JP2007148115A - Liquid crystal composition, method of manufacturing laminated optical compensation film and laminated optical compensation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition which is satisfactorily applied on a retardation film made of cycloolefin type resin, and does not degrade retardation of the retardation film made of cycloolefin type resin even when applied, to provide a method of manufacturing a laminated optical compensation film which is used for improvement of image quality of a liquid crystal display device, and also to provide the laminated optical compensation film manufactured by the method of manufacturing laminated optical compensation film. <P>SOLUTION: The liquid crystal composition comprises: a liquid crystal compound; a photopolymerization initiator; and a solvent mixture of a ketone type solvent and/or an ester type solvent and an aromatic type solvent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention provides a liquid crystal composition that can be satisfactorily coated on a retardation film made of a cycloolefin-based resin, and does not reduce the retardation of the retardation film even when coated, and a liquid crystal display device The present invention relates to a method for producing a laminated optical compensation film and a laminated optical compensation film that are used for improving the image quality.

Liquid crystal display devices are used for notebook personal computers, personal computer monitors, and the like, but in recent years, they have also been used for large-sized televisions, and the demand is rapidly increasing.
Liquid crystal display devices used for such applications are required to be viewed well from a wider range, and a method called a VA method or an IPS method that improves the viewing angle dependency of the conventional TN method is often adopted. Has been. However, in these methods, although the viewing angle characteristics in the vertical and horizontal directions on the image display surface are improved, for example, when viewed from an oblique direction, contrast and color reproducibility are insufficient, and further improvement is possible. It has been demanded.

Such a decrease in viewing angle from an oblique direction is considered to be caused by viewing angle characteristics of a polarizing plate used in a liquid crystal display device. As a method for improving this, for example, Patent Document 1 discloses using an optical compensation film having an Nz coefficient of 0.5.

Conventionally, as such an optical compensation film, as disclosed in Patent Document 2, after bonding the shrinkable film to the resin film to be stretched so that the shrinking direction is orthogonal to the stretching direction, Since it is produced by a method of heating and stretching, it has been difficult to produce a large optical compensation film for use in a large liquid crystal display device which has a particularly low yield in the film width direction and is in great demand in recent years.

Recently, for example, as described in Patent Document 3, a liquid crystal composition is directly applied on a retardation film formed of a uniaxially or biaxially stretched film, as described in Patent Document 3. A liquid crystal laminated type optical compensation film has been proposed in which a liquid crystal layer subjected to vertical alignment treatment is laminated by removing a solvent in the product.

As a material for the retardation film of the liquid crystal laminated optical compensation film, a polycarbonate or a triacetyl cellulose film is used.
However, a liquid crystal display device manufactured using an optical compensation film having a retardation film made of such a material has an internal stress generated by heating the film layer of the optical compensation film due to heat generation of the backlight during use. As a result, there is a problem that a display defect called light leakage occurs.

In response to such problems, as described in Patent Document 4, in recent years, cycloolefin resins having excellent heat resistance and low photoelasticity are being used as materials for retardation films.
However, coating a liquid crystal composition on a retardation film made of a stretched cycloolefin-based resin film to form a liquid crystal layer is difficult to apply because it causes repelling, and is not stretched. In addition, the retardation film made of the cycloolefin resin film and the liquid crystal layer had a problem of poor adhesion.
Further, when a liquid crystal composition is applied on a retardation film made of a stretched cycloolefin resin film, there is a problem that the retardation of the retardation film may be lowered.
JP-A-4-305602 JP-A-5-157911 JP 2003-149441 A JP 2004-279437 A

In view of the present situation, the present invention provides a liquid crystal composition that can be satisfactorily coated on a retardation film made of a cycloolefin-based resin and that does not lower the retardation of the retardation film even when coated. An object of the present invention is to provide a method for producing a laminated optical compensation film and a laminated optical compensation film used for improving the image quality of a liquid crystal display device.

The present invention is a liquid crystal composition containing a liquid crystal compound, a photopolymerization initiator, and a mixed solvent of a ketone solvent and / or an ester solvent and an aromatic solvent.
The present invention is described in detail below.

In recent years, the present inventors have performed a normal pressure plasma treatment on a surface in contact with a liquid crystal layer of a retardation film composed of a cycloolefin-based resin film (hereinafter, also simply referred to as a retardation film), thereby obtaining a retardation film It has been found that the adhesion with the liquid crystal layer can be improved, and has solved the problem of adhesion.
In addition, the inventors of the present invention, after coating the liquid crystal composition on the retardation film, the retardation of the retardation film decreases because the aromatic solvent which is a good solvent for the liquid crystal composition is a retardation film. It was considered that it has a plasticizing effect on the film and penetrates into the retardation film in the coating-drying process, resulting in relaxation of the orientation. Therefore, it was considered that an aromatic solvent was not used as the solvent, but in this case, when the liquid crystal composition was applied onto the retardation film, the repelling became noticeable or during storage of the liquid crystal composition. It has been found that problems such as precipitation of liquid crystal occur.
Therefore, as a result of further intensive studies, the present inventors can achieve both coating properties and stability of the liquid crystal composition by using a mixed solvent of an aromatic solvent and a specific solvent as a solvent. In addition, the present inventors have found that it is possible to produce a liquid crystal composition that does not lower the retardation of the retardation film after coating the liquid crystal composition, and have completed the present invention.

The liquid crystal composition of the present invention contains a liquid crystal compound, a photopolymerization initiator, and a mixed solvent of a ketone solvent and / or an ester solvent and an aromatic solvent.

The liquid crystal compound is not particularly limited, and examples thereof include a main chain polymer liquid crystal compound, a side chain polymer liquid crystal compound, and a polymerizable low molecular liquid crystal compound. These may be used alone or in combination.
Here, in the present invention, since the liquid crystal composition is directly applied onto a retardation film made of a cycloolefin resin film, the liquid crystallizing temperature is about 100 in order to prevent relaxation of the retardation due to heat at the liquid crystal transition temperature. It is preferable that it is below ℃.
Considering this, a polymerizable low-molecular liquid crystal compound is preferable because the liquid crystallizing temperature is low.

The main chain polymer liquid crystal compound is not particularly limited. For example, polyester-based, polyamide-based, polycarbonate-based, polyimide-based, polyurethane-based, polybenzimidazole-based, polybenzoxazole-based, polybenzthiazole-based, polyazomethine-based , Polyester amide-based, polyester carbonate-based, polyester imide-based polymer liquid crystal substances, and mixtures thereof.

The side chain type polymer liquid crystal compound is not particularly limited, and examples thereof include linear or cyclic structures such as polyacrylate, polymethacrylate, polyvinyl, polysiloxane, polyether, polymalonate, and polyester. Examples thereof include a polymer liquid crystal substance in which a mesogenic group is bonded as a side chain to a substance having a skeleton chain, and a mixture thereof.

The polymerizable low-molecular liquid crystal compound is not particularly limited. However, since the liquid crystal layer after coating the liquid crystal composition of the present invention on a retardation film can be homeotropically aligned as described later, for example, It is preferably at least one selected from the group consisting of formulas (1), (2) and (3).

上記式（１）において、Ｗ^１は水素又はメチルを表し、ｌは４〜６の整数である。
上記式（２）において、Ｗ^２及びＷ^３は水素、塩素又はフッ素を表し、Ｗ^４及びＷ^５は水素、塩素、メチル又はトリフルオロメチルを表し、Ｘは単結合、エチレン結合又はエタン結合を表し、ｍは４〜６の整数である。
上記式（３）において、ｎは４〜６の整数である。

In the above formula (1), W ¹ represents hydrogen or methyl, and l is an integer of 4-6.
In the above formula (2), W ² and W ³ represent hydrogen, chlorine or fluorine, W ⁴ and W ⁵ represent hydrogen, chlorine, methyl or trifluoromethyl, and X represents a single bond, an ethylene bond or an ethane bond. M is an integer of 4-6.
In said formula (3), n is an integer of 4-6.

In the above formula (1), a compound in which W ¹ is methyl and l is 4 or 6 can be synthesized by the method described in JP-A-2003-238491.

In the above formula (2), W ² and W ³ are hydrogen, W ⁴ and W ⁵ are hydrogen, X is a single bond, and m is 6, as described in Makromol. Chem. 190, 2255-2268 (1989).

In the above formula (2), W ² and W ³ are hydrogen, W ⁴ is hydrogen, W ⁵ is methyl, X is a single bond, and m is 6, Makromol. Chem. 190, 3201-3215 (1989).

In the above formula (2), W ² and W ³ are hydrogen, W ⁴ is trifluoromethyl, W ⁵ is trifluoromethyl, X is a single bond, and m is 6. It can be synthesized by the method described in 2004-231638.

In the above formula (2), W ² and W ³ are chlorine or fluorine, W ⁴ is hydrogen, W ⁵ is chlorine, X is a single bond, and m is 6 is a Liquid Crystals Vol 30, It can synthesize | combine by the method as described in No8,979-984 (2003).

In the above formula (3), a compound in which n is 4 or 6 can be synthesized by the method described in Macromolecules, 26, 6132-6134 (1993).

The photopolymerization initiator is not particularly limited, and examples thereof include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2,2-dimethoxy-1,2-diphenylethane. -1-ON, Irgacure 500, Irgacure 2959, Irgacure 907, Irgacure 369, Irgacure 1300, Irgacure 819, Irgacure 1700, Irgacure 1800, Irgacure 1850, Darocur 4265, Irgacure 784, Irgacure 754, Irgacure OXE01, p-methoxyphenyl-2,4-bis (trichloromethyl) triazine, 2- (p-butoxystyryl) -5-trichloromethyl-1,3,4-oxadiazole, 9-pheni Acridine, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, benzyldimethyl ketal, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1- ON, and a mixture of 2,4-diethylxanthone and methyl p-dimethylaminobenzoate. Darocur and Irgacure are both manufactured by Ciba Specialty Chemicals. Furthermore, known sensitizers (isopropyl thioxanthone, diethyl thioxanthone, etc.) may be added thereto.

Other examples of the photopolymerization initiator include p-methoxyphenyl-2,4-bis (trichloromethyl) triazine, 2- (p-butoxystyryl) -5-trichloromethyl-1,3, 4-oxadiazole, 9-phenylacridine, 9,10-benzphenazine, benzophenone / Michler's ketone mixture, hexaarylbiimidazole / mercaptobenzimidazole mixture, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane -1-one, benzyldimethyl ketal, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2,4-diethylxanthone / methyl p-dimethylaminobenzoate, benzophenone / Methyltriethanolamine mixture etc. It is below.

The preferred addition amount of the photopolymerization initiator is not particularly limited, but based on the total amount of the liquid crystal composition of the present invention, the preferred lower limit is 0.01% by weight, the preferred upper limit is 10% by weight, and the more preferred lower limit is 0. 0.1% by weight, and a more preferable upper limit is 7% by weight.

The mixed solvent includes a ketone solvent and / or an ester solvent and an aromatic solvent.
Since the mixed solvent has such a configuration, the conventional problem that the retardation of the retardation film is lowered after the liquid crystal composition of the present invention is applied to the retardation film as described later. Can be solved.

The ketone solvent is not particularly limited, and examples thereof include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone.

The ester solvent is not particularly limited, and examples thereof include ethyl acetate, ethyl lactate, methyl lactate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone.

The aromatic solvent is not particularly limited, and examples thereof include benzene, toluene, xylene, mesitylene, n-butylbenzene, diethylbenzene, tetralin, methoxybenzene, 1,2-dimethoxybenzene and the like.
Among these, a combination using ethyl lactate as an ester solvent and toluene as an aromatic solvent is preferable from the viewpoint of easy availability and handling safety.

The blending amount of the aromatic solvent in the mixed solvent is not particularly limited, but a preferred lower limit is 10% by weight and a preferred upper limit is 85% by weight. If it is less than 10% by weight, there may be a problem in the solubility and stability of the liquid crystal composition of the present invention. If it exceeds 85% by weight, plasticization to the retardation film may not be suppressed. A more preferred lower limit is 20% by weight, and a more preferred upper limit is 80% by weight.

A laminated optical compensation film can be produced by using the liquid crystal composition of the present invention.
The method for producing the laminated optical compensation film is not particularly limited. For example, the liquid crystal composition of the present invention is directly coated on a retardation film made of a cycloolefin resin, and the solvent is dried to form a liquid crystal layer. And a method of forming a liquid crystal layer by coating the liquid crystal composition of the present invention directly on a retardation film made of a cycloolefin resin, drying the solvent, and then curing by polymerization. Such a method for producing a laminated optical compensation film is also one aspect of the present invention.

The retardation film is obtained by orienting cycloolefin resin molecules in a predetermined direction by stretching a cycloolefin resin film obtained by forming a cycloolefin resin.
The cycloolefin-based resin is not particularly limited, and examples thereof include norbornene-based resins and dicyclopentadiene-based resins. Among these, those having no unsaturated bond or having an unsaturated bond hydrogenated are preferably used. For example, a ring-opening (co) polymer of one or more norbornene monomers is used. Hydrogenated products, addition (co) polymers of one or more norbornene monomers, addition copolymers of norbornene monomers and olefin monomers (ethylene, α-olefin, etc.), norbornene monomers and cycloolefins And addition copolymers with a series monomer (cyclopentene, cyclooctene, 5,6-dihydrodicyclopentadiene, etc.), and modified products thereof, specifically, ZEONEX, ZEONOR (manufactured by Nippon Zeon Co., Ltd.) , ARTON (manufactured by JSR), TOPAS (manufactured by Chicona), APEL (manufactured by Mitsui Chemicals) and the like.

The film forming method is not particularly limited, and a conventionally known film forming method may be used. Specifically, for example, a cycloolefin-based resin is supplied to an extruder and melted and kneaded. Extruded into a film shape from a mold attached to a film (melt extrusion method), a solution obtained by dissolving a cycloolefin resin in an organic solvent is allowed to flow on a drum or band Examples thereof include a method of evaporating an organic solvent and then forming a long cycloolefin-based resin film (solution casting method).
In addition, when the thickness of the cycloolefin-based resin film is 80 μm or more, it may be difficult to sufficiently evaporate and remove the organic solvent by the solution casting method. Therefore, it is preferable to use the melt extrusion method. .

As a method for the stretching treatment, for example, a long cycloolefin resin film is used in a lateral direction (width direction) or a longitudinal direction (length direction) in a temperature region near the glass transition temperature Tg of the cycloolefin resin. The long cycloolefin-based resin film is stretched in the transverse direction (width direction) and then in the longitudinal direction (length direction) in the temperature region near the glass transition temperature Tg of the cycloolefin resin. A method of stretching a long cycloolefin resin film in the longitudinal direction (length direction) and the transverse direction (width direction) simultaneously in a temperature region near the glass transition temperature Tg of the cycloolefin resin, Thin film of olefin resin film by applying pressing force in the thickness direction in the temperature range near the glass transition temperature Tg of cycloolefin resin A method in which simultaneously stretched in the machine direction (longitudinal direction) and lateral direction (width direction) can be mentioned by.

The retardation film made of the cycloolefin resin is preferably subjected to atmospheric pressure plasma treatment with an inert gas having an oxygen concentration of 15% by volume or less on the surface in contact with the liquid crystal layer.
By performing the normal pressure plasma treatment, it becomes easy to apply the liquid crystal composition of the present invention on the retardation film, and the liquid crystal layer composed of the liquid crystal composition and the retardation film composed of the cycloolefin-based resin Excellent adhesion.

In the normal pressure plasma treatment, a voltage is applied to a gas introduced between electrodes to excite the gas into a plasma gas, and the surface of the object to be processed is hydrophilized with the plasma gas.

The atmospheric pressure plasma treatment is preferably performed in an apparatus having a pair of counter electrodes, and a solid dielectric is installed on at least one of the counter surfaces of the electrodes. When the solid dielectric is installed on one of the electrodes, the plasma is generated between the solid dielectric and the electrode. When the solid dielectric is installed on both of the electrodes, the plasma is generated between the solid dielectrics. Space. A normal pressure plasma treatment is performed by disposing a hydrophobic resin film as a target object of the hydrophilization treatment between the solid dielectric and the electrode or between the solid dielectrics.

The electrode is not particularly limited, and examples thereof include those made of simple metals such as copper and aluminum, alloys such as stainless steel and brass, and metal compounds.

The counter electrode preferably has a structure in which the distance between the counter electrodes is substantially constant in order to avoid occurrence of arc discharge due to electric field concentration. Examples of the electrode structure that satisfies this condition include a parallel plate type, a cylindrical opposed flat plate type, a spherical opposed flat plate type, a hyperboloid, an opposed flat plate type, and a coaxial cylindrical type structure.

The solid dielectric is preferably disposed on one or both of the opposing surfaces of the electrode. At this time, the solid dielectric and the electrode on the side to be installed are in close contact with each other, and the opposing surface of the electrode in contact is completely covered. This is because if there is a portion where the electrodes directly face each other without being covered by the solid dielectric, arc discharge occurs from there.
The solid dielectric may be in the form of a sheet or a film, but the lower limit of the preferred thickness is 0.01 mm, and the upper limit of the preferred thickness is 4 mm. If it is less than 0.01 mm, a high voltage is required to generate discharge plasma. If it exceeds 4 mm, dielectric breakdown may occur when voltage is applied, and arc discharge may occur.

The material of the solid dielectric is not particularly limited, and examples thereof include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide, and titanium dioxide, and barium titanate. Examples include double oxides.
The solid dielectric preferably has a relative dielectric constant of 2 or more in a 25 ° C. environment. Specific examples of the dielectric having a relative dielectric constant of 2 or more include, for example, polytetrafluoroethylene, glass, and metal oxide film. Furthermore, in order to stably generate a high-density discharge plasma, it is preferable to use a solid dielectric having a relative dielectric constant of 10 or more.
The upper limit of the relative dielectric constant is not particularly limited, but an actual material of about 18500 is known. The solid dielectric having a relative dielectric constant of 10 or more is composed of a metal oxide film mixed with 5 to 50% by weight of titanium oxide and 50 to 95% by weight of aluminum oxide, or a metal oxide film containing zirconium oxide. It is preferable to use a film having a thickness of 10 to 1000 μm.

The distance between the electrodes is not particularly limited and is determined in consideration of the pressure of the atmospheric gas, the oxygen concentration, the thickness of the solid dielectric, the magnitude of the applied voltage, the purpose of using the film subjected to plasma discharge treatment, and the like. The preferred lower limit is 0.5 mm, and the preferred upper limit is 50 mm. If the thickness is less than 0.5 mm, the variation in the atmospheric gas concentration between the electrodes is large, the processing is likely to be non-uniform, and the thickness of the workpiece to be installed between the electrodes is limited. If it exceeds 50 mm, it is difficult to generate uniform discharge plasma.
The applied voltage is preferably a pulse voltage. The pulse waveform may be any of an impulse type, a square wave type, and a modulation type waveform. Furthermore, even if the applied voltage is positive and negative, a single-wave shape waveform in which voltage is applied to either the positive or negative polarity side. It may be.

The voltage rise time of the pulse voltage is not particularly limited, but a preferable lower limit is 40 ns, and a preferable upper limit is 100 μs. Here, the voltage rise time of the pulse voltage means a time during which the voltage change is continuously positive. It is difficult to realize a pulse voltage having a voltage rise time of less than 40 ns. If the pulse voltage exceeds 100 μs, the discharge state tends to shift to an arc and becomes unstable, and a high-density plasma state due to the pulse voltage cannot be expected. A more preferable lower limit is 50 ns, and a more preferable upper limit is 5 μs.
Further, the voltage fall time of the pulse voltage is preferably steep, and the time scale is preferably 100 μs or less, which is the same as the voltage rise time of the pulse voltage. For example, in the power supply device used in the embodiments of the present invention, the voltage rise time and the voltage fall time of the pulse voltage can be set to the same time, although it depends on the pulse electric field generation technique.

Although it does not specifically limit as a frequency of a pulse voltage, A preferable minimum is 0.5 kHz and a preferable upper limit is 100 kHz. If it is less than 0.5 kHz, the plasma density is low, so that the process takes too much time. If it exceeds 100 kHz, arc discharge tends to occur. A more preferred lower limit is 1 kHz.

Although it does not specifically limit as pulse duration in the said pulse voltage, A preferable minimum is 1 microsecond and a preferable upper limit is 1000 microseconds. If it is less than 1 μs, the discharge becomes unstable, and if it exceeds 1000 μs, it tends to shift to arc discharge. A more preferable lower limit is 3 μs, and a more preferable upper limit is 200 μs. Here, the pulse duration means a time for which a pulse continues in a pulse voltage consisting of repetition of ON and OFF.
Furthermore, in order to stabilize the discharge, it is preferable to have an OFF time that lasts at least 1 μs within a discharge time of 1 ms. Further, a direct current may be superimposed when applying a pulse voltage.

The atmospheric gas that generates plasma discharge is a gas containing at least oxygen gas. Nitrogen gas, argon gas, etc. are mentioned as mixed gas other than oxygen gas, The volume ratio of gas other than oxygen gas and oxygen can be mixed by substantially arbitrary ratios in the range of 15:85 to 1:99. . When the oxygen gas concentration in the mixed gas exceeds 15% by volume, the adhesion of the liquid crystal layer is rapidly lowered. In addition, although the lower limit of the oxygen gas concentration in the mixed gas is not particularly limited, in the present invention, since the treatment is performed near normal pressure, it does not become completely oxygen-free, and substantially no oxygen is present. It only has to exist. A more preferable upper limit of the oxygen gas concentration is 10% by volume.

The pressure of the atmospheric plasma treatment is not particularly limited, but a preferable lower limit is 100 Torr (about 1.33 × 10 ⁴ Pa), a preferable upper limit is 800 Torr (about 10.6 × 10 ⁴ Pa), and a more preferable lower limit is 700 Torr (about 9.31 × 10 ⁴ Pa), and a more preferable upper limit is 780 Torr (about 10.4 × 10 ⁴ Pa).

The coating method is not particularly limited, and examples thereof include a die coating method, a roll coating method, a gravure coating method, a micro gravure method, a spin coating method, and a bar coating method.
In the method for producing a laminated optical compensation film of the present invention, it is possible to easily apply a liquid crystal composition to a retardation film by performing the plasma discharge treatment step, and a liquid crystal layer after coating. And excellent adhesion between the retardation film.

When coating the liquid crystal composition, the solvent is removed after the coating to form a liquid crystal composition layer having a uniform film thickness, that is, a liquid crystal layer, on the retardation film. The conditions for removing the solvent are not particularly limited, and it may be dried until the solvent is generally removed and the fluidity of the coating film of the liquid crystal composition is lost. The solvent can be removed using air drying at room temperature, drying on a hot plate, drying in a drying furnace, blowing warm air or hot air, and the like. Depending on the type and composition ratio of the compound used in the liquid crystal composition, nematic alignment of the liquid crystal composition in the coating film may be completed in the process of drying the coating film. Therefore, the coating film that has undergone the drying process can be subjected to the polymerization process without going through a heat treatment process to be described later. However, in order to make the alignment of the liquid crystal molecules in the coating film more uniform, it is preferable to heat-treat the coating film that has undergone the drying step and then to perform photopolymerization.

The temperature and time when the coating film is heat-treated, the wavelength of light used for light irradiation, the amount of light irradiated from the light source, etc. are the types and composition ratios of the compounds used in the liquid crystal composition, and whether a photopolymerization initiator is added. The preferred range varies depending on the amount of addition and the amount thereof. Accordingly, the conditions regarding the temperature and time of the heat treatment of the coating film described below, the wavelength of the light used for light irradiation, and the amount of light irradiated from the light source are merely an approximate range.

The heat treatment of the coating film is preferably performed under the condition that the solvent is removed and the uniform alignment of the liquid crystal is obtained, and may be performed at a temperature higher than the liquid crystal phase transition point of the liquid crystal composition of the present invention. Examples of the heat treatment method include a method of heating the coating film to a temperature at which the liquid crystal composition of the present invention exhibits a nematic liquid crystal phase and forming a nematic alignment in the liquid crystal composition in the coating film. The nematic alignment may be formed by changing the temperature of the coating film within a temperature range in which the liquid crystal composition exhibits a nematic liquid crystal phase. This method is a method in which a nematic orientation is substantially completed in a coating film by heating the coating film to a high temperature range of the above temperature range, and then the order is further ordered by lowering the temperature. In any of the above heat treatment methods, the preferred lower limit of the heat treatment temperature is room temperature, the preferred upper limit is 120 ° C., the more preferred upper limit is 90 ° C., and the still more preferred upper limit is 70 ° C.
The preferable lower limit of the heat treatment time is 5 seconds, the preferable upper limit is 2 hours, the more preferable lower limit is 10 seconds, the more preferable upper limit is 40 minutes, the still more preferable lower limit is 20 seconds, and the further preferable upper limit is 20 minutes. is there. In order to raise the temperature of the layer made of the liquid crystal composition to a predetermined temperature, the heat treatment time is preferably 5 seconds or more. In order not to lower the productivity, it is preferable to set the heat treatment time within 2 hours. In this way, a liquid crystal layer is obtained.

The wavelength of the light used for the light irradiation is not particularly limited, but the preferred lower limit is 150 nm, the preferred upper limit is 500 nm, the more preferred lower limit is 250 nm, the more preferred upper limit is 450 nm, the still more preferred lower limit is 300 nm, and the still more preferred upper limit. Is 400 nm. As said light, an electron beam, an ultraviolet-ray, visible light, infrared rays (heat ray) etc. can be utilized, for example, Usually, an ultraviolet-ray or visible light should just be used. Specific examples of the light source include, for example, a low-pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high-pressure discharge lamp (high-pressure mercury lamp, metal halide lamp), a short arc discharge lamp (ultra-high-pressure mercury lamp, xenon lamp, Mercury xenon lamp) and the like. Of these, metal halide lamps, xenon lamps, and high-pressure mercury lamps are preferably used. The wavelength region of the irradiation light source may be selected by installing a filter or the like between the light source and the liquid crystal layer and passing only a specific wavelength region. No particular limitation is imposed on the amount of light emitted from the light source, the preferred lower limit is 2 mJ / cm ^2, a preferred upper limit is 5000 mJ / cm ^2, and more preferable lower limit is 10 mJ / cm ^2, and more preferred upper limit is 3000 mJ / cm ^2, A more preferred lower limit is 100 mJ / cm ² , and a more preferred upper limit is 2000 mJ / cm ² . It is preferable that the temperature condition at the time of light irradiation is set similarly to the above heat treatment temperature.

Further, a laminated optical compensation film comprising a retardation film made of a cycloolefin resin and a liquid crystal layer, which is produced by the method for producing a laminated optical compensation film of the present invention, is also a laminated optical compensation film of the present invention. One.
The laminated optical compensation film of the present invention can be used for improving the image quality of a liquid crystal display device by having the above-described configuration.

The liquid crystal layer is preferably homeotropically aligned. When the liquid crystal layer is homeotropically aligned, the viewing angle characteristics of a liquid crystal display device using a laminated optical compensation film can be improved.

According to the present invention, by using a mixed solvent of an aromatic solvent and a specific solvent as the solvent, it is possible to achieve both coating properties and stability of the liquid crystal composition and to apply the liquid crystal composition. A liquid crystal composition that does not lower the retardation of the retardation film after the process can be produced.
According to the present invention, a liquid crystal composition that can be satisfactorily coated on a retardation film made of a cycloolefin-based resin and does not decrease the retardation of the retardation film even when coated, a liquid crystal A method for producing a laminated optical compensation film and a laminated optical compensation film used for improving the image quality of a display device can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Production of retardation film A thermoplastic saturated norbornene resin (trade name “Zeonor # 1420” manufactured by Nippon Zeon Co., Ltd.) is used as a cycloolefin resin, and this is supplied to a single screw extruder and melted and kneaded. Melt extrusion was performed from a T die attached to the tip of a uniaxial extruder to obtain a long film having a width of 650 mm and an average thickness of 65 μm.
The film was continuously unwound at a constant unwinding speed of 2 m / min, preheated through a preheating zone at 130 ° C., and then stretched in the longitudinal direction by 1.4 times in a stretching zone at 135 ° C. Then, the film was passed through a cooling zone at 100 ° C. to fix the orientation, and then rolled up again to obtain a retardation film. It was 142 nm when the front phase difference of the obtained retardation film was measured using the automatic birefringence measuring apparatus (The Oji Scientific Instruments company make, brand name "KOBRA-21ADH").

(2) Normal pressure plasma treatment The obtained retardation film was continuously unwound at a constant unwinding speed of 3 m / min, and passed between electrodes (electrode width 700 mm × electrode length 40 mm) held at 2 mm by a spacer, It wound up with the winding roll, carrying out plasma processing. A glow discharge plasma was generated by applying a pulse voltage having a rise time of 5 μs, a pulse width of 100 μs, a frequency of 3 kHz, and a voltage of ± 5 kV to the electrode after converting alternating current into direct current with a DC power source. Further, a mixed gas (nitrogen: oxygen = 95: 5 (V / V)) was introduced as a processing gas between the electrodes.

(3) Preparation of liquid crystal composition (synthesis of polymerizable liquid crystal compound (4))
(First stage)
While stirring a solution of 3- (4-hydroxyphenyl) propionic acid (1150 g) in ethanol (1500 mL), sulfuric acid (230 g) was added dropwise over 10 minutes, and then refluxed for 5 hours. The reaction solution was concentrated, and the resulting concentrated solution was poured into water (1000 mL), and ethyl acetate was added and stirred. After liquid separation, the ethyl acetate layer was neutralized with a saturated sodium carbonate solution, washed with a small amount of water, and dried over anhydrous magnesium sulfate. From this ethyl acetate layer, ethyl acetate and unreacted components were distilled off to obtain 1400 g of a concentrate. The concentrate was purified by vacuum distillation to give 1144 g of ethyl 3- (4-hydroxyphenyl) propionate. The boiling point was 160 ° C./4.0 hPa.

(Second stage)
6-Chlorohexanol (800 g) was added to acetic anhydride (1200 mL) cooled to 10 ° C. with an ice bath, and then pyridine (934 g) was added dropwise over 10 minutes. After defeating the enemy, it was refluxed for 2 hours. The reaction solution was poured into water, and toluene was added thereto and stirred. The toluene layer was separated, neutralized with a saturated aqueous sodium carbonate solution, and washed with a small amount of water. Then, it dried with anhydrous magnesium sulfate. Toluene and unreacted components were distilled off from this toluene layer to obtain a concentrate. This concentrate was purified by distillation under reduced pressure to obtain 983 g of 6-acetoxychlorohexane. The boiling point was 82 ° C./5.3 hPa.

(3rd stage)
Ethyl 3- (4-hydroxyphenyl) propionate (400 g) was dissolved in dimethylformamide (2800 mL). Sodium hydroxide (98 g) was added thereto, and the mixture was stirred at 40 ° C. for 30 minutes. The formation of salt could be observed visually. 6-Acetoxychlorohexane (515 g) was added and the mixture was stirred at 80 ° C. for 7 hours. The reaction solution was poured into water (2000 mL), and toluene was added thereto and stirred. After separation, the toluene layer was washed with 6N hydrochloric acid, saturated sodium carbonate solution and water in this order, and dried over anhydrous magnesium sulfate. The solvent was distilled off from this toluene layer to obtain 709 g of a concentrate. Sodium hydroxide (185 g) was dissolved in water (400 mL), ethanol (600 mL) and concentrate 709 g were added thereto, heated and refluxed for 2 hours. The reaction solution was concentrated under reduced pressure using an evaporator, and the obtained concentrate was poured into 6N hydrochloric acid. The obtained slurry was filtered to obtain a solid, which was recrystallized with ethanol to obtain 281 g of (4- (6-hydroxyhexyloxy) phenyl) propionic acid. The melting point was 109-112 ° C.

(Fourth stage)
(4- (6-Hydroxyhexyloxy) phenyl) propionic acid (200 g), N, N-dimethylaniline (100 g) and BHT (0.3 g) were dissolved in dioxane (1000 mL). Acrylic acid chloride (74.3g) was dripped there over 10 minutes, and it stirred at 60 degreeC for 5 hours. The reaction solution was poured into water, ethyl acetate was added and stirred. The ethyl acetate layer was separated, washed with water, and dried over anhydrous magnesium sulfate. The solvent was distilled off from the ethyl acetate layer to obtain a solid. This solid was dissolved in toluene, poured into a large amount of heptane and reprecipitated to obtain 213 g of (4- (6-acryloyloxyhexyloxy) phenyl) propionic acid. The melting point was 64-68 ° C.

(5th stage)
(4- (6-acryloxyhexyloxy) phenyl) propionic acid (150 g), 2,3-bis (trifluoromethyl) hydroquinone (52.2 g), BHT (0.75 g), dimethylaminopyridine (15 g) Dissolved in methylene chloride (900 ml). To this solution, a solution of DCC (N, N′-dicyclohexylcarbodiimide) (100 g) in methylene chloride (300 mL) was added dropwise over 1 hour. After further stirring for 2 hours, water was added to separate the layers. The methylene chloride layer was washed with 6N hydrochloric acid and 10% aqueous sodium hydroxide and dried over anhydrous magnesium sulfate. The concentrate obtained from the methylene chloride layer was purified by silica gel column chromatography to obtain 125 g of a polymerizable liquid crystal compound (4) represented by the following formula (4).

(Synthesis of polymerizable liquid crystal compound (5))
(First stage)
A mixture of fluorene (78.3 g) and THF (700 mL) was cooled to −70 ° C., and n-BuLi (300 mL, corresponding to 0.47 mol) was added dropwise while maintaining the temperature at −60 ° C. or lower. Subsequently, methyl iodide (66.8 g) was added and the temperature was gradually returned to room temperature. The mixture was cooled again to 0 ° C., 3M hydrochloric acid (300 mL) was added, and the reaction mixture was extracted with toluene. The obtained organic layer was washed well with saturated sodium hydrogen carbonate, saturated sodium hydrogen sulfite and water successively, and dried over anhydrous magnesium sulfate. The solvent was removed from the organic layer under reduced pressure, and the residue was purified by column chromatography (silica gel, eluent: toluene / heptane [40/60]) and recrystallization (ethanol) to obtain 9- Methyl fluorene (57.4 g) was obtained. The melting point was 47.3-48.8 ° C.

(Second stage)
Anhydrous aluminum chloride (162.7 g) was added to a mixture of 9-methylfluorene (55 g) and methylene chloride (800 mL) while maintaining the temperature at 0 ° C. or lower to obtain a dark green reaction mixture. To this mixture, a solution of acetyl chloride (47.9 g) in methylene chloride (200 mL) was added dropwise while maintaining 0 ° C., and the mixture was gradually returned to room temperature and stirred for 12 hours. The reaction mixture was poured into a mixture of 6M hydrochloric acid and ice, and the organic layer was separated. This organic layer was thoroughly washed with saturated sodium hydrogen carbonate and water successively and dried over anhydrous magnesium sulfate. The solvent was removed from the organic layer under reduced pressure, and the resulting residue was purified by column chromatography (silica gel, eluent: heptane / ethyl acetate [7/3]) and recrystallization (ethanol) to give yellow crystals. Of 2,7-diacetyl-9-methylfluorene (30 g) was obtained. The melting point was 127.9-129.0 ° C.

(3rd stage)
To a mixture of 2,7-diacetyl-9-methylfluorene (30 g), methylene chloride (300 mL), acetic anhydride (35 g) and 34% aqueous hydrogen peroxide (34.6 g), 36 M-sulfuric acid (12 mL) was added at 3 ° C. It was dropped slowly while maintaining the following. The resulting mixture was stirred at 24 ° C. for 7 hours and poured into water. The separated organic layer was thoroughly washed with saturated sodium hydrogen carbonate, 10% sodium hydrogen sulfite and water successively and dried over anhydrous magnesium sulfate. The solvent was removed from the organic layer under reduced pressure, and the resulting residue was purified by column chromatography (silica gel, eluent: heptane / toluene [6/4]) and recrystallization (ethanol) to give colorless crystals. 2,7-Diacetyloxy-9-methylfluorene (12.4 g) was obtained. The melting point was 138.6-139.7 ° C.

(Fourth stage)
A mixture of 2,7-diacetyloxy-9-methylfluorene (12 g), lithium hydroxide monohydrate (3.42 g) and ethylene glycol (120 mL) was heated to reflux for 1 hour. The reaction mixture was poured into 6M-hydrochloric acid and extracted with ethyl acetate. The organic layer was sufficiently washed with water and dried over anhydrous magnesium sulfate. The solvent was removed from the organic layer under reduced pressure to obtain 2,7-dihydroxy-9-methylfluorene (7.24 g) as light brown crystals. The melting point was 191.5-196.3 ° C.

(5th stage)
2,7-dihydroxy-9-methylfluorene (0.5 g), 4- (6-acryloyloxyhexyloxy) benzoic acid (1.52 g), EDC (0.99 g), DMAP (5.76 mg) and methylene chloride (30 mL) of the mixture was stirred at room temperature for 12 hours. Water was added to the reaction mixture, and the separated organic layer was washed with water and then dried over anhydrous magnesium sulfate. The solvent was removed from the organic layer under reduced pressure, and the resulting residue was purified by column chromatography (silica gel, eluent: toluene / ethyl acetate [95/5]) and recrystallization (ethanol / ethyl acetate). Then, 0.19 g of a polymerizable liquid crystal compound (5) represented by the following formula (5) was obtained.

(Synthesis of polymerizable liquid crystal compound (6))
ω-Bromohexanoic acid (33.6 g) and thionyl chloride (20.5 g) were refluxed in benzene, and a fraction at 143-145 ° C. was collected by distillation under reduced pressure at 1 Torr to obtain 31.3 g of the corresponding acid chloride.
Subsequently, 5.6 g of LiAlH ₄ was added in 20 ° C. anhydrous ether for reduction to obtain 14.0 g of ω-bromoalcohol.
This was subjected to refluxing reaction in methanol with 18.1 g of 4-hydroxy-4'-cyanobiphenyl potassium salt obtained from 4-hydroxy-4'-cyanobiphenyl and KOH for 12 hours. After the reaction, extraction with water-chloroform, washing with water, and concentration through an Al ₂ O ₃ column, the residue was recrystallized with benzene to obtain 12.6 g of 4- (hydroxohexyloxy) -4′-cyanobiphenyl. It was.
This was reacted with 3.8 g of acrylic acid chloride in the presence of triethylamine in anhydrous benzene at room temperature. The reaction solution was washed with water and dried over MgSO ₄ , then benzene was distilled off and recrystallized from methanol. Next, the mixture was passed through a silica gel column with benzene as a solvent and recrystallized again with methanol to obtain 10.0 g of a polymerizable liquid crystal compound (6) represented by the following formula (6).

(Preparation of liquid crystal composition)
Polymerization initiator Irgacure 907 having a weight ratio of 0.03 with respect to 20% by weight of the polymerizable liquid crystal compound (4), 60% by weight of the polymerizable liquid crystal compound (5), and 20% by weight of the polymerizable liquid crystal compound (6). Specialty Chemicals Co., Ltd.) and a weight ratio of 0.10 compound (7) (Syra Ace S330 Chisso Co.) were added. To this composition, 70 parts by weight of toluene (aromatic solvent) and 30 parts by weight of cyclohexanone (ketone solvent) were added to prepare a liquid crystal composition.

(4) Production of laminated optical compensation film Liquid crystal composition at a flow rate of 9.1 g / min using a slit coater while continuously unwinding the retardation film treated with atmospheric pressure plasma at a constant unwinding speed of 2 m / min. The product was applied to the plasma treated surface and the solvent was removed in a drying oven maintained at 75 ° C.
Thereafter, the polymer was cured by ultraviolet rays from a halogen lamp through a heat ray cut filter to fix the alignment state, and wound up with a winder. Curing was performed with an integrated light amount of 500 mJ / cm ² and an oxygen concentration of 5%.

(Example 2)
A liquid crystal composition was prepared in the same manner as in Example 1 except that the solvent was 50 parts by weight of toluene (aromatic solvent) and 50 parts by weight of cyclohexanone (ketone solvent) to prepare a laminated optical compensation film.

(Example 3)
A liquid crystal composition was prepared in the same manner as in Example 1 except that the solvent was 70 parts by weight of toluene (aromatic solvent) and 30 parts by weight of ethyl lactate (ester solvent) to prepare a laminated optical compensation film. .

Example 4
A liquid crystal composition was prepared in the same manner as in Example 1 except that the solvent was 50 parts by weight of toluene (aromatic solvent) and 50 parts by weight of ethyl lactate (ester solvent) to prepare a laminated optical compensation film. .

(Comparative Example 1)
A liquid crystal composition was produced in the same manner as in Example 1 except that the solvent was 100 parts by weight of toluene (aromatic solvent), and a laminated optical compensation film was produced.

(Comparative Example 2)
A liquid crystal composition was produced in the same manner as in Example 1 except that the solvent was 100 parts by weight of cyclohexanone (ketone solvent), and a laminated optical compensation film was produced.

(Comparative Example 3)
A liquid crystal composition was produced in the same manner as in Example 1 except that the solvent was 100 parts by weight of ethyl lactate (ester solvent), and a laminated optical compensation film was produced.

<Evaluation>
The following evaluation was performed about the manufacturing process of the liquid crystal composition, laminated optical compensation film, and laminated optical compensation film obtained in Examples 1 to 4 and Comparative Examples 1 to 3. The results are shown in Table 1.

(Coating property evaluation)
The repelling condition of the liquid crystal composition with respect to the retardation film when the liquid crystal composition was coated on the retardation film was visually observed, and the coating property was evaluated according to the following criteria.
○: Uniform coating was possible without repelling.
X: It was difficult to coat due to repelling.

(Appearance evaluation)
The laminated optical compensation film after the formation of the liquid crystal layer is cut out to a length of 50 cm, and crater-like or island-like defects of 1 mm or more are counted by visual inspection. Items that can be confirmed were Δ, and those that could be confirmed were 10 ×.

(Front phase difference measurement)
The front phase difference was measured with a phase difference measuring device KOBRA-21ADH (manufactured by Oji Scientific Instruments).

Liquid crystal compositions and laminated optical compensation films (Examples 1 to 4) containing an aromatic solvent and a ketone solvent or an ester solvent as the solvent are compatible with suppression of coating property and retardation reduction. Moreover, it turns out that the external appearance is also excellent.
On the other hand, if only an aromatic solvent is used as the solvent (Comparative Example 1), a decrease in retardation cannot be suppressed, and if no aromatic solvent is contained as the solvent (Comparative Examples 2 to 3), repelling occurs. The coating property of the liquid crystal composition is poor.

According to the present invention, a liquid crystal composition that can be satisfactorily coated on a retardation film made of a cycloolefin-based resin and does not decrease the retardation of the retardation film even when coated, a liquid crystal A method for producing a laminated optical compensation film and a laminated optical compensation film used for improving the image quality of a display device can be provided.

Claims (8)

A liquid crystal composition comprising a liquid crystal compound, a photopolymerization initiator, and a mixed solvent of a ketone solvent and / or an ester solvent and an aromatic solvent. The liquid crystal composition according to claim 1, wherein the blending amount of the aromatic solvent in the mixed solvent is 10 to 85% by weight. 3. The liquid crystal composition according to claim 1, wherein the liquid crystal compound is at least one compound selected from the group consisting of the following formulas (1), (2) and (3).

In the above formula (1), W ¹ represents hydrogen or methyl, and l is an integer of 4-6.
In the above formula (2), W ² and W ³ represent hydrogen, chlorine or fluorine, W ⁴ and W ⁵ represent hydrogen, chlorine, methyl or trifluoromethyl, and X represents a single bond, an ethylene bond or an ethane bond. M is an integer of 4-6.
In said formula (3), n is an integer of 4-6. 3. A laminated optical compensation film, wherein a liquid crystal layer is formed by directly coating the liquid crystal composition according to claim 1 on a retardation film comprising a cycloolefin resin and drying the solvent. Method. A laminated optical compensation comprising: coating a liquid crystal composition according to claim 3 directly on a retardation film comprising a cycloolefin-based resin; drying the solvent; and then polymerizing and curing to form a liquid crystal layer. A method for producing a film. 5. The retardation film made of a cycloolefin-based resin is subjected to atmospheric pressure plasma treatment with an inert gas having an oxygen concentration of 15% by volume or less on the surface in contact with the liquid crystal layer. Or the manufacturing method of the laminated optical compensation film of 5. A laminated optical compensation film comprising a retardation film comprising a cycloolefin-based resin and a liquid crystal layer, wherein the laminated optical compensation film is produced by the method for producing a laminated optical compensation film according to claim 4, 5 or 6. Optical compensation film. 8. The laminated optical compensation film according to claim 7, wherein the liquid crystal layer is homeotropically aligned.