JPH11142645A - Protective film for polarizing plate and polarizing plate using that film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain various performances required for a protective film such as transparency, UV-shielding property, light resistance, heat resistance, non- orientation, surface hardness and adhesion property to a polarizing element by forming a film having specified water absorption, moisture permeability, folding endurance and transmittance for rays and showing substantially no orientation. SOLUTION: The water absorption of the film is controlled to <=0.1 wt.%, preferably <=0.05 wt.%, and more preferably <=0.01 wt.%. The moisture permeability is controlled to <=150 g/m<2> .24 hr, preferably <=30 g/m<2> .24 hr, and more preferably <=5 g/m<2> .24 hr. The folding endurance is >=500 times, preferably >=750 times, and more preferably >=1000 times. The transmittance for rays is >=90.0%, preferably >=91.0%, and more preferably >=91.5%. The protective film is preferably substantially non-oriented. Namely, since the film is not subjected to a process of molecular orientation such as a stretching process, accurate alignment of the orientation direction of a polarizing element is not required when the film is laminated with the polarizing element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a polarizing plate and a polarizing plate using the same.

[0002]

2. Description of the Related Art A cellulose triacetate film has been frequently used as a protective film for a polarizing element comprising a polyvinyl alcohol-iodine system. However, in fields where moisture resistance is particularly required, such as for outdoor use, cellulose triacetate films are unsuitable due to their high water absorption and moisture permeability, and there has been a demand for an alternative film.

Therefore, a cyclic polyolefin film having excellent water absorption and moisture permeability has been studied (JP-A-6-5111).
No. 7, JP-A-7-77608).

However, cyclic polyolefin films are generally brittle, and crazing and severe cracking and goby cracks occur during the manufacturing process of the polarizing plate, particularly when passing through a roll of a machine, cutting or punching, and the polarizing plate is stably formed. Could not be manufactured.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned disadvantages, and furthermore, the transparency and the ultraviolet shielding property required for a protective film,
An object of the present invention is to provide a protective film having various properties such as light resistance, heat resistance, non-orientation, surface hardness, and adhesion to a polarizing element.

Another object of the present invention is to provide a polarizing plate having excellent initial performance and durability such as moisture resistance, light resistance and heat resistance.

[0007]

According to the present invention, as a means for solving the above problems, the water absorption is 0.1 wt% or less.
Moisture permeability of 150 g / m ² · 24 hr or less, folding resistance of 50
An object of the present invention is to provide a protective film made of a substantially non-oriented film having a light transmittance of at least 0 times and a light transmittance of 90.0% or more, and a polarizing plate using the protective film.

Another object of the present invention is to provide a protective film comprising a film having an ultraviolet transmittance of 10% or less and a polarizing plate using the protective film.

Further, the protective film has an ethylene content of 50 to 80.
A protective film comprising at least one film selected from the group consisting of an ethylene-norbornene addition copolymer and an ethylene-tetracyclododecene addition copolymer, wherein the protective film is Characterized in that it is a polarizing plate comprising:

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film useful as a protective film for a polarizing plate. The film according to the present invention has a water absorption of 0.1 wt% or less, preferably 0.0 wt% or less.
5 wt% or less, more preferably 0.01 wt% or less. When the water absorption increases, the dew condensation resistance and the moisture resistance of the polarizing plate tend to decrease.

The moisture permeability is 150 g / m ² · 24 hr or less,
It is preferably 30 g / m ² · 24 hr or less, more preferably 5 g / m ² · 24 hr or less. When the moisture permeability is large, the moisture resistance of the polarizing plate tends to decrease.

The folding endurance is 500 times or more, preferably 750
Times or more, more preferably 1000 times or more. If the fold resistance is low, the polarizing plate manufacturing process, especially when passing through a roll of a machine or cutting or punching, crazing or severe cracks and goby cracks occur, making it difficult to stably manufacture a polarizing plate Become.

The light transmittance is at least 90.0%, preferably at least 91.0%, more preferably at least 91.5%. When the light transmittance is small, the single light transmittance of the polarizing plate tends to decrease.

The light resistance is, for example, 500 with a fade meter.
It is sufficient that the deterioration of mechanical strength and the change of coloring and the like do not substantially occur for at least an hour, preferably at least 750 hours, more preferably at least 1000 hours.

The heat resistance is, for example, 70 ° C.
Or higher, preferably 75 ° C or higher, more preferably 80 ° C
All that is required is the above.

The protective film is preferably substantially non-oriented. “Substantially non-oriented” means that a step of actively molecular orientation such as a stretching step has not been performed. This is because if they are oriented, they need to be aligned with the orientation direction of the polarizing element without any deviation when bonding to the polarizing element.

The thickness of the protective film on one side is usually 10 to 150
μm, preferably 15 to 100 μm, and more preferably 20 to 80 μm. In the case where the protective film is provided on both sides, a range of a thickness twice as large as the total thickness is exemplified. If the thickness is too thin, it tends to be difficult to handle and it is difficult to ensure moisture permeability. If the thickness is too thick, the cost increases and the folding resistance tends to decrease.

The polarizing element used in the present invention is not particularly limited. For example, a polarizing element obtained by adsorbing and orienting iodine or a dichroic dye on a film made of polyvinyl alcohol, polyethylene terephthalate, polyamide or the like to have a polarizing property. Can be exemplified. In particular, a polarizing element comprising a polyvinyl alcohol-iodine system or a polyvinyl alcohol-dichroic dye system is more preferable from the viewpoint of initial performance.

Examples of the dichroic dye include azo, anthraquinone and tetrazine dichroic dyes.

The adhesive used for bonding the protective film of the present invention and the polarizing element is not particularly limited.
Examples thereof include polyvinyl alcohol-based, acrylic-based, urethane-based, polyester-based, and epoxy-based adhesives and those obtained by adding a curing agent thereto.

As described above, the initial performance is excellent, and the durability is about 95% or more, usually 99% or more after the moisture resistance test and the heat resistance test. Both the initial performance and the durability are excellent. Polarizing plate can be easily obtained.

The protective film of the present invention is preferably a protective film for a polarizing plate having an ultraviolet transmittance of 10% or less and excellent in light resistance. In order to impart light resistance to the polarizing element and prevent deterioration of the liquid crystal due to ultraviolet rays, it is desirable that the protective film has ultraviolet absorbing performance. For that purpose, an ultraviolet absorber may be added to the protective film. The UV absorber may be a known one such as a benzophenone type or a benzotriazole type, but in order to further enhance the effect, it is more preferable to use at least two types of mixtures based on the UV absorption wavelength. In order to impart light resistance to the polarizing element and prevent deterioration of the liquid crystal, the protective film must have an ultraviolet transmittance of 10%.
%, Preferably 3% or less, more preferably 1% or less.

In this way, the deterioration of the liquid crystal due to ultraviolet rays is prevented, and the degree of polarization retention of the polarizing plate after the light resistance test is 95% or more, usually 99% or more.

The present invention also relates to a polarizing plate comprising a specific polarizing element and a protective film.

The polarizing element is made of a polyvinyl alcohol-iodine system or a polyvinyl alcohol-dichroic dye system, and the protective film is as described above.

The polarizing element is manufactured by immersing a film made of polyvinyl alcohol or a derivative thereof in an aqueous solution of iodine to adsorb iodine, and then performing uniaxial stretching orientation in boric acid water. Alternatively, it can be obtained by uniaxially stretching a film made of polyvinyl alcohol or a derivative thereof, adsorbing iodine, and treating with boric acid water. A polarizing element using a dichroic dye instead of iodine is similarly manufactured.

The adhesive used for bonding the protective film and the polarizing element is not particularly limited. For example, an adhesive of polyvinyl alcohol type, acrylic type, urethane type, polyester type, epoxy type or the like or a curing agent therefor Can be exemplified. In particular, aqueous solutions and emulsions are more preferable from the viewpoint of durability.

As described above, the initial performance is as follows: the single transmittance is 42.0% or more, the degree of polarization is 99.9% or more, and the durability is measured after the moisture resistance test, the heat resistance test, and the light resistance test. Each has a retention of 95% or more, usually 99% or more, and a polarizing plate excellent in both initial performance and durability can be easily obtained. By changing the manufacturing conditions of the polarizing element, the initial performance polarization degree may be appropriately manufactured according to the field of use from a general-purpose polarization degree of about 90% to a high polarization degree of 99.9% or more depending on the field of use. It goes without saying.

The protective film having the above excellent properties is preferably made of a cyclic polyolefin film.

The cyclic polyolefin is a generic name. Specifically, (a) a ring-opened (co) polymer of a cyclic olefin is represented by
If necessary, after modification such as addition of maleic acid or cyclopentadiene, a hydrogenated polymer, (b) an addition polymer of a cyclic olefin, or (c) an addition copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene. It is a polymer.

However, after the (a) ring-opening (co) polymer of a cyclic olefin is modified, if necessary, with addition of maleic acid or cyclopentadiene, the hydrogenated polymer is brittle and is used as a protective film. When used, there is a problem that crazing or cracks or goby cracks occur in the manufacturing process of the polarizing plate, and it is difficult to stably manufacture the polarizing plate. In addition, since hydrogenation cannot be completely performed, there is also a problem that light resistance is lacking due to a very small number of remaining double bonds.

The (b) addition polymer of a cyclic olefin is also brittle, and has the above-mentioned problems. On the other hand, (c) addition copolymers of cyclic olefins and α-olefins such as ethylene and propylene can be freely designed from brittle to non-adhesive by adjusting the amount of α-olefin. Can be obtained without problems.

Further, by copolymerizing an α-olefin, there is also an advantage that a protective film having a lower moisture permeability than the above-mentioned resins (a) and (b) can be obtained.

(C) An addition copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene will be described in more detail.

As the cyclic olefin monomer of the copolymer, for example, the following general formula (I)

[0036]

Embedded image

[Wherein, R ^{1 to} R ¹⁶ , R ^a and R ^b each independently represent a hydrogen atom, a halogen atom or a hydrocarbon group. n is 0 or 1, and m represents 0 or 1. q
Is 0 or 1. However, when q is 0, the respective bonds are combined to form a 5-membered ring. And a cyclic olefin of the formula (1).

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the hydrocarbon group include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, and an aromatic hydrocarbon group.

More specifically, examples of the alkyl group having 1 to 20 carbon atoms include methyl, ethyl, propyl, isopropyl, amyl, hexyl, octyl, decyl, dodecyl, octadecyl and the like. And a linear or branched alkyl group.

Examples of the cycloalkyl group having 3 to 15, preferably 5 to 6 carbon atoms include a cyclopentyl group and a cyclohexyl group.

Examples of the aromatic hydrocarbon group include an aryl group and an aralkyl group such as a phenyl group, a tolyl group, a xylyl group, a benzyl group, a phenylethyl group and a naphthyl group.

The hydrocarbon group may be substituted with a halogen atom.

Further, in the general formula (I), R ^{15 to} R
¹⁸ may be bonded to each other (to form a monocyclic or polycyclic ring in combination with each other, and the monocyclic or polycyclic ring may have a double bond. Specific examples of the monocyclic or polycyclic ring are shown below.

[0045]

Embedded image

In the above examples, the carbon atoms numbered 1 or 2 represent the carbon atoms to which R ¹⁵ (R ¹⁶ ) or R ¹⁷ (R ¹⁸ ) are bonded in the above general formula.

Further, R ¹⁵ and R ¹⁶ or R ¹⁷ and R ¹⁸
And may form an alkylidene group. Examples of such an alkylidene group include an alkylidene group having 2 to 20 carbon atoms, such as an ethylidene group, a propylidene group and an isopropylidene group.

The cyclic olefin raw material of the copolymer (c) further includes a compound represented by the following general formula (II).

[0049]

Embedded image

[Wherein, R ^{1 to} R ¹⁹ each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group. p represents an integer of 0 or 1. q represents an integer of 0 or 1. m is 0, 1 or 2. n is 0, 1 or 2. The halogen atom and the hydrocarbon group have the same meaning as in the compound of the formula (I).

Examples of the alkoxy group include a linear or branched alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group and a propoxy group. The alkoxy group may be substituted by a fluorine, chlorine, bromine or iodine atom.

Here, the carbon atom to which R ⁹ and R ¹⁰ are bonded and the carbon atom to which R ¹³ is bonded or the carbon atom to which R ¹¹ is bonded are directly or directly having 1 to 3 carbon atoms. They may be bonded via an alkylene group. That is, the above 2
If the carbon atoms are bonded via an alkylene group, a group represented by R ⁹ and R ^13, or R ¹⁰ and R
^The groups represented by ¹¹ together form an alkylene group of either a methylene group, an ethylene group or a propylene group.

Further, when n = m = 0, R ¹⁵ and R ¹²
May be combined with R ¹⁵ and R ¹³ to form a monocyclic or polycyclic aromatic ring. In this case, as a monocyclic or polycyclic aromatic ring, for example, And the like.

[0054]

Embedded image

Wherein q is as defined above. Specific examples of the cyclic olefin represented by the general formula (I) or (II) are shown below. (1) Bicyclo [2.2.1] -2-heptene (norbornene) optionally substituted by a hydrocarbon group represented by the following formula:

[0056]

Embedded image

As the substituent of norbornene, for example, 5-
Methyl, 5,6-dimethyl, 1-methyl, 5-ethyl, 5-n-butyl, 5-isobutyl, 7-methyl, 5-phenyl, 5-methyl-5
-Phenyl, 5-benzyl, 5-tolyl, 5- (ethylphenyl), 5- (isopropylphenyl), 5- (biphenylyl), 5- (β-naphthyl), 5- (α-naphthyl), 5-
(Anthryl), 5,6-diphenyl and the like.

Still other derivatives include cyclopentadiene-acenaphthylene adduct, 1,4-methano-1,4,4a, 9a-
Tetrahydrofluorene, 1,4-methano-1,4,4a, 5,10,10a
-Bicyclo [2.2.1] such as hexahydroanthracene
2-heptene derivative; tricyclo [4.3.0.1 ^2,5 ] -3-decene, 2-methyltricyclo [4.3.0.1 ^2,5 ] -3-decene, 5
- methyltricyclo [4.3.0.1 ^2,5] -3- tricyclo such decene [4.3.0.1 ^2,5] -3- decene derivatives; tricyclo [4.4.0.1 ^2,5] -3- undecene, 10-methyl Tricyclo [4.4.0.1 ^2,5 ] -3-undecene and other tricyclo [4.4.
0.1 ^2,5 ] -3-undecene derivatives.

[0059] (2) optionally substituted with a hydrocarbon group represented by the following formula tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] -3-
Dodecene:

[0060]

Embedded image

[0061] Examples of the substituent of tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] -3- dodecene, for example 8-methyl, 8-ethyl,
8-propyl, 8-butyl, 8-isobutyl, 8-hexyl, 8-
Cyclohexyl, 8-stearyl, 5,10-dimethyl, 2,10-
Dimethyl, 8,9-dimethyl, 8-ethyl-9-methyl, 11,12-
Dimethyl, 2,7,9-trimethyl, 2,7-dimethyl-9-ethyl, 9-isobutyl-2,7-dimethyl, 9,11,12-trimethyl, 9-ethyl-11,12-dimethyl, 9- Isobutyl-11,12-dimethyl, 5,8,9,10-tetramethyl, 8-ethylidene, 8-ethylidene-9-methyl, 8-ethylidene-9-ethyl, 8-ethylidene-9-isopropyl, 8-ethylidene -9-butyl, 8-n-propylidene, 8-n-propylidene-9-methyl, 8-n-propylidene-
9-ethyl, 8-n-propylidene-9-isopropyl, 8-n-propylidene-9-butyl, 8-isopropylidene, 8-isopropylidene-9-methyl, 8-isopropylidene-9-ethyl, 8-isopropylidene Den-9-isopropyl, 8-isopropylidene-9-butyl,
8-chloro, 8-bromo, 8-fluoro, 8,9-dichloro, 8-phenyl, 8-methyl-8-phenyl, 8-benzyl, 8-tolyl, 8- (ethylphenyl), 8- (isopropylphenyl ), 8,9-diphenyl, 8- (biphenylyl), 8- (β-
Naphthyl), 8- (α-naphthyl), 8- (anthryl),
5,6-diphenyl and the like.

[0062] In yet other derivatives, (cyclopentadiene - acenaphthylene adduct) and adduct of cyclopentadiene; pentacyclo ^{[6.5.1.1 3,6 .0 2,7 .0 9,13]} -
4-pentadecene and its derivatives; pentacyclo [7.4.0.
1 ^2,5 .1 ^{9,12.0 8,13} ] -3-pentadecene and its derivatives;
Pentacyclo ^{[6.5.1.1 3,6 .0 2,7 .0 9,13]} -4,10- Penta cyclopentadiene octadecadienoic compounds such penta decadiene; pentacyclo [8.4.0.1 ^2,5 .1 ^9,12. 0 ^8,13] -3-hexadecene and derivatives thereof; pentacyclo [6.6.1.1 ^{3, 6} .0
^2,7 .0 ^9,14] -4-hexadecene and derivatives thereof; hexacyclo ^{[6.6.1.1 3,6 .1 10,13 .0 2,7 .0} 9,14] -4- heptadecene and derivatives thereof; heptacyclo [8.7.0.1 ^2,9 .1 ^4,7 .1
^11,17 .0 ^3,8 .0 ^12,16] -5-eicosene and derivatives thereof; heptacyclo ^{[8.8.0.1 2,9 .1 4,7 .1 11,18 .0} 3,8 .0 12,17 ]-Five
-Hyneecocene and its derivatives; octacyclo [8.8.
0.1 ^2,9 .1 ^4,7 .1 ^11,18 .1 ^13,16 .0 ^3,8 .0 ^12,17] -5-docosene and derivatives thereof; Nonashikuro [10.9.1.1 ^4,7 .1 ^{13, 20} .1
^15,18 .0 ^2,10 .0 ^3,8 .0 ^12,21 .0 ^14,19] -5-pentacosene and derivatives thereof; Nonashikuro [10.10.1.1 ^5,8 .1 ^14,21 .1
^16,19 .0 ^2,11 .0 ^4,9 .0 ^{13, 22} .0 ^15,20] -6-hexacosenoic and derivatives thereof.

The specific examples of the cyclic olefin represented by the general formula (I) or (II) are described above. More specific structural examples of these compounds are described in Japanese Patent Application No. 5-196.
No. 475, paragraphs [0032] to [0] of the original specification.
054].

The cyclic olefin resin used in the present invention may be a copolymer containing two or more of the above-mentioned cyclic olefin monomers.

The cyclic olefin represented by the above general formula (I) or (II) can be produced by subjecting cyclopentadiene and an olefin having a corresponding structure to a Diels-Alder reaction. .

The cyclic olefin resin used in the present invention is prepared by using one or more of the cyclic olefins represented by the general formula (I) or (II) as described above, for example, in JP-A-60-168708. No., JP-A-61-12081
No. 6, No. 61-115912, No. 61-11
Nos. 5916 and 61-271308 and 61
JP-A-272216, JP-A-62-252406 and JP-A-62-252407 can be produced by appropriately selecting conditions in accordance with the method proposed by the present applicant.

Α-olefin / cyclic olefin random
Copolymer The random copolymer of α-olefin and cyclic olefin is usually 5 to 95 mol% of α-olefin and 95 to 5 mol% of cyclic olefin;
0-80 mol%, 80-20 mol% of cyclic olefin;
More preferably, it contains 70 to 50 mol% of α-olefin and 30 to 50 mol% of cyclic olefin. Note that α-
The composition of the olefin and the cyclic olefin can be measured by ¹³ C-NMR.

In the α-olefin / cyclic olefin random copolymer, a unit derived from the α-olefin and a unit derived from the cyclic olefin are randomly arranged and bonded to have a substantially gel-like crosslinked structure. This can be confirmed by the fact that when this copolymer is dissolved in an organic solvent, this solution does not contain any insoluble matter. For example, when the intrinsic viscosity [η] is measured, it can be confirmed by completely dissolving the copolymer with decalin at 135 ° C.

In the α-olefin / cyclic olefin random copolymer used in the present invention, at least a part of the cyclic olefin represented by the general formula (I) is
It is considered to constitute a repeating unit represented by the following general formula (III), and at least a part of the cyclic olefin represented by the above general formula (II) constitutes a repeating unit represented by the following general formula (IV) it seems to do.

[0070]

Embedded image

Wherein n, m, q, R ^{1 to} R ¹⁸ , R ^a and R ^b are as defined above. ]

[0072]

Embedded image

[Wherein n, m, p, q and R ^{1 to} R
¹⁹ is as defined above. Examples of the α-olefin copolymerized with the above-mentioned cyclic olefin monomer include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, and 3-methyl-1-. Pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-
Methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1
-Hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1
Α-olefins having 3 to 20 carbon atoms, such as -hexadecene, 1-octadecene and 1-eicosene, preferably ethylene and propylene, more preferably ethylene. The copolymerization can be carried out by appropriately combining one or more of the above α-olefin monomers with a cyclic olefin monomer. Of these α-olefins, ethylene is particularly preferably used.

Further, as long as the object of the present invention is not impaired, 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7
-A non-conjugated diene such as octadiene, dicyclopentadiene and 5-vinylnorbornene may be used.

The above-mentioned cyclic olefin monomer and α-olefin can be used in combination of two or more kinds for polymerization.

The α-olefin / cyclic olefin random copolymer is produced by using the α-olefin and the cyclic olefin represented by the general formula (I) or (II) according to the production method disclosed in the above publication. be able to. Among these, the copolymerization reaction is performed in a hydrocarbon solvent,
An α-olefin / cyclic olefin random copolymer can be produced using a catalyst formed from a vanadium compound and an organoaluminum compound soluble in the hydrocarbon solvent as a catalyst.

An α-olefin / cyclic olefin random copolymer can be produced using a solid Group 4 metallocene catalyst.

The solid Group 4 metallocene catalyst comprises a transition metal compound containing at least one ligand having a cyclopentadienyl skeleton (metallocene compound), an organic aluminum oxy compound (aluminoxane), and if necessary. And an organoaluminum compound. Here, the transition metal of Group 4 is zirconium, titanium or hafnium. Examples of the ligand having a cyclopentadienyl skeleton include a cyclopentadienyl group, an indenyl group, a tetrahydroindenyl group, and a fluorenyl group, and these may be substituted with an alkyl group. When the transition metal compound includes two or more ligands having a cyclopentadienyl skeleton, two of these groups may be bonded via another group such as an alkylene group or a silylene group. good. The ligand other than the ligand having a cyclopentadienyl skeleton is usually an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a halogen atom, or the like.

As the organic aluminum oxy compound and the organic aluminum compound, those usually used for producing an olefin polymer can be used. Such a solid group 4 metallocene catalyst is described in detail in, for example, JP-A-61-221206, JP-A-64-106, and JP-A-2-173112.

The cyclic polyolefin useful as the protective film according to the present invention is very limited among the cyclic polyolefins. That is, when the cyclic olefin is norbornene or tetracyclododecene and the α-olefin is ethylene, the ethylene content is 50 to 80 mo.
1%, preferably 52 to 78 mol%, more preferably 55 to 78 mol% of one kind of ethylene-norbornene addition copolymer or ethylene-tetracyclododecene addition copolymer, or the total ethylene content is within the above range. It is a mixture of two or more kinds of ethylene-norbornene addition copolymers and ethylene-tetracyclododecene addition copolymers. If the ethylene content is less than 50 mol%, the film is brittle, and in the manufacturing process of the polarizing plate,
Crazing, cracking, and goby cracking occur, making it difficult to stably produce a polarizing plate. On the other hand, when the ethylene content exceeds 80%, a problem occurs in heat resistance.

Further, the MFR of the cyclic polyolefin is
0.5 to 300 g / 10 min, preferably 2 to 150 g
g / 10 min, more preferably 5 to 100 g / 10
Those within the range of min are preferred. 0.5g / 10
If it is less than min, when the protective film is manufactured by the solution casting method,
The solution viscosity tends to be too high to obtain a uniform film, and if it exceeds 300 g / 10 min, the mechanical strength of the obtained film tends to be weak.

The cyclic polyolefin may be blended with other resins, for example, the above-mentioned resins (a) and (b) or other resins as long as the properties are not significantly impaired.

Further, various additives such as a plasticizer, a lubricant, a stabilizer, and an antistatic agent may be blended.

The method for obtaining the protective film from the cyclic polyolefin resin is not particularly limited. For example, a method utilizing thermoplasticity such as an extrusion method and a calendering method may be used.
From the standpoint of uneven thickness accuracy, a production method using a solution casting method is more desirable.

The solvent used for the casting solution is not particularly limited. Examples thereof include alicyclic hydrocarbons such as cyclohexane and cyclohexene and derivatives thereof, and aromatic hydrocarbons such as toluene, xylene and ethylbenzene and derivatives thereof. Etc. can be exemplified.

Although one kind of solvent may be used, it may be difficult to obtain a smooth film depending on the solution viscosity and drying conditions. At that time, a desirable film can be obtained by adding a leveling agent or the like to the solution or by using at least two kinds of mixed solvents having a difference in boiling point of 10 ° C. or more.

To the casting solution, the above-mentioned ultraviolet absorber may be added in order to prevent deterioration of the liquid crystal due to ultraviolet rays. Since the cyclic polyolefin of the present invention has good compatibility with various ultraviolet absorbers, there is an advantage that the addition amount of the ultraviolet absorber can be freely selected according to the target value of the ultraviolet transmittance.

The thickness of the protective film is usually 10 to 150 μm, preferably 15 to 100 μm, more preferably 20 to 8 μm.
0 μm. If the thickness is too thin, it is difficult to handle,
Also, it tends to be difficult to secure moisture permeability, and if it is too thick, cost tends to increase, and it tends to be difficult to secure folding resistance.

In order to improve the adhesiveness to the polarizing element and the adhesive to be described later, the surface of the protective film is subjected to corona discharge treatment, ozone spraying, ultraviolet irradiation, flame treatment, chemical treatment, and other known surfaces. Processing may be performed. The treatment degree is such that the wetting tension is 37 dyn / cm or more, preferably 40 dyn / cm.
dyn / cm or more, more preferably 45 dyn / cm
That is all.

Thus, the water absorption is 0.1 wt% or less, preferably 0.05 wt% or less, more preferably 0.01 wt% or less, and the moisture permeability is 150 g / m ² · 24 h.
r, preferably 30 g / m ² · 24 hr or less, more preferably 5 g / m ² · 24 hr or less, and a folding resistance of 50
0 times or more, preferably 750 times or more, more preferably 1000 times or more, the light transmittance is 90.0% or more, preferably 91.0% or more, more preferably 91.5% or more, and the ultraviolet light transmittance is 10%. Or less, preferably 3% or less,
If the content is more preferably 1% or less, a protective film made of a substantially non-oriented film having excellent heat resistance and light resistance can be easily obtained. The present invention relates to a polarizing plate comprising a polarizing element and the above-mentioned cyclic polyolefin protective film. As a method of bonding the protective film and the polarizing element, any known method may be used. In the case of bonding using an adhesive, for example, polyvinyl alcohol-based, acrylic-based, urethane-based, polyester-based, epoxy-based adhesives, or those obtained by adding a curing agent thereto can be exemplified. In particular, aqueous solutions and emulsions are more desirable from the viewpoint of durability. In this case, it is desirable that the surface of the protective film be treated as described above. The treatment degree is 37 dyn / cm or more, preferably 40 dyn, in terms of wet tension.
/ Cm, more preferably 45 dyn / cm, and the contact angle with water is 90 degrees or less, preferably 75 degrees or less.

Next, the sheet is cut and, if necessary, punched to obtain a polarizing plate. As described above, the protective film has a fold resistance of 500 times or more, preferably 750 times or more, and more preferably 1000 times or more. Therefore, crazing, cracking, and goby cracking do not occur at the time of bonding, cutting, or punching.

The initial performance of the polarizing plate thus obtained was such that the single transmittance was 42.0% or more and the degree of polarization was 99.9%.
Above, as the durability, after the moisture resistance test, after the heat resistance test,
And the degree of polarization retention after light resistance test is 95% or more,
Usually, it is 99% or more, and both initial performance and durability are excellent.

The polarizing plate is usually coated on one side with an adhesive for sticking to a liquid crystal substrate, a separator is attached, and on the other side, a protective film is attached. The thus manufactured one is used as a transmission type, but a reflection layer may be provided on one side to be used as a reflection type or a semi-transmission type.

The surface of the protective film may be subjected to various processings conventionally applied to a polarizing plate, such as a hard coat layer, an antireflection layer, and an antiglare layer.

[0095]

Next, a description will be given of a typical embodiment of the present invention.

The methods for measuring and evaluating the physical properties used in the present invention are as follows.

The water absorption was 23 ° C. according to ASTM D570.
X 24 hours.

The moisture permeability is PERMARTRAN manufactured by Mocon.
-40 ° C, relative humidity 90% with W600 type moisture permeability measuring device
It measured on condition of.

The folding endurance was measured according to JIS P8115. The smaller the number, the more brittle the film.

In order to evaluate the processability of the protective film, a punching test was performed using a circular dumbbell having a diameter of 11 mm in addition to the bending resistance. When 10 sheets were punched out, all 10 sheets were punched out without abnormality, ○: 1 to 9 sheets were cracked or goby cracked, Δ: All 10 sheets were cracked or goby cracked.

The wetting tension was measured according to JIS K6768.

The retardation is KOB manufactured by Oji Scientific Instruments.
It was calculated from the birefringence using RA-21ADH.

The light transmittance was measured using a spectrophotometer (hereinafter the same) U-3410 spectroph manufactured by Hitachi, Ltd.
400 nm to 700 n using an ometer
It is the average value of the light transmittance values measured continuously up to m. The higher the value, the better the transparency.

The ultraviolet transmittance was measured using a spectrophotometer.
It is the maximum value of the ultraviolet transmittance continuously measured from 250 nm to 380 nm. The smaller the value, the greater the effect of absorbing ultraviolet light.

The single transmittance of the polarizing plate was continuously measured from 400 nm to 700 nm using a spectrophotometer.
This is the average value of the light transmittance of one polarizing plate. The larger the value, the better the transparency of the polarizing plate.

The degree of polarization of the polarizing plate was calculated by the following method.

That is, 2
The polarizing plates are superimposed on each other, and 40
The average value of the light transmittance values continuously measured from 0 nm to 700 nm is defined as T1. Next, two polarizing plates were overlapped so that the orientation directions were orthogonal to each other, and the average value of the light transmittance values measured in the same manner was calculated as T2.
And Then, the degree of polarization was calculated by the following equation (1). The larger the value, the better the polarization performance.

[0108]

(Equation 1)

The humidity test of the polarizing plate was performed at 70 ° C. × 93% RH.
Was carried out in a thermo-hygrostat for 1000 hours.

The degree of polarization retention (the same applies hereinafter) is a value obtained by dividing the polarization degree after the test by the polarization degree before the test and multiplying by 100. The higher the value, the better the durability.

The dew condensation test of the polarizing plate was carried out by using a constant temperature and humidity chamber at 70
The setting was alternately changed for 12 hours each between a temperature of 93 ° C. × 93% RH and an atmosphere of 25 ° C. × 99% RH, and left for 1000 hours in this thermo-hygrostat.

The heat resistance test of the polarizing plate was performed by leaving the polarizing plate in a thermostat at 75 ° C. for 1000 hours.

The light resistance test of the polarizing plate was performed using a FADE TESTER CF-2 manufactured by Shimadzu Corporation as a fade meter.
Irradiation was performed at 40 ° C. for 1000 hours using 0N.

Example 1 As a cyclic polyolefin, an ethylene-norbornene random copolymer (ethylene content: 68 mol%, MFR: 30 g / 10 min, number average molecular weight: 67000) produced by addition polymerization of ethylene and norbornene was used. Was. A test piece was molded using an injection molding machine using this resin, and the physical properties were evaluated. Table 1 shows the results. Example 2 Ethylene-tetracyclododecene random copolymer produced by addition polymerization of ethylene and tetracyclododecene as a cyclic polyolefin (ethylene content: 76 mol%, MFR: 30 g / 10 min, number average molecular weight: 45000) ) Was used. A test piece was prepared using an injection molding machine using this resin, and the physical properties were evaluated. Table 1 shows the results.

Comparative Example 1 Ethylene-norbornene random copolymer produced by addition polymerization of ethylene and norbornene as a cyclic polyolefin (ethylene content: 48 mol%, MFR: 3.0 g / 10 min, number average molecular weight: 56000) Was used. A test piece was molded using an injection molding machine using this resin, and the physical properties were evaluated. Table 1 shows the results.

(Comparative Example 2) As the cyclic polyolefin, 6
-Methyl-1,4,5,8-dimetano-1,4,4a,
Hydrogenated product of a ring-opened polymer of 5,6,7,8,8a-octahydronaphthalene (MFR: 5.0 g / 10 min,
(Number average molecular weight: 40000, hydrogenation rate: 99.8% or more). A test piece was molded using an injection molding machine using this resin, and the physical properties were evaluated. Table 1 shows the results.

[0117]

[Table 1]

(Example 3) 100 parts by weight of the resin obtained in Example 1 was dissolved in a mixed solvent of 80 parts by weight of cyclohexane, 80 parts by weight of toluene and 80 parts by weight of xylene, and a film having a thickness of 30 μm was cast by a casting method. Was produced, and the surface was subjected to a corona discharge treatment in air to obtain a protective film. Table 2 shows the physical property values and evaluation results of the protective film.

Comparative Example 3 A protective film was obtained in the same manner as in Example 3 except that the resin obtained in Comparative Example 1 was used. Table 2 shows the evaluation results of the folding endurance and the dumbbell punching property. Folding endurance,
It turns out that dumbbell punching property is bad.

Comparative Example 4 A protective film was obtained in the same manner as in Example 3 except that the resin obtained in Comparative Example 2 was used. Table 2 shows the evaluation results of the folding endurance and the dumbbell punching property. Folding endurance,
It turns out that dumbbell punching property is bad.

[0121]

[Table 2]

Example 4 A polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., having a thickness of 75 microns) was treated with 1000 parts of water.
It was immersed in an aqueous solution comprising 5 parts by weight, 7 parts by weight of iodine and 105 parts by weight of potassium iodide for 5 minutes to adsorb iodine.
Next, this film was stretched in the longitudinal direction uniaxially by a factor of 4.4 in a 4% by weight aqueous solution of boric acid at 40 ° C., and dried under tension to obtain a polarizing element.

(Example 5) Using a polyvinyl alcohol aqueous solution as an adhesive, the protective films obtained in Example 3 were bonded to both surfaces of the polarizing element obtained in Example 4 to obtain a polarizing plate.
Table 3 shows the initial performance of this polarizing plate and the results of a moisture resistance test, a dew condensation resistance test, and a heat resistance test.

Comparative Example 5 A polarizing plate was obtained in the same manner as in Example 5 except that a cellulose triacetate film having a thickness of 80 μm whose surface was saponified beforehand was used as a protective film. Table 3 shows the initial performance of this polarizing plate and the results of a moisture resistance test, a dew condensation resistance test, and a heat resistance test. It turns out that the results of the humidity resistance test and the dew condensation resistance test are poor. For reference, the water absorption and the moisture permeability of the cellulose acetate film are shown to be 3%.
%, And the moisture permeability is 930 g / m ² · 24 hr, indicating that both the water absorption rate and the moisture permeability are poor.

[0125]

[Table 3]

(Example 6) 100 parts by weight of the resin obtained in Example 2 and 2- (2'-hydroxy-
3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole 1 part by weight, and 2,4-di-
t-butylphenyl-3 ', 5'-di-t-butyl-
1 part by weight of 4′-hydroxybenzoate was dissolved in a mixed solvent of 80 parts by weight of cyclohexane and 160 parts by weight of xylene to produce a 70 μm thick film by a casting method. A protective film was obtained by corona discharge treatment. Table 4 shows the physical property values and evaluation results of this protective film.

[0127]

[Table 4]

Example 7 A polyvinyl alcohol film having a thickness of 75 μm was uniaxially stretched 4.0 times in the machine direction. The film is then kept in tension and water 100
It was immersed in an aqueous solution consisting of 0 parts by weight, 6 parts by weight of iodine, and 90 parts by weight of potassium iodide for 1 minute to adsorb iodine.
Then, in a 5% by weight aqueous solution of boric acid at 60 ° C., 1.1
After stretching uniaxially in the longitudinal direction by a factor of two, drying was performed in a tensioned state to obtain a polarizing element.

The protective films obtained in Example 6 were adhered to both surfaces of the polarizing element using an acrylic emulsion adhesive and a polyisocyanate-based curing agent to obtain a polarizing plate. Table 5 shows the initial performance and the results of the moisture resistance test, the dew condensation resistance test, the heat resistance test, and the light resistance test of the polarizing plate.

[0130]

[Table 5]

[0131]

According to the present invention, a protective film having various properties required for a protective film, such as transparency, ultraviolet shielding property, light resistance, heat resistance, non-orientation, surface hardness, and adhesion to a polarizing element, is provided. A membrane can be provided.

Further, the polarizing plate of the present invention is excellent in initial performance and durability such as moisture resistance, light resistance and heat resistance.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Ken Yamamoto 1 Ikurashinmachi Ishiburo, Ayabe-shi, Kyoto Gunze Co., Ltd. Kyoto Research Institute (72) Inventor Hirose Toshiyuki 6-1, Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture No. 2 In the polymer market development center of Mitsui Chemicals, Inc.

Claims (4)

[Claims] 1. A water absorption rate of 0.1% by weight or less and a moisture permeability of 15% or less.
A protective film for a polarizing plate, comprising a substantially non-oriented film having 0 g / m ² · 24 hr or less, a fold resistance of 500 times or more, and a light transmittance of 90.0% or more. 2. An ultraviolet ray transmittance of 10% or less.
3. The protective film for a polarizing plate according to item 1. 3. The protective film has an ethylene content of 50 to 80 mol%.
The protective film for a polarizing plate according to claim 1 or 2, which is at least one film selected from the group consisting of an ethylene-norbornene addition copolymer and an ethylene-tetracyclododecene addition copolymer. 4. A polarizing plate comprising a polarizing element comprising iodine or a dichroic dye and a polyvinyl alcohol-based film, and the protective film according to claim 1 attached to at least one side of the polarizing element.