WO2017082164A1 - Polarizing plate and inspection method for polarizing plate - Google Patents

Abstract

[Problem] The purpose of the present invention is to provide a thin polarizing plate in which cracks do not easily form in the polarizer. The purpose of the present invention is also to provide a polarizing plate which suppresses the occurrence of appearance defects, such as cracks forming in the polarizer, in an environment that switches back and forth between high temperatures and low temperatures. [Solution] A polarizing plate in which a first adhesive layer, a first protective film comprising a cellulose ester resin, a polarizer having a thickness of 10 μm or less, a second adhesive layer, and a second protective film are layered, the second protective film having a cut in the surface of the second protective film on the opposite side from the second adhesive layer and/or in the surface of the second protective film on the second adhesive layer side, and the cut being a cut with a length of 0.001–500 μm, a width of 0.001–500 μm, and a depth of 0.001–10 μm and/or a cut with a depth of 0.001–10 μm and an area of 0.001–1.0 mm².

Description

Polarizing plate and inspection method of polarizing plate

The present invention relates to a polarizing plate that can be used for various optical applications. The present invention also relates to a method for inspecting a polarizing plate.

In recent years, mobile terminals such as smartphones are rapidly becoming larger and slimmer from the viewpoint of design and portability. In order to achieve long-time driving with a limited thickness, the polarizing plate used is also required to have higher brightness and thinner thickness.

In order to solve such a demand, a polarizing plate is usually proposed in which a protective film made of a transparent resin bonded to both sides of a polarizer is disposed only on one side and a brightness enhancement film is bonded. For example, Patent Document 1 discloses a thin and high-brightness polarizing plate in which a protective film made of a transparent resin, a polarizer in which iodine is adsorbed and oriented on a polyvinyl alcohol film, a pressure-sensitive adhesive layer, and a brightness enhancement film are laminated in this order. It is disclosed.

JP 2010-039458 A

However, as a result of the progress of thinning the polarizer, when the polarizing plate described in the cited document 1 is used in an environment where high and low temperatures are repeated, the polarizer is cracked.
Such cracking of the polarizer may be caused by, for example, biting of foreign matter into the surface of the protective film during the manufacturing process of the polarizing plate, biting of foreign matter when the protective film is laminated, and handling of the polarizing plate. It may be caused by a scratch generated near the part.

With the recent thinning of polarizing plates, cracks in the polarizer are more likely to occur, so a solution is required.

Therefore, an object of the present invention is to provide a thin polarizing plate in which the polarizer is not easily cracked. Furthermore, an object of the present invention is to provide a polarizing plate in which occurrence of defective appearance such as cracking of a polarizer and light leakage is suppressed even when used in an environment where high and low temperatures are repeated.

The present invention includes the following.
[1] Polarized light in which a first pressure-sensitive adhesive layer, a first protective film containing a cellulose ester resin, a polarizer having a thickness of 10 μm or less, a second pressure-sensitive adhesive layer, and a second protective film are laminated. A board,
The second protective film has a scratch on at least one of the surface of the second protective film opposite to the second pressure-sensitive adhesive layer and the surface of the second protective film on the second pressure-sensitive adhesive layer side, The scratch has a length of 0.001 to 500 μm, a width of 0.001 to 500 μm, and a depth of 0.001 to 10 μm, and a depth of 0.001 to 10 μm and an area of 0.001 to 1.0 mm ^2. A polarizing plate that is at least one of the scratches.
[2] As described in [1], the first pressure-sensitive adhesive layer, the first protective film, the polarizer, the second pressure-sensitive adhesive layer, and the second protective film are laminated in this order. Polarizing plate.
[3] The polarizing plate according to [1] or [2], wherein the second protective film has a scratch on a surface of the second protective film opposite to the second pressure-sensitive adhesive layer.
[4] The polarizing plate according to any one of [1] to [3], wherein the second protective film is a brightness enhancement film.
[5] Polarized light in which a first pressure-sensitive adhesive layer, a first protective film containing a cellulose ester resin, a polarizer having a thickness of 10 μm or less, a second pressure-sensitive adhesive layer, and a second protective film are laminated. A method for inspecting a board,
(1) measuring the maximum dimension of the scratch in the second protective film;
(2) The maximum dimension of the scratch in the second protective film is the surface of the second protective film opposite to the second pressure-sensitive adhesive layer and the surface of the second protective film on the second pressure-sensitive adhesive layer side. In at least one of the polarizing plates having a length of 0.001 to 500 μm, a width of 0.001 to 500 μm, and a depth of 0.001 to 10 μm, and / or the maximum size of scratches in the second protective film, At least one of the surface opposite to the second pressure-sensitive adhesive layer in the protective film and the surface on the second pressure-sensitive adhesive layer side of the second protective film has a depth of 0.001 to 10 μm and an area of 0.001 to A step of judging a polarizing plate having a thickness of 1.0 mm ² as a non-defective product,
The inspection method of a polarizing plate including these.

The polarizing plate of the present invention exhibits good polarization characteristics without causing light leakage or cracking of the polarizer even in an environment where high and low temperatures are repeated.

The polarizing plate of the present invention is a thin polarizing plate with excellent strength and durability.

FIG. 1 illustrates a schematic cross-sectional view of a preferred layer structure in the polarizing plate of the present invention.

Hereinafter, the polarizing plate according to the present invention will be described with reference to the drawings as appropriate, but the present invention is not limited to these embodiments.

In the present invention, the polarizing plate is formed by laminating a first pressure-sensitive adhesive layer, a first protective film, a polarizer having a thickness of 10 μm or less, a second pressure-sensitive adhesive layer, and a second protective film, These stacking orders are not particularly limited. In a preferred embodiment, as shown in FIG. 1, the polarizing plate 100 of the present invention includes a first pressure-sensitive adhesive layer 13, a first protective film 12, a polarizer 11, a second pressure-sensitive adhesive layer 23, and a second protective film 22. It may have a configuration in which layers are stacked in order.

The polarizer in the present invention is a member having a thickness of 10 μm or less and a function of converting light such as natural light into linearly polarized light. Preferably, the polarizer has a thickness of 8 μm or less. The polarizer in the present invention usually has a thickness of 2 μm or more.

The second protective film in the present invention has a scratch on the surface on the side opposite to the second pressure-sensitive adhesive layer in the second protective film and / or the surface on the second pressure-sensitive adhesive layer side in the second protective film, A wound having a length of 0.001 to 500 μm, a width of 0.001 to 500 μm and a depth of 0.001 to 10 μm, and a wound having a depth of 0.001 to 10 μm and an area of 0.001 to 1.0 mm ² At least one.
Since the second protective film has scratches of such a size, the polarizing plate of the present invention has good polarization characteristics without causing light leakage or cracking even in an environment where high and low temperatures are repeated. Can show. Although the reason is not certain, the difference between the behavior of the first protective film and the behavior of the polarizer in an environment in which high temperature and low temperature are repeated due to the first protective film containing a cellulose ester resin. Becomes smaller, and the force applied to the polarizer can be reduced. Furthermore, when the second protective film in the polarizing plate has scratches in the above range on the surface, when a thermal shock is applied in an environment where high and low temperatures are repeated, This is thought to be because stress easily escapes. On the other hand, a scratch exceeding the above range may itself cause deterioration in visibility.

Here, the shape of the “scratch” in the present invention is not limited as long as the size of the scratch is included in the above range. For example, linear scratches, polygonal scratches, curved scratches, scratches with multiple scratches (eg, scratches), dents (eg, cylinders, polygonal columns, cones, polygonal pyramids, tapered shapes) It is.

Further, in the “scratch” in the present invention, as long as the size of the scratch is included in the above range, the dimensions such as the depth and the width of the scratch may vary. For example, it may have a depth of 6 μm at a point with a flaw and a depth of 7 μm at another point of the flaw.

For the measurement of the size of such a scratch, a conventional method is used, and examples thereof include measurement with a laser beam and measurement with a microscope.

The dimension of the scratch according to the present invention is the maximum value of the dimension of the largest scratch present in the second protective film.

Moreover, the area of a flaw means the area in the surface parallel to the plane of a 2nd protective film.
That is, the scratch area does not need to consider the depth of the scratch, and it is only necessary to measure the area of the scratch observed on the plane of the second protective film. Further, the area of the flaw can be calculated using a conventional method.

The position where the scratch exists is not particularly limited. For example, scratches may be present randomly throughout the film surface. Preferably, the scratch exists on the surface edge portion of the second protective film.

Preferably, there is a scratch on the surface of the second protective film opposite to the second pressure-sensitive adhesive layer.
In this case, the scratch has, for example, dimensions of 0.001 to 500 μm in length, 0.001 to 500 μm in width, and 0.001 to 10 μm in depth.

Further, it is sufficient that at least one scratch is present on the surface of the second protective film, and the scratch exists at a density of 0.0001 to 0.001 per 1 mm ² . For example, in the case of a 65 mm × 130 mm size polarizing plate, there may be about 0.8 to about 8.5 scratches. If the number of scratches exceeds such a range, the haze value of the polarizing plate becomes high, and the optical properties of the polarizing plate may be insufficient.

In addition, the shape of the scratch formed in the depth direction of the second protective film may be formed in a direction perpendicular to the plane of the second protective film, and the plane of the second protective film. It may be formed in an oblique direction or may be a combination of these.

The method of forming scratches is not particularly limited. For example, the surface of the polarizing plate may be affected by the inclusion of foreign matter into the surface of the protective film during the manufacturing process of the polarizing plate, the inclusion of foreign matter when the protective film is laminated, and the handling of the polarizing plate. It is also possible to use scratches generated near the end. Moreover, you may provide a predetermined | prescribed damage | wound in the surface edge part of a 2nd protective film at the time of manufacture of a polarizing plate, for example. In this case, a scratch may be provided on the surface end of the second protective film using a scratch hardness tester or the like.

As long as the dimensions of the scratch in the present invention are included in the above range, the scratch can be a combination of the dimensions described below.

Preferably, the length of the scratch is 0.001 to 500 μm, more preferably 0.001 to 400 μm. In the case of a wound that is bent, the length of the scratch is indicated by the total length of the scratches.

The width of the scratch is preferably 0.001 to 500 μm, more preferably 0.001 to 400 μm.

The depth of the scratch is 0.001 to 10 μm, more preferably 1 to 10 μm.

For example, in the case of a concave scratch, it has an area of 0.01 to 1.0 mm ² , preferably an area of 0.1 to 0.50 mm ² , more preferably 0.1 to 0.25 mm ² . Has an area.

In a more preferred embodiment, the wound has dimensions of length 0.001 to 500 μm, width 0.001 to 500 μm, and depth 0.001 to 10 μm.

In a more preferred embodiment, the wound is 0.001 to 10 μm deep and has an area of 0.001 to 1.0 mm ² .

[Polarizer]
The polarizer in the present invention generally has a transmission axis and an absorption axis. Such a transmission axis direction of a polarizer is understood as a vibration direction of transmitted light when natural light is transmitted through the polarizer. On the other hand, the absorption axis of the polarizer is orthogonal to the transmission axis of the polarizer. In general, the polarizer can be a stretched film, and the absorption axis direction of the polarizer coincides with the stretched direction.

In the present invention, the term “direction parallel to the transmission axis direction of the polarizer” refers to a direction that is parallel or substantially parallel (the angle formed is within ± 7 degrees) with the transmission axis direction of the polarizer described above. .

The polarizer may be obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin layer.

As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acid, olefin, vinyl ether, unsaturated sulfonic acid, and acrylamide having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more. The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified. For example, the polyvinyl alcohol resin may be an olefin such as ethylene and propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, and crotonic acid. And those modified with alkyl esters of unsaturated carboxylic acids and acrylamide. The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 to 10,000, more preferably 1500 to 8000, and still more preferably 2000 to 5000.

For example, a polarizer is a uniaxially stretched raw film made of polyvinyl alcohol resin, dyed with a dichroic dye (dyeing treatment), treated with an aqueous boric acid solution (boric acid treatment), and washed with water (washed with water). Treatment) and finally dried.

Uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. Good. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in these plural stages. In order to perform uniaxial stretching, the film may be stretched through rolls having different peripheral speeds, or may be stretched by a method of sandwiching between hot rolls. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The final draw ratio of the polyvinyl alcohol-based resin film is usually about 4 to 8 times.

In the dyeing treatment, the polyvinyl alcohol resin film is dyed with a dichroic dye, and the dichroic dye is adsorbed on the film. For the dyeing treatment, for example, a polyvinyl alcohol-based resin film may be immersed in an aqueous solution containing a dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye.

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine content in this aqueous solution is usually about 0.01 to 0.5 parts by weight per 100 parts by weight of water, and the potassium iodide content is usually 0.5 to 10 parts by weight per 100 parts by weight of water. About a part. The temperature of this aqueous solution is usually about 20 to 40 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment is performed, for example, by immersing a dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of water. The immersion time of the film in the boric acid aqueous solution is usually about 100 to 1200 seconds, preferably 150 seconds or more, more preferably 200 seconds or more, and preferably 600 seconds or less, more preferably 400 seconds or less. . The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C. To the boric acid aqueous solution, sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid or the like may be added as a pH adjuster.

The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment.
The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. After washing with water, drying is performed to obtain a polarizer. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying performed thereafter is usually performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100 ° C., and the drying time is usually about 120 to 600 seconds.

[Protective film]
In a preferred embodiment, the first protective film and the polarizer are bonded via an adhesive layer. The thickness of the adhesive layer is, for example, 0.001 μm to 10 μm. As the adhesive layer, those known in the art can be used. By bonding the first protective film and the polarizer through the adhesive layer, light leakage, cracking, and the like of the polarizer can be suppressed even in an environment where high and low temperatures are repeated.

In a preferred embodiment, the first protective film containing the cellulose ester resin protects the dimensional change rate after 1 hour at 85 ° C. and 5% relative humidity in a direction parallel to the transmission axis direction of the polarizer. Dimensional change rate of film (85 ° C)
The dimensional change rate of the protective film after 0.5 hours under the condition of 95% relative humidity at 30 ° C. in the direction parallel to the transmission axis direction of the polarizer was defined as the dimensional change rate of the protective film (30 ° C.). Sometimes, the absolute value of the difference between the dimensional change rate of the protective film (85 ° C.) and the dimensional change rate of the protective film (30 ° C.) is, for example, 0.00 to 0.50.

In the present invention, the dimensional change rate after 1 hour under the condition of 85 ° C. and 5% relative humidity is measured according to the following formula.
For example, in the present invention, the dimensional change rate after 1 hour under the condition of 85 ° C. and 5% relative humidity in the direction parallel to the transmission axis direction of the polarizer is expressed as the dimensional change rate of the protective film (85 ° C).

Dimensional change rate of protective film (85 ° C.) = [(L0−L85) / L0] × 100
[In the formula, L0 means the film size of the cut film in a direction (long direction or width direction) parallel to the transmission axis direction of the polarizer,
L85 means the film dimension in a direction (long direction or width direction) parallel to the transmission axis direction of the polarizer after 1 hour has passed under the condition of 85 ° C. and 5% relative humidity. ]
For example, when the dimension (L0) in the width direction is measured at the time of film cutting, the dimension (L85) in the width direction of the film is measured even after standing for 1 hour at 85 ° C. and 5% relative humidity. Calculate the rate of change. Moreover, after manufacturing a polarizing plate, when measuring the dimension (L0) of the direction parallel to the transmission-axis direction of a polarizer in the protective film obtained by removing a polarizer etc. from a polarizing plate, conditions of 85 degreeC relative humidity 5% Even after standing for 1 hour below, the dimension (L85) in the direction parallel to the transmission axis direction of the polarizer is measured, and the dimensional change rate is calculated.
The dimensional change rate (85 ° C.) calculated in this way may indicate either a positive value (ie, contraction) or a negative value (ie, expansion). The first protective film containing a cellulose ester resin having a positive dimensional change rate (85 ° C.) is made of, for example, a cellulose ester resin selected from cellulose triacetate and cellulose diacetate.

Similarly to the above, in the present invention, the calculation of the dimensional change rate after the elapse of 0.5 hours under the condition of 30 ° C. and relative humidity of 95% is performed on the film after measuring the dimensional change rate (85 ° C.). It is measured according to the following formula.
For example, in the present invention, the dimensional change rate of the protective film after passing 0.5 hours under the condition of 95% relative humidity at 30 ° C. in the direction parallel to the transmission axis direction of the polarizer, (30 ° C.).

Dimensional change rate (30 ° C.) = [(L0 ₃₀ −L30) / L0] × 100
[In the formula, L0 ₃₀ means a film dimension after measuring a dimensional change rate (85 ° C.) in a direction (long direction or width direction) parallel to the transmission axis direction of the polarizer,
L30 means the film dimension in a direction (long direction or width direction) parallel to the transmission axis direction of the polarizer after 0.5 hours have passed under the condition of 30 ° C. and a relative humidity of 95%. ]
For example, after measuring the dimensional change rate (85 ° C.), the sample is allowed to stand at a temperature of 23 ° C. and a humidity of 55% for 15 minutes, and then L ₃₀ can be measured.
The dimensional change rate (30 ° C.) calculated in this way may indicate either a positive value (ie, contraction) or a negative value (ie, expansion).

As long as the absolute value of the difference between the dimensional change rate (85 ° C.) and the dimensional change rate (30 ° C.) is within the scope of the present invention, the protective film in the present invention has a sign of the dimensional change rate (85 ° C.) and the dimensional change rate. The signs of (30 ° C.) may be the same sign (positive, negative or zero), or may be different signs.

In the present invention, preferably, the first protective film has an absolute value of a difference between a dimensional change rate of the first protective film (85 ° C.) and a dimensional change rate of the first protective film (30 ° C.) of 0.00 to 0. .50. More preferably, the absolute value of the difference between the dimensional change rate (85 ° C.) of the first protective film and the dimensional change rate (30 ° C.) of the first protective film is 0.02 to 0.30.

In the polarizing plate of the present invention, the first protective film has an absolute value of the difference in dimensional change rate in such a range, so that cracking and light leakage occurring in the polarizer under high temperature conditions and high humidity conditions can be further suppressed. Furthermore, it can have excellent durability. Furthermore, the polarizing plate having the protective film having such characteristics can make the polarizer thin, and can suppress cracking of the polarizer even when the surface of the protective film is scratched.

The first protective film contains a cellulose ester resin. A 2nd protective film may be a transparent resin film comprised from a thermoplastic resin. Examples of the thermoplastic resin include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins such as polypropylene resins; cellulose resins such as cellulose ester resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins selected from polymethyl methacrylate resins; or a mixture of at least two of these. Moreover, you may use the copolymer of the at least 2 or more types of monomer which comprises the said resin.

Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit, and is described in, for example, JP-A Nos. 1-240517, 3-14882, 3-122137, etc. The resin currently used is mentioned. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymers of chain olefins and cyclic olefins such as ethylene and propylene (typically Random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

Various products are commercially available for cyclic polyolefin resins. Examples of commercial products of cyclic polyolefin resin are “TOPAS” (registered trademark) produced by TOPAS 生産 ADVANCED POLYMERS GmbH and sold in Japan by Polyplastics Co., Ltd., JSR Corporation. "Arton" (registered trademark) sold by Zeon Corporation, "ZEONOR" (registered trademark) and "ZEONEX" (registered trademark) sold by Nippon Zeon Co., Ltd., and "Appel" sold by Mitsui Manabu Co., Ltd. (Registered trademark).

Also, a commercial product of the formed cyclic polyolefin resin film may be used as the protective film. Examples of commercially available products are “Arton Film” sold by JSR Corporation (“Arton” is a registered trademark of the company) and “Essina” sold by Sekisui Chemical Co., Ltd. ( Registered trademark) and “SCA40”, “ZEONOR FILM” (registered trademark) sold by Zeon Corporation.

Cellulose ester resins are usually esters of cellulose and fatty acids. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, those copolymerized with these, and those in which a part of the hydroxyl group is modified with another substituent can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercial products of cellulose triacetate are “Fujitac (registered trademark) TD80”, “Fujitac (registered trademark) TD80UF”, and “Fujitac (registered trademark) TD80UZ” sold by FUJIFILM Corporation. And “Fujitac (registered trademark) TD40UZ”, TAC films “KC8UX2M”, “KC2UA” and “KC4UY” manufactured by Konica Minolta Co., Ltd.

Polymethacrylic acid esters and polyacrylic acid esters (hereinafter, polymethacrylic acid esters and polyacrylic acid esters may be collectively referred to as (meth) acrylic resins) can be easily obtained from the market.

Examples of (meth) acrylic resins include methacrylic acid alkyl esters or homopolymers of acrylic acid alkyl esters, and copolymers of methacrylic acid alkyl esters and acrylic acid alkyl esters. Specific examples of the methacrylic acid alkyl ester include methyl methacrylate, ethyl methacrylate, and propyl methacrylate, and specific examples of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, and propyl acrylate. As such a (meth) acrylic resin, a commercially available (meth) acrylic resin can be used. As the (meth) acrylic resin, a so-called impact resistant (meth) acrylic resin may be used.

(Meth) acrylic resin is usually a polymer mainly composed of methacrylic acid ester. The methacrylic resin may be a homopolymer of one kind of methacrylic acid ester or a copolymer of methacrylic acid ester with other methacrylic acid ester or acrylic acid ester. Examples of the methacrylic acid esters include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate and the like. The alkyl group usually has about 1 to 4 carbon atoms. Also, use cycloalkyl methacrylate such as cyclopentyl methacrylate, cyclohexyl methacrylate, methacrylic acid, aryl methacrylate such as phenyl methacrylate, cycloalkylalkyl methacrylate such as cyclohexylmethyl methacrylate, and aralkyl methacrylate such as benzyl methacrylate. You can also.

Examples of the other polymerizable monomer that can constitute the (meth) acrylic resin include acrylic acid esters and polymerizable monomers other than methacrylic acid esters and acrylic acid esters. As the acrylate ester, alkyl acrylate ester can be used. Specific examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic And alkyl acrylates having 1 to 8 carbon atoms in the alkyl group, such as t-butyl acid, 2-ethylhexyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, and the like. The alkyl group preferably has 1 to 4 carbon atoms. In the (meth) acrylic resin, acrylic ester may be used alone or in combination of two or more.

Examples of polymerizable monomers other than methacrylic acid esters and acrylic acid esters include, for example, monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, and polymerizable carbon-carbon double bonds in the molecule. Can be mentioned, but a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrene monomers such as styrene, α-methylstyrene, vinyl toluene, halogenated styrene, and hydroxystyrene; vinyl cyanide such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid, anhydrous Unsaturated acids such as maleic acid and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide; allyl alcohols such as methacryl alcohol and allyl alcohol; vinyl acetate, vinyl chloride, ethylene, propylene, Including other monomers such as 4-methyl-1-pentene, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, N-vinyl carbazole.

Specific examples of the polyfunctional monomer include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane triacrylate; allyl acrylate, allyl methacrylate, allyl cinnamate Alkenyl esters of unsaturated carboxylic acids such as polyallyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate and triallyl isocyanurate, and aromatic polyalkenyl compounds such as divinylbenzene. As the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester, only one kind may be used alone, or two or more kinds may be used in combination.

A preferred monomer composition of the (meth) acrylic resin is 50 to 100% by weight of methacrylic acid alkyl ester, 0 to 50% by weight of acrylic acid alkyl ester based on the total monomer amount, and 0 to 50% of other polymerizable monomers. 50% by weight, more preferably 50 to 99.9% by weight of methacrylic acid alkyl ester, 0.1 to 50% by weight of acrylic acid alkyl ester, and 0 to 49.9% by weight of other polymerizable monomers. is there.

Also, the (meth) acrylic resin may have a ring structure in the polymer main chain because the durability of the film can be improved. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone ring 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. As the content of the ring structure in the main chain is increased, the glass transition temperature of the (meth) acrylic resin can be increased. The cyclic acid anhydride structure or cyclic imide structure is introduced by copolymerizing monomers having a cyclic structure such as maleic anhydride or maleimide, and the cyclic acid anhydride structure is introduced by dehydration / demethanol condensation reaction after polymerization. It can be introduced by a method, a method of reacting an amino compound and introducing a cyclic imide structure. A resin having a lactone ring structure (polymer) is prepared by preparing a polymer having a hydroxyl group and an ester group in a polymer chain, and then heating the hydroxyl group and the ester group in the obtained polymer by heating. Accordingly, it can be obtained by a method in which a lactone ring structure is formed by cyclocondensation in the presence of a catalyst such as an organic phosphorus compound.

Polymers having a hydroxyl group and an ester group in the polymer chain include, for example, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- It can be obtained by using a (meth) acrylic acid ester having a hydroxyl group and an ester group such as n-butyl (hydroxymethyl) acrylate and t-butyl 2- (hydroxymethyl) acrylate as a part of the monomer. . A more specific method for preparing a polymer having a lactone ring structure is described in, for example, JP-A-2007-254726.

(Meth) acrylic resin can be prepared by radical polymerization of a monomer composition containing the monomer as described above. A monomer composition can contain a solvent and a polymerization initiator as needed.

The (meth) acrylic resin may contain a resin other than the (meth) acrylic resin described above. The content of the other resin is preferably 0 to 70% by weight, more preferably 0 to 50% by weight, and still more preferably 0 to 30% by weight. Examples of the resin include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins; polystyrene, styrene -Styrenic polymers such as methyl methacrylate copolymer and styrene-acrylonitrile copolymer; Polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; Polyarylate composed of aromatic diol and aromatic dicarboxylic acid; Polylactic acid, Biodegradable polyester such as polybutylene succinate; polycarbonate; polyamide such as nylon 6, nylon 66, nylon 610; polyacetal; polyphenylene oxide; polyphenylene sulfide; Ether ketone; polyether nitrile; polysulfone; polyether sulfone; and the like polyamideimide; polyoxyethylene Penji Ren.

(Meth) acrylic resin may contain rubber particles from the viewpoint of improving the impact resistance and film-forming property of the film. The rubber particle may be a particle composed only of a layer exhibiting rubber elasticity, or may be a particle having a multilayer structure having another layer together with a layer exhibiting rubber elasticity. Examples of rubber elastic bodies include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, and acrylic-based elastic polymers. Among these, an acrylic elastic polymer is preferably used from the viewpoint of light resistance and transparency.

The acrylic elastic polymer may be a polymer mainly composed of alkyl acrylate, that is, a polymer containing 50 wt% or more of a structural unit derived from alkyl acrylate based on the total amount of monomers. The acrylic elastic polymer may be a homopolymer of alkyl acrylate, and contains 50 wt% or more of structural units derived from alkyl acrylate and 50 wt% or less of structural units derived from other polymerizable monomers. A copolymer may also be used.

As the alkyl acrylate constituting the acrylic elastic polymer, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of the other polymerizable monomers include, for example, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate; styrene monomers such as styrene and alkyl styrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; A monofunctional monomer, an alkenyl ester of an unsaturated carboxylic acid such as allyl (meth) acrylate and methacrylic (meth) acrylate; a dialkenyl ester of a dibasic acid such as diallyl maleate; an alkylene glycol di (meth) Polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as acrylates.

The rubber particles containing an acrylic elastic polymer are preferably multi-layered particles having an acrylic elastic polymer layer. Specifically, a two-layer structure having a hard polymer layer mainly composed of alkyl methacrylate outside the acrylic elastic polymer layer, or an alkyl methacrylate inside the acrylic elastic polymer layer. And a three-layer structure having a hard polymer layer mainly composed of.

An example of the monomer composition in the polymer mainly composed of alkyl methacrylate constituting the hard polymer layer formed outside or inside the acrylic elastic polymer layer is given as an example of the (meth) acrylic resin. This is the same as the monomer composition example of a polymer mainly composed of alkyl methacrylate, and a monomer composition mainly composed of methyl methacrylate is preferably used.
Such acrylic rubber elastic particles having a multilayer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

From the viewpoint of film-forming properties of (meth) acrylic resin, impact resistance of the film, and slipperiness of the film surface, the rubber particles are included in the rubber elastic layer (acrylic elastic polymer layer) contained therein. The average particle size is preferably in the range of 10 to 350 nm. The average particle diameter is more preferably 30 nm or more, further 50 nm or more, and more preferably 300 nm or less, further 280 nm or less.

The average particle diameter of the rubber particles up to the rubber elastic layer (acrylic elastic polymer layer) is measured as follows. That is, when such rubber particles are mixed with a (meth) acrylic resin to form a film and the cross section thereof is dyed with an aqueous solution of ruthenium oxide, only the rubber elastic body layer is colored and observed in a substantially circular shape. This (meth) acrylic resin is not dyed. Therefore, from the cross section of the film dyed in this way, a thin piece is prepared using a microtome or the like, and this is observed with an electron microscope. And after extracting 100 dye | stained rubber particles at random and calculating each particle diameter (diameter to a rubber elastic body layer), the number average value is made into the said average particle diameter. In order to measure by such a method, the obtained average particle diameter is a number average particle diameter.

When the outermost layer is a hard polymer mainly composed of methyl methacrylate, and rubber particles in which a rubber elastic layer (acrylic elastic polymer layer) is encapsulated, the matrix (meta ) When mixed with an acrylic resin, the outermost layer of rubber particles is mixed with the base (meth) acrylic resin. Therefore, when the cross section is dyed with ruthenium oxide and observed with an electron microscope, the rubber particles are observed as particles in a state excluding the outermost layer. Specifically, when the inner layer is an acrylic elastic polymer and the outer layer is a rubber particle having a two-layer structure, which is a hard polymer mainly composed of methyl methacrylate, the acrylic elastic polymer portion of the inner layer Are dyed and observed as particles having a single layer structure. The innermost layer is a hard polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is a rigid polymer mainly composed of methyl methacrylate. In the case of rubber particles, the central part of the innermost layer is not dyed, and only the acrylic elastic polymer part of the intermediate layer is dyed and observed as a two-layered particle.

From the viewpoint of the film-forming property of the (meth) acrylic resin, the impact resistance of the film, and the slipperiness of the film surface, the rubber particles are combined with the (meth) acrylic resin constituting the (meth) acrylic resin film. Is preferably 3 to 60% by weight, more preferably 45% by weight or less, and still more preferably 35% by weight or less. If the amount of the elastic rubber particles exceeds 60% by weight, the dimensional change of the film becomes large, and the heat resistance is lowered. On the other hand, when the amount of rubber elastic particles is less than 3% by weight, the heat resistance of the film is good, but the winding property during film formation is poor, and the productivity may be lowered. In the present invention, when the rubber elastic particle is a multi-layered particle having another layer together with the rubber elastic layer, the weight of the portion composed of the rubber elastic layer and the inner layer is determined. The weight of the elastic rubber particles. For example, when the acrylic rubber elastic particles having the above three-layer structure are used, the total weight of the acrylic rubber elastic polymer portion of the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate of the innermost layer Is the weight of the rubber elastic particles. When the acrylic rubber elastic particles having the above three-layer structure are dissolved in acetone, the acrylic rubber elastic polymer portion of the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate in the innermost layer are insoluble. Therefore, the total weight ratio of the intermediate layer and the innermost layer in the acrylic rubber elastic particles having a three-layer structure can be easily obtained.

When the (meth) acrylic resin film contains rubber particles, the (meth) acrylic resin composition containing the rubber particles used for producing the film is obtained by melt-kneading the (meth) acrylic resin and the rubber particles. In addition, it can be obtained by a method of first producing rubber particles and polymerizing a monomer composition as a raw material of the (meth) acrylic resin in the presence thereof.

The protective film may contain usual additives such as ultraviolet absorbers, organic dyes, pigments, inorganic dyes, antioxidants, antistatic agents, surfactants and the like. Among these, an ultraviolet absorber is preferably used for improving weather resistance. Examples of ultraviolet absorbers include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (5 -Methyl-2-hydroxyphenyl) -2H-benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di -Tert-butyl-2-hydroxyphenyl) -2H-benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5 -Di-tert-butyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-tert-amyl-2-hydroxypheny ) Benzotriazole UV absorbers such as -2H-benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) -2H-benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy -4-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4 2-hydroxybenzophenone ultraviolet absorbers such as' -dimethoxybenzophenone; salicylic acid phenyl ester ultraviolet absorbers such as p-tert-butylphenylsalicylic acid ester and p-octylphenylsalicylic acid ester; 2,4-diphenyl-6- (2 -Hide Xyl-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- ( 2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6 -(2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) ) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2- (2-hydroxy-4- [1 -Octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine, 4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4- Dibutoxyphenyl) -1,3,5-triazine, 2- [4-[(2-hydroxy-3- (2′-ethyl) hexyloxy] -2-hydroxyphenyl] -4,6-bis (2, 4-dimethylphenyl) -1,3,5-triazine, 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl, -[4,6-bis (2 , 4-Dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- [2,6-di (2,4-xylyl) -1,3,5- Triazin-2-yl] -5-octyloxyphenol, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- [2- (2-ethylhexanoyl) ethoxy] phenol , 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methoxyphenyl) -1,3,5 triazine and other triazine-based UV absorbers, etc. The above may be used.

Commercially available products may be used as the UV absorber. For example, as a triazine UV absorber, “Kemisorb 102” (registered trademark) manufactured by Chemipro Kasei Co., Ltd., “Adekastab (registered trademark)” manufactured by ADEKA Co., Ltd. “LA46”, “Adeka Stub (registered trademark) LAF70”, “TINUVIN (registered trademark) 460”, “TINUVIN (registered trademark) 405”, “TINUVIN (registered trademark) 400” and “TINUVIN (registered trademark) 477 manufactured by BASF Corporation "CYASORB (registered trademark) UV-1164" (all are trade names) manufactured by Sun Chemical Co., Ltd. As the benzotriazole-based ultraviolet absorbers, “ADEKA STAB LA31” and “ADEKA STAB LA36” manufactured by ADEKA Corporation, “Sumisorb (registered trademark) 200”, “Sumisorb (registered trademark) 250”, “Sumisorb (registered trademark) 250” manufactured by Sumika Chemtex Co., Ltd. "Sumisorb (registered trademark) 300", "Sumisorb (registered trademark) 340" and "Sumisorb (registered trademark) 350", "Kemisorb 74" (registered trademark), "Kemisorb 79" (registered trademark) manufactured by Chemipro Kasei Co., Ltd. and “Kemisorb 279” (registered trademark), “TINUVIN (registered trademark) 99-2”, “TINUVIN (registered trademark) 900” and “TINUVIN (registered trademark) 928” (all are trade names) manufactured by BASF, etc. Is mentioned. When the (meth) acrylic resin film contains an ultraviolet absorber, the amount thereof is usually 0.1% by weight or more, preferably 0.3% by weight or more with respect to 100% by weight of the (meth) acrylic resin. And preferably 3% by weight or less.

A conventionally known film forming method can be employed for producing the (meth) acrylic resin film. The (meth) acrylic resin film may have a multilayer structure, and the (meth) acrylic resin film having a multilayer structure is generally known in various ways such as a method using a feed block and a method using a multi-manifold die. Can be used. Among them, for example, a method of laminating via a feed block, multilayer melt extrusion from a T die, and forming a film by contacting at least one surface of the obtained laminated film with a roll or a belt is a film having good surface properties. It is preferable at the point obtained. In particular, from the viewpoint of improving the surface smoothness and surface gloss of the (meth) acrylic resin film, the film is obtained by bringing both sides of the laminated film obtained by the multilayer melt extrusion molding into contact with the roll surface or the belt surface. The method of making is preferable. In the roll or belt used in this case, the surface of the roll or belt in contact with the (meth) acrylic resin is a mirror surface for imparting smoothness to the (meth) acrylic resin film surface. Is preferred.

The (meth) acrylic resin film may be a film produced as described above and subjected to a stretching treatment. A stretching process may be required to obtain a film having desired optical properties and mechanical properties. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction orthogonal to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.

The second protective film may be a protective film having both optical functions such as a retardation film and a brightness enhancement film as long as it is included in the scope of the present invention. For example, a retardation film provided with an arbitrary retardation value by stretching a transparent resin film made of the above material (uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film. It can be.

The first protective film and the second protective film have surface treatment layers (coating layers) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer on the surface opposite to the polarizer. It can also be formed. A well-known method can be used for forming the surface treatment layer on the surface of the protective film.

The first protective film and the second protective film may be the same protective film or different protective films. Examples of cases where the protective film is different include combinations in which the types of thermoplastic resins constituting the protective film are at least different; presence / absence of the optical function of the protective film or combinations different in the type; presence / absence of a surface treatment layer formed on the surface Or there are at least different combinations of the types.

The thickness of the first protective film and the second protective film is preferably thin from the viewpoint of reducing the thickness of the polarizing plate, but if it is too thin, the strength is lowered and the workability is poor. Therefore, the thickness of the first protective film and the second protective film is preferably 5 to 90 μm or less, more preferably 60 μm or less, still more preferably 50 μm or less, and particularly preferably 30 μm or less.

(Adhesive)
As the pressure-sensitive adhesive forming the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer, conventionally known ones may be appropriately selected, and a high-temperature environment, a humid heat environment or an environment where high and low temperatures are repeated are exposed to the polarizing plate. It is sufficient that the adhesive layer has a degree of adhesion that does not cause peeling. Specific examples include acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, and acrylic pressure-sensitive adhesives are particularly preferable in terms of transparency, weather resistance, heat resistance, and processability.
Moreover, the 1st adhesive layer and the 2nd adhesive layer may use the same kind of adhesive, and may use a different kind of adhesive.

For the adhesive, if necessary, a tackifier, plasticizer, glass fiber, glass beads, metal powder, other inorganic powders, fillers, pigments, colorants, fillers, antioxidants, UV absorbers Various additives such as an antistatic agent and a silane coupling agent may be appropriately blended.

The pressure-sensitive adhesive layer is usually formed by applying a pressure-sensitive adhesive solution onto a release sheet and drying. For application onto the release sheet, for example, roll coating methods such as reverse coating and gravure coating, spin coating methods, screen coating methods, fountain coating methods, dipping methods, spraying methods and the like can be employed. The release sheet provided with the pressure-sensitive adhesive layer is used by a method of transferring the release sheet. The thickness of the pressure-sensitive adhesive layer is usually about 3 to 100 μm, preferably 5 to 50 μm.

Preferably, the storage elastic modulus of the pressure-sensitive adhesive layer at 23 ° C. is preferably 0.01 MPa to 1 MPa. When the storage elastic modulus of the pressure-sensitive adhesive layer is less than 0.01 MPa, shrinkage of the polarizing plate during a high temperature test cannot be suppressed, and appearance defects such as peeling tend to occur. On the other hand, when the storage elastic modulus of the pressure-sensitive adhesive layer is greater than 1 MPa, the pressure-sensitive adhesive cannot relieve the strain generated between the glass and the polarizing plate during the thermal shock test, and cracks tend to occur in the polarizing plate.
In a preferred embodiment, the storage elastic modulus of the pressure-sensitive adhesive layer at 80 ° C. is 0.01 MPa to 1 MPa.

[Inspection method of polarizing plate]
The present invention further provides a method for inspecting a polarizing plate. The inspection method of the present invention comprises:
Inspection of a polarizing plate in which a first pressure-sensitive adhesive layer, a first protective film containing a cellulose ester-based resin, a polarizer having a thickness of 10 μm or less, a second pressure-sensitive adhesive layer, and a second protective film are laminated. A method,
(1) measuring the maximum dimension of the scratch in the second protective film;
(2) The maximum dimension of the scratch in the second protective film is the surface of the second protective film opposite to the second pressure-sensitive adhesive layer and the surface of the second protective film on the second pressure-sensitive adhesive layer side. In at least one of the polarizing plates having a length of 0.001 to 500 μm, a width of 0.001 to 500 μm, and a depth of 0.001 to 10 μm, and / or the maximum size of scratches in the second protective film, At least one of the surface opposite to the second pressure-sensitive adhesive layer in the protective film and the surface on the second pressure-sensitive adhesive layer side of the second protective film has a depth of 0.001 to 10 μm and an area of 0.001 to A step of judging a polarizing plate having a thickness of 1.0 mm ² as a non-defective product,
Is a method for inspecting a polarizing plate.

In the inspection method of the present invention, the maximum dimension of the scratch is measured in the step (1).

(1) In the step (1), the maximum dimension of the polarizing plate that may have a scratch is measured using a conventional method, for example, an electron microscope or a laser microscope.

In the subsequent step (2), for the polarizing plate whose maximum dimension was measured in the step (1), the maximum dimension of scratches in the second protective film is the surface opposite to the second pressure-sensitive adhesive layer in the second protective film. And / or a polarizing plate having a length of 0.001 to 500 μm, a width of 0.001 to 500 μm, and a depth of 0.001 to 10 μm on at least one of the surfaces of the second protective film on the second pressure-sensitive adhesive layer side, and / or The maximum dimension of the scratches in the second protective film has a depth of 0. 0 in at least one of the surface of the second protective film opposite to the second pressure-sensitive adhesive layer and the surface of the second protective film on the second pressure-sensitive adhesive layer side. A step of judging a polarizing plate having an area of 001 to 10 μm and an area of 0.001 to 1.0 mm ² as a good product is included.
Here, when the maximum dimension of the scratch | flaw in a 2nd protective film is contained in the said range, such a polarizing plate is judged as a good product. The polarizing plate determined to be non-defective in the inspection method of the present invention can be used without being discarded. In addition, the dimension of a flaw etc. may have the preferable range mentioned above.

The polarizing plate selected as a non-defective product in the step (2) can be used for various optical applications. The polarizing plate selected as a non-defective product in the step (2) may be used as it is, or may be further processed as necessary.

The polarizing plate obtained through such an inspection process can exhibit good polarization characteristics without causing light leakage or cracking even in an environment where high and low temperatures are repeated. Moreover, it can contribute to thickness reduction of a polarizing plate.

According to the inspection method of the polarizing plate according to the present invention, for example, the polarizing plate after panel bonding can also be inspected. When inspecting the polarizing plate after panel pasting, for example, scratches and dents that may occur at the time of panel pasting, after panel pasting, and at the time of pasting the backlight unit are limited as long as they have a predetermined size. It can be included in the wound in the invention.

The present invention can further provide a liquid crystal panel in which the polarizing plate of the present invention is bonded to a liquid crystal cell via an adhesive layer. Moreover, an organic electroluminescent display apparatus can be obtained by bonding a polarizing plate to an organic electroluminescent display through an adhesive layer.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “%” and “part” representing the content or the amount used are based on weight unless otherwise specified.

[Manufacture of polarizers]
A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further kept at 60 ° C. while maintaining the tension state. After being immersed in pure water for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a 7 μm-thick polarizer in which iodine was adsorbed and oriented on a polyvinyl alcohol film.

[First adhesive layer]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on a release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm that had been subjected to the mold release treatment was used. No urethane acrylate oligomer is blended in the acrylic adhesive. The storage elastic modulus of the pressure-sensitive adhesive layer obtained by removing the release film from the pressure-sensitive adhesive sheet was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

[Second adhesive layer]
Mold release treatment of a 38 μm thick polyethylene terephthalate film (release film) obtained by subjecting an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate crosslinking agent to a copolymer of butyl acrylate and acrylic acid. The surface was coated with a die coater so that the thickness after drying was 5 μm and dried to obtain a pressure-sensitive adhesive sheet on which a pressure-sensitive adhesive layer was laminated. The storage elastic modulus of the pressure-sensitive adhesive layer obtained by removing the release film from the pressure-sensitive adhesive sheet was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

[Third pressure-sensitive adhesive layer]
Mold release treatment of a 38 μm thick polyethylene terephthalate film (release film) obtained by subjecting an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate crosslinking agent to a copolymer of butyl acrylate and acrylic acid. The surface was coated with a die coater so that the thickness after drying was 5 μm and dried to obtain an adhesive sheet. The storage elastic modulus of the pressure-sensitive adhesive layer obtained by removing the release film from the pressure-sensitive adhesive sheet was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

[First protective film-1]
Triacetylcellulose film manufactured by Konica Minolta Co., Ltd. (thickness 20 μm, in-plane retardation value at wavelength 590 nm = 1.2 nm, thickness direction retardation value at wavelength 590 nm = 1.3 nm)

[First protective film-2]
A cycloolefin resin film (manufactured by Nippon Zeon Co., Ltd.) having a thickness of 13 μm was used.
In-plane retardation value at wavelength 590 nm (Re (590)) = 0.8 nm, thickness direction retardation value at wavelength 590 nm (Rth (590)) = 3.4 nm, thickness direction retardation at wavelength 483 nm Value (Rth (483)) = 3.5 nm, thickness direction retardation value at wavelength 755 nm (Rth (755)) = 2.8 nm.

[Second protective film]
A brightness enhancement film (made by 3M, trade name Advanced Polarized Film, Version 3) having a thickness of 26 μm was used.

[Preparation of water-based adhesive]
3 parts of carboxyl group-modified polyvinyl alcohol (KL-318 manufactured by Kuraray Co., Ltd.) is dissolved in 100 parts of water, and a polyamide-epoxy additive which is a water-soluble epoxy compound (manufactured by Sumika Chemtex Co., Ltd.) is dissolved in the aqueous solution. Of Sumirez Resin (registered trademark) 650 (30), aqueous solution with a solid content of 30%] was added 1.5 parts to obtain an aqueous adhesive.

[Preparation of Polarizing Plate Precursor A]
A first protective film-1 was laminated on one side of the polarizer via a water-based adhesive. After lamination, the first protective film and the polarizer were bonded by drying at 80 ° C. for 5 minutes. The 2nd adhesive layer laminated | stacked on the peeling film was bonded to the surface on the opposite side to the bonding surface with the 1st protective film in a polarizer. The 1st adhesive layer laminated | stacked on the peeling film was bonded to the surface on the opposite side to the bonding surface with the polarizer in a 1st protective film.
In addition, it bonded so that the transmission axis direction of a polarizer and the width direction of a protective film might become parallel.
Thus, a polarizing plate precursor A-1 in which the first pressure-sensitive adhesive layer, the protective film, the polarizer, and the second pressure-sensitive adhesive layer were laminated in this order was produced.
Similarly, a polarizing plate precursor prepared using the first protective film-2 instead of the first protective film-1 was used as a polarizing plate precursor A-2. A polarizing plate precursor was prepared in the same manner for other protective films.

[Preparation of Polarizing Plate A]
The release film on the second pressure-sensitive adhesive layer in the polarizing plate precursor was peeled off. The second pressure-sensitive adhesive layer and the brightness enhancement film in the polarizing plate precursor A are bonded together, and the first pressure-sensitive adhesive layer, the first protective film, the polarizer, the second pressure-sensitive adhesive layer, and the brightness enhancement film (second protection) A polarizing plate A was obtained, which was laminated in this order. For example, a polarizing plate prepared using the first protective film-1 (polarizing plate precursor A-1) was designated as polarizing plate A1. Similarly, a polarizing plate having such a structure prepared using the first protective film-2 (polarizing plate precursor A-2) was designated as polarizing plate A2.

The produced polarizing plate was cut into 100 mm × 60 mm. The release film on the first pressure-sensitive adhesive layer was peeled off, and a polarizing plate was bonded to alkali-free glass (Corning Corporation, EAGLE XG (registered trademark)) via the first pressure-sensitive adhesive layer. A 5 N load was applied to the surface of the polarizing plate by a scratch hardness meter (Model 318, ball diameter: 0.75 mm, manufactured by Eriksen, Germany) at a location 1.0 mm from the edge of the polarizing plate bonded to this glass, and pressed. I scratched it. That is, the surface of the second protective film opposite to the second pressure-sensitive adhesive layer was scratched. The depth of the pressed wound was 2-5 μm or less and the diameter was 0.3 mm (the area of the wound was about 0.071 mm ² ).

Moreover, the sample which applied the load of 10N and 20N to the surface of the polarizing plate by the scratch-type hardness meter in the place of 1.0 mm from the edge part of another polarizing plate bonded to glass was also produced, respectively. The depth of the pressed wound produced by applying a load of 10 N was 5 to 8 μm and the diameter was 0.4 mm (the area of the wound was about 0.13 mm ² ). The depth of the pressed wound produced by applying a load of 20 N was 11 to 15 μm and the diameter was 0.6 mm (the area of the wound was about 0.28 mm ² ).

A thermal shock environment test (250 cycles) at a temperature of 85 ° C. and −40 ° C. (one cycle for 30 minutes each) was performed on the polarizing plate having a 5N, 10N or 20N load and having a scratch on the surface.

[Thermal shock test]
The thermal shock environment test is performed with a polarizing plate attached to a glass plate using a thermal shock test apparatus (product name “TSA-71L-A-3” sold by Espec Corporation) under high temperature conditions ( 85 ° C.) holding time of 30 minutes and low temperature condition (−40 ° C.) holding time of 30 minutes were performed as one cycle. The temperature transition time was set to 1 minute, and conditions were set so that no external air was introduced and no condensation occurred on the optical member at a temperature transition time of 0 minutes during the temperature transition. This cycle was repeated 250 cycles for the test. The judgment was as follows. The results are shown in Table 1.

[Judgment]
After conducting a thermal shock environment test (number of cycles: 250), the presence or absence of light leakage was visually confirmed. No change was observed before and after the test, and no light leakage occurred under the crossed Nicols after the test.

From this result, it can be seen that the polarizing plate of the present invention has an excellent effect in the thermal shock environment test. That is, according to the present invention, even in an environment where high and low temperatures are repeated, the polarizing plate of the present invention can exhibit good polarization characteristics without causing light leakage or cracks.

According to the present invention, even in an environment where high and low temperatures are repeated, the polarizing plate of the present invention can exhibit good polarization characteristics without causing light leakage or cracks. The polarizing plate of the present invention is a thin polarizing plate that is excellent in strength and durability.

DESCRIPTION OF SYMBOLS 11 Polarizer 12 1st protective film 13 1st adhesive layer 22 2nd protective film 23 2nd adhesive layer 100 Polarizing plate

Claims (5)

1. A polarizing plate in which a first pressure-sensitive adhesive layer, a first protective film containing a cellulose ester resin, a polarizer having a thickness of 10 μm or less, a second pressure-sensitive adhesive layer, and a second protective film are laminated. And
   The second protective film has a scratch on at least one of the surface of the second protective film opposite to the second pressure-sensitive adhesive layer and the surface of the second protective film on the second pressure-sensitive adhesive layer side,
   The scratch has a length of 0.001 to 500 μm, a width of 0.001 to 500 μm, and a depth of 0.001 to 10 μm, and a depth of 0.001 to 10 μm and an area of 0.001 to 1.0 mm ^2. A polarizing plate that is at least one of the scratches.
2. The polarizing plate according to claim 1, wherein the first pressure-sensitive adhesive layer, the first protective film, the polarizer, the second pressure-sensitive adhesive layer, and the second protective film are laminated in this order.
3. The polarizing plate according to claim 1 or 2, wherein the second protective film has a scratch on a surface of the second protective film opposite to the second pressure-sensitive adhesive layer.
4. The polarizing plate according to any one of claims 1 to 3, wherein the second protective film is a brightness enhancement film.
5. Inspection of a polarizing plate in which a first pressure-sensitive adhesive layer, a first protective film containing a cellulose ester-based resin, a polarizer having a thickness of 10 μm or less, a second pressure-sensitive adhesive layer, and a second protective film are laminated. A method,
   (1) measuring the maximum dimension of the scratch in the second protective film;
   (2) The maximum dimension of the scratch in the second protective film is the surface of the second protective film opposite to the second pressure-sensitive adhesive layer and the surface of the second protective film on the second pressure-sensitive adhesive layer side. In at least one of the polarizing plates having a length of 0.001 to 500 μm, a width of 0.001 to 500 μm, and a depth of 0.001 to 10 μm, and / or the maximum size of scratches in the second protective film, At least one of the surface opposite to the second pressure-sensitive adhesive layer in the protective film and the surface on the second pressure-sensitive adhesive layer side of the second protective film has a depth of 0.001 to 10 μm and an area of 0.001 to A step of judging a polarizing plate having a thickness of 1.0 mm ² as a non-defective product,
   The inspection method of a polarizing plate including these.

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