JP2021165826A - Polarizer and image display unit using the polarizer - Google Patents

Abstract

To provide a polarizer that is suppressed from decreasing in transmissivity even when used for an image display device having an inter-layer filling constitution, or even when exposed to a high-temperature environment of, for example, 105°C in temperature.SOLUTION: A polarizer has a polarizing element formed by adsorbing and aligning dichroic dye in a polyvinyl alcohol-based resin layer, and a transparent protective film, wherein a polyvinyl alcohol-based resin used to form the polyvinyl alcohol-based resin layer has a boron adsorption factor of 5.70 mass% or larger, and the polarizing element has a moisture content equal to or larger than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and equal to or less than an equilibrium moisture content at 20°C and 50% RH.SELECTED DRAWING: None

Description

The present invention relates to a polarizing plate. Further, the present invention relates to an image display device in which one surface of the polarizing plate is attached to an image display cell and the other surface is attached to a transparent member such as a touch panel or a front plate.

Liquid crystal displays (LCDs) are widely used not only in liquid crystal televisions but also in mobile devices such as personal computers and mobile phones, and in-vehicle applications such as car navigation systems. Usually, a liquid crystal display device has a liquid crystal panel member in which polarizing plates are attached to both sides of a liquid crystal cell with an adhesive, and display is performed by controlling the light from the backlight member by the liquid crystal panel member. Further, in recent years, organic EL display devices, like liquid crystal display devices, have been widely used in mobile applications such as televisions and mobile phones, and in-vehicle 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 visually recognized as a mirror surface, a circular polarizing plate (polarizing element and a λ / 4 plate) is provided on the visible side surface of the image display panel. (Laminated body containing) may be arranged.

As described above, polarizing plates are increasingly mounted on automobiles as members of liquid crystal display devices and organic EL display devices. Polarizing plates used in in-vehicle image display devices are often exposed to high-temperature environments and have less characteristic changes at higher temperatures than other mobile applications such as televisions and mobile phones. 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, a front plate such as a transparent resin plate or a glass plate (also referred to as a "window layer" or the like) is further visible side than the polarizing plate of the image display panel. The number of configurations that provide ()) is increasing. Further, in a display device provided with a touch panel, a configuration in which a touch panel is provided on the viewing side of the image display panel on the viewing side and a front transparent plate is provided on the viewing side of the image display panel is widely adopted.

In such a configuration, if an air layer exists between the image display panel and a transparent member such as a front transparent plate or a touch panel, external light is reflected due to light reflection at the interface of the air layer, and the visibility of the screen is increased. Tends to decrease. Therefore, the space between the polarizing plate and the transparent member arranged on the visible surface of the image display panel is a layer other than the air layer and is usually referred to as a solid layer (hereinafter, referred to as "interlayer filler"). ) (Hereinafter, sometimes referred to as an "interlayer filling configuration"), preferably a configuration in which a material having a refractive index close to that of these materials is adopted is widely used. As the interlayer filler, an adhesive or a UV curable adhesive is used for the purpose of suppressing deterioration of visibility due to reflection at the interface and adhesively fixing the members to each other (see, for example, Patent Document 1).

The above-mentioned interlayer filling configuration is widely adopted in mobile applications such as mobile phones, which are often used outdoors. In addition, due to the increasing demand for visibility in recent years, even in in-vehicle applications such as car navigation devices, a front transparent plate is arranged on the surface of an image display panel, and the space between the panel and the front transparent plate is filled with an adhesive layer or the like. Adoption of an interlayer filling configuration is being considered.

However, when such a configuration is adopted, when the polarizing plate is left in an environment of 95 ° C. for 200 hours, for example, a significant decrease in the transmittance is observed in the central portion of the polarizing plate surface, while the polarizing plate alone is used. It has been reported that no significant decrease in transmittance is observed even when left in an environment at a temperature of 95 ° C. for 1000 hours. From these results, it has been reported that a significant decrease in the transmittance of a polarizing plate in a high temperature environment is caused by a polarizing plate. When an image display device that employs an interlayer filling configuration in which one surface is bonded to an image display cell and the other surface is bonded to a transparent member such as a touch panel or a front transparent plate is exposed to a high temperature environment. It has also been reported that this is a peculiar problem (Patent Document 2).

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 saturated water absorption amount of the transparent protective film adjacent to the polarizing element is set to a predetermined amount or less to increase the transmittance. We are proposing a method to suppress the decrease.

Japanese Unexamined Patent Publication No. 11-174417 Japanese Unexamined Patent Publication No. 2014-102353

However, with conventional polarizing plates, the temperature in a high temperature environment is raised to 105 ° C., and when exposed to this high temperature environment for a certain period of time, the effect of suppressing a decrease in transmittance may not be sufficient. The present invention provides a polarizing plate having an excellent effect of suppressing a decrease in transmittance even when used in an image display device having an interlayer filling structure, for example, even when exposed to a high temperature environment of 105 ° C., and the polarized light. An object of the present invention is to provide an image display device using a board.

The present invention provides the following polarizing plate, an image display device, and a method for manufacturing the polarizing plate.
[1] A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, and a transparent protective film.
The polyvinyl alcohol-based resin used for forming the polyvinyl alcohol-based resin layer has a boron adsorption rate of 5.70% by mass or more.
A polarizing plate having a water content of the polarizing element of 20 ° C. and 30% relative humidity or more and 20 ° C. and 50% relative humidity or less.
[2] A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, and a transparent protective film.
The polyvinyl alcohol-based resin used for forming the polyvinyl alcohol-based resin layer has a boron adsorption rate of 5.70% by mass or more.
A polarizing plate having a water content of the polarizing plate at a temperature of 20 ° C. and a relative humidity of 30% or more and at a temperature of 20 ° C. and a relative humidity of 50% or less.
[3] The polarizing plate according to [1] or [2], wherein the polarizing element has a boron content of 4.0% by mass or more and 8.0% by mass or less.
[4] Further having an adhesive layer for adhering the polarizing element and the transparent protective film,
The polarizing plate according to any one of [1] to [3], wherein the adhesive layer is a coating layer of a water-based adhesive.
[5] The polarizing plate according to [4], wherein the aqueous adhesive has a methanol concentration of 10% by mass or more and 70% by mass or less.
[6] The polarizing plate according to [4] or [5], wherein the water-based adhesive contains a polyvinyl alcohol-based resin.
[7] The polarizing plate according to any one of [4] to [6], wherein the adhesive layer has a thickness of 0.01 μm or more and 7 μm or less.
[8] The transparent protective film is a retardation film including a first optical compensation layer and a second optical compensation layer in order from the polarizing element side.
The absorption axis of the polarizing element and the slow axis of the first optical compensation layer are substantially orthogonal to each other.
The slow axis of the first optical compensation layer and the slow axis of the second optical compensation layer are substantially parallel to each other.
The polarizing plate according to any one of [1] to [7], wherein the first optical compensation layer and the second optical compensation layer satisfy the following formulas (1) to (4).
80nm ≤ Re ₁ (590) ≤ 120nm (1)
20 nm <Re ₁ (590) ≤ 60 nm (2)
1 <Nz ₁ <2 (3)
-4 <Nz ₂ <-1 (4)
[9] The polarizing plate is used in an image display device, and is used in an image display device.
The polarizing plate according to any one of [1] to [8], wherein a solid layer is provided in contact with both surfaces of the polarizing plate in the image display device.
[10] Any of [1] to [9] laminated on the image display cell, the first pressure-sensitive adhesive layer laminated on the visible side surface of the image display cell, and the visible side surface of the first pressure-sensitive adhesive layer. An image display device comprising the polarizing plate according to item 1.
[11] The image display according to [10], further comprising a second pressure-sensitive adhesive layer laminated on the visible side surface of the polarizing plate and a transparent member laminated on the visible side surface of the second pressure-sensitive adhesive layer. Device.
[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.
[14] The method for manufacturing a polarizing plate according to [1].
A method for manufacturing a polarizing plate having a polarizing element and a transparent protective film.
A water content adjusting step for adjusting the water content of the polarizing element so that the water content is equal to or higher than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 30% and equal to or lower than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 50%.
A laminating step of laminating the polarizing element and the transparent protective film,
A method for producing a polarizing plate.
[15] The method for manufacturing a polarizing plate according to [2].
A method for manufacturing a polarizing plate having a polarizing element and a transparent protective film.
A water content adjusting step for adjusting the water content of the polarizing plate so that the water content is equal to or higher than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 30% and equal to or lower than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 50%.
A laminating step of laminating the polarizing element and the transparent protective film,
A method for producing a polarizing plate.

INDUSTRIAL APPLICABILITY According to the present invention, even when used in an image display device having an interlayer filling configuration, a decrease in transmittance when exposed to a high temperature environment of, for example, 105 ° C. is suppressed, and a polarizing plate having excellent high temperature durability is provided. Further, by using the polarizing plate of the present invention, it is possible to provide an image display device in which a decrease in transmittance is suppressed in a high temperature environment.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[Polarizer]
The polarizing plate according to the embodiment of the present invention includes a polarizing element formed by adsorbing and orienting a dichroic dye on a layer containing a polyvinyl alcohol-based resin, and a transparent protective film. The polarizing element is formed by using a polyvinyl alcohol-based resin having a boron adsorption rate of 5.70% by mass or more. The polarizing plate according to the present embodiment has at least one of the following features (a) and (b).
(A) The water content of the polarizing element is equal to or greater than the equilibrium moisture content of a temperature of 20 ° C. and a relative humidity of 30%, and equal to or less than the equilibrium moisture content of a temperature of 20 ° C. and a relative humidity of 50%.
(B) The water content of the polarizing plate is equal to or higher than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 30%, and equal to or lower than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 50%.

The polarizing plate of the present embodiment has at least one of the above-mentioned characteristics (a) and (b), and the boron adsorption rate of the polyvinyl alcohol-based resin used for the polarizing element is within the above range. As a component of the image display device having a filling configuration, it is possible to suppress a decrease in transmittance even when exposed to a high temperature environment for a long time.

<Polarizing element>
As a polarizing element formed by adsorbing and orienting a dichroic dye on a layer (hereinafter, also referred to as "PVA-based resin layer" in the present specification) containing a polyvinyl alcohol (hereinafter, also referred to as "PVA")-based resin of the present invention. Can use a well-known polarizing element. As such a polarizing element, a PVA-based resin film is used, and the PVA-based resin film is dyed with a bicolor dye and uniaxially stretched to form a coating liquid, or a coating liquid containing a PVA-based resin is used as a base material. Examples thereof include those formed by dyeing a PVA-based resin layer, which is a coating layer of this laminated film, with a bicolor dye using a laminated film obtained by coating on a film, and uniaxially stretching the laminated film. ..

The polarizing element is formed from a PVA-based resin obtained by saponifying a polyvinyl acetate-based resin.
Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

In the present invention, a PVA-based resin layer is formed from a PVA-based resin having a boron adsorption rate of 5.70% by mass or more. That is, the boron adsorption rate of the PVA-based resin at the stage of the raw material before dyeing or stretching is 5.70% by mass or more. By using such a PVA-based resin, the transmittance is less likely to decrease even when exposed to a high temperature environment of, for example, 105 ° C. A polarizing element is produced using a PVA-based resin having a boron adsorption rate of more preferably 5.72% by mass or more, further preferably 5.75% by mass, and most preferably 5.80% by mass or more. do. Further, the boron adsorption rate of the PVA-based resin is preferably 10% by mass or less. By manufacturing a polarizing element using such a PVA-based resin, it is possible to shorten the treatment time by boric acid treatment without increasing the boric acid concentration in the boric acid treatment tank, which is desired. The polarizing element of the above can be easily obtained, and the productivity of the polarizing element can be increased. When the boron adsorption rate of the PVA-based resin is 10% by mass or less, an appropriate amount of boron is taken into the PVA-based resin layer, and the shrinkage force of the polarizing element can be easily reduced. As a result, when incorporated into the image display device, problems such as peeling between the polarizing plate and other members such as the front plate are less likely to occur. Further, when the boron adsorption rate of the PVA-based resin is less than 5.70%, the transmittance tends to decrease even when exposed to a high temperature environment of, for example, 105 ° C., and the productivity is further as described above. May decrease. The boron adsorption rate of the PVA-based resin can be measured by the method described in Examples described later.

The boron adsorption rate of the PVA-based resin is a characteristic that reflects the spacing between the molecular chains and the crystal structure in the PVA-based resin. The PVA-based resin having a boron adsorption rate of 5.70% by mass or more has a wider interval between molecular chains than the PVA-based resin having a boron adsorption rate of less than 5.70% by mass, and the crystals of the PVA-based resin are formed. It is considered that there are few. Therefore, it is presumed that boron easily enters the PVA-based resin layer, and polyene formation is easily prevented in a high-temperature environment.

For the boron adsorption rate of the PVA-based resin, for example, the PVA-based resin is subjected to pretreatment such as hot water treatment, acidic solution treatment, ultrasonic irradiation treatment, and irradiation treatment before manufacturing the polarizing element. Can be adjusted by. By these treatments, the distance between the molecular chains in the PVA-based resin can be widened and the crystal structure can be destroyed. Examples of the hot water treatment include a treatment in which the product is immersed in pure water at 30 ° C. to 100 ° C. for 1 second to 90 seconds and dried.
Examples of the acidic solution treatment include a treatment in which the boric acid aqueous solution having a concentration of 10% to 20% is immersed for 1 to 90 seconds and dried. Examples of the ultrasonic treatment include a treatment in which ultrasonic waves having a frequency of 20 to 29 kc are irradiated with an output of 200 W to 500 W for 30 seconds to 10 minutes. Sonication can be performed in a solvent such as water.

The degree of saponification of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and further preferably about 99 mol% to 100 mol%. The degree of polymerization of the PVA-based resin is 1000 to 10000, preferably 1500 to 5000. This PVA-based resin may be modified, and may be, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes.

The thickness of the polarizing element of the present embodiment is preferably 5 to 50 μm, more preferably 8 to 28 μm, further preferably 12 to 22 μm, and most preferably 12 to 15 μm. When the thickness of the polarizing element is 50 μm or less, it is possible to suppress the influence of polyene formation of the PVA-based resin on the deterioration of optical characteristics in a high temperature environment, and it is desirable that the thickness of the polarizing element is 5 μm or more. It becomes easy to make a configuration that achieves the optical characteristics of.

The polarizing element has a boron content of preferably 4.0% by mass or more and 8.0% by mass or less, more preferably 4.2% by mass or more and 7.0% by mass or less, still more preferably 4.4% by mass or more. It is 6.0% by mass or less. When the boron content of the polarizing element exceeds 8.0% by mass, the contraction force of the polarizing element becomes large, and the polarizing element is separated from other members such as the front plate to be bonded when it is incorporated into an image display device. May occur. Further, when the boron content is less than 2.4% by mass, the desired optical characteristics may not be achieved. The content of boron in the polarizing element can be calculated as a mass fraction (mass%) of boron with respect to the mass of the polarizing element, for example, by high frequency inductively coupled plasma (ICP) emission spectroscopic analysis. Boron is considered to be present in the polarizing element in a state where boric acid or it forms a crosslinked structure with a component of a polyvinyl alcohol-based resin, and the content of boron referred to here is as a boron atom (B). The value.

By setting the boron content of the polarizing element to 4.0% by mass or more and 8.0% by mass or less, the transmittance is reduced even when exposed to a high temperature environment as a component of an image display device having an interlayer filling structure. It is suppressed. This is because when the boron content of the polarizing element is 4.0% by mass or more and 8.0% by mass or less, polyene formation is less likely to occur even in a high temperature environment, and a decrease in transmittance is suppressed. It is presumed to be.

The potassium content in the polarizing element is preferably 0.28% by mass or more, more preferably 0.32% by mass or more, from the viewpoint of suppressing deterioration of the optical characteristics of the polarizing element in a high temperature environment. , 0.34% by mass or more, and from the viewpoint of suppressing the hue change in a high temperature environment, it is preferably 0.60% by mass or less, and preferably 0.55% by mass or less. More preferably, it is 0.50% by mass or less.

Although the detailed mechanism is unknown, the hydroxyl group of polyvinyl alcohol in the polarizing element is protected (stabilized) by boric acid cross-linking because the content of boron is higher and the content of potassium is lower than that of the conventional polarizing element. It is presumed that polyene formation can be suppressed because iodine ions, which are counterions in the polarizing element, are stabilized by an appropriate amount of potassium content.

The luminous efficiency correction simple substance transmittance of the polarizing element is preferably 38.8% to 44.8%, more preferably 40.4% to 43.2%, and further preferably 40.7% to 43.0%. Is.
If the transmittance of the luminosity factor correction unit exceeds 44.8%, the optical characteristics may deteriorate significantly, such as turning red in a high temperature environment. If the transmittance of the luminosity factor correction unit is less than 38.8%, the optical characteristics may deteriorate in a high temperature environment. Polyene formation is likely to proceed, and the deterioration of optical characteristics may be large.

The luminosity factor correction single transmittance can be obtained by measuring the Y value after luminosity factor correction with a two-degree visual field (C light source) defined in JIS Z8701-1982.
The luminous efficiency correction single transmittance can be easily measured with, for example, a spectrophotometer (model number: V7100) manufactured by JASCO Corporation.

The manufacturing method of the polarizing element is not particularly limited, but a method of feeding a polyvinyl alcohol-based resin film wound in a roll shape in advance and performing stretching, dyeing, cross-linking, etc. (hereinafter referred to as “manufacturing method 1”). A method including a step of applying a coating liquid containing a polyvinyl alcohol-based resin or a polyvinyl alcohol-based resin on a base film to form a polyvinyl alcohol-based resin layer as a coating layer, and stretching the obtained laminate (hereinafter, “Manufacturing method 2”). ”) Is typical.

The production method 1 includes a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, and a dichroic dye. It can be produced through a step of treating the adsorbed polyvinyl alcohol-based resin film with an aqueous boric acid solution and a step of washing with water after the treatment with the aqueous boric acid solution.

The content of boron and potassium contained in the polarizing element is determined by the boric acid, borate, and borax contained in any of the treatment baths in the swelling step, dyeing step, cross-linking step, stretching step, and washing step. It can be controlled by the concentration of the boron component donor such as a boron compound such as, the concentration of the potassium component donor such as potassium halide such as potassium iodide, the treatment temperature and the treatment time in each of the above treatment baths. In particular, in the crosslinking step and the stretching step, the boron content can be easily adjusted to a desired range depending on the treatment conditions such as the concentration of the boron component donor substance. In the washing step, the components such as boron and potassium are made of polyvinyl alcohol in consideration of the treatment conditions such as the amount of the boron component donor and the potassium component donor used in the dyeing step, the cross-linking step, the stretching step, and the like. From the viewpoint of being able to be eluted from the based resin film or adsorbed on the polyvinyl alcohol based resin film, it is easy to adjust the boron content and the potassium content within desired ranges.

The swelling step is a treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath, and can remove stains and blocking agents on the surface of the polyvinyl alcohol-based resin film, and also swells the polyvinyl alcohol-based resin film. Can suppress uneven dyeing. As the swelling bath, a medium containing water as a main component, such as water, distilled water, and pure water, is usually used. A surfactant, alcohol, or the like may be appropriately added to the swelling bath according to a conventional method. Further, from the viewpoint of controlling the potassium content of the polarizing element, potassium iodide may be used in the swelling bath, and in this case, the concentration of potassium iodide in the swelling bath is 1.5% by weight or less. It is more preferable, it is more preferably 1.0% by weight or less, and further preferably 0.5% by weight or less.

The temperature of the swelling bath is preferably about 10 to 60 ° C, more preferably about 15 to 45 ° C, and even more preferably about 18 to 30 ° C. The immersion time in the swelling bath cannot be unconditionally determined because the degree of swelling of the polyvinyl alcohol-based resin film is affected by the temperature of the swelling bath, but is preferably about 5 to 300 seconds, preferably 10 to 200 seconds. It is more preferably about 20 to 100 seconds. The swelling step may be performed only once or multiple times as needed.

The dyeing step is a treatment step of immersing the polyvinyl alcohol-based resin film in a dyeing bath (iodine solution), and adsorbs and orients a dichroic substance such as iodine or a dichroic dye on the polyvinyl alcohol-based resin film. Can be done. The iodine solution is usually preferably an aqueous iodine solution and contains iodine and iodide as a solubilizing agent. The iodide includes potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. And so on. Among these, potassium iodide is preferable from the viewpoint of controlling the content of potassium in the polarizing element.

In the dyeing bath, the iodine concentration is preferably about 0.01 to 1% by weight, more preferably about 0.02 to 0.5% by weight. In the dyeing bath, the concentration of iodide is preferably about 0.01 to 10% by weight, more preferably about 0.05 to 5% by weight, and more preferably about 0.1 to 3% by weight. Is even more preferable.

The temperature of the dyeing bath is preferably about 10 to 50 ° C., more preferably about 15 to 45 ° C., and even more preferably about 18 to 30 ° C. The immersion time in the dyeing bath cannot be unconditionally determined because the degree of dyeing of the polyvinyl alcohol-based resin film is affected by the temperature of the dyeing bath, but is preferably about 10 to 300 seconds, preferably about 20 to 240 seconds. More preferably. The dyeing step may be performed only once or multiple times as needed.

The cross-linking step is a treatment step of immersing the polyvinyl alcohol-based resin film dyed in the dyeing step in a treatment bath (cross-linking bath) containing a boron compound, and the polyvinyl alcohol-based resin film is cross-linked by the boron compound. Iodine molecules or dye molecules can be adsorbed on the crosslinked structure. Examples of the boron compound include boric acid, borate, borax and the like. The cross-linking bath is generally an aqueous solution, but may be, for example, a mixed solution of an organic solvent and water that is miscible with water. Further, the crosslinked bath preferably contains potassium iodide from the viewpoint of controlling the content of potassium in the polarizing element.

In the cross-linking bath, the concentration of the boron compound is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and even more preferably about 2 to 5% by weight. When potassium iodide is used in the cross-linking bath, the concentration of potassium iodide in the cross-linking bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight. , 2 to 5% by weight, more preferably.

The temperature of the cross-linking bath is preferably about 20 to 70 ° C, more preferably about 30 to 60 ° C. The immersion time in the cross-linking bath cannot be unconditionally determined because the degree of cross-linking of the polyvinyl alcohol-based resin film is affected by the temperature of the cross-linking bath, but is preferably about 5 to 300 seconds, preferably 10 to 200 seconds. More preferably. The cross-linking step may be carried out only once, or may be carried out a plurality of times as needed.

The stretching step is a treatment step of stretching the polyvinyl alcohol-based resin film to a predetermined magnification in at least one direction. Generally, the polyvinyl alcohol-based resin film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either the wet stretching method or the dry stretching method can be adopted. The stretching step may be carried out only once, or may be carried out 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 a mixed solution of water and an organic solvent miscible with water can be usually used. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the content of potassium in the polarizing element. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight, and 3 to 3 to 1% by weight. More preferably, it is about 6% by weight. Further, the treatment bath (stretching bath) can contain a boron compound from the viewpoint of suppressing film breakage during stretching. In this case, the concentration of the boron compound in the stretching bath is about 1 to 15% by weight. It is preferably about 1.5 to 10% by weight, more preferably about 2 to 5% by weight.

The temperature of the stretching bath is preferably about 25 to 80 ° C, more preferably about 40 to 75 ° C, and even more preferably about 50 to 70 ° C. The immersion time in the stretching bath cannot be unconditionally determined because the degree of stretching of the polyvinyl alcohol-based resin film is affected by the temperature of the stretching bath, but is preferably about 10 to 800 seconds, preferably about 30 to 500 seconds. More preferably. The stretching treatment in the wet stretching method may be performed together with any one or more of the swelling step, the dyeing step, the cross-linking step, and the washing step.

Examples of the dry stretching method include an inter-roll stretching method, a heating roll stretching method, and a compression stretching method. The dry stretching method may be performed together with the drying step.

The total draw ratio (cumulative draw ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set according to the purpose, but is preferably about 2 to 7 times, and preferably about 3 to 6.8 times. More preferably, it is more preferably about 3.5 to 6.5 times.

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

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

The drying step is a step of drying the polyvinyl alcohol-based resin film washed in the washing step to obtain a polarizing element. The drying is carried out by any suitable method, and examples thereof include natural drying, blast drying, and heat drying.

The production method 2 includes a step of applying the coating liquid containing the polyvinyl alcohol-based resin on the base film, a step of uniaxially stretching the obtained laminated film, and a two-color polyvinyl alcohol-based resin layer of the uniaxially stretched laminated film. A step of adsorbing the dichroic dye to form a polarizing element by dyeing with a sex dye, a step of treating a film on which the dichroic dye is adsorbed with an aqueous boric acid solution, and a step of treating with an aqueous boric acid solution and then washing with water. It can be manufactured through a process. The base film used for forming the polarizing element may be used as a protective layer for the polarizing element. If necessary, the base film may be peeled off from the polarizing element.

<Transparent protective film>
The transparent protective film used in the present embodiment (hereinafter, also simply referred to as “protective film”) is attached to at least one surface of the polarizing element via an adhesive layer. This transparent protective film is attached to one side or both sides of the polarizing element, but it is more preferable that the transparent protective film is attached to both sides.

The protective film may have other optical functions at the same time, or may be formed in a laminated structure in which a plurality of layers are laminated. The film thickness of the protective film is preferably thin from the viewpoint of optical characteristics, but if it is too thin, the strength is lowered and the workability is inferior. The appropriate film thickness is 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 70 μm.

As the protective film, a film such as a cellulose acylate resin film, a polycarbonate resin film, a cycloolefin resin film such as norbornene, a (meth) acrylic polymer film, or a polyester resin film such as polyethylene terephthalate is used. be able to. In the case of a configuration having protective films on both sides of the polarizing element, when bonding using a water-based adhesive such as PVA adhesive, the protective film on at least one side is a cellulose acylate film or (meth) acrylic in terms of moisture permeability. Any of the polymer films is preferable, and a cellulose acylate film is particularly preferable.

At least one protective film may have a retardation function for the purpose of compensating the viewing angle, and in that case, the film itself may have a retardation function and has a separate retardation layer. It may be a combination of both.
Although the configuration in which the film having the retardation function is directly bonded to the polarizing element via an adhesive has been described, the film is directly bonded to the polarizing element via an adhesive or an adhesive via another protective film bonded to the polarizing element. It may be a structure in which they are pasted together.

For example, the viewing angle compensating film used for optical compensation of a liquid crystal cell (hereinafter referred to as an IPS mode liquid crystal cell) including a liquid crystal layer containing liquid crystal molecules oriented in a homogeneous arrangement in the absence of an electric field includes the polarizing element side. It can be a retardation film composed of a first optical compensation layer and a second optical compensation layer in this order. At this time, the surface of the second optical compensation layer is attached to the liquid crystal cell using an adhesive or the like. The absorption axis of the polarizing element and the slow axis of the first optical compensation layer are substantially orthogonal to each other. The slow axis of the first optical compensation layer and the slow axis of the second optical compensation layer are substantially parallel to each other. The first optical compensation layer and the second optical compensation layer can satisfy the following formulas (1) to (4).
80nm ≤ Re ₁ (590) ≤ 120nm (1)
20nm <Re ₂ (590) ≤ 60nm (2)
1 <Nz ₁ <2 (3)
-4 <Nz ₂ <-1 (4)

Here, the refractive indexes of the first optical compensation layer and the second optical compensation layer in the slow axis direction in the plane are nx ₁ , nx ₂ , and the refractive indexes in the phase advance axis direction in the plane are ny ₁ . ny ₂ , the refractive index in the thickness direction is nz ₁ , nz _2, and Re ₁ (λ) = (nx ₁ −ny ₁ ) × d ₁ , Re ₂ (λ) = (nx _2- ny ₂ ) × d ₂ , Nz ₁ = (nx _1- nz ₁ ) / (nx _1- ny ₁ ), Nz ₂ = (nx _2- nz ₂ ) / (nx _2- ny ₂ ), and d ₁ and d ₂ are the first, respectively. The thickness of the optical compensation layer and the second optical compensation layer, and λ represents the measurement wavelength.

In addition, "substantially parallel" includes not only those that are completely parallel but also those that are substantially parallel, and the angle is generally within ± 2 °, preferably within ± 1 °, more preferably. Is within ± 0.5 °. Further, "substantially orthogonal" includes not only the case of being completely orthogonal but also the case of being substantially orthogonal, and the angle is generally in the range of 90 ± 2 °, preferably 90 ± 1 °, more preferably. Is in the range of 90 ± 0.5.

(First optical compensation layer)
As described above, the first optical compensation layer _{satisfies Nz 1} > 1. Such a retardation film may be referred to as a "negative biaxial plate", a "negative biaxial plate" or the like.

The first optical compensation layer preferably satisfies the following equations (1) and (3).
80nm ≤ Re ₁ (590) ≤ 120nm (1)
1 <Nz ₁ <2 (3)

_{The front retardation Re 1} (590) of the first optical compensation layer is more preferably 81 to 119 nm, further preferably 85 to 115 nm, and particularly preferably 90 to 110 nm.

The value of Nz ₁ is more preferably 1.15 to 1.6, further preferably 1.2 to 1.55, and particularly preferably 1.25 to 1.5.

Further, the first optical compensation layer preferably satisfies the following formula (5).
60 nm ≤ Rth ₁ (590) ≤ 100 nm (5)
Here, an _{Rth 1 (590) = Re 1} (590) × (Nz 1 -0.5), represents a retardation in the thickness direction.

_{The retardation Rth 1} (590) in the thickness direction of the first optical compensation layer is more preferably 61 to 99 nm, further preferably 65 to 95 nm, and particularly preferably 70 to 90 nm.

The material, manufacturing method, and the like of the first optical compensation layer are not particularly limited as long as they satisfy the above optical characteristics. The first optical compensation layer may be a retardation film alone or a laminate of two or more retardation films. Preferably, the first optical compensation layer is a single retardation film. This is because it is possible to reduce the deviation and unevenness of the retardation value due to the shrinkage stress of the polarizing element and the heat of the light source, and to make the liquid crystal panel thinner. When the first optical compensation layer is a laminated body, it may include an adhesive layer or an adhesive layer for adhering two or more retardation films. When the laminate contains two or more retardation films, these retardation films may be the same or different.

The optical characteristics of the retardation film used for the first optical compensation layer can be appropriately selected depending on the number of retardation films used. For example, when the first optical compensation layer is composed of the retardation film alone, the front retardation of the retardation film and the thickness direction retardation are respectively the front retardation Re _{1 of the first optical compensation layer.} It is preferable to make it equal to (590) or thickness direction retardation Rth _{1 (590).} Therefore, it is preferable that the retardation value of the pressure-sensitive adhesive layer, the adhesive layer, or the like used when laminating the first optical compensation layer on the polarizing element or the second optical compensation layer is as small as possible.

The total thickness of the first optical compensation layer is preferably 5 to 200 μm, more preferably 10 to 100 μm, and most preferably 15 to 50 μm. The first optical compensation layer has a thickness in such a range. Therefore, it is possible to improve the handleability at the time of manufacturing and to improve the optical uniformity such as the phase difference value.

The retardation film used for the first optical compensation layer is preferably one that is excellent in transparency, mechanical strength, thermal stability, moisture shielding property, etc., and is less likely to cause optical unevenness due to distortion. As the retardation film, a stretched film of a polymer film containing a thermoplastic resin as a main component is preferably used. As used herein, the term "stretched film" refers to a plastic film in which tension is applied to an unstretched film at an appropriate temperature, or tension is further applied to a pre-stretched film to increase the orientation of molecules in a specific direction. ..

The transmittance of the retardation film measured with light having a wavelength of 590 nm is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The theoretical upper limit of the light transmittance is 100%, but since surface reflection occurs between air and the film due to the difference in refractive index, the feasible upper limit of the light transmittance is about 94%. It is preferable that the first optical compensation layer as a whole has the same transmittance.

The absolute value of the photoelastic modulus of the retardation film ^{is preferably 1.0 × 10 -10} m ² / N or less, more preferably 5.0 × 10 ^-11 m ² / N or less. It is more preferably 3.0 × ^10-11 m ² / N or less, and ^{particularly preferably 1.0 × 10-11} m ² / N or less. By setting the value of the photoelastic coefficient in the above range, it is possible to obtain a liquid crystal display device having excellent optical uniformity, small change in optical characteristics even in an environment such as high temperature and high humidity, and excellent durability. can. The lower limit of the photoelastic coefficient is not particularly limited, but is generally 5.0 × 10 ^-13 m ² / N or more, and preferably 1.0 × 10 ^-12 m ² / N or more. If the photoelastic modulus is excessively small, the expression of the retardation tends to be small _{, so that it may be difficult to set the front retardation Re 1} (590) in the range of the above formula (1). .. The photoelastic coefficient is a value peculiar to the chemical structure of a polymer or the like, but the photoelastic coefficient can be suppressed to a low value by copolymerizing or mixing a plurality of components having different signs (positive or negative) of the photoelastic coefficient. can.

The thickness of the retardation film can be appropriately selected depending on the material used for the retardation film and the laminated structure of the optical compensation layer, but when the first optical compensation layer is composed of the retardation film alone, the thickness of the retardation film can be appropriately selected. It is 5 to 300 μm, more preferably 10 to 200 μm, and most preferably 15 to 100 μm. Within the above range, a retardation film having excellent mechanical strength and display uniformity can be obtained.

As a method for obtaining a polymer film containing the above thermoplastic resin as a main component, any appropriate molding processing method is used, for example, a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, or a blow molding method. , A powder molding method, an FRP molding method, a solve casting method and the like can be appropriately selected. Among these production methods, an extrusion molding method or a solvent casting method is preferably used. This is because it is possible to obtain a retardation film having high smoothness and good optical uniformity. More specifically, in the above extrusion molding method, a resin composition containing a thermoplastic resin, a plasticizer, an additive, etc. as a main component is heated and melted, and this is formed into a thin film on the surface of a casting roll by a T-die or the like. It is a method of producing a film by extruding it into a plasticizer and cooling it. Further, in the above-mentioned solve casting method, a concentrated solution (dope) in which a resin composition containing a thermoplastic resin, a plasticizer, an additive, etc. as a main component is dissolved in a solvent is defoamed, and a metal endless belt or a rotating drum is used. Or, it is a method of producing a film by uniformly spreading it on the surface of a plastic base material or the like in the form of a thin film and evaporating the solvent. The molding conditions can be appropriately selected depending on the composition and type of the resin to be used, the molding processing method, and the like.

The material for forming the thermoplastic resin is not particularly limited, but for the _{purpose of obtaining a negative birefringence plate satisfying the characteristics of Nz 1} > 1, it is preferable to use a polymer having positive birefringence.

Here, "having positive birefringence" means that when a polymer is oriented by stretching or the like, the refractive index in the orientation direction becomes relatively large, and many polymers correspond to this. Examples of the polymer having positive compound refraction include a cellulose fatty acid ester such as a polycarbonate resin, a polyvinyl alcohol resin, a triacetyl cellulose, a diacetyl cellulose, a tripropionyl cellulose, and a dipropionyl cellulose, or a cellulose resin such as a cellulose ether. , Polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate-based resins, polyimide-based resins, cyclic polyolefin-based (polynorbornene-based) resins, polysulfone-based resins, polyether sulfone-based resins, polyamide resins, polyethylene and polypropylene, etc. Examples thereof include polyolefin resins. These polymers may be used alone or in admixture of two or more. Further, these can also be modified and used by copolymerization, branching, cross-linking, molecular terminal modification (or sealing), stereoregular modification and the like.

The polymer film containing the thermoplastic resin as a main component may further contain any suitable additive, if necessary. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, cross-linking agents, and thickeners. And so on. The type and amount of the additive used can be appropriately set according to the purpose. The amount of the additive used is typically 10 parts by weight with respect to 100 parts by weight of the total solid content of the polymer film. If the amount of the additive used is excessively large, the transparency of the film may be impaired or the additive may seep out from the film surface.

Any suitable stretching method can be adopted as the method for forming the stretched film of the polymer film. Specific examples include a vertical and horizontal uniaxial stretching method, a horizontal uniaxial stretching method, a vertical and horizontal sequential biaxial stretching method, and a vertical and horizontal simultaneous biaxial stretching method. As the stretching means, any suitable stretching machine such as a roll stretching machine, a tenter stretching machine, a pantograph type or a linear motor type biaxial stretching machine can be used. When stretching while heating, the temperature may be changed continuously or stepwise. Further, the stretching step may be divided into two or more times. From the viewpoint of obtaining a biaxial retardation film, a horizontal uniaxial stretching method, a vertical and horizontal sequential biaxial stretching method, and a vertical and horizontal simultaneous biaxial stretching method can be preferably used.

In the case of a polymer having positive double refraction, the refractive index in the orientation direction becomes relatively large as described above. Therefore, in the case of the lateral uniaxial stretching method, the direction orthogonal to the transport direction of the film, that is, the width of the film. It has a slow axis in the direction (in other words, the refractive index in the width direction is nx1). In the case of the longitudinal-horizontal sequential biaxial stretching method and the longitudinal / horizontal simultaneous biaxial stretching method, either the transport direction or the width direction can be set as the slow axis depending on the ratio of the longitudinal / horizontal stretching ratios. That is, when the stretching ratio in the vertical (conveying) direction is relatively large, the vertical (conveying) direction becomes the slow-phase axis, and when the stretching ratio in the horizontal (width) direction is relatively large, the horizontal (width) direction is slow. It becomes the phase axis.

Whether it is preferable to stretch the film so that the slow axis is in the transport direction or the width direction depends on the configuration of the liquid crystal panel, but the slow axis of the first optical compensation layer and the second optical compensation From the viewpoint of making the slow phase axis of the layer parallel, it is preferable to adjust so that the slow phase axis directions of both are the same. That is, when the second optical compensation layer also has a slow-phase axis in the film transport direction, it is preferable that the first optical compensation layer also has a slow-phase axis in the film transport direction, and the second optical compensation layer has a film width. When the first optical compensation layer also has a slow-phase axis in the direction, it is preferable that the first optical compensation layer also has a slow-phase axis in the film width direction. By adjusting the direction of the slow-phase axis in this way, it is possible to obtain a laminated body in which the slow-phase axes are parallel by laminating the two in a roll-to-roll manner, which is excellent in productivity.

The temperature in the stretching oven (also referred to as stretching temperature) when stretching the polymer film is preferably around the glass transition temperature (Tg) of the polymer film. Specifically, it is preferably Tg-10 ° C to Tg + 30 ° C, more preferably Tg to Tg + 25 ° C, and even more preferably Tg + 5 to Tg + 20 ° C. If the stretching temperature is too low, the retardation value and the direction of the slow phase axis tend to be non-uniform in the width direction, and the film tends to crystallize (white turbidity). Further, if the stretching temperature is excessively high, the film tends to melt or the phase difference tends to be insufficiently developed. The stretching temperature is typically in the range of 110-200 ° C. The glass transition temperature can be determined by the DSC method according to JIS K7121-1987.

The specific method for controlling the temperature in the stretching oven is not particularly limited, and is an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, and heating for temperature control. It can be appropriately selected from heating methods and temperature control methods such as a roll, a heat pipe roll, or a metal belt.

The draw ratio when stretching the polymer film is determined by the composition of the polymer film, the type of volatile components, the residual amount of the volatile components, the retardation value to be designed, etc., and is particularly limited. However, for example, 1.05 to 5.00 times is preferably used. The feed rate during stretching is not particularly limited, but is preferably 0.5 to 20 m / min from the viewpoint of mechanical accuracy, stability, etc. of the stretching device.

As the retardation film used for the first optical compensation layer, a commercially available optical film can be used as it is in addition to the above. Further, a commercially available optical film may be used after being subjected to secondary processing such as stretching treatment and / or relaxation treatment.

(Second optical compensation layer)
The second optical compensation layer _{satisfies Nz 1} <-1 as described above. Such a retardation film may be referred to as a "positive biaxial plate", a "positive biaxial plate" or the like.

The second optical compensation layer preferably satisfies the following equations (2) and (4).
20nm <Re ₂ (590) ≤ 60nm (2)
-4 <Nz ₂ <-1 (4)

_{The front retardation Re 2} (590) of the second optical compensation layer is more preferably 21 to 59 nm, further preferably 25 to 55 nm, and particularly preferably 30 to 50 nm.

The value of Nz ₂ is more preferably -3.5 to -1.5, further preferably -3.3 to -1.8, and -3.0 to -2.0. It is particularly preferable to have.

Further, the second optical compensation layer preferably satisfies the following formula (6).
-150nm ≤ Rth ₂ (590) ≤ -60nm (6)
Here, a _{Rth 2 (590) = Re 2} (590) × (Nz 2 -0.5), represents a retardation in the thickness direction.

_{The retardation Rth 2 in} the thickness direction of the second optical compensation layer is more preferably −140 to −70 nm, further preferably −130 to −80 nm, and particularly preferably −120 to −85 nm. preferable.

Further, the first plane retardation _Re 2 of the optical compensation layer (590) and the front retardation of the second optical compensation layer Deployment _Re 2 (590) preferably satisfies the formula (7) below.
110nm <Re ₁ (590) + Re ₂ (590) <150nm (7)

The sum of Re ₁ (590) and Re ₂ (590) is more preferably 115 to 145 nm, further preferably 120 to 140 nm, and particularly preferably 125 to 135 nm.

The material, manufacturing method, and the like of the second optical compensation layer are not particularly limited as long as they satisfy the above optical characteristics. The second optical compensation layer may be a retardation film alone or a laminate of two or more retardation films. Preferably, the second optical compensation layer is a single retardation film. This is because the liquid crystal panel can be made thinner by reducing the deviation and unevenness of the retardation value due to the shrinkage stress of the polarizing element and the heat of the light source. When the second optical compensation layer is a laminated body, it may include an adhesive layer or an adhesive layer for adhering two or more retardation films. When the laminate contains two or more retardation films, these retardation films may be the same or different.

The optical characteristics of the retardation film used for the second optical compensation layer can be appropriately selected depending on the number of retardation films used. For example, when the second optical compensation layer is composed of the retardation film alone, the front retardation of the retardation film and the thickness direction retardation are respectively the front retardation Re _{2 of the second optical compensation layer.} It is preferable to make it equal to the thickness direction retardation Rth _2. Therefore, it is preferable that the retardation value of the pressure-sensitive adhesive layer, the adhesive layer, or the like used when laminating the second optical compensation layer on the polarizing element or the second optical compensation layer is as small as possible.

The retardation film used for the second optical compensation layer is excellent in transparency, mechanical strength, thermal stability, moisture shielding property, etc., like the retardation film used for the first optical compensation layer, and is distorted. Those that are less likely to cause optical unevenness are preferably used. As the retardation film, a stretched film of a polymer film containing a thermoplastic resin as a main component is preferably used. The thickness, transmittance, photoelastic coefficient, and the like of the film are not particularly limited, but are preferably in the same range as described in the first optical compensation layer.

The material for forming the thermoplastic resin is not particularly limited, but for the _{purpose of obtaining a positive birefringence plate satisfying the characteristics of Nz 2} <-1, it is preferable to use a polymer having negative birefringence.

Here, "having negative birefringence" means that when the polymer is oriented by stretching or the like, the refractive index in the orientation direction becomes relatively small, in other words, the refractive index in the direction orthogonal to the orientation direction. Is the one that becomes larger. Examples of such a polymer include those in which a chemical bond or functional group having a large polarization anisotropy such as an aromatic group or a carbonyl group is introduced into the side chain of the polymer. Specific examples thereof include acrylic resins, styrene resins, and maleimide resins.

As a method for producing the above acrylic resin, styrene resin, and maleimide resin, for example, it can be obtained by addition polymerization of an acrylic monomer, a styrene monomer, a maleimide monomer, or the like, respectively. Further, after the polymerization, the birefringence characteristic can be controlled by substituting the side chain, performing a maleimide formation, a grafting reaction, or the like.

Examples of the acrylic resin include polymethylmethacrylate (PMMA), polybutylmethacrylate, polycyclohexylmethacrylate and the like.

Examples of the styrene-based monomer which is the raw material monomer of the styrene-based resin include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, and p. Examples thereof include -carboxystyrene, p-phenylstyrene, 2,5-dichlorostyrene, pt-butylstyrene and the like.

Examples of the raw material monomer of the maleimide-based resin include N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, and N-(. 2-propylphenyl) maleimide, N- (2-isopropylphenyl) maleimide, N- (2,6-dimethylphenyl) maleimide, N- (2,6-dipropylphenyl) maleimide, N- (2,6-diisopropyl) Phenyl) maleimide, N- (2-methyl-6-ethylphenyl) maleimide, N- (2-chlorophenyl) maleimide, N- (2,6-dichlorophenyl), N- (2-bromophenyl) maleimide, N-( Examples thereof include 2,6-dibromophenyl) maleimide, N- (2-biphenyl) maleimide, and N- (2-cyanophenyl) maleimide. The maleimide-based monomer can be obtained from, for example, Tokyo Chemical Industry Co., Ltd.

The polymer exhibiting negative compound refraction may be copolymerized with other monomers for the purpose of improving brittleness, moldability, heat resistance, etc., as other monomer components used for such purposes. For example, ethylene, propylene, 1-butene, 1,3-butadiene, 2-methyl-1-butene, 2-methyl-1-pentene, 1-hexene, acrylonitrile, methyl acrylate, methyl methacrylate, maleine anhydride. Acids, vinyl acetate and the like can be mentioned.

When the polymer showing negative birefringence is a copolymer of a styrene-based monomer and another monomer, the content of the styrene-based monomer component is preferably 50 to 80 mol%. When the polymer showing negative birefringence is a copolymer of a maleimide-based monomer and another monomer, the content of the maleimide-based monomer component is preferably 2 to 50 mol%. When the content of the monomer component is within the above range, a film having excellent toughness and moldability can be obtained.

Among the polymers showing negative compound refraction, styrene-maleic anhydride copolymer, achloronitrile copolymer, styrene- (meth) acrylate copolymer, styrene-maleimide copolymer, vinyl ester-maleimide copolymer weight Combined, olefin-maleimide copolymers can be preferably used. These can be used alone or in combination of two or more. These polymers show high negative birefringence expression and are excellent in heat resistance. These polymers can be obtained from, for example, Nova Chemical Japan and Arakawa Chemical Industry Co., Ltd.

Further, as a polymer showing negative birefringence, a polymer having a repeating unit represented by the following general formula (I) can also be preferably used. Such a polymer can be obtained by using an N-phenyl-substituted maleimide having a phenyl group having a substituent at least at the ortho position as an N-substituted group as a maleimide-based monomer as a starting material. Such a polymer has even higher negative birefringence, and is excellent in heat resistance and mechanical strength.

In the above general formula (I), R _{1 to} R ₅ are independently of hydrogen, halogen atom, carboxylic acid, carboxylic acid ester, hydroxyl group, nitro group, or linear or branched group having 1 to 8 carbon atoms. Represents an alkyl group or an alkoxy group (however, R ₁ and R ₅ are not hydrogen atoms at the same time), and R ₆ and R ₇ are hydrogen atoms or linear or branched alkyl or alkoxy groups having 1 to 8 carbon atoms. Represents, and n represents an integer of 2 or more.

Further, the polymer exhibiting negative birefringence is not limited to those described above, and for example, Japanese Patent Application Laid-Open No. 2
Cyclic olefin copolymers and the like as disclosed in Japanese Patent Application Laid-Open No. 005-350544 can also be used. Further, a composition of a polymer and inorganic fine particles as disclosed in Japanese Patent Application Laid-Open No. 2005-156862, Japanese Patent Application Laid-Open No. 2005-227427, etc. can also be preferably used. Further, as the polymer showing negative birefringence, one kind may be used alone, or two or more kinds may be mixed and used. Further, these can be modified and used by copolymerization, branching, cross-linking, molecular terminal modification (or sealing), stereoregular modification and the like.

The polymer film containing the thermoplastic resin as a main component may further contain any suitable additive, if necessary, as described above for the first optical compensating layer.

As a method for forming the stretched film of the polymer film, any suitable stretching method can be adopted as described above for the first optical compensation layer.

In the case of a polymer having negative birefringence, the refractive index in the orientation direction is relatively small as described above. Therefore, in the case of the lateral uniaxial stretching method, the polymer has a slow axis in the film transport direction (in other words, in other words. The refractive index in the transport direction is nx1). In the case of the longitudinal-horizontal sequential biaxial stretching method and the longitudinal / horizontal simultaneous biaxial stretching method, either the transport direction or the width direction can be set as the slow axis depending on the ratio of the longitudinal / horizontal stretching ratios. That is, when the stretching ratio in the vertical (conveying) direction is relatively large, the horizontal (width) direction becomes the slow-phase axis, and when the stretching ratio in the horizontal (width) direction is relatively large, the vertical (conveying) direction is slow. It becomes the phase axis.

The stretching temperature, the method for controlling the temperature in the stretching oven, the stretching ratio, and the like are not particularly limited, but the same stretching temperature, temperature control method, and stretching ratio as described in the first optical compensation layer can be preferably applied.

The method of obtaining a positive birefringence plate used for the second optical compensation layer using a polymer having negative birefringence has been described above, but the positive birefringence plate is a polymer having positive birefringence. It can also be manufactured using.

As a method for obtaining a positive biaxial plate using a polymer having positive birefringence, for example, JP-A-2000-23101, JP-A-2000-206328, JP-A-2002-207123 and the like are disclosed. As such, a stretching method that increases the refractive index in the thickness direction can be used. That is, a film having a polymer having a positive double refraction is adhered to one side or both sides of a film having a polymer having a positive double refraction, and a film having a polymer having a positive double refraction is applied under the action of the shrinkage force of the heat shrinkable film by heat treatment. By contracting both the length direction and the width direction of the film to increase the refractive index in the thickness direction, it is possible to obtain a positive biaxial plate satisfying the characteristics of _{Nz 2> -1.} can.

As described above, the positive birefringence plate used as the second optical compensation layer can be produced by using a polymer having either positive or negative birefringence, but generally, when a positive birefringence polymer is used. Has an advantage in that there are many types of polymers that can be selected, and when a negative birefringent polymer is used, it is due to the stretching method as compared with the case where a positive birefringence polymer is used. Therefore, it has an advantage that a retardation film having high uniformity in the slow axis direction can be easily obtained.

As the retardation film used for the second optical compensation layer, a commercially available optical film can be used as it is in addition to the above. Further, a commercially available optical film may be used after being subjected to secondary processing such as stretching treatment and / or relaxation treatment.

The polarizing element, the first optical compensation layer, and the second optical compensation layer are laminated by using an adhesive or an adhesive described later. Further, an optically isotropic film described later may be arranged between the polarizing element and the first optical compensation layer. The polarizing element and the optically isotropic film, and the optically isotropic film and the first optical compensation layer are also laminated by using an adhesive or an adhesive which will be described later.

When a polarizing plate provided with such an optical compensation film is applied to an O-mode IPS-mode liquid crystal cell, the polarizing plate of the present invention is preferably arranged on the visual side of the liquid crystal display device. Further, when applied to an E-mode IPS-mode liquid crystal cell, the polarizing plate of the present invention is preferably arranged on the light source side of the liquid crystal display device.

When the polarizing plate of the present invention is laminated on one surface of a liquid crystal display device in IPS mode, the polarizing plate laminated on the other surface of the liquid crystal cell is polarized by laminating a polarizing element and an optically isotropic film. It is preferably a plate in which the optically isotropic film side thereof is laminated on the liquid crystal cell via an adhesive.

The optically isotropic film is a film that satisfies the following formulas (8) and (9).
0 nm ≤ | Re ₃ (590) | ≤ 20 nm (8)
0 nm ≤ | Rth ₃ (590) | ≤ 20 nm (9)
Here, the refractive index in the slow axis direction in the plane of the optically isotropic film is nx ₃ , the refractive index in the phase advance axis direction in the plane is ny ₃ , and the refractive index in the thickness direction is nz _3, and Re ₃ ( λ) = (nx _3- ny ₃ ) × d ₃ , Rth ₃ (λ) = {(nx ₃ + ny ₃ ) / 2-nz} × d ₃ , and d ₃ is the thickness of the optically isotropic film. show.

The material, manufacturing method, and the like of the isotropic optical element are not particularly limited as long as they satisfy the above optical characteristics. The isotropic optical element may be a single optical film or a laminate of two or more optical films. Preferably, the isotropic optical element is a single film. This is because the liquid crystal panel can be made thinner by reducing the occurrence and unevenness of birefringence due to the contraction stress of the polarizing element and the heat of the light source. When the isotropic optical element is a laminated body, it may include an adhesive layer or an adhesive layer for adhering two or more retardation films. When the laminate contains two or more retardation films, these retardation films may be the same or different. For example, when two retardation films are laminated, it is preferable that the retardation films are arranged so that their slow phases are orthogonal to each other. By arranging in this way, the in-plane retardation value can be reduced. Further, it is preferable that each retardation film is laminated with films in which the positive and negative of the retardation value in the thickness direction are opposite to each other. By laminating in this way, the retardation value in the thickness direction can be reduced.

The optical film used for the isotropic optical element is excellent in transparency, mechanical strength, thermal stability, moisture shielding property, etc., like the retardation film used for the first and second optical compensation layers. , Those that are less likely to cause optical unevenness due to distortion are preferably used. As the film, a polymer film is preferably used. The thickness, transmittance, molding method, etc. of the film are not particularly limited, but are preferably in the same range as described in the first optical compensation layer.

The absolute value of the photoelastic coefficient of the optical film used for the isotropic optical element ^{is preferably 1.0 × 10 -10} m ² / N or less, preferably 5.0 × 10 ^-11 m ² / N or less. It is more preferably 1.0 × ^10-11 m ² / N or less, and ^{particularly preferably 5.0 × 10-12} m ² / N or less. By setting the value of the photoelastic coefficient in the above range, it is possible to obtain a liquid crystal display device having excellent optical uniformity, small change in optical characteristics even in an environment such as high temperature and high humidity, and excellent durability. can. The lower limit of the photoelastic coefficient is not particularly limited, but is generally 5.0 × 10 ^-13 m ² / N or more. The value of the photoelastic coefficient can be suppressed low by the same method as described above for the first optical compensation layer.

Examples of the material constituting the optically isotropic film include polycarbonate resin, polyvinyl alcohol resin, cellulose resin, polyester resin, polyarylate resin, polyimide resin, cyclic polyolefin resin, polysulfone resin, and polyether. Examples thereof include sulfone-based resins, polyolefin-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof. Further, a thermosetting resin such as urethane-based, acrylic urethane-based, epoxy-based, or silicone-based resin or an ultraviolet curable resin can also be used. Similar to the first and second optical compensation layers, the optically isotropic film may contain one or more kinds of arbitrary suitable additives.

As the cellulosic resin, esters of cellulose and fatty acids are preferable. Specific examples of such a cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose and the like. Of these, triacetyl cellulose is particularly preferred. Many products of triacetyl cellulose are commercially available, which is advantageous in terms of availability and cost. Most triacetyl celluloses have a thickness direction retardation (Rth) of more than 10 nm, but depending on the use of additives that cancel these retardations or the film forming method, not only the front retardation but also the thickness direction retardation can be used. A small cellulosic resin film can be obtained. As the above-mentioned film forming method, for example, a base film such as polyethylene terephthalate, polypropylene, or stainless steel coated with a solvent such as cyclopentanone or methyl ethyl ketone is attached to a general cellulose-based film and heat-dried (for example, 80). A method of peeling off the base film after (about 3 to 10 minutes at ~ 150 ° C.); Examples thereof include a method of applying a coating to a based resin film, heating and drying (for example, about 3 to 10 minutes at 80 to 150 ° C.), and then peeling off the coating film.

Further, as the cellulosic resin film having a small thickness direction retardation, a fatty acid cellulosic resin film having a controlled fat substitution degree can be used. The commonly used triacetyl cellulose has an acetic acid substitution degree of about 2.8, but preferably the Rth can be reduced by controlling the acetic acid substitution degree to 1.8 to 2.7. Rth can be controlled to be small by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, or acetyltriethyl citrate to the fatty acid-substituted cellulosic resin. The amount of the plasticizer added is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and further preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid cellulosic resin.

Further, as the optically isotropic film, a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain described in JP-A-2001-334527 (WO01 / 37007) and the like, and a thermoplastic resin in which the side chain is substituted and / non-substituted. A polymer film containing a resin composition containing a substituted phenyl and a thermoplastic resin having a nitrile group, JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002. A polymer film containing an acrylic resin having a lactone ring structure described in JP-A-254544, JP-A-2005-146804, JP-A-2006-171464, etc., JP-A-2004-70290, JP-A-2004- 70296, 2004-163924, 2004-292812, 2005-314534, 2006-131898, 2006-206881, 2006-265532 Acrylic having structural units of unsaturated thermoplastic alkyl esters and structural units of glutaric anhydrides described in JP-A, JP-A-2006-283013, JP-A-2006-299005, JP-A-2006-335902, etc. Polymer film containing resin, JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328334, JP-A-2006-337491, JP-A-2006 It is also possible to use a film or the like containing a thermoplastic resin having a glutarimide structure described in JP-A-337492, JP-A-2006-337493, JP-A-2006-337569 and the like. Since both the front retardation and the thickness direction retardation of these films are small and the photoelastic coefficient is also small, even if the polarizing plate is distorted due to heating or the like, problems such as unevenness are unlikely to occur, and the moisture permeability is further increased. Since it is small, it is preferable because it has excellent humidification durability.

It is also preferable to use a cyclic polyolefin resin as the optically isotropic film. Specific examples of the cyclic polyolefin-based resin are norbornene-based resins. Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefins as a polymerization unit. Resin is mentioned. Specific examples include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a cyclic olefin and an α-olefin such as ethylene and propylene, and a copolymer thereof (typically, a random copolymer). Examples thereof include graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene-based monomers.

As the cyclic polyolefin resin, various products are commercially available. Specific examples include the product name "Zeonoa" manufactured by Zeon Corporation, the product name "Arton" manufactured by JSR Corporation, the product name "Topus" manufactured by TICONA, and the product name "Apel" manufactured by Mitsui Chemicals, Inc. Can be mentioned.

An adhesive or an adhesive described later can also be used for laminating the polarizing element and the optically isotropic film.

<Adhesive layer>
Any suitable adhesive can be used as the adhesive constituting the adhesive layer for adhering the protective film to the polarizing element. As the adhesive, a water-based adhesive, a solvent-based adhesive, an active energy ray-curable adhesive, or the like can be used, but a water-based adhesive is preferable. From the viewpoint of improving heat resistance, the adhesive layer preferably contains at least one urea compound selected from urea, a urea derivative, thiourea and a thiourea derivative.

The thickness of the adhesive when applied can be set to any suitable value. For example, after curing or heating (drying), an adhesive layer having a desired thickness is set so as to be obtained. The thickness of the adhesive layer 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 more and 1 μm. It is as follows.

(Water-based adhesive)
As the water-based adhesive, any suitable water-based adhesive can be adopted. Of these, 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 about 100 to 5500, more preferably 1000 to 4500, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, and more preferably 90 mol% to 100 mol% from the viewpoint of adhesiveness.

The PVA-based resin contained in the water-based adhesive preferably contains an acetoacetyl group, because the PVA-based resin layer and the protective film have excellent adhesion and durability. .. The acetoacetyl group-containing PVA-based resin can be obtained, for example, by reacting the PVA-based resin with diketene by an arbitrary method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 20 mol%.
The resin concentration of the water-based adhesive is preferably 0.1% by mass to 15% by mass, and more preferably 0.5% by mass to 10% by mass.

The water-based adhesive may also contain a cross-linking agent. As the cross-linking agent, a known cross-linking agent can be used. For example, water-soluble epoxy compounds, dialdehydes, isocyanates and the like can be mentioned.

When the PVA-based resin is an acetoacetyl group-containing PVA-based resin, the cross-linking agent is preferably any one of glyoxal, glyoxyphosphate, and methylolmelamine, and may be glyoxal or glyoxalate. Glyoxal is preferable, and glyoxal is particularly preferable.

The water-based adhesive can also contain an organic solvent. The organic solvent is preferably alcohols in that it is miscible with water, and more preferably methanol or ethanol among the alcohols. Some urea compounds have low solubility in water, but some have sufficient solubility in alcohol. In that case, it is also preferable to dissolve the urea compound in alcohol to prepare an alcohol solution of the urea compound, and then add the alcohol solution of the urea compound to the PVA aqueous solution to prepare an adhesive. be.

The concentration of methanol in the water-based adhesive is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and further preferably 20% by mass or more and 60% by mass or less. When the concentration of methanol is 10% by mass or more, it becomes easier to suppress polyene formation in a high temperature environment. Further, when the content of methanol is 70% by mass or less, deterioration of hue can be suppressed.

(Active energy ray-curable adhesive)
The active energy ray-curable adhesive is an adhesive that cures by irradiating with active energy rays such as ultraviolet rays, and is, for example, an adhesive containing a polymerizable compound and a photopolymerizable initiator, and an adhesive containing a photoreactive resin. , Adhesives containing a binder resin and a photoreactive cross-linking agent, and the like. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, 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 cationic radicals by irradiating them with active energy rays such as ultraviolet rays.

(Urea compound)
When the adhesive layer contains a urea compound, the urea compound is at least one selected from urea, a urea derivative, thiourea and a thiourea derivative. As a method for incorporating the urea-based compound in the adhesive layer, it is preferable to include the urea-based compound in the above-mentioned adhesive. In the process of forming the adhesive layer from the adhesive through a drying step or the like, a part of the urea-based compound may be transferred from the adhesive layer to the polarizing element or the like. That is, the polarizing element may contain a urea-based compound. There are water-soluble and poorly water-soluble urea-based compounds, and both urea-based compounds can be used in the adhesive of the present embodiment. When a poorly water-soluble urea compound is used as an aqueous adhesive, it is preferable to devise a dispersion method so that haze does not increase after the adhesive layer is formed.

When the adhesive is a water-based adhesive containing a PVA-based resin, the amount of the urea-based compound added is preferably 0.1 to 400 parts by mass with respect to 100 parts by mass of the PVA resin, and is 1 to 200 parts by mass. It is more preferable that the amount is 3 to 100 parts by mass.

(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 composed of a carbon atom, a hydrogen atom and an oxygen atom.

Specific examples of urea derivatives include methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, hydroxyurea, acetylurea, allylurea, and 2-propynyl as monosubstituted ureas. Examples thereof include urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, benzoyl urea, o-tolyl urea and p-tolyl urea.
As the disubstituted urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-bis (hydroxymethyl) urea, 1,3-tert- Butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-bis (4-methoxyphenyl) urea, 1-acetyl-3-methylurea, 2-imidazolidinone (ethyleneurea), tetrahydro -2-Pyrimidinone (propylene urea) can be mentioned.
As tetra-substituted urea, tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1,3-dimethylurea, 1,3-dimethyl- Examples thereof include 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 composed of a carbon atom, a hydrogen atom and an oxygen atom.

As a specific example of the thiourea derivative, as monosubstituted thiourea, 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, Examples thereof include o-tolylthiourea and p-tolylthiourea.
As the 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, Examples thereof include 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N-allyl-N'-(2-hydroxyethyl) thiourea and ethylenethiourea.
Examples of the 3-substituted thiourea include trimethylthiourea, and examples of the 4-substituted thiourea include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

Among the urea-based compounds, a urea derivative or a thiourea derivative is preferable, and a urea derivative is preferable because it can further suppress a decrease in transmittance in a high temperature environment when used in an image display device having an interlayer filling structure. More preferred. Among the urea derivatives, mono-substituted urea or di-substituted urea is preferable, and mono-substituted urea is more preferable. The di-substituted urea includes 1,1-substituted urea and 1,3-substituted urea, but 1,3-substituted urea is more preferable.

<Urea compound-containing layer>
The urea compound is not limited to the case where it is contained in the adhesive layer as described above, and may be contained in a layer other than the adhesive layer from the viewpoint of improving the heat resistance of the polarizing plate. .. As another layer, as described in the description of the transparent protective film, in recent years, in order to meet the demand for thinning of the polarizing plate, a polarizing plate having a protective film on only one side of the polarizing element has been developed. In such a configuration, a cured layer may be laminated on a surface of the polarizing element that does not have a protective film for the purpose of increasing the physical strength.

In the present embodiment, such a cured layer can also contain a urea compound. Normally, such a cured layer is formed from a curable composition containing an organic solvent, but paragraphs [0020] to [0042] of JP-A-2017-075986 describe the aqueous active energy ray-curable polymer composition. A method of forming such a cured layer from a solution is described. Since many urea-based compounds are water-soluble, a water-soluble urea-based compound may be contained in such a composition.

<Moisture content>
(Feature (a))
When it has the feature (a), the water content of the polarizing element is equal to or more than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 30%, and is equal to or less than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 50%. More preferably, the temperature is 20 ° C. and the relative humidity is 45% or less, more preferably, the temperature is 20 ° C. and the relative humidity is 42% or less, and most preferably the temperature is 20 ° C. and the relative humidity is 38%. It is less than or equal to the equilibrium moisture content. If the temperature is lower than the equilibrium water content of 20 ° C. and the relative humidity of 30%, the handleability of the polarizing element is lowered and the polarizing element is easily cracked. When the water content of the polarizing element exceeds the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 50%, the transmittance of the polarizing element tends to decrease. It is presumed that when the water content of the polarizer is high, polyene formation of the PVA-based resin is likely to proceed. The water content of the polarizing element is the water content of the polarizing element in the polarizing plate.

As a method of confirming whether the water content of the polarizing element is within the range of the equilibrium water content of the temperature of 20 ° C. and the relative humidity of 30% and the equilibrium water content of the temperature of 20 ° C. and the relative humidity of 50% or less, the above temperature and the above relative humidity If it is stored in an environment adjusted to the range of, and if there is no change in mass for a certain period of time, it can be considered that it has reached equilibrium with the environment, or the environment adjusted to the above temperature and the above relative humidity range. It can be confirmed by calculating the equilibrium water content of the polarizing element in advance and comparing the water content of the polarizing element with the pre-calculated equilibrium water content.

The method for manufacturing a polarizing element having a water content of 20 ° C. and a relative humidity of 30% or more and an equilibrium water content of a temperature of 20 ° C. and a relative humidity of 50% or less is not particularly limited. Examples thereof include a method of storing the polarizing element in an environment adjusted to a relative humidity range of 10 minutes or more and 3 hours or less, or a method of heat-treating at 30 ° C. or higher and 90 ° C. or lower.

As another preferable method for producing a polarizing element having the water content, a laminated body in which a protective film is laminated on at least one surface of the polarizing element, or a polarizing plate formed by using the polarizing element is provided with the temperature and the relative humidity. Examples thereof include a method of storing in an environment adjusted to the above range 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. At the time of manufacturing an image display device adopting an interlayer filling 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 the above relative humidity range for 10 minutes or more and 3 hours or less. The front plate may be attached after heating at 30 ° C. or higher and 90 ° C. or lower.

The water content of the polarizing element shall be adjusted so that the water content is within the above numerical range at the material stage of the polarizing element alone or a laminate of the polarizing element and the protective film and used to form the polarizing plate. Is preferable. If the water content is adjusted after the polarizing plate is formed, the curl becomes too large, and problems may easily occur when the polarizing plate is attached to the image display cell. By constructing a polarizing plate using a polarizing element adjusted to have the above water content at the material stage before forming the polarizing plate, it is easy to obtain a polarizing plate having a polarizing element whose water content satisfies the above numerical range. Can be configured in. With the polarizing plate attached to the image display cell, the water content of the polarizing element in the polarizing plate may be adjusted to be within the above numerical range. In this case, since the polarizing plate is attached to the image display cell, curling is unlikely to occur.

(Feature (b))
When it has the feature (b), the water content of the polarizing plate is equal to or more than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 30%, and is equal to or less than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 50%. The water content of the polarizing plate is preferably equal to or less than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 45%, more preferably not more than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 42%, and further preferably relative to the temperature of 20 ° C. The humidity is 38% or less and is equal to or less than the equilibrium moisture content. When the water content of the polarizing plate is lower than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 30%, the handleability of the polarizing plate is lowered and the polarizing plate is easily cracked. When the water content of the polarizing plate exceeds the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 50%, the transmittance of the polarizing element tends to decrease. It is presumed that when the water content of the polarizing plate is high, polyene formation of the PVA-based resin is likely to proceed.

As a method of confirming whether the water content of the polarizing plate is within the range of the equilibrium water content of the temperature of 20 ° C. and the relative humidity of 30% and the equilibrium water content of the temperature of 20 ° C. and the relative humidity of 50% or less, the above temperature and the above relative humidity If it is stored in an environment adjusted to the range of, and if there is no change in mass for a certain period of time, it can be considered that it has reached equilibrium with the environment, or the environment adjusted to the above temperature and the above relative humidity range. It can be confirmed by calculating the equilibrium water content of the polarizing plate in advance and comparing the water content of the polarizing plate with the pre-calculated equilibrium water content.

The method for producing a polarizing plate having a water content of 20 ° C. and a relative humidity of 30% or more and an equilibrium water content of a temperature of 20 ° C. and a relative humidity of 50% or less is not particularly limited. Examples thereof include a method of storing the polarizing plate in an environment adjusted to a relative humidity range of 10 minutes or more and 3 hours or less, or a method of heat-treating at 30 ° C. or higher and 90 ° C. or lower.

At the time of manufacturing an image display device adopting an interlayer filling 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 the above relative humidity range for 10 minutes or more and 3 hours or less. The front plate may be attached after heating at 30 ° C. or higher and 90 ° C. or lower.

[Manufacturing method of polarizing plate]
The method for manufacturing a polarizing plate of the present embodiment includes a laminating step of laminating a polarizing element and a transparent protective film, and a water content adjusting step. In the water content adjusting step, when producing a polarizing plate having the characteristic (a), the water content of the polarizing element is equal to or higher than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 30%, and the equilibrium water content of the temperature of 20 ° C. and a relative humidity of 50%. Adjust the water content of the polarizing element so that it is less than or equal to the rate. The water content of the polarizing element can be adjusted according to the above description of the water content of the polarizing element. In the water content adjusting step, when producing a polarizing plate having the characteristic (b), the water content of the polarizing plate is equal to or higher than the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 30%, and the equilibrium water content of a temperature of 20 ° C. and a relative humidity of 50%. Adjust the water content of the polarizing plate so that it is less than or equal to the rate. The water content of the polarizing plate can be adjusted according to the above description of the water content of the polarizing plate. The order of the water content adjusting step and the laminating step is not limited, and the water content adjusting step and the laminating step may be performed in parallel. The laminating step can be a step of laminating the polarizing element and the transparent protective film via the adhesive layer.

[Configuration of image display device]
The polarizing plate of the present embodiment is used in various image display devices such as a liquid crystal display device and an organic EL display device. When the image display device has an interlayer filling structure in which both sides of the polarizing plate are in contact with a layer other than the air layer, specifically, a solid layer such as an adhesive layer, the transmittance in a high temperature environment. Is likely to decrease. In the image display device using the polarizing plate of the present embodiment, it is possible to suppress a decrease in the transmittance of the polarizing plate in a high temperature environment even in the interlayer filling configuration. An example of the image display device is a configuration having an image display cell, a first pressure-sensitive adhesive layer laminated on the visible side surface of the image display cell, and a polarizing plate laminated on the visible side surface of the first pressure-sensitive adhesive layer. Will be done. Such an image display device may further include a second pressure-sensitive adhesive layer laminated on the visible 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 arranged on the visual side of the image display device, the polarizing plate and the image display cell are bonded by the first pressure-sensitive adhesive layer, and the polarizing plate and the transparent member are second-bonded. It is suitably used for an image display device having an interlayer filling structure bonded by an agent layer. In the present specification, either one or both of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be simply referred to as a "sticky agent layer". The member used for bonding the polarizing plate and the image display cell and the member used for bonding the polarizing plate and the transparent member are not limited to the pressure-sensitive adhesive layer, but are an adhesive layer. May be good.

<Image display cell>
Examples of the image display cell include a liquid crystal cell and an organic EL cell. The liquid crystal cell includes a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, and a semi-transmissive semi-reflective type that uses both external light and light from the light source. Any liquid crystal cell may be used. When the liquid crystal cell uses the light from the light source, the image display device (liquid crystal display device) has a polarizing plate arranged on the side opposite to the viewing side of the image display cell (liquid crystal cell), and further arranges the light source. Will be done. It is preferable that the polarizing plate on the light source side and the liquid crystal cell are bonded to each other via an appropriate adhesive layer. As the driving method of the liquid crystal cell, for example, any type such as VA mode, IPS mode, TN mode, STN mode and bend orientation (π type) can be used.

As the organic EL cell, a cell in which a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitting body (organic electroluminescence light emitting body) or the like 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 made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or a laminate of these. Various layer configurations can be adopted, such as a laminate of an electron-injected layer composed of a light-emitting layer and a perylene derivative, or a laminate of a hole-injected layer, a light-emitting layer, and an electron-injected layer.

<Attachment of image display cell and polarizing plate>
An adhesive layer (adhesive sheet) is preferably used for bonding the image display cell and the polarizing plate. Above all, a method in which a polarizing plate with an adhesive layer having an adhesive layer attached to one surface of the polarizing plate is attached to an image display cell is preferable from the viewpoint of workability and the like. The pressure-sensitive adhesive layer can be attached to the polarizing plate by an appropriate method. As an example, for example, a pressure-sensitive adhesive solution of about 10 to 40% by mass is prepared by dissolving or dispersing the base polymer or its composition in a solvent composed of a single substance or a mixture of appropriate solvents such as toluene and ethyl acetate. , A method of directly attaching it on a polarizing plate by an appropriate developing method such as a casting method or a coating method, or a method of forming an adhesive layer on the separator and transferring it to the polarizing plate. ..

<Adhesive layer>
The pressure-sensitive adhesive layer may be composed of one layer or two or more layers, but is preferably composed of one layer. The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition containing a (meth) acrylic resin, a rubber-based resin, a urethane-based resin, an ester-based resin, a silicone-based resin, and a polyvinyl ether-based resin as main components. Among them, a pressure-sensitive adhesive composition using a (meth) acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer is preferable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type.

Examples of the (meth) acrylic resin (base polymer) used in the pressure-sensitive adhesive composition include butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. A polymer or copolymer containing one or more of the (meth) acrylic acid esters as monomers is preferably used. It is preferable that the base polymer is copolymerized with a polar monomer. Examples of the polar monomer include (meth) acrylic acid compound, (meth) acrylic acid 2-hydroxypropyl compound, (meth) acrylic acid hydroxyethyl compound, (meth) acrylamide compound, and N, N-dimethylaminoethyl (meth) acrylate compound. , A monomer having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as a glycidyl (meth) acrylate compound.

The pressure-sensitive adhesive composition may contain only the above-mentioned base polymer, but usually further contains a cross-linking agent. The cross-linking agent is a metal ion having a divalent value or higher and forming a carboxylic acid metal salt with a carboxyl group, a polyamine compound forming an amide bond with the carboxyl group, and a carboxyl group. Examples thereof include a polyepoxy compound that forms an ester bond with, a polyol, and a polyisocyanate compound that forms an amide bond with a carboxyl group. Of these, polyisocyanate compounds are preferable.

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 and electron beams, and has adhesiveness even before irradiation with active energy rays, such as a film. It has the property that it can be brought into close contact with the adherend of the above, and can be cured by irradiation with active energy rays to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably 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 cross-linking agent. If necessary, a photopolymerization initiator, a photosensitizer, or the like may be contained.

The pressure-sensitive adhesive composition includes fine particles for imparting light scattering, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, pressure-sensitive adhesives, fillers (metal powders and other inorganic powders). Etc.), antioxidants, UV absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators and other additives can be included.

The pressure-sensitive adhesive layer can be formed by applying an organic solvent diluted solution of the pressure-sensitive adhesive composition on the surface of a base film, an image display cell, or a polarizing plate and drying it. The base film is generally a thermoplastic resin film, and a typical example thereof is a separate film that has been subjected to a mold release treatment. The separate film can be, for example, one in which a mold release treatment such as a silicone treatment is applied to the surface on which the pressure-sensitive adhesive layer of the film made of a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyarate is formed. ..

For example, the pressure-sensitive adhesive composition may be directly applied to the release-treated surface of the separate film to form a pressure-sensitive adhesive layer to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer with a separate film may be laminated on the surface of a polarizing body. The pressure-sensitive adhesive composition may be directly applied to the surface of the polarizing plate to form a pressure-sensitive adhesive layer, and a separate film may be laminated on the outer surface of the pressure-sensitive adhesive layer.
When the pressure-sensitive adhesive layer is provided on the surface of the polarizing plate, it is preferable to perform surface activation treatment, for example, plasma treatment, corona treatment, etc. on the bonding surface of the polarizing plate and / or the bonding surface of the pressure-sensitive adhesive layer. It is more preferable to apply the treatment.
Further, the pressure-sensitive adhesive composition is applied onto the second separate film to form a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet in which the separate film is laminated on the formed pressure-sensitive adhesive layer is prepared, and the second pressure-sensitive adhesive sheet is used as a second. The pressure-sensitive adhesive layer with the separate film after the separate film is peeled off may be laminated on the polarizing plate. As the second separate film, a film having a weaker adhesion to the pressure-sensitive adhesive layer than the separate film and being easily peeled off 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.

<Transparent member>
Examples of the transparent member arranged on the visual side of the image display device include a front plate (window layer) and a touch panel. As the front plate, a front plate having appropriate mechanical strength and thickness is used. Examples of such a front plate include a polyimide resin, a transparent resin plate such as an acrylic resin and a polycarbonate resin, a glass plate, and the like. A functional layer such as an antireflection layer may be laminated on the visible side of the front plate. When the front plate is a transparent resin plate, a hard coat layer may be laminated to increase the physical strength, or a low moisture permeability layer may be laminated to reduce the moisture permeability.
As the touch panel, various touch panels such as a resistive film method, a capacitance method, an optical method, and an ultrasonic method, a glass plate having a touch sensor function, a transparent resin plate, and the like are used. When a capacitive touch panel is used as the transparent member, it is preferable that a front plate made of glass or a transparent resin plate is provided on the visual side of the touch panel.

<Lasting of polarizing plate and transparent member>
A pressure-sensitive adhesive or an active energy ray-curable adhesive is preferably used for bonding the polarizing plate and the transparent member. When a pressure-sensitive adhesive is used, the pressure-sensitive adhesive can be attached by an appropriate method. As a specific attachment method, for example, the attachment method of the pressure-sensitive adhesive layer used for bonding the image display cell and the polarizing plate described above can be mentioned.

When an active energy ray-curable adhesive is used, a dam material is provided so as to surround the peripheral edge on the image display panel in order to prevent the adhesive solution from spreading before curing, and a transparent member is placed on the dam material. A method of placing and injecting an adhesive solution is preferably used. After the injection of the adhesive solution, alignment and defoaming are performed as necessary, and then active energy rays are irradiated to perform curing.

Hereinafter, the present invention will be specifically described based on Examples. The materials, reagents, amounts of substances and their ratios, operations, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention.
Therefore, the present invention is not limited to the following examples.

(1) Measurement of polarizing element thickness:
The measurement was performed using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) Luminous efficiency correction of polarizing element Measurement of single transmittance:
The measurement was performed using a spectrophotometer with an integrating sphere [“V7100” manufactured by JASCO Corporation; 2 degree field of view; C light source].

(3) Measurement of boron content:
0.2 g of the polarizing element was dissolved in 200 g of a 1.9 mass% mannitol aqueous solution. Next, the obtained aqueous solution was titrated with a 1 mol / L sodium hydroxide aqueous solution, and the boron content of the polarizing element was calculated by comparing the amount of the sodium hydroxide aqueous solution required for neutralization with the calibration curve.

(4) Measurement of yellow index (yellowness):
A spectrophotometer CM-3700A manufactured by Konica Minolta was used.

(5) Measurement of boron adsorption rate of PVA-based resin film:
A PVA-based resin film cut into 100 mm squares was immersed in pure water at 30 ° C. for 60 seconds, and then immersed in an aqueous solution at 60 ° C. containing 5 parts of boric acid for 120 seconds. The PVA-based resin film taken out from the boric acid aqueous solution was dried in an oven at 80 ° C. for 11 minutes. Humidity was adjusted for 24 hours in an environment of 23 ° C. and 55%% RH to obtain a boron-containing PVA film. 0.2 g of the boron-containing PVA-based resin film thus obtained was dissolved in 200 g of a 1.9 mass% mannitol aqueous solution. Next, the obtained aqueous solution was titrated with a 1 mol / L sodium hydroxide aqueous solution, and the boron content of the PVA-based resin film was calculated by comparing the amount of the sodium hydroxide aqueous solution required for neutralization with the calibration curve. .. The boron content of the PVA-based resin film thus obtained was used as the boron adsorption rate of the PVA-based resin film.

(Manufacturing of polarizing element 1)
A polyvinyl alcohol-based resin film having a thickness of 45 μm having a boron adsorption rate of 5.90% by mass is immersed in pure water at 21.5 ° C. for 79 seconds, and then the weight ratio of potassium iodide / boric acid / water is 2 /. It was 2/100 and was immersed in an aqueous solution containing 1.0 mM of iodine at 23 ° C. for 151 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 2.5 / 4/100 at 60.8 ° C. for 76 seconds. Subsequently, the mixture was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 3 / 5.5 / 100 at 45 ° C. for 11 seconds. Then, it was dried at 38 ° C. to obtain a polarizing element having a thickness of 18 μm in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly carried out in the steps of iodine dyeing and boric acid treatment, and the total stretching ratio was 5.85 times. The visible sensitivity-corrected simple substance transmittance of the obtained polarizing element was 41.07%, and the boron content was 4.84% by mass.

(Manufacturing of polarizing element 2)
A polyvinyl alcohol-based resin film having a thickness of 45 μm having a boron adsorption rate of 5.73% by mass is immersed in pure water at 21.5 ° C. for 79 seconds, and then the weight ratio of potassium iodide / boric acid / water is 2 /. It was 2/100 and was immersed in an aqueous solution containing 1.0 mM of iodine at 23 ° C. for 151 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 2.5 / 4/100 at 60.8 ° C. for 76 seconds. Subsequently, the mixture was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 3 / 5.5 / 100 at 45 ° C. for 11 seconds. Then, it was dried at 38 ° C. to obtain a polarizing element having a thickness of 18 μm in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly carried out in the steps of iodine dyeing and boric acid treatment, and the total stretching ratio was 5.85 times. The visible sensitivity-corrected simple substance transmittance of the obtained polarizing element was 41.06%, and the boron content was 4.62% by mass.

(Manufacturing of polarizing element 3)
A polyvinyl alcohol-based resin film having a thickness of 45 μm having a boron adsorption rate of 5.71% by mass is immersed in pure water at 21.5 ° C. for 79 seconds, and then the weight ratio of potassium iodide / boric acid / water is 2 /. It was 2/100 and was immersed in an aqueous solution containing 1.0 mM of iodine at 23 ° C. for 151 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 2.5 / 4/100 at 60.8 ° C. for 76 seconds. Subsequently, the mixture was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 3 / 5.5 / 100 at 45 ° C. for 11 seconds. Then, it was dried at 38 ° C. to obtain a polarizing element having a thickness of 18 μm in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly carried out in the steps of iodine dyeing and boric acid treatment, and the total stretching ratio was 5.85 times. The visible sensitivity-corrected simple substance transmittance of the obtained polarizing element was 40.96%, and the boron content was 4.48% by mass.

(Manufacturing of polarizing element 4)
A polyvinyl alcohol-based resin film having a thickness of 45 μm having a boron adsorption rate of 5.68% by mass is immersed in pure water at 21.5 ° C. for 79 seconds, and then the weight ratio of potassium iodide / boric acid / water is 2 /. It was 2/100 and was immersed in an aqueous solution containing 1.0 mM of iodine at 23 ° C. for 151 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 2.5 / 4/100 at 60.8 ° C. for 76 seconds. Subsequently, the mixture was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 3 / 5.5 / 100 at 45 ° C. for 11 seconds. Then, it was dried at 38 ° C. to obtain a polarizing element having a thickness of 18 μm in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly carried out in the steps of iodine dyeing and boric acid treatment, and the total stretching ratio was 5.85 times. The visible sensitivity-corrected simple substance transmittance of the obtained polarizing element was 40.88%, and the boron content was 4.35% by mass.

(Preparation of PVA solution for adhesive)
50 g of a modified PVA resin containing an acetoacetyl group (manufactured by Mitsubishi Chemical Corporation: Gosenex Z-410) is dissolved in 950 g of pure water, heated at 90 ° C. for 2 hours, cooled to room temperature, and cooled to room temperature to provide a PVA solution for adhesives. Got

(Preparation of Adhesive 1 for Polarizing Plate)
The prepared PVA solution for adhesive, pure water, and methanol were blended so as to have a PVA concentration of 3.0%, a methanol concentration of 35%, and a urea concentration of 0.5% to obtain an adhesive 1 for a polarizing plate.

(Preparation of Adhesive 2 for Polarizing Plate)
The prepared PVA solution for adhesive, pure water, and methanol were blended so as to have a PVA concentration of 3.0%, a methanol concentration of 5%, and a urea concentration of 0.5% to obtain an adhesive 2 for a polarizing plate.

(Saponification of cellulose acylate film)
A commercially available cellulose acylate film KC4UYW (manufactured by Konica Minolta Co., Ltd .: film thickness 40 μm) was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55 ° C. for 2 minutes, and then the film was washed with water. Then, after immersing the film in a 0.05 mol / L sulfuric acid aqueous solution at 25 ° C. for 30 seconds, the film was further passed through a water washing bath for 30 seconds under running water to neutralize the film. Then, draining with an air knife was repeated three times, and after the water was dropped, the film was allowed to stay in a drying zone at 70 ° C. for 15 seconds to be dried to prepare a saponified film.

(Preparation of polarizing plate 1)
The saponified cellulose acylate film prepared above was applied to both sides of the polarizing element 1 via a polarizing plate adhesive 1 so that the thickness of the adhesive layer after drying was 100 nm on both sides, and rolled. After bonding using a bonding machine, the mixture was dried at 80 ° C. for 3 minutes to obtain a polarizing plate 1 with a double-sided cellulose acylate film.

(Preparation of polarizing plate 2)
The polarizing plate 2 was produced in the same manner as the polarizing plate 1 except that the polarizing element 1 of the polarizing plate 1 was replaced with the polarizing element 2.

(Preparation of polarizing plate 3)
The polarizing plate 3 was produced in the same manner as the polarizing plate 1 except that the polarizing element 1 of the polarizing plate 1 was replaced with the polarizing element 3.

(Preparation of polarizing plate 4)
A polarizing plate 4 was produced in the same manner as the polarizing plate 3 except that the polarizing plate adhesive 1 of the polarizing plate 3 was replaced with the polarizing plate adhesive 2.

(Preparation of polarizing plate 5)
A polarizing plate 5 was produced in the same manner as the polarizing plate 2 except that the polarizing plate adhesive 1 of the polarizing plate 2 was replaced with the polarizing plate adhesive 2.

(Preparation of polarizing plate 6)
A polarizing plate 6 was produced in the same manner as the polarizing plate 1 except that the polarizing element 1 of the polarizing plate 1 was replaced with the polarizing element 4.

(Preparation of Optical Laminated Body 1)
By applying an acrylic pressure-sensitive adhesive (manufacturer: Lintec Corporation) to both sides of the polarizing plate 1 produced above with reference to the examples of JP-A-2018-025756, a pressure-sensitive adhesive having a thickness of 25 μm is applied to both sides. An optical laminate 1 having an agent layer was produced.

(Preparation of optical laminates 2 to 6)
Optical laminates 2 to 6 were produced in the same manner as the optical laminate 1 except that the polarizing plate 1 was replaced with the polarizing plates 2 to 6.

[High temperature durability test (105 ° C)]
The optical laminates 1 to 6 produced above are each cut into a size of 50 mm × 100 mm, and the surfaces of the adhesive layers on both sides are attached to non-alkali glass [trade name “EAGLEXG”, manufactured by Corning Inc.). By combining, an evaluation sample was prepared. When these samples were prepared, the optical laminate was stored for 72 hours in an environment of a temperature of 20 ° C. and a relative humidity of 40% in order to adjust the water content of the polarizing element before bonding the glass plates. The masses of all the samples after 66 hours, 69 hours, and 72 hours of storage were measured and there was no change. Therefore, it can be considered that the water content of the optical laminates 1 to 6 is the same as the equilibrium water content of the storage environment of 72 hours used in this experimental example. When the water content of the optical laminate reaches equilibrium in a certain storage environment, the water content of the polarizing plate in the optical laminate and the water content of the polarizing element in the polarizing plate also reach equilibrium in the storage environment. Can be regarded as having done. Further, when the water content of the polarizing element in the polarizing plate reaches equilibrium in a certain storage environment, it can be considered that the water content of the polarizing plate also reaches equilibrium in the storage environment.

This evaluation sample was autoclaved at a temperature of 50 ° C. and a pressure of 5 kgf / cm ² (490.3 kPa) for 1 hour, and then left to stand in an environment of a temperature of 23 ° C. and a relative humidity of 55% for 24 hours. Then, the transmittance was measured (initial value), stored in a high temperature environment at a temperature of 105 ° C., and the yellow index after 168 hours was measured. For the measurement of the yellow index, the evaluation sample was placed on a mirror surface, and the value of the reflected hue when light was incident was used. Tables 1 and 2 show the measured values of the yellow index.

Since the optical laminates 1 to 5 have a yellow index of 50 or less, it can be seen that the decrease in transmittance is suppressed even when stored in a high temperature environment.

Claims (15)

A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer and a transparent protective film.
The polyvinyl alcohol-based resin used for forming the polyvinyl alcohol-based resin layer has a boron adsorption rate of 5.70% by mass or more.
A polarizing plate having a water content of the polarizing element of 20 ° C. and 30% relative humidity or more and 20 ° C. and 50% relative humidity or less. A polarizing plate having a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer and a transparent protective film.
The polyvinyl alcohol-based resin used for forming the polyvinyl alcohol-based resin layer has a boron adsorption rate of 5.70% by mass or more.
A polarizing plate having a water content of the polarizing plate at a temperature of 20 ° C. and a relative humidity of 30% or more and at a temperature of 20 ° C. and a relative humidity of 50% or less. The polarizing plate according to claim 1 or 2, wherein the polarizing element has a boron content of 4.0% by mass or more and 8.0% by mass or less. Further having an adhesive layer for adhering the polarizing element and the transparent protective film,
The polarizing plate according to any one of claims 1 to 3, wherein the adhesive layer is a coating layer of a water-based adhesive. The polarizing plate according to claim 4, wherein the aqueous adhesive has a methanol concentration of 10% by mass or more and 70% by mass or less. The polarizing plate according to claim 4 or 5, wherein the water-based adhesive contains a polyvinyl alcohol-based resin. The polarizing plate according to any one of claims 4 to 6, wherein the adhesive layer has a thickness of 0.01 μm or more and 7 μm or less. The transparent protective film is a retardation film including a first optical compensation layer and a second optical compensation layer in order from the polarizing element side.
The absorption axis of the polarizing element and the slow axis of the first optical compensation layer are substantially orthogonal to each other.
The slow axis of the first optical compensation layer and the slow axis of the second optical compensation layer are substantially parallel to each other.
The polarizing plate according to any one of claims 1 to 7, wherein the first optical compensation layer and the second optical compensation layer satisfy the following formulas (1) to (4).
80nm ≤ Re ₁ (590) ≤ 120nm (1)
20 nm <Re ₁ (590) ≤ 60 nm (2)
1 <Nz ₁ <2 (3)
-4 <Nz ₂ <-1 (4) The polarizing plate is used in an image display device, and is used in an image display device.
The polarizing plate according to any one of claims 1 to 8, wherein in the image display device, solid layers are provided in contact with both surfaces of the polarizing plate. The first aspect of the image display cell, the first pressure-sensitive adhesive layer laminated on the visible side surface of the image display cell, and any one of claims 1 to 9 laminated on the visible side surface of the first pressure-sensitive adhesive layer. An image display device having a polarizing plate of. The image display device according to claim 10, further comprising a second pressure-sensitive adhesive layer laminated on the visible side surface of the polarizing plate and a transparent member laminated on the visible side surface of the second pressure-sensitive adhesive layer. 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. The method for manufacturing a polarizing plate according to claim 1.
A method for manufacturing a polarizing plate having a polarizing element and a transparent protective film.
A water content adjusting step for adjusting the water content of the polarizing element so that the water content is equal to or higher than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 30% and equal to or lower than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 50%.
A laminating step of laminating the polarizing element and the transparent protective film,
A method for producing a polarizing plate. The method for manufacturing a polarizing plate according to claim 2.
A method for manufacturing a polarizing plate having a polarizing element and a transparent protective film.
A water content adjusting step for adjusting the water content of the polarizing plate so that the water content is equal to or higher than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 30% and equal to or lower than the equilibrium water content at a temperature of 20 ° C. and a relative humidity of 50%.
A laminating step of laminating the polarizing element and the transparent protective film,
A method for producing a polarizing plate.