KR20230088487A - Polarizer and image display device - Google Patents

Abstract

The present invention provides a polarizing plate in which a decrease in transmittance in a high-temperature environment is suppressed. A polarizing plate comprising a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, a transparent protective layer, and a pressure-sensitive adhesive layer in this order, wherein the pressure-sensitive adhesive layer is composed of urea, urea derivative, thiourea, and thiourea derivative. It contains at least one urea-based compound selected from the group consisting of, and the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 30%, and equal to or less than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 50%. A polarizing plate.

Description

Polarizer and image display device

The present invention relates to a polarizing plate and an image display device.

BACKGROUND OF THE INVENTION Liquid crystal display devices (LCDs) are widely used not only for liquid crystal televisions, but also for mobile devices such as personal computers and mobile phones, and for in-vehicle applications such as car navigation systems. Usually, a liquid crystal display device has a liquid crystal panel in which polarizing plates are bonded with an adhesive to both sides of a liquid crystal cell, and display is performed by controlling light from a backlight to the liquid crystal panel. [0003] Recently, organic EL display devices, like liquid crystal display devices, have been widely used for mobile applications such as televisions and mobile phones, as well as vehicle-mounted applications such as car navigation systems. In an organic EL display device, in order to prevent external light from being reflected by a metal electrode (cathode) and being viewed as a specular surface, a circular polarizing plate (a laminate including a polarizing element and a λ/4 plate) is placed on the viewer-side surface of an image display panel. sieve) may be placed.

As described above, the polarizing plate is a member of an image display device such as a liquid crystal display device and an organic EL display device, and the opportunity to mount it in a vehicle is increasing. Polarizing plates used in vehicle-mounted image display devices are often exposed to high temperature environments compared to mobile applications such as televisions and mobile phones, so the change in properties at higher temperatures is smaller (high temperature durability) is required.

On the other hand, for the purpose of preventing damage to the image display panel due to impact from the outer surface, etc., a configuration in which a front plate such as a transparent resin plate or glass plate (also called a "window layer") is provided on the viewer side rather than the image display panel It is increasing. BACKGROUND OF THE INVENTION [0002] In an image display device including a touch panel, a configuration in which the touch panel is provided on the viewer side rather than the image display panel and a front plate is provided on the viewer side more than the touch panel is widely adopted.

In this configuration, when an air layer exists between the image display panel and a transparent member such as a front plate or a touch panel, reflection of light at the interface between the air layer causes reflection of external light, and screen visibility tends to deteriorate. . Therefore, a structure in which the space between the transparent member and the polarizing plate disposed on the visual side surface of the image display panel is filled with a layer other than the air layer and usually a solid layer (hereinafter sometimes referred to as "interlayer filler") (hereinafter referred to as "interlayer filler"). , sometimes referred to as "interlayer filling configuration") is spreading. The interlayer filler is preferably a material having a refractive index similar to that of the polarizing plate or the transparent member. As the interlayer filler, a pressure-sensitive adhesive or a UV curable adhesive is used for the purpose of suppressing the decrease in visibility due to reflection at the interface and bonding and fixing between the respective members (see, for example, Patent Document 1).

Adoption of the interlayer charging configuration in mobile applications such as mobile phones, which are often used outdoors, is spreading. In addition, as the demand for visibility has recently increased, even in vehicle-mounted applications such as car navigation devices, interlayer filling by disposing a front transparent plate on the surface of an image display panel and filling the gap between the panel and the front transparent plate with an adhesive layer or the like Adoption of the configuration is being considered.

However, it has been reported that the transmittance of the polarizing plate significantly decreases in a high-temperature environment when such a configuration is employed. In Patent Document 2, as a solution to the problem, the amount of water per unit area of the polarizing plate is set to a predetermined amount or less, and the saturation absorption of the transparent protective film adjacent to the polarizing element is set to a predetermined amount or less, thereby suppressing the decrease in transmittance. A method is proposed. .

[Patent Document 1] Japanese Unexamined Patent Publication No. Heisei 11-174417 [Patent Document 2] Japanese Unexamined Patent Publication No. 2014-102353

However, even with such a polarizing plate, the effect of suppressing the decrease in transmittance in a high-temperature environment was not sufficient. An object of the present invention is to provide a novel polarizing plate capable of suppressing a decrease in transmittance under a high-temperature environment and an image display device using the polarizing plate.

The present invention provides a polarizing plate and an image display device exemplified below.

[1] A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, a transparent protective layer, and an adhesive layer in this order,

The pressure-sensitive adhesive layer contains at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives,

The moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 30%, and is equal to or less than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 50%.

[2] A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, a transparent protective layer, and an adhesive layer in this order,

The pressure-sensitive adhesive layer contains at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives,

The moisture content of the polarizing plate is equal to or greater than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 30%, and less than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 50%.

[3] The polarizing plate according to [1] or [2], wherein the transparent protective layer has a moisture permeability of 100 g/(m 2 ·day) or more at a temperature of 40°C and a relative humidity of 90%.

[4] The polarizing plate according to any one of [1] to [3], wherein the pressure-sensitive adhesive layer contains at least one urea-based compound selected from the group consisting of urea derivatives and thiourea derivatives.

[5] The pressure-sensitive adhesive layer contains a (meth)acrylic resin,

The polarizing plate according to any one of [1] to [4], wherein the content of the urea compound in the pressure-sensitive adhesive layer is 0.01 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic resin.

[6] An adhesive layer containing at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives is formed in contact with at least one surface of the polarizing element from [1] to [6]. The polarizing plate described in any one of [5].

[7] The polarizing plate according to [6], wherein the adhesive layer further contains a polyvinyl alcohol-based resin.

[8] The polarizing plate according to [7], wherein the content of the urea compound in the adhesive layer is 1 part by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

[9] The polarizing plate according to any one of [6] to [8], wherein the adhesive layer contains at least one type of urea compound selected from the group consisting of urea derivatives and thiourea derivatives.

[10] The polarizing plate according to any one of [1] to [9] used for an image display device having an interlayer filling configuration.

[11] An image display device comprising an image display cell, the polarizing plate according to any one of [1] to [10] laminated on the visual side of the image display cell, and a transparent member laminated on the visual side surface of the polarizing plate.

[12] The image display device according to [11], wherein the transparent member is a glass plate or a transparent resin plate.

[13] The image display device according to [11], wherein the transparent member is a touch panel.

According to the present invention, it is possible to provide a polarizing plate with improved durability at high temperatures and suppressed decrease in transmittance due to high temperatures even when used in an image display device having an interlayer filling configuration. In addition, by using the polarizing plate according to the present invention, it is possible to provide an image display device in which a decrease in transmittance under a high-temperature environment is suppressed.

Hereinafter, although embodiment of this invention was described, this invention is not limited to the following embodiment.

[Polarizer]

The polarizing plate according to the present embodiment has a polarizing element in which a dichroic dye is adsorbed and oriented on a layer containing a polyvinyl alcohol-based resin, a transparent protective layer, and an adhesive layer in this order. The pressure-sensitive adhesive layer contains a urea compound. The polarizing plate according to the present embodiment has at least one of the following characteristics (a) and (b).

(a) The moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

(b) The moisture content of the polarizing plate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

As a conventional polarizing plate excellent in high-temperature durability, for example, a polarizing plate in which a decrease in transmittance is suppressed even when left alone in an environment at a temperature of 95° C. for 1000 hours is known. However, even with such a polarizing plate, when used in an interlayer filling structure, a significant decrease in transmittance may be observed at the central portion of the polarizing plate in-plane when left in an environment at a temperature of 95°C for 200 hours. A significant decrease in the transmittance of the polarizing plate in a high-temperature environment is caused by an image display device employing an interlayer filling structure in which one side of the polarizing plate is bonded to an image display cell and the other side is bonded to a transparent member such as a touch panel or a front plate. It is considered to be a problem that is particularly likely to occur when exposed to a high temperature environment.

The polarizer with significantly reduced transmittance due to the interlayer filling configuration has peaks around 1100 cm ^-1 (derived from =CC= bond) and 1500 cm ^-1 (derived from -C=C- bond) in Raman spectroscopy measurement. , It is considered that the polyene structure (-C=C) _n - is formed. It is presumed that the polyene structure is formed when polyvinyl alcohol constituting the polarizing element is polyenified by dehydration (Patent Document 2, paragraph [0012]).

The polarizing plate according to the present invention can further improve high-temperature durability. The polarizing plate according to the present invention is incorporated in an image display device having an interlayer filling configuration, and can suppress a decrease in transmittance even when exposed to a high-temperature environment of, for example, a temperature of 105°C.

<Polarizing element>

As a polarizing element in which a dichroic dye is adsorbed and oriented in a layer containing polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (hereinafter also referred to as "PVA-based resin layer"), a well-known polarizing element can be used. . As the polarizing element, a stretched film obtained by dyeing a PVA-based resin film with a dichroic dye and uniaxially stretching it, or a laminated film having a coating layer formed by applying a coating solution containing a PVA-based resin on a base film, is used. , a stretched layer obtained by dyeing the coated layer with a dichroic dye and uniaxially stretching the laminated film. Stretching may be performed after dyeing with a dichroic dye, stretching may be performed while dyeing, or dyeing may be performed after stretching.

PVA type resin is obtained by saponifying polyvinyl acetate type resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable with this. Examples of the other copolymerizable monomer include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The degree of saponification of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, still more preferably about 99 mol% or more and 100 mol% or less. The polymerization degree 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 may be modified, such as polyvinyl formal, polyvinyl acetal, or polyvinyl butyral modified with aldehydes.

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, still more preferably 5 μm or more and 25 μm or less. When the thickness of the polarizing element is 35 μm or less, the influence of the polyenization of the PVA-based resin on the decrease in optical properties can be suppressed in a high-temperature environment. When the thickness of the polarizing element is 3 μm or more, it becomes easy to set it as a structure that achieves desired optical characteristics.

In this embodiment, the pressure-sensitive adhesive layer contains a urea compound. In the polarizing plate of the present embodiment, it is preferable that at least one side of the polarizing element is provided with an adhesive layer containing a urea compound in contact with it. The polarizing element may contain a part of the urea compound transferred from at least one of the pressure-sensitive adhesive layer and the adhesive layer. The polarizing element may be manufactured so that a urea-based compound is included before lamination.

In this embodiment, even if a polarizing plate is exposed to a high-temperature environment by providing the pressure-sensitive adhesive layer containing a urea-based compound, the transmittance becomes difficult to decrease. In this embodiment, by providing a polarizing element containing a urea-based compound, the transmittance is less likely to decrease even when the polarizing plate is exposed to a high-temperature environment. Although the reason for this is not clear, it is estimated that the polyenization of the PVA-based resin in the polarizing element is suppressed by the urea-based compound contained in the pressure-sensitive adhesive layer or the polarizing element, and the decrease in transmittance is suppressed.

As a method for incorporating a urea-based compound into the polarizing element, a method of immersing a PVA-based resin film or a PVA-based resin layer in a treatment solution containing a urea-based compound, or a treatment solution containing a urea-based compound is immersed in a PVA-based resin. The method of spraying, flowing down, or dripping on a film or a PVA-type resin layer is mentioned. Among them, a method in which a PVA-based resin-based resin film or a PVA-based resin layer is immersed in a treatment solution containing a urea-based compound is preferably used. Specific examples of the urea compound include those exemplified as being contained in the pressure-sensitive adhesive layer described later.

The step of immersing the PVA-based resin film or the PVA-based resin layer in a treatment solution containing a urea-based compound may be performed simultaneously with steps such as swelling, stretching, dyeing, crosslinking, and washing in the method for manufacturing a polarizing element described later. Alternatively, it may be provided separately from these steps. The step of incorporating the urea compound into the PVA-based resin film or PVA-based resin layer is preferably performed after dyeing with iodine, and more preferably performed simultaneously with the crosslinking step after dyeing. According to this method, color change is small, and the effect on the optical properties of the polarizing element can be reduced.

In order to contain the urea compound in the polarizing element, both addition at the time of production of the polarizing element and addition to the pressure-sensitive adhesive layer may be performed, or addition to the adhesive layer may be further performed.

(Feature (a))

In the case of having feature (a), the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and 30% relative humidity, and less than or equal to the equilibrium moisture content at a temperature of 20°C and 50% relative humidity. The moisture content of the polarizing element is preferably equal to or less than the equilibrium moisture content at a temperature of 20°C and 45% relative humidity, more preferably equal to or less than the equilibrium moisture content at a temperature of 20°C and 42% relative humidity, and still more preferably equal to or less than the equilibrium moisture content at a temperature of 20°C and 38% relative humidity. is less than the equilibrium moisture content of If the moisture content of the polarizing element is less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the handling properties of the polarizing element deteriorate and crack easily. When the moisture content of the polarizing element exceeds the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element tends to decrease. When the water content of the polarizing element is high, it is estimated that polyenization of the PVA-based resin proceeds easily. The moisture content of the polarizing element is the moisture content of the polarizing element in the polarizing plate.

As a method of confirming whether the moisture content of the polarizer is within the range of more than the equilibrium moisture content at a temperature of 20 ° C and a relative humidity of 30% and less than the equilibrium moisture content at a temperature of 20 ° C and a relative humidity of 50%, When stored in the environment and there is no change in mass for a certain period of time, it is considered that equilibrium with the environment has been reached, or the equilibrium moisture content of the polarizing element in the environment adjusted to the range of the temperature and the relative humidity is calculated in advance, and the polarizing element There is a way to check by comparing the moisture content of and the equilibrium moisture content calculated in advance.

The method for producing a polarizing element having a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50% is not particularly limited, but is adjusted within the range of the temperature and the relative humidity, for example. a method of storing the polarizing element in a heated environment for 10 minutes or more and 3 hours or less, or a method of heat treatment at 30°C or more and 90°C or less.

As another preferable method for producing a polarizing element having the above moisture content, a laminate in which a protective film is laminated on at least one side of the polarizing element or a polarizing plate constituted using a polarizing element is prepared in an environment adjusted to the above temperature and the above relative humidity ranges. For example, a method of storing for 10 minutes or more and 120 hours or less, or a method of heat treatment at 30°C or more and 90°C or less is exemplified. In the manufacture of an image display device employing an interlayer charging configuration, an image display panel in which a polarizing plate is laminated on an image display cell is stored in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes or more and 3 hours or less or 30 After heating at 90°C or more and 90°C or less, the front plate may be bonded.

The moisture content of the polarizing element is preferably adjusted so that the moisture content is within the above numerical range at the stage of the material used for constituting the polarizing plate, which is a polarizing element alone or a laminate of a polarizing element and a protective film. In the case where the water content is adjusted after forming the polarizing plate, the curl becomes excessively large, and a problem may easily occur when bonding the polarizing plate to an image display cell. By constructing a polarizing plate using a polarizing element adjusted to have the moisture content in a material step prior to constructing the polarizing plate, it is possible to easily construct a polarizing plate having a polarizing element having a moisture content satisfying the numerical range. In the state where the polarizing plate is bonded to the image display cell, the moisture content of the polarizing element in the polarizing plate may be adjusted so as to fall within the above numerical range. In this case, since the polarizing plate is bonded to the image display cell, curling is unlikely to occur.

(Feature (b))

In the case of having feature (b), the moisture content of the polarizing plate is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and is equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. The moisture content of the polarizing plate is preferably equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%, more preferably equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 42%, and still more preferably equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%. less than the equilibrium moisture content. When the moisture content of the polarizing plate is less than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30%, the handling properties of the polarizing plate decrease and cracking becomes easy. When the moisture content of the polarizing plate exceeds the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element tends to decrease. When the water content of the polarizing plate is high, it is estimated that it is because polyenization of PVA-type resin advances easily.

As a method of checking whether the moisture content of the polarizer is within the range of more than the equilibrium moisture content at a temperature of 20 ° C and a relative humidity of 30% and less than the equilibrium moisture content at a temperature of 20 ° C and a relative humidity of 50%, the environment adjusted to the range of the temperature and the relative humidity Stored in, a method of considering that equilibrium has been reached with the environment if there is no change in mass for a certain period of time, or pre-calculating the equilibrium moisture content of the polarizer in the environment adjusted to the range of the temperature and the relative humidity, and the moisture content of the polarizer A method of confirming by comparing the pre-calculated equilibrium moisture content may be mentioned.

The method for producing a polarizing plate having a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and less than or equal to an equilibrium moisture content at a temperature of 20° C. and a relative humidity of 50% is not particularly limited, but, for example, adjusted to the range of the temperature and the relative humidity A method of storing the polarizing plate in the environment for 10 minutes or more and 3 hours or less, or a method of heat treatment at 30°C or more and 90°C or less is exemplified.

In the manufacture of an image display device employing an interlayer charging configuration, an image display panel in which a polarizing plate is laminated on an image display cell is stored in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes or more and 3 hours or less or 30 After heating at 90°C or higher and lower than 90°C, the front plate may be bonded.

(Method of manufacturing polarizing element)

The manufacturing method of the polarizing element is not particularly limited, but a method of sending out a PVA-based resin film wound in a roll shape in advance and performing stretching, dyeing, crosslinking, etc. (hereinafter referred to as "manufacturing method 1") or a PVA-based resin A method including a step of applying the containing coating liquid on a base film to form a PVA-based resin layer as a coating layer and stretching the resulting laminate (hereinafter referred to as "manufacturing method 2") is typical.

Manufacturing method 1 is a step of uniaxially stretching the PVA-based resin film, a step of dyeing the PVA-based resin film with a dichroic dye such as iodine and adsorbing the dichroic dye, and a PVA-based resin film adsorbed with the dichroic dye in a boric acid solution It can be produced through a process of treating with and a process of washing with water after treatment with an aqueous solution of boric acid.

The swelling step is a treatment step in which the PVA-based resin film is immersed in a swelling bath. In addition to being able to remove contamination, a blocking agent, etc. on the surface of a PVA system resin film by a swelling process, dyeing unevenness can be suppressed by swelling a PVA system resin film. A medium containing water as a main component, such as water, distilled water, and pure water, is usually used for the swelling bath. A surfactant, an alcohol, etc. may be suitably added to the swelling bath in accordance with a conventional method. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide may be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, It is more preferable that it is 0.5 mass % or less.

The temperature of the swelling bath is preferably 10°C or more and 60°C or less, more preferably 15°C or more and 45°C or less, and still more preferably 18°C or more and 30°C or less. The immersion time in the swelling bath cannot be determined uniformly because the degree of swelling of the PVA-based resin film is affected by the swelling bath temperature, but is preferably 5 seconds or more and 300 seconds or less, more preferably 10 seconds or more and 200 seconds or less, , more preferably 20 seconds or more and 100 seconds or less. The swelling process may be performed only once, or may be performed a plurality of times as needed.

The dyeing process is a treatment process in which the PVA-based resin film is immersed in a dyeing bath (iodine solution), and dichroic dyes such as iodine can be adsorbed and oriented on the PVA-based resin film. The iodine solution is preferably an iodine aqueous solution, and contains iodine and iodide as a solubilizing agent. Examples of the iodide 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.

It is preferable that it is 0.01 mass % or more and 1 mass % or less, and, as for the iodine concentration in a dyeing bath, it is more preferable that it is 0.02 mass % or more and 0.5 mass % or less. The concentration of iodide in the dyeing bath is preferably 0.01 mass% or more and 10 mass% or less, more preferably 0.05 mass% or more and 5 mass% or less, and still more preferably 0.1 mass% or more and 3 mass% or less.

The temperature of the dyeing bath is preferably 10°C or more and 50°C or less, more preferably 15°C or more and 45°C or less, and still more preferably 18°C or more and 30°C or less. The immersion time in the dyeing bath cannot be determined uniformly because the degree of dyeing of the PVA-based resin film is affected by the dyeing bath temperature, but it is preferably 10 seconds or more and 300 seconds or less, and more preferably 20 seconds or more and 240 seconds or less. . The dyeing process may be performed only once, or may be performed a plurality of times as needed.

The crosslinking step is a treatment step in which the PVA-based resin film dyed in the dyeing step is immersed in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol-based resin film is crosslinked by the boron compound to form iodine molecules or Dye molecules may be adsorbed to the cross-linked structure. Examples of boron compounds include boric acid, borate salts, and borax. The crosslinking bath is generally an aqueous solution, but may be a mixed solution of a water-miscible organic solvent and water. The crosslinking bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element.

The concentration of the boron compound 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 still more preferably 2% by mass or more and 5% by mass or less. When potassium iodide is used for 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 2% by mass or more and 5% by mass. % or less is more preferable.

The temperature of the crosslinking bath is preferably 20°C or more and 70°C or less, and more preferably 30°C or more and 60°C or less. The immersion time in the crosslinking bath cannot be determined uniformly because the degree of crosslinking of the PVA-based resin film is affected by the temperature of the crosslinking bath, but it is preferably 5 seconds or more and 300 seconds or less, and more preferably 10 seconds or more and 200 seconds or less. . The crosslinking step may be performed only once, or may be performed a plurality of times as needed.

The stretching step is a treatment step of stretching the PVA-based resin film at a predetermined magnification in at least one direction. In general, the PVA-based resin film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. The stretching step may be performed only once, or may be performed a plurality of times as needed. The stretching step may be performed at any stage in the manufacture of the polarizing element.

As the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or an organic solvent miscible with water and a mixed solution of water can be used. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element. 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 3% by mass or more and 6% by mass. % or less is more preferable. The treatment bath (stretching bath) may contain a boron compound from the viewpoint of suppressing breakage of the film during stretching. 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 2% by mass or more and 5% by mass or less. more preferable

The temperature of the stretching bath is preferably 25°C or more and 80°C or less, more preferably 40°C or more and 75°C or less, and still more preferably 50°C or more and 70°C or less. The immersion time in the stretching bath cannot be determined uniformly because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching bath, but it is preferably 10 seconds or more and 800 seconds or less, and more preferably 30 seconds or more and 500 seconds or less. . The stretching treatment in the wet stretching method may be performed together with any one or more treatment steps of a swelling step, a dyeing step, a crosslinking step, and a washing step.

Examples of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. In addition, you may perform dry stretching method together with a drying process.

The total draw ratio (cumulative draw ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set depending on the purpose, but it is preferably 2 times or more and 7 times or less, more preferably 3 times or more and 6.8 times or less, and 3.5 It is more preferable that it is more than twice and 6.5 times or less.

The washing step is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a washing bath, and foreign substances remaining on the surface of the polyvinyl alcohol-based resin film or the like can be removed. As the washing bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. Further, from the viewpoint of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the washing bath, and in this case, the concentration of potassium iodide in the washing bath is preferably 1% by mass or more and 10% by mass or less, It is more preferable that it is 1.5 mass % or more and 4 mass % or less, and it is still more preferable that it is 1.8 mass % or more and 3.8 mass % or less.

The temperature of the washing bath is preferably 5°C or more and 50°C or less, more preferably 10°C or more and 40°C or less, and still more preferably 15°C or more and 30°C or less. The immersion time in the washing bath cannot be determined uniformly because the degree of washing of the PVA-based resin film is affected by the washing bath temperature, but it is preferably 1 second or more and 100 seconds or less, more preferably 2 seconds or more and 50 seconds or less, , more preferably 3 seconds or more and 20 seconds or less. The cleaning step may be performed only once, or may be performed a plurality of times as needed.

The drying process is a process of obtaining a polarizing element by drying the PVA-based resin film washed in the washing process. Drying is performed by any suitable method, and examples thereof include natural drying, blow drying, and heat drying.

Production method 2 is a step of applying a coating liquid containing a PVA-based resin onto a base film, a step of uniaxially stretching the obtained laminated film, and dyeing the PVA-based resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb it. It can be manufactured through a process of making a polarizing element, a process of treating a film adsorbed with a dichroic dye with an aqueous solution of boric acid, and a process of washing with water after treatment with an aqueous solution of boric acid. A base film used to form the polarizing element may be used as a protective layer for the polarizing element. You may peel and remove a base film from a polarizing element as needed.

<Transparent protective layer>

The transparent protective layer (hereinafter, simply referred to as "protective film") used in the present embodiment includes a transparent protective film and a transparent resin cured layer (for example, Japanese Unexamined Patent Publication No. 2011-221185). The transparent protective film is bonded to at least one side of the polarizing element via an adhesive layer. Although this transparent protective film is bonded to one side or both sides of a polarizing element, it is preferable to be bonded to both sides. At least one of the adhesive layers used to bond the transparent protective film to the surface of the polarizing element is preferably a layer containing a urea compound.

The protective layer may have different optical functions at the same time, or may be formed in a laminated structure in which a plurality of layers are laminated. When the protective layer is a protective film, the film thickness is preferably thin from the viewpoint of optical properties, but if too thin, the strength is lowered and the workability is poor. A suitable 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.

The protective film is a cellulose acylate-based film, a film containing a polycarbonate-based resin, a film containing a cycloolefin-based resin such as norbornene, a (meth)acrylic polymer film, a polyester resin-based film such as polyethylene terephthalate, etc. of film can be used.

At least one protective film may have a phase difference function for the purpose of viewing angle compensation or the like. In that case, the protective layer itself may have a retardation function, may have a retardation layer separately, or a combination of both may be sufficient. The film having the retardation function may be directly bonded to the polarizing element through an adhesive, but may also have a structure bonded through an adhesive layer or an adhesive layer through another protective layer bonded to the polarizing element.

When the protective film includes a transparent resin cured layer, it can be directly formed on the polarizing element without passing through an adhesive layer. Further, a urea compound may be contained in the transparent resin cured layer. The transparent resin cured layer containing a urea compound can be formed from a curable resin composition containing an organic solvent, and is described, for example, in Japanese Unexamined Patent Publication No. 2017-075986, paragraphs [0020] to [0042]. In the method for forming such a cured layer from an aqueous solution of an active energy ray-curable polymer composition such as the above, it can be formed by containing a water-soluble urea-based compound in the aqueous solution. The transparent resin cured layer preferably contains a binder. Examples of the binder include polymer binders, thermosetting resin binders, active energy ray curable resin binders, and the like, and any binder can be suitably used.

The thickness of the cured transparent resin layer is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less, still more preferably 1 μm or more and 10 μm or less.

In the polarizing plate of the present invention, the transparent protective layer on which the pressure-sensitive adhesive layer containing the urea compound is laminated has a moisture permeability at a temperature of 40°C and a relative humidity of 90%, preferably 100 g/(m 2 ·day) or more, It is preferably 300 g/(m 2 ·day) or more, and more preferably 500 g/(m 2 ·day) or more. Although the upper limit is not particularly limited, the water vapor transmission rate at a temperature of 40°C and a relative humidity of 90% may be 1500 g/(m 2 ·day) or less. By providing a pressure-sensitive adhesive layer containing a urea-based compound on such a transparent protective layer, the transmittance is less likely to decrease even when the polarizing plate is exposed to a high-temperature environment. This is presumed to be because, according to such a transparent protective layer, the urea-based compound in the pressure-sensitive adhesive layer easily migrates to the polarizing element and polyenization of the polarizing element is easily suppressed. As the transparent protective layer, a cellulose acylate-based film is suitably used from the viewpoint of being easy to obtain one within the above-mentioned range with respect to moisture permeability.

<Adhesive layer>

The polarizing plate includes, as a pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer containing a urea-based compound laminated on the side opposite to the polarizing element layer side of the transparent protective layer. The polarizing plate may further include another pressure-sensitive adhesive layer. Each pressure-sensitive adhesive layer may include one layer or two or more layers, but preferably includes one layer. The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition containing (meth)acrylic resin, rubber-based resin, urethane-based resin, ester-based resin, silicone-based resin, or polyvinyl ether-based resin as a main component. Among them, a pressure-sensitive adhesive composition comprising a (meth)acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer is suitable. The pressure-sensitive adhesive composition may be of an active energy ray curing type or a heat curing type.

Examples of the (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition include (meth)acrylic acid esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. The polymer or copolymer which uses 1 type, or 2 or more types of as a monomer is used suitably. It is preferable to copolymerize a polar monomer into the base polymer. As the polar monomer, (meth)acrylic acid compound, (meth)acrylic acid 2-hydroxypropyl compound, (meth)acrylic acid hydroxyethyl compound, (meth)acrylamide compound, N,N-dimethylaminoethyl (meth)acrylate compound and monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as glycidyl (meth)acrylate compounds.

The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. As the crosslinking agent, as a divalent or higher metal ion, a metal ion that forms a carboxylic acid metal salt between a carboxyl group, a polyamine compound that forms an amide bond between a carboxyl group, and a polyepoxy that forms an ester bond between a carboxyl group A polyisocyanate compound that forms an amide bond between a compound or polyol and a carboxyl group is exemplified. Among them, polyisocyanate compounds are preferred.

The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by being irradiated with active energy rays such as ultraviolet rays or electron beams, and has adhesiveness even before active energy ray irradiation, so that it can be adhered to an adherend such as a film, and is irradiated with active energy rays. It has a property that can be hardened by adjusting the adhesion. It is preferable that the active energy ray curable adhesive composition is an ultraviolet curable type. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray polymerizable compound in addition to the base polymer and the crosslinking agent. You may contain a photoinitiator, a photosensitizer, etc. as needed.

The pressure-sensitive adhesive composition includes fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powder or other inorganic powders, etc.), antioxidants, Additives such as ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, and photopolymerization initiators may be included.

The pressure-sensitive adhesive layer can be formed by applying a diluted organic solvent of the pressure-sensitive adhesive composition on the surface of a substrate film, an image display cell, or a polarizing plate and drying it. It is common for a base film to be a thermoplastic resin film, and a separator film subjected to release treatment is exemplified as a typical example thereof. The separation film may be, for example, a film made of a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyarylate, to which release treatment such as silicone treatment is performed on the surface on which the pressure-sensitive adhesive layer is formed.

In the method of laminating a pressure-sensitive adhesive layer containing a urea-based compound on a transparent protective layer, a pressure-sensitive adhesive composition is directly applied to the release treatment surface of a separate film to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer with the separate film is applied to the surface of the transparent protective layer. It may be laminated, or a pressure-sensitive adhesive layer may be formed by directly applying the pressure-sensitive adhesive composition to the surface of the transparent protective layer, and a separate film may be laminated on the outer surface of the pressure-sensitive adhesive layer. Specifically, a pressure-sensitive adhesive solution of 10% by mass or more and 40% by mass or less is prepared by dissolving or dispersing the base polymer or its composition in a solvent containing a single substance or mixture of suitable solvents such as toluene and ethyl acetate, and casting it ( A method of laying directly on the transparent protective layer by an appropriate development method such as a flow-through method or a coating method, a method of forming an adhesive layer on a separate film and transferring it to the surface of the transparent protective layer, and the like can be cited. there is.

When forming the pressure-sensitive adhesive layer on the surface of the transparent protective layer, it is preferable to perform a surface activation treatment such as plasma treatment or corona treatment on the bonding surface of the transparent protective layer and/or the bonding surface of the pressure-sensitive adhesive layer, and corona treatment is preferred. more preferable

Further, a pressure-sensitive adhesive composition is applied on the second separate film to form an adhesive layer, a pressure-sensitive adhesive sheet obtained by laminating the separate film on the formed pressure-sensitive adhesive layer is prepared, and the second separate film is separated from the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive layer may be bonded to the transparent protective layer. As for the 2nd separate film, the adhesive force with the adhesive layer is weaker than a separate film, and the thing which peels easily is used.

The thickness of the pressure-sensitive 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 be 20 μm or more.

(urea compound)

The urea-based compound included in the pressure-sensitive adhesive layer containing the urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The same applies to the urea-based compound used when adding the urea-based compound to other layers such as a polarizing element and an adhesive layer. A urea compound can be used individually by 1 type or in combination of 2 or more types. Urea-based compounds include those that are water-soluble and those that are poorly water-soluble, but either urea-based compounds can be used. When a poorly water-soluble urea-based compound is used for a water-soluble adhesive, it is preferable to devise a dispersion method so that the haze or the like does not occur after forming the adhesive layer.

In the pressure-sensitive adhesive layer containing a urea compound, when the pressure-sensitive adhesive layer contains a (meth)acrylic resin, the amount of the urea compound added is 0.01 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic resin. It is preferably 0.05 parts by mass or more and 50 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less. By setting the content of the urea compound to 0.01 part by mass or more, the effect of suppressing the polyenization of the polarizing element is more easily obtained. On the other hand, if the content of the urea-based compound is 100 parts by mass or less, it becomes difficult for the urea-based compound to precipitate, and troubles such as an increase in haze can be easily prevented.

(urea derivative)

A urea derivative is a compound in which at least one of the four hydrogen atoms of a urea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, but is preferably a substituent containing a carbon atom, a hydrogen atom and an oxygen atom.

Specific examples of urea derivatives include, as monosubstituted urea, methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, hydroxy urea, acetyl urea, allyl urea, 2-propynyl urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, benzoyl urea, o-tolyl urea, and p-tolyl urea.

2 As replacement elements, 1,1-dimethyl urea, 1,3-dimethyl urea, 1,1-diethyl urea, 1,3-diethyl urea, 1,3-bis(hydroxymethyl) urea, 1,3 -tert-butyl urea, 1,3-dicyclohexyl urea, 1,3-diphenyl urea, 1,3-bis(4-methoxyphenyl) urea, 1-acetyl-3-methyl urea, 2-imida Zolidinone (ethylene urea) and tetrahydro-2-pyrimidinone (propylene urea) are exemplified.

4 Substituents, tetramethyl urea, 1,1,3,3-tetraethyl urea, 1,1,3,3-tetrabutyl urea, 1,3-dimethoxy-1,3-dimethyl urea, 1,3 -Dimethyl-2-imidazolidinone and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

(thiourea derivative)

A thiourea derivative is a compound in which at least one of the four hydrogen atoms of a thiourea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, but is preferably a substituent containing a carbon atom, a hydrogen atom and an oxygen atom.

Specific examples of thiourea derivatives include N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, cyclohexylthiourea, N-acetylthiourea, N as monosubstituted thiourea. -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.

As disubstituted thiourea, 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.

As the trisubstituted thiourea, trimethylthiourea is exemplified, and as the tetrasubstituted thiourea, tetramethylthiourea and 1,1,3,3-tetraethylthiourea are exemplified.

Among urea-based compounds, urea derivatives or thiourea derivatives are used in an image display device having an interlayer filling configuration, in that a decrease in transmittance in a high temperature environment is suppressed and a decrease in polarization degree is small (cross leakage is suppressed). is preferred, and urea derivatives are more preferred. Among the urea derivatives, those in which at least one of the four hydrogen atoms of the urea molecule is substituted with a benzyl, phenyl or cyclohexyl group are preferable, and any one of benzyl urea, cyclohexyl urea and phenyl urea is more preferable.

<Adhesive layer>

The polarizing plate may be equipped with an adhesive layer for bonding two layers together. For example, it may be provided with an adhesive layer formed in contact with the polarizing element in order to bond another layer to the polarizing element, and specifically, it is preferable to provide an adhesive layer in contact with the polarizing element in order to bond the transparent protective layer to the polarizing element. also good As an adhesive constituting such an adhesive layer, it is preferable to use an adhesive containing a urea compound. As the adhesive, a water-based adhesive, a solvent-based adhesive, an active energy ray curable adhesive, or the like can be used, but it is preferably a water-based adhesive, and preferably contains a PVA-based resin.

The thickness at the time of application of the adhesive may be set to an arbitrary value, and may be set so as to obtain an adhesive layer having a desired thickness after curing or heating (drying), for example. The thickness of the adhesive layer composed of 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, still more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or less. It is 1 micrometer or more and 1 micrometer or less.

The adhesive layer may contain a urea compound. By providing an adhesive layer containing a urea-based compound, and furthermore, when the adhesive layer in contact with the polarizing element contains a urea-based compound, the transmittance becomes less likely to decrease even when the polarizing plate is exposed to a high-temperature environment. This is presumed to be because, according to such an adhesive layer, the urea compound in the adhesive layer is easily migrated to the polarizing element, and polyenization of the polarizing element is easily suppressed. As for specific examples of the urea-based compound contained in the adhesive layer, the examples of the urea-based compound contained in the pressure-sensitive adhesive layer described above can be applied as they are.

When the adhesive is a water-based adhesive containing a PVA-based resin, the content of the urea-based compound is preferably 1 part by mass or more and 400 parts by mass or less, more preferably 2 parts by mass or more, based on 100 parts by mass of the PVA-based resin. It is 200 parts by mass or less, more preferably 3 parts by mass or more and 100 parts by mass or less. By setting it as 1 mass part or more, the inhibitory effect of the polyenization of the polarizing element in high temperature environment can fully be acquired. On the other hand, when it exceeds 400 parts by mass, urea compounds precipitate, which may cause problems such as an increase in haze.

In the configuration in which a transparent protective film is bonded to both sides of the polarizing element via an adhesive layer, it is preferable that, among the adhesive layers on both sides of the polarizing element, the adhesive layer on at least one side is an adhesive layer containing a urea compound, and the adhesive on both sides It is more preferable that all of the layers are layers containing a urea-based compound.

In order to meet the request for thinning polarizing plates, polarizing plates having a transparent protective layer on only one side of a polarizing element have been developed. In this configuration, a transparent protective film can be laminated via the adhesive layer. As a method for producing a polarizing plate having a transparent protective film on only one side of such a polarizing element, a method in which a transparent protective film is first bonded to both surfaces through an adhesive layer to prepare a polarizing plate, and then the transparent protective film on one side is peeled off can be considered. .

(water-based adhesive)

As the water-based adhesive, any suitable water-based adhesive may be employed, but a water-based adhesive containing a PVA-based resin (PVA-based adhesive) is preferably used. 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, in terms of adhesiveness. 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, from the viewpoint of adhesiveness.

As the PVA-based resin contained in the water-based adhesive, those containing an acetoacetyl group are preferable, because the adhesion between the PVA-based resin layer and the protective film is excellent and durability is excellent. The acetoacetyl group-containing PVA-based resin is obtained by, for example, reacting a PVA-based resin with diketene by an arbitrary method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA-based resin is typically 0.1 mol% or more, and 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, and more preferably 0.5% by mass or more and 10% by mass or less.

A water-based adhesive may contain a crosslinking agent. As the crosslinking agent, a known crosslinking agent can be used. Examples of the crosslinking agent include water-soluble epoxy compounds, dialdehydes, and isocyanates.

When the PVA-based resin is an acetoacetyl group-containing PVA-based resin, the crosslinking agent is preferably any one of glyoxal, glyoxylate, and methylolmelamine, and more preferably any one of glyoxal and glyoxylate, Glyoxal is particularly preferred.

Water-based adhesives may contain organic solvents. Since the organic solvent has miscibility with water, alcohols are preferable, and among alcohols, methanol or ethanol is more preferable. The methanol concentration of the water-based adhesive is preferably 10 mass% or more and 70 mass% or less, more preferably 15 mass% or more and 60 mass% or less, still more preferably 20 mass% or more and 60 mass% or less. When the methanol concentration is 10% by mass or more, polyenization of the PVA-based resin in a high-temperature environment is more easily suppressed. Moreover, deterioration of hue can be suppressed because methanol content rate is 70 mass % or less. Some of the urea derivatives have low solubility in water, while some have sufficient solubility in alcohol. In that case, it is one of the preferred embodiments to prepare an adhesive by dissolving the urea compound in alcohol to prepare an alcohol solution of the urea compound and then adding the alcohol solution of the urea compound to the PVA aqueous solution.

(active energy ray curing adhesive)

An active energy ray-curable adhesive is an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, and includes, for example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, a binder resin, and a photoreactive crosslinking agent. adhesives, etc. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals by irradiation with active energy rays such as ultraviolet rays.

Examples of the active energy ray curable adhesive include adhesives containing a compound (eg, monomer and/or oligomer) having a radical polymerizable group such as a (meth)acrylate group or a (meth)acrylamide group as a polymerizable compound. there is. Specific examples of active energy ray-curable adhesives and their curing methods are described in, for example, Japanese Patent Laid-Open No. 2012-144690.

[Method for producing polarizing plate]

The manufacturing method of the polarizing plate of this embodiment has a moisture content adjustment process and a lamination process. In the moisture content adjustment step, when producing a polarizing plate having the feature (a), polarization is performed such that the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. Adjust the moisture content of the element. The moisture content of the polarizing element can be adjusted according to the description of the moisture content of the polarizing element described above. In the moisture content adjustment step, when producing a polarizing plate having the feature (b), the moisture content of the polarizing plate is equal to or higher than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 30%, and less than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 50%. Adjust the moisture content. The moisture content of the polarizing plate can be adjusted according to the above description of the moisture content of the polarizing plate. In the lamination process, the polarizing element and the transparent protective layer are laminated via, for example, an adhesive layer, and a pressure-sensitive adhesive layer containing a urea-based compound is laminated on the surface of the transparent protective layer opposite to the polarizing element. The order of the moisture content adjusting step and the lamination step is not limited, and the moisture content adjusting step and the lamination step may be performed in parallel.

[Configuration of image display device]

The polarizing plate of this embodiment is used for various image display devices, such as a liquid crystal display device and an organic EL display device. Regarding the image display device, in the case of an interlayer filling configuration in which both sides of the polarizing plate are configured to contact layers other than the air layer, specifically, a solid layer such as an adhesive layer, the transmittance tends to decrease in a high-temperature environment. In the image display device using the polarizing plate of the present embodiment, a decrease in transmittance of the polarizing plate in a high-temperature environment can be suppressed even in an interlayer filling configuration. As an image display device, a structure having an image display cell, a first pressure sensitive adhesive layer laminated on the visual side surface of the image display cell, and a polarizing plate laminated on the visual side surface of the first pressure sensitive adhesive layer is exemplified. Such an image display device may further have a second pressure sensitive adhesive layer laminated on the visual side surface of the polarizing plate and a transparent member laminated on the surface of the second pressure sensitive adhesive layer. In particular, in the polarizing plate of the present embodiment, a transparent member is disposed on the viewing side of the image display device, the polarizing plate and the image display cell are bonded by the first adhesive layer, and the polarizing plate and the transparent member are bonded by the second adhesive layer. It is suitably used for an image display device having a charging configuration. It is preferable that at least one of the 1st adhesive layer and the 2nd adhesive layer is the above-mentioned adhesive layer containing a urea type compound.

<Image display cell>

As an image display cell, a liquid crystal cell and an organic electroluminescent cell are mentioned. As the liquid crystal cell, any of a reflection type liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, or a transflective liquid crystal cell using both external light and light from a light source may be used. good night. When the liquid crystal cell uses light from a light source, in the image display device (liquid crystal display device), a polarizing plate is disposed on the side opposite to the viewing side of the image display cell (liquid crystal cell), and a light source is further disposed. It is preferable that the polarizing plate and the liquid crystal cell on the light source side are bonded via an appropriate pressure-sensitive adhesive layer. As the driving method of the liquid crystal cell, any type such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type) can be used, for example.

As the organic EL cell, a light-emitting body (organic electroluminescent light-emitting body) formed by sequentially laminating a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate is preferably used. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer containing a triphenylamine derivative and the like and a light emitting layer containing a fluorescent organic solid such as anthracene, or a laminate of these light emitting layers and a perylene derivative. Various layer configurations can be employed, such as a laminate of electron injection layers or a laminate of a hole injection layer, a light emitting layer, and an electron injection layer.

<Bonding of image display cell and polarizer>

A pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) is suitably used for bonding the image display cell and the polarizing plate. Among them, a method of bonding the polarizing plate according to the present invention to the image display cell via the pressure-sensitive adhesive layer is preferable from the viewpoint of workability and the like.

<transparent member>

A transparent plate (window layer), a touch panel, etc. are mentioned as a transparent member arrange|positioned on the viewing side of an image display apparatus. As the transparent plate, a transparent plate having appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a transparent resin plate such as a polyimide-based resin, an acrylic resin, or a polycarbonate-based resin, or a glass plate, and the like are exemplified. A functional layer such as an antireflection layer may be laminated on the viewing side of the transparent plate. In addition, when the transparent board is a transparent resin board, a hard coat layer for increasing physical strength or a low moisture permeability layer for lowering the moisture permeability may be laminated. As a touch panel, various touch panels, such as a resistive film type, a capacitance type, an optical type, an ultrasonic type, etc., a glass plate with a touch sensor function, a transparent resin board, etc. are used. When a capacitance-type touch panel is used as the transparent member, it is preferable that a transparent plate made of glass or a transparent resin plate is provided on the viewing side more than the touch panel.

<Bonding of polarizing plate and transparent member>

For bonding between the polarizing plate and the transparent member, a pressure-sensitive adhesive layer or an active energy ray curable adhesive layer is suitably used. When an adhesive layer is used, it may be the adhesive layer provided with the polarizing plate mentioned above, or it may be a newly provided adhesive layer. Laying of the pressure-sensitive adhesive layer can be performed in an appropriate manner. As a specific laying method, the laying method of the adhesive layer used for bonding of the above-mentioned image display cell and polarizing plate is mentioned, for example.

In the case of using an active energy ray curable adhesive layer, for the purpose of preventing the diffusion of the adhesive solution before curing, a dam material is installed so as to surround the periphery on the image display panel, a transparent member is disposed on the dam material, and the adhesive solution is injected. This is suitably used. After injection of the adhesive solution, positioning and degassing are performed as necessary, and then active energy rays are irradiated to cure the adhesive.

Example

Hereinafter, the present invention will be specifically described based on examples. Materials, reagents, amounts of substances and their ratios, operations, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples.

<Production of Polarizing Element 1>

A PVA film with a thickness of 40 μm containing PVA having an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more was uniaxially stretched about 5 times in a dry manner, and then immersed in pure water at 60 ° C. for 1 minute while maintaining a tension state, It was immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.05/5/100 at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72°C for 300 seconds. Subsequently, after washing with pure water at 26°C for 20 seconds, drying was performed at 65°C to obtain a polarizing element 1 having a thickness of 15 µm in which iodine was adsorbed and oriented in PVA. For the measurement of the thickness of the polarizing element, a digital micrometer "MH-15M" manufactured by Nikon Corporation was used.

<Preparation of adhesives 1 and 2>

(Preparation of PVA solution for adhesive)

50 g of a modified PVA-based resin containing an acetoacetyl group (“Gosenex Z-410” manufactured by Mitsubishi Chemical Corporation) was dissolved in 950 g of pure water, heated at 90° C. for 2 hours, cooled to room temperature, and used for adhesives. A PVA solution was obtained.

(Preparation of adhesive 1)

A PVA solution for adhesive, urea, pure water, and methanol were blended to a PVA concentration of 3.0% by mass, a methanol concentration of 20% by mass, and a urea concentration of 1% by mass (33 parts by mass relative to 100 parts by mass of PVA) to obtain adhesive 1 for polarizing plates. got it

(Preparation of adhesive 2)

The PVA solution for adhesives, pure water, and methanol were mix|blended so that it might become 3.0 mass % of PVA concentrations, and 20 mass % of methanol concentrations, and the adhesive 2 for polarizing plates was obtained.

<Preparation of transparent protective film (transparent protective layer)>

A commercially available cellulose acylate film TD40 (manufactured by Fujifilm Co., Ltd., film thickness 40 μm) was immersed in a 1.5 mol/L NaOH aqueous solution (saponification liquid) maintained at 55° C. for 2 minutes, and then the film was washed with water. . Then, after being immersed in 0.05 mol/L sulfuric acid aqueous solution at 25° C. for 30 seconds, a water washing bath was further passed for 30 seconds under running water to neutralize the film. And after repeating the water removal with an air knife three times and removing water, it was made to stay in a 70 degreeC drying zone for 15 seconds, and dried, and the film which carried out the saponification process was produced and the transparent protective film for polarizing plates was obtained. The water vapor permeability of this transparent protective film at a temperature of 40°C and a relative humidity of 90% was 850 g/(m 2 ·day). The moisture permeability was measured at a temperature of 40°C and a relative humidity of 90% by the cup method specified in JIS Z 0208.

<Production of polarizers 1 and 2 (before application of adhesive layer)>

(Production of polarizer 1)

On both sides of the polarizing element 1, the transparent protective film was bonded via the adhesive 1 for polarizing plates using a roll bonding machine. After bonding, it was made to dry at 60 degreeC for 10 minutes, and the polarizing plate 1 before adhesive layer laying was obtained. Adhesive layer 1 formed with adhesive 1 was adjusted so that the thickness after drying was 50 nm on both sides.

(Production of polarizer 2)

A polarizing plate 2 before applying the pressure-sensitive adhesive layer was obtained in the same manner as in the production method of the polarizing plate 1 before applying the pressure-sensitive adhesive layer, except that the adhesive 1 was changed to the adhesive 2. Regarding the adhesive layer 2 formed with the adhesive 2, the thickness after drying was adjusted to be 50 nm on both sides.

<Preparation of pressure-sensitive adhesive layers 1 and 2>

(Preparation of pressure-sensitive adhesive layer 1)

0.1 part by mass of an isocyanate crosslinking agent, 0.2 part by mass of a silane coupling agent, and 0.34 part by mass of phenyl urea were blended with respect to 100 parts by mass of the solid content of the acrylic polymer solution (100 parts by weight of (meth)acrylic resin) to prepare an acrylic adhesive composition solution. The solution of the acrylic pressure-sensitive adhesive composition obtained above was applied to one side of a polyethylene terephthalate film (separator film) treated with a silicone-based release agent so that the thickness of the adhesive layer after drying was 25 μm, and dried at 90 ° C. for 3 minutes to obtain a separator film An adhesive layer 1 was formed on the surface of

(Preparation of pressure-sensitive adhesive layer 2)

0.1 part by mass of an isocyanate crosslinking agent and 0.2 part by mass of a silane coupling agent were blended with respect to 100 parts by mass of the solid content of the acrylic polymer solution (100 parts by weight of (meth)acrylic resin) to prepare a solution of an acrylic pressure-sensitive adhesive composition. The solution of the acrylic pressure-sensitive adhesive composition obtained above was applied to one side of a polyethylene terephthalate film (separator film) treated with a silicone-based release agent so that the thickness of the adhesive layer after drying was 25 μm, and dried at 90 ° C. for 3 minutes to obtain a separator film An adhesive layer 2 was formed on the surface of

<Manufacture of optical laminates 1 to 7 (polarizing plate after application of pressure-sensitive adhesive layer)>

(Manufacture of optical laminate 1)

Optical laminate 1 was produced by transferring pressure-sensitive adhesive layer 1 to one side of polarizing plate 1.

(Production of optical laminates 2 to 7)

As shown in Table 1, using the polarizing plate 1 or the polarizing plate 2, the adhesive layer 1 or the adhesive layer 2, it carried out similarly to the optical laminated body 1, and produced optical laminated bodies 2-7.

<Adjustment of Moisture Content of Optical Laminate (Polarizing Element)>

The optical laminates 1 to 7 obtained above were stored for 72 hours at a temperature of 20°C and a relative humidity of 30%, 35%, 40%, 45%, 50% or 55%. Moisture content was measured using the Karl Fischer method at 66 hours, 69 hours, and 72 hours of storage. In any humidity conditions, the value of moisture content did not change at 66 hours, 69 hours, and 72 hours of storage. Therefore, it can be considered that the moisture content of the optical laminates 1 to 7 is the same as the equilibrium moisture content of the 72-hour storage environment used in this experimental example. When the moisture content of the optical laminate (polarizing plate) reaches equilibrium in a certain storage environment, it can be considered that the moisture content of the polarizing element in the optical laminate (polarizing plate) has reached equilibrium in the storage environment as well. In addition, when the moisture content of the polarizing element in the optical layered body (polarizing plate) reaches equilibrium in a certain storage environment, it can be regarded that the moisture content of the optical layered body (polarizing plate) has reached equilibrium in the storage environment as well.

The optical laminates 1 to 7 were prepared by storing for 72 hours under conditions of 35%, 45%, 50% or 55% relative humidity at a temperature of 20 ° C so that the moisture content of the optical laminates 1 to 7 becomes the equilibrium moisture content of the environment shown in Table 1.

<High temperature durability evaluation>

(Production of samples for evaluation)

Regarding the optical laminates 1 to 7, an acrylic pressure-sensitive adhesive layer (manufactured by Lintec Co., Ltd., product number: #7) is formed on the surface opposite to the surface on which the pressure-sensitive adhesive layer is formed, and the absorption axis is parallel to the long side. It was cut into a size of 50 mm × 100 mm. An evaluation sample was produced by bonding alkali-free glass ("EAGLE XG" by Corning Corporation) to the surface of the pressure-sensitive adhesive on both sides.

(Evaluation of single transmittance (105 ° C))

The evaluation samples of the optical laminates 1 to 7 were subjected to an autoclave treatment at a temperature of 50 ° C. and a pressure of 5 kgf / cm 2 (490.3 kPa) for 1 hour, and then left for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 55%. Thereafter, the transmittance of the evaluation samples of optical laminates 1 to 7 was measured (initial value), stored in a heating environment at a temperature of 105°C, and transmittance was measured at 50-hour intervals from 200 to 500 hours. Based on the time at which the decrease in transmittance reached 5% or more with respect to the initial value, evaluation was performed according to the following criteria. The obtained results are shown in Table 1.

A decrease in transmittance of 5% or less after 400 hours : A

A decrease in transmittance of 5% or more in 300 to 400 hours :B

A decrease in transmittance of 5% or more in 200 to 300 hours :C

A decrease in transmittance of 5% or more after 200 hours :D

A polarizing plate having a water content equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and less than or equal to an equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, and a transparent protective film, further comprising an adhesive layer containing a urea-based compound. It was found that the transmittance of (Optical laminates 1 to 4) was less likely to decrease even when exposed to a high-temperature environment of 105°C.

Claims (13)

A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, a transparent protective layer, and an adhesive layer in this order,
The pressure-sensitive adhesive layer contains at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives,
The moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 30%, and is equal to or less than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 50%. A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, a transparent protective layer, and an adhesive layer in this order,
The pressure-sensitive adhesive layer contains at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives,
The moisture content of the polarizing plate is equal to or greater than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 30%, and less than the equilibrium moisture content at a temperature of 20 ° C. and a relative humidity of 50%. The polarizing plate according to claim 1 or 2, wherein the transparent protective layer has a moisture permeability of 100 g/(m 2 ·day) or more at a temperature of 40°C and a relative humidity of 90%. The polarizing plate according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer contains at least one urea-based compound selected from the group consisting of urea derivatives and thiourea derivatives. The method according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer contains a (meth)acrylic resin,
The polarizing plate in which the content of the urea compound in the pressure-sensitive adhesive layer is 0.01 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic resin. The method according to any one of claims 1 to 5, wherein at least one side of the polarizing element contains at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives. A polarizing plate in which an adhesive layer is formed in contact with each other. The polarizing plate according to claim 6, wherein the adhesive layer further contains a polyvinyl alcohol-based resin. The polarizing plate according to claim 7, wherein the content of the urea compound in the adhesive layer is 1 part by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate according to any one of claims 6 to 8, wherein the adhesive layer contains at least one urea-based compound selected from the group consisting of urea derivatives and thiourea derivatives. The polarizing plate according to any one of claims 1 to 9 used in an image display device having an interlayer filling structure. An image display device comprising an image display cell, the polarizing plate according to any one of claims 1 to 10 laminated on the viewer side of the image display cell, and a transparent member laminated on the viewer side surface of the polarizing plate. The image display device according to claim 11, wherein the transparent member is a glass plate or a transparent resin plate. The image display device according to claim 11, wherein the transparent member is a touch panel.