TW201617378A - Optical film, polarizing plate equipped with the optical film, liquid crystal display device, and method for producing an optical film - Google Patents

Abstract

An optical film (polarizing plate protecting film) is equipped with a substrate and a hard coat layer provided on the substrate. The hard coat layer is a layer obtained by curing a photocurable composition on the substrate. The photocurable composition includes an epoxide represented by Chemical Formula I below, a bisphenol compound, and a cationic photopolymerization initiator.

Description

Optical film, polarizing plate therewith, liquid crystal display device, and method of manufacturing optical film

The present invention relates to an optical film, a polarizing plate, a liquid crystal display device, and a method for producing an optical film which are suitable as a protective film for a polarizing plate.

In recent years, liquid crystal display devices have been widely used for liquid crystal televisions, liquid crystal panels such as personal computers, mobile phones, and digital cameras. Generally, a liquid crystal display device has a liquid crystal panel member in which polarizing plates are provided on both sides of a liquid crystal cell, and display is performed by controlling light from a backlight member with a liquid crystal panel member. The polarizing plate is configured to have a polarizing mirror and at least one protective film of a polarizing plate.

The recent liquid crystal display devices are high-quality and versatile in use, and are intended to be used in various environments, and are required to meet environmental durability and performance stability. It is assumed that a liquid crystal display device used outside the house is in a polarizing plate, and the polarizing plate protective film for protecting the surface thereof is required to have durability such as hardness or brittleness for use outside the house, dimensional stability against temperature or humidity change, and optics. Characteristic stability. In particular, in a high-humidity environment, deterioration of the polarizing lens due to moisture absorption is a problem, and low moisture permeability of the polarizing plate protective film is an important issue.

Patent Document 1 discloses an optical film excellent in durability in an environment of high temperature and high humidity, which is a thermosetting property containing a polycarboxylic acid resin and an epoxy resin and/or an oxetane resin as essential components. The resin composition is obtained by hardening. The example of Patent Document 1 discloses that a film having a film thickness of 80 μm formed on a PET film (polyethylene terephthalate film) has a pencil hardness as high as H and as low as 6 B, and a water absorption rate of 2.8% is the lowest. .

Patent Document 2 discloses a polarizing plate comprising at least one polarizing plate protective film, the polarizing plate protective film comprising at least one resin, and a ratio of molecular weight/aromatic ring number having at least one hydrogen-bonding hydrogen-donating group of 300 or less A polarizer durability improver for the compound.

According to the polarizing plate of Patent Document 2, even in a high-temperature and high-humidity environment, the polarizer is excellent in durability and curl is small, and it is difficult to cause a cause even when incorporated in a liquid crystal display device. The warpage or skew of the liquid crystal panel caused by the use environment, and the display unevenness caused by them.

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open Publication No. 2007-297604

Patent Document 2 Japanese Patent Laid-Open Publication No. 2013-174861

However, in the polarizing plate of Patent Document 1, the evaluation of the hardness and water absorption of the polarizing plate protective film was carried out by using a thick film having a film thickness of 80 μm. In consideration of the film thickness required for the polarizing plate protective film in the years in which the liquid crystal display has been developed to be lighter and thinner, the polarizing plate protective film of Patent Document 1 is difficult to satisfy sufficient hardness and moisture permeability (see the comparative example described later). ).

Further, in Patent Document 2, the evaluation of the durability is performed only on the change in the size or optical characteristics with respect to the change in temperature or humidity, and the evaluation of the hardness of the protective film for the polarizing plate is not performed at all. As the hardness level of the film required for development of thinning becomes high, it is difficult to consider the purpose of protecting the film to sacrifice the hardness in order to impart environmental resistance.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical film suitable as a polarizing plate protective film having high hardness and low moisture permeability.

Another object of the present invention is to provide a polarizing plate and a liquid crystal display device which are less deteriorated from moisture absorption.

The optical film of the present invention is an optical film comprising a hard coat layer on a substrate, the hard coat layer is a layer which hardens the photocurable composition on the substrate, and the photocurable composition contains the following chemical formula I The epoxide, bisphenol compound and photocationic polymerization initiator are represented. In addition, this issue The method for producing an optical film according to the invention is a method for producing an optical film comprising a hard coat layer on a substrate, and coating the substrate with an epoxide represented by the following chemical formula I, a bisphenol compound, and photocationic polymerization. The photocurable composition of the initiator is formed into a film to form a coating film, and the coating film is irradiated with light to cure the coating film to form a hard coat layer.

In the method for producing an optical film or an optical film of the present invention, the bisphenol compound is preferably represented by the following general formula II-1, and more preferably represented by the following general formula II-2.

In the formula, R ¹ and R ^{2 each} represent a hydrogen atom, a halogen atom or a hydrocarbon group having 1 to 15 carbon atoms. X is a divalent linking group composed of at least one selected from a single bond, a hydrocarbon group having 1 to 15 carbon atoms, an oxygen atom, a sulfur atom, and a sulfonyl group.

Wherein R ¹ , R ² , R ³ and R ⁴ represent hydrogen or a hydrocarbon group having 1 to 15 carbon atoms, and R ³ and R ⁴ may be bonded to form a cyclic structure.

In the chemical formula I, the general formula II-1, and the general formula II-2, the hydrocarbon group having 1 to 15 carbon atoms may be any of a straight chain, a branch, and a ring.

In the general formulae II-1 and II-2, R ¹ and R ^{2 are} preferably hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, more preferably R ¹ -based hydrogen and R ² -methyl.

In the method for producing an optical film or an optical film of the present invention, the content of the bisphenol compound is preferably from 1 to 40% based on the total solid content of the photocurable composition.

Further, the substrate is preferably a cellulose ester substrate.

The light to be applied to the coating film formed by coating the photocurable composition is preferably ultraviolet light. The irradiation of light is preferably carried out in a state where the substrate on which the coating film is formed is heated, and it is more preferable that the heating is not performed after the light irradiation.

The optical film of the present invention is suitable as a polarizing plate protective film.

The polarizing plate of the present invention comprises a polarizing mirror and an optical film of the present invention on at least one surface of the polarizing mirror.

The liquid crystal display device of the present invention is a liquid crystal display device having a pair of polarizing plates and liquid crystal cells held by them, and at least one of the pair of polarizing plates has the above-described polarizing plate of the present invention.

In the present specification, the "low moisture permeability (low moisture permeability)" of the optical film means that the moisture permeability of the optical film is a value of JIS Z 0208 after 24 hours at 40 ° C and a relative humidity of 90%. It is 200 g/m ² /day or less.

Further, the "high hardness (high hardness)" of the optical film means that the hardness of the optical film is JIS K5600-5-4 and the pencil hardness is F or more.

The optical film of the present invention is an optical film comprising a hard coat layer on a substrate, and is produced by coating an epoxide, a bisphenol compound and a photocation represented by the above Chemical Formula I on a substrate. The photocurable composition of the polymerization initiator is formed into a film to form a coating film, and the coating film is irradiated with light to cure the coating film to form a hard coat layer. The hard coat layer in which the photocurable composition is photohardened has a high hardness and a low moisture permeability. Thus, according to the present invention, it is possible to provide an optical film which is high in hardness and low in moisture permeability and is suitable as a protective film for a polarizing plate.

The polarizing plate of the present invention comprises the optical film of the present invention as a polarizing plate protective film. Thus, according to the present invention, it is possible to provide a polarizing plate and a liquid crystal display device which are less deteriorated from moisture absorption.

1‧‧‧Liquid crystal display device

2‧‧‧LCD

10‧‧‧Polarizing plate, upper polarizing plate, front polarizing plate, viewing side polarizing plate

12‧‧‧Direction of the absorption axis of the polarizing plate

13‧‧‧The upper substrate of the electrode of the liquid crystal cell

14‧‧‧Orientation control direction of electrode substrate

15‧‧‧Liquid layer

16‧‧‧The lower substrate of the electrode of the liquid crystal cell

17‧‧‧Orientation control direction of electrode substrate

18‧‧‧Lower polarizer and rear polarizer

19‧‧‧Direction of the absorption axis of the polarizing plate

100‧‧‧ polarizer

110‧‧‧Optical film, polarizing plate protective film

111‧‧‧Substrate

112‧‧‧hard coating

120‧‧‧Polarizer protective film

130‧‧‧Optical anisotropic layer

Fig. 1 is a schematic cross-sectional view showing the configuration of an optical film according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing a configuration of a polarizing plate according to an embodiment of the present invention.

Fig. 3 is a schematic perspective view showing a configuration of a liquid crystal display device according to an embodiment of the present invention.

[Formation for carrying out the invention] "Optical film (polarizer protective film)"

An optical film (polarizing plate protective film) according to an embodiment of the present invention will be described with reference to the drawings. Figure 1 shows the invention A schematic view of the configuration of the optical film 110 of one embodiment. Moreover, for the sake of easy viewing, the drawings of the present specification are displayed by appropriately changing the scale and size of each part. In the present specification, when the numerical value indicates the physical property value and the characteristic value, the description "(value 1) to (value 2)" means "(value 1) or more (value 2) or less".

As shown in Fig. 1, the optical film 110 is provided with a hard coat layer 112 on the substrate 111, and the hard coat layer 112 is a layer on the substrate 111 which cures the photocurable composition. The photocurable composition contains an epoxide (compound 1a) represented by the following chemical formula I, a bisphenol compound, and a photocationic polymerization initiator.

The hard coat layer 112 obtained by curing the photocurable composition is high in hardness and low in moisture permeability, and therefore is suitable as a film member requiring high hardness and low moisture permeability. Each component of the optical film 110 will be described.

<Substrate>

The base material 111 is not particularly limited, and examples thereof include a cellulose ester film, a polycarbonate film, a polyester film such as polyethylene terephthalate or polyethylene naphthalate, and a polymethyl group. A (meth)acrylic film such as methyl acrylate, a styrene copolymer film such as polystyrene or an acrylonitrile-styrene copolymer, or a cyclic polyolefin film. The substrate 111 is preferably a cellulose ester film because the epoxide (monomer) of the compound 1a is easily permeable and the adhesion between the substrate and the polarizing plate resin film is high.

As the cellulose ester film, a known film, a plate, a sheet, or the like containing a cellulose ester can be used, and is not particularly limited. As the cellulose ester film, a deuterated cellulose film (for example, a cellulose triacetate film (refractive index 1.48), a cellulose diacetate film, a cellulose acetate butyrate film, cellulose B can be used. Acid ester propionate film) and the like.

Among them, a cellulose-deposited cellulose film having high transparency, low optical birefringence, easy production, and generally used as a protective film for a polarizing plate is more preferable, and a cellulose triacetate film is more preferable. The transparency of the substrate 111 is preferably such that the transmittance of visible light is 80% or more.

As the deuterated cellulose film, cellulose acetate having a degree of acetylation of 59.0 to 61.5% is preferably used.

The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is measured and calculated according to the degree of acetylization in ASTM: D-817-91 (test method for cellulose acetate, etc.). The viscosity average polymerization degree (DP) of the deuterated cellulose is preferably 250 or more, more preferably 290 or more.

Further, the deuterated cellulose film substrate preferably has a value of Mw/Mn (Mw is a weight average molecular weight, and Mn is a number average molecular weight) based on gel permeation chromatography, and is close to 1.0, in other words, a molecular weight distribution is narrow. The specific value of Mw/Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, most preferably 1.4 to 1.6.

In general, the hydroxyl groups of 2, 3, and 6 of the deuterated cellulose are not uniformly distributed to 1/3 of the overall degree of substitution, and the degree of substitution of the 6-position hydroxyl group tends to be small. In the present invention, the degree of substitution of the hydroxyl group at the 6-position of the deuterated cellulose is preferably more than the 2,3 position. 6-hydroxyl is preferred over the overall degree of substitution More than 32% are replaced by sulfhydryl groups, more preferably 33% or more, and particularly preferably 34% or more. Further, it is preferred that the degree of substitution of the fluorenyl group at the 6-position of the deuterated cellulose is 0.88 or more. In addition to the ethyl ketone group, the 6-position hydroxyl group may be substituted with a fluorenyl group having a carbon number of 3 or more, a fluorenyl group, a butyl group, a pentamidine group, a benzamidine group, an acryl group or the like. The measurement of the degree of substitution at each position can be determined by NMR.

For example, the paragraphs "0043" to "0044" [Examples], [Synthesis Example 1], and paragraphs "0048" to "0049" of JP-A No. 11-5851 can be exemplified. [Synthesis Example 2], cellulose acetate obtained by the method described in the paragraphs "0051" to "0052" [Synthesis Example 3].

The thickness of the substrate 111 is usually set to about 20 μm to 1000 μm. When the base material 111 is a cellulose ester base material, the film thickness is preferably 20 μm or more and 70 μm or less.

<hard coating>

As described above, the hard coat layer 112 is formed by curing a photocurable composition coated on the substrate 111 to form a film. First, the photocurable composition of the present embodiment will be described.

<Photocurable composition>

The photocurable composition coated on the substrate 111 contains an epoxide (compound 1a) represented by the following chemical formula I, a bisphenol compound, and a photocationic polymerization initiator.

(epoxide (compound 1a))

The above epoxide (compound 1a) is a bifunctional epoxide. By the bifunctionality, a crosslinked hard coat layer having a three-dimensional mesh structure can be produced. The hardness of the crosslinked polymer film-based film becomes higher than that of the uncrosslinked film.

When the content of the compound 1a is 50% by mass or more based on the total solid content in the photocurable composition, it is preferable in terms of both low moisture permeability and high hardness, and more preferably 60% by mass or more. .

In addition, the content of the compound 1a is preferably 99.5% by mass or less, and more preferably 99% by mass or less based on the total solid content in the photocurable composition.

The present inventors have found that when the molecular weight of the polyfunctional epoxy monomer is 270 or less, preferably 140 or more and 260 or less, the molecular weight between the crosslinking points in the polymer can be reduced, and the moisture permeability can be lowered. Further, the present inventors have found that a polyfunctional epoxy monomer, in addition to an epoxy ring, can have an excessive development of plasticization while imparting an additive having low moisture permeability and the like by having a cycloalkane as a cyclic skeleton. The case of reduced hardness. From the viewpoint of the molecular design, the present inventors have found an epoxy monomer which is suitable for low moisture permeability and hardness.

The compound 1a is an epoxy monomer capable of imparting a polymer having low moisture permeability and hardness, and by polymerizing a bisphenol compound as an additive, the polymer of the compound 1a can be further reduced in moisture permeability.

(bisphenol compound)

The present inventors have carefully examined the additives which can further reduce the moisture permeability without using the epoxy resin of the compound 1a in the case of using the epoxy monomer of the compound 1a.

As a result, the present inventors have found that the bisphenol compound can be the low moisture permeability agent, and completed the present invention. The bisphenol compound is known to be useful as an antioxidant, but this time it has been found to have a very high effect of imparting low moisture permeability, and even if it is added at a high concentration, it does not have a significant influence on the hardness of the resin.

Examples 2 to 5 which will be described later show that even when the amount of the bisphenol compound added is 2, 4, or 6 times, the pencil hardness is maintained at H, and on the other hand, the moisture permeability is increased with the amount of addition. The increase, the low moisture permeability is significantly improved.

In the patent formula 2, the general formula (1) which is a polarizer durability improver containing a compound having a molecular weight/aromatic ring number of at least one hydrogen bondable hydrogen group of 300 or less is disclosed as having a phenol structure. Compound. However, Patent Document 2 does not describe a specific example of the bisphenol compound, nor does it describe or suggest the characteristics of the bisphenol compound.

Hereinafter, a bisphenol compound which is suitable in the present embodiment will be described.

The bisphenol compound is not particularly limited, but is preferably a bisphenol compound represented by the following general formula II-1, more preferably a bisphenol compound represented by the following general formula II-2.

In the formula, R ¹ and R ^{2 each} represent a hydrogen atom, a halogen atom or a hydrocarbon group having 1 to 15 carbon atoms. X is a divalent linking group composed of at least one selected from a single bond, a hydrocarbon group having 1 to 15 carbon atoms, an oxygen atom, a sulfur atom, and a sulfonyl group.

Wherein R ¹ , R ² , R ³ and R ⁴ represent hydrogen or a hydrocarbon group having 1 to 15 carbon atoms, and R ³ and R ⁴ may be bonded to form a cyclic structure.

In the general formulae II-1 and II-2, R ¹ and R ^{2 are} preferably hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, more preferably an R ¹ system, from the viewpoints of compatibility and moisture permeability. Hydrogen, R ² is a methyl group.

The content of the bisphenol compound is preferably from 1 to 40% based on the total solid content of the photocurable composition.

Hereinafter, preferred specific examples of the bisphenol compound are shown, but the present invention is not limited to these specific examples.

(Photocationic polymerization initiator)

The epoxy ring of the above compound 1a generates a polymerization reaction when irradiated with active energy in the presence of a photocationic polymerization initiator. As the photocationic polymerization initiator, an onium salt, a phosphonium salt, a diazonium salt or the like can be used. Specifically, "Irgacure 290 (trade name, BASF)", "Irgacure 250 (same)", and "Irgacure 270" can be used. ")), "CPI-100P (trade name, Sun Apollo)", "CPI-101A (same)", "CPI-200K (same)", "CPI-210S (same)", "WPI-170 ( The product name, Wako Pure Chemical Industries, Ltd.) or the diaryl sulfonium salt described in claim 1 of Patent No. 4,841,935.

In view of the reason that the epoxy ring is polymerized and the initiation point is not excessively increased, the content of the photocationic polymerization initiator is preferably from 0.5 to 8 by mass based on the total solid content of the photocurable composition. %, more preferably 1 to 5% by mass.

(solvent)

The photocurable composition can contain a solvent. As the solvent, various solvents can be used in consideration of solubility of the monomer, drying property at the time of coating, dispersibility of the light-transmitting particles, and the like. Examples of such an organic solvent include dibutyl ether, dimethoxyethane, diethoxyethane, propylene oxide, and 1,4-two. Alkane, 1,3-dioxolane, 1,3,5-three Alkane, tetrahydrofuran, anisole, phenylethyl ether, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, acetone, methyl ethyl ketone (MEK), diethyl ketone, dipropyl ketone, diiso Butyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, ethyl formate, propyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate Ester, γ-butyrolactone, methyl 2-methoxyacetate, methyl 2-ethoxyacetate, ethyl 2-ethoxyacetate, ethyl 2-ethoxypropionate, 2-methoxy Methyl such as ethanol, 2-propoxyethanol, 2-butoxyethanol, 1,2-diethoxypropenylacetone, etidylacetone, diacetone alcohol, methyl acetate, ethyl acetate Alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, cyclohexyl alcohol, isobutyl acetate, methyl isobutyl ketone (MiBK), 2-octanone, 2-pentanone, 2-hexanone, Ethylene glycol ethyl ether, ethylene glycol isopropyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, ethyl carbitol, butyl carbitol, hexane, pentane, octane, cyclohexane Alkane, methylcyclohexane, ethylcyclohexane, benzene, toluene, xylene, etc. They can be used alone or in a combination of two or more thereof.

Among the above solvents, at least one of methyl acetate, ethyl acetate, methyl ethyl ketone, etidyl acetone, acetone, cyclohexanone, toluene, and xylene is preferably used.

Among them, in particular, in the viewpoint of having permeability to the cellulose ester substrate, the substrate 111 is preferably at least one selected from the group consisting of methyl acetate, methyl ethyl ketone, acetone, and cyclohexanone.

In addition, the solvent is preferably used in such a manner that the concentration of the solid content in the photocurable composition is in the range of 5 to 90% by mass.

In the photocurable composition, a solvent, an inorganic filler, an ultraviolet absorber, a surfactant, and a light-transmitting resin particle can be further added as needed. Hereinafter, each component will be described.

[Inorganic Filler]

The inorganic filler can be added to the photocurable composition in accordance with the desired refractive index, film strength, film thickness, coatability, and the like.

The shape of the inorganic filler is not particularly limited, and for example, any of a spherical shape, a plate shape, a fiber shape, a rod shape, an amorphous shape, and a hollow shape can be preferably used.

Further, the type of the inorganic filler is not particularly limited, and an amorphous one may preferably be used, preferably an oxide, a nitride, a sulfide or a halide containing a metal, particularly preferably a metal oxide. It is yttrium oxide. Examples of the metal atom include Na, K, Mg, Ca, Ba, Al, Zn, Fe, Cu, Ti, Sn, In, W, Y, Sb, Mn, Ga, V, Nb, Ta, Ag, Si, B, Bi, Mo, Ce, Cd, Be, Pb, Ni, and the like. In order to increase the affinity of the inorganic filler to the organic component, it is also possible to treat the surface of the inorganic filler with a surface modifying agent comprising an organic segment.

In order to obtain a transparent cured film, the average particle diameter of the inorganic filler is preferably in the range of 0.001 to 0.2 μm, more preferably 0.001 to 0.1 μm, still more preferably 0.001 to 0.06 μm. Here, the average particle diameter of the particles was measured using a Coulter counter.

Further, the inorganic filler can be used in a dry state or can be used in a state of being dispersed in water or an organic solvent.

[UV absorber]

The polarizing plate protective film of the present invention can be used for a polarizing plate or a video display device member, but can also be formed by photocurability in forming a hard coat layer from the viewpoint of preventing deterioration of a polarizing plate or a liquid crystal cell or the like. The ultraviolet absorber is contained in the material to impart ultraviolet absorbing property to the polarizing plate protective film.

As the ultraviolet absorber, a known one can be used. For example, the ultraviolet absorber described in JP-A-2001-72782 or JP-A-2002-543265 can be cited.

As the ultraviolet absorber, from the viewpoint of excellent absorption of ultraviolet light having a wavelength of 370 nm or less and good liquid crystal display property, it is preferable to use a small amount of visible light having a wavelength of 400 nm or more. The ultraviolet absorber may be used alone or in combination of two or more. For example, the ultraviolet absorber described in JP-A-2001-72782 or JP-A-2002-543265 can be cited. Specific examples of the ultraviolet absorber include, for example, an oxybenzophenone-based compound, a benzotriazole-based compound, a salicylate-based compound, a benzophenone-based compound, and a cyanoacrylate-based compound. Nickel mismatched salt compound, three A compound or the like.

[Translucent resin particles]

The photocurable resin composition for forming a hard coat layer of the present embodiment may contain translucent resin particles (also referred to as light-diffusing particles). By including the light-transmitting particles in the photocurable resin composition for forming a hard coat layer, the surface of the hard coat layer 112 can be provided with an uneven shape to impart internal haze.

The average particle diameter of the light-transmitting resin particles is 1.0 μm or more and 8.0 μm or less, preferably 1.2 μm or more and 6.0 μm or less, and more preferably 1.4 μm or more and 3.0 μm or less. In the present specification, the average particle diameter means a primary particle diameter. If the average particle size is 1.0 μm or more, it is possible to control the particles. The agglomeration of the particles moderately increases the surface unevenness of the hard coat layer 112, exhibiting anti-glare properties. Further, in the case of particles having an average particle diameter of 3.0 μm or less, in the case where a desired surface shape is to be formed, it is not necessary to excessively thicken the thickness of the hard coat layer 112, that is, it is possible to suppress a decrease in curl or brittleness.

As means for adjusting the surface unevenness shape to a specific range, it is also preferred to use two or more kinds of particles having different average particle diameters.

When the method for measuring the particle diameter of the light-transmitting resin particles is a method for measuring the particle diameter of the particles, an arbitrary measurement method can be applied, and there is a method of measuring the particle size distribution of the particles by the Coulter counter method. The measured distribution is converted into a particle distribution obtained by the particle number distribution; or a transmission electron microscope (magnification: 500,000 to 2,000,000 times) is used to observe the particles, and 100 particles are observed, and the average value thereof is taken as the average particle diameter. Methods.

Further, in the present specification, the average particle diameter is a value obtained by a Coulter counter method.

In order to produce the surface uneven shape in the hard coat layer 112, the ratio of the film thickness of the hard coat layer to the average particle diameter of the light-transmitting resin particles (the film thickness of the hard coat layer/the average particle size of the light-transmitting resin particles) is preferable. The diameter is designed to be 1.0 to 2.0, more preferably 1.1 to 1.9, and even more preferably 1.2 to 1.8. When the ratio is 1.0 or more, the unevenness of the surface of the film does not become excessively large, and is excellent from the viewpoint of denseness of black or point defects. On the other hand, when it is 2.0 or less, it is not necessary to add a large amount of particles in order to achieve desired anti-glare property, and it is excellent in the viewpoint of the hardness of a film.

In the case where the uneven shape is provided on the surface of the hard coat layer 112, it is preferable to design the arithmetic mean roughness Ra of the surface uneven shape. It is 0.01 to 0.25 μm, more preferably 0.01 to 0.20 μm, still more preferably 0.01 to 0.15 μm. When the value of Ra is 0.01 μm or more, clear anti-glare properties can be obtained. On the other hand, when the value of Ra is 0.25 μm or less, high darkness is exhibited.

The haze value in the hard coat layer 112 is preferably from 0.3 to 5.0%, more preferably from 0.5 to 3.0%, still more preferably from 0.5 to 2.0%. By designing the haze within this range, it is possible to achieve both excellent anti-glare properties and blackening properties.

The refractive index of the light-transmitting resin particles is obtained by dispersing the light-transmitting particles in an equal amount in two kinds of solvents having different refractive indexes selected from diiodomethane, 1,2-dibromopropane, and n-hexane. The mixing ratio was changed so that the turbidity was measured in a solution in which the refractive index was changed, and the refractive index of the solvent when the turbidity reached extremely small was measured by an Abbe refractometer.

The translucent resin particles can impart internal scattering properties by controlling the difference in refractive index between the binder and the binder. However, if the internal scattering property is large, the contrast is lowered. Therefore, it is preferable to remove the antiglare layer from the translucent resin particles. The difference in refractive index is designed to be 0.010 or less, and the difference in refractive index between the translucent resin particles and the binder is 0.01 or less, preferably 0.005 or less, and more preferably 0. By setting the refractive index difference within this range, the reduction in contrast due to internal scattering can be almost eliminated.

Specific examples of the light-transmitting resin particles include crosslinked polymethyl methacrylate particles, crosslinked methyl methacrylate-styrene copolymer particles, crosslinked polystyrene particles, and crosslinked methyl groups. Methyl acrylate-methyl acrylate copolymer particles, crosslinked methyl methacrylate-styrene copolymer particles, melamine-formaldehyde resin particles, benzoguanamine-A Resin particles such as aldehyde resin particles. Among them, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, crosslinked methyl methacrylate-styrene copolymer particles, and the like are preferable. Further, a surface-modified particle chemically bonded to a surface of the resin particles by a compound containing a fluorine atom, a halogen atom, a carboxyl group, a hydroxyl group, an amine group, a sulfonic acid group, a phosphoric acid group or the like; and a cerium oxide or zirconium oxide may also be exemplified. The nanoparticles of the nanometer size are bonded to the particles on the surface.

The light-transmitting resin particles used in the present embodiment may be one type or two or more types. The content of the light-transmitting resin particles is from 0.5 to 12% by mass based on the total solid content in the photocurable composition for forming a hard coat layer, from the viewpoint of imparting anti-glare properties and high-concentration blackness. 1 to 10% by mass, more preferably 2 to 8% by mass.

[Surfactant]

In particular, in order to ensure uniformity of surface condition such as coating unevenness, uneven drying, and point defects, the photocurable composition of the present embodiment preferably contains a surfactant of any of a fluorine-based or an anthrone-based surfactant. Or contain both. In particular, the fluorine-based surfactant can be preferably used because it exhibits an effect of improving surface state defects such as uneven coating, uneven drying, and point defects with a small amount of addition. Productivity can be improved by improving the uniformity of the surface state and holding a suitable high-speed coating property.

A preferred example of the fluorine-based surfactant is a copolymer containing a fluoroaliphatic group (hereinafter, abbreviated as "fluorine-based polymer"). Specific examples of the fluorine-based polymer are described in [0037] to [0045] of JP-A-2005-115359, and [0063] to [0071] of JP-A-2006-117915.

The amount of the fluorine-based polymer to be added as a surfactant is preferably 0.001 to 5 parts by mass, more preferably 0.005 to 3 parts by mass, even more preferably 0.01 to 1 by mass, per 100 parts by mass of the coating liquid. The scope of the share. When the amount of the fluorine-based polymer to be added is 0.001 parts by mass or more, the effect of adding the fluorine-based polymer can be sufficiently obtained, and if it is 5 parts by mass or less, the coating film is not sufficiently dried, and the coating film is not sufficiently dried. There is a problem that the performance (for example, reflectance and scratch resistance) of the coating film adversely affects.

The photocurable composition of the present embodiment is configured as described above.

In the optical film 110, the hard coat layer 112 is formed by applying the photocurable composition to the substrate 111, and then irradiating the obtained coating film with light to cure the photocurable composition. The light to be irradiated is preferably ultraviolet light, and the illuminance of the ultraviolet ray is preferably from 10 to 5,000 mW/cm ² , and the irradiation amount is preferably from 10 to 10,000 mJ/cm ² .

Further, it is preferable that the hard coat layer 112 irradiates light to the substrate 111 coated with the photocurable composition in a range of from 10 to 90 ° C, and more preferably in a state of from 30 to 90 ° C. By being set in this temperature range, the reaction of the epoxy monomer can be performed more efficiently. Further, in order to be set in this temperature range, heating may be performed as needed. The temperature of the substrate 111 at this time can be measured by PT-2LD manufactured by OPTEX Corporation.

Further, the hard coat layer 112 can also be formed by heating after irradiation with ultraviolet rays. However, if the desired performance can be obtained after light irradiation, the complexity of the process and the suppression of damage to the substrate or other layers are obtained. In view of the above, it is preferred not to perform heating after the light irradiation.

The film thickness of the hard coat layer 112 formed as described above is not particularly limited, but is preferably 3 μm or more and 30 μm or less, more preferably 4 μm or more and 20 μm or less, and still more preferably 5 μm or more and 15 μm or less. By setting the film thickness of the hard coat layer to 3 μm or more, it is possible to obtain sufficient hard coat properties and to reduce moisture permeability. When the thickness is 30 μm or less, drying is easy in the step of applying and drying the substrate. In addition, excellent brittleness can be obtained.

Further, the film thickness of the hard coat layer 112 can be measured from the difference between the thicknesses of the hard coat layer and the laminate.

The optical film 110 is described as a representative example in the absence of any layer between the substrate 111 and the hard coat layer 112, but in the range in which the effects of the present invention can be obtained, the substrate 111 and the hard coat layer are provided. There may be other layers between 112.

For example, from the viewpoint of the adhesion between the substrate 111 and the hard coat layer 112, the optical film 110, or between the substrate 111 and the hard coat layer 112, preferably has a composition before the hard coat layer 112 is cured. A layer (mixed layer) which is infiltrated into the substrate 111 before the end of the hardening and is hardened in the infiltrated state. By having this layer, the adhesion between the substrate 111 and the hard coat layer 112 is improved. The thickness of the mixed layer is preferably 0.1 μm or more and 3 μm or less. The presence or absence of the mixed layer and the thickness thereof can be confirmed by observing the cross section of the polarizing plate protective film 110 by an electron microscope. For example, it can be confirmed and measured by observation using a scanning electron microscope S-5200 (manufactured by Hitachi, Ltd.).

The optical film 110 is an optical film having a hard coat layer 112 on a substrate 111, and is coated on the substrate 111. The photocurable composition of the epoxide, the bisphenol compound and the photocationic polymerization initiator represented by Chemical Formula I is formed into a film to form a coating film, and the coating film is irradiated with light to cure the coating film to form the hard coat layer 112. Manufacturer. The hard coat layer 112 which hardens the photocurable composition is high in hardness and low in moisture permeability. Thus, the optical film 110 is suitable as a polarizing plate protective film which requires high hardness and low moisture permeability.

<Polarizing Plate Protective Film>

Since the polarizing plate protective film is the optical film 110 of this embodiment, it has high hardness and low moisture permeability. The polarizing plate protective film is used to protect the film member of the polarizer in the polarizing plate 10 to be described later. Therefore, in the polarizing plate 10, it is preferable to arrange the hard coat layer 112 so as to be attached to the surface on the outer side of the polarizer.

When the optical film 110 is used as the polarizing plate protective film, a surface treatment may be performed as needed, or may be on the surface (back surface) of the substrate 111 opposite to the side on which the hard coat layer 112 is formed, or Another functional layer or the like is provided between the substrate 111 and the hard coat layer 112.

The functional layer in the case where the optical film 110 is used as a polarizing plate protective film is not particularly limited, and examples thereof include an antireflection layer (a refractive index such as a low refractive index layer, a medium refractive index layer, and a high refractive index layer). The layer), the antiglare layer, the antistatic layer, the ultraviolet absorbing layer, the adhesion layer (the layer which improves the adhesion between the substrate and the hard coat layer), and the like.

The above functional layer may be one layer or a plurality of layers. The lamination method of the above functional layer is not particularly limited.

An anti-reflection layer may be provided on the surface of the hard coat layer 112. A known person can be preferably used as the antireflection layer. Among them, a UV curable antireflection layer is preferred. The antireflection layer may have a low reflectance layer having a thickness of λ/4 and a multilayer structure, or may be a multilayer structure, but is preferably a low reflectance layer having a thickness of λ/4.

An example of a preferred layer constitution of the polarizing plate protective film 110 is shown below, but is not particularly limited to these layer constitutions.

‧Substrate / hard coating

‧Substrate / hard coating / anti-reflective layer

‧Substrate/adhesion layer/hard coating

‧Substrate/adhesion layer/hard coating/anti-reflection layer

‧Substrate / UV absorbing layer / hard coating

‧Substrate / UV absorbing layer / hard coating / anti-reflective layer

‧Substrate/Adhesion layer/UV absorbing layer/hard coating

‧Substrate/Adhesion layer/UV absorbing layer/hard coating/anti-reflection layer

‧Substrate / hard coating / anti-glare layer

‧Substrate / hard coating / anti-glare layer / anti-reflection layer

Further, the polarizing plate protective film 110 may further have an optical anisotropic layer. The optically anisotropic layer may be an optically anisotropic layer in which a film having a certain phase difference is uniformly formed in-plane, or may be a phase difference region in which the direction of the slow phase axis or the phase difference is different from each other. An optically anisotropic layer of a pattern that is regularly disposed in the plane.

The optically anisotropic layer is preferably formed on the back side of the substrate 111, but the optically anisotropic layer may be formed on the same side as the hard coat layer 112.

In the polarizing plate protective film of the present embodiment, an optically anisotropic layer having a suitable in-plane uniformity is provided in the Japanese Patent Publication No. 2012-098721 and JP-A-2012-127982. In the case of the optically anisotropic layer formed in the form of a pattern, it is described in Japanese Patent No. 4,825, 934, and Japanese Patent No. 4,948, 463, and the disclosure of Japanese Patent Publication No. 2012-517024 (WO2010/090429) The light alignment film and pattern are exposed.

<Optical compensation film>

In addition to the polarizing plate protective film described above, the optical film 110 can also be used in a wide variety of applications. For example, it can also be preferably used as an optical compensation film in a liquid crystal display device. The optical compensation film refers to an optical member that is generally used for a liquid crystal display device to compensate for a phase difference, and is equivalent to a phase difference plate and an optical compensation sheet. The optical compensation film has birefringence and is used for the purpose of removing the coloration of the display screen of the liquid crystal display device and improving the viewing angle characteristics.

The optical film 110 may be an optical compensation film itself or a substrate of an optical compensation film, and an optically anisotropic layer may be provided thereon as needed. The optically anisotropic layer to be used may be formed of a composition containing a liquid crystalline compound or a thermoplastic film having birefringence.

"Polarizing plate, liquid crystal display device"

As described above, the optical film 110 is suitable as a polarizing plate protective film which requires high hardness and low moisture permeability. By making polarized light protected by at least one surface of the polarizing plate protective film containing the optical film 110 A plate and a liquid crystal display device including the polarizing plate as a polarizing plate on at least the viewing side can provide a polarizing plate and a liquid crystal display device which are excellent in durability and which are less deteriorated by moisture absorption.

The optical film 110 can be used as a protective film for any of two polarizing plates. On the other hand, in the liquid crystal display device 1, since the surface on the viewing side is most susceptible to environmental changes, the present embodiment adopts a configuration in which the polarizing plate 10 on the viewing side (front side) is on the most viewed side. The polarizing plate protective film 110 of this embodiment is provided (refer FIG. 2).

Further, in the two polarizing plates, the optical film 110 is disposed as a protective film on the viewing side of the viewing-side polarizing plate, and the optical film 110 is further disposed as a backlight-side protective film of the backlight-side polarizing plate, and is capable of suppressing 2 The expansion and contraction of the polarizer included in the polarizing plate is preferable in terms of preventing warpage of the panel, but it is preferable to use the optical film 110 as a protective film for viewing the viewing side of at least the side polarizing plate among the two polarizing plates.

Fig. 3 is a schematic view showing the configuration of a liquid crystal display device 1 according to an embodiment of the present invention. As shown in the figure, the liquid crystal display device 1 has a pair of polarizing plates (the upper polarizing plate 10 and the lower polarizing plate 18) and liquid crystal cells 2 held by them, and the liquid crystal cell 2 has a liquid crystal layer 15 disposed thereon. The upper substrate 13 of the electrode of the liquid crystal cell and the lower substrate 16 of the electrode of the liquid crystal cell.

The upper and lower substrates 13 and 16 to which the electrodes are attached are generally formed by forming a transparent conductive film on the substrate. In the liquid crystal display device 1, a voltage is applied to the liquid crystal layer 15 through the transparent substrate. This embodiment The state in which the liquid crystal layer 15 is formed by the formation of the transparent conductive film on the substrate 13 and 16 is taken as an example. However, a gas barrier layer, a hard coat layer, a reinforcing substrate, and a transparent conductive layer may be provided on the substrate. An undercoat layer for adhesion of a film or the like. The substrate holding the liquid crystal layer 15 generally has a thickness of 50 μm to 2 mm.

Further, when the liquid crystal display device 1 is used as a transmissive type, the upper polarizing plate 10 is a front side (viewing side) polarizing plate, and the lower side polarizing plate 18 is a rear side (backlight side) polarizing plate. Although not shown, a backlight unit is provided on the lower side of the rear side polarizing plate 18, and a color filter is provided between the liquid crystal layer 15 and the front side polarizing plate 10. In Fig. 3, 12 and 19 indicate the directions of the absorption axes of the respective polarizing plates which are slightly orthogonal to each other, and 14 and 17 indicate the direction of the alignment control of the respective electrode substrates.

In the present embodiment, the optical film 110 is used as the protective film on the viewing side of the viewing-side polarizing plate 10 in the two polarizing plates 10 and 18. However, as described above, the present invention is not limited to this.

Fig. 2 is a cross-sectional view in the thickness direction of the polarizing plate 10 having the polarizing plate protective film (optical film) 110 of the present embodiment. As shown in the figure, the polarizing plate 10 is provided with a polarizing plate protective film 110 including an optical film 110 on the upper surface of the polarizing mirror 100. In Fig. 2, the configuration is such that the upper surface of the polarizer 100 is mounted on the side closer to the outside.

Further, in the present embodiment, the polarizing plate protective film 120 on the liquid crystal cell side is provided with the optical anisotropic layer 130 on the liquid crystal cell side. The lower polarizing plate 18 has a configuration in which the lamination direction of each layer is opposite to the upper polarizing plate 10.

The method for producing the polarizing plate 10 is not particularly limited, and can be produced by a general method. There is a method in which the obtained polarizing plate protective film is alkali-treated and adhered to both sides of a polarizing mirror by using a completely saponified polyvinyl alcohol aqueous solution, which is obtained by immersing a polyvinyl alcohol film in an iodine solution for stretching. Production. Instead of the alkali treatment, it is possible to carry out an easy-to-process process as described in JP-A-6-94915 and JP-A-6-118232. The bonding surface of the polarizing plate protective film 110 and the polarizing mirror 100 may be a surface on which the hard coat layer 112 is laminated, or may be a surface on the opposite side.

Examples of the adhesive used for bonding the polarizing plate protective film treatment surface and the polarizing lens include polyvinyl alcohol-based adhesives such as polyvinyl alcohol and polyvinyl butyral, or acrylic acid butyl acrylate. A vinyl latex such as an ester. The polarizing plate protective films 110 and 120 and the polarizing mirror 100 may be bonded together with another adhesive or an adhesive, or may be directly laminated without passing through an adhesive or an adhesive.

The polarizing plate protective film is the optical film 110 having high hardness and low moisture permeability of the present invention, and the liquid crystal display device 1 includes the polarizing plate protective film 110 on the front side (viewing side) polarizing plate 10 on the viewing side. . Thus, according to the present embodiment, it is possible to provide the polarizing plate 10 and the liquid crystal display device 1 which are less deteriorated from moisture absorption.

"Design changes"

In the above embodiment, a transmissive liquid crystal display device is described as an example. However, the liquid crystal display device is not limited to a transmissive type, and the present invention is also effective in a liquid crystal display device of either a reflective type or a semi-transmissive type.

Although an embodiment of the liquid crystal display device described above has been described, the display mode of the liquid crystal cell to which the present invention is applicable is not particularly limited. As an effective display mode of the present invention, currently, in TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric liquid crystal) Anti-ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Super Twisted Nematic), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence) It is also effective to display various display modes such as H, and HAN (Hybrid Aligned Nematic) or display mode in which the display mode is divided.

[Examples]

In order to explain the present invention in detail, the following examples are described, but the invention is not limited to the examples.

(Example 1)

First, each component was mixed with the following composition, and filtered with a polypropylene filter having a pore size of 5 μm to prepare a photocurable composition for forming a hard coat layer.

[Composition of photocurable composition for hard coat formation]

In the form of a roll, FUJITAC TG40 (manufactured by Fuji Film Co., Ltd., width: 1340 mm, thickness: 40 μm) is used as a base material, and the photocurable composition for forming a hard coat layer is used, and the use of Japanese Laid-Open Patent Publication No. 2006-122889 is used. The die coating method of the slit die described in Example 1 was carried out under the conditions of a transport speed of 30 m/min, and the temperature of the substrate was adjusted to 60 ° C by adjusting the temperature in the coating apparatus, and dried for 150 seconds. bell. The temperature was measured using PT-2LD manufactured by OPTEX Corporation. Thereafter, further, under nitrogen purge, the oxygen concentration was about 0.1% by volume, the temperature of the substrate was set to a temperature of 25 ° C, and an air-cooled metal halide illuminator (manufactured by Eyegraphics Co., Ltd.) of 160 W/cm was used, and the irradiation illuminance was 400 mW/ cm & lt ^2, irradiation amount of 300mJ / cm ² of ultraviolet rays, the coating layer was cured, to be wound to obtain a polarizing plate protective film (Example 1) having a hard coat layer on the substrate. Further, the coating amount was adjusted so that the film thickness of the hard coat layer became 10 μm.

(Examples 2 to 19, Comparative Examples 1 to 5)

The polycarboxylic acid resin (which is a polycarboxylic acid resin 1) described in Synthesis Example 1 of JP-A-2007-297604 is synthesized.

Next, as shown in Table 1, each of the photocurable composition for forming a hard coat layer which changes the type and amount of the epoxy monomer and the additive was prepared. The same procedure as in Example 1 was carried out, and the hard coat layer formation of each example was used. The photocurable composition was used to obtain a polarizing plate protective film (Examples 2 to 19) and a comparative polarizing plate protective film (Comparative Examples 1 to 5). Moreover, the coating amount was adjusted so that the film thickness of the hard-coat layer might become the film thickness of Table 1. The drug systems used in the examples and comparative examples are shown in Table 2.

The content of the polymerizable compound in Table 1 is a ratio (% by mass) in the total solid content of the photocurable composition for forming a hard coat layer.

(Evaluation of polarizing plate protective film)

The film thickness of the polarizing plate protective film of each of the produced examples and the comparative examples was measured, and the moisture permeability and the pencil hardness were measured and evaluated. The measurement methods and conditions are described later in the following (1) to (3). The evaluation results of the respective examples are shown in Table 1.

As shown in Table 1, in Examples 1 to 19, a moisture permeability of 200 g/m ² /day or less was achieved. Examples 2 to 6 show changes in moisture permeability and pencil hardness when the concentration of the same bisphenol compound 2b was changed and added. In the examples 2 to 6, it is shown that the higher the concentration of the bisphenol compound in the photocurable composition, the lower the moisture permeability becomes, but the hardness does not change from 5 mass% to 30 mass% while maintaining the hardness H, even if it is In the case of a concentration of 40% by mass, the hardness F which is a problem as a protective film for a polarizing plate can be obtained.

Further, Examples 5 and 7 to 16 are polarizing plate protective films obtained by using a photocurable composition of a bisphenol compound different from that of Example 1 at the same concentration. Thus, from the comparison of Example 1, Example 5, and 7 to 16, it was confirmed that the bisphenol compound has an effect on the moisture permeability or the pencil hardness.

In Example 5, the compound 2b in which one methyl group was introduced into each hydroxyphenyl group in the bisphenol compound 2a of Example 1 was used. In Example 7, a compound 2c in which two methyl groups were introduced into each hydroxyphenyl group was used. Compared to Example 1, Examples 5 and 7 reduced the moisture permeability. These results show that the effect of lowering the moisture permeability is increased by introducing a methyl group into the bisphenol compound.

In contrast to Example 5, Examples 8 and 9 are examples in which a bisphenol compound having a bulky group introduced into a hydroxyphenyl group is used. It is shown that the introduction of the group has less effect of lowering the moisture permeability than the methyl group.

In Example 10, a cyclohexane type skeleton was introduced into a portion in which a hydroxyphenyl group was bonded to each other with respect to the bisphenol compound of Example 1. It is shown that the effect of lowering the moisture permeability is increased by the introduction of the base. Further, Example 11 is an example in which a methyl group was introduced into each hydroxyphenyl group relative to the bisphenol compound 3a of Example 10, and a comparison between Example 10 and Example 11 revealed that the introduction of the group enabled The effect of reducing the moisture permeability becomes high.

On the other hand, in Example 12, an example of the compound 4 in which the moiety of the cyclohexyl group of Example 10 was replaced with a methyl group was used. When a methyl group was introduced into the cyclohexyl group, the effect of lowering the moisture permeability was not observed.

In Examples 13 to 16, an example in which a hydroxyphenyl group is bonded to each other is not a cyclohexane type skeleton but a bulky skeleton having a phenyl group is introduced. It was confirmed that the introduction of the group had less effect of lowering the moisture permeability than the cyclohexyl group.

In Examples 17, 18, and 19, the film thickness of the film formation was changed with respect to Example 4, and the results of the change in the moisture permeability and the hardness were examined. From these results, it was confirmed that the thicker the film thickness, the lower the moisture permeability and the higher the hardness.

Comparative Example 1 was carried out in the same manner as in Example 1 except that the bisphenol compound was not added, and Comparative Example 2 was used in place of the epoxide of Compound 1a except that the following epoxide (Compound 1b) was used. An example in which a polarizing plate protective film was produced in the same manner as in Example 1 was carried out. Further, Comparative Examples 3 to 5 are examples in which an additive other than the bisphenol compound is added to the compound 1. From these examples, it was confirmed that a combination of the epoxide of the compound 1a and the bisphenol compound can achieve sufficient low moisture permeability in a film thickness of 10 μm.

(1) Film thickness

The film thickness of the hard coat layer was measured by measuring the film thickness before and after the hard coat layer was laminated. The layer thickness of the mixed layer is a scanning electron micrograph (section) of the film thickness direction section of the protective film of the polarizing plate The SEM image was obtained by photographing with a scanning electron microscope S-5200 manufactured by Hitachi, Ltd.).

(2) Moisture permeability (moisture permeability at 40 ° C, 90% relative humidity)

The polarizing plate protective film samples of each of the examples and the comparative examples were each incubated at 40 ° C and a relative humidity of 90% for 24 hours, and measured according to the method described in JIS Z 0208.

The moisture permeability of the hard coat layer is used to measure the moisture permeability of each of the polarizing plate protective film and the cellulose ester substrate, and the moisture permeability of the cellulose ester substrate and the polarizing plate are used to protect the moisture permeability of the film by the following formula (1). To calculate.

When using a gas-permeable type of a composite film (for example, "Science of Barrier Properties of Packaging Materials (Packaging Fundamentals Lecture 5)", pp. 68-72, Nakagawa Hiroshi, Japan Packaging Society), a constant-state polarizing plate protective film The moisture permeability is set to J _f , the moisture permeability of the cellulose ester substrate is J _s , and the moisture permeability of the hard coat layer when the polarizing plate protective film is separated into the cellulose ester substrate and the hard coat layer is set to J. _{When b} , the following formula holds.

1/J _f =1/J _s +1/J _b ‧‧‧‧‧(1)

The moisture permeability J _{f of the} polarizing plate protective film and the moisture permeability J _{s of the} cellulose ester substrate can be directly measured, and the moisture permeability J _{b of} the hard coat layer can be calculated based on those measured values.

(3) Pencil hardness evaluation

As an indicator of scratch resistance, the pencil hardness evaluation described in JIS K 5600 was performed. The polarizing plate protective film was moistened for 2 hours at a temperature of 25 ° C and a humidity of 60% RH, and then evaluated by the following test using a test pencil of 2B to 3H prescribed in JIS S 6006 at a load of 4.9 N. The highest hardness to achieve OK is the evaluation value.

OK: 4 or more without scratches in the evaluation of n=5

NG: no scratches in 3 or less in the evaluation of n=5

(Evaluation of liquid crystal display device) (1) Production of liquid crystal display device

Each of the polarizing plate protective films produced by the above method was used to produce a liquid crystal display device, and evaluation was performed.

<Production of polarizing plate> 1) Saponification of the film

A commercially available deuterated cellulose film (FUJITAC ZRD40, manufactured by Fuji Film Co., Ltd.), a commercially available deuterated cellulose film TD60 (manufactured by Fuji Film Co., Ltd.), and a polarizing plate protective film sample prepared as described above 1 to 19 And the comparative polarizing plate protective film samples 1 to 5 were immersed in a 1.5 mol/L NaOH aqueous solution (saponification liquid) maintained at 55 ° C for 2 minutes, and then the film was washed with water, and then immersed in a 0.05 mol/L sulfuric acid aqueous solution at 25 ° C. After 30 seconds, the water was further passed through a water bath for 30 seconds to make the film neutral. Then, the drainage by the air knife was repeated three times, and after the water was removed, it was allowed to stand in a drying zone of 70 ° C for 15 seconds and dried to prepare a saponified film.

2) Production of polarizer

According to Example 1 of JP-A-2001-141926, iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizer having a film thickness of 20 μm.

3) Fit (Front polarizing plate: Example polarizing plates 1 to 19, and comparative polarizing plates 1 to 5)

The saponified polarizing plate protective film 1 to 19 and the comparative polarizing plate protective film samples 1 to 5 were sequentially applied by using a PVA-based adhesive to face the unlaminated hard coat layer of the polarizing plate protective film. The polarizing mirrors were placed in contact with each other, and the polarizing mirror prepared above and the saponified deuterated cellulose film ZRD40 were thermally dried to prepare polarizing plates 1 to 19 of the examples and comparative polarizing plates 1 to 5.

At this time, in each example, the longitudinal direction of the reel of the produced polarizer and the longitudinal direction of the polarizing plate protective film are arranged in parallel. Further, the longitudinal direction of the reel of the polarizer and the longitudinal direction of the reel of the deuterated cellulose film ZRD40 are arranged in parallel.

(production of rear polarizer)

The saponified deuterated cellulose film TD60, the stretched iodine-based PVA polarizer, and the saponified deuterated cellulose film ZRD40 were laminated in this order with a PVA-based adhesive, followed by thermal drying to obtain a rear-side polarizing plate.

At this time, the longitudinal direction of the reel of the produced polarizer and the longitudinal direction of the deuterated cellulose film TD60 are arranged in parallel. Further, the longitudinal direction of the reel of the polarizer and the longitudinal direction of the reel of the deuterated cellulose film ZRD40 are arranged in parallel.

<Installation of IPS panel>

The upper and lower polarizing plates of the IPS mode liquid crystal cell (42LS5600, manufactured by LGD) were peeled off, and the cellulose-deposited film ZRD40 was set to the liquid crystal cell side, and the adhesive was applied to the front side and the rear side, respectively, on the front side (viewing side). The polarizing plates 1 to 19 of the above-described embodiments and the polarizing plates 1 to 5 of the comparative examples are attached as the front polarizing plate, and the polarizing plate is attached to the rear side as the polarizing plate. Rear polarizer. The absorption axis of the polarizing plate on the front side is in the longitudinal direction (left-right direction), and the transmission axis of the polarizing plate on the rear side is in the longitudinal direction (left-right direction), and is arranged in a crossed-polar (Cross Nicol) arrangement. The thickness of the glass used for the liquid crystal cell was 0.5 mm.

The obtained liquid crystal display devices were designated as liquid crystal display devices 1 to 19 (Examples 1 to 19) and Comparative Examples Liquid Crystal Display devices 1 to 5 (Comparative Examples 1 to 5).

(2) Light leakage evaluation

The light leakage of the liquid crystal display device produced above was evaluated. The results are shown in Table 1 below.

The liquid crystal display devices 1 to 19 of the examples and the liquid crystal display devices 1 to 5 of the comparative examples were kept at 60 ° C and a relative humidity of 90% for 96 hours, and then left at 25 ° C and a relative humidity of 60% for 2 hours to illuminate the liquid crystal. The backlight of the display device was evaluated for light leakage at four corners of the panel after 5 hours and 10 hours from the lighting.

The light leakage evaluation system uses a camera for measuring the brightness of the camera "ProMetric" (manufactured by Radiant Imaging Co., Ltd.) to take a black display screen from the front of the screen, and performs a five-stage evaluation based on the average brightness of the entire screen and the difference in brightness between the four corners. . In the present invention, the degree of A and B is acceptable, and the degree of C to E is unacceptable.

A: After 5 hours, the light leakage in the four corners of the panel is not visible.

After 10 hours, no light leakage from the four corners of the panel was observed.

B: After 5 hours, in the four corners of the panel, some light leakage was observed in one or two corners.

After 10 hours, no light leakage from the four corners of the panel was observed.

C: After 5 hours, in the four corners of the panel, slight light leakage was observed in one or two corners.

After 10 hours, in the four corners of the panel, slight light leakage was observed in one or two corners.

D: After 5 hours, in the four corners of the panel, some slight light leakage was seen in the three to four corners.

After 10 hours, in the four corners of the panel, slight light leakage was observed in one or two corners.

E: After 5 hours, in the four corners of the panel, some slight light leakage was seen in the three to four corners.

After 10 hours, in the four corners of the panel, some light leakage was seen in the three to four corners.

As shown in the above Table 1, Examples 1 to 19 were high in hardness and low in moisture permeability. Further, the liquid crystal display device produced by using the polarizing plate protective films of Examples 1 to 19 had less light leakage.

[Industrial availability]

The present invention can be applied to an image display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), or a cathode tube display device (CRT).

110‧‧‧Optical film, polarizing plate protective film

111‧‧‧Substrate

112‧‧‧hard coating

Claims (16)

An optical film obtained by providing a hard coat layer on a substrate, wherein the hard coat layer is a layer on which the photocurable composition is cured, and the photocurable composition is used. An epoxide, a bisphenol compound and a photocationic polymerization initiator represented by the chemical formula I, The optical film of claim 1, wherein the bisphenol compound is represented by the following general formula II-1, In the general formula II-1, R ¹ and R ^{2 each} represent a hydrogen atom, a halogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and X is a hydrocarbon group having a single bond, a carbon number of 1 to 15, an oxygen atom, a sulfur atom, and A divalent linking group composed of at least one selected from a sulfonyl group. The optical film of claim 1, wherein the bisphenol compound is represented by the following general formula II-2, In the general formula II-2, R ¹ , R ² , R ³ and R ⁴ represent hydrogen or a hydrocarbon group having 1 to 15 carbon atoms, and R ³ and R ⁴ may be bonded to form a cyclic structure. The optical film of claim 2 or 3, wherein the R ¹ and R ² are hydrogen or a hydrocarbon group having 1 to 6 carbon atoms. The optical film of claim 4, wherein the R ¹ is hydrogen and the R ² is methyl. The optical film according to any one of claims 1 to 3, wherein the bisphenol compound is contained in an amount of from 1 to 40% based on the total solid content of the photocurable composition. The optical film of any one of claims 1 to 3, wherein the substrate is a cellulose ester substrate. The optical film of any one of claims 1 to 3 which is a polarizing plate protective film. A polarizing plate comprising a polarizing mirror and an optical film of claim 8 on at least one surface of the polarizing mirror. A liquid crystal display device comprising a pair of polarizing plates and liquid crystal cells sandwiched by the pair of polarizing plates, at least one of which is a polarizing plate of claim 9. A method for producing an optical film comprising a method of producing an optical film comprising a hard coat layer on a substrate, wherein the substrate comprises an epoxide, a bisphenol compound and a photocation represented by the following chemical formula I. a photocurable composition of a polymerization initiator, which is formed into a film to form a coating film, and the coating film is irradiated with light to cure the coating film to form the hard coat layer. The method for producing an optical film according to claim 11, wherein the bisphenol compound is represented by the following general formula II-1, In the general formula II-1, R ¹ and R ^{2 each} represent a hydrogen atom, a halogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and X is a hydrocarbon group having a single bond, a carbon number of 1 to 15, an oxygen atom, a sulfur atom, and A divalent linking group composed of at least one selected from a sulfonyl group. The method for producing an optical film according to claim 12, wherein the bisphenol compound is represented by the following general formula II-2, In the general formula II-2, R ¹ , R ² , R ³ and R ⁴ represent hydrogen or a hydrocarbon group having 1 to 15 carbon atoms, and R ³ and R ⁴ may be bonded to form a cyclic structure. The method of producing an optical film according to any one of claims 11 to 13, wherein the light irradiated to the coating film is ultraviolet light. The method for producing an optical film according to any one of claims 11 to 13, wherein the irradiation of the light is performed in a state where the substrate on which the coating film is formed is heated. The method of producing an optical film according to any one of claims 11 to 13, wherein the hard coat layer is produced without heating after the light is irradiated.