Polarizing film with bonding layer, polarizing plate, and method for manufacturing the same.

Abstract

[Problem] The purpose of the present invention is to provide a bonding layer–coated polarizing film that has, at the surface thereof, a bonding layer that makes it possible to achieve excellent adhesion between a polarizing film and another member such as a support substrate. [Solution] According to the present invention, a bonding layer–coated polarizing film includes a polarizing film that comprises a polyvinyl alcohol resin and, at at least one surface of the polarizing film, a bonding layer that comprises a molecular bonding agent that bonds by chemical bonding. The bonding layer–coated polarizing film is characterized in that the molecular bonding agent includes a triazine derivative and in that the nitrogen (N) atom concentration at the surface of the bonding layer as measured by X-ray photoelectron spectroscopy is no more than 12.0 atm%.

Description

Technical Field

[0001] The present invention relates to a polarizing film having a bonding layer on its surface, and more particularly to a polarizing film with a bonding layer comprising a polarizing film made of a polyvinyl alcohol-based resin and a bonding layer made of a molecular bonding agent, a polarizing plate using the polarizing film with a bonding layer, and a method for manufacturing the same.

Background Art

[0002] Conventionally, as an optical member that allows light polarized or polarized in a specific direction to pass through, a polarizing film (PVA polarizing film) made of a polyvinyl alcohol-based resin is known. The PVA polarizing film is usually laminated with a support substrate made of a light-transmissive organic material or inorganic material through an adhesive or bonding agent and used as a polarizing plate (see Patent Document 1).

[0003] The PVA polarizing film is a uniaxially stretched polyvinyl alcohol-based resin film in which iodine or a dichroic dye is adsorbed and oriented. However, due to its characteristics, the PVA polarizing film absorbs light parallel to the absorption axis, so shrinkage stress is generated in the stretching direction due to the temperature rise of the PVA polarizing film caused by the absorbed light energy, and there is a problem of thermal shrinkage. When the PVA polarizing film thermally shrinks, external deformations (or appearance defects) such as unevenness and wrinkles occur on the PVA polarizing film. In an image display device such as a liquid crystal display, the PVA polarizing film with appearance defects causes image defects and a decrease in contrast.

[0004] The inventors of the present invention, in a previous invention, aimed to suppress appearance defects due to thermal shrinkage of the PVA polarizing film and provide a polarizing plate with excellent durability, and found that a molecular bonding technique for chemically bonding the PVA polarizing film and the support substrate is used (see Patent Document 2). The polarizing plate using the molecular bonding technique can efficiently dissipate the heat generated in the PVA polarizing film to the support substrate, reduce the heat load of the PVA polarizing film, and suppress appearance defects due to thermal shrinkage of the PVA polarizing film.

Prior Art Documents

[0005] [Patent Document 1] WO13 / 154139 [Patent Document 2] PCT / JP2022 / 2859 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Molecular bonding technology is a technique that joins components together by chemical bonds using one or more layers of molecules. It transforms the surface of the adherend into a surface of one type of functional group, and the bonding is achieved by the bonding of these functional groups. Therefore, the amount of molecular bonding agent introduced to the adherend surface is crucial to ensuring adequate adhesion (or peel strength) between components. According to the findings of the present inventors, the range of molecular bonding agent amounts that can be introduced to the adherend surface to obtain appropriate adhesion is very narrow. If the amount of molecular bonding agent introduced is too much or too little, the adhesion between components will be insufficient, and adequate adhesion cannot be ensured.

[0007] The present invention has been made in view of these problems, and aims to provide a PVA polarizing film with a bonding layer having a bonding layer on its surface made of a molecular bonding agent that appropriately ensures adhesion between the PVA polarizing film and other members such as a support substrate, or has excellent adhesion to other members. [Means for solving the problem]

[0008] The present inventors have diligently investigated the amount of molecular bonding agent introduced onto the surface of a PVA polarizing film having a bonding layer made of a molecular bonding agent on its surface, in order to achieve excellent adhesion to other components such as a support substrate. As a result, they have found that by setting the nitrogen (N) atom concentration at the bonding layer surface, measured by X-ray photoelectron spectroscopy, to a specific range, excellent adhesion to other components such as a support substrate can be achieved, thus completing the present invention.

[0009] According to the present invention, (1) A polarizing film with a bonding layer is provided, comprising a polarizing film made of a polyvinyl alcohol-based resin and a bonding layer made of a molecular bonding agent that is chemically bonded to at least one surface of the polarizing film, wherein the molecular bonding agent contains a triazine derivative, and the nitrogen (N) atom concentration on the surface of the bonding layer, as measured by X-ray photoelectron spectroscopy, is 12.0 atm% or less. (2) A polarizing film with a bonding layer according to (1) is provided, characterized in that the nitrogen (N) atom concentration measured by X-ray photoelectron spectroscopy on the surface of the bonding layer is 0.15 atm% or more and 10.0 atm% or less. (3) The polarizing film with a bonded layer according to (1) or (2) is provided, characterized in that the triazine derivative is a compound containing two or more OH groups and / or OH generating groups and one triazine ring. A polarizing plate is provided, characterized in that a polarizing film with a bonding layer as described in any of (1) to (3) and a light-transmitting support substrate are laminated via the bonding layer. (5) A polarizing plate according to (4) is provided, characterized in that the OH groups on the surface of the polarizing film and / or the OH groups on the surface of the support substrate are chemically bonded to the OH groups or OH-generating groups of the triazine derivative by dehydration condensation. (6) The polarizing plate according to (4) or (5) is provided, characterized in that the support substrate consists of one or more selected from organic materials, inorganic materials, and organic-inorganic hybrid materials. (7) A method for manufacturing a polarizing plate according to any one of (4) to (6) is provided, comprising the steps of: laminating the polarizing film with a bonding layer and the support substrate via the bonding layer; and thermally bonding the polarizing film with a bonding layer and the support substrate to bond the polarizing film with a bonding layer and the support substrate by chemical bonding. [Effects of the Invention]

[0010] The polarizing film with a bonding layer of the present invention has excellent adhesion to other components such as support substrates because the amount of molecular bonding agent introduced to the surface of the PVA polarizing film is appropriately adjusted, making it possible to appropriately ensure adhesion to other components such as support substrates. Furthermore, polarizing plates using the polarizing film with a bonding layer of the present invention can reduce the thermal load on the PVA polarizing film and firmly bond the support substrate and the polarizing film, thereby suppressing appearance defects due to thermal shrinkage of the PVA polarizing film and providing high durability that maintains the performance of the PVA polarizing film over a long period of time. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing an example of a polarizing film with a bonding layer according to the present invention. [Figure 2] This is a cross-sectional view showing an example of a polarizing plate of the present invention. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and various embodiments are possible within the scope of achieving the effects of the present invention.

[0013] [Bonded polarizing film] Figure 1 shows an example of a polarizing film with a bonding layer according to the present invention. The polarizing film with a bonding layer shown in Figure 1 comprises 1 a polarizing film 2 made of a polyvinyl alcohol-based resin and 3 a bonding layer 3 made of a molecular bonding agent using molecular bonding technology, which is bonded by chemical bonding, on at least one surface of the polarizing film 2. Although not shown, the other surface of the polarizing film may also have a bonding layer made of a molecular bonding agent.

[0014] [Polarizing film] Polarizing films exhibit absorbing dichroism at wavelengths between 380 and 780 nm and are made of polyvinyl alcohol-based resin film. Examples of polarizing films exhibiting absorbing dichroism at wavelengths between 380 and 780 nm include polyvinyl alcohol-based resin films (H-type polarizing films) on which iodine and / or dichroic dyes are adsorbed and oriented, and polyvinyl alcohol-based resin films (K-type polarizing films) in which light-absorbing vinylene block segments are formed in the polymer by dehydrating the polyvinyl alcohol resin.

[0015] An H-type polarizing film made of a polyvinyl alcohol-based resin on which iodine and / or dichroic dyes are adsorbed and oriented can be manufactured, for example, by a method including the steps of uniaxially stretching a polyvinyl alcohol-based resin film, dyeing the polyvinyl alcohol-based resin film with iodine and / or dichroic dyes and adsorbing them, crosslinking the polyvinyl alcohol-based resin film on which iodine and / or dichroic dyes have been adsorbed with a crosslinking solution such as an aqueous boric acid solution, and washing the polyvinyl alcohol-based resin film with water.

[0016] As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. 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 with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

[0017] The saponification degree of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The average polymerization degree of the polyvinyl alcohol-based resin is usually 1000 to 10000, preferably 1500 to 5000. The average polymerization degree of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

[0018] A film made of such a polyvinyl alcohol-based resin is used as the raw film of the polarizing film. The method for forming a film from the polyvinyl alcohol-based resin is not particularly limited, and known methods are adopted. The thickness of the polyvinyl alcohol-based raw film is not particularly limited, but for example, a film with a thickness of 10 to 200 μm is preferably used.

[0019] Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing with iodine and / or dichroic dyes. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during the crosslinking treatment. Also, uniaxial stretching may be performed at these multiple stages. For uniaxial stretching, it may be stretched uniaxially between rolls with different peripheral speeds, or it may be stretched uniaxially using a hot roll. Also, uniaxial stretching may be dry stretching performed in the air, or wet stretching performed in a state where the polyvinyl alcohol-based resin film is swollen using a solvent or water. The stretching ratio is usually 3 to 8 times.

[0020] As a method for dyeing the polyvinyl alcohol-based resin film with iodine and / or dichroic dyes, for example, a method of immersing the film in an aqueous solution containing iodine and / or dichroic dyes is adopted. In addition, it is preferable that the polyvinyl alcohol-based resin film is subjected to an immersion treatment in water before the dyeing treatment.

[0021] One example of a cross-linking treatment after dyeing is immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The cross-linking treatment may be performed in one step or in multiple steps.

[0022] The post-crosslinking washing treatment can be carried out, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in water after dyeing, spraying it with water as a shower, or using a combination of immersion and spraying. After the washing treatment, the polyvinyl alcohol-based resin film may be dried by a known method.

[0023] A K-type polarizing film made of a polyvinyl alcohol-based resin, in which light-absorbing vinylene block segments are formed in the polymer by dehydrating the polyvinyl alcohol resin, can be manufactured, for example, by a method including the steps of uniaxially stretching the polyvinyl alcohol-based resin film, dehydrating the polyvinyl alcohol-based resin film, crosslinking the dehydrated polyvinyl alcohol-based resin film with a crosslinking solution such as an aqueous boric acid solution, and washing the polyvinyl alcohol-based resin film with water. The raw material film is as described above.

[0024] Uniaxial stretching of polyvinyl alcohol-based resin films can be performed at various stages. Uniaxial stretching may be performed, for example, before dehydration, simultaneously with dehydration, simultaneously with or before / after boric acid crosslinking after dehydration. Alternatively, uniaxial stretching may be performed at multiple stages. The method of uniaxial stretching is as described above.

[0025] One method for dehydrating a polyvinyl alcohol-based resin film is to expose it to an acid with a pH of 3 or higher, and then heat the exposed film. Specifically, the polyvinyl alcohol-based resin film can be immersed in deionized water for about 1 second to about 5 minutes, and then immersed in an acid with a pH of 3 or higher for a desired time. Alternatively, the polyvinyl alcohol-based resin film can be exposed to a dehydration catalyst in a different way. For example, the film can be dipped or immersed in an aqueous dehydration catalyst for a sufficient residence time to diffuse the catalyst into the film.

[0026] Any acid with a pH of 3 or higher that can remove hydrogen and oxygen atoms from the hydroxylated portions of the linear polymer while leaving conjugated vinylene units in the presence of heat or other suitable treatment conditions can be used for the dehydration treatment. Specifically, examples include hydrochloric acid, hydrobromic acid, hydroiodic acid, phosphoric acid, and sulfuric acid. These acids may also be diluted with water or an alcohol such as methanol.

[0027] After exposing a polyvinyl alcohol-based resin film to a dehydration catalyst, the polyvinyl alcohol-based resin film and the adsorption catalyst can be heated, thereby converting a portion of the oriented film into polyvinylene, the desired dehydration product. The film can be heated by conduction, convection, radiation, or a combination thereof. For example, the film and catalyst can be passed through a heating oven at a temperature range of approximately 88°C to 205°C for approximately a few seconds to approximately 10 minutes. Alternatively, the film and catalyst can be exposed to microwave radiation heating, laser heating, or infrared radiation heating.

[0028] During the dehydration process, a portion of the vinyl alcohol polymer in the polyvinyl alcohol resin film is converted into polarizing molecules of the poly(vinylene-co-vinyl alcohol) block copolymer. The effect of the dehydration process is to form conjugated polyvinylene blocks from the polyvinyl alcohol blocks. By orienting the PVA matrix in one direction, the transition moment of the conjugated polyvinylene blocks is also oriented, and the material becomes visibly dichroic.

[0029] One example of a crosslinking treatment after dehydration is immersion of the dehydrated polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. Specifically, the dehydrated polyvinyl alcohol-based resin film can be brought into contact with a 10-20% boric acid aqueous solution at a temperature of 85-95°C.

[0030] The post-crosslinking washing treatment can be carried out, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in water after dehydration, spraying it with water as a shower, or using a combination of water and spraying. After the washing treatment, the polyvinyl alcohol-based resin film may be dried by a known method.

[0031] The thickness of the polarizing film is not particularly limited, but is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. The thickness of the polarizing film is usually 1 μm or more, and preferably 3 μm or more.

[0032] [Joining layer] The bonding layer consists of a molecular bonding agent that uses molecular bonding technology to bond materials together through chemical bonds. Molecular bonding technology is a technique that joins materials together using one or more molecular layers through chemical bonds. For example, it involves converting the surface of the adherend into a surface with one type of functional group, and then bonding the materials together through the bonding of these functional groups.

[0033] The molecular bonding agent includes a triazine derivative having a functional group that chemically bonds the polarizing film to other members such as a support substrate. The bonding layer made of the molecular bonding agent containing the triazine derivative preferably contains the triazine derivative as the main component. Here, "main component" means that the composition ratio of the components constituting the bonding layer is 50% by weight or more, preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0034] The triazine derivative is preferably a compound containing two or more OH groups and / or OH-producing groups and one triazine ring. In a triazine derivative containing two or more OH groups and / or OH-producing groups and one triazine ring, the OH groups of the triazine derivative or OH-producing groups form a chemical bond with the OH groups of the polarizing film surface and / or other components such as the support substrate through dehydration condensation. Conventionally known compounds can be used as the triazine derivative. The OH groups or OH-producing groups are preferably alkoxysilyl groups (including cases where the alkoxy group is an OH group).

[0035] The molecular bonding agent may contain components other than triazine derivatives, as long as they do not impair the effects of the present invention. Examples of components other than triazine derivatives include crosslinking agents, fine particles, ultraviolet absorbers, defoaming agents, thickeners, dispersants, surfactants, catalysts, lubricants, and antistatic agents.

[0036] The bonding layer has a nitrogen (N) atom concentration of 12.0 atm% or less, as measured by X-ray photoelectron spectroscopy (XPS) on the bonding layer surface. The polarizing film with a bonding layer of the present invention exhibits excellent adhesion to other components such as a support substrate by keeping the nitrogen (N) atom concentration at the bonding layer surface, as measured by X-ray photoelectron spectroscopy, within the above range. The upper limit of the nitrogen (N) atom concentration at the bonding layer surface is preferably 10.0 atm% or less, more preferably 9.0 atm% or less, even more preferably 8.0 atm% or less, particularly preferably 6.0 atm% or less, and most preferably 3.0 atm% or less. The lower limit of the nitrogen (N) atom concentration at the bonding layer surface is preferably 0.15 atm% or more, more preferably 0.20 atm% or more, even more preferably 0.25 atm% or more, particularly preferably 0.30 atm% or more, and most preferably 0.35 atm% or more.

[0037] The nitrogen (N) atom concentration measured by X-ray photoelectron spectroscopy (XPS) on the surface of the bonding layer is calculated by using an X-ray photoelectron spectrometer to irradiate the sample with X-rays under the following measurement conditions, performing a narrow scan of carbon, oxygen, nitrogen, and silicon atoms, and determining the ratio of nitrogen atoms to the total sum of carbon, oxygen, nitrogen, and silicon atoms on the surface of the bonding layer (nitrogen atom concentration). ·Equipment: ULVACΦ QuanteraSXM • X-ray source: Monochromatic AI (25.0W) ·Measurement area: 1000μm×1000μm ·Measurement depth: 7.2nm • Sweep: 1 time • Pass energy: 69eV Step size: 0.125eV Angle: 45°

[0038] There is no particular upper limit to the thickness of the bonding layer, but it is preferably 5 μm or less, more preferably 1 μm or less, even more preferably 0.01 μm or less, and particularly preferably 0.001 μm or less. There is no particular lower limit to the thickness of the bonding layer, but since molecular bonding technology is a technology that joins members together by chemical bonds using one or more molecular layers, ideally it is the thickness of one molecular layer.

[0039] [Manufacturing method for polarizing film with bonding layer] Next, a method for manufacturing a polarizing film with a bonding layer will be described. A polarizing film with a bonding layer can be manufactured by providing a bonding layer made of a molecular bonding agent on the surface of a polarizing film made of a polyvinyl alcohol-based resin.

[0040] <Step 1: Preparation> First, prepare the polarizing film described above. The polarizing film may be in the form of a long roll or a single sheet. The surface of the polarizing film may be cleaned as needed, for example, by cleaning with a cleaning agent such as ethanol or acetone. The surface of the polarizing film may be activated as needed, for example, by ultraviolet irradiation, corona discharge treatment, plasma treatment, etc.

[0041] Furthermore, a solution or dispersion of the molecular bonding agent described above is prepared. The molecular bonding agent may be diluted with a solvent, and examples of solvents include water, alcohol (e.g., methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, cellosorb, carbitol), ketone (e.g., acetone, methyl ethyl ketone, cyclohexanone), aromatic hydrocarbons (e.g., benzene, toluene, xylene), aliphatic hydrocarbons (e.g., hexane, octane, decane, dodecane, octadecane), esters (e.g., ethyl acetate, methyl propionate, methyl phthalate), ethers (e.g., tetrahydrofuran, ethyl butyl ether, anisole), and mixtures thereof. The content of the triazine derivative can be set appropriately considering the coating process, etc., for example, 0.00001 to 10 wt%, preferably 0.0001 to 1 wt%, more preferably 0.0005 to 0.5 wt%, and even more preferably 0.001 to 0.2 wt%.

[0042] <Step 2: Application> A molecular bonding agent is applied to the surface of a polarizing film to form a bonding layer on the surface of the polarizing film. Specifically, this is achieved by applying a solution in which the above-mentioned molecular bonding agent is dissolved to the surface of the polarizing film. Subsequently, drying is performed as necessary, and as the solvent evaporates, the molecular bonding agent remains on the surface of the polarizing film, forming a bonding layer. The application method is not particularly limited, and known methods can be used, such as wire bar coating, dip coating, spray coating, spin coating, roll coating, gravure coating, air knife coating, curtain coating, slide coating, extrusion coating, and die coating. The drying method is not particularly limited, and known methods can be used.

[0043] [Polarizing plate] Figure 2 shows an example of a polarizing plate of the present invention. The polarizing plate 10 shown in Figure 2 comprises a polarizing film with a bonding layer 1 and a support substrate 4. More specifically, the polarizing plate 1 has a bonding layer 3 made of a molecular bonding agent using molecular bonding technology to bond at least one surface of the polarizing film 2, and the support substrate 4 are laminated together via the bonding layer 3. In the polarizing plate of the present invention, the polarizing film and the support substrate are laminated together via a bonding layer made of a molecular bonding agent, so that the OH groups on the surface of the polarizing film and / or the OH groups of the support substrate and the OH groups or OH generating groups of the molecular bonding agent form chemical bonds through dehydration condensation. Although not shown, the other surface of the polarizing film may also have another support substrate via a bonding layer made of a molecular bonding agent.

[0044] [Supporting base material] The support substrate supports the polarizing film, which is fragile and difficult to handle on its own, making it easier to handle and protecting the polarizing film. It is made of a material that is transparent to visible light. Here, transparency means that the total light transmittance is 80% or more, preferably 85% or more, and more preferably 90% or more. The light transmittance can be measured using a spectrophotometer (UV-Vis-Near-Infrared Spectrophotometer "V-570" manufactured by JASCO Corporation) in accordance with JIS K0115.

[0045] Examples of materials that are translucent to visible light include organic materials, inorganic materials, and organic-inorganic hybrid materials. Examples of organic materials include triacetylcellulose, diacetylcellulose, polyester resins, polyimide resins, polyamides, polyethylene, polypropylene and other polyolefin resins, cycloolefin polymers and other cycloolefin copolymers, polyethersulfone, polysulfone, polyvinyl chloride, acrylic resins, polycarbonate resins, and urethane resins. Examples of inorganic materials include silicate glass, borosilicate glass, titanium silicate glass, fluoride glass such as zirconium fluoride, fused silica, quartz, sapphire, YAG crystal, fluorite, magnesia, and spinel (MgO·Al2O3). Examples of organic-inorganic hybrid materials include resins made from silsesquioxane derivatives having organic functional groups such as (meth)acryloyl groups.

[0046] From the viewpoint of efficiently dissipating the heat generated by the polarizing film to the outside and suppressing thermal shrinkage of the polarizing film, it is preferable that the support substrate laminated on at least one surface of the polarizing film has a higher thermal conductivity than the polarizing film. The thermal conductivity is preferably 0.7 W / mK or higher, more preferably 1 W / mK or higher, and even more preferably 5 W / mK or higher. Examples of such materials include sapphire (thermal conductivity: 40 W / mK) and quartz (thermal conductivity: 8 W / mK).

[0047] The thickness of the support substrate is not particularly limited and should be appropriately designed to facilitate handling of the polarizing film and protect the polarizing film. For example, it is 10 to 3000 μm, preferably 20 to 1500 μm, and more preferably 30 to 1000 μm.

[0048] A bonding layer made of the molecular bonding agent described above may be formed on the surface of the support substrate, if necessary. The nitrogen (N) atom concentration measured by X-ray photoelectron spectroscopy (XPS) on the bonding layer surface of the support substrate is not particularly limited, but for example, the upper limit is preferably 50.0 atm% or less, more preferably 40.0 atm% or less, and even more preferably 30.0 atm% or less. The lower limit of the nitrogen (N) atom concentration is preferably 0.15 atm% or more, more preferably 0.50 atm% or more, and even more preferably 1.00 atm% or more.

[0049] Furthermore, various functional layers may be formed on the surface of the supporting substrate as needed. Examples of functional layers include conductive layers, antistatic layers, anti-glare layers, anti-fouling layers such as photocatalytic layers, anti-reflective layers, hard coat layers, ultraviolet shielding layers, heat shielding layers, electromagnetic wave shielding layers, and gas barrier layers.

[0050] [Manufacturing method for polarizing plates] Next, a method for manufacturing a polarizing plate will be described. The method for manufacturing a polarizing plate includes the steps of laminating the aforementioned polarizing film with a bonding layer and a support substrate via a bonding layer, and heat-pressing the polarizing film with a bonding layer and the support substrate together to bond the polarizing film with a bonding layer and the support substrate by chemical bonding.

[0051] <Process 3: Lamination> The polarizing film with a bonding layer and the support substrate are laminated via the bonding layer of the polarizing film with a bonding layer. Specifically, this is achieved by laminating the polarizing film with a bonding layer, which has a bonding layer made of molecular bonding agent formed on its surface, so that the surface of the bonding layer of the polarizing film faces the surface of the support substrate.

[0052] <Process 4: Heat compression bonding> Next, the polarizing film with the bonding layer and the support substrate are heat-pressed together, and the polarizing film with the bonding layer and the support substrate are integrally bonded by chemical bonding. Specifically, this is achieved by heating the polarizing film with the bonding layer while applying pressure toward the support substrate, heating the support substrate while applying pressure toward the polarizing film with the bonding layer, or heating the polarizing film with the bonding layer and the support substrate while applying pressure from each side.

[0053] The pressing force is the pressure at which the OH groups generated from the OH groups or OH-generating groups of the triazine derivative present on the surface of the polarizing film and / or the support substrate come into contact with the other surface. The pressing force is preferably 0.01 to 50 MPa, more preferably 0.1 to 20 MPa, even more preferably 0.5 to 15 MPa, and particularly preferably 1 to 10 MPa. The action time is, for example, 0.1 to 200 minutes. As a result, even if there are minute irregularities on the surface of the polarizing film with the bonding layer or the support substrate, the polarizing film with the bonding layer or the support substrate deforms accordingly, and the OH groups or OH-generating groups of the triazine derivative present on these surfaces reach and bond with the other surface. In other words, the polarizing film with the bonding layer and the support substrate are strongly bonded by chemical bonding (reaction) by the triazine derivative. The heating temperature is the temperature at which the chemical reaction of the triazine derivative is promoted. The heating temperature is, for example, 30 to 300°C, preferably 50 to 250°C, more preferably 70 to 200°C, and even more preferably 80 to 150°C. [Examples]

[0054] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

[0055] [Fabrication of polarizing film with bonding layer] A 25μm thick iodine-based polarizing film (100mm long x 100mm wide) with a surface protective film laminated on it was prepared. The side of the polarizing film opposite to the side with the surface protective film laminated on it was cleaned with ethanol and dried, and then the surface was subjected to corona discharge treatment (150W·min / m²). 2A triazine derivative aqueous solution (product name: MB1015 aqueous solution, manufactured by Iou Chemical Research Institute Co., Ltd.), which was adjusted to the solid content concentration (triazine derivative content) shown in Table 1 by applying a bonding layer to the corona discharge treated surface of a polarizing film, was applied by spin coating (application amount: 2 ml, spin rotation speed: 3000 rpm), and then dried in a constant temperature and humidity dryer (50°C for 10 minutes) to produce polarizing films with a bonding layer on the surface of the polarizing film (Samples 1 to 5). In addition, a polarizing film without a bonding layer on the surface (Sample 6) was prepared.

[0056] The nitrogen (N) atom concentration on the surface of the bonding layer of polarizing films with a bonding layer (Samples 1 to 5) and the nitrogen (N) atom concentration on the surface of a polarizing film without a bonding layer (Sample 6) were measured. The measurement results are shown in Table 1. <Measurement of Nitrogen (N) Atom Concentration> Using an X-ray photoelectron spectrometer, the sample was irradiated with X-rays under the following measurement conditions to perform a narrow scan of carbon, oxygen, nitrogen, and silicon atoms. The ratio of nitrogen atoms to the total sum of carbon, oxygen, nitrogen, and silicon atoms on the bonding layer surface or the polarizing film surface was calculated. Five arbitrary locations on the sample surface were then measured, and the average value was defined as the nitrogen (N) atom concentration. ·Equipment: ULVACΦ QuanteraSXM • X-ray source: Monochromatic AI (25.0W) ·Measurement area: 1000μm×1000μm ·Measurement depth: 7.2nm • Sweep: 1 time • Pass energy: 69eV Step size: 0.125eV Angle: 45°

[0057] [Table 1]

[0058] As shown in Table 1, in the polarizing films with bonded layers (Samples 1 to 5), where a coating solution containing a molecular bonding agent was applied to the surface of the polarizing film to form a bonded layer made of the molecular bonding agent, the nitrogen atom concentration on the surface of the bonded layer increased as the solid content concentration of the molecular bonding agent in the coating solution increased. Furthermore, the polarizing film of Sample 6, which did not have a bonded layer on its surface, showed a higher nitrogen atom concentration than Sample 1, which is presumed to be due to the detection of atmospheric nitrogen on the sample surface.

[0059] [Fabrication of polarizing plates] (Example 1) A quartz substrate (length 23.5 mm x width 20.0 mm x thickness 0.7 mm) was prepared as the support substrate. The quartz substrate was ultrasonically cleaned in acetone (10 minutes) and dried, and then corona discharge treatment (150 W·min / m) was applied to its surface. 2 After applying the above treatment, an aqueous solution containing 0.1% by weight of a triazine derivative (product name: MB1015 aqueous solution, manufactured by Iou Chemical Research Institute Co., Ltd.) was applied to the corona discharge treated surface of the quartz substrate by spin coating (coating amount: 2 ml, spin rotation speed: 3000 rpm). The substrate was then placed in a hot air dryer and dried at 80°C for 10 minutes to provide the surface of the quartz substrate with the triazine derivative. Next, the polarizing film with a bonded layer prepared above (sample 4) and the surface of the quartz substrate with the triazine derivative were superimposed and heat-pressed together using a hot press (pressure: 10 MPa, temperature: 100°C, time: 12 minutes) to produce a polarizing plate. The nitrogen atom concentration on the surface of the quartz substrate containing the triazine derivative was measured by the method described above.

[0060] (Example 2) A polarizing plate was prepared in the same manner as in Example 1, except that Sample 3 was used as the polarizing film with a bonding layer.

[0061] (Example 3) A polarizing plate was prepared in the same manner as in Example 1, except that Sample 2 was used as the polarizing film with a bonding layer.

[0062] (Example 4) A polarizing plate was prepared in the same manner as in Example 1, except that the solid content concentration of the aqueous solution containing the triazine derivative applied to the quartz substrate was set to 0.01% by weight, and Sample 3 was used as the polarizing film with a bonding layer.

[0063] (Example 5) A polarizing plate was prepared in the same manner as in Example 1, except that the solid content concentration of the aqueous solution containing the triazine derivative applied to the quartz substrate was set to 0.01% by weight, and Sample 2 was used as the polarizing film with a bonding layer.

[0064] (Example 6) A polarizing plate was prepared in the same manner as in Example 1, except that the solid content concentration of the aqueous solution containing the triazine derivative applied to the quartz substrate was set to 0.01% by weight, and Sample 1 was used as the polarizing film with a bonding layer.

[0065] (Example 7) A polarizing plate was prepared in the same manner as in Example 1, except that the solid content concentration of the aqueous solution containing the triazine derivative applied to the quartz substrate was set to 0.001% by weight, and Sample 3 was used as the polarizing film with a bonding layer.

[0066] (Example 8) A polarizing plate was prepared in the same manner as in Example 1, except that the solid content concentration of the aqueous solution containing the triazine derivative applied to the quartz substrate was set to 0.001% by weight, and Sample 2 was used as the polarizing film with a bonding layer.

[0067] (Example 9) A polarizing plate was fabricated in the same manner as in Example 1, except that the support substrate was a quartz substrate without a triazine derivative on its surface, and Sample 3 was used as the polarizing film with a bonding layer.

[0068] (Example 10) A polarizing plate was fabricated in the same manner as in Example 1, except that the support substrate was a quartz substrate without a triazine derivative on its surface, and Sample 2 was used as the polarizing film with a bonding layer.

[0069] (Example 11) A polarizing plate was fabricated in the same manner as in Example 1, except that the support substrate was a quartz substrate without a triazine derivative on its surface, and Sample 1 was used as the polarizing film with a bonding layer.

[0070] (Example 12) A polarizing plate was prepared in the same manner as in Example 1, except that the support substrate was a UV-curable organic-inorganic copolymer film (23.5 mm in length and 20.0 mm in width) made of a silsesquioxane derivative having (meth)acryloyl groups with a thickness of 50 μm, and Sample 3 was used as the polarizing film with a bonding layer.

[0071] (Example 13) A polarizing plate was prepared in the same manner as in Example 1, except that the support substrate was a UV-curable organic-inorganic copolymer film (23.5 mm in length and 20.0 mm in width) made of a silsesquioxane derivative having (meth)acryloyl groups with a thickness of 50 μm, and Sample 2 was used as the polarizing film with a bonding layer.

[0072] (Comparative Example 1) A polarizing plate was prepared in the same manner as in Example 1, except that the solid content concentration of the aqueous solution containing the triazine derivative applied to the quartz substrate was set to 0.5% by weight, and Sample 5 was used as the polarizing film with a bonding layer.

[0073] (Comparative Example 2) A polarizing plate was prepared using the same method as in Example 1, except that Sample 6 was used as the polarizing film.

[0074] The polarizing plates obtained in Examples 1 to 13 and Comparative Examples 1 and 2 were evaluated as follows. The evaluation results are shown in Table 1. Note that polarizing plates with the surface protective film removed were used for the following evaluations.

[0075] <Peel strength measurement> In each example and comparative example, a polyethylene terephthalate film (thickness: 100 μm, model number: A4100, manufactured by Toyobo Co., Ltd.) was laminated onto the polarizing film surface of the polarizing plate obtained in the example and comparative example via an adhesive layer (thickness: 15 μm, NCF-211S, manufactured by Lintec Corporation), and pressed with a hand roller to obtain a laminate. Next, with the support substrate of the laminate fixed to a base, the polarizing film and polyethylene terephthalate film laminated via the adhesive layer were grasped, and the peel strength at 90 degrees was measured in accordance with JIS Z 0237-2009. The peel strength was expressed in units of (N / 25 mm).

[0076] [Table 2]

[0077] As shown in Table 2, polarizing films with a bonding layer in which the nitrogen (N) atom concentration due to the molecular bonding agent, as measured by X-ray photoelectron spectroscopy on the bonding layer surface, was 12.0 atm% or less, showed excellent adhesion to other components such as the support substrate, regardless of the type of support substrate or the presence or absence of the molecular bonding agent on the support substrate side. On the other hand, polarizing films with a bonding layer in which the nitrogen (N) atom concentration due to the molecular bonding agent, as measured by X-ray photoelectron spectroscopy on the bonding layer surface, exceeded 12.0 atm%, showed poor adhesion to other components such as the support substrate. Furthermore, polarizing films without a bonding layer made of molecular bonding agent on their surface did not exhibit thermal bonding when simply heat-pressed with the support substrate, resulting in poor adhesion between the polarizing film and the support substrate.

[0078] As can be seen from the above results, in molecular bonding technology, which joins components by chemical bonding using one or more molecular layers, excellent adhesion to other components such as support substrates can be achieved by introducing a very small amount of molecular bonding agent onto the surface of the polarizing film. This can be achieved by keeping the nitrogen (N) atom concentration due to the molecular bonding agent, as measured by X-ray photoelectron spectroscopy, below 12.0 atm%. However, due to the measurement principle of the X-ray photoelectron spectroscopy device, it is difficult to determine the lower limit of the amount of molecular bonding agent introduced onto the surface of the polarizing film using the nitrogen (N) atom concentration measured by X-ray photoelectron spectroscopy. Nevertheless, as long as the molecular bonding agent is present on the surface of the polarizing film, it is possible to achieve excellent adhesion to other components such as support substrates. [Explanation of Symbols]

[0079] 1: Polarizing film with bonding layer 2: Polarizing film 3: Bonding layer 4: Support base material 10: Polarizing plate

Claims

1. A polarizing film with a bonding layer, comprising a polarizing film made of a polyvinyl alcohol-based resin and a bonding layer made of a molecular bonding agent that is chemically bonded to at least one surface of the polarizing film, wherein the molecular bonding agent comprises a triazine derivative containing one or more alkoxysilyl groups, two amino groups, and one triazine ring, and the nitrogen (N) atom concentration on the surface of the bonding layer, as measured by X-ray photoelectron spectroscopy, is 12.0 atm% or less.

2. The polarizing film with a bonded layer according to claim 1, characterized in that the nitrogen (N) atom concentration measured by X-ray photoelectron spectroscopy on the surface of the bonded layer is 0.15 atm% or more and 10.0 atm% or less.

3. The polarizing film with a bonding layer according to claim 1 or 2, characterized in that the triazine derivative is a compound containing two or more OH groups and / or OH generating groups.

4. A polarizing plate characterized in that a polarizing film with a bonding layer according to any one of claims 1 to 3 and a light-transmitting support substrate are laminated via the bonding layer.

5. The polarizing plate according to claim 4, characterized in that the OH groups on the surface of the polarizing film and / or the OH groups on the surface of the supporting substrate are chemically bonded to the OH groups or OH-generating groups of the triazine derivative by dehydration condensation.

6. The polarizing plate according to claim 4 or 5, characterized in that the support substrate consists of one or more materials selected from organic materials, inorganic materials, and organic-inorganic hybrid materials.

7. A method for manufacturing a polarizing plate according to any one of 4 to 6, comprising the steps of: laminating the bonding layer-equipped polarizing film and the support substrate via the bonding layer; and thermally pressing the bonding layer-equipped polarizing film and the support substrate together to bond the bonding layer-equipped polarizing film and the support substrate together by chemical bonding.

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