JP6724930B2 - Polarizing plate protective film, method for producing the same, and polarizing plate - Google Patents

Description

The present invention relates to a polarizing plate protective film, a method for producing the same, and a polarizing plate. More specifically, the present invention is a polarizing plate protective film in which, when a polarizing plate is produced by laminating it to a polarizer, cracks are less likely to occur even under use conditions such as heat cycle tests where it is repeatedly exposed to high and low temperature environments. Etc.

Liquid crystal display devices have been conventionally used in desk calculators, electronic timepieces, and the like. Further, recently, mobile devices such as mobile phones and large-sized televisions have come to be used regardless of the screen size, and the applications thereof are rapidly expanding.

In addition, as an image display device other than the liquid crystal display device, an organic electroluminescence (organic EL) display device has a tendency to increase in demand mainly for mobile applications.

In a liquid crystal display device, a pair of polarizing plates are usually arranged on the front and back of a liquid crystal cell to form a liquid crystal panel.

In an organic EL display device, a polarizing plate, particularly an elliptical or circular polarizing plate is arranged on the viewing side of an organic EL element, and an organic EL panel having an antireflection function is often used. The elliptically or circularly polarizing plate is a linearly polarizing plate on which a quarter-wave retarder (that is, a λ/4 plate) is laminated such that the slow axes of both retard at a predetermined angle.

With respect to the polarizing plates used in these image display devices, not only are the demands increasing along with the development thereof, but also the performance suitable for each application is required.

The polarizing plate (linear polarizing plate) widely used in the image display device as described above has a liquid adhesive between both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. And a transparent protective film, typically a triacetyl cellulose film, are adhered. An image display such as a liquid crystal cell or an organic EL element using a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) in a form in which an optical layer such as a retardation film having optical characteristics is attached as it is. The display panel and the image display device are attached to the element.

Examples of the retardation film include those obtained by stretching and orienting a film made of a hydrogenated (hereinafter referred to as hydrogenated) norbornene-based resin that has excellent properties such as heat resistance, optical properties, transparency, and electrical properties. , Widely used.

However, assuming that the film produced using the hydrogenated norbornene-based resin is used in a liquid crystal panel, the film surface is attached to a polarizer to form a polarizing plate, and the film is left in a high temperature environment. When a heat cycle test in which the film was left standing in a low temperature environment was repeated, cracks sometimes occurred in the film.

Then, when the surface of the polarizing plate protective film of the polarizing plate was attached to the glass substrate, the polarizing plate sometimes peeled from the glass substrate in a high temperature environment.

As a method for improving the generation of cracks in the hydrogenated norbornene-based resin during the heat cycle test, Patent Document 1 discloses that the hydrogenated norbornene-based resin and the rubber component are dissolved or dispersed in a solvent and cast ( A film formed by the cast method is disclosed. This is to improve the elongation by adding a rubber component to the hydrogenated norbornene-based resin. However, the obtained film is inferior in optical properties such as parallel light transmittance and cannot be used as a polarizing plate protective film.

Furthermore, the present inventor has conducted a durability test (after exposing the polarizing plate using the hydrogenated norbornene-based resin film as a polarizing plate protective film on a glass substrate of a liquid crystal cell with an adhesive agent (after exposing to high temperature conditions). It was discovered that there is a problem that cracks occur in the polarizing plate protective film on the surface in contact with air on the side opposite to the liquid crystal cell after the durability test. Such cracks occur even if the residual stress of the film is small.

It has been conventionally known that an injection-molded product made of a cyclic olefin-based resin containing a hydrogenated norbornene-based resin causes cracks (see Patent Document 2, for example), but this is caused by a large residual stress generated in injection molding. No cracking is known to occur in a polarizing plate protective film obtained by a production method such as cast film production in which residual stress in film formation is small.

Patent Document 3 describes that in order to improve cracks, it is important to prevent the strength of the film from decreasing under stress, and the change in tensile strength before and after the constant load tensile test is small. It is also effective to add rubber, but it is not enough to add it, and it is described that it is necessary to devise such as finely and evenly dispersing the rubber.

JP-A-5-148413 JP, 11-178690, A JP, 2005-242171, A

The present invention has been made in view of the above problems, and a problem to be solved is to prepare a polarizing plate by laminating a polarizing plate protective film containing a hydrogenated norbornene resin on a polarizer, It is an object of the present invention to provide a polarizing plate protective film capable of forming a polarizing plate in which cracks hardly occur even when a cycle test is performed, and a method for producing the same. Moreover, it is providing the polarizing plate provided with the said polarizing plate protective film.

The present inventors, in order to solve the above problems, as a result of examining the causes of the above problems, the cracks when using a polarizing plate protective film containing a hydrogenated norbornene-based resin in the polarizing plate, problems such as peeling However, it was found that the above problems can be solved by causing a change in shrinkage stress of a polarizer with a change in ambient temperature and by incorporating a specific compound in the polarizing plate protective film into a polarizer film. The present invention has been completed.

That is, the above-mentioned subject concerning the present invention is solved by the following means.

1. A polarizing plate protective film containing a norbornene resin, wherein the norbornene resin is a hydrogenated norbornene resin, and a polymerizable compound having a chemical structure represented by the following general formula (1) is contained. A polarizing plate protective film characterized by being.

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a methyl group or a halogen atom.
Ring A ₁ , ring A ₂ and ring A ₃ each independently represent a benzene ring, a cyclohexane ring, a cyclohexene ring, a naphthalene ring, a tetrahydronaphthalene ring, a decahydronaphthalene ring, an anthracene ring or a phenanthrene ring. During these rings, -CH = is a -N =, -CH ₂ - may be replaced by -S- or -O-.

X, Y and Z each independently represent an alkyl group having 1 to 8 carbon atoms which may have a substituent, an alkoxy group having 1 to 8 carbon atoms which may have a substituent, and a substituent. It represents an alkenyl group having 2 to 6 carbon atoms, a halogen atom, a cyano group or a group having a chemical structure represented by the following general formula (2).

L _{1, L 2} and _{L 3} represent a bond, each independently represents a single _{bond, -COO -, - OCO -,} - (CH 2) d -, - CH = CH -, - (CH 2) e _{O -, - O (CH 2} ) f -, - O (CH 2) g O -, - OCOO (CH 2) h -, - (CH 2) i OCOO -, - (CH 2) j O (CH 2 _{) k -, - O (CH} 2) l - [Si (CH 3) 2 O] m -Si (CH 3) 2 (CH 2) o -, - (OCH 2 CH 2) p -, - (CH 2 _{CH 2 O) q -, -} (OCH 2 CH (CH 3)) r -, - (CH (CH 3) CH 2) s -, - CH = CHCH 2 O -, - OCH 2 CH = CH -, - CH = CH-COO -, - OCO-CH = CH -, - C≡C -, - (CH 2) 2 COO -, - OCO (CH 2) 2 -, - CF = CF -, - OCF 2 -, _{-CF 2 O -, - C≡C-} COO -, - representing the OCO-C≡C- or -O-. However, some carbon atoms may be silicon atoms.

d to m and o each independently represent an integer of 1 to 8. p to s each independently represent an integer of 1 to 3. n represents 0 or 1.

a, b, and c are the numbers of substituents in ring A ₁ , ring A _2, and ring A ₃ , respectively, where t is the number of 6-membered rings contained in each substituted monocycle or condensed ring. , A, b and c each independently represent an integer of 2t+2 or less, and when n is 0, at least one of a and b is 1 or more. When n is 1, at least one of a, b and c is 1 or more. )

（式中、Ｒ_３は、水素原子、メチル基又はハロゲン原子を表す。）

(In the formula, R ₃ represents a hydrogen atom, a methyl group or a halogen atom.)

2. The polymerizable compound having the chemical structure represented by the general formula (1) is contained within a range of 5 to 25 mass% with respect to the hydrogenated norbornene-based resin. Polarizing plate protective film.

3. 3. The polymerizable compound having a chemical structure represented by the general formula (1) is a compound having a chemical structure represented by the following general formula (3). Polarizing plate protective film.

(In the formula, X ₁ and X ₃ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or a carbon atom having 1 to 8 which may have a substituent. Represents an alkoxy group, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, a halogen atom, a cyano group or a group represented by the above general formula (2): X ₂ , X ₄ , Y ₁ to. Y ₄ and Z _{1 to} Z ₄ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or an alkyl group having 1 to 8 carbon atoms which may have a substituent. It represents an alkoxy group, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, a halogen atom or a cyano group, at least one of X _{1 to} X ₄ , Y _{1 to} Y ₄ and Z _{1 to} Z _4. Represents a substituent other than hydrogen, and rings A ₁ , A ₂ and A ₃ each independently represent a benzene ring or a cyclohexane ring, in which —CH═ is —N═ and —CH ₂ - have the same meanings as _{R 1, R 2,} f and n -S- or -O- optionally substituted by _{.R 1, R 2,} f and n are the general formula (1)).

4. 3. The polymerizable compound having a chemical structure represented by the general formula (1) is a compound having a chemical structure represented by the following general formula (4). Polarizing plate protective film.

（式中、Ｒ_１、Ｒ_２、Ｘ_１、Ｘ_２、Ｘ_３、Ｘ_４、Ｙ_１〜Ｙ_４、Ｚ_１〜Ｚ_４、Ａ_１、Ａ_２及びＡ_３は、前記一般式（３）のＲ_１、Ｒ_２、Ｘ_１、Ｘ_２、Ｘ_３、Ｘ_４、Ｙ_１〜Ｙ_４、Ｚ_１〜Ｚ_４、Ａ_１、Ａ_２及びＡ_３と同義である。ｆは前記一般式（１）のｆと同義である。）

_{(Wherein, R 1, R 2, X} 1, X 2, X 3, X 4, Y 1 ~Y 4, Z 1 ~Z 4, A 1, A 2 and _{A 3} in the general formula (3) R ₁ , R ₂ , X ₁ , X ₂ , X ₃ , X ₄ , Y _{1 to} Y ₄ , Z _{1 to} Z ₄ , A ₁ , A ₂ and A ₃ are synonymous with f in the above general formula ( It is synonymous with f in 1).)

5. 3. The polymerizable compound having a chemical structure represented by the general formula (1) is a compound having a chemical structure represented by the following general formula (5). Polarizing plate protective film.

（式中、Ｒ_１、Ｒ_２、Ｘ_１、Ｘ_２、Ｘ_３、Ｘ_４、Ｙ_１〜Ｙ_４、Ａ_１及びＡ_２は、前記一般式（４）のＲ_１、Ｒ_２、Ｘ_１、Ｘ_２、Ｘ_３、Ｘ_４、Ｙ_１〜Ｙ_４、Ａ_１及びＡ_２と同義であ
る。）

_{(Wherein, R 1, R 2, X} 1, X 2, X 3, X 4, Y 1 ~Y 4, A 1 and _{A 2, R 1, R 2, X} 1 in the general formula (4) , X ₂ , X ₃ , X ₄ , Y _{1 to} Y ₄ , A ₁ and A ₂ have the same meaning.)

6. The polarizing plate protective film according to any one of items 1 to 5, wherein a tensile strength of the polarizing plate protective film before and after a constant load tensile test is 0.6 or more.

7. A method for producing a polarizing plate protective film for producing the polarizing plate protective film according to any one of items 1 to 6, wherein at least the hydrogenated norbobornene-based resin and the polymerizable compound are used as a solvent. And a step of forming a casting film by casting the dope on a support, and a step of peeling the casting film from the support. Of manufacturing a polarizing plate protective film.

8. The polarizing plate protective film according to any one of items 1 to 6 is bonded to a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin. Polarizer.

By the above-mentioned means of the present invention, when a polarizing plate is produced by laminating a polarizing plate protective film containing a hydrogenated norbornene-based resin on a polarizer, a polarizing plate in which cracks are hard to occur even if a heat cycle test is carried out It is possible to provide a polarizing plate protective film capable of having the above and a manufacturing method thereof. In addition, a polarizing plate provided with the polarizing plate protective film can be provided.

Although the mechanism of action or mechanism of action of the present invention has not been clarified, it is presumed that the reason is as follows.

The present inventors, in order to solve the above problems, as a result of examining the causes of the above problems, the cracks when using a polarizing plate protective film containing a hydrogenated norbornene-based resin in the polarizing plate, problems such as peeling However, due to the change in shrinkage stress of the polarizer due to the change in environmental temperature and by containing a specific compound in the polarizing plate protective film, expansion and contraction of the polarizing plate protective film due to temperature changes to the polarizer film. It was found that the above problems can be solved by combining them.

That is, the shrinkage stress of the polarizer is very large, and when the polarizer is left at 90° C. for a long time, the shrinkage stress becomes 20 N per 10 mm width. A large contraction stress of the polarizer leads to a large contraction stress of the polarizing plate. Therefore, it is preferable that the contraction stress be small in order to prevent the occurrence of cracks.

Actually, when a tensile stress corresponding to the above stress was applied to the film in a simulated manner, a phenomenon that the strength of the film was lowered was observed.

In constructing a polarizing plate, the polarizing plate protective film is present in a state of being adhered to the polarizer, and under the conditions of 90° C. as described above, a large shrinkage force is always applied. It is known that when the above is reproduced in a constant load tensile test, the strength of the polarizing plate protective film is lowered.

It is speculated that this decrease in film strength affects the occurrence of cracks. In the first place, it is presumed that cracks in the polarizing plate protective film of the polarizing plate are caused by the impact of the blade during cutting, and (1) invisible ultrafine cracks occur in the film, and (2) It can be thought of as two separate stages: the crack grows to a visible level. Step (1) is mainly due to the impact of the blade during cutting, and step (2) is due to the difference in the strength and dimensional variation of each film constituting the polarizing plate in the heat durability after cutting. ing.
In the case of the hydrogenated norbornene-based resin-containing film, the strength at room temperature becomes a problem in the step (1), but the strength is lower than the strength of the polarizer, and it cannot withstand impact and easily cracks. In the step (2), the adjacent polarizers are thermally contracted, and at the same time, the film strength is reduced and the cracks are expanded. Further, in the absorption axis direction of the polarizer, the polarizer expands in the same manner as the hydrogenated norbornene-based resin film, and it is considered that cracks expand as the difference in this part increases.

From this, in order to suppress the occurrence of cracks in the polarizing plate, it is of utmost importance to bring the thermal expansion of the polarizing plate protective film close to that of the polarizer and prevent the strength of the film from being reduced under stress by the polarizer. Conceivable.

Therefore, the inventors of the present invention were able to prevent the reduction in strength by including the compound having the chemical structure represented by the general formula (1) in the polarizing plate protective film containing the hydrogenated norbornene resin. It is assumed that this is due to the following mechanism.

That is, the rings A1, A2, and A3 in the chemical structure represented by the general formula (1) are restricted in rotation by L1, L2, and L3, and the rings are arranged to form a rigid planar structure. This rigid planar structure is mixed and arranged in parallel with the casting direction of the hydrogenated norbornene-based resin, and is densely oriented between the norbornene-based resins. Further, the vinyl groups bonded to both ends of the rigid planar structure play a role of bonding between the polymerizable compounds represented by the general formula (1) to reinforce the maintenance of the dense orientation. It is presumed that this makes it possible to prevent the generation of extremely fine cracks that occur during cutting and the expansion of cracks due to the contracting stress of the polarizer.

Schematic cross section of polarizing plate

The polarizing plate protective film of the present invention is a polarizing plate protective film containing a norbornene-based resin, the norbornene-based resin is a hydrogenated norbornene-based resin, and the chemical structure represented by the general formula (1). It is characterized in that it contains a polymerizable compound having. This feature is a technical feature common to or corresponding to the claimed invention.

As an embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, the polymerizable compound having the chemical structure represented by the general formula (1) is in the range of 5 to 25% by weight with respect to the hydrogenated norbornene resin. It is preferably contained in

In the present invention, from the viewpoint of solving the problems of the present invention, the polymerizable compound having the chemical structure represented by the general formula (1) is a compound having the chemical structure represented by the general formula (3). That is, the compound having the chemical structure represented by the general formula (4) or the compound having the chemical structure represented by the general formula (5) is preferable.

In the present invention, from the viewpoint of solving the problems of the present invention, the tensile strength of the polarizing plate protective film before and after the constant load tensile test is preferably 0.6 or more.

As the method for producing a polarizing plate protective film of the present invention, at least the hydrogenated norbobornene-based resin and the polymerizable compound, a step of preparing a dope dissolved in a solvent, and casting the dope on a support. It is preferable that the production method has a step of forming a cast film by means of a method and a step of peeling the cast film from the support.

The polarizing plate protective film of the present invention can be suitably used for a polarizing plate by being attached to a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, "-" shown in the present invention is used to mean that numerical values described before and after the "-" are included as a lower limit value and an upper limit value.
(Overview of polarizing plate protective film)
The polarizing plate protective film of the present invention is a polarizing plate protective film containing a norbornene-based resin, the norbornene-based resin is a hydrogenated norbornene-based resin, and the chemical structure represented by the general formula (1). It is characterized in that it contains a polymerizable compound having.

Hereinafter, the components will be described in detail.
<Hydrogenated norbornene resin>
The “hydrogenated norbornene-based resin” used in the present invention means that a norbornene derivative (monomer) is used alone, or the norbornene derivative and an unsaturated cyclic compound copolymerizable therewith are developed using a metathesis polymerization catalyst. A hydrogenated norbornene-based resin obtained by further hydrogenating a polymer obtained by ring polymerization or the like.
The hydrogenated norbornene-based resin is preferably a resin derived from a norbornene monomer having a chemical structure represented by the following general formula (I). In the present invention, the resin derived from the norbornene monomer having the chemical structure represented by the general formula (I) means a polymerization using the norbornene monomer having the chemical structure represented by the general formula (I) as a component. It is a resin derived from.

(In the formula, A, B, X, and Y are each independently a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, an alkoxy group, a hydroxy group, an ester group, a cyano group, an amide group, or an imide. Represents an atom or a group selected from a group and a silyl group, and m represents 0 or 1.)
The copolymerizable monomer copolymerizable with the norbornene-based monomer represented by the general formula (I) is not particularly limited, and examples thereof include a cyclic olefin-based monomer having no norbornene skeleton.

Examples of the cyclic olefin-based monomer having no norbornene skeleton include cyclooctadiene, cyclooctene, cyclohexene, cyclododecene, cyclododecatriene, and the like.

In the above norbornene-based monomer or copolymerizable monomer, it is preferable to have a polar group other than a halogen atom in the monomer structure in order to give a certain moisture permeability to the resin obtained.

The method for polymerizing the norbornene-based monomer represented by the general formula (I) or the norbornene-based monomer represented by the general formula (I) and a copolymerizable monomer copolymerizable therewith As a method of copolymerizing, for example, a conventionally known method such as ring-opening metathesis polymerization or addition polymerization can be adopted.

When the norbornene-based resin has an unsaturated bond in the molecule, it is preferably saturated by hydrogenation, and the hydrogenation rate is preferably 95% or more, more preferably 99% or more. If the hydrogenation rate is less than 95%, the resulting polarizing plate protective film is inferior in light resistance and heat deterioration resistance.

The polystyrene-converted number average molecular weight of the norbornene-based resin is preferably 10,000 to 1,000,000. When it is less than 10,000, the mechanical strength of the resulting polarizing plate protective film may be insufficient, and when it exceeds 1 million, melt extrusion moldability may be significantly lowered. More preferably, it is 15,000 to 700,000.

Examples of commercially available norbornene-based resins include, for example, "Zeonor" series, "Zeonex" series manufactured by Nippon Zeon Co., Ltd., "Opttrez" series manufactured by Hitachi Chemical Co., Ltd., "Arton" series manufactured by JSR Co., Ltd., and the like. Can be mentioned. Among them, the "Arton" series, which has a proper moisture permeability necessary for producing a polarizing plate using an aqueous adhesive, is particularly preferable because it has a polar group in the molecular skeleton.
<Polymerizable compound>
The polarizing plate protective film of the present invention is characterized by containing a polymerizable compound having a chemical structure represented by the following general formula (1).

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a methyl group or a halogen atom.
Ring A ₁ , ring A ₂ and ring A ₃ each independently represent a benzene ring, a cyclohexane ring, a cyclohexene ring, a naphthalene ring, a tetrahydronaphthalene ring, a decahydronaphthalene ring, an anthracene ring or a phenanthrene ring. During these rings, -CH = is a -N =, -CH ₂ - may be replaced by -S- or -O-.

X, Y and Z each independently represent an alkyl group having 1 to 8 carbon atoms which may have a substituent, an alkoxy group having 1 to 8 carbon atoms which may have a substituent, and a substituent. It represents an alkenyl group having 2 to 6 carbon atoms, a halogen atom, a cyano group or a group having a chemical structure represented by the following general formula (2).

L _{1, L 2} and _{L 3} represent a bond, each independently represents a single _{bond, -COO -, - OCO -,} - (CH 2) d -, - CH = CH -, - (CH 2) e _{O -, - O (CH 2} ) f -, - O (CH 2) g O -, - OCOO (CH 2) h -, - (CH 2) i OCOO -, - (CH 2) j O (CH 2 _{) k -, - O (CH} 2) l - [Si (CH 3) 2 O] m -Si (CH 3) 2 (CH 2) o -, - (OCH 2 CH 2) p -, - (CH 2 _{CH 2 O) q -, -} (OCH 2 CH (CH 3)) r -, - (CH (CH 3) CH 2) s -, - CH = CHCH 2 O -, - OCH 2 CH = CH -, - CH = CH-COO -, - OCO-CH = CH -, - C≡C -, - (CH 2) 2 COO -, - OCO (CH 2) 2 -, - CF = CF -, - OCF 2 -, _{-CF 2 O -, - C≡C-} COO -, - representing the OCO-C≡C- or -O-. However, some carbon atoms may be silicon atoms.

d to m and o each independently represent an integer of 1 to 8. p to s each independently represent an integer of 1 to 3. n represents 0 or 1.

a, b, and c are the numbers of substituents in ring A ₁ , ring A _2, and ring A ₃ , respectively, where t is the number of 6-membered rings contained in each substituted monocycle or condensed ring. , A, b and c each independently represent an integer of 2t+2 or less, and when n is 0, at least one of a and b is 1 or more. When n is 1, at least one of a, b and c is 1 or more. )
Examples of the halogen atom represented by R ₁ , R ₂ , X, Y and Z in the general formula (1) include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 8 carbon atoms which may have a substituent represented by X, Y and Z include methyl, chloromethyl, trifluoromethyl, cyanomethyl, ethyl, dichloroethyl, propyl, isopropyl and butyl. , Secondary butyl, tertiary butyl, isobutyl, amyl, isoamyl, tertiary amyl, hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 1-methylcyclohexyl, heptyl, 2-heptyl, 3-heptyl, isoheptyl, tertiary Heptyl, n-octyl, isooctyl, tertiary octyl, 2-ethylhexyl and the like can be mentioned, and as the alkoxy group having 1 to 8 carbon atoms which may have a substituent, methyloxy, chloromethyloxy, trifluoromethyl. Oxy, cyanomethyloxy, ethyloxy, dichloroethyloxy, propyloxy, isopropyloxy, butyloxy, sec-butyloxy, tert-butyloxy, isobutyloxy, amyloxy, isoamyloxy, tert-amyloxy, hexyloxy, cyclohexyloxy, heptyloxy, iso Heptyloxy, tertiary heptyloxy, n-octyloxy, isooctyloxy, tertiary octyloxy, 2-ethylhexyloxy and the like can be mentioned, and as the alkenyl group having 2 to 6 carbon atoms which may have a substituent. , Vinyl, 1-methylethenyl, propenyl, butenyl, isobutenyl, pentenyl, hexenyl and the like.

In the general formula (2), examples of the halogen atom represented by R ₃ include those exemplified as R _{1 and the} like.

In the general formula (1), when the ring A ₁ , the ring A ₂ or the ring A ₃ is a condensed ring, the position of the substituent is, for example, when the ring A ₁ is a naphthalene ring, the 1-position of the naphthalene ring. When attached is _CH 2 ₌ CR 1 -COO group, _{L 1} is attached in the 5-position and take the _CH 2 ₌ CR 1 -COO group at the 2-position, _{L 1} is as that attached to the _6-position, CH 2 = CR _{The 1-} COO group and L ₁ are bonded to the ring A ₁ at a position parallel to each other.

Even when the ring A ₁ is a decahydronaphthalene ring or a tetrahydronaphthalene ring, the same applies as in the case where the ring A ₁ is a naphthalene ring, but when the ring A ₁ is a tetrahydronaphthalene ring, CH ₂ = It suffices that the CR ₁ —COO group is bound and the L ₁ is bound to the other. When the ring A ₁ is an anthracene ring, when a CH ₂ ═CR ₁ —COO group is attached to the 1-position of the anthracene ring, L ₁ is attached to the 6-position and a CH ₂ ═CR ₁ —COO group is attached to the ₂ -position, L ₁ is at the 7-position, and when a CH ₂ =CR ₁ -COO group is attached at the 3-position, L ₁ is attached at the 8-position.

When the ring A ₁ is a phenanthrene ring, when a CH ₂ ═CR ₁ —COO group is attached to the 1-position of the phenanthrene ring, L ₁ is at the 6-position and a CH ₂ ═CR ₁ —COO group is attached to the ₂ -position, L ₁ is at the 7-position, and if a CH ₂ ═CR ₁ —COO group is attached at the 3rd position, L ₁ is attached at the 8th position. In ring A ₁ , a CH ₂ ═CR ₁ —COO group and L ₁ Is bonded to ring A ₁ so that the molecular structure of the polymerizable compound can be kept linear.

With respect to the ring A ₂ and the ring A ₃ , the bond of L ₁ , L ₂ or L ₃ is bonded according to the ring A ₁ so that the molecular structure of the polymerizable compound can be kept linear.

Further, as the polymerizable compound according to the present invention having the chemical structure represented by the above general formula (1), a polymerizable compound having the chemical structure represented by the following general formula (3) can be exemplified. The polymerizable compound represented by the general formula (3) has a large regulation of rotation due to its molecular structure. Therefore, the effect of preventing cracks of the present invention is large and more preferable.

(In the formula, X ₁ and X ₃ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or a carbon atom having 1 to 8 which may have a substituent. Represents an alkoxy group, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, a halogen atom, a cyano group or a group represented by the above general formula (2): X ₂ , X ₄ , Y ₁ to. Y ₄ and Z _{1 to} Z ₄ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or an alkyl group having 1 to 8 carbon atoms which may have a substituent. An alkoxy group, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, a halogen atom or a cyano group is represented by at least one of X _{1 to} X ₄ , Y _{1 to} Y ₄ and Z _{1 to} Z _4. Represents a substituent other than hydrogen, and rings A ₁ , A ₂ and A ₃ each independently represent a benzene ring or a cyclohexane ring, in which —CH═ is —N═ and —CH ₂ - have the same meanings as _{R 1, R 2,} f and n -S- or -O- optionally substituted by _{.R 1, R 2,} f and n are the general formula (1)).
In addition, as the polymerizable compound of the present invention represented by the general formula (1), a polymerizable compound represented by the following general formula (4) can also be mentioned. The polymerizable compound represented by the general formula (4) has a large plane rigidity in terms of molecular structure. Therefore, the effect of preventing cracks of the present invention is large and more preferable.

_{(Wherein, R 1, R 2, X} 1, X 2, X 3, X 4, Y 1 ~Y 4, Z 1 ~Z 4, A 1, A 2 and _{A 3} in the general formula (3) R ₁ , R ₂ , X ₁ , X ₂ , X ₃ , X ₄ , Y _{1 to} Y ₄ , Z _{1 to} Z ₄ , A ₁ , A ₂ and A ₃ are synonymous with f in the above general formula ( It is synonymous with f in 1).)
Further, as the polymerizable compound having the chemical structure represented by the general formula (1), a polymerizable compound represented by the following general formula (5) can also be mentioned. The polymerizable compound represented by the general formula (5) has a small molecular structure and is effective in increasing the density. Therefore, the effect of preventing cracks of the present invention is large and more preferable.

_{(Wherein, R 1, R 2, X} 1, X 3, X 2, X 4, Y 1 ~Y 4, A 1 and _{A 2, R} 1 in the general formula _{(4), R 2, X} 1 , X ₂ , X ₃ , X ₄ , Y _{1 to} Y ₄ , A ₁ and A ₂ have the same meaning.)
Specific examples of the polymerizable compound having the chemical structure represented by the general formula (1) include the following compound No. 1-29 are mentioned. However, the present invention is not limited to the following compounds.

The polymerizable compound having the chemical structure represented by the general formula (4) can be produced, for example, according to the following reaction scheme.

The polarizing plate protective film of the present invention contains the polymerizable compound having the chemical structure represented by the general formula (1) within the range of 5 to 25 mass% with respect to the hydrogenated norbornene-based resin. Is preferable from the viewpoint of expressing the effects of the present invention.

In the present invention, it is preferable that the polymerizable compound having the chemical structure represented by the general formula (1) is further contained within the range of 10 to 20 mass% with respect to the hydrogenated norbornene resin. Within such a range, it is easy to control the expansion/contraction of the polarizing plate protective film due to the temperature change to match the polarizer fill.

<Various additives for polarizing plate protective film>
The polarizing plate protective film of the present invention may contain various additives for the purpose of imparting various functions.

The typical additives applicable to the polarizing plate protective film of the present invention are shown below.

Additives applicable to the present invention are not particularly limited, as long as the effects of the present invention are not impaired, for example, ultraviolet absorbers, plasticizers, deterioration inhibitors, matting agents, retardation increasing agents, wavelength dispersion improving Agents and the like can be used.

The typical additives applicable to the polarizing plate protective film of the present invention are shown below.
<Ultraviolet absorber>
The polarizing plate protective film of the present invention may contain an ultraviolet absorber.

Examples of the ultraviolet absorber include oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like, but less colored benzotriazole-based compounds Compounds are preferred. Further, the ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574, and the polymer ultraviolet absorber described in JP-A-6-148430 are also preferably used. As the ultraviolet absorber, from the viewpoint of preventing deterioration of the polarizer and the organic EL element, it has excellent absorption of ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of displayability of the organic EL element, absorption of visible light having a wavelength of 400 nm or more is preferable. It is preferable to have few characteristics.

Examples of the benzotriazole-based ultraviolet absorber useful in the present invention include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 2-(2'-hydroxy-3',5'-di-t. -Butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl Phenyl)-5-chlorobenzotriazole, 2-[2'-hydroxy-3'-(3",4",5",6"-tetrahydrophthalimidomethyl)-5'-methylphenyl]benzotriazole, 2,2 -Methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(2'-hydroxy-3'-t-butyl-5 '-Methylphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol, octyl-3-[3-t- Butyl-4-hydroxy-5-(chloro-2H-benzotriazol-2-yl)phenyl]propionate and 2-ethylhexyl-3-[3-t-butyl-4-hydroxy-5-(5-chloro-2H- Examples thereof include, but are not limited to, a mixture of benzotriazol-2-yl)phenyl]propionate.

Further, as commercially available products, "TINUVIN 109", "TINUVIN 171", "TINUVIN 326", "TINUVIN 328" (above, BASF Japan (registered trademark)) It can be preferably used.

The addition amount of the ultraviolet absorber is preferably in the range of 0.1 to 5.0 mass% with respect to the cellulose derivative, and more preferably in the range of 0.5 to 5.0 mass %.
<Plasticizer>
Generally, a polarizing plate protective film is poor in flexibility, and when a bending stress or a shear stress is applied to the film, the film is likely to be cracked or the like. In addition, when processed as a polarizing plate protective film, cracks are likely to occur in the cut portion, and chips are likely to occur. The generated chips contaminate the polarizing plate protective film and cause optical defects. In order to improve these problems, the polarizing plate protective film may contain a plasticizer.

Specific examples of the plasticizer include phthalic acid ester-based, trimellitic acid ester-based, aliphatic dibasic acid ester-based, orthophosphoric acid ester-based, acetic acid ester-based, polyester/epoxidized ester-based, ricinoleic acid ester Examples thereof include polyolefin-based compounds, polyolefin-based compounds, and polyethylene glycol-based compounds.

The plasticizer that can be used in the polarizing plate protective film of the present invention is preferably selected from compounds that are liquid at room temperature, atmospheric pressure, and have a boiling point of 200° C. or higher. Specific compound names include, for example, aliphatic dibasic acid ester-based compounds, phthalic acid ester-based compounds, and polyolefin-based compounds.

The addition amount of the plasticizer is preferably in the range of 0.5 to 40.0 mass%, and in the range of 1.0 to 30.0 mass% with respect to the hydrogenated norbornene-based resin. Is more preferable, and it is particularly preferable that it is in the range of 3.0 to 20.0 mass %. When the added amount of the plasticizer is 0.5% by mass or more, the plasticizing effect is sufficient and the processability is improved. Further, when the content is 40% by mass or less, separation and elution of the plasticizer after a long time can be suppressed, and optical unevenness, contamination of other parts, and the like can be more reliably suppressed.

<Anti-deterioration agent>
The polarizing plate protective film of the present invention may contain a deterioration inhibitor such as an antioxidant, a peroxide decomposing agent, a radical polymerization inhibitor, a metal deactivator, an acid scavenger, and amines. ..

The deterioration preventive agent is described in, for example, JP-A-3-199201, JP-A-5-97073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854.

The addition amount of the anti-deterioration agent is the dope (water content) used in the production of the polarizing plate protective film from the viewpoint that the effect of the anti-deterioration agent is added and the bleed-out (bleeding) of the anti-deterioration agent onto the film surface is suppressed. The added norbornene-based resin solution) is preferably in the range of 0.01 to 1% by mass, more preferably 0.01 to 0.2% by mass.

Examples of particularly preferable deterioration preventing agents include butylated hydroxytoluene (abbreviation: BHT) and tribenzylamine (abbreviation: TBA).

<Fine particles of matting agent>
The polarizing plate protective film of the present invention may contain fine particles as a matting agent.

Examples of the matting agent particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, and silicic acid. Examples thereof include magnesium and calcium phosphate. Of these matting agent fine particles, those containing silicon are preferable in that the turbidity (haze) is lowered, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle size in the range of 1 to 20 nm and an apparent specific gravity of 70 g/liter or more. The average primary particle size is more preferably in the range of 5 to 16 nm from the viewpoint of reducing the haze of the polarizing plate protective film. The apparent specific gravity is more preferably in the range of 90 to 200 g/liter, and particularly preferably in the range of 100 to 200 g/liter. The larger the apparent specific gravity is, the higher the concentration of the dispersion liquid can be made, and the haze and the aggregates are improved, which is preferable.

These fine particles usually form secondary particles having an average particle size in the range of 0.05 to 2.0 μm. These secondary particles are present as aggregates of primary particles in the polarizing plate protective film, and form irregularities of 0.05 to 2.0 μm on the surface of the optical film. The secondary average particle size is preferably in the range of 0.05 to 1.0 μm, more preferably in the range of 0.1 to 0.7 μm, and in the range of 0.1 to 0.4 μm. It is particularly preferable that The primary particles and the secondary particle sizes were determined by observing the fine particles in the polarizing plate protective film with a scanning electron microscope and determining the diameter of the circle circumscribing the particles as the particle size. Further, 200 particles are observed at different places, and the average value thereof is taken as the average particle size.

As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (all manufactured by Nippon Aerosil Co., Ltd., trade name) may be used. it can. The fine particles of zirconium oxide are commercially available, for example, as Aerosil R976 and R811 (these are registered trademarks of Nippon Aerosil Co., Ltd.) and can be used.

Among these, Aerosil 200V and Aerosil R812V are fine particles of silicon dioxide having a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g/liter or more, and while maintaining low haze of the polarizing plate protective film, friction It is particularly preferable because it has a large effect of lowering the coefficient.

The matting agent particles are preferably prepared by the following method and applied to a polarizing plate protective film. That is, a matting agent fine particle dispersion liquid is prepared in advance by stirring and mixing a solvent and matting agent fine particles, and this matting agent fine particle dispersion liquid is separately prepared into various additive solutions having a hydrogenated norbornene resin concentration of less than 5% by mass. A method is preferred in which after adding and stirring and dissolving, the main hydrogenated norbornene-based resin dope is further mixed.

Since the surface of the matting agent particles is subjected to a hydrophobizing treatment, when an additive having hydrophobicity is added, the additive agent is adsorbed on the surface of the matting agent particles and the aggregate of the additives is used as a core. Is likely to occur. Therefore, by mixing a relatively hydrophilic additive in advance with the matting agent particle dispersion, and then mixing a hydrophobic additive, aggregation of the additive on the matting agent surface can be suppressed, and haze Is low, and a polarizing plate protective film with less light leakage in black display when incorporated in a liquid crystal display device can be produced, which is preferable.

It is preferable to use an in-line mixer for mixing the matting agent fine particle dispersant and the additive solution, and for mixing the hydrogenated norbornene-based resin dope. The present invention is not limited to these methods, but when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like, the concentration of silicon dioxide is preferably in the range of 5 to 30% by mass, and 10 to 25% by mass. The range is more preferable, and the range of 15 to 20% by mass is particularly preferable. The higher the dispersion concentration, the lower the turbidity with respect to the same amount added, and the haze and the generation of aggregates are suppressed, which is preferable. The addition amount of the matting agent in the final dope of the hydrogenated norbornene-based resin is preferably in the range of 0.001 to 1.0% by mass, and in the range of 0.005 to 0.5% by mass. It is more preferable that the content is in the range of 0.01 to 0.1% by mass. Next, a method for producing the polarizing plate protective film of the present invention will be described. The polarizing plate protective film of the present invention is preferably a polarizing plate protective film produced by a solution casting method or a melt casting method. Here, the manufacturing method by the solution casting method will be described.

Production of the polarizing plate protective film of the present invention, a step of dissolving the hydrogenated norbornene-based resin, and the polymerizable compound in a solvent to prepare a dope, cast on an endless metal support that transfers the dope infinitely It is carried out by a step, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or holding the width, a step of further drying, and a step of winding the finished film.

The step of preparing the dope will be described. Hydrogenated norbornene-based resin in the dope, the soluble concentration of the polymerizable compound is preferable because the thicker one can reduce the drying load after casting on the metal support, but if the concentration is too thick, the load at the time of filtration increases. As a result, the filtration accuracy becomes poor.

The concentration satisfying these requirements is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

The solvent used in the dope may be used alone or in combination of two or more kinds, but it is preferable to use a mixture of a good solvent and a poor solvent for cellulose ester in terms of production efficiency, and many good solvents are used. It is more preferable in terms of solubility of the hydrogenated norbornene resin.

A preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass of the good solvent and 2 to 30% by mass of the poor solvent. A good solvent and a poor solvent are defined as a good solvent that dissolves the hydrogenated norbornene resin used alone, and a poor solvent that swells or does not dissolve alone.

The good solvent used in the present invention is not particularly limited, but examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. Further, it is preferable that water is contained in the dope in an amount of 0.01 to 2% by mass.

As the solvent used for dissolving the hydrogenated norbornene-based resin, the polymerizable compound and the additive, the solvent removed from the film by drying in the film forming step is recovered and reused.
As a method of dissolving the hydrogenated norbornene-based resin when preparing the dope described above, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

It is preferable to dissolve with stirring while heating at a temperature not lower than the boiling point of the solvent at atmospheric pressure and under pressure so that the solvent does not boil because the formation of undissolved lumps called gel or mamako is prevented. Also preferably used is a method in which a hydrogenated norbornene-based resin is mixed with a poor solvent to wet or swell it, and then a good solvent is further added to dissolve it.

Next, the hydrogenated norbornene-based resin, the polymerizable compound and the additive solution are filtered using a suitable filter material such as filter paper.

The filter material preferably has a small absolute filtration accuracy in order to remove insoluble matters and the like, but if the absolute filtration accuracy is too small, there is a problem that the filter material is likely to be clogged.

Therefore, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium having 0.001 to 0.008 mm is more preferable, and a filter medium having 0.003 to 0.006 mm is further preferable.

The material of the filter medium is not particularly limited, and a normal filter medium can be used, but a plastic filter medium such as polypropylene or Teflon (registered trademark) or a metal filter medium such as stainless steel does not have fibers falling off. preferable.

It is preferable to remove and reduce the impurities contained in the hydrogenated norbornene-based resin as a raw material, especially the bright spot foreign matter, by filtration.

The bright spot foreign matter is obtained by arranging two polarizing plates in a crossed Nicols state, placing a polarizing plate protective film between them, irradiating light from one polarizing plate side, and observing from the other polarizing plate side. Sometimes, it is a point (foreign matter) where light from the opposite side appears to leak, and it is preferable that the number of bright spots having a diameter of 0.01 mm or more is 200 pieces/cm ² or less.

It is more preferably 100/cm ² or less, further preferably 50/m ² or less, and further preferably 0 to 10/cm ² or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

Filtration of the dope can be carried out by a usual method, but a method of filtering while heating at a temperature not lower than the boiling point of the solvent under normal pressure, and the solvent under pressure does not boil, the filtration pressure before and after filtration is The increase in the difference (called differential pressure) is small, which is preferable.

The preferred temperature is 45 to 120°C, more preferably 45 to 70°C, and even more preferably 45 to 55°C.

It is preferable that the filtration pressure is small. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

Next, casting of the dope will be described.

The metal support used in the casting step is preferably one having a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The width of the cast can be 1 to 4 m.

The surface temperature of the metal support in the casting step is −50° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the drying speed of the web can be increased, but if the temperature is too high, the web foams or becomes flat. There is a case that the property deteriorates. The preferred support temperature is 0 to 40°C to 0 to 50°C, more preferably 5 to 30°C.

Alternatively, it is also a preferable method that the web is gelated by cooling and peeled from the drum in a state of containing a large amount of residual solvent.

The method of controlling the temperature of the metal support is not particularly limited, but there are a method of blowing warm air or cold air and a method of bringing hot water into contact with the back side of the metal support.

It is preferable to use warm water because the heat can be efficiently transferred, so that the time until the temperature of the metal support becomes constant is short. When using warm air, the temperature may be higher than the target temperature.

In order for the roll-shaped polarizing plate protective film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass.

In the present invention, the residual solvent amount is defined by the following formula.

Residual solvent amount (mass %)={(M−N)/N}×100
In addition, M is the mass of the sample taken at any time during or after the production of the web or film, and N is the mass of M after heating at 115° C. for 1 hour.

In the step of drying the roll-shaped polarizing plate protective film, the web is preferably peeled off from the metal support and further dried so that the residual solvent amount is 1% by mass or less, more preferably 0.1% by mass or less. And particularly preferably 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which a large number of rolls arranged above and below are alternately passed through the web to dry) or a tenter method in which the web is conveyed and dried is employed.

In order to produce the polarizing plate protective film of the present invention, the web immediately after being peeled from the metal support is stretched in the conveying direction (=long direction) at a place where the residual solvent amount is large, and the both ends of the web are further clipped. It is particularly preferable to perform stretching in the width direction by a tenter method of gripping.

<Surface treatment>
Among the above-mentioned polarizing plate protective films, the polarizing plate protective film (outer polarizing plate protective film) arranged on the outer side may have its surface subjected to any appropriate surface treatment. Examples of the surface treatment include antiglare treatment, diffusion treatment (antiglare treatment), antireflection treatment (antireflection treatment), hard coat treatment, antistatic treatment and the like. Any appropriate method can be used as the antiglare treatment method. For example, the surface can be formed by an appropriate method in which the surface-reflected light is diffused by imparting a fine uneven structure to the surface by an appropriate method such as embossing, sandblasting, or etching.

<Characteristics of polarizing plate protective film>
As the polarizing plate protective film of the present invention, a film made of a hydrogenated norbornene-based resin is used, but it may be an unstretched film or a uniaxially stretched film. By adding the polymerizable compound described below to the resin, the degree of orientation of the resin is increased. As a result, the tensile elastic modulus is increased, and the weakness of the blade against impact during cutting, which is one of the factors causing cracks, is improved.

Further, the orientation also lowers the linear expansion coefficient of the film. Orientation is generated by cast film formation, and due to the solvent diffusion process, the contraction force acting on the film (web) on the film formation belt and the conveyance tension in the film conveyance.
<Measurement of degree of orientation>
The orientation coefficient of the polarizing plate protective film was measured according to the following method.

First, the orientation coefficient will be described.

In the present invention, the uniaxial orientation coefficient (orientation coefficient fxy) was used for measuring the orientation coefficient.

The orientation coefficient fxy can be obtained according to the following equation. For details of fxy, see P. A. Floumoy, and W. J. Reference can be made to Schaffers, Spectrochimica Acta, 22, 5 (1966).
fxy=(Dxy−1)/(Dxy+2)·(Dxy+2)/(Dxy−1)
fxz=(Dxz−1)/(Dxz+2)·(Dxz+2)/(Dxz−1)
fxy represents the orientation coefficient in the in-plane direction. Further, fxz represents an orientation coefficient in the film thickness direction. Dxy and Dxz represent infrared dichroic ratios, and both have a value of 1.00 in a completely spatially isotropic non-oriented sample.

here,
D0=cot2δ
Where δ is the angle between the transition moment vector formed by molecular vibration and the molecular axis. To calculate this exactly, it is necessary to check the direction of the moment of molecular vibration, but it is usually sufficient to select a vibration mode parallel to the molecular axis and a mode perpendicular to it, and calculate it as 0° and 90°, respectively. Information about the orientation is obtained.

Theoretically, this orientation coefficient is 0 in the case of no orientation, 1.0 in the case of being completely oriented in the observation direction, and -0.5 in the case of being orthogonal to the observation direction, conversely.

Regarding the polarizing plate protective film, the ethylene chain CC stretching vibration of the hydrogenated norbornene resin skeleton (maximum peak value of 1273 cm -1 ± 10 cm -1) was measured in a vibration mode parallel to the molecular axis (δ = 0°). Was calculated as

The infrared dichroic ratio was measured using attenuated total reflection infrared spectroscopy (ATR-IR method). The specific calculation method is described in J. P. Hobbs, C.I. S. P. Sung (JP Hobbs, C. S. P. Sung, K. Krishan, and, S. Hill, Macromolecules, 16, 193 (1983)) was referred to.

The infrared dichroic ratio was determined by measuring the intensity of a peak derived from the ethylene chain C—C stretching vibration of the hydrogenated norbornene-based resin skeleton (the strongest peak appearing in the range of 1273 cm−1±10 cm−1). The peak intensity connects the wave number at the top of the peak (assumed to be xcm-1), the point having the smallest absorbance in x to x+50 cm-1, and the point having the smallest absorbance in x to x-50 cm-1, Using this as a baseline, the peak intensity from there was measured and determined.

First, light is incident parallel to the longitudinal direction, the absorbance (ATEx) when the polarized light is perpendicular to the incident plane and the absorbance (ATMx) when the polarized plane is parallel to the incident plane, and then the parallel to the width direction. Upon incidence, ATEy and ATMy were measured in the same manner, and the infrared dichroic ratios fxy and fxz were calculated using the above-mentioned formulas.

The specific orientation coefficient fxy in the present invention was measured by the polarization ATR method under the following measurement conditions.

Measuring device: NICOLET380 manufactured by Thermo
Prism: Germanium Pressure between prism and sample: 30 cN・m
Area of jig for pressing sample to prism: 1 cm ²
Incident angle: 45°
Number of reflections: 1 time Resolution: 4 cm ^-1
Data interpolation: 0.5 cm ^-1
The refractive index of the sample was calculated as 1.477 for the cellulose derivative of the present invention. The prism (germanium) was set to 4.00. Vertically polarized light and horizontally polarized light were made incident with a wire grid polarizer on an incident plane composed of light incident on the sample surface and light reflected by the sample, and an FTIR-ATR spectrum was measured. The measurement was performed by setting the MD direction as the x-axis, the vertical direction (width direction TD) as the y-axis, and the thickness direction as the z-axis.
<Linear expansion coefficient>
The linear expansion coefficient α of the polarizing plate protective film is preferably 4.5×10 ⁻⁵ /° C. or less (PVA value), and more preferably −5.0×10 ^{−5 to} 4.5×10 ^−5. /° C., more preferably −4.5×10 ^{−5 to} 4.0×10 ⁻⁵ /° C. When the linear expansion coefficient α is within the above range, a polarizing plate having excellent crack durability can be obtained.

Preferably, the difference between the linear expansion coefficient of the polarizer in the transmission axis direction and the linear expansion coefficient α of the polarizing plate protective film is more than 0 and 4×10 ⁻⁵ /° C., more preferably 0.5. ×10 ^{−5 to} 4.0×10 ⁻⁵ /° C. When the difference between the linear expansion coefficient of the polarizer in the transmission axis direction and the linear expansion coefficient α of the polarizing plate protective film is within the above range, a polarizing plate having excellent crack durability can be obtained.

<Polarizer>
Any appropriate polarizer can be used as the polarizer used in the present invention. For example, a dichroic substance such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene/vinyl acetate copolymer partially saponified film. Uniaxially stretched film, polyene oriented film such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching the film is particularly preferable because of high polarization dichroic ratio. The thickness of these polarizers is not particularly limited and is generally about 1 to 80 μm.

A polarizer obtained by uniaxially stretching a polyvinyl alcohol film by adsorbing iodine can be produced by, for example, immersing polyvinyl alcohol in an aqueous solution of iodine, dyeing it, and stretching it to 3 to 7 times its original length. .. If necessary, it may contain boric acid, zinc sulfate, zinc chloride or the like, or may be immersed in an aqueous solution of potassium iodide or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing.

Not only can stains and antiblocking agents on the surface of the polyvinyl alcohol film be washed by washing the polyvinyl alcohol film with water, but also the effect of preventing unevenness such as uneven dyeing by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

The polarizer used in the present invention preferably satisfies 0.030≦Rpva≦0.040. Here, Rpva is a wavelength of 1000 nm, where nx is the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer, and ny is the refractive index in the direction orthogonal to the direction in which the refractive index is maximum. It is represented by Rpva=nx-ny. Rpva is more preferably 0.030≦Rpva≦0.039, and particularly preferably 0.030≦Rpva≦0.035. It is presumed that such characteristics are satisfied by increasing the amount of crystals that do not contribute to the orientation (typically, the orientation is low) in the polarizer. When the Rpva is a polarizer in such a range, it may have excellent dimensional stability and optical durability in a high temperature and high humidity environment. As a result, even when the polarizer is used for a polarizing plate in which a polarizing plate protective film is provided on only one side of the polarizer, dimensional change and deterioration of optical characteristics hardly occur, and practically acceptable dimensional stability and optical properties are obtained. Durability can be realized.

The polarizer used in the present invention has a dichroic ratio DR of preferably 160 or more, more preferably 160 to 220, particularly preferably 170 to 210, and most preferably 175 to 185. When the dichroic ratio DR is in such a range, a liquid crystal panel and a liquid crystal display device having high front contrast can be obtained by using the polarizing plate of the present invention. Such a liquid crystal panel and a liquid crystal display device are suitable for television applications, for example. The dichroic ratio DR can be obtained from the following formula.

Dichroic ratio DR=log(0.919/k ₂ )/log(0.919/k ₁ ).
Here, k ₁ is the transmittance in the transmission axis direction of the polarizer, k ₂ is the transmittance in the absorption axis direction of the polarizer, and the constant 0.919 is the interface reflectance.

The polarizer used in the present invention has a transmittance (single transmittance) Ts of preferably 42% or more, more preferably 42. To 44.0%, particularly preferably 42.5 to 43.0%. When the transmittance Ts is in such a range, a liquid crystal panel or a liquid crystal display device having high brightness can be obtained by using the polarizing plate of the present invention. Such a liquid crystal panel and a liquid crystal display device are suitable for television applications, for example. The transmittance of the polarizing plate can be calculated from the following formula.

Transmittance=(k ₁ +k ₂ )/2×100 [%]
Here, k ₁ is the transmittance in the transmission axis direction of the polarizer, and k ₂ is the transmittance in the absorption axis direction of the polarizer.

As described above, the polarizer used in the present invention may be a polarizer whose main component is a polyvinyl alcohol (PVA) resin containing a dichroic substance such as iodine or a dichroic dye.

The iodine content of the polarizer used in the present invention is preferably 1.8 to 5.0 mass%, more preferably 2.0 to 4.0 mass%. By setting the iodine content in the above range, a polarizing plate having a transmittance in a preferable range can be obtained, and a liquid crystal display device having a high contrast ratio in the front direction can be obtained.

The boric acid content of the polarizer used in the present invention is, in terms of boron, preferably 0.5% by mass to 3.0% by mass, more preferably 1.0 to 2.8% by mass, and particularly preferably Is 1.5 to 2.6 mass %. As described above, according to the present invention, a polarizer having excellent dimensional stability and optical durability in a humid environment can be obtained without increasing the amount of boric acid.

The polarizer used in the present invention may preferably further contain potassium. The potassium content is preferably 0.2 to 1.0% by mass, more preferably 0.3 to 0.9% by mass, and particularly preferably 0.4 to 0.8% by mass. By setting the potassium content in the above range, it is possible to obtain a polarizing plate having a transmittance in a preferable range and a high degree of polarization.

The linear expansion coefficient of the polarizer in the transmission axis direction is not particularly limited and may be any appropriate value. For example, when a polarizer mainly containing a polyvinyl alcohol (PVA) resin containing a dichroic substance is used, the linear expansion coefficient of the polarizer in the transmission axis direction is 4.0×10 ^{−5 to} 5.0. It may be ×10 ^-5 /°C.
<Polarizing plate>
FIG. 1 is a schematic sectional view of a polarizing plate according to a preferred embodiment of the present invention. In the embodiment of FIG. 1, the polarizing plate 101 includes the polarizer 10 and the polarizing plate protective films 20 and 30 arranged on both surfaces of the polarizer 10. The polarizer 10 and the polarizing plate protective films 20 and 30 are attached to each other via an optional adhesive layer (not shown).

A linear expansion coefficient α (hereinafter, also simply referred to as a linear expansion coefficient α) of the polarizing plate protective film 20 in a direction parallel to the transmission axis of the polarizer 10 is smaller than a linear expansion coefficient of the polarizer in the transmission axis direction. Generally, in a polarizer, the stretching direction of the film in the manufacturing process thereof coincides with the absorption axis direction. Therefore, the transmission axis direction, which is the direction orthogonal to the absorption axis of the polarizer, is very fragile and tends to tear. By using a polarizing plate protective film having a linear expansion coefficient α smaller than the linear expansion coefficient of the polarizer itself in the transmission axis direction, a polarizing plate excellent in crack durability can be obtained.

In the polarizing plate 101 illustrated in FIG. 1, the linear expansion coefficient α of at least one of the polarizing plate protective films 20 and 30 may be smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. Both of the linear expansion coefficients α may be smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. Typically, the linear expansion coefficient α of the polarizing plate protective film outside the polarizing plate 101 is a value smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. The polarizing plate protective films 20 and 30 may be polarizing plate protective films having the same material and the same linear expansion coefficient α, or different polarizing plate protective films may be used.

Polarizers generally tend to expand at higher temperatures. In the polarizing plate of the present invention, a polarizing plate protective film having a property of expanding as the temperature lowers is used.
Therefore, the polarizing plate of the present invention has a large difference in dimensional change in the transmission axis direction of the polarizer between the polarizer and the polarizing plate protective film when the temperature of the environment in which the polarizing plate is placed is increased, By using, it is possible to improve crack durability.
In the conventional polarizing plate, in order to suppress the generation of stress at the interface between the polarizer and the protective film for the polarizing plate, the difference in the linear expansion coefficient between the polarizer and the protective film is reduced, and the difference in dimensional change due to temperature change is reduced. Designed to be small.

On the other hand, in the present invention, as described above, the crack durability can be further improved by setting the linear expansion coefficient α of the polarizing plate protective film to a value smaller than the linear expansion coefficient in the transmission axis direction of the polarizer.

In the present invention, at least one of the dimensional variation in the alignment direction and the dimensional variation in the vertical direction needs to be smaller than the dimensional variation in the transmission axis direction of the polarizer.
That is, in the hydrogenated norbornene-based resin described above, a film obtained by adding the polymerizable compound described below, the dimensional variation in the direction parallel to the transmission axis of the polarizer from the dimensional variation in the transmission axis direction of the polarizer The polarizing plate of the present invention can be obtained by disposing the polarizing plate protective film so that it becomes smaller.

Further, in the present invention, since the crack durability is improved as described above, it is peeled from the glass substrate in a high temperature environment when it is laminated on a polarizer to form a polarizing plate and the polarizing plate is laminated on a glass substrate. It is possible to make a polarizing plate that is difficult to do.

<Other layers>
The polarizing plate of the present invention may further have other layers. Examples of other layers include an antireflection layer, an antistatic layer, a retardation layer, a brightness enhancement film layer, an adhesive layer, and the like. In one embodiment, the polarizing plate of the present invention is attached to a liquid crystal cell via the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer preferably has a storage elastic modulus at 23° C. of 8.0×10 ⁴ or more and less than 1.0×10 ⁷ , and 1.0×10 ^{5 to} 8.0×10 ^6. More preferable. As the other layers, any appropriate layer may be selected according to the purpose and application, the configuration of the liquid crystal display device in which the polarizing plate of the present invention is used, and the number, type, position, arrangement, etc. are appropriately set. obtain.

<Liquid crystal display>
A liquid crystal display device of the present invention includes a liquid crystal cell and the polarizing plate of the present invention arranged on at least one side of the liquid crystal cell. By using the polarizing plate of the present invention, it is possible to provide a liquid crystal display device in which the deterioration of display performance due to the occurrence of cracks is suppressed.

Driving modes of the liquid crystal cell include vertical alignment (VA) mode, twisted nematic (TN) mode, in-plane switching (IPS) mode, vertical alignment electric field controlled birefringence (ECB) mode, and optical compensation birefringence. (OCB) mode and the like.

The liquid crystal display device may be of a transmissive type in which light is radiated from the back surface of the liquid crystal panel to view the screen, or may be of a reflective type in which light is radiated from the viewing side of the liquid crystal panel to view the screen. good. Alternatively, the liquid crystal display device may be a semi-transmissive type having both transmissive and reflective properties.

The liquid crystal display device of the present invention is used for any appropriate application. Its applications are, for example, office automation equipment such as personal computer monitors, laptop computers, copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), mobile devices such as portable game consoles, video cameras, televisions, microwave ovens, etc. Household electric appliances, back monitors, car navigation system monitors, car audio and other in-vehicle equipment, commercial store information monitors and other display equipment, surveillance monitors and other security equipment, nursing monitors, medical monitors, etc. Nursing care and medical equipment.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, "%" is used, but "% by mass" is used unless otherwise specified.
[Synthesis Example 1] Synthesis of Compound A-1 Compound A-1 was synthesized according to the procedure of steps 1 to 4 below.

<Step 1> Synthesis of acrylic acid ester The following acrylic acid ester was synthesized as follows according to the reaction formula shown in the following scheme.

18.36 g (110 mmol) of 3-(4-hydroxyphenyl)propionic acid, 11.05 g (280 mmol) of sodium hydroxide and 100 g of water were charged, and 10 g (110 mmol) of acryloyl chloride was added dropwise with stirring at 20° C. for 2 hours. It was made to react. After the reaction, 4 mol/l hydrochloric acid was added dropwise to make the mixture acidic, and the precipitate was collected by filtration and air-dried. This precipitate was recrystallized from a mixed solvent of methanol/water=3/4 to obtain a white solid (yield 11.68 g, yield 48%).

The infrared absorption spectrum (IR) measurement results of the obtained white solid are as follows, and it was confirmed that the white solid was the target acrylic ester.

[IR] (cm ^-1 )
2920, 1740, 1697, 1508, 1447, 1408, 1366, 1296, 1254, 1200, 1173, 1150, 1018
<Step 2> Synthesis of benzyl ether The following benzyl ether was synthesized as follows according to the reaction formula shown in the following scheme.

1.20 g (5.6 mmol) of the acrylic ester obtained in Step 1, 1.00 g (4.7 mmol) of 4-benzyloxy-2-methylphenol, 0.171 g of N,N-dimethylaminopyridine (DMAP) ( 1.4 mmol) and 12 g of chloroform were charged, and while stirring at 20° C., a solution of 1.16 g (5.6 mmol) of dicyclohexylcarbodiimide dissolved in 12 g of chloroform was added dropwise and stirred for 3 hours. The precipitate was filtered off, the solvent was distilled off from the filtrate, and the residue was purified by column chromatography (ethyl acetate:n-hexane=1:3, SiO ₂ ) to obtain benzyl ether, which was the target substance as white crystals. Was obtained (1.83 g, yield 94%).

<Step 3> Synthesis of Phenol The following phenol was synthesized as follows according to the following reaction scheme.

After dissolving 1.76 g (13 mmol) of anhydrous aluminum chloride in 9 g of anisole and cooling with ice water, a solution of 1.83 g (4.4 mmol) of benzyl ether obtained in step 2 in 9 g of anisole was added dropwise. After stirring for 30 minutes, hydrochloric acid was added dropwise to dissolve the precipitate, followed by washing with water. The solvent was distilled off, and the residue was purified by column chromatography (ethyl acetate:n-hexane=1:5, SiO ₂ ) to obtain the target phenol as white crystals (1.00 g, yield 70). %).

<Step 4> Synthesis of Compound A-1 Compound A-1 was synthesized according to the following reaction scheme as follows.

0.90 g (3.1 mmol) of 4-(6-acryloyloxy-hex-1-yloxy)benzoic acid was dissolved in 10 g of tetrahydrofuran (THF), and after cooling with ice water, 0.42 g (3.7 mmol) of methanesulfonyl chloride. Was added and 0.74 g (7.4 mmol) of triethylamine was added dropwise at 10°C or lower. After stirring for 30 minutes, 38 mg (0.31 mmol) of DMAP was added, and 1.00 g (3.1 mmol) of the phenol obtained in step 3 dissolved in 10 g of THF was added dropwise and stirred for 30 minutes. The precipitate was filtered off, the solvent was distilled off from the filtrate, the residue was purified by column chromatography (ethyl acetate:n-hexane=1:3, SiO ₂ ), and then dissolved in chloroform and cooled in methanol. Then, white crystals were obtained (0.18 g, yield 10%). When the obtained white crystals were analyzed, it was confirmed that the white crystals were the target compound A-1. The analysis results are shown below.

In addition, when a homopolymer of the obtained compound A-1 was produced, it was confirmed that the polymer had a different refractive index depending on the direction and functioned as an optically anisotropic body.

(result of analysis)
(1) IR (cm-1)
2939, 2866, 1728, 1605, 1508, 1408, 1300, 1246, 1165, 1080, 1007
(2) NMR (ppm)
8.2 (d; 2H), 7.3-6.9 (m; 9H), 6.6-5.7 (m; 6H), 4.3-3.9 (m; 4H), 3. 2-2.8 (m; 4H), 2.1 (s; 3H), 1.7-1.4 (m; 8H)
[Synthesis Example 2] Synthesis of Compound A-29 Compound A-29 was synthesized according to the procedure of steps 1 to 3 below.

<Step 1> Synthesis of benzyl ether The following benzyl ether was synthesized according to the following reaction scheme as follows.

1.90 g (7.86 mmol) of 6-acryloyloxy-2-naphthoic acid was dissolved in 10 g of THF and cooled to -30°C, then 0.99 g (8.65 mmol) of methanesulfonyl chloride was added, and triethylamine (TEA) 1 .91 g (18.87 mmol) was added dropwise. After stirring for 1 hour, 4-dimethylaminopyridine (DMAP) 10 mg (0.08 mmol) was added, and 4-benzyloxy-2-propylphenol 2.00 g (8.25 mmol) dissolved in THF 7 g was added dropwise. Stir for 1 hour. The precipitate was filtered off and the filtrate was washed with water. The solvent was evaporated, the residue was purified by column chromatography (dichloromethane, SiO ₂ ), and recrystallized with an acetone solvent to obtain the desired benzyl ether as a white solid (yield 2.27 g, yield 61). .9%).

<Step 2> Synthesis of Phenol The following phenol was synthesized as follows according to the reaction scheme shown below.

2.01 g (15.08 mmol) of anhydrous aluminum chloride was dissolved in 9 g of anisole, cooled with ice water, and then 2.27 g (4.87 mmol) of the benzyl ether obtained in step 1 was dissolved in 9 g of anisole. After stirring for 1 hour, hydrochloric acid was added dropwise to dissolve the precipitate, followed by washing with water. The solvent was distilled off, the residue was purified by column chromatography (developing solvent: ethyl acetate/toluene=1/5, SiO ₂ ), and then recrystallized with a mixed solvent of acetone/methanol to obtain the desired product as a white solid. Phenol was obtained (1.20 g, yield 65.6%).

<Step 3> Synthesis of Compound A-29 Compound A-29 was synthesized according to the following reaction scheme as follows.

1.04 g (3.04 mmol) of 6-(6-acryloyloxy-hexyloxy)-2-naphthoic acid was dissolved in 12 g of THF and cooled to -30°C, and then 0.38 g (3.34 mmol) of methanesulfonyl chloride was added. In addition, 0.74 g (7.29 mmol) of triethylamine was added dropwise. After stirring for 1 hour, 4 mg (0.03 mmol) of DMAP was added, and 1.20 g (3.19 mmol) of the phenol obtained in Step 2 dissolved in 8 g of THF was added dropwise and stirred for 1 hour. The precipitate was filtered off, the filtrate was washed with water, the solvent was distilled off, and the residue was purified by column chromatography (developing solvent: ethyl acetate/toluene=1/5, SiO ₂ ) and then a mixed solvent of ethyl acetate/hexane. Recrystallization was performed to obtain a white solid (0.67 g, yield 31.5%). When the obtained white solid was analyzed, it was confirmed that the white solid was the target compound, Compound A-29. The analysis results are shown below.

Moreover, when a homopolymer of the obtained compound A-29 was produced, it was confirmed that the polymer had a different refractive index depending on the direction and thus functioned as an optically anisotropic body.

(result of analysis)
(1) IR (cm ^-1 )
2936, 2866, 1624, 1474, 1404, 1339, 1273, 1246, 1200, 1169, 1150, 1065, 1022
(2) 1H-NMR (ppm)
0.9 (t; 3H), 1.5-1.9 (m; 10H), 2.6 (q; 2H), 3.9-4.3 (m; 4H), 5.7-6. 6 (m; 6H), 7.1-7.5 (m; 6H), 7.7-8.3 (m; 7H), 8.7 (s; 1H), 8.9 (s; 1H)

Example 1 [Polarizing plate protective film (hereinafter simply referred to as "protective film")]

<Production of protective film 101>
<Particle dispersion liquid 1>
Fine particles (Aerosil R812V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass The above components were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton-Gaulin.

<Particle addition liquid 1>
The fine particle dispersion liquid 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the secondary particles were dispersed by an attritor so that the particle diameter became a predetermined size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive liquid 1.

Methylene chloride 95 parts by mass Fine particle dispersion 1 5 parts by mass A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Hydrogenated norbornene-based resin I was put into a pressure dissolution tank containing a solvent while stirring. It was heated and stirred to dissolve completely. This is Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. The main dope was prepared by filtration using 244.

<Main dope composition>
Methylene chloride 300 parts by mass Ethanol 19 parts by mass Hydrogenated norbornene-based resin I 100 parts by mass The polymerizable compound A-1 5 parts by mass Fine particle additive liquid 1 1 part by mass The above is charged into a closed container and dissolved while stirring to dope. Was prepared. Then, using an endless belt casting device, the dope was uniformly cast on a stainless belt support at a temperature of 33° C. and a width of 1500 mm. The temperature of the stainless belt was controlled at 30°C.

The solvent was evaporated on the stainless belt support until the amount of residual solvent in the cast film was 100%, and then the film was peeled off from the stainless belt support with a peeling tension of 130 N/m.

The peeled protective film was stretched by 5% in the width direction using a tenter while applying heat of 180°C. The residual solvent at the start of stretching was 30%.

Then, the drying was completed while being conveyed by a large number of rolls in the drying zone. The drying temperature was 130° C. and the transport tension was 90 N/m.

As described above, the protective film 101 having a dry film thickness of 20 μm was obtained. Hereinafter, in the same manner as in the protective film 101, except that the types of hydrogenated norbornene-based resins, the types of polymerizable compounds, the amounts of polymerizable compounds added, and the amounts of plasticizers and plasticizers were changed as shown in Table 1. The polarizing plate protective films 102-123 were produced.
(resin)
Hydrogenated norbornene resin I: Arton (registered trademark) (G7810) manufactured by JSR Corporation
Hydrogenated norbornene-based resin II: JSR Corporation's Arton (registered trademark) (RX4500) (preparation of plasticizer A)
62 g of ethylene glycol, 144 g of adipic acid, 30 g of benzoic acid, and 0.181 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube, and the temperature was 230°C in a nitrogen stream. The temperature was gradually increased with stirring until the temperature reached. A dehydration condensation reaction was carried out for 15 hours, and after the reaction was completed, unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain a polyester as a plasticizer. The acid value was 0.10 mgKOH/g and the number average molecular weight was 1900.
(Preparation of plasticizer B)
60 g of 1,6-hexanediol, 101 g of sebacic acid, 122 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube, and charged with nitrogen. The temperature was gradually raised with stirring until the temperature reached 230°C in the air flow. A dehydration condensation reaction was carried out for 15 hours, and after the reaction was completed, unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain a polyester as a plasticizer. The acid value was 0.10 mgKOH/g and the number average molecular weight was 600.

[Evaluation]
<Breaking strength (protective film)>
Using the polarizing plate protective films obtained in the above Examples and Comparative Examples, the film was cut in the casting direction (MD) into a width of 20 mm and a length of 250 mm, and a tensile tester was used. A constant load tensile test was performed by leaving the weight corresponding to the load hanging and leaving it for 24 hours under the condition of 23° C.-55% RH.
Then, with respect to the polarizing plate protective film before the constant load tensile test and after the constant load tensile test (within 12 hours after the constant load tensile test), using a tensile tester (Tensilon UTA-500, manufactured by Orientec Co., Ltd.), JIS The tensile strength of the film was measured according to K 7127.

In this case, the dimensions of the test pieces were all aligned to a width of 20 mm and a length of 150 mm, and the distance between chucks was 100 mm and the pulling speed was 13.3 mm/min under the conditions of 23° C. and 50% RH. The higher point strength was taken as the tensile strength.

The tensile strength before the constant load tensile test was evaluated as the breaking strength (MPa).

Further, the ratio of tensile strength=tensile strength after constant load tensile test (B)/tensile strength before constant load tensile test (A) was calculated from these measured values.

The tensile strength ratio was evaluated as a breaking strength ratio (before and after durability).

In addition, the measurement was performed 5 times for each sample, and the average value was adopted.
<Linear expansion coefficient (protective film)>
Adjust the condition for 12 hours at 25°C and 55%RH for each 3 test pieces cut out from each end and the center of the rectangular parallelepiped molded product in the length x width x thickness = 10 mm x 4 mm x 0.04 mm. After that, it was measured according to JIS K7197 using a linear expansion coefficient measuring device [model name "TMA/SS7100", manufactured by Seiko Instruments Inc.]. The dimensional change at 25 to 80°C was measured, and the average dimensional change rate per 1°C at 30 to 60°C was calculated. This measurement was performed for three end portions and three central portions of each test piece, and an average value was obtained. Furthermore, the average value of each of the three test pieces was determined and used as the linear expansion coefficient of the molded product.
<Method of measuring storage elastic modulus (protective film)>
The storage elastic modulus of the protective film is a cylinder having a diameter of 8 mm and a thickness of 1 mm as a test piece, and using a measuring instrument "RSA III" manufactured by TA Instruments Co., a torsion shearing method with a frequency of 1 Hz is used at 23° C. and 80° C. The storage elastic modulus (G′), loss elastic modulus (G″), and tan δ were measured for <Crack occurrence rate (protective film)>.
The number of corners (m) obtained by observing the number of corners (n) in which punching defects such as cracks, cracks, and chips were detected by punching 100 sheets of protective films (same configuration) and punching 100 sheets with a 10 cm square Thomson blade (m) The ratio of occurrence of punching defects was expressed as a percentage as follows.
Punching defect occurrence rate (%)=100×(n/m)
<Orientation>
It was measured according to the method described above.

These evaluation items and the degree of orientation of the polarizing plate protective films 101 to 123 were measured.

The composition of the polarizing plate protective film and the above evaluation results are shown together in Table 1.

From the results in Table 1, it can be seen that in the present invention, the crack occurrence rate is low and the degree of orientation is high.

Example 2
[Polarizing plate 1]
<Production of Polarizing Plate 301>
The protective film 101 is attached to one surface (hereinafter referred to as the A surface side) of the polarizer 1 via a PVA adhesive so as to be parallel to the transmission axis of the polarizer, and the other surface of the polarizer 1 is attached. The following protective film 205 was attached to the surface (hereinafter referred to as the B surface side) to obtain a polarizing plate 301. As described in Table 2, the polarizing plates 302 to 336 were produced in the same manner as the polarizing plate 301 except that the protective film and the polarizer were combined.
Protective film 201
(Polyethylene naphthalate film, Teonex Q83 (trade name) (manufactured by Teijin DuPont), thickness: 40 μm)
Protective film 202
(Stretched film of polyimide film, Kapton (trade name) (manufactured by Toray) Thickness: 50 μm) Protective film 203
(Polyethylene terephthalate film, MRF50 (trade name) (manufactured by Mitsubishi Plastics Co., Ltd., thickness: 50 μm)
Protective film 204
(Polyethylene terephthalate film, MRF25 (trade name) (manufactured by Mitsubishi Plastics Co., Ltd., thickness: 25 μm)
Protective film 205
(Triacetyl cellulose film, KC4UAW (trade name) (manufactured by Konica Minolta), thickness: 40 μm)
Protective film 206
(Triacetyl cellulose film, KC2UAW (trade name) (manufactured by Konica Minolta), thickness: 25 μm)

[Polarizer 1]
A PVA-based resin film having a polymerization degree of 2400, a saponification degree of 99.7 mol% and a thickness of 75 μm was prepared. The film was stretched 3 times in the film transport direction while being dyed in an aqueous iodine solution at 30° C., and then in a 4% by weight boric acid, 5% by weight potassium iodide aqueous solution at 60° C., the total draw ratio was It was stretched to be 6 times the original length. Furthermore, the stretched film was washed by immersing it in a 2% by mass aqueous potassium iodide solution at 30° C. for several seconds. The obtained stretched film was dried at 90° C. to obtain Polarizer 1. The linear expansion coefficient of the obtained polarizer 1 in the transmission axis direction was 4.5×10 ⁻⁵ /° C.

[Polarizer 2]
A polarizer 2 was obtained in the same manner as the polarizer 1, except that the total draw ratio was 5 times the original length. The linear expansion coefficient of the obtained polarizer 2 in the transmission axis direction was 4.8×10 ⁻⁵ /° C.

The following evaluations were performed on the polarizing plates 301 to 335 obtained as described above.

[Evaluation]
<Crack occurrence rate (punching)> (Polarizing plate)
100 sheets of polarizing plates were punched with a 10 cm square Thomson blade, and the number of corners (n) in which punching defects such as cracks, breaks and chips were detected was divided by the number of observed corners (m), and the punching defect occurrence rate was calculated as follows. As shown in percentage, the polarizing plate crack occurrence rate was obtained.
Polarization plate crack occurrence rate (%)=100×(n/m)
<Crack occurrence rate (durability)> (Polarizing plate)
(3-3) Heat shock acceleration test (polarizing plate)
The polarizing plate punched with a 10 cm square Thomson blade was evaluated using a thermal shock tester (made by ESPEC).

The polarizing plate punched out with a 10 cm square Thomson blade was put in the test area of the thermal shock tester, and the temperature in the test area was lowered to -40°C over 30 minutes from room temperature. Then, the temperature in the test area was raised to 85°C over 30 minutes, and then the temperature was lowered again to -40°C over 30 minutes. The number of corners at which defects such as cracks, breaks, and chips were detected after taking out the polarizing plate after repeating 20 cycles, with the process of raising the temperature from -40°C to 85°C and lowering it again to -40°C as one cycle (N) was divided by the number of observed corners (m) and expressed as a percentage as follows.
In this way, the failure occurrence rate in the heat shock acceleration test was measured and evaluated as the crack occurrence rate (durability) (polarizing plate).
Crack occurrence rate (durability) (%) = 100 x (n/m)
These items were evaluated for the polarizing plates 301 to 335.

The configuration of the polarizing plate and the above evaluation results are shown together in Table 2.

From the results of Table 2, in the polarizing plate of the present invention, cracks did not occur even after the heat shock acceleration test, and had good crack durability.
As shown in the results of Tables 1 and 2, it can be seen that the samples of the present invention can provide a polarizing plate protective film and a polarizing plate having a small crack occurrence rate.

INDUSTRIAL APPLICABILITY The present invention can be used as a polarizing plate protective film capable of forming a polarizing plate in which cracks are unlikely to occur even when a heat cycle test is carried out when a polarizing plate is produced by bonding it to a polarizer. You can Further, it can be used as a polarizing plate provided with the polarizing plate protective film.

10 Polarizer 20,30 Polarizing plate protective film 101 Polarizing plate

Claims (8)

A polarizing plate protective film containing a norbornene-based resin,
The norbornene-based resin is a hydrogenated norbornene-based resin, and
A polarizing plate protective film comprising a polymerizable compound having a structure represented by the following general formula (1).

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a methyl group or a halogen atom.
Ring A ₁ , ring A ₂ and ring A ₃ each independently represent a benzene ring, a cyclohexane ring, a cyclohexene ring, a naphthalene ring, a tetrahydronaphthalene ring, a decahydronaphthalene ring, an anthracene ring or a phenanthrene ring. During these rings, -CH = is a -N =, -CH ₂ - may be replaced by -S- or -O-.
X, Y and Z each independently represent an alkyl group having 1 to 8 carbon atoms which may have a substituent, an alkoxy group having 1 to 8 carbon atoms which may have a substituent, and a substituent. It represents an alkenyl group having 2 to 6 carbon atoms, a halogen atom, a cyano group or a group represented by the following general formula (2) that may be possessed.
L _{1, L 2} and _{L 3} represent a bond, each independently represents a single _{bond, -COO -, - OCO -,} - (CH 2) d -, - CH = CH -, - (CH 2) e _{O -, - O (CH 2} ) f -, - O (CH 2) g O -, - OCOO (CH 2) h -, - (CH 2) i OCOO -, - (CH 2) j O (CH 2 _{) k -, - O (CH} 2) l - [Si (CH 3) 2 O] m -Si (CH 3) 2 (CH 2) o -, - (OCH 2 CH 2) p -, - (CH 2 _{CH 2 O) q -, -} (OCH 2 CH (CH 3)) r -, - (CH (CH 3) CH 2) s -, - CH = CHCH 2 O -, - OCH 2 CH = CH -, - CH = CH-COO -, - OCO-CH = CH -, - C≡C -, - (CH 2) 2 COO -, - OCO (CH 2) 2 -, - CF = CF -, - OCF 2 -, _{-CF 2 O -, - C≡C-} COO -, - representing the OCO-C≡C- or -O-. However, some carbon atoms may be silicon atoms.
d to m and o each independently represent an integer of 1 to 8. p to s each independently represent an integer of 1 to 3. n represents 0 or 1.
a, b and c are the numbers of substituents in ring A ₁ , ring A ₂ and ring A ₃ , respectively, where t is the number of 6-membered rings contained in each substituted monocycle or condensed ring. , A, b and c each independently represent an integer of 2t+2 or less, and when n is 0, at least one of a and b is 1 or more. When n is 1, at least one of a, b and c is 1 or more. )

(In the formula, R ₃ represents a hydrogen atom, a methyl group or a halogen atom.) The polymerizable compound having the structure represented by the general formula (1) is contained within a range of 5 to 25 mass% with respect to the hydrogenated norbornene-based resin. Polarizing plate protective film. The polymerizable compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (3), and the polarized light according to claim 1 or claim 2. Board protection film.

(In the formula, X ₁ and X ₃ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or a carbon atom having 1 to 8 which may have a substituent. Represents an alkoxy group, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, a halogen atom, a cyano group or a group represented by the above general formula (2): X ₂ , X ₄ , Y ₁ to. Y ₄ and Z _{1 to} Z ₄ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or an alkyl group having 1 to 8 carbon atoms which may have a substituent. An alkoxy group, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, a halogen atom or a cyano group is represented by at least one of X _{1 to} X ₄ , Y _{1 to} Y ₄ and Z _{1 to} Z _4. Represents a substituent other than hydrogen, and rings A ₁ , A ₂ and A ₃ each independently represent a benzene ring or a cyclohexane ring, in which —CH═ is —N═ and —CH ₂ - have the same meanings as _{R 1, R 2,} f and n -S- or -O- optionally substituted by _{.R 1, R 2,} f and n are the general formula (1)). The polymerizable compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (4), and the polarized light according to claim 1 or claim 2. Board protection film.

_{(Wherein, R 1, R 2, X} 1, X 2, X 3, X 4, Y 1 ~Y 4, Z 1 ~Z 4, A 1, A 2 and _{A 3} in the general formula ₍₃₎ R ₁ , R ₂ , X ₁ , X ₂ , X ₃ , X ₄ , Y _{1 to} Y ₄ , Z _{1 to} Z ₄ , A ₁ , A ₂ and A ₃ are synonymous with f in the above general formula ( It is synonymous with f in 1).) The polarized compound according to claim 1 or 2, wherein the polymerizable compound having a structure represented by the general formula (1) is a compound having a structure represented by the following general formula (5). Board protection film.

_{(Wherein, R 1, R 2, X} 1, X 2, X 3, X 4, Y 1 ~Y 4, A 1 and _{A 2, R 1, R 2, X} 1 in the general formula (4) , X ₂ , X ₃ , X ₄ , Y _{1 to} Y ₄ , A ₁ and A ₂ have the same meaning.) The polarizing plate protective film according to any one of claims 1 to 5, wherein a tensile strength of the polarizing plate protective film before and after a constant load tensile test is 0.6 or more. A method of manufacturing a polarizing plate protective film to produce a polarizing plate protective film according to any one of claims 1 to 6, and at least the hydrogenated Noruboorunen resin the polymerizable compound, the solvent And a step of forming a casting film by casting the dope on a support, and a step of peeling the casting film from the support. Of manufacturing a polarizing plate protective film. The polarizing plate protective film according to any one of claims 1 to 6 is bonded to a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin. Polarizer.

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