TW202239605A - Polarizing plate and image display device - Google Patents

Abstract

The present invention provides a polarizing plate in which reduction in transmittance in a high temperature environment is suppressed. Provided is 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 laminated on at least one surface of the polarizing element, wherein the polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing a urea-based compound and a cyclodextrin, wherein the urea-based compound is at least one selected from the group consisting of urea, urea derivative, thiourea and a thiourea derivative.

Description

Polarizing plate and image display device

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

Liquid crystal display devices (LCD) are not only used in LCD TVs, but are also widely used in portable applications such as computers and mobile phones, and automotive applications such as car navigation. Usually, a liquid crystal display device has a liquid crystal panel with a polarizing plate attached to both sides of the liquid crystal cell with an adhesive (pressure-sensitive adhesive), and the liquid crystal panel controls the light from the backlight to display. In recent years, like liquid crystal display devices, organic EL display devices have been widely used in portable applications such as televisions and mobile phones, and in vehicle applications such as car navigation systems. In an organic EL display device, external light is reflected on a metal electrode (cathode) and viewed as a mirror. In order to suppress this situation, a circular polarizing plate (with a polarizing element and a λ /4 laminates).

As mentioned above, opportunities for polarizing plates to be mounted in automobiles as components of image display devices such as liquid crystal display devices and organic EL display devices are increasing. Compared with portable applications such as TVs and mobile phones, polarizers used in automotive image display devices are more often exposed to high-temperature environments, so it is more required that the characteristics change at high temperatures be small (high-temperature durability).

On the other hand, in order to prevent damage to the image display panel due to impact from the outer surface, a front panel such as a transparent resin plate or glass plate (also called a "window layer") is additionally provided on the viewing side of the image display panel. (window layer)) composition. Image display devices with touch panels are widely used in A touch panel is provided on the viewing side of the image display panel, and a front panel is provided on the viewing side of the touch panel.

In this configuration, if there is an air layer between the image display panel and a transparent member such as a front panel or a touch panel, glare of external light will be generated due to light reflection at the interface of the air layer, and the visibility of the screen may be reduced. tendency. Therefore, it is often used to fill the space between the polarizer and the transparent member arranged on the viewing side surface of the image display panel with a layer other than the air layer, usually with a solid layer (hereinafter sometimes referred to as "interlayer filler"). The composition (hereinafter sometimes referred to as "interlayer filling composition"). The interlayer filler is preferably a material having a refractive index close to that of the polarizing plate or the transparent member. An adhesive or UV-curable adhesive is used as an interlayer filler for the purpose of suppressing deterioration of visibility due to reflection at the interface and bonding and fixing each member (for example, refer to Patent Document 1).

The interlayer filling structure is widely used in portable applications such as mobile phones, which are mostly used outdoors. In addition, in recent years, due to the increasing requirements for visibility, car navigation devices and other automotive applications have also been reviewed and used to arrange the front transparent plate on the surface of the image display panel, and fill the interlayer between the panel and the front transparent plate with an adhesive layer. filling composition.

However, it has been pointed out that when this structure is adopted, the transmittance of the polarizing plate in a high-temperature environment will be significantly reduced. In Patent Document 2, as a solution to the problem, it is proposed to reduce the water content per unit area of the polarizing plate to a certain amount or less, and to reduce the saturated water absorption of the transparent protective film adjacent to the polarizer to a certain amount or less, thereby suppressing the The method of reducing the transmittance.

[Prior Art Literature]

[Patent Document]

Patent Document 1: Japanese Patent Application Laid-Open No. 11-174417.

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2014-102353.

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

The present invention provides polarizing plates and image display devices exemplified below.

[1] A polarizing plate comprising a polarizing element in which a polyvinyl alcohol-based resin layer adsorbs an aligned dichroic dye, and a transparent protective film laminated on at least one side of the polarizing element,

The aforementioned polarizing element and the aforementioned transparent protective film are attached by an adhesive layer, and the adhesive layer is formed of an adhesive containing a urea-based compound and a cyclodextrin,

The aforementioned urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives.

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

[3] The polarizing plate according to [1] or [2], wherein the adhesive contains a polyvinyl alcohol-based resin.

[4] The polarizing plate according to [3], wherein in the adhesive, the content of the urea-based compound is 0.1 to 400 parts by mass based on 100 parts by mass of the polyvinyl alcohol-based resin.

[5] The polarizing plate according to [3] or [4], wherein the content of the cyclodextrin in the adhesive is 1 part by mass to 50 parts by mass based on 100 parts by mass of the polyvinyl alcohol-based resin the following.

[6] The polarizing plate according to any one of [1] to [5], wherein the adhesive layer has a thickness of not less than 0.01 μm and not more than 7 μm.

[7] The polarizing plate according to any one of [1] to [6], wherein the cyclodextrins are selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin At least one of the groups of .

[8] The polarizing plate according to any one of [1] to [7], wherein the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and the temperature is 20°C and the relative humidity is 50%. % below the equilibrium moisture content.

[9] The polarizing plate according to any one of [1] to [7], wherein the polarizing plate has a moisture content equal to or higher than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and a temperature of 20°C and a relative humidity of 50%. % below the equilibrium moisture content.

[10] The polarizing plate according to any one of [1] to [9], wherein the polarizing plate is used in an image display device,

In the aforementioned image display device, both surfaces of the aforementioned polarizing plate are provided in contact with a solid layer.

[11] An image display device comprising an image display unit, a first adhesive layer laminated on the viewing side surface of the image display unit, and a layer such as [ The polarizing plate according to any one of 1] to [10].

[12] The image display device according to [11], further comprising a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the viewing side surface of the second adhesive layer .

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

[14] The image display device according to [12], wherein the transparent member is a touch panel.

According to the present invention, a polarizing plate having improved high-temperature durability can be provided. According to the present invention, it is possible to provide a polarizing plate capable of suppressing decrease in transmittance due to high temperature even when used in an image display device having an interlayer filling structure. In addition, an image display device can be provided which can suppress the decrease in transmittance in a high-temperature environment by using the polarizing plate of the present invention.

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

[polarizer]

The polarizing plate of this embodiment has a polarizing element in which an alignment dichroic dye is adsorbed to a layer containing a polyvinyl alcohol-based resin, and a transparent protective film. The polarizer and the transparent protective film are bonded together through an adhesive layer formed of an adhesive containing urea-based compounds and cyclodextrins. The polarizing plate of this embodiment preferably has at least one of the following features (a) and (b).

(a) The moisture content of the polarizing element is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

(b) The moisture content of the polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

Conventionally, a polarizing plate excellent in high-temperature durability is known, for example, a polarizing plate in which a decrease in transmittance is suppressed even if the polarizing plate is left alone in an environment at a temperature of 95° C. for 1000 hours. However, even this kind of polarizer, when used in the interlayer filling structure, if it is left for 240 hours in an environment at a temperature of 105°C, a significant decrease in the transmittance and polarization degree will be observed at the center of the polarizer surface. In the image display device, one side of the polarizer is attached to the image display unit, and the other side is attached to a transparent member such as a touch panel or a front panel. Combined with the interlayer filling configuration, when the image display device is exposed to a high temperature environment, the transmittance and polarization degree of the polarizing plate in the high temperature environment are particularly likely to be significantly reduced.

The polarizing plate whose transmittance is significantly reduced due to the interlayer filling is around 1100cm ^-1 (derived from =CC=bond) and 1500cm ^-1 (derived from -C=C-bond) in Raman spectrometry It has a peak, so it is considered to form a polyene structure (-C=C) _n -. The polyene structure is estimated to be produced by dehydration of polyvinyl alcohol constituting the polarizing element (Patent Document 2, paragraph [0012]).

The polarizing plate of the present invention can further improve high temperature durability. The polarizing plate of the present invention is assembled in an image display device composed of interlayer filling, and even if it is exposed to a high-temperature environment with a temperature of 105° C., it can suppress the decrease in transmittance and polarization degree.

<Polarizer>

A known polarizing element can be used for the polarizing element in which an alignment dichroic dye is adsorbed on a layer containing polyvinyl alcohol (hereinafter also referred to as "PVA") resin (hereinafter also referred to as "PVA-based resin layer"). Examples of the polarizing element include: a stretched film obtained by dyeing a PVA-based resin film with a dichroic dye and stretching it uniaxially; The coating liquid is formed, using the laminated film, the coated layer is dyed with a dichroic dye, and the laminated film is uniaxially stretched to obtain a stretched layer. The stretching may be performed after dyeing with a dichroic dye, may be stretched while dyeing, or may be dyed after stretching.

PVA-based resin is obtained by saponifying polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include copolymers of vinyl acetate and other monomers copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The degree of saponification of the PVA-based resin is preferably at least 85 mol%, more preferably at least 90 mol%, and more preferably at least 99 mol% and not more than 100 mol%. The degree of polymerization of the PVA-based resin is, for example, not less than 1,000 and not more than 10,000, preferably not less than 1,500 and not more than 5,000. PVA-based resins can be modified, such as polyvinyl formal, polyvinyl acetal, and polyvinyl butyral modified with aldehydes.

The thickness of the polarizing element is preferably from 3 μm to 35 μm , more preferably from 4 μm to 30 μm , and still more preferably from 5 μm to 25 μm . The thickness of the polarizing element is less than 35 μm , thereby suppressing the effect of polyeneization of the PVA-based resin on the reduction of optical properties in a high-temperature environment. The thickness of the polarizing element is 3 μm or more, thereby making it easy to achieve the desired optical characteristics.

The polarizing element preferably contains urea compounds and cyclodextrins. In this embodiment, the polarizer and the transparent protective film are bonded by an adhesive layer. The adhesive layer is formed of an adhesive containing a urea-based compound and a cyclodextrin. Therefore, it is assumed that a part of the urea-based compound A part of the cyclodextrins is transferred from the adhesive layer and contained in the polarizing element. The urea compounds and cyclodextrins in the polarizing element may also include those added during the manufacturing process of the polarizing element. Equipped with a polarizing element containing urea compounds and cyclodextrins, even if the polarizing plate is exposed to a high temperature environment, the transmittance is not easily reduced. Furthermore, by providing an adhesive layer containing a urea-based compound and cyclodextrins, even when the polarizing plate is exposed to a high-temperature environment, it is possible to suppress a decrease in the degree of polarization. When two polarizers are arranged and used in a relationship of crossed polarizers, if the degree of polarization of the polarizers is lowered, light leakage (hereinafter also referred to as "orthogonal light leakage") is likely to occur, but according to this embodiment , Even if exposed to high temperature environment, the degree of polarization is not easy to decrease, so it is easy to suppress the orthogonal light leakage. The reason for exhibiting this effect is presumably that the polyeneization of the PVA-based resin is suppressed by the urea-based compound and cyclodextrins contained in the polarizing element.

The method of containing urea-based compounds and cyclodextrins in the polarizing element includes: a method of impregnating the PVA-based resin layer in a treatment solvent containing urea-based compounds and/or cyclodextrins; or spraying on the PVA-based resin layer, The method of flowing down or dripping the treatment solvent.

Among them, a method of impregnating the PVA-based resin layer with a treatment solvent containing both urea-based compounds and cyclodextrins is preferable.

The step of impregnating the PVA-based resin layer in the treatment solvent containing urea-based compounds and cyclodextrins can be carried out simultaneously with the steps of swelling, extending, dyeing, cross-linking, and washing in the manufacturing method of the polarizing element described later, or can be carried out in conjunction with the and other steps are set separately. The step of containing urea compounds and cyclodextrins in the PVA-based resin layer is preferably performed after dyeing the PVA-based resin layer with iodine, more preferably simultaneously with the crosslinking step after dyeing. According to the method, the hue change can be reduced, and the influence on the optical properties of the polarizing element can be reduced.

In order to contain the urea-based compound and the cyclodextrins in the polarizing element, both addition at the time of manufacturing the polarizing element and addition of a bonding agent may be performed. In addition, one of the urea compound and the cyclodextrin may be contained in the production of the polarizing element, and the other or both may be contained in the adhesive, or both may be contained in the production of the polarizing element, and the adhesive may contain one.

(urea compound)

The urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The urea compound can be used alone or in combination of two or more. The urea-based compound is either water-soluble or poorly water-soluble, and both can be used. When a water-soluble adhesive is used with a poorly water-soluble urea compound, it is preferable to develop a dispersion method after forming the adhesive layer so that the haze does not increase.

(urea derivatives)

A urea derivative is a compound in which at least one of the 4 hydrogen atoms of a urea molecule is substituted as a substituent. In this case, the substituent is not particularly limited, and is preferably a substituent composed of carbon atoms, hydrogen atoms, and oxygen atoms.

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

2-substituted urea includes 1,1-dimethyl urea, 1,3-dimethyl urea, 1,1-diethyl urea, 1,3-diethyl urea, 1,3-bis(hydroxymethyl urea base) urea, 1,3-tert-butyl urea, 1,3-dicyclohexyl urea, 1,3-diphenyl urea, 1,3-bis(4-methoxyphenyl) urea, 1- Acetyl-3-methylurea, 2-imidazolidinone (ethylene urea), tetrahydro-2-pyrimidinone (propylene urea).

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

(thiourea derivative)

Thiourea derivatives are compounds in which at least one of the four hydrogen atoms of the thiourea molecule is substituted as a substituent. In this case, the substituent is not particularly limited, and is preferably a substituent composed of carbon atoms, hydrogen atoms, and oxygen atoms.

Specific examples of thiourea derivatives include N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, and cyclohexylthiourea. , N-acetylthiourea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N- (2-methoxyphenyl)thiourea, N-(1-naphthyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, p-tolylthiourea.

Examples of 2-substituted thiourea include 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3 -Dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N'-diphenylthiourea, 1 ,3-bis(o-tolyl)thiourea, 1,3-bis(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N -Allyl-N'-(2-hydroxyethyl)thiourea, ethylenethiourea.

Examples of 3-substituted thiourea include trimethylthiourea, and examples of 4-substituted thiourea include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

When used in an image display device composed of interlayer filling, from the viewpoint of suppressing the decrease in transmittance in a high temperature environment and reducing the degree of polarization (suppressing orthogonal light leakage), among urea-based compounds, urea derivatives or Thiourea derivatives, more preferably urea derivatives. Among the urea derivatives, mono-substituted urea or di-substituted urea is preferred, and mono-substituted urea is more preferred. The 2-substituted urea includes 1,1-substituted urea and 1,3-substituted urea, more preferably 1,3-substituted urea.

(cyclodextrins)

Cyclodextrins are non-reducing cyclic oligosaccharides in which glucose is cyclically bonded by α- 1,4 linkages. The greater the number of glucose constituting cyclodextrins, the larger the inner diameter of the cavity in the molecule. The cyclodextrins used in the present invention are preferably composed of 6 or more glucose, for example, α , β , γ , δ -rings with 6, 7, 8, 9 glucose dextrin. Cyclodextrins include branched cyclodextrins with oligosaccharides such as glucose and maltose in branched sugar chains among α , β , γ , and δ -cyclodextrins. Cyclodextrins include alkyl groups such as methyl groups that are further bonded to the above cyclodextrins or branched cyclodextrins; 2-hydroxyethyl, 2-hydroxypropyl, 2,3-dihydroxypropyl, 2-hydroxybutyl Cyclodextrin derivatives such as hydroxyalkyl, etc. Cyclodextrins can be used alone or in combination of two or more.

(feature (a))

In the case of feature (a), the moisture content of the polarizing element is above the equilibrium moisture content at 20°C and 30% relative humidity and below the equilibrium moisture content at 20°C and 50% relative humidity. The moisture content of the polarizing element is preferably below the equilibrium moisture content at 20°C and 45% relative humidity, more preferably below the equilibrium moisture content at 20°C and 42% relative humidity, and more preferably at 20°C and 38% relative humidity % below the equilibrium moisture content. If the moisture content of the polarizing element is lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the handling properties of the polarizing element will be reduced and it will be easily broken. If the moisture content of the polarizing element is higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element will easily decrease. It is estimated that if the water content of the polarizer is higher, the polyeneization of the PVA-based resin will be easier. The water content of the polarizing element is the water content of the polarizing element in the polarizing plate.

The method of confirming whether the moisture content of the polarizing element is above the equilibrium moisture content of temperature 20°C and relative humidity of 30% and below the equilibrium moisture content of temperature of 20°C and relative humidity of 50% can include: storing the polarizing element in the adjustment The environment within the range of the above-mentioned temperature and the above-mentioned relative humidity, when there is no change in the quality of the fixed time, it is regarded as a method of balancing with the environment; or pre-calculated and adjusted to the equilibrium moisture content of the polarizing element in the environment within the above-mentioned temperature and the above-mentioned relative humidity range rate, and compare the moisture content of the polarizing element with the pre-calculated equilibrium moisture content to confirm the method.

There is no particular limitation on the manufacturing method of the polarizing element whose moisture content is above the equilibrium moisture content at 20°C and relative humidity of 30% and below the equilibrium moisture content at 20°C and relative humidity of 50%. For example, adjusting the polarizing element to The method of storing in the environment of the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes to 3 hours, or the method of heat treatment at 30°C to 90°C.

Another preferred method of manufacturing a polarizing element with the above moisture content can be listed as follows: a laminated body of a protective film layered on at least one side of the polarizing element, or a polarizing plate composed of a polarizing element, is adjusted to the above-mentioned temperature and the above-mentioned relative humidity. The method of storing in the environment within the scope of 10 minutes to 120 hours, or The method of heat treatment at 30°C to 90°C. When making an image display device that uses interlayer filling, assemble the polarizer into the image display device, and store the image display device assembled with the polarizer in an environment adjusted to the above-mentioned temperature and relative humidity range for 10 minutes The front panel is bonded after heating for the above 3 hours or less, or at 30°C to 90°C.

The moisture content of the polarizing element is preferably adjusted so that the moisture content of the polarizing element alone falls within the above numerical range, or the laminate of the polarizing element and the protective film is used to make the moisture content of the polarizing plate within the above numerical range. way to adjust. When the water content is adjusted after the polarizing plate is formed, the curl becomes too large, and defects tend to occur when bonding to an image display unit. By adjusting the polarizing element so that the above moisture content is achieved at the material stage before forming the polarizing plate, and constituting the polarizing plate using the polarizing element, a polarizing plate having a polarizing element having a moisture content satisfying the above numerical range can be easily constructed. In the state where the polarizing plate is bonded to the image display unit, the moisture content of the polarizing element in the polarizing plate can be adjusted so that it becomes the above-mentioned numerical range. At this time, since the polarizing plate is bonded to the image display unit, curling is less likely to occur.

(feature (b))

In the case of feature (b), the moisture content of the polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. The moisture content of the polarizing plate is preferably below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%, more preferably below the equilibrium moisture content of a temperature of 20°C and a relative humidity of 42%, and even more preferably at a temperature of 20°C and a relative humidity of 38 % below the equilibrium moisture content. If the moisture content of the polarizing plate is lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the handling properties of the polarizing element will be reduced and it will be easily broken. If the moisture content of the polarizing plate is higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element will easily decrease. It is estimated that if the moisture content of the polarizing plate is higher, the polyeneization of the PVA-based resin will be easier.

The method of confirming whether the moisture content of the polarizing plate is above the equilibrium moisture content of temperature 20°C and relative humidity of 30% and below the equilibrium moisture content of temperature of 20°C and relative humidity of 50% can include: storing the polarizing plate in a conditioning The environment within the range of the above-mentioned temperature and the above-mentioned relative humidity, when there is no mass change for a fixed time, it is regarded as a method of balancing with the environment; or pre-calculated to adjust the equilibrium moisture content of the polarizing plate adjusted to the environment within the above-mentioned temperature and the above-mentioned relative humidity range , and compare the moisture content of the polarizing plate with the pre-calculated equilibrium moisture content to confirm the method.

There is no particular limitation on the method of manufacturing a polarizing plate with a moisture content above the equilibrium moisture content at 20°C and relative humidity of 30% and below the equilibrium moisture content at 20°C and relative humidity of 50%. For example, adjusting the polarizing plate to The method of storing in the environment of the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes to 3 hours, or the method of heat treatment at 30°C to 90°C.

When making an image display device that uses interlayer filling, assemble the polarizer into the image display device, and store the image display device assembled with the polarizer in an environment adjusted to the above-mentioned temperature and relative humidity range for 10 minutes The front panel is bonded after heating for the above 3 hours or less, or at 30°C to 90°C.

(Manufacturing method of polarizing element)

The manufacturing method of the polarizing element is not particularly limited, but is typically: a method in which a PVA-based resin film wound in a roll shape is sent out in advance, and then stretched, dyed, cross-linked, etc. (hereinafter referred to as "manufacturing method 1") ); or a method in which a coating solution containing a PVA-based resin is coated on a base film to form a PVA-based resin layer of the coating layer, and the resulting laminate is extended (hereinafter referred to as "manufacturing method 2").

Manufacturing method 1 can go through the steps of uniaxially stretching the PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye such as iodine and adsorbing the dichroic dye, and absorbing the dichroic dye. The PVA-based resin film is produced by a step of treating with an aqueous solution of boric acid and a step of washing with water after the treatment with an aqueous solution of boric acid.

The swelling step is a treatment step of immersing the PVA-based resin film in a swelling bath. Stains and sealants on the surface of the PVA-based resin film can be removed by the swelling step, and the PVA-based resin film can be swelled, thereby suppressing uneven dyeing. Swelling baths usually use water, distilled water, pure water and other media with water as the main component. Surfactant, alcohol, etc. can be suitably added to a swelling bath according to a normal method. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide can be used in the swelling bath. At this time, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and more preferably 1.0% by mass or less. 0.5% by mass or less.

The temperature of the swelling bath is preferably above 10°C and below 60°C, more preferably above 15°C and below 45°C, and more preferably above 18°C and below 30°C. The swelling degree of the PVA-based resin film will be affected by the temperature of the swelling bath, so the immersion time of the swelling bath cannot be determined uniformly, preferably between 5 seconds and 300 seconds, more preferably between 10 seconds and 200 seconds, and more preferably between 10 seconds and 200 seconds More than 20 seconds and less than 100 seconds. The swelling step may be performed only once, or may be performed multiple times as necessary.

The dyeing step is a treatment step of immersing the PVA-based resin film in a dyeing bath (iodine solution), which can absorb and orient dichroic pigments such as iodine on the PVA-based resin film. The iodine solution is generally preferably an aqueous iodine solution, containing iodide as iodine and a dissolution aid. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among these, potassium iodide is preferable from the viewpoint of controlling the content rate of potassium in the polarizing element.

The concentration of iodine in the dyeing bath is preferably from 0.01% by mass to 1% by mass, more preferably from 0.02% by mass to 0.5% by mass. The concentration of iodide in the dyeing bath is preferably from 0.01% by mass to 10% by mass, more preferably from 0.05% by mass to 5% by mass, still more preferably from 0.1% by mass to 3% by mass.

The temperature of the dyeing bath is preferably from 10°C to 50°C, more preferably from 15°C to 45°C, and more preferably from 18°C to 30°C. The degree of dyeing of the PVA resin film will be affected by the temperature of the dyeing bath, so the immersion time of the dyeing bath cannot be determined uniformly. It is preferably between 10 seconds and 300 seconds, and more preferably between 20 seconds and 240 seconds. The dyeing step may be carried out only once, or may be carried out a plurality of times if necessary.

The cross-linking step is a treatment step in which the PVA-based resin film dyed in the dyeing step is immersed 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, and iodine Molecules or dye molecules are adsorbed to this cross-linked structure. The boron compound may, for example, be boric acid, borate, borax or the like. The crosslinking bath is generally an aqueous solution, but may also be a mixed solution of an organic solvent having miscibility with water and water. From the viewpoint of controlling the content of potassium in the polarizer, the crosslinking bath preferably contains potassium iodide.

The concentration of the boron compound in the crosslinking bath is preferably from 1% by mass to 15% by mass, more preferably from 1.5% by mass to 10% by mass, still more preferably from 2% by mass to 5% by mass. When potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably from 1 mass % to 15 mass %, more preferably from 1.5 mass % to 10 mass %, and more preferably from 2 mass % to 5 mass % the following.

The temperature of the crosslinking bath is preferably above 20°C and below 70°C, more preferably above 30°C and below 60°C. The degree of cross-linking of the PVA-based resin film will be affected by the temperature of the cross-linking bath, so the immersion time in the cross-linking bath cannot be determined uniformly. It is preferably between 5 seconds and 300 seconds, and more preferably between 10 seconds and 200 seconds.

The crosslinking step may be carried out only once, or may be carried out a plurality of times as necessary.

The stretching step is a processing step of stretching the PVA-based resin film at a specific ratio in at least one direction. Generally, a PVA-type resin film is uniaxially stretched in a conveyance direction (longitudinal direction). The stretching method is not particularly limited, and a wet stretching method or a dry stretching method can be used. The elongation step may be carried out only once, or may be carried out a plurality of times as necessary. The extending step can be performed at any stage in the manufacture of the polarizer.

As the treating bath (stretching bath) in the wet stretching method, a solvent such as water or a mixed solution of an organic solvent having miscibility with water and water can generally be used. From the viewpoint of controlling the potassium content in the polarizer, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably from 1 mass % to 15 mass %, more preferably from 2 mass % to 10 mass %, and more preferably from 3 mass % to 6 mass %. From the viewpoint of suppressing film breakage during stretching, the treatment bath (stretching bath) may contain a boron compound. When a boron compound is contained, the concentration of the boron compound in the stretching bath is preferably from 1 mass % to 15 mass %, more preferably from 1.5 mass % to 10 mass %, still more preferably from 2 mass % to 5 mass %.

The temperature of the stretching bath is preferably from 25°C to 80°C, more preferably from 40°C to 75°C, and more preferably from 50°C to 70°C. The degree of stretching of the PVA-based resin film will be affected by the temperature of the stretching bath, so the immersion time of the stretching bath cannot be determined uniformly. It is preferably between 10 seconds and 800 seconds, and more preferably between 30 seconds and 500 seconds. 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 crosslinking 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. Also, the dry stretching method can be carried out together with the drying step.

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

The washing step is a treatment step of immersing the polyvinyl alcohol-based resin film in a washing bath to remove foreign matter remaining on the surface of the polyvinyl alcohol-based resin film. Cleaning baths usually use water, distilled water, pure water and other media with water as the main component. Also, from the viewpoint of controlling the content of potassium in the polarizing element, potassium iodide is preferably used in the cleaning bath. At this time, the concentration of potassium iodide in the cleaning bath is preferably 1% by mass or more. % by mass, more preferably not less than 1.5% by mass and not more than 4% by mass, more preferably not less than 1.8% by mass and not more than 3.8% by mass.

The temperature of the cleaning bath is preferably from 5°C to 50°C, more preferably from 10°C to 40°C, and more preferably from 15°C to 30°C. The degree of cleaning of the PVA resin film will be affected by the temperature of the cleaning bath, so the immersion time of the cleaning bath cannot be determined uniformly. It is preferably between 1 second and 100 seconds, and more preferably between 2 seconds and 50 seconds. More preferably, it is not less than 3 seconds and not more than 20 seconds. The washing step may be performed only once, or may be performed a plurality of times as necessary.

The drying step is a step of drying the PVA-based resin film washed in the washing step to obtain a polarizing element. Drying can be performed by any appropriate method, and examples thereof include natural drying, air drying, and heat drying.

Production method 2 can go through the steps of applying a coating liquid containing PVA-based resin on the base film, the step of uniaxially stretching the obtained laminated film, and dyeing the PVA-based resin layer of the uniaxially stretched laminated film with a dichroic pigment. It is produced by the step of adsorbing and forming a polarizing element, the step of treating the film adsorbed with a dichroic dye with an aqueous solution of boric acid, and the step of washing with water after the treatment with an aqueous solution of boric acid. The base film used to form the polarizer can be used as a protective layer of the polarizer. The base film can be peeled and removed from the polarizing element as needed.

<Transparent protective film>

The transparent protective film (hereinafter referred to simply as "protective film") used in this embodiment is pasted on at least one side of the polarizing element through the adhesive layer. The transparent protective film is pasted on one or both sides of the polarizer, preferably on both sides.

The protective film may have other optical functions at the same time, and may also form a laminated structure of a plurality of layers. From the viewpoint of optical properties, the film thickness of the protective film is preferably thinner, but if it is too thin, the strength will decrease low and poor workability. An appropriate film thickness is not less than 5 μm and not more than 100 μm, preferably not less than 10 μm and not more than 80 μm, more preferably not less than 15 μm and not more than 70 μm.

As the protective film, cellulose acylate films, films made of polycarbonate resins, films made of cycloolefin resins such as norcamphene, (meth)acrylic polymer films, polyethylene terephthalate films, etc., can be used. Films such as polyester resin films such as diesters. When a water-based adhesive such as PVA adhesive is used to attach a protective film to both sides of the polarizer, it is preferable that the protective film on at least one side is a cellulose acylate film or (meth)acrylic acid from the viewpoint of moisture permeability. It is any one of polymer films, among which cellulose acylate film is more preferable.

At least one protective film can have a phase difference function for purposes such as viewing angle compensation. In this case, the protective film itself may have a retardation function, may have a retardation layer separately, or may be a combination of both. The film with retardation function can be directly bonded to the polarizing element through an adhesive, but it can also be bonded through an adhesive or an adhesive through another protective film bonded to the polarizing element.

<Adhesive layer>

The adhesive layer is used to attach the protective film to the polarizer, and the adhesive constituting the adhesive layer uses an adhesive containing urea-based compounds and cyclodextrins. As the adhesive, water-based adhesives, solvent-based adhesives, and active energy ray-curable adhesives can be used. Water-based adhesives are preferred, and PVA-based resins are preferred. By using an adhesive containing a urea-based compound and a cyclodextrin, the decrease in transmittance in a high-temperature environment of a polarizing plate can be suppressed.

The thickness at the time of applying the adhesive can be set to any value, for example, it can be set so that an adhesive layer having a desired thickness can be obtained after hardening or heating (drying). The thickness of the adhesive layer formed by the adhesive is preferably from 0.01 μm to 7 μm, more preferably from 0.01 μm to 5 μm, more preferably from 0.01 μm to 2 μm, most preferably from 0.01 μm to 1 μm.

In the following description about the adhesive agent, the case where the polarizing element does not contain urea-based compounds and cyclodextrins when manufacturing the polarizing element is described as a preferable range. When the polarizing element contains urea compounds or cyclodextrins, the following values may be appropriately adjusted. Specific examples of urea-based compounds and cyclodextrins can be directly applied to the examples of urea-based compounds and cyclodextrins contained in the polarizing element described above. When bonding the polarizer and the protective film, a part of the urea-based compound and a part of the cyclodextrins can move from the adhesive layer to the polarizer and the like during the drying process to form the adhesive layer.

When the adhesive is a water-based adhesive containing PVA-based resin, the content of the urea-based compound is preferably from 0.1 to 400 parts by mass, more preferably from 1 to 200 parts by mass, relative to 100 parts by mass of the PVA-based resin. Furthermore, it is more preferably 3 parts by mass or more and 100 parts by mass or less. When it is less than 0.1 parts by mass, the effect of suppressing polyene formation of a polarizing element in a high-temperature environment may not be sufficient. On the other hand, when it exceeds 400 parts by mass, urea may precipitate after producing a polarizing plate to increase haze.

When the adhesive is a water-based adhesive containing PVA-based resin, the content of cyclodextrins is preferably from 1 part by mass to 50 parts by mass, more preferably from 1.5 parts by mass to 40 parts by mass, based on 100 parts by mass of PVA-based resin At most, it is more preferably at least 2 parts by mass and at most 35 parts by mass. When it is less than 0.1 parts by mass, the effect of suppressing polyene formation of a polarizing element in a high-temperature environment may not be sufficient. On the other hand, when it exceeds 50 parts by mass, cyclodextrins may precipitate after producing a polarizing plate.

In the configuration in which the transparent protective film is pasted on both sides of the polarizing element through the adhesive layer, if the polarizing element is not treated to contain urea compounds and cyclodextrins, the adhesive layer on both sides of the polarizing element may be only a single The surface adhesive layer is a layer containing a urea-based compound and a cyclodextrin, and it is preferable that the adhesive layers on both sides are layers containing a urea-based compound and a cyclodextrin.

In response to the requirement of thinning the polarizing plate, a polarizing plate with a transparent protective film on only one side of the polarizing element was developed. In this composition, an adhesive layer containing urea-based compounds and cyclodextrins is also used And laminated transparent protective film. As a method of manufacturing the polarizing plate with a transparent protective film on only one side of the polarizing element, there is a method of first attaching a transparent protective film to both sides through an adhesive layer to produce a polarizing plate, and then peeling off a transparent protective film. When this production method is used, only one of the adhesive layers may contain the urea-based compound and cyclodextrins, but it is preferable that the adhesive layers on both sides are layers containing the urea-based compound and the cyclodextrins. When only one adhesive layer contains a urea-based compound and cyclodextrins, it is preferable that the adhesive layer on the side of the unpeeled film contains a urea-based compound and cyclodextrins.

(water-based adhesive)

Any suitable water-based adhesive can be used as the water-based adhesive, and it is preferable to use a water-based adhesive containing PVA-based resin (PVA-based adhesive). From the viewpoint of adhesion, the average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably from 100 to 5,500, more preferably from 1,000 to 4,500. From the viewpoint of adhesion, the average degree of saponification is preferably from 85 mol % to 100 mol %, more preferably from 90 mol % to 100 mol %.

The PVA-based resin contained in the water-based adhesive is preferably one containing an acetoacetyl group, because the PVA-based resin layer has excellent adhesion to the protective film and excellent durability. The PVA-type resin containing an acetoacetyl group can be obtained by reacting PVA-type resin and diacetone by arbitrary methods, for example. The modification degree of acetyl acetyl group of the PVA-based resin containing acetyl acetyl group is typically 0.1 mol % or more, preferably 0.1 mol % or more and 20 mol % or less. The resin concentration of the water-based adhesive is preferably from 0.1% by mass to 15% by mass, more preferably from 0.5% by mass to 10% by mass.

The water-based adhesive may also contain a crosslinking agent. As the crosslinking agent, known crosslinking agents can be used. As a crosslinking agent, a water-soluble epoxy compound, dialdehyde, isocyanate, etc. are mentioned, for example.

When the PVA-based resin is a PVA-based resin containing acetoacetyl group, the crosslinking agent is preferably any one of glyoxal, glyoxylate, and methylol melamine, more preferably glyoxal or acetaldehyde Any of acid salts, particularly preferably glyoxal.

The water-based adhesive may also contain an organic solvent. The organic solvent is preferably alcohols in terms of miscibility with water, and among alcohols, methanol or ethanol is preferable. The concentration of methanol in the water-based adhesive is preferably from 10% by mass to 70% by mass, more preferably from 15% by mass to 60% by mass, still more preferably from 20% by mass to 60% by mass. By setting the concentration of methanol to 10% by mass or more, polyeneization of the PVA-based resin in a high-temperature environment can be more easily suppressed. Moreover, deterioration of hue can be suppressed by making the content rate of methanol 70 mass % or less. Some urea derivatives have low solubility in water, but conversely have sufficient solubility in alcohol. At this time, as one of the preferable aspects, after preparing the alcohol solution of the urea compound by dissolving the urea compound in alcohol, the alcohol solution of the urea compound is added to the PVA aqueous solution to prepare an adhesive.

(Active energy ray hardening type adhesive)

Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, and examples include adhesives containing polymerizable compounds and photopolymerizable initiators, adhesives containing photoreactive resins, adhesives containing Adhesives for adhesive resins and photoreactive crosslinking agents, etc. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, photocurable urethane monomers, and oligosaccharides derived from these monomers. polymer etc. Examples of the photopolymerization initiator include compounds containing substances that generate active species by irradiation with active energy rays such as ultraviolet rays. The active species include neutral radicals, anion radicals, cationic radicals, and the like.

<Layer containing urea compound>

The urea-based compound and cyclodextrins are not limited to being included in the above-mentioned adhesive layer, and may be included in other layers than the adhesive layer from the viewpoint of improving the high-temperature durability of the polarizing plate. In a polarizing plate having a transparent protective film on only one side, a hardened layer may be formed on the surface of the polarizing element opposite to the transparent protective film from the viewpoint of improving physical strength.

In this embodiment, a urea-based compound-containing layer may be formed by containing a urea-based compound and cyclodextrins in the hardened layer as described above. Usually, the cured layer is formed from a curable composition containing an organic solvent, but paragraphs [0020] to [0042] of JP-A-2017-075986 describe an aqueous solution of an active energy ray-curable polymer composition. A method of forming the hardened layer. Water-soluble urea-based compounds and cyclodextrins may also be contained in the composition.

The layer containing a urea-based compound preferably has at least one urea-based compound, at least one cyclodextrin, and a binder. Examples of the binder include polymer binders, thermosetting resin binders, and active energy ray-curable resin binders, and any binder can be preferably used.

The thickness of the layer containing the urea compound is preferably from 0.1 μm to 20 μm , more preferably from 0.5 μm to 15 μm , still more preferably from 1 μm to 10 μm .

[Manufacturing method of polarizing plate]

The manufacturing method of the polarizing plate of this embodiment may include a moisture content adjustment step and a layering step. In the moisture content adjustment step, when manufacturing the polarizing plate having the feature (a), the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and at a balance of a temperature of 20°C and a relative humidity of 50%. Adjust the water content of the polarizing element in a way that the water content is lower than the water content. The moisture content of the polarizing element can be adjusted according to the above description of the moisture content of the polarizing element. In the moisture content adjustment step, when manufacturing the polarizing plate having the characteristic (b), the moisture content of the polarizing plate is not less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50% Adjust the moisture content of the polarizing plate in a way below the ratio. of polarizer The moisture content can be adjusted according to the description of the moisture content of the above-mentioned polarizing plate. In the lamination step, the polarizer and the transparent protective film are laminated through the adhesive layer. In the lamination step, for example, the polarizer that has not been treated to contain urea-based compounds and cyclodextrins is bonded to the transparent protective film with an adhesive containing urea-based compounds and cyclodextrins. The order of the moisture content adjustment step and the layer accumulation step is not limited, and the moisture content adjustment step and the layer accumulation step may be performed in parallel.

[Configuration of image display device]

The polarizing plate of this embodiment is used in various image display devices such as liquid crystal display devices and organic EL display devices. Regarding the image display device, when both sides of the polarizing plate are layers other than the air layer, specifically, interlayer filling structure in which a solid layer such as an adhesive layer is in contact, the transmittance tends to decrease in a high temperature environment. In the image display device using the polarizing plate of this embodiment, even with the interlayer filling structure, the decrease in the transmittance of the polarizing plate in a high-temperature environment can be suppressed. Examples of the image display device include an image display unit, a first adhesive layer laminated on the viewing side surface of the image display unit, and a polarizing plate laminated on the viewing side surface of the first adhesive layer. The image display device may further include a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the viewing side surface of the second adhesive layer. In particular, the polarizing plate of this embodiment is suitable for use in an image display device having the following interlayer filling structure, that is, a transparent member is arranged on the viewing side of the image display device, so that the polarizing plate and the image display unit are bonded by the first adhesion The adhesive layer is pasted together, and the polarizer and the transparent member are formed by interlayer filling through the bonding of the second adhesive layer. In this specification, either or both of the 1st adhesive layer and the 2nd adhesive layer may only be called an "adhesive layer". In addition, the member used for bonding the polarizing plate and the image display unit, and the member used for bonding the polarizing plate and the transparent member are not limited to the adhesive layer, and may be an adhesive layer.

<Image display unit>

As the image display unit, a liquid crystal unit or an organic EL unit may be mentioned. The liquid crystal cell can use any one of a reflective liquid crystal cell that utilizes external light, a transmissive liquid crystal cell that utilizes light from a light source such as a backlight, and a transflective liquid crystal cell that utilizes both external light and light from a light source. . When the liquid crystal unit utilizes light from a light source, in an image display device (liquid crystal display device), a polarizing plate is also arranged on the side opposite to the viewing side of the image display unit (liquid crystal unit), and a light source is further arranged. The polarizer on the light source side and the liquid crystal unit are preferably bonded through 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, or bend orientation (π type) can be used.

As the organic EL unit, 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 electroluminescent light emitting body).

The organic light-emitting layer is a laminate of various organic thin films. For example, a laminate of a hole injection layer composed of triphenylamine derivatives and a light-emitting layer composed of fluorescent organic solids such as anthracene, or these light-emitting layers can be used. Various layer configurations such as a laminate of an electron injection layer composed of a perylene derivative, or a laminate of a hole injection layer, a light emitting layer, and an electron injection layer.

<Adhesion of Image Display Unit and Polarizer>

An adhesive layer (adhesive sheet) is suitably used for bonding the image display unit and the polarizing plate. Among them, a method of bonding a polarizing plate with an adhesive layer attached to one surface of the polarizing plate and an image display unit is preferred from the viewpoint of workability and the like. An adhesive layer can be attached to the polarizing plate in an appropriate manner. Examples thereof include the method of dissolving or dispersing the base polymer or its composition in a solvent composed of a suitable solvent such as toluene or ethyl acetate alone or in a mixture to prepare an adhesiveness of 10% by mass to 40% by mass. solution, and the adhesive solution is directly attached to the polarizing plate in an appropriate way such as casting or coating; or an adhesive layer is formed on the separator, and the adhesive layer is transferred and adhered to the polarizing plate. way etc.

<Adhesive layer>

The adhesive layer may be composed of one layer or two or more layers, preferably one layer. The adhesive layer can be composed of an adhesive composition mainly composed of (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, and polyvinyl ether resin. Among them, an adhesive composition using a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is preferable. The adhesive composition may be an active energy ray curing type or a thermosetting type.

The (meth)acrylic resin (base polymer) used in the adhesive composition is suitable to use butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, (meth) A polymer or copolymer of one or more (meth)acrylates such as 2-ethylhexyl acrylate as a monomer. It is preferable to copolymerize a polar monomer in a base polymer. Examples of polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, (meth)acrylic acid N , N-dimethylaminoethyl ester compound, glycidyl (meth)acrylate compound and other monomers having carboxyl group, hydroxyl group, amido group, amino group, epoxy group, etc.

The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. The crosslinking agent can be, for example, a metal ion having a valence of two or more and forming a metal carboxylate salt with a carboxyl group, a polyamine compound forming an amide bond with a carboxyl group, and a polyamine compound forming an ester bond with a carboxyl group. Epoxy compounds or polyols, polyisocyanate compounds that form amide bonds with carboxyl groups. Among them, polyisocyanate compounds are preferred.

The active energy ray-curable adhesive composition has the property of being cured by being irradiated with active energy rays such as ultraviolet rays or electron rays, and has adhesiveness even before irradiating active energy rays, and can be adhered to a substrate such as a film, And it has the property of being hardened by irradiating active energy rays and can adjust the adhesion force. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. Active energy ray hardening adhesive The composition further contains an active energy ray polymerizable compound in addition to a base polymer and a crosslinking agent. A photopolymerization initiator, a photosensitizer, etc. may be contained as needed.

The adhesive composition may contain fine particles, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, adhesiveness imparting agents, fillers (metal powder or other inorganic powders, etc.) for imparting light scattering properties. ), antioxidants, UV absorbers, dyes, pigments, colorants, defoamers, anti-corrosion agents, photopolymerization initiators and other additives.

An adhesive layer can be formed by coating the above-mentioned organic solvent dilution of the adhesive composition on the substrate film, the image display unit or the surface of the polarizing plate and drying it. The base film is generally a thermoplastic resin film, and a typical example thereof is a separation film subjected to mold release treatment. The separation membrane can be, for example, coated with polysiloxane on the adhesive layer formation surface of the membrane (which is composed of resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate). Handling and other release handlers.

The adhesive composition can be directly coated on the release-treated surface of the separation film to form an adhesive layer, and then the adhesive layer with the separation film can be laminated on the surface of the polarizer. It is also possible to directly coat the adhesive composition on the surface of the polarizing plate to form an adhesive layer, and then lay a separation film on the outside of the adhesive layer.

When the adhesive layer is arranged on the surface of the polarizing plate, it is preferable to perform surface activation treatment such as plasma treatment and corona treatment on the bonding surface of the polarizing plate and/or the bonding surface of the adhesive layer, and it is more preferable to perform corona treatment .

In addition, an adhesive sheet (which is formed by coating an adhesive composition on a second separation membrane to form an adhesive layer, and then a separation membrane is laminated on the formed adhesive layer) can be prepared, and the second separation membrane can be peeled off from the adhesive sheet. The final adhesive layer with separation film is laminated on the polarizing plate. The second separation membrane is used: compared with the separation membrane, it has weaker adhesion to the adhesive layer and is easier to peel off.

The thickness of the adhesive layer is not particularly limited, for example, it is preferably 1 μm to 100 μm , more preferably 3 μm to 50 μm , and may be 20 μm or more.

<transparent component>

Examples of the transparent member arranged on the viewing side of the image display device include a transparent plate (window layer) or a touch panel. The transparent board is a transparent board with appropriate mechanical strength and thickness. The transparent plate may, for example, be a transparent resin plate such as polyimide resin, acrylic resin or polycarbonate resin, or a glass plate. Functional layers such as anti-reflection layer can be laminated on the viewing side of the transparent plate. Also, when the transparent plate is a transparent resin plate, a hard coat layer for improving physical strength or a low moisture permeability layer for reducing moisture permeability may be laminated. Various types of touch panels such as resistive film method, electrostatic capacitance method, optical method, and ultrasonic method, or glass plates or transparent resin plates with touch sensing functions can be used for the touch panel. When a capacitive touch panel is used as the transparent member, it is preferable to use a transparent plate made of glass or a transparent resin plate on the viewing side of the touch panel.

<Adhesion of polarizing plate and transparent member>

Adhesives or active energy ray-curable adhesives are suitable for bonding the polarizing plate and the transparent member. When an adhesive is used, the adhesive may be attached in an appropriate manner. The specific attaching method can be, for example, the adhesive layer attaching method used for laminating the image display unit and the polarizing plate mentioned above.

When using an active energy ray-curable adhesive, in order to prevent the diffusion of the adhesive solution before hardening, it is suitable to use a weir material that surrounds the edge of the image display panel, and place a transparent member on the weir material. The method of injecting the adhesive solution again. After injecting the adhesive solution, align and defoam if necessary, and then irradiate with active energy rays to harden.

(Example)

Hereinafter, the present invention will be specifically described based on examples. Materials, reagents, amounts of substances, ratios thereof, operations, etc. shown in the following examples can be appropriately changed within the scope not departing from the gist of the present invention.

Therefore, the present invention is not limited to the following examples.

<Production of polarizing element A>

A PVA film with a thickness of 40 μm made of PVA with an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more was prepared. This PVA film was uniaxially stretched approximately 5 times in dry type, and further immersed in pure water at 60° C. for 1 minute while maintaining tension. Thereafter, the PVA film was immersed in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.05/5/100 at 28° C. for 60 seconds. Thereafter, the PVA film was immersed in an aqueous solution with a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72° C. for 300 seconds. Next, the PVA film was washed with pure water at 26° C. for 20 seconds, and then dried at 65° C. to obtain a polarizing element A with a thickness of 15 μm in which PVA adsorbed oriented iodine. The thickness of the polarizing element was measured using a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.

<Preparation Adhesive 1 to 7>

(PVA Solution A for Adhesive Preparation)

50 g of a modified PVA-based resin containing an acetoacetyl group ("GOHSENX Z-410" manufactured by Mitsubishi Chemical Corporation) was dissolved in 950 g of pure water. The solution was heated at 90° C. for 2 hours and then cooled to normal temperature to obtain PVA solution A for adhesive.

(Prepare Adhesives 1 to 7)

Adhesives 1 to 7 were prepared by blending PVA solution A, urea compounds, cyclodextrins, and pure water so that PVA contained 3.0% by mass, and urea compounds and cyclodextrins contained the amounts shown in Table 1.

[Table 1]

<Preparation of transparent protective film A>

A commercially available cellulose acylate membrane TD40 (manufactured by FUJIFILM 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 washed with water. Thereafter, after immersing in 0.05 mol/L sulfuric acid aqueous solution at 25°C for 30 seconds, it was immersed in running water for 30 seconds and bathed in water to bring the membrane into a neutral state. Repeat the air knife draining for 3 times to drain the water, stay in a drying area at 70°C for 15 seconds and dry to obtain a saponification-treated transparent protective film A.

<Making Polarizing Plates 1 to 7>

The transparent protective film A is bonded to both surfaces of the polarizer A through the adhesive 1 . Lamination uses a roll laminating machine. This laminate was dried at 80° C. for 5 minutes to obtain a polarizing plate 1 . The coating thickness of the adhesive layer was adjusted so that the thickness after drying would be 50 nm on both sides.

In the production of the polarizing plate 1 , the adhesive 1 was changed to the adhesives 2 to 7 to obtain the polarizing plates 2 to 7 .

<Production of optical laminates 1 to 7>

An acrylic adhesive (LINTEC Co., Ltd., product number: #7) was applied to both sides of the polarizing plate 1 produced above to produce an optical laminate 1 having an adhesive layer with a thickness of 25 μm on both sides.

In producing the optical layered body 1 , the polarizing plate 1 was changed to the polarizing plates 2 to 7 to obtain the optical layered bodies 2 to 7 .

<Evaluation of high temperature durability>

(Preparation of samples for evaluation)

The optical laminates 1 to 7 were cut into a size of 50 mm×100 mm so that the absorption axis was parallel to the long side. An alkali-free glass ("EAGLE XG" manufactured by Corning Incorporated) was attached to the surface of each adhesive to prepare a sample for evaluation. In order to adjust the moisture content of the optical layered body, the optical layered body was stored for 72 hours at a temperature of 20° C. and a relative humidity of 35% before bonding the glass plates. For all samples, the weight was measured after 66 hours, 69 hours, and 72 hours of storage, and the weight did not change. It can be considered that the moisture content of the polarizing element, polarizing plate, and optical laminate has reached the equilibrium at a temperature of 20°C and a relative humidity of 35%. moisture content.

(Single transmittance evaluation after high temperature durability test (105°C))

After autoclaving the evaluation samples with optical laminates 1 to 7 at a temperature of 50°C and a pressure of 5kgf/cm ² (490.3kPa) for 1 hour, they were placed in an environment of a temperature of 23°C and a relative humidity of 55% for 24 hours . The transmittance of the optical layered body at this time was measured and used as an initial value. Thereafter, it was stored in a heating environment at a temperature of 105°C, and the transmittance was measured every 24 hours from 72 to 240 hours. Based on the time taken for the transmittance to decrease by 5% or more from the initial value, the single transmittance was evaluated using the following criteria. The results are shown in Table 2.

After 240 hours, the transmittance decreases to less than 5%: A

Those whose transmittance decreases by more than 5% within 120 to 240 hours: B

Those whose transmittance decreases by more than 5% in 72 to 120 hours: C

After 72 hours, the transmittance decreases to more than 5%: D

[Table 2]

It can be seen that compared to the polarizing plate (optical laminates 5 to 7) in which the polarizing element and the transparent protective film are bonded by an adhesive containing only one of urea-based compounds or cyclodextrins, the polarizing element and the transparent protective film are bonded together by Polarizing plates (optical laminates 1 to 4) bonded with urea-based compounds and cyclodextrin-based adhesives are less prone to decrease in transmittance even when exposed to a high-temperature environment of 105°C, and have excellent high-temperature durability.

Claims (14)

A polarizing plate comprising a polarizing element in which a dichroic dye is adsorbed on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element, The aforementioned polarizing element and the aforementioned transparent protective film are attached by an adhesive layer, and the adhesive layer is formed of an adhesive containing a urea-based compound and a cyclodextrin, The aforementioned urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The polarizing plate according to claim 1, wherein the adhesive contains at least one urea-based compound selected from the group consisting of urea derivatives and thiourea derivatives. The polarizing plate according to claim 1 or 2, wherein the adhesive contains a polyvinyl alcohol-based resin. The polarizing plate according to claim 3, wherein, in the adhesive, the content of the urea-based compound is 0.1 to 400 parts by mass relative to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate according to claim 3 or 4, wherein, in the adhesive agent, the content of the cyclodextrins is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate according to any one of claims 1 to 5, wherein the thickness of the adhesive layer is not less than 0.01 μm and not more than 7 μm . The polarizing plate according to any one of claims 1 to 6, wherein the aforementioned cyclodextrins are at least 1 species. The polarizing plate according to any one of Claims 1 to 7, wherein the moisture content of the aforementioned polarizing element is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and is an equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. the following. The polarizing plate according to any one of Claims 1 to 7, wherein the moisture content of the polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and at an equilibrium moisture content of at a temperature of 20°C and a relative humidity of 50%. the following. The polarizing plate according to any one of claims 1 to 9, wherein the aforementioned polarizing plate is used in an image display device, In the aforementioned image display device, both surfaces of the aforementioned polarizing plate are provided in contact with a solid layer. An image display device, which has an image display unit, a first adhesive layer laminated on the viewing side surface of the aforementioned image display unit, and a first adhesive layer laminated on the viewing side surface of the first adhesive layer according to claims 1 to 1. The polarizing plate according to any one of 10. The image display device according to claim 11, further comprising a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the viewing side surface of the second adhesive layer. The image display device according to claim 12, wherein the transparent member is a glass plate or a transparent resin plate. The image display device according to claim 12, wherein the transparent member is a touch panel.