JP2009098663A - Optical compensation film, polarizer, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film for suppressing the generation of peripheral irregularities and enlarging a lateral viewing angle since it has high weatherability and a negative value of a photo-elasticity coefficient and has a two-axis property, and to provide a polarizer and a liquid crystal display thereof. <P>SOLUTION: The optical compensation film having a transparent film containing a polymer having either of a lactone ring unit and a gultaric anhydride has 20-150 nm of retardation Re 550 in a face in 550 nm of a wavelength and 70-190 nm of retardation Rth 550 out of a face in 550 nm of a wavelength. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical compensation film, a polarizing plate having the optical compensation film, and a liquid crystal display device having the polarizing plate.

  A polarizing plate used in a liquid crystal display device or the like is generally configured by attaching protective films made of a polymer film on both surfaces of a deflection film. The deflection film includes a polyvinyl alcohol film, an ethylene vinyl alcohol film, a cellulose film, a polycarbonate film, etc., but a film obtained by stretching a polyvinyl alcohol film dyed with iodine for reasons of workability or the like, or a polyvinyl alcohol system A film that has been stretched and then dyed with iodine is generally used. The cellulose acetate film is characterized by high optical isotropy (low retardation value) compared to other polymer films.

  On the contrary, optical anisotropy (high retardation value) is required for the optical compensation film (retardation film) of the liquid crystal display device. Therefore, it is common to use a synthetic polymer film having a high retardation value such as a polycarbonate film or a polysulfone film as the optical compensation film.

  As described above, in the technical field of optical materials, when a polymer film requires optical anisotropy (high retardation value), a synthetic polymer film is used, and optical isotropy (low retardation value) is required. In this case, it is common to use a cellulose acetate film. However, with the recent increase in the size of liquid crystal display screens, there has been a demand for further improvement in productivity and widening of the viewing angle. An optical compensation film having a cellulose acetate film that satisfies such requirements is disclosed (for example, Patent Document 1).

However, since a liquid crystal display device is generally overheated by heat rays generated from a backlight immediately after lighting, retardation is generated in the glass substrate of the liquid crystal cell base material, and in addition, as a protective film due to contraction of the polarizing plate due to overheating. In the optical compensation film to be used, retardation is generated in the same direction as the retardation generated in the glass substrate. Here, these retardations generated by heating are recognized as light leakage at the periphery of the liquid crystal display device.
That is, since the optical compensation film having the cellulose acetate film usually has a positive photoelastic coefficient, water escapes from the polarizing plate having the optical compensation film due to heat generation, and the polarizing plate contracts. There has been a problem that a phase difference caused by glass and pressure-sensitive adhesive occurs due to an environmental change such as the generation of tension due to the contraction of the polarizing plate, and peripheral unevenness (so-called frame failure) occurs.

JP 2004-133171 A

An object of the present invention is to solve the conventional problems and achieve the following objects.
That is, the present invention is an optical compensation film that has high weather resistance, a negative photoelastic coefficient, a biaxial property, and suppresses peripheral unevenness and expands the lateral viewing angle, and the optical compensation film It is an object to provide a polarizing plate having a liquid crystal display and a liquid crystal display device having the polarizing plate.

Means for solving the above-mentioned problems are as follows. That is,
<1> An optical compensation film having a transparent film containing a polymer having either a lactone ring unit or a glutaric anhydride unit, wherein an in-plane retardation Re550 at a wavelength of 550 nm is 20 to 150 nm, and a wavelength of 550 nm An optical compensation film having an out-of-plane retardation Rth550 of 70 to 190 nm.
<2> The optical compensation film according to <1>, wherein the in-plane retardation Re550 at a wavelength of 550 nm is 70 to 110 nm, and the out-of-plane retardation Rth550 at a wavelength of 550 nm is 110 to 150 nm.
<3> The optical compensation film according to any one of <1> to <2>, wherein the transparent film includes a retardation increasing agent having two or more aromatic rings in one molecule.
<4> The transparent film according to any one of <1> to <3>, wherein the transparent film is stretched at a magnification of 1.1 to 2.0 in any direction parallel or perpendicular to the transport direction. It is an optical compensation film.
<5> The optical compensation film according to any one of <1> to <4>, wherein a transparent film, an alignment film, and an optically anisotropic layer made of a liquid crystal compound are laminated in this order.
<6> A polarizing plate comprising the optical compensation film according to any one of <1> to <5>.
<7> The polarizing plate according to <6>, further including a polarizing film, wherein the crossing angle between the in-plane transmission axis of the polarizing film and the in-plane slow axis of the optical compensation film is approximately 0 degrees. It is.
<8> A liquid crystal display device comprising the optical compensation film according to any one of <1> to <5>.
<9> A pair of opposed substrates having electrodes on at least one side, a liquid crystal cell having a liquid crystal layer sandwiched between the pair of substrates, and a first and a second disposed with the liquid crystal cell sandwiched therebetween The liquid crystal display device according to <8>, wherein an optical compensation film is disposed between the liquid crystal layer and the first and second polarizing films. .
<10> The liquid crystal layer includes a nematic liquid crystal material, and the liquid crystal molecules of the nematic liquid crystal material are aligned substantially perpendicular to the surfaces of the pair of substrates during black display, and the thickness d (micron) of the liquid crystal layer is The liquid crystal display device according to any one of <8> to <9>, wherein a product Δn · d with a refractive index anisotropy Δn of liquid crystal molecules is 0.1 to 1.5 microns.

According to the present invention, since the weather resistance is high, the photoelastic coefficient is a negative value, and it has biaxiality, the optical compensation film that suppresses the occurrence of peripheral unevenness and expands the lateral viewing angle is provided. A polarizing plate having a polarizing plate and a liquid crystal display device having the polarizing plate can be provided.
That is, since the optical compensation film of the present invention has a negative photoelastic coefficient, when the polarizing plate is heated and shrunk, the retardation generated in the conventional protective film (positive photoelastic coefficient) is perpendicular to the retardation. Retardation occurs. When this retardation is offset with the glass-induced retardation, it is possible to significantly improve the peripheral unevenness of the liquid crystal display device.

Hereinafter, the present invention will be described in detail.
(Optical compensation film)
The optical compensation film has a transparent film (transparent support), and further has other layers appropriately selected as necessary.

  The optical compensation film preferably has 20 nm ≦ Re550 (in-plane retardation at a wavelength of 550 nm) ≦ 150 nm and 70 nm ≦ Rth550 (out-of-plane retardation at a wavelength of 550 nm) ≦ 190 nm (in the region A in FIG. 1), preferably 70 nm. ≦ Re550 ≦ 130 nm and 90 nm ≦ Rth550 ≦ 150 nm are more preferable, and 70 nm ≦ Re550 ≦ 110 nm and 110 nm ≦ Rth550 ≦ 150 nm (in the region B in FIG. 1) are more preferable.

  The Re and Rth may be obtained by adding a retardation increasing agent having two or more aromatic rings in one molecule to the optical compensation film, or at a magnification of 1.1 in either the direction parallel or perpendicular to the transport direction. It can be obtained by subjecting the transparent film to a stretching treatment of ~ 2.0.

<Transparent film (transparent support)>
The transparent film (transparent support) is a film containing a polymer having either a lactone ring unit or a glutaric anhydride unit, and further having other components appropriately selected as necessary.

<< Polymer Having Lactone Ring Unit >>
The polymer having a lactone ring unit has a lactone ring structure in the polymer, and preferably has a lactone ring structure represented by the following general formula (1).

^{Wherein, R 1, R 2, R} 3 each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue referred to here may contain an oxygen atom. 1-15 are preferable, as for carbon number of an organic residue, 1-12 are more preferable, 1-8 are more preferable, and 1-5 are still more preferable. Examples of the organic residue include a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, and the like, and an alkyl group is preferable. Examples of the substituent include an alkyl group, an aryl group, and an alkoxy group. R ¹ , R ² and R ³ are more preferably a hydrogen atom, a methyl group, an ethyl group or a propyl group, still more preferably a hydrogen atom, a methyl group or an ethyl group, still more preferably a hydrogen atom or a methyl group. It is.

  The content of the lactone ring structure represented by the general formula (1) in the polymer structure having a lactone ring unit is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and still more preferably 10 to 60%. It is 10 mass%, Most preferably, it is 10-50 mass%. If the content of the lactone ring structure represented by the general formula (1) in the polymer structure having a lactone ring unit is 5% by mass or more, sufficient heat resistance, solvent resistance, and surface hardness tend to be obtained. There is. Further, if the content of the lactone ring structure represented by the general formula (1) in the polymer structure having a lactone ring unit is 90% by mass or less, higher moldability tends to be easily obtained.

  The polymer having a lactone ring unit may have a structure other than the lactone ring structure represented by the general formula (1). The structure other than the lactone ring structure represented by the general formula (1) is not particularly limited, but a (meth) acrylic acid ester or a hydroxyl group-containing unit as will be described later as a method for producing a polymer having a lactone ring unit. A polymer structural unit (repeating structural unit) constructed by polymerizing at least one selected from a monomer, an unsaturated carboxylic acid, and a monomer represented by the following general formula (2a) is preferable.

(Wherein R ⁴ represents a hydrogen atom or a methyl group, X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an acetate group, a cyano group, a —CO—R ⁵ group, or —CO—O. represents -R ⁶ group, the organic residue ^{R 5} and ^{R 6} represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. having 1 to 20 carbon atoms, the organic residue in the formula (1) You can refer to the explanation of
The content ratio of the structure other than the lactone ring structure represented by the general formula (1) in the polymer structure having a lactone ring unit is a polymer structural unit (repeated structure) constructed by polymerizing (meth) acrylic acid ester. Unit) is preferably 10 to 95% by mass, more preferably 10 to 90% by mass, still more preferably 40 to 90% by mass, and particularly preferably 50 to 90% by mass. In the case of a polymer structural unit (repeating structural unit) constructed in this manner, it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass. It is. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing an unsaturated carboxylic acid, it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, particularly Preferably it is 0-10 mass%. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing the monomer represented by the general formula (2a), it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and still more preferably. Is 0 to 15% by mass, particularly preferably 0 to 10% by mass.

  The method for producing the polymer having a lactone ring unit is not particularly limited, but preferably, the polymer obtained after obtaining the polymer (a) having a hydroxyl group and an ester group in the molecular chain by a polymerization step. This is a method of performing a lactone cyclization condensation step in which a lactone ring structure is introduced into a polymer by heat-treating the compound (a).

  In the polymerization step, for example, a polymer having a hydroxyl group and an ester group in a molecular chain is obtained by performing a polymerization reaction using a monomer composition containing a monomer represented by the following general formula (1a). Obtainable.

(In the formula, R ⁷ and R ⁸ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. For the organic residue having 1 to 20 carbon atoms, the organic group in the above general formula (1)). (See description of residues.)
Examples of the monomer represented by the general formula (1a) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- ( Hydroxymethyl) n-butyl acrylate, tert-butyl 2- (hydroxymethyl) acrylate, and the like. Among these, methyl 2- (hydroxymethyl) acrylate and 2- (hydroxymethyl) ethyl acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate is particularly preferable in that the effect of improving heat resistance is high. As for the monomer represented by the general formula (1a), only one type may be used, or two or more types may be used in combination.

  The content ratio of the monomer represented by the general formula (1a) in the monomer composition to be subjected to the polymerization step is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and even more preferably 10 to 10% by mass. 60% by mass, particularly preferably 10 to 50% by mass. If the content ratio of the monomer represented by the general formula (1a) in the monomer composition to be subjected to the polymerization step is 5% by mass or more, sufficient heat resistance, solvent resistance, and surface hardness are easily obtained. Tend. If the content of the monomer represented by the general formula (1a) in the monomer composition to be subjected to the polymerization step is 90% by mass or less, it is possible to sufficiently prevent gelation during lactone cyclization. And a polymer having higher moldability tends to be obtained.

  The monomer composition used for the polymerization step may contain a monomer other than the monomer represented by the general formula (1a). Such a monomer is not particularly limited, and for example, (meth) acrylic acid ester, a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a monomer represented by the general formula (2a) are preferable. It is done. Only one type of monomer other than the monomer represented by the general formula (1a) may be used, or two or more types may be used in combination.

  The (meth) acrylic acid ester is not particularly limited as long as it is a (meth) acrylic acid ester other than the monomer represented by the general formula (1a). For example, methyl acrylate, ethyl acrylate, and acrylic acid n -Acrylic acid esters such as butyl, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid methacrylic acid esters such as tert-butyl, cyclohexyl methacrylate, benzyl methacrylate; and the like. These may be used alone or in combination of two or more. Among these, methyl methacrylate is particularly preferable from the viewpoint of excellent heat resistance and transparency.

  When a (meth) acrylic acid ester other than the monomer represented by the general formula (1a) is used, the content ratio in the monomer composition to be subjected to the polymerization step is sufficient to exert the effect of the present invention. And preferably 10 to 95% by mass, more preferably 10 to 90% by mass, still more preferably 40 to 90% by mass, and particularly preferably 50 to 90% by mass.

  The hydroxyl group-containing monomer is not particularly limited as long as it is a hydroxyl group-containing monomer other than the monomer represented by the general formula (1a). For example, α-hydroxymethyl styrene, α-hydroxyethyl styrene, 2 -2- (hydroxyalkyl) acrylic acid ester such as methyl (hydroxyethyl) acrylate; 2- (hydroxyalkyl) acrylic acid such as 2- (hydroxyethyl) acrylic acid; and the like. Or two or more of them may be used in combination.

  In the case of using a hydroxyl group-containing monomer other than the monomer represented by the general formula (1a), the content ratio in the monomer composition to be subjected to the polymerization step is sufficient to exert the effect of the present invention. The content is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, further preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These may be used alone or in combination of two or more. May be. Among these, acrylic acid and methacrylic acid are preferable in that the effects of the present invention are sufficiently exhibited.

  In the case of using an unsaturated carboxylic acid, the content ratio in the monomer composition to be subjected to the polymerization step is preferably 0 to 30% by mass, more preferably 0 to 20%, in order to sufficiently exhibit the effects of the present invention. It is 0 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  Examples of the monomer represented by the general formula (2a) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. These are used alone. Or two or more of them may be used in combination. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited.

  When using the monomer represented by the general formula (2a), the content ratio in the monomer composition to be subjected to the polymerization step is preferably 0 to 30 mass in order to sufficiently exhibit the effects of the present invention. %, More preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, particularly preferably 0 to 10% by mass.

  The form of the polymerization reaction for polymerizing the monomer composition to obtain a polymer having a hydroxyl group and an ester group in the molecular chain is preferably a polymerization form using a solvent, and solution polymerization is particularly preferred. .

  The polymerization temperature and polymerization time vary depending on the type of monomer used, the ratio of use, etc., but preferably the polymerization temperature is 0 to 150 ° C. and the polymerization time is 0.5 to 20 hours, more preferably polymerization. The temperature is 80 to 140 ° C. and the polymerization time is 1 to 10 hours.

  In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, an aromatic hydrocarbon solvent such as toluene, xylene, or ethylbenzene; a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone ketone; an ether system such as tetrahydrofuran. A solvent; etc. are mentioned, Only 1 type of these may be used and 2 or more types may be used together. Moreover, since the residual volatile matter of the polymer which finally has a lactone ring unit will increase when the boiling point of the solvent to be used is too high, a thing with a boiling point of 50-200 degreeC is preferable.

  During the polymerization reaction, a polymerization initiator may be added as necessary. The polymerization initiator is not particularly limited. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-tert-butyl peroxide, lauroyl peroxide, benzoyl peroxide, tert-butylperoxyisopropyl carbonate, tert-amyl Organic peroxides such as peroxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2, Azo compounds such as 4-dimethylvaleronitrile), and the like. These may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of the monomers used and the reaction conditions.

  The polymer having a lactone ring unit has a weight average molecular weight of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, Especially preferably, it is 50,000-500,000.

  The polymer having a lactone ring unit preferably has a mass reduction rate of 150% to 300 ° C in dynamic TG measurement of 1% or less, more preferably 0.5% or less, and still more preferably 0.3%. It is as follows.

  Since the polymer having a lactone ring unit has a high cyclization condensation reaction rate, it is possible to avoid the disadvantage that bubbles and silver streaks enter the molded product after molding. Furthermore, since the lactone ring structure is sufficiently introduced into the polymer due to a high cyclization condensation reaction rate, the obtained polymer having a lactone ring unit has sufficiently high heat resistance.

  The polymer having a lactone ring unit preferably has a coloration degree (YI) in a chloroform solution of 15% by mass of 6 or less, more preferably 3 or less, further preferably 2 or less, and most preferably 1 or less. is there. If the degree of coloring (YI) is 6 or less, coloring tends to be prevented and higher transparency tends to be obtained.

  The polymer having a lactone ring unit preferably has a 5% mass reduction temperature in thermal mass spectrometry (TG) of 280 ° C. or higher, more preferably 290 ° C. or higher, and further preferably 300 ° C. or higher. The 5% mass loss temperature in thermal mass spectrometry (TG) is an indicator of thermal stability. If this is 280 ° C. or higher, sufficient thermal stability is likely to be exhibited.

  The polymer having a lactone ring unit has a glass transition temperature (Tg) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, further preferably 130 ° C. or higher, more preferably 135 ° C. or higher, and most preferably 140 ° C. or higher. It is.

  The polymer having a lactone ring unit has a total amount of residual volatile components contained therein of preferably 5000 ppm or less, more preferably 2000 ppm or less. If the total amount of residual volatile components is 5000 ppm or less, molding defects such as coloring, foaming, and silver streaking due to deterioration during molding tend to be more effectively prevented.

  The polymer having a lactone ring unit has a total light transmittance, as measured by a method according to ASTM-D-1003, of a molded product obtained by injection molding, preferably 85% or more, more preferably 88% or more, More preferably, it is 90% or more. Total light transmittance is a measure of transparency.

<< Glutaric anhydride unit >>
The glutaric anhydride unit is represented by the following structural formula (3).
In the above formula, R 1 and R 2 represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.

<< Other ingredients >>
The thermoplastic resin composition containing a polymer having either the lactone ring unit or the glutaric anhydride unit may contain other additives. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as: antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; Inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants;

  The content ratio of the other additives in the optical planar thermoplastic resin molded article is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 0.5% by mass.

<Other layers>
The other layers are not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. Examples thereof include an alignment film and an optically anisotropic layer made of a liquid crystal compound.

<< Alignment film >>
In the present invention, the alignment film is preferably a layer made of a crosslinked polymer.
The polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent.
The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like, or is a highly reactive compound. It can be formed by introducing a bonding group derived from a cross-linking agent between polymers using an agent and cross-linking the polymers.

<< Optically anisotropic layer >>
The optically anisotropic layer may be formed directly on the surface of the support, or may be formed on the alignment film by forming an alignment film on the support. Moreover, it is also possible to produce the optical compensation film of the present invention by transferring a liquid crystal compound layer formed on another substrate onto a support using an adhesive or the like.
Examples of the liquid crystal compound used for forming the optically anisotropic layer include a rod-like liquid crystal compound and a discotic liquid crystal compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a polymer liquid crystal or a low molecular liquid crystal, and further include those in which the low molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity.

(Polarizer)
The said polarizing plate has the said optical compensation film and a polarizing film, and also has the other film (film | membrane) selected suitably as needed.
The crossing angle between the transmission axis in the plane of the polarizing film and the slow axis in the plane of the optical compensation film is approximately 0 degrees.

<< Polarizing film >>
The polarizing film used for the polarizing plate of the present invention is Optiva Inc. And a polarizing film comprising a binder and iodine, or a dichroic dye is preferable.
The iodine and the dichroic dye exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal.
A commercially available polarizing film is produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. It is common.
In addition, commercially available polarizing films have iodine or dichroic dye distributed about 4 μm from the polymer surface (about 8 μm on both sides), and a thickness of at least 10 μm is necessary to obtain sufficient polarization performance. is there. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time.
Therefore, as described above, the lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of the light leakage phenomenon that occurs when the polarizing plate is used in a liquid crystal display device.

<< Other films (membrane) >>
The other film (film) is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected depending on the purpose.

(Liquid crystal display device)
The liquid crystal display device includes the optical compensation film, a liquid crystal cell, and first and second polarizing films disposed so as to sandwich the liquid crystal cell. The optical compensation film is disposed between the liquid crystal layer and the first and second polarizing films.

<Liquid crystal cell>
It has a pair of opposing substrates having electrodes on at least one side, a liquid crystal layer sandwiched between the pair of substrates, and other layers appropriately selected as necessary.
The liquid crystal layer preferably includes a nematic liquid crystal material, and the liquid crystal molecules of the nematic liquid crystal material are preferably aligned substantially perpendicular to the surfaces of the pair of substrates during black display. The product Δn · d of the thickness d (micron) and the refractive index anisotropy Δn is preferably 0.1 to 1.5 microns. Conventionally, TN cells have a product Δn · d of 0.3 to 0.5 microns. However, the product Δn · d is set to the above value in consideration of application to other types of cells (for example, VA, OCB, ECB, etc.).

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. Hereinafter, for convenience, “part by mass” may be simply referred to as “part”, and “liter” may be simply referred to as “L”.

<Dynamic TG>
The polymer (or polymer solution or pellet) is once dissolved or diluted in tetrahydrofuran, poured into excess hexane or methanol for reprecipitation, and the taken out precipitate is vacuum dried (1 mmHg (1.33 hPa), 80 ° C. Volatile components and the like were removed by conducting the reaction for 3 hours or more, and the obtained white solid resin was analyzed by the following method (dynamic TG method).
Measuring apparatus: Thermo Plus2 TG-8120 Dynamic TG (manufactured by Rigaku Corporation)
Measurement conditions: Sample amount 5-10 mg
Temperature increase rate: 10 ° C / min
Atmosphere: Nitrogen flow 200ml / min
Method: Step-like isothermal control method (controlled at a mass reduction rate of 0.005% / second or less between 60 ° C and 500 ° C)

<Weight average molecular weight>
The weight average molecular weight of the polymer was determined by polystyrene conversion of GPC (GPC system manufactured by Tosoh Corporation). Tetrahydrofuran was used as the developing solution.

<Thermal analysis of resin>
Thermal analysis of the resin was performed using DSC (manufactured by Rigaku Corporation, apparatus name: DSC-8230) under the conditions of about 10 mg of sample, a temperature rising rate of 10 ° C./min, and a nitrogen flow of 50 ml / min. The glass transition temperature (Tg) was determined by the midpoint method according to ASTM-D-3418.

<Melt flow rate>
The melt flow rate was measured at a test temperature of 240 ° C. and a load of 10 kg based on JIS-K6874.

<Optical characteristics>
The refractive index anisotropy of the optical compensation film, in-plane retardation Re550 at a wavelength of 550 nm, and out-of-plane retardation Rth550 at a wavelength of 550 nm were measured using KOBRA-21ADH manufactured by Oji Scientific Instruments. Visible light transmittance was measured using NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

<Photoelastic coefficient>
The photoelastic coefficient is defined by birefringence (Δn) generated when stress (σ) is applied, and can be expressed as follows.

  Photoelastic coefficient (C) = Δn / σ

  In the present example, the photoelastic coefficient measurement method was performed as follows. Measurement is performed by applying a tensile force in the range of 0 to 10 N to a 2 cm square sample (measurement wavelength is 632.8 nm) using an ellipsometer M-220 manufactured by JASCO Corporation in an environment of 25 ° C. and 60%. When the load area changes due to deformation of the sample, the area is corrected and an accurate stress is calculated.

[Production Example 1]
In a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction pipe, 8000 g of methyl methacrylate (MMA), 2000 g of methyl 2- (hydroxymethyl) methyl acrylate (MHMA), 10000 g of 4-methyl- 2-Pentanone (methyl isobutyl ketone, MIBK), 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing through nitrogen, and when refluxed, 5.0 g of tertiary butyl peroxyisopropyl was used as an initiator. While adding carbonate (manufactured by Akzo Kayaku Co., Ltd., trade name: Kaya-Carbon Bic-75), a solution comprising 10.0 g of tertiary butyl peroxyisopropyl carbonate and 230 g of MIBK was added dropwise over 2 hours under reflux ( Solution polymerization at about 105 to 120 ° C.) The aging was further performed for 4 hours.

  To the obtained polymer solution, 30 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 120 ° C.) for 5 hours. A condensation reaction was performed. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. A transparent pellet (1A) was obtained by extrusion.

  When the obtained pellet (1A) was measured for dynamic TG, a mass loss of 0.17% by mass was detected. Moreover, the weight average molecular weight of the pellet was 133,000, the melt flow rate was 6.5 g / 10 min, and the glass transition temperature was 131 ° C.

(Examples 1-12, Comparative Examples 1-10)
The pellet (1A) obtained in Production Example 1 and acrylonitrile-styrene (AS) resin (manufactured by Toyo Styrene Co., Ltd .; trade name: Toyo AS AS20) are mixed at a weight ratio of 1A / AS resin = 90/10 (φ) = 30 mm) to obtain transparent pellets. The obtained pellet had a glass transition temperature of 127 ° C.

  This pellet was dissolved in methyl ethyl ketone, and each component described in the following table was mixed to prepare a pellet solution. A 180 μm film (1B) was prepared from this pellet solution by a solution casting method. This film was hot-press-stretched at a glass transition temperature of + 10 ° C. (137 ° C.) at an area ratio of 1.5 times, 2 times, and 3 times for 10 minutes, respectively, and (lactone ring 2), (lactone ring 12), (lactone ring 5 ) Further, the obtained (lactone ring 2), (lactone ring 12), and (lactone ring 5) were stretched to 20% at 240 ° C. to thereby obtain (lactone ring 8), (lactone ring 9), and (lactone ring 4), respectively. ) Made.

──────────────────────────────────────
Pellet solution composition ───────────────────────────────────────
Pellet (1A) 100 parts by weight triphenyl phosphate 3 parts by weight biphenyl phosphate 2 parts by weight retardation control agent (1) 5 parts by weight retardation control agent (2) 2 parts by weight ──────────── ──────────────────────────

Further, by appropriately changing the mixing ratio of the retardation control agents (1) and (2), hot press stretching, and the subsequent stretching ratio under the conditions shown in Table 1 below, (lactone ring 1), (lactone ring 3), (Lactone ring 6), (Lactone ring 7), (Lactone ring 10) (Lactone ring 11) (Lactone ring 13) to (Lactone ring 22) were prepared.

(Example 13)
<Formation of alignment film>
On the lactone ring 11, an alignment film coating solution having the following composition was applied at 24 mL / m ² with a # 14 wire bar coater. It was dried for 120 seconds with 100 ° C. warm air. Next, the longitudinal direction (conveying direction) of the lactone ring 11 was set to 0 °, and the formed film was rubbed in the 0 ° direction.

──────────────────────────────────────
Composition of alignment film coating solution ──────────────────────────────────────
Denatured polyvinyl alcohol 40 parts by weight Water 728 parts by weight Methanol 228 parts by weight Glutaraldehyde (crosslinking agent) 2 parts by weight Citric acid ester (AS3, Sankyo Chemical Co., Ltd.) 0.69 parts by weight ──────── ──────────────────────────────

<Formation of optically anisotropic layer>
On the alignment film, an optically anisotropic layer coating liquid having the following composition was conveyed at 20 m / min by rotating the wire bar of # 3.4 at 781 rpm in the same direction as the film conveying direction. It was continuously applied to the alignment film surface of the roll film. In the process of continuously heating from room temperature to 100 ° C., the solvent was dried, and then heated in a drying zone at 135 ° C. for about 120 seconds to align the discotic liquid crystal compound. Next, it is transported to a drying zone at 100 ° C., and irradiated with ultraviolet rays with an illuminance of 600 mW for 4 seconds by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m), and the crosslinking reaction proceeds, The tick liquid crystal compound was fixed in its orientation. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to obtain a roll-shaped optical film.

──────────────────────────────────────
Optically anisotropic layer coating composition ──────────────────────────────────────
The following discotic liquid crystal compound (1) 41 parts by mass ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 4 parts by mass cellulose acetate butyrate (CAB551-0.2, Eastman Chemical) 0.14 parts by mass cellulose acetate butyrate (CAB531-1, manufactured by Eastman Chemical Co., Ltd.) 0.22 parts by mass fluoroaliphatic group-containing polymer (Megafac F780, manufactured by Dainippon Ink) 0.45 parts by mass light Polymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.35 parts by mass sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts by mass Methyl ethyl ketone 200 parts by mass ───────── ─────────────────────────────

Discotic liquid crystal compound (1)

(Comparative Example 11)
“Zeonor ZF-14” (manufactured by Nippon Zeon Co., Ltd., thickness: 100 μm) was longitudinally stretched at a supply temperature of 140 ° C. and a film film surface temperature of 130 ° C. at a stretching ratio of 15% in a longitudinal uniaxial stretching machine. Thereafter, in a tenter stretching machine, a biaxially stretched optical film was produced by transversely stretching at a draw temperature of 35% at an air supply temperature of 140 ° C. and a film film surface temperature of 130 ° C. and winding up as a roll film. The thickness of the obtained film was 80 μm, Re (550) was 60 nm, and Rth (550) was 155 nm.

  This film was subjected to glow discharge treatment (frequency 3,000 Hz, 4,200 V applied between the upper and lower electrodes, treated for 20 seconds) between the upper and lower electrodes made of brass (argon gas atmosphere), and a ring-opening polymerization ring. A polyolefin film was prepared.

(Comparative Example 12)
(Preparation of ring-opening polymerized cyclic polyolefin dope)
The following composition was put into a mixing tank, stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm.

―――――――――――――――――――――――――――――――――
Cyclic polyolefin solution A
―――――――――――――――――――――――――――――――――
Arton G (manufactured by JSR Corporation) 150 parts by mass Methylene chloride 550 parts by mass Ethanol 50 parts by mass ――――――――――――――――――――――――――――― ―――

  Next, the following composition containing the ring-opening polymerization cyclic polyolefin solution prepared by the above method was put into a disperser to prepare a mat agent dispersion.

――――――――――――――――――――――――――――――――――
Matting agent dispersion ――――――――――――――――――――――――――――――――――
Silica particles having an average particle diameter of 16 nm (aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride 75 parts by mass Ethanol 5 parts by mass Cyclic polyolefin solution A 10 parts by mass ――――――――――――― ――――――――――――――――――――

  100 parts by mass of the cyclic polyolefin solution and 1.1 parts by mass of the matting agent dispersion were mixed to prepare a dope for film formation.

  The above dope was cast using a band casting machine. The film peeled off from the band with a residual solvent amount of about 22% by mass was stretched in the width direction at a stretch rate of 50% using a tenter. Thereafter, the tenter transport was shifted to the roll transport, and further dried at 120 to 140 ° C. and wound up. The produced cyclic polyolefin film had a thickness of 80 μm, Re (550) of 60 nm, and Rth (550) of 155 nm. This film was subjected to glow discharge treatment as in Comparative Example 11 to produce a ring-opening polymerized cyclic polyolefin film.

(Comparative Example 13)
A cellulose acylate film (TAC-TD80U manufactured by FUJIFILM Corporation) was stretched at 240 ° C. in the 20% TD direction. The film thickness after stretching was 80 μm. Re (550) was 60 nm and Rth (550) was 155 nm.

(Preparation of polarizing plate)
About the film produced in Examples 1-13 and Comparative Examples 1-13, the polarizing plate was produced as follows.
A polyvinyl alcohol (PVA) film having a thickness of 80 μm is dyed by immersing it in an aqueous iodine solution having an iodine concentration of 0.05% by mass at 30 ° C. for 60 seconds, and then in an aqueous boric acid solution having a boric acid concentration of 4% by mass. The film was vertically stretched to 5 times the original length while being immersed for 2 seconds, and then dried at 50 ° C. for 4 minutes to obtain a polarizing film having a thickness of 20 μm.
A commercially available cellulose acetate film was immersed in an aqueous sodium hydroxide solution at 55 ° C. at 1.5 mol / L, and then the sodium hydroxide was sufficiently washed away with water. Then, after being immersed in a diluted sulfuric acid aqueous solution at 35 ° C. for 1 minute at 0.005 mol / L, the diluted sulfuric acid aqueous solution was sufficiently washed away by immersion in water. Finally, the sample was thoroughly dried at 120 ° C.
As described above, a polyvinyl alcohol adhesive is used so as to sandwich the polarizing film in combination with the films prepared in Examples 1 to 13 and Comparative Examples 1 to 13 and a commercially available cellulose acetate film subjected to saponification treatment. To obtain a polarizing plate. Here, in Example 13, the optically anisotropic layer of the film was disposed so as to be on the outside. As a commercially available cellulose acetate film, Fujitac TF80UL (manufactured by FUJIFILM Corporation) was used. At this time, since the polarizing film and the protective films on both sides of the polarizing film are produced in a roll form, the longitudinal directions of the roll films are parallel to each other and are continuously bonded. Therefore, the roll length direction of the film and the polarizer absorption axis were parallel to each other.

(Production of TN mode liquid crystal cell)
A polyimide film was provided as an alignment film on a 22-inch glass substrate with an ITO electrode, and the alignment film was rubbed. About the obtained two glass substrates, the rubbing direction of the upper glass substrate is arranged in the upper right 45 degree direction, the rubbing direction of the lower glass substrate is arranged in the lower right 45 degree direction and face each other, and the cell gap is 4 A nematic liquid crystal material having an anisotropic layer with a positive dielectric constant of 0.7 μm was sealed between the substrates by drop injection, and Δn · d of the liquid crystal layer was 400 nm. The liquid crystal material has a positive dielectric anisotropy, a refractive index anisotropy, Δn = 0.0854 (589 nm, 20 ° C.), and a nematic liquid crystal of about Δε = + 8.5 (for example, MLC-9100 manufactured by Merck). It was used. Thus, a TN mode liquid crystal cell was produced.

(Production of TN mode liquid crystal display device)
A TN mode liquid crystal display device was produced by bonding the produced polarizing plate and the liquid crystal cell together.
When the polarizing plate was bonded onto the glass of the liquid crystal cell, the rubbing direction of the glass substrate and the absorption axis of the polarizing plate were arranged in parallel. In the case of Example 13, the rubbing direction of the glass substrate and the absorption axis of the polarizing plate are parallel to each other, and the anti-parallel to the rubbing treatment direction performed before applying the optically anisotropic layer. Arranged.

(Viewing angle measurement method)
About the liquid crystal display device produced in Examples 1-13 and Comparative Examples 1-13, it is a visual field from a black display (L1) to a white display (L8) using measuring machine "EZ-Contrast160D" (made by ELDIM). The corner was measured. The contrast ratio (white transmittance / black transmittance) at a polar angle of 80 degrees was determined vertically and horizontally. Here, those having a contrast ratio of 10 or more in the left-right direction (average) polar angle of 80 degrees were judged to have good viewing angles.

(Peripheral light leakage measurement method)
About the liquid crystal display device produced in Examples 1-13 and Comparative Examples 1-13, after storing for 100 hours in a 60 degreeC dry thermostat, it preserve | saved for 100 hours in the environment of 25 degreeC60% RH, and liquid crystal in the same environment The display device was turned on, and the in-plane distribution of luminance in the black display state after holding for 2 hours was observed with a Topcon luminance meter SR-3 at multiple points. The evaluation criteria are as shown below.
<Evaluation criteria>
A: The average luminance of the upper, lower, left, and right diagonal edge portions is 1.2 times or less than the luminance of the central portion. The average brightness of the left and right diagonal edges is greater than 1.4 and 2.5 times less than the brightness of the center. Xx: The average brightness of the top, bottom, left and right diagonal edges is greater than 2.5 times the brightness of the center

In Table 2, Re represents Re550 and Rth represents Rth550.

(Examples 14 to 20)
In the same manner as in Example 13, an alignment film was formed on the lactone ring 11 and rubbed.

  On the alignment film, the coating solution of optically anisotropic layer having the following composition is conveyed at 36 m / min by rotating the # 2.9 wire bar at 1,406 rpm in the same direction as the film conveyance direction. It was continuously applied to the alignment film surface of the roll film. In the process of continuously heating from room temperature to 100 ° C., the solvent was dried, and then heated in a drying zone at 115 ° C. for about 90 seconds to align the discotic liquid crystal compound. Next, it is transported to a drying zone at 80 ° C., and irradiated with ultraviolet rays having an illuminance of 600 mW for 4 seconds by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, light emission length 1.6 m) to advance the crosslinking reaction, The tick liquid crystal compound was fixed in its orientation. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to obtain a roll-shaped optical film.

<Optical anisotropic layer coating solution composition>
90 parts by mass of the discotic liquid crystal compound A shown in Table 3 below 10 parts by mass of the discotic liquid crystal compound B shown in Table 3 below 1 air part orientation control agent shown in the following chemical formula 1 part by mass photopolymerization initiator “Irgacure 907” manufactured by Ciba Geigy 3 parts by mass sensitizer “Kayacure DETX” manufactured by Nippon Kayaku Co., Ltd. 1 part by mass Methyl ethyl ketone 340 parts by mass

(Air interface orientation control agent)

  About the optical film produced in Examples 14-20, the polarizing plate was produced similarly to Example 13 and the liquid crystal display device was produced.

(Viewing angle measurement)
About the liquid crystal display device produced in Examples 14-20, the viewing angle was measured similarly to Example 13. FIG. The results are shown in Table 4.

(Measurement of light leakage at the periphery)
About the liquid crystal display device produced in Examples 14-20, the peripheral part light leakage was measured similarly to Example 13. FIG. The results are shown in Table 4.

In Table 4, Re represents Re550 and Rth represents Rth550.

From Tables 2 and 4, in the liquid crystal display devices of Examples 4, 6, 8, and 9 and Comparative Examples 4, 7, 8, and 10, the luminance at the periphery of the display surface is about 1.2 times that at the center of the display surface. In Examples 1 to 3, 5, 7, 10 to 20, and Comparative Examples 1 to 3, 5, 6, and 9, it is about 1.4 times, and it is understood that light leakage around the display surface is small. It was. On the other hand, in the devices of Comparative Examples 11 to 13, it was found that the luminance at the periphery of the display surface was about 2.5 compared with the central portion of the display surface, and light leakage at the periphery of the display surface was increased.
Furthermore, from Table 2, in Examples 5 to 7 (lactone rings 5 to 7, Re550: in the range of 90 to 100 nm, Rth550: in the range of 120 to 130 nm), the right and left viewing angle is increased to 100 or more, which is preferable. I understood.

FIG. 1 is a graph showing the retardation of the optical compensation film of the present invention, wherein the vertical axis shows in-plane retardation Re550 at a wavelength of 550 nm, the horizontal axis shows out-of-plane retardation Rth550 at a wavelength of 550 nm, Shows examples, and white crosses indicate comparative examples.

Claims (10)

  An optical compensation film having a transparent film containing a polymer having either a lactone ring unit or a glutaric anhydride unit, wherein the in-plane retardation Re550 at a wavelength of 550 nm is 20 to 150 nm, and the out-of-plane at a wavelength of 550 nm An optical compensation film having a retardation Rth550 of 70 to 190 nm.   The optical compensation film according to claim 1, wherein the in-plane retardation Re550 at a wavelength of 550 nm is 70 to 110 nm, and the out-of-plane retardation Rth550 at a wavelength of 550 nm is 110 to 150 nm.   The optical compensation film according to any one of claims 1 to 2, wherein the transparent film contains a retardation increasing agent having two or more aromatic rings in one molecule.   The optical compensation film according to any one of claims 1 to 3, wherein the transparent film is subjected to a stretching treatment in which the film is stretched at a magnification of 1.1 to 2.0 in any direction parallel or perpendicular to the transport direction.   The optical compensation film according to claim 1, wherein a transparent film, an alignment film, and an optically anisotropic layer made of a liquid crystal compound are laminated in this order.   A polarizing plate comprising the optical compensation film according to claim 1.   The polarizing plate according to claim 6, further comprising a polarizing film, wherein an intersection angle between a transmission axis in the plane of the polarizing film and a slow axis in the plane of the optical compensation film is approximately 0 degrees.   A liquid crystal display device comprising the optical compensation film according to claim 1.   A pair of opposed substrates having electrodes on at least one side, a liquid crystal cell having a liquid crystal layer sandwiched between the pair of substrates, and first and second polarizing films disposed with the liquid crystal cell sandwiched therebetween The liquid crystal display device according to claim 8, wherein an optical compensation film is disposed between the liquid crystal layer and the first and second polarizing films.   The liquid crystal layer includes a nematic liquid crystal material, and the liquid crystal molecules of the nematic liquid crystal material are aligned substantially perpendicular to the surfaces of the pair of substrates during black display, and the thickness d (micron) of the liquid crystal layer and the liquid crystal molecules The liquid crystal display device according to claim 8, wherein a product Δn · d with a refractive index anisotropy Δn is 0.1 to 1.5 microns.