TWI601767B - Polarizing plate protective film, polarizing plate provided with the same, Method of manufacturing liquid crystal display device and polarizing plate protective film - Google Patents

Description

Polarizing plate protective film, polarizing plate therewith, liquid crystal display device, and manufacturing method of polarizing plate protective film

The present invention relates to a polarizing plate protective film having high surface hardness and excellent dimensional stability and haze stability even in a high-temperature environment, a polarizing plate including the same, a liquid crystal display device, and a method for producing a polarizing plate protective film.

In recent years, in display devices, demands for enlargement, thinning, and the like have been strong, and development of various members including a polarizing plate has been progressing.

A polarizing plate that is combined with an image display device including an organic electroluminescence device (hereinafter also referred to as an organic EL device) generally has a configuration in which a polarizer is disposed between two protective films, and an antireflection is added to the polarizing plate. For the function, a protective film having a phase difference imparted to the side of the organic EL element is used. Further, a liquid crystal display device (LCD) has a liquid crystal cell and a polarizing plate that is paired with the liquid crystal cell.

Among the polarizing plates of the display device using the display device, in particular, the polarizing plate on the identification side is required to have high scratch resistance in order to prevent damage to the surface, and therefore, the polarizing plate for the polarizing plate used for the identification side is improved. The surface hardness of the protective film is discussed. For example, a technique of laminating a hard coat layer on a base film in order to increase the surface hardness of the polarizing plate protective film has been known (for example, refer to Patent Document 1).

On the other hand, as a base film, a cellulose acetate film which has been widely used in the past has a drawback of having hygroscopicity or moisture permeability, and a cycloolefin-based resin has few disadvantages, such as water resistance, heat resistance, and transparency. The properties, dimensional stability, and the like are good, and have been attracting attention as an excellent thermoplastic resin as a protective film. However, in the case where a cycloolefin-based resin is used as the polarizing plate protective film, there is a surface which is required for the thinning of the polarizing plate protective film accompanying the enlargement of the display screen in recent years or the expansion of the portable market. The hardness is insufficient and it is easy to cause damage.

As a countermeasure against this, it is considered that an additive can be added to the cycloolefin resin in order to obtain a high surface hardness of the film. For example, Patent Document 2 discloses a technique for increasing the surface hardness by adding a derivative of barbituric acid to a cycloolefin resin.

However, when such an additive is added to the cycloolefin-based resin, the hardness is improved, but the heat resistance is poor, and the dimensional stability or haze is deteriorated when placed in a high-temperature environment, especially as a smart type in recent years. A polarizing plate protective film that is mounted on a small portable device such as a mobile phone is not sufficient.

Therefore, it is desired to use a polarizing plate protective film which is a film having a high degree of film and has a high surface hardness and a cycloolefin resin excellent in heat resistance.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2013-127058

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2014-132071

The present invention has been made in view of the above problems, and it is an object of the invention to provide a polarizing plate protective film which has high surface hardness and excellent dimensional stability and haze stability even in a high temperature environment. Further, a polarizing plate and a liquid crystal display device including the same are provided. Further, a method of producing the polarizing plate protective film is provided.

In order to solve the above problems, the inventors of the present invention have found that the surface hardness can be improved by using a polyester-based additive having a specific structure represented by the following general formula (1) in the course of the above-mentioned problems. The present invention has been completed to realize a polarizing plate protective film which is excellent in dimensional stability and haze stability even in a high temperature environment.

That is, the above problems of the present invention are solved by the following means.

1. A polarizing plate protective film comprising a resin layer containing a cycloolefin resin, wherein the resin layer has a thickness of 50 μm or less and contains a general formula (1): Polyester additive, general formula (1): B-(GA) _n -GB (wherein B represents a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure; and G system represents a carbon number of 2~ Selected from the group consisting of 12 alkylene glycol, cycloalkylene glycol having 6 to 12 carbon atoms, oxygen alkylene glycol having 4 to 12 carbon atoms and exoarylene glycol having 6 to 12 carbon atoms At least one of the derived groups; A represents a cycloalkane dicarboxylic acid having 4 to 12 carbon atoms, a cycloalkane dicarboxylic acid having 6 to 12 carbon atoms, and a distilling aromatic group having 8 to 16 carbon atoms. At least one selected group selected from the group consisting of dicarboxylic acids; n is an integer of 0 or more).

2. The polarizing plate protective film according to Item 1, wherein the B in the above general formula (1) represents a group derived from a hydroxyl group-containing monocarboxylic acid containing an aromatic ring.

3. The polarizing plate protective film according to Item 1, wherein the polyester-based additive has a number average molecular weight of from 300 to 700.

4. The polarizing plate protective film according to the first aspect, wherein the content of the polyester-based additive in the resin layer is in the range of 2 to 10% by mass based on the cycloolefin resin.

5. The polarizing plate protective film of item 1, which has a hard coat layer on the resin layer.

6. The polarizing plate protective film of item 1, wherein the aforementioned tree The thickness of the lipid layer is in the range of 15 to 50 μm.

A polarizing plate comprising the polarizing plate protective film according to any one of the items 1 to 6 on one side of the polarizer.

A liquid crystal display device comprising the polarizing plate of item 7.

A method for producing a polarizing plate protective film, which is a method for producing a polarizing plate protective film having a polarizing plate protective film containing a resin layer of a cycloolefin resin, characterized in that it will contain a general formula (1) ) polyester and an additive represented by step on the base casting a solution containing cyclic olefin-based resin to form the resin layer, the general formula (1): B- (GA) n -GB ( wherein, B represents a line a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure; G system represents an alkylene glycol having 2 to 12 carbon atoms, a cycloalkanediol having 6 to 12 carbon atoms, and 4 to 12 carbon atoms. a group derived from a compound selected from the group consisting of an alkylene oxide diol and a condensed aromatic diol having 6 to 12 carbon atoms; and the A system represents a alkylene dicarboxylic acid having 4 to 12 carbon atoms and a carbon atom. a group derived from a compound selected from the group consisting of a cycloalkane dicarboxylic acid having 6 to 12 and a stretching aromatic dicarboxylic acid having 8 to 16 carbon atoms; and n is an integer of 0 or more).

According to the above-described means of the present invention, it is possible to provide a polarizing plate protective film which has high surface hardness and excellent dimensional stability and haze stability even in a high temperature environment. Further, a polarizing plate and a liquid crystal display device including the same can be provided. Further, a method of producing the polarizing plate protective film can be provided.

Although the expression mechanism or the action mechanism regarding the effects of the present invention has not been clarified, it is estimated as follows.

The polyester-based additive having a specific structure represented by the general formula (1) has a cyclic structure having a hydroxyl group at the terminal. It is considered that when this compound is added to the cycloolefin-based resin, the density of the resin layer is increased by the fact that the additive dissolves the free volume of the cycloolefin resin. Therefore, the increase in hardness is large, and it is presumed that a polarizing plate protective film having a small dimensional stability or a small decrease in haze can be obtained even in a high-temperature environment.

1‧‧‧Polarizer protective film

2‧‧‧ resin layer

3‧‧‧hard coating

10‧‧‧Liquid crystal display device

30‧‧‧Liquid Crystal Unit

50‧‧‧First polarizer

51‧‧‧First polarizer

53‧‧‧Protective film (F1)

55‧‧‧Protective film (F2)

70‧‧‧Second polarizer

71‧‧‧Second polarizer

73‧‧‧Protective film (F3)

75‧‧‧Protective film (F4)

90‧‧‧ Backlight

[Fig. 1] An example of the configuration of a polarizing plate protective film

[Fig. 2] An example of the configuration of a liquid crystal display device

The polarizing plate protective film of the present invention has a polarizing plate protective film containing a resin layer of a cycloolefin resin, and the resin layer has a thickness of 50 μm or less and contains the polyester represented by the above general formula (1). Additives. This feature is a technical feature common to the invention of the claims of claims 1 to 9.

As an embodiment of the present invention, in view of the effect of the present invention, it is preferred that B in the general formula (1) is a group derived from a hydroxyl group-containing monocarboxylic acid containing an aromatic ring. Further, it is preferred that the polyester-based additive has a number average molecular weight of from 300 to 700. When the number average molecular weight is 300 or more, it is easy to suppress the overflow. When the number average molecular weight is 700 or less, the compatibility with the cycloolefin resin is not easily impaired, and the increase in haze is easily suppressed.

Furthermore, in the present invention, it is preferable that the content of the polyester-based additive in the resin layer is in the range of 2 to 10% by mass based on the cycloolefin-based resin. Thereby, the surface hardness is high, and the effect of being low haze and excellent in heat resistance can be obtained.

As an embodiment of the present invention, it is preferable to have a hard coat layer on the resin layer to increase the hardness of the outermost surface.

Further, it is preferable that the thickness of the resin layer is in the range of 15 to 50 μm.

The polarizing plate protective film of the present invention can be suitably disposed on a polarizing plate. The polarizing plate of the present invention can be suitably provided in a liquid crystal display device.

The method for producing a polarizing plate protective film of the present invention is a method for producing a polarizing plate protective film having a polarizing plate protective film containing a resin layer of a cycloolefin resin, preferably containing the above formula (1) The polyester-based additive is a step of casting a solution containing a cycloolefin-based resin onto a substrate to form the resin layer.

Hereinafter, the present invention and its constituent elements, and aspects/patterns for carrying out the present invention will be described in detail. In addition, in this application In the case, "~" is used under the definition that the numerical values described before and after are used as the lower limit and the upper limit.

<<Overview of polarizing plate protective film>>

The polarizing plate protective film of the present invention has a polarizing plate protective film containing a resin layer of a cycloolefin resin, and the resin layer has a thickness of 50 μm or less and contains a polyester represented by the following general formula (1). Additives.

General formula (1): B-(GA) _n -GB

(wherein B represents a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure; and G system represents an alkylene glycol having 2 to 12 carbon atoms and a cycloalkanediol having 6 to 12 carbon atoms. At least one selected group selected from the group consisting of an alkylene oxide diol having 4 to 12 carbon atoms and an extended aromatic diol having 6 to 12 carbon atoms; and the A system is represented by a carbon number of 4 to 12 a group derived from at least one selected from the group consisting of an alkylene dicarboxylic acid, a cycloalkylene dicarboxylic acid having 6 to 12 carbon atoms, and a perylene dicarboxylic acid having 8 to 16 carbon atoms; Indicates an integer greater than 0).

Fig. 1 is an example of a polarizing plate protective film of the present invention. The polarizing plate protective film 1 of the present invention may directly use the resin layer 2 as a base film, but preferably has a hard coat layer 3 on the resin layer 2.

The thickness of the polarizing plate protective film 1 is preferably 15 to the thickness of the protective film of the polarizing plate. Within the range of 50 μm. Further, it is preferable that the thickness of the hard coat layer is in the range of 1 to 10 μm. More preferably in the range of 1 to 8 μm. More preferably, it is in the range of 3 to 5 μm.

<<Polyester additive>>

The polarizing plate protective film of the present invention has a polarizing plate protective film containing a resin layer of a cycloolefin resin, and is characterized by containing the polyester-based additive represented by the above general formula (1).

The present inventors have found that the hardness of the surface is increased by including the polyester-based additive having the structure represented by the above general formula (1) in the cycloolefin resin. Such a phenomenon is not found in cellulose acetate-based resins, and is a characteristic of a cycloolefin-based resin. In this way, the phenomenon that the above characteristics change in a specific compound is not clear, but it is presumed that the density of the substrate is increased by the free volume of the resin which is well dissolved by the additive. Therefore, since the increase in hardness is large and the decrease in heat resistance is small, it is presumed that the dimensional stability is excellent even in a high-temperature environment.

The polyester-based additive is subjected to a dehydration condensation reaction of a diol with a dicarboxylic acid, and then a hydroxyl group (from a diol) at a molecular terminal of the obtained reaction product is subjected to a carboxyl group of a hydroxyl group-containing monocarboxylic acid having a ring structure. A compound obtained by a dehydration condensation reaction.

The polyester-based additive has a structure represented by the following general formula (1).

General formula (1): B-(GA) _n -GB

In the formula, B represents a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure. The ring structure means a structure having an aliphatic hydrocarbon ring, an aliphatic heterocyclic ring, an aromatic hydrocarbon ring or an aromatic hetero ring, and preferably a structure having an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring. The hydroxyl group-containing monocarboxylic acid having a ring structure may be an alicyclic monocarboxylic acid having 5 to 20 carbon atoms, an aromatic monocarboxylic acid having 7 to 20 carbon atoms, and a mixture thereof.

The alicyclic monocarboxylic acid having 5 to 20 carbon atoms is preferably an alicyclic monocarboxylic acid having 6 to 15 carbon atoms. In the case of an alicyclic monocarboxylic acid, it includes 4-hydroxyacetic acid cyclohexyl ester, 3-hydroxyacetic acid cyclohexyl ester, 2-hydroxyacetic acid cyclohexyl ester, 4-hydroxypropionic acid cyclohexyl ester, 4-hydroxybutyric acid. Cyclohexyl ester, cyclohexyl 4-hydroxyglycolate, cyclohexyl 4-hydroxy-o-methylacetate, cyclohexyl 4-hydroxy-m-methylacetate, 4-hydroxy-p-methylacetate ring Hexyl ester, 5-hydroxy-m-methyl acetate cyclohexyl ester, 6-hydroxy-o-methyl acetate cyclohexyl ester, 2,4-dihydroxyacetic acid cyclohexyl ester, 2,5-dihydroxyacetic acid cyclohexyl ester , cyclohexyl 2-(hydroxymethyl)acetate, cyclohexyl 3-(hydroxymethyl)acetate, cyclohexyl 4-(hydroxymethyl)acetate, 2-(1-hydroxy-1-methylethyl Cyclohexyl acetate, cyclohexyl 3-(1-hydroxy-1-methylethyl)acetate, cyclohexyl 4-(1-hydroxy-1-methylethyl)acetate, and the like.

The aromatic monocarboxylic acid having 7 to 20 carbon atoms is preferably an aromatic monocarboxylic acid having 7 to 15 carbon atoms. In the case of an aromatic monocarboxylic acid, 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-o-toluic acid, 3-hydroxy-p-toluic acid, 5-hydroxyl group are contained. -m-toluic acid, 6-hydroxy-o-toluic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2- (hydroxymethyl)benzoic acid, 3-(hydroxymethyl)benzoic acid, 4-(hydroxymethyl)benzoic acid, 2-(1-hydroxy-1-methylethyl)benzoic acid, 3-(1- Hydroxy-1-methylethyl)benzoic acid, 4-(1-hydroxy-1-methylethyl)benzoic acid, and the like.

Among these, from the viewpoint of imparting sufficient hydrophobicity to the polarizing plate protective film and easily suppressing deterioration of the polarizer due to moisture, it is preferred to contain a hydroxyl group-containing monocarboxylic acid (including a hydroxyl group) containing an aromatic ring. a group derived from a monocarboxylic acid).

In the formula, G represents an alkylene glycol having 2 to 12 carbon atoms, a cycloalkylene glycol having 6 to 12 carbon atoms, an oxygen alkylene glycol having 4 to 12 carbon atoms, and a carbon number of 6~. At least one derivatized group selected from the group consisting of exo-aradiols of 12.

In the case of an alkylene glycol having 2 to 12 carbon atoms, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1 are contained. , 2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentylene glycol) ), 2,2-dimethyl-1,3-propanediol (3,3-dihydroxymethylpentane), 2-n-butyl-2-ethyl-1,3 propanediol (3,3-di) Hydroxymethylheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl- 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-nonanediol, 1,12-dodecanediol, and the like.

In the case of a cycloalkanediol having 6 to 12 carbon atoms, hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane) and hydrogenated bisphenol B (2,2-dual (4) are contained. -Hydroxycyclohexyl)butane and the like.

In the case of an alkylene glycol having 4 to 12 carbon atoms Containing diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like.

In the case of the aromatic diol having 6 to 12 carbon atoms, bisphenol A, bisphenol B and the like are contained.

The diol is used as one type or a mixture of two or more types. Among them, a point which is excellent in compatibility with a cycloolefin resin is preferably an alkylene glycol having 2 to 12 carbon atoms.

In the formula, the A system is represented by an alkylene dicarboxylic acid having 4 to 12 carbon atoms, a cycloalkane dicarboxylic acid having 6 to 12 carbon atoms, and a perylene dicarboxylic acid having 8 to 16 carbon atoms. At least one of the selected groups selected from the group.

In the case of an alkylene dicarboxylic acid having 4 to 12 carbon atoms, it comprises succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, sebacic acid, sebacic acid, and dodecanedicarboxylic acid. Acid, etc.

In the case of a cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms, it comprises 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Acid, 1,5-decahydronaphthalene dicarboxylic acid, 1,4-decahydronaphthalene dicarboxylic acid, and the like.

In the case of a diaryl dicarboxylic acid having 8 to 16 carbon atoms, it comprises phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalene dicarboxylic acid, and 1,4-naphthalene dicarboxylic acid. Wait.

The dicarboxylic acid is preferably used as one type or a mixture of two or more types. The dicarboxylic acid is preferably a mixture of a stretched dicarboxylic acid and an aromatic dicarboxylic acid. The content ratio of the alkylene dicarboxylic acid to the aromatic dicarboxylic acid is preferably a linear dicarboxylic acid: an aromatic dicarboxylic acid = 40:60 to 99:1, more preferably a 50:50 to 90: 10.

In the formula, n represents an integer of 0 or more.

The number average molecular weight of the polyester-based additive is preferably from 300 to 30,000, more preferably from 300 to 700, and even more preferably from 300 to 600. When the number average molecular weight is a certain value or more, it is easy to suppress the overflow. When the number average molecular weight is at most a certain value, the compatibility with the cycloolefin resin is not easily impaired, and the increase in haze is easily suppressed.

The number average molecular weight of the polyester-based additive can be determined by gel permeation chromatography. Specifically, a gel permeation chromatography (GPC) measuring apparatus ("HLC-8330" manufactured by TOSOH Co., Ltd.) can be used to measure the number average molecular weight of the ester compound in terms of standard polystyrene (Mn) under the following measurement conditions. ).

(measurement conditions)

Column: "TSK gel SuperHZM-M" × 2 roots and "TSK gel SuperHZ-2000" × 2

Protection column: "TSK SuperH-H"

Developing solvent: tetrahydrofuran

Flow rate: 0.35 mL/min

The number average molecular weight of the polyester-based additive can be adjusted by the reaction time of condensation or polycondensation.

The acid value of the polyester-based additive is preferably 0.5 mgKOH/g or less, more preferably 0.3 mgKOH/g or less. The valence of the hydroxyl group of the polyester-based additive is preferably 25 mgKOH/g or less, more preferably 15 mgKOH/g or less.

The synthesis of the polyester-based additive can be carried out by a hot melt condensation method or a dicarboxylic acid and a terminal seal by a conventional method and an esterification reaction or a transesterification reaction of a dicarboxylic acid, a diol, and a terminal sealing monocarboxylic acid. It is carried out by any one of the methods of interfacial condensation of a monocarboxylic acid chloride with a diol. The ratio of the diol to the dicarboxylic acid is adjusted such that the molecular end becomes a diol.

The amount of the cycloolefin-based resin added to the polyester-based additive having the structure represented by the general formula (1) is preferably in the range of 2 to 10% by mass. More preferably in the range of 3 to 7 mass%. When the amount of addition is 2% by mass or more, the effect of increasing the hardness of the protective film of the polarizing plate can be confirmed. When the amount is 10% by mass or less, it is preferable from the viewpoint of improving dimensional stability and haze stability in a high-temperature environment. .

<<Cycloolefin resin>>

The polarizing plate protective film of the present invention has a resin layer containing a cycloolefin resin. The cycloolefin resin of the present invention may, for example, be a (co)polymer having a cycloolefin monomer having the following structure.

Wherein R ¹ to R ⁴ are each independently a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxyl group, an ester group, a carboxyl group, an alkoxy group, a cyano group, a decylamino group, a fluorenylene group, a decyl group, or a polar group. A hydrocarbon group substituted with a group (i.e., a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, a decylamino group, a guanidino group, or a decyl group). However, R ¹ to R ⁴ may be bonded to each other by two or more to form an unsaturated bond, a monocyclic ring or a polycyclic ring, and the monocyclic or polycyclic ring may have a double bond or an aromatic ring. R ¹ and R ² , or R ³ and R ⁴ may also be formed to form an alkylene group. p, m is an integer of 0 or more].

In the above general formula (2), R ¹ and R ^{3 each} represent a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. R ² and R ⁴ are a hydrogen atom or a monovalent organic group, and at least one of R ² and R ⁴ represents a polar group having a polarity other than a hydrogen atom or a hydrocarbon group. m is an integer of 0~3, p is an integer of 0~3, more preferably m+p=0~4, even more preferably 0~2, especially preferably m=1, p=0. The specific single system of m=1 and p=0 is preferable because the glass transition temperature of the obtained cycloolefin resin is high and the mechanical strength is also excellent.

Examples of the polar group of the specific monomer include a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amine group, a decylamino group, and a cyano group. These polar groups can be bonded via a linking group such as a methylene group. Knot. Further, a hydrocarbon group having a polar two-valent organic group such as a carbonyl group, an ether group, a decyl ether group, a thioether group or an imine group, which is a linking group and bonded, may also be mentioned as a polar group. Among these, a carboxyl group, a hydroxyl group, an alkoxycarbonyl group or an aryloxycarbonyl group is preferred, and an alkoxycarbonyl group or an aryloxycarbonyl group is particularly preferred.

Further, at least one of R ² and R ⁴ is a monomer having a polar group represented by the formula -(CH ₂ ) _n COOR , and the obtained cycloolefin-based resin has a high glass transition temperature and low hygroscopicity, and various The point of the excellent adhesion of the material is preferred. In the above formula of the specific polar group, R is a hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms, preferably an alkyl group.

Specific examples of the copolymerizable monomer include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, dicyclopentadiene, and norbornene.

The carbon number of the cycloolefin is preferably 4 to 20, and more preferably 5 to 12.

In the present invention, the cycloolefin resin may be used alone or in combination of two or more.

The preferred molecular weight of the cycloolefin resin of the present invention is 0.2 to 5 dL/g, more preferably 0.3 to 3 dL/g, particularly preferably 0.4 to 1.5 dL/g, in terms of intrinsic viscosity [η] in _h . The polystyrene-equivalent number average molecular weight (Mn) measured by permeation chromatography (GPC) is 8,000 to 100,000, more preferably 10,000 to 80,000, particularly preferably 12,000 to 50,000, and a weight average molecular weight (Mw) of 20,000 to 300,000. More preferably, it is 30,000~250000, and the best range is from 40000 to 200000.

By intrinsic viscosity [η] _inh, the number average molecular weight and weight average molecular weight within the above range, the cyclic olefin-based resin in heat resistance, water resistance, chemical resistance, mechanical properties, and good solubility in solvents become.

The glass transition temperature (Tg) of the cycloolefin resin of the present invention is usually 110 ° C or higher, preferably 110 to 350 ° C, more preferably 120 to 250 ° C, and particularly preferably 120 to 220 ° C. At a Tg of 110 ° C or higher The situation is not deformed by use under high temperature conditions or secondary processing such as coating, printing, and the like. On the other hand, when Tg is 350 ° C or less, the solubility in a solvent will become favorable.

The polarizing plate protective film has a resin layer containing a cycloolefin resin. 50% by mass or more of the resin layer is preferably a cycloolefin resin, more preferably 70 to 90% by mass or more.

In the cycloolefin-based resin, a specific hydrocarbon-based resin described in, for example, Japanese Laid-Open Patent Publication No. Hei 9-221577, No. Hei 10-287732, and the like, can be blended, for example, in the range of the present invention. Or a well-known thermoplastic resin, thermoplastic elastomer, rubber polymer, ultraviolet absorber, organic fine particles, inorganic fine particles, etc., and may also contain a specific wavelength dispersant, a sugar ester compound, an antioxidant, a peeling accelerator, and a rubber particle. Additives such as plasticizers.

A commercially available product is preferably used as the cycloolefin resin described above, and a commercially available product is sold by JSR (stock) under the trade names of ARTON G, ARTON F, ARTON R, and ARTON RX. Japan ZEON Co., Ltd. is sold under the trade names of ZEONOR ZF14, ZF16, ZEONEX 250 or ZEONEX 280, and can be used.

<UV absorber>

The base film is further provided with an ultraviolet absorber as needed in order to improve weather resistance. The ultraviolet absorber preferably has a transmittance at a wavelength of 370 nm of 10% or less, more preferably 5% or less, and still more preferably 2% or less. By.

Examples of the ultraviolet absorber include an oxydiphenyl ketone compound, a benzotriazole compound, a salicylate compound, a diphenyl ketone compound, a cyanoacrylate compound, and a triazine compound. Nickel composite salt compound, inorganic powder, and the like. Among them, a benzotriazole-based ultraviolet absorber, a diphenylketone-based ultraviolet absorber, and a triazine-based ultraviolet absorber are preferred, and a benzotriazole-based ultraviolet absorber and a diphenylketone-based ultraviolet absorber are preferred. .

The content of the ultraviolet absorber varies depending on the type of the ultraviolet absorber, the conditions of use, and the like, but is preferably 1.0 to 5% by mass based on the base film.

<microparticle>

The base film may further contain fine particles (matting agent) in order to impart a smoothness to the surface. The microparticles may be composed of an inorganic compound or a resin.

Examples of the inorganic compound include cerium oxide, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium citrate, calcium citrate hydrate, aluminum citrate, magnesium citrate. And calcium phosphate and the like.

Examples of the resin include an anthrone resin, a fluororesin, and an acrylic resin. Among them, a ketone ketone resin is preferable, and a mesh structure having a three-dimensional shape is preferable, and for example, TOSPEARL 103, the same 105, the same 108, the same 120, the same 145, the same 3120, and the same 240 (above Toshiba) The seller of the trade name of the Silicones (share) system.

Among these, in terms of reducing the turbidity of the film, fine particles of cerium oxide are preferred. Examples of the fine particles of cerium oxide include AEROSIL R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (manufactured by Nippon Aerosil Co., Ltd.), while maintaining the haze of the film. In order to reduce the friction coefficient on the lower side, AEROSIL 200V, AEROSIL R972V, and AEROSIL R812 are preferred.

<<The physical properties of the resin layer>> <Martens hardness>

The surface hardness of the resin layer can be evaluated by measuring the Martens hardness. The Martens hardness (Vickers hardness) is a hardness measured by a micro-hardness tester using a triangular cone indenter at an angle of 115 degrees from each other using a Vickers indenter and a ridge line, and the hardness measured in the state of the load test force is increased according to the load. The relationship between the test force and the indentation depth curve is defined as "the value of the test surface F divided by the surface area As from the surface indenter", and the unit is expressed as N/mm ² . The Martens hardness (HMT115) is represented by the following formula (A).

Formula (A): HMT115=Fmax/(26.43×hmax ² )

Fmax = maximum test force

Hmax=depth maximum

The measurement of Martens hardness was carried out at 23 °C. For example, it can carry out using the ultra-fine hardness meter DUH-211 (made by Shimadzu Corporation).

When the resin layer of the present invention is at 23 ° C, the resin layer preferably has a Martens hardness of 143 N/mm ² or more, more preferably 159 N/mm ² or more. When the Martens hardness is higher, the surface of the polarizing plate protective film is less likely to be damaged. However, the upper limit is about 200 N/mm ² due to limitations in material acquisition and production conditions such as additives.

(haze)

The substrate film has a haze of 0.8% or less, preferably 0.5% or less, measured by the method of JIS K-7136.

The haze can be adjusted by the molecular weight or content of the polyester-based additive. In order to reduce the haze, for example, the molecular weight or the content of the polyester-based additive is not more than a certain value, or an aromatic ring having a high affinity with the cellulose ester is introduced into the terminal-containing hydroxyl group-containing monocarboxylic acid.

<<Manufacturing method of resin layer>>

Although the resin layer can be produced by any method, it is preferable to use a solution casting method because it is easy to form a film in comparison with a resin having a large molecular weight, and it is easy to uniformly add an additive to the resin layer. Preferably, the resin layer is formed by casting a solution containing a cycloolefin-based resin onto a substrate, and specifically, a step of casting a solution containing a cycloolefin-based resin onto a substrate to form a resin layer. good.

The resin layer can be produced by the following steps: 1) a step of dissolving the above components in a solvent to prepare a doping solution, 2) a step of casting a doping solution on an endless substrate, and 3) pouring the same. Doping into After drying, the step of peeling off to obtain a film, and 4) the step of drying and stretching the film.

Further, in the following description, the resin-only film (base film) of the present invention is also referred to as a resin film.

The solvent to be used in the step 1) may, for example, be a chlorine-based solvent such as chloroform or dichloromethane; an aromatic solvent such as toluene, xylene, benzene or a mixed solvent thereof; methanol or ethanol; Alcohol solvent such as isopropanol, n-butanol or 2-butanol; methyl sirolius, ethyl sirolius, butyl sirlo, dimethylformamide, dimethyl hydrazine, Dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether and the like. These solvents may be used alone or in combination of two or more.

In the solution casting method, the higher concentration of the cycloolefin resin in the dopant can reduce the drying load after casting on the substrate, but if the concentration of the cycloolefin resin is too high, the load during filtration will be Increase, and the filtering accuracy is deteriorated. The concentration of these two stands is preferably in the range of 10 to 35 mass%, more preferably 15 to 25 mass%. The substrate in the casting (cast) step is preferably a mirror-polished surface, and as the substrate, a stainless steel belt or a drum in which the surface is plated with a casting is preferably used.

The width of the mold can be set to 1~4m. The surface temperature of the substrate of the casting step is set at -50 ° C until the temperature at which the solvent will boil without foaming. Although the temperature is higher, the drying speed of the web speed is better, but if it is too high, the belt may be foamed or flattened.

The preferred substrate temperature is suitably determined in the range of 0 to 100 ° C, more preferably 5 to 30 ° C. Alternatively, it is also preferred to carry out gelation by cooling and peeling from the drum in a state containing a large amount of residual solvent. Although there is no particular limitation on the method of controlling the temperature of the substrate, there is a method of blowing warm air or cold air, or a method of bringing warm water into contact with the back side of the substrate. The use of warm water allows for efficient heat transfer, so that the time until the temperature of the substrate is constant is relatively short.

In the case of using warm air, consider the temperature drop of the belt due to the latent heat of evaporation of the solvent, and the case where the temperature of the boiling point or higher of the solvent is used, and the temperature of the temperature higher than the target temperature is prevented while foaming is used. .

In particular, it is preferred to carry out drying efficiently by changing the temperature of the substrate and the temperature of the drying air from the time of pouring to peeling.

In order to exhibit good planarity of the resin film, the amount of residual solvent when the tape is peeled off from the substrate is preferably in the range of 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. It is particularly preferably in the range of 20 to 30% by mass or 70 to 120% by mass.

The amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(M - N) / N} × 100

Further, M is the mass of the sample taken at any time during or after the production of the tape or film, and N is the mass after heating M at 115 ° C for 1 hour.

Further, in the drying step of the resin film, it is preferred to peel the tape from the substrate and then dry it so that the amount of the residual solvent becomes 1% by mass. Hereinafter, it is more preferably 0.1% by mass or less, and particularly preferably 0% to 0.01% by mass.

In the film drying step, a roll drying method (a method in which a belt is alternately dried by a plurality of rolls placed on the upper and lower sides) or a belt-like method in which the belt is conveyed while being conveyed is generally employed.

In the stretching step, the elongation in the maximum extending direction (the direction in which the elongation becomes the largest) is preferably in the range of 5 to 80%, more preferably in the range of 12 to 60%. For example, in the case of extending in two axial directions orthogonal to each other, the transport direction (MD direction) is 0 to 60%, and the width direction (TD direction) is 5 to 70%. The elongation (%) is defined by the following formula.

Elongation (%) = {(length of (stretching direction) of the film after stretching - length of (stretching direction) of film before stretching / length of (stretching direction) of film before stretching)} × 100

The extension temperature is 120 to 180 ° C, preferably 140 to 180 ° C, and more preferably 145 to 165 ° C.

The residual solvent of the film at the start of the stretching is preferably less than 5% by mass, more preferably 4% by mass or less, and still more preferably 2% by mass or less from the viewpoint of suppressing an increase in haze. Preferably, in order to keep the residual solvent at the start of stretching at less than 5% by mass, the film (film material) after casting the dopant is peeled off from the substrate, and the drying step is carried out to evaporate the solvent during the transfer. .

The method of extending the film is not particularly limited, and a plurality of rollers plus a peripheral speed difference, wherein a method of extending the circumferential speed difference to the MD direction is used; or the both ends of the membrane may be fixed by clips or pins by a tenter to make a clip or a needle A method in which the interval is extended in the TD direction, and the extension is performed. The extension of the TD direction is preferably performed by a tenter, and may be a pin tenter or a cloth tenter.

Further, a resin layer may be formed by a step of extending in an oblique direction by using a tenter which can be obliquely extended. The tenter which can be obliquely extended is a device which widens the film material in a heating environment in an oven in a direction in which it is inclined in the direction in which the film moves in the direction of the film width direction. The tenter is provided with an oven and a pair of left and right rails positioned in the traveling direction of the gripper for transporting the film, and a plurality of grippers that travel on the rail. Both ends of the film which are taken up from the film roll and sequentially supplied to the entrance portion of the tenter are held by the gripper, the film is guided into the oven, and the film is released from the gripper at the exit portion of the tenter. The film after the handle is released is wound around the core. Each of the pair of track systems has a continuous track having an endless shape, and the gripper that releases the holding of the film at the exit portion of the tenter moves on the outside and sequentially returns to the entrance portion.

The other steps can be carried out in the same manner as the well-known solution casting method; for example, paragraphs 0109 to 0140 of JP-A-2012-48214.

<<hard coating>>

The polarizing plate protective film of the present invention preferably has a hard coat layer. By having a hard coat layer, the impact resistance of the polarizing plate or the ease of handling can be improved.

The material for forming the hard coat layer is not particularly limited as long as it exhibits a hardness of "H" or more in accordance with the pencil hardness test prescribed in JIS K5700, and is preferably a cured product containing a reactive wire curable compound, which is hardened as an active wire. As the compound, a component containing a monomer having an ethylenically unsaturated double bond is preferably used. Although the ultraviolet curable compound or the electron beam curable compound is used as the active wire curable compound, the compound which is cured by ultraviolet irradiation is preferably excellent in terms of mechanical film strength (scratch resistance, pencil hardness). .

For example, an organic hard coat material such as an organic fluorenone type, a melamine type, an epoxy type, an acrylate type or a polyfunctional (meth)acrylic compound; an inorganic hard coat material such as cerium oxide; . Among them, the use of a hard coat layer forming material of a (meth) acrylate type or a polyfunctional (meth) acryl type compound is preferable from the viewpoint of excellent adhesion and excellent productivity. Here, (meth)acrylic acid means acrylic acid and methacrylic acid.

The (meth) acrylate type is exemplified by a (meth)acrylic acid having one polymerizable unsaturated group in the molecule, two or more, three or more, and three or more polymerizable unsaturated groups in the molecule. Ester oligomer. For example, pentaerythritol polyfunctional acrylate, dipentaerythritol polyfunctional acrylate, pentaerythritol polyfunctional methacrylate, dipentaerythritol polyfunctional methacrylate, or the like can be used as the polyfunctional acrylate. The (meth) acrylate may be used singly or in combination of two or more.

Moreover, in the hard coat layer of the present invention, it is possible not to damage the present Within the scope of the effects of the invention, various additives are further blended as needed. For example, an antioxidant, an ultraviolet stabilizer, an ultraviolet absorber, a surfactant, a leveling agent, an antistatic agent, or the like can be used. Further, the hard coat layer of the present invention contains a range of an average particle size of 0.2 to 10 μm. The particles can impart a lubricity, and can also disperse the particles containing the high refractive index to impart a refractive index.

The leveling agent is particularly advantageous for surface unevenness reduction when the hard coat layer is coated. As the leveling agent, for example, a ketone-based leveling agent is preferably a dimethyl polyoxyalkylene-polyoxyalkylene copolymer.

The particles having an average particle size of 0.2 to 10 μm are preferably inorganic particles, and examples of the inorganic particles include zinc oxide, ITO (indium oxide/tin oxide), ATO (yttria/tin oxide), and oxidation. At least one selected from the group consisting of tin, indium oxide, tungsten oxide, composite tungsten oxide, and cerium oxide. Among them, the cerium oxide microparticle system is particularly preferable because it can particularly improve the surface hardness and can particularly improve the strength. Further, from the viewpoint of adding ultraviolet absorption performance to the hard coat layer and suppressing deterioration of the hard coat layer with time, it is preferred to use ITO, ATO, tungsten oxide or composite tungsten oxide.

As the ultraviolet stabilizer, for example, a hindered amine-based ultraviolet stabilizer which is highly stable to ultraviolet rays is preferably used. By containing an ultraviolet stabilizer, the hard coat layer can inactivate inertia, active oxygen, and the like generated by ultraviolet rays, thereby improving ultraviolet stability and weather resistance.

Examples of the ultraviolet absorber include a salicylic acid-based ultraviolet absorber, a diphenylketone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, a cyanoacrylate-based ultraviolet absorber, and a triazine-based ultraviolet absorber. Benzo For the ketone-based ultraviolet absorber or the like, one or more selected from the group of the above-mentioned groups can be used. Among them, in terms of dispersibility, a triazine-based ultraviolet absorber, benzo is preferred. Ketone UV absorber. Moreover, as the ultraviolet absorber, a polymer having an ultraviolet absorbing group in a molecular chain is also suitably used. By using a polymer having an ultraviolet absorbing group in the molecular chain, deterioration of the ultraviolet absorbing function due to overflow of the ultraviolet absorbing agent or the like can be prevented. Examples of the ultraviolet absorbing group include a benzotriazole group, a diphenylketone group, a cyanoacrylate group, a triazine group, a decanoate group, and a benzalmalonate group. Among them, a benzotriazole group, a diphenylketone group, and a triazinyl group are particularly preferred.

<Method for Producing Polarizing Plate Protective Film with Hard Coating Layer>

A polarizing plate protective film having a hard coat layer (also referred to as a polarizing plate protective film having an HC layer) can be produced by the following steps: 1) preparing a resin film as described above, and 2) coating an active film on the resin film After the coating liquid for the energy ray-hardened layer, it is dried and hardened to obtain an active energy ray-hardened layer (hard coat layer).

The step of preparing the resin film of the above 1) is as described above.

The coating system of the coating liquid for an active energy ray-hardening layer of the above 2) can be carried out by any means such as a dipping method, a die coating method, a wire bar method, or a spray method.

The curing of the coating film of the coating liquid for an active energy ray-hardening layer of the above 2) can be carried out by irradiating an active energy ray. Examples of the light source that illuminates the active energy ray (preferably ultraviolet ray) include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, and the like. The amount of irradiation light may be about 20 to 10000 mJ/cm ² , preferably 50 to 2000 mJ/cm ² . The irradiation time is preferably 0.5 second to 5 minutes, and more preferably 3 seconds to 2 minutes from the viewpoint of work efficiency and the like.

The dry layer thickness of the hard coat layer is preferably in the range of 1 to 8 μm, more preferably in the range of 3 to 5 μm.

<Polarizer>

A polarizer is a member that passes only light of a plane of polarization in a certain direction, and is now a representative polarizer-based polyvinyl alcohol-based polarizing film. The polyvinyl alcohol-based polarizing film is obtained by dyeing a polyvinyl alcohol-based film with iodine and dyeing with a dichroic dye.

The polyvinyl alcohol-based polarizing film may be a film obtained by dyeing a polyvinyl alcohol-based film by uniaxial stretching and then dyeing with iodine or a dichroic dye (preferably, a film obtained by applying a durability treatment to a boron compound) Further, after the polyvinyl alcohol-based film is dyed with iodine or a dichroic dye, the film may be subjected to uniaxial stretching (preferably, a film obtained by applying a durability treatment to a boron compound). The absorption axis of the polarizer is parallel to the direction in which the film extends.

For example, the content of the ethylene unit described in JP-A-2003-248123, JP-A-2003-342322, and the like can be 1 to 4 mol%, the polymerization degree is 2000 to 4000, and the degree of saponification is 99.0. 99.99% of ethylene modified polyvinyl alcohol. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cut-off temperature of 66 to 73 ° C is preferably used.

The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 10 to 20 μm in order to reduce the thickness of the polarizing plate.

<Other polarizing plate protective film>

The polarizing plate protective film or the base film may be disposed on the other side of the polarizer as needed, and other polarizing plate protective films may be disposed.

In the case of other polarizing plate protective films, commercially available cellulose halide films are included (for example, KONICA MINOLTA TAC KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR). -1, KC8UY-HA, KC8UX-RHA, KC8UE, KC4UE, KC4HR-1, KC4KR-1, KC4UA, KC6UA or higher Konica Minolta (share) system, etc.

In the present invention, it is preferable that the polarizing plate protective film of the present invention is provided on one side of the polarizer, and the retardation film is provided on the other side of the polarizer.

Other polarizing plate protective films are preferably phase difference films. The hysteresis of the retardation film varies depending on the type of the liquid crystal cell to be combined. However, for example, at 23 ° C and 55% RH, the retardation Ro (590) measured in the in-plane direction at a wavelength of 590 nm is preferably 20 to 100 nm. The retardation Rth (590) in the thickness direction is preferably 70 to 300 nm. A protective film having a hysteresis of the above range is suitable as a phase difference of, for example, a VA liquid crystal cell or the like. film. Each hysteresis value can be measured by the following method.

The hysteresis Ro and Rth are defined by the following equations.

Formula (I): Ro = (n _{x -} n _y ) × _d (nm)

Formula (II): Rth={(n _x +n _y )/2-n _z }×d(nm)

(In the formulae (I) and (II), n _x represents the refractive index of the retardation axis direction x in which the refractive index becomes the largest in the in-plane direction of the film; n _y is expressed in the in-plane direction of the film and the foregoing The refractive index of the direction y in which the slow axis direction x is orthogonal; n _z is the refractive index in the thickness direction z of the film; d (nm) is the thickness of the film)

The hysteresis Ro and the Rth system can be obtained by, for example, the following method.

1) The polarizing plate protective film was conditioned at 23 ° C and 55% RH. The average refractive index of the polarizing plate protective film after the humidity adjustment is measured by an Abbe refractometer or the like.

2) The protective film of the polarizing plate after the humidity control was measured by KOBRA-21DH and the prince measuring machine (strand), and Ro of the light having a wavelength of 590 nm was incident on the normal line of the surface of the film in parallel.

3) The KOCRA-21ADH was used to measure the slow axis in the plane of the protective film of the polarizing film as the tilt axis (rotation axis), and the incident angle (the incident angle (θ)) from the normal to the surface of the film was θ. The hysteresis value R(θ) at the time of measuring light having a wavelength of 590 nm. The hysteresis value R(θ) is measured in the range of θ from 0 to 50°, and can be measured at every 10° scale. set. The in-plane retardation axis refers to the axis in which the refractive index becomes the largest in the plane of the film, which can be confirmed by KOBRA-21ADH.

4) From the measured Ro and R(θ), and the average refractive index and film thickness described above, n _{x ,} n _{y , and} n _z were calculated by KOBRA-21ADH, and Rth at a measurement wavelength of 590 nm was calculated. The measurement of the hysteresis can be carried out at 23 ° C, 55% RH.

The polarizing plate of the present invention can be obtained by the following steps: a step of bonding a polarizer to the polarizing plate protective film of the present invention via an adhesive; and a step of cutting the bonded laminate into a predetermined size. The adhesive used for the bonding may be a completely saponified polyvinyl alcohol aqueous solution (water paste), or may be carried out using an active energy ray-curable adhesive.

<<LCD display device>>

The liquid crystal display device of the present invention comprises a liquid crystal cell and a polarizing plate which is paired with the liquid crystal cell.

Fig. 2 is a schematic view showing an example of a basic configuration of a liquid crystal display device. As shown in FIG. 2, the liquid crystal display device 10 of the present invention includes a liquid crystal cell 30, a first polarizing plate 50, a second polarizing plate 70, and a backlight 90 which are held by the liquid crystal cell 30.

The display mode of the liquid crystal cell 30 may be various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, etc., in order to obtain high contrast, a VA (MVA, PVA) mode is preferred.

The first polarizing plate 50 includes a first polarizer 51 and a polarizing plate protection thin film disposed on a surface opposite to the liquid crystal cell of the first polarizer 51. The film 53 (F1) and the polarizing plate protective film 55 (F2) disposed on the liquid crystal cell side of the first polarizer 51.

The second polarizing plate 70 includes a second polarizer 71, a polarizing plate protective film 73 (F3) disposed on a surface of the liquid crystal cell side of the second polarizer 71, and a liquid crystal cell disposed opposite to the second polarizer 71. The polarizing plate of the side faces protects the film 75 (F4). One of the polarizing plate protective films 55 (F2) and 73 (F3) is omitted as needed.

Next, the polarizing plate protects at least one of the films 53 (F1) and 75 (F4); preferably, the polarizing plate protective film 53 (F1) may be the polarizing plate protective film of the present invention. The polarizing plate protective film 53 (F1) has a base film 53A and an active energy ray-hardened layer 53B, and the base film 53A is in contact with the first polarizer 51. The polarizing plate protective film 53 (F1) is a liquid crystal display device of the polarizing plate protective film of the present invention, and since the scratch resistance of the surface is high, the display screen can be easily damaged.

The polarizing plate protective film of the present invention is not only used as a polarizing plate protective film for a liquid crystal display device, but also preferably used as an image display device including a touch panel, or an image display device such as an organic EL display or a plasma display device. Protective film.

[Examples]

Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited thereto. In addition, in the embodiment, the expression "part" or "%" is used, but unless otherwise stated, it means "mass portion" or "mass%".

The compounds used in the following examples are indicated together with their symbols.

[Synthesis of Polyester Additives]

The polyester-based additives PE1 to PE9 having the structure represented by the general formula (1) and the polyester-based additives PE10 and PE11 as comparative polyester-based additives were synthesized. Further, (A-4) described in JP-A-2014-132071 is used as the comparative compound PE12.

<Synthesis of Polyester Additive PE1>

In a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube, 341 parts of ethylene glycol, terephthalic acid and succinic acid were used in a molar ratio of 5:5 to 410 parts, 4-hydroxybenzoic acid. 610 parts and 0.35 parts of tetraisopropyl titanate as an esterification catalyst, while stirring under a nitrogen stream, while adding a reflux condenser to reflux an excess amount of the monovalent alcohol, and continuing to heat at 230 ° C until the acid value When it is 2 or less, the generated water is continuously removed. Next, unreacted ethylene glycol was distilled off at 200 ° C under a reduced pressure of 4 × 10 ² Pa or less to obtain a polyester-based additive PE1.

<Synthesis of polyester additives PE2~PE4 and PE9~PE11>

The polyester additives PE2 to PE4 and PE9 were obtained in the same manner except that the diol (G), the dicarboxylic acid (A), and the terminal blocking monocarboxylic acid (B) were changed as shown in Table 1. PE11.

<Synthesis of polyester additive PE5~PE8>

In the synthesis of PE4, the reaction time was changed to synthesize different molecular weight polyester additives PE5~PE8.

The number average molecular weight of the obtained polyester-based additive was measured by the following method.

(Measurement of number average molecular weight (Mn))

Using a gel permeation chromatography (GPC) measuring apparatus ("HLC-8330" manufactured by TOSOH Co., Ltd.), the number average molecular weight (Mn) of the polyester compound in terms of standard polystyrene was measured under the following conditions.

Column: "TSK gel SuperHZM-M" × 2 roots and "TSK gel SuperHZ-2000" × 2

Protection column: "TSK SuperH-H"

Developing solvent: tetrahydrofuran

Flow rate: 0.35 mL/min

The results of these are shown in Table 1.

[Cycloolefin resin]

COP1: cycloolefin resin (manufactured by ARTON G7810, JSR)

COP2: cycloolefin resin (manufactured by ARTON R5000, JSR)

COP3: cycloolefin resin (manufactured by ARTON RX4500, JSR)

[hard coating liquid] (Modulation of Hard Coating Liquid 1 (HCl))

The hard coat coating liquid 1 of the following composition was prepared. After the ultraviolet curable resin and the surfactant were mixed with propylene glycol monomethyl ether, the mixture was stirred for 30 minutes to prepare a hard coat coating liquid 1.

<<Production of polarizing plate protective film 1>> [Modulation of main dopants]

A main dopant of the following composition is prepared. First, dichloromethane and ethanol were added to the pressure dissolution tank. The cycloolefin resin was placed in a pressure dissolution tank containing a mixed solution of dichloromethane and ethanol while stirring. This was heated and completely dissolved while stirring. The main dopant was prepared by filtering it using an filter paper No. 244 made of an augmentation filter paper.

(main dopant)

The above components were placed in a sealed container, and dissolved while stirring to prepare a main dopant. Next, the dopant was uniformly cast on the stainless steel strip substrate at a temperature of 31 ° C and a width of 1800 mm using an endless belt casting apparatus. The temperature of the stainless steel belt was controlled at 28 °C.

On the stainless steel belt substrate, the solvent was evaporated until the amount of residual solvent in the film after casting (molding) became 30%. Next, peeling was performed from the stainless steel tape base at a peeling tension of 128 N/m. The residual solvent at the start of stretching of the peeled film was 5% by mass. After peeling off the film raw material, the peeled film raw material was uniaxially stretched in the width direction (TD direction) at an elongation of 30% under conditions of 160 °C. Then, the drying zone was dried while being conveyed by a plurality of rolls, and the end portion sandwiched by the tenter cloth was cut by a laser cutter, and then wound to prepare a resin film 1 having a thickness of 40 μm ( Resin layer 1).

On one side of the resin film 1 obtained above, the hard coat layer coating liquid 1 was applied by a micro gravure printing so as to have a dry film thickness of 3 μm, and dried.

Then, using a high-pressure mercury lamp, the coating film is irradiated with ultraviolet light at a light amount of 270 mJ/cm ² in the atmosphere to be cured, and the polarizing plate protective film 1 in which the resin film 1 is formed into a hard coat layer is produced.

<<Production of polarizing plate protective film 2>>

In the production of the polarizing plate protective film 1, the resin film 2 and the polarizing plate protective film 2 were produced in the same manner as in the production of the polarizing plate protective film 1 except that the main dopant was changed as follows.

(main dopant)

<<Manufacture of polarizing plate protective film 3~24>>

In the production of the polarizing plate protective film 2, as shown in Table 2, the type of the cycloolefin-based resin contained in the main dopant, the type and amount of the polyester-based additive, and the thickness of the resin layer, and the polarized light are changed. The protective film 2 is produced in the same manner, and the resin film 3 to 24 and the polarizing plate protective film 3 to 24 are produced.

<<Evaluation of polarizing plate protective film>>

For the resin films 1 to 24 and the resin film 1 to 24 having a hard coat layer, and for the resin layer (resin film) having no hard coat layer, Martens hardness, heat resistance dimensional stability, and heat resistance haze are performed. Evaluation. The polarizing plate protective film having a hard coat layer on the resin layer was evaluated for pencil hardness, heat-resistant curl, and heat-resistant haze.

<Martens hardness>

The measurement of the Martens hardness is performed on a resin layer (resin film) having no hard coat layer.

The surface hardness of the resin layer was evaluated by measuring the Martens hardness. The Martens hardness (Vickers hardness) is a hardness measured by the state of the load test force using a microhardness tester using a triangular cone indenter whose angle between the Vickers indenter and the ridge line is 115 degrees, and the test according to the load increase. The relationship of the force-pressing depth curve is defined as "the value of the surface area As in which the test force F is divided by the intrusion from the surface indenter", and the unit is expressed as N/mm ² . The Martens hardness (HMT115) is represented by the following formula.

HMT115=Fmax/(26.43×hmax ² )

Fmax = maximum test force (measured at 12mN)

Hmax=depth maximum

Further, the measurement conditions here are implemented by "Fmax = 12 mN".

Both sides of the resin film were measured, and Table 2 shows the average value thereof.

<heat-resistant dimensional stability>

The dimensional change rate in the extension (MD) direction after each sample was placed in a thermostat at 90 ° C for 500 hours was measured using a measuring microscope STM6 (manufactured by OLYMPUS). The absolute value of the rate of change is evaluated according to the following ratings.

◎: The rate of change is less than 0.05%

○: The rate of change is 0.05% or more and less than 0.20%.

×: the rate of change is 0.20% or more

<heat-resistant haze>

The haze at a high temperature environment was evaluated by measuring the change in haze after conditioning each resin film at 23 ° C, 55% RH for 12 hours, and after 120 hours in an environment of 80 ° C / 90% RH. Stability.

The measurement of haze was carried out by haze (full haze) by HAZE METER NDH-2000 (made by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136. The HAZE METER light source is a 5V9W halogen lamp, and the light receiving unit is a neon battery (with a relative visibility filter).

The measurement of the haze was carried out under the conditions of 23 ° C and 55% RH, and the difference between the haze value after the treatment and the haze value before the treatment was evaluated by the following classification.

◎: the difference is less than 0.03%

○: the difference is 0.03% or more and less than 0.05%

△: the difference is 0.05% or more

<pencil hardness>

The surface hardness of the polarizing plate protective film having a hard coat layer was measured by a pencil hardness evaluation method according to JIS K 5400. Specifically, the hard coat film was subjected to humidity conditioning at 23 ° C 55% / RH for 24 hours. Thereafter, the operation of scratching the surface of the hard coat layer with a pencil of each hardness was repeated five times using a scale of 1 kg, and the maximum value of the hardness of the flaw was determined to be one or less. The larger the value of the maximum value, the higher the hardness.

<heat resistant curl>

When a hard coat layer is provided on the resin layer, since the thermal expansion ratio of the resin layer and the hard coat layer is different in an environment at a high temperature, curling occurs. Therefore, the curl was measured as an index of heat resistance dimensionality. Each sample was conditioned at 23 ° C and 55% RH for 12 hours, and then curled in the extension (MD) direction after being placed in a thermostat at 90 ° C for 500 hours.

The template for crimp measurement of Method A in "Method for Measuring Curl of Photo Film" in JIS K 7619-1988 was used. Here, the positive curl means that the hard coat coating side of the film is a curled inner side, and the negative side means that the coated side is a curl on the outer side of the bend. Further, the crimp is represented by the following formula A.

(Formula A) Curl = 1 / R R system radius of curvature (m)

The absolute value of the curl amount of the measurement result was classified as follows.

◎: The absolute value is less than 5

○: Absolute value of 5 or more, less than 10

△: Absolute value of 10 or more, less than 15

×: absolute value of 15 or more

<heat-resistant haze>

In the same manner as the measurement of the heat-resistant haze of the resin film, for the resin film having a hard coat layer, the measurement was carried out in an environment of 80 ° C / 90% RH. The change in haze after hourly treatment.

Based on the above results, it was found that the polarizing plate protective film which satisfies the requirements of the present invention has a high surface hardness and is excellent in dimensional stability and haze even in a high temperature environment. Further, it has been found that it can be used for a polarizing plate and a liquid crystal display device having the same.

In addition, in the production of the polarizing plate protective film 4, the thickness of the resin layer is changed to 80 μm, and the results of evaluation of the resin film and the polarizing plate protective film produced in the same manner as the polarizing plate protective film 4 are The pencil hardness was 2H, and the other characteristics were the same as those of the resin layer 16 and the polarizing plate protective film 16 having a thickness of 50 μm. However, the requirements for a high film were not compatible.

[Industrial availability]

The polarizing plate protective film of the present invention is a film having a high surface hardness and excellent dimensional stability and haze stability even in a high temperature environment, and can be preferably provided in a polarizing plate or a liquid crystal display device.

Claims (8)

A polarizing plate protective film comprising a resin layer containing a cycloolefin resin, wherein the resin layer has a thickness of 50 μm or less, and is represented by the following general formula (1), and the number average a polyester-based additive having a molecular weight of 300 to 700, and a general formula (1): B-(GA) _n -GB (wherein B represents a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure; G system represents an alkylene glycol having 2 to 12 carbon atoms, a cycloalkanediol having 6 to 12 carbon atoms, an oxygen alkylene glycol having 4 to 12 carbon atoms, and a carbon number of 6 to 12 a group derived from at least one selected from the group consisting of aromatic diols; and A is a cycloalkane dicarboxylic acid having 4 to 12 carbon atoms; a cycloalkane dicarboxylic acid having 6 to 12 carbon atoms; At least one of the groups selected from the group consisting of the aromatic aryl dicarboxylic acids having 8 to 16 carbon atoms; n is an integer of 0 or more). The polarizing plate protective film of claim 1, wherein the B in the above general formula (1) represents a group derived from a hydroxyl group-containing monocarboxylic acid containing an aromatic ring. The polarizing plate protective film of claim 1, wherein the content of the polyester-based additive in the resin layer is in the range of 2 to 10% by mass based on the cycloolefin resin. The polarizing plate protective film of claim 1, which has a hard coat layer on the resin layer. The polarizing plate protective film of claim 1, wherein the thickness of the resin layer is in the range of 15 to 50 μm. A polarizing plate comprising a polarizing plate protective film according to any one of claims 1 to 5 on one side of a polarizer. A liquid crystal display device comprising the polarizing plate of claim 6. A method for producing a polarizing plate protective film, which is a method for producing a polarizing plate protective film having a polarizing plate protective film containing a resin layer of a cycloolefin resin, characterized in that it is contained in the following general formula (1) a polyester-based additive, wherein a solution containing a cycloolefin-based resin is cast on a substrate to form the resin layer, and the general formula (1): B-(GA) _n -GB (wherein B is represented by a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure; G system represented by an alkylene glycol having 2 to 12 carbon atoms, a cycloalkanediol having 6 to 12 carbon atoms, and a carbon number of 4 to 12; a group derived from a compound selected from the group consisting of an alkylene oxide diol and a condensed aromatic diol having 6 to 12 carbon atoms; and the A system represents a alkylene dicarboxylic acid having 4 to 12 carbon atoms and a carbon number. a group derived from a compound selected from the group consisting of 6 to 12 cycloalkane dicarboxylic acids and a aryl dicarboxylic acid having 8 to 16 carbon atoms; n is an integer of 0 or more).