JP7096066B2 - Polarizer - Google Patents

Description

The present invention relates to an adhesive composition and a polarizing plate using the same.

A polarizing plate widely used in an image display device represented by a liquid crystal display device usually has a structure in which a thermoplastic resin film such as a protective film is laminated and laminated on one side or both sides of a polarizing element. An adhesive is usually used for bonding the splitter and the thermoplastic resin film. As the adhesive, an active energy ray-curable adhesive and a water-based adhesive are known [for example, Japanese Patent Application Laid-Open No. 2009-008660 (Patent Document 1)].

Japanese Unexamined Patent Publication No. 2009-008660

An object of the present invention is to provide an adhesive composition that gives good adhesion and a polarizing plate using the same.

The present invention provides the following adhesive compositions and polarizing plates.
[1] An adhesive composition containing a carboxyl group-modified polyvinyl alcohol-based polymer (A) and an oxazoline group-containing polymer (B).
[2] The adhesive composition according to [1], wherein the oxazoline group-containing polymer (B) is a water-soluble polymer.
[3] The content of the oxazoline group-containing polymer (B) is 100 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A), [1] or [2]. ]. The adhesive composition according to.
[4] The adhesive composition according to any one of [1] to [3], which is used for bonding a polarizing element and a (meth) acrylic resin film.
[5] Polarizer and
A (meth) acrylic resin film laminated on the polarizing element via an adhesive layer, and
Including
A polarizing plate in which the adhesive layer is a layer formed from the adhesive composition according to any one of [1] to [4].

It is possible to provide an adhesive composition that gives good adhesion and a polarizing plate using the same.

It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows another example of the layer structure of the polarizing plate which concerns on this invention.

<Adhesive composition>
The adhesive composition according to the present invention contains a carboxyl group-modified polyvinyl alcohol polymer (A) and an oxazoline group-containing polymer (B). The adhesive composition may contain components other than the carboxyl group-modified polyvinyl alcohol polymer (A) and the oxazoline group-containing polymer (B).

The adhesive composition according to the present invention can exhibit good adhesion and can be used for producing a polarizing plate. More specifically, it is useful as an adhesive composition used for bonding a polarizing element and a thermoplastic resin film.
Further, since the adhesive composition according to the present invention contains a carboxyl group-modified polyvinyl alcohol polymer (A) and an oxazoline group-containing polymer (B), it has a good pot life (lifetime that can be used as an adhesive composition). Can be shown.
Unless otherwise specified, the compounds exemplified as the components contained or may be contained in the adhesive composition in the present specification may be used alone or in combination of two or more.

[1] Carboxyl group-modified polyvinyl alcohol-based polymer (A)
The carboxyl group-modified polyvinyl alcohol-based polymer (A) is a polyvinyl alcohol-based polymer modified by introducing a carboxyl group or a derivative thereof into a side chain.
Examples of the derivative of the carboxyl group include a carboxylate anion group. Examples of the cation as a counter ion of the carboxylate anion group include alkali metal ions such as lithium ion, sodium ion and potassium ion; and organic cations such as ammonium ion, sulfonium ion and phosphonium ion. An example of a preferred cation is a sodium ion.

The polyvinyl alcohol-based polymer constituting the main chain of the carboxyl group-modified polyvinyl alcohol-based polymer (A) is a vinyl alcohol homopolymer obtained by saponifying treatment of polyvinyl acetate, which is a homopolymer of vinyl acetate (completely). It may be saponified polyvinyl alcohol or partially saponified polyvinyl alcohol), or a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith. It may be a coalescence.
Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.
As used herein, the term "(meth) acrylic" refers to at least one selected from the group consisting of acrylic and methacrylic. The same applies to the notations such as "(meth) acryloyl" and "(meth) acrylate".

The degree of saponification of the carboxyl group-modified polyvinyl alcohol-based polymer (A) is usually 80 mol% or more and 100 mol% or less, preferably 85 mol% or more (for example, 88 mol% or more).
The degree of saponification of the carboxyl group-modified polyvinyl alcohol-based polymer (A) can be measured according to JIS K 6726: 1994.

The degree of modification (modification amount) of the carboxyl group-modified polyvinyl alcohol polymer (A) with the carboxyl group (or its derivative thereof) is usually 0.1 mol% or more. When the degree of denaturation is in this range, it tends to show good adhesion. The degree of modification of the carboxyl group-modified polyvinyl alcohol polymer (A) is preferably 0.5 mol% or more and 40 mol% or less, and more preferably 1 mol% or more and 20 mol% or less. The degree of denaturation can be measured, for example, by ¹ H-NMR.

From the viewpoint of adhesion and water resistance of the adhesive layer, the average degree of polymerization of the carboxyl group-modified polyvinyl alcohol polymer (A) is preferably 100 or more and 3000 or less, and more preferably 500 or more and 3000 or less. ..
The average degree of polymerization of the carboxyl group-modified polyvinyl alcohol-based polymer (A) can be measured according to JIS K 6726: 1994.

As the carboxyl group-modified polyvinyl alcohol-based polymer (A), a commercially available product may be used, for example, AP-17, AF-17 (Japan Vam & Poval Co., Ltd.), Gosenex T series (Nippon Synthetic Chemical Co., Ltd.). ), KL series such as KL-506, KL-318 and KL-118, and KM series such as KM-618 and KM-118 (all manufactured by Kuraray Co., Ltd.) and the like.

[2] Oxazoline group-containing polymer (B)
The oxazoline group-containing polymer (B) is a polymer having an oxazoline group in the molecule, and is preferably a polymer having an oxazoline group in the side chain. The main chain of the polymer is not particularly limited, and may consist of, for example, one or more skeletons selected from a (meth) acrylic skeleton, a styrene skeleton, and the like.

The oxazoline group-containing polymer (B) can have an oxazoline group in the side chain of the main chain.
A preferred example of the oxazoline group-containing polymer (B) is an oxazoline group-containing (meth) acrylic polymer having a main chain composed of a (meth) acrylic skeleton and having an oxazoline group in the side chain of the main chain.
When the oxazoline group-containing polymer (B) has an oxazoline group in the side chain, there may be a linking group between the main chain and the oxazoline group, but the polymer in which the main chain and the oxazoline group are directly bonded. Is preferable.

Examples of the oxazoline group include a 2-oxazoline group, a 3-oxazoline group, a 4-oxazoline group and the like. The oxazoline group is preferably a 2-oxazoline group or the like.

The number average molecular weight of the oxazoline group-containing polymer (B) is preferably 5,000 or more, and more preferably 10,000 or more. When the number average molecular weight is in the above range, it tends to show good adhesion. The number average molecular weight of the oxazoline group-containing polymer (B) is usually 100,000 or less.
The number average molecular weight of the oxazoline group-containing polymer (B) can be measured as a standard polystyrene-equivalent value by gel permeation chromatography (GPC).

The amount of oxazoline group (the number of moles of oxazoline group per 1 g of solid content of the oxazoline group-containing polymer (B)) of the oxazoline group-containing polymer (B) is preferably 0.4 mmol / g · solid or more and 10 mmol / g · solid or less. Is. If the amount of oxazoline groups is excessively high, it is difficult to obtain good adhesion, and if the amount of oxazoline groups is smaller than the above range, the water resistance of the adhesive layer may decrease. From this point of view, the amount of the oxazoline group of the oxazoline group-containing polymer (B) is more preferably 3 mmol / g · solid or more and 9 mmol / g · solid or less.

The oxazoline group-containing polymer (B) is water-based, that is, water-soluble, when the adhesive composition is a water-based adhesive composition (an adhesive in which the adhesive component is dissolved in water or dispersed in water). It is preferably a sex polymer or a water-dispersible polymer. From the viewpoint of the optical properties of the adhesive layer, the oxazoline group-containing polymer (B) is preferably a water-soluble polymer.

As the oxazoline group-containing polymer (B), a commercially available product may be used. Specifically, oxazoline group-containing acrylic polymers such as Epocross WS-300, Epocross WS-500, and Epocross WS-700 (all trade names) manufactured by Nippon Shokubai Co., Ltd .; Epocross K-1000 series and Epocross manufactured by Nippon Shokubai Co., Ltd. Examples thereof include oxazoline group-containing acrylic / styrene polymers such as K-2000 series and Epocross RPS series (both are trade names).
The oxazoline group-containing polymer (B) can be used in combination of two or more.
From the viewpoint of adhesion, optical properties of the adhesive layer, and water resistance, the oxazoline group-containing polymer (B) is preferably an oxazoline group-containing acrylic polymer such as Epocross WS-300 and Epocross WS-700.

The content of the oxazoline group-containing polymer (B) in the adhesive composition is usually 100 parts by mass or more and 1000 parts by mass or less, preferably 100 parts by mass or less, based on 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A). It is 120 parts by mass or more and 900 parts by mass or less, and more preferably 150 parts by mass or more and 850 parts by mass or less. When the content of the oxazoline group-containing polymer (B) is in this range, good adhesion tends to be easily exhibited.

The content of the oxazoline group-containing polymer (B) is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more, when the total amount of the adhesive composition is 100% by mass. It is 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less. It is preferable to keep the content of the oxazoline group-containing polymer (B) within the above range from the viewpoints of adhesion, optical properties of the adhesive layer, and water resistance.

[3] Other Components The adhesive composition may contain other components other than the carboxyl group-modified polyvinyl alcohol-based polymer (A) and the oxazoline group-containing polymer (B).
Other components include curable components such as polyhydric aldehydes, melamine compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, water-soluble epoxy resins, and cross-linking agents; coupling agents, tackifiers, antioxidants, etc. Examples thereof include additives such as an ultraviolet absorber, a heat stabilizer, and an antioxidant.

The adhesive composition may contain a polyvinyl alcohol-based polymer other than the carboxyl group-modified polyvinyl alcohol-based polymer (A). By containing another polyvinyl alcohol-based polymer, an adhesive composition showing higher adhesion can be obtained.

Other polyvinyl alcohol-based polymers include partially saponified polyvinyl alcohol, polyvinyl alcohol polymers such as fully saponified polyvinyl alcohol, and modified polyvinyl alcohol-based polymers (carboxyl group-modified polyvinyl alcohol) which are modified products of polyvinyl alcohol polymers. (Other than the system polymer (A)) can be mentioned.
Examples of the modified polyvinyl alcohol-based polymer other than the carboxyl group-modified polyvinyl alcohol-based polymer (A) include acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified polyvinyl alcohol, and carbonyl-modified polyvinyl alcohol.

Other polyvinyl alcohol-based polymers are not limited to vinyl alcohol homopolymers (fully saponified polyvinyl alcohol or partially saponified polyvinyl alcohol) obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and acetic acid. It may be a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl and another monomer copolymerizable therewith.
Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

Above all, from the viewpoint of improving adhesion, the other polyvinyl alcohol-based polymer preferably contains a modified polyvinyl alcohol-based polymer, and more preferably contains an acetoacetyl group-modified polyvinyl alcohol polymer (C).

The saponification degree of the other polyvinyl alcohol-based polymer is usually 85 mol% or more and 100 mol% or less, preferably 90 mol% or more (for example, 95 mol% or more).
The degree of saponification of other polyvinyl alcohol-based polymers can be measured according to JIS K 6726: 1994.

The degree of modification (modification amount) of the acetoacetyl group-modified polyvinyl alcohol polymer (C) with an acetoacetyl group is usually 0.1 mol% or more. When the degree of denaturation is in this range, it tends to be easy to improve the adhesion. The degree of modification is preferably 0.5 mol% or more and 40 mol% or less, and more preferably 1 mol% or more and 20 mol% or less. The degree of denaturation can be measured, for example, by ¹ H-NMR.

From the viewpoint of adhesion and water resistance of the adhesive layer, the average degree of polymerization of the acetacetyl group-modified polyvinyl alcohol polymer (C) is preferably 100 or more and 3000 or less, and more preferably 500 or more and 3000 or less. ..
The average degree of polymerization of the acetoacetyl group-modified polyvinyl alcohol polymer (C) can be measured according to JIS K 6726: 1994.

When the adhesive composition contains another polyvinyl alcohol-based polymer, the content of the other polyvinyl alcohol-based polymer in the adhesive composition is based on 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A). Usually, it is 1 part by mass or more and 100 parts by mass or less, preferably 2 parts by mass or more and 50 parts by mass or less. When the content of the other polyvinyl alcohol-based polymer is in this range, the effect of enhancing the adhesion tends to be easily exhibited.

The adhesive composition preferably contains a solvent. Examples of the solvent include water, an organic solvent, or a mixture thereof. The solvent preferably contains water, but water and a water-soluble organic solvent may be used in combination. Examples of the organic solvent include ethanol, 1-methoxy-2-propanol and the like.
The main component of the solvent is preferably water. The main component means that it occupies 50% by mass or more of the total solvent.
The solid content concentration of the adhesive composition is usually 0.5% by mass or more and 20% by mass or less, preferably 1% by mass or more and 15% by mass or less.
The solid content concentration refers to the total concentration of components other than the solvent contained in the adhesive composition.
The concentration of the carboxyl group-modified polyvinyl alcohol-based polymer (A) in the adhesive composition is usually 0.1% by mass or more and 30% by mass or less, preferably 0.5% by mass or more and 20% by mass or less, and more. It is preferably 1% by mass or more and 15% by mass or less. When the concentration of the carboxyl group-modified polyvinyl alcohol-based polymer (A) is less than the above lower limit value, it becomes difficult to obtain sufficient adhesion, and when it exceeds the above upper limit value, the viscosity of the adhesive composition increases. Problems such as clogging of piping may occur.

The adhesive composition is preferably a water-based adhesive. That is, the adhesive composition is a solution obtained by dissolving components such as the carboxyl group-modified polyvinyl alcohol-based polymer (A) and the oxazoline group-containing polymer (B) in a solvent containing water, or a solvent containing water. A dispersion (for example, an emulsion) in which components such as a carboxyl group-modified polyvinyl alcohol-based polymer (A) and an oxazoline group-containing polymer (B) are dispersed is preferable.

The viscosity of the adhesive composition at 25 ° C. is preferably 50 mPa · sec or less, more preferably 2 mPa · sec or more and 30 mPa · sec or less, and further preferably 4 mPa · sec or more and 20 mPa · sec or less. .. If the viscosity at 25 ° C. exceeds 50 mPa · sec, it becomes difficult to apply the coating uniformly, which may cause uneven coating, and may cause problems such as clogging of pipes.
The viscosity of the adhesive composition at 25 ° C. can be measured by an E-type viscometer.

The pH of the adhesive composition at 25 ° C. is preferably 3 or more and 10 or less, and more preferably 4 or more and 9 or less. If the pH of the adhesive composition is less than 3, the water resistance of the adhesive layer may not be sufficiently developed, and if the pH of the adhesive composition exceeds 10, the adhesive composition may not be sufficiently developed. Pot life may be shortened.
The pH of the adhesive composition can be measured using a handy pH meter (eg, "D-51" manufactured by HORIBA).

<Polarizer>
The adhesive composition according to the present invention can be suitably used as an adhesive for adhering a polarizing element constituting a polarizing plate and a thermoplastic resin film such as a protective film laminated on the polarizing element. ..
The polarizing plate according to the present invention includes a polarizing element and a thermoplastic resin film laminated on at least one surface thereof via an adhesive layer formed from the adhesive composition according to the present invention.
In the polarizing plate according to one preferred embodiment, the adhesive layer is a cured product layer of the adhesive composition according to the present invention.

In the polarizing plate according to the present invention, since the polarizing element and the thermoplastic resin film are bonded to each other by using the adhesive composition according to the present invention, the adhesion between the polarizing element and the thermoplastic resin film is good. Can be.

[1] Structure of polarizing plate Examples of the layer structure of the polarizing plate according to the present invention are shown in FIGS. 1 and 2.
As shown in FIG. 1, the polarizing plate according to the present invention includes a polarizing element 30 and a first thermoplastic resin film 10 laminated and bonded to one surface thereof via a first adhesive layer 15. be able to.
It is preferable that the first adhesive layer 15 and the first thermoplastic resin film 10 are in direct contact with each other.
It is preferable that the splitter 30 and the first adhesive layer 15 are in direct contact with each other.
Further, as shown in FIG. 2, the polarizing plate according to the present invention includes a polarizing element 30, a first thermoplastic resin film 10 laminated and bonded to one surface thereof via a first adhesive layer 15, and a polarizing plate. The other surface of the child 30 may include a second thermoplastic resin film 20 laminated and bonded via the second adhesive layer 25.
It is preferable that the first adhesive layer 15 and the first thermoplastic resin film 10 are in direct contact with each other.
It is preferable that the splitter 30 and the first adhesive layer 15 are in direct contact with each other.
It is preferable that the second adhesive layer 25 and the second thermoplastic resin film 20 are in direct contact with each other.
It is preferable that the splitter 30 and the second adhesive layer 25 are in direct contact with each other.

When the polarizing plate has the first adhesive layer 15 and the second adhesive layer 25, either one may be formed from the adhesive composition according to the present invention, or both adhesive layers may be the present. It may be formed from the adhesive composition according to the invention.
When both adhesive layers are formed from the adhesive composition according to the present invention, these adhesive compositions may have the same composition or different compositions.

Not limited to the examples of FIGS. 1 and 2, the polarizing plate according to the present invention may include a layer (or film) other than the above. Examples of the other layer include a pressure-sensitive adhesive layer laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20 and / or the polarizing element 30; and a separate layer laminated on the outer surface of the pressure-sensitive adhesive layer. Film (also referred to as "release film"); Protective film laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20 and / or the polarizing element 30 (also referred to as "surface protective film"). Examples thereof include an optically functional film (or layer) laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20 and / or the polarizing element 30 via an adhesive layer or an adhesive layer. ..

[2] Polarizer The splitter 30 is a film having a function of selectively transmitting linearly polarized light in a certain direction from natural light. The splitter 30 includes, for example, an iodine-based polarizing element in which iodine as a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a dichroic dye as a dichroic dye is adsorbed on a polyvinyl alcohol-based resin film. -Examples include an oriented dye-based polarizing element and a coating type polarizing element coated with a dichroic dye in a Riotrovic liquid crystal state and oriented / immobilized. These splitters are called absorption-type splitters because they selectively transmit linear polarization in one direction from natural light and absorb linear polarization in the other direction.

The polarizing element 30 is not limited to the absorption type polarizing element, but is a reflective polarizing element that selectively transmits linear polarization in one direction from natural light and reflects the linear polarization in the other direction, or linear polarization in the other direction. Although a scattering type polarizing element that scatters the above-mentioned material may be used, an absorption-type polarizing element is preferable because of its excellent visibility. Above all, the polarizing element 30 is more preferably a polyvinyl alcohol-based polarizing element composed of a polyvinyl alcohol-based resin, and a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented on the polyvinyl alcohol-based resin film. It is more preferable that it is a polyvinyl alcohol-based polarizing element, and it is particularly preferable that it is a polyvinyl alcohol-based polarizing element in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film.

As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based polarizing element, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is usually 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726: 1994.

A film formed of such a polyvinyl alcohol-based resin is used as a raw film for the polarizing element 30. The method for forming a film of the polyvinyl alcohol-based resin is not particularly limited, and a known method is adopted. The thickness of the polyvinyl alcohol-based raw film is, for example, 150 μm or less, preferably 100 μm or less (for example, 50 μm or less), and usually 5 μm or more.

The decoder 30 is a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye; polyvinyl alcohol on which the dichroic dye is adsorbed. It can be produced by a method including a step of treating (cross-linking) the based resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. If the uniaxial stretching is performed after staining, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Further, uniaxial stretching may be performed at these a plurality of steps.

In uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched, or thermal rolls may be used to uniaxially stretch the rolls. Further, the uniaxial stretching may be a dry stretching performed in the atmosphere, or a wet stretching performed in a state where the polyvinyl alcohol-based resin film is swollen with a solvent such as water. The draw ratio is usually 3 times or more and 8 times or less.

Examples of the method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye include a method of immersing the film in an aqueous solution containing a dichroic dye. As the dichroic dye, iodine or a dichroic organic dye is used. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

Examples of the dyeing treatment method with iodine include a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide. The iodine content in this aqueous solution can be 0.01 parts by mass or more and 1 part by mass or less per 100 parts by mass of water. The content of potassium iodide can be 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of water. Further, the temperature of this aqueous solution can be 20 ° C. or higher and 40 ° C. or lower.
On the other hand, as a dyeing treatment method with a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye and the like can be mentioned. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing aid. The content of the dichroic organic dye in this aqueous solution can be 1 × 10 ^-4 parts by mass or more and 10 parts by mass or less per 100 parts by mass of water. The temperature of this aqueous solution can be 20 ° C. or higher and 80 ° C. or lower.

Examples of the boric acid treatment method after dyeing with a dichroic dye include a method of immersing a dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of boric acid in the boric acid-containing aqueous solution can be 2 parts by mass or more and 15 parts by mass or less per 100 parts by mass of water. The amount of potassium iodide in this aqueous solution can be 0.1 part by mass or more and 20 parts by mass or less per 100 parts by mass of water. The temperature of this aqueous solution can be 50 ° C. or higher, for example, 50 ° C. or higher and 85 ° C. or lower.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the washing treatment is usually 5 ° C. or higher and 40 ° C. or lower. After washing with water, a drying treatment is performed to obtain a polarizing element 30.
The drying process can be performed using a hot air dryer or a far-infrared heater. A polarizing plate can be obtained by laminating a thermoplastic resin film as a protective film or the like on one side or both sides of the polarizing element 30 using an adhesive composition.

Further, as another example of the method for producing the polarizing element 30, for example, the methods described in JP-A-2000-338329 and JP-A-2012-159778 can be mentioned. In this method, a solution containing a polyvinyl alcohol-based resin is applied to the surface of a base film to provide a resin layer, and then a laminated film composed of the base film and the resin layer is stretched, followed by dyeing treatment, cross-linking treatment, and the like. To form a polarizing element layer (polarizer layer) from the resin layer. This polarizing laminated film composed of a base film and a polarizing element layer has a configuration shown in FIG. 1 by laminating a thermoplastic resin film as a protective film or the like on the surface of the polarizing element layer and then peeling off the base film. Can be used as a polarizing plate. If a thermoplastic resin film is further attached to the surface of the substituent layer exposed by peeling of the base film, the polarizing plate having the configuration shown in FIG. 2 can be obtained.

The thickness of the splitter 30 can be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less, further 15 μm or less, further 10 μm or less, or 8 μm or less). According to the methods described in JP-A-2000-338329 and JP-A-2012-159778, the thin-film polarizing element 30 can be manufactured more easily, and the thickness of the polarizing element 30 can be reduced to, for example, 20 μm or less. Is 15 μm or less, and even more easily 10 μm or less or 8 μm or less. The thickness of the splitter 30 is usually 2 μm or more. Reducing the thickness of the splitter 30 is advantageous for reducing the thickness of the polarizing plate and, by extension, the image display device.

[3] Thermoplastic Resin Film Each of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is a translucent (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin resin. (Polypropylene resin, etc.), Cyclic polyolefin resin (Norbornen resin, etc.) and other polyolefin resins; Triacetyl cellulose, diacetyl cellulose and other cellulose ester resins; Polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate and other polyester resins A film made of a resin; a polycarbonate resin; a (meth) acrylic resin; or a mixture thereof, a copolymer, or the like can be used.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be either an unstretched film or a uniaxially or biaxially stretched film, respectively. The biaxial stretching may be simultaneous biaxial stretching in which the two stretching directions are simultaneously stretched, or sequential biaxial stretching in which the stretching is performed in the first direction and then in a different second direction.
The first thermoplastic resin film 10 and / or the second thermoplastic resin film 20 may be a protective film that plays a role of protecting the polarizing element 30, or is a protective film that also has an optical function such as a retardation film. You can also do it.
The retardation film is an optical functional film used for the purpose of compensating for the phase difference by a liquid crystal cell which is an image display element. For example, an arbitrary retardation value was given by stretching a film made of the thermoplastic resin (uniaxial stretching or biaxial stretching, etc.) or forming a liquid crystal layer or the like on the thermoplastic resin film. It can be a retardation film.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more kinds of chain olefins.

The cyclic polyolefin resin is a general term for resins containing norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene), or a cyclic olefin typified by a derivative thereof as a polymerization unit. Examples of the cyclic polyolefin resin include a ring-opened (co) polymer of a cyclic olefin and a hydrogenated product thereof, an addition polymer of a cyclic olefin, a cyclic olefin and a chain olefin such as ethylene and propylene, or an aromatic compound having a vinyl group. Examples thereof include the copolymers of the above, and modified (co) polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof.
Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

The cellulose ester-based resin is a resin in which at least a part of the hydroxyl groups in cellulose is esterified with acetate, a part is esterified with acetate, and a part is esterified with another acid. It is also good. The cellulose ester-based resin is preferably an acetyl cellulose-based resin.
Examples of the acetyl cellulose-based resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The polyester-based resin is a resin other than the above-mentioned cellulose ester-based resin having an ester bond, and is generally composed of a polyvalent carboxylic acid or a derivative thereof and a polycondensate of a polyhydric alcohol.
Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethylterephthalate, and polycyclohexanedimethylnaphthalate.
Of these, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost and the like. The polyethylene terephthalate refers to a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and may contain a constituent unit derived from other copolymerization components.

Examples of other copolymerization components include a dicarboxylic acid component and a diol component.
The dicarboxylic acid components include isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, 1 , 4-Dicarboxycyclohexane and the like.
Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.
The dicarboxylic acid component and the diol component may be used in combination of two or more, if necessary.
Further, it is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid, p-hydroxyethoxybenzoic acid, β-hydroxyethoxybenzoic acid in combination with the above dicarboxylic acid component and diol component.
As the other copolymerization component, a dicarboxylic acid component and / or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond and the like may be used in a small amount.

The polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among them, aromatic polycarbonate having a diphenylalkane in the molecular chain is preferably used from the viewpoint of heat resistance, weather resistance and acid resistance.
Examples of polycarbonate include 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane, and 1, Examples thereof include polycarbonate derived from bisphenols such as 1-bis (4-hydroxyphenyl) isobutane and 1,1-bis (4-hydroxyphenyl) ethane.

The (meth) acrylic resin can be, for example, a polymer containing a methacrylic acid ester as a main monomer (containing 50% by mass or more), and the methacrylic acid ester and other copolymerization components are copolymerized with each other. It is preferably a copolymer.
In one preferred embodiment, the (meth) acrylic resin comprises methyl methacrylate as a copolymerization component, or comprises methyl methacrylate and methyl acrylate.

Examples of the copolymerization component other than methyl acrylate include ethyl methacrylate, n-, i- or t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate and methacrylic acid. Methacrylic acid esters other than methyl methacrylate, such as 2-hydroxyethyl acid;
Acrylic acid esters such as ethyl acrylate, n-, i- or t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate;
Methyl 2- (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, n-, i- or t-butyl 2- (hydroxymethyl) acrylate, etc. Hydroxyalkyl acrylates of
Unsaturated acids such as methacrylic acid and acrylic acid;
Halogenated styrenes such as chlorostyrene and bromostyrene;
Substituted styrenes such as vinyltoluene and α-methylstyrene;
Unsaturated nitriles such as acrylonitrile and methacrylonitrile;
Unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride;
Unsaturatedimides such as phenylmaleimide and cyclohexylmaleimide;
Examples thereof include monofunctional monomers such as.
As the above-mentioned other monofunctional monomers, only one kind may be used alone, or two or more kinds may be used in combination.

A polyfunctional monomer may be used as the above-mentioned other copolymerization component.
Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and nonaethylene glycol di (meth). Ethylene glycol such as acrylate, tetradecaethylene glycol di (meth) acrylate, or the hydroxyl groups at both ends of the oligomer are esterified with (meth) acrylic acid;
Esterification of both end hydroxyl groups of propylene glycol or its oligomers with (meth) acrylic acid;
A hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, butanediol di (meth) acrylate esterified with (meth) acrylic acid;
Bisphenol A, an alkylene oxide adduct of bisphenol A, or the hydroxyl groups at both ends of these halogen substituents esterified with (meth) acrylic acid;
Polyhydric alcohols such as trimethylolpropane and pentaerythritol esterified with (meth) acrylic acid, and glycidyl (meth) acrylate epoxy groups added to these terminal hydroxyl groups by ring opening;
Succinic acid, adipic acid, terephthalic acid, phthalic acid, dibasic acids such as these halogen substituents, or alkylene oxide adducts thereof to which an epoxy group of glycidyl (meth) acrylate is ring-opened and added;
Aryl (meth) acrylate; aromatic divinyl compounds such as divinylbenzene;
And so on.
Of these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

The (meth) acrylic resin may be modified by the reaction between the functional groups of the copolymer. Examples of the reaction include a demethanol condensation reaction in a polymer chain of a methyl ester group of methyl (meth) acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, and a carboxyl group of (meth) acrylate. Examples thereof include a dehydration condensation reaction in a polymer chain with a hydroxyl group of methyl 2- (hydroxymethyl) acrylate.

The glass transition temperature of the (meth) acrylic resin is preferably 80 ° C. or higher and 160 ° C. or lower. The glass transition temperature is the polymerization ratio of the methacrylic acid ester-based monomer and the acrylic acid ester-based monomer, the carbon chain length of each ester group, the types of functional groups having them, and the polyfunctional monomer for the entire monomer. It can be controlled by adjusting the polymerization ratio of the monomer.

It is also effective to introduce a ring structure into the main chain of the polymer as a means for increasing the glass transition temperature of the (meth) acrylic resin. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure and a lactone structure. Specific examples thereof include a cyclic acid anhydride structure such as a glutaric anhydride structure and a succinic anhydride structure; a cyclic imide structure such as a glutarimide structure and a succinic anhydride structure; and a lactone ring structure such as butyrolactone and valerolactone.
The larger the content of the ring structure in the main chain, the higher the glass transition temperature of the (meth) acrylic resin tends to be.
The cyclic acid anhydride structure and the cyclic imide structure are introduced by copolymerizing a monomer having a cyclic structure such as maleic anhydride and maleimide; a cyclic acid anhydride structure is obtained by a dehydration / demethanol condensation reaction after polymerization. Method of introduction; It can be introduced by a method of reacting an amino compound to introduce a cyclic imide structure or the like.
For a resin (polymer) having a lactone ring structure, after preparing a polymer having a hydroxyl group and an ester group in a polymer chain, the hydroxyl group and the ester group in the obtained polymer are required by heating. Therefore, it can be obtained by a method of forming a lactone ring structure by cyclization condensation in the presence of a catalyst such as an organic phosphorus compound.

The (meth) acrylic resin and the thermoplastic resin film formed from the acrylic resin may contain additives, if necessary. Examples of the additive include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistant agent, an impact resistance improving agent, a surfactant and the like.
These additives can also be used when a thermoplastic resin other than the (meth) acrylic resin is used as the thermoplastic resin constituting the thermoplastic resin film.

The (meth) acrylic resin may contain acrylic rubber particles which are impact resistance improving agents from the viewpoint of film forming property on the film, impact resistance of the film, and the like. Acrylic rubber particles are particles containing an elastic polymer mainly composed of an acrylic acid ester as an essential component, and have a single-layer structure substantially composed of only this elastic polymer, or one elastic polymer. Examples thereof include a multi-layer structure having layers.
Examples of the elastic polymer include a crosslinked elastic copolymer containing an alkyl acrylate as a main component and copolymerized with another copolymerizable vinyl-based monomer and a crosslinkable monomer.
The alkyl acrylate which is the main component of the elastic polymer includes, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl hexyl acrylate, etc., which have an alkyl group having 1 or more and 8 or less carbon atoms. , And alkyl acrylate having an alkyl group having 4 or more carbon atoms is preferably used.
Examples of the other vinyl-based monomer copolymerizable with the alkyl acrylate include a compound having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methyl methacrylate. Methacrylic acid esters such as; aromatic vinyl compounds such as styrene; vinyl cyan compounds such as acrylonitrile and the like can be mentioned.
Examples of the crosslinkable monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di (meth) acrylate and butane. Examples thereof include (meth) acrylates of polyhydric alcohols such as diol di (meth) acrylate; alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate; divinylbenzene and the like.

A laminate of a film made of a (meth) acrylic resin containing no rubber particles and a film made of a (meth) acrylic resin containing rubber particles is used as a thermoplastic resin film to be bonded to the stator 30. You can also. Further, a (meth) acrylic resin layer is formed on one side or both sides of a retardation-developing layer made of a resin different from the (meth) acrylic resin, and the one in which the retardation is expressed is bonded to the polarizing element 30. It can also be a thermoplastic resin film.

At least one of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is preferably a film containing a (meth) acrylic resin ((meth) acrylic resin film), and the (meth) acrylic resin film. The acrylic resin film is preferably laminated and bonded to the polarizing element 30 via an adhesive layer formed from the adhesive composition according to the present invention.
The adhesive composition according to the present invention has good adhesion (adhesion under normal environment and moist heat environment (high temperature and high humidity environment)) particularly when the thermoplastic resin film is a (meth) acrylic resin film. Adhesion after being placed in) can be shown. Therefore, the adhesive composition according to the present invention can be suitably used for bonding a polarizing element and a (meth) acrylic resin film.
The (meth) acrylic resin film is preferably made of a (meth) acrylic resin.

The first thermoplastic resin film 10 and / or the second thermoplastic resin film 20 may contain an ultraviolet absorber. When the polarizing plate is applied to an image display device such as a liquid crystal display device, a thermoplastic resin film containing an ultraviolet absorber is placed on the visual side of an image display element (for example, a liquid crystal cell) so that the ultraviolet rays of the image display element can be used. Deterioration can be suppressed.
Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds and the like.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be films made of the same thermoplastic resin, or may be films made of different thermoplastic resins. The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be the same or different in terms of thickness, presence / absence of additives, their types, retardation characteristics, and the like.
In one embodiment, the first thermoplastic resin film 10 is a (meth) acrylic resin film, and the second thermoplastic resin film 20 is a polyolefin resin film, a cellulose ester resin, or a polyester resin film.
In another embodiment, the first thermoplastic resin film 10 and the second thermoplastic resin film 20 are (meth) acrylic resin films.

The first thermoplastic resin film 10 and / or the second thermoplastic resin film 20 has a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, and a charge on the outer surface thereof (the surface opposite to the polarizing element 30). A surface treatment layer (coating layer) such as an antifouling layer, an antifouling layer, and a conductive layer may be provided.

The thicknesses of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 are usually 5 μm or more and 200 μm or less, preferably 10 μm or more and 120 μm or less, more preferably 10 μm or more and 85 μm or less, and further preferably 15 μm or more and 65 μm or less. Is. The thickness of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be 50 μm or less, or 40 μm or less, respectively. Reducing the thickness of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is advantageous for reducing the thickness of the polarizing plate and the image display device.

On the surface to which the adhesive composition of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is applied, from the viewpoint of improving adhesion, surfaces such as saponification treatment, plasma treatment, corona treatment, and primer treatment are performed. The modification treatment may be performed, or the surface modification treatment may not be performed from the viewpoint of simplifying the process.
When the first thermoplastic resin film 10 or the second thermoplastic resin film 20 is a cellulose acetate-based resin film, it is preferable to carry out a saponification treatment from the viewpoint of improving adhesion. Examples of the saponification treatment include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

[4] Manufacture of a polarizing plate and an adhesive layer By laminating and adhering a first thermoplastic resin film 10 to one surface of a polarizing element 30 via a first adhesive layer 15, the configuration shown in FIG. 1 is configured. A polarizing plate can be obtained, and the second thermoplastic resin film 20 is further laminated and adhered to the other surface of the polarizing element 30 via the second adhesive layer 25 to obtain a polarizing plate having the configuration shown in FIG. Obtainable.
When producing a polarizing plate having both a first thermoplastic resin film 10 and a second thermoplastic resin film 20 (hereinafter, these are collectively simply referred to as “thermoplastic resin film”), these thermoplastic resins are used. The film may be laminated and bonded one side at a time step by step, or the thermoplastic resin films on both sides may be laminated and bonded at the same time.

In the polarizing plate having the structure shown in FIG. 1, the first adhesive layer 15 is formed from the adhesive composition according to the present invention. The first adhesive layer 15 can be a cured product layer of the adhesive composition according to the present invention.
In the polarizing plate having the configuration shown in FIG. 2, at least one of the first adhesive layer 15 and the second adhesive layer 25 is formed from the adhesive composition according to the present invention. The first adhesive layer 15 and / or the second adhesive layer 25 can be a cured product layer of the adhesive composition according to the present invention.

In the polarizing plate having the configuration shown in FIG. 2, one of the first adhesive layer 15 and the second adhesive layer 25 is formed from the adhesive composition according to the present invention, and the other is the adhesive composition according to the present invention. It may be formed from another adhesive composition different from the one.
Examples of other adhesive compositions include conventionally known water-based adhesives and active energy ray-curable adhesives.

Examples of the water-based adhesive include conventionally known adhesive compositions using a polyvinyl alcohol-based resin or a urethane resin as a main component.

When a polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be a polyvinyl alcohol-based resin such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, or a modified polyvinyl alcohol-based resin.
The polyvinyl alcohol-based resin is a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as the co-weight of vinyl acetate and other monomers copolymerizable therewith. It may be a polyvinyl alcohol-based copolymer obtained by saponifying the coalescence.

Water-based adhesives containing polyvinyl alcohol-based resins have curable components such as polyhydric aldehydes, melamine-based compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, water-soluble epoxy resins, and cross-linking agents in order to improve adhesiveness. Can be contained.

Examples of the water-based adhesive containing a urethane resin as a main component include a water-based adhesive containing a polyester-based ionomer type urethane resin and a compound having a glycidyloxy group. The polyester-based ionomer type urethane resin is a urethane resin having a polyester skeleton, in which a small amount of an ionic component (hydrophilic component) is introduced.

The active energy ray-curable adhesive is an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. When an active energy ray-curable adhesive is used, the adhesive layer of the polarizing plate is a cured product layer of the adhesive.

The active energy ray-curable adhesive can be an adhesive containing an epoxy-based compound that is cured by cationic polymerization as a curable component, and preferably an ultraviolet curable adhesive containing such an epoxy-based compound as a curable component. It is an agent. The epoxy-based compound means a compound having an average of one or more, preferably two or more epoxy groups in the molecule. Only one kind of epoxy compound may be used, or two or more kinds may be used in combination.

As the epoxy-based compound, a hydride-based epoxy compound (having an alicyclic ring) obtained by reacting an alicyclic polyol obtained by reacting an aromatic ring of an aromatic polyol with epichlorohydrin. Polyglycidyl ether of polyol); Aromatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof; epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule. Examples thereof include certain alicyclic epoxy compounds.

The active energy ray-curable adhesive can contain, as a curable component, a (meth) acrylic compound which is radically polymerizable in place of or together with the epoxy-based compound. The (meth) acrylic compound is a (meth) acrylate monomer having one or more (meth) acryloyloxy groups in the molecule; obtained by reacting two or more kinds of functional group-containing compounds, and at least two in the molecule. Examples thereof include (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having a (meth) acryloyloxy group.

When the active energy ray-curable adhesive contains an epoxy-based compound that is cured by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes and the like.
When the active energy ray-curable adhesive contains a radically polymerizable component such as a (meth) acrylic compound, it preferably contains a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone and the like.

The adhesive composition is applied to the bonding surface of the polarizing element 30 and / or the bonding surface of the thermoplastic resin film, or the polarizing element 30 and the thermoplastic resin are bonded to each other. It is possible to include a step of injecting an adhesive composition between the film and the film, laminating both films via a layer of the adhesive composition, and pressing the films from above and below using, for example, a bonding roll or the like to bond the films. ..

For the formation of the adhesive composition layer, 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. Further, a method may be used in which the polarizing element 30 and the thermoplastic resin film are continuously supplied so that the bonding surface of both is on the inner side, and the adhesive composition is cast between them.

After the bonding step, it is preferable to heat-treat the laminate containing the polarizing element 30, the adhesive composition layer, and the thermoplastic resin film. The temperature of the heat treatment is, for example, 40 ° C. or higher and 100 ° C. or lower, preferably 50 ° C. or higher and 90 ° C. or lower. The solvent contained in the adhesive composition layer can be removed by heat treatment. Further, when the adhesive composition is a curable adhesive composition, the curing / crosslinking reaction can be promoted by the heat treatment.

Before applying the adhesive composition, one or both of the bonded surfaces of the polarizing element 30 and the thermoplastic resin film are subjected to saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, and anchor coating treatment. You may perform easy-adhesion treatment (surface activation treatment) such as.

When an active energy ray-curable adhesive is used, the adhesive composition layer is dried as necessary, and then irradiated with active energy rays to cure the adhesive composition layer.
The light source used for irradiating the active energy ray may be any light source capable of generating ultraviolet rays, electron beams, X-rays and the like. In particular, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave pumped mercury lamp, a metal halide lamp and the like having a emission distribution having a wavelength of 400 nm or less are preferably used.

The thickness of the adhesive layer formed from the adhesive composition according to the present invention is, for example, 10 nm or more and 10 μm or less, preferably 20 nm or more and 5 μm or less, and more preferably 30 nm or more and 1 μm or less in the polarizing plate. More preferably, it is 40 nm or more and 500 nm or less. The adhesive layer formed from the above-mentioned conventionally known water-based adhesive can also have the same thickness.
The thickness of the adhesive layer formed from the active energy ray-curable adhesive is, for example, 10 nm or more and 20 μm or less, preferably 100 nm or more and 10 μm or less, and more preferably 500 nm or more and 5 μm or less.
The first adhesive layer 15 and the second adhesive layer 25 may have the same thickness or may be different in thickness.

[5] Other components of the polarizing plate [5-1] Optical functional film The polarizing plate can be provided with an optical functional film other than the polarizing element 30 for imparting a desired optical function. A suitable example thereof is a retardation film.
As described above, the first thermoplastic resin film 10 and / or the second thermoplastic resin film 20 can also serve as the retardation film, but the retardation film can also be laminated separately from the thermoplastic resin film. .. In the latter case, the retardation film can be laminated on the outer surface of the first thermoplastic resin film 10 and / or the second thermoplastic resin film 20 via the pressure-sensitive adhesive layer and the adhesive layer. Further, a retardation film can be laminated instead of the first thermoplastic resin film 10 or the second thermoplastic resin film 20. To give a specific example, for example, a retardation film is formed on the other surface of the polarizing element 30 in the single-sided protective polarizing plate in which the first thermoplastic resin film 10 is bonded to one surface of the polarizing element 30 shown in FIG. It is a composition in which is pasted together. In this case, the retardation film can be laminated on the surface of the polarizing element 30 via the pressure-sensitive adhesive layer or the adhesive layer.

The retardation film is a birefringent film composed of a stretched film of a translucent thermoplastic resin; a film in which a discotic liquid crystal or a nematic liquid crystal is oriented and fixed; the above liquid crystal layer is formed on a base film. The ones that have been made are mentioned.
The base film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester resin such as triacetyl cellulose.
As the thermoplastic resin forming the birefringent film, those described for the first and second thermoplastic resin films 10 and 20 can be used.

Examples of other optically functional films (optical members) that may be included in the polarizing plate include a condenser plate, a brightness improving film, a reflective layer (reflective film), a semi-transmissive reflective layer (semi-transmissive reflective film), and a light diffusing layer (light). Diffusing film) etc. These are generally provided when the polarizing plate is a polarizing plate arranged on the back surface side (backlight side) of the liquid crystal cell.

The light collecting plate is used for the purpose of controlling the optical path, and may be a prism array sheet, a lens array sheet, a sheet with dots, or the like.

The luminance improving film is used for the purpose of improving the luminance in a liquid crystal display device to which a polarizing plate is applied. Specifically, a reflective polarizing separation sheet designed to generate anisotropy in the refractive index by laminating a plurality of thin films having different refractive index anisotropies, an alignment film of a cholesteric liquid crystal polymer, and its orientation. Examples thereof include a circular polarization separation sheet in which a liquid crystal layer is supported on a base film.

The reflective layer, the semi-transmissive reflective layer, and the light diffusing layer are provided in order to make the polarizing plate into a reflective type, a semi-transmissive type, and a diffuse type optical member, respectively. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects and displays incident light from the visual recognition side, and since a light source such as a backlight can be omitted, it is easy to make the liquid crystal display device thinner. The transflective polarizing plate is used in a liquid crystal display device of a type that displays light from a backlight in a dark place as a reflective type in a bright place. Further, the diffusion type polarizing plate is used in a liquid crystal display device that imparts light diffusivity and suppresses display defects such as moire. The reflective layer, the transflective reflective layer and the light diffusing layer can be formed by a known method.

[5-2] Adhesive Layer The polarizing plate according to the present invention may include an adhesive layer for attaching the polarizing plate to an image display element such as a liquid crystal cell or another optical member. The pressure-sensitive adhesive layer is the outer surface of the polarizing element 30 in the polarizing plate having the structure shown in FIG. 1, and the outer surface of the first thermoplastic resin film 10 or the second thermoplastic resin film 20 in the polarizing plate having the structure shown in FIG. Can be laminated to.

As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a (meth) acrylic resin, a silicone-based resin, a polyester-based resin, a polyurethane-based resin, a polyether-based resin, or the like as a base polymer can be used. Among them, a (meth) acrylic pressure-sensitive adhesive is preferable from the viewpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability and the like.
The (meth) acrylic pressure-sensitive adhesive includes a (meth) acrylic acid alkyl ester having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, an n-, i- or t-butyl group, and (meth). A functional group-containing (meth) acrylic monomer such as acrylic acid or hydroxyethyl (meth) acrylic acid is blended so that the glass transition temperature is preferably 25 ° C. or lower, more preferably 0 ° C. or lower, and has a weight average molecular weight. A (meth) acrylic resin having a value of 100,000 or more is useful as a base polymer.

To form the pressure-sensitive adhesive layer on the polarizing plate, for example, the pressure-sensitive adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare a pressure-sensitive adhesive liquid, which is directly applied to the target surface of the polarizing plate. The adhesive layer is formed in the form of a sheet on the separate film that has been subjected to the mold release treatment, and the adhesive layer is transferred to the target surface of the polarizing plate. Can be done.
The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive strength and the like, but a range of 1 μm or more and 50 μm or less is appropriate, and preferably 2 μm or more and 40 μm or less.

The polarizing plate may include the above-mentioned separate film. The separate film can be a film made of a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate, or the like. Of these, a stretched film of polyethylene terephthalate is preferable.

The pressure-sensitive adhesive layer contains, if necessary, a filler made of glass fiber, glass beads, resin beads, metal powder or other inorganic powder, a pigment, a colorant, an antioxidant, an ultraviolet absorber, an antioxidant and the like. be able to.

Examples of the antistatic agent include ionic compounds, conductive fine particles, conductive polymers and the like, and ionic compounds are preferably used.
The cation component constituting the ionic compound may be an inorganic cation or an organic cation.
Examples of the organic cation include pyridinium cation, imidazolium cation, ammonium cation, sulfonium cation, phosphonium cation, piperidinium cation, pyrrolidinium cation and the like, and examples of the inorganic cation include lithium ion and potassium ion.
On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but an anion component containing a fluorine atom is preferable because it provides an ionic compound having excellent antistatic performance. As anion components containing a fluorine atom, hexafluorophosphate anion [(PF _6- ⁾ ], bis (trifluoromethanesulfonyl) imide anion [(CF ₃ SO ₂ ) ₂ N- ^] anion, bis (fluorosulfonyl) imide anion [ (FSO ₂ ) ₂ N- ^] Anions and the like can be mentioned.

[5-3] Protective film The polarizing plate according to the present invention may include a protective film for protecting the surface thereof (typically, the surface of a thermoplastic resin film). After the polarizing plate is attached to, for example, an image display element or another optical member, the protective film is peeled off and removed together with the pressure-sensitive adhesive layer contained therein.

The protective film is composed of, for example, a base film and an adhesive layer laminated on the base film. The above description is cited for the pressure-sensitive adhesive layer.
The resin constituting the base film is, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a thermoplastic resin such as a polycarbonate resin. be able to. A polyester resin such as polyethylene terephthalate is preferable.

<Liquid crystal panel and liquid crystal display device>
The polarizing plate according to the present invention can be used for a liquid crystal panel and a liquid crystal display device. The liquid crystal panel includes a liquid crystal cell and polarizing plates arranged on both sides thereof. The liquid crystal display device includes a liquid crystal panel and a backlight.
The polarizing plate according to the present invention can be arranged on one side or both sides of the liquid crystal cell. An adhesive layer can be used for attaching the polarizing plate and the liquid crystal cell.
The liquid crystal cell may be any one, and various liquid crystal cells such as an active matrix drive type liquid crystal cell typified by a thin film transistor type and a simple matrix drive type liquid crystal cell typified by a super twisted nematic type are used. It is possible to form a liquid crystal panel and a liquid crystal display device. The polarizing plates provided on both sides of the liquid crystal cell may be the same or different.
The polarizing plate according to the present invention can also be suitably used for other image display devices such as organic EL devices.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples,% and parts representing the content or the amount used are based on mass unless otherwise specified.
In Table 1, the carboxyl group-modified polyvinyl alcohol polymer (A) and the oxazoline group-containing polymer (B) are abbreviated as (A) and (B), respectively.

(Manufacturing Example 1: Fabrication of Meta (Acrylic) Resin Film)
As a (meth) acrylic resin, a copolymer of methyl methacrylate / methyl acrylate = 96% / 4% (mass ratio) was prepared. As rubber particles, the innermost layer is made of a hard polymer polymerized with methyl methacrylate and a small amount of allyl methacrylate, and the intermediate layer is mainly composed of butyl acrylate, and further contains styrene and a small amount of allyl methacrylate. The outermost layer is a three-layered elastic particle composed of a hard polymer polymerized with a small amount of ethyl acrylate in methyl methacrylate, and is composed of a soft elastic body polymerized using the intermediate layer. A polymer having an average particle size of 240 nm up to a certain elastic body was prepared. In the rubber particles, the total mass of the innermost layer and the intermediate layer was 70% of the total mass of the particles.

68.5% by mass of the (meth) acrylic resin, 29.6% by mass of the rubber particles, and 1.9% by mass of the ultraviolet absorber "Adecastab LA31" manufactured by ADEKA Co., Ltd. are mixed with a super mixer and biaxial. It was melt-kneaded with an extruder to obtain pellets. These pellets are put into a 65 mmφ uniaxial extruder, extruded through a T-type die having a set temperature of 275 ° C., sandwiched between both sides of two mirrored policing roll films, cooled, and (meth) acrylic having a thickness of 60 μm. A based resin film was obtained.

(Manufacturing Example 2: Fabrication of Polarizer)
A polyvinyl alcohol film having an average degree of polymerization of about 2,400 and a degree of polymerization of 99.9 mol% or more and a thickness of 60 μm was immersed in pure water at 30 ° C., and then the mass ratio of iodine / potassium iodide / water was 0. It was immersed in a 02/2/100 aqueous solution at 30 ° C. Then, it was immersed in an aqueous solution having a mass ratio of potassium iodide / boric acid / water of 12/5/100 at 56.5 ° C. Subsequently, the product was washed with pure water at 8 ° C. and then dried at 65 ° C. to obtain a substituent in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly carried out in the steps of iodine staining and boric acid treatment, the total stretching ratio was 5.5 times, and the thickness of the obtained polarizing element was 23 μm.

<Example 1>
(1) Preparation of Adhesive Composition An adhesive composition (adhesive aqueous solution) was prepared by mixing the components shown in Table 1 with pure water as a solvent in the blending amounts shown in Table 1. The unit of the blending amount of each component shown in Table 1 is a mass part, and the blending amount of each component is the amount in terms of solid content. The solid content concentration in the obtained adhesive composition (the solid content concentration here means the total concentration of the components (A) and (B) in the adhesive composition. The same applies to other examples). , 6.0% by mass.

(2) Preparation of Platelet A corona treatment is applied to one side of the (meth) acrylic resin film produced in Production Example 1 above, and the corona-treated side of the (meth) acrylic resin film and a saponification treatment are applied. The adhesive composition prepared in (1) above was applied to one side of a triacetyl cellulose (TAC) film [trade name "KC2UAW" manufactured by Konica Minolta Opto Co., Ltd., thickness: 25 μm] using a bar coater. I worked on it. A (meth) acrylic resin film is laminated on one surface of the polarizing element produced in Production Example 2 above, and a saponified TAC film is laminated on the other surface so that the adhesive composition layer is on the polarizing element side. Then, a laminate having a layer structure of (meth) acrylic resin film / adhesive composition layer / polarizing element / adhesive composition layer / TAC film was obtained. The laminate was heat-treated at 80 ° C. for 300 seconds by passing it through a hot air dryer, and then cured at 25 ° C. for 72 hours to prepare a polarizing plate.

(3) Evaluation of Initial Adhesion The initial adhesion between the (meth) acrylic resin film and the polarizing element in the polarizing plate obtained in (2) above was evaluated according to the following.

A corona discharge treatment was applied to the surface of the (meth) acrylic resin film in the polarizing plate, and a (meth) acrylic pressure-sensitive adhesive sheet was attached to the corona discharge-treated surface to obtain a polarizing plate with a pressure-sensitive adhesive layer. A test piece having a width of 25 mm and a length of about 200 mm was cut from the obtained polarizing plate with an adhesive layer, and the surface of the adhesive layer was bonded to a soda glass substrate.
Next, insert a cutter blade between the (meth) acrylic resin film and the polarizing element, peel off 30 mm from the end in the length direction, and peel off the peeled part with a universal tensile tester [Product name manufactured by Shimadzu Corporation]. I grabbed it with the grip of "AG-1"]. The test piece in this state was placed in an atmosphere at a temperature of 23 ° C. and a relative humidity of 55% according to JIS K 6854-2: 1999 “Adhesive-Peeling Adhesive Strength Test Method-Part 2: 180 ° Peeling”. A 180-degree peeling test was performed at a gripping movement speed of 300 mm / min, and an average peeling force over a length of 170 mm excluding 30 mm of the gripped portion was obtained and used as the adhesion force. The results are shown in Table 1. In Table 1, "*" has high adhesion, so when the above peeling test is performed, the (meth) acrylic resin film is before peeling occurs at the interface between the (meth) acrylic resin film and the polarizing element. Or it means that the stator has broken.
Further, based on the obtained measured values of the adhesion force, the initial adhesion between the (meth) acrylic resin film and the polarizing element was evaluated as follows. The results are also shown in Table 1.
A: Adhesion force exceeds 1N.
B: The adhesion is less than 1N.

<Examples 2 to 8, Comparative Example 1>
An adhesive composition was prepared in the same manner as in Example 1 except that the compounding components and their compounding amounts were changed as shown in Table 1.
The solid content concentration in the obtained adhesive composition is also shown in Table 1.
Further, a polarizing plate was produced in the same manner as in Example 1 except that the obtained adhesive composition was used, and the initial adhesion between the (meth) acrylic resin film and the substituent was measured, and the initial adhesion was measured. The initial adhesion was evaluated. The results are shown in Table 1.

The details of each component shown in Table 1 are as follows.
a1: Product name "AP-17" manufactured by Japan Vam & Poval Co., Ltd. [Carboxyl group-modified polyvinyl alcohol, average degree of polymerization: 1700, saponification degree: 88-90 mol%]
a2: Product name "AF-17" manufactured by Japan Vam & Poval Co., Ltd. [Carboxyl group-modified polyvinyl alcohol, average degree of polymerization: 1700, saponification degree: 96.5 mol% or more]
b1: Trade name "Epocross WS-300" manufactured by Nippon Catalyst Co., Ltd. [2-Aqueous solution of oxazoline group-containing acrylic polymer having an oxazoline group as a side chain, solid content concentration: 10% by mass, oxazoline value (theoretical value) : 130 g solid / eq. , Oxazoline group weight (theoretical value): 7.7 mmol / g, solid, number average molecular weight: 4 × 10 ⁴ , weight average molecular weight: 12 × 10 ⁴ ]

Further, with respect to the adhesive composition of Example 8, the following evaluations (4) to (6) are performed every 12 hours after preparation, and the following evaluations (4) to (6) are performed up to a total of 168 hours. Was done. The results are shown in Table 2.

(4) Presence or absence of gelation of the adhesive composition The prepared adhesive composition is stored in an environment of a temperature of 23 ° C. and a relative humidity of 55%, and the prepared adhesive composition is observed every 12 hours. The presence or absence of gelation was confirmed. The case where gelation did not occur was designated as "A", and the case where gelation occurred was designated as "B".
(5) Changes in Adhesiveness of Adhesive Composition over Time The prepared adhesive composition is stored in an environment with a temperature of 23 ° C. and a relative humidity of 55%, and the stored adhesive composition is used every 12 hours. A polarizing plate was produced in the same manner as in (2) of Example 1 above. The prepared polarizing plate was evaluated for adhesion in the same manner as in (3) of Example 1 above, and the presence or absence of a change in adhesion was confirmed. When the adhesion was less than 1N as compared with the initial adhesion (1.5N), the adhesion was considered to be changed, and in other cases, the adhesion was not changed. The case where there was no change in adhesion was designated as "A", and the case where there was a change in adhesion was designated as "B".
(6) Changes in Optical Properties of Polarizing Plate with Time The prepared adhesive composition was stored in an environment with a temperature of 23 ° C. and a relative humidity of 55%, and the above-mentioned implementation was carried out every 12 hours using the stored adhesive composition. A polarizing plate was produced in the same manner as in (2) of Example 1. One of the protective film surfaces of the obtained polarizing plate was subjected to corona treatment, and a (meth) acrylic pressure-sensitive adhesive sheet was bonded to the corona discharge-treated surface to obtain a polarizing plate with a pressure-sensitive adhesive layer. The obtained polarizing plate with an adhesive layer was cut into a size of 30 mm × 30 mm, the release film was peeled off, and non-alkali glass [trade name “EAGLE XG”, manufactured by Corning Inc.) was attached to the adhesive layer side. Each sample was autoclaved at a temperature of 50 ° C. and a pressure of 5 kg / cm ² (490.3 kPa) for 1 hour, and then left for 24 hours in an environment with a temperature of 23 ° C. and a relative humidity of 55%. For this sample, an optional accessory "Film holder with polarizing film" was set in an ultraviolet visible spectrophotometer (UV2450, manufactured by Shimadzu Corporation), and the transmission axis direction and absorption of the polarizing plate in the wavelength range of 380 to 700 nm. The transmission spectra in the axial direction were measured, and the degree of polarization Py (unit:%) was determined based on them.
It was confirmed whether or not there was a change in the degree of polarization Py (unit:%) obtained as described above. When the value of the degree of polarization Py changes by 1.0% or more as compared with the degree of polarization Py in the polarizing plate prepared immediately after preparing the adhesive composition, it is considered that the optical characteristics change. The case where the value of the degree of polarization Py did not change by 1.0% or more was designated as “A”, and the case where there was a change of 1.0% or more was designated as “B”.

The adhesive composition described in Example 8 was good, with no gelation occurring even after 168 hours had passed since the preparation. Further, even if a polarizing plate was produced using the adhesive composition 168 hours after the adhesive composition described in Example 8 was prepared, the adhesiveness did not change, which was good. In addition, there was no change in the optical characteristics of the polarizing plate produced by using the adhesive composition 168 hours after the adhesive composition described in Example 8 was prepared, which was good. The adhesive composition according to the present invention showed a good pot life.

10 1st thermoplastic resin film, 15 1st adhesive layer, 20 2nd thermoplastic resin film, 25 2nd adhesive layer, 30 extruder.

Claims (4)

With a splitter,
A (meth) acrylic resin film laminated on the polarizing element via an adhesive layer, and
Including
The adhesive layer is an adhesive composition in which a carboxyl group-modified polyvinyl alcohol-based polymer (A) and an oxazoline group-containing polymer (B) are dissolved in a solvent containing water (however, adhesion containing a dispersion). A polarizing plate, which is a layer formed from (excluding the agent composition) . The polarizing plate according to claim 1, wherein the oxazoline group-containing polymer (B) is a water-soluble polymer. Claimed that the content of the oxazoline group-containing polymer (B) in the adhesive composition is 100 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A). Item 2. The polarizing plate according to Item 1 or 2. With a splitter,
A (meth) acrylic resin film laminated on the polarizing element via an adhesive layer, and
Including
The adhesive layer is a layer formed of an adhesive composition containing a carboxyl group-modified polyvinyl alcohol-based polymer (A) and an oxazoline group-containing polymer (B).
In the adhesive composition, the content of the oxazoline group-containing polymer (B) is 100 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A). Board.

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