JPWO2013094435A1 - Polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

Disclosed is a polarizing plate capable of suppressing the occurrence of luminance unevenness during panel display of a liquid crystal display device, having excellent reworkability during manufacture, and capable of achieving a thin liquid crystal display device. A polarizing plate according to the present invention has a stretched laminate obtained by stretching a direct laminate of a hydrophilic polymer layer and a base material layer. And the dichroic substance is adsorbed to the hydrophilic polymer layer constituting the stretched laminate, the thickness of the hydrophilic polymer layer is 2 to 10 μm, and the thickness of the base material layer is 5 to 30 μm. The substrate layer is characterized in that the moisture permeability of the base material layer is 130 g / m2 / 24h or more.

Description

  The present invention relates to a polarizing plate and a liquid crystal display device using the same.

  Commonly known TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type and the like are well known as liquid crystal display systems. The liquid crystal display device usually includes a liquid crystal cell having a liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer, and polarizing plates respectively disposed on both sides (viewing side and backlight side) of the liquid crystal cell. is there. In particular, IPS (In-Plane Switching) mode type liquid crystal display devices (hereinafter, also simply referred to as “IPS type liquid crystal display devices”) are widely used in portable devices such as tablet display devices and smartphones. It has been. In the IPS liquid crystal display device, the liquid crystal molecules contained in the liquid crystal layer are aligned in parallel to the surfaces of the pair of substrates during black display, and thus the IPS liquid crystal display device has an advantage of excellent black display performance. Further, the IPS liquid crystal display device has an advantage that a certain high viewing angle can be secured without using a so-called optical compensation film (viewing angle widening film). On the other hand, due to the optical characteristics of the liquid crystal cell provided in the IPS liquid crystal display device, there is a problem that light leakage occurs when the screen is viewed from an oblique direction, and the contrast of the display image is lowered.

  In general, a retardation film is used in a liquid crystal display device for the purpose of preventing such a decrease in contrast. However, in order to further improve the performance, a retardation film capable of supporting various optical designs is required. It is getting to be. In addition, regarding the retardation film mounted on the portable device as described above, there is a strong demand for further reduction in thickness and weight.

  One of important constituent members of a liquid crystal display device is a polarizing plate. The polarizing plate has a configuration in which a polarizer and a polarizing plate protective film for protecting the polarizer are laminated. Therefore, conventionally, as a technique for thinning both the polarizer and the polarizing plate protective film, a technique for thinning a so-called coating-type polarizer by stretching treatment has been proposed (see Patent Document 1).

US Patent Application Publication No. 2010/202051

  The inventor has studied the technique described in Patent Document 1 described above. As a result, it has been found that in a liquid crystal display device manufactured using the polarizing plate described in Patent Document 1, uneven brightness occurs during panel display.

  In addition, a liquid crystal display device is usually manufactured by laminating a liquid crystal display panel and a polarizing plate via an adhesive or the like. After peeling off, the polarizing plate may be attached again. Therefore, the polarizing plate is required to have no peeling residue on the liquid crystal display panel at the time of peeling, and no peeling between layers occurs (that is, high reworkability). However, when a liquid crystal display device is manufactured using the polarizing plate described in Patent Document 1, it has also been found that there is a problem in the reworkability of the polarizing plate during manufacturing.

  Accordingly, an object of the present invention is to provide a polarizing plate that can suppress the occurrence of luminance unevenness during panel display of a liquid crystal display device, is excellent in reworkability at the time of manufacture, and can achieve a thin liquid crystal display device. To do.

  The present inventor has intensively studied in view of the above problems. As a result, in the polarizing plate having the stretched laminate obtained by stretching the laminate of the hydrophilic polymer layer and the base material layer, the above-mentioned problem is achieved by employing a base material layer having a moisture permeability of a predetermined value or more. Has been found to be solved, and the present invention has been completed.

  That is, the above object of the present invention is achieved by the following configuration.

1. A polarizing plate having a stretched laminate obtained by stretching a laminate of a hydrophilic polymer layer and a base material layer,
A dichroic substance is adsorbed on the hydrophilic polymer layer constituting the stretched laminate,
The hydrophilic polymer layer has a thickness of 2 to 10 μm,
The thickness of the base material layer is 5 to 30 μm,
Moisture permeability of the substrate layer is 130g ^/ m 2 ^/ 24h or more, the polarizer;
2. The base material layer contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70 and in a compatible state,
The acyl group total substitution degree (T) of the cellulose ester resin (B) is 2.0 to 3.0, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0, The polarizing plate according to 1 above, wherein the weight average molecular weight Mw is 75,000 or more;
3. The base material layer contains acrylic resin (A) and cellulose ester resin (B) in a mass ratio of 95: 5 to 50:50 and in a compatible state,
The acrylic resin (A) is represented by the following general formula (1):

In the formula, MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one amide group, Y represents a monomer unit copolymerizable with MMA and X, p, q, and r Is the mole percentage of each structural unit, 55 ≦ p ≦ 99, 1 ≦ q ≦ 50, p + q + r = 100.
The polarizing plate according to 1 or 2 above, wherein the weight average molecular weight Mw is from 20,000 to 1,000,000;
4). The polarizing plate according to any one of the above 1 to 3, wherein the hydrophilic polymer layer and the base material layer are adhered by a photocurable adhesive containing an epoxy compound and a cationic polymerization initiator;
5. The polarizing plate according to any one of the above 1 to 4, wherein the hydrophilic polymer layer contains polyvinyl alcohol as a hydrophilic polymer;
6). The polarizing plate according to any one of 1 to 5 above, wherein the dichroic substance is iodine;
7). The liquid crystal display device provided with the polarizing plate of any one of said 1-6;
8). 8. The liquid crystal display device according to 7 above, which is an IPS mode liquid crystal display device.

  Hereinafter, embodiments of the present invention will be described in detail.

≪Polarizing plate≫
One embodiment of the present invention relates to a polarizing plate having a stretched laminate obtained by stretching a laminate of a hydrophilic polymer layer and a base material layer. And the polarizing plate concerning this form is
(1) The dichroic substance is adsorbed on the hydrophilic polymer layer constituting the stretched laminate.
(2) The hydrophilic polymer layer has a thickness of 2 to 10 μm.
(3) The thickness of the base material layer is 5 to 30 μm.
(4) they are water-vapor permeability of the substrate layer 130g ^/ m 2 ^/ 24h or more,
It has the characteristics. By using a polarizing plate with such a configuration, it is possible to suppress the occurrence of uneven brightness during panel display of a liquid crystal display device, excellent reworkability during manufacturing, and achieving a thin liquid crystal display device. It becomes. The reason why such an effect is achieved is not necessarily clear, but the hydrophilic polymer layer is obtained by applying a hydrophilic polymer layer on a base film and stretching it to form a stretched laminate. The thickness of the layer can be reduced, and a thin film polarizing plate can be formed. On the other hand, by stretching the hydrophilic polymer layer together with the base film, voids are easily formed between the layers. Therefore, if the adhesion between the base film and the hydrophilic polymer layer is poor, Peeling is likely to occur. For adhesion, it is important that the moisture characteristics (moisture permeability and moisture content) of the base film and the hydrophilic polymer layer are particularly close, and that the film thickness difference between the base film and the hydrophilic polymer layer is not large. It is. This is because the adhesion is ensured when the hydrophilic polymer layer is dried, so that sufficient adhesion cannot be obtained if the moisture characteristics are separated, and there is a difference in film thickness between the base film and the hydrophilic polymer layer. If it is too large, the force will not be applied uniformly during reworking, and it will be applied to the base film side, so that it will peel off between the layers. Further, in order to further improve the adhesion, the adhesion layer can be increased by adhesion using a UV curable adhesive. In addition, the closer the moisture characteristics (moisture permeability, moisture content) of the base film and hydrophilic polymer layer, the more the influence of moisture from the outside and the heat generated from the backlight will be the same. It seems difficult to get up.

  As described above, the polarizing plate according to this embodiment has a stretched laminate obtained by stretching a laminate of a hydrophilic polymer layer and a base material layer. Hereinafter, the constituent elements of the stretched laminate will be described in more detail.

[Hydrophilic polymer layer]
The stretched laminate is first provided with a hydrophilic polymer layer. The hydrophilic polymer layer is a layer containing a hydrophilic polymer as a main component. And in the polarizing plate which concerns on this form, a hydrophilic polymer layer adsorb | sucks a dichroic substance. Thereby, the hydrophilic polymer layer functions as a polarizer in the polarizing plate according to the present embodiment.

  The hydrophilic polymer layer constituting the stretched laminate is characterized in that its thickness is 2 to 10 μm. From the viewpoint of manifesting the effects of the present invention, the thickness is preferably 2 to 5 μm, and more preferably 2 to 3 μm. The thickness value of the hydrophilic polymer layer can be measured using a film thickness meter.

  Although there is no restriction | limiting in particular about the hydrophilic polymer which comprises a hydrophilic polymer layer, A polyvinyl alcohol-type material is illustrated preferably. Examples of the polyvinyl alcohol material include polyvinyl alcohol and derivatives thereof. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. Can be mentioned. The degree of polymerization of polyvinyl alcohol is preferably about 100 to 10,000, and more preferably 1,000 to 10,000. A saponification degree of about 80 to 100 mol% is generally used. In addition to the above, examples of the hydrophilic polymer include partially saponified ethylene / vinyl acetate copolymer, dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. As the hydrophilic polymer, it is preferable to use polyvinyl alcohol among polyvinyl alcohol materials.

  The hydrophilic polymer layer may contain additives such as a plasticizer and a surfactant in addition to the above-described hydrophilic polymer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but it is preferably 20% by mass or less with respect to 100% by mass of the total amount of the hydrophilic polymer layer.

[Base material layer]
The stretched laminate also includes a substrate layer. The base material layer can function as a base material for preparing the hydrophilic polymer layer when the stretched laminate (polarizing plate) is prepared. Moreover, a base material layer functions as a protective layer (protective film) for protecting a polarizer in the polarizing plate which concerns on this form.

  The base material layer constituting the stretched laminate is characterized in that its thickness is 5 to 30 μm. From the viewpoint of manifesting the effects of the present invention, the thickness is preferably 10 to 30 μm, and more preferably 20 to 30 μm. In addition, the value of the thickness of a base material layer can be measured using a film thickness meter. Moreover, as for the film thickness ratio of the base material layer and the hydrophilic polymer layer, the thickness of the base material layer is preferably 10 to 20 times the thickness of the hydrophilic polymer layer, more preferably 10 to 10 times. 15 times.

Base layer constituting the stretched laminate is also its water vapor permeability has a characteristic in point is 130g / m 2 / ^24h or more. From the viewpoint of expression of effects of the invention, the moisture permeability is preferably 150g ^/ m 2 ^/ 24h, more preferably at 200g ^/ m 2 ^/ 24h or more, further preferably 250g ^/ m 2 ^/ 24h That's it. In addition, there is no restriction | limiting in particular about the upper limit of the water vapor transmission rate of a hydrophilic polymer layer, Usually, it is 1500 g / m < ² > / 24h or less, Preferably it is 1000 g / m < ² > / 24h or less. Moreover, as a value of the water vapor transmission rate of the base material layer, a value measured by the method described in the column of Examples described later with respect to a film obtained by stretching only the base material film under the same conditions shall be adopted.

  There is no restriction | limiting in particular about the material which comprises a base material layer, Any thing can be used if it is a material which can achieve the comparatively high moisture permeability mentioned above. Preferably, the base material layer is composed of a stretchable resin material. Especially, in preferable embodiment, a base material layer is comprised from the film which contains acrylic resin (A) and cellulose-ester resin (B) by mass ratio of 95: 5-30: 70, and a compatible state. The Hereinafter, although such a form is demonstrated, it is not necessarily limited to the following form.

  The acrylic resin used in this embodiment includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms in the alkyl group, alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, acrylic acid, methacrylic acid, and the like. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more monomers.

  In a preferred embodiment, the acrylic resin (A) is represented by the following general formula (1).

  In the general formula (1), MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one amide group, and Y represents a monomer unit copolymerizable with MMA and X. Moreover, p, q, and r are the mole percentage of each structural unit, and are 50 <= p <= 99, 1 <= q <= 50 (preferably 5 <= q <= 30), and p + q + r = 100.

  Specific examples of the monomer unit X (monomer unit copolymerizable with MMA having at least one amide group) include monomers derived from acryloylmorpholine, vinylpyrrolidone, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, and the like. Units are listed. Of these, monomer units derived from acryloylmorpholine or vinylpyrrolidone are preferred from the viewpoint of compatibility with cellulose ester. When the acrylic resin (A) contains such a monomer unit X, the heat resistance of the base material layer can be improved. This is presumed to be due to the fact that the amide group of the monomer unit X has an electron loan pair that coordinates with water molecules, thereby suppressing the crystal orientation of the resin that occurs over time. In addition, since the amide group is non-dissociable, it is considered that the acid is not generated due to decomposition over time and is physically stable.

  Specific examples of the monomer units Y (monomer units copolymerizable with MMA and X) include (meth) acrylic monomers other than MMA, olefins, acrylonitrile, styrene, vinyl acetate, and the like. May be used alone or in combination of two or more. However, the monomer unit Y can only be used as needed, and it is most preferable not to use it.

  The acrylic resin (A) has a weight average molecular weight (Mw) of 20,000 to 1,000,000 particularly from the viewpoint of improving brittleness as an optical film and improving transparency when it is compatible with the cellulose ester resin (B). preferable. If the weight average molecular weight (Mw) of an acrylic resin (A) is 20000 or more, sufficient brittle improvement will be obtained and compatibility with a cellulose-ester resin (B) will fully be ensured. On the other hand, if the weight average molecular weight (Mw) of an acrylic resin (A) is 1000000 or less, manufacture of a base material layer will be easy. The weight average molecular weight (Mw) of the acrylic resin (A) is more preferably in the range of 80,000 to 800,000, particularly preferably in the range of 100,000 to 600,000, and most preferably in the range of 100,000 to 400,000. preferable.

The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography. The measurement conditions are as follows.
Solvent: Methylene chloride column: Shodex K806, K805, K803G (Used by connecting three products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples are used. The 13 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of an acrylic resin (A), You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension polymerization or emulsion polymerization may be performed at 30 to 100 ° C, and bulk polymerization or solution polymerization may be performed at 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  A commercially available thing can also be used as an acrylic resin. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dialal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination.

  On the other hand, the specific form of the cellulose ester resin (B) is not particularly limited. However, from the viewpoint of improvement in brittleness and transparency when made compatible with the acrylic resin (A), the acyl group total substitution degree ( T) is preferably 2.0 to 3.0, and the degree of substitution of the acyl group having 3 to 7 carbon atoms is preferably 1.2 to 3.0, and the substitution of the acyl group having 3 to 7 carbon atoms is preferred. The degree is preferably 2.0 to 3.0. That is, the cellulose ester resin (B) is preferably a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used. Is preferably used.

  If the total acyl group substitution degree of the cellulose ester resin (B) is 2.0 or more (that is, if the residual degree of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is 1.0 or less), the acrylic resin (A) and cellulose-ester resin (B) can fully be compatible, and also when a base material layer functions as a polarizing plate protective film, a raise of haze is prevented. In addition, if the total acyl group substitution degree is 2.0 or more and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 or more, sufficient compatibility is obtained and brittleness is prevented from being lowered. Is done.

  The acyl substitution degree of the cellulose ester resin (B) is 2.0 to 3.0 in total substitution degree (T), and 1.2 to 3.0 substitution degree of the acyl group having 3 to 7 carbon atoms. If there is no problem, it is preferable that the total degree of substitution of acyl groups having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms is 1.3 or less. The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

  The acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in the present invention includes an acyl group substituent.

  When cellulose-ester resin (B) has an aromatic acyl group as a substituent, it is preferable that the number of the substituents X substituted to an aromatic ring is 0-5. Also in this case, it is necessary to pay attention so that the substitution degree of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 to 3.0. For example, since the benzoyl group has 7 carbon atoms, when it has a substituent containing carbon, the benzoyl group has 8 or more carbon atoms and is not included in the acyl group having 3 to 7 carbon atoms. Become.

  Further, when the number of substituents substituted on the aromatic ring is 2 or more, these may be the same or different from each other, and are connected to each other to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, Quinoline, isoquinoline, chromene, chromane, phthalazine, acridine, indole, indoline, etc.).

  The cellulose ester resin (B) is particularly preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate. Among these, cellulose ester resins that are particularly preferred are cellulose acetate propionate and cellulose propionate.

  The portion that is not substituted with an acyl group is usually present as a hydroxyl group. These can be synthesized by known methods. Moreover, the substitution degree of an acetyl group and the substitution degree of other acyl groups are determined by the method prescribed in ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose ester resin (B) is preferably 75,000 or more, more preferably in the range of 75,000 to 300,000, particularly from the viewpoint of improving compatibility with the acrylic resin (A) and brittleness. More preferably, it is within the range of 100,000 to 240,000, particularly preferably 160000 to 240,000. When the weight average molecular weight (Mw) of the cellulose ester resin (B) is less than 75,000, the effect of improving heat resistance and brittleness may not be sufficiently obtained. In the present invention, two or more kinds of cellulose resins can be mixed and used.

  In the base material layer constituting the stretched laminate, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and in a compatible state, preferably 95. : 5 to 50:50, more preferably 90:10 to 60:40. If the mass ratio of the acrylic resin (A) and the cellulose ester resin (B) is more than 95: 5, the moisture permeability of the base material layer may not be sufficiently increased, and the mass ratio is the same. However, if the amount of acrylic resin is less than 30:70, the moisture resistance may be insufficient.

  In the base material layer constituting the stretched laminate, the acrylic resin (A) and the cellulose ester resin (B) need to be contained in a compatible state. This is because the physical properties and quality necessary for functioning as a polarizing plate protective film are achieved by mutually complementing different resins by making them compatible. Note that whether or not the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state can be determined by, for example, the glass transition temperature Tg. For example, when the two resins have different glass transition temperatures, when the two resins are mixed, there are two or more glass transition temperatures for each resin because there is a glass transition temperature for each resin. When they are compatible, the glass transition temperature specific to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin. The glass transition temperature referred to here is an intermediate point determined according to JISK7121 (1987), measured using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer) at a heating rate of 20 ° C./min. The glass transition temperature (Tmg).

  In addition, “containing acrylic resin (A) and cellulose ester resin (B) in a compatible state” means mixing each resin (polymer) as described above, resulting in a compatible state This means that a state in which a precursor of acrylic resin such as monomer, dimer or oligomer is mixed with cellulose ester resin (B) and then polymerized by polymerization is not included. .

  For example, the process of obtaining a mixed resin by mixing a precursor of an acrylic resin such as a monomer, dimer or oligomer with the cellulose ester resin (B) and then polymerizing it is complicated by the polymerization reaction. The resin is difficult to control the reaction, and it is difficult to adjust the molecular weight. In addition, when a resin is synthesized by such a method, graft polymerization, cross-linking reaction or cyclization reaction often occurs. In many cases, the resin is soluble in a solvent or cannot be melted by heating. Since it is difficult to elute the resin and measure the weight average molecular weight (Mw), it is difficult to control the physical properties and it cannot be used as a resin for stably producing a film.

  The acrylic resin (A) and the cellulose ester resin (B) are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. However, in the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably compatible with each other to become an amorphous resin.

  In the optical film of the present invention, the weight average molecular weight (Mw) of the acrylic resin (A), the weight average molecular weight (Mw) of the cellulose ester resin (B), and the degree of substitution are different in solubility in the solvent of both resins. It is obtained by measuring each after using and separating. When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be. A combination of these solvents may be combined in two or more steps to separate the resin. The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying. These fractionated resins can be identified by general structural analysis of polymers. When the film which comprises a base material layer contains resin other than an acrylic resin (A) and a cellulose-ester resin (B), it can fractionate by the same method.

  If the weight average molecular weights (Mw) of the compatible resins are different, the high molecular weight substances are eluted earlier by gel permeation chromatography (GPC), and the lower molecular weight substances are eluted after a longer time. Therefore, it can be easily fractionated and the molecular weight can be measured.

  In addition, the molecular weight of the compatible resin is measured by GPC, and at the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the dried resin is different by quantitatively analyzing the structure. By detecting the resin composition for each molecular weight fraction, it is possible to identify each compatible resin. By measuring the molecular weight distribution of each of the resins separated in advance based on the difference in solubility in a solvent by GPC, it is possible to detect each of the compatible resins.

  In addition, as long as the function as a polarizing plate protective film is not impaired, the base material layer may contain resin and additives other than an acrylic resin (A) and a cellulose-ester resin (B). When the resin other than the acrylic resin (A) and the cellulose ester resin (B) is contained, even if the added resin is in a compatible state, it may be mixed without being dissolved. In addition, the total mass of the acrylic resin (A) and the cellulose ester resin (B) in the base material layer is preferably 55% by mass or more, more preferably 60% by mass or more, and particularly preferably. 70% by mass or more.

<Other additive resins>
When a resin other than the acrylic resin (A) and the cellulose ester resin (B) is used for the base material layer of the present invention, the addition amount can be adjusted within a range that does not impair the function of the base material layer of the present invention. preferable.

  As a preferred resin, a low molecular acrylic resin obtained by polymerizing an ethylenically unsaturated monomer described in paragraphs (0072) to (0123) of JP 2010-32655 A (weight average molecular weight Mw of 500 or more and 30000 or less) Polymer).

  Most preferably, Mw is 2000-30000. If it is 1000 or less, a problem occurs in bleed-out, and if it exceeds 30000, the transparency deteriorates.

  Also, a vinyl polymer having an amide bond described in Japanese Patent No. 413895 can be used.

  The low molecular acrylic resin of the present invention and the vinyl polymer having an amide bond are 0 to 15% by mass, preferably 0 to 10% by mass, based on the total mass of the optical film.

<Acrylic particles (D)>
The base material layer of the present invention may contain acrylic particles (D) described in Patent Document 1.

  As an example of a commercial item of such a multilayer structure acrylic granular composite, for example, “Metablene W-341” manufactured by Mitsubishi Rayon Co., “Kaneace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., Examples include “Acryloid” manufactured by Rohm and Haas, “Staffroid” manufactured by Gantz Kasei Kogyo Co., Ltd., Chemisnow MR-2G, MS-300X (manufactured by Soken Chemical Co., Ltd.), and “Parapet SA” manufactured by Kuraray Co., Ltd. These can be used alone or in combination of two or more.

  In the base material layer of the present invention, it is preferable to contain 0 to 30% by mass of acrylic particles (D) with respect to the total mass of the resin constituting the film, and it is contained in the range of 1.0 to 15% by mass. More preferably.

<Other additives>
The base material layer of the present invention is provided with a retardation control agent for the purpose of controlling retardation, a plasticizer for imparting processability to the film, an antioxidant for preventing deterioration of the film, and an ultraviolet absorbing function. It is preferable to contain additives such as ultraviolet absorbers and fine particles (matting agents) that impart slipperiness to the film.

<Plasticizer>
Examples of the plasticizer include aromatic polyesters, polyhydric alcohol esters, sugar esters, phthalates, fatty esters, trimellitic esters, phosphate esters, polyesters, and epoxies. .

  It can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the resin composition. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use. These plasticizers may be used alone or in combination of two or more.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, those including those commercially available from BASF Japan under the trade names of “IrgafosXP40” and “IrgafosXP60” are preferable.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, BASF Japan Ltd., “Irganox 1076”, “Irganox 1010”, and ADEKA “ADEKA STAB AO-50” are trade names. What is marketed is preferable.

  The phosphorous compounds are, for example, from Sumitomo Chemical Co., Ltd., “Sumizer GP”, from ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, from BASF Japan Co., Ltd. IRGAFOS P-EPQ ", commercially available from Sakai Chemical Industry Co., Ltd. under the trade name" GSY-P101 "is preferred.

  As the hindered amine compound, for example, those commercially available from BASF Japan Ltd. under the trade names “Tinuvin 144” and “Tinvin 770”, and ADEKA Co., Ltd. under the name “ADK STAB LA-52” are preferable.

  As the sulfur compound, for example, those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer TPL-R” and “Sumilizer TP-D” are preferable.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Ultraviolet absorber>
The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. In particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products made by BASF Japan Ltd. and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. . In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber. As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  It is preferable that an ultraviolet absorber is contained in the quantity of 0.5-5 mass% with respect to 100 mass% of base material layers, and it is more preferable that it is contained in the quantity of 0.5-3 mass%.

<Matting agent>
In the present invention, it is preferable to add a matting agent in order to impart film slipperiness.

  The matting agent used in the present invention may be either an inorganic compound or an organic compound as long as it does not impair the transparency of the obtained film and has heat resistance during melting. These matting agents can be used alone or in combination of two or more.

  By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible.

  Among these, silicon dioxide is particularly preferably used because it has a refractive index close to that of cellulose ester and is excellent in transparency (haze).

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), Nip Seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs), etc. Goods etc. can be preferably used.

  The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is particularly preferable because the transparency of the resulting film can be improved.

  When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. . If the size of the particles is too small, the slipperiness may not be improved.

  The particle size means the size of the aggregate when the particle is an aggregate of primary particles. Moreover, when a particle is not spherical, it means the diameter of a circle corresponding to the projected area.

  The matting agent (fine particles) is preferably contained in an amount of 0.1 to 2% by mass, more preferably 0.1 to 1% by mass with respect to 100% by mass of the base material layer.

<Production method of polarizing plate>
Hereinafter, an example of the manufacturing method of the polarizing plate using an adhesive agent is demonstrated.

  For example, as described in the examples described later, the polarizing plate is a pretreatment step for easily adhering the surface of the base material layer to which the hydrophilic polymer layer is bonded, and the hydrophilic polymer layer of the base material layer. Adhesive application step of applying an adhesive to the adhesive surface, a laminate forming step of obtaining a laminate by applying a hydrophilic polymer layer forming material to the surface of the adhesive layer, and the obtained laminate Can be manufactured by a manufacturing method including a stretching process for stretching the layer, a dyeing process for dyeing the hydrophilic polymer layer of the laminate with a dichroic substance, and a curing process for curing the adhesive layer. Hereinafter, a preferred embodiment of a method for producing a polarizing plate will be described in the order of steps.

(Pretreatment process)
In the pretreatment step, the surface of the base material layer that adheres to the hydrophilic polymer layer is subjected to easy adhesion treatment. In the next adhesive application step, the surface subjected to the easy adhesion treatment is treated as an adhesive surface with the hydrophilic polymer layer (polarizer).

  The easy adhesion treatment is performed in order to improve the hydrophilicity of the base material layer on the adhesive surface with the hydrophilic polymer layer, thereby improving the adhesiveness of the base material layer to the hydrophilic polymer layer. The easy adhesion treatment is performed on the adhesive surface of the base material layer with the hydrophilic polymer layer, but may be performed on both surfaces of the base material layer.

  Examples of the easy adhesion treatment include corona (discharge) treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment, primer coating treatment, and the like, and at least one of them is performed. Of these easy adhesion treatments, corona treatment and plasma treatment are preferred from the viewpoint of productivity.

  Corona discharge treatment is a method of treating the surface of a sample by generating a corona by applying a high frequency / high voltage between an electrode insulated from a dielectric and passing the sample between the dielectric and the electrode. . Although depending on the type of electrode, electrode interval, voltage, humidity, and type of the substrate layer to be treated, generally, the film surface subjected to the corona discharge treatment is imparted with adhesiveness.

  As a material of the electrode, for example, ceramics, aluminum and the like are preferable. The distance between the electrode and the dielectric is preferably in the range of 1 to 5 mm, and more preferably in the range of 1 to 3 mm. The line speed (moving speed) is preferably about 3 to 70 m / min, and more preferably about 3 to 50 m / min.

  Further, the corona output intensity is preferably set within a range of 0.2 kW to 3 kW, and more preferably within a range of 0.5 kW to 1.5 kW. When the corona output intensity is less than 0.2 kW, corona discharge becomes unstable, and it may be difficult to give a stable adhesive force to the surface of the base material layer. Moreover, when corona output intensity | strength is larger than 2.0 kW, malfunctions, such as a base material layer becoming easy to be damaged, may arise.

  The plasma treatment is a treatment for activating the surface of the base material layer by performing plasma discharge in a gas atmosphere such as an inert gas or oxygen gas generated under reduced pressure or atmospheric pressure. In order to produce efficiently under conveyance using a roll, plasma treatment under atmospheric pressure is preferable.

In the plasma treatment, the surface of the object to be processed can be variously modified by variously changing the type of the gas. Therefore, the type of gas can be arbitrarily selected when activating the substrate layer surface. it can. Examples of the gas used include fluorine compounds such as nitrogen, oxygen, argon, helium, acrylic acid, hydroxyalkyl, CF ₄ , CHF ₃ , and C ₂ F ₆ . These may be used alone or in combination of two or more.

  The plasma output is preferably set in the range of 0.2 kW to 3 kW. The line speed (moving speed) is preferably about 3 to 70 m / min, more preferably about 3 to 50 m / min. The frequency range is preferably 3 to 30 kH, more preferably 5 to 20 kH.

The surface free energy (mJ / m ² ) on the surface of the base material layer bonded to the hydrophilic polymer layer after the easy adhesion treatment has a dispersion force component satisfying the following formula (3a) and a polar component represented by the following formula (3b ) Is preferably satisfied.

Formula (3a) 24.5 ≦ dispersion force component ≦ 40.0
Formula (3b) 10.0 ≦ polar component ≦ 33.0
The surface free energy of the base material layer according to the present invention is measured according to the Kitazaki-Hata theory. According to the Kitazaki-Hata theory, the contact angle θ with respect to several kinds of liquids whose surface free energies are known is expressed by the following formula.

In the formula, γ _S represents the surface free energy of the substrate layer, γ _SL represents the surface free energy between the substrate layer and the liquid, and γ _L represents the surface free energy of the liquid.

The surface free energy γ _S can also be expressed as γ _S = γ ^d + γ ^p + γ ^h by three components, that is, a dispersion force component γ ^d , a polar component γ ^p , and a hydrogen bond component γ ^h .

  Specifically, the surface free energy is measured by the following measuring method.

For measurement, an average contact angle of the probe liquid is obtained by a droplet method using a solid-liquid interface analyzer (DropMaster 500) manufactured by Kyowa Interface Science Co., Ltd. Water, ethylene glycol, or diiodomethane is used as the probe liquid. Specifically, about 30 μl of the probe liquid is dropped on the base material layer, and the contact angle θ of the droplet T is measured as shown in FIG. An average value of the contact angles θ measured 10 times is calculated to obtain an average contact angle θ _av for each probe liquid. After that, by analyzing the Kitazaki-Hata method using the FAMAS surface free energy analysis add-in software, which is an accessory software, the dispersion force component, polar component, hydrogen bonding component of the surface free energy of the base material layer Three components are obtained.

(Adhesive application process)
In the adhesive application step, an adhesive is applied to the adhesive surface of the base material layer with the hydrophilic polymer layer. When applying an adhesive agent directly to the surface of a base material layer, there is no special limitation in the application method. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used.

The adhesive used for bonding is preferably an adhesive having a storage elastic modulus at a temperature of 25 ° C. in the range of 1.0 × 10 ^{4 to} 1.0 × 10 ⁹ Pa when used as an adhesive layer. Moreover, after apply | coating and bonding an adhesive agent, the curable adhesive agent which forms a high molecular weight body or a crosslinked structure by various chemical reaction is used suitably.

  Specific examples of adhesives include urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, and polyether methacrylate types. Anaerobic adhesives such as ester methacrylate type and oxidized polyether methacrylate, cyanoacrylate instant adhesives, acrylate and peroxide type two-component instant adhesives, among which photocurable adhesives are preferred . The pressure-sensitive adhesive may be a one-component type or a two-component type in which two or more components are mixed before use.

  The adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The concentration of the adhesive liquid may be appropriately determined depending on the film thickness after bonding, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

(Photo curable adhesive)
As a preferable example of the photocurable adhesive for laminating the hydrophilic polymer layer and the base material layer, for example, (α) a cationic polymerizable compound as disclosed in JP2011-028234, (Β) a photocationic polymerization initiator, (γ) a photosensitizer exhibiting maximum absorption in light having a wavelength longer than 380 nm, and (δ) a photocurable adhesive containing each component of a naphthalene photosensitizer. A composition. Of course, other photocurable adhesives may be used.

(Laminate formation process)
In the laminated body formation process of this embodiment, the formation material of a hydrophilic polymer layer is applied to the surface of an adhesive bond layer, and a laminated body is obtained. In addition, it is preferable to apply a hydrophilic polymer layer forming material on the surface of the adhesive layer described above. However, in some cases, the formation of the adhesive layer is omitted, and the base material layer subjected to the easy adhesion treatment is used. A laminate may be obtained by applying a hydrophilic polymer layer forming material directly on the surface.

  Examples of the material for forming the hydrophilic polymer layer include an aqueous solution of a hydrophilic polymer such as polyvinyl alcohol (PVA). The aqueous solution can be prepared by dissolving a powder of a hydrophilic polymer or a pulverized product or a cut product of a hydrophilic polymer film in appropriately heated water (hot water). Application of the aqueous solution onto the base material layer is performed by a wire bar coating method, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, or a spray method. Etc. can be selected and adopted as appropriate. When the base material layer has a primer layer, the aqueous solution is directly applied to the primer layer. When the base material layer does not have a primer layer, the aqueous solution is directly applied to the base material layer. The drying temperature is usually 50 to 200 ° C., preferably 80 to 150 ° C., and the drying time is usually about 5 to 30 minutes.

(Stretching process / dyeing process)
Then, the polarizing plate which concerns on this invention is obtained as a form of an extending | stretching laminated body by giving the extending | stretching process and the dyeing | staining process by a dichroic substance to the laminated body obtained above. The stretched laminate formed by the above treatments is subjected to the stretching treatment to the hydrophilic polymer layer and the dyeing treatment with the dichroic material so that the dichroic material is adsorbed to the obtained hydrophilic polymer layer. Function as a polarizer.

  The stretching treatment is usually performed by subjecting the laminate to uniaxial stretching. Uniaxial stretching can employ any of longitudinal stretching performed in the longitudinal direction of the laminate and transverse stretching performed in the width direction of the laminate. In transverse stretching, the film can be contracted in the longitudinal direction while stretching in the width direction. Examples of the transverse stretching method include a fixed end uniaxial stretching method in which one end is fixed via a tenter, and a free end uniaxial stretching method in which one end is not fixed. Examples of the longitudinal stretching method include an inter-roll stretching method, a compression stretching method, and a stretching method using a tenter. The stretching process can be performed in multiple stages. The stretching treatment may be performed by performing biaxial stretching, oblique stretching, or the like.

  In addition, as the stretching treatment, either a wet stretching method or a dry stretching method can be adopted, but in the present invention, the dry stretching method can be used, and the temperature range when stretching the laminate can be set wide. Is preferable. In the dry stretching method, the stretching is usually performed in a state where the laminate is heated to about 50 to 200 ° C., preferably 80 to 180 ° C., and more preferably 100 to 160 ° C.

  In the stretching treatment, the total stretching ratio is 1.5 to 17 times the original length of the laminate. Preferably it is 1.5-10 times, More preferably, it is 1.5-8 times. In addition, the said total draw ratio means the cumulative draw ratio including the extension in those processes, when extending in processes other than an extending process process. The total draw ratio is appropriately determined in consideration of the draw ratio in other steps. When the total draw ratio is low, the orientation is insufficient and it is difficult to obtain a polarizer having high optical properties (polarization degree). On the other hand, if the total draw ratio is too high, stretch breakage is likely to occur, and the polarizer becomes too thin, which may reduce the workability in the subsequent process.

  The dyeing process is performed by adsorbing a dichroic substance to the hydrophilic polymer layer of the laminate. Examples of the dichroic substance include iodine and organic dyes. Organic dyes include, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First orange S, first black, etc. can be used. One kind of these dichroic substances may be used, or two or more kinds may be used in combination.

  For example, the dyeing process is performed by immersing the laminate in a solution (dyeing solution) containing the dichroic substance. As the staining solution, a solution in which the dichroic substance is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic substance is preferably in the range of 0.01 to 10% by weight, more preferably in the range of 0.02 to 7% by weight, and 0.025 to 5% by weight. Is particularly preferred.

  Further, when iodine is used as the dichroic substance, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01 to 10% by weight, and more preferably 0.1 to 5% by weight in the dyeing solution. Among these, it is preferable to add potassium iodide, and the ratio (mass ratio) of iodine and potassium iodide is preferably in the range of 1: 5 to 1: 100, and 1: 6 to 1:80. More preferably, it is in the range of 1: 7 to 1:70.

  The immersion time of the laminate in the dyeing solution is not particularly limited, but usually it is preferably in the range of 15 seconds to 5 minutes, more preferably 1 minute to 3 minutes. Moreover, it is preferable that it is in the range of 10-60 degreeC, and, as for the temperature of a dyeing | staining solution, it is more preferable that it exists in the range of 20-40 degreeC.

  In the dyeing process, the dichroic substance is oriented by adsorbing the dichroic substance to the hydrophilic polymer layer of the laminate. The dyeing treatment can be performed before, simultaneously with, or after the stretching treatment. From the viewpoint of favorably orienting the dichroic material adsorbed on the hydrophilic polymer layer, the dyeing treatment is performed on the laminate. It is preferable to carry out after the treatment.

  The polarizing plate of the present invention can be subjected to a crosslinking treatment in addition to the stretching treatment and the dyeing treatment. The crosslinking treatment can be performed, for example, by immersing the laminate in a solution containing a crosslinking agent (crosslinking solution). A conventionally known substance can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

  As the crosslinking solution, a solution obtained by dissolving the crosslinking agent in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density | concentration of the crosslinking agent in the said solution is not limited to this, It is preferable to exist in the range of 1-10 mass%, and it is more preferable that it is 2-6 weight%.

  Iodide may be added to the crosslinking solution from the viewpoint that uniform characteristics in the plane of the polarizer can be obtained. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

  The immersion time of the laminate in the crosslinking solution is usually preferably from 15 seconds to 5 minutes, and more preferably from 30 seconds to 3 minutes. Moreover, it is preferable that the temperature of a bridge | crosslinking solution exists in the range of 10-60 degreeC, and it is more preferable that it exists in the range of 20-50 degreeC.

  Furthermore, the crosslinking treatment can also be performed using a method of coating or spraying the crosslinking solution, similarly to the dyeing treatment. In the crosslinking treatment, the crosslinking treatment and the dyeing treatment can be performed simultaneously by blending the crosslinking agent into the dyeing solution. Moreover, you may perform a crosslinking process with an extending | stretching process.

  In addition to the above treatment, the polarizing plate of the present invention can be subjected to metal ion treatment. The metal ion treatment is performed by immersing the laminate in an aqueous solution containing a metal salt. Various metal ions can be contained in the hydrophilic polymer layer of the laminate by metal ion treatment.

  As metal ions, metal ions of transition metals such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, and iron are particularly preferably used in terms of color tone adjustment and durability. Among these metal ions, zinc ions are preferable from the viewpoints of color tone adjustment and heat resistance. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate.

  A metal salt solution is used for the metal ion impregnation treatment. The concentration of zinc ions in the metal salt solution is about 0.1 to 10% by mass, preferably 0.3 to 7% by mass. In addition, it is preferable to use an aqueous solution containing an iodide such as potassium iodide as the metal salt solution because it is easy to impregnate metal ions. The iodide concentration in the metal salt solution is preferably about 0.1 to 10% by mass, and more preferably 0.2 to 5% by mass.

  In the metal ion impregnation treatment, the temperature of the metal salt solution is usually about 15 to 85 ° C, preferably 25 to 70 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. The stage of the metal ion impregnation treatment is not particularly limited, and it may be carried out simultaneously with the dyeing treatment and / or the crosslinking treatment in the presence of a zinc salt in the dyeing solution and / or the crosslinking solution. It can also be performed simultaneously with the stretching treatment.

  After the treatment, the obtained stretched laminate can be washed. The washing treatment can be performed with an iodide solution such as potassium iodide. The iodide concentration in the iodide solution is usually in the range of about 0.5 to 10% by mass, further 0.5 to 8% by mass, and further 1 to 6% by mass.

  In the washing treatment with an iodide solution, the treatment temperature is usually about 15 to 60 ° C, preferably 25 to 40 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. The stage of the washing treatment with the iodide solution is not particularly limited as long as it is before the drying treatment.

  Further, as a cleaning process, a water cleaning process can be performed. The water washing treatment can usually be performed by immersing the stretched laminate in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 5 to 50 ° C, preferably 10 to 45 ° C, more preferably 15 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably about 20 to 240 seconds.

  After the washing process, a drying process can be performed. Arbitrary appropriate methods (For example, natural drying, ventilation drying, heat drying) can be employ | adopted for a drying process. For example, the drying temperature in the case of heat drying is usually about 20 to 80 ° C., and the drying time is usually about 1 to 10 minutes.

(Curing process)
In the curing step, when a photocurable adhesive is used as an adhesive, the active energy ray is irradiated to the uncured photocurable adhesive to cure the adhesive layer, and the photocurable adhesive is passed through the photocurable adhesive. The superposed hydrophilic polymer layer and the base material layer are adhered. When a base material layer is bonded to one side of the hydrophilic polymer layer, the active energy ray may be irradiated from either the hydrophilic polymer layer side or the base material layer side. Visible light, ultraviolet rays, X-rays, electron beams, and the like can be used as the active energy rays, but ultraviolet rays are generally preferably used because they are easy to handle and have a sufficient curing rate. The light source of the active energy ray is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less. An LED lamp or the like can be used.

The light irradiation intensity to the photocurable adhesive is determined for each target composition and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is UV. It is preferable to adjust so that it may become the range of 1-3000 mW / cm < ² > as -B (280-320 nm medium wavelength range ultraviolet-ray). When the irradiation intensity is less than 1 mW / cm ² , the reaction time becomes too long, and when the irradiation intensity exceeds 3,000 mW / cm ² , due to the heat radiated from the lamp and the heat generated during polymerization of the photocurable adhesive, There is a possibility of causing yellowing of the photocurable adhesive and deterioration of the hydrophilic polymer layer.

The light irradiation time to the photocurable adhesive is controlled for each composition to be cured and is not particularly limited, but the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5000 mJ / cm. It is preferably set to be in the range of ² . When the integrated light quantity is less than 10 mJ / cm ² , active species derived from the polymerization initiator are not sufficiently generated, and the adhesive layer may be insufficiently cured. On the other hand, if the integrated light quantity exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  When curing the photocurable adhesive by irradiating with active energy rays, it should be cured under conditions that do not deteriorate the various functions of the polarizing plate, such as the degree of polarization of the polarizer, transmittance, hue, and transparency of the base material layer. Is preferred.

  The polarizing plate (stretched laminate) of the present invention has a base material layer on one side of a hydrophilic polymer layer (polarizer). A base material layer can be used as it is as a transparent protective film of a polarizing plate. On the other hand, a transparent protective film can be bonded to the side without the base material layer in the hydrophilic polymer layer.

As the transparent protective film, materials similar to those exemplified as the base material layer can be used. The aforementioned polarizing plate can be provided with an adhesive layer for adhering to other members such as a liquid crystal cell. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  The attachment of the adhesive layer to the polarizing plate can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by mass in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method of attaching it directly on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or forming an adhesive layer on a separator according to the above and transferring it onto the polarizing plate The method to do.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 40 μm, preferably 5 to 30 μm, particularly preferably 10 to 25 μm. When the thickness is less than 1 μm, the durability is deteriorated. When the thickness is more than 40 μm, floating or peeling due to foaming is liable to occur, resulting in poor appearance. On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used. In order to improve the adhesion between the polarizing plate and the pressure-sensitive adhesive layer, an anchor layer can be provided between the layers.

  As the material for forming the anchor layer, an anchor agent selected from polyurethane, polyester, and polymers containing an amino group in the molecule is preferably used, and polymers containing an amino group in the molecule are particularly preferred. . Polymers containing an amino group in the molecule ensure good adhesion because the amino group in the molecule exhibits an interaction such as a reaction or ionic interaction with the carboxyl group in the pressure-sensitive adhesive.

  Examples of polymers containing an amino group in the molecule include polymers of amino-containing group-containing monomers such as polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidine, dimethylaminoethyl acrylate, and the like.

  An antistatic agent may be added to the anchor layer in order to impart antistatic properties. Antistatic agents for imparting antistatic properties include ionic surfactant systems, conductive polymer systems such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline, metal oxide systems such as tin oxide, antimony oxide, and indium oxide. In particular, from the viewpoint of optical properties, appearance, antistatic effect, and antistatic effect heating and stability during humidification, a conductive polymer system is preferably used. Among these, water-soluble conductive polymers such as polyaniline and polythiophene or water-dispersible conductive polymers are particularly preferably used.

  When a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer, it is possible to suppress deterioration of the optical film substrate due to an organic solvent during coating.

  In the present invention, the polarizer, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, and a cyanoacrylate. It may be a compound having ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a nickel compound or a nickel complex salt compound.

[Liquid Crystal Display]
The polarizing plate of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply conventionally. As the liquid crystal cell, any type such as a TN type, STN type, π type, VA type, IPS type, or the like can be used. In particular, an IPS liquid crystal display device is preferable.

(IPS mode liquid crystal cell)
The liquid crystal layer of the liquid crystal panel in the IPS mode type liquid crystal display device is homogeneously aligned parallel to the substrate surface in the initial state, and the director of the liquid crystal layer is parallel to the electrode wiring direction when no voltage is applied. The direction of the director of the liquid crystal layer shifts to a direction perpendicular to the electrode wiring direction when a voltage is applied, and the director direction of the liquid crystal layer is the direction of the director when no voltage is applied. When tilted in the direction of the electrode wiring by 45 ° compared to the liquid crystal layer when the voltage is applied, the azimuth angle of the polarization is rotated by 90 ° like a half-wave plate, and the transmission axis and polarization of the output side polarizing plate are rotated. The azimuth angles of the two coincide with each other to display white.

  In general, the thickness of the liquid crystal layer is constant, but since it is driven by a transverse electric field, it may be possible to increase the response speed to switching by slightly increasing the thickness of the liquid crystal layer, but the thickness of the liquid crystal layer is constant. Even if it is not, it is possible to make the most of the effect, and there is little influence on the change in the thickness of the liquid crystal layer. The thickness of the liquid crystal layer is 2 to 6 μm, and preferably 3 to 5.5 μm. The liquid crystal display device according to this embodiment can be preferably used for portable devices such as a tablet display device and a smartphone in addition to being used for a large liquid crystal television.

  The details of the IPS mode type liquid crystal cell are not particularly limited, and the present invention may of course be carried out by referring to other conventionally known technical matters (for example, JP 2010-3060 A). .

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<< Production of Polarizing Plate 1 >>
(Preparation of aqueous polyvinyl alcohol solution)
A polyvinyl alcohol film (average polymerization degree 2400, saponification degree 99 mol%, trade name: VF-PS2400) manufactured by Kuraray Co., Ltd., which is a film made of a hydrophilic polymer, is cut into small pieces having a side of 5 mm or less. And dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 10% by mass.

(Production of laminate: formation of hydrophilic polymer layer)
The film 2 shown in Table 1 below was prepared as a base material layer. In addition, preparation of this film 2 was performed as follows. First, the following materials were further dried while being mixed at 80 ° C. and 1 Torr for 3 hours with a vacuum nauter mixer, and the resulting mixture was melt-mixed at 235 ° C. using a twin-screw extruder to be pelletized.

Acrylic resin (methyl methacrylate / acryloylmorpholine = 80/20 (molar ratio); Mw = 100000; dried at 90 ° C. for 3 hours and water content 1000 ppm by mass) 70 parts by weight Cellulose ester resin (cellulose acetate propionate: acyl group) Total substitution degree 2.7, acetyl group substitution degree 0.1, propionyl group substitution degree 2.6, Mw = 200000, dried at 100 ° C. for 3 hours and water content 500 mass ppm) 30 parts by mass Tinuvin 928 (BASF Japan Ltd.) 1.1 parts by mass ADK STAB PEP-36 (manufactured by ADEKA Corporation) 0.25 parts by mass Irganox 1010 (manufactured by BASF Japan Ltd.) 0.5 parts by mass Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.24 parts by mass Part Aerosil R972V (Nippon Aerosil Co., Ltd.) 0.2 The parts by weight resulting pellet was circulated over 5 hours 70 ° C. dehumidified air and dried, the while keeping the temperature of 100 ° C., and introduced into the next step uniaxial extruder.

The pellet was melt extruded from a T die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder to obtain a 120 μm cast film. At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface.
(Preparation of photocurable adhesive liquid)
Each of the following components was mixed and then defoamed to prepare a photocurable adhesive liquid. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.
(Composition of photocurable adhesive liquid)
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (Daicel Co., Ltd. alicyclic epoxy resin) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass Next, the prepared film 2 was longitudinally treated at 140 ° C. ( (MD direction) was stretched at a stretch ratio of 2 times. Thereafter, the surface of the stretched film 2 was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the prepared photocurable adhesive liquid was applied to the corona discharge treated surface of the stretched film with a bar coater so that the film thickness after curing was about 3 μm, thereby forming an adhesive layer.

  Furthermore, after applying the polyvinyl alcohol aqueous solution prepared above on the adhesive layer formed above, it was dried at 120 ° C. for 10 minutes to form a hydrophilic polymer layer comprising a polyvinyl alcohol coating film having a thickness of 10 μm. Thus, a laminate was obtained.

(Extension process)
The laminate obtained above was stretched at a stretch ratio of 5 times in the width direction (TD direction) at 140 ° C. to obtain a stretched laminate.

(Dyeing process)
The stretched laminate produced above was immersed in an iodine solution (mass ratio: iodine / potassium iodide / water = 1/10/100) at 30 ° C. for 60 seconds while maintaining the tension. Thereafter, drying was performed at 60 ° C. for 4 minutes.

(Curing process)
Using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems, Inc.), the adhesive layer was cured by irradiating ultraviolet rays so that the integrated light amount became 750 mJ / cm ² .

The polarizing plate 1 was obtained through the above steps. In addition, the thickness of the base material layer (film 2; after extending | stretching) in the obtained polarizing plate 1 was 20 micrometers. The thickness of the hydrophilic polymer layer (after stretching) in the polarizing plate 1 was 2 μm. Furthermore, the base material layer in the polarizing plate 1; moisture permeability of (film 2 after stretching) was 900 g ^/ m 2 / 24h (see Table 2 below).

In addition, the value of the moisture permeability shown in Table 2 is a temperature of 40 ° C. according to the moisture permeability test (cup method) of JIS Z0208 using a film obtained by stretching only a base film under the same stretching conditions as a sample. In an atmosphere having a humidity of 92% RH, a sample having an area of 1 m ² was measured as the number of grams of water vapor passing through in 24 hours.

<< Production of Polarizing Plates 2-37 >>
Polarizing plates 2 to 37 were produced by the same method as the production of the polarizing plate 1 described above. At this time, as shown in Table 2, the base material layer and the hydrophilic polymer layer were prepared by adjusting the conditions of the stretching treatment using any of the films 1 to 15 shown in Table 1 as the film constituting the base material layer. The thickness of the was controlled. Further, in some polarizing plates (polarizing plates 18 and 19 and polarizing plates 23 to 26), a hydrophilic polymer layer was formed without using a photocurable adhesive (that is, corona discharge treatment of the stretched film). A hydrophilic polymer layer was prepared by applying an aqueous polyvinyl alcohol solution on the surface). In Table 2, when a polarizing plate (such as polarizing plate 2) in which the column of the base material layer is stretched is prepared, the base material layer alone is not stretched. Drawing was performed at a draw ratio and a drawing temperature. Furthermore, the expressions “dry stretching” and “wet stretching” described in Table 2 mean stretching in air and stretching in a boric acid solution, respectively.

<< Production of liquid crystal display devices 1-15, 20-33 >>
Liquid crystal display devices 1 to 15 and 20 to 33 were produced using any of the polarizing plates 1 to 37 produced above (see Table 3 below). A conventionally known IPS mode type liquid crystal display panel was used as the liquid crystal display panel. The polarizing plate was bonded to the panel using an acrylic pressure-sensitive adhesive so that the hydrophilic polymer layer side faces the liquid crystal display panel. These examples assume an embodiment in which a layer functioning as a polarizing plate protective film does not exist between a liquid crystal display panel and a layer functioning as a polarizer (hydrophilic polymer layer).

<< Production of liquid crystal display devices 16 to 19 >>
A polarizing plate protective film mainly composed of triacetyl cellulose (manufactured by Konica Minolta Advanced Layer Co., Ltd.) on the exposed surface of each of the polarizing plates 1, 5, 9 and 16 prepared above on the hydrophilic polymer layer side. A Konica Minolta Tac KC-2UA) was attached via an aqueous adhesive to prepare a polarizing plate having a three-layer structure of base material layer / hydrophilic polymer layer / 2UA. A liquid crystal display device was produced in the same manner as described above using any of the polarizing plates thus obtained. Under the present circumstances, the polarizing plate was bonded together with the said panel so that the base-material layer side might face a liquid crystal display panel. In these examples, a layer (base material layer) that functions as a polarizing plate protective film exists between a liquid crystal display panel and a layer that functions as a polarizer (hydrophilic polymer layer). On the other hand, an embodiment in which a conventionally known polarizing plate protective film (here 2UA) is arranged on the side opposite to the base material layer is assumed.

<< Evaluation of Liquid Crystal Display >>
The liquid crystal display device produced above was evaluated for the presence / absence of brightness unevenness and the reworkability. The evaluation methods and evaluation criteria are as follows.

(Luminance unevenness)
The IPS mode type liquid crystal display device was subjected to wet heat treatment at 50 ° C. and 90% RH for 24 hours, and the luminance unevenness (strong / weak) in black display after 2 hours of lighting of the backlight and the effect when displaying the image were visually evaluated. Note that there is no problem if the luminance unevenness evaluation result is Δ or more.

○: Uneven brightness is not visible △: Uneven brightness unevenness is visible but not noticeable in image display ×: Strong brightness unevenness is also annoying in image display (Reworkability)
The reworkability of the polarizing plate produced above was evaluated as follows.

  First, the polarizing plate was cut into a test piece having a size of 25 mm × 150 mm.

  Next, a test sample was obtained by attaching the base material layer side of this test piece to a glass substrate for a liquid crystal cell using a laminator, and then autoclaving at 50 ° C. and 5 atm for 15 minutes. The polarizing plate was peeled off from one corner in the diagonal direction at 90 degrees, and the determination was made according to the following criteria.

  The results are shown in Table 3 below.

◯: The film can be peeled in a state where the films are in close contact with each other, and almost no fogging or adhesive residue is observed on the glass plate surface. Δ: The film is slightly peeled off at the corner.

  X: Peeling between films is observed.

  As shown in Table 3, according to the present invention, polarized light that can suppress the occurrence of luminance unevenness during panel display of the liquid crystal display device, has excellent reworkability during manufacturing, and can achieve a thin liquid crystal display device. It can be seen that a plate can be provided.

Claims (8)

A polarizing plate having a stretched laminate obtained by stretching a laminate of a hydrophilic polymer layer and a base material layer,
A dichroic substance is adsorbed on the hydrophilic polymer layer constituting the stretched laminate,
The hydrophilic polymer layer has a thickness of 2 to 10 μm,
The thickness of the base material layer is 5 to 30 μm,
The polarizing plate whose moisture permeability of the said base material layer is 130 g / m < ² > / 24h or more. The base material layer contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70 and in a compatible state,
The acyl group total substitution degree (T) of the cellulose ester resin (B) is 2.0 to 3.0, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0, The polarizing plate of Claim 1 whose weight average molecular weight Mw is 75000 or more. The base material layer contains acrylic resin (A) and cellulose ester resin (B) in a mass ratio of 95: 5 to 50:50 and in a compatible state,
The acrylic resin (A) is represented by the following general formula (1):
In the formula, MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one amide group, Y represents a monomer unit copolymerizable with MMA and X, p, q, and r Is the mole percentage of each structural unit, 55 ≦ p ≦ 99, 1 ≦ q ≦ 50, p + q + r = 100.
The polarizing plate according to claim 1 or 2, which is represented by formula (1) and has a weight average molecular weight Mw of 20,000 to 1,000,000.   The polarizing plate according to any one of claims 1 to 3, wherein the hydrophilic polymer layer and the base material layer are bonded by a photocurable adhesive containing an epoxy compound and a cationic polymerization initiator. .   The polarizing plate according to claim 1, wherein the hydrophilic polymer layer contains polyvinyl alcohol as a hydrophilic polymer.   The polarizing plate according to claim 1, wherein the dichroic substance is iodine.   The liquid crystal display device provided with the polarizing plate of any one of Claims 1-6.   The liquid crystal display device according to claim 7, which is an IPS mode type liquid crystal display device.