WO2018038028A1

WO2018038028A1 - Polarizing plate

Info

Publication number: WO2018038028A1
Application number: PCT/JP2017/029714
Authority: WO
Inventors: 沙樹岡山; 絵美川崎; 修風藤
Original assignee: 株式会社クラレ
Priority date: 2016-08-22
Filing date: 2017-08-21
Publication date: 2018-03-01
Also published as: JPWO2018038028A1; CN109642977A; TW201811559A; TWI712496B; KR20190033603A; CN109642977B; KR102290005B1

Abstract

Provided is a polarizing plate formed by laminating a polarizing film layer and a cured product layer formed of a resin composition, wherein the polarizing plate is characterized in that: the thickness of the cured product layer is 10 μm or less; the boric acid permeation in terms of boron atoms is 2.25 g/m²∙day or less; and the cured product layer is disposed directly adjacent to at least one surface of the polarizing film layer. Due to this configuration, provided is a polarizing plate that has excellent resistance to heat and humidity and that can maintain an initial polarizing function even if the thickness of a cured product layer, which is formed of a resin composition and which is laminated on the polarizing film layer, is 10 μm or less.

Description

Polarizer

The present invention relates to a polarizing plate having a thin film and excellent heat and moisture resistance.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Conventional polarizing plates are manufactured by attaching a protective film to one or both sides of a polarizing film layer obtained by dyeing and stretching a polyvinyl alcohol film (hereinafter, “polyvinyl alcohol” may be abbreviated as “PVA”). I came.

As the protective film, a film such as triacetyl cellulose (TAC) has been widely used. In recent years, with the development of liquid crystal displays in mobile devices, there has been a demand for thin film weight reduction. From this point of view, photocurability is not applied to the surface of the polarizing film layer without providing a protective film on the polarizing film layer. A polarizing plate in which a cured product layer of a resin composition is formed has been proposed. (For example, see Patent Documents 1 to 5). However, there is a case where the polarizing performance may be deteriorated when used under high temperature and high humidity conditions, and a polarizing plate excellent in wet heat resistance has been demanded.

Special table 2013-513832 gazette JP 2011-221185 A JP-A-11-030715 JP 2004-245924 A JP 2007-334307 A

The present invention has been made to solve the above-described problems, and maintains the initial polarization performance even when the thickness of the cured product layer made of the resin composition laminated on the polarizing film layer is 10 μm or less. An object of the present invention is to provide a polarizing plate excellent in moisture and heat resistance.

As a result of intensive studies to achieve the above object, the present inventors have determined that the boric acid permeability is 2.25 g / m ² · day in terms of boron atom even when the thickness of the cured product layer is 10 μm. By laminating the following cured product layer on the polarizing film layer, it was found that the above-mentioned problems could be solved, and further studies were made based on the findings to complete the present invention.

That is, the present invention
[1] A polarizing plate in which a polarizing film layer and a cured product layer made of a resin composition are laminated,
The thickness of the cured product layer is 10 μm or less, the boric acid permeability is 2.25 g / m ² · day or less in terms of boron atom, and the cured product layer is directly adjacent to at least one surface of the polarizing film layer. Polarizing plate;
[2] The polarizing plate of the above [1], which does not have a protective film layer on the cured product layer;
[3] The polarizing plate according to the above [1] or [2], which does not have a protective film layer on the polarizing film layer on the surface opposite to the surface on which the cured product layer is laminated;
[4] The polarizing plate according to any one of [1] to [3], wherein the resin composition is a photocurable resin composition;
[5] The polarizing plate according to any one of [1] to [4], wherein the content of boric acid in the polarizing film layer is 1 to 8% by mass with respect to the polarizing film layer in terms of boron atoms;
[6] The polarizing plate according to any one of [1] to [5], wherein the polarizing film layer has a thickness of 20 μm or less;
[7] The polarizing plate according to any one of [1] to [6], wherein the entire polarizing plate has a thickness of 40 μm or less;
[8] The polarizing plate according to any one of [1] to [7], wherein a water vapor permeability of the cured product layer is 2500 g / m ² · day or less;
[9] The above-mentioned [1] to [8], wherein the layer structure is a two-layer structure of a polarizing film layer / the cured product layer, or a three-layer structure of the cured product layer / polarizing film layer / the cured product layer. Any one polarizing plate;
[10] The polarizing plate according to any one of [1] to [9], wherein the total light transmittance is 40 to 45% and the degree of polarization is 99.9% or more;
[11] The amount of change in the total light transmittance after performing a hygrothermal resistance test for 48 hours under the conditions of 60 ° C. and 90% RH is 1.5% or less, and the degree of polarization is 99.9% or more. Any one of the above polarizing plates [1] to [10];
About.

According to the present invention, there is provided a polarizing plate excellent in moisture and heat resistance capable of maintaining the initial polarization performance even when the thickness of the cured layer made of the resin composition laminated on the polarizing film layer is 10 μm or less. Can do.

It is the schematic about the method of measuring the boric acid permeability in conversion of a boron atom.

The present invention is a polarizing plate in which a polarizing film layer and a cured product layer made of a resin composition are laminated, wherein the cured product layer has a thickness of 10 μm or less, and boric acid permeability is 2. The polarizing plate is 25 g / m ² · day or less, and the cured product layer is a polarizing plate directly adjacent to at least one surface of the polarizing film layer. Even if the thickness of the cured product layer made of the resin composition laminated on the polarizing film layer is 10 μm or less, the boric acid permeability of the cured product layer is not more than 2.25 g / m ² · day, The present inventors have clarified that a polarizing plate having excellent thermal properties can be obtained. That is, the polarizing plate of the present invention is excellent in moisture and heat resistance even if it is a thin film, and can maintain the initial polarization performance.

(Polarizing film layer)
In the polarizing film layer of the present invention, a dichroic dye is adsorbed on a PVA film (typically a uniaxially stretched PVA film). Such a polarizing film layer is formed by stretching a PVA film containing a dichroic dye in advance, adsorbing a dichroic dye simultaneously with the stretching of the PVA film, or forming a matrix by stretching the PVA film. It can be produced by adsorbing a dichroic dye.

The PVA includes one of vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and isopropenyl acetate. What can be obtained by saponifying polyvinyl ester obtained by polymerizing 2 or more types can be used. Among the vinyl esters, vinyl acetate is preferable from the viewpoints of ease of production of PVA, availability, cost, and the like.

The PVA is a product obtained by converting a vinyl ester unit of a polyvinyl ester copolymer obtained by copolymerizing a vinyl ester monomer and another monomer copolymerizable therewith into a vinyl alcohol unit. May be. Examples of other monomers copolymerizable with the vinyl ester monomer include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; (meth) acrylic acid or a salt thereof; Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate; (meth) acrylamide; N-methyl (Meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acrylic (Meth) acrylamide derivatives such as amide, (meth) acrylamide propanesulfonic acid or a salt thereof, (meth) acrylamide propyldimethylamine or a salt thereof, N-methylol (meth) acrylamide or a derivative thereof; N-vinylformamide, N-vinyl N-vinylamides such as acetamide and N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc. Vinyl ether; vinyl cyanide such as (meth) acrylonitrile; halogenated vinyl such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; vinegar Allyl compounds such as allyl acid and allyl chloride; maleic acid or its salt, ester or acid anhydride; itaconic acid or its salt, ester or acid anhydride; vinylsilyl compound such as vinyltrimethoxysilane; unsaturated sulfonic acid be able to. The vinyl ester copolymer can have a structural unit derived from one or more of the other monomers described above. The other monomer may be pre-existed in the reaction vessel when the vinyl ester monomer is subjected to the polymerization reaction, or may be added to the reaction vessel during the polymerization reaction. Can be used. From the viewpoint of polarization performance, the content of units derived from other monomers is preferably 10 mol% or less, more preferably 5 mol% or less, and more preferably 2 mol% or less. Further preferred.

The degree of polymerization of the PVA is preferably in the range of 1,500 to 6,000, more preferably in the range of 1,800 to 5,000, and in the range of 2,000 to 4,000. More preferably. When the polymerization degree is 1,500 or more, the durability of the polarizing film obtained by uniaxially stretching the film can be improved. On the other hand, when the degree of polymerization is 6,000 or less, it is possible to suppress an increase in manufacturing cost, poor process passability during film formation, and the like. In this specification, the degree of polymerization of PVA means the average degree of polymerization measured according to the description of JIS K6726-1994.

The saponification degree of the PVA is preferably 95 mol% or more, more preferably 98 mol% or more, and further preferably 98.5 mol% or more from the viewpoint of the polarizing performance of the polarizing film layer. Preferably, it is 99.0 mol% or more. When the degree of saponification is less than 95 mol%, PVA is likely to be eluted during the production process of the polarizing film layer, and the eluted PVA may adhere to the film and reduce the polarizing performance of the polarizing film layer. The saponification degree of PVA in the present specification is based on the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification, and vinyl alcohol units, which PVA has. The proportion (mol%) occupied by the number of moles of the vinyl alcohol unit. The degree of saponification can be measured according to the description of JIS K6726-1994.

The PVA film may contain a plasticizer. When the PVA film contains a plasticizer, the handleability and stretchability are improved. A polyhydric alcohol is preferably used as the plasticizer, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. One or more of these plasticizers can be included. Among these, glycerin is preferable from the viewpoint of further improving the stretchability of the PVA film.

The content of the plasticizer in the PVA film is preferably 1 to 20 parts by mass, more preferably 3 to 17 parts by mass, and further preferably 5 to 15 parts by mass with respect to 100 parts by mass of PVA. preferable. When the content of the plasticizer is 1 part by mass or more, the stretchability of the PVA film is further improved. On the other hand, when the content of the plasticizer is 20 parts by mass or less, it is possible to suppress the plasticizer from bleeding out on the surface of the PVA film and reducing the handleability of the PVA film.

The PVA film further includes a filler, a processing stabilizer such as a copper compound, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, and other thermoplastics. Additives such as resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization rate retarders are required It can mix | blend suitably according to.

The thickness of the polarizing film layer in the present invention is preferably 20 μm or less. Usually, the thinner the polarizing film layer, the more easily the heat and humidity resistance is lowered, and the effect of the present invention is more remarkably exhibited for such a polarizing film layer. The thickness of the polarizing film layer is more preferably 15 μm or less, and further preferably 12 μm or less. On the other hand, when the thickness of the polarizing film layer is too thin, problems such as wrinkles and tearing are likely to occur during production. Therefore, the thickness of the polarizing film layer is preferably 1 μm or more, and preferably 2 μm or more. More preferably, it is 3 μm or more, more preferably 5 μm or more.

The boric acid content of the polarizing film layer in the present invention is preferably 1 to 8% by mass with respect to the polarizing film layer in terms of boron atoms. When the boric acid content is less than 1% by mass, the effect of improving the heat and moisture resistance may be reduced. The boric acid content is more preferably 2% by mass or more. On the other hand, when the boric acid content exceeds 8% by mass, the dimensional change of the polarizing film at high temperatures may be increased. The boric acid content is more preferably 5% by mass or less.

As explained in the examples described later, the boric acid content in terms of boron atoms is measured by ICP emission spectrometry by dissolving a polarizing film in distilled water so as to be 0.0005% by mass. By measuring the boron concentration in the sample, it is calculated by the following formula (1).
[(X × 10 ⁻⁶ × Y) / Z] × 100 (1)
X: Boron concentration of measurement sample [ppm]
Y: Mass of the measurement sample in which the polarizing film was dissolved [g]
Z: Mass of polarizing film [g]

(Method for producing polarizing film layer)
The method for producing the polarizing film layer in the present invention is not particularly limited. The polarizing film layer is preferably manufactured through a manufacturing process in which the process of uniaxially stretching the PVA film, the process of adsorbing the dichroic dye, the process of treating with a boric acid aqueous solution, and the process of washing with water are arbitrarily combined. The The total draw ratio of the PVA film throughout the production process is preferably about 4 to 8 times. Moreover, you may perform a swelling process, a fixing process, a drying process, heat processing, etc. as needed.

The swelling treatment can be performed by immersing the PVA film in water. The temperature of the water when immersed in water is preferably in the range of 20 to 40 ° C., more preferably in the range of 22 to 38 ° C., and preferably in the range of 25 to 35 ° C. Further preferred. Further, the time for immersion in water is, for example, preferably within a range of 0.1 to 5 minutes, and more preferably within a range of 0.2 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

The step of uniaxially stretching the PVA film may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be performed in an aqueous solution containing boric acid, or can be performed in a dyeing bath or a fixing treatment bath described later. In the case of the dry stretching method, the uniaxial stretching treatment may be performed at room temperature, the uniaxial stretching treatment may be performed while heating, or the uniaxial stretching treatment is performed in the air using the PVA film after water absorption. You can also Among these, the wet stretching method is preferable, and it is more preferable to perform the uniaxial stretching process in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably in the range of 0.5 to 15% by mass, and more preferably in the range of 1 to 7% by mass. Further, the aqueous boric acid solution may contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass. The stretching temperature in the uniaxial stretching treatment is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and particularly preferably in the range of 50 to 70 ° C. Further, the draw ratio (total draw ratio from the raw material PVA film) in the uniaxial stretching treatment is preferably 4 to 8 times from the viewpoint of the polarizing performance of the obtained polarizing film.

The step of adsorbing the dichroic dye may be at any stage before the uniaxial stretching treatment, during the uniaxial stretching treatment, or after the uniaxial stretching treatment. It can be performed by immersing the PVA film in an aqueous solution containing a dichroic dye as a dyeing bath. The concentration of the dichroic dye in the aqueous solution can be appropriately set according to the type of the dichroic dye, and can be, for example, in the range of 0.001 to 2% by mass. When an iodine-potassium iodide aqueous solution [an aqueous solution containing iodine (I ₂ ) and potassium iodide (KI)] is used as the aqueous solution, the iodine dye can be efficiently adsorbed on the PVA film. The concentration of iodine (I ₂ ) in the aqueous solution is preferably 0.01 to 1% by mass, and the concentration of potassium iodide (KI) is preferably 0.01 to 50% by mass. The temperature of the aqueous solution containing the dichroic dye during the dyeing treatment is preferably 5 to 50 ° C. from the viewpoint that the dichroic dye can be efficiently adsorbed to the PVA film. The time for immersing the PVA film in the aqueous solution is preferably 0.1 to 10 minutes.

Examples of the dichroic dye, for example, I ₃ is iodine dye ^-, and the like ^- and I _5. Examples of these counter cations include alkali metals such as potassium. The iodine dye can be obtained, for example, by bringing iodine (I ₂ ) into contact with potassium iodide.

The step of treating with the boric acid aqueous solution can be performed by immersing the PVA film in an aqueous solution containing a boric acid crosslinking agent. By performing such treatment, it is possible to effectively prevent the PVA in the film from eluting into water when performing wet stretching at a relatively high temperature. From this viewpoint, the treatment with the boric acid aqueous solution is preferably performed after the step of adsorbing the dichroic dye. As the boric acid crosslinking agent, one or more boron compounds such as borates such as boric acid and borax can be used. The concentration of the aqueous solution containing the boric acid crosslinking agent is preferably 1 to 15% by mass, and more preferably 2 to 7% by mass. The aqueous solution containing the boric acid crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution during the crosslinking treatment is preferably 20 to 50 ° C.

In the production of the polarizing film, it is preferable to perform a fixing process after the uniaxial stretching process in order to strengthen the adsorption of the dichroic dye (iodine dye or the like) to the PVA film. As the fixing treatment bath used for the fixing treatment, an aqueous solution containing one or more boron compounds such as borates such as boric acid and borax can be preferably used. The concentration of the boron compound is preferably 2 to 15% by mass, and the temperature of the fixing treatment liquid is preferably 15 to 60 ° C. Moreover, you may add an iodine compound and a metal compound in a fixed process liquid as needed.

The water washing process is generally performed by immersing the film in water, distilled water, pure water or the like. At this time, from the viewpoint of improving the polarization performance, the aqueous solution used for the washing treatment preferably contains an iodide such as potassium iodide as an auxiliary agent, and the concentration of the iodide is preferably 0.5 to 10% by mass. . In addition, the temperature of the aqueous solution in the washing treatment is generally 5 to 50 ° C., preferably 10 to 45 ° C., more preferably 15 to 40 ° C. From an economical viewpoint, it is not preferable that the temperature of the aqueous solution is too low. If the temperature of the aqueous solution is too high, the polarization performance may be deteriorated.

Further, if necessary, drying treatment, heat treatment, etc. may be performed after the above washing treatment. The conditions for the drying treatment are not particularly limited, but drying at 30 to 150 ° C. is preferable. A polarizing film excellent in dimensional stability is easily obtained by drying at a temperature within the above range. By performing a heat treatment after the drying treatment, a polarizing film having further excellent dimensional stability can be obtained. Here, the heat treatment is a treatment for further heating the polarizing film after the drying treatment having a moisture content of 5% or less to improve the dimensional stability of the polarizing film. The heat treatment conditions are not particularly limited, but the heat treatment is preferably performed at 60 to 150 ° C. If the heat treatment is performed at a temperature lower than 60 ° C., the dimensional stabilization effect by the heat treatment may be insufficient, and if the heat treatment is performed at a temperature higher than 150 ° C., the polarizing film may be significantly reddened.

The polarizing film obtained as described above is normally used as a polarizing plate in which a protective film that is optically transparent and has mechanical strength is bonded to both sides or one side. In the polarizing plate of the present invention, a cured product layer described later is directly laminated on at least one surface of the polarizing film layer, and no protective film layer is provided on the other surface of the polarizing film layer and the cured product layer. It can be in the form. With such a configuration, the polarizing plate can be reduced in weight and the cost can be reduced. Examples of the protective film include cellulose acetate-based resin films such as triacetyl cellulose (TAC) and diacetyl cellulose; polyester-based resin films such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; and polycarbonate-based resin films.

(Cured product layer)
The cured product layer in the present invention has a thickness of 10 μm or less and satisfies a boric acid permeability of 2.25 g / m ² · day or less in terms of boron atom. In particular, it is important that the boric acid permeability of the cured product layer is 2.25 g / m ² · day or less in terms of boron atom, and a polarizing plate excellent in moisture and heat resistance that can maintain the initial polarization performance. Can be provided. When the boric acid permeability exceeds 2.25 g / m ² · day in terms of boron atom, the wet heat resistance of the polarizing plate cannot be sufficiently improved. From this viewpoint, it is preferable that borate permeability is not more than 1.50g ^/ m 2 · day boron atoms terms, more preferably less ^{1.00g / m 2 · day, 0.50g} / m 2 More preferably, it is not more than day, and particularly preferably not more than 0.20 g / m ² · day. On the other hand, there is no particular limitation on the lower limit of boric acid permeability in terms of boron atom in the cured product layer, but when the boric acid permeability in terms of boron atom is too low, the flexibility of the cured product layer tends to be lost. since, it is preferred that boric acid permeability is 0.02g ^/ m 2 · day or more boron atoms terms, more preferably 0.05g ^/ m 2 · day or more, 0.10 g / ^{m 2} · More preferably, it is not less than day.

As will be described later in the examples, the boric acid permeability (A) in terms of boron atoms is obtained by fixing a cured product layer to be measured to a moisture permeable cup filled with pure water, and at 8 ° C. at 60 ° C. It is immersed in an aqueous boric acid solution, and the boron concentration in the moisture permeable cup before the start of the test and after 24 hours is analyzed by an ICP emission analysis method, and is calculated by the following formula (2) from the amount of increase in the concentration.
A = {(a ₂₄ −a ₀ ) × 10 ⁻⁶ × M} / S (2)
A: Boric acid permeability in terms of boron atom [g / m ² · day]
a ₂₄ : Boron concentration [ppm] in the sample water after 24 hours
a ₀ : Boron concentration [ppm] in the sample water before the start of the test
M: Weight of sample water [g]
S: Area where cured product layer and boric acid aqueous solution are in contact (permeation area of moisture-permeable cup) [m ² ]
In addition, about the hardened | cured material layer which a single-piece | unit measurement is difficult, using the multilayer film by which the hardened | cured material layer was formed on base film, such as a cellulose triacetate (TAC) film, is carried out similarly to said Formula (2). By measuring the boric acid permeability (A ′) in terms of total boron atoms of the multilayer film, the boric acid permeability (q ₂ / l ₂ ) in terms of boron atoms in the cured product layer is calculated by the following formula (3). The
1 / A ′ = L / Q = l ₁ / q ₁ + l ₂ / q ₂ (3)
A ′: Boric acid permeability [g / m ² · day] in terms of total boron atoms of the cured product layer and the base film
L: Total film thickness [μm] of the cured product layer and the substrate film
Q: Whole boric acid permeability coefficient of the cured product layer and the base film [g · μm / m ² · day]
l ₁ : Film thickness [μm] of the base film
q ₁ : boric acid permeability coefficient of base film [g · μm / m ² · day]
l ₂ : film thickness [μm] of the cured product layer
q ₂ : boric acid permeability coefficient [g · μm / m ² · day] of the cured product layer

As the cured layer, a thermoplastic resin composition, a thermosetting resin composition, or a sol-gel method is applied as long as the boric acid permeability satisfies 2.25 g / m ² · day or less in terms of boron atom. Any resin composition such as an organic / inorganic hybrid resin composition can be used. When the polarizing film layer is strongly heated, the polarizing performance is likely to be lowered. Therefore, it is preferable to use a photocurable resin composition that can be laminated with the polarizing film layer under mild conditions. Especially, it is a suitable embodiment that a photocurable resin composition is an acrylic resin acrylate. Here, the acrylic resin acrylate is an acrylic resin obtained by copolymerizing an acrylic monomer having a functional group such as a carboxyl group, a glycidyl group, or a hydroxy group, and reacts with an acrylate having a group capable of reacting with these functional groups. In which a double bond (C = C) is introduced. Although it does not specifically limit as a weight average molecular weight of an acrylic resin acrylate, It is preferable that it is 62000 or more, It is more preferable that it is 65000 or more, It is still more preferable that it is 70000 or more. On the other hand, the weight average molecular weight of the acrylic resin acrylate is usually 1000000 or less.

In the present invention, it is important that the thickness of the cured product layer is 10 μm or less. When the thickness exceeds 10 μm, sufficient thinning cannot be achieved with respect to a polarizing plate on which a conventional protective film is laminated. From this viewpoint, the thickness of the cured product layer is preferably 8 μm or less, more preferably 7 μm or less, and further preferably 6 μm or less. On the other hand, the lower limit of the thickness of the cured product layer is not necessarily limited, but when achieving the boric acid permeability in terms of boron atoms in a thin cured product layer, the flexibility of the cured product layer tends to be lost, The thickness is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more.

In this invention, it is preferable that the water vapor permeability of the said hardened | cured material layer is 2500 g / m < ² > * day or less. When the water vapor permeability of the cured product layer exceeds 2500 g / m ² · day, problems such as poor appearance of the polarizing plate may occur. From this viewpoint, the water vapor permeability of the cured product layer is more preferably 2000 g / m ² · day or less, and further preferably 900 g / m ² · day or less. On the other hand, the water vapor permeability of the cured product layer is usually 500 g / m ² · day or more.

As described in the examples described later, the water vapor permeability (B) of the cured product layer is determined in accordance with JIS Z-0208.
As for a cured product layer that is difficult to measure by itself, a multilayer film in which a cured product layer is formed on a substrate film such as a cellulose triacetate (TAC) film is used, and the above-mentioned in accordance with JIS Z-0208. By measuring the total water vapor permeability (B ′) of the multilayer film, the water vapor permeability (p ₂ / l ₂ ) of the cured product layer is calculated by the following formula (4).
1 / B ′ = L / P = l ₁ / p ₁ + l ₂ / p ₂ (4)
B ′: Whole water vapor permeability [g / m ² · day] of the cured product layer and the base film
L: Total film thickness [μm] of the cured product layer and the substrate film
P: Whole water vapor transmission coefficient [g · μm / m ² · day] of cured product layer and substrate film
l ₁ : Film thickness [μm] of the base film
p ₁ : Water vapor transmission coefficient of base film [g · μm / m ² · day]
l ₂ : film thickness [μm] of the cured product layer
p ₂ : Water vapor transmission coefficient [g · μm / m ² · day] of the cured product layer

(Polarizer)
In the polarizing plate of the present invention, the cured product layer is directly adjacent to at least one surface of the polarizing film layer. It is a preferred embodiment that there is no protective film layer on the cured product layer, and there is no protective film layer on the polarizing film layer on the surface opposite to the surface on which the cured product layer is laminated. This is a preferred embodiment. As a layer structure of the polarizing plate of the present invention, a two-layer structure of polarizing film layer / cured material layer may be used, but a more excellent durability can be obtained by adopting a three-layer structure of cured material layer / polarizing film layer / cured material layer. It is preferable because it can obtain the properties and curl of the polarizing film can be suppressed. In the case of a three-layer structure, the cured product layer laminated on one surface of the polarizing film and the cured product layer laminated on the other surface of the polarizing film may be different resin compositions.

In addition, the cured product layer in the present invention may be a single layer that satisfies the boron atom-equivalent boric acid permeability and thickness, but has a multilayer structure in which two or more types of cured product layers are laminated. It may be a composition layer.

In the present invention, the adhesive force between the polarizing film layer and the cured product layer is preferably 0.06 N / mm or more. When the adhesive strength is less than 0.06 N / mm, delamination may occur during processing of the polarizing plate. From this viewpoint, the adhesive force is more preferably 0.08 N / mm or more, and further preferably 0.12 N / mm or more.

The thickness of the entire polarizing plate of the present invention is 40 μm or less because the thinner the polarizing film layer, the more easily the heat and moisture resistance is lowered, and the effect of the present invention is more remarkably exhibited in such a polarizing film layer. Is preferably 35 μm or less, more preferably 30 μm or less, and particularly preferably 25 μm or less. On the other hand, when the thickness of the whole polarizing plate is thin, the mechanical strength is lowered, so that it is preferably 2 μm or more, more preferably 5 μm or more.

The polarizing plate of the present invention preferably has a total light transmittance of 40 to 45%. From the viewpoint of polarization performance, the total light transmittance is more preferably 41% or more, and further preferably 42% or more. On the other hand, from the viewpoint of the degree of polarization, the total light transmittance is more preferably 44% or less. The total light transmittance can be measured by the method described later in Examples.

The polarizing plate of the present invention preferably has a polarization degree of 99.9% or more. From the viewpoint of polarization performance, the degree of polarization is more preferably 99.92% or more, and further preferably 99.95% or more. The degree of polarization can be measured by the method described later in the examples.

The polarizing plate of the present invention has a change in total light transmittance of 1.5% or less after a 48-hour moist heat resistance test at 60 ° C. and 90% RH, and a degree of polarization of 99.9. % Or more is preferable. Thus, since the amount of change in the total light transmittance of the polarizing plate after the moisture and heat resistance test is below a certain level and the degree of polarization is above a certain level, the polarizing plate of the present invention is resistant to moisture and heat even if it is a thin film. It can be seen that the initial polarization performance is excellent and can be maintained. The change amount of the total light transmittance is more preferably 1.3% or less, and further preferably 1.1% or less. On the other hand, the amount of change in the total light transmittance is usually 0.1% or more. The degree of polarization is more preferably 99.92% or more, further preferably 99.95% or more, and particularly preferably 99.98% or more.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples. In addition, each measurement of the boric acid content of the polarizing film layer, the boric acid transmittance of the cured product layer, the total light transmittance and the polarization degree of the polarizing plate, which were employed in the following Examples and Comparative Examples, The evaluation method is shown below.

[Boric acid content of polarizing film layer]
The mass Z (g) of the polarizing film was measured and dissolved in 20 mL of distilled water so that the polarizing film was 0.0005 mass%. An aqueous solution in which the polarizing film was dissolved was used as a measurement sample, and its mass Y (g) was measured. Thereafter, the boron concentration X (ppm) of the measurement sample was measured using a multi-type ICP emission spectrometer (ICPE-9000) manufactured by Shimadzu Corporation. Thereafter, the value calculated by substituting the value into the following formula (1) was defined as the mass% of boric acid in the polarizing film layer.
Boric acid content of the polarizing film layer (% by mass)
[(X × 10 ⁻⁶ × Y) / Z] × 100 (1)
X: Boron concentration of measurement sample [ppm]
Y: Mass of the measurement sample in which the polarizing film was dissolved [g]
Z: Mass of polarizing film [g]

[Boric acid permeability in terms of boron atoms in the cured product layer]
In the present invention, as a method for measuring the boric acid permeability of the cured product layer in terms of boron atoms, a moisture-permeable cup (clamping type, JIS Z-0208) in which pure water is previously added to the cured product layer to be measured. ), Immersed in an 8% by weight boric acid aqueous solution at 60 ° C., and the boron concentration of the sample water in the cup before the start of the test and 24 hours later was measured by ICP emission spectrometry (Shimadzu Corporation Shimadzu multi-type ICP emission) Analytical apparatus ICPE-9000), and the boric acid permeability (A) in terms of boron atom was calculated by the following formula (2) from the increase in concentration (see FIG. 1).
A = {(a ₂₄ −a ₀ ) × 10 ⁻⁶ × M} / S (2)
A: Boric acid permeability in terms of boron atom [g / m ² · day]
a ₂₄ : Boron concentration [ppm] in the sample water after 24 hours
a ₀ : Boron concentration [ppm] in the sample water before the start of the test
M: Weight of sample water [g]
S: Area where cured product layer and boric acid aqueous solution are in contact (permeation area of moisture-permeable cup) [m ² ]
In addition, for a cured product layer of a resin composition that is difficult to measure by itself, a cured product layer is formed on a base film (for example, a cellulose triacetate (TAC) film) having a high boric acid permeability in terms of boron atoms. Using the multilayer film thus prepared, the boric acid permeability (A ′) in terms of the total boron atoms of the cured product layer and the base film was measured, and the boric acid permeability in terms of boron atom (q ₂ ) of each cured product layer. / L ₂ ) was calculated by the following formula (3).
1 / A ′ = L / Q = l ₁ / q ₁ + l ₂ / q ₂ (3)
A ′: Boric acid permeability [g / m ² · day] in terms of total boron atoms of the cured product layer and the base film
L: Total film thickness [μm] of the cured product layer and the substrate film
Q: Whole boric acid permeability coefficient of the cured product layer and the base film [g · μm / m ² · day]
l ₁ : Film thickness [μm] of the base film
q ₁ : boric acid permeability coefficient of base film [g · μm / m ² · day]
l ₂ : film thickness [μm] of the cured product layer
q ₂ : boric acid permeability coefficient [g · μm / m ² · day] of the cured product layer

[Water vapor permeability of cured product layer]
In the present invention, the water vapor permeability of the cured product layer was measured according to JIS Z-0208. That is, the cured product layer to be measured is fixed to a moisture permeable cup (clamping type) containing calcium chloride, and the weight increase is measured every 24 hours in an environment of 40 ° C. and 90% RH. (B) was calculated.
For a cured product layer of a resin composition that is difficult to measure by itself, a multilayer film in which a cured product layer is formed on a base film having a high water vapor permeability (for example, cellulose triacetate (TAC) film). The water vapor permeability (B ′) of the cured product layer and the base film is measured, and the water vapor permeability (p ₂ / l ₂ ) of each cured product layer is calculated by the following formula (4). It was.
1 / B ′ = L / P = l ₁ / p ₁ + l ₂ / p ₂ (4)
B ′: Whole water vapor permeability [g / m ² · day] of the cured product layer and the base film
L: Total film thickness [μm] of the cured product layer and the substrate film
P: Whole water vapor transmission coefficient [g · μm / m ² · day] of cured product layer and substrate film
l ₁ : Film thickness [μm] of the base film
p ₁ : Water vapor transmission coefficient of base film [g · μm / m ² · day]
l ₂ : film thickness [μm] of the cured product layer
p ₂ : Water vapor transmission coefficient [g · μm / m ² · day] of the cured product layer

[Total light transmittance and polarization degree of polarizing plate]
From the central part in the width direction (TD) of the polarizing plate obtained in the following examples or comparative examples, a rectangular sample of 2 cm in the length direction (MD) of the polarizing plate and 3 cm in the width direction (TD) is obtained in the TD direction. In the same manner as above, two samples in the MD direction are collected, and using a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation), in accordance with JIS Z 8722 (object color measurement method), C light source The visibility of the visible light region with a 2 ° field of view was corrected, and the light transmittance when the sample was tilted 45 ° relative to the length direction and the light transmittance when tilted −45 ° were measured. The average value (%) was defined as the total light transmittance of the polarizing plate. Further, the light transmittance T∥ (%) in the parallel Nicol state and the light transmittance T⊥ (%) in the crossed Nicol state were measured in the same manner as described above, and the degree of polarization was calculated by the following equation (5). Asked.
Polarization degree = {(T∥−T⊥) / (T∥ + T⊥)} ^1/2 × 100 (5)

[Moisture and heat resistance of polarizing plate]
A polarizing plate is fixed to a metal frame, put in a constant temperature and humidity chamber (HUMIDIC CHAMBER IG400, manufactured by Yamato Scientific Co., Ltd.) at 60 ° C. and 90% RH, and a 48-hour humidity and heat resistance test is performed. The light transmittance and the degree of polarization were measured, and this was used as an indicator of the heat and humidity resistance of the polarizing plate.

[Example 1]
(Preparation of polarizing film)
100 parts by mass of PVA (saponified copolymer of vinyl acetate and ethylene, average polymerization degree 2,400, saponification degree 99.4 mol%, ethylene unit content 2.5 mol%), glycerin 10 as plasticizer For a PVA film having a thickness of 30 μm obtained by casting a film using a film-forming stock solution consisting of 0.1 parts by mass of sodium polyoxyethylene lauryl ether sulfate and water as a surfactant, The polarizing film was manufactured by performing a dyeing process, a crosslinking process, a stretching process, a fixing process, and a drying process.
That is, the amount of the PVA film used is uniaxially stretched (MD) in the length direction (MD) up to twice the original length while immersed in water at a temperature of 30 ° C. for 1 minute. As an initial length of 2.3 while being immersed in a dyeing bath at a temperature of 32 ° C. in which iodine is mixed with water at a concentration of 0.03% by mass and potassium iodide at a concentration of 0.7% by mass. While uniaxially stretching in the length direction (MD) (second-stage stretching) up to twice, and then immersed in a crosslinking bath at a temperature of 32 ° C. containing boric acid at a concentration of 2.6 mass% for 2 minutes. A temperature of 57 ° C., which is uniaxially stretched in the length direction (MD) up to 2.6 times the length (third-stage stretch), and further contains 2.8% by mass of boric acid and 5% by mass of potassium iodide. Uniaxially stretched in the length direction (MD) up to 6 times the original length while immersed in an aqueous solution of boric acid / potassium iodide The film is then washed by dipping in a potassium iodide aqueous solution at a temperature of 22 ° C. containing 1.5% by mass of boric acid and 5% by mass of potassium iodide for 5 seconds. Subsequently, a polarizing film having a thickness of 12 μm was produced by drying for 240 seconds with a dryer at 40 ° C.

(Preparation of polarizing plate)
20 g of the product name “Hitaroid 7975 (weight average molecular weight: 80000)” manufactured by Hitachi Chemical Co., Ltd. as a resin composition and 1-hydroxycyclohexyl phenyl ketone manufactured by Ciba Specialty Chemicals 0.25 g of the name “Irquagua 184” was weighed into a sample bottle and mixed. Using a 13 bar coater, coating was performed on the surface of a polarizing film layer having a thickness of 12 μm. The coated polarizing film layer was dried at 70 ° C. for 1 minute, and then irradiated with a black light so that the integrated light amount was 400 mJ / cm ² to cure the resin composition. Furthermore, it applied similarly to the opposite surface of a polarizing film layer, and produced the polarizing plate whose thickness of the hardened | cured material layer of one side is 5.9 micrometers, and thickness 24 micrometers in total. Using the obtained polarizing plate, the total light transmittance and the degree of polarization were measured by the above methods, and the wet heat resistance was evaluated. The results are shown in Table 1.
In addition, a TAC film having a cured product layer was produced in the same manner as described above except that it was coated on one side of a cellulose triacetate (TAC) film, and the water vapor permeability and The acid permeability was measured. The results are shown in Table 1.

Comparative Example 1
A polarizing plate was prepared in the same manner as in Example 1 except that the photo-curable resin composition used was a product name “Unidic V-6841”, which is a product of an acrylic acid ester polymer and an acrylate monomer mixture manufactured by DIC Corporation. Manufactured. Using the obtained polarizing plate, the total light transmittance and the degree of polarization were measured to evaluate the heat and moisture resistance. The results are shown in Table 1.
In addition, a TAC film having a cured product layer laminated thereon was produced in the same manner as described above except that it was applied to one side of a cellulose triacetate (TAC) film, and the water vapor permeability, The acid permeability was measured. The results are shown in Table 1.

Comparative Example 2
A polarizing plate was prepared in the same manner as in Example 1 except that the photo-curable resin composition used was a product name “Hitaroid 7988 (weight average molecular weight: 60000)” which is an acrylic resin acrylate product manufactured by Hitachi Chemical Co., Ltd. Manufactured. Using the obtained polarizing plate, the total light transmittance and the degree of polarization were measured, and the heat and moisture resistance was evaluated. The results are shown in Table 1.
In addition, a TAC film having a cured product layer laminated thereon was produced in the same manner as described above except that it was applied to one side of a cellulose triacetate (TAC) film, and the water vapor permeability, The acid permeability was measured. The results are shown in Table 1.

Comparative Example 3
A polarizing plate was prepared in the same manner as in Example 1 except that the product name “Hitaroid 7975D (weight average molecular weight: 15000)”, an acrylic resin acrylate product manufactured by Hitachi Chemical Co., Ltd., was used as the photocurable resin composition. Manufactured. Using the obtained polarizing plate, the total light transmittance and the degree of polarization were measured, and the heat and moisture resistance was evaluated. The results are shown in Table 1.
In addition, a TAC film having a cured product layer laminated thereon was produced in the same manner as described above except that it was applied to one side of a cellulose triacetate (TAC) film, and the water vapor permeability, The acid permeability was measured. The results are shown in Table 1.

Comparative Example 4
A polarizing plate was produced in the same manner as in Example 1 except that the product name “Unidic V-6840”, which is an acrylic ester polymer product manufactured by DIC Corporation, was used as the photocurable resin composition. Using the obtained polarizing plate, the total light transmittance and the degree of polarization were measured, and the heat and moisture resistance was evaluated. The results are shown in Table 1.
In addition, a TAC film having a cured product layer laminated thereon was produced in the same manner as described above except that it was applied to one side of a cellulose triacetate (TAC) film, and the water vapor permeability, The acid permeability was measured. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Hardened | cured material layer 2 TAC film 3 Moisture-permeable cup 4 Pure water 5 Airtight container 6 8 mass% boric acid aqueous solution of 60 degreeC 7 Sample water 8 Sampling device

Claims

A polarizing plate in which a polarizing film layer and a cured product layer made of a resin composition are laminated,
The cured product layer has a thickness of 10 μm or less, and boric acid permeability is 2.25 g / m 2 · day or less in terms of boron atom,
The polarizing plate in which the cured product layer is directly adjacent to at least one surface of the polarizing film layer.
The polarizing plate according to claim 1, wherein a protective film layer is not provided on the cured product layer.
The polarizing plate according to claim 1 or 2, wherein a protective film layer is not provided on the polarizing film layer on the surface opposite to the surface on which the cured product layer is laminated.
The polarizing plate according to any one of claims 1 to 3, wherein the resin composition is a photocurable resin composition.
The polarizing plate according to any one of claims 1 to 4, wherein a content of boric acid in the polarizing film layer is 1 to 8% by mass with respect to the polarizing film layer in terms of boron atoms.
6. The polarizing plate according to claim 1, wherein the polarizing film layer has a thickness of 20 μm or less.
The polarizing plate according to any one of claims 1 to 6, wherein the entire polarizing plate has a thickness of 40 µm or less.
The polarizing plate according to any one of claims 1 to 7, wherein the cured product layer has a water vapor permeability of 2500 g / m 2 · day or less.
The layer structure according to any one of claims 1 to 8, wherein the layer structure is a two-layer structure of a polarizing film layer / the cured product layer, or a three-layer structure of the cured product layer / polarizing film layer / the cured product layer. Polarizing plate.
The polarizing plate according to any one of claims 1 to 9, wherein the total light transmittance is 40 to 45% and the degree of polarization is 99.9% or more.
The amount of change in the total light transmittance after performing a hygrothermal resistance test for 48 hours under the conditions of 60 ° C. and 90% RH is 1.5% or less, and the degree of polarization is 99.9% or more. The polarizing plate according to any one of 1 to 10.