KR102522332B1 - Adhesive composition and polarizing plate - Google Patents

Abstract

(Problem) An adhesive composition imparting good adhesiveness and a polarizing plate using the same are provided.
(Solution) An adhesive composition comprising a carboxyl group-modified polyvinyl alcohol polymer (A) and an oxazoline group-containing polymer (B), and a polarizer and a (meth)acrylic resin film laminated on the polarizer through an adhesive layer. Including, wherein the adhesive layer is provided with a polarizing plate formed from the adhesive composition.

Description

Adhesive composition and polarizing plate {ADHESIVE COMPOSITION AND POLARIZING PLATE}

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

BACKGROUND OF THE INVENTION [0002] A polarizing plate widely used in an image display device represented by a liquid crystal display device or the like usually has a configuration in which a thermoplastic resin film such as a protective film is laminated and bonded on one side or both sides of a polarizer. An adhesive is normally used for bonding between a polarizer and a thermoplastic resin film. Active energy ray-curable adhesives and water-based adhesives are known as the adhesive [for example, Japanese Unexamined Patent Publication No. 2009-008860 (Patent Document 1)].

Patent Document 1: Japanese Unexamined Patent Publication No. 2009-008860

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

The present invention provides the adhesive composition and polarizing plate shown below.

[1] An adhesive composition comprising 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 adhesive composition according to [1] or [2], wherein 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). .

[4] The adhesive composition according to any one of [1] to [3], which is used for bonding the polarizer and the (meth)acrylic resin film.

[5] with a polarizer,

A (meth)acrylic resin film laminated on the polarizer through an adhesive layer

including,

The polarizing plate in which the said adhesive bond layer is a layer formed from the adhesive composition as described in any one of [1]-[4].

An adhesive composition imparting good adhesiveness and a polarizing plate using the same can be provided.

1 is a schematic cross-sectional view showing an example of the layer configuration of a polarizing plate according to the present invention.
2 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate according to the present invention.

<Adhesive composition>

The adhesive composition according to the present invention includes 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 between a polarizer and a thermoplastic resin film. In addition, since the adhesive composition according to the present invention contains the carboxyl group-modified polyvinyl alcohol polymer (A) and the oxazoline group-containing polymer (B), it can exhibit a good pot life (life that can be used as an adhesive composition). .

In addition, the compounds exemplified as each component contained or may be contained in the adhesive composition in the present specification may be used alone or in combination of plural types unless otherwise specified.

[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.

As a derivative of a carboxyl group, a carboxylate anion group is mentioned. Examples of the cation serving as a counter ion of the carboxylate anion group include alkali metal ions such as lithium ion, sodium ion, and potassium ion; Organic cations, such as an ammonium ion, a sulfonium ion, and a phosphonium ion, etc. are mentioned. An example of a preferable cation is 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 polyvinyl acetate, which is a homopolymer of vinyl acetate (completely saponified polyvinyl alcohol or partially saponified). polyvinyl alcohol) may be used, or a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith may be used.

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.

In this specification, "(meth)acryl" shows at least 1 sort(s) selected from the group which consists of an acryl and methacryl. The same applies to expressions 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-based polymer (A) by the carboxyl group (or a derivative thereof) is usually 0.1 mol% or more. When the degree of modification is within this range, good adhesion tends to be exhibited. The degree of modification of the carboxyl group-modified polyvinyl alcohol-based polymer (A) is preferably 0.5 mol% or more and 40 mol% or less, more preferably 1 mol% or more and 20 mol% or less. Modification degree can be measured by ¹ H-NMR, for example.

From the viewpoint of adhesion and water resistance, the average degree of polymerization of the carboxyl group-modified polyvinyl alcohol-based 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 commercial product may be used, for example, AP-17, AF-17 (Nippon Sacubi-Poval Co., Ltd.), Gosenex T series (manufactured by Nippon Synthetic Chemical Co., Ltd.) ), KL series such as KL-506, KL-318, and KL-118, KM series such as KM-618 and KM-118 (all manufactured by Kuraray), 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 a side chain. The main chain of the polymer is not particularly limited, but may be composed of, for example, one or more skeletons selected from (meth)acrylic skeletons and styrene skeletons.

The oxazoline group-containing polymer (B) may have an oxazoline group on 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 that includes a main chain composed of a (meth)acryl skeleton and has an oxazoline group on the side chain of the main chain.

When the oxazoline group-containing polymer (B) has an oxazoline group in its side chain, a linking group may be present between the main chain and the oxazoline group, but it is preferably a polymer in which the main chain and the oxazoline group are directly bonded.

As an oxazoline group, a 2-oxazoline group, 3-oxazoline group, 4-oxazoline group etc. are mentioned, for example. 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 5000 or more, more preferably 10000 or more. When the number average molecular weight is within the above range, good adhesiveness tends to be exhibited. The number average molecular weight of the oxazoline group-containing polymer (B) is usually 100000 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 groups of the oxazoline group-containing polymer (B) (the number of moles of oxazoline groups per 1 g solid content of the oxazoline group-containing polymer (B)) is preferably 0.4 mmol/g solid content or more and 10 mmol/g solid content or less. am. When the amount of oxazoline groups is excessively high, it is difficult to obtain good adhesion, and when 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 oxazoline group content of the oxazoline group-containing polymer (B) is more preferably 3 mmol/g solid content or more and 9 mmol/g solid content or less.

The oxazoline group-containing polymer (B) is a water-based, that is, a water-soluble polymer, or a water-dispersible polymer, when the adhesive composition is a water-based adhesive composition (adhesive in which the adhesive component is dissolved in water or dispersed in water). It is desirable to be 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), you may use a commercial item. Specifically, oxazoline group-containing acrylic polymers such as Epochros WS-300, Epochros WS-500, and Epocros WS-700 (all are trade names) manufactured by Nippon Shokubai Co., Ltd.; and oxazoline group-containing acrylic/styrene polymers such as Epocros K-1000 series, Epocros K-2000 series, and Epocros RPS series (all are trade names) manufactured by Nippon Shokubai Co., Ltd.

An oxazoline group-containing polymer (B) can be used in combination of 2 or more types.

From the viewpoints of adhesion, optical properties, and water resistance, oxazoline group-containing acrylic polymers such as Epocross WS-300 and Epochros WS-700 are preferred.

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 120 parts by mass, based on 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A). It is 900 parts by mass or less, 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 within this range, good adhesiveness tends to be 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 and 20% by mass or less, when the total amount of the adhesive composition is 100% by mass, More preferably, it is 1 mass % or more and 15 mass % or less. It is preferable from the viewpoint of adhesiveness, optical characteristics, and water resistance that the content of the oxazoline group-containing polymer (B) is within the above range.

[3] Other ingredients

The adhesive composition may contain components other than the carboxyl group-modified polyvinyl alcohol-based polymer (A) and the oxazoline group-containing polymer (B).

Examples of other components include curable components and crosslinking agents such as polyhydric aldehydes, melamine compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins; Additives, such as a coupling agent, a tackifier, an antioxidant, a ultraviolet absorber, a heat stabilizer, and a hydrolysis inhibitor, are mentioned.

The adhesive composition may contain other polyvinyl alcohol-based polymers other than the carboxyl group-modified polyvinyl alcohol-based polymer (A). By containing another polyvinyl alcohol-based polymer, an adhesive composition exhibiting 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 that are modified products of polyvinyl alcohol polymers (carboxyl group-modified polyvinyl alcohol-based polymers (A ) other than).

Examples of the modified polyvinyl alcohol polymers other than the carboxyl group-modified polyvinyl alcohol polymer (A) include acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified polyvinyl alcohol, carbonyl-modified polyvinyl alcohol, and the like. can be heard

Other polyvinyl alcohol-based polymers are not limited to vinyl alcohol homopolymers (completely saponified polyvinyl alcohol or partially saponified polyvinyl alcohol) obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymerized with vinyl acetate. It may be a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer with other possible monomers.

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.

Especially, 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 degree of saponification of other polyvinyl alcohol-based polymers 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 acetoacetyl group modification (amount of modification) of the acetoacetyl group-modified polyvinyl alcohol polymer (C) is usually 0.1 mol% or more. When the degree of modification is within this range, there is a tendency to increase adhesion easily. 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. Modification degree can be measured by ¹ H-NMR, for example.

From the standpoint of adhesion and water resistance, the average degree of polymerization of the acetoacetyl 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 usually 1 part by mass or more relative to 100 parts by mass of the carboxyl group-modified polyvinyl alcohol-based polymer (A). It is 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 within this range, the effect of increasing adhesion tends to be easily expressed.

It is preferable that adhesive composition contains a solvent. As a solvent, water, an organic solvent, or mixtures thereof are mentioned. The solvent preferably contains water, but water and a water-soluble organic solvent may be used in combination. Ethanol, 1-methoxy-2-propanol, etc. are mentioned as an organic solvent.

The solid content concentration of the adhesive composition is usually 0.5% by mass or more and 20% by mass or less, and preferably 1% by mass or more and 15% by mass or less.

Solid content concentration means the total concentration of components other than the solvent contained in adhesive composition.

The concentration of the carboxyl group-modified polyvinyl alcohol 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, more preferably 1% by mass. It is more than 15 mass % or less. When the concentration of the carboxyl group-modified polyvinyl alcohol-based polymer (A) is less than the lower limit described above, it becomes difficult to obtain sufficient adhesiveness, and when the concentration exceeds the upper limit described above, the viscosity of the adhesive composition increases and problems such as clogging of piping occur. There is a possibility that this will happen.

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 carboxyl group-modified polyvinyl alcohol-based polymer in a water-containing solvent. It is preferably a dispersion (e.g., emulsion) in which components such as the vinyl alcohol-based polymer (A) and the oxazoline group-containing polymer (B) are dispersed.

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 more 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 uniformly, possibly resulting in non-uniformity in coating, and also possibly causing problems such as clogging of piping.

The viscosity of the adhesive composition at 25°C can be measured with an E-type viscometer.

It is preferable that they are 3 or more and 10 or less, and, as for the pH in 25 degreeC of adhesive composition, it is more preferable that they are 4 or more and 9 or less. When the pH of the adhesive composition is less than 3, there is a possibility that the adhesive layer may not sufficiently exhibit water resistance, and when the pH of the adhesive composition exceeds 10, the pot life of the adhesive composition may be shortened.

The pH of the adhesive composition can be measured using a handy pH meter (for example, “D-51” manufactured by HORIBA).

<Polarizer>

The adhesive composition according to the present invention can be suitably used as an adhesive for bonding a polarizer constituting a polarizing plate and a thermoplastic resin film such as a protective film laminated thereon.

A polarizing plate according to the present invention includes a polarizer 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 layer of the adhesive composition according to the present invention.

In the polarizing plate according to the present invention, since the polarizer and the thermoplastic resin film are bonded using the adhesive composition according to the present invention, adhesion between the polarizer and the thermoplastic resin film can be improved.

[1] Configuration of polarizer

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 may include a polarizer 30 and a first thermoplastic resin film 10 laminated and bonded to one side of the polarizer through a first adhesive layer 15. there is.

In addition, as shown in FIG. 2, the polarizing plate according to the present invention includes a polarizer 30, a first thermoplastic resin film 10 laminated and bonded on one side thereof through a first adhesive layer 15, and a polarizer ( 30) may include a second thermoplastic resin film 20 laminated and bonded via a second adhesive layer 25 on the other side.

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, and both adhesive layers are formed from the adhesive composition according to the present invention it may be

In the case where 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.

It is not limited to the example of FIGS. 1 and 2, and the polarizing plate according to the present invention may include other layers (or films) other than the above. Other layers include, for example, an adhesive layer laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, and/or the polarizer 30; a separate film laminated on the outer surface of the pressure-sensitive adhesive layer (also referred to as a "release film"); A first thermoplastic resin film 10, a second thermoplastic resin film 20 and / or a protective film laminated on the outer surface of the polarizer 30 (also referred to as "surface protection film"); An optical 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 polarizer 30 through an adhesive layer or a pressure-sensitive adhesive layer, and the like.

[2] Polarizer

The polarizer 30 is a film having a function of selectively transmitting linearly polarized light in one direction from natural light. For example, an iodine-based polarizer obtained by adsorbing and orienting iodine as a dichroic dye on a polyvinyl alcohol-based resin film, a dye-based polarizer obtained by adsorbing and orienting a dichroic dye as a dichroic dye on a polyvinyl alcohol-based resin film, and a lyotropic liquid crystal. Coating type polarizer etc. which coated the dichroic dye of the state, and oriented and fixed were mentioned. These polarizers are called absorption-type polarizers because they selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in the other direction.

The polarizer 30 is not limited to an absorption type polarizer, but a reflection type polarizer that selectively transmits linearly polarized light in one direction from natural light and reflects linearly polarized light in another direction, or a scattering type that scatters linearly polarized light in another direction. Although it may be a polarizer, an absorption type polarizer is preferable from the viewpoint of excellent visibility. Among them, a polyvinyl alcohol-based polarizer composed of a polyvinyl alcohol-based resin is more preferable, and a polyvinyl alcohol-based polarizer obtained by adsorbing and orienting a dichroic dye such as iodine or a dichroic dye on a polyvinyl alcohol-based resin film is more preferable. Preferably, a polyvinyl alcohol-based polarizer obtained by adsorbing and orienting iodine on a polyvinyl alcohol-based resin film is particularly preferred.

As the polyvinyl alcohol-based resin constituting the polyvinyl-alcohol-based polarizer, 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, as well as copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate. 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 polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726:1994.

What produced such a polyvinyl alcohol-type resin into a film is used as a raw film of the polarizer 30. The method for forming a polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based raw film is, for example, 150 μm or less, preferably 100 μm or less (eg 50 μm or less), and 5 μm or more.

The polarizer 30 includes a step of uniaxially stretching a polyvinyl alcohol-based resin film; adsorbing the dichroic dye by dyeing the polyvinyl alcohol-based resin film with the dichroic dye; a step of treating (crosslinking treatment) the polyvinyl alcohol-based resin film to which the dichroic dye is adsorbed with an aqueous solution of boric acid; And it can manufacture by the method including the process of washing with water after the process by boric acid aqueous solution.

Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When performing uniaxial stretching after dyeing, you may perform this uniaxial stretching before boric acid treatment or during boric acid treatment. Moreover, you may perform uniaxial stretching in these several steps.

In uniaxial stretching, it may be uniaxially stretched between rolls having different circumferential speeds, or may be uniaxially stretched using a hot roll. Further, uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state in which a polyvinyl alcohol-based resin film is swollen using a solvent such as water. A draw ratio is 3 times or more and 8 times or less normally.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye is exemplified. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, the polyvinyl alcohol-based resin film is preferably immersed in water before dyeing.

As a dyeing treatment method by iodine, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide, and the like are exemplified. The content of iodine in this aqueous solution may be 0.01 part by mass or more and 1 part by mass or less per 100 parts by mass of water. The content of potassium iodide may be 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of water. In addition, the temperature of this aqueous solution may be 20°C or more and 40°C or less.

On the other hand, as a dyeing treatment method using 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 are exemplified. The aqueous solution containing a dichroic organic dye may contain inorganic salts, such as sodium sulfate, as a dyeing aid. The content of the dichroic organic dye in this aqueous solution may 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 may be 20°C or more and 80°C or less.

As a boric acid treatment method after dyeing with a dichroic dye, a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution, and the like are exemplified. When using iodine as a dichroic dye, it is preferable that this aqueous solution containing boric acid contains potassium iodide. The amount of boric acid in the boric acid-containing aqueous solution may 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 may 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 may be 50°C or higher, such as 50°C or higher and 85°C or lower.

The polyvinyl alcohol-based resin film after boric acid treatment is usually washed with water. Water washing treatment can be performed, for example, by immersing the polyvinyl alcohol-type resin film treated with boric acid in water. The water temperature in the water washing treatment is usually 5°C or more and 40°C or less. A drying process is performed after water washing, and the polarizer 30 is obtained.

The drying treatment can be performed using a hot air dryer or a far-infrared heater. A polarizing plate can be obtained by bonding a thermoplastic resin film as a protective film or the like to one side or both sides of the polarizer 30 using an adhesive composition.

Moreover, as another example of the manufacturing method of the polarizer 30, the method of Unexamined-Japanese-Patent No. 2000-338329 or Unexamined-Japanese-Patent No. 2012-159778 is mentioned, for example. In this method, after forming a resin layer by applying a solution containing a polyvinyl alcohol-based resin to the surface of a base film, the laminated film composed of the base film and the resin layer is stretched, followed by dyeing treatment, crosslinking treatment, etc. This is carried out to form a polarizer layer (polarizer layer) from the resin layer. This light-polarizing laminated film composed of a base film and a polarizer layer can be used as a polarizing plate having the configuration shown in FIG. 1 by bonding a thermoplastic resin film as a protective film or the like to the polarizer layer surface and then peeling off the base film. When a thermoplastic resin film is further bonded to the polarizer layer surface exposed by peeling of the base film, a polarizing plate having the configuration shown in FIG. 2 is obtained.

The thickness of the polarizer 30 can be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less, more preferably 15 μm or less, more preferably 10 μm or less or 8 μm or less). According to the method described in Japanese Unexamined Patent Publication No. 2000-338329 or Japanese Unexamined Patent Publication No. 2012-159778, it is possible to more easily manufacture a thin film polarizer 30, and the thickness of the polarizer 30 is, for example, 20 μm Hereafter, it becomes easier to further set it as 15 micrometers or less, and furthermore, 10 micrometers or less, or 8 micrometers or less. The thickness of the polarizer 30 is 2 micrometers or more normally. Reducing the thickness of the polarizer 30 is advantageous for reducing the thickness of the polarizing plate and, consequently, the image display device.

[3] Thermoplastic resin film

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 are each a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin-based resin (polypropylene-based resin, etc.), a ring polyolefin-based resins such as type polyolefin-based resins (norbornene-based resins and the like); cellulose ester-based resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin; (meth)acrylic resin; Or it may be a film made of a mixture or copolymer thereof.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may each be an unstretched film or a uniaxially or biaxially stretched film. Biaxial stretching may be simultaneous biaxial stretching in which the film is simultaneously stretched in two stretching directions, or sequential biaxial stretching in which the film is stretched in a second direction different from the first direction after stretching in the first 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 polarizer 30, or may be a protective film having an optical function such as a retardation film. there is.

The retardation film is an optical functional film used for the purpose of, for example, compensation of retardation by a liquid crystal cell serving as an image display element. For example, by stretching the film made of the thermoplastic resin (eg, uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the thermoplastic resin film, a retardation film having an arbitrary retardation value can be obtained.

Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, as well as copolymers composed of two or more types of chain olefins.

The cyclic polyolefin-based resin is a general term for resins containing, as a polymerized unit, a cyclic olefin representative of norbornene, tetracyclododecene (alias: dimethanooctahydronaphthalene) or derivatives thereof. Examples of the cyclic polyolefin resin include ring-opening (co)polymers of cyclic olefins and their hydrogenated products, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene, or aromatic compounds having a vinyl group. polymers, modified (co)polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and the like.

Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as the cyclic olefin is preferably used.

The cellulose ester-based resin is a resin in which at least one part of the hydroxyl groups in cellulose is acetic acid esterified, and a mixed ester in which a part is acetic acid esterified and a part is esterified with another acid may be used. 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 butylate.

Polyester-based resins are resins other than the above cellulose ester-based resins that have ester bonds, and are generally composed of polycondensates of polyhydric carboxylic acids or derivatives thereof and polyhydric alcohols.

As the polyester resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl A phthalate etc. are mentioned.

Among them, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost and the like. Polyethylene terephthalate means a resin in which 80 mol% or more of repeating units are constituted by ethylene terephthalate, and may contain structural units derived from other copolymerization components.

As another copolymerization component, a dicarboxylic acid component and a diol component are mentioned.

As the dicarboxylic acid component, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, 5-sodium Sulfoisophthalic acid, 1,4-dicarboxycyclohexane, etc. are mentioned.

Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

A dicarboxylic acid component and a diol component can also be used combining two or more types, respectively as needed.

It is also possible to use hydroxycarboxylic acids such as p-hydroxybenzoic acid, p-hydroxyethoxybenzoic acid, and β-hydroxyethoxybenzoic acid in combination with the dicarboxylic acid component and diol component.

As other copolymerization components, dicarboxylic acid components and/or diol components having amide bonds, urethane bonds, ether bonds, carbonate bonds and the like may be used in small amounts.

Polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among them, an aromatic polycarbonate having diphenylalkane in its molecular chain is preferably used from the viewpoints of heat resistance, weather resistance and acid resistance.

As the polycarbonate, 2,2-bis(4-hydroxyphenyl)propane (alias bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl) and polycarbonates derived from bisphenols such as cyclohexane, 1,1-bis(4-hydroxyphenyl)isobutane, and 1,1-bis(4-hydroxyphenyl)ethane.

The (meth)acrylic resin may be, for example, a polymer containing methacrylic acid ester as a main monomer (containing 50% by mass or more), and is preferably a copolymer in which methacrylic acid ester and other copolymerization components are copolymerized.

In one preferable embodiment, (meth)acrylic-type resin contains methyl methacrylate as a copolymerization component, or contains methyl methacrylate and methyl acrylate.

Other copolymerization components other than methyl acrylate include, for example, ethyl methacrylate, n-, i- or t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methacrylic acid 2 - Methacrylic acid esters other than methyl methacrylate, such as ethylhexyl and 2-hydroxyethyl methacrylate;

acrylic esters such as ethyl acrylate, n-, i- or t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate;

2-(hydroxymethyl)methyl acrylate, 2-(1-hydroxyethyl)methyl acrylate, 2-(hydroxymethyl)ethyl acrylate, 2-(hydroxymethyl)n-, i- or t-butyl acrylate, etc. hydroxyalkyl acrylic acid esters 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;

unsaturated imides such as phenyl maleimide and cyclohexyl maleimide;

Monofunctional monomers, such as these, are mentioned.

These other monofunctional monomers may be used alone or in combination of two or more.

A polyfunctional monomer may be used as the 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. ethylene glycol such as di(meth)acrylate or tetradecaethylene glycol di(meth)acrylate or those obtained by esterifying hydroxyl groups at both terminals of oligomers thereof with (meth)acrylic acid;

What esterified the hydroxyl groups of both terminals of propylene glycol or its oligomer with (meth)acrylic acid;

What esterified the hydroxyl group of dihydric alcohols, such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate, with (meth)acrylic acid;

bisphenol A, alkylene oxide adducts of bisphenol A, or those obtained by esterifying the hydroxyl groups at both terminals of halogen-substituted products thereof with (meth)acrylic acid;

What esterified polyhydric alcohols, such as trimethylol propane and pentaerythritol, with (meth)acrylic acid, and what ring-opened the epoxy group of glycidyl (meth)acrylate to these terminal hydroxyl groups;

dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, halogen-substituted products thereof, or alkylene oxide adducts thereof with ring-opening addition of an epoxy group of glycidyl (meth)acrylate;

aryl (meth)acrylate; Aromatic divinyl compounds, such as divinylbenzene;

etc. can be mentioned.

Especially, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are used preferably.

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

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 determined by adjusting the polymerization ratio of the methacrylic acid ester monomer and the acrylic acid ester monomer, the carbon chain length of each ester group and the type of functional groups they have, and the polymerization ratio of the polyfunctional monomer to the entire monomer. can be controlled

As a means for increasing the glass transition temperature of (meth)acrylic resin, it is also effective to introduce a cyclic structure into the main chain of the polymer. The cyclic structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, and a lactone structure. Specifically, cyclic acid anhydride structures, such as a glutaric anhydride structure and a succinic anhydride structure; Cyclic imide structures, such as a glutarimide structure and a succinimide structure; and lactone ring structures such as butyrolactone and valerolactone.

As the content of the cyclic structure in the main chain is increased, the glass transition temperature of the (meth)acrylic resin tends to be increased.

A method of introducing a cyclic acid anhydride structure or a cyclic imide structure by copolymerizing a monomer having a cyclic structure such as maleic anhydride or maleimide; a method of introducing a cyclic acid anhydride structure by dehydration/demethanol condensation reaction after polymerization; It can be introduced by a method of reacting an amino compound to introduce a cyclic imide structure or the like.

The resin (polymer) having a lactone ring structure is prepared by preparing a polymer having a hydroxyl group and an ester group in the polymer chain, and then heating the hydroxyl group and ester group in the obtained polymer to, if necessary, an organic phosphorus compound or the like. It can be obtained by a method of forming a lactone ring structure by cyclocondensation in the presence of a catalyst.

The (meth)acrylic resin and the thermoplastic resin film formed therefrom may contain additives as needed. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance modifiers, and surfactants.

These additives can be used even when other thermoplastic resins other than (meth)acrylic resin are used as the thermoplastic resin constituting the thermoplastic resin film.

The (meth)acrylic resin may contain acrylic rubber particles as an impact improver from the viewpoint of the film formability to the film and the impact resistance of the film. The acrylic rubber particles are particles containing an acrylic acid ester-based elastomer as an essential component, and examples thereof include single-layered particles consisting essentially of only the elastic polymer and multilayered particles containing the elastic polymer as one layer.

As an example of the elastic polymer, a crosslinked elastic copolymer obtained by copolymerizing alkyl acrylate as a main component with other vinylic monomers and crosslinkable monomers copolymerizable therewith can be given.

Examples of the alkyl acrylate serving as the main component of the elastomer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc., and those having an alkyl group having from 1 to 8 carbon atoms, and having an alkyl group of 4 or more carbon atoms. Alkyl acrylate is preferably used.

Examples of other vinyl monomers copolymerizable with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid esters such as methyl methacrylate; Aromatic vinyl compounds, such as styrene; Vinyl cyan compounds, such as acrylonitrile, etc. are mentioned.

Examples of the crosslinkable monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, more specifically, ethylene glycol di(meth)acrylate and butanedioldi(meth)acrylate (meth)acrylates of polyhydric alcohols such as the like; alkenyl esters of (meth)acrylic acid such as allyl (meth)acrylate; Divinylbenzene etc. are mentioned.

A laminate of a film made of (meth)acrylic resin containing no rubber particles and a film made of (meth)acrylic resin containing rubber particles can also be used as a thermoplastic resin film bonded to the polarizer 30. In addition, a (meth)acrylic resin layer is formed on one side or both sides of a retardation expression layer made of a resin different from the (meth)acrylic resin, and the retardation is expressed as a thermoplastic resin film bonded to the polarizer 30. may be

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 resin film is preferably laminated and bonded to the polarizer 30 via an adhesive layer formed from the adhesive composition according to the present invention.

The adhesive composition according to the present invention, when the thermoplastic resin film is a (meth)acrylic resin film, can exhibit particularly good adhesion (adhesion under a normal environment and adhesion after being placed under a humid heat environment (high temperature and high humidity environment)). Therefore, the adhesive composition concerning this invention can be used suitably for bonding of a polarizer and a (meth)acrylic-type resin film.

The (meth)acrylic resin film is preferably made of (meth)acrylic resin.

The first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 may contain a UV absorber. When a polarizing plate is applied to an image display device such as a liquid crystal display device, deterioration by ultraviolet rays of the image display device can be suppressed by disposing a thermoplastic resin film containing an ultraviolet absorber on the viewing side of the image display device (for example, a liquid crystal cell). can

Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be films composed of the same thermoplastic resin or films composed of mutually different thermoplastic resins. The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be the same or different in thickness, the presence or absence of additives, their types, phase difference 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-based resin film, a cellulose ester-based resin, or a polyester-based 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, an antistatic layer, You may be equipped with surface treatment layers (coating layers), such as an antifouling layer and a conductive layer.

The thickness of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is 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, respectively. or less, more preferably 15 μm or more and 65 μm or less. The thicknesses of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be 50 μm or less and 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, consequently, the image display device.

On the surface of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 to which the adhesive composition is applied, surface modification treatment such as saponification treatment, plasma treatment, corona treatment, priming treatment, etc. is performed from the viewpoint of improving adhesion. It may be performed, or the surface modification treatment may not be performed from the viewpoint of simplifying the process.

When the 1st thermoplastic resin film 10 or the 2nd thermoplastic resin film 20 is a cellulose acetate type resin film, it is preferable to perform a saponification process from a viewpoint of improving adhesiveness. As the saponification treatment, a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide is exemplified.

[4] Preparation of polarizing plate and adhesive layer

By laminating and adhering the first thermoplastic resin film 10 on one side of the polarizer 30 via the first adhesive layer 15, a polarizing plate having the configuration shown in FIG. 1 can be obtained, and the other side of the polarizer 30 By further laminating and adhering the second thermoplastic resin film 20 to the other side through the second adhesive layer 25, a polarizing plate having the configuration shown in FIG. 2 can be obtained.

In the case of manufacturing a polarizing plate having both the first thermoplastic resin film 10 and the second thermoplastic resin film 20 (hereinafter collectively referred to simply as "thermoplastic resin film"), these thermoplastic resin films are prepared in stages. One side may be laminated and bonded, or both sides of the thermoplastic resin film may be laminated and bonded simultaneously.

In the polarizing plate having the configuration 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 may 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 may be a cured layer of the adhesive composition according to the present invention.

In the polarizing plate of the configuration shown in FIG. 2, the first adhesive layer 15 and the second adhesive layer 25, either one is formed from the adhesive composition according to the present invention, and the other is formed from the adhesive composition according to the present invention may be formed from other, different adhesive compositions.

Examples of other adhesive compositions include conventionally known water-based adhesives and active energy ray-curable adhesives.

Examples of water-based adhesives 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 resin such as partially saponified polyvinyl alcohol or completely saponified polyvinyl alcohol or a modified polyvinyl alcohol-based resin.

Polyvinyl alcohol-based resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as polyvinyl alcohol-based copolymers obtained by saponifying vinyl acetate and copolymers of other monomers copolymerizable therewith. A composite may be used.

Water-based adhesives containing polyvinyl alcohol-based resins contain curable components such as polyhydric aldehydes, melamine-based compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins or crosslinking agents to improve adhesion. can do.

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. A polyester ionomer type urethane resin is a urethane resin having a polyester skeleton, into which a small amount of ionic component (hydrophilic component) is introduced.

An 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. In the case of using an active energy ray-curable adhesive, the adhesive layer of the polarizing plate is a cured product layer of the adhesive.

The active energy ray-curable adhesive may be an adhesive containing an epoxy-based compound curable by cationic polymerization as a curable component, and is preferably an ultraviolet curable adhesive containing such an epoxy-based compound as a curable component. An epoxy-based compound means a compound having an average of one or more, preferably two or more epoxy groups in a molecule. An epoxy-type compound may use only 1 type, and may use 2 or more types together.

Examples of the epoxy-based compound include a hydrogenated epoxy-based compound (glycidyl ether of a polyol having an alicyclic ring) obtained by reacting epichlorohydrin with an alicyclic polyol obtained by performing a hydrogenation reaction on an aromatic ring of an aromatic polyol; aliphatic epoxy-type compounds such as polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof; and an alicyclic epoxy-based compound which is an epoxy-based compound having one or more epoxy groups bonded to an alicyclic ring in a molecule.

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

When the active energy ray-curable adhesive contains an epoxy-based compound curable by cationic polymerization as a curable component, it is preferable to contain a photocationic polymerization initiator. Examples of photocationic polymerization initiators include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; An iron-alene complex etc. are mentioned.

When the active energy ray-curable adhesive contains a radically polymerizable component such as a (meth)acrylic compound, it is preferable to contain an optical radical polymerization initiator. Examples of the photo-radical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, and the like.

Adhesion between the polarizer 30 and the thermoplastic resin film is performed by applying an adhesive composition to the bonding surface of the polarizer 30 and/or the bonding surface of the thermoplastic resin film, or injecting the adhesive composition between the polarizer 30 and the thermoplastic resin film. Then, it may include a step of overlapping both films through a layer of the adhesive composition and bonding them by pressing from the top and bottom using, for example, a bonding roll or the like.

For the formation of the adhesive composition layer, various coating methods such as doctor blade, wire bar, die coater, comma coater, and gravure coater can be used. Moreover, the method of casting|flow_spreading an adhesive composition between them may be sufficient, continuously supplying the polarizer 30 and the thermoplastic resin film so that both bonding surfaces may become inside.

It is preferable to heat-process with respect to the laminated body containing the polarizer 30, the adhesive composition layer, and the thermoplastic resin film after the said bonding process. The temperature of the heat treatment is, for example, 40°C or more and 100°C or less, and preferably 50°C or more and 90°C or less. The solvent contained in the adhesive composition layer can be removed by heat treatment. In addition, when the adhesive composition is a curable adhesive composition, the curing and crosslinking reaction can be promoted by the heat treatment.

Before applying the adhesive composition, easy adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment, flame treatment, priming treatment, anchor coating treatment ( surface activation treatment) may be performed.

When using an active energy ray-curable adhesive, after drying an adhesive composition layer as needed, an active energy ray is irradiated and the adhesive composition layer is hardened.

The light source used to irradiate an active energy ray may be one capable of generating ultraviolet rays, electron beams, X-rays, or the like. In particular, low-pressure mercury-vapor lamps, medium-pressure mercury-vapor lamps, high-pressure mercury-vapor lamps, ultra-high-pressure mercury-vapor lamps, chemical lamps, black light lamps, microwave-excited mercury-vapor lamps, metal halide lamps, etc., which have a luminescence distribution at a wavelength of 400 nm or less, are suitably used.

The thickness of the adhesive layer formed from the adhesive composition according to the present invention, in a polarizing plate, is, for example, 10 nm or more and 10 μm or less, preferably 20 nm or more and 5 μm or less, more preferably 30 nm or more and 1 μm or less. , more preferably 40 nm or more and 500 nm or less. An adhesive layer formed from the above-mentioned conventionally known water-based adhesive may have the same thickness as this.

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 thickness of the first adhesive layer 15 and the second adhesive layer 25 may be the same or different.

[5] Other components of the polarizer

[5-1] Optical functional film

The polarizing plate may include other optical functional films other than the polarizer 30 for imparting a desired optical function, and a suitable example thereof is a retardation film.

As described above, although the first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 may serve as a retardation film, a retardation film may be laminated separately from the thermoplastic resin film. In the latter case, the retardation film may be laminated on the outer surface of the first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 through an adhesive layer or an adhesive layer. In addition, a retardation film may be laminated instead of the first thermoplastic resin film 10 or the second thermoplastic resin film 20 . As a specific example thereof, for example, on the other side of the polarizer 30 in the one-sided protective polarizing plate in which the first thermoplastic resin film 10 is bonded to one side of the polarizer 30 shown in FIG. 1, the phase difference It is a structure in which the film is bonded. In this case, the retardation film may be laminated on the surface of the polarizer 30 through a pressure-sensitive adhesive layer or an adhesive layer.

Examples of the retardation film include a birefringent film composed of a stretched film of a thermoplastic resin having light transmission properties; A film in which discotic liquid crystals or nematic liquid crystals are aligned and fixed; What the above liquid crystal layer was formed on the base film, etc. are mentioned.

A base film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester-based 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 optical functional films (optical members) that can be included in the polarizing plate are light collecting plates, brightness enhancing films, reflective layers (reflective films), transflective layers (transflective reflective films), light diffusion layers (light diffusion films), and the like. These are generally formed when the polarizing plate is a polarizing plate arranged on the back side (backlight side) of the liquid crystal cell.

The light collecting plate is used for optical path control and the like, and may be a prism array sheet, a lens array sheet, a dot laying sheet, or the like.

A luminance improving film is used for the purpose of improving luminance in a liquid crystal display device to which a polarizing plate is applied. Specifically, a reflective polarization separation sheet designed to generate an anisotropy in reflectance by laminating a plurality of thin films having different refractive index anisotropy, an orientation film of cholesteric liquid crystal polymer or an alignment liquid crystal layer thereof supported on a base film circularly polarized light separation sheets; and the like.

A reflective layer, a transflective reflective layer, and a light diffusing layer are formed to make the polarizing plate into a reflective, semi-transmissive, or diffusive optical member, respectively. A reflective polarizing plate is used for a liquid crystal display device that displays by reflecting incident light from the viewing side, and since a light source such as a backlight can be omitted, the liquid crystal display device can be easily reduced in thickness. A transflective type polarizing plate is a reflective type in bright light and is used for a type of liquid crystal display device that displays with light from a backlight in a dark place. Further, the diffusion-type polarizing plate is used for a liquid crystal display device in which light diffusivity is imparted and display defects such as moiré are suppressed. The reflective layer, semi-transmissive reflective layer, and light-diffusing layer can be formed by known methods.

[5-2] Adhesive layer

The polarizing plate according to the present invention may contain a pressure-sensitive adhesive layer for bonding it 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 polarizer 30 in the configuration shown in FIG. 1, and the outer surface of the first thermoplastic resin film 10 or the second thermoplastic resin film 20 in the configuration shown in FIG. 2. can be stacked on

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, those using (meth)acrylic resins, silicone-based resins, polyester-based resins, polyurethane-based resins, polyether-based resins, and the like as base polymers can be used. Among them, from the viewpoints of transparency, adhesive strength, reliability, weatherability, heat resistance, reworkability and the like, (meth)acrylic pressure-sensitive adhesives are preferable.

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, (meth)acrylic acid or hydroxyethyl (meth)acrylate A (meth)acrylic resin having a weight average molecular weight of 100,000 or more, in which a functional group-containing (meth)acrylic monomer such as the like is blended so that the glass transition temperature is preferably 25°C or less, more preferably 0°C or less, is used as the base polymer. useful.

The formation of the pressure-sensitive adhesive layer on the polarizing plate is, for example, a method of dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an pressure-sensitive adhesive liquid, and directly applying this to the target surface of the polarizing plate to form a pressure-sensitive adhesive layer, A pressure-sensitive adhesive layer may be formed in a sheet shape on the separated film subjected to the release treatment, and the method of transferring it to the target surface of the polarizing plate or the like may be used.

The thickness of the pressure-sensitive adhesive layer is determined depending on its adhesive strength and the like, and is suitably in the range of 1 µm or more and 50 µm or less, preferably 2 µm or more and 40 µm or less.

A polarizing plate may contain the above-mentioned separation film. The separation film may be a film made of polyethylene-based resins such as polyethylene, polypropylene-based resins such as polypropylene, and polyester-based resins such as polyethylene terephthalate. Especially, the stretched film of polyethylene terephthalate is preferable.

If necessary, the pressure-sensitive adhesive layer may contain glass fibers, glass beads, resin beads, fillers made of metal powder or other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, and the like.

Examples of the antistatic agent include ionic compounds, conductive fine particles, and conductive polymers, but ionic compounds are preferably used.

The cation component constituting the ionic compound may be an inorganic cation or an organic cation.

Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, phosphonium cations, piperidinium cations, and pyrrolidinium cations. Examples of inorganic cations include lithium ions and potassium ions. can be heard

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 from the viewpoint of providing an ionic compound with excellent antistatic performance. As the anion component 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 ^- ] anion; and the like.

[5-3] Protection film

The polarizing plate according to the present invention may include a protective film for protecting its surface (typically, the surface of the thermoplastic resin film). After a polarizing plate is bonded to an image display element or another optical member, for example, the protection film is peeled off along with the pressure-sensitive adhesive layer it has.

A protection film is comprised, for example of a base film and the adhesive layer laminated|stacked on it. Regarding the pressure-sensitive adhesive layer, the above description is cited.

The resin constituting the base film may be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, and a polycarbonate-based resin. there is. Preferably, they are polyester-based resins, such as polyethylene terephthalate.

Example

Hereinafter, the present invention will be described more specifically by disclosing examples, but the present invention is not limited by these examples. In the examples, % and parts representing content or amount used are based on mass unless otherwise specified.

In Table 1, carboxyl group-modified polyvinyl alcohol polymer (A), oxazoline group-containing polymer (B), and acetoacetyl group-modified polyvinyl alcohol (C) are abbreviated as (A), (B), and (C), respectively. there is.

(Production Example 1: Production of (meth)acrylic resin film)

As the (meth)acrylic resin, a copolymer of methyl methacrylate/methyl acrylate = 96%/4% (mass ratio) was prepared. Further, as a rubber particle, the innermost layer is made of a hard polymer polymerized using methyl methacrylate and a small amount of allyl methacrylate, and the middle layer is composed of butyl acrylate as a main component, and further contains styrene and a small amount of allyl methacrylate. The outermost layer is made of a soft elastic material polymerized using methyl methacrylate and a hard polymer polymerized using a small amount of ethyl acrylate, and the average particle diameter up to the middle layer of the elastic material is 240 nm was prepared. In addition, in this rubber particle, the total mass of the innermost layer and the middle layer was 70% of the entire particle.

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 "ADEKA STAB LA31" manufactured by ADEKA Co., Ltd. were mixed with a super mixer, and melt-kneaded with a twin-screw extruder to form pellets. did. The pellets were fed into a 65 mmφ single screw extruder, extruded through a T-shaped die at a set temperature of 275 ° C, and cooled by sandwiching both surfaces of two polishing roll films having a mirror surface, and a (meth) acrylic with a thickness of 60 μm A resin film was obtained.

(Production Example 2: Production of Polarizer)

A polyvinyl alcohol film having an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more and having a thickness of 60 μm was immersed in pure water at 30 ° C, and then in an aqueous solution having a mass ratio of iodine / potassium iodide / water of 0.02/2/100 at 30 ° C. Immersed. Then, it was immersed at 56.5 degreeC in the aqueous solution whose mass ratio of potassium iodide/boric acid/water was 12/5/100. Subsequently, after washing with pure water at 8°C, drying was performed at 65°C to obtain a polarizer in which iodine was adsorbed and oriented in polyvinyl alcohol. Extending|stretching was mainly performed in the process of iodine dyeing and boric acid treatment, and the thickness of the light polarizer obtained by 5.5 times the total draw ratio was 23 micrometers.

<Example 1>

(1) Preparation of adhesive composition

The components shown in Table 1 were mixed with pure water as a solvent in the compounding amounts shown in Table 1 to prepare an adhesive composition (adhesive aqueous solution). The unit of the compounding quantity of each component shown in Table 1 is a mass part, and the compounding quantity of each component is quantity by solid content conversion. The solid content concentration (total concentration of components (A), (B) and (C) in the adhesive composition) in the obtained adhesive composition was 6.0% by mass.

(2) Fabrication of polarizer

Corona treatment was performed on one side of the (meth)acrylic resin film produced in Production Example 1, and the corona treated side of the (meth)acrylic resin film and the triacetyl cellulose (TAC) film subjected to saponification treatment [ The adhesive composition prepared in (1) above was coated on one side of [trade name "KC2UAW", thickness: 25 µm, manufactured by Konica Minolta Opto Co., Ltd.] using a bar coater. A (meth)acrylic resin film was laminated on one side of the polarizer prepared in Production Example 2, and a saponified TAC film was laminated on the other side so that the adhesive composition layer was on the polarizer side. A laminate having a layer configuration of resin film/adhesive composition layer/polarizer/adhesive composition layer/TAC film was obtained. After heat-processing at 80 degreeC for 300 second by passing this laminated body through a hot-air dryer, it was made to cure at 25 degreeC for 72 hours, and the polarizing plate was produced.

(3) Evaluation of initial adhesion

The initial stage adhesiveness between the (meth)acrylic-type resin film and the polarizer in the polarizing plate obtained in said (2) was evaluated according to the following.

Corona discharge treatment was performed on the surface of the (meth)acrylic-based resin film in the polarizing plate, and a (meth)acrylic-based pressure-sensitive adhesive sheet was bonded to the corona discharge-treated surface to obtain a polarizing plate with a pressure-sensitive adhesive layer. From the obtained polarizing plate with the pressure-sensitive adhesive layer, a test piece having a width of 25 mm and a length of about 200 mm was cut out, and the pressure-sensitive adhesive layer surface was bonded to the soda glass substrate.

Subsequently, a cutter blade is inserted between the (meth)acrylic resin film and the polarizer, and 30 mm is peeled from the end in the longitudinal direction, and the peeled portion is placed in a universal tensile tester [trade name "AG-1" manufactured by Shimadzu Corporation] ] with the grip part. The test piece in this state was subjected to JIS K 6854-2: 1999 "Adhesive-Peel Adhesion Strength Test Method-Part 2: 180-degree Peel" in an atmosphere of a temperature of 23 ° C. and a relative humidity of 55%, and the grip movement speed was 300 mm / A 180-degree peel test was performed in minutes, and the average peel force over a length of 170 mm excluding 30 mm of the grip portion was determined, and this was taken as the adhesive force. The results are shown in Table 1. In Table 1, since "*" has high adhesion, when the peeling test is performed, the (meth)acrylic resin film or polarizer is broken before peeling occurs at the interface between the (meth)acrylic resin film and the polarizer. Means that do.

Moreover, based on the measured value of the obtained adhesive force, the initial stage adhesiveness between a (meth)acrylic-type resin film and a polarizer was evaluated as follows. The results are shown in Table 1 together.

A: Adhesion strength exceeds 1 N.

B: Adhesion is less than 1 N.

<Examples 2 to 8, Comparative Example 1>

An adhesive composition was prepared in the same manner as in Example 1 except that the blending components and their blending amounts were changed as shown in Table 1.

Solid content concentration in the obtained adhesive composition is shown together with Table 1.

Moreover, while carrying out similarly to Example 1 except having used the obtained adhesive composition, and producing a polarizing plate, and measuring the initial stage adhesive force between a (meth)acrylic-type resin film and a polarizer, initial stage adhesiveness was evaluated. The results are shown in Table 1.

Details of each component described in Table 1 are as follows.

a1: trade name "AP-17" manufactured by Nippon Sakubi Forval Co., Ltd. [carboxyl group-modified polyvinyl alcohol, average degree of polymerization: 1700, degree of saponification: 88 to 90 mol%]

a2: "AF-17", trade name manufactured by Nippon Sakubi Forval Co., Ltd. [carboxyl group-modified polyvinyl alcohol, average degree of polymerization: 1700, degree of saponification: 96.5 mol% or more]

b1: Nippon Shokubai Co., Ltd. trade name "Epocross WS-300" [aqueous solution of an oxazoline group-containing acrylic polymer having a 2-oxazoline group as a side chain, solid content concentration: 10% by mass, oxazoline value (theoretical value): 130 g solid content /eq., oxazoline group amount (theoretical value): 7.7 mmol/g, solid content, number average molecular weight: 4×10 ⁴ , weight average molecular weight: 12×10 ⁴ )]

In addition, regarding the adhesive composition described in Example 8, the following (4) to (6) were evaluated every 12 hours after preparation, and the following (4) to (6) were evaluated until a total of 168 hours. . The results are shown in Table 2.

(4) presence or absence of gelation of adhesive composition

The prepared adhesive composition was stored in an environment of a temperature of 23°C and a relative humidity of 55%, and the prepared adhesive composition was observed every 12 hours to confirm the presence or absence of gelation. The case where gelation did not occur was set as "○", and the case where gelation occurred was set as "x".

(5) Adhesion stability of adhesive composition

The prepared adhesive composition was stored in an environment of a temperature of 23°C and a relative humidity of 55%, and a polarizing plate was produced in the same manner as above using the stored adhesive composition every 12 hours. The produced polarizing plate was carried out similarly to the above, and adhesiveness was evaluated, and the presence or absence of a change in adhesiveness was confirmed. In addition, compared with the initial contact force, when the contact force fell to less than 1 N, it was assumed that there was a change in the contact force. The case where there was no change in adhesiveness was made into "○", and the case where there was a change in adhesiveness was made into "x".

(6) Stability of optical properties of polarizer

The prepared adhesive composition was stored in an environment of a temperature of 23°C and a relative humidity of 55%, and a polarizing plate was produced in the same manner as above using the stored adhesive composition every 12 hours. Corona treatment was performed on one protective film surface of the obtained polarizing plate, 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. From the obtained polarizing plate with an adhesive layer, each was cut to a size of 30 mm × 30 mm, the release film was peeled, and an alkali-free glass (trade name “EAGLE XG”, manufactured by Corning Co., Ltd.) was bonded to the adhesive layer side. Each sample was subjected to an autoclave treatment at a temperature of 50°C and a pressure of 5 kg/cm ² (490.3 kPa) for 1 hour, and then left in an environment of a temperature of 23°C and a relative humidity of 55% for 24 hours. Regarding this sample, a "film holder with polarizing film" as an optional accessory was set in an ultraviolet and visible spectrophotometer (UV2450, manufactured by Shimadzu Corporation), and the transmission axis direction of the polarizing plate in the wavelength range of 380 to 700 nm was measured. The transmission spectrum in the direction of the absorption axis was measured, and the polarization degree Py (unit: %) was determined based on these spectra.

The presence or absence of a change in the polarization degree Py (unit: %) obtained as described above was confirmed. Moreover, compared with polarization degree Py in the polarizing plate produced immediately after preparing adhesive composition, when the value of polarization degree Py changed by 1.0% or more, it was assumed that optical characteristics had a change. The case where there was no change of 1.0% or more in the value of polarization degree Py was set as "○", and the case where there was a change of 1.0% or more was set as "x".

The adhesive composition described in Example 8 did not generate gelation even after 168 hours had elapsed after preparation, and was good. Moreover, even if it produced a polarizing plate using the adhesive composition which passed 168 hours after preparing the adhesive composition of Example 8, there was no change in adhesive force, and it was favorable. Moreover, there was no change in the optical characteristics of the polarizing plate produced using the adhesive composition which passed 168 hours after preparing the adhesive composition of Example 8, and it was favorable. The adhesive composition according to the present invention exhibited good pot life.

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

Claims (5)

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. The adhesive composition according to claim 1, wherein the oxazoline group-containing polymer (B) is a water-soluble polymer. The adhesive composition according to claim 1, wherein 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). The adhesive composition according to any one of claims 1 to 3 used for bonding between a polarizer and a (meth)acrylic resin film. with a polarizer,
A (meth)acrylic resin film laminated on the polarizer through an adhesive layer
including,
A polarizing plate in which the adhesive layer is a layer formed from the adhesive composition according to any one of claims 1 to 3.

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