JP2020181213A - Polarizing plate, liquid crystal display device, and organic electroluminescent display device - Google Patents

Abstract

To provide a thin polarizing plate excellent in strength, in which no light leakage occurs even under exposure to high-temperature and high-humidity conditions, and in which occurrence of appearance defects such as cracks generated in the polarizer is suppressed under environment to repeat high temperature and low temperature.SOLUTION: A polarizing plate has a polarizer, a protection film, and an adhesive layer. In the polarizing plate, when dimensional change rate (85°C) of the protection film is dimensional change rate of the protection film in a direction parallel to a direction of a light transmission axis of the polarizer after 1 hour has elapsed under a condition at 85°C and relative humidity of 5%, and dimensional change rate (30°C) of the protection film is dimensional change rate of the protection film in the direction parallel to the direction of the light transmission axis of the polarizer after 0.5 hour has elapsed under a condition at 30°C and relative humidity of 95%, an absolute value of difference between the dimensional change rate (85°C) of the protection film and the dimensional change rate (30°C) of the protection film is 0.02 to 0.50.SELECTED DRAWING: Figure 1

Description

The present invention relates to a polarizing plate that can be used for various optical applications. The present invention also relates to a liquid crystal display device and an organic electroluminescence display device having this polarizing plate.

Polarizing plates are widely used as polarization supply elements and polarization detection elements in display devices such as liquid crystal display devices. A polarizer obtained by stretching and dyeing a polyvinyl alcohol film is preferably used for such a polarizing plate.

Patent Document 1 (Japanese Unexamined Patent Publication No. 2012-145645) discloses a polarizing plate in which the smaller the linear expansion of the protective film than the linear expansion of the polarizing element in the transmission axis direction, the smaller the cracks in the polarizing element. According to Patent Document 1, cracks in the polarizer have been evaluated by a test (heat shock acceleration test) in which the steps of simply raising and lowering the temperature of the polarizing plate between -40 ° C and 85 ° C are repeated. There is. Such an evaluation by linear expansion described in Patent Document 1 is generally a temperature-dependent parameter.

Further, in recent years, there has been a demand for a thin polarizing plate, and there is a demand for making the polarizer thinner.

Japanese Unexamined Patent Publication No. 2012-145645

However, the polarizing element produced by stretching has a problem that cracks are likely to occur along the stretching axis direction. For example, when the polarizing plate is exposed to an environment with a rapid temperature change, Cracks may occur in the polarizer, which may cause external defects and optical defects such as light leakage. With the recent thinning of the polarizing plate, cracking of the polarizer is more likely to occur, so that a solution is required.

In addition, polarizers containing polyvinyl alcohol have low resistance to humidity, which limits their use under humid conditions.

For example, in the invention described in Patent Document 1, evaluation by linear expansion is performed. However, in general, the evaluation method by linear expansion is expressed by a parameter depending on the temperature, and therefore, in Reference Document 1, the relationship between the cracks of the polarizer and the humidity is not considered at all. Absent.

Further, if the polarizer is thinned in order to satisfy the demand for thinning the polarizing plate, cracks may occur in the thin-film polarizing element, for example, when the surface of the protective film is scratched.

An object of the present invention is to provide a polarizing plate in which light does not escape even when exposed to high temperature and high humidity conditions. Another object of the present invention is to provide a polarizing plate in which the occurrence of appearance defects such as cracks in the polarizer is suppressed in an environment where high temperature and low temperature are repeated.

The present invention includes:
[1] A polarizing plate having a polarizer, a protective film, and an adhesive layer.
The dimensional change rate of the protective film 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 defined as the dimensional change rate (85 ° C.) of the protective film.
The dimensional change rate of the protective film after 0.5 hours under the condition of a relative humidity of 95% at 30 ° C. in the direction parallel to the transmission axis direction of the polarizer, is the dimensional change rate of the protective film (30 ° C.) When
A polarizing plate in which the absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is 0.02 to 0.50.
[2] The dimensional change rate after 1 hour has passed under the condition of 85 ° C. and 5% relative humidity in the transmission axis direction of the polarizer is defined as the dimensional change rate (85 ° C.) of the polarizer.
The dimensional change rate after 0.5 hours has passed under the condition of 30 ° C. and 95% relative humidity in the transmission axis direction of the polarizer is defined as the dimensional change rate (30 ° C.) of the polarizer.
The absolute value of the difference between the dimensional change rate of the polarizer (85 ° C.) and the dimensional change rate of the polarizer (30 ° C.) is defined as _FPZ .
The absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is defined as _FPF .
The difference obtained by subtracting the _{F PF} from the _{F PZ} and [Delta] F _TD, and [Delta] F ratio _{F PZ} of _TD (ΔF _TD / _{F PZ)} is in the range of 0.5 to 0.95, according to [1] Polarizer.
[3] The polarizing plate according to [1] or [2], wherein the polarizing element, the protective film, and the pressure-sensitive adhesive layer are arranged in this order.
[4] The polarizing plate according to [1] or [2], wherein the protective film, the polarizer, and the pressure-sensitive adhesive layer are arranged in this order.
[5] The protective film is a transparent resin film composed of a cellulose ester resin; a polyester resin; a polycarbonate resin; a (meth) acrylic resin; or a mixture of at least two or more thereof [1]. The polarizing plate according to any one of [4].
[6] A liquid crystal display device in which the polarizing plate according to any one of [1] to [5] is laminated on a liquid crystal cell via the pressure-sensitive adhesive layer.
[7] An organic electroluminescence display device in which the polarizing plate according to any one of [1] to [5] is laminated on an organic electroluminescence display via the pressure-sensitive adhesive layer.

According to the present invention, a polarizing plate having excellent durability is provided in which cracks and cracks generated in a polarizer are suppressed even under high temperature conditions and high humidity conditions. Further, even in an environment where high temperature and low temperature are repeated, and even in an environment where dew condensation occurs, the polarizing plate of the present invention has good polarization without causing light loss or cracking of the polarizer. Can show characteristics. Therefore, the polarizing plate of the present invention can be used under various conditions such as high temperature conditions and high humidity conditions, which have not been conventionally applicable, without causing light leakage or cracking.

Further, according to the present invention, the polarizer can be made thin, and cracking of the polarizer can be suppressed even when the surface of the protective film is scratched. Therefore, the polarizing plate of the present invention is a thin polarizing plate having excellent strength and durability.

FIG. 1A is a schematic cross-sectional view showing an example of the layered structure of the polarizing plate according to the present invention, and FIG. 1B is a schematic cross-sectional view showing another example of the layered structure of the polarizing plate according to the present invention. is there. FIG. 2A is a schematic plan view showing an axial angle between the transmission axis and the absorption axis in a polarizing plate having a transmission axis (solid line) in the width direction, and FIG. 2B is a transmission axis (transmission axis (solid line) in the long direction. It is a schematic plan view which shows the axis angle of a transmission axis and an absorption axis in the polarizing plate which has (solid line). FIG. 3 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate and the polarizing plate bonded glass substrate according to 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.

FIG. 1 shows a schematic cross-sectional view of an example of a preferable layer structure in the polarizing plate according to the present invention. In FIG. 1A, the polarizing plate 100 is a laminate of a polarizing element 11, a protective film 12, and an adhesive layer 13. Similarly, in FIG. 1B, the polarizing plate 100 is a laminate of a protective film 12, a polarizer 11, and an adhesive layer 13. As described above, in the present invention, the stacking order of the polarizer, the protective film and the pressure-sensitive adhesive layer is not particularly limited.

The polarizer in the present invention is a member having a function of converting light such as natural light into linearly polarized light, and the polarizer generally has a transmission axis and an absorption axis. The transmission axis direction of such a polarizer is understood as the vibration direction of the 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. The polarizer can be a stretched film in general, and the absorption axis direction of the polarizer coincides with the stretching direction.

In the present invention, the term "direction parallel to the transmission axis direction of the polarizer" indicates a direction that is parallel to or substantially parallel to the transmission axis direction of the above-mentioned polarizer (the angle formed is within ± 7 degrees). ..

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. The dimensional change rate after 1 hour under the condition of 85 ° C. and 5% relative humidity may be described as the dimensional change rate (85 ° C.).
For example, in the present invention, the dimensional change rate of the protective film 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 defined as the dimensional change rate of the protective film (85). ℃).
Further, the dimensional change rate after 1 hour has elapsed under the condition of 85 ° C. and 5% relative humidity in the transmission axis direction of the polarizer is described as the dimensional change rate (85 ° C.) of the polarizer.
Hereinafter, for the sake of explanation, the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (85 ° C.) of the polarizer may be simply referred to as the dimensional change rate (85 ° C.).

Dimensional change rate (85 ° C) = [(L0-L85) / L0] × 100
[In the formula, L0 means the film size of the cut film in the direction parallel to the transmission axis direction of the polarizer (long direction or width direction).
L85 means the film size in the direction parallel to the transmission axis direction (long direction or width direction) of the polarizer after 1 hour has passed under the condition of 85 ° C. and 5% relative humidity. ]
For example, when the film is cut and the dimension in the width direction (L0) is measured, the dimension in the width direction (L85) of the film is measured even after standing for 1 hour under the condition of 85 ° C. and a relative humidity of 5%. Calculate the dimensional change rate. Further, after manufacturing the polarizing plate, when the dimension (L0) in the direction parallel to the transmission axis direction of the polarizing element in the protective film obtained by removing the polarizing element from the polarizing plate is measured, the condition of 85 ° C. and relative humidity of 5% is measured. Even after standing for 1 hour underneath, 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 manner may indicate either a positive value (that is, contraction) or a negative value (that is, expansion). The protective film having a positive dimensional change rate (85 ° C.) is, for example, a polyolefin resin selected from a chain polyolefin resin and a cyclic polyolefin resin; a cellulose ester type selected from cellulose triacetate and cellulose diacetate. It is composed of a (meth) acrylic resin selected from a resin, a polymethyl methacrylate resin (PMMA resin), and the like.

Similar to the above, in the present invention, the calculation of the dimensional change rate after 0.5 hours under the condition of 30 ° C. and 95% relative humidity is based on the film after the dimensional change rate (85 ° C.) is measured. It is measured according to the following formula. The dimensional change rate after 0.5 hours under the condition of 30 ° C. and 95% relative humidity may be described as the dimensional change rate (30 ° C.).
For example, in the present invention, the dimensional change rate of the protective film after 0.5 hours under the condition of 30 ° C. and 95% relative humidity in the direction parallel to the transmission axis direction of the polarizer is set as the dimensional change rate of the protective film. It may be described as (30 ° C.). On the other hand, the dimensional change rate after 0.5 hours under the condition of 30 ° C. and 95% relative humidity in the direction parallel to the transmission axis direction of the polarizer is described as the dimensional change rate (30 ° C.) of the polarizer. There is.
Hereinafter, for the sake of explanation, the dimensional change rate (30 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the polarizer may be simply referred to as the dimensional change rate (30 ° C.).

Dimensional change rate (30 ° C) = [(L030-L30) / L0] × 100
[In the formula, L030 means the film size after measuring the dimensional change rate (85 ° C.) in the direction parallel to the transmission axis direction (long direction or width direction) of the polarizer.
L30 means the film size in the direction parallel to the transmission axis direction (long direction or width direction) of the polarizer after 0.5 hours have passed under the condition of 30 ° C. and 95% relative humidity. ]
For example, after measuring the dimensional change rate (85 ° C.), it is left at a temperature of 23 ° C. and a humidity of 55% for 15 minutes, and then L030 can be measured.
The dimensional change rate (30 ° C.) calculated in this way may indicate either a positive value (that is, contraction) or a negative value (that is, expansion). The protective film having a positive dimensional change rate (30 ° C.) is composed of, for example, a polyolefin resin such as a chain polyolefin resin and a cyclic polyolefin resin; a polyester resin; and for example, polyethylene terephthalate.
On the other hand, the protective film having a negative dimensional change rate (30 ° C.) (expanding) includes, for example, a cellulose ester resin such as cellulose triacetate and cellulose diacetate, and for example, a polymethylmethacrylate resin (PMMA resin). It is composed of (meth) acrylic resin such as.

The protective film in the present invention has a sign and a dimensional change of the dimensional change rate (85 ° C.) 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 range of the present invention. The sign of the rate (30 ° C.) may be the same sign (positive, negative or zero), or may be different signs.

In the present invention, the protective film has an 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.) of 0.02 to 0.50. Preferably, the absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is 0.03 to 0.30, and more preferably 0.03. ~ 0.20.

By having the absolute value of the difference in the dimensional change rate in such a range, the polarizing plate of the present invention suppresses cracks that occur in the polarizer under high temperature conditions and high humidity conditions, can suppress light leakage, and has durability. An excellent polarizing plate is provided. Further, even in an environment where high temperature and low temperature are repeated, the polarizing plate of the present invention can exhibit good polarization characteristics without causing light leakage or cracking.

Further, a polarizing plate having a protective film having such characteristics can make the polarizing element thin, and can suppress cracking of the polarizing element even when the surface of the protective film is scratched.

In a preferred embodiment, the polarizing plate according to the present invention is
The dimensional change rate after 1 hour has passed under the condition of 85 ° C. and 5% relative humidity in the transmission axis direction of the polarizer is defined as the dimensional change rate (85 ° C.) of the polarizer.
The dimensional change rate after 0.5 hours has passed under the condition of 30 ° C. and 95% relative humidity in the transmission axis direction of the polarizer is defined as the dimensional change rate (30 ° C.) of the polarizer.
The absolute value of the difference between the dimensional change rate of the polarizer (85 ° C.) and the dimensional change rate of the polarizer (30 ° C.) is defined as _FPZ .
The absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is defined as _FPF .
When ΔF _TD is the difference obtained by subtracting the F _PF from the F _PZ ,
Represented by ΔF _TD = F _PZ −F _PF
The dimensional change rate can be calculated according to the above.
Preferably, the ratio _{F PZ} of _{ΔF TD (ΔF TD / F PZ} ) is in the range of 0.5 to 0.95. More preferably, ΔF _TD / F _PZ is 0.55 to 0.95, still more preferably 0.60 to 0.95.
When ΔF _TD / F _PZ exceeds 0.95, the shrinkage and / or expansion behavior of the protective film is smaller than the shrinkage / expansion behavior of the polyvinyl alcohol film, and the polyvinyl alcohol film cracks due to the strain between the polyvinyl alcohol film and the protective film. Can occur.

By having such a relationship between the polarizer and the protective film, cracking that occurs in the polarizer under high temperature conditions and high humidity conditions is suppressed, and a polarizing plate having excellent durability is provided. Further, even in an environment where high temperature and low temperature are repeated, the polarizing plate of the present invention can exhibit good polarization characteristics without causing light leakage or cracking. Further, a polarizing plate having a protective film having such characteristics can make the polarizing element thin, and can suppress cracking of the polarizing element even when the surface of the protective film is scratched.

In a preferred embodiment, the polarizing plate of the present invention is a polarizing plate in which a polarizer, a protective film, and an adhesive layer are arranged in this order. In another preferred embodiment, the polarizing plate of the present invention is a polarizing plate in which a protective film, a polarizer, and an adhesive layer are arranged in this order. In a preferred embodiment, the polarizer and protective film of the present invention are bonded together via an adhesive layer. The thickness of the adhesive layer is, for example, 0.01 μm to 5 μm. As the adhesive layer, those known in the art can be used.

For example, the polarizing plate of the present invention may have an absorption axis and a transmission axis of the polarizer as shown in FIG.
For example, FIG. 2A shows the axial angles of the transmission axis 11a and the absorption axis 11b in a polarizing plate 100 having a polarizing element transmission axis 11a in the width direction and a polarizing element absorption axis 11b in the longitudinal direction. It is a schematic plan view which shows. FIG. 2B is a schematic diagram showing the axial angles of the transmission axis 11a and the absorption axis 11b in the polarizing plate 100 having the polarizing element transmission axis 11a in the long direction and the polarizing element absorption axis 11b in the width direction. It is a plan view.

In a preferred embodiment, as shown in FIG. 2A, the outer shape of the polarizing plate 100 may be, for example, a square shape having a long side and a short side. In this case, the transmission axis 11a of the polarizing plate 100 (polarizer 11) and the short side of the polarizing plate 100 may be parallel or substantially parallel (the angle formed is within ± 7 degrees). On the other hand, the absorption axis 11b is orthogonal to the transmission axis 11a.

Further, in another preferred embodiment, as shown in FIG. 2B, the transmission axis 11a of the polarizing plate 100 (polarizer 11) and the long side of the polarizing plate 100 are parallel or substantially parallel to each other. The angle may be within ± 7 degrees). On the other hand, the absorption axis 11b is orthogonal to the transmission axis 11a.

[Polarizer]
The polarizer may be a uniaxially stretched polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented. Generally, when the thickness of the polarizer is 20 μm or less, the polarizing plate can be thinned. In the present invention, for example, a polarizer having a thickness of 10 μm or less, more preferably a polarizer having a thickness of 8 μm or less can be adopted. Further, the polarizer in the present invention usually has a thickness of 2 μm or more.

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides with ammonium groups and the like.

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, and more preferably 95 mol% or more. The polyvinyl alcohol-based resin may be a partially modified modified polyvinyl alcohol. For example, the polyvinyl alcohol-based resin may be an olefin such as ethylene and propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid and crotonic acid. ; Examples include those modified with alkyl esters of unsaturated carboxylic acids and acrylamide. The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000.

For the polarizer, for example, a raw film composed of a polyvinyl alcohol-based resin is uniaxially stretched, dyed with a dichroic dye (dyeing treatment), treated with an aqueous boric acid solution (boric acid treatment), and washed with water (washing with water). Treatment), and finally it can be dried and manufactured.

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with the dichroic dye, at the same time as dyeing with the dichroic dye, or after dyeing with the dichroic dye. Good. When the uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Of course, it is also possible to perform uniaxial stretching at these a plurality of stages. In order to perform uniaxial stretching, it may be stretched through rolls having different peripheral speeds, or it may be stretched by sandwiching it with thermal rolls. Further, it may be a dry stretching performed in the air, or a wet stretching performed in a state of being swollen with a solvent. 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-based 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. As the dichroic dye, specifically, iodine or a dichroic dye is used.

When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted. 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 content of potassium iodide is usually 0.5 to 10 parts by weight per 100 parts by weight of water. It is 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 a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye and dyeing is usually adopted. 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-based resin film in an aqueous boric acid solution. The content of boric acid 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 pigment, this boric acid aqueous 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, further preferably 400 seconds or less. .. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C. Sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid and the like may be added to the boric acid aqueous solution as a pH adjuster.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed by immersing, for example, a boric acid-treated polyvinyl alcohol-based resin film in water. After washing with water, it is dried to obtain a polarizer. The temperature of water in the washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. Subsequent drying 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]
As described above, in the protective film of the present invention, the absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is 0.02 to 0.50. ..

The protective film is laminated on at least one side of the polarizer. A protective film (first protective film) may be laminated on one side of the polarizer, and another protective film (second protective film) may be laminated on the other side. Preferably, a protective film (first protective film) is laminated on one side of the polarizer. The first protective film and the second protective film may be a single layer, or a plurality of films may be laminated with an adhesive or an adhesive.

The protective film (first protective film) and the second protective film can be transparent resin films each made of 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 ester resins such as cellulose triacetate and cellulose diacetate; polyethylene terephthalate and polyethylene naphthalate. And polyester resins such as polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins selected from polymethylmethacrylate resins; or mixtures of at least two or more of these. Further, a copolymer of at least two or more monomers constituting the resin may be used.

Cyclic polyolefin-based resin is a general term for resins that are usually polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A No. 1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Examples of the resin used. Specific examples of the cyclic polyolefin resin include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a chain olefin such as ethylene and propylene and a cyclic olefin (typically). Random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Of these, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

Various products of the cyclic polyolefin resin are commercially available. Examples of commercially available cyclic polyolefin resins are "TOPAS" (registered trademark) and JSR Corporation, which are produced by TOPAS ADVANCED POLYMERS GmbH and sold by Polyplastics Co., Ltd. in Japan. "Arton" (registered trademark) sold by, "Zeonoa" (registered trademark) and "Zeonex" (registered trademark) sold by Nippon Zeon Co., Ltd., and "Apel" sold by Mitsui Manabu Co., Ltd. (Registered trademark) and so on.

Further, a commercially available product of the formed cyclic polyolefin resin film may be used as the protective film. Examples of commercially available products are "Arton Film" ("Arton" is a registered trademark of JSR Corporation) sold by JSR Corporation and "Scina" sold by Sekisui Chemical Industry Co., Ltd. Examples include "SCA40" (registered trademark) and "Zeonoa film" (registered trademark) sold by Nippon Zeon Co., Ltd.

Cellulose ester-based 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. Further, those obtained by copolymerizing these or 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 commercially available cellulose triacetate products are all trade names, such as "Fujitac (registered trademark) TD80", "Fujitac (registered trademark) TD80UF", and "Fujitac (registered trademark) TD80UZ" sold by FUJIFILM Corporation. And "Fujitac (registered trademark) TD40UZ", TAC film "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) are easily available on the market.

Examples of the (meth) acrylic resin include homopolymers of methacrylic acid alkyl esters or 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 the (meth) acrylic resin, those commercially available as general-purpose (meth) acrylic resins can be used. As the (meth) acrylic resin, what is called an impact resistant (meth) acrylic resin may be used.

The (meth) acrylic resin is usually a polymer mainly composed of a methacrylic acid ester. The methacrylic acid resin may be a homopolymer of one kind of methacrylic acid ester, or may be a copolymer of a methacrylic acid ester and another methacrylic acid ester, an acrylic acid ester, or the like. 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 methacrylic acid, aryl aryl methacrylate such as phenyl methacrylate, cycloalkylalkyl methacrylate such as cyclohexylmethyl methacrylate, and aralkyl methacrylate such as benzyl methacrylate should be used. You can also.

Examples of the above-mentioned other polymerizable monomers that can constitute the (meth) acrylic resin include acrylic acid esters and polymerizable monomers other than methacrylic acid esters and acrylic acid esters. Acrylic acid alkyl ester can be used as the acrylic acid ester, and specific examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and acrylic. Includes acrylic acid alkyl esters having 1 to 8 carbon atoms in alkyl groups such as t-butyl acid acid, 2-ethylhexyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate. The alkyl group preferably has 1 to 4 carbon atoms. In the (meth) acrylic resin, only one type of acrylic acid ester may be used alone, or two or more types 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 polymerizable carbon-carbon double bond in the molecule. A polyfunctional monomer having at least two of these can be mentioned, but a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, styrene halide, and hydroxystyrene; vinyl cyanide such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid, and anhydrous. Unsaturated acids such as maleic acid and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide; allyl alcohols such as methacrylic alcohol and allylalcohol; vinyl acetate, vinyl chloride, ethylene and propylene, Includes other monomers such as 4-methyl-1-pentene, 2-hydroxymethyl-1-butene, methylvinylketone, N-vinylpyrrolidone, N-vinylcarbazole.

Specific examples of the polyfunctional monomer are polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethyl propantriacrylate; allyl acrylate, allyl methacrylate, and allyl silicate. Alkenyl esters of unsaturated carboxylic acids such as; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, 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.

The preferable 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, and 0 to 0 to other polymerizable monomers based on the total amount of monomers. It is 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.

Further, the (meth) acrylic resin may have a ring structure in the polymer main chain because the durability of the film can be enhanced. 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 thereof include a cyclic acid anhydride structure such as a glutaric anhydride structure and a succinic anhydride structure, a cyclic imide structure such as a glutarimide structure and a succinic anhydride structure, and a lactone ring structure such as butyrolactone and valerolactone. The 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 are introduced by a method of introducing by copolymerizing a monomer having a cyclic structure such as maleic anhydride or maleimide, and introducing a cyclic acid anhydride structure by a dehydration / demethanol condensation reaction after polymerization. It can be introduced by a method, a method of reacting an amino compound to introduce a cyclic imide structure, or the like. For a resin (polymer) having a lactone ring structure, after preparing a polymer having a hydroxyl group and an ester group in a polymer chain, the hydroxyl group and the ester group in the obtained polymer are required by heating. Accordingly, it can be obtained by cyclization condensation in the presence of a catalyst such as an organic phosphorus compound to form a lactone ring structure.

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, Japanese Patent Application Laid-Open No. 2007-254726.

A (meth) acrylic resin can be prepared by radically polymerizing a monomer composition containing the above-mentioned monomers. The monomer composition can contain a solvent and a polymerization initiator, if necessary.

The (meth) acrylic resin may contain a resin other than the above-mentioned (meth) acrylic resin. The content of the other resin is preferably 0 to 70% by weight, more preferably 0 to 50% by weight, and further preferably 0 to 30% by weight. The resin is, for example, an olefin polymer such as polyethylene, polypropylene, an ethylene-propylene copolymer, poly (4-methyl-1-pentene); a halogen-containing polymer such as vinyl chloride or a chlorinated vinyl resin; polystyrene, styrene. Sterite polymers such as -methyl methacrylate copolymer, styrene-acrylonitrile copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; polyarylate composed of aromatic diols and aromatic dicarboxylic acids; polylactic acid, Biodegradable polyesters such as polybutylene succinate; polycarbonates; polyamides such as nylon 6, nylon 66, nylon 610; polyacetals; polyphenylene oxides; polyphenylene sulfides; polyether ether ketones; polyether nitriles; polysulfones; polyether sulfones; poly Oxypendylene; may be polyamideimide or the like.

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

The acrylic elastic polymer may be a polymer containing alkyl acrylate as a main component, that is, containing 50% by weight or more of structural units 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% by weight or more of structural units derived from alkyl acrylate and 50% by weight or less of structural units derived from other polymerizable monomers. It may be a copolymer.

As the alkyl acrylate constituting the acrylic elastic polymer, one having an alkyl group having 4 to 8 carbon atoms is usually used. Examples of the above other polymerizable monomers include, for example, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate; styrene-based monomers such as styrene and alkylstyrene; unsaturated nitriles such as acrylonitrile and methylonitrile. Monofunctional monomers of the above, and alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methacrylic (meth) acrylate; dialkenyl esters of dibasic acids such as diallyl maleate; alkylene glycol di (meth). It is a polyfunctional monomer such as an unsaturated carboxylic acid diester of glycol such as acrylate.

The rubber particles containing the acrylic elastic polymer are preferably particles having a multilayer structure having a layer of the acrylic elastic polymer. Specifically, it has a two-layer structure having a hard polymer layer mainly composed of alkyl methacrylate on the outside of the layer of the acrylic elastic polymer, and an alkyl methacrylate on the inside of the layer of the acrylic elastic polymer. Examples thereof include 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 on the outside or the inside of the layer of the acrylic elastic polymer is given as an example of the (meth) acrylic resin. This is the same as the example of the monomer composition of the polymer mainly composed of alkyl methacrylate, and the monomer composition mainly composed of methyl methacrylate is particularly preferably used. Acrylic rubber elastic particles having such a multi-layer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

The rubber particles include the rubber elastic layer (layer of acrylic elastic polymer) contained therein from the viewpoint of film forming property of (meth) acrylic resin, impact resistance of film, and slipperiness of film surface. The average particle size is preferably in the range of 10 to 350 nm. The average particle size 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 size of the rubber particles up to the rubber elastic layer (layer of acrylic elastic polymer) 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 is dyed with an aqueous solution of ruthenium oxide, only the rubber elastic layer is colored and observed in an almost circular shape, and the mother layer is observed. (Meta) acrylic resin is not dyed. Therefore, a slice is prepared from the cross section of the film dyed in this manner using a microtome or the like, and this is observed with an electron microscope. Then, 100 dyed rubber particles are randomly extracted, the diameter of each particle (diameter to the rubber elastic layer) is calculated, and then the number average value is taken as the above average particle diameter. Since the measurement is performed by such a method, the obtained average particle size is a number average particle size.

When the outermost layer is a hard polymer mainly composed of methyl methacrylate and the rubber elastic body layer (layer of acrylic elastic polymer) is wrapped in the rubber particles, it is used as the base material (meth). ) When mixed with an acrylic resin, the outermost layer of the rubber particles is mixed with the parent (meth) acrylic resin. Therefore, when the cross section is stained with ruthenium oxide and observed with an electron microscope, the rubber particles are observed as particles in a state where the outermost layer is removed. 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 Is stained and observed as monolayered particles. Further, 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, which has a three-layer structure. In the case of rubber particles, the innermost particle center portion is not dyed, and only the acrylic elastic polymer portion of the intermediate layer is observed as stained two-layer structure particles.

From the viewpoint of film forming property of (meth) acrylic resin, impact resistance of film, and slipperiness of film surface, the total amount of rubber particles is the total amount of the rubber particles with the (meth) acrylic resin constituting the (meth) acrylic resin film. It is preferable that the mixture is blended in a proportion of 3% by weight or more and 60% by weight or less, more preferably 45% by weight or less, still more preferably 35% by weight or less. When the amount of rubber elastic particles is more than 60% by weight, the dimensional change of the film becomes large and the heat resistance decreases. 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 take-up property at the time of film formation is poor, and the productivity may be lowered. In the present invention, when a multi-layered particle having a layer exhibiting rubber elasticity and another layer is used as the rubber elastic body particle, the weight of the portion composed of the layer exhibiting rubber elasticity and the inner layer thereof is determined. , The weight of the rubber elastic particles. For example, when the acrylic rubber elastic particles having the above-mentioned 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 in the innermost layer. Let be the weight of the rubber elastic body particles. When the acrylic rubber elastic particles having the above-mentioned 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. The total weight ratio of the intermediate layer and the innermost layer to the acrylic rubber elastic particles having a three-layer structure can be easily determined.

When the (meth) acrylic resin film contains rubber particles, the (meth) acrylic resin composition containing the rubber particles used for producing the film melts and kneads the (meth) acrylic resin and the rubber particles. In addition to being obtained by mixing with or the like, it can also be obtained by first producing rubber particles and then polymerizing a monomer composition as a raw material for a (meth) acrylic resin in the presence of the rubber particles.

The protective film may contain ordinary additives such as an ultraviolet absorber, an organic dye, a pigment, an inorganic dye, an antioxidant, an antistatic agent, and a surfactant. Among them, the ultraviolet absorber is preferably used for enhancing the weather resistance. Examples of UV absorbers are 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-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-hydroxyphenyl) -2H-benzotriazole, 2- (2) Benzoliazole-based ultraviolet absorbers such as'-hydroxy-5'-tert-octylphenyl) -2H-benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2,4-dihydroxy 2-Hydroxybenzophenone-based ultraviolet rays such as benzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, etc. Absorbent; Salicylic acid phenyl ester-based ultraviolet absorber such as p-tert-butylphenyl salicylate ester, p-octylphenyl salicylate ester; 2,4-diphenyl-6- (2-hydroxy-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-dodecyloxyphenol) Nyl) -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-triazine-2-yl) -5-hydroxyphenyl, 2 -[4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine-2-yl] -5- (octyloxy) phenol, 2- [2,6-di (2,4-di) Kisilyl) -1,3,5-triazine-2-yl] -5-octyloxyphenol, 2- (4,6-diphenyl-1,3,5-triazine-2-yl) -5- [2-( Examples thereof include 2-ethylhexanoyl) ethoxy] phenol, triazine-based ultraviolet absorbers such as 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methoxyphenyl) -1,3,5triazine. , Two or more of them may be used if necessary.

As the ultraviolet absorber, a commercially available product may be used. For example, as a triazine-based ultraviolet absorber, "Kemisorb 102" (registered trademark) manufactured by Chemipro Kasei Co., Ltd. and "Adecastab (registered trademark)" manufactured by ADEKA Co., Ltd. LA46 ”,“ Adecastab® LAF70 ”, BASF“ TINUVIN® 460 ”,“ TINUVIN® 405 ”,“ TINUVIN® 400 ”and“ TINUVIN® 477 , "CYASORB (registered trademark) UV-1164" manufactured by Sun Chemical Co., Ltd. (all of which are trade names) and the like. As benzotriazole-based ultraviolet absorbers, "Adecastab LA31" and "Adecastab LA36" manufactured by ADEKA Co., Ltd., "Sumisorb (registered trademark) 200", "Sumisorb (registered trademark) 250" and "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) and Kemipro Kasei Co., Ltd. "Kemisorb 279" (registered trademark), BASF's "TINUVIN (registered trademark) 99-2", "TINUVIN (registered trademark) 900" and "TINUVIN (registered trademark) 928" (all of which are trade names), etc. Can be 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, based on 100% by weight of the (meth) acrylic resin. Yes, and preferably 3% by weight or less.

A conventionally known film-forming method can be adopted 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 has various generally known methods 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, multi-layer melt extrusion molding from a T-die, and contacting at least one side of the obtained laminated film-like material with a roll or belt to form a film has a good surface quality. It is preferable in that it can be obtained. In particular, from the viewpoint of improving the surface smoothness and surface glossiness of the (meth) acrylic resin film, both sides of the laminated film-like material obtained by the above-mentioned multilayer melt extrusion molding are brought into contact with the roll surface or the belt surface to form a film. The method of converting is preferable. In the roll or belt used at this time, the surface of the roll or belt in contact with the (meth) acrylic resin has a mirror surface in order to impart smoothness to the surface of the (meth) acrylic resin film. Is preferable.

The (meth) acrylic resin film may be a film produced as described above that has been stretched. Stretching may be required to obtain a film with the desired optical and mechanical properties. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a mechanical flow direction (MD) of the unstretched film, a direction orthogonal to the mechanical flow direction (TD), and a direction obliquely intersecting the mechanical flow direction (MD). The biaxial stretching may be a simultaneous biaxial stretching that simultaneously stretches in two stretching directions, or may be a sequential biaxial stretching that stretches in a predetermined direction and then in another direction.

The first protective film and the second protective film may be protective films having optical functions such as a retardation film and a brightness improving film as long as they are included in the scope of the present invention. For example, a retardation film to which an arbitrary retardation value is given by stretching a transparent resin film made of the above material (uniaxial stretching, biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film. Can be.

The first protective film and the second protective film have 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 on the surface opposite to the polarizer. It can also be formed. A known method can be used as a method 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 films are different are combinations in which the types of thermoplastic resins constituting the protective film are at least different; presence / absence of optical function of the protective film or at least different combinations 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 thinning the polarizing plate, but if it is too thin, the strength is lowered and the processability is inferior. 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.

As long as the protective film (first protective film) has an appropriate dimensional change due to water absorption, the effect of the present application can be easily obtained. A transparent resin film composed of a cellulose ester-based resin, a polyester-based resin, a polycarbonate-based resin, a (meth) acrylic-based resin, or a mixture thereof of at least two or more thereof is preferable, and a cellulose ester-based resin is more preferable. A transparent resin film composed of a (meth) acrylic resin or a mixture of at least two or more thereof.

(Adhesive)
As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, a conventionally known pressure-sensitive adhesive may be appropriately selected, and peeling or the like occurs in a high-temperature environment where the polarizing plate is exposed, a moist heat environment, or an environment where high temperature and low temperature are repeated. Anything may be used as long as it has a degree of adhesiveness. Specific examples thereof include acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, and rubber-based pressure-sensitive adhesives. Acrylic-based pressure-sensitive adhesives are particularly preferable in terms of transparency, weather resistance, heat resistance, and processability.

Adhesives include fillers, pigments, colorants, fillers, antioxidants, UV absorbers, etc., which are made of tackifiers, plasticizers, glass fibers, glass beads, metal powders, other inorganic powders, etc., as required. , Antistatic agent, silane coupling agent, and various other additives may be appropriately blended.

The pressure-sensitive adhesive layer is usually formed by applying a pressure-sensitive adhesive solution on a release sheet and drying it. For coating on the release sheet, for example, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, a spray method or the like can be adopted. The release sheet provided with the pressure-sensitive adhesive layer is used by a method of transferring the release sheet or the like. 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 0.01 MPa to 1 MPa. If the storage elastic modulus of the pressure-sensitive adhesive layer is less than 0.01 MPa, the shrinkage of the polarizing plate during the high-temperature test cannot be suppressed, and there is a tendency for appearance defects such as peeling to occur. Further, if the storage elastic modulus of the pressure-sensitive adhesive layer is larger than 1 MPa, the pressure-sensitive adhesive cannot alleviate the strain generated between the glass and the polarizing plate during the thermal impact test, and the polarizing plate tends to be cracked easily.
In a preferred embodiment, the storage elastic modulus of the pressure-sensitive adhesive layer at 80 ° C. is 0.01 MPa to 1 MPa.

A liquid crystal panel can be obtained by adhering a polarizing plate to a liquid crystal cell via an adhesive layer. Further, an organic electroluminescence display device can be obtained by attaching a polarizing plate to an organic electroluminescence display via an adhesive layer. For example, in a liquid crystal panel and an organic electroluminescence display, as shown in FIG. 3, a glass substrate 40, 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 It can have the configuration of the protective film 22.

According to the polarizing plate of the present invention, a polarizing plate having a thin wall thickness and excellent strength is provided.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples. In the examples,% and parts representing the content or the amount used are based on weight unless otherwise specified.

[Manufacturing of polarizer]
A 20 μm-thick polyvinyl alcohol film (average degree of polymerization of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further uniaxially stretched at 60 ° C. while maintaining a tense state. After immersing 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 mixture was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizer having a thickness of 7 μm in which iodine was adsorbed and oriented on a polyvinyl alcohol film.

[First adhesive]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on the mold-release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm was used. Urethane acrylate oligomer is not blended in the acrylic pressure-sensitive adhesive. The storage elastic modulus of the pressure-sensitive adhesive layer from which the release film was removed from the pressure-sensitive adhesive sheet was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

[Second adhesive layer]
A mold release treatment of a 38 μm-thick polyethylene terephthalate film (release film) that has been subjected to a mold release treatment of an organic solvent solution in which a urethane acrylate oligomer and an isocyanate-based cross-linking agent are added to a copolymer of butyl acrylate and acrylic acid. The surface was coated with a die coater so as to have a thickness of 5 μm after drying, and dried to obtain an adhesive sheet on which an adhesive layer was laminated. The storage elastic modulus of the pressure-sensitive adhesive layer from which the release film was removed from the pressure-sensitive adhesive sheet was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

[1st protective film-1]
A triacetyl cellulose film manufactured by Konica Minolta Co., Ltd. (thickness 20 μm, in-plane retardation value at a wavelength of 590 nm = 1.2 nm, thickness direction retardation value at a wavelength of 590 nm = 1.3 nm) was used.

[1st protective film-2]
An unstretched TAC film having a thickness of 25 μm and a trade name of “KC2UA” manufactured by Konica Minolta Co., Ltd. was used.

[1st protective film-3]
A cycloolefin resin film (manufactured by Nippon Zeon Corporation) having a thickness of 13 μm was used. In-plane phase difference at wavelength 590 nm (Re (590)) = 0.8 nm, thickness direction phase difference at wavelength 590 nm (Rth (590)) = 3.4 nm, thickness direction phase difference at wavelength 483 nm (Rth (483)) )) = 3.5 nm, thickness direction phase difference at a wavelength of 755 nm (Rth (755)) = 2.8 nm.

[1st protective film-4]
A cyclic polyolefin resin film having a thickness of 23 μm and a trade name of “Zeonoa Film (registered trademark) ZF14-023” manufactured by Nippon Zeon Corporation was used.

[1st protective film-5]
A triacetyl cellulose film (manufactured by Toppan TOMOEGAWA Optical Film Co., Ltd., 25KCHC-TC thickness 32 μm) whose surface was hard-coated (thickness 7 μm) was used.

[1st protective film-6]
The first protective film-1 was dissolved in 1,3-dioxolane, adjusted to 12 wt%, and coated on a glass substrate with a bar coater (count: 60) to a thickness of 10 μm after drying. After drying in an oven at 60 ° C. for 3 minutes, the coating film was peeled off from the glass to obtain a first protective film-6.

[Second protective film]
A luminance-improving film (manufactured 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 (manufactured by Sumika Chemtex Co., Ltd.), which is a water-soluble epoxy compound, is added to the aqueous solution. 650 (30) of violet resin (registered trademark), an aqueous solution having a solid content concentration of 30%] was added in an amount of 1.5 parts to prepare an aqueous adhesive.

[Preparation of polarizing plate precursor A]
The first protective film-1 was laminated on one side of the polarizer via a water-based adhesive. After laminating, the first protective film-1 and the polarizer were bonded together by drying at 80 ° C. for 5 minutes. A second pressure-sensitive adhesive layer laminated on the release film was bonded to the surface of the polarizer opposite to the surface to be bonded to the first protective film-1. The first pressure-sensitive adhesive layer laminated on the release film was bonded to the surface of the first protective film-1 opposite to the surface to be bonded to the polarizer.
The polarizing element was attached so as to be parallel to the transmission axis direction and the width direction of the protective film.
In this way, the 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, the polarizing plate precursor prepared by using the first protective film-2 instead of the first protective film-1 was designated as the polarizing plate precursor A-2. For other protective films, polarizing plate precursors were prepared in the same manner.

[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-improving film in the polarizing plate precursor A are bonded to each other, and the first pressure-sensitive adhesive layer, the protective film (first protective film), the polarizer, the second pressure-sensitive adhesive layer, and the brightness-improving film are bonded together. (Second protective film), obtained a polarizing plate A laminated in this order. For example, the polarizing plate prepared by using the first protective film-1 was designated as the polarizing plate A1. Similarly, a polarizing plate having such a structure prepared by using the first protective film-2 was designated as polarizing plate A2.

[Preparation of polarizing plate B]
A polarizing plate B1 was produced in the same manner as the polarizing plate A1 except that the lamination positions of the polarizing element and the protective film in the polarizing plate precursor A-1 were exchanged. In the obtained polarizing plate B1, a first pressure-sensitive adhesive layer, a polarizer, a protective film (first protective film), a second pressure-sensitive adhesive layer, and a brightness improving film (second protective film) are laminated in this order. It is a polarizing plate.

[Preparation of polarizing plate C]
The first protective film-1 was laminated on one side of the polarizer via a water-based adhesive. After laminating, the first protective film and the polarizer were bonded together by drying at 80 ° C. for 5 minutes. The first pressure-sensitive adhesive layer laminated on the release film is attached to the surface of the polarizer opposite to the surface to be bonded to the first protective film, and then the release film is peeled off to obtain a polarizing plate C. It was. The obtained polarizing plate is a polarizing plate in which a first pressure-sensitive adhesive layer, a polarizer, and a protective film (first protective film) are laminated in this order. Regarding the polarizing plate C, the polarizing plate using the first protective film-1 was designated as the polarizing plate C1, and the polarizing plate using the first protective film-5 was designated as the polarizing plate C5, for example.

[Calculation of dimensional change rate]
For the protective film, the difference in dimensional change rate was measured by the following method.
In the protective films used in Examples and Comparative Examples, the width direction is parallel to the transmission axis direction of the polarizer.
First, each of the long protective films was cut into a square having a length direction of 100 mm and a width direction of 100 mm. After cutting the protective film, the dimension (L0) in the width direction was measured using a two-dimensional measuring instrument "NEXIV VMR-12072" (manufactured by Nikon Corporation). Similarly, the dimensions in the long direction were also measured.
Then, the protective film was allowed to stand in an environment of 85 ° C. for 1 hour (humidity: 5%). After this step, the width direction dimension (L85) and the length direction dimension of the protective film were measured in the same manner as described above.
The dimensional change rate (%) was obtained from the following formula, and the dimensional change rate (85 ° C.) in the width direction and the dimensional change rate in the long direction of the protective film were calculated.
Dimensional change rate (85 ° C) = [(L0-L85) / L0] × 100

Further, after calculating the dimensional change rate in an environment of 85 ° C., the same sample was left at a temperature of 23 ° C. and a humidity of 55% for 15 minutes, and then allowed to stand for 0.5 hours under a condition of 30 ° C. and a relative humidity of 95%. did. After this step, the width direction dimension (L30) and the length direction dimension of the protective film were measured in the same manner as described above. The dimensional change rate (%) was calculated from the following formula, and the dimensional change rate in the width direction and the dimensional change rate in the long direction of the protective film were calculated. For "L030", after measuring the dimensional change rate (85 ° C.) in the direction parallel to the transmission axis direction of the polarizer (long direction or width direction), the temperature is 23 ° C. and the humidity is 55% for 15 minutes. Dimensional change rate (30 ° C.) = [(L030-L30) / L0] × 100, which means the film size after being left to stand.

The absolute value of the difference between the obtained dimensional change rate (85 ° C.) and the dimensional change rate (30 ° C.) was calculated. These results are shown in Table 1. In the table, " _FTD " is an abbreviation indicating the absolute value of the difference between the dimensional change rate (85 ° C.) and the dimensional change rate (30 ° C.). The Fpz of the polarizer was also measured by the same method as described above.

Further, ΔF _TD (the difference between the absolute value F _PZ of the difference in the dimensional change rate of the polarizer and the absolute value F _PF of the difference in the dimensional change rate of the protective film) was calculated. Further, the ratio of ΔF _TD to F _PZ (ΔF _TD / F _PZ ) was calculated. The results are shown in Table 1.

[Cold thermal shock environment test and condensation Cold thermal shock environment test]
The polarizing plate with an adhesive layer prepared as described above is cut into 100 mm × 60 mm, the release film is peeled off from the first adhesive layer side, and the polarizing plate is attached to a glass plate via the exposed adhesive layer. did. The obtained evaluation sample was subjected to a cold shock environment test and a dew condensation cold shock environment test described later.

[Cold thermal shock environment test]
The thermal shock environment test is performed under high temperature conditions (product name "TSA-71L-A-3" sold by ESPEC CO., LTD.) With the polarizing plate attached to the glass plate. A holding time of 30 minutes at 85 ° C. and a holding time of 30 minutes under low temperature conditions (-40 ° C.) were set as one cycle. The temperature transition time was set to 1 minute, and a condition was set in which no outside air was introduced and dew condensation did not occur on the optical member at the temperature transition time of 0 minutes at the time of temperature transition. This cycle was repeated 400 cycles to carry out the test.

[Condensation cold heat shock environment test]
Condensation The cold-heat shock environment test was carried out under the condition that dew condensation was intentionally generated on the optical member by introducing outside air into the apparatus for 5 minutes at the time of temperature transition in the above-mentioned cold-heat shock environment test. This cycle was repeated for 400 cycles to perform the test.
In this test, the temperature of the outside air was 23 ° C. and the relative humidity was 55%.

[Judgment]
After conducting a cold shock environment test (number of cycles: 400 times) and a dew condensation cold shock environment test (number of cycles: 400 times), the presence or absence of cracks was visually confirmed. Those that did not change from before the test and did not cause light loss under the cross Nicol after the test were marked with "○", and those with light loss under the cross Nicol after the test were marked with "x".
In addition, the maximum length of cracks generated in the sample subjected to the dew condensation cold thermal shock environment test was measured under cross Nicol. Table 2 shows the results obtained in the cold shock environment test and the dew condensation cold shock environment test.

From this result, it can be seen that the polarizing plate of the present invention has an excellent effect in both the cold shock environment test and the dew condensation cold heat shock environment test. That is, according to the present invention, there is provided a polarizing plate having excellent durability under high temperature conditions and high humidity conditions without causing light leakage to the polarizer. Further, even in an environment where high temperature and low temperature are repeated, the polarizing plate of the present invention can exhibit good polarization characteristics without causing light leakage or cracking.
Further, in the polarizing plate of the present invention, the maximum length of cracks generated by the dew condensation cold thermal shock environment test is remarkably shorter than that of the polarizing plate of the comparative example. Therefore, the polarizing plate of the present invention can suppress crack growth of the polarizer even under humid conditions where dew condensation occurs, and can maintain good polarization characteristics.

[Cold thermal shock environment test after piercing]
Scratches were formed on the surface of the polarizing plate, and the polarizing plate was subjected to a thermal shock environment test to confirm the presence or absence of cracks in the polarizer. Specifically, it was evaluated through the following steps.
It was cut into a polarizing plate of 100 mm × 60 mm prepared as described above. The release film on the first pressure-sensitive adhesive layer was peeled off, and a polarizing plate was attached to non-alkali glass (EAGLE XG (registered trademark) manufactured by Corning Inc.) via the first pressure-sensitive adhesive layer. A load of 3N is applied to the surface of the polarizing plate by a scratch-type hardness tester (model 318 ball diameter 0.75 mm, manufactured by Ericssen, Germany) at a location 1.0 mm from the end of the polarizing plate bonded to the glass, and pressed. I scratched it. The depth of the dent was 1 μm or less, and the size was 0.2 mm in diameter.

Further, a sample was prepared in which a load of 5 N was applied to the surface of another polarizing plate by a scratch-type hardness tester at a location 1.0 mm from the end of another polarizing plate bonded to glass, and a load of 10 N was applied to the surface of another polarizing plate.

Scratches caused by applying a load to the surface of the polarizing plate are usually caused by foreign matter when the protective film laminated on the polarizing plate is peeled off with a sharp instrument such as tweezers, or when the backlight and the polarizing plate are bonded together. It is intended for scratches that occur when the particles are stuck together in a bitten state.

A thermal shock environment test (250 cycles) at temperatures of 85 ° C and -40 ° C (1 cycle for 30 minutes each) was performed on a polarizing plate with scratches formed on the surface by applying a load of 3N, 5N, or 10N. did. The judgment was as follows. The results are shown in Table 3.

[Judgment]
No matter which load was applied, the case where light leakage of the polarizer did not occur under the cross Nicol after the thermal shock environment test was marked with “◯”. When any of the loads was applied, the polarizer cracked after the thermal shock environment test, and the case where light leakage could be confirmed under the cross Nicol or visually was marked with "x".

According to the present invention, there is provided a polarizing plate that is less likely to cause light leakage under high temperature conditions and high humidity conditions and has excellent durability. Further, even in an environment where high temperature and low temperature are repeated, the polarizing plate of the present invention can exhibit good polarization characteristics without causing light leakage or cracking. Further, according to the present invention, the polarizer can be made thin, and cracking of the polarizer can be suppressed even when the surface of the protective film is scratched.

The present application claims priority based on Japanese Patent Application No. 2015-223443 filed on November 13, 2015 and Japanese Patent Application No. 2016-079655 filed on April 12, 2016, and all of the contents thereof. Is incorporated herein by reference.

11 Polarizer 12 Protective film (1st protective film)
13 Adhesive layer (first adhesive layer)
22 Second protective film 23 Second adhesive layer 40 Glass substrate 100 Polarizing plate

Claims (7)

A polarizing plate having a polarizer, a protective film, and an adhesive layer.
The dimensional change rate of the protective film 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 defined as the dimensional change rate (85 ° C.) of the protective film.
The dimensional change rate of the protective film after 0.5 hours under the condition of a relative humidity of 95% at 30 ° C. in a direction parallel to the transmission axis direction of the polarizer is defined as the dimensional change rate of the protective film (30 ° C.). When
A polarizing plate in which the absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is 0.02 to 0.50. The dimensional change rate after 1 hour has passed under the condition of 85 ° C. and 5% relative humidity in the transmission axis direction of the polarizer is defined as the dimensional change rate (85 ° C.) of the polarizer.
The dimensional change rate after 0.5 hours has passed under the condition of 30 ° C. and 95% relative humidity in the transmission axis direction of the polarizer is defined as the dimensional change rate (30 ° C.) of the polarizer.
The absolute value of the difference between the dimensional change rate of the polarizer (85 ° C.) and the dimensional change rate of the polarizer (30 ° C.) is defined as _FPZ .
The absolute value of the difference between the dimensional change rate (85 ° C.) of the protective film and the dimensional change rate (30 ° C.) of the protective film is defined as _FPF .
The difference obtained by subtracting the _{F PF} from the _{F PZ} and [Delta] F _TD, and [Delta] F ratio _{F PZ} of _TD (ΔF _TD / _{F PZ)} is in the range of 0.5 to 0.95, according to claim 1 Polarizer. The polarizing plate according to claim 1 or 2, wherein the polarizing element, the protective film, and the pressure-sensitive adhesive layer are arranged in this order. The polarizing plate according to claim 1 or 2, wherein the protective film, the polarizer, and the pressure-sensitive adhesive layer are arranged in this order. The protective film is a transparent resin film composed of a cellulose ester resin; a polyester resin; a polycarbonate resin; a (meth) acrylic resin; or a mixture of at least two or more thereof. The polarizing plate according to any one item. A liquid crystal display device in which the polarizing plate according to any one of claims 1 to 5 is laminated on a liquid crystal cell via the pressure-sensitive adhesive layer. An organic electroluminescence display device in which the polarizing plate according to any one of claims 1 to 5 is laminated on an organic electroluminescence display via the pressure-sensitive adhesive layer.

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