KR102517834B1 - Polarizing film, its manufacturing method and image display device - Google Patents

Abstract

The present invention is a polarizing film comprising a polarizer and a functional layer formed directly on at least one side of the polarizer, wherein the functional layer has a urethane prepolymer (a) which is a reaction product of an isocyanate compound and a polyhydric alcohol, and isocyanate group reactivity. A cured product of a forming material containing a compound (b) containing at least two functional groups containing active hydrogen and having a molecular weight divided by the number of functional groups of 350 or less. The polarizing film of the present invention can efficiently form a functional layer having good adhesion to a polarizer and good cohesion.

Description

Polarizing film, its manufacturing method and image display device

The present invention relates to a polarizing film and a manufacturing method thereof. The polarizing film may form an image display device such as a liquid crystal display (LCD) or an organic EL display as a single polarizing film or an optical film in which the polarizing film is laminated.

It is indispensable for a liquid crystal display device to arrange polarizing films on both sides of a glass substrate forming the surface of a liquid crystal panel from its image forming method. A polarizing film is generally used in which a protective film is bonded to one side or both sides of a polarizer made of a polyvinyl alcohol-based film and a dichroic material such as iodine with a polyvinyl alcohol-based adhesive or the like.

In addition, polarizing films are exposed to harsh environments depending on their intended use or usage conditions. Therefore, durability capable of maintaining optical properties even under harsh environments is required of the polarizing film. For example, it has been proposed to cure a urethane prepolymer on at least one side of a polarizer to provide a urethane resin layer (Patent Documents 1 and 2). According to Patent Literatures 1 and 2, it is described that the orthogonal transmittance of the polarizing film can be maintained even under high temperature. Further, for example, a polarizing plate with a pressure-sensitive adhesive layer provided with a primer layer formed from a primer composition containing an isocyanate compound between the polarizing plate and the pressure-sensitive adhesive layer is described (Patent Document 3). According to Patent Document 3, it is described that a polarizing plate with a pressure-sensitive adhesive layer excellent in adhesion between the polarizing plate and the pressure-sensitive adhesive layer can be obtained by the primer layer.

Japanese Unexamined Patent Publication No. 11-030715 Japanese Unexamined Patent Publication No. 11-183726

However, urethane resins such as Patent Documents 1 and 2 and primer layers such as Patent Document 3 directly formed on the polarizer have slow reactions to form these layers, and it takes time to improve the cohesive force of the formed layer. Therefore, it caused peeling of the formed layer obtained.

An object of the present invention is to provide a polarizing film comprising a functional layer formed directly on at least one side of a polarizer, which can efficiently form a functional layer having good adhesion to the polarizer and cohesive force, and a method for manufacturing the same. to be

In addition, an object of the present invention is to provide an image display device including the polarizing film.

As a result of earnest examination, the inventors of this application discovered that the above-mentioned problems could be solved with the following polarizing film or the like, and reached the present invention.

That is, the present invention is a polarizing film comprising a polarizer and a functional layer formed directly on at least one side of the polarizer,

The functional layer includes a urethane prepolymer (a), which is a reaction product of an isocyanate compound and a polyhydric alcohol, and at least two functional groups containing active hydrogens reactive with isocyanate groups, and the molecular weight divided by the number of the functional groups is It relates to a polarizing film characterized by being a cured product of a forming material containing a compound (b) having a molecular weight of 350 or less.

In the polarizing film, it is preferable that the number of functional groups containing active hydrogen in the compound (b) is 3 or more.

In the polarizing film, it is preferable that the molecular weight of the compound (b) is 1000 or less.

In the polarizing film, a polyhydric alcohol can be used as the compound (b). As said compound (b), trimethylol propane can be illustrated.

In the polarizing film, it is preferable that at least one selected from tolylene diisocyanate and diphenylmethane diisocyanate is used as the isocyanate compound in the urethane prepolymer (a).

In the polarizing film, the forming material preferably contains 5% by weight of the compound (b) based on 100 parts by weight (solid content) of the urethane prepolymer (a) and the compound (b) in total.

In the polarizing film, it is preferable that the thickness of the functional layer is 3 μm or less.

In the polarizing film, it is preferable that the thickness of the polarizer is 10 μm or less.

In addition, the polarizing film includes the functional layer on the other side of the polarizer,

A protective film may be included on the other side through an intervening layer. The polymer forming the protective film preferably contains at least one selected from cellulose-based polymers, acrylic-based polymers, and polyolefins having a cyclo- or norbornene structure.

In addition, the polarizing film may include a pressure-sensitive adhesive layer on a side opposite to a side including the polarizer in the functional layer.

In addition, the present invention is a method for producing the polarizing film,

A urethane prepolymer (a), which is a reaction product of an isocyanate compound and a polyhydric alcohol, and a compound containing at least two functional groups containing active hydrogens reactive with isocyanate groups and having a molecular weight divided by the number of the functional groups of 350 or less (b) Step (1) of preparing a forming material containing ), step (2) of directly applying the forming material prepared in the above step (1) to at least one side of the polarizer, and

Including a step (3) of curing the forming material applied in the coating step (2)

It relates to a method for producing a polarizing film characterized by.

In the method for producing the polarizing film, the value of the peak area of the isocyanate group in the forming material measured by FT-IR immediately after preparing in the step (1) of the forming material prepared in the step (1) is reduced by 5% or more It is preferable to use for the said process (2) after leaving it to stand until it does.

Also, the present invention relates to an image display device including the polarizing film.

In addition to the urethane prepolymer (a), the functional layer included in the polarizing film of the present invention includes at least two functional groups containing active hydrogens reactive with isocyanate groups, and a compound whose molecular weight divided by the number of functional groups is 350 or less. It is formed by the hardened|cured material of the forming material containing (b). In the forming material, in addition to self-crosslinking of the urethane prepolymer (a), by including the compound (b), the reaction between the isocyanate group of the urethane prepolymer (a) and the functional group of the compound (b) proceeds. Compared to the case of forming a cured product using the urethane prepolymer (a), the reaction progresses quickly, and the time until the functional layer acquires cohesive force by sufficiently curing the forming material is fast. As a result, a polarizing film capable of forming a functional layer having good adhesion to a polarizer and suppressing peeling based on the functional layer can be provided.

1 is an example of a schematic cross-sectional view of a polarizing film of the present invention.
2 is an example of a schematic cross-sectional view of the polarizing film of the present invention.
3 is an example of a schematic cross-sectional view of the polarizing film of the present invention.
4 is an example of a schematic cross-sectional view of the polarizing film of the present invention.

Below, the polarizing film of this invention is demonstrated, referring FIGS. 1-4.

The polarizing film of this invention contains the polarizer P and the functional layer 1 like the polarizing film 11 shown, for example in FIGS. 1-4. In addition, in FIG. 1, the case where the functional layer 1 is included only on one side of the polarizer P is illustrated. The functional layer 1 may be provided on both sides of the polarizer P. 1 to 4, the functional layer 1 is directly provided on the polarizer P.

Moreover, the polarizing film of this invention can provide the adhesive layer 2 further to the functional layer 1 of the said polarizing film 11 like the polarizing film 12 shown in FIG. 2, for example. The pressure-sensitive adhesive layer 2 can be directly provided on the functional layer 1 .

On the other hand, the polarizing film of the present invention, like the polarizing film 13 shown in FIG. 3, includes the functional layer 1 on one side of the polarizer P, and the protective film through the intervening layer 3 on the other side. (4) can be provided. When a material with low moisture permeability is used as the protective film 4, since moisture diffusion from the polarizer P is inhibited together with the intervening layer 3, the present invention is a protective film only on one side of the polarizer P. It is preferably applied in the aspect of the piece protection polarizing film comprising (4). 4 shows a case where the pressure-sensitive adhesive layer 2 is provided on the functional layer 1 of the polarizing film 13.

Moreover, in the polarizing films 12 and 14 of this invention, when using an adhesive layer as the adhesive layer 2, a separator can be provided in the said adhesive layer (adhesive layer). On the other hand, the polarizing films 11-14 of this invention can be provided with a surface protection film suitably.

In addition, a polarizing film may be used under a high-temperature, high-humidity environment other than under a high-temperature environment. Under such a severe environmental atmosphere, it was found that moisture in the environmental atmosphere affects the optical properties of the polarizer, and the degree of polarization greatly decreases at the end portion of the polarizing film. However, by providing the urethane resin like the said patent document 1, 2 to a polarizer, the fall of the polarization degree at the edge part of the said polarizing film could not be suppressed sufficiently.

Since the polarizer, which is a component of the polarizing film, is formed of a water-based material, moisture in the environmental atmosphere is easily incorporated into the polarizer. Therefore, when a polarizing film is maintained in a high-temperature, high-humidity environment, it is thought that the saturation moisture content in the polarizer rises. As a result, the optical properties of the polarizing film tend to deteriorate. In particular, it is considered that under a high-temperature, high-humidity environment, since there is a large amount of water penetration into the polarizer, the polarization degree is greatly reduced at the end portion of the polarizing film, and a phenomenon called end color loss has occurred.

In the polarizing film of the present invention,

In the case where, for example, an intervening layer 3 is provided in addition to the functional layer 1,

For the functional layer (1), the saturation moisture content at 85 ° C. and 85% R.H. is lower than that of the polarizer at 85 ° C. and 85% R.H.,

The functional layer 1 functions as a permeable film that helps discharge of moisture in the polarizer,

The saturation moisture content of the intervening layer 3 at 85° C. and 85% R.H. is 5% by weight or less.

By adjusting to , it is possible to respond effectively to the above problems.

The polarizing film of the above aspect includes a functional layer functioning as a permeable film that helps discharge of moisture in the polarizer on one side of the polarizer. Since the saturation moisture content of the functional layer in a high-temperature, high-humidity environment is designed to be lower than the saturation moisture content of the polarizer, even if moisture in the environmental atmosphere penetrates into the polarizer, the moisture in the polarizer has a saturation moisture content lower than the saturation moisture content of the polarizer. It can transmit positively to the layer (permeation membrane) side, and by this action, the moisture in the polarizer can be discharged to the outside of the polarizer. On the other hand, on the other side of the polarizer, an intervening layer having a saturated moisture content of 5% by weight or less is included, and the penetration of moisture into the polarizer is suppressed by the intervening layer having a low saturated moisture content, and moisture from the polarizer (P) is suppressed. Diffusion can be inhibited, and moisture of the polarizer can be transmitted to the functional layer (permeable film) side. In this way, the polarizing film of the above aspect can suppress an increase in the saturation moisture content of the polarizer even under a high-temperature, high-humidity environment by including the functional layer and the intervening layer, and can suppress the amount of color loss at the ends of the polarizing film.

<Polarizer>

A polarizer is not specifically limited, Various things can be used. As the polarizer, a dichroic substance such as iodine or a dichroic dye is adsorbed to a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film, and uniaxially stretched. polyene-based oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products; and the like. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is suitable. The thickness of these polarizers is not particularly limited, but is generally about 80 μm or less.

A polarizer in which a polyvinyl alcohol-based film is dyed with iodine and uniaxially stretched can be created by, for example, dyeing a polyvinyl alcohol-based film by immersing it in an aqueous solution of iodine and stretching it 3 to 7 times the original length. It can also be immersed in aqueous solution, such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride, etc. as needed. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, stains and antiblocking agents on the surface of the polyvinyl alcohol-based film can be cleaned, and unevenness such as dyeing unevenness is prevented by swelling the polyvinyl alcohol-based film. Stretching may be performed after dyeing with iodine, stretching may be performed while dyeing, or dyeing with iodine may be performed after stretching. It can also be stretched in an aqueous solution such as boric acid or potassium iodide or in a water bath.

In the present invention, a polarizer having a thickness of 10 μm or less can be used. The thickness of the polarizer is preferably 8 μm or less from the viewpoint of thinning, more preferably 7 μm or less, and more preferably 6 μm or less. On the other hand, the thickness of the polarizer is 2 μm or more, and it is preferable that it is 3 μm or more. Such a thin polarizer has little thickness unevenness, excellent visibility, and also excellent durability against thermal shock because there is little dimensional change.

As a thin polarizer, typically

Specification of Japanese Patent No. 4751486;

Specification of Japanese Patent No. 4751481;

Specification of Japanese Patent No. 4815544;

Specification of Japanese Patent No. 5048120;

International Publication No. 2014/077599 Pamphlet,

International Publication No. 2014/077636 Pamphlet

The thin polarizer described in the etc. or the thin polarizer obtained by the manufacturing method described in these can be mentioned.

The polarizer has optical properties represented by single transmittance (T) and degree of polarization (P) of the following equation

P＞-(10 ^0.929T-42.4 -1)×100 (where T＜42.3), or

It is configured to satisfy the condition of P≥99.9 (however, T≥42.3). A polarizer configured to satisfy the above conditions uniquely has performance required as a display for a liquid crystal TV using a large display element. Specifically, the contrast ratio is 1000:1 or more, and the maximum luminance is 500 cd/m ² or more. As another application, for example, it is bonded to the viewing side of an organic EL display device.

As the thin polarizer, among manufacturing methods including a step of stretching and a step of dyeing in the state of a laminate, Japanese Patent No. 4751486 and Japanese Patent No. 4751481 disclose that it can be stretched at a high magnification and polarization performance can be improved. It is preferably obtained by a production method including a step of stretching in a boric acid aqueous solution as described in the specification and Japanese Patent No. 4815544, and is particularly stretched in a boric acid aqueous solution described in the specification of Japanese Patent No. 4751481 and Japanese Patent No. 4815544 What is obtained by the manufacturing method including the process of air-stretching auxiliary before carrying out is preferable. These thin polarizers can be obtained by a manufacturing method including a process of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as a PVA-based resin) layer and a resin substrate for stretching in a laminated state, and a dyeing process. According to this production method, even if the PVA-based resin layer is thin, it is possible to extend it without problems such as breakage due to stretching because it is supported by the resin base material for stretching.

The polarizer of the present invention typically has a saturated water content of 10 to 40% by weight at 85° C. and 85% R.H. The saturation water content of the polarizer may be 25% by weight or less, and further 18% by weight or less from the viewpoint of suppression of end color loss. In addition, the saturation moisture content of the polarizer has no lower limit in particular as long as the saturation moisture content of the functional layer is lower than the saturation moisture content of the polarizer in relation to the functional layer.

What is necessary is just to adjust the saturated moisture content of the polarizer of this invention by arbitrary appropriate methods. For example, the method of controlling by adjusting the conditions of the drying process in the manufacturing process of light polarizer is mentioned.

<Functional Layer>

The functional layer includes a urethane prepolymer (a), which is a reaction product of an isocyanate compound and a polyhydric alcohol, and at least two functional groups containing active hydrogens reactive with isocyanate groups, and the molecular weight divided by the number of the functional groups is 350 or less. It is a cured product of a forming material containing the compound (b).

As the isocyanate compound forming the urethane prepolymer (a), for example, a polyfunctional isocyanate compound is preferable, and specifically, a polyfunctional aromatic isocyanate compound, an alicyclic isocyanate, an aliphatic isocyanate compound or a dimer thereof is exemplified.

Examples of the polyfunctional aromatic isocyanate compound include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate. Isocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, methylenebis 4-phenyl Isocyanate, p-phenylene diisocyanate, etc. are mentioned.

Examples of the polyfunctional alicyclic isocyanate compound include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-bisisocyanatomethylcyclohexane, and isophorone. Diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated tetramethylxylylene diisocyanate, etc. are mentioned.

Examples of the polyfunctional aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, and dodecamethylene diisocyanate. Isocyanate, 2,4,4-trimethylhexamethylene diisocyanate, etc. are mentioned.

Moreover, as a polyfunctional isocyanate compound, what contains 3 or more isocyanate groups, such as isocyanuric-acid tris (6-isocyanate hexyl), is mentioned.

Polyhydric alcohols include, for example, ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3- Propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1 , 8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, polypropylene glycol and the like.

As the urethane prepolymer (a), in the present invention, it is preferable to use a rigid structure in which a cyclic structure (benzene ring, cyanurate ring, isocyanurate ring, etc.) occupies a large proportion in the structure in terms of molecular structure. For example, although the said polyfunctional isocyanate compound can use individually by 1 type or in combination of 2 or more types, the aromatic isocyanate compound is preferable from a viewpoint of preparation of the said saturated water content. Another polyfunctional isocyanate compound can be used together with an aromatic isocyanate compound. In particular, among aromatic isocyanate compounds, it is preferable to use at least any one selected from tolylene diisocyanate and diphenylmethane diisocyanate as the isocyanate compound.

As the urethane prepolymer (a), trimethylolpropane-tri-tolylene isocyanate and trimethylol-propane-tri-diphenylmethane diisocyanate are preferably used.

In addition, the urethane prepolymer (a) is a compound having a terminal isocyanate group, and can be obtained, for example, by mixing an isocyanate compound and a polyhydric alcohol, stirring, and reacting. Usually, it is preferable to mix an isocyanate compound and a polyhydric alcohol so that the isocyanate group is excessive with respect to the hydroxyl group of the polyhydric alcohol. In addition, in the case of the said reaction, it is suitably carried out in an organic solvent (for example, ethyl acetate, methyl ethyl ketone, chloroform, etc.), and catalyst (for example, organometallic catalysts, such as a tin chloride and organotin compound; Organic bases, such as a tertiary amine compound; Organic acids such as acetic acid and acrylic acid; etc.) can be used.

Further, as the urethane prepolymer (a), one having a terminal isocyanate group provided with a protecting group can also be used. Examples of the protecting group include oxime and lactam. When the isocyanate group is protected, heating dissociates the protecting group from the isocyanate group, and the isocyanate group reacts.

In addition to the urethane prepolymer (a), the forming material forming the functional layer contains at least two functional groups containing active hydrogens reactive with isocyanate groups, and the molecular weight divided by the number of the functional groups is 350 or less. Compound (b) contains A hydroxyl group, an amino group, etc. are mentioned as a functional group containing an active hydrogen which has reactivity with an isocyanate group. Since the number of functional groups containing active hydrogen contained in the compound (b) increases, the number of reaction points with the isocyanate group of the urethane prepolymer (a) increases and the cured product is easily formed. Therefore, the number of functional groups is preferably 3 or more.

In addition, compound (b) is used in which the value obtained by dividing its molecular weight by the number of functional groups is 350 or less. By defining the relationship between the molecular weight and the number of functional groups in this way, the reactivity between the compound (b) and the isocyanate group of the urethane prepolymer (a) can be secured.

In addition, it is preferable that the molecular weight of the compound (b) is 1000 or less. It is preferable that the molecular weight of the compound (b) is in the range of 1000 or less from the point of compatibility at the time of preparing the forming material as a solution with the urethane prepolymer (a).

Examples of the compound (b) include polyhydric alcohols, polyhydric amines, and compounds having a hydroxyl group and an amino group in the molecule.

Polyhydric alcohols include, for example, ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3- Propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1 Bifunctional alcohols, such as 8-octanediol, 1,8-decanediol, octadecanediol, and polypropylene glycol; trifunctional alcohols such as glycerin and trimethylolpropane; tetrafunctional alcohols such as pentaerythritol, hexanetriol, and sorbitol; In addition, alkylene oxide (for example, propylene oxide) adducts with the above polyhydric alcohols, such as polyoxypropylene glyceryl ether, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether, etc. are mentioned.

Examples of the polyhydric amine include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and dimerdiamine.

Examples of compounds having a hydroxyl group and an amino group in the molecule include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, and 2-hydroxyethylpropylenediamine. diamines having a hydroxyl group in the molecule, such as hydroxypropylethylenediamine and di-2-hydroxypropylethylenediamine; and alkanolamines such as ethanolamine, diethanolamine, and triethanolamine.

As the compound (b), it is preferable to use a polyhydric alcohol from the viewpoint of preventing deterioration in the optical reliability of the polarizer, and trimethylolpropane is particularly preferable from the viewpoint of reactivity with the urethane prepolymer (a).

The forming material contains the urethane prepolymer (a) as a main component. It is preferable that the urethane prepolymer (a) contains 50% by weight or more of the solid content of the forming material.

The blending ratio of the compound (b) to the urethane prepolymer (a) is preferably 5% by weight or more relative to 100% by weight (solid content ratio) of the urethane prepolymer (a) and the compound (b) in total. The compounding ratio of the compound (b) is preferably 10% by weight or more from the viewpoint of improving the cohesive force. On the other hand, when the compounding ratio of the compound (b) increases, the optical reliability of the polarizing plate may deteriorate, so the compounding ratio of the compound (b) is 80% by weight or less, preferably 50% by weight or less.

The forming material may also use a reaction catalyst to increase the reactivity of isocyanate groups. The reaction catalyst is not particularly limited, but a tin-based catalyst or an amine-based catalyst is suitable. 1 type or 2 or more types can be used for a reaction catalyst. The amount of the reaction catalyst is usually 5 parts by weight or less based on 100 parts by weight of the urethane prepolymer (a). When the amount of the reaction catalyst is large, the crosslinking reaction rate is increased and foaming of the forming material occurs. Even if a forming material after foaming is used, sufficient adhesiveness cannot be obtained. Usually, when using a reaction catalyst, it is 0.01-5 weight part, Furthermore, 0.05-4 weight part is preferable.

As the tin-based catalyst, either inorganic or organic catalysts can be used, but organic catalysts are preferred. Examples of the inorganic tin catalyst include stannous chloride and stannous chloride. The organic tin catalyst preferably contains at least one organic group such as an aliphatic group or an alicyclic group having a skeleton such as a methyl group, an ethyl group, an ether group, or an ester group. Examples thereof include tetra-n-butyltin, tri-n-butyltin acetate, n-butyltin trichloride, trimethyltin hydroxide, dimethyltin dichloride, and dibutyltin dilaurate.

Also, the amine-based catalyst is not particularly limited. For example, it is preferable to include at least one organic group such as an alicyclic group such as quinuclidine, amidine, and diazabicycloundecene. In addition, triethylamine etc. are mentioned as an amine catalyst. Moreover, as a reaction catalyst other than the above, cobalt naphthenate, benzyltrimethylammonium hydroxide, etc. can be illustrated.

The forming material is usually used as a solution containing the urethane prepolymer (a) and the compound (b). The solution may be a solvent system in which a forming material is dissolved in an organic solvent, or may be an aqueous system such as an emulsion, a colloidal dispersion, or an aqueous solution.

The organic solvent is not particularly limited as long as it does not have a functional group containing an active hydrogen reactive with an isocyanate group and uniformly dissolves the urethane prepolymer (a) and the compound (b) constituting the forming material. The organic solvent can be used alone or in combination of two or more. Also, as the organic solvent, different solvents may be used for the urethane prepolymer (a) and the compound (b). In this case, after preparing each solution, the formation material can be prepared by mixing each solution. In addition, the viscosity of the forming material can be adjusted by further adding an organic solvent to the prepared forming material. In addition, even in the case of a solvent-based solution dissolved in an organic solvent, alcohols, water, and the like of the following examples may be included as the solvent.

As an organic solvent, Aromatic hydrocarbons, such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane; halogenated alkanes such as 1,2-dichloroethane; ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, and acetylacetone; etc. can be mentioned.

Moreover, in the case of setting it as a water system, alcohols, such as n-butyl alcohol and isopropyl alcohol, and ketones, such as acetone, can also be mix|blended, for example. In the case of using an aqueous system, it can be carried out by using a dispersant or introducing a water-dispersible component such as polyethylene glycol or a functional group having low reactivity with isocyanate groups such as carboxylate salts, sulfonic acid salts and quaternary ammonium salts into the urethane prepolymer.

Formation of the said functional layer can be performed, for example by hardening after apply|coating the said forming material directly to a polarizer.

Specifically, step (1) of preparing a forming material containing the urethane prepolymer (a) and compound (b);

Step (2) of directly applying the forming material prepared in step (1) to at least one side of the polarizer, and

Step (3) of curing the forming material applied in the above application step (2)

By carrying out, a polarizing film containing a functional layer can be obtained.

The forming material prepared in the step (1) can be used in the step (2) immediately after preparation, or can be used in the step (2) after being allowed to stand for some time after the step (1). It is preferable to perform the time shifting from the step (1) to the step (2) by managing the peak area of the isocyanate group in the forming material measured by FT-IR. That is, it is preferable to use in the step (2) after leaving it to stand until the peak area value of the forming material immediately after preparing in the step (1) decreases by 5% or more. When the peak area is reduced at the above ratio, it is recognized that the reaction between the urethane prepolymer (a) and the compound (b) is progressing to some extent in the forming material, and it is suitable for efficiently forming a functional layer having good cohesive force. The reduction ratio of the peak area value is preferably 10% or more, and more preferably 15% or more. On the other hand, if the reduction ratio of the peak area value is too large, the reaction between the urethane prepolymer (a) and the compound (b) proceeds excessively, and handling of the forming material may be difficult. Therefore, the reduction ratio of the peak area value is 80% It is preferably less than or equal to, and more preferably 50% or less. Since the standing time until the peak area value decreases by 5% or more varies depending on the types of urethane prepolymer (a) and compound (b) contained in the forming material and is further affected by humidity, the peak area value The reduction is appropriately determined in consideration of the above factors. The standing time is usually about 24 hours or less at room temperature (23 ° C.), preferably controlled in the range of about 0.5 to 5 hours.

In the step (3), the functional layer is formed by curing the forming material by drying at about 30 to 100° C., preferably about 50 to 80° C. for about 0.5 to 15 minutes. In addition, in order to promote the reaction of the isocyanate component in the forming material, an annealing treatment may be performed at about 30 to 100 ° C., preferably at 50 to 80 ° C. for about 0.5 to 24 hours. In addition, you may perform an annealing process by humidifying together with the said heating. The humidification may be performed at, for example, a relative humidity of about 50 to 95%.

The thickness of the functional layer is preferably 3 μm or less, more preferably 2 μm or less, and more preferably 1.5 μm or less from the viewpoint of thinning and optical reliability. When the functional layer is too thick, there is a possibility that the function cannot be exhibited because it has a thickness. On the other hand, the thickness of the functional layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and more preferably 0.3 μm or more from the viewpoint of securing functions.

The functional layer is a layer that functions as a permeable film that helps discharge of moisture in the polarizer, and the saturation moisture content of the functional layer at 85° C. and 85% R.H. can be designed to be lower than that of the polarizer.

The difference between the saturated moisture content of the polarizer and the saturated moisture content of the functional layer is preferably 1 to 20% by weight, and more preferably 3 to 15% by weight from the viewpoint of function as a permeable film. In addition, there is no problem even if the difference in saturated water content is too large, but if it is too small, it becomes impossible to exhibit a sufficient function as a permeable membrane, so it is preferable to control it within the above range. In addition, the saturated water content of the functional layer is preferably 1 to 10% by weight, and preferably 3 to 8% by weight.

It is preferable that the functional layer has a structure having an inclination distribution such that the saturation water concentration at 85° C. and 85% R.H. in the functional layer gradually decreases from the polarizer side toward the opposite side to the polarizer. With such a structure, the function as a permeable film can be exhibited more effectively.

<Adhesive layer>

In the polarizing film of the present invention, an adhesive layer may be further formed on the functional layer. As the pressure-sensitive adhesive layer, various layers can be formed.

The thickness of the pressure-sensitive adhesive layer is about 1 to 100 μm from the viewpoint of functioning as a permeable film. Preferably it is 2-50 micrometers, More preferably, it is 2-40 micrometers, More preferably, it is 5-35 micrometers.

As said adhesive layer, it can form with resin films, such as an adhesive layer, an adhesive bond layer, a hard coat layer, etc., and a protective film, for example. Among these, an adhesive layer is preferable from a viewpoint of suppression of discoloration at the edge part of a polarizing film.

An appropriate pressure-sensitive adhesive can be used for forming the pressure-sensitive adhesive layer, and there is no particular restriction on the type thereof. Examples of the adhesive include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, and vinylalkyl ether-based adhesives.

Among these pressure-sensitive adhesives, those having excellent optical transparency, appropriate adhesive properties such as wettability, cohesiveness, and adhesiveness, and excellent weatherability, heat resistance, and the like are preferably used. As one exhibiting such characteristics, an acrylic pressure-sensitive adhesive is preferably used.

As a method of forming the pressure-sensitive adhesive layer, for example, a method of applying the pressure-sensitive adhesive to a separator or the like subjected to peeling treatment, forming an pressure-sensitive adhesive layer by drying and removing a polymerization solvent, and then transferring the pressure-sensitive adhesive to a functional layer, or applying the pressure-sensitive adhesive to the functional layer , It is manufactured according to a method of forming an adhesive layer on a polarizer by drying and removing a polymerization solvent or the like. Moreover, in application|coating of an adhesive, you may newly add 1 or more types of solvents other than a polymerization solvent suitably.

As the separator subjected to the peeling treatment, a silicone peeling liner is preferably used. In the step of forming the pressure-sensitive adhesive layer by applying and drying the pressure-sensitive adhesive of the present invention on such a liner, as a method of drying the pressure-sensitive adhesive, an appropriate method may be employed depending on the purpose. Preferably, a method of heating and drying the coating film is used. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. A pressure-sensitive adhesive having excellent adhesive properties can be obtained by setting the heating temperature within the above range.

As for the drying time, an appropriate, appropriate time may be employed. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

Various methods are used as a method of forming the pressure-sensitive adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, extrusion by die coater, etc. Methods, such as a coating method, are mentioned.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm. It is preferably 2 to 50 μm, more preferably 2 to 40 μm, and still more preferably 5 to 35 μm.

In the case where the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected with a peeled sheet (separator) until actual use.

Examples of materials constituting the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabrics, nets, foam sheets, metal foils, and appropriate thin sheets such as laminates thereof. Although these etc. are mentioned, a plastic film is used suitably from the point which is excellent in surface smoothness.

The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, and vinyl chloride copolymer. A film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene-vinyl acetate copolymer film, etc. are mentioned.

The thickness of the separator is usually about 5 to 200 μm, preferably about 5 to 100 μm. If necessary, the separator may be subjected to release and antifouling treatment using silicone, fluorine, long-chain alkyl or fatty acid amide release agents, silica powder, etc., or antistatic treatment such as coating, kneading-type, and deposition-type. . In particular, peelability from the pressure-sensitive adhesive layer can be further improved by appropriately subjecting the surface of the separator to a peeling treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment.

From the viewpoint that the pressure-sensitive adhesive layer exhibits a function as a permeable membrane more, it is preferable to provide an pressure-sensitive adhesive layer having a saturation moisture content lower than the saturation moisture content of the functional layer.

The difference between the saturated moisture content of the functional layer and the saturated moisture content of the pressure-sensitive adhesive layer is preferably 0.1 to 8% by weight, more preferably 0.5 to 5% by weight from the viewpoint of function as a permeable membrane. In addition, there is no problem even if the above difference is too large, but on the other hand, since a sufficient function as a permeable membrane cannot be exhibited when it is too small, it is preferable to control within the above range. In addition, the saturation moisture content of the pressure-sensitive adhesive layer is suitably used within a range lower than the saturation moisture content of the functional layer, but is usually preferably 0.1 to 8%, and more preferably 0.5 to 5% by weight.

<intervening layer>

As said intervening layer, intervening layers, such as an adhesive bond layer applied between a polarizer and a protective film, an adhesive layer, and an undercoat layer (primer layer), are mentioned. In addition, an easily adhesive layer applied to the protective film is exemplified. In addition, an easily bonding layer may be provided on the protective film or an activation treatment may be applied to laminate the easily bonding layer and the adhesive layer.

A material forming the intervening layer can be used that has transparency and functions as the intervening layer. At this time, it is preferable to laminate both of them without an air gap by means of an intervening layer.

The adhesive layer is formed by an adhesive. The type of adhesive is not particularly limited, and various types can be used. The adhesive layer is not particularly limited as long as it is optically transparent, and various types of adhesives such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives are used, but water-based adhesives or active energy ray-curable adhesives are suitable.

Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. Water-based adhesives are usually used as adhesives made of aqueous solutions, and usually contain 0.5 to 60% by weight of solids.

An active energy ray curable adhesive is an adhesive that is cured by active energy rays such as electron beams and ultraviolet rays (radical curing type and cationic curing type), and can be used in the form of electron beam curing type and ultraviolet curing type, for example. As the active energy ray curable adhesive, for example, an optical radical curable adhesive can be used. In the case where an active energy ray curable adhesive of an optical radical curable type is used as an ultraviolet curable adhesive, the adhesive contains a radical polymerizable compound and a photopolymerization initiator.

The coating method of the adhesive is appropriately selected according to the viscosity of the adhesive or the target thickness. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater, and the like. In addition, methods such as a dipping method can be appropriately used for coating.

In the case of using a water-based adhesive or the like, the coating of the adhesive is preferably performed so that the thickness of the finally formed adhesive layer is 30 to 300 nm. The thickness of the adhesive layer is more preferably 60 to 250 nm. On the other hand, in the case of using an active energy ray curable adhesive, the thickness of the adhesive layer is preferably 0.1 to 200 µm. More preferably, it is 0.5-50 micrometers, More preferably, it is 0.5-10 micrometers.

The easily bonding layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based skeleton, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins can be used individually by 1 type or in combination of 2 or more types. Further, other additives may be added to the formation of the easily bonding layer. Specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat-resistant stabilizers may also be used.

An easily bonding layer is usually provided in advance in a protective film, and the easily bonding layer side of the said protective film and a polarizer are laminated|stacked with an adhesive bond layer. Formation of an easily bonding layer is performed by coating and drying the formation material of an easily bonding layer by a well-known technique on a protective film. The material for forming the easily bonding layer is usually adjusted as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of coating, and the like. The thickness of the easily adhesive layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, still more preferably 0.05 to 1 μm. In addition, although a plurality of easily bonding layers can be provided, it is preferable to make the total thickness of an easily bonding layer become the said range also in this case.

An adhesive layer is formed from an adhesive. Various adhesives can be used as the adhesive, and examples thereof include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinylalkyl ether-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. An adhesive base polymer is selected according to the type of the adhesive. Among the above pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are preferably used because of their excellent optical transparency, adequate wettability, cohesiveness, and adhesive properties, and excellent weather resistance and heat resistance.

An undercoat layer (primer layer) is formed to improve adhesion between the polarizer and the protective film. The material constituting the primer layer is not particularly limited as long as it exhibits strong adhesion to both the base film and the polyvinyl alcohol-based resin layer to some extent. For example, a thermoplastic resin having excellent transparency, thermal stability, stretchability, and the like is used. Examples of the thermoplastic resin include acrylic resins, polyolefin resins, polyester resins, polyvinyl alcohol resins, and mixtures thereof.

The intervening layer is a layer whose saturation moisture content at 85°C and 85% R.H. is adjusted to 5% by weight or less. The saturated water content of the intervening layer is preferably 4% by weight or less, and more preferably 3.5% by weight or less. On the other hand, there is no particular lower limit to the saturated water content of the intervening layer.

<Protective Film>

As materials constituting the protective film, materials having excellent transparency, mechanical strength, thermal stability, water barrier properties, isotropic properties, and the like are preferred. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene and acrylonitrile-styrene copolymers (AS resin), styrenic polymers, polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene-propylene copolymers, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamides, imide-based polymers, and sulfone-based polymers. Polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy Examples of the polymer forming the protective film include a polymer based polymer or a blend of the above polymers. As the protective film, it is preferable to use at least one selected from cellulose polymers, acrylic polymers, and polyolefins having a cyclo or norbornene structure.

Based on the polarizer, since it is optional to provide the functional layer of the present invention on the side to which the protective film is applied, from the viewpoint of suppressing moisture penetration from the protective film side as the material of the protective film, an acrylic polymer with low moisture permeability , It is preferable to use a polyolefin-based polymer or the like.

Moreover, one or more types of arbitrary suitable additives may be contained in the protective film. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants and the like. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the protective film is 50% by weight or less, there is a possibility that the high transparency and the like inherently possessed by the thermoplastic resin may not be sufficiently expressed.

As the protective film, a retardation film, a brightness enhancing film, a diffusion film, and the like can be used. Examples of the retardation film include those having a retardation of 40 nm or more in front retardation and/or 80 nm or more in thickness direction retardation. The frontal retardation is typically controlled in the range of 40 to 200 nm, and the thickness direction retardation is typically controlled in the range of 80 to 300 nm. When using retardation film as a protective film, since the said retardation film also functions as a polarizer protective film, thickness reduction can be aimed at.

Examples of the retardation film include a birefringent film formed by uniaxially or biaxially stretching a thermoplastic resin film. The temperature of the stretching, the stretching ratio, and the like are appropriately set according to the retardation value, the material of the film, and the thickness.

Although the thickness of the protective film can be determined appropriately, it is generally about 1 to 500 µm in view of workability such as strength and handling, and thin layer properties. In particular, 1 to 300 μm is preferable, 5 to 200 μm is more preferable, and furthermore, 5 to 150 μm, particularly suitable in the case of a thin shape of 20 to 100 μm.

A functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer or an antiglare layer may be provided on the surface of the protective film to which the polarizer is not adhered. In addition, functional layers such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer and the anti-glare layer can be provided on the protective film itself or separately from the protective film.

<Surface protection film>

A surface protection film can be provided in the polarizing film of this invention. A surface protection film contains a base film and an adhesive layer normally, and protects a polarizer through the said adhesive layer.

As the base film of the surface protection film, a film material having isotropy or close to isotropy is selected from the viewpoints of inspectability, manageability, and the like. Examples of the film material include polyester-based resins such as polyethylene terephthalate films, cellulose-based resins, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, and transparent polymers such as acrylic resins. Among these, polyester-type resin is preferable. The base film may be used as a laminate of one type or two or more types of film materials, or a stretched product of the above film may be used. The thickness of the base film is generally 500 µm or less, preferably 10 to 200 µm.

As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the surface protection film, a pressure-sensitive adhesive having (meth)acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer as a base polymer can be appropriately selected and used. there is. From the viewpoints of transparency, weather resistance, heat resistance and the like, an acrylic pressure-sensitive adhesive containing an acrylic polymer as a base polymer is preferable. The thickness of the pressure-sensitive adhesive layer (dry film thickness) is determined according to the required adhesive strength. It is usually about 1 to 100 μm, preferably 5 to 50 μm.

Further, on the surface protection film, a release treatment layer can be provided on the surface opposite to the surface of the base film on which the pressure-sensitive adhesive layer is provided by a low-adhesive material such as silicone treatment, long-chain alkyl treatment, or fluorine treatment.

<Other optical layers>

The polarizing film of the present invention can be used as an optical film laminated with other optical layers in actual use. The optical layer is not particularly limited, but is used for forming a liquid crystal display device such as a reflection plate, a transflective plate, a retardation plate (including a 1/2 or 1/4 wave plate), and a visual compensation film. One layer or two or more layers may be used for the optical layer having a coating. In particular, a reflective polarizing film or transflective polarizing film obtained by laminating a reflector or a semi-transmissive reflector on the polarizing film of the present invention, an elliptically polarizing film or a circular polarizing film formed by laminating a retardation plate on the polarizing film, and a polarizing film A wide viewing angle polarizing film formed by further laminating a visual compensation film or a polarizing film formed by further laminating a brightness enhancing film on the polarizing film is preferable.

An optical film in which the optical layer is laminated on a polarizing film can be formed by sequentially laminating separately in the manufacturing process of a liquid crystal display device, etc., but an optical film obtained by laminating in advance has excellent quality stability and assembly work. Thus, there is an advantage in that a manufacturing process of a liquid crystal display device or the like can be improved. Appropriate bonding means such as an adhesive layer can be used for lamination. When attaching the polarizing film or other optical films described above, their optical axes can be set at appropriate angles depending on the target retardation characteristics and the like.

The polarizing film or optical film of the present invention can be suitably used for formation of various image display devices such as liquid crystal display devices and organic EL display devices. Formation of the liquid crystal display device can be performed according to the conventional method. That is, a liquid crystal display device is generally formed by properly assembling constituent parts such as a liquid crystal cell, a polarizing film or optical film, and, if necessary, a lighting system and incorporating a driving circuit, but in the present invention, the polarizing film or optical film according to the present invention Except for the point of using, there is no particular limitation, and it may conform to the prior art. As for the liquid crystal cell, for example, any type such as IPS type or VA type can be used, but it is particularly suitable for the IPS type.

An appropriate liquid crystal display device, such as a liquid crystal display device in which a polarizing film or an optical film is disposed on one side or both sides of a liquid crystal cell, or a lighting system using a backlight or a reflector, can be formed. In that case, the polarizing film or optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When providing a polarizing film or an optical film on both sides, these may be the same thing or different things may be sufficient as them. In addition, when forming the liquid crystal display device, for example, a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are disposed in one or two or more layers at appropriate locations. can do.

[Example]

Hereinafter, the present invention will be described by giving examples, but the present invention is not limited to the examples shown below. In addition, all parts and % in each case are based on weight. Room temperature leaving conditions, which are not particularly specified below, are all 23° C. 65% R.H.

(Manufacture of thin polarizer A)

Corona treatment was performed on one side of a base material of an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 µm) with a water absorption of 0.75% and a Tg of 75 ° C., and polyvinyl alcohol (polymerization degree 4200 , Saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Japan Synthetic Chemical Industry Co., Ltd., trade name 'Gosepamer Z200') at a ratio of 9: 1 The containing aqueous solution was applied and dried at 25 ° C. to form a PVA-based resin layer having a thickness of 11 μm to prepare a laminate.

The obtained layered product was uniaxially stretched at the free end by 2.0 times in the machine direction (longitudinal direction) between rolls having different circumferential speeds in a 120°C oven (air assisted stretching treatment).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insolubilization treatment).

Then, the polarizing plate was immersed in a dyeing bath having a liquid temperature of 30°C while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine and 1.0 parts by weight of potassium iodide were blended with respect to 100 parts by weight of water, and immersed in an iodine aqueous solution for 60 seconds (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (crosslinking treatment).

After that, while immersing the layered product in an aqueous solution of boric acid at a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water), rolls with different circumferential speeds In between, uniaxial stretching was performed so that the total stretching ratio in the machine direction (longitudinal direction) was 5.5 times (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30°C (washing treatment).

By the above, the optical film layered product containing the polarizer with a thickness of 5 micrometers was obtained.

(protective film)

TAC: A triacetyl cellulose-based resin film having a thickness of 25 μm, product name “TJ25” manufactured by Fujifilm, was used.

<Material for Forming Intervening Layer (Block Layer)>

(Forming material a: preparation of adhesive a)

10 parts by weight of N-hydroxyethyl acrylamide, 30 parts by weight of acryloylmorpholine, 45 parts of 1,9-nonanediol diacrylate, and (meth) acrylic oligomer (ARUFONUP1190, manufactured by Dong-A Synthetic Co., Ltd.) 10 Part, 3 parts of a photopolymerization initiator (IRGACURE 907, manufactured by BASF) and 2 parts of a polymerization initiator (KAYACURE DETX-S, manufactured by Nippon Chemical Co., Ltd.) were mixed to prepare an ultraviolet curable adhesive.

<Formation of pressure-sensitive adhesive layer (pressure-sensitive adhesive layer)>

The pressure-sensitive adhesive solution prepared with the above forming agent c was applied to the surface of a release sheet (separator) made of a polyethylene terephthalate film (thickness: 38 μm) subjected to peeling treatment so that the thickness after drying was 20 μm, and dried to form an adhesive layer. .

Example 1

<Production of piece protection polarizing film>

After attaching the protective film (TAC) to the surface of the polarizer A of the optical film layered body while applying the ultraviolet curable adhesive a so that the thickness of the adhesive layer after curing is 1 μm, ultraviolet rays are irradiated as active energy rays, The adhesive was cured. For ultraviolet irradiation, gallium-encapsulated metal halide lamp, irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., valve: V-valve, peak illuminance: 1600 mW/cm ² , cumulative irradiation amount 1000/mJ/cm ² (wavelength 380 to 440 nm) was used, and the illuminance of ultraviolet rays was measured using a Sola-Check system manufactured by Solatell. Subsequently, the amorphous PET substrate was peeled off, and a polarizing film with polarization protection using a thin polarizer was produced. The optical properties of the obtained piece-protected polarizing film were 42.8% of single transmittance and 99.99% of polarization degree.

<Material for Forming Functional Layer>

<<solution of urethane prepolymer (a)>>

A 75% ethyl acetate solution of a urethane prepolymer composed of tolylene diisocyanate and trimethylolpropane (manufactured by Tosoh Corporation, trade name 'Colonate L') was used.

<<Preparation of solution of compound (b)>>

Trimethylolpropane was dissolved in cyclopentanone to a solid content concentration of 10% to prepare a trimethylolpropane solution.

≪Preparation of forming material≫

The above trimethylolpropane solution was added to 100 parts of a 75% ethyl acetate solution of the above urethane prepolymer (manufactured by Tosoh Corporation, trade name 'Colonate L') so that the solid content ratio of the urethane prepolymer:trimethylolpropane was 90:10, , In addition, 0.1 part of a dioctyltin dilaurate-based catalyst (manufactured by Tokyo Fine Chemical Co., Ltd., trade name 'Envirizer-OL-1' was added. After adding methyl isobutyl ketone as a solvent, stirring for 15 minutes with a variable speed stirrer was carried out to prepare a forming material (coating solution) prepared at a solid content concentration of 10%.

<Production of single-protection polarizing film with functional layer>

After applying the material for forming the functional layer (coating liquid: after standing) by a bar coater to the surface of the polarizer of the polarizing film with protection film (the surface of the polarizer without a protective film), treatment was performed at 60° C. for 5 minutes. It performed by carrying out, and the 1.5 micrometer-thick urethane resin layer was formed.

<Peak area of isocyanate group in forming material measured by FT-IR>

The forming material was applied after preparing the forming material and leaving it to stand until the reduction rate (B/A) x 100 (%) of the peak area of the isocyanate group reached 30%. The forming material had an isocyanate group peak area (A) of 5.7 immediately after preparation (specifically, immediately after the above 15-minute stirring was completed), and an isocyanate group peak area (B) before application was 4.0.

In addition, the peak area of the isocyanate group in the forming material by FT-IR was measured using FT-IR (body: Spectrum Two, manufactured by Parkin Elmer).

Measuring conditions:

Measurement unit: QuestGe-ATR manufactured by Specac

Number of integrations: 8

Isocyanate Peak Calculation Conditions

Area calculation range: 2500-2080 cm ^-1

Base: 2600-2000 cm ^-1

Sample preparation method: Immediately before evaluation, 3 to 5 drops of the prepared liquid were dropped onto a PET film (diafoil T390-38 manufactured by Mitsubishi Resin). Then, after leaving it to stand in a room temperature (23 degreeC) environment for 5 minutes to volatilize and solidify the solvent, FT-IR measurement was performed. Area calculation was performed under the above conditions according to the attached area calculation program.

<Preparation of single-protection polarizing film with pressure-sensitive adhesive layer>

Next, a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer) having a thickness of 20 μm formed on the release-treated surface of the release sheet (separator) was bonded to the functional layer formed on the piece-protective polarizing film to prepare a piece-protective polarizing film with a pressure-sensitive adhesive layer. .

Examples 2-6, Comparative Examples 1-3

A piece-protected polarizing film with a functional layer and a piece-protected polarizing film with an adhesive layer in the same manner as in Example 1, except that the type and compounding amount of the compound (b) used in the forming material of the functional layer in Example 1 were changed as shown in Table 1. was produced. The optical properties of the obtained piece-protected polarizing film were 42.8% of transmittance and 99.99% of polarization degree for each single unit.

In Comparative Example 3, a piece-protected polarizing film with a functional layer and a piece-protected polarizing film with an adhesive layer were produced in the same manner as in Example 1 except not using the compound (b).

The following evaluation was performed about the piece-protection polarizing film with a functional layer (however, Comparative Example 3 was about a piece-protection polarizing film) and the piece-protection polarizing film with an adhesive layer obtained by the said Example and comparative example. The results are shown in Table 1.

<Single Transmittance (T) and Polarization Degree (P) of Polarizer>

The single transmittance (T) and polarization degree (P) of the resulting piece-protected polarizing film were measured using a spectral transmittance meter with an integrating sphere (Dot-3c of Murakami Color Research Institute).

In addition, the polarization degree (P) is the transmittance when two identical polarizing films are overlapped so that both transmission axes are parallel (parallel transmittance: Tp) and the transmittance when both transmission axes are overlapped so that they are orthogonal (orthogonal transmittance: It is obtained by applying Tc) to the following formula. Polarization degree (P) (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 × 100

Each transmittance is expressed as a Y value corrected for visibility by a 2-degree field of view (C light source) of JIS Z8701, with complete polarization obtained through the Glenn-Taylor prism polarizer as 100%.

<Measurement of cohesive force>

After the obtained piece-protected polarizing film with a functional layer was left to stand at room temperature (23°C) for one week, the cohesive force was measured by Autograph AG-IS manufactured by Shimatsu Works. In the measurement, a double-sided tape (No. 500, manufactured by Nitto Denko Co., Ltd.) was attached to the functional layer of the polarizing film with functional layer protection, and a sample was cut into a strip of 150 mm x 25 mm. Next, the double-sided tape side of the sample was bonded to a glass plate (alkali glass manufactured by Matsunami Glass, 165 mm x 65 mm x 1.3 mm). Thereafter, a peel test was performed from the end of the interface between the functional layer and the double-sided tape in the sample so that the tensile direction was in the direction of 90 ° with respect to the glass plate, and the test force (N / 25 mm) at that time was taken as cohesive force.

The test was conducted under the following conditions.

Test conditions: Stroke (the distance that the part where the film is held by the machine moves in the tensile direction) 80 mm, peeling speed 1000 mm/min

<Peel Test: Adhesion>

After the obtained piece-protection polarizing film with an adhesive layer was left to stand at room temperature (23 degreeC) for 1 week, what was cut into 10 cm x 10 cm was used as the sample. In the peel test, the adhesive layer side of the sample was bonded to a glass plate (alkali glass 165 mm × 65 mm × 1.3 mm manufactured by Matsunami Glass Co., Ltd.), and then tape (cellotape manufactured by Sekisui Chemical Co., Ltd.) was applied to the four corners of the sample (protective film side). After bonding (registered trademark) No.252, 24 mm width), the tape was pulled vigorously in a direction of tension of 90° with respect to the glass plate. At that time, it was confirmed whether peeling occurred in the functional layer portion.

The peel test was evaluated according to the following criteria.

◎: No peeling.

○: Peeling occurred at one edge.

Δ: Peeling occurs at two corners.

x: Peeling occurred in 3 or more places.

In Table 1, GP1000 and GP3000 represent polyoxypropylene glyceryl ethers manufactured by Sanyo Kasei, and T5650J represents polycarbonate polyols manufactured by Asahi Kasei Chemicals.

From Table 1, it can be seen that the examples according to the present invention have the effect of efficiently forming a functional layer having good adhesion to a polarizer and cohesive force. On the other hand, in the comparative example, it turns out that sufficient adhesiveness and cohesive force were not obtained. In addition, according to the examples according to the present invention, it is effective to exhibit the above effect by increasing the reduction rate of the peak area of the isocyanate group, but in the comparative example, it can be seen that there is no significant change in characteristics even though the reduction rate is increased.

P: polarizer
1: functional layer
2: adhesive layer
3: intervening layer
4: protective film

Claims (15)

A polarizing film comprising a polarizer and a functional layer formed directly on at least one side of the polarizer,
The functional layer includes a urethane prepolymer (a), which is a reaction product of an isocyanate compound and a polyhydric alcohol, and at least two functional groups containing active hydrogens reactive with isocyanate groups, and the molecular weight divided by the number of the functional groups is It is a cured product of a forming material containing a compound (b) of 350 or less,
A polarizing film characterized by including a protective film on the other side via an intervening layer. According to claim 1,
The polarizing film, characterized in that the number of functional groups containing active hydrogen in the compound (b) is 3 or more. According to claim 1,
A polarizing film, wherein the compound (b) has a molecular weight of 1000 or less. According to claim 1,
A polarizing film characterized in that the compound (b) is a polyhydric alcohol. According to claim 4,
A polarizing film characterized in that the compound (b) is trimethylolpropane. According to claim 1,
The polarizing film characterized in that the isocyanate compound in the urethane prepolymer (a) contains at least any one selected from tolylene diisocyanate and diphenylmethane diisocyanate. According to claim 1,
The forming material contains 5% by weight or more of the compound (b) based on 100% by weight (solid content ratio) of the total of the urethane prepolymer (a) and the compound (b). According to claim 1,
The polarizing film, characterized in that the functional layer has a thickness of 3 μm or less. According to claim 1,
The polarizing film, characterized in that the thickness of the polarizer is 10㎛ or less. delete According to claim 1,
A polarizing film characterized in that the polymer forming the protective film contains at least one selected from cellulose-based polymers, acrylic-based polymers, and polyolefins having a cyclo-based or norbornene structure. According to claim 1,
In the functional layer, a polarizing film characterized in that it comprises a pressure-sensitive adhesive layer on the side opposite to the side containing the polarizer. As a manufacturing method of the polarizing film in any one of Claims 1-9, 11, and 12,
A urethane prepolymer (a), which is a reaction product of an isocyanate compound and a polyhydric alcohol, and a compound containing at least two functional groups containing active hydrogens reactive with isocyanate groups and having a molecular weight divided by the number of the functional groups of 350 or less (b) ) Step (1) of preparing a forming material containing
Step (2) of directly applying the forming material prepared in step (1) to at least one side of the polarizer, and
Step (3) of curing the forming material applied in the above application step (2)
A method for producing a polarizing film comprising a. According to claim 13,
The forming material prepared in the step (1) was allowed to stand until the value of the peak area of the isocyanate group in the forming material, measured by FT-IR immediately after preparing in the step (1), decreased by 5% or more, and then The manufacturing method of the polarizing film characterized by providing to process (2). An image display device comprising the polarizing film according to any one of claims 1 to 9, 11 and 12.

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