Method for manufacturing polarizing plate with adhesive layer

Abstract

The present application aims to provide a polarizing plate with an adhesive layer in which peeling failure is further suppressed even in an environmental change from a high-temperature high-humidity environment to a high-temperature environment. A method for producing a polarizing plate with an adhesive layer, which has: a step of producing an alcohol content of 4 μg / cm 2 230 μg / cm 2 The following steps of a polarizing plate; forming an adhesive layer with a gel fraction of 70% or less on one face of the above-mentioned polarizing plate, a step of producing a polarizing plate with an adhesive layer, and a step of storing the above-mentioned polarizing plate with an adhesive layer in an environment with a temperature of 18°C or higher and 28°C or lower and a relative humidity of 40% or higher and 70% or lower for 2 days or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a polarizing plate with an adhesive layer. BACKGROUND

[0002] Liquid crystal display devices (LCDs) are widely used not only for liquid crystal televisions but also for personal computers, mobile devices such as mobile phones, and car-mounted uses such as navigation systems. Generally, a liquid crystal display device has a liquid crystal panel to which a polarizing plate with an adhesive layer is attached on both sides thereof via the adhesive layer, and displays by controlling light from a backlight using the liquid crystal panel. In recent years, organic EL display devices are also widely used in televisions, mobile devices such as mobile phones, and car-mounted uses such as navigation systems, as well as liquid crystal display devices. In organic EL display devices, in order to suppress a situation in which external light is reflected at a metal electrode (cathode) and observed like a mirror surface, a circularly polarizing plate (a laminate including a polarizing element and a λ / 4 plate) is sometimes disposed on a visible side surface of an image display panel.

[0003] As described above, polarizing plates are increasingly used as components of image display devices such as liquid crystal display devices and organic EL display devices in cars. The polarizing plates used in car-mounted image display devices are exposed to various severe environments such as high-temperature environments and high-temperature high-humidity environments more than those used in mobile devices such as televisions and mobile phones. Therefore, it is required that no adverse situations such as lifting or peeling of a polarizing plate with an adhesive layer from a liquid crystal cell occur even for strict environmental changes.

[0004] In order to cope with such strict environments, a technique for improving color tone by suppressing dimensional changes of a polarizing plate in a high-temperature environment is known (for example, Patent Literature 1).

[0005] Prior Art Documents

[0006] Patent Literature

[0007] Patent Literature 1: Japanese Patent Application Laid-Open (kokai) No. 2013-148806 SUMMARY

[0008] Problems to be Solved by the Invention

[0009] However, even such a polarizing plate is not sufficient in suppression of peeling in an environmental change from a high-temperature high-humidity environment to a high-temperature environment. An object of the present application is to provide a polarizing plate with an adhesive layer in which peeling is further suppressed even in an environmental change from a high-temperature high-humidity environment to a high-temperature environment.

[0010] Means for Solving the Problems

[0011] The present application provides a manufacturing method of a polarizing plate with an adhesive layer exemplified below.

[0012] [1] A method for manufacturing a polarizing plate with an adhesive layer, comprising:

[0013] The alcohol content was 4 μg / cm³. 2 Above and 230 μg / cm 2 The following are the processes for manufacturing polarizing plates;

[0014] The process of manufacturing a polarizing plate with an adhesive layer, wherein an adhesive layer with a gel content of 70% or less is formed on one side of the aforementioned polarizing plate; and

[0015] The process of storing the above-mentioned polarizing plate with adhesive layer in an environment with a temperature of 18°C ​​or higher and 28°C or lower, and a relative humidity of 40% or higher and 70% or lower for more than 2 days.

[0016] [2] According to the method for manufacturing a polarizing plate with an adhesive layer described in [1], wherein the alcohol is selected from at least one of methanol, ethanol and n-propanol.

[0017] [3] The method for manufacturing a polarizing plate with an adhesive layer as described in [1] or [2] includes a step of bonding a polarizing element formed by adsorbing iodine onto a polyvinyl alcohol resin layer and orienting the iodine to a transparent protective film with an adhesive layer formed by an adhesive containing an alcohol.

[0018] [4] The method for manufacturing a polarizing plate with an adhesive layer as described in [3], wherein the adhesive comprises a polyvinyl alcohol resin.

[0019] [5] According to the method for manufacturing a polarizing plate with an adhesive layer described in [4], the content of the alcohol in the adhesive is 100 parts by mass or more and 2000 parts by mass or less relative to 100 parts by mass of the polyvinyl alcohol resin.

[0020] [6] A method for manufacturing a polarizing plate with an adhesive layer according to any one of [3] to [5], wherein the thickness of the adhesive layer is 0.01 μm to 7 μm.

[0021] Invention Effects

[0022] According to the present invention, it is possible to manufacture a polarizing plate with an adhesive layer that can further suppress poor peeling even during environmental changes from a high-temperature and high-humidity environment to a high-temperature environment. Detailed Implementation

[0023] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0024] [Processes for manufacturing polarizing plates]

[0025] The polarizing plate uses an alcohol-containing polarizing plate. The aforementioned polarizing plate can use a polarizing element having a dichroic pigment adsorbed and oriented in a layer containing a polyvinyl alcohol-based resin, and a transparent protective film.

[0026] The amount of alcohol contained in the polarizing plate is 4 μg / cm. 2 Above and 230 μg / cm 2 The preferred value is 13 μg / cm³. 2 Above and 200 μg / cm 2 The following is more preferably 20 μg / cm 2 Above and 190 μg / cm 2 The following values ​​can also be 60 μg / cm³. 2 The above can also be 100 μg / cm 2 The above describes how setting the amount of alcohol contained in the polarizing plate within such a range ensures sufficient transfer of alcohol to the adhesive layer in subsequent processes without impairing the characteristics of the polarizing element. Prior to the later step of "holding the polarizing plate with the adhesive layer," the amount of alcohol contained in the polarizing plate is expected to be within the aforementioned range.

[0027] <Polarization element>

[0028] Well-known polarizing elements can be used as polarizing elements in which dichroic pigments are adsorbed onto a layer containing polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (hereinafter also referred to as "PVA-based resin layer") and the dichroic pigments are oriented. Examples of polarizing elements include: a stretched film obtained by dyeing a PVA-based resin film with a dichroic pigment and then uniaxially stretching it; and a stretched layer obtained by using a laminated film having a coating layer formed by coating a substrate film with a coating liquid containing a PVA-based resin, dyeing the coating layer with a dichroic pigment, and then uniaxially stretching the laminated film. Stretching can be performed after dyeing with the dichroic pigment, or while dyeing, or after stretching.

[0029] PVA-based resins can be obtained by saponifying polyvinyl acetate-based resins. Besides polyvinyl acetate as a homopolymer of vinyl acetate, copolymers of vinyl acetate with other monomers that can be copolymerized can also be mentioned as polyvinyl acetate-based resins. Examples of other monomers that can be copolymerized include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0030] The degree of saponification of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and even more preferably about 99 mol% or more and 100 mol% or less. The degree of polymerization of the PVA-based resin is, for example, 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The PVA-based resin can be modified, for example, it can be aldehyde-modified polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc.

[0031] The thickness of the polarizing element is preferably 3 μm or more and 35 μm or less, more preferably 4 μm or more and 30 μm or less, and even more preferably 5 μm or more and 25 μm or less. By making the thickness of the polarizing element 35 μm or less, the effect of polyolefination of PVA-based resin on the reduction of optical properties under high-temperature conditions can be suppressed. By making the thickness of the polarizing element 3 μm or more, it is easy to manufacture a configuration that achieves the desired optical properties.

[0032] The polarizing element preferably contains an alcohol. In this embodiment, the process may include bonding the polarizing element to a transparent protective film using an adhesive layer formed from an adhesive containing an alcohol. Therefore, it is presumed that a portion of the alcohol is transferred from the adhesive layer and contained within the polarizing element. The alcohol in the polarizing element may also include alcohol added during the manufacturing process of the polarizing element.

[0033] (alcohol)

[0034] Examples of alcohols used in this invention include lower alcohols having 1 to 4 carbon atoms. Specifically, examples include methanol, ethanol, n-propanol, isopropanol, and tert-butanol. The polarizing plate and adhesive (or adhesive layer) may contain alcohols preferably selected from at least one of methanol, ethanol, n-propanol, isopropanol, and tert-butanol. These can be used alone or in combination of two or more. At least one of methanol, ethanol, n-propanol, and isopropanol is preferred. Their low molecular weight allows for efficient transfer from the polarizing plate to the adhesive layer, making them preferable.

[0035] Examples of methods for incorporating alcohol into polarizing elements include: immersing a PVA-based resin layer in a processing solvent containing alcohol, or spraying, dripping, or sprinkling the processing solvent onto the PVA-based resin layer. The method of immersing the PVA-based resin layer in a processing solvent containing alcohol is preferred.

[0036] The process of impregnating the PVA-based resin layer in a processing solvent containing alcohol can be performed simultaneously with the swelling, stretching, dyeing, crosslinking, and cleaning processes described later in the polarization element manufacturing method, or it can be performed separately from these processes. The process of containing alcohol in the PVA-based resin layer is preferably performed after dyeing the PVA-based resin layer with iodine, and more preferably simultaneously with the cleaning process. According to this method, the color variation is small, which reduces the impact on the optical properties of the polarization element.

[0037] To make the polarizing element contain alcohol, it can be added during the manufacturing of the polarizing element and added to the adhesive.

[0038] (Urea compounds)

[0039] The polarizing element may further contain a urea-based compound. A polarizing element containing a urea-based compound can further suppress the decrease in transmittance. The urea-based compound may be the same as that contained in the adhesive described later. As a method for containing the urea-based compound in the polarizing element, the same method as for containing an alcohol in the polarizing element can be used. The urea-based compound may be included during the manufacturing process of the polarizing element, or it may be included in the adhesive described later for laminating the polarizing element with the transparent protective film, thereby being incorporated into the polarizing element.

[0040] (Dicarboxylic acid)

[0041] The polarizing element may also contain a dicarboxylic acid. A polarizing element containing a dicarboxylic acid can further suppress the decrease in transmittance. The dicarboxylic acid can be the same as that which may be contained in the adhesive described later. As a method for containing the dicarboxylic acid in the polarizing element, the same method as for containing an alcohol in the polarizing element can be used. The dicarboxylic acid can be included in the manufacturing process of the polarizing element, or it can be included in the adhesive described later for laminating the polarizing element with the transparent protective film, thereby being contained within the polarizing element.

[0042] (Manufacturing method of polarization element)

[0043] There is no particular limitation on the manufacturing method of polarization elements. Typical methods include: a method of producing a PVA-based resin film pre-wound into a roll and then stretching, dyeing, cross-linking, etc. (hereinafter referred to as "manufacturing method 1"); and a method including a process of coating a coating liquid containing PVA-based resin onto a substrate film to form a PVA-based resin layer as a coating layer, and stretching the resulting laminate (hereinafter referred to as "manufacturing method 2").

[0044] Manufacturing method 1 can be carried out by a process of uniaxially stretching a PVA-based resin film, dyeing the PVA-based resin film with dichroic pigments such as iodine to adsorb dichroic pigments, treating the PVA-based resin film with adsorbed dichroic pigments with a boric acid aqueous solution, and washing with water after treatment with boric acid aqueous solution.

[0045] The swelling process involves immersing a PVA-based resin film in a swelling bath. This process removes surface contaminants and anti-blocking agents from the PVA-based resin film, and also suppresses uneven dyeing by causing the film to swell. The swelling bath typically uses a water-based medium, such as water, distilled water, or pure water. Surfactants or alcohols can also be added to the swelling bath as needed. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide can 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.

[0046] The temperature of the swelling bath is preferably 10°C or higher and 60°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C ​​or higher and 30°C or lower. Regarding the immersion time in the swelling bath, since the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling bath, it cannot be fixed indefinitely; however, it is preferably 5 seconds or higher and 300 seconds or lower, more preferably 10 seconds or higher and 200 seconds or lower, and even more preferably 20 seconds or higher and 100 seconds or lower. The swelling process can be performed only once or multiple times as needed.

[0047] The dyeing process involves immersing a PVA-based resin film in a dyeing bath (iodine solution). This process allows the PVA-based resin film to adsorb dichroic pigments such as iodine and orient these pigments. The iodine solution is typically an aqueous solution containing iodine and iodides as a dissolving 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 suitable from the viewpoint of controlling the potassium content in the polarizing element.

[0048] The concentration of iodine in the staining bath is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.5% by mass or less. The concentration of iodide in the staining bath 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.

[0049] The temperature of the dyeing bath is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C ​​or higher and 30°C or lower. The immersion time in the dyeing bath cannot be fixed because the degree of dyeing of the PVA-based resin film is affected by the temperature of the dyeing bath; however, it is preferably 10 seconds or higher and 300 seconds or lower, more preferably 20 seconds or higher and 240 seconds or lower. The dyeing process can be performed only once or multiple times as needed.

[0050] The crosslinking process involves immersing a PVA-based resin film, dyed in the dyeing process, in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the polyvinyl alcohol-based resin film, allowing iodine molecules or dye molecules to adsorb onto the crosslinked structure. Examples of boron compounds include boric acid, borates, and borax. The crosslinking bath is generally an aqueous solution; however, it can also be a mixture of an organic solvent miscible with water and water. From the viewpoint of controlling the potassium content in the polarizing element, the crosslinking bath preferably contains potassium iodide.

[0051] 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 even 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 even more preferably 2% by mass or more and 5% by mass or less.

[0052] The temperature of the crosslinking bath is preferably 20°C or higher and 70°C or lower, more preferably 30°C or higher and 60°C or lower. The immersion time in the crosslinking bath cannot be fixed because the degree of crosslinking of the PVA resin film is affected by the temperature of the crosslinking bath; however, it is preferably 5 seconds or higher and 300 seconds or lower, more preferably 10 seconds or higher and 200 seconds or lower.

[0053] The crosslinking process can be performed only once, or it can be performed multiple times as needed.

[0054] The stretching process is a procedure in which a PVA-based resin film is stretched to a specified ratio in at least one direction. Generally, the PVA-based resin film is uniaxially stretched along the transport direction (length direction). There are no particular restrictions on the stretching method; either wet stretching or dry stretching can be used. The stretching process can be performed once or multiple times as needed. The stretching process can be performed at any stage in the manufacturing of polarization elements.

[0055] The treatment bath (stretching bath) in the wet stretching process can typically be water or a mixture of water and an organic solvent miscible with 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 even 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 even more preferably 2% by mass or more and 5% by mass or less.

[0056] The temperature of the stretching bath is preferably 25°C or higher and 80°C or lower, more preferably 40°C or higher and 75°C or lower, and even more preferably 50°C or higher and 70°C or lower. The immersion time in the stretching bath cannot be fixed because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching bath; however, it is preferably 10 seconds or higher and 800 seconds or lower, more preferably 30 seconds or higher and 500 seconds or lower. The stretching treatment in the wet stretching method can be performed together with any one or more of the following processing steps: swelling, dyeing, crosslinking, and cleaning.

[0057] Examples of dry stretching methods include inter-roll stretching, heated roll stretching, and compression stretching. It should be noted that dry stretching can be performed concurrently with the drying process.

[0058] The total stretch ratio (cumulative stretch ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set according to 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.

[0059] The cleaning process involves immersing the polyvinyl alcohol (PVA) resin film in a cleaning bath to remove 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, potassium iodide is preferably used 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.

[0060] The temperature of the cleaning bath is preferably 5°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, and even more preferably 15°C or higher and 30°C or lower. Regarding the immersion time in the cleaning bath, since the degree of cleaning of the PVA resin film is affected by the temperature of the cleaning bath, it cannot be fixed in general; however, it is preferably 1 second or higher and 100 seconds or lower, more preferably 2 seconds or higher and 50 seconds or lower, and even more preferably 3 seconds or higher and 20 seconds or lower. The cleaning process can be performed only once or multiple times as needed.

[0061] The drying process involves drying the PVA-based resin film, which has been cleaned in the cleaning process, to obtain the polarizing element. Drying can be performed using any suitable method, such as natural drying, forced-air drying, or heat drying.

[0062] Manufacturing method 2 can be performed through the following steps: applying a coating solution containing PVA-based resin onto a substrate film; uniaxially stretching the resulting laminated film; adsorbing the dichroic pigment by dyeing the PVA-based resin layer of the uniaxially stretched laminated film with a dichroic pigment to form a polarizing element; treating the film with the adsorbed dichroic pigment with a boric acid aqueous solution; and washing with water after treatment with the boric acid aqueous solution. The substrate film used to form the polarizing element can also be used as a protective layer for the polarizing element. The substrate film can be peeled off from the polarizing element as needed.

[0063] <Transparent Protective Film>

[0064] The transparent protective film used in this embodiment (hereinafter also referred to as the "protective film") is adhered to at least one side of the polarizing element via an adhesive layer. The transparent protective film may be adhered to one or both sides of the polarizing element, but it is preferred to adhere to both sides.

[0065] The protective film can also possess other optical functions and can be fabricated into a multilayered structure. From an optical property point of view, a thin protective film is preferred; however, if it is too thin, its strength decreases and its processability suffers. An appropriate film thickness is 5 μm or more and 100 μm or less, preferably 10 μm or more and 80 μm or less, and more preferably 15 μm or more and 70 μm or less.

[0066] The protective film can be made of cellulose acylated film, polycarbonate resin-based film, cyclic olefin resin-based film containing norbornene, (meth)acrylic polymer film, polyethylene terephthalate (PET) and other polyester resin-based film. When using a water-based adhesive such as PVA adhesive to bond the protective film to both sides of the polarizing element, from a moisture permeability perspective, it is preferable that at least one side of the protective film is either a cellulose acylated film or a (meth)acrylic polymer film, with a cellulose acylated film being preferred.

[0067] For purposes such as viewing angle compensation, at least one of the protective films can have a phase difference function. In this case, the protective film itself can have a phase difference function, or it can have a separate phase difference layer, or a combination of both. The film with the phase difference function can be directly attached to the polarization element via an adhesive, or it can be a structure in which another protective film attached to the polarization element is sandwiched between the two films and attached via an adhesive or bonding agent.

[0068] <Adhesive layer>

[0069] An adhesive forms the adhesive layer used to bond the protective film to the polarizing element. As the adhesive, an alcohol-containing adhesive is preferred. Water-based adhesives, solvent-based adhesives, and active energy radiation-cured adhesives can be used; however, from the viewpoint of containing an alcohol, a water-based adhesive is preferred, and one containing a PVA-based resin is even more desirable. By using an alcohol-containing adhesive, the decrease in transmittance of the polarizing plate under high-temperature conditions can also be suppressed.

[0070] The thickness of the adhesive during application can be set to an optional value, for example, in a manner that allows for the formation of an adhesive layer with a desired thickness after curing or heating (drying). The thickness of the adhesive layer formed by the adhesive is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, further preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

[0071] The following description of the adhesive is based on a preferred range for the case where the polarizing element does not contain alcohol during manufacturing. If the polarizing element contains alcohol, the following values ​​can be adjusted appropriately. For a specific example of alcohol, the same alcohol as that contained in the polarizing element described above can be used. During the drying process of forming the adhesive layer when bonding the polarizing element to the protective film, a portion of the alcohol can migrate from the adhesive layer to the polarizing element, etc.

[0072] When the adhesive is an aqueous adhesive containing PVA-based resin, the alcohol content in the adhesive is preferably 30 parts by weight or more and 2000 parts by weight or less relative to 100 parts by weight of the PVA-based resin, more preferably 100 parts by weight or more and 2000 parts by weight or less, further preferably 500 parts by weight or more and 1800 parts by weight or less, and most preferably 800 parts by weight or more and 1500 parts by weight or less. If it is less than 30 parts by weight, the peeling inhibition effect may not be sufficiently obtained during changes from a high-temperature and high-humidity environment to a high-temperature environment. On the other hand, when the alcohol content exceeds 2000 parts by weight, the color tone may sometimes deteriorate. By setting the alcohol content in the adhesive to the above range, the drying efficiency can be improved in the drying process after the protective film is laminated with the adhesive between the polarizing element and the polarizing element, and the alcohol content in the polarizing plate can be easily adjusted to the desired amount.

[0073] In a configuration in which a transparent protective film is bonded to both sides of a polarizing element via an adhesive layer, the adhesive layer on both sides of the polarizing element may be an alcohol-containing layer on only one side, but it is preferable that the adhesive layer on both sides is an alcohol-containing layer.

[0074] To meet the demand for thinner polarizing plates, a polarizing plate with a transparent protective film on only one side of the polarizing element has been developed. In this configuration, the transparent protective film is also laminated via an adhesive layer containing alcohol. As a method for manufacturing this type of polarizing plate with a transparent protective film on only one side of the polarizing element, a method can be considered that involves first manufacturing a polarizing plate with transparent protective films adhered to both sides via adhesive layers, and then peeling off one side of the transparent protective film. In using this manufacturing method, alcohol can be contained in the adhesive layer on either side, but it is preferable that both adhesive layers contain alcohol. When using an adhesive layer containing alcohol only on one side of the polarizing element, it is preferable that the adhesive layer on the side of the film that is not peeled off contains alcohol.

[0075] (Water-based adhesive)

[0076] As a water-based adhesive, any suitable water-based adhesive can be used; however, it is preferred to use a water-based adhesive containing PVA-based resin (PVA-based adhesive). From an adhesiveness perspective, the average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably 100 or more and 5500 or less, more preferably 1000 or more and 4500 or less. From an adhesiveness perspective, the average degree of saponification is preferably 85 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less.

[0077] As the PVA-based resin contained in the water-based adhesive, a resin containing acetyl groups is preferred because it exhibits excellent adhesion and durability to the protective film. The PVA-based resin containing acetyl groups can be obtained, for example, by reacting a PVA-based resin with a diene using an optional method. The degree of acetyl group modification in the PVA-based resin containing acetyl groups is typically 0.1 mol% or more, preferably 0.1 mol% or more and 20 mol% or less. The resin concentration of the water-based adhesive is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less.

[0078] Water-based adhesives may also contain crosslinking agents. Known crosslinking agents can be used. Examples of crosslinking agents include water-soluble epoxy compounds, dialdehydes, and isocyanates.

[0079] When the PVA resin is a PVA resin containing acetyl groups, the crosslinking agent is preferably any one of glyoxal, glyoxylate, or hydroxymethyl melamine, more preferably any one of glyoxal or glyoxylate, and particularly preferably glyoxal.

[0080] (Active energy radiation curing adhesive)

[0081] Reactive energy radiation-cured adhesives are adhesives that cure upon exposure to reactive energy radiation such as ultraviolet rays. Examples include adhesives containing polymerizable compounds and photopolymerization initiators, adhesives containing photoreactive resins, and adhesive resins containing photoreactive crosslinking agents. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from these monomers. Examples of photopolymerization initiators include compounds containing substances that generate reactive species such as neutral free radicals, anionic free radicals, and cationic free radicals upon exposure to reactive energy radiation such as ultraviolet rays.

[0082] (Urea compounds)

[0083] The adhesive also contains at least one urea compound selected from urea, urea derivatives, thiourea, and thiourea derivatives. By including a urea compound in the adhesive layer formed by the adhesive, high-temperature durability can be further improved. During the drying process of the adhesive layer formed by bonding the adhesive to a protective film, a portion of the urea compound can migrate from the adhesive layer to polarizing elements, etc. Urea compounds include water-soluble and poorly water-soluble compounds; either type of urea compound can be used. When using a poorly water-soluble urea compound in a water-soluble adhesive, a dispersion method is preferably designed to prevent an increase in turbidity after the adhesive layer is formed.

[0084] When the adhesive is an aqueous adhesive containing PVA-based resin, the amount of urea compound added is preferably 0.1 parts by weight or more and 400 parts by weight or less relative to 100 parts by weight of PVA, more preferably 1 part by weight or more and 200 parts by weight or less, and even more preferably 3 parts by weight or more and 100 parts by weight or less.

[0085] (Urea derivatives)

[0086] Urea derivatives are compounds in which at least one of the four hydrogen atoms of a urea molecule is substituted with a substituent. In this case, there are no particular limitations on the substituent, but substituents containing carbon, hydrogen, and oxygen atoms are preferred. Some urea derivatives have low solubility relative to water, but sufficient solubility relative to alcohols. In this case, dissolving the urea compound in an alcohol to prepare an alcoholic solution of the urea compound, and then adding the alcoholic solution of the urea compound to an aqueous PVA solution to prepare an adhesive, is also a preferred method.

[0087] Specific examples of urea derivatives, for monosubstituted ureas, include: methylurea, ethylurea, propylurea, butylurea, isobutylurea, N-octadecylurea, 2-hydroxyethylurea, hydroxyurea, acetylurea, allylurea, 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzylurea, benzoylurea, o-tolylurea, and p-tolylurea. For disubstituted ureas, include: 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-di(hydroxymethyl)urea, 1,3-tert-butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-di(4-methoxyphenyl)urea, 1-acetyl-3-methylurea, 2-imidazolinone (vinylurea), and tetrahydro-2-pyrimidinone (acrylurea). Examples of tetrasubstituted ureas include: tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1,3-dimethylurea, 1,3-dimethyl-2-imidazolinone, and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

[0088] (Thiocarbamide derivatives)

[0089] Thiourea derivatives are compounds in which at least one of the four hydrogen atoms of a thiourea molecule has been substituted with a substituent. In this case, there are no particular restrictions on the substituent, but substituents containing carbon, hydrogen, and oxygen atoms are preferred.

[0090] Specific examples of thiourea derivatives, in terms of monosubstituted thioureas, include: N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, cyclohexylthiourea, N-acetylthiourea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N-(2-methoxyphenyl)thiourea, N-(1-naphthyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, and p-tolylthiourea. Examples of disubstituted thioureas include: 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3-dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N'-diphenylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N-allyl-N'-(2-hydroxyethyl)thiourea, and ethylenethiourea. Examples of trisubstituted thioureas include trimethylthiourea. Examples of tetrasubstituted thioureas include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

[0091] From the perspective of further suppressing the decrease in transmittance under high-temperature environments when used in image display devices with interlayer filling, urea derivatives or thiourea derivatives are preferred among urea compounds, and urea derivatives are more preferred. Among urea derivatives, monosubstituted urea or disubstituted urea are preferred, and monosubstituted urea is more preferred. Disubstituted urea includes 1,1-substituted urea and 1,3-substituted urea, and 1,3-substituted urea is more preferred.

[0092] (Dicarboxylic acid)

[0093] The adhesive may also contain dicarboxylic acids. By using an adhesive containing dicarboxylic acids, the decrease in transmittance of the polarizer under high-temperature conditions can be suppressed. Examples of dicarboxylic acids include: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, tartaric acid, glutamic acid, malic acid, maleic acid, fumaric acid, itaconic acid, kojic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4-biphenyldicarboxylic acid, 2,5-pyridinedicarboxylic acid, 3,5-pyridinedicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylmethanedicarboxylic acid, oxaloacetic acid, methyl fumaric acid, 2,6-pyridinedicarboxylic acid, etc. Among these, citric acid, malic acid, maleic acid, or tartaric acid are preferred. These dicarboxylic acids can be used alone, or in combination of two or more.

[0094] [Manufacturing method of polarizing plate]

[0095] The manufacturing method of the polarizing plate is not particularly limited, but for example, it may include the following steps: after applying an adhesive layer between the first transparent protective film, the polarizing element, and the second transparent protective film and stacking them, a drying process is performed to bond them together. At least one adhesive layer preferably uses an adhesive containing alcohol. The manufacturing process of the polarizing plate preferably includes: bonding the polarizing element, which has been iodine adsorbed and oriented in a polyvinyl alcohol-based resin layer, to the transparent protective film using an adhesive layer formed by an adhesive containing alcohol. Furthermore, for at least one side of the manufactured polarizing plate, a peelable surface protective film may be laminated to protect its surface. It should be noted that when surface protective films are laminated on both sides of the polarizing plate, the surface protective film on the adhesive forming side can be peeled off before the formation of the adhesive in subsequent processes.

[0096] [Process for manufacturing polarizing plates with adhesive layers]

[0097] Next, an adhesive layer is formed on the fabricated polarizing plate. The gel content of the adhesive layer used is less than 70%.

[0098] <Adhesive layer>

[0099] The adhesive layer can be formed in one or more layers, preferably in one layer. The adhesive layer can be formed from an adhesive composition with (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin as the main component. Among these, adhesive compositions with (meth)acrylic resin as the base polymer are particularly suitable, exhibiting excellent transparency, weather resistance, and heat resistance. The adhesive composition can also be of the active energy radiation curing type or the thermosetting type.

[0100] The (meth)acrylic resin (base polymer) used as a component of the adhesive can suitably be a polymer or copolymer of one or more (meth)acrylates such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer in the base polymer. Examples of polar monomers include (meth)acrylate compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, N,N-dimethylaminoethyl (meth)acrylate compounds, and glycidyl (meth)acrylate compounds, which are monomers having carboxyl, hydroxyl, amide, amino, or epoxy groups.

[0101] The adhesive composition may contain only the aforementioned base polymer, but it typically also contains a crosslinking agent. Examples of crosslinking agents include: metal ions with a valence of divalent or higher that form a carboxylic acid metal salt with a carboxyl group; polyamine compounds that form an amide bond with a carboxyl group; polyepoxide compounds or polyols that form an ester bond with a carboxyl group; and polyisocyanate compounds that form an amide bond with a carboxyl group. Among these, polyisocyanate compounds are preferred.

[0102] Examples of the aforementioned polyisocyanate compounds include: polyisocyanate compounds, trimers of polyisocyanate compounds, urethane prepolymers with isocyanate groups at the ends obtained by reacting polyisocyanate compounds with polyol compounds, and trimers of the urethane prepolymers. Examples of polyisocyanate compounds include: 2,4-toluene diisocyanate, 2,5-toluene diisocyanate, 1,3-phenylenedimethylene diisocyanate, 1,4-phenylenedimethylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, dicyclohexylmethane-2,4′-diisocyanate, lysine isocyanate, etc.

[0103] The aforementioned polyisocyanate compound can be used alone, or two or more can be used in combination. However, regarding the total content, relative to 100 parts by weight of the base polymer, it is preferable to contain 0.01 to 2 parts by weight of the aforementioned polyisocyanate compound, more preferably 0.02 to 2 parts by weight, and even more preferably 0.05 to 1.5 parts by weight. The content can be appropriately adjusted to take into account factors such as coagulation strength and peel resistance in durability tests.

[0104] It should be noted that commercially available isocyanate compounds such as L45 (manufactured by Soken Chemical Co., Ltd.), TD75 (manufactured by Soken Chemical Co., Ltd.), BXX5627 (manufactured by Toyo-Chem Co., Ltd.), X-301-422SK (manufactured by Saiden Chemical Co., Ltd.), and Coronate L (manufactured by Tosoh Co., Ltd.) can be used as commercially available products.

[0105] The active energy radiation-curable adhesive composition possesses the property of curing upon irradiation by active energy radiation such as ultraviolet rays or electron beams. It also exhibits adhesiveness even before irradiation, enabling it to adhere tightly to substrates such as films, and the ability to adjust the adhesion strength upon curing due to irradiation. The active energy radiation-curable adhesive composition is preferably ultraviolet-curable. In addition to containing a base polymer and a crosslinking agent, the active energy radiation-curable adhesive composition also contains an active energy radiation polymerizable compound. Depending on the requirements, it may contain photopolymerization initiators, photosensitizers, etc.

[0106] The adhesive composition may contain additives such as microparticles, beads (resin beads, glass beads, etc.) for imparting light scattering properties, glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders, other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

[0107] The adhesive layer can be formed by applying an organic solvent dilution of the adhesive composition described above to the surface of a substrate film or a polarizing plate and then drying it. The substrate film is typically a thermoplastic resin film; a typical example is a release film that has undergone a release treatment. For example, the release film may be a film in which the adhesive layer-forming side of a film containing resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyarylate has undergone a silicone treatment or other release treatment.

[0108] The process of manufacturing a polarizing plate with an adhesive layer may include the following steps: directly applying an adhesive composition to the release surface of a release film to form an adhesive layer, and then laminating the adhesive layer with the release film on the surface of the polarizing plate. Alternatively, the process may include the following steps: directly applying an adhesive composition to the surface of the polarizing plate to form an adhesive layer, and then laminating a release film on the outer surface of the adhesive layer.

[0109] When the adhesive layer is applied to the surface of the polarizing plate, it is preferable to perform surface activation treatments such as plasma treatment or corona treatment on the bonding surface of the polarizing plate and / or the bonding surface of the adhesive layer, and more preferably to perform corona treatment.

[0110] Alternatively, an adhesive sheet can be prepared by coating an adhesive composition onto a second release liner to form an adhesive layer, and then stacking a release liner on the formed adhesive layer. The adhesive layer with the release liner after peeling the second release liner from the adhesive sheet is then stacked on a polarizing plate. The second release liner is a membrane with weaker adhesion to the adhesive layer and easier to peel off compared to the release liner.

[0111] The thickness of the adhesive layer is not particularly limited, but is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and may also be 20 μm or more.

[0112] The adhesive layer used in the process of manufacturing a polarizing plate with an adhesive layer has a gel content within a specified range. It is believed that a higher gel content in the adhesive layer results in more cross-linking reactions within the adhesive layer, thus achieving the target cross-linking density. The gel content of the adhesive layer is preferably 70% or less, more preferably 50% or less, and even more preferably 30% or less. The most preferred case is a gel content of essentially 0%. An essentially 0% gel content means a gel content of 5% or less. When the gel content is greater than 70%, the peeling inhibition effect may become insufficient when exposed to environmental changes from a high-temperature, high-humidity environment to a high-temperature environment. It is also desirable that the gel content of the adhesive layer be within the above-mentioned range before proceeding to the "process of storing the polarizing plate with the adhesive layer" described later.

[0113] There are no particular limitations on the method for obtaining an adhesive layer with a gel fraction within a specified range; known methods can be used. Specifically, an adhesive layer with the desired gel fraction can be obtained by adjusting the drying temperature and drying time of the adhesive. For example, when setting the drying temperature to 70°C or higher and less than 100°C, the desired adhesive layer can be obtained by setting the drying time to 30 seconds or more and 5 minutes or less. Since the gel fraction of the adhesive layer immediately after fabrication is essentially 0%, it is most preferable to laminate the immediately fabricated adhesive layer onto a polarizing plate.

[0114] [Process for storing polarizing plates with adhesive layers]

[0115] The manufactured polarizing plate with adhesive layer should be stored in an environment with a temperature of 18°C ​​or higher and 28°C or lower, and a relative humidity of 40% or higher and 70% or lower for at least 2 days. If the polarizing plate with adhesive layer is a long strip produced continuously in a roll-to-roll manner, it can be stored directly while wound on a roll.

[0116] The preferred storage temperature is 20°C or higher and 26°C or lower. The preferred storage humidity is 50% or higher and 60% or lower. The preferred storage period is 3 days or more, more preferably 5 days or more, and most preferably 7 days or more. There is no particular limit to the upper limit of the storage period, but it can be, for example, 365 days or less.

[0117] The polarizing plate with an adhesive layer manufactured using the method of the present invention can suppress poor peeling even when exposed to environmental changes from high temperature and high humidity to high temperature. The details of the mechanism are not clear, but it can be presumed as follows: Generally, the adhesive layer is stored, for example, in an environment with a temperature of 23°C and a relative humidity of 55% for more than 2 days until the crosslinking reaction reaches stability. It is presumed that during this period, the crosslinking reaction proceeds uniformly in the thickness direction of the adhesive layer. However, the polarizing plate used in the manufacturing method of the present invention contains a specified amount of alcohol, and after the adhesive layer is formed on the polarizing plate, it is supplied to the storage process. It is presumed that during such storage, the alcohol transfers from the polarizing plate to the adhesive layer. It is presumed that, as a result, alcohol is present in the adhesive layer closer to the polarizing plate in the thickness direction. This transferred alcohol reacts with the crosslinking agent, thereby deactivating the crosslinking agent and inhibiting the crosslinking reaction. For the adhesive layer after such storage, it is presumed that the crosslinking density is low near the polarizing plate in the thickness direction and increases with distance from the polarizing plate. For such an adhesive layer, the storage modulus of elasticity is low near the polarizer and increases with distance from the polarizer. Therefore, it can mitigate stress caused by dimensional changes in the polarizer on one side, while ensuring sufficient adhesion to the display device bonded to the polarizer on the other side. It is speculated that this allows for the suppression of poor peeling even when exposed to environmental changes from high temperature and humidity to high temperature.

[0118] The gel content of the adhesive layer supplied to the display device (which may be at the end of the process of storing the polarizing plate with the adhesive layer) is 60% or more, preferably 70% or more, and most preferably 80% or more. If the gel content is less than 60%, peeling is likely to occur under high-temperature conditions. The gel content can typically be less than 100%.

[0119] When the gel fraction of the adhesive layer formed on the polarizing plate exceeds 70%, the cross-linking reaction has been sufficiently advanced, which may prevent the full realization of the deactivation effect of the cross-linking agent brought about by alcohol transfer in the polarizing plate. Therefore, it may be impossible to fully achieve the effect of inhibiting peeling when exposed to environmental changes from a high-temperature and high-humidity environment to a high-temperature environment.

[0120] Example

[0121] The present invention will now be described in detail based on embodiments. The materials, reagents, quantities, proportions, and operations shown in the following embodiments may be appropriately modified without departing from the spirit of the invention.

[0122] Therefore, the present invention is not limited or restricted by the following embodiments.

[0123] (1) Measurement of the thickness of the polarization element:

[0124] The measurements were performed using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

[0125] (2) Determination of the amount of alcohol (methanol) in the polarizing plate:

[0126] The polarizing plate was cut into 1 cm square pieces to obtain the evaluation sample. 5 mL of ultrapure water was added to the evaluation sample, and the mixture was heated at 70 °C for 30 minutes. After stirring, the sample was measured using the GC-FID method under the following conditions.

[0127] (Gas Chromatography Analysis Conditions)

[0128] Column: DB-WAX 30m×0.250mm×0.25μm, ID (Agilent Technologies) or equivalent;

[0129] Carrier gas: Helium, 1.0 mL / min;

[0130] Column temperature: 40℃ (hold for 5 minutes) → increase temperature at 20℃ / minute → 240℃ (hold for 10 minutes);

[0131] Inlet temperature: 240℃, injection volume: 1μL, split ratio: 50:1;

[0132] Detector temperature: 240℃, Detector: FID.

[0133] (3) Determination of gel fraction of adhesive layer

[0134] The gel fraction in the adhesive layer of the present invention is a value determined according to the following (a) to (d).

[0135] (a) Attach an adhesive layer of approximately 8 cm × approximately 8 cm in area to a metal mesh of approximately 10 cm × approximately 10 cm formed of SUS304 (with a weight of Wm).

[0136] (b) Weigh the composite obtained in (a) above and set its mass as Ws. Then fold it 4 times to wrap the adhesive layer, staple it with a stapler, and weigh it again. Set its mass as Wb.

[0137] (c) Place the wire mesh stapled in (b) above into a glass container, add 60 mL of ethyl acetate for impregnation, and then keep the glass container at room temperature for 3 days.

[0138] (d) Remove the mesh from the glass container, dry it at 120°C for 24 hours, weigh it, set its mass as Wa, and calculate the gel fraction based on the following formula.

[0139] Gel fraction (mass%) = [{Wa - (Wb - Ws) - Wm} / (Ws - Wm)] × 100

[0140] <Fabrication of Polarizing Elements>

[0141] A 60 μm thick polyvinyl alcohol (PVA) resin film with an average degree of polymerization of approximately 2400 and a saponification degree of 99.9 mol% or higher was immersed in pure water at 21.5 °C for 79 seconds, followed by immersion in an aqueous solution containing 1.0 mM iodine at 23 °C for 151 seconds. Then, it was immersed in an aqueous solution with a potassium iodide / boric acid / water weight ratio of 2.5 / 4 / 100 at 60.8 °C for 76 seconds. Next, it was immersed in an aqueous solution with a potassium iodide / boric acid / water weight ratio of 3 / 5.5 / 100 at 45 °C for 11 seconds. Finally, it was dried at 38 °C to obtain a 22 μm thick polarizing element with iodine adsorbed and oriented in the PVA. Stretching was mainly performed during the iodine dyeing and boric acid treatment processes, with a total stretching ratio of 5.85 times.

[0142] [Preparation of Adhesives 1-2]

[0143] (Preparation of PVA solution A for adhesives)

[0144] 50g of a modified PVA resin containing acetyl groups (GOHSENX Z-410 manufactured by Mitsubishi Chemical Corporation) was dissolved in 950g of pure water. The solution was heated at 90°C for 2 hours and then cooled to room temperature to obtain a PVA solution for adhesives (hereinafter referred to as "PVA solution A").

[0145] (Preparation of adhesives 1-2)

[0146] The PVA solution A prepared above, pure water, maleic acid, 40% glyoxal solution, and methanol were combined in the amounts shown in Table 1 to prepare adhesives 1-2.

[0147] [Table 1]

[0148]

[0149] <Preparation of Transparent Protective Film>

[0150] [Transparent Protective Film 1]

[0151] A cellulose acylated membrane, KC8UX2MSW (manufactured by Konica Minolta, Inc., 80 μm thick), was used. The membrane was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, followed by washing with water. Then, it was immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, and further washed with running water for 30 seconds to neutralize the membrane. After repeated dehydration three times using an air knife, the membrane was dried in a drying zone at 70°C for 15 seconds, thus undergoing saponification.

[0152] [Transparent Protective Film 2]

[0153] ZB12 series cyclic olefin polymer membranes (manufactured by Zeon Corporation, Japan, membrane thickness 52 μm) were used. Both sides of the above cyclic olefin polymer membrane were subjected to 40 W·min / m 2 Corona treatment was performed under the specified conditions.

[0154] <Making of Polarizing Plates>

[0155] [Making Polarizing Plate 1]

[0156] Using adhesive 1, a transparent protective film 1 is bonded to one side of the polarizing element using a roller laminator, and a transparent protective film 2 is bonded to the other side. After bonding, a heat treatment at 60°C for 10 minutes is performed to dry the adhesive, resulting in a polarizing plate 1. The thickness of the adhesive layer of the polarizing plate 1 is 50 nm on both sides of the polarizing element. A surface protective film is then bonded to the transparent protective film 1 side of the polarizing plate thus fabricated. Regarding the surface protective film, an acrylic adhesive layer (15 μm thick) is formed on a polyester resin film (38 μm thick).

[0157] [Making Polarizing Plate 2]

[0158] Except for the use of adhesive 2, polarizing plate 2 is made in the same way as polarizing plate 1, and a surface protective film is attached to the transparent protective film 1.

[0159] [Preparation of Adhesive Compositions]

[0160] Prepare the following acrylic-based base polymer (G-1), isocyanate-based crosslinking agent (G-2), and silane coupling agent (G-3).

[0161] (H-1) A copolymer of butyl acrylate, methyl acrylate, acrylic acid, and hydroxyethyl acrylate;

[0162] (H-2) Ethyl acetate solution of trimethylolpropane adduct of toluene diisocyanate (75% solids) ("Coronate L" (trade name), manufactured by Tosoh Corporation);

[0163] (H-3)3-Epoxypropoxypropyltrimethoxysilane, liquid (“KBM-403” (trade name), manufactured by Shin-Etsu Chemical Co., Ltd.).

[0164] 100 parts by weight of the above-mentioned acrylic base polymer (H-1), 0.2 parts by weight of the isocyanate crosslinking agent (H-2) and 0.2 parts by weight of the silane coupling agent (H-3) were mixed and stirred thoroughly, and then diluted with ethyl acetate to obtain the adhesive composition.

[0165] [Creating the Adhesive Layer]

[0166] The obtained acrylic adhesive composition solution was applied to the release surface of a demolded polyethylene terephthalate film to achieve a dried adhesive layer thickness of 25 μm. The film was then dried at 90°C for 3 minutes to form the adhesive layer. The resulting adhesive layer had a gel content of 0%.

[0167] [Fabrication of Polarizing Plate 1 with Adhesive Layer]

[0168] The adhesive layer was immediately bonded to the transparent protective film 2 side of the polarizing plate 1 to create a polarizing plate 1 with an adhesive layer. The resulting polarizing plate 1 with the adhesive layer was stored for 7 days at a temperature of 23°C and a relative humidity of 50%. The methanol content of the polarizing plate before the adhesive layer was laminated was 75 μg / cm³. 2 The gel content of the adhesive layer after storage was 75%.

[0169] [Fabrication of Polarizing Plate 2 with Adhesive Layer]

[0170] Polarizing plate 1 with adhesive layer 1 was replaced with polarizing plate 2, and polarizing plate 2 with adhesive layer 2 was manufactured in the same manner as polarizing plate 1 with adhesive layer 1. The resulting polarizing plate 2 with adhesive layer 2 was stored in an environment with a temperature of 23°C and a relative humidity of 50% for 7 days. The methanol content of the polarizing plate before the adhesive layer was laminated was 0 μg / cm³. 2 The gel fraction of the adhesive layer after storage was 80%. The reason for the difference in gel fraction between polarizing plates 1 and 2 with adhesive layers is presumed to be that polarizing plate 1 with adhesive layers contains alcohol, so the gel fraction is lower near the polarizing plate.

[0171] [Fabrication of Polarizing Plate 3 with Adhesive Layer]

[0172] On the side of the polyethylene terephthalate film without the adhesive layer mentioned above, a polyethylene terephthalate film that has undergone a release treatment is further laminated. The adhesive layer with release-treated polyethylene terephthalate films laminated on both sides is stored for 7 days at 23°C and 50% relative humidity. The gel content of the adhesive layer after storage is 81%. A release-treated polyethylene terephthalate film is peeled off from the stored adhesive layer and attached to the transparent protective film 2 side of polarizing plate 1 to create a polarizing plate 3 with an adhesive layer. The methanol content of the polarizing plate before laminating the adhesive layer is 75 μg / cm³. 2 .

[0173] <Durability Evaluation>

[0174] (Preparation of the evaluation sample)

[0175] Polarizing plates 1-3 with adhesive layers were cut to a size of 110mm × 60mm, with the absorption axis of the polarizing plates parallel to the long side. These plates were then bonded to alkali-free glass (Corning "EAGLE XG", size 120mm × 70mm) via the adhesive layer. Next, the glass was subjected to a temperature of 50°C and a pressure of 5 kgf / cm². 2 The samples were subjected to autoclave treatment for 15 minutes under conditions of 490.3 kPa, and then placed in an environment of 23°C and 55% relative humidity for 24 hours to prepare evaluation samples.

[0176] The prepared evaluation samples were stored at 50°C and 95% relative humidity for 24 hours, followed by storage at 95°C for 96 hours. The results were then used to confirm whether the samples had floated or peeled off. The results are shown in Table 2.

[0177] [Table 2]

[0178]

Claims

1. A method for manufacturing a polarizing plate with an adhesive layer, comprising: The alcohol content was 4 μg / cm³. 2 Above and 230 μg / cm 2 The following are the processes for manufacturing polarizing plates; The process of manufacturing a polarizing plate with an adhesive layer, wherein an adhesive layer with a gel content of less than 5% is formed on one side of the polarizing plate; and The process of storing the polarizing plate with the adhesive layer in an environment with a temperature of 18°C ​​or higher and 28°C or lower, and a relative humidity of 40% or higher and 70% or lower for more than 2 days. The process of manufacturing the polarizing plate includes: The process of bonding a polarizing element, formed by adsorbing and orienting iodine in a polyvinyl alcohol-based resin layer, to a transparent protective film using an adhesive layer formed by an adhesive containing the alcohol. The alcohol is at least one selected from methanol, ethanol and n-propanol.

2. The method for manufacturing a polarizing plate with an adhesive layer according to claim 1, wherein, The adhesive comprises a polyvinyl alcohol-based resin.

3. The method for manufacturing a polarizing plate with an adhesive layer according to claim 2, wherein, In the adhesive, the content of the alcohol is more than 100 parts by weight and less than 2000 parts by weight relative to 100 parts by weight of the polyvinyl alcohol resin.

4. A method for manufacturing a polarizing plate with an adhesive layer according to any one of claims 1 to 3, wherein, The thickness of the adhesive layer is 0.01 μm to 7 μm.

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