JP7345241B2 - Polarizer - Google Patents

Description

The present invention relates to a polarizing plate.

Polarizing plates widely used in image display devices such as liquid crystal display devices usually have a structure in which a thermoplastic resin film such as a protective film is laminated on one or both sides of a polarizer. An adhesive is usually used to bond the polarizer and the thermoplastic resin film. Active energy ray-curable adhesives and water-based adhesives are known as such adhesives [for example, Japanese Patent Laid-Open No. 2009-008860 (Patent Document 1)].

JP2009-008860A

An object of the present invention is to provide a polarizing plate that includes a polarizer and a (meth)acrylic resin film, and after being placed in a moist heat environment (high temperature and high humidity environment), the polarizer and (meth)acrylic resin film The object of the present invention is to provide a polarizing plate that has good adhesion to a film.

The present invention provides the following polarizing plate.
[1] Includes a polarizer, a first adhesive layer, and a (meth)acrylic resin film in this order,
A polarizing plate, wherein the first adhesive layer is a layer formed from an adhesive composition containing an oxazoline group-containing compound.
[2] The polarizing plate according to [1], wherein the adhesive composition further contains an acetoacetyl group-modified polyvinyl alcohol polymer.
[3] The polarized light according to [1] or [2], which includes a thermoplastic resin film, a second adhesive layer, the polarizer, the first adhesive layer, and the (meth)acrylic resin film in this order. Board.
[4] The polarizing plate according to any one of [1] to [3], wherein the first adhesive layer and the (meth)acrylic resin film are in contact with each other.
[5] The polarizing plate according to [4], wherein the (meth)acrylic resin film has a water contact angle of 80° or less on the surface of the first adhesive layer side.
[6] The polarizing plate according to any one of [1] to [5], wherein the polarizer and the first adhesive layer are in contact with each other.
[7] An adhesive composition for bonding a polarizer and a (meth)acrylic resin film,
An adhesive composition containing an oxazoline group-containing compound.
[8] The adhesive composition according to [7], further comprising an acetoacetyl group-modified polyvinyl alcohol polymer.
[9] The adhesive composition according to [7] or [8], further comprising water.

A polarizing plate with good adhesion between the polarizer and the (meth)acrylic resin film after being placed in a moist heat environment (high temperature and high humidity environment) can be provided.

1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate according to the present invention. FIG. 3 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate according to the present invention.

<Polarizing plate>
The polarizing plate according to the present invention includes a polarizer, a first adhesive layer, and a (meth)acrylic resin film in this order, and the first adhesive layer is formed from an adhesive composition containing an oxazoline group-containing compound. This is the adhesive layer.
The polarizing plate according to the present invention has good adhesion between the polarizer and the (meth)acrylic resin film after being placed in a moist heat environment (high temperature and high humidity environment).
In this specification, "(meth)acrylic" represents at least one selected from the group consisting of acrylic and methacryl. The same applies to expressions such as "(meth)acryloyl" and "(meth)acrylate."

[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 polarizer 30 and a (meth)acrylic resin film 10 laminated on one surface of the polarizer with a first adhesive layer 15 interposed therebetween. can be something that
It is preferable that the first adhesive layer 15 and the (meth)acrylic resin film 10 are in direct contact with each other.
It is preferable that the polarizer 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 polarizer 30, a (meth)acrylic resin film 10 laminated and bonded to one surface of the polarizer 30 via a first adhesive layer 15, The thermoplastic resin film 20 may be laminated and bonded to the other surface of the polarizer 30 via the second adhesive layer 25. That is, the polarizing plate according to the present invention includes a thermoplastic resin film 20, a second adhesive layer 25, a polarizer 30, a first adhesive layer 15, and a (meth)acrylic resin film 10 in this order. It's okay.
It is preferable that the first adhesive layer 15 and the (meth)acrylic resin film 10 are in direct contact with each other.
It is preferable that the polarizer 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 thermoplastic resin film 20 are in direct contact.
It is preferable that the polarizer 30 and the second adhesive layer 25 are in direct contact with each other.
The polarizing plate according to the present invention is a polarizing plate that includes a thermoplastic resin film 20, a second adhesive layer 25, a polarizer 30, a first adhesive layer 15, and a (meth)acrylic resin film 10 in this order. is preferred.

The polarizing plate according to the present invention is not limited to the examples shown in FIGS. 1 and 2, and may include other layers (or films) than those described above. Other layers include, for example, an adhesive layer laminated on the outer surface of the (meth)acrylic resin film 10, thermoplastic resin film 20, and/or polarizer 30; a separate film laminated on the outer surface of the adhesive layer; (Also referred to as a "release film."); A protection film (also referred to as a "surface protection film") laminated on the outer surface of the (meth)acrylic resin film 10, thermoplastic resin film 20, and/or polarizer 30; Examples include an optically functional film (or layer) laminated on the outer surface of the meth)acrylic resin film 10, the thermoplastic resin film 20, and/or the polarizer 30 via an adhesive layer or a pressure-sensitive adhesive layer.

[2] First adhesive layer The first adhesive layer 15 is a layer formed from an adhesive composition (S) containing an oxazoline group-containing compound (A).
The oxazoline group-containing compound (A) is preferably an oxazoline group-containing polymer.
The oxazoline group-containing polymer is a polymer having an oxazoline group in its molecule, and preferably a polymer having an oxazoline group in its side chain. The main chain of the polymer is not particularly limited, but may be composed of one or more types of skeletons selected from, for example, (meth)acrylic skeletons, styrene skeletons, and the like.

The oxazoline group-containing polymer can have an oxazoline group in the side chain of the main chain.
A preferred example of the oxazoline group-containing polymer is an oxazoline group-containing (meth)acrylic polymer that includes a main chain consisting of a (meth)acrylic skeleton and has an oxazoline group in the side chain of the main chain.
When the oxazoline group-containing polymer 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 must have a direct bond between the main chain and the oxazoline group. is preferred.

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

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

The amount of oxazoline groups in the oxazoline group-containing polymer (the number of moles of oxazoline groups per gram of solid content of the oxazoline group-containing polymer) is preferably 0.4 mmol/g-solid or more and 10 mmol/g-solid or less. If the amount of oxazoline groups is too 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 first adhesive layer 15 may decrease. From this viewpoint, the amount of oxazoline groups in the oxazoline group-containing polymer is more preferably 3 mmol/g·solid or more and 9 mmol/g·solid or less.

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

A commercially available product may be used as the oxazoline group-containing polymer. Specifically, acrylic polymers containing oxazoline groups 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 include acrylic/styrene polymers containing oxazoline groups, such as the K-2000 series and the Epocross RPS series (all trade names).
Two or more types of oxazoline group-containing polymers can be used in combination.
From the viewpoint of adhesion, optical properties, and water resistance, the oxazoline group-containing polymer is preferably an oxazoline group-containing acrylic polymer such as Epocross WS-300 and Epocross WS-700.

The content of the oxazoline group-containing compound (A) (preferably the oxazoline group-containing polymer) is preferably 0.1% by mass or more and 30% by mass when the total amount of the adhesive composition (S) is 100% by mass. % or less, more preferably 0.5% by mass or more and 20% by mass or less, still more preferably 1% by mass or more and 15% by mass or less. Setting the content of the oxazoline group-containing polymer within the above range is important for ensuring close contact between the polarizer 30 and the (meth)acrylic resin film 10 after being placed in a moist heat environment (high temperature and high humidity environment). Preferable from a gender perspective.

The adhesive composition (S) can further contain an acetoacetyl group-modified polyvinyl alcohol polymer (B). Further containing the acetoacetyl group-modified polyvinyl alcohol polymer (B) may be advantageous in improving the adhesion between the polarizer 30 and the (meth)acrylic resin film 10.
The acetoacetyl group-modified polyvinyl alcohol polymer (B) is a polyvinyl alcohol polymer modified by introducing an acetoacetyl group into the side chain.

The polyvinyl alcohol polymer constituting the main chain of the acetoacetyl group-modified polyvinyl alcohol polymer (B) is a vinyl alcohol homopolymer (completely saponified) obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate. polyvinyl alcohol or partially saponified polyvinyl alcohol), or a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate. It may be.
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 acetoacetyl group-modified polyvinyl alcohol polymer (B) is usually 80 mol% or more and 100 mol% or less, preferably 85 mol% or more.
The degree of saponification of the acetoacetyl group-modified polyvinyl alcohol polymer (B) can be measured according to JIS K 6726:1994.

The degree of modification (amount of modification) by acetoacetyl groups in the acetoacetyl group-modified polyvinyl alcohol polymer (B) is usually 0.1 mol% or more and 40 mol% or less, preferably 0.5 mol%, from the viewpoint of adhesion. % or more and 40 mol% or less, more preferably 1 mol% or more and 20 mol% or less. The degree of modification can be measured, for example, by ¹ H-NMR.

From the viewpoint of adhesion, the average degree of polymerization of the acetoacetyl group-modified polyvinyl alcohol polymer (B) is preferably from 100 to 3,000, more preferably from 500 to 3,000.
The average degree of polymerization of the acetoacetyl group-modified polyvinyl alcohol polymer (B) can be measured according to JIS K 6726:1994.

The content of the acetoacetyl group-modified polyvinyl alcohol polymer (B) is usually 1 part by mass or more and 300 parts by mass or less, preferably 5 parts by mass or more and 250 parts by mass, based on 100 parts by mass of the oxazoline group-containing compound (A). parts, more preferably 10 parts by mass or more and 200 parts by mass or less. When the content of the acetoacetyl group-modified polyvinyl alcohol polymer (B) is within this range, the effect of increasing adhesion tends to be easily exhibited.

The adhesive composition (S) may further contain an aziridine compound (C). The aziridine compound (C) means a compound having one or more aziridine rings in the molecule. The aziridine compound (C) is preferably a compound having two or three aziridine rings in the molecule. Further containing the aziridine compound (C) may be advantageous in improving the adhesion between the polarizer 30 and the (meth)acrylic resin film 10.
The aziridine compound (C) is preferably a monomer, and the molecular weight of the aziridine compound (C) may be 150 or more and 1000 or less.
The aziridine compound (C) may be a commercially available product, and specifically, Chemitite PZ-33, Chemitite DZ-22E (both trade names) manufactured by Nippon Shokubai Co., Ltd.; CROSSLINKER CL-422, CROSSLINKER manufactured by MENADIONA Co., Ltd. Examples include aziridine compounds such as CL-427 and CROSSLINKER CL-467 (both trade names). In particular, from the viewpoint of adhesion, CROSSLINKER CL-427 is preferably a commercially available product that can be used as the aziridine compound (C).
The content of the aziridine compound (C) is usually 0.1 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the oxazoline group-containing compound (A), from the viewpoint of effectively expressing the effect of increasing adhesion. The content is preferably 0.2 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less.

It is preferable that the adhesive composition (S) contains a solvent. Solvents include water, organic solvents, or mixtures thereof. The solvent preferably contains water, but water and a water-soluble organic solvent may be used in combination. Examples of organic solvents include alcohol solvents such as ethanol and 1-methoxy-2-propanol.
The main component of the solvent is preferably water. The main component means that it accounts for 50% by mass or more of the total solvent.
The solid content concentration of the adhesive composition (S) 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 (S).

The adhesive composition (S) can contain components other than the oxazoline group-containing compound (A), the acetoacetyl group-modified polyvinyl alcohol polymer (B), the aziridine compound (C), and the solvent.
Other components include curable components and crosslinking agents such as polyvalent aldehydes, melamine compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins; coupling agents, tackifiers, antioxidants, Examples include additives such as ultraviolet absorbers, heat stabilizers, and hydrolysis inhibitors.

The adhesive composition (S) is preferably a water-based adhesive. That is, the adhesive composition (S) is preferably a solution in which the ingredients are dissolved in a solvent containing water, or a dispersion (e.g., an emulsion) in which the ingredients are dispersed in a solvent containing water. .

The viscosity of the adhesive composition (S) at 25° C. is preferably 50 mPa·sec or less, more preferably 2 mPa·sec or more and 30 mPa·sec or less, and 4 mPa·sec or more and 20 mPa·sec or less. is even more preferable. If the viscosity at 25° C. exceeds 50 mPa·sec, it may be difficult to apply uniformly, resulting in uneven coating, and problems such as clogging of piping may occur.
The viscosity of the adhesive composition (S) at 25°C can be measured with an E-type viscometer.

The pH of the adhesive composition (S) at 25° C. is preferably 3 or more and 10 or less, more preferably 4 or more and 9 or less. If the pH of the adhesive composition (S) is less than 3, the water resistance of the first adhesive layer 15 may not be sufficiently developed, and if the pH of the adhesive composition (S) exceeds 10. In some cases, the pot life of the adhesive composition (S) may be shortened.
The pH of the adhesive composition (S) can be measured using a handy pH meter (for example, "D-51" manufactured by HORIBA).

[3] Polarizer The polarizer 30 is a film that has the function of selectively transmitting linearly polarized light in one direction from natural light. The polarizer 30 may be, for example, an iodine polarizer in which iodine as a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film, or a dichroic dye as a dichroic dye is adsorbed on a polyvinyl alcohol resin film. - Examples include oriented dye-based polarizers, and coated polarizers coated with dichroic dye in a lyotropic liquid crystal state, oriented and fixed. These polarizers are called absorption 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 may be a reflection type polarizer that selectively transmits linearly polarized light in one direction from natural light and reflects linearly polarized light in the other direction, or a reflective polarizer that selectively transmits linearly polarized light in the other direction. Although a scattering type polarizer that scatters the light may be used, an absorption type polarizer is preferable from the viewpoint of excellent visibility. Among these, it is more preferable that the polarizer 30 is a polyvinyl alcohol polarizer made of polyvinyl alcohol resin, in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film. It is more preferable to use a polyvinyl alcohol-based polarizer, and it is particularly preferable to use a polyvinyl alcohol-based polarizer in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film.

As the polyvinyl alcohol resin constituting the polyvinyl alcohol polarizer, a saponified polyvinyl acetate resin can be used. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers that can be copolymerized. 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 resin is usually 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The average degree of polymerization of the polyvinyl alcohol resin is usually 1,000 or more and 10,000 or less, preferably 1,500 or more and 5,000 or less. The average degree of polymerization of polyvinyl alcohol resin can be determined in accordance with JIS K 6726:1994.

A film made of such a polyvinyl alcohol resin is used as the original film of the polarizer 30. The method of forming a polyvinyl alcohol resin into a film is not particularly limited, and any known method may be employed. The thickness of the polyvinyl alcohol 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 polarizer 30 is produced by uniaxially stretching a polyvinyl alcohol resin film; dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; and polyvinyl alcohol to which the dichroic dye has been adsorbed. It can be produced by a method including a step of treating a resin film with an aqueous boric acid solution (crosslinking treatment); and a step of washing with water after the treatment with an aqueous boric acid solution.

The uniaxial stretching of the polyvinyl alcohol resin film can be performed before, simultaneously with, or after dyeing with the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during boric acid treatment. Further, uniaxial stretching may be performed in these plural steps.

In the uniaxial stretching, it may be uniaxially stretched between rolls having different circumferential speeds, or it may be uniaxially stretched using hot rolls. Further, the uniaxial stretching may be dry stretching performed in the atmosphere, or wet stretching performed after the polyvinyl alcohol resin film is swollen using a solvent such as water. The stretching ratio is usually 3 times or more and 8 times or less.

Examples of a method for dyeing a polyvinyl alcohol resin film with a dichroic dye include a method in which the film is immersed in an aqueous solution containing a dichroic dye. Iodine and dichroic organic dyes are used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol resin film is subjected to a immersion treatment in water before the dyeing treatment.

Examples of the dyeing treatment method using iodine include a method in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing iodine and potassium iodide. The content of iodine 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. Moreover, the temperature of this aqueous solution can be 20°C or more and 40°C or less.
On the other hand, examples of the dyeing treatment method using a dichroic organic dye include a method in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing a dichroic organic dye. 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 more and 80°C or less.

Examples of the boric acid treatment method after dyeing with a dichroic dye include a method in which the dyed polyvinyl alcohol resin film is immersed in an aqueous solution containing boric acid. When using iodine 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 parts 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 resin film treated with boric acid is usually washed with water. The water washing treatment can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing process is usually 5°C or more and 40°C or less. After washing with water, a drying process is performed to obtain a polarizer 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 the (meth)acrylic resin film 10 as a protective film or the like on one side of the polarizer 30 using the adhesive composition (S). The thermoplastic resin film 20 may be bonded to the other surface of the polarizer 30 using an adhesive composition.

Furthermore, other examples of the method for manufacturing the polarizer 30 include methods described in JP-A-2000-338329 and JP-A-2012-159778. In this method, a solution containing a polyvinyl alcohol resin is applied to the surface of a base film to form a resin layer, and then a laminated film consisting of the base film and the resin layer is stretched, and then dyed, crosslinked, etc. to form a polarizer layer (polarizer layer) from the resin layer. This polarizing laminated film consisting of a base film and a polarizer layer is prepared by laminating a (meth)acrylic resin film 10 as a protective film or the like on the polarizer layer surface, and then peeling and removing the base film. A polarizing plate having the configuration shown in FIG. If a thermoplastic resin film 20 is further bonded to the polarizer layer surface exposed by peeling off the base film, a polarizing plate having the configuration shown in FIG. 2 will be obtained.

The thickness of the polarizer 30 can be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less, further 15 μm or less, still further 10 μm or less, or 8 μm or less). According to the method described in JP-A No. 2000-338329 and JP-A No. 2012-159778, the thin film polarizer 30 can be manufactured more easily, and the thickness of the polarizer 30 can be set to, for example, 20 μm or less, and It is easier to set the thickness to 15 μm or less, more preferably 10 μm or less, or 8 μm or less. The thickness of the polarizer 30 is usually 2 μm or more. Reducing the thickness of the polarizer 30 is advantageous in reducing the thickness of the polarizing plate and, by extension, the image display device.

[4] (Meth)acrylic resin film The (meth)acrylic resin film 10 may be either an unstretched film or a uniaxially or biaxially stretched film. The biaxial stretching may be simultaneous biaxial stretching in which the film is stretched in two stretching directions at the same time, or sequential biaxial stretching in which the film is stretched in a first direction and then in a second direction different from the first direction.
The (meth)acrylic resin film 10 may be a protective film that plays a role in protecting the polarizer 30, or may be a protective film that also has an optical function such as a retardation film.

The (meth)acrylic resin constituting the (meth)acrylic resin film 10 is a polymer containing structural units derived from (meth)acrylic monomers, and the (meth)acrylic monomers include methacrylic Examples include acid esters and acrylic esters.
Examples of methacrylate esters include methyl methacrylate, ethyl methacrylate, n-, i- or t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate. etc.
Examples of acrylic esters include ethyl acrylate, n-, i- or t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc. .
The (meth)acrylic resin may be a polymer consisting only of structural units derived from (meth)acrylic monomers, or may contain other structural units.
In one preferred embodiment, the (meth)acrylic resin contains methyl methacrylate as a copolymerization component, or contains methyl methacrylate and methyl acrylate.
In one preferred embodiment, the (meth)acrylic resin may be a polymer containing methacrylic acid ester as a main monomer (containing 50% by mass or more), and may contain methacrylic acid ester and other copolymer components. A copolymer in which these are copolymerized is preferable.

Other copolymerization components other than the above-mentioned acrylic esters include, for example, 2-(hydroxymethyl)methyl acrylate, 2-(1-hydroxyethyl)methyl acrylate, 2-(hydroxymethyl)ethyl acrylate, and 2-(hydroxymethyl)methyl acrylate. Hydroxyalkyl acrylates such as n-, i- or t-butyl (hydroxymethyl)acrylate;
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 phenylmaleimide and cyclohexylmaleimide;
Examples include monofunctional monomers such as.
The other monofunctional monomers mentioned above 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 di(meth)acrylate. Acrylate, ethylene glycol such as tetradecaethylene glycol di(meth)acrylate or its oligomer, with both terminal hydroxyl groups esterified with (meth)acrylic acid;
propylene glycol or its oligomer, with both terminal hydroxyl groups esterified with (meth)acrylic acid;
Those obtained by esterifying the hydroxyl group of a dihydric alcohol such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, butanediol di(meth)acrylate with (meth)acrylic acid;
Bisphenol A, alkylene oxide adducts of bisphenol A, or halogen-substituted products of which both terminal hydroxyl groups are esterified with (meth)acrylic acid;
Those obtained by esterifying polyhydric alcohols such as trimethylolpropane and pentaerythritol with (meth)acrylic acid, and those obtained by ring-opening addition of the epoxy group of glycidyl (meth)acrylate to the terminal hydroxyl group;
Dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, halogen-substituted products thereof, or alkylene oxide adducts thereof, etc., with ring-opening addition of an epoxy group of glycidyl (meth)acrylate;
Aryl (meth)acrylate; aromatic divinyl compounds such as divinylbenzene;
etc.
Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

The (meth)acrylic resin may be modified by a reaction between functional groups of the copolymer. The reaction includes, for example, intra-polymer chain demethanol condensation reaction between the methyl ester group of methyl (meth)acrylate and the hydroxyl group of 2-(hydroxymethyl)methyl acrylate, and the reaction between the carboxyl group of (meth)acrylic acid and the hydroxyl group of methyl 2-(hydroxymethyl)acrylate. Examples include dehydration condensation reaction within 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 determined by the polymerization ratio of the methacrylic ester monomer and the acrylic ester monomer, the carbon chain length of each ester group, the type of functional group they have, and the polyfunctional monomer relative to the entire monomer. It can be controlled by adjusting the polymerization ratio of polymers.

As a means for increasing the glass transition temperature of (meth)acrylic resins, it is also effective to introduce a ring structure into the main chain of the polymer. 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 include cyclic acid anhydride structures such as glutaric anhydride structure and succinic anhydride structure; cyclic imide structures such as glutarimide structure and succinimide structure; and lactone ring structures such as butyrolactone and valerolactone.
There is a tendency that the glass transition temperature of the (meth)acrylic resin can be increased as the content of the ring structure in the main chain is increased.
A cyclic acid anhydride structure and a cyclic imide structure are introduced by copolymerizing monomers having a cyclic structure such as maleic anhydride and maleimide; a cyclic acid anhydride structure is introduced by dehydration and 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.
A resin (polymer) having a lactone ring structure is obtained by preparing a polymer having a hydroxyl group and an ester group in the polymer chain, and then converting the hydroxyl group and ester group in the obtained polymer to the necessary amount by heating. Depending on the case, it can be obtained by a method in which a lactone ring structure is formed by cyclization condensation in the presence of a catalyst such as an organic phosphorus compound.

The (meth)acrylic resin and the (meth)acrylic resin film 10 formed from it may contain additives as necessary. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, light resistance agents, impact resistance modifiers, and surfactants.
Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

The (meth)acrylic resin may contain acrylic rubber particles as an impact modifier from the viewpoint of film formability and impact resistance of the film. Acrylic rubber particles are particles whose essential component is an elastic polymer mainly composed of acrylic acid ester. Examples include rubber particles having a multilayer structure in one layer.
Examples of the above-mentioned elastic polymers include crosslinked elastic copolymers containing acrylic acid ester as a main component and copolymerizing other copolymerizable vinyl monomers and crosslinkable monomers therewith.
Examples of acrylic esters that are the main component of the elastic polymer include those in which the number of carbon atoms in the alkyl group is approximately 1 to 8, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. are mentioned, and alkyl acrylates having an alkyl group having 4 or more carbon atoms are preferred.
Other vinyl monomers that can be copolymerized with the above acrylic ester include compounds having one polymerizable carbon-carbon double bond in the molecule, more specifically, methyl methacrylate. methacrylic acid esters such as; aromatic vinyl compounds such as styrene; and vinyl cyanide compounds such as acrylonitrile.
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, butane Examples 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.

The average diameter of the acrylic rubber particles is usually 50 nm or more and 400 nm or less.
The content of the acrylic rubber particles is usually 5 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the (meth)acrylic resin.
The (meth)acrylic resin mixed with acrylic rubber particles may be a commercially available product, such as "HT55X" (trade name: Sumitomo Chemical Co., Ltd.).

The (meth)acrylic resin film 10 may be a laminate of a layer made of a (meth)acrylic resin not containing rubber particles and a layer made of a (meth)acrylic resin containing rubber particles.

The thickness of the (meth)acrylic resin film 10 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 or less, and even more preferably 15 μm or more and 65 μm or less.
In addition, when the (meth)acrylic resin film 10 is multilayer, it is preferable that the total thickness is within the above range.

The (meth)acrylic resin film 10 has a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, and an antifouling layer on its outer surface (the surface opposite to the first adhesive layer 15). , a surface treatment layer (coating layer) such as a conductive layer may be provided.

From the viewpoint of improving adhesion, the bonding surface of the (meth)acrylic resin film 10 may be subjected to surface modification treatment such as saponification treatment, plasma treatment, corona treatment, and primer treatment. The surface modification treatment may be performed on the bonding surface of the polarizer 30 instead of or together with the bonding surface of the (meth)acrylic resin film 10.

In the polarizing plate according to the present invention, from the viewpoint of adhesion between the polarizer 30 and the (meth)acrylic resin film 10, the first adhesive layer 15 and the (meth)acrylic resin film 10 are in direct contact with each other. Preferably.
When the first adhesive layer 15 and the (meth)acrylic resin film 10 are in direct contact, the water contact angle (contact with water) of the surface of the (meth)acrylic resin film 10 on the first adhesive layer 15 side is The angle) is preferably 80° or less, more preferably 70° or less, and even more preferably 65° or less. The lower limit of the water contact angle is not particularly limited, but is usually 20° or more.
The fact that the water contact angle of the surface of the (meth)acrylic resin film 10 on the first adhesive layer 15 side is 80° or less means that the adhesion between the polarizer 30 and the (meth)acrylic resin film 10 is It is advantageous in that it can be good not only after being placed in a humid heat environment (high temperature and high humidity environment) but also when being placed at room temperature (for example, temperature 23° C. and relative humidity 55%).
The water contact angle of the surface of the (meth)acrylic resin film 10 on the first adhesive layer 15 side is measured according to the method described in the Examples section below.

[5] Thermoplastic resin film The thermoplastic resin film 20 is preferably a translucent thermoplastic resin film. Examples of thermoplastic resin films include polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.) and cyclic polyolefin resins (norbornene resins, etc.); cellulose ester resins such as triacetyl cellulose and diacetyl cellulose; The film may be made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin; or a mixture or copolymer thereof.
In the case where the thermoplastic resin film 20 is a (meth)acrylic resin film, the above description regarding the (meth)acrylic resin film 10 is cited.

The thermoplastic resin film 20 may be an unstretched film or a uniaxially or biaxially stretched film. The biaxial stretching may be simultaneous biaxial stretching in which the film is stretched in two stretching directions at the same time, or sequential biaxial stretching in which the film is stretched in a first direction and then in a second direction different from the first direction.
The thermoplastic resin film 20 may be a protective film that plays the role of protecting the polarizer 30, or may be a protective film that also has an optical function such as a retardation film.

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

Cyclic polyolefin resin is a general term for resins containing a cyclic olefin as a polymer unit, representative examples of which are norbornene, tetracyclododecene (also known as dimetanooctahydronaphthalene), or derivatives thereof. Cyclic polyolefin resins include ring-opened (co)polymers of cyclic olefins and their hydrogenated products, addition polymers of cyclic olefins, cyclic olefins and chain olefins such as ethylene and propylene, or aromatic compounds having vinyl groups. and modified (co)polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof.
Among them, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin is preferably used.

Cellulose ester resin is a resin in which at least some of the hydroxyl groups in cellulose are acetate-esterified, and is a mixed ester in which some are acetate-esterified and some are esterified with other acids. Good too. The cellulose ester resin is preferably an acetylcellulose resin.
Examples of the acetylcellulose resin include triacetylcellulose, diacetylcellulose, cellulose acetate propionate, cellulose acetate butyrate, and the like.

The polyester resin is a resin other than the above-mentioned cellulose ester resin that has an ester bond, and is generally a polycondensate of a polycarboxylic acid or a derivative thereof and a polyhydric alcohol.
Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl naphthalate, and the like.
Among them, polyethylene terephthalate is preferably used from the viewpoint of mechanical properties, solvent resistance, scratch resistance, cost, etc. Polyethylene terephthalate refers to a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may contain structural units derived from other copolymer components.

Other copolymerization components include dicarboxylic acid components and diol components.
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 can also be used in combination of two or more types, if necessary.
It is also possible to use hydroxycarboxylic acids such as p-hydroxybenzoic acid, p-hydroxyethoxybenzoic acid, and β-hydroxyethoxybenzoic acid together with the dicarboxylic acid component and diol component.
As other copolymerization components, a small amount of dicarboxylic acid components and/or diol components having amide bonds, urethane bonds, ether bonds, carbonate bonds, etc. may be used.

Polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among these, aromatic polycarbonates having diphenylalkane in their molecular chains are preferably used from the viewpoints of heat resistance, weather resistance, and acid resistance.
Examples of polycarbonates include 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1, Examples include polycarbonates derived from bisphenols such as 1-bis(4-hydroxyphenyl)isobutane and 1,1-bis(4-hydroxyphenyl)ethane.

The thermoplastic resin film 20 is preferably a cellulose ester resin film or a cyclic polyolefin resin film.

The thermoplastic resin film 20 may contain additives as necessary. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, light resistance agents, impact resistance modifiers, and surfactants.
Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.
When applying a polarizing plate to an image display device such as a liquid crystal display device, the thermoplastic resin film 20 containing an ultraviolet absorber or the (meth)acrylic resin film 10 containing an ultraviolet absorber is attached to an image display element (for example, a liquid crystal cell). ), it is possible to suppress deterioration of the image display element due to ultraviolet rays.

The thickness of the 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 or less, and even more preferably 15 μm or more and 60 μm or less. The thickness of the thermoplastic resin film 20 may be 50 μm or less, or 40 μm or less. Reducing the thickness of the thermoplastic resin film 20 is advantageous for reducing the thickness of the polarizing plate and, by extension, the image display device.

The thermoplastic resin film 20 has a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, an antifouling layer, and a conductive layer on its outer surface (the surface opposite to the second adhesive layer 25). It may be provided with a surface treatment layer (coating layer) such as.

From the viewpoint of improving adhesion, the bonding surface of the thermoplastic resin film 20 may be subjected to surface modification treatment such as saponification treatment, plasma treatment, corona treatment, and primer treatment. The surface modification treatment may be performed on the bonding surface of the polarizer 30 instead of or together with the bonding surface of the thermoplastic resin film 20.
When the thermoplastic resin film 20 is a cellulose acetate resin film, it is preferable to perform saponification treatment from the viewpoint of improving adhesion. Examples of the saponification treatment include immersion in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

[6] Second adhesive layer The adhesive forming the second adhesive layer 25 may be the above-mentioned adhesive composition (S) or another adhesive composition different from this. Good too. The second adhesive layer 25 is preferably an adhesive layer formed from adhesive composition (S).
The second adhesive layer 25 may be a cured layer of an adhesive composition.
In the case where the first adhesive layer 15 and the second adhesive layer 25 are formed from the adhesive composition (S), these adhesive compositions may have the same composition or different compositions. It's okay.
Examples of other adhesive compositions include known water-based adhesives in which adhesive components are dissolved or dispersed in water, and known active energy ray-curable adhesives containing active energy ray-curable compounds.

Examples of the water-based adhesive composition include water-based adhesive compositions in which adhesive components such as polyvinyl alcohol resins and urethane resins are dissolved or dispersed in water.
Water-based adhesives containing polyvinyl alcohol resins contain curable components and crosslinking agents such as polyvalent aldehydes, melamine compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins to improve adhesive properties. can contain.
Examples of the water-based adhesive containing a urethane resin include a water-based adhesive containing a polyester-based ionomer type urethane resin and a compound having a glycidyloxy group. A polyester-based ionomer type urethane resin is a urethane resin having a polyester skeleton into 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 using an active energy ray-curable adhesive, the second adhesive layer 25 is a cured layer of the adhesive.

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

Examples of epoxy compounds include hydrogenated epoxy compounds (having an alicyclic ring) obtained by reacting epichlorohydrin with an alicyclic polyol obtained by hydrogenating the aromatic ring of an aromatic polyol. (Glycidyl ether of polyol); Aliphatic epoxy compounds such as polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct; Epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule. Examples include certain alicyclic epoxy compounds.

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

When the active energy ray-curable adhesive contains an epoxy 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-alene 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 acetophenone initiators, benzophenone initiators, benzoin ether initiators, thioxanthone initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone.

The polarizing plate may include an adhesive layer instead of the second adhesive layer 25. That is, the thermoplastic resin film 20 may be bonded to the polarizer 30 via an adhesive layer. Regarding the adhesive layer, the description regarding the adhesive layer described below is cited.

[7] Manufacture of polarizing plate A polarizing plate having the configuration shown in FIG. 1 is obtained by laminating and adhering the (meth)acrylic resin film 10 to one surface of the polarizer 30 via the first adhesive layer 15. By further laminating and adhering the thermoplastic resin film 20 to the other surface of the polarizer 30 via the second adhesive layer 25, a polarizing plate having the configuration shown in FIG. 2 can be obtained.
When manufacturing a polarizing plate having both the (meth)acrylic resin film 10 and the thermoplastic resin film 20, these films may be laminated and bonded on one side in stages, or the films on both sides may be laminated and bonded simultaneously. You may.
The first adhesive layer 15 and/or the second adhesive layer 25 may be a cured product layer of an adhesive composition.

As a method for bonding the polarizer 30 and the (meth)acrylic resin film 10, the adhesive composition (S) is applied to one or both of the bonding surfaces of the polarizer 30 and the (meth)acrylic resin film 10. An example of a method is to coat both surfaces, laminate the other bonding surface thereon, and press the layer from above and below using a bonding roll or the like to bond the layer.
Various coating methods can be used to apply the adhesive composition (S), such as a doctor blade, wire bar, die coater, comma coater, and gravure coater. Further, the adhesive composition (S) is cast while continuously supplying the polarizer 30 and the (meth)acrylic resin film 10 so that the bonded surfaces of the two are on the inside. Good too.

After bonding the polarizer 30 and the (meth)acrylic resin film 10, the laminate including the polarizer 30, the first adhesive layer 15, and the (meth)acrylic resin film 10 is subjected to heat treatment. It is preferable to apply 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. Furthermore, when the adhesive composition is a curable adhesive composition, the heat treatment can advance the curing/crosslinking reaction.

The above bonding method can also be applied to bonding the polarizer 30 and the thermoplastic resin film 20.

When using an active energy ray-curable adhesive, the adhesive composition layer is dried if necessary, and then the adhesive composition layer is cured by irradiation with active energy rays.
The light source used to irradiate the active energy rays may be any light source that can generate ultraviolet rays, electron beams, X-rays, etc. In particular, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc., which have an emission distribution at a wavelength of 400 nm or less, are preferably used.

The thickness of the first adhesive layer 15 formed from the adhesive composition (S) 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, and even more preferably is 40 nm or more and 500 nm or less. An adhesive layer formed from the above-mentioned known water-based adhesive can also have a similar 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 have different thicknesses.

[8] Other components of the polarizing plate [8-1] Optical functional film The polarizing plate can include an optically functional film other than the polarizer 30 to impart a desired optical function, A suitable example thereof is a retardation film.
As described above, the (meth)acrylic resin film 10 and/or the thermoplastic resin film 20 can also serve as a retardation film, but a retardation film can also be laminated separately from these films. In the latter case, the retardation film can be laminated on the outer surface of the (meth)acrylic resin film 10 and/or the thermoplastic resin film 20 via a pressure-sensitive adhesive layer or an adhesive layer.

As a retardation film, a birefringent film composed of a stretched film of a thermoplastic resin having translucency; a film in which discotic liquid crystal or nematic liquid crystal is aligned; the above liquid crystal layer is formed on a base film; Examples include those that were
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 triacetylcellulose.

Examples of other optically functional films (optical members) that can be included in the polarizing plate include light condensing plates, brightness enhancement films, reflective layers (reflective films), semi-transparent reflective layers (semi-transparent reflective films), and light diffusing layers (light diffusion film) etc. These are generally provided when the polarizing plate is a polarizing plate placed on the back side (backlight side) of the liquid crystal cell.

The light condensing plate is used for the purpose of optical path control, etc., and can be a prism array sheet, a lens array sheet, a dot-attached sheet, or the like.

A brightness enhancement film is used for the purpose of improving brightness in a liquid crystal display device to which a polarizing plate is applied. Specifically, we are developing reflective polarization separation sheets designed to create anisotropy in reflectance by laminating multiple thin films with different anisotropy of refractive index, and oriented films of cholesteric liquid crystal polymers and their orientation. Examples include circularly polarized light separating sheets 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 to make the polarizing plate a reflective, semi-transmissive, and diffusive optical member, respectively. A reflective polarizing plate is used in a type of 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, it is easy to make the liquid crystal display device thinner. A semi-transmissive polarizing plate is used in a type of liquid crystal display device that uses light from a backlight to display information in a dark place and as a reflective type in a bright place. Further, a diffusion type polarizing plate is used in a liquid crystal display device that provides light diffusivity and suppresses display defects such as moire. The reflective layer, the semi-transparent reflective layer, and the light diffusing layer can be formed by a known method.

[8-2] Adhesive layer The polarizing plate according to the present invention can include an adhesive layer. Examples of the adhesive layer include adhesive layers for bonding the polarizing plate to an image display element such as a liquid crystal cell, or other optical member. The adhesive layer is applied to the outer surface of the polarizer 30 in the polarizing plate having the structure shown in FIG. 1, and the outer surface of the (meth)acrylic resin film 10 or the thermoplastic resin film 20 in the polarizing plate having the structure shown in FIG. Can be stacked on top of each other.

As the adhesive used in the adhesive layer, those having base polymers such as (meth)acrylic resins, silicone resins, polyester resins, polyurethane resins, and polyether resins can be used. Among these, (meth)acrylic adhesives are preferred from the viewpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability, and the like.
The (meth)acrylic adhesive contains a (meth)acrylic acid alkyl ester having an alkyl group having 20 or less carbon atoms, such as a methyl group, an ethyl group, or an n-, i-, or t-butyl group; A weight average molecular weight compound containing a functional group-containing (meth)acrylic monomer such as acrylic acid or hydroxyethyl (meth)acrylate so that the glass transition temperature is preferably 25°C or lower, more preferably 0°C or lower. (Meth)acrylic resins having a carbon content of 100,000 or more are useful as base polymers.

To form an adhesive layer on a polarizing plate, for example, an adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, and this is directly applied to the target surface of the polarizing plate. A method of forming an adhesive layer on a separate film that has been subjected to a release treatment, or a method of forming an adhesive layer in the form of a sheet on a separate film that has been subjected to a release treatment, and then transferring it to the target surface of a polarizing plate. I can do it.
The thickness of the adhesive layer is determined depending on its adhesive strength, etc., but 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.

The polarizing plate may include the above-described 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. Among these, a stretched film of polyethylene terephthalate is preferred.

The adhesive layer contains glass fibers, glass beads, resin beads, fillers made of metal powder and other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, etc., as necessary. be able to.

Examples of the antistatic agent include ionic compounds, conductive fine particles, conductive polymers, etc., and 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, and examples of inorganic cations include lithium ions and potassium ions.
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 preferred since it provides an ionic compound with excellent antistatic performance. Examples of anion components containing a fluorine atom include hexafluorophosphate anion [(PF ₆ ⁻ )], bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ] anion, and bis(fluorosulfonyl)imide anion [ (FSO ₂ ) ₂ N ⁻ ] anion and the like.

[8-3] Protective film The polarizing plate according to the present invention includes a protective film for protecting its surface (typically, the surface of the (meth)acrylic resin film 10 or the thermoplastic resin film 20). I can do it. For example, after a polarizing plate is bonded to an image display element or other optical member, the protect film is peeled off together with the adhesive layer it has.

The protect film is composed of, for example, a base film and an adhesive layer laminated thereon. Regarding the adhesive layer, the above description is cited.
The resin constituting the base film is, for example, a thermoplastic resin such as a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate resin. be able to. Preferably, it is a polyester resin such as polyethylene terephthalate.

<Liquid crystal panel and liquid crystal display device>
The polarizing plate according to the present invention can be used for liquid crystal panels and liquid crystal display devices. A liquid crystal panel includes a liquid crystal cell and polarizing plates arranged on both sides of the liquid crystal cell. A liquid crystal display device includes a liquid crystal panel and a backlight.
The polarizing plate according to the present invention can be placed on one or both sides of a liquid crystal cell. An adhesive layer can be used to adhere the polarizing plate and the liquid crystal cell.
The liquid crystal cell may be of any type; for example, various liquid crystal cells may be used, such as an active matrix drive type liquid crystal cell represented by a thin film transistor type, or a simple matrix drive type liquid crystal cell represented by a super twisted nematic type. Thus, a liquid crystal panel and a liquid crystal display device can be formed. 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.

EXAMPLES Hereinafter, the present invention will be explained 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 amount used are based on mass, unless otherwise specified.
In Table 1, the oxazoline group-containing compound (A), the acetoacetyl group-modified polyvinyl alcohol (B), and the aziridine compound (C) are abbreviated as (A), (B), and (C), respectively.

(Production Example 1: Production of meth (acrylic) resin film)
As a (meth)acrylic resin, a copolymer of methyl methacrylate/methyl acrylate = 96%/4% (mass ratio) was prepared. In addition, as rubber particles, the innermost layer is made of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of allyl methacrylate, and the middle layer is made 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 hard polymer made by polymerizing methyl methacrylate with a small amount of ethyl acrylate. A material having an average particle diameter of 240 nm up to a certain elastic body was prepared. In addition, in this rubber particle, the total mass of the innermost layer and the intermediate layer was 70% of the entire particle.

68.5% by mass of the above (meth)acrylic resin, 29.6% by mass of the above rubber particles, and 1.9% by mass of the ultraviolet absorber "ADEKA STAB LA31" manufactured by ADEKA Co., Ltd. were mixed in a super mixer. The mixture was melt-kneaded using an extruder to form pellets. The pellets were put into a 65 mmφ single-screw extruder, extruded through a T-shaped die with a set temperature of 275°C, cooled by sandwiching both sides of two mirror-finished polishing roll films, and made into a 60 μm thick (meth)acrylic A resin film was obtained.

(Manufacturing example 2: Preparation of polarizer)
After immersing a 60 μm thick polyvinyl alcohol film with an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more in pure water at 30°C, the mass ratio of iodine/potassium iodide/water was 0. It was immersed in an aqueous solution of 02/2/100 at 30°C. Thereafter, 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, it was washed with pure water at 8°C and then dried at 65°C to obtain a polarizer in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly performed in the steps of iodine dyeing and boric acid treatment, the total stretching ratio was 5.5 times, and the thickness of the obtained polarizer was 23 μm.

<Example 1>
(1) Preparation of adhesive composition The components shown in Table 1 were mixed in the amounts shown in Table 1 with pure water as a solvent to prepare an adhesive composition (adhesive aqueous solution). The unit of the blending amount of each component shown in Table 1 is parts by mass, 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 components (A) and (B) in the adhesive composition. The same applies to other examples) is , 2.0% by mass.

(2) Preparation of polarizing plate One side of the (meth)acrylic resin film prepared in Production Example 1 above is subjected to corona treatment, and the corona-treated side of the (meth)acrylic resin film is treated with saponification. The adhesive composition prepared in (1) above was coated on 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 was laminated on one side of the polarizer prepared in Production Example 2 above, and a saponified TAC film was laminated on the other side so that the adhesive composition layer was on the polarizer side. As a result, a laminate having a layer structure of (meth)acrylic resin film/adhesive composition layer/polarizer/adhesive composition layer/TAC film was obtained. This 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 produce a polarizing plate.

(3) Evaluation of adhesion after moist heat treatment The adhesiveness between the (meth)acrylic resin film and the polarizer in the polarizing plate obtained in (2) above after moist heat treatment was evaluated according to the following.

The surface of the (meth)acrylic resin film in the polarizing plate was subjected to corona discharge treatment, and a (meth)acrylic adhesive sheet was laminated to the corona discharge treated surface to obtain a polarizing plate with an adhesive layer. A test piece having a width of 25 mm and a length of approximately 200 mm was cut from the obtained polarizing plate with an adhesive layer, and the adhesive layer surface thereof was bonded to a soda glass substrate.
This test piece was stored at a temperature of 85° C. and a relative humidity of 85% for 48 hours, and then stored overnight at a temperature of 23° C. and a relative humidity of 55%.
Next, insert a cutter blade between the (meth)acrylic resin film and the polarizer, peel it off 30 mm from the end in the length direction, and test the peeled part with a universal tensile tester (trade name manufactured by Shimadzu Corporation). I grabbed it with the grip part of "AG-1". The test piece in this state was tested in an atmosphere at a temperature of 23°C and a relative humidity of 55% in accordance with JIS K 6854-2:1999 "Adhesives - Peeling adhesive strength test method - Part 2: 180 degree peeling". A 180 degree peeling test was conducted at a gripping movement speed of 300 mm/min, and the average peeling force over a length of 170 mm excluding 30 mm of the gripping portion was determined, and this was taken as the adhesion force. The results are shown in Table 1. In Table 1, "*" indicates high adhesion, so when the above peeling test is performed, the (meth)acrylic resin film is removed before peeling occurs at the interface between the (meth)acrylic resin film and the polarizer. Or it means that the polarizer has broken.
Furthermore, based on the obtained adhesion strength measurements, the adhesion between the (meth)acrylic resin film and the polarizer after the moist heat treatment was evaluated in the following three grades. The results are also shown in Table 1.
A: Adhesion force exceeds 5N.
B: Adhesion strength is in the range of 1 to 5N.
C: Adhesion force is less than 1N.

<Examples 2 to 37, Comparative Example 1>
An adhesive composition was prepared in the same manner as in Example 1 except that the ingredients and their amounts were changed as shown in Table 1.
The solid content concentration in the obtained adhesive composition is also shown in Table 1.
In addition, a polarizing plate was produced in the same manner as in Example 1 except that the obtained adhesive composition was used, and the adhesion between the (meth)acrylic resin film and the polarizer after the moist heat treatment was measured. At the same time, the adhesion after moist heat treatment was evaluated. The results are shown in Table 1.

ｄ１：日本合成化学工業株式会社製の商品名「Ｓａｆｅｌｉｎｋ ＳＰＭ－０１」〔グリオキシル酸塩系の架橋剤、固形分濃度：１０質量％〕 Details of each component shown in Table 1 are as follows.
a1: Product name “Epocross WS-300” manufactured by Nippon Shokubai Co., Ltd. [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) :130g solid/eq. , oxazoline group weight (theoretical value): 7.7 mmol/g, solid, number average molecular weight: 4 x 10 ⁴ , weight average molecular weight: 12 x 10 ⁴ ]
a2: Product name “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd. [solution of oxazoline group-containing acrylic polymer having 2-oxazoline groups as side chains (solvent: water and 1-methoxy-2-propanol), solid Minute concentration: 39% by mass, oxazoline value (theoretical value): 220g solid/eq. , oxazoline group weight (theoretical value): 4.5 mmol/g, solid, number average molecular weight: 2 x 10 ⁴ , weight average molecular weight: 7 x 10 ⁴ ]
a3: Product name “Epocross WS-700” manufactured by Nippon Shokubai Co., Ltd. [Aqueous solution of an oxazoline group-containing acrylic polymer having a 2-oxazoline group as a side chain, solid content concentration: 25% by mass, oxazoline value (theoretical value) :220g solid/eq. , oxazoline group weight (theoretical value): 4.5 mmol/g, solid, number average molecular weight: 2 x 10 ⁴ , weight average molecular weight: 4 x 10 ⁴ ]
b1: Product name “Gosenex Z-100” manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd. [acetoacetyl group-modified polyvinyl alcohol, average degree of polymerization: 500, saponification degree: 98.5 mol% or more]
b2: Product name “Gosenex Z-200” manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd. [acetoacetyl group-modified polyvinyl alcohol, average degree of polymerization: 1100, saponification degree: 99.0 mol% or more]
b3: Product name “Gosenex Z-300” manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd. [acetoacetyl group-modified polyvinyl alcohol, average degree of polymerization: 1700, saponification degree: 98.0 to 99.0 mol%]
c1: Product name “CROSSLINKER CL-427” manufactured by MENADIONA [the following compound having three aziridine rings in the molecule]

d1: Product name “Safelink SPM-01” manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd. [Glyoxylate-based crosslinking agent, solid content concentration: 10% by mass]

<Example 38>
(1) Measurement of water contact angle The surface of the (meth)acrylic resin film produced in Production Example 1 above that was bonded to the polarizer was subjected to corona treatment at the discharge amount (W min/m ² ) shown in Table 2. provided. The temperature of the corona-treated surface of the (meth)acrylic resin film was 23°C relative to the temperature of the corona-treated surface of the (meth)acrylic resin film using the data physics contact angle measurement device "OCA35" with a water droplet volume of 8.0μL and the analysis method: θ/2 method. The water contact angle was measured at a humidity of 55%. The results are shown in Table 2.

(2) Preparation of polarizing plate A corona-treated surface of a (meth)acrylic resin film and a saponified triacetyl cellulose (TAC) film [product name “KC2UAW” manufactured by Konica Minolta Opto Co., Ltd.] , thickness: 25 μm] was coated with the adhesive composition prepared in Example 35 above using a bar coater. A (meth)acrylic resin film was laminated on one side of the polarizer prepared in Production Example 2 above, and a saponified TAC film was laminated on the other side so that the adhesive composition layer was on the polarizer side. As a result, a laminate having a layer structure of (meth)acrylic resin film/adhesive composition layer/polarizer/adhesive composition layer/TAC film was obtained. This 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 produce a polarizing plate.

(3) Evaluation of initial adhesion The initial adhesion between the (meth)acrylic resin film and the polarizer in the polarizing plate obtained in (2) above was evaluated according to the following. Initial adhesion refers to the adhesion of a polarizing plate that has not been subjected to the moist heat treatment described below and that has been stored in an environment at a temperature of 23° C. and a relative humidity of 55% after production.

The surface of the (meth)acrylic resin film in the polarizing plate was subjected to corona discharge treatment, and a (meth)acrylic adhesive sheet was laminated to the corona discharge treated surface to obtain a polarizing plate with an adhesive layer. A test piece having a width of 25 mm and a length of approximately 200 mm was cut from the obtained polarizing plate with an adhesive layer, and the adhesive layer surface thereof was bonded to a soda glass substrate.
Next, insert a cutter blade between the (meth)acrylic resin film and the polarizer, peel it off 30 mm from the end in the length direction, and test the peeled part with a universal tensile tester (trade name manufactured by Shimadzu Corporation). I grabbed it with the grip part of "AG-1". The test piece in this state was tested in an atmosphere at a temperature of 23°C and a relative humidity of 55% in accordance with JIS K 6854-2:1999 "Adhesives - Peeling adhesive strength test method - Part 2: 180 degree peeling". A 180 degree peeling test was conducted at a gripping movement speed of 300 mm/min, and the average peeling force over a length of 170 mm excluding 30 mm of the gripping portion was determined, and this was taken as the adhesion force. "Not cuttable" in Table 2 means that the cutter blade did not enter between the (meth)acrylic resin film and the polarizer, indicating that the adhesion was very high.

(4) Evaluation of adhesion after moist heat treatment Adhesion after moist heat treatment between the (meth)acrylic resin film and the polarizer in the polarizing plate obtained in the same manner as in (3) of Example 1 above was measured and evaluated. In Table 2, "*" indicates high adhesion, so when the above peeling test is performed, the (meth)acrylic resin film is removed before peeling occurs at the interface between the (meth)acrylic resin film and the polarizer. Or it means that the polarizer has broken.
Furthermore, based on the obtained adhesion strength measurements, the adhesion between the (meth)acrylic resin film and the polarizer after the moist heat treatment was evaluated in the following three grades. The results are also shown in Table 2.
A: Adhesion force exceeds 5N.
B: Adhesion strength is in the range of 1 to 5N.
C: Adhesion force is less than 1N.

<Example 39 and Example 40>
A polarizing plate was produced in the same manner as in Example 38, except that the discharge amount in the corona treatment was changed as shown in Table 2. Furthermore, the obtained polarizing plate was evaluated for initial adhesion and adhesion after moist heat treatment in the same manner as in Example 38.

10 (meth)acrylic resin film, 15 first adhesive layer, 20 thermoplastic resin film, 25 second adhesive layer, 30 polarizer.

Claims (6)

including a polarizer, a first adhesive layer, and a (meth)acrylic resin film in this order,
The first adhesive layer is a layer formed from an adhesive composition containing an oxazoline group-containing compound and an acetoacetyl group-modified polyvinyl alcohol polymer,
The content of the acetoacetyl group-modified polyvinyl alcohol polymer in the adhesive composition is 5 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the oxazoline group-containing compound,
A polarizing plate in which the first adhesive layer and the (meth)acrylic resin film are in contact with each other. The polarizing plate according to claim 1, comprising a thermoplastic resin film, a second adhesive layer, the polarizer, the first adhesive layer, and the (meth)acrylic resin film in this order. The polarizing plate according to claim 1 or 2, wherein a surface of the (meth)acrylic resin film on the first adhesive layer side has a water contact angle of 80° or less. The polarizing plate according to claim 1, wherein the polarizer and the first adhesive layer are in contact with each other. An adhesive composition for bonding a polarizer and a (meth)acrylic resin film,
Contains an oxazoline group-containing compound and an acetoacetyl group-modified polyvinyl alcohol polymer,
The content of the acetoacetyl group-modified polyvinyl alcohol polymer is 5 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the oxazoline group-containing compound. 6. The adhesive composition of claim 5, further comprising water.

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