive layer (hereinafter referred to as the first adhesive layer) is deposited directly or indirectly on the surface of the polarizing element layer. Other resin layers are directly deposited on the surface of the adhesive layer. In other words, other resin layers are deposited directly or indirectly on the surface of the polarizing element layer via the adhesive layer. For example, the other resin layers may be a retardation layer, an optical compensation layer, or a protective layer (hereinafter referred to as the third protective layer). When any two layers constituting an optical laminate are denoted as layer A and layer B, layer B directly laminated to layer A means layer B laminated to layer A without passing through other layers. Layer B indirectly laminated to layer A means layer B laminated to layer A through other layers.

[0028] Figure 2 shows an example of the stacked structure of an optical stack. However, the stacked structure of the optical stack according to the first embodiment is not limited to the structure shown in Figure 2. The optical stack B shown in Figure 2 includes: a substrate stack A; an alignment layer 4 directly stacked on the surface of the surface treatment layer 3 (first protective layer) included in the substrate stack A; a polarizing element layer 5 directly stacked on the surface of the alignment layer 4; a second protective layer 6 (outer coating layer) directly stacked on the surface of the polarizing element layer 5; a first adhesive layer 7 directly stacked on the surface of the second protective layer 6; a phase retardation layer 8 (other resin layer) directly stacked on the surface of the first adhesive layer 7; a second adhesive layer 9 directly stacked on the surface of the phase retardation layer 8; an optical compensation layer 10 directly stacked on the surface of the second adhesive layer 9; and a third protective layer 11 directly stacked on the surface of the optical compensation layer 10. The thickness of each layer included in the optical stack can be substantially uniform. In a direction substantially perpendicular to the stacking direction of the optical stack B (the thickness direction of the polarizing element layer 5), the shape of the optical stack B and its layers can be substantially the same as the shape of the screen of the image display device. For example, in a direction substantially perpendicular to the stacking direction of the optical stack B (the thickness direction of the polarizing element layer 5), the shape of the optical stack B and its layers can be rectangular (or square). However, the shape of the optical stack B and its layers in a direction substantially perpendicular to the stacking direction of the optical stack B (the thickness direction of the polarizing element layer 5) is not limited. One or more notches (grooves) can be formed at the ends of the optical stack B. One or more through holes can be formed in the optical stack B.

[0029] As shown in Figures 2 and 3, in a direction substantially parallel to the surface of the surface treatment layer 3 (X-axis direction), one end AE of the substrate laminate A may be partially or entirely located outside the area surrounded by the outer periphery 7c of the first adhesive layer 7. That is, in a direction substantially parallel to the surface of the surface treatment layer 3, at least one end AE of the substrate laminate A may protrude more than the end of the first adhesive layer 7. In a direction substantially parallel to the surface of the surface treatment layer 3, each of the two ends AE of the substrate laminate A may be partially or entirely located outside the area surrounded by the outer periphery 7c of the first adhesive layer 7.

[0030] As shown in Figures 2 and 3, in a direction substantially parallel to the surface of the surface treatment layer 3, at least one end AE of the substrate laminate A may be located outside the area surrounded by the outer periphery 5c of the polarizing element layer 5. That is, in a direction substantially parallel to the surface of the surface treatment layer 3, at least one end AE of the substrate laminate A may protrude more than the end of the polarizing element layer 5. In a direction substantially parallel to the surface of the surface treatment layer 3, part or all of each of the two ends AE of the substrate laminate A may be located outside the area surrounded by the outer periphery 5c of the polarizing element layer 5.

[0031] As shown in Figures 2 and 3, in a direction substantially parallel to the surface of the surface treatment layer 3, at least one end of the polarizing element layer 5 may be partially or entirely located outside the area surrounded by the outer periphery 7c of the first adhesive layer 7. That is, in a direction substantially parallel to the surface of the surface treatment layer 3, at least one end of the polarizing element layer 5 may protrude more than the end of the first adhesive layer 7. In a direction substantially parallel to the surface of the surface treatment layer 3, each of the two ends of the polarizing element layer 5 may be partially or entirely located outside the area surrounded by the outer periphery 7c of the first adhesive layer 7.

[0032] As shown in Figure 2, at least one end of the alignment layer 4 may protrude more than the end of the first adhesive layer 7 in a direction substantially parallel to the surface of the surface treatment layer 3. Both ends of the alignment layer 4 may protrude more than the ends of the first adhesive layer 7 in a direction substantially parallel to the surface of the surface treatment layer 3.

[0033] As shown in Figure 2, at least one end of the second protective layer 6 may protrude more than the end of the first adhesive layer 7 in a direction substantially parallel to the surface of the surface treatment layer 3. Both ends of the second protective layer 6 may protrude more than the ends of the first adhesive layer 7 in a direction substantially parallel to the surface of the surface treatment layer 3.

[0034] The two ends of the second protective layer 6, which protrude further than the end of the first adhesive layer 7 in a direction parallel to the surface of the surface treatment layer 3, are a pair of uncovered portions not covered by the first adhesive layer 7. The two ends of each of the surface treatment layer 3 (first protective layer), alignment layer 4, and polarizing element layer 5, which are stacked between the first adhesive layer 7 and the substrate layer 2, indirectly overlap with the pair of uncovered portions (the two ends of the second protective layer 6). In other words, the two ends of each of the surface treatment layer 3, alignment layer 4, polarizing element layer 5, and second protective layer 6 protrude further than the end of the first adhesive layer 7 in a direction parallel to the surface of the surface treatment layer 3. Therefore, the two ends of each of the surface treatment layer 3, alignment layer 4, and polarizing element layer 5, together with the pair of uncovered portions, constitute a pair of end pieces E. Since the pair of end pieces E are not fixed by the first adhesive layer 7, they are easily detached from the optical stack B during the manufacturing process of the polarizing plate.

[0035] As shown in Figure 4, the manufacturing method of polarizing plate C includes the step of peeling the substrate layer 2 (and the substrate protective layer 1) from the optical laminate B.

[0036] The layers in contact between the first adhesive layer 7 and the substrate layer 2 (i.e., the surface treatment layer 3 and the alignment layer 4, the alignment layer 4 and the polarizing element layer 5, and the polarizing element layer 5 and the second protective layer 6) are firmly bonded to each other during the lamination process. That is, the layers in contact between the first adhesive layer 7 and the substrate layer 2 are not easily peeled off. In contrast, the peel strength Ic of the substrate layer 2 at the central portion AC of the substrate laminate A to the surface treatment layer 3 is sufficiently low. That is, the central portion of the substrate layer 2 is easily peeled off from the surface treatment layer 3. On the other hand, the peel strength Ie of the substrate layer 2 at each of the two ends AE of the substrate laminate A to the surface treatment layer 3 is higher than Ic. That is, compared to the central portion of the substrate layer 2, the two ends of the substrate layer 2 are more firmly bonded to the surface treatment layer 3. In other words, the two ends of the substrate layer 2 are not easily peeled off from the surface treatment layer 3. Therefore, as the central portion of the substrate layer 2 is peeled off from the surface treatment layer 3, the pair of end pieces E that are closely bonded to the two ends of the substrate layer 2 can be easily separated from the ends of the optical laminate B together with the substrate layer 2. Regarding the lamination structure of the polarizing plate C obtained by peeling the substrate layer 2 (and the substrate protective layer 1) from the optical laminate B, except for the substrate layer 2, the substrate protective layer 1 and the end piece E, it can be the same as the above-mentioned lamination structure of the optical laminate B.

[0037] According to the first embodiment, by peeling the substrate layer 2 from the optical laminate B, one pair of end pieces E, which are closely attached to both ends of the substrate layer 2, can be easily removed from the ends of the optical laminate B. As a result, the end pieces E can be prevented from detaching from the optical laminate B during the manufacturing process of the polarizer. By preventing the end pieces E from detaching from the optical laminate B, contamination of the polarizer C production line by the end pieces E can be prevented, and the mixing of end pieces E into the polarizer C can be prevented. As a result, the quality of the polarizer C is improved.

[0038] According to the first embodiment, the previous step of cutting off the ends of the optical laminate B before the substrate layer 2 is isolated is unnecessary in order to remove the end piece E from the optical laminate B. As a result, the number of steps required to manufacture the polarizing plate C is reduced, and the productivity of the polarizing plate C is improved. According to the first embodiment, since it is not necessary to cut off the normal ends that do not need to be cut off together with the end piece from the optical laminate B, the portion that can be used as the polarizing plate C after removing the end piece is easily retained on the optical laminate B, which can suppress the waste of raw materials for the polarizing plate. As a result, the productivity of the polarizing plate C is improved.

[0039] Ie is higher than Ic, and can be between 0.40 N / 25 mm and 1.80 N / 25 mm. Ic is lower than Ie, and can be between 0.05 N / 25 mm and 0.55 N / 25 mm. The higher Ie is, the easier it is for the end piece E to adhere closely to the end of the substrate layer 2, and the easier it is to remove the end piece E from the optical laminate B by peeling off the substrate layer 2. The lower Ic is, the easier it is for the substrate layer 2 to peel off from the surface treatment layer 3 in the central part of the substrate laminate A, and the more likely the surface treatment layer 3 will be damaged as the substrate layer 2 is peeled off.

[0040] As shown in Figure 3, in a direction (X-axis direction) that is substantially parallel to the surface of the surface treatment layer 3 and substantially perpendicular to the outer periphery 7c of the first adhesive layer 7, the width WAE of at least one end AE of the substrate laminate A can be 0.1 mm or more but less than 55 mm. The width WAE of each of at least two ends AE of the substrate laminate A can be 0.1 mm or more but less than 55 mm. When the width WAE of the end AE is 0.1 mm or more, the end piece E can easily adhere to the end of the substrate layer 2, thereby making it easy to reliably remove the end piece E from the optical laminate B. When the width WAE of the end AE is less than 55 mm, the normal end piece removed from the optical laminate B along with the end piece E is sufficiently small, resulting in a portion that can be used as the polarizing plate C after the end piece E is removed.

[0041] For example, the thickness of the protective layer 1 for the substrate can be between 5 μm and 100 μm. For example, the thickness of the substrate layer 2 can be between 5 μm and 100 μm. For example, the thickness of the surface treatment layer 3 (first protective layer) can be 0.1 μm to 13 μm, 0.3 μm to 8 μm, or 0.5 μm to 5 μm. For example, the thickness of the alignment layer 4 can be 10 nm or more but less than 5000 nm, 10 nm or more but less than 1000 nm, 10 nm or more but less than 500 nm, or 10 nm or more but less than 300 nm. For example, the thickness of the polarizing element layer 5 can be 0.5 μm or more and 10 μm or less, 0.5 μm or more and 8 μm or more and 1 μm or less and 5 μm or less. For example, the thickness of the second protective layer 6 can be 0.1 μm to 13 μm, 0.3 μm to 8 μm, or 0.5 μm to 5 μm. For example, the thickness of the first adhesive layer 7 can be 0.1 μm or more and 15 μm or less, 0.5 μm or more and 10 μm or less, or 1 μm or more and 5 μm or less. For example, the thickness of the phase retardation layer 8 (other resin layers) can be 0.1 μm to 10 μm, 0.5 μm to 8 μm, or 1 μm to 6 μm. For example, the thickness of the second adhesive layer 9 can be 0.1 μm to 15 μm, 0.5 μm to 10 μm, or 1 μm to 5 μm. For example, the thickness of the optical compensation layer 10 can be 0.1 μm or more and 10 μm or less, 0.5 μm or more and 8 μm or less, or 1 μm or more and 6 μm or less. For example, the thickness of the third protective layer 11 can be between 5 μm and 100 μm. When the thicknesses of the surface treatment layer 3, alignment layer 4, polarizing element layer 5, and second protective layer 6 are within the aforementioned range, each layer is thin enough that it is easy for each layer to break at its ends as the substrate layer 2 is peeled off. As a result, the end piece E, which is formed by the ends of the surface treatment layer 3, alignment layer 4, polarizing element layer 5, and second protective layer 6, can be easily removed from the optical laminate B.

[0042] (Manufacturing method of substrate laminate A) One example of a method for manufacturing a substrate laminate A includes the following steps: directly depositing a surface treatment layer 3 onto the surface of a substrate layer 2 to obtain a laminate; winding the laminate to obtain a roll; and heating at least one of a pair of opposite end faces of the roll. Alternatively, both of the pair of opposite end faces of the roll may be heated. By heating the end faces of the roll, the ends of the substrate layer 2 and the surface treatment layer 3 located on the end faces of the roll are firmly fused together. As a result, a substrate laminate A with Ie higher than Ic can be obtained. The method for heating the end faces of the roll can be a flame (e.g., a gas appliance) or radiant heat (e.g., an infrared heater).

[0043] Another example of a method for manufacturing a substrate laminate A includes the following steps: performing corona treatment on at least one of a pair of opposing ends of a substrate layer 2; and, after the corona treatment, directly depositing a surface treatment layer 3 onto the surface of the substrate layer 2. The corona treatment can be performed on both of the opposing ends of the substrate layer 2. The corona treatment modifies the surface of the ends of the substrate layer 2. By depositing the surface treatment layer 3 onto the surface-modified substrate layer 2 at the ends, the surface treatment layer 3 can be firmly bonded to the ends of the substrate layer 2. As a result, a substrate laminate A with Ie higher than Ic can be obtained.

[0044] (Substrate protective layer 1, substrate layer 2 and third protective layer 11) For example, the substrate protective layer 1, the substrate layer 2, and the third protective layer 11 can each be a thermoplastic resin film selected from the group consisting of the following films: polyester resin films containing resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; cyclic polyolefin resin films; cellulose acetate resin films containing resins such as triacetyl cellulose and diacetyl cellulose; polycarbonate resin films; acrylic resin films; methacrylic resin films; and polypropylene resin films. An adhesive layer can be formed on the surface of one of the surfaces of the substrate protective layer 1 facing the substrate layer 2.

[0045] (Surface treatment layer 3) The surface treatment layer 3 (first protective layer) protects the polarizing element layer 5 (and alignment layer 4) in both the optical laminate B and the polarizing plate C, and inhibits the diffusion of dichroic pigments from the polarizing element layer 5. For example, the surface treatment layer 3 can be a cured product of an ultraviolet-curable resin. For example, the ultraviolet-curable resin can be at least one selected from the group consisting of acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. To improve the mechanical strength of the surface treatment layer 3, inorganic microparticles, organic microparticles, or mixtures thereof can be added to the surface treatment layer 3. The surface treatment layer 3 can be deposited on the surface of the substrate layer 2 using a transfer method. For example, the method for forming the surface treatment layer 3 may include the following steps: forming a coating film containing an uncured ultraviolet-curable resin on the surface of a substrate film coated with a release agent; transferring the coating film from the substrate film to the surface of the substrate layer 2; and curing the coating film transferred to the surface of the substrate layer 2 by irradiation with ultraviolet light.

[0046] When the surface treatment layer 3 contains an acrylic resin that is cured by irradiation with ultraviolet light, and the substrate layer 2 contains polyethylene terephthalate (PET), it is easy to form a substrate laminate A with Ie higher than Ic, and it is easy to control Ie and Ic within the above-mentioned value ranges respectively.

[0047] (Orientation layer 4) Alignment layer 4 is a film containing a polymer compound, which has the function of aligning the polymeric liquid crystal compound constituting the polarizing element layer 5 in a desired direction. For example, alignment layer 4 can be one of the alignment films selected from the group consisting of alignment films containing alignment polymers, photoalignment films, and groove alignment films.

[0048] The orientation polymer may be at least one polymeric compound selected from the group consisting of: polyamides having intramolecular amide bonds, gelatin having intramolecular amide bonds, polyimides having intramolecular imine bonds, polyamide acid as a hydrolysate of the polyimide, polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyacrylamide, polyazole, polyethylimide, polystyrene, polyvinylpyrrolidone, polyacrylic acid, and polyacrylate.

[0049] For example, the method for forming the alignment layer 4 may include the following steps: forming a coating film containing an alignment polymer and a solvent on the surface of the surface treatment layer 3; removing the solvent from the coating film; and treating the solvent-removed coating film by rubbing.

[0050] The solvent used to form alignment layer 4 may be at least one solvent selected from the group consisting of the following solvents: water; alcohol solvents such as methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl pentyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; and chlorinated hydrocarbon solvents such as chloroform and chlorobenzene.

[0051] The photoalignment film comprises a polymer having photoreactive groups. A method for forming the photoalignment film may include the following steps: forming a coating film comprising a polymer or monomer having photoreactive groups and the aforementioned solvent on the surface of the surface treatment layer 3; and irradiating the coating film with polarized light (preferably polarized ultraviolet light).

[0052] Photoreactive groups are functional groups that exhibit liquid crystal alignment ability upon illumination. For example, a photoreactive group can be a functional group that induces molecular alignment upon illumination. A photoreactive group can also be a functional group that initiates a photoreaction (isomerization, dimerization, photocrosslinking, or photodecomposition) that becomes the source of liquid crystal alignment ability. For example, a photoreactive group can be a functional group having at least one bond structure selected from the group consisting of carbon-carbon double bonds (C=C), carbon-nitrogen double bonds (C=N), nitrogen-nitrogen double bonds (N=N), and carbon-oxygen double bonds (C=O).

[0053] The photoreactive group having a C=C bond can be at least one selected from the group consisting of vinyl, polyenyl, piracene, styrylpyridyl, styrylpyridinium, chalcone, and cinnamyl. The photoreactive group having a C=N bond can be at least one selected from the group consisting of aromatic Schiff bases and aromatic hydrazones. The photoreactive group having an N=N bond can be at least one selected from the group consisting of azophenyl, azonaphthyl, aromatic heterocyclic azo, diazo, formazanyl, and azobenzene-type structures. The photoreactive group having a C=O bond can be at least one selected from the group consisting of benzophenone, coumarin, anthraquinone, and maleimino. Polymers with photoreactive groups may have at least one substituent selected from the group consisting of alkyl, alkoxy, aryl, allyloxy, cyano, alkoxycarbonyl, hydroxyl, sulfonic acid, and halogenated alkyl groups.

[0054] A groove alignment film is a film with a plurality of raised or recessed patterns or a plurality of grooves formed on its surface. The polymeric liquid crystal compound constituting the polarizing element layer 5 is aligned in a specific direction along the raised or recessed patterns or the plurality of grooves.

[0055] A method for forming a grooved alignment film may include the following steps: exposing the surface of a photosensitive polyimide film with a photomask having a plurality of slits using an exposure mask, followed by development and rinsing, to form a raised or recessed pattern on the surface of the photosensitive polyimide film. A method for forming a grooved alignment film may include the following steps: forming a coating containing uncured ultraviolet-curable resin on the surface of a plate-shaped master disc with grooves; transferring the coating from the master disc to the surface of a surface treatment layer 3; and curing the coating transferred to the surface of the surface treatment layer 3 by irradiation with ultraviolet light. A method for forming a grooved alignment film may include the following steps: forming a coating containing uncured ultraviolet-curable resin on the surface of the surface treatment layer 3; pressing the surface of a roll having a plurality of grooves against the surface of the coating; and curing the grooved coating on the surface by irradiation with ultraviolet light.

[0056] (Polarizing element layer 5) The polarizing element 5 can be a previously known polarizing element. Typically, the polarizing element layer 5 comprises a polymer of a polymeric liquid crystal compound and a dichroic pigment. The method for forming the polarizing element layer 5 may include the following steps: coating a polarizing element layer material comprising a polymeric liquid crystal compound, a dichroic pigment, and a solvent onto the surface of the alignment layer 4 to form a coating film; and polymerizing the polymeric liquid crystal compound in the coating film. For example, the "Composition for Forming a Polarizing Film" disclosed in Japanese Patent Application Publication No. 2017-83843 and the "Coloring Composition" disclosed in International Publication No. 2017 / 154907 may be used as the raw material for the polarizing element layer.

[0057] Polymerizable liquid crystal compounds are compounds that possess a polymerizable group and exhibit liquid crystal properties. The polymerizable group is the group that participates in the polymerization reaction. For example, the polymerizable group can be a photopolymerizable group. The photopolymerizable group can be a group that participates in the polymerization reaction via an active free radical generated from a photopolymerization initiator or an acid. For example, the polymerizable group can be at least one functional group selected from the group consisting of: vinyl, ethoxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloxy, methacryloxy, ethylene oxide, and oxetyl. Polymerizable liquid crystal compounds can be thermotropic or liquidtropic liquid crystals.

[0058] Polymerizable liquid crystal compounds can be thermally oriented liquid crystal compounds that form nematic liquid crystal phases, smectic liquid crystal phases, or higher-order smectic liquid crystal phases. Specifically, they can be thermally oriented liquid crystal compounds that form smectic phases B, D, E, F, G, H, I, J, K, or L. The X-ray diffraction pattern of the polarizing element layer 5, exhibiting excellent polarization performance, includes peaks of diffracted X-rays from higher-order structures such as hexagonal and crystalline phases. These higher-order diffracted X-ray peaks can originate from periodic structures of molecular alignment. The periodic interval of molecular alignment can be 3–6 Å.

[0059] The polymerizable liquid crystal compound may be at least one compound represented by the following chemical formula A. U 1-V 1-W 1-X 1-Y 1-X 2-Y 2-X 3-W 2-V 2-U 2(A) X1, X2, and X3 independently represent either a 1,4-epenylphenyl group that may have substituents or a cyclohexane-1,4-diyl group that may have substituents. At least one of X1, X2, and X3 is a 1,4-epenylphenyl group that may have substituents. The -CH2- group constituting the cyclohexane-1,4-diyl group may be substituted with -O-, -S-, or -NR-. R represents an alkyl or phenyl group having 1 to 6 carbon atoms. Y1 and Y2 independently represent -CH2CH2-, -CH2O-, -COO-, -OCOO-, single bond, -N=N-, -CRa=CRb-, -C≡C-, or -CRa=N-. Ra and Rb independently represent hydrogen atoms or alkyl groups with 1 to 4 carbon atoms. U 1 represents a hydrogen atom or a polymeric group. U2 represents a polymeric group. W1 and W2 independently represent single bonds, -O-, -S-, -COO-, or -OCOO-, respectively. V1 and V2 independently represent alkadiyl groups with 1 to 20 carbon atoms and which may have substituents. The -CH2- group constituting the alkadiyl group may be substituted with -O-, -S-, or -NH-.

[0060] Dichroic pigments may be pigments with a maximum absorption wavelength (λMAX) in the range of 300–700 nm. For example, dichroic pigments may be at least one pigment selected from the group consisting of acridine pigments, cyanine pigments, anthocyanin pigments, naphthalene pigments, azo pigments, and anthraquinone pigments. For example, azo pigments may be at least one pigment selected from the group consisting of monoazo pigments, diazo pigments, triazo pigments, tetraazo pigments, and succinylazo pigments. The polarizing element layer 5 may contain two or more dichroic pigments (especially azo pigments) or three or more dichroic pigments (especially azo pigments).

[0061] For example, azo dyes can be compounds represented by the following chemical formula B. A 1(-N=NA 2) pN=NA 3(B) A1 and A3 independently represent a phenyl group that may have substituents, a naphthyl group that may have substituents, or a monovalent heterocyclic group that may have substituents. A2 represents a 1,4-epiphenyl group that may have substituents, a naphthalene-1,4-diyl group that may have substituents, or a divalent heterocyclic group that may have substituents. p represents an integer from 1 to 4. When p is 2 or higher, the complex numbers A2 can be the same or different.

[0062] The solvent used in the raw materials for the polarizing element layer may be at least one solvent selected from the group consisting of the following solvents: alcohol solvents such as methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; and chlorine-containing solvents such as chloroform and chlorobenzene.

[0063] The raw materials used in the polarizing element layer may include polymerization initiators (photopolymerization initiators, etc.). For example, the polymerization initiator may be at least one compound selected from the group consisting of: benzoin compounds, benzophenone compounds, benzyl ketone compounds, acetylsene oxide compounds, triterpenoid compounds, ferrous salts, and strontium salts.

[0064] In addition to polymerizable liquid crystal compounds, dichroic pigments, solvents and polymerization initiators, the raw materials used in polarizing element layers may also include sensitizers, polymerization inhibitors, leveling agents and reactive additives.

[0065] The "photoalignment layer" described in International Publication No. 2020 / 122117 can be used as alignment layer 4, and the "liquid crystal layer" described in that document can be used as polarizing element layer 5. The "photoalignment film" described in International Publication No. 2020 / 179864 can be used as alignment layer 4, and the "polarizing layer" described in that document can be used as polarizing element layer 5.

[0066] (Second protective layer 6) For example, the second protective layer 6 may comprise a polyvinyl alcohol-based resin. For instance, the polyvinyl alcohol-based resin may be at least one polyvinyl alcohol selected from the group consisting of: partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, acetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol, and amino-modified polyvinyl alcohol. The method for forming the second protective layer 6 may include the following steps: forming a coating film comprising a polyvinyl alcohol-based resin and water on the surface of the polarizing element layer 5; and drying the coating film by heating.

[0067] The second protective layer 6 may contain a cured form of a cationic polymerizable compound such as an epoxy compound, an oxobutane compound, or an ethylene compound. The second protective layer 6 may also contain a cured form of a free radical polymerizable compound.

[0068] (First adhesive layer 7 and second adhesive layer 9) The first adhesive layer 7 and the second adhesive layer 9 may each contain a polymer (cured product) of at least one polymerizable compound selected from the group consisting of: polyfunctional acrylate compounds and polyfunctional methacrylate compounds, etc. (meth)acrylate compounds; polyfunctional urethane acrylate compounds and polyfunctional urethane methacrylate compounds, etc. urethane (meth)acrylate compounds; polyfunctional epoxy acrylate compounds and polyfunctional epoxy methacrylate compounds, etc. epoxy (meth)acrylate compounds; carboxyl-modified epoxy acrylate compounds, carboxyl-modified epoxy methacrylate compounds, polyester acrylate compounds, polyester methacrylate compounds, epoxy compounds having epoxy groups, oxetane compounds having oxetane groups, and vinyl compounds. The polymerization method (curing method) of the polymerizable compound may be irradiation (ultraviolet light, etc.) or heating. An uncured first adhesive layer 7 containing a polymeric compound and a solvent can be formed on the surface of the second protective layer 6 or the phase retardation layer 8. The phase retardation layer 8 can be bonded to the surface of the second protective layer 6 via the uncured first adhesive layer 7, and the first adhesive layer 7 can be cured immediately after the phase retardation layer 8 is bonded. An uncured second adhesive layer 9 containing polymeric compounds and solvents can be formed on the surface of the phase retardation layer 8 or the optical compensation layer 10. The optical compensation layer 10 can be bonded to the surface of the phase retardation layer 8 via the uncured second adhesive layer 9, and the second adhesive layer 9 can be cured immediately after the optical compensation layer 10 is bonded. The composition of the first adhesive layer 7 may be the same as that of the second adhesive layer 9. Alternatively, the composition of the first adhesive layer 7 may differ from that of the second adhesive layer 9.

[0069] (Phase difference layer 8 and optical compensation layer 10) The optical compensation layer 10 can be renamed a phase retardation layer different from the phase retardation layer 8. For example, the phase retardation layer 8 and the optical compensation layer 10 can each be at least one selected from the group consisting of positive A plates such as λ / 4 plates and λ / 2 plates, and positive C plates (vertical alignment films of photo-alignment materials). The phase retardation layer 8 and the optical compensation layer 10 can each be formed by coating the aforementioned polymeric liquid crystal compound onto an alignment layer different from the aforementioned alignment layer 4. The method for forming the alignment layers used to form the phase retardation layer 8 and the optical compensation layer 10 can be the same as that used for the aforementioned alignment layer 4 in the polarizing element layer 5.

[0070] This invention is not necessarily limited to the embodiments described above. Various modifications can be made to this invention without departing from its spirit, and such modifications are also included within this invention.

[0071] For example, the manufacturing method of the polarizing plate C according to the second embodiment of the present invention includes the following steps: a first step of directly depositing the surface treatment layer 3 onto the surface of the substrate layer 2; a second step of directly or indirectly depositing the polarizing element layer 5 onto the surface of the surface treatment layer 3; a third step of directly or indirectly depositing other resin layers onto the surface of the polarizing element layer 5 via the first adhesive layer 7; a fourth step of simultaneously heating the ends of the substrate layer 2 and the surface treatment layer 3 after the third step; and a fifth step of peeling off the substrate layer 2 after the fourth step. In the second embodiment, the polarizing element layer 5 comprises a polymer of a polymeric liquid crystal compound and a dichroic pigment. In the second embodiment, other resin layers may be a phase retardation layer 8, an optical compensation layer 10, or a third protective layer 11. In the fourth step, by simultaneously heating the ends of both the substrate layer 2 and the surface treatment layer 3, the ends of the substrate layer 2 and the surface treatment layer 3 are fused together. As a result, the peel strength of the ends of the substrate layer 2 to the ends of the surface treatment layer 3 is increased. On the other hand, the peel strength of the substrate layer 2 to the surface treatment layer 3 remains unchanged in the portions of both the substrate layer 2 and the surface treatment layer 3 other than their ends. Therefore, by means of the fourth step, a substrate laminate A with Ie higher than Ic can be obtained in the same manner as in the first embodiment described above. In other words, in the second embodiment, by means of the steps performed before the fifth step, an optical laminate B can be obtained in the same manner as in the first embodiment. Therefore, similarly to the first embodiment, in the second embodiment, the end piece E that is in close contact with the end of the substrate layer 2 can also be easily removed from the end of the optical laminate B by means of the fifth step of peeling off the substrate layer 2.

[0072] The polarizing plate of this invention can be a circular polarizing plate or an elliptical polarizing plate having one or more phase retardation layers. Alternatively, the polarizing plate of this invention can be a linear polarizing plate without a phase retardation layer. [Industrial Applicability]

[0073] For example, the substrate laminate and optical laminate of one embodiment of the present invention can be used to manufacture polarizing plates.

[0074] 1: Protective layer for substrate 2: Substrate layer 3: Surface treatment layer (first protective layer) 4: Alignment layer 5: Polarizing element layer 6: Second protective layer 7: First adhesive layer 8: Phase retardation layer (other resin layers) 9: Second adhesive layer 10: Optical compensation layer (another phase retardation layer) 11: Third protective layer A: Substrate laminate AC: Central Division AE: End B: Optical laminate C: Polarizing plate E: End piece WAE: width

Claims

1. An optical laminate comprising: a substrate laminate having a substrate layer and a surface treatment layer directly deposited on the surface of the substrate layer; an alignment layer directly deposited on the surface of the surface treatment layer; and a polarizing element layer directly deposited on the surface of the alignment layer, wherein the surface treatment layer is a cured product of an ultraviolet-curable resin, the polarizing element layer comprises a polymer of a polymeric liquid crystal compound and a dichroic pigment, the substrate laminate comprising a pair of opposing ends in a direction substantially parallel to the surface of the substrate layer, and a central portion located between the pair of ends, wherein the peel strength of the substrate layer at at least one of the ends to the surface treatment layer is denoted as Ie, the peel strength of the substrate layer at the central portion to the surface treatment layer is denoted as Ic, and Ie is higher than Ic.

2. The optical laminate of claim 1, wherein the aforementioned Ie is higher than the aforementioned Ic and is 0.40 N / 25 mm or more, and the aforementioned Ic is lower than the aforementioned Ie and is 0.55 N / 25 mm or less.

3. The optical laminate as claimed in claim 1 or 2, wherein at least one of the ends of the substrate laminate is located outside the region surrounded by the outer periphery of the polarizing element layer in a direction substantially parallel to the surface of the surface treatment layer.

4. The optical laminate as claimed in claim 1 or 2, comprising an adhesive layer and other resin layers, wherein the adhesive layer is deposited directly or indirectly on the surface of the polarizing element layer, and the other resin layers are deposited directly on the surface of the adhesive layer.

5. The optical laminate as claimed in claim 4, wherein the other resin layers are phase retardation layers.

6. The optical laminate of claim 4, wherein at least one end of the substrate laminate is located outside the region surrounded by the outer periphery of the adhesive layer in a direction substantially parallel to the surface of the surface treatment layer.

7. The optical laminate of claim 6, wherein, in a direction substantially parallel to the surface of the surface treatment layer and substantially perpendicular to the outer periphery of the adhesive layer, the width of at least one of the ends of the substrate laminate is 0.1 mm or more but less than 55 mm.

8. The optical laminate of claim 4, wherein at least one end of the polarizing element layer is located outside the region surrounded by the outer periphery of the adhesive layer in a direction substantially parallel to the surface of the surface treatment layer.

9. A method for manufacturing an optical laminate, comprising the steps of: directly depositing the surface treatment layer onto the surface of the substrate layer to obtain the laminate; winding the laminate to obtain a roll; and heating at least one of a pair of opposite end faces of the roll.

10. A method for manufacturing an optical laminate, comprising the steps of: performing corona treatment on at least one of a pair of opposite ends of the substrate layer; and, after the corona treatment, directly depositing the surface treatment layer onto the surface of the substrate layer.

11. A method for manufacturing a polarizing plate, comprising the step of peeling off the substrate layer of an optical laminate according to any one of claims 1 to 8.

12. A method for manufacturing a polarizing plate, comprising the following steps: a step of directly depositing a surface treatment layer onto the surface of a substrate layer; a step of directly or indirectly depositing a polarizing element layer onto the surface of the surface treatment layer; a step of directly or indirectly depositing other resin layers onto the surface of the polarizing element layer via an adhesive layer; a step of simultaneously heating the ends of the substrate layer and the surface treatment layer after the step of simultaneously heating the ends of the substrate layer and the surface treatment layer; and a step of peeling off the substrate layer after the step of simultaneously heating the ends of the substrate layer and the surface treatment layer; wherein the peel strength of the ends of the substrate layer to the ends of the surface treatment layer is improved by the step of simultaneously heating the ends of the substrate layer and the surface treatment layer, wherein the polarizing element layer comprises a polymer of a polymeric liquid crystal compound and a dichroic pigment.

13. The method for manufacturing a polarizing plate as claimed in claim 12, wherein the other resin layers mentioned above are phase retardation layers.

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