Manufacturing method of composite polarizing plates

Abstract

To provide a method for manufacturing a composite polarizing plate that can reduce air bubbles entering between a polarizing plate and / or a surface treatment film and an adhesive layer.SOLUTION: A composite polarizing plate has a polarizing plate and a surface treatment film laminated thereon. The surface treatment film has a base material film, and a surface treatment layer formed on a surface of the base material film. The polarizing plate includes at least a polarizing element. The method for manufacturing a composite polarizing plate includes: a step (a) of pasting the surface treatment film and the polarizing plate with an adhesive layer with a stress at an elongation of 800% of 0.8 N / mm2 or less therebetween, thereby obtaining a laminate; and a step (b) of adjusting, in the laminate, the stress at an elongation of 800% of the adhesive layer at a temperature of 23°C to be 0.9 N / mm2 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] In display devices such as liquid crystal displays and organic EL displays, surface treatment films are sometimes used to improve visibility and suppress scratches. To improve visibility by suppressing the reduction in visibility caused by reflection of ambient light, a display device is known that uses a laminate in which an anti-glare hard coat film is bonded to a polarizing element (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-81219 [Overview of the project] [Problems that the invention aims to solve]

[0005] When manufacturing a composite polarizing plate by laminating a polarizing plate containing a polarizing element with a surface treatment film, an adhesive layer is sometimes used to bond the polarizing plate and the surface treatment film. To ensure the surface hardness of the composite polarizing plate, a hard (less plastically deformable) adhesive layer is sometimes used as the adhesive layer. It has been found that when a hard adhesive layer is used to bond the polarizing plate and the surface treatment film, air bubbles are introduced between the polarizing plate and / or the surface treatment film and the adhesive layer.

[0006] The present invention aims to provide a method for manufacturing a composite polarizing plate that can suppress the formation of air bubbles between the polarizing plate and / or surface treatment film and the adhesive layer. [Means for solving the problem]

[0007] The present invention provides a method for manufacturing the following composite polarizing plate. [1] A method for manufacturing a composite polarizing plate in which a surface treatment film and a polarizing plate are laminated, The surface-treated film comprises a base film and a surface-treated layer formed on the surface of the base film. The polarizing plate includes at least a polarizing element, The aforementioned manufacturing method is The stress at 800% elongation is 0.8 N / mm². 2 Step (a) of bonding the surface treatment film and the polarizing plate via an adhesive layer in the following state to obtain a laminate, In the laminate, the stress of the adhesive layer at an elongation of 800% at a temperature of 23°C is 0.9 N / mm 2 A method for manufacturing a composite polarizing plate, comprising the step (b) of adjusting to the above. [2] The above step (a) is: The process of forming the adhesive layer on the surface treatment film (a1), A method for manufacturing a composite polarizing plate according to [1], comprising the step (a2) of laminating the polarizing plate on the adhesive layer formed on the surface treatment film. [3] A method for manufacturing a composite polarizing plate according to [2], wherein step (a2) is performed within 6 days after step (a1). 〔4〕The step (b) is a step of storing the laminate, and is a method for manufacturing a composite polarizing plate according to any one of 〔1〕to 〔3〕. 〔5〕The surface treatment film has the surface treatment layer on one side of the base film, The laminate has the adhesive layer on the base film side of the surface treatment film, and is a method for manufacturing a composite polarizing plate according to any one of 〔1〕to 〔4〕. 〔6〕The polarizing plate has a protective film on one or both sides of the polarizing element, and is a method for manufacturing a composite polarizing plate according to any one of 〔1〕to 〔5〕. 〔7〕The thickness of the adhesive layer is 10 μm or less, and is a method for manufacturing a composite polarizing plate according to any one of 〔1〕to 〔6〕. 〔8〕The adhesive layer is formed using an adhesive composition containing a (meth)acrylic resin, The glass transition temperature of the (meth)acrylic resin is -30°C or lower, and is a method for manufacturing a composite polarizing plate according to any one of 〔1〕to 〔7〕. 〔9〕The surface treatment layer is one or more selected from the group consisting of an antireflection layer, an antiglare layer, a hard coat layer, and an antifouling layer, and is a method for manufacturing a composite polarizing plate according to any one of 〔1〕to 〔8〕.

Advantages of the Invention

[0008] According to the method for manufacturing a composite polarizing plate of the present invention, it is possible to suppress bubbles from being mixed between the polarizing plate and / or the surface treatment film and the adhesive layer.

Brief Description of the Drawings

[0009] [Figure 1] It is a cross-sectional view schematically showing a composite polarizing plate according to an embodiment of the present invention. [Figure 2] It is a graph showing the results of measuring the stress with respect to the elongation of the adhesive layer produced in the examples.

Modes for Carrying Out the Invention

[0010] The embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

[0011] (Composite polarizer) Figure 1 is a schematic cross-sectional view of a composite polarizing plate according to one embodiment of the present invention. The composite polarizing plate 1 is made up of a laminated surface treatment film 20 and a polarizing plate 10. The composite polarizing plate 1 has an adhesive layer 31 between the surface treatment film 20 and the polarizing plate 10. The adhesive layer 31 in the composite polarizing plate 1 has a stress of 0.9 N / mm at an elongation of 800% at a temperature of 23°C (hereinafter sometimes referred to as "elongation stress (23°C)"). 2 That's all.

[0012] The surface treatment film 20 has a base film 21 and a surface treatment layer 22 formed on the surface of the base film 21. In the composite polarizing plate 1, it is preferable that the surface treatment layer 22 is on one side of the base film 21 of the surface treatment film 20, and that the base film 21 side of the surface treatment film 20 faces the adhesive layer 31. The surface treatment layer 22 can be one or more selected from the group consisting of an anti-reflective layer, an anti-glare layer, a hard coat layer, and an anti-fouling layer.

[0013] The polarizing plate 10 includes at least a polarizing element 11. Preferably, the polarizing plate 10 has a protective film 13 on one or both sides of the polarizing element 11. The polarizing element 11 and the protective film 13 may be laminated with a bonding layer 12 (adhesive layer or adhesive layer) in between, and preferably the bonding layer 12 is in direct contact with the polarizing element 11 and the protective film 13.

[0014] In the composite polarizing plate 1, the adhesive layer 31 is in direct contact with the surface treatment film 20 and the polarizing plate 10. The tensile stress (at 23°C) of the adhesive layer 31 in the composite polarizing plate 1 is 0.9 N / mm². 2 The above is 1.0 N / mm 2 It may be greater than or equal to 1.2 N / mm 2 It may be greater than or equal to 1.3 N / mm 2The values ​​may be greater than or equal to the above range. By having the tensile stress (23°C) of the adhesive layer 31 within the above range, the surface hardness of the surface on the surface treatment film 20 side of the composite polarizing plate 1 can be improved, thereby suppressing scratches on the surface of the composite polarizing plate 1. The tensile stress (23°C) of the adhesive layer 31 can be determined by the method described in the examples below.

[0015] The composite polarizing plate 1 may further have another adhesive layer on the polarizing plate 10 side, and may have a release film on the side opposite to the polarizing plate 10 to cover and protect the other adhesive layer. The other adhesive layer is, for example, a bonding layer for bonding to an image display element of a display device. The other adhesive layer may be provided in direct contact with the polarizing plate 10, or it may be provided via another layer located on the side opposite to the surface treatment film 20 side of the polarizing plate 10.

[0016] The composite polarizing plate 1 may further have a protective film laminated on the side of the surface treatment film 20 opposite to the polarizing plate 10, which is peelable from the surface treatment film 20. The protective film is for protecting the surface of the surface treatment film 20.

[0017] The pencil hardness of the surface of the surface treatment film 20 on the composite polarizing plate 1 is preferably HB or higher, more preferably F or higher, even more preferably H or higher, and particularly preferably 2H or higher. When the pencil hardness is equal to or higher than the above hardness, it is easier to suppress the occurrence of scratches and other damage on the surface of the surface treatment film 20 on the composite polarizing plate 1. The pencil hardness can be measured in accordance with JIS K 5600-5-4:1999, as described in the examples below.

[0018] The composite polarizing plate 1 can be used by stacking it on the image display element of a display device such as a liquid crystal display device or an organic EL display device.

[0019] (Manufacturing method for composite polarizing plates) The method for manufacturing the composite polarizing plate 1 is a method for manufacturing the composite polarizing plate 1 having the structure described above, The stress at 800% elongation (hereinafter sometimes referred to as "elongation stress") is 0.8 N / mm 2 A step (a) of obtaining a laminate by laminating a surface treatment film 20 and a polarizing plate 10 through an adhesive layer in a state where the following conditions are satisfied, In the laminate obtained in step (a), the stress at 800% elongation (elongation stress (23°C)) of the adhesive layer 31 at a temperature of 23°C is 0.9 N / mm 2 A step (b) of adjusting so as to be the above, and the method includes these steps.

[0020] The elongation stress of the adhesive layer 31 in step (a) may be 0.8 N / mm 2 or less, may be less than 0.8 N / mm 2 or less, may be 0.75 N / mm 2 or less, may be 0.7 N / mm\] 2 or less. The elongation stress in step (a) is usually 0.2 N / mm 2 or more, may be 0.3 N / mm 2 or more, may be 0.4 N / mm 2 or more. The elongation stress can be measured by the method described in the examples below.

[0021] The elongation stress (23°C) of the adhesive layer 31 in step (b) may be 1.0 N / mm 2 or more, may be 1.1 N / mm 2 or more, may be 1.2 N / mm 2 or more, may be 1.3 N / mm 2 or more, and is usually 2.0 N / mm 2 or less. The elongation stress (23°C) can be measured by the method described in the examples below.

[0022] Methods for setting the tensile stress of the adhesive layer 31 within the above range in step (a) and the tensile stress of the adhesive layer 31 (at 23°C) within the above range in step (b) include adjusting the components in the adhesive composition used to form the adhesive layer 31, and adjusting the environmental conditions for carrying out step (a). Methods for adjusting the components in the adhesive composition include adjusting the type and / or molecular weight of the base polymer contained in the adhesive composition; adjusting the type and / or amount of monomers having reactive functional groups that constitute the base polymer; adjusting the type and / or amount of crosslinking agents contained in the adhesive composition; and using a base polymer having reactive groups and a polymerization initiator as components in the adhesive composition. Methods for adjusting the environmental conditions for carrying out step (a) include adjusting the temperature at which step (a) is carried out.

[0023] If step (b) is a step of storing the laminate described later, the adhesive composition used to form the adhesive layer 31 preferably contains a base polymer and a crosslinking agent. In this case, it is preferable that the adhesive layer 31 used for bonding in step (a) is in a state where the reaction between the base polymer and the crosslinking agent has not progressed sufficiently, and that the adhesive layer 31 after step (b) is in a state where the reaction between the base polymer and the crosslinking agent has progressed sufficiently.

[0024] As described above, the bonding of the surface treatment film 20 and the polarizing plate 10 in process (a) has an elongation stress of 0.8 N / mm 2 The process is carried out using an adhesive layer 31 in the following state. Since the adhesive layer 31 with an tensile stress in this range is in a soft state, it is easier to adhere the adhesive layer 31 to the surface treatment film 20 and / or polarizing plate 10. This makes it possible to suppress the incorporation of air bubbles between the surface treatment film 20 and / or polarizing plate 10 and the adhesive layer 31 in the laminate obtained in step (a). In step (b), the hardness of the adhesive layer 31 can be improved by adjusting the tensile stress (23°C) of the adhesive layer 31 to fall within the above range in the laminate in which the incorporation of air bubbles has been suppressed. This makes it possible to obtain a composite polarizing plate 1 with high surface hardness and suppressed incorporation of air bubbles.

[0025] The tensile stress mentioned above is an indicator of the plastic deformation region of the adhesive layer 31, and is a value that changes with the elapsed time since the formation of the adhesive layer 31. On the other hand, it was confirmed that the Young's modulus, which is an indicator of the elastic deformation region of the adhesive layer 31, does not change significantly with the elapsed time since the formation of the adhesive layer 31, and remains at approximately the same value regardless of the elapsed time. Therefore, in the manufacturing method of the composite polarizing plate 1 of this embodiment, the composite polarizing plate 1 is manufactured based on the tensile stress mentioned above, which is an indicator of the plastic deformation region of the adhesive layer 31, in order to suppress the inclusion of air bubbles between the polarizing plate and / or surface treatment film and the adhesive layer.

[0026] The manufacturing method for the composite polarizing plate 1 may be carried out using a single sheet or a long sheet. From the viewpoint of continuously producing the composite polarizing plate 1, it is preferable to use a long sheet. In this case, the layers or films obtained in or during each process can be wound into a roll to form a reel, and the layers or films can be unwound from this reel to carry out the next process. In this specification, a long sheet refers to, for example, a layer or film having a length of 30 to 10,000 m.

[0027] The following describes in detail each step in the manufacturing process of the composite polarizing plate 1. (Step (a)) Process (a) involves an tensile stress of 0.8 N / mm 2 The following is a step to obtain a laminate by bonding the surface treatment film 20 and the polarizing plate 10 using an adhesive layer in the following state. The environmental conditions for performing step (a) are such that the tensile stress of the adhesive layer 31 is 0.8 N / mm 2 The following conditions can be met, but the requirements are not particularly limited. The preferred temperature when performing step (a) is, for example, 10°C or higher, may be 15°C or higher, may be 20°C or higher, and may also be, for example, 35°C or lower, or 30°C or lower. The preferred relative humidity when performing step (a) is usually 30%RH or higher, may be 40%RH or 45%RH, and may also be 70%RH or lower, may be 65%RH or 60%RH.

[0028] Step (a) may include, for example, a step (a1') of forming an adhesive layer 31 on one of the surface treatment film 20 and the polarizing plate 10, and a step (a2') of laminating the other of the surface treatment film 20 and the polarizing plate 10 onto the adhesive layer 31 formed in step (a1'). If step (a) includes steps (a1') and (a2'), the tensile stress of the adhesive layer 31 in both steps (a1') and (a2') is within the range (0.8 N / mm²) described in step (a) above. 2 The following applies.

[0029] Step (a1') may be performed by laminating the adhesive layer 31 formed on the release film with the surface treatment film 20 or polarizing plate 10, and then peeling off the release film. If this step is included, it is preferable that the tensile stress of the adhesive layer 31 in step (a1') is the same as, or smaller than, the tensile stress of the adhesive layer 31 in step (a2'). It is preferable that the tensile stress of the adhesive layer 31 in step (a2') is within the range described above as the tensile stress in step (a).

[0030] The period between process (a1') and process (a2') may be 6 days or less, 5 days or less, 4 days or less, 3 days or less, 2 days or less, or 1 day or less. Within the above period, the tensile stress of the adhesive layer 31 is 0.8 N / mm 2 The following conditions make it easier to perform step (a2').

[0031] When performing step (a1') and using the adhesive layer 31 formed on the release film, it is preferable to bond the adhesive layer 31 to the surface treatment film 20 or polarizing plate 10 immediately after forming the adhesive layer 31 on the release film. This allows the period from forming the adhesive layer 31 on the release film to performing step (a2') to be substantially the same as the period from performing step (a1') to performing step (a2'). When performing step (a1') using the adhesive layer 31 formed on the release film, the period from forming the adhesive layer 31 on the release film to performing step (a2') via step (a1') may be 6 days or less, 5 days or less, 4 days or less, 3 days or less, 2 days or less, or 1 day or less. Within the above period, the tensile stress of the adhesive layer 31 is 0.8 N / mm 2 The following conditions make it easier to perform step (a2').

[0032] Preferably, step (a1') is a step (a1) in which an adhesive layer 31 is formed on the surface treatment film 20, and step (a2') is a step (a2) in which a polarizing plate 10 is laminated on the adhesive layer 31 formed on the surface treatment film 20.

[0033] The polarizing plate 10 used in step (a) may have the above-mentioned adhesive layer (a bonding layer for bonding to the image display element) and a release film laminated on it. The surface treatment film 20 used in step (a) may have a protective film laminated on it.

[0034] Surface activation treatments such as corona treatment, plasma treatment, or itro treatment may be performed on the bonding surface between the surface treatment film 20 and the polarizing plate 10 and the adhesive layer 31 in order to improve their adhesion.

[0035] (Step (b)) Step (b) is to ensure that the tensile stress (at 23°C) of the adhesive layer 31 in the laminate obtained in step (a) is 0.9 N / mm². 2This is a process to adjust the laminate to the above state. By going through process (b), the adhesive layer 31, which is in a soft state in the laminate obtained in process (a), can be made hard, and the surface hardness of the composite polarizing plate 1 can be improved. Process (b) may be performed on the laminate in sheet form, or on the laminate in a rolled form.

[0036] Step (b) is not particularly limited as long as the tensile stress (23°C) of the adhesive layer 31 can be within the above range. Step (b) can be performed according to the components contained in the adhesive layer 31, for example, it may be a step of storing the laminate obtained in step (a), or if the adhesive layer 31 contains a polymerization initiator, it may be a step of heating or irradiation with active energy rays. It is preferable that step (b) is a step of storing the laminate. The step of storing the laminate may be, for example, a step of curing the laminate obtained in step (a) to allow the reaction of the reactive components (e.g., base polymer and crosslinking agent) contained in the adhesive layer 31 to proceed.

[0037] If process (b) is a process for storing the laminate, the environmental conditions for storage are such that the tensile stress of the adhesive layer 31 (at 23°C) is 0.9 N / mm². 2 The above is not particularly limited as long as it can be achieved. The preferred temperature when performing step (b) is usually 10°C or higher, may be 15°C or higher, may be 20°C or higher, and is usually 35°C or lower, may be 30°C or lower. The preferred relative humidity when performing step (b) is usually 30%RH or higher, may be 40%RH or higher, may be 45%RH or higher, and is usually 70%RH or lower, may be 65%RH or lower, or may be 60%RH or lower.

[0038] If step (b) is a step of storing the laminate, the storage period can be selected according to the type of adhesive composition used to form the adhesive layer 31, the environmental conditions described above, etc. For example, it may be 6 days or more, 7 days or more, 8 days or more, 9 days or more, or 10 days or more. Within the above period, step (b) will bring the tensile stress (23°C) of the adhesive layer 31 to 0.9 N / mm 2 It's even easier to adjust.

[0039] The following describes the details of the layers and films that make up the composite polarizing plate 1. (Adhesive layer) The adhesive layer is a layer formed using an adhesive composition. The adhesive composition exhibits adhesive properties by being attached to the substrate itself, and is known as a pressure-sensitive adhesive.

[0040] The thickness of the adhesive layer is not particularly limited, but is preferably 10 μm or less, may be 8 μm or less, 7 μm or less, or 6 μm or less, and is usually 1 μm or more, but may also be 3 μm or more. By having the adhesive layer thickness within the above range, the surface hardness of the composite polarizing plate can be improved.

[0041] The adhesive composition for forming the adhesive layer may have (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin as its main component (base polymer). The main component refers to a component that makes up 50% by weight or more of the total solid content of the adhesive composition. Among these, an adhesive composition using (meth)acrylic resin as the base polymer, which has excellent transparency, weather resistance, heat resistance, etc., is preferred. The adhesive composition may be of the active energy ray curing type or thermosetting type. (Meth)acrylic refers to at least one of acrylic and methacrylic.

[0042] As the (meth)acrylic resin used as the base polymer in the adhesive composition, polymers or copolymers using one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, are preferably used.

[0043] It is preferable to copolymerize a monomer having a reactive functional group into the base polymer. Examples of monomers having a reactive functional group include monomers having carboxyl groups, hydroxyl groups, amide groups, amino groups, epoxy groups, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylic acid, 2-hydroxyethyl (meth)acrylic acid, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0044] The glass transition temperature of the (meth)acrylic resin contained in the adhesive composition is preferably -30°C or lower, more preferably -35°C or lower, and is usually -50°C or higher, and may also be -45°C or higher. Having the glass transition temperature of the (meth)acrylic resin within the above range makes it easier to obtain an adhesive layer with the above-mentioned tensile stress and tensile stress (23°C) within the above range. The glass transition temperature can be measured by the method described in the examples below.

[0045] The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylate salts, etc., with carboxyl groups; polyamine compounds that form amide bonds, etc., with carboxyl groups; polyepoxy compounds and polyols that form ester bonds, etc., with carboxyl groups; and isocyanate compounds that form amide bonds, etc., with carboxyl groups. Among these, isocyanate compounds are preferred.

[0046] Isocyanate compounds are compounds having at least two isocyanate groups (-NCO) in their molecule. Examples of isocyanate compounds include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, chlorphenyl diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. The isocyanate compound may be a derivative of the above-mentioned compound, such as a polyhydric alcohol compound adduct (for example, an adduct with glycerol, trimethylolpropane, etc.), isocyanurate, or biuret-type compound, or a urethane prepolymer-type isocyanate compound obtained by addition reaction with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc., or a blocked isocyanate compound in which the isocyanate group of an organic polyhydric isocyanate compound is blocked.

[0047] The isocyanate compound content is 0.1 parts by mass or more, may be 1 part by mass or more, may be 3 parts by mass or more, or may be 10 parts by mass or less, may be 8 parts by mass or less, or may be 6 parts by mass or less, per 100 parts by mass of the base polymer (especially (meth)acrylic resin).

[0048] (Surface treatment film) The surface-treated film comprises a base film and a surface-treated layer formed on the surface of the base film. The surface-treated layer 22 may be a part of the base film 21, or it may be a separate layer from the base film 21 that is laminated on the base film 21. If the surface-treated layer 22 is a separate layer from the base film 21, it is preferable that the base film 21 and the surface-treated layer 22 are in direct contact.

[0049] The base film can be the resin film described later as a material used for the protective film.

[0050] As described above, the surface treatment layer may be one or more selected from the group consisting of an anti-reflective layer, an anti-glare layer, a hard coat layer, and an anti-fouling layer. The surface treatment layer may also be a laminate of an anti-glare hard coat layer, an anti-reflective layer, and an anti-fouling layer. The surface treatment layer may be a coated layer formed by applying a coating liquid to the surface of a substrate film, or it may be a film-forming layer formed by chemical vapor deposition or physical vapor deposition.

[0051] The anti-reflective layer has the function of suppressing the reflection of external light. When the surface treatment film of a composite polarizer has an anti-reflective layer, the reduction in contrast due to reflection of external light can be suppressed.

[0052] Examples of anti-reflective layers include those in which the surface treatment layer is a textured pattern structure on the surface of the base film, and the period of the texture is controlled to be less than or equal to the wavelength of visible light (a base film having a moth-eye structure on its surface); those in which the surface treatment layer is a fine textured pattern formed on the surface of the base film by coating a composition or the like; and those in which the surface treatment layer has a single or multilayer layer with an adjusted refractive index.

[0053] The anti-reflective layer is preferably a thin film with precisely controlled thickness and refractive index, or a layer of two or more thin films stacked together. A thin film is defined as a film with a thickness of 1 μm or less. The anti-reflective layer can be configured to exhibit anti-reflective functionality by utilizing the interference effect of light to cancel out the inverted phases of incident and reflected light. The wavelength range of visible light in which the anti-reflective function is exhibited is, for example, 380 to 780 nm, with the wavelength range of 450 to 650 nm being particularly sensitive, and it is preferable to design the anti-reflective layer to minimize the reflectance at its central wavelength of 550 nm. The thickness of the anti-reflective layer is preferably 100 nm to 350 nm, and more preferably 150 nm to 300 nm.

[0054] In designing anti-reflective layers based on the interference effect of light, one way to improve the interference effect is to increase the refractive index difference between the anti-reflective layer and the anti-glare layer described later. Generally, in multilayer anti-reflective layers with a structure of stacked 2 to 15 thin films (thin films with precisely controlled thickness and refractive index), forming multiple layers of components with different refractive indices to a predetermined thickness increases the degree of freedom in the optical design of the anti-reflective layer, further improving the anti-reflective effect and making the spectral reflectance characteristics uniform (flat) in the visible light region. Since thin films require high thickness precision, each layer is generally formed using dry methods such as vacuum deposition, sputtering, and CVD (chemical vapor deposition). By using an anti-reflective film in which each layer is formed by sputtering, a composite polarizer with high scratch resistance can be obtained.

[0055] Preferably, the anti-reflective layer consists of alternating layers of low refractive index and high refractive index. The high refractive index layers do not need to have the same refractive index, but it is preferable to use the same material and have the same refractive index.

[0056] Materials that can be used to construct a low refractive index layer include silicon dioxide (SiO2), silicon oxynitride (SiON), gallium oxide (Ga2O3), aluminum oxide (Al2O3), lanthanum oxide (La2O3), lanthanum fluoride (LaF3), magnesium fluoride (MgF2), and sodium aluminum fluoride (Na3AlF6). Among these, silicon dioxide (SiO2) is the most preferred from the viewpoint of low refractive index, no absorption in the visible light range, and high film strength.

[0057] Materials that constitute a high refractive index layer include niobium pentoxide (Nb2O5), titanium dioxide (TiO2), zirconium dioxide (ZrO2), tantalum pentoxide (Ta2O5), silicon oxynitride (SiON), silicon nitride (Si3N4), and silicon niobium oxide (SiNbO). Among these, niobium pentoxide (Nb2O5) or titanium dioxide (TiO2) are more preferred from the viewpoint of high refractive index and high film strength, and niobium pentoxide (Nb2O5) is most preferred because it does not absorb in the visible light range.

[0058] The refractive index of any of these compounds can be altered to some extent by controlling the ratio of constituent elements to deviate from the stoichiometric ratio, or by controlling the film deposition density during film formation. The materials constituting the low-reflectance layer and the high-reflectance layer are not limited to the compounds mentioned above, as long as they satisfy the refractive index conditions described above. In addition, unavoidable impurities may be present.

[0059] When a surface-treated film has a structure in which an anti-reflective layer is laminated on a base film, the arithmetic mean roughness Ra of the surface on the side of the base film where the anti-reflective layer is formed is preferably 1.5 nm or less, and more preferably 1.0 nm or less. The arithmetic mean roughness Ra may be 0.00 nm or more, and may be 0.05 nm or more. The arithmetic mean roughness Ra is determined from a 1 μm square observation image using an atomic force microscope (AFM).

[0060] The anti-glare layer can have functions such as improving visibility, suppressing reflection of external light, and reducing moiré patterns (interference fringes). The anti-glare layer can have a fine uneven surface. This fine uneven surface can be formed by adding fillers or by applying a fine emboss to the surface.

[0061] The anti-glare layer may be, for example, an anti-glare hard coat layer formed by dispersing fine particles in a coating solution containing a curable resin for forming the hard coat layer described later. The fine particles dispersed in the coating solution can be various metal oxide fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide; glass fine particles; crosslinked or uncrosslinked organic fine particles made from various transparent polymers such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate; and transparent silicone fine particles, etc., without particular limitation. One or more of these fine particles can be appropriately selected and used. Among these, fine particles with a refractive index higher than that of the curable resin contained in the coating solution are preferred, for example, organic fine particles with a refractive index of 1.5 or higher, such as styrene beads (refractive index 1.59), are preferred. The average particle size of the fine particles is preferably 1 to 10 μm, more preferably 2 to 5 μm. The proportion of fine particles is not particularly limited, but 6 to 20 parts by weight per 100 parts by weight of the matrix resin is preferred.

[0062] The coating solution for forming the anti-glare layer may contain a thixotropic agent (such as silica or mica with a particle size of 0.1 μm or less). This makes it easy to form a fine uneven structure with protruding particles.

[0063] The hard coat layer has the function of improving the surface hardness of the base film and can improve the scratch resistance of the surface. When the surface treatment film is a hard coat layer, the surface hardness of the surface treatment layer side of the surface treatment film is, for example, HB or higher, may be F or higher, may be H or higher, may be 2H or higher, or may be 3H or higher. The pencil hardness can be measured in accordance with JIS K 5600-5-4:1999, as described in the examples below.

[0064] A hard coat layer can be formed, for example, by applying a coating solution containing a curable resin onto a substrate film. In addition to the curable resin, the coating solution may also contain additives such as leveling agents, thixotropic agents, and antistatic agents.

[0065] Examples of curable resins include thermosetting resins, ultraviolet curing resins, and electron beam curing resins. Types of curable resins include polyester resins, acrylic resins, urethane resins, acrylic urethane resins, amide resins, silicone resins, silicate resins, epoxy resins, melamine resins, oxetane resins, and acrylic urethane resins. One or more of these curable resins can be used, selected as appropriate.

[0066] Among these, curable resins are preferably (meth)acrylic resins, (meth)acrylic urethane resins, and epoxy resins, and (meth)acrylic urethane resins are preferred, due to their high hardness, ability to be cured by ultraviolet irradiation, and excellent productivity. UV-curable resins include UV-curable monomers, oligomers, polymers, etc. Preferably used UV-curable resins include those having UV-polymerizable functional groups, and among these, those containing (meth)acrylic monomers or oligomers having two or more, particularly three to six, such functional groups as components.

[0067] The thickness of the hard coat layer is not particularly limited, but to achieve high hardness, it is preferably 0.5 μm or more, and more preferably 1 μm or more. Considering the ease of formation by coating, the thickness of the hard coat layer is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 10 μm or less.

[0068] When a surface-treated film has a structure in which a hard coat layer is laminated onto a base film, the arithmetic mean roughness of the hard coat layer is equal to the arithmetic mean roughness of the surface of the base film on the side where the hard coat layer is formed. The arithmetic mean roughness Ra can be determined from a 1 μm square observation image using an atomic force microscope (AFM). As described above, forming a hard coat layer by coating can reduce the arithmetic mean roughness of the surface of the base film.

[0069] The antifouling layer can impart functions such as water repellency, oil repellency, sweat resistance, and antifouling properties to the surface treatment film. The antifouling layer may contain antifouling agents such as fluorine-containing organic compounds, including fluorocarbons, perfluorosilanes, and polymer compounds thereof.

[0070] (Polarizing element) A polarizing element is an absorbing polarizing film that has the property of absorbing linearly polarized light with a vibration plane parallel to its absorption axis and transmitting linearly polarized light with a vibration plane perpendicular to the absorption axis (parallel to the transmission axis).

[0071] The polarizing element is a polyvinyl alcohol-based resin layer (hereinafter sometimes referred to as "PVA-based resin layer") on which a dichroic dye is adsorbed and oriented. Known polarizing elements can be used. Examples of polarizing elements include a stretched film obtained by dyeing a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as "PVA-based resin film") with a dichroic dye and uniaxially stretching it, and a stretched layer obtained by using a laminated film having a coated layer formed by applying a coating solution containing polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") to a base film, dyeing the coated layer with a dichroic dye, and uniaxially stretching the laminated film. Stretching may be performed after dyeing with the dichroic dye, stretching while dyeing, or dyeing after stretching.

[0072] PVA-based resins are obtained by saponifying polyvinyl acetate-based resins. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers copolymerizable thereto. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0073] The degree of saponification of the PVA resin is preferably 85 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more and 100 mol% or less. The degree of polymerization of the PVA resin is, for example, 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The PVA resin may be modified, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc., modified with aldehydes.

[0074] Examples of dichroic dyes adsorbed and oriented on the PVA resin layer include iodine or dichroic dyes. Iodine is preferred as the dichroic dye. Examples of dichroic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc.

[0075] The thickness of the polarizing element is preferably 3 μm to 35 μm, more preferably 4 μm to 30 μm, and even more preferably 5 μm to 25 μm. A polarizing element thickness of 35 μm or less suppresses the effect of polyene formation of the PVA resin on the degradation of optical properties, for example, under high-temperature environments. A polarizing element thickness of 3 μm or more facilitates the creation of a configuration that achieves desired optical properties.

[0076] (Manufacturing method for polarizing elements) The method for manufacturing polarizing elements is not particularly limited, but typical methods include a method in which a PVA-based resin film, which has been pre-wound into a roll, is fed out and stretched, dyed, crosslinked, etc. (hereinafter referred to as "manufacturing method 1"), and a method in which a coating solution containing PVA-based resin is applied to a base film to form a PVA-based resin layer which is a coating layer, and the resulting laminate is stretched (hereinafter referred to as "manufacturing method 2").

[0077] Manufacturing method 1 can be produced by following the steps of: uniaxial stretching of a PVA-based resin film; dyeing the PVA-based resin film with a dichroic dye such as iodine and adsorbing the dichroic dye; treating the PVA-based resin film on which the dichroic dye has been adsorbed with a boric acid aqueous solution; and washing with water after treatment with the boric acid aqueous solution.

[0078] The swelling process is a treatment process in which the PVA resin film is immersed in a swelling bath. The swelling process can remove dirt and blocking agents from the surface of the PVA resin film, and can also suppress uneven dyeing by swelling the PVA resin film. Typically, a water-based medium such as water, distilled water, or pure water is used as the swelling bath. The swelling bath may also have surfactants, alcohol, etc., added as appropriate according to conventional methods. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide may be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less.

[0079] The temperature of the swelling bath is preferably 10°C to 60°C, more preferably 15°C to 45°C, and even more preferably 18°C ​​to 30°C. The immersion time in the swelling bath cannot be determined definitively because the degree of swelling of the PVA resin film is affected by the temperature of the swelling bath, but it is preferably 5 seconds to 300 seconds, more preferably 10 seconds to 200 seconds, and even more preferably 20 seconds to 100 seconds. The swelling process may be performed only once, or multiple times as needed.

[0080] The dyeing process involves immersing a PVA-based resin film in a treatment bath (dyeing bath) containing a dichroic dye, which allows the PVA-based resin film to adsorb and orient a dichroic dye such as iodine. The dyeing bath is a dyeing solution containing a dichroic dye, and is preferably an iodine solution. The iodine solution is preferably an aqueous iodine solution and preferably contains iodine and an iodide as a solubilizing agent. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred from the viewpoint of controlling the potassium content in the polarizing element.

[0081] The concentration of iodine in the iodine solution is preferably 0.01% by mass or more and 1% by mass or less, and more preferably 0.02% by mass or more and 0.5% by mass or less. The concentration of iodide in the iodine solution is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less.

[0082] The temperature of the dyeing bath is preferably between 10°C and 50°C, more preferably between 15°C and 45°C, and even more preferably between 18°C ​​and 30°C. The immersion time in the dyeing bath cannot be determined definitively because the degree of dyeing of the PVA resin film is affected by the temperature of the dyeing bath, but it is preferably between 10 seconds and 300 seconds, and more preferably between 20 seconds and 240 seconds. The dyeing process may be performed only once, or multiple times as necessary.

[0083] The crosslinking process involves immersing the PVA resin film, dyed in the dyeing process, in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the PVA resin film, allowing iodine molecules or dye molecules to be adsorbed onto the crosslinked structure. Examples of boron compounds include boric acid, borates, and borax. The crosslinking bath is generally an aqueous solution, but it may also be a mixed solution of a water-miscible organic solvent and water. From the viewpoint of controlling the potassium content in the polarizing element, the crosslinking bath preferably contains potassium iodide.

[0084] In the crosslinking bath, the concentration of the boron compound is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less. When potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less.

[0085] The temperature of the crosslinking bath is preferably 20°C to 70°C, and more preferably 30°C to 60°C. The immersion time in the crosslinking bath cannot be determined definitively because the degree of crosslinking of the PVA resin film is affected by the temperature of the crosslinking bath, but it is preferably 5 seconds to 300 seconds, and more preferably 10 seconds to 200 seconds. The crosslinking process may be performed only once, or multiple times as necessary.

[0086] The stretching process is a process in which a PVA-based resin film is stretched to a predetermined magnification in at least one direction. Generally, the PVA-based resin film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either wet stretching or dry stretching can be used. The stretching process may be performed only once, or multiple times as needed. The stretching process may be performed at any stage in the manufacturing of the polarizing element.

[0087] In the wet stretching method, the treatment bath (stretching bath) can usually be a solvent such as water or a mixed solution of a water-miscible organic solvent and water. From the viewpoint of controlling the potassium content in the polarizing element, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 6% by mass or less. From the viewpoint of suppressing film breakage during stretching, the treatment bath (stretching bath) may contain a boron compound. When a boron compound is included, the concentration of the boron compound in the stretching bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less.

[0088] The temperature of the stretching bath is preferably 25°C to 80°C, more preferably 40°C to 80°C, even more preferably 50°C to 75°C, and particularly preferably 65°C to 75°C. The immersion time in the stretching bath cannot be determined definitively because the degree of stretching of the PVA resin film is affected by the temperature of the stretching bath, but it is preferably 10 seconds to 800 seconds, and more preferably 30 seconds to 500 seconds. The stretching treatment in the wet stretching method may be performed together with one or more of the following treatment steps: swelling, dyeing, crosslinking, and washing.

[0089] Examples of dry stretching methods include the inter-roll stretching method, the heated roll stretching method, and the compression stretching method. The dry stretching method may also be performed in conjunction with the drying process.

[0090] The total stretching ratio (cumulative stretching ratio) applied to the PVA resin film can be set appropriately depending on the purpose, but it is preferably 2 times or more and 7 times or less, more preferably 3 times or more and 6.8 times or less, and even more preferably 3.5 times or more and 6.5 times or less.

[0091] The cleaning process involves immersing the PVA resin film in a cleaning bath, which removes any foreign matter remaining on the surface of the PVA resin film. The cleaning bath typically uses a water-based medium such as water, distilled water, or pure water. Furthermore, from the viewpoint of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably 1% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 4% by mass or less, and even more preferably 1.8% by mass or more and 3.8% by mass or less.

[0092] The temperature of the washing bath is preferably 5°C to 50°C, more preferably 10°C to 40°C, and even more preferably 15°C to 30°C. The immersion time in the washing bath cannot be determined definitively because the degree of cleaning of the PVA resin film is affected by the temperature of the washing bath, but it is preferably 1 second to 100 seconds, more preferably 2 seconds to 50 seconds, and even more preferably 3 seconds to 20 seconds. The washing process may be performed only once, or multiple times as necessary.

[0093] The drying process involves drying the PVA-based resin film, which has been cleaned in the washing process, to obtain a polarizing element. Drying can be carried out by any suitable method, such as natural drying, forced-air drying, or heat drying.

[0094] Manufacturing method 2 can be carried out by the steps of applying a coating solution containing a PVA resin onto a base film, uniaxially stretching the obtained laminated film, staining the PVA resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb it and form a polarizing element, treating the film on which the dichroic dye has been adsorbed with an aqueous boric acid solution, and washing with water after treatment with the aqueous boric acid solution. The base film used to form the polarizing element may also be used as a protective film for the polarizing element. If necessary, the base film may be peeled off from the polarizing element.

[0095] (Polarizing plate) A polarizing plate includes at least a polarizing element. The polarizing plate may have a protective film on one or both sides of the polarizing element. If the polarizing plate has protective films on both sides, the protective films may be of the same type and / or thickness, or they may be different.

[0096] It is preferable that the polarizing element and the protective film are laminated together via a bonding layer (adhesive layer or bonding agent layer). The bonding layer that bonds the polarizing element and the protective film is preferably a bonding agent layer, and is preferably a cured product layer of a water-based adhesive or an active energy ray adhesive, as described later.

[0097] The polarizer may be a linear polarizer or a circular polarizer. If the polarizer is a circular polarizer, it may have a λ / 4 wave plate or the like. The polarizer may have one or more phase difference layers, and the phase difference layers can be laminated via a bonding layer.

[0098] (Protective film) The protective film is preferably excellent in terms of transparency, mechanical strength, thermal stability, moisture shielding, and phase difference stability. A resin film is preferably used as the protective film.

[0099] Examples of resin materials that constitute the protective film include (meth)acrylate resins, polyolefin resins, cyclic olefin resins, polyvinyl chloride resins, cellulose resins, styrene resins, acrylonitrile-butadiene-styrene resins, acrylonitrile-styrene resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene tephthalate resins, polyethylene tephthalate resins, polysulfone resins, polyethersulfone resins, polyarylate resins, polyamide-imide resins, polyimide resins, and combinations of two or more of these. These resins can also be used after undergoing any appropriate polymer modification, which may include copolymerization, crosslinking, molecular end modification, stereoregularity control, and mixing, including cases involving reactions between different polymers.

[0100] Cellulosic resins can be organic acid esters or mixed organic acid esters of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups, and / or butyryl groups. Examples include those consisting of cellulose acetate esters, propionic acid esters, butyrate esters, and mixed esters thereof. Among these, triacetylcellulose, diacetylcellulose, cellulose acylate, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

[0101] Cyclic olefin resins are a general term for resins polymerized using cyclic olefins as polymerization units, and examples include resins described in Japanese Patent Publication No. 1-240517, Japanese Patent Publication No. 3-14882, Japanese Patent Publication No. 3-122137, etc. Cyclic olefin resins are preferably norbornene-based resins. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with α-olefins such as ethylene and propylene (typically random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and their hydrides. Specific examples of cyclic olefins include norbornene-based monomers.

[0102] The resin material constituting the protective film may contain appropriate additives in addition to the resin mentioned above, as long as transparency is not impaired. Examples of additives include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact-resistant aids, matting agents, antibacterial agents, and antifungal agents. Multiple types of these additives may be used in combination.

[0103] The thickness of the protective film is usually between 1 μm and 100 μm, but from the viewpoint of strength and handling, it is preferably between 5 μm and 60 μm, more preferably between 10 μm and 55 μm, and even more preferably between 15 μm and 50 μm.

[0104] The protective film may also have other optical functions and may be formed in a laminated structure with multiple layers stacked on top of each other. From the viewpoint of optical properties, a thin protective film is preferable, but if it is too thin, its strength will decrease and its processability will be poor. An appropriate film thickness is 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 70 μm.

[0105] The protective film may have a single-layer structure or a multi-layer structure. The protective film may have an antistatic layer on one or both sides.

[0106] The protective film may have a phase difference function for purposes such as viewing angle compensation. In this case, the film itself may have the phase difference function, or it may have a separate phase difference layer, or a combination of both. The protective film having a phase difference function may be configured to be bonded to the polarizing element via another protective film bonded to it, through a bonding layer (adhesive layer or bonding agent layer).

[0107] (Bonding layer, other adhesive layers) The bonding layer is either an adhesive layer (hereinafter referred to as "adhesive layer [bonding layer]") or an adhesive layer. Examples of bonding layers that are adhesive layers [bonding layer], and other adhesive layers for bonding composite polarizing plates to image display elements, include those described in the section on adhesive layers for bonding surface treatment films and polarizing plates.

[0108] The thickness of the adhesive layer (bonding layer) and the other adhesive layers is preferably 1 μm or more and 200 μm or less, more preferably 2 μm or more and 100 μm or less, even more preferably 2 μm or more and 80 μm or less, and particularly preferably 3 μm or more and 50 μm or less.

[0109] Any suitable adhesive can be used to constitute the adhesive layer. While water-based adhesives, solvent-based adhesives, and active energy ray-curing adhesives can be used, a water-based adhesive is preferred.

[0110] The thickness of the adhesive during application can be set to any appropriate value. For example, it can be set so that an adhesive layer of the desired thickness is obtained after curing or heating (drying). The thickness of the adhesive layer is preferably 0.01 μm to 7 μm, more preferably 0.01 μm to 5 μm, even more preferably 0.01 μm to 2 μm, and most preferably 0.01 μm to 1 μm.

[0111] As the water-based adhesive, any known water-based adhesive can be used. A water-based adhesive containing a PVA resin (hereinafter sometimes referred to as "PVA adhesive") is preferably used. From the viewpoint of adhesive properties, the average degree of polymerization of the PVA resin contained in the water-based adhesive is preferably 100 to 5500, and more preferably 1000 to 4500. From the viewpoint of adhesive properties, the average degree of saponification of the PVA resin is preferably 85 mol% to 100 mol%, and more preferably 90 mol% to 100 mol%.

[0112] The PVA-based resin used in the PVA-based adhesive for bonding the polarizing element and the protective film is preferably one that contains acetoacetyl groups. This is because it provides excellent adhesion and durability between the PVA-based resin layer constituting the polarizing element and the protective film. A PVA-based resin containing acetoacetyl groups can be obtained, for example, by reacting a PVA-based resin with diketene in any way. The degree of modification of the acetoacetyl groups in the PVA-based resin containing acetoacetyl groups is typically 0.1 mol% or more, and preferably 0.1 mol% to 20 mol%.

[0113] The concentration of the PVA resin in the PVA adhesive is preferably 0.1% to 15% by weight, and more preferably 0.5% to 10% by weight.

[0114] When the PVA resin contains an acetoacetyl group, the PVA adhesive preferably contains one or more of glyoxal, glyoxylate, and methylolmelamine as a crosslinking agent, preferably at least one of glyoxal and glyoxylate, and particularly preferably glyoxal.

[0115] PVA-based adhesives may contain organic solvents. In this case, since they are miscible with water, alcohols are preferred as the organic solvent, and among alcohols, methanol or ethanol is preferred.

[0116] From the viewpoint of improving heat resistance, PVA-based adhesives may further contain urea compounds such as urea, urea derivatives, thiourea, and thiourea derivatives; reducing agents such as ascorbic acid, erythorbic acid, thiosulfate, and sulfite; dicarboxylic acids such as maleic acid and phthalic acid; ammonium compounds such as ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride; dextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin; blocked isocyanate compounds in which isocyanate compounds are blocked by a blocking agent; nitroxyl radicals such as N-oxyl compounds; and compounds having a nitroxide group.

[0117] Active energy ray curing adhesives are adhesives that harden when irradiated with active energy rays such as ultraviolet light. Examples include adhesives containing polymerizable compounds and photopolymerization initiators, adhesives containing photoreactive resins, and adhesives containing binder resins and photoreactive crosslinking agents. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth)acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from these monomers. Examples of photopolymerization initiators include compounds containing substances that generate active species such as neutral radicals, anionic radicals, and cationic radicals when irradiated with active energy rays such as ultraviolet light.

[0118] (Release film) The release film is provided so as to be removable from other adhesive layers used to bond the composite polarizing plate to the image display element, and covers and protects the surface of the other adhesive layers. The release film comprises a base layer and a release treatment layer. The base layer may be a resin film. The resin film can be formed, for example, from a resin material used to form the protective film described above. The release treatment layer may be any known release treatment layer, for example, a layer formed by coating the base layer with a release agent such as a fluorine compound or a silicone compound.

[0119] (Protective film) The protective film is provided so as to be removable from the surface treatment film. The protective film may include a base layer and an adhesive layer, or it may be a self-adhesive film. The base layer may be a resin film, and the base layer can be formed from, for example, a resin material used to form the protective film described above. Examples of adhesive layers include those described above in the section on adhesive layers (laminating layers). Examples of thermoplastic resins constituting the self-adhesive film include polypropylene resins and polyethylene resins. [Examples]

[0120] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0121] [Measurement of glass transition temperature] The glass transition temperature (Tg) of (meth)acrylic resins was measured using a differential scanning calorimeter (DSC) "EXSTAR DSC6000" manufactured by SII Nanotechnology Co., Ltd., under nitrogen atmosphere conditions, with a measurement temperature range of -80 to 50°C and a heating rate of 10°C / min.

[0122] [Measurement of stress in the adhesive layer (Y)] Adhesive sheets (Y) formed using the adhesive composition described later were laminated with a release film (a 38 μm thick polyethylene terephthalate film with a release treatment layer) to the surface of the adhesive layer (Y) side of the adhesive sheet (Y). These double-sided release film adhesive sheets (layer structure: release film / adhesive layer (Y) / release film) having a 5 μm thick adhesive layer (Y) were stored for 2, 3, 8, and 10 days under conditions of a temperature of 23°C and a relative humidity of 50% RH. After storage, one release film was peeled off from each double-sided release film adhesive sheet, and an adhesive layer (Y) measuring 150 mm in length and 30 mm in width was extracted. This adhesive layer (Y) was then rolled in the length direction (150 mm direction) to prepare a cylindrical sample with a diameter of approximately 1 mm and a height (width) of 30 mm. For each prepared sample, stress was measured in the range of 0% to 1600% elongation using a material testing machine (STA-1225S, manufactured by Orientec Co., Ltd.) under conditions of a temperature of 23°C and a relative humidity of 50%RH, with a chuck distance of 10 mm and a tensile speed of 300 mm / min. The measurement results are shown in Figure 2. As shown in Figure 2, the stress at 800% elongation was higher in samples stored for longer periods (8 days, 10 days) compared to samples stored for shorter periods (2 days, 3 days).

[0123] [Surface hardness measurement] The release film was peeled off from the composite polarizing plates obtained in the examples and comparative examples, and the exposed adhesive layer (X) was bonded to a glass plate. In this state, a pencil hardness test was performed on the surface treatment film side of the composite polarizing plate, as specified in JIS K 5600-5-4:1999 "General test methods for paints - Part 5: Mechanical properties of coatings - Section 4: Scratch hardness (pencil method)".

[0124] [Measuring adhesive strength] The composite polarizing plates obtained in the examples and comparative examples were cut to a size of 200 mm in length (length parallel to the absorption axis direction of the polarizing element) x 25 mm in width, the release film was peeled off, and the adhesive layer (X) was bonded to a glass plate to obtain a test specimen. This test specimen was placed in an environment of 23°C and 50% RH relative humidity for 24 hours. After that, a cutter blade was inserted between the polarizing plate and the surface treatment film of the test specimen, and 30 mm was peeled off from the edge in the length direction. The peeled portion was grasped by the upper part of the grip of the testing machine, and the lower part of the grip grasped the glass plate. For the test specimens in this state, a peel test was performed in an atmosphere of 23°C and 55% relative humidity, in accordance with JIS K 6854-2:1999 "Adhesives - Test method for peel strength - Part 2: 180-degree peel", at a gripping speed of 300 mm / min. The average peel force (unit: N / 25 mm) over a length of 60 mm excluding the 30 mm gripping portion was determined, and this was defined as the adhesive strength of the adhesive layer (Y) between the surface treatment film and the polarizing plate in the composite polarizing plate. The results are shown in Table 1.

[0125] <Fabrication of polarizing elements> A 75 μm thick polyvinyl alcohol resin film, made of polyvinyl alcohol with an average degree of polymerization of approximately 2,400 and a degree of saponification of 99.9 mol% or more, was uniaxially stretched approximately 5 times by dry process. While maintaining tension, it was then immersed in pure water at 60°C for 1 minute, followed by immersion in an aqueous solution at 28°C with an iodine / potassium iodide / water weight ratio of 0.05 / 5 / 100 for 60 seconds. Subsequently, it was immersed in an aqueous solution at 72°C with a potassium iodide / boric acid / water weight ratio of 8.5 / 8.5 / 100 for 300 seconds. Afterward, it was washed with pure water at 26°C for 20 seconds, and then dried at 65°C to obtain a 28 μm thick polarizing element in which iodine was adsorbed and oriented on the polyvinyl alcohol resin film.

[0126] <Preparation of water-based adhesives> 50 g of a modified polyvinyl alcohol resin containing acetoacetyl groups (Mitsubishi Chemical Corporation: Gosenex Z-410) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain a PVA solution. This PVA solution, pure water, maleic acid, and glyoxal were blended so that the concentration of the polyvinyl alcohol resin was 3.0% by weight, the concentration of the maleic acid was 0.01% by weight, and the concentration of the glyoxal was 0.15% by weight to obtain a water-based adhesive.

[0127] <Fabrication of polarizing plates and polarizing plates with adhesive layer (X)> (Fabrication of polarizing plates) A cellulose acylate film "TD40" (manufactured by Fujifilm Corporation: 40 μm thick), used as a protective film, was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, and then the film was washed with water. After that, it was immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water bath under running water for 30 seconds to neutralize the film. Subsequently, the film was drained three times using an air knife. After draining, the film was left in a drying zone at 70°C for 15 seconds to dry, and a saponified protective film was prepared.

[0128] The saponified protective film was bonded to both sides of the polarizing element prepared above using a roll laminating machine via the water-based adhesive prepared above, and dried at 80°C for 5 minutes to obtain a polarizing plate. The water-based adhesive interposed between the polarizing element and the protective film was adjusted so that the thickness of the adhesive layer after drying was 100 nm on both sides.

[0129] (Fabrication of polarizing plates with adhesive layer (X)) An adhesive sheet (X) was prepared by forming a 25 μm thick adhesive layer (X) on a release film (a 38 μm thick polyethylene terephthalate film with a release treatment layer). The adhesive layer (X) side of the adhesive sheet (X) was laminated onto one side of the polarizing plate obtained above to obtain a polarizing plate with an adhesive layer (X). Corona treatment was performed on the bonding surface between the adhesive layer (X) and the polarizing plate. The layer structure of the obtained polarizing plate with an adhesive layer (X) was protective film / adhesive layer / polarizing element / adhesive layer / protective film / adhesive layer (X) / release film.

[0130] <Preparation of surface-treated films> (Formation of an anti-glare hard coat layer) A 40% solids solution was prepared by mixing 50 parts by weight of UV-curable urethane (meth)acrylate monomer (refractive index 1.51), 50 parts by weight of UV-curable (meth)acrylate monomer (refractive index 1.51), 14 parts by weight of methyl methacrylate-styrene copolymer beads with an average particle size of 3.5 μm (refractive index 1.55), 5 parts by weight of a benzophenone-based photopolymerization initiator, and toluene. This solution was applied to a base film (a 40 μm thick triacetylcellulose film (refractive index 1.49)) and dried at 120°C for 5 minutes. Subsequently, curing treatment was performed by UV irradiation to produce an anti-glare hard coat film in which an anti-glare hard coat layer with an uneven structure and a thickness of approximately 4 μm was formed on the base film.

[0131] (Formation of anti-reflective layer) Following the example described in Japanese Patent Publication No. 2019-035969, the anti-glare hard coat film obtained above was introduced into a roll-to-roll sputtering deposition apparatus. While the film was being moved, bombardment (plasma treatment with Ar gas) was performed on the surface where the anti-glare hard coat layer was to be formed. Then, a 5 nm SiOx layer (x<2) was deposited as an adhesion-improving layer, and on top of that, a 20 nm Nb2O5 layer, a 35 nm SiO2 layer, a 35 nm Nb2O5 layer, and a 100 nm SiO2 layer were sequentially deposited to form a 4-layer anti-reflective layer with a thickness of 190 nm. A fluorine-based resin was formed on the anti-reflective layer to a thickness of 5 nm as an anti-fouling layer to produce a surface-treated film. The surface-treated film had a laminated structure of an anti-glare hard coat layer, an anti-reflective layer, and an anti-fouling layer.

[0132] <Preparation of adhesive sheet (Y)> (Manufacturing of meth-acrylic resins) In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 74.5 parts by mass of butyl acrylate, 20 parts by mass of methyl acrylate, 5 parts by mass of 2-hydroxyethyl acrylate, 0.5 parts by mass of acrylic acid, and 0.2 parts by mass of azobisisobutyronitrile were charged together with 120 parts by mass of ethyl acetate. After introducing nitrogen gas and purging the mixture with nitrogen while gently stirring, the polymerization reaction was carried out for 8 hours while maintaining the temperature of the liquid in the flask at around 60°C to obtain a (meth)acrylic resin solution. The glass transition temperature Tg of the (meth)acrylic resin was measured using the above method and found to be -40°C.

[0133] (Preparation of adhesive composition) To the (meth)acrylic resin solution obtained above, 4 parts by mass of Coronate L (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate: solid content concentration 75% by mass, manufactured by Tosoh Corporation) was mixed with 100 parts by mass of (meth)acrylic resin to obtain an adhesive composition.

[0134] (Formation of adhesive layer (Y)) The adhesive composition prepared above was applied to a release film (a polyethylene terephthalate film with a release treatment layer and a thickness of 38 μm) to form an adhesive layer (Y) with a thickness of 5 μm, thereby producing an adhesive sheet (Y).

[0135] [Example 1] Immediately after creating the adhesive sheet (Y) described above, the adhesive layer (Y) side of the adhesive sheet (Y) was bonded to the base film side of the surface treatment film prepared above. Two days after creating the adhesive sheet (Y) (substantially, after bonding the adhesive sheet (Y) to the surface treatment film), the release film on the adhesive layer (Y) was peeled off, and the polarizing plate side of the polarizing plate with adhesive layer (X) was laminated onto the exposed adhesive layer (Y) to obtain a laminate. Corona treatment was performed on the bonded surfaces of the surface treatment film, the adhesive layer (Y), and the polarizing plate with adhesive layer (X).

[0136] The processes of preparing the adhesive sheet (Y), laminating the adhesive sheet (Y), and obtaining the laminate were all carried out under conditions of 23°C and 50% RH relative humidity. The obtained laminate was stored for 6 days under conditions of 23°C and 50% RH relative humidity to obtain a composite polarizing plate (1). The preparation of the adhesive sheet (Y) and the lamination of the adhesive sheet (Y) were performed based on the graph shown in Figure 2, where the stress at 800% elongation of the adhesive layer (Y) was 0.6 N / mm². 2 The process to obtain the laminate is carried out under the following conditions, where the stress at which the elongation of the adhesive layer (Y) reaches 800% is 0.6 N / mm². 2 The test was performed under these conditions. Furthermore, the stress in the adhesive layer (Y) of the composite polarizing plate (1) at a temperature of 23°C and an elongation of 800% was 1.1 N / mm². 2 That was the case.

[0137] The layer structure of the composite polarizer (1) was: surface treatment film (surface treatment layer / base film) / adhesive layer (Y) / polarizer (protective film / adhesive layer / polarizing element / adhesive layer / protective film) / adhesive layer (X) / release film. The composite polarizer (1) was observed using a microscope (VHX-5000, manufactured by Keyence Corporation), and the number of air bubbles between the surface treatment film and the adhesive layer (Y), and between the adhesive layer (Y) and the polarizer (composite polarizer 1 m 2The number of particles per unit was counted. Furthermore, the surface hardness and adhesive strength of the composite polarizer (1) were measured using the method described above. The results are shown in Table 1.

[0138] [Comparative Example 1] A composite polarizing plate (2) was obtained using the same procedure as in Example 1, except that eight days after laminating an adhesive sheet (Y) onto the surface-treated film, the polarizing plate side of a polarizing plate with an adhesive layer (X) was laminated onto the adhesive layer (Y) of the surface-treated film to obtain a laminate. The preparation of the adhesive sheet (Y) and the lamination of the adhesive sheet (Y) were based on the graph shown in Figure 2, where the stress at 800% elongation of the adhesive layer (Y) was 0.6 N / mm 2 The following procedure was performed, but the process for obtaining the laminate was such that the stress at 800% elongation of the adhesive layer (Y) was 1.1 N / mm². 2 The test was performed under these conditions. Furthermore, as seen in the graph in Figure 2, the stress of the adhesive layer (Y) of the composite polarizing plate (2) at a temperature of 23°C and an elongation of 800% is 1.1 N / mm². 2 The number of bubbles between the surface treatment film and the adhesive layer (Y) of the composite polarizing plate (2), and between the adhesive layer (Y) and the polarizing plate, was determined using the same procedure as in Example 1 (composite polarizing plate 1m 2 The number of particles per unit area was counted, and the surface hardness and adhesive strength were measured. The results are shown in Table 1.

[0139] [Table 1] [Explanation of symbols]

[0140] 1 composite polarizing plate, 10 polarizing plate, 11 polarizing element, 12 bonding layer, 13 protective film, 20 surface treatment film, 21 base film, 22 surface treatment layer, 31 adhesive layer.

Claims

1. A method for manufacturing a composite polarizing plate in which a surface treatment film and a polarizing plate are laminated, The surface treatment film comprises a base film and a surface treatment layer formed on one side of the base film. The polarizing plate includes at least a polarizing element, The aforementioned manufacturing method is The stress at 800% elongation is 0.8 N / mm². ２ Step (a) of bonding the surface treatment film and the polarizing plate via an adhesive layer in the following state to obtain a laminate, In the laminate, the stress of the adhesive layer at an elongation of 800% at a temperature of 23°C is 0.9 N / mm ２ The process includes (b) adjusting to the above, The laminate has the adhesive layer on the base film side of the surface treatment film, The adhesive layer is in direct contact with the base film. The aforementioned base film is a resin film, A method for manufacturing a composite polarizing plate, wherein the resin material constituting the resin film is a methyl (meth)acrylate resin, a polyolefin resin, a cyclic olefin resin, a polyvinyl chloride resin, a cellulose resin, a styrene resin, an acrylonitrile-butadiene-styrene resin, an acrylonitrile-styrene resin, a polyvinyl acetate resin, a polyvinylidene chloride resin, a polyamide resin, a polyacetal resin, a polycarbonate resin, a modified polyphenylene ether resin, a polybutylene tephthalate resin, a polyethylene tephthalate resin, a polysulfone resin, a polyethersulfone resin, a polyarylate resin, a polyamide-imide resin, a polyimide resin, or a combination of two or more of these.

2. The above step (a) is, The process of forming the adhesive layer on the surface treatment film (a1), A method for manufacturing a composite polarizing plate according to claim 1, comprising the step (a2) of laminating the polarizing plate on the adhesive layer formed on the surface treatment film.

3. A method for manufacturing a composite polarizing plate according to claim 2, wherein step (a2) is performed within 6 days after step (a1).

4. The method for manufacturing a composite polarizing plate according to any one of claims 1 to 3, wherein step (b) is a step of storing the laminate.

5. The method for manufacturing a composite polarizing plate according to any one of claims 1 to 4, wherein the pencil hardness of the surface on the surface treatment film side of the composite polarizing plate is HB or higher.

6. The method for manufacturing a composite polarizing plate according to any one of claims 1 to 5, wherein the polarizing plate has a protective film on one or both sides of the polarizing element.

7. The method for manufacturing a composite polarizing plate according to any one of claims 1 to 6, wherein the thickness of the adhesive layer is 10 μm or less.

8. The adhesive layer is formed using an adhesive composition containing a (meth)acrylic resin, The method for manufacturing a composite polarizing plate according to any one of claims 1 to 7, wherein the glass transition temperature of the (meth)acrylic resin is -30°C or lower.

9. The method for manufacturing a composite polarizing plate according to any one of claims 1 to 8, wherein the surface treatment layer is one or more selected from the group consisting of an anti-reflective layer, an anti-glare layer, a hard coat layer, and an anti-fouling layer.

Images