CN109154688B

CN109154688B - Polarizing plate

Info

Publication number: CN109154688B
Application number: CN201780029708.1A
Authority: CN
Inventors: 白石贵志
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2016-05-16
Filing date: 2017-04-07
Publication date: 2021-03-23
Anticipated expiration: 2037-04-07
Also published as: JP2017207557A; TW201741701A; CN109154688A; TWI722177B; WO2017199632A1; KR20190007435A; KR102418731B1; JP6700964B2

Abstract

The invention aims to provide a thin polarizing plate which is difficult to generate cracks of a polarizer. Another object of the present invention is to provide a polarizing plate that can suppress the occurrence of appearance defects such as cracks in a polarizing plate under an environment of repeated high and low temperatures. The polarizing plate of the present invention is a polarizing plate in which a first pressure-sensitive adhesive layer, a polarizing plate having a thickness of 10 [ mu ] m or less, and a first protective film containing a cellulose resin are laminated, wherein the first protective film has a flaw on at least one of a surface of the first protective film on a side opposite to the polarizing plate and a surface of the first protective film on a side of the polarizing plate, and the flaw has a length of 0.001 to 500 [ mu ] m, a width of 0.001 to 500 [ mu ] m, and a depth of 0.001 to 10 [ mu ] m, and an area of 0.001 to 1.0mm²At least one of the scars of (1).

Description

Polarizing plate

Technical Field

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

Background

In recent years, mobile terminals such as smartphones have been rapidly increasing in size and fineness from the viewpoint of design and portability. In order to realize long-term driving with a limited thickness, the polarizing plate used is also required to have high brightness and thin thickness.

In order to solve such a demand, a polarizing plate has been proposed in which a protective film made of a transparent resin and generally bonded to both surfaces of a polarizing plate is disposed only on one side, and a brightness enhancement film is further bonded thereto. For example, patent document 1 discloses a thin and high-brightness polarizing plate in which a protective film made of a transparent resin, an oriented polarizer in which iodine is adsorbed on a polyvinyl alcohol film, a pressure-sensitive adhesive layer, and a brightness enhancement film are sequentially laminated.

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. 2010-039458

Disclosure of Invention

Problems to be solved by the invention

However, as the polarizing plate described in cited document 1 is used under an environment where high and low temperatures are repeated, cracks are generated in the polarizing plate as a result of progress in the thinning of the polarizing plate.

For example, the polarizer may be cracked near the end of the surface of the polarizer due to contamination of foreign substances into the surface of the protective film during the production of the polarizer, contamination of foreign substances during lamination of the protective film, handling of the polarizer, and the like.

As polarizing plates have recently been made thinner, cracks in the polarizing plate are more likely to occur, and therefore, a solution is desired.

Accordingly, an object of the present invention is to provide a thin polarizing plate in which cracks in a polarizer are less likely to occur. Another object of the present invention is to provide a polarizing plate that can suppress appearance defects such as cracks and light leakage in a polarizer even when used in an environment of repeated high and low temperatures.

Means for solving the problems

The present invention includes the following.

[1] A polarizing plate comprising a first pressure-sensitive adhesive layer, a polarizing plate having a thickness of 10 [ mu ] m or less, and a first protective film comprising a cellulose-based resin,

the first protective film has a flaw on at least one of a surface of the first protective film on a side opposite to the polarizing plate and a surface of the first protective film on a side of the polarizing plate,

the flaw 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 1.0mm²At least one of the scars of (1).

[2] The polarizing plate according to [1], wherein the first adhesive layer, the polarizer and the first protective film are sequentially stacked.

[3] The polarizing plate according to [1] or [2], wherein the first protective film has a scratch on a surface of the first protective film on a side opposite to the polarizer.

Effects of the invention

The polarizing plate of the present invention exhibits good polarization characteristics without causing light leakage, cracks, and the like in the polarizing plate even under an environment of repeated high and low temperatures.

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

Drawings

Fig. 1 is a schematic cross-sectional view illustrating a layer structure of a polarizing plate of the present invention.

Detailed Description

Hereinafter, the polarizing plate of 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 adhesive layer, a polarizer having a thickness of 10 μm or less, and a first protective film, and the lamination order is not particularly limited. In one embodiment, as shown in fig. 1, the polarizing plate 100 of the present invention may have a structure in which a first adhesive layer 11, a polarizing plate 12, and a first protective film 13 are sequentially stacked. In the case where the protective film is provided only on one side of the polarizing plate, cracks in the polarizing plate are likely to occur under an environment where high temperature and low temperature are repeated.

The polarizing plate of the present invention has a thickness of 10 μm or less and has a function of converting light such as natural light into linearly polarized light. For example, the polarizing plate has a thickness of 8 μm or less. The polarizing plate of the present invention may have a thickness of 2 μm or more. In one embodiment, the polarizing plate may have a thickness of 2 μm to 8 μm.

Conventionally, as the polarizer is thinner, the influence of cracks on the polarizer due to scratches existing in the polarizing plate tends to be more pronounced. However, the present invention can solve such problems, and the polarizing plate can exhibit excellent optical characteristics without causing cracks even in a thin polarizing plate in the above range.

The first protective film of the present invention has a flaw on at least one of a surface of the first protective film on a side opposite to the polarizing plate and a surface of the first protective film on a polarizing plate side. The flaw 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 1.0mm²At least one of the scars of (1).

By providing the first protective film with such a size of scratches, the polarizing plate of the present invention can exhibit good polarization characteristics without light leakage, cracks, and the like even under an environment of repeated high and low temperatures. The reason is not clear, but it is considered that the difference between the behavior of the first protection film in an environment where high and low temperatures are repeated and the behavior of the polarizing plate is small by providing the first protection film with the above-described flaw, and the force applied to the polarizing plate can be reduced. Further, by providing the first protective film of the polarizing plate with the scratches in the above range on the surface thereof, when thermal shock is applied under an environment of repeated high temperature and low temperature, stress inside the polarizing plate is easily released from the scratches as a starting point.

By including the cellulose resin in the first protective film, the polarizing plate of the present invention can further exhibit good polarization characteristics without light leakage, cracks, or the like. On the other hand, a flaw itself exceeding the above range may cause deterioration of visibility.

In the present invention, the shape of the "scar" is not limited as long as the size of the scar is within the above range. Examples of the scratches include linear scratches, polygonal scratches, curved scratches, scratches in which a plurality of scratches are branched (for example, scratches), and pits (for example, cylinders, polygonal columns, cones, polygonal pyramids, and cones).

In the "flaw" of the present invention, the dimensions such as the depth and width of the flaw may be changed as long as the size of the flaw is within the above range. For example, it may have a depth of 6 μm at one location of the scar and a depth of 7 μm at another location of the scar.

The measurement of the size of such a flaw can be carried out by a conventional method, and examples thereof include measurement with a laser and measurement with a microscope.

The size of the flaw in the present invention is a size obtained by measuring the maximum value of each side of the largest flaw existing in the first protective film. For example, in the present invention, the maximum scar is assumed to be the scar having the largest total value of the length, width, and thickness of the scar.

The area of the flaw is an area in a plane parallel to the plane of the first protection film.

That is, the area of the flaw may be determined by simply measuring the area of the flaw observed on the plane of the first protective film, regardless of the depth of the flaw. The area of the scar can be calculated by a conventional method.

The position where the flaw is present is not particularly limited. For example, scratches may be randomly present throughout the entire surface of the film. For example, a flaw is present at a surface end portion of the first protection film.

For example, the flaw is present on the surface of the first protective film on the side opposite to the polarizing plate. In this case, the flaw has a size of 0.001 to 500 μm in length, 0.001 to 500 μm in width, and 0.001 to 10 μm in depth, for example.

In addition, the number of scratches may be at least 1 on the surface of the first protective film, and may be 1mm per surface²Wherein the density of 0.0001-0.001 exists. For example, in the case of a polarizing plate having a size of 65mm × 130mm, there may be about 0.8 to about 8.5 scratches. If the number of scratches exceeds this range, the haze value of the polarizing plate increases, and the optical properties of the polarizing plate may become insufficient.

The shape of the scratch formed in the depth direction of the first protection film may be a shape formed in the vertical direction with respect to the plane of the first protection film, a shape formed in the oblique direction with respect to the plane of the first protection film, or a combination thereof.

The method of forming the flaw is not particularly limited, and for example, flaws generated in the vicinity of the end of the surface of the polarizing plate due to mixing of foreign substances into the surface of the protective film in the process of manufacturing the polarizing plate, mixing of foreign substances in the process of laminating the protective film, handling of the polarizing plate, and the like may be used. In addition, in the manufacture of the polarizing plate, a predetermined flaw may be provided at the end portion of the surface of the first protective film, for example. In this case, a scratch may be formed on the surface end of the first protection film using a scratch type hardness tester or the like.

The size of the flaw of the present invention may be a combination of the sizes described below, as long as the size is within the above range.

The length of the scar is 0.001 to 500 μm, and in another embodiment, 0.001 to 400 μm. In the case of a bending scar or a curved scar, the length of the scar can be represented by the total length of the scars.

The width of the scar is 0.001 to 500 μm, and in another embodiment, 0.001 to 400 μm.

The depth of the scar is 0.001 to 10 μm, and in another embodiment, the depth of the scar is 1 to 10 μm.

For example, in the case of a concave flaw, the size of the flaw may be calculated from the area of the flaw without measuring the length, width, and the like of the flaw. In this case, the scar has a thickness of 0.01 to 1.0mm²Has an area of, for example, 0.1 to 0.50mm²In another embodiment, the area of (a) is 0.1 to 0.30mm²The area of (a).

In another embodiment, the scar 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.

In another embodiment, the depth of the scar is 0.001 to 10 μm and has a thickness of 0.01 to 1.0mm²The area of (a).

[ polarizing plate ]

Polarizers of the present invention generally have a transmission axis and an absorption axis. The transmission axis direction of such a polarizing plate is understood as a vibration direction of transmitted light when natural light is transmitted through the polarizing plate. On the other hand, the absorption axis of the polarizing plate is orthogonal to the transmission axis of the polarizing plate. The polarizing plate may be a stretched film in general, and the absorption axis direction of the polarizing plate coincides with the stretching direction thereof.

In the present invention, the term "direction parallel to the transmission axis direction of the polarizing plate" means a direction parallel or substantially parallel (forming an angle within ± 7 degrees) to the transmission axis direction of the above-mentioned polarizing plate.

The polarizing plate may be one in which a uniaxially stretched polyvinyl alcohol resin layer is oriented by adsorbing a dichroic dye.

As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and a monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin may be 80 mol% or more. For example, the range is 90 mol% or more, and in another embodiment, the range is 95 mol%. The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified, and examples thereof include polyvinyl alcohol resins modified with an olefin such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; and resins obtained by modifying an alkyl ester of an unsaturated carboxylic acid, acrylamide, and the like. The polyvinyl alcohol resin has an average degree of polymerization of, for example, 100 to 10000, in another embodiment 1500 to 8000, and in another embodiment 2000 to 5000.

The polarizing plate can be produced, for example, by uniaxially stretching a raw material film made of a polyvinyl alcohol resin, dyeing with a dichroic dye (dyeing treatment), treating with an aqueous boric acid solution (boric acid treatment), washing with water (washing treatment), and finally drying.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before the dyeing with the dichroic dye, simultaneously with the dyeing with the dichroic dye, or after the dyeing with the dichroic dye. In the case where uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before boric acid treatment or may be performed during boric acid treatment. It is needless to say that the uniaxial stretching may be performed in these plural stages. When the uniaxial stretching is performed, the stretching may be performed by passing between rolls having different peripheral speeds, or the stretching may be performed by a method of nipping with a hot roll. The stretching may be performed in a dry manner by stretching in the air, or may be performed in a wet manner by stretching in a state of being swollen with a solvent. The final draw ratio of the polyvinyl alcohol 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 film is allowed to adsorb the dichroic dye. The dyeing treatment may be carried out by, for example, immersing the polyvinyl alcohol resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, specifically, iodine or a dichroic dye is used.

When iodine is used as the dichroic dye, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide to dye the film is generally used. The content of iodine in the aqueous solution is usually about 0.01 to 0.5 parts by mass per 100 parts by mass of water, and the content of potassium iodide is usually about 0.5 to 10 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution is usually about 20 to 40 ℃, and the immersion time in the 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 the polyvinyl alcohol resin film in an aqueous solution containing a water-soluble dichroic dye to dye the film is generally used. The content of the dichroic dye in the aqueous solution is usually 1X 10 per 100 parts by mass of water^－3～1×10^－2About the mass portion. The aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of the aqueous solution is usually about 20 to 80 ℃, and the immersion time in the aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment is performed by, for example, immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content of the aqueous boric acid solution is usually about 2 to 15 parts by mass, for example, 5 to 12 parts by mass per 100 parts by mass of water. In the case of using iodine as the dichroic pigment, the aqueous boric acid solution may contain potassium iodide. The content of potassium iodide in the aqueous boric acid solution is usually about 2 to 20 parts by mass, for example 5 to 15 parts by mass, per 100 parts by mass of water. The immersion time of the film in the aqueous boric acid solution is usually about 100 to 1200 seconds, for example, 150 seconds or more, and in another embodiment, 200 seconds or more. On the other hand, the immersion time is, for example, 600 seconds or less, and in another embodiment, 400 seconds or less. The temperature of the aqueous boric acid solution is usually 50 ℃ or higher, for example, 50 to 85 ℃. Sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid, and the like may be added as a pH adjuster to the boric acid aqueous solution.

The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment.

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

[ protective film ]

In one embodiment, the first protective film and the polarizing plate are bonded with an adhesive layer interposed therebetween. The thickness of the adhesive layer is, for example, 0.001 to 10 μm. The adhesive layer may be made of a material known in the art. As the adhesive for forming the adhesive layer, an aqueous adhesive or an active energy ray-curable adhesive can be used. By bonding the first protective film and the polarizing plate with an adhesive layer interposed therebetween, light leakage, cracks, and the like of the polarizing plate can be suppressed even under an environment of repeated high temperature and low temperature.

The thickness of the first protective film is 5 to 90 μm, for example, 60 μm or less, and in another embodiment, 30 μm or less. By having the thickness in such a range, the polarizing plate of the present invention may have excellent mechanical and optical properties.

For example, the first protective film may have a dimensional change rate in a given range in the absorption axis direction and the transmission axis direction of the polarizing plate.

(dimensional Change in absorption axis of polarizing plate)

For example, when the change in dimension of the first protective film after 1 hour under the condition of a relative humidity of 5% at 85 ℃ in a direction parallel to the absorption axis direction of the polarizing plate (also referred to as MD direction) is taken as the change in dimension of the protective film in the MD direction (85 ℃), the change in dimension of the protective film in the MD direction (85 ℃) is preferably 0.06 to 0.25, more preferably 0.06 to 0.20, and still more preferably 0.06 to 0.15.

By having the dimensional change rate in such a range, cracks of the polarizing plate in an environment where high and low temperatures are repeated can be more effectively suppressed.

On the other hand, when the dimensional change rate of the protective film after 0.5 hours under the condition of a relative humidity of 95% at 30 ℃ in the direction (MD direction) parallel to the absorption axis direction of the polarizing plate is taken as the MD dimensional change rate (30 ℃) of the protective film, the MD dimensional change rate (30 ℃) of the protective film is preferably-0.25 to 0.00, and more preferably-0.15 to 0.00. By having the dimensional change rate in such a range, cracks of the polarizing plate in an environment where high and low temperatures are repeated can be more effectively suppressed.

In the present invention, the rate of change in the dimension in the MD direction after 1 hour under the condition of a relative humidity of 5% at 85 ℃ was measured according to the following formula.

Here, for example, in the present invention, the dimensional change rate of the protective film after 1 hour under the condition of a relative humidity of 5% at 85 ℃ in the direction parallel to the absorption axis direction of the polarizing plate may be referred to as the MD direction dimensional change rate (85 ℃).

The MD direction dimension change rate (85 ℃) [ (L0-L85)/L0 ] × 100[ wherein L0 denotes the film dimension of the cut film in the direction (MD direction) (longitudinal direction or width direction) parallel to the absorption axis direction of the polarizing plate,

l85 indicates the film size in the direction (MD direction) (longitudinal direction or width direction) parallel to the absorption axis direction of the polarizing plate after 1 hour under the condition of 85 ℃ relative humidity of 5%. ]

For example, when the MD dimension (L0) was measured at the time of film cutting, the MD dimension (L85) of the film was also measured after standing for 1 hour under the condition of 85 ℃ relative humidity of 5%, and the dimensional change rate was calculated. In addition, when the polarizer and the like were removed from the polarizing plate after the production of the polarizing plate and the dimension (L0) of the obtained protective film in the direction (MD direction) parallel to the absorption axis direction of the polarizer was measured, the protective film was left standing at 85 ℃ under a relative humidity of 5% for 1 hour, and then the dimension (L85) in the direction (MD direction) parallel to the absorption axis direction of the polarizer was also measured to calculate the dimensional change rate.

The dimensional change rate (85 ℃) calculated as described above means shrinkage if it is a positive value, and expansion if it is a negative value.

In one embodiment, the direction (MD direction) of the first protection film parallel to the absorption axis direction of the polarizing plate may be the stretching direction of the first protection film, or may be the longitudinal direction.

In the present invention, the dimensional change rate after 0.5 hours at 30 ℃ and 95% relative humidity was calculated as described above, and the dimensional change rate (85 ℃) of the film was measured according to the following equation.

For example, in the present invention, the MD direction dimension change rate after 0.5 hours under the condition of 30 ℃ relative humidity of 95% in the direction (MD direction) parallel to the absorption axis direction of the polarizing plate of the protective film may be referred to as the MD direction dimension change rate (30 ℃).

MD direction dimension change rate (30 ℃) [ (L0)₃₀－L30)/L0]×100

[ in the formula, L0₃₀The film size is measured after measuring the dimensional change rate (85 ℃) in the direction (MD direction) (longitudinal direction or width direction) parallel to the absorption axis direction of the polarizing plate,

l30 indicates the film size in the direction (MD direction) (longitudinal direction or width direction) parallel to the absorption axis direction of the polarizing plate after 0.5 hour under the condition of 30 ℃ relative humidity of 95%.]For example, the measurement of the dimensional change rate (85 ℃), followed by leaving the sample at 23 ℃ and 55% humidity for 15 minutes and then measuring L0₃₀。

The MD direction dimension change rate (30 ℃) calculated as described above means shrinkage if it is a positive value, and expansion if it is a negative value.

The sign of the dimensional change rate (85 ℃) and the sign of the dimensional change rate (30 ℃) of the protective film of the present invention may be the same sign (positive, negative, or zero) or may be different signs. In one embodiment, the sign of the size change rate (85 ℃ C.) and the sign of the size change rate (30 ℃ C.) are different signs.

The polarizing plate of the present invention can further suppress cracks and light leakage occurring in the polarizer under high temperature and high humidity conditions because the first protective film has a dimensional change rate in such a range, and can have more excellent durability. In addition, the polarizing plate having the protective film having such characteristics can reduce the thickness of the polarizer and can suppress cracks in the polarizer even when physical changes such as depressions are generated in the surface of the protective film.

(rate of change in dimension in the direction perpendicular to the absorption axis of the polarizing plate)

For example, when the dimension change rate of the first protective film after 1 hour under the condition of 5% relative humidity at 85 ℃ in the direction perpendicular to the absorption axis direction of the polarizing plate, that is, in the direction parallel to the transmission axis direction of the polarizing plate (also referred to as TD direction), is set as the TD dimension change rate (85 ℃) of the protective film, the TD dimension change rate (85 ℃) of the protective film is preferably 0.05 to 0.25, and more preferably 0.05 to 0.20. By having the dimensional change rate in such a range, cracks of the polarizing plate in an environment where high and low temperatures are repeated can be more effectively suppressed.

On the other hand, when the dimensional change rate of the protective film after 0.5 hours under the condition of a relative humidity of 95% at 30 ℃ in the direction (TD direction) parallel to the transmission axis direction of the polarizing plate is taken as the dimensional change rate of the protective film in the TD direction (30 ℃), the dimensional change rate of the protective film in the TD direction (30 ℃) is preferably-0.25 to 0.00, more preferably-0.20 to 0.00. By having the dimensional change rate in such a range, cracks of the polarizing plate in an environment where high and low temperatures are repeated can be more effectively suppressed.

For example, the absolute value of the difference between the TD direction dimension change rate (85 ℃) of the protective film and the TD direction dimension change rate (30 ℃) of the protective film is, for example, preferably 0.20 to 0.50, and more preferably 0.03 to 0.30. By having the absolute value of the difference in the dimensional change rate in such a range, cracks of the polarizing plate in an environment where high and low temperatures are repeated can be more effectively suppressed.

The polarizing plate of the present invention has the absolute value of the difference between the dimensional change rate and the dimensional change rate in the above range, and thus can further suppress cracks and light leakage occurring in the polarizer under high-temperature and high-humidity conditions, and can have more excellent durability. In addition, the polarizing plate having the protective film having such characteristics can reduce the thickness of the polarizer and can suppress cracks in the polarizer even when physical changes such as depressions are generated in the surface of the protective film.

The first protective film is a film containing a cellulose resin. In one embodiment, the first protective film is a film containing a cellulose-based resin as a main component, as described later. The first protective film may be a single-layer film mainly composed of a resin such as a cellulose-based resin, or may be a multilayer film having a layer mainly composed of a resin such as a cellulose-based resin.

Here, the term "main component" refers to a resin component contained in the first protective film in an amount of more than 50 parts by mass, 80 parts by mass or more in another embodiment, or 90 parts by mass or more in another embodiment, with respect to 100 parts by mass of the resin component in the first protective film.

Both or one side of these single-layer films or multilayer films may be subjected to surface treatment.

The surface treatment may be surface modification by corona treatment, saponification treatment, heat treatment, ultraviolet irradiation, electron beam irradiation, or the like. Further, the film may be formed by coating or vapor deposition of a polymer, a metal, or the like.

For example, the first protective film may be formed with a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. As a method for forming a surface treatment layer on the surface of the protective film, a known method can be used. For example, the first protective film may have a hard coat layer on a surface on the opposite side to the polarizing plate. For example, by providing the first protective film with a hard coat layer, scratch or the like can be prevented from occurring on the surface of the polarizing plate. In the present invention, the polarizing plate is not affected as long as the size of the scratch or the like is within the range of the present invention. However, generally, scratch often spreads over a wide range, and it is preferable to suppress the generation of scratch and the like.

In one embodiment, the hard coat layer of the first protective film provided on the surface opposite to the polarizing plate has a thickness of 1 to 10 μm. For example, the thickness of the hard coating layer is smaller than the thickness of the first protective film.

In another mode, a ratio of the thickness of the hard coat layer to the thickness of the first protective film is 0.9: 1-0.01: 1, in the above range.

If the ratio of the thickness of the hard coat layer to the thickness of the first protective film is in the above range, the stress such as shrinkage generated in the polarizer in an environment where high-temperature conditions and low-temperature conditions are repeated (for example, in a cold and heat shock environment) is suppressed by the protective film, and cracks are less likely to be generated in the polarizer, and thus the polarizer having further excellent durability is obtained.

When the first protective film has a surface-treated layer such as a hard coat layer, the first protective film may have a flaw 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 an area of 0.001 to 1.0mm, for example, on the surface of the surface-treated layer of the first protective film disposed on the side opposite to the polarizing plate, for example, on the visible side surface of the surface-treated layer²At least one of the scars of (1).

When the first protective film has a surface treatment layer such as a hard coat layer, a commercially available protective film subjected to hard coat treatment may be used. In this case, the flaw according to the present invention may be provided on the surface treatment layer, and for example, the flaw may be provided on the visible-side surface of the surface treatment layer.

The first protective film may be a transparent resin film made of a thermoplastic resin containing a cellulose-based resin. The cellulose resin is, for example, a cellulose ester resin such as cellulose triacetate, cellulose diacetate, cellulose tripropionate, or cellulose dipropionate.

The first protective film may contain, in addition to the cellulose-based resin, another thermoplastic resin, for example, a polyolefin-based resin selected from a chain polyolefin-based resin and a cyclic polyolefin-based resin exemplified by a polypropylene-based resin; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins among polymethyl methacrylate resins; or a mixture of at least two of them, and the like. In addition, a copolymer of at least two or more monomers constituting the resin may be used. In one embodiment, the percentage of the cellulose-based resin in the entire protective film is, for example, 50 mass% or more, in another embodiment 70 mass% or more, and in another embodiment 90 mass% or more, when the entire protective film is 100 mass%.

The cellulose ester resin is usually an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, a resin obtained by copolymerizing these, or a resin obtained by modifying a part of the hydroxyl groups with another substituent may be used. Among them, for example, cellulose triacetate (triacetyl cellulose: TAC) can be selected. Many cellulose triacetate products are commercially available, and this is advantageous in terms of ease of acquisition and cost. Examples of commercially available cellulose triacetate are shown by trade names, and include "FUJITAC (registered trademark) TD 80", "FUJITAC (registered trademark) TD80 UF", "FUJITAC (registered trademark) TD80 UZ", and "FUJITAC (registered trademark) TD40 UZ", and TAC films "KC 8UX 2M", "KC 2 UA", and "KC 4 UY" manufactured by Konica Minolta co.

For example, the first protective film containing a cellulose-based resin may be a film obtained by subjecting the produced film to a stretching treatment. In order to obtain a film having desired optical properties and mechanical properties, stretching treatment is sometimes required. 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 (TD) orthogonal thereto, and a direction oblique to the machine flow direction (MD). The 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 given direction and then stretching is performed in the other direction.

The cyclic polyolefin resin is generally a general term for resins polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include resins described in Japanese patent application laid-open Nos. 1-240517, 3-14882, and 3-122137. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of linear olefins such as ethylene and propylene with cyclic olefins (a random copolymer is a typical example), graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrogenated products thereof. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

Various cyclic polyolefin resins are commercially available. Examples of commercially available products of cyclic polyolefin resins are all shown by trade names, including "TOPAS" (registered trademark) manufactured by TOPAS ADVANCED POLYMERS GmbH, sold by Poly Plastics corporation in japan, "Arton" (registered trademark) sold by JSR corporation, "Zeonor" (registered trademark) and "Zeonex" (registered trademark) sold by japan ZEON corporation, and "Apel" (registered trademark) sold by mitsui corporation.

Further, a commercially available product of the produced cyclic polyolefin resin film may be used as the protective film. Examples of commercially available products are all indicated by trade names, and include "Arton Film" sold by JSR corporation ("Arton" is a registered trademark of JSR corporation), "Escena" (registered trademark) and "SCA 40" sold by waterlogging chemical industry co.

Polymethacrylates and polyacrylates (hereinafter, polymethacrylates and polyacrylates are sometimes referred to collectively as (meth) acrylic resins) are readily available from the market.

Examples of the (meth) acrylic resin include homopolymers of alkyl methacrylate or alkyl acrylate, and copolymers of alkyl methacrylate and alkyl acrylate. Specific examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, and propyl methacrylate, and specific examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, and propyl acrylate. As the (meth) acrylic resin, a commercially available (meth) acrylic resin can be used. As the (meth) acrylic resin, a resin called an impact-resistant (meth) acrylic resin can be used.

The (meth) acrylic resin is generally a polymer mainly composed of a 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 another methacrylic acid ester or acrylic acid ester. Examples of the methacrylic acid ester include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate and butyl methacrylate, and the number of carbon atoms in the alkyl group is usually about 1 to 4. In addition, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloalkyl methacrylate such as methacrylate (メタクリル), aryl methacrylate such as phenyl methacrylate, cycloalkyl methacrylate such as cyclohexylmethyl methacrylate, and aralkyl methacrylate such as benzyl methacrylate may also be used.

Examples of the other polymerizable monomers that can constitute the (meth) acrylic resin include acrylic acid esters, methacrylic acid esters, and polymerizable monomers other than acrylic acid esters. As the acrylic ester, an alkyl acrylate may be used, and specific examples thereof include alkyl acrylates having an alkyl group of 1 to 8 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate. The number of carbon atoms of the alkyl group is, for example, 1 to 4. In the (meth) acrylic resin, only one kind of the acrylate may be used alone, or two or more kinds may be used in combination.

Examples of the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester include a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule and a polyfunctional monomer having at least two polymerizable carbon-carbon double bonds in the molecule, and a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrene monomers such as styrene, α -methylstyrene, vinyltoluene, halogenated styrene, and hydroxystyrene; vinyl cyanides such as acrylonitrile and methacrylonitrile; unsaturated acids such as acrylic acid, methacrylic acid, maleic anhydride, and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide; allyl alcohols such as methallyl alcohol and allyl alcohol; vinyl acetate, vinyl chloride, ethylene, propylene, 4-methyl-1-pentene, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, N-vinyl carbazole and other monomers.

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

In a preferred monomer composition of the (meth) acrylic resin, based on the total monomer amount, the alkyl methacrylate is 50 to 100 mass%, the alkyl acrylate is 0 to 50 mass%, and the other polymerizable monomers are 0 to 50 mass%, and in another embodiment, the alkyl methacrylate is 50 to 99.9 mass%, the alkyl acrylate is 0.1 to 50 mass%, and the other polymerizable monomers are 0 to 49.9 mass%.

In addition, the (meth) acrylic resin may have a ring structure in the main chain of the polymer in order to improve the durability of the film. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone ring structure. Specifically, a cyclic acid anhydride structure such as a glutaric anhydride structure or a succinic anhydride structure, a cyclic imide structure such as a glutarimide structure or a succinimide structure, and a lactone ring structure such as butyrolactone or valerolactone may be mentioned. 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. The cyclic acid anhydride structure and the cyclic imide structure can be introduced by a method of introducing a monomer having a cyclic structure such as maleic anhydride or maleimide by copolymerization, a method of introducing a cyclic acid anhydride structure by dehydration/demethanization condensation reaction after polymerization, a method of introducing a cyclic imide structure by reacting an amino compound, or the like. The resin (polymer) having a lactone ring structure can be obtained by preparing a polymer having a hydroxyl group and an ester group in a polymer chain, and then cyclizing and condensing the hydroxyl group and the ester group in the obtained polymer by heating in the presence of a catalyst such as an organic phosphorus compound if necessary to form a lactone ring structure.

The polymer having a hydroxyl group and an ester group in the polymer chain can be obtained by using, as a part of the monomers, (meth) acrylic acid esters having a hydroxyl group and an ester group, such as methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, n-butyl 2- (hydroxymethyl) acrylate, and tert-butyl 2- (hydroxymethyl) acrylate. A more specific method for producing a polymer having a lactone ring structure is described in, for example, Japanese patent laid-open No. 2007-254726.

The (meth) acrylic resin can be prepared by radical-polymerizing a monomer composition containing the monomer as described above. The monomer composition may contain a solvent or a polymerization initiator as necessary.

The (meth) acrylic resin may contain other resins than the above-mentioned (meth) acrylic resin. The content of the other resin is, for example, 0 to 70% by mass, in another embodiment 0 to 50% by mass, and in still another embodiment 0 to 30% by mass. The resin may be, for example, an olefin polymer such as polyethylene, polypropylene, an ethylene-propylene copolymer, or poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and vinyl chloride resins; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, and styrene-acrylonitrile copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyarylates formed from aromatic diols and aromatic dicarboxylic acids; biodegradable polyesters such as polylactic acid and polybutylene succinate; a polycarbonate; polyamides such as nylon 6, nylon 66, and nylon 610; a polyacetal; polyphenylene ether; polyphenylene sulfide; polyether ether ketone; polyether nitrile; polysulfones; polyether sulfone; polyoxybenzyl ester (ポリオキシペンジレン); polyamideimide, and the like.

The (meth) acrylic resin may contain rubber particles from the viewpoint of improving the impact resistance and film formability of the film. The rubber particles may be particles formed only of the layer exhibiting rubber elasticity, or may be particles having a multilayer structure having another layer together with the layer exhibiting rubber elasticity. Examples of the rubber elastomer include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, acrylic elastic polymers, and the like. Among them, acrylic elastic polymers are preferably used from the viewpoint of light resistance and transparency.

The acrylic elastic polymer may be a polymer mainly composed of an alkyl acrylate, that is, a polymer containing 50 mass% or more of a constituent unit derived from an alkyl acrylate based on the total monomer amount. The acrylic elastic polymer may be a homopolymer of an alkyl acrylate, or may be a copolymer containing 50 mass% or more of a constituent unit derived from an alkyl acrylate and 50 mass% or less of a constituent unit derived from another polymerizable monomer.

As the alkyl acrylate constituting the acrylic elastic polymer, a compound having 4 to 8 carbon atoms in the alkyl group is generally used. Examples of the other polymerizable monomers include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate; styrene monomers such as styrene and alkylstyrene; monofunctional monomers such as unsaturated nitriles including acrylonitrile and methacrylonitrile, and alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate; dienyl esters of dibasic acids such as diallyl maleate; and a polyfunctional monomer such as an unsaturated carboxylic diester of a diol such as an alkylene glycol di (meth) acrylate.

The rubber particles containing an acrylic elastic polymer are preferably particles having a multilayer structure having a layer of an acrylic elastic polymer. Specifically, there may be mentioned particles having a 2-layer structure comprising a hard polymer layer mainly composed of an alkyl methacrylate on the outer side of the layer of the acrylic elastic polymer, and particles having a 3-layer structure comprising a hard polymer layer mainly composed of an alkyl methacrylate on the inner side of the layer of the acrylic elastic polymer.

Examples of the monomer composition of the alkyl methacrylate-based polymer constituting the hard polymer layer formed on the outer side or the inner side of the acrylic elastic polymer layer are the same as the monomer composition of the alkyl methacrylate-based polymer exemplified as the (meth) acrylic resin, and particularly, the monomer composition mainly containing methyl methacrylate is preferably used.

Such acrylic rubber elastomer particles having a multilayer structure can be produced by the method described in Japanese patent application laid-open No. 55-27576.

From the viewpoint of film-forming properties of the (meth) acrylic resin, impact resistance of the film, and lubricity of the film surface, it is preferable that the average particle diameter of the rubber elastic layer (acrylic elastic polymer layer) contained in the rubber particles is in the range of 10 to 350 nm. The average particle diameter is, for example, 30nm or more, and in another embodiment 50nm or more. On the other hand, the particle size is, for example, 300nm or less, and in another embodiment 280nm or less.

The average particle diameter of the rubber particles up to the rubber elastic layer (acrylic elastic polymer layer) was measured as follows. That is, when such rubber particles are mixed with a (meth) acrylic resin and formed into a film, and the cross section thereof is dyed with an aqueous solution of ruthenium oxide, only the rubber elastomer layer is observed to be colored and to be substantially circular, and the (meth) acrylic resin of the matrix layer is not dyed. Thus, a thin section is prepared from the thus dyed film section using a microtome or the like, and the thin section is observed with an electron microscope. Thereafter, 100 dyed rubber particles were randomly extracted, and the particle diameters (up to the diameter of the rubber elastic body layer) were calculated, and the arithmetic average value thereof was defined as the average particle diameter. Since the measurement is performed by this method, the average particle diameter obtained is an arithmetic average particle diameter.

In the case where the rubber particles are composed of a hard polymer mainly composed of methyl methacrylate as the outermost layer and a rubber elastic layer (a layer of an acrylic elastic polymer) is enclosed therein, if they are mixed with a (meth) acrylic resin as a matrix, the outermost layer of the rubber particles is mixed with the (meth) acrylic resin as a matrix. Therefore, when the cross section is stained with ruthenium oxide and observed with an electron microscope, the rubber particles can be observed as particles with the outermost layer removed. Specifically, in the case of rubber particles having a 2-layer structure in which the inner layer is an acrylic elastic polymer and the outer layer is a hard polymer mainly composed of methyl methacrylate, the acrylic elastic polymer portion of the inner layer is dyed and observed as particles having a single-layer structure. In addition, in the case of rubber particles having a 3-layer structure in which 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 hard polymer mainly composed of methyl methacrylate, the rubber particles are observed as particles having a 2-layer structure in which the particle center portion of the innermost layer is not dyed, and only the acrylic elastic polymer portion of the intermediate layer is dyed.

From the viewpoint of film-forming properties of the (meth) acrylic resin, impact resistance of the film, and lubricity of the film surface, the rubber particles may be blended in a proportion of, for example, 3 mass% or more and 60 mass% or less, in another embodiment 45 mass% or less, and in another embodiment 35 mass% or less, based on the total amount of the (meth) acrylic resin constituting the (meth) acrylic resin film. If the rubber elastomer particles are more than 60 mass%, the dimensional change of the film becomes large and the heat resistance is lowered. On the other hand, if the rubber elastomer particles are less than 3 mass%, 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 particles having a multilayer structure having a layer exhibiting rubber elasticity and another layer are used as the rubber elastomer particles, the mass of a portion composed of the layer exhibiting rubber elasticity and the layer inside the layer is used as the mass of the rubber elastomer particles. For example, in the case of using the acrylic rubber elastomer particles having the 3-layer structure described above, the total mass of the acrylic rubber elastic polymer portion in the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate in the innermost layer is defined as the mass of the rubber elastomer particles. When the acrylic rubber elastomer particles having a 3-layer structure are dissolved in acetone, the acrylic rubber elastic polymer portion in the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate in the innermost layer remain as insoluble components, and therefore the mass ratio of the total of the intermediate layer and the innermost layer to the acrylic rubber elastomer particles having a 3-layer structure can be easily determined.

When the (meth) acrylic resin film contains rubber particles, the (meth) acrylic resin composition containing rubber particles used for producing the film can be obtained by mixing the (meth) acrylic resin and the rubber particles by melt kneading or the like, or can be obtained by a method of preparing rubber particles first and polymerizing a monomer composition which is a raw material of the (meth) acrylic resin in the presence of the rubber particles.

In the production of the (meth) acrylic resin film, a conventionally known film-forming method can be used. The (meth) acrylic resin film may have a multilayer structure, and various generally known methods may be used for the multilayer structure of the (meth) acrylic resin film, such as a method using a feed block (フィードブロック), a method using a multi-manifold die, and the like. Among them, from the viewpoint of obtaining a film having good surface properties, for example, a method of laminating the films with a feed block interposed therebetween, performing multilayer melt extrusion molding from a T-die, and bringing at least one surface of the obtained laminated film into contact with a roll or a belt to form a film is preferable. In particular, from the viewpoint of improving the surface smoothness and surface gloss of the (meth) acrylic resin film, a method of bringing both surfaces of the multilayer melt-extrusion-molded multilayer film into contact with a roll surface or a belt surface to form a film is preferable. Of the rollers or belts used in this case, the surface of the roller or belt in contact with the (meth) acrylic resin is preferably a mirror surface in order to impart smoothness to the surface of the (meth) acrylic resin film.

The protective film may contain a conventional additive, for example, an ultraviolet absorber, an organic dye, a pigment, an inorganic pigment, an antioxidant, an antistatic agent, a surfactant, and the like. Among them, ultraviolet absorbers are often used in order to improve weather resistance.

The polarizing plate may have a layer formed of a cured product of a curable resin composition on a surface opposite to a surface to which the first protective film is attached. The curable resin composition is not particularly limited, but examples thereof include solvent-soluble resin compositions, water-dispersible resin compositions, solvent-free resin compositions, and the like. Examples of the method for curing the curable resin composition include a thermosetting type and an active energy ray curing type. When the polarizing plate has a layer formed of a cured product of the curable resin composition, cracks of the polarizing plate in an environment where high and low temperatures are repeated can be more effectively suppressed.

In one embodiment, the polarizing plate of the present invention may have a layer formed of a cured product of a curable resin composition between the polarizer and the first adhesive layer.

The thickness of the layer formed from the cured product of the curable resin composition is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

(adhesive layer)

As the adhesive for forming the first adhesive layer, any adhesive may be appropriately selected as long as it has adhesiveness to such an extent that peeling or the like does not occur in a high-temperature environment, a moist-heat environment, or an environment where high and low temperatures are repeated, to which the polarizing plate is exposed. Specifically, an acrylic adhesive, a silicone adhesive, a rubber adhesive, and the like are mentioned, and from the viewpoint of transparency, weather resistance, heat resistance, and processability, for example, an acrylic adhesive can be used.

The pressure-sensitive adhesive may contain various additives such as a tackifier, a plasticizer, glass fibers, glass beads, a metal powder, a filler made of other inorganic powder, a pigment, a colorant, a filler, an antioxidant, an ultraviolet absorber, an antistatic agent, and a silane coupling agent, as required.

The adhesive layer is generally formed by applying a solution of the adhesive to a release sheet and drying. The coating on the release sheet may be performed by, for example, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a spray coating method, a dipping method, a spraying method, or the like. The release sheet provided with the adhesive layer is used by a method of transferring the release sheet. The thickness of the adhesive layer is usually about 3 to 100 μm, for example, 5 to 50 μm.

For example, the storage modulus of the pressure-sensitive adhesive layer at 23 ℃ is 0.01MPa to 1 MPa. If the storage modulus of the pressure-sensitive adhesive layer is less than 0.01MPa, shrinkage of the polarizing plate in a high-temperature test cannot be suppressed, and appearance defects such as peeling tend to be easily caused. In addition, if the storage modulus of the adhesive layer is greater than 1MPa, the adhesive cannot relieve the strain generated between the glass and the polarizing plate in the cold-heat impact test, and cracks tend to be easily generated in the polarizing plate.

In one embodiment, the adhesive layer has a storage modulus at 80 ℃ of 0.01MPa to 1 MPa.

A liquid crystal panel in which the polarizing plate of the present invention is bonded to a liquid crystal cell with a first pressure-sensitive adhesive layer interposed therebetween can be obtained. In addition, an organic electroluminescent display device can be obtained by bonding a polarizing plate to an organic electroluminescent display with a first pressure-sensitive adhesive layer interposed therebetween. The polarizing plate of the present invention is preferably bonded to the visible side of the liquid crystal cell.

[ examples ]

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. In the examples,% and parts indicating the content or amount used are based on mass unless otherwise specified.

[ production of polarizing plate ]

A polyvinyl alcohol film (average degree of polymerization: about 2,400, degree of saponification: 99.9 mol% or more) having a thickness of 20 μm was uniaxially stretched by dry stretching by about 5 times while keeping the film under tension, immersed in pure water at 60 ℃ for 1 minute, and then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.05/5/100 at 28 ℃ for 60 seconds. Thereafter, the plate was immersed in an aqueous solution having a potassium iodide/boric acid/water mass ratio of 8.5/8.5/100 at 72 ℃ for 300 seconds. Subsequently, the substrate was washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃ to obtain a polarizing plate having a thickness of 7 μm, in which iodine was adsorbed and oriented on a polyvinyl alcohol film.

[ first adhesive layer ]

A commercially available pressure-sensitive adhesive sheet was used in which an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on the release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm and subjected to release treatment. The urethane acrylate oligomer is not blended in the acrylic adhesive. The storage modulus of the adhesive layer from which the release film was removed from the adhesive sheet was 0.05MPa at 23 ℃ and 0.04MPa at 80 ℃.

[ first protective film-1 ]

A triacetyl cellulose film (thickness: 20 μm) manufactured by Konica Minolta K.K. was prepared.

[ first protective film-2 ]

A triacetyl cellulose film (25 KCHC-TC, 32 μm thick, manufactured by TOPPAN TOMOEGAWA OPTICAL FILMS) having a hard coat layer (7 μm thick) on the surface thereof was prepared.

[ first protective film-3 ]

A cycloolefin resin film (manufactured by ZEON K.K.) having a thickness of 13 μm was prepared.

[ first protective film-4 ]

A cycloolefin resin film (manufactured by ZEON Co., Ltd.) having a thickness of 23 μm was prepared.

(measurement of the dimensional Change Rate)

The MD dimension change rate (85 ℃) of the protective film was measured according to the following equation.

The MD direction dimension change rate (85 ℃) [ (L0-L85)/L0 ] × 100[ wherein L0 denotes the film dimension of the cut film in the direction parallel to the absorption axis direction of the polarizing plate (MD direction, longitudinal direction of the protective film),

l85 indicates the film size in the direction (MD direction, longitudinal direction of the protective film) parallel to the absorption axis direction of the polarizing plate after 1 hour under the condition of 85 ℃ relative humidity of 5%. ]

The MD dimensional change rate (30 ℃) of the protective film was measured according to the following equation.

MD direction dimension change rate (30 ℃) [ (L0)₃₀－L30)/L0]×100

[ in the formula, L0₃₀The film size is measured after measuring the dimensional change rate (85 ℃) in the direction parallel to the absorption axis direction of the polarizing plate (MD direction, length direction of the protective film),

l30 indicates the film size in the direction (MD direction, longitudinal direction of the protective film) parallel to the absorption axis direction of the polarizing plate after 0.5 hour under the condition of 30 ℃ relative humidity of 95%.]After measuring the dimensional change rate (85 ℃ C.), the sample was left at 23 ℃ and 55% humidity for 15 minutes, and then L0 was measured₃₀。

The TD-direction dimensional change rate (85 ℃ C.) of the protective film was measured in the same manner. In the examples and comparative examples, the dimensional change rate (85 ℃) of the protective film in the width direction (direction parallel to the transmission axis direction of the polarizing plate) was measured. In addition, the TD dimensional change rate (30 ℃) of the protective film was measured in the same manner.

The results of the dimensional change ratios obtained for the protective films 1 to 4 are shown in table 1.

[ Table 1]

[ preparation of aqueous adhesive ]

To the aqueous solution, 3 parts of carboxyl-modified polyvinyl alcohol (KL-318, manufactured by Kuraray Co., Ltd.) was dissolved with 100 parts of water, and 1.5 parts of a polyamide epoxy additive (Sumirez Resin (registered trademark) 650(30), manufactured by Sumika Chemtex Co., Ltd., aqueous solution having a solid content concentration of 30%) as a water-soluble epoxy compound was added as a water-based adhesive.

[ production of polarizing plate A ]

A first protective film-1 is laminated on one surface of the polarizing plate with an aqueous adhesive interposed therebetween. After the lamination, the first protective film was dried at 80 ℃ for 5 minutes, thereby bonding the first protective film to the polarizing plate. The first pressure-sensitive adhesive layer laminated on the release film was laminated to the surface of the polarizer opposite to the surface to which the first protective film was laminated, and a polarizing plate a-1 in which the first protective film, the polarizer, and the first pressure-sensitive adhesive layer were laminated in this order was manufactured.

The polarizing plate is bonded so that the transmission axis direction thereof is parallel to the width direction (TD direction) of the protective film.

Similarly, the polarizing plate manufactured using the first protective film-2 in place of the first protective film-1 is referred to as a polarizing plate a-2.

The polarizing plate manufactured using the first protective film-3 in place of the first protective film-1 is referred to as a polarizing plate a-3, and the polarizing plate manufactured using the first protective film-4 in place of the first protective film-1 is referred to as a polarizing plate a-4.

The polarizing plate thus produced was cut into pieces of 100mm × 60 mm. Peeling off the release film on the first adhesive layer to sandwich the first adhesive layerThe vibration plate was bonded to alkali-free glass (EAGLE XG (registered trademark) manufactured by Corning corporation). A 5N load was applied to the surface of the polarizing plate with a scratch type durometer (model 318 ball diameter 0.75mm, product of Erichsen, germany) at a position 1.0mm from the end of the polarizing plate bonded to the glass, and a pressing scratch was given. That is, a pressing scratch is given to the surface of the first protective film on the side opposite to the polarizing plate. The depth of the pressing scar is 2-5 μm, and the diameter is 0.3mm (the area of the scar is about 0.071 mm)²)。

Further, samples were prepared in which a load of 10N and 20N was applied to the surface of the polarizing plate by a scratch durometer at a position 1.0mm away from the end of another polarizing plate bonded to glass. The depth of the pressed scar made by applying a load of 10N is 5-8 μm, and the diameter is 0.4mm (the area of the scar is about 0.13 mm)²). The depth of the pressed scar made by applying a load of 20N is 11-15 μm, and the diameter is 0.6mm (the area of the scar is about 0.28 mm)²)。

A polarizing plate having a pressing flaw on the surface thereof to which a load of 5N, 10N, or 20N was applied was subjected to a cold-heat impact environment test (250 cycles) at temperatures of 85 ℃ and-40 ℃ (1 cycle for 30 minutes each).

[ Cold and Heat shock Environment test ]

The cold-heat shock environment test was performed by using a cold-heat shock test apparatus (product name "TSA-71L-A-3" sold by ESPEC corporation) in a state where a polarizing plate was bonded to a glass plate, and the holding time under a high temperature condition (85 ℃) was 30 minutes and the holding time under a low temperature condition (-40 ℃) was 30 minutes as 1 cycle. The temperature transition time was set to 1 minute, and when the temperature transition time at the time of temperature transition was 0 minute, the conditions for preventing condensation of the optical member were set without introducing the outside air. The test was performed by repeating this cycle for 250 cycles. The determination was performed as follows. The results are shown in table 2.

[ determination ]

After a cold/heat shock environment test (cycle number: 250 times), the presence or absence of light leakage was visually confirmed. A sample which was unchanged from the sample before the test and did not generate light leakage under the crossed nicols after the test was "o", and a sample which generated light leakage under the crossed nicols after the test was "x".

[ Table 2]

From the results, it is understood that the polarizing plate of the present invention has an excellent effect in a cold and heat impact environment test. That is, according to the present invention, even under an environment of repeated high and low temperatures, the polarizing plate of the present invention does not cause cracks or the like in the polarizing plate, and maintains a good appearance, and a liquid crystal display device in which the polarizing plate of the present invention is incorporated on the visible side does not cause light leakage.

Industrial applicability

According to the present invention, the polarizing plate of the present invention can exhibit good polarization characteristics without light leakage, cracks, and the like even under an environment of repeated high and low temperatures. The polarizing plate of the present invention is thin and has excellent strength and durability.

Description of the symbols

11 a first adhesive layer, 12 a polarizer, 13 a first protective film, 100 a polarizing plate.

Claims

1. A polarizing plate comprising a first pressure-sensitive adhesive layer, a polarizing plate having a thickness of 10 [ mu ] m or less, and a first protective film comprising a cellulose-based resin,

the scar is a scar with a length of 0.3-0.4 mm, a width of 0.3-0.4 mm and a depth of 2-8 μm, and a depth of 2-8 μm and an area of 0.071mm²～0.13mm²At least one of the scars of (1).

2. The polarizing plate of claim 1,

the first adhesive layer, the polarizing plate, and the first protective film are stacked in this order.

3. The polarizing plate according to claim 1 or 2,

the first protection film has a scratch on a surface of the first protection film on a side opposite to the polarizing plate.