JP2011128356A - Protective film for polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective film for polarizing plate which has high transparency and excellent knurling aptitude. <P>SOLUTION: The protective film 1 for polarizing plate is composed by laminating, with a melt co-extrusion molding, a polynorbornene based resin (A) and a polynorbornene based resin (B) containing 0.1 wt.% to 1.0 wt.% fine spherical silica particles having mean primary particle diameter of 0.1 μm to 1.0 μm. Knurled parts 4 are provided at end parts 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a protective film for a polarizing plate using a polynorbornene resin.

Polynorbornene-based resins are excellent in heat resistance, transparency, moldability, and the like and have been conventionally used as materials for films for optical applications. For example, a polynorbornene resin film may be used as a film constituting the liquid crystal display device.
In such a polynorbornene-based resin film, the polynorbornene-based resin may contain fine particles from the viewpoint of improving the slipperiness of the film surface. For example, silica is known as the fine particles (see Patent Documents 1 to 5).

Japanese Patent No. 3499974 JP 2008-274102 A JP 2008-7746 A JP 2006-348114 A JP 2007-106081 A

  One application of the polynorbornene resin film is a polarizing plate protective film. In addition to high transparency, the protective film for polarizing plates is required to have excellent handling properties.

  In view of this, it is conceivable to improve the handling properties by adding silica fine particles to a polarizing plate protective film using a polynorbornene resin to improve the surface slipperiness. However, when a large amount of silica fine particles are included in the protective film for polarizing plate in order to realize high handling properties, the internal haze increases, and the transparency of the protective film for polarizing plate tends to be impaired.

  For this reason, high handling is realized by combining the improvement of slipperiness by including silica fine particles and the application of knurling (also referred to as knurling) to the edge of the protective film for polarizing plate. Can be considered. However, in the conventional polarizing plate protective film using a polynorbornene-based resin containing silica fine particles, when the knurling is performed, the knurling portion is crushed over time and an appropriate knurling portion is not formed, or the knurling portion is cracked. There was a tendency to occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a protective film for a polarizing plate having high transparency and excellent knurling suitability.

As a result of diligent investigations by the present inventors to solve the above-mentioned problems, a laminate obtained by melt coextrusion molding of a polynorbornene resin and a polynorbornene resin containing a predetermined amount of spherical silica fine particles having a predetermined average primary particle diameter is used. The present inventors have found that the film has excellent properties as a protective film for polarizing plates and has excellent suitability for knurling, and has completed the present invention.
That is, the gist of the present invention is the following [1] to [4].

[1] A layer of the polynorbornene resin (A) obtained by melt coextrusion molding of the polynorbornene resin (A) and the polynorbornene resin (B) containing silica fine particles, and the polynorbornene resin A protective film for a polarizing plate comprising a B layer comprising (B),
The silica fine particles are spherical with an average primary particle size of 0.1 μm to 1.0 μm,
The polynorbornene-based resin (B) contains 100 wt% of the total amount of the polynorbornene-based resin (B), and contains 0.1 to 1.0 wt% of the silica fine particles,
The protective film for polarizing plates which has a knurling part in the edge part of the said protective film for polarizing plates.
[2] The knurling portion is a convex assembly.
The top of the convex portion is formed of a quadrilateral with one side having a length of 0.2 mm to 0.6 mm,
The distance between the adjacent convex portions is 0.5 mm to 1.2 mm,
The protective film for a polarizing plate according to [1], wherein a ratio d1 / d2 between the height (d1) of the convex portion and the thickness (d2) of the protective film for a polarizing plate is 0.2 to 0.8.
[3] The thickness of the polarizing plate protective film is 40 μm or less,
The protective film for a polarizing plate according to [1] or [2], wherein 5A ≦ dA / dB ≦ 30 is satisfied when the thickness of the A layer is dA and the thickness of the B layer is dB.
[4] The protective film for a polarizing plate according to any one of [1] to [3], which includes the B layer, the A layer, and the B layer in this order.

  The protective film for polarizing plates of the present invention is excellent in transparency and has an excellent aptitude for knurling. Therefore, a knurling part that is less likely to be crushed over time can be formed, so that handling properties superior to those of the conventional art can be exhibited. Furthermore, since the knurling part can be easily formed, the manufacturing efficiency is excellent.

FIG. 1 is a perspective view schematically showing a protective film for a polarizing plate according to one embodiment of the present invention. FIG. 2 is a plan view schematically showing an enlarged part of the knurling part of the protective film for polarizing plate according to one embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing an enlarged part of a protective film for a polarizing plate according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the following embodiments and examples, and departs from the gist of the present invention and its equivalent scope. Any change can be made without departing from the scope. In the following description, “polynorbornene resin (A)” “A”, “polynorbornene resin (B)” “B”, “A layer” “A”, The symbol “B” of “B layer” and the symbol “H” of “six-membered ring structure H” are symbols assigned to distinguish the component with the symbol from other components, respectively. It is not a sign representing meaning other than element distinction.

[1. Overview〕
The protective film for polarizing plate of the present invention comprises a polynorbornene resin (A) and a polynorbornene resin (B) containing a predetermined amount of predetermined spherical silica fine particles (hereinafter referred to as “spherical silica fine particles” as appropriate). It is a film having a laminated structure formed by lamination by melt coextrusion molding. Therefore, the protective film for polarizing plates of the present invention comprises a layer composed of the polynorbornene resin (A) (hereinafter referred to as “A layer” as appropriate) and a layer composed of the polynorbornene resin (B) (hereinafter referred to as “appropriately” B layer "). Moreover, the protective film for polarizing plates of this invention has a knurling part in the edge part.

  The protective film for polarizing plate of the present invention is provided with a B layer containing a predetermined amount of predetermined spherical silica fine particles, so that it has high transparency and excellent knurling suitability even though it contains silica fine particles. For this reason, by applying an appropriate knurling to the protective film for polarizing plate of the present invention, the handling property can be improved not only by the surface slipperiness by the spherical silica fine particles but also by the action of the knurling part.

[2. Layer of polynorbornene resin (A): A layer]
The protective film for polarizing plates of this invention is equipped with A layer which consists of polynorbornene-type resin (A). A polynorbornene resin is a resin containing a norbornene polymer.

  Norbornene polymers include ring-opening polymers of norbornene monomers, ring-opening copolymers of norbornene monomers and other monomers capable of ring-opening copolymerization, hydrides thereof, and addition polymers of norbornene monomers. And an addition copolymer of a norbornene-based monomer and another monomer copolymerizable therewith. Moreover, a norbornene polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Examples of the norbornene-based monomer include bicyclo [2.2.1] -hept-2-ene (common name: norbornene) and derivatives thereof (having a substituent in the ring), tricyclo [4.3.1 ^{2, 5} . 0 ^1,6 ] -deca-3,7-diene, tetracyclo [7.4.1 ^10,13 . 0 ^1,9 . 0 ^2,7 ] -trideca-2,4,6,11-tetraene, tetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] -dodecaene and derivatives having a substituent on these rings. Examples of the substituent present in the ring include an alkyl group, an alkylene group, a vinyl group, and an alkoxycarbonyl group. In addition, the said norbornene-type monomer may have only 1 type of these substituents, and may have 2 or more types. Furthermore, each of these norbornene monomers may be used alone or in combination of two or more at any ratio.

Examples of other monomers capable of ring-opening copolymerization with norbornene-based monomers include monocyclic olefin-based monomers such as cyclohexene, cycloheptene, and cyclooctene.
Examples of other monomers that can be addition copolymerized with norbornene-based monomers include α-olefins having 2 to 12 carbon atoms such as ethylene, propylene, and 1-butene; styrenes such as styrene and α-methylstyrene; Examples include chain conjugated dienes such as 3-butadiene and isoprene; vinyl ethers such as ethyl vinyl ether.
In addition, the other monomer copolymerizable with the norbornene-based monomer may be used alone or in combination of two or more at any ratio.

  When copolymerizing a norbornene monomer and another monomer copolymerizable therewith, the ratio of the structural unit derived from the norbornene monomer and the structural unit derived from the other monomer copolymerizable in the copolymer is The weight ratio (norbornene monomer / other monomer) is usually 30/70 or more, preferably 50/50 or more, more preferably 70/30 or more, and usually 99/1 or less, preferably 97/3. Hereinafter, it is appropriately selected so as to be in a range of 95/5 or less.

  Among the norbornene polymers, in particular, a hydrogenated product of a ring-opening polymer of a polycyclic norbornene monomer containing 50% by weight or more of a norbornene monomer represented by the following formula (1), A norbornene polymer having a double bond hydrogenation rate of 98% or more and a hydrogenation rate of the six-membered ring structure H of 90% or more (hereinafter referred to as “specific norbornene polymer” as appropriate) is preferred. In addition, in the following formula (1), the six-membered ring structure H located below may have at least one double bond.

Hereinafter, the specific norbornene polymer will be described. In addition, the patent 3465807 gazette can be referred for the manufacturing method of a specific norbornene polymer.
Specific examples of the norbornene monomer represented by the formula (1) include 1,4-methano-1,4,4a, 4b, 5,8,8a, 9a-octahydro-9H-fluorene, 1,4 -Methano-1,4,4a, 4b, 5,6,7,8,9a-decahydro-9H-fluorene, 1,4-methano-1,4,4a, 9a-tetrahydrofluorene (hereinafter referred to as “ MTF ”)) and the like. Among them, MTF that is easy to manufacture and purify is preferably used. For example, MTF can be obtained by adding indene and cyclopentadiene by Diels-Alder reaction.

  You may use together the norbornene-type monomer represented by Formula (1), and the other monomer which can be ring-opening copolymerized. Examples of such other monomers include, for example, JP-A-51-80400, JP-A-60-26024, JP-A-1-168725, JP-A-1-190726, and JP-A-3. Norbornene monomers known from -14882, JP-A-3-122137, JP-A-4-63807, JP-A-2-227424, JP-A-2-276842, etc. , Norbornene, derivatives thereof substituted with alkyl groups, alkylidene groups, or aromatic groups, and these norbornene or derivatives thereof are polar such as halogen, hydroxyl group, ester group, alkoxy group, cyano group, amide group, imide group, silyl group, etc. Substituted norbornene substituted with a group (specifically, 2-norbornene, 5-methyl-2-norbornene 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5-cyano-2-norbornene , 5-methyl-5-methoxycarbonyl-2-norbornene, 5-hexyl-2-norbornene, 5-octyl-2-norbornene, 5-octadecyl-2-norbornene, etc.); one or more cyclopentadiene is added to norbornene Monomers, derivatives and substitutes similar to those described above, for example, 1,4: 5,8-dimethano-1,2,3,4,4a, 5,8,8a-2,3-cyclopentadienoocta Hydronaphthalene, 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydrona Talen, 1,4: 5,10: 6,9-trimethano-1,2,3,4,4a, 5,5a, 6,9,9a, 10,10a-dodecahydro-2,3-cyclopentadieno Anthracene and the like; a monomer having a polycyclic structure in which cyclopentadiene is multimerized, and derivatives and substitutes thereof similar to those described above, such as dicyclopentadiene and 2,3-dihydrodicyclopentadiene; cyclobutene, 1-methylcyclopentene, 3 -Methylcyclobutene, 3,4-diisopropenylcyclobutene, cyclopentene, 3-methylcyclopentene, cyclooctene, 1-methylcyclooctene, 5-methylcyclooctene, cyclooctatetraene, 1,5-cyclooctazine, Monocyclic cycloolefins such as cyclododecene; acetylene, propyne, 1-butene, etc. Acetylenes which are substituted acetylenes; dienes having double bonds at both ends such as 1,6-heptadiene; In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The amount of other monomers capable of ring-opening copolymerization with the norbornene monomer represented by the formula (1) varies depending on the reactivity of these monomers, but in the resulting ring-opening polymer. The repeating structural unit derived from the norbornene monomer represented by the formula (1) is usually 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more. It is the quantity which becomes. If the number of repeating structural units derived from the norbornene-based monomer represented by the formula (1) is too small in the obtained ring-opening polymer, the birefringence of the specific norbornene polymer that is a polymer hydrogenated product is not reduced. Moreover, when oil and fat adhere, mechanical strength may fall.

  The method for ring-opening polymerization of the monomer is not particularly limited, and for example, ring-opening polymerization may be performed using a metathesis polymerization catalyst (metathesis polymerization). Examples of the metathesis polymerization catalyst include Japanese Patent Publication No. 41-20111, Japanese Patent Publication No. 46-14910, Japanese Patent Publication No. 57-17883, Japanese Patent Publication No. 57-61044, Japanese Patent Publication No. 54-86600. These are known from Japanese Utility Model Laid-Open No. 58-127728, Japanese Patent Laid-Open No. 1-240517, and the like, and essentially comprise (a) a transition metal compound catalyst component and (b) a metal compound promoter component.

The (a) transition metal compound catalyst component used as the metathesis polymerization catalyst is a compound of a transition metal of group IVB, VB, VIB, VIIB, or VIII of Deming, for example, a halide, oxy of these transition metals Halides, alkoxy halides, alkoxides, carboxylates, (oxy) acetylacetonates, carbonyl complexes, acetonitrile complexes, hydride complexes, derivatives thereof, complexes of these or derivatives of these, such as P (C ₅ H ₅ ) ₃ And a complexed product of the agent. Specific _{examples, TiCl 4, TiBr 4, VOBr} 3, WBr 4, WBr 6, WCl 2, WCl 4, WCl 5, WCl 6, WF 4, WI 2, WOCl 4, MoBr 2, MoBr 3, MoBr 4 , MoCl ₃ , MoCl ₄ , MoF ₄ , MoOCl ₄ , WO ₂ , H ₂ WO ₄ , NaWO ₄ , K ₂ WO ₄ , (H ₄ N) ₂ WO ₄ , CaWO ₄ , CuWO ₄ , MgWO _4, etc. The In addition, (a) transition metal compound catalyst component may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The (b) metal compound promoter component used as a metathesis polymerization catalyst is a compound of Group IA, IIA, IIB, IIIA, or IVA metal of the Deming periodic table, and has at least one metal-carbon bond or metal-hydrogen bond. Examples thereof include organic compounds such as Al, Sn, Li, Na, Mg, Zn, Cd, and B. Specific examples include organoaluminum compounds such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, triisobutylaluminum, triphenylaluminum, di-n-propylaluminum monochloride; tetramethyltin, diethyl Organotin compounds such as dimethyltin, tetraethyltin, dibutyldiethyltin, tetrabutyltin; organolithium compounds such as n-butyllithium; organosodium compounds such as n-pentyl sodium; methylmagnesium iodide, ethylmagnesium bromide, t-butyl Organomagnesium compounds such as magnesium chloride and allylmagnesium chloride; Organozinc compounds such as diethylzinc; Diethylcadmium Machine cadmium compounds; organoboron compounds such as trimethylboron; and the like. In addition, (b) a metal compound promoter component may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The metal atom of the (b) metal compound promoter component is usually 1 mol or more, preferably 2 mol or more, and usually 100 mol or less, preferably 1 mol of the metal atom of the transition metal compound catalyst component. It is used in the range of 50 mol or less. If the amount of the (b) metal compound promoter component is too small relative to the (a) transition metal compound catalyst component, sufficient activity cannot be obtained with respect to the amount of the (a) transition metal compound catalyst component. b) The removal of the metal compound promoter component becomes difficult and the cost becomes high.

  In addition to the (a) transition metal compound catalyst component and the (b) metal compound promoter component, a third component can be used in combination to increase the metathesis polymerization activity. Examples of such third components include aliphatic tertiary amines, aromatic tertiary amines, molecular oxygen, alcohols, ethers, peroxides, carboxylic acids, acid anhydrides, acid chlorides, esters, ketones. , Nitrogen-containing compounds, sulfur-containing compounds, halogen-containing compounds, molecular iodine, and other Lewis acids. Of these, aliphatic, aromatic tertiary amines or ethers are preferred. Specific examples thereof include triethylamine, dimethylaniline, tri-n-butylamine, pyridine, α-picoline, diethyl ether, di-i-propyl ether, di-n-butyl ether and the like. Moreover, since the compound which has OH groups, such as alcohol, functions as an inactivating agent which inhibits metathesis polymerization activity when it is used in excess of the stoichiometric amount, it is preferably used in a stoichiometric amount or less. Here, the stoichiometric amount is a compound having an OH group as a product of a) the number of moles of the transition metal compound catalyst component and a) the oxidation number of the transition metal contained in the transition metal compound catalyst component. The molar amount expressed by the value divided by the number of OH groups per molecule. In addition, a 3rd component may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  (A) The third component is usually 0.005 mol or more, preferably 0.05 mol or more, and usually 10 mol or less, preferably 3 mol or less with respect to 1 mol of the transition metal compound catalyst component. It is done. (A) If the third component is too small relative to the transition metal compound catalyst component, the effect of the third component will be small, and if it is too large, it will be difficult to remove the excess third component or the cost will be high.

Metathesis polymerization is usually carried out in an inert organic solvent. Examples of the inert organic solvent include aromatic hydrocarbons such as benzene and toluene; aliphatic hydrocarbons such as n-pentane and hexane; alicyclic hydrocarbons such as cyclohexane and decalin; ethers such as tetrahydrofuran and ethylene glycol dimethyl ether. And the like. In addition, an inert organic solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
The amount of the inert organic solvent used is usually 0.8 parts by weight or more, preferably 1 part by weight or more, and usually 20 parts by weight or less, preferably 10 parts by weight or less with respect to 1 part by weight of the monomer. is there.

The method for recovering the ring-opened polymer from the polymerization reaction solution is not particularly limited. For example, if necessary, the polymerization reaction solution may be added to a large amount of a poor solvent (methanol, isopropanol, acetone, etc.), the ring-opened polymer is folded and solidified, and the solvent is removed by filtration. However, when the solvent of the polymerization reaction solution is used as it is as a solvent for the subsequent hydrogenation reaction as described later, it is not always necessary to separate and recover the ring-opened polymer.
As will be described later, when a specific norbornene polymer having a number average molecular weight (Mn) of 12,000 or more is to be obtained, the ring-opening polymer obtained by the metathesis polymerization is measured by a gel permeation chromatography method using a toluene solvent. The number average molecular weight (Mn) in terms of polystyrene is usually 12,000 or more, preferably 14,000 or more, more preferably 15,000 or more, and usually 50,000 or less, preferably 40,000 or less. The molecular weight is preferably 30,000 or less, and the weight average molecular weight (Mw) is usually 20,000 or more, preferably 25,000 or more, more preferably 30,000 or more, and usually 80,000 or less. , Preferably 70,000 or less, more preferably 60,000 or less.

  A specific norbornene polymer is obtained by hydrogenating the obtained ring-opening polymer. Hydrogenation is usually carried out by bringing the ring-opening polymer and hydrogen into contact in the presence of a hydrogenation catalyst. Usually, hydrogenation is carried out in a solvent, and the same solvent as used for the polymerization is used. When the solvent of the polymerization reaction solution is used as it is as the solvent for the hydrogenation reaction, it is not always necessary to prepare the hydrogenation reaction solution after depositing and solidifying the ring-opened polymer. A hydrogenation reaction liquid can be prepared by mixing with a catalyst. In that case, before mixing the hydrogenation catalyst, a polymerization catalyst deactivator (for example, an alcohol such as methanol, butanol, isopropanol, or a compound having an OH group such as water) is mixed in the polymerization reaction solution to react. It may be stopped. However, the deactivator causes a decrease in the hydrogenation activity and tends to make it impossible to increase the hydrogenation rate. Therefore, it is preferable to perform hydrogenation without mixing the deactivator. In particular, when a homogeneous catalyst is used, the deactivator tends to greatly inhibit the hydrogenation catalyst, so it is particularly preferable to hydrogenate without using the deactivator.

  The hydrogenation catalyst may be, for example, a homogeneous catalyst composed of (c) a transition metal compound and (d) a reducing metal compound, or a heterogeneous catalyst in which a catalyst metal is supported on a support. Homogeneous catalysts are easy to disperse in the hydrogenation reaction solution, so the amount of catalyst may be small, and since they are active without high temperature and pressure, the polymer does not decompose or gel, and low cost and stable quality Excellent in properties. On the other hand, a heterogeneous catalyst becomes highly active by increasing the temperature and pressure, and can be hydrogenated in a short time. Further, the catalyst can be easily removed and the production efficiency is excellent.

The homogeneous catalyst is known, for example, in JP-A-58-43412, JP-A-60-26024, JP-A-64-24826, JP-A-1-138257, and the like. is there.
(C) Transition metal compounds include compounds of transition metals belonging to any of Group I or Groups IV to VIII of the Deming Periodic Table, such as Cr, Mo, Fe, Mn, Co, Ni , Halides of transition metals such as Pd and Ru, alkoxides, acetylacetonates, sulfonates, carboxylates, naphthenates, trifluoroacetates, stearates and the like. Specific examples include manganese (III) acetylacetonate, cobalt (III) acetylacetonate, bis (triphenylphosphine) cobalt dichloride, nickel (II) acetylacetonate, bis (tributylphosphine) palladium and the like. In addition, (c) a transition metal compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  (D) The reducing metal compound is a compound of Group IA, IIA, IIB, IIIA, or IVA metal of the Deming periodic table, and has at least one metal-carbon bond or metal-hydrogen bond Examples thereof include Al compounds, Li compounds, Zn compounds, Mg compounds, and the like. Specific examples include trimethylaluminum, triphenylaluminum, diethylaluminum chloride, ethylaluminum sesquichloride, diethylaluminum hydride, n-propyllithium, sec-butyllithium, p-tolyllithium and the like. In addition, (d) a reducing metal compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the combination of (c) transition metal compound and (d) reducing metal compound include (c) organometallic compound of Mn, Ti, Fe, Co or Ni, halide, alkoxide, acetylacetate as transition metal compound. Catalysts combining nates, sulfonates, or naphthenates with (d) organic compounds such as Al, Li, Zn, Mg, or hydrides as reducing metal compounds are highly active, and reaction inhibition and activity reduction due to impurities This is preferable because of the small influence. Further, (c) a catalyst in which Ti, Fe, Co or Ni organometallic compound, halide, alkoxide or acetylacetonate as transition metal compound and (d) alkylaluminum or alkyllithium as reducing metal compound are combined. However, it is particularly preferable because it is highly active and the influence of reaction inhibition and activity reduction due to impurities is particularly small.

  The amount ratio of the component of (c) transition metal compound and (d) reducible metal compound depends on the type of each component, but in general, (d) reduction with respect to 1 mol of metal atom of (c) transition metal compound. The metal atom of the conductive metal compound is usually 0.5 mol or more, preferably 1 mol or more, and usually 50 mol or less, preferably 8 mol or less. If it is too much or too little, the catalytic activity of the hydrogenation reaction is insufficient. In particular, when it is too much, gelation or side reaction may occur.

Heterogeneous catalysts are also known and include, for example, those in which a hydrogenation catalyst metal such as Ni or Pd is supported on a carrier. In particular, when it is desirable that the amount of impurities and the like is small, it is preferable to use an adsorbent such as alumina or diatomaceous earth as the carrier, and the pore volume is usually 0.5 cm ³ / g or more, preferably 0.8. Alumina having a specific surface area of 7 cm ³ / g or more and preferably 250 cm ² / g or more is used. When such a carrier is used, a transition metal atom or the like derived from the catalyst or the like used in the polymerization can be adsorbed on the carrier, and a hydrogenated product with less impurities can be obtained.

  The amount of the hydrogenation catalyst used in the hydrogenation reaction varies depending on the type and combination of each component in the case of a homogeneous catalyst, but the transition metal compound (c) of the transition metal compound is usually 0 with respect to 100 g of the ring-opening polymer. 0.001 mmol or more, preferably 0.1 mmol or more, usually 1000 mmol or less, preferably 100 mmol or less. In the case of a heterogeneous catalyst, the amount of the hydrogenation catalyst used in the hydrogenation reaction varies depending on the type of catalyst metal, the state of loading on the carrier, etc., but the amount of catalyst metal relative to 100 g of the ring-opening polymer. Is usually 0.1 g or more, preferably 1.0 g or more, and usually 20 g or less, preferably 15 g or less. If an excessive amount of the hydrogenation catalyst is contained in the hydrogenation reaction solution, the cost is high, and post-treatment such as removal of the hydrogenation catalyst is difficult. If the amount is too small, the reaction efficiency tends to deteriorate.

The hydrogenation reaction is performed by introducing hydrogen into the hydrogenation reaction solution. For example, a method of sufficiently bringing the introduced hydrogen into contact with the polymer under stirring is preferable. The pressure of hydrogen is usually 0.1 kgf / cm ² or more, preferably 2 kgf / cm ² or more, usually 100 kgf / cm ² or less, preferably 50 kgf / cm ² or less. If the hydrogen pressure is too low, the hydrogenation reaction may not proceed. If it is too high, it is difficult to control the reaction, and side reactions and gelation may occur.

  The hydrogenation reaction is usually 0 ° C. or higher and 250 ° C. or lower, preferably 20 ° C. or higher and 200 ° C. or lower when a homogeneous catalyst is used, and preferably 200 ° C. or higher, more preferably 210 ° C. when a heterogeneous catalyst is used. Above and preferably, it is carried out at 240 ° C. or lower, more preferably 230 ° C. or lower. If the temperature is too low, the reaction rate tends to be slow, and if it is too high, the ring-opening polymer or the hydrogenated product tends to be decomposed or gelled, and the energy cost tends to increase.

  The hydrogenation rate of the double bond in the main chain of the specific norbornene polymer is usually 98% or more, preferably 99% or more, more preferably 99.5% or more, and the hydrogenation rate of the six-membered ring structure H is usually 90%. % Or more, preferably 95% or more, more preferably 98% or more. If the hydrogenation rate of the main chain is too low, the hydrogenated product tends to deteriorate due to oxidation in high temperature environments, etc., and birefringence may not be reduced if the hydrogenation rate of the six-membered ring structure H is too low. There is sex. When the six-membered ring structure H is an aromatic ring structure, the hydrogenation rate of the aromatic ring structure is lower than the hydrogenation rate of the double bond in the main chain depending on the type of hydrogenation catalyst, the hydrogenation reaction conditions, and the like. However, in the case of other six-membered ring structures, the hydrogenation rate of the six-membered ring structure is usually equal to the hydrogenation rate of the double bond in the main chain.

  The method for recovering the specific norbornene polymer which is a ring-opening polymer hydrogenated product from the hydrogenation reaction liquid is not particularly limited. For example, as in the above-described recovery of the ring-opening polymer, the hydrogenation reaction liquid is added to a large amount of a poor solvent (methanol, isopropanol, acetone, etc.) to precipitate and solidify the ring-opening polymer hydrogenated product. What is necessary is just to remove by filtration.

  The norbornene polymer has a number average molecular weight (Mn) measured by gel permeation chromatography using a cyclohexane solvent, and is usually 12,000 or more, preferably 14,000 or more, more preferably 15,000 or more in terms of polyisoprene. Yes, usually 50,000 or less, preferably 40,000 or less, more preferably 30,000 or less. The norbornene polymer also has a weight average molecular weight (Mw) of usually 20,000 or more, preferably 25,000 or more, more preferably 30,000 or more, and usually 80,000 or less, preferably 70,000. Below, more preferably 60,000 or less. Furthermore, the molecular weight distribution (Mw / Mn) of the norbornene polymer is preferably 3.0 or less, more preferably 2.8 or less, and particularly preferably 2.5 or less. In particular, the number average molecular weight (Mn) of the specific norbornene polymer is preferably in the above range. That is, the norbornene polymer is a hydrogenated product of a ring-opening polymer of a polycyclic norbornene monomer containing 50% by weight or more of the norbornene monomer represented by the formula (1), The hydrogenation rate of the heavy bond is 98% or more, the hydrogenation rate of the six-membered ring structure H is 90% or more, and the number average molecular weight (Mn) measured by gel permeation chromatography is 12,000 or more in terms of polyisoprene. The hydrogenated product is particularly preferred. If the molecular weight is too small, the mechanical strength is greatly reduced when oil or fat adheres, and the limit stress tends to be reduced. If the molecular weight is too large, the moldability may be deteriorated. Further, if the molecular weight distribution is too large, the moldability may be deteriorated.

The polynorbornene resin (A) may contain other components in addition to the norbornene polymer as long as the effects of the present invention are not significantly impaired.
For example, the polynorbornene-based resin (A) includes an ultraviolet absorber, a plasticizer (for example, phthalate esters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP); tributyl phosphate (TBP), triethyl phosphate ( TEP) and other phosphoric acid esters; fatty acid esters such as butyl oleate; adipic acid esters such as dioctyl adipate (DOA); and polymers other than norbornene polymers (eg, dicyclopentadiene, diene, aliphatic And water white-based petroleum resins or hydrogenated products thereof), antioxidants, lubricants, and the like. In addition, the polynorbornene-based resin (A) may include one of the other components alone, or may include two or more in combination at any ratio.

  If the amount of the other component contained in the polynorbornene resin (A) is too large, bleeding out and white turbidity may occur. Therefore, it is desirable that the above-mentioned bleed out and white turbidity do not occur. Moreover, since the other components exemplified here usually have an action of lowering the glass transition temperature Tg (A) of the polynorbornene resin (A), by appropriately adjusting the amount of the other components exemplified, The glass transition temperature Tg (A) of the polynorbornene resin (A) can be kept within a desired range.

  The glass transition temperature Tg (A) of the polynorbornene resin (A) is usually 148 ° C. or higher and 180 ° C. or lower. By keeping the glass transition temperature Tg (A) of the polynorbornene resin (A) within the above range, the moldability of the polynorbornene resin (A) is improved and knurling can be easily performed.

Although the protective film for polarizing plates of this invention may be equipped with two or more A layers which consist of a polynorbornene-type resin (A), it usually has only one layer.
The thickness of the A layer is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 40 μm or less, preferably 35 μm or less, more preferably 30 μm or less. In addition, in the protective film for polarizing plates of this invention, unless otherwise indicated, thickness refers to the thickness of parts other than a knurling part. In addition, the thickness of the layer is measured by measuring the total thickness of the film using a commercially available contact thickness gauge, then cutting the thickness measurement portion and observing the cross section with an optical microscope, and determining the thickness ratio of each layer. Obtain and calculate from the ratio. The above operation is performed at regular intervals in the MD direction of the film (the film flow direction in the stretching apparatus, that is, the longitudinal direction of the film) and the TD direction (the direction perpendicular to the MD direction on the film surface), and the average thickness is calculated. The average value is determined as the layer thickness.

[3. Layer of polynorbornene resin (B): B layer]
The protective film for polarizing plates of this invention is equipped with B layer which consists of polynorbornene-type resin (B). The polynorbornene resin (B) is a polynorbornene resin containing predetermined spherical silica fine particles.

  The norbornene polymer contained in the polynorbornene resin (B) is the same as the norbornene polymer contained in the polynorbornene resin (A). Further, the norbornene polymer contained in the polynorbornene resin (B) and the norbornene polymer contained in the polynorbornene resin (A) may be the same or different.

  The spherical silica fine particles contained in the polynorbornene resin (B) are silica fine particles having a sphericity of 0.8 or more and 1.2 or less. Here, the sphericity means the aspect ratio of the silica fine particles. Specifically, 50 silica fine particles were observed with a scanning electron microscope (SEM), and all of the observed silica fine particles had no corners, and the average of the ratio of length to width (aspect ratio) was 0.8. If it is 1.2 or less, it is assumed to be spherical silica fine particles.

  The average primary particle size of the spherical silica fine particles contained in the polynorbornene resin (B) is usually 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more, and usually 1.0 μm or less, preferably Is 0.9 μm or less, more preferably 0.8 μm or less. The average primary particle diameter of the spherical silica fine particles can be measured as an average particle diameter (median diameter d50) by a laser diffraction particle size distribution measurement method.

  The amount of the spherical silica fine particles contained in the polynorbornene resin (B) is usually 0.1% by weight or more, preferably 0.3% by weight or more, with the total amount of the polynorbornene resin (B) being 100% by weight, Usually 1.0% by weight or less, preferably 0.9% by weight or less, more preferably 0.8% by weight or less.

  As described above, the protective film for polarizing plate of the present invention has a spherical shape and is a B layer made of a polynorbornene resin (B) containing a predetermined amount of silica fine particles having a predetermined average primary particle diameter. Is provided. Thereby, the protective film for polarizing plates of this invention can improve knurling aptitude, maintaining transparency high and enabling it to exhibit the surface slipperiness improvement effect | action by a silica particle. Such an effect is not simply an effect obtained by simply optimizing the particle size of silica particles, optimizing the amount of silica particles, or optimizing the shape of silica particles, but satisfies all the above requirements. This is the first effect.

The spherical silica fine particles have a heating weight reduction rate of 0.3% or less at a normal temperature of 180 ° C. or higher, preferably 200 ° C. or higher, more preferably 250 ° C. or higher and usually 300 ° C. or lower in an N ₂ atmosphere. By using spherical silica fine particles having a high heating weight reduction temperature in this way, it is possible to prevent foaming of the fine particles during extrusion molding of the polynorbornene-based resin (B), and to prevent cracks from occurring during knurling starting from the foaming. .

  The difference in refractive index between the norbornene polymer contained in the polynorbornene-based resin (B) and the spherical silica fine particles is usually 0.05 or more, preferably 0.06 or more, more preferably 0.07 or more, usually 0. .2 or less, preferably 0.18 or less, more preferably 0.15 or less. In the protective film for a polarizing plate of the present invention, the transparency of the protective film for a polarizing plate can be increased even if fine particles having such a large refractive index difference are included in the resin.

  The polynorbornene resin (B) may contain other components in addition to the norbornene polymer and the spherical silica fine particles as long as the effects of the present invention are not significantly impaired. When the example is given, the example similar to the other component which polynorbornene-type resin (A) may contain is given. In addition, the polynorbornene-based resin (B) may include one of the other components alone, or may include two or more in combination at any ratio.

  If the amount of the other component contained in the polynorbornene resin (B) is too large, bleeding out and white turbidity may occur. Therefore, it is desirable that the above-mentioned bleed out and white turbidity do not occur. In addition, since the above other components usually have an action of lowering the glass transition temperature Tg (B) of the polynorbornene resin (B), the polynorbornene can be adjusted by appropriately adjusting the amount of the exemplified other components. The glass transition temperature Tg (B) of the system resin (B) can be kept in a desired range.

  The glass transition temperature Tg (B) of the polynorbornene resin (B) is usually 148 ° C. or higher, preferably 152 ° C. or higher, more preferably 155 ° C. or higher, and usually 180 ° C. or lower, preferably 175 ° C. or lower, more preferably. Is 170 ° C. or lower. By setting the glass transition temperature Tg (B) of the polynorbornene resin (B) within the above range, the moldability of the polynorbornene resin (B) is improved and knurling can be easily performed.

  The glass transition temperature Tg (A) of the polynorbornene resin (A) and the glass transition temperature Tg (B) of the polynorbornene resin (B) preferably satisfy the relationship of Tg (B) ≧ Tg (A). More preferably, the relationship of Tg (B) −Tg (A) ≧ 10 ° C. is satisfied. In addition, Tg (B) -Tg (A) is 50 degrees C or less normally. In the protective film for polarizing plate of the present invention, it is preferable to make the A layer thicker than the B layer in order to increase transparency, but in this case, if Tg (A) is higher than Tg (B) The knurling becomes easy, and the knurling portion to be formed can be made difficult to be crushed over time.

The shear viscosity difference between the polynorbornene resin (A) and the polynorbornene resin (B) at a temperature of 290 ° C. and a shear rate of 100 s ⁻¹ is preferably 500 Pa · s or less, more preferably 400 Pa · s or less, and 300 Pa · s. The following are particularly preferred: The lower limit is ideally 0 Pa · s. When the difference in shear viscosity is small, the polynorbornene-based resin (A) and the polynorbornene-based resin (B) can be easily formed into a film during extrusion, and a wide protective film for a polarizing plate can be easily produced.

  The protective film for a polarizing plate of the present invention may be provided with only one B layer made of polynorbornene resin (B), or may be provided with two or more layers. Usually, the protective film for polarizing plates of the present invention comprises two B layers, preferably a laminated film comprising B layer, A layer and B layer in this order. In addition, when the protective film for polarizing plates of this invention is equipped with two or more B layers, each B layer may be the same and may differ. By making the layer structure in which the A layer is sandwiched between the B layers containing the spherical silica fine particles as described above, it is possible to effectively exhibit the slip improvement effect by the spherical silica fine particles.

  As for the thickness of the B layer, when the thickness of the A layer is dA and the thickness of the B layer is dB, the ratio dA / dB of the thickness is preferably 5 or more, more preferably 8 or more, and preferably 30 or less. More preferably, it should be 17 or less. In addition, when the protective film for polarizing plates of this invention is provided with 2 or more layers of A layer and B layer, dA and dB represent the sum total of the thickness of a layer. Thus, by making the thickness dA of the A layer thicker than the thickness dB of the B layer, it becomes possible to improve the transparency while improving the handling property of the protective film for polarizing plate of the present invention.

  The static friction coefficient of the exposed surface of the B layer is usually 1.0 or less, preferably 0.8 or less, more preferably 0.7 or less, and usually 0.2 or more. Since the exposed surface of the B layer has such excellent slipperiness, the B layer is preferably the outermost layer from the viewpoint of improving the handling properties of the protective film for polarizing plate of the present invention. Therefore, when the protective film for polarizing plate of the present invention is provided with the B layer, the A layer, and the B layer in this order as described above, another layer is not provided on the side opposite to the A layer of the B layer, It is preferable to expose the surface of the B layer opposite to the A layer.

[4. (Knurling part)
The protective film for polarizing plates of this invention has a knurling part in the edge part of the protective film for polarizing plates. Hereinafter, the knurling part of the protective film for polarizing plate of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view schematically showing a protective film for a polarizing plate according to one embodiment of the present invention. As shown in FIG. 1, the protective film 1 for a polarizing plate is usually a long film, stored and transported in the state of a wound body 2 wound up in a roll shape, and a necessary amount is drawn from the wound body 2. Used. Here, the long film is a film having a dimension in the length direction (MD direction) that is long (for example, a length of 10 times or more) with respect to the dimension in the width direction (TD direction). Such a long film can be obtained by carrying out the production process while continuously transporting it in the length direction on the production line, and the advantage that a part or all of the production process can be carried out simply and efficiently in-line. There is.

  In the conventional protective film for polarizing plates, due to its low handling property, when the film is damaged, when a roll-shaped wound body is formed, a gauge band is formed in the circumferential direction of the wound body, or the wound body is In some cases, it was deformed into a prismatic shape instead of a cylindrical shape. A gauge band is a band extending in the circumferential direction of a wound body formed by bending a part of the film, and when this gauge band occurs, a bent mark remains on the protective film for a polarizing plate drawn out, It causes quality degradation. Moreover, when a wound body deform | transforms into prismatic shape, a bending trace will remain in the part which hits the corner | corner of a prism in the protective film for polarizing plates, and will cause quality degradation.

  Then, in the protective film 1 for polarizing plates of this embodiment, the knurling part 4 is formed in the strip | belt shape along the length direction MD in the edge part 3 of the width direction TD of the protective film 1 for polarizing plates. Here, the knurling part 4 is a convex part assembly in which a large number of convex parts 5 are formed in the protective film 1 for a polarizing plate. Usually, the shape of the convex part 5 formed in the knurling part 4 is similar. Repeated shape. Since the knurling part 4 improves the peelability and slipperiness of the protective film 1 for polarizing plate, the handling property of the protective film 1 for polarizing plate is improved. Therefore, the generation of the gauge band and the deformation of the wound body 2 can be prevented. Moreover, the wound of the center part of the width direction at the time of winding of the protective film 1 for polarizing plates can be prevented, winding property can be improved, or the conveyance property of the protective film 1 for polarizing plates can be improved. Furthermore, since the protective film 1 for polarizing plates can be wound up independently without sticking protective films, such as a masking film, and it can be set as the wound body 2, it can reduce the cost of conveyance and a preservation | save. .

  In the knurling portion 4, the surface shape is uneven, so that the transparency is usually impaired. However, in the protective film 1 for polarizing plates, the central portion in the width direction is an effective portion that effectively exhibits the optical function, and the end portion 3 is removed during use, so that the optical function is not affected. For this reason, even if the knurling part 4 is formed at the end part 3, the optical function is not usually deteriorated during use in the polarizing plate protective film 1.

  The knurling part 4 should just be formed in at least one edge part 3 among the width direction edge parts 3 of the protective film 1 for polarizing plates, and it should be formed in both edge parts 3. Is preferred. Moreover, when the knurling part 4 is formed in both the edge parts 3, the shape and arrangement | positioning of the convex part 5 in the formed knurling part 4 may be the same, and may differ. In this embodiment, the same knurling part 4 shall be formed in the both ends 3 of the protective film 1 for polarizing plates.

  FIG. 2 is an enlarged plan view schematically showing a part of the knurling part 4 of the protective film 1 for polarizing plates according to one embodiment of the present invention, and FIG. 3 shows the polarization according to one embodiment of the present invention. It is sectional drawing which expands and shows typically a part of protective film 1 for boards. As shown in FIG. 2, the top 5 </ b> T of the convex portion 5 is preferably configured as a quadrangle having a length L of 0.2 mm to 0.6 mm on one side. Moreover, in the knurling part 4, it is preferable that the distance P between the adjacent convex parts 5 shall be 0.5 mm-1.2 mm. Furthermore, as shown in FIG. 3, it is preferable that ratio d1 / d2 of the height (d1) of the convex part 5 and the thickness (d2) of the protective film 1 for polarizing plates is 0.2-0.8. . By setting it as such a shape and a dimension, the handleability of the protective film 1 for polarizing plates can be improved effectively, and it can prevent stably that the knurling part 4 is crushed or a crack is produced. .

  Usually, the knurling part 4 is formed by knurling, which is a process of forming minute irregularities on the protective film 1 for polarizing plates, and therefore, a concave part 6 is often formed on the back side of the convex part 5 (see FIG. 3). ). In the protective film 1 for polarizing plates, the convex part 5 should just be formed in at least one of the front surface and the back surface.

  The knurling part 4 may be formed at a position separated from the edge 7 of the polarizing plate protective film 1 by a predetermined distance in the end part 3 of the polarizing plate protective film 1, or to be formed immediately inside the edge 7. It may be. In the present embodiment, as shown in FIG. 1, the knurling portion 4 is formed at a position separated from the edge 7 of the protective film 1 for polarizing plate by a predetermined distance.

  As shown in FIG. 1, the width (that is, the size in the width direction TD) W of the knurling portion 4 is usually 5 mm or more, preferably 10 mm or more, and usually 25 mm or less, preferably 20 mm or less. Moreover, when expressed as a ratio with respect to the width of the protective film 1 for polarizing plate, the width W of the knurling part 4 is usually 0.5% or more with respect to the total width of the protective film 1 for polarizing plate, usually 5% or less, preferably Is 2% or less. If the width W of the knurling portion 4 is too narrow, the effect of preventing winding misalignment or the like that occurs during winding of the protective film 1 for polarizing plate may be reduced and the handling property may be lowered. If it is too wide, in the protective film 1 for polarizing plate, the effective portion that effectively exhibits the protective function of the polarizing plate is narrowed and the manufacturing cost tends to increase.

[5. Other matters about polarizing plate protective film]
The protective film for polarizing plate of the present invention comprises the A layer made of the polynorbornene resin (A) and the B layer made of the polynorbornene resin (B) as described above, but the effect of the present invention is remarkably impaired. As long as there is not, you may provide layers other than A layer and B layer. However, from the viewpoint of thinning and cost reduction, the protective film for polarizing plate of the present invention is preferably a film including only the A layer and the B layer, and is a film including the B layer, the A layer, and the B layer in this order. It is particularly preferred.

  The protective film for polarizing plate of the present invention preferably has a total light transmittance of 85% or more, more preferably 90% or more. It is preferable for the optical member that the total light transmittance is in the above-mentioned preferable range. The total light transmittance is an average value obtained by measuring five places using a “turbidimeter NDH-2000” manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1997.

  The protective film for a polarizing plate of the present invention has an advantage that the haze is small in spite of having a B layer containing spherical silica fine particles having a refractive index difference from the norbornene polymer. When mentioning a specific range, the internal haze of the protective film for polarizing plate of the present invention is usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less. The internal haze is 55 mm in height, 36 mm in width and 10 mm in optical path length in a silica cell SH710 made by Toray Dow Corning Co., Ltd. It can measure using NDH-2000). When the internal haze is small, the sharpness of a display image can be improved in a display device or the like provided with a polarizing plate protective film.

  The retardation Re in the in-plane direction of the protective film for polarizing plate of the present invention is usually 5 nm or less, preferably 3 nm or less, more preferably 2 nm or less. The absolute value of retardation Rth in the thickness direction of the protective film for polarizing plate of the present invention is usually 5 nm or less, preferably 4 nm or less, more preferably 3 nm or less.

  The retardation Re in the in-plane direction is | nx−ny | × d (where nx represents a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and giving the maximum refractive index). , Ny represents a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and orthogonal to the nx direction, and d represents a film thickness). Further, the retardation Rth in the thickness direction is {| nx + ny | / 2-nz} × d (where nx is a direction perpendicular to the thickness direction (in-plane direction) and is the direction of refraction giving the maximum refractive index. Ny is a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and orthogonal to the nx direction, nz is a refractive index in the thickness direction, and d is a film thickness. ). Unless otherwise specified, retardation Re and Rth are measured at a wavelength of 550 nm.

  In the protective film for polarizing plate of the present invention, ΔYI is preferably 2 or less. When ΔYI is small, there is no coloration in a display device or the like provided with a protective film for a polarizing plate, and visibility can be improved. Here, ΔYI is measured using “Spectral Color Difference Meter SE2000” manufactured by Nippon Denshoku Industries Co., Ltd. according to ASTM E313, and the same measurement is performed five times to obtain the arithmetic average value.

The thickness of the protective film for polarizing plates of the present invention is usually 40 μm or less, preferably 35 μm or less, more preferably 30 μm or less. Moreover, although there is no restriction | limiting in a lower limit, it is usually 10 micrometers or more.
Moreover, the width | variety of the protective film for polarizing plates of this invention is 1300 mm-2300 mm normally.

[6. Production method〕
In the method for producing a protective film for a polarizing plate of the present invention, at least a polynorbornene-based resin (A) and a polynorbornene-based resin (B) are melt-coextruded to obtain a laminated film having an A layer and a B layer. An extrusion process and a knurling process of knurling the manufactured laminated film are performed. Moreover, you may make it perform processes other than a co-extrusion process and a knurling process as needed.

  In the coextrusion step, at least the polynorbornene resin (A) and the polynorbornene resin (B) are melt coextruded to obtain a laminated film. In this case, when trying to obtain a laminated film having layers other than the A layer and the B layer, the resins corresponding to the layers other than the A layer and the B layer are selected from the polynorbornene-based resin (A) and the polynorbornene. You may make it co-extrusion molding with a system resin (B).

  Melt coextrusion molding is an excellent film molding method from the viewpoint of production efficiency and not leaving volatile components such as solvents in the resulting film. Examples of the melt coextrusion molding method include a coextrusion T-die method, a coextrusion inflation method, and a coextrusion lamination method. Among the melt coextrusion molding methods, the coextrusion T-die method is preferable. The coextrusion T-die method includes a feed block method and a multi-manifold method, and the multi-manifold method is particularly preferable in that variation in layer thickness can be reduced.

In the melt coextrusion molding method, a sheet-shaped molten resin extruded from an opening of a die is usually brought into close contact with a cooling drum, and the resin is cured to obtain a laminated film. The method for bringing the molten resin into close contact with the cooling drum is not particularly limited, and examples thereof include an air knife method, a vacuum box method, and an electrostatic contact method.
The number of cooling drums is not particularly limited, but is usually two or more. Examples of the arrangement method of the cooling drum include, but are not limited to, a linear type, a Z type, and an L type. Further, the way of passing the molten resin extruded from the opening of the die through the cooling drum is not particularly limited.

  It is preferable to reduce the content of the residual solvent in the produced laminated film. As means for that, (1) the residual solvent of the polynorbornene-based resin (A) and polynorbornene-based resin (B) as raw materials is reduced; (2) the polynorbornene-based resin (A ) And the polynorbornene resin (B) are pre-dried. For example, the preliminary drying is performed with a hot air dryer or the like by converting the polynorbornene-based resin (A) and the polynorbornene-based resin (B) into a form of pellets or the like. The drying temperature is preferably 100 ° C. or more, and the drying time is preferably 2 hours or more. By performing preliminary drying, the residual solvent in the obtained laminated film can be reduced, and foaming of the extruded sheet-shaped resin material can be prevented.

After preparing a laminated film in the co-extrusion process, a knurling process for knurling the laminated film is performed. Specifically, a knurling part is formed by knurling the end part of the laminated film to obtain the protective film for polarizing plate of the present invention.
As the knurling, any processing that can form the knurling portion described above on the laminated film can be adopted, but usually the following embossing processing is performed.

  When knurling is performed by embossing, for example, a roll-shaped or ring-shaped mold having a concavo-convex pattern corresponding to the shape of the knurling portion on the side is prepared, and the laminated film is heated as necessary. The laminated film is pressed with the above mold while being heated. In addition, when a heated mold is pressed against the laminated film (for example, when a self-heating roll (a roll using a dielectric) or the like is used), the thermal deformation of the laminated film is suppressed as compared with the case where the laminated film is heated. There are advantages that can be made. At this time, pressing may be performed by a single mold, but pressing may be performed by sandwiching a laminated film between two opposing roll-shaped or ring-shaped molds. Thereby, the uneven | corrugated pattern of the side surface of a type | mold is transcribe | transferred to a laminated | multilayer film, and a knurling part is formed.

  If knurling is performed by embossing, the knurling portion can be formed simply by pressing the mold, so that the manufacturing method is simple and the cost can be reduced. In addition, normally, a long laminated film is transported in the length direction using a roll or the like and continuously pressed by the above mold, but the shape of the knurling portion formed at this time is a roll shape or a ring shape It becomes a repeated shape corresponding to the concavo-convex pattern for one rotation of the mold. For this reason, the embossing process is suitable for forming a knurling portion having a repetitive shape. Further, according to the embossing treatment, a convex portion is usually formed on one surface of the laminated film, and a concave portion is formed on the other surface. At this time, the concave portion on one surface becomes a convex portion on the other surface. As a result, the substantial thickness of the knurling portion is increased, and the handling properties of the laminated film can be further improved.

  The temperature during knurling is usually Tg (B) -40 ° C or higher, preferably Tg (B) -30 ° C or higher, and usually Tg (B) + 30 ° C or lower, preferably Tg (B) + 20 ° C or lower, More preferably, Tg (B) + 10 ° C. or lower. By setting it as such temperature, a knurling part can be formed stably, without a crack generating or a convex part being crushed.

  The magnitude of the pressure (knurling pressure) for pressing the laminated film with a mold when knurling is usually 0.05 MPa or more, preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and usually 1.0 MPa or less. , Preferably 0.8 MPa or less, more preferably 0.6 MPa or less. By using such a knurling pressure, it is possible to stably form a knurling portion having a convex portion having an appropriate height while avoiding excessive internal stress due to knurling.

[7. Main advantages and uses)
The main advantages of the polarizing plate protective film of the present invention include the following (i) to (iii).

  (I) The protective film for polarizing plates of this invention is excellent in transparency. In particular, the entire layer constituting the film contains fine particles by adopting a laminated structure of the A layer made of the polynorbornene resin (A) and the B layer made of the polynorbornene resin (B) containing spherical silica fine particles. The internal haze can be lowered as compared with the case where it is present. In particular, when the thickness of the B layer is made thinner than that of the A layer, the transparency can be remarkably increased.

  (Ii) The protective film for polarizing plates of the present invention has excellent aptitude for knurling. Therefore, even if knurling is performed, cracks are hardly generated, and the formed knurling portion is not easily crushed. Therefore, if a knurling part having an appropriate size and shape is formed, the knurling part is not crushed by stress or the like, and a good knurling part can be maintained over a long period of time. Moreover, the protective film for polarizing plates of this invention has the advantage which can form knurling easily and is excellent in manufacturing efficiency.

  (Iii) Since the protective film for polarizing plates of the present invention comprises a B layer containing silica fine particles, the surface slipperiness is excellent if the B layer is exposed. For this reason, since it can exhibit high handling property with the effect | action by the said knurling part, even if it does not use a masking film, it can wind up in roll shape and can be set as a wound body. Furthermore, when a roll-shaped wound body is used, the quality can be maintained by preventing gauge bands and deformation over a long period of time.

Since it has the above outstanding advantages, the protective film for polarizing plates of this invention can protect a polarizing plate appropriately.
The protective film for polarizing plate of the present invention may be provided on at least one side of the polarizing plate, but is usually provided on both sides. For example, what is necessary is just to laminate | stack the protective film for polarizing plates of this invention on the single side | surface or both surfaces of a polarizing plate through a suitable adhesive agent.

  Any polarizing plate can be used, for example, a polyvinyl alcohol film doped with iodine or the like and then stretched can be used. Moreover, as an adhesive agent, the adhesive etc. which use polymers, such as an acrylic polymer, a silicone type polymer, polyester, a polyurethane, polyether, and synthetic rubber, as a base polymer are mentioned, for example.

  In addition to the protective film for the polarizing plate, another layer may be provided on the polarizing plate. Other layers include, for example, an antireflection layer, a hard coat layer, a primer layer; an anchor layer; a highly homogeneous transparent porous material layer (refracted) composed of a three-dimensional skeleton of SiOx (x = 1.5 to 2.0) ultrafine particles. Rate 1.25 to 1.46); pressure-sensitive adhesive layer; antifouling layer; and the like.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist of the present invention and its equivalent scope. Can be implemented.

[Explanation of evaluation method]
(1) Evaluation Method of Shape of Silica Fine Particles 50 silica fine particles were observed with a scanning electron microscope (SEM), and the ratio of length to width (length / width ratio) was measured. If all of the observed silica particles have no corners and the average aspect ratio is 0.8 or more and 1.2 or less, the silica particles are determined to be spherical silica particles.

(2) Measuring method of average primary particle diameter of silica fine particles The average primary particle diameter of silica fine particles is determined as an average particle diameter (median diameter d50) by a laser diffraction particle size distribution measuring device (SALD-2100 manufactured by Shimadzu Corporation). It was measured.
Moreover, it was confirmed by SEM observation that the measured particle size was an average primary particle size in a state where particles were not aggregated.

(3) Method for measuring film layer thickness Using a contact-type thickness meter (code No. 547-401, manufactured by Mitutoyo Corporation), the thickness of a portion other than the knurling portion of the film was measured. Next, a portion other than the knurling portion was cut as a thickness measurement portion, the cross section was observed with an optical microscope, the thickness ratio of each layer was obtained, and the thickness of each layer was calculated from the ratio. The above operation was performed at 30 locations at intervals of 50 mm in the MD direction and TD direction of the film, the average value of the thickness was determined, and this average value was taken as the thickness of the film and the layer.

(4) Evaluation method of the knurling portion With the digital microscope VHX-900 manufactured by Keyence Corporation, the width of the knurling portion of the film, the length of one side of the quadrilateral of the top of the convex portion, the interval between the convex portions, and the height of the convex portion Each was measured.

(5) Internal haze measurement method Into a quartz cell having a height of 55 mm, a width of 36 mm, and an optical path length of 10 mm, a silicone oil SH710 manufactured by Toray Dow Corning Co., Ltd. is placed, and a film is placed therein. The internal haze of the film was measured using NDH-2000 manufactured by Color Industries Co., Ltd.

(6) Evaluation method of film (a) Evaluation of initial winding form appearance The appearance of the roll-shaped wound body wound with the film is visually observed to confirm whether it corresponds to the following i, ii, v, and vi. did.
i. The knurling part is cracked.
ii. The knurling part is crushed.
v. There is a gauge band on the roll.
vi. The roll is not a cylinder but a prism.

(B) Evaluation after storage for 3 months The wound roll-shaped wound body was stored for 3 months under constant temperature and humidity at a temperature of 25 ° C. and a humidity of 50% RH. The appearance of the roll-shaped wound body after storage was visually observed to confirm whether it corresponds to the following i, ii, v, and vi. Furthermore, 1000 m was loosened from the roll-shaped wound body, and 0.74 m was cut out in the length direction. About the cut-out film, the following i-iv was observed visually and microscopically, and v and vi were confirmed visually. Of the six items i to vi below, “excellent” indicates that all of i to vi are not applicable, “good” indicates that only one of i and ii is applicable, and “allows” indicates that iii is applicable. ”And any one of iv to vi were regarded as“ bad ”.
i. The knurling part is cracked.
ii. The knurling part is crushed.
iii. The film is scratched with a length of 0.5 mm or less.
iv. The film has scratches with a length of 0.5 mm or more.
v. There is a gauge band on the roll.
vi. The roll is not a cylinder but a prism.

[Production Example 1. Synthesis of norbornene polymer]
Tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as “DCP” where appropriate), 7,8-benzotricyclo [4.4.0. 12,5.17,10] dec-3-ene (methanotetrahydrofluorene, hereinafter abbreviated as “MTF” where appropriate) and tetracyclo [4.4.0.12,5.17,10] dodeca-3 A mixture of ene (tetracyclododecene, hereinafter abbreviated as “TCD” where appropriate) at a weight ratio of 5/70/25 is subjected to ring-opening polymerization by a known method, and then hydrogenated to obtain DCP / MTF. / TCD ring-opening polymer hydride polymer was obtained.
When the copolymerization ratio of each norbornene monomer in the obtained hydrogenated polymer was calculated from the composition of residual norbornenes in the solution after polymerization by gas chromatography analysis, DCP / MTF / TCD = 5/70/25, almost equal to the charged composition.
Further, the weight average molecular weight (Mw) of this hydrogenated polymer is 35,000, the molecular weight distribution (Mw / Mn; Mn is the number average molecular weight) is 2.1, the hydrogenation rate is 99.9%, and the glass transition temperature Tg is The refractive index at 164 ° C. and 25 ° C. was 1.53.

[Production Example 2. Production of polynorbornene-based resins for Examples 1 and 2, Comparative Examples 1 to 5, and Reference Examples 1 to 5]
94% by weight of the DCP / MTF / TCD ring-opening polymer hydride polymer synthesized in Production Example 1 was added with 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl)- 6- (2H-benzotriazol-2-yl) phenol] 5.0% by weight and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy ] -1.0% by weight of phenol was added, kneaded with a twin screw extruder, extruded into a strand, and cut with a pelletizer to produce a polynorbornene resin. This polynorbornene resin is hereinafter referred to as “resin A1” as appropriate.

[Production Example 3. Production of polynorbornene resin for Example 3 and Reference Example 6]
Into 97% by weight of the DCP / MTF / TCD ring-opening polymer hydride polymer synthesized in Production Example 1, 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl)- 6- (2H-benzotriazol-2-yl) phenol] 2.5% by weight and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -0.5% by weight of phenol was added, kneaded with a twin screw extruder, extruded into a strand, and cut with a pelletizer to produce a polynorbornene resin. This polynorbornene resin is hereinafter referred to as “resin A2” as appropriate.

[Production Example 4. Production of amorphous silica fine particles for Comparative Example 1]
Silica filler FS-3DC (average particle size: 2.9 μm) manufactured by Denki Kagaku Kogyo Co., Ltd. was charged into a ball mill and pulverized to prepare a pulverized silica filler having an irregular shape. When the average primary particle diameter of the produced pulverized silica filler was measured, it was 0.8 μm. The refractive index at 25 ° C. was 1.43.

[Example 1]
Resin A1 produced in Production Example 2 was prepared as a resin for the A layer.
Further, 99.7% by weight of the resin A1 produced in Production Example 2 and silica beads Admafine SO-E2 manufactured by Admatechs Co., Ltd. as spherical silica fine particles (average primary particle diameter 0.5 μm, aspect ratio 1.1) , A refractive index of 1.43) at 25 ° C. was mixed with 0.3% by weight, and melt-kneaded with a twin-screw extruder to prepare a resin for the B layer.
The prepared A layer resin and B layer resin are respectively supplied to a single screw extruder, and melt coextrusion molding is performed so that a laminated film in which B layer / A layer / B layer are laminated in this order is obtained. By doing so, a laminated film was obtained. The thickness of the A layer of the obtained laminated film was 25 μm, and the total thickness of the B layer was 3 μm.

Knurling was performed with a blade type heated to 140 ° C. at a position 1 mm from the edge of the film at both ends in the width direction of the laminated film. As the blade mold, a convex part formed on the knurling part of the film by adjusting the knurling pressure by using a plurality of convex parts having a square top on the outer surface of the roll-shaped mold at regular intervals. The height of can be adjusted. In Example 1, the knurling pressure was 0.3 MPa.
After knurling, the obtained protective film for polarizing plate was wound up to 2000 m, and the above evaluation was performed as a roll-shaped wound body. The results are shown in Tables 1 and 2.

[Example 2]
A protective film for polarizing plate was produced and evaluated in the same manner as in Example 1 except that the total thickness of the B layer was 1.5 μm. The results are shown in Tables 1 and 2.

[Comparative Example 1]
A protective film for a polarizing plate was produced and evaluated in the same manner as in Example 1 except that the amorphous silica fine particles produced in Production Example 4 were used as the silica fine particles contained in the resin for the B layer. The results are shown in Tables 1 and 2.

[Comparative Example 2]
A protective film for a polarizing plate was produced in the same manner as in Example 1 except that the amount of the resin A1 contained in the resin for the B layer was 98.8% by weight and the amount of the silica fine particles was 1.2% by weight. ,evaluated. The results are shown in Tables 1 and 2.

[Comparative Example 3]
A protective film for a polarizing plate was produced in the same manner as in Example 1 except that the amount of the resin A1 contained in the resin for the B layer was 99.95% by weight and the amount of the silica fine particles was 0.05% by weight. ,evaluated. The results are shown in Tables 1 and 2.

[Comparative Example 4]
Protection for polarizing plate in the same manner as in Example 1 except that Admatex silica beads Admafine SO-E5 (average primary particle diameter 1.5 μm) was used as the silica fine particles contained in the resin for the B layer. Films were manufactured and evaluated. The results are shown in Tables 1 and 2.

[Comparative Example 5]
A protective film for polarizing plate is produced in the same manner as in Example 1 except that silica beads AEROSIL R972 (average primary particle diameter 0.016 μm) manufactured by Nippon Aerosil Co., Ltd. is used as the silica fine particles to be included in the resin for the B layer. And evaluated. The results are shown in Tables 1 and 2.

  From Tables 1 and 2, Comparative Example 1 in which spherical particles were not used, Comparative Example 2 in which the amount of spherical silica particles was excessive, Comparative Example 3 in which the amount of spherical silica particles was excessive, spherical In both Comparative Example 4 in which the average primary particle size of the silica fine particles was excessively large and Comparative Example 5 in which the average primary particle size of the spherical silica fine particles was excessively small, both transparency and knurling suitability were achieved. Although an excellent protective film for a polarizing plate has not been obtained, it can be seen that in Examples 1 and 2, a protective film for a polarizing plate excellent in both transparency and knurling suitability is obtained. From this, transparency and knurling aptitude are not provided for the first time by providing a B layer made of a polynorbornene-based resin (B) having a spherical shape and containing a predetermined amount of silica fine particles having a predetermined average primary particle diameter. It has been confirmed that a polarizing plate protective film excellent in both transparency and film appearance can be realized. In particular, in the evaluation of the film appearance, there is a remarkable difference between the example and the comparative example in the evaluation after storage for 3 months. It can be evaluated that the suppressing effect is remarkably exhibited.

[Reference Example 1]
A polarizing plate protective film was produced and evaluated in the same manner as in Example 1 except that a blade mold used in knurling had a different spacing between the convex portions. The results are shown in Tables 3 and 4.

[Reference Example 2]
A polarizing plate protective film was produced and evaluated in the same manner as in Example 1 except that a blade having a different length on one side of the quadrilateral of the top of the convex portion was used as the blade type used in the knurling. The results are shown in Tables 3 and 4.

[Reference Example 3]
A protective film for a polarizing plate was produced and evaluated in the same manner as in Example 1 except that the knurling pressure was 0.6 MPa. The results are shown in Tables 3 and 4.

[Reference Example 4]
A protective film for a polarizing plate was produced and evaluated in the same manner as in Example 1 except that the knurling pressure was 0.1 MPa. The results are shown in Tables 3 and 4.

  By comparing Examples 1 and 2 with Reference Examples 1 to 4, the relationship between the shape of the knurling portion and the film appearance was examined. From Tables 3 and 4, it can be seen that the shape of the knurling part affects the film appearance. Further, even if the protective film for polarizing plate of the present invention has high suitability for knurling, the knurling shape may be destroyed and the effect cannot be obtained in a shape greatly deviating from an appropriate range. You can see that there is sex. From the above, it was confirmed that in the protective film for polarizing plate of the present invention, it is preferable to keep the shape of the knurling part within an appropriate range.

[Reference Example 5]
A protective film for a polarizing plate was produced and evaluated in the same manner as in Example 1 except that the thickness of the A layer was 18 μm and the total thickness of the B layer was 10 μm. The results are shown in Table 5.

  By comparing Examples 1 and 2 with Reference Example 5, the influence of the thickness of the A layer and the B layer on the film appearance was examined. From Table 5, it can be seen that when the B layer is thicker than the A layer, the knurling shape is destroyed over time and the film appearance tends to deteriorate. Therefore, even though the protective film for polarizing plate of the present invention has high suitability for knurling, in the protective film for polarizing plate of the present invention, the B layer is thinner than a predetermined value with respect to the A layer. It was confirmed that the thickness is preferable.

[Example 3]
A protective film for a polarizing plate was produced and evaluated in the same manner as in Example 1 except that the resin A2 produced in Production Example 3 was used as the resin for the A layer. The results are shown in Table 6.

[Reference Example 6]
A protective film for a polarizing plate was produced and evaluated in the same manner as in Example 3 except that the knurling pressure was 0.6 MPa. The results are shown in Table 6.

  By comparing Examples 1 to 3 with Reference Example 6, the influence of the difference in glass transition temperature between the polynorbornene resin (A) and the polynorbornene resin (B) was examined. When Examples 1 and 2 are compared with Example 3, the difference between the glass transition temperature Tg (A) of the polynorbornene resin (A) and the glass transition temperature Tg (B) of the polynorbornene resin (B) is 10. It can be seen that the evaluation after storage for 3 months is good when the temperature is not lower than ° C. Therefore, it can be seen that if the difference between Tg (A) and Tg (B) is too small, the deformation mainly due to stress tends to be amplified. In this regard, in view of the fact that the evaluation deteriorated after 3 months in Reference Example 6 in which the height of the convex portion of the knurling portion was increased, the glass transition temperature Tg (A) of the polynorbornene resin (A) is high. Thus, a large stress due to knurling remains in the film, and it is assumed that the knurling shape was destroyed due to deformation of the film over time due to the residual stress.

  The protective film for polarizing plates of the present invention has excellent properties as a protective film for polarizing plates, and is suitable as a protective film for polarizing plates for display devices such as liquid crystal display devices.

DESCRIPTION OF SYMBOLS 1 Protective film for polarizing plates 2 Winding body 3 End part of protective film for polarizing plates 4 Knurling part 5 Convex part 5T Top part of convex part 6 Concave part 7 Edge of protective film for polarizing plate

Claims (4)

A layer made of the polynorbornene resin (A) obtained by melt-coextrusion molding of the polynorbornene resin (A) and the polynorbornene resin (B) containing silica fine particles, and the polynorbornene resin (B) It is a protective film for polarizing plates provided with B layer which consists of,
The silica fine particles are spherical with an average primary particle size of 0.1 μm to 1.0 μm,
The polynorbornene-based resin (B) contains 100 wt% of the total amount of the polynorbornene-based resin (B), and contains 0.1 to 1.0 wt% of the silica fine particles,
The protective film for polarizing plates which has a knurling part in the edge part of the said protective film for polarizing plates. The knurling part is a convex part aggregate;
The top of the convex portion is formed of a quadrilateral with one side having a length of 0.2 mm to 0.6 mm,
The distance between the adjacent convex portions is 0.5 mm to 1.2 mm,
The protective film for polarizing plates of Claim 1 whose ratio d1 / d2 of the height (d1) of the said convex part and the thickness (d2) of the said protective film for polarizing plates is 0.2-0.8. The thickness of the polarizing plate protective film is 40 μm or less,
The protective film for polarizing plates according to claim 1 or 2, satisfying 5≤dA / dB≤30 when the thickness of the A layer is dA and the thickness of the B layer is dB.   The protective film for polarizing plates as described in any one of Claims 1-3 provided with the said B layer, the said A layer, and the said B layer in this order.

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