KR20210143226A - Laminated optical film and manufacturing method thereof, polarizing plate and image display device - Google Patents

Abstract

The laminated optical film 10 includes an alignment liquid crystal layer 3 in which a rod-shaped liquid crystal compound is homogeneously oriented on a film substrate 1 . The film substrate is a polymer film stretched in at least one direction. The film base material and the liquid crystal aligning layer are in contact with each other, and the slow axis direction of the film base material and the slow axis direction of the alignment liquid crystal layer are non-parallel. The rod-shaped liquid crystal compound can be homogeneously aligned in a direction not parallel to the stretching direction of the film substrate by the orientation regulating force of the film substrate.

Description

Laminated optical film and manufacturing method thereof, polarizing plate and image display device

The present invention relates to a laminated optical film having an alignment liquid crystal layer on a film substrate and a method for manufacturing the same. Moreover, this invention relates to the polarizing plate and image display apparatus which laminated|stacked the laminated optical film and the polarizer.

A liquid crystal display device has a polarizer disposed on both surfaces of a liquid crystal cell from the display principle thereof, and a retardation plate is disposed between the liquid crystal cell and the polarizer for the purpose of performing optical compensation such as contrast improvement and viewing angle expansion. For example, when a liquid crystal display device is visually recognized from the diagonal direction, since the apparent angle of the absorption axis direction of two polarizers shifts|deviates from 90 degrees, light leakage arises and it becomes a cause of a contrast fall. Therefore, the retardation plate is used for the purpose of compensating the shift|offset|difference in the absorption axis direction of the apparent absorption of two polarizers. In an organic EL display device, in order to suppress external light from being reflected from a metal electrode (cathode) and viewed like a mirror surface, a circularly polarizing plate (polarizing plate and a retardation film having 1/4 wavelength retardation) on the viewing side surface of the cell laminate) is placed.

As the retardation plate, a stretched film of a non-liquid crystalline polymer and an alignment liquid crystal layer in which a liquid crystal compound is oriented in a predetermined direction are used. The retardation plate used for a circular polarizing plate for compensation or anti-reflection for the apparent deviation of the absorption axis of the polarizer has a larger retardation as the wavelength is longer, and it is ideal that the ratio of the wavelength to the retardation is constant over the entire wavelength range of visible light. am. However, there are a limited number of materials that have a larger retardation at longer wavelengths (so-called 'reverse wavelength dispersion'), and most polymer and liquid crystal materials have a smaller retardation (normal dispersion) at longer wavelengths, or a retardation that is almost constant at any wavelength (lower wavelength dispersion). dispersion).

A method of adjusting the wavelength dispersion of retardation by laminating a plurality of retardation plates has been proposed. For example, Patent Document 1 proposes a method in which two retardation plates having different wavelength dispersions of retardation are laminated so that the slow axis direction is orthogonal to form a laminate retardation plate in which retardation exhibits reverse wavelength dispersion. Patent Document 2 discloses that wavelength dispersion can be adjusted by laminating two retardation plates at an angle in which the slow axis directions of both are neither parallel nor orthogonal.

Patent Document 3 discloses a laminated retardation plate comprising an oriented liquid crystal layer in which a liquid crystal compound is homogeneously oriented on a retardation plate including a polymer stretched film.

Japanese Laid-Open Patent Publication No. 5-27118 Japanese Patent Laid-Open No. 10-63816 WO2016/121856

In a roll-to-roll system, it is not easy to laminate|stack a some stretched film so that a slow-axis direction may become non-parallel. Therefore, it is difficult to say that the laminated retardation plate described in Patent Document 1 or Patent Document 2 has high productivity. Moreover, the laminated retardation plate which laminated|stacked the some stretched film through the adhesive etc. becomes large, and is not suitable for thickness reduction or weight reduction.

The alignment liquid crystal layer has a greater birefringence than a polymer stretched film. Moreover, as described in patent document 3, when the orientation regulating force of a stretched film is used, since an oriented liquid crystal can be laminated|stacked in contact with a stretched film, it is advantageous for thickness reduction and weight reduction. However, when the liquid crystal compound is oriented on the stretched film, the liquid crystal compound is generally oriented parallel to the orientation direction (stretching direction) of the polymer. It is necessary to provide an alignment film having an orientation regulating force in a direction non-parallel to the stretching direction. In this method, since it is necessary to perform rubbing in a direction non-parallel to the extending|stretching direction of a polymer film, application of a roll-to-roll method is difficult, and it is hard to say that productivity is high.

The laminated optical film of the present invention includes an aligned liquid crystal layer in which rod-shaped liquid crystal compounds are homogeneously aligned on a polymer film substrate stretched in at least one direction. An alignment film is not provided on the surface of the film substrate, and the film substrate and the alignment liquid crystal layer are in contact with each other. The slow axis direction of a film base material and the slow axis direction of an aligning liquid crystal layer are non-parallel. The angle between the slow axis direction of the film substrate and the slow axis direction of the aligning liquid crystal layer is, for example, 5° or more, and may be larger than 45°.

By using the orientation regulating force of the film substrate, the rod-shaped liquid crystal compound can be homogeneously aligned in a direction not parallel to the stretching direction of the film substrate. As a film substrate having such an orientation regulating force, a film including a polymer having an asymmetric carbon in the repeating unit of the main chain may be used.

The film base material may contain the ester type polymer. Examples of the ester-based polymer include polyester, polycarbonate, and polyarylate. The ester-type polymer may contain the cyclic diol which has asymmetric carbon as a diol component. As a cyclic diol containing asymmetric carbon, isosorbide, isomannide, isoidide, etc. are mentioned. In addition to the diol component which has an asymmetric carbon, the ester type polymer may contain the diol component which does not have asymmetric carbon. The diol component having no asymmetric carbon may be an alicyclic diol.

The rod-shaped liquid crystal compound is preferably a thermotropic liquid crystal. A liquid crystal polymer may be sufficient as the rod-shaped liquid crystal compound, and the polymer of a polymerizable liquid crystal compound may be sufficient as it. As for the polymer of a polymerizable liquid crystal compound, the monomer before superposition|polymerization should just show liquid crystallinity, and may not show liquid crystallinity after superposition|polymerization.

For example, a laminated optical film is obtained by apply|coating the liquid crystal composition containing a liquid crystal compound on a film base material, heating the liquid crystal composition on a film base material, and orientating a liquid crystal compound as a liquid crystal state. When the liquid crystal compound is a photopolymerizable liquid crystal monomer, it is preferable to heat the liquid crystal composition containing the photopolymerizable liquid crystal monomer on a film substrate to align the liquid crystal monomer, and then polymerize or crosslink the liquid crystal monomer by light irradiation.

In a laminated optical film, ratio Re(450)/Re(550) of front retardation Re(450) in wavelength 450nm and front retardation Re(550) in wavelength 550nm may be less than 1.00.

0.90-1.05 of ratio Re(450)/Re(550) of front retardation Re(450) in wavelength 450nm and front retardation Re(550) in wavelength 550nm may be sufficient as a film base material. In this case, it is preferable that Re(450)/Re(550) of an aligning liquid crystal layer is larger than Re(450)/Re(550) of a film base material.

A polarizing plate with a retardation plate can be formed by laminating|stacking the said laminated optical film with a polarizer. A laminated optical film and a polarizing plate provided with a laminated optical film can be used as an optical member for image display apparatuses.

A laminated optical film in which a stretched film substrate and an oriented liquid crystal layer, each of which can function independently as a retardation plate, are arranged non-parallel in the slow axis direction, can adjust the wavelength dispersion of retardation, It can be used as a laminated retardation plate for the purpose of reflection prevention etc.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the laminated optical film of one Embodiment.
It is sectional drawing of the polarizing plate of one Embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the laminated optical film which concerns on one Embodiment of this invention. The laminated optical film 10 is provided with the alignment liquid crystal layer 3 closely laminated in contact with the film substrate 1 .

[Liquid crystal compound and liquid crystal composition]

In the alignment liquid crystal layer, the rod-shaped liquid crystal compound is homogeneously aligned in a predetermined direction. An alignment liquid crystal layer is formed by applying a liquid crystal composition on a film substrate and heating the liquid crystal composition to orient the liquid crystal compound in a predetermined direction, and then fix the alignment state.

The rod-shaped liquid crystal compound may be a main chain liquid crystal or a side chain liquid crystal. A liquid crystal polymer may be sufficient as the rod-shaped liquid crystal compound, and the polymer of a polymerizable liquid crystal compound may be sufficient as it. As long as the liquid crystal compound (monomer) before superposition|polymerization shows liquid crystallinity, the thing which does not show liquid crystallinity after superposition|polymerization may be sufficient.

Examples of the polymerizable liquid crystal compound include a polymerizable liquid crystal compound in which the alignment state of the rod-shaped liquid crystal compound can be fixed by using a polymer binder, and a polymerizable liquid crystal compound having a polymerizable functional group in which the alignment state of the liquid crystal compound can be fixed by polymerization. and the like. Among these, the polymerizable liquid crystal compound which has a photopolymerizable functional group is preferable.

It is preferable that the liquid crystal compound is a thermotropic liquid crystal which expresses liquid crystal by heating. A thermotropic liquid crystal causes a phase transition of a crystalline phase, a liquid crystal phase, and an isotropic phase with temperature change. Examples of the rod-shaped liquid crystal compound exhibiting thermotropic properties include azomethines; Azoxis, cyanobiphenyls, cyanophenyl esters, benzoate esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxane and tolanes, alkenylcyclohexylbenzonitriles, and the like.

The photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesogenic group and at least one photopolymerizable functional group in one molecule. 40-200 degreeC is preferable, as for the temperature (liquid crystal phase transition temperature) at which a liquid crystal monomer shows liquid crystallinity, 50-150 degreeC is more preferable, 55-100 degreeC is still more preferable.

Examples of the mesogenic group of the liquid crystal monomer include a biphenyl group, phenylbenzoate group, phenylcyclohexane group, azoxybenzene group, azomethine group, azobenzene group, phenylpyrimidine group, diphenylacetylene group, diphenylbenzoate group, and bicyclohexane. Cyclic structures, such as group, a cyclohexylbenzene group, and a terphenyl group, are mentioned. The terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, and a halogen group.

As a photopolymerizable functional group, a (meth)acryloyl group, an epoxy group, a vinyl ether group, etc. are mentioned. Especially, a (meth)acryloyl group is preferable. It is preferable that a photopolymerizable liquid crystal monomer has two or more photopolymerizable functional groups in 1 molecule. By using the liquid crystal monomer containing two or more photopolymerizable functional groups, since a crosslinked structure is introduce|transduced into the liquid crystal layer after photocuring, there exists a tendency for durability of an alignment liquid crystal layer to improve.

As an example of the photopolymerizable thermotropic liquid crystal monomer which has a mesogenic group and a some (meth)acryloyl group in 1 molecule, the compound represented by the following general formula (I) is mentioned.

In formula (I), R is a hydrogen atom or a methyl group, A and D are each independently a 1,4-phenylene group or a 1,4-cyclohexylene group, and B is a 1,4-phenylene group, 1,4- a cyclohexylene group, a 4,4'-biphenylene group, or a 4,4'-bicyclohexylene group, and Y and Z are each independently -COO-, -OCO- or -O-. g and h are each independently an integer of 2-6.

As a commercial item of the photopolymerizable liquid crystal monomer represented by the said General formula (I), "Paliocolor LC242" by BASF can be illustrated.

The liquid crystal composition may contain the photoinitiator. In the case of curing the liquid crystal monomer by irradiation with ultraviolet rays, in order to promote photocuring, the liquid crystal composition preferably contains a photopolymerization initiator (photoradical generator) that generates radicals by irradiation with light. Depending on the kind of the liquid crystal monomer (the kind of the photopolymerizable functional group), a photocation generator or a photoanion generator may be used. The usage-amount of a photoinitiator is about 0.01-10 weight part with respect to 100 weight part of liquid crystal monomers. You may use a sensitizer etc. other than a photoinitiator.

A liquid crystal composition can be prepared by mixing a liquid crystal monomer, a polymerization initiator, etc. with a solvent. The solvent is not particularly limited as long as it is capable of dissolving the liquid crystal monomer and does not corrode (or has low erosion property) the film substrate, and includes chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, halogenated hydrocarbons such as chlorobenzene and orthodichlorobenzene; phenols such as phenol and parachlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene and 1,2-dimethoxybenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, and N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; ether solvents such as diethyl ether, dibutyl ether and tetrahydrofuran; Ethyl cellosolve, butyl cellosolve, etc. are mentioned. A mixed solvent of two or more solvents may be used.

The solid content concentration of the liquid crystal composition is usually about 5 to 60% by weight. The liquid crystal composition may contain additives, such as surfactant and a leveling agent.

[Film base]

By using the film substrate as a support for applying the liquid crystal composition, a series of steps from application of the liquid crystal composition to curing by photopolymerization of the liquid crystal monomer can be performed by roll-to-roll, thereby improving the productivity of the laminated optical film can do.

The film base material 1 is a stretched film. By stretching the polymer film, the molecular chains of the polymer constituting the film are preferentially oriented in the stretching direction, and the liquid crystal compound of the alignment liquid crystal layer 3 provided on the film substrate 1 is homogeneously aligned in a predetermined direction. Orientation regulating force works.

The draw ratio of a stretched film should just be a grade which can exhibit an orientation regulating force, for example, it is about 1.05 times - about 5 times. The stretched film may be a biaxially stretched film. Even if it is a biaxially stretched film, if a film with a different draw ratio in a longitudinal direction and a transverse direction is used, the effect|action which orientates a liquid crystal compound in a predetermined direction can be given.

As for the front retardation of the stretched film used as the film base material 1, 10 nm or more is preferable. When the film substrate is a stretched film having a front retardation of 10 nm or more, since the polymer constituting the film is preferentially oriented in a predetermined direction, an orientation regulating force for homogeneously aligning the liquid crystal compound in a predetermined direction is likely to act.

When using the laminate of the film base material 1 and the aligning liquid crystal layer 3 as a laminated retardation plate, it is good to set the front retardation etc. of the film base material 1 according to the optical design of the laminated retardation plate. Front retardation Re(550) in wavelength 550nm of the film base material 1 is 10-1000 nm, for example.

Although the thickness of the film base material 1 is not specifically limited, When handling properties etc. are considered, about 10-300 micrometers is preferable. From the viewpoint of applying an orientation regulating force to the liquid crystal compound, the in-plane birefringence Δn (the value obtained by dividing the front retardation by the thickness) of the film substrate 1 ^{is preferably 1×10 -5} or more, and more preferably 3×10 ^-5 or more. Preferably, 5×10 ^-5 or more is more preferable. The in-plane birefringence Δn of the film substrate 1 may be 1×10 ^-4 or more, 3×10 ^-4 or more, or 5×10 ^-4 or more.

As the polymer material constituting the film substrate, one that does not dissolve in the solvent of the liquid crystal composition and has heat resistance upon heating for orienting the liquid crystal compound is used. Examples of the polymer include ester-based polymers having an ester bond in the main chain, such as polyester, polyarylate, and polycarbonate; Polyolefin, cyclic polyolefin, a cellulose polymer, an acrylic polymer, a styrenic polymer, etc. are mentioned.

It is preferable that a film base material has the orientation regulating force which makes a liquid crystal compound homogeneously orientate non-parallel to the extending|stretching direction of a film (orientation direction of a polymer). When a liquid crystal composition is apply|coated on the film base material which has such an orientation regulating force, and when it is made into a liquid crystal phase by heating, the liquid crystal compound is homogeneously oriented in a predetermined direction by the orientation regulating force of the film base material.

A general polymer stretched film has an orientation regulating force for homogeneously aligning a liquid crystal compound in a direction parallel to the stretching direction (the orientation direction of the polymer). When the rod-shaped liquid crystal compound is orientated on such a stretched polymer film, a laminated film is formed in which the stretching direction of the polymer film and the orientation direction of the liquid crystal compound are parallel to each other.

On the other hand, by using a film substrate having an action of aligning the rod-shaped liquid crystal compound non-parallel to the orientation direction of the polymer, the alignment direction of the polymer in the film substrate 1 and the liquid crystal compound in the alignment liquid crystal layer 3 are used. The orientation direction becomes non-parallel. Therefore, the laminated optical film in which the slow axis direction of the film base material 1 and the slow axis direction of the oriented liquid crystal layer 3 were non-parallel is obtained.

As a polymer having an orientation regulating force for aligning the liquid crystal compound non-parallel to the stretching direction, the repeating unit of the main chain is Polymers having an asymmetric carbon are mentioned. A polymer having an asymmetric carbon in the repeating unit of the main chain is obtained by using a compound having an asymmetric carbon as a monomer component. When the polymer constituting the film substrate contains a repeating unit having an asymmetric carbon in the main chain, and the polymer is oriented in a predetermined direction, when the liquid crystalline compound is oriented thereon as a liquid crystal phase, it contains an asymmetric carbon (chiral center) It is thought that the effect|action which orientates a liquid crystalline compound in the direction different from the orientation direction of a polymer molecule arises by the interaction of the structural unit and the liquid crystal compound to be used.

Although the kind of polymer is not specifically limited, From the point of being easy to control the orientation regulating force with respect to a liquid crystal compound, an ester type polymer is preferable. The ester-based polymer is a polymer having an ester bond in the main chain, and is obtained by condensation, polyaddition or transesterification of a dihydroxy compound (diol) with a compound containing carbonyl. Examples of the ester-based polymer include polyester, polycarbonate, and polyarylate. Among them, polycarbonate (carbonic acid ester) is preferable because the ratio of the structure derived from the diol component in the main chain is high.

Examples of the diol component of the ester polymer include alicyclic diols, diols having a cyclic ether structure, aliphatic diols, oxyalkylene glycols, aromatic diols, and the like. By using a diol having an asymmetric carbon, a polymer including a repeating unit having an asymmetric carbon is obtained. Examples of the diol having asymmetric carbon include cyclic diol. It is preferable that at least one of the carbon atoms constituting the ring is an asymmetric carbon, and, as for the cyclic diol, it is preferable that it is a non-aromatic cyclic diol.

The ring structure of the cyclic diol may be an alicyclic structure having only carbon or a non-aromatic heterocyclic ring containing heteroatoms such as oxygen, nitrogen and sulfur. As a heterocyclic ring, cyclic ether is mentioned, for example. The ring structure of cyclic diol may be monocyclic or polycyclic may be sufficient as it.

In the cyclic diol, a hydroxyl group may be directly bonded to a carbon atom constituting the ring, or a hydroxyl group may be bonded to a carbon atom constituting the ring through an alkylene group such as methylene or propylene. Examples of the cyclic diol having an asymmetric carbon include isosorbide and its optical isomers, isomannide and isoidide.

In addition to the diol containing an asymmetric carbon as a diol component, the ester polymer may contain the diol which does not contain an asymmetric carbon.

Examples of the alicyclic diol include cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, decalindimethanol, 2,3-novonanedimethanol, adamantanedimethanol, cyclohexanediol, decalindiol, norbornanediol; Adamantanediol etc. are mentioned.

Examples of the aliphatic diol include ethylene glycol, propanediol, butanediol, heptanediol, and hexanediol. Examples of the oxyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol. Examples of the aromatic diol include bisphenols represented by 2,2-bis(4-hydroxyphenyl)propane (=bisphenol A).

It is preferable that ester-type polymers, such as a polycarbonate, contain an alicyclic diol in addition to the diol containing an asymmetric carbon as a diol component. When the ester-based polymer contains an alicyclic structure in its main chain, the heat resistance of the polymer tends to improve. Further, when the ester-based polymer contains an alicyclic structure in the main chain, retardation of the stretched film tends to exhibit flat wavelength dispersion. Among the alicyclic diols mentioned above, cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol, and pentacyclopentadecanedimethanol are preferable, and among these, 1,4-cyclohexanedimethanol and 1,3-cyclohexane Dimethanol, 1,2-cyclohexanedimethanol and tricyclodecanedimethanol are preferred.

Among 100 mol% of the total amount of the diol component of the ester polymer, the amount of the diol containing an asymmetric carbon is preferably 30 mol% or more, more preferably 40 mol% or more, and still more preferably 50 mol% or more. The proportion of the diol containing asymmetric carbon may be 55 mol% or more or 60 mol% or more. When the amount of the diol containing the asymmetric carbon is within the above range, the orientation regulating force for the liquid crystal compound on the film substrate tends to increase. The amount of one or more diols selected from the group consisting of isosorbide, isomannide and isoidide may be within the above range, and the amount of isosorbide may be within the above range.

The proportion of the diol containing asymmetric carbon may be 95 mol% or less, 90 mol% or less, 85 mol% or less, or 80 mol% or less. The ester polymer may contain 5 mol% or more, 10 mol% or more, or 20 mol% or more of an alicyclic diol as a diol component.

The film base material may contain several types of ester type polymer. Moreover, you may contain polymers other than an ester type polymer. The content of the ester polymer having an asymmetric carbon in the repeating unit of the main chain is preferably 50 parts by weight or more, more preferably 60 parts by weight or more, and 70 parts by weight with respect to 100 parts by weight of the total resin material constituting the film substrate. The above is more preferable. The content of the ester polymer having an asymmetric carbon in the repeating unit of the main chain may be 80 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, or 100 parts by weight.

[Formation of alignment liquid crystal layer on film substrate]

A liquid crystal composition is applied on the film substrate 1 and the liquid crystal compound is orientated in a liquid crystal state by heating to form a laminated optical film in which the film substrate 1 and the alignment liquid crystal layer 3 are closely laminated. The method of applying the liquid crystal composition on the film substrate is not particularly limited, and spin coat, die coat, kiss roll coat, gravure coat, reverse coat, spray coat, wire bar coat, knife roll coat, air knife coat, etc. can be employed. have. A liquid crystal composition layer is formed on a film base material by removing a solvent after apply|coating a solution. It is preferable to adjust application|coating thickness so that the thickness of the liquid-crystal composition layer (thickness of an orientation liquid-crystal layer) after drying a solvent may be set to about 0.1-20 micrometers.

By heating the liquid-crystal composition layer formed on the film base material and setting it as a liquid-crystal phase, a liquid-crystal compound orientates. Specifically, after the liquid crystal composition is applied on the film substrate, the liquid crystal composition is heated above the N (nematic phase)-I (isotropic liquid phase) transition temperature (hereinafter abbreviated as NI transition temperature) of the liquid crystal composition to convert the liquid crystal composition to an isotropic liquid state. do. There, if necessary, it cools gradually, and a nematic phase is expressed. At this time, it is preferable to temporarily maintain the temperature at which the liquid crystal phase is exhibited, and to grow the liquid crystal phase domain to form a mono domain. Alternatively, after the liquid crystal composition is applied on the film substrate, the temperature may be maintained within the temperature range in which the nematic phase is expressed for a certain period of time to align the liquid crystal compound. As described above, by using the film substrate containing a predetermined polymer, the liquid crystal compound can be homogeneously aligned in a direction different from the stretching direction of the film substrate.

What is necessary is just to select suitably the heating temperature at the time of orientating a liquid crystal compound according to the kind of liquid crystal composition, and it is about 40-200 degreeC normally. When the heating temperature is excessively low, the transition to the liquid crystal phase tends to be insufficient, and when the heating temperature is excessively high, there are cases in which alignment defects increase. The heating time may be adjusted so that the liquid crystal domains grow sufficiently, and is usually about 30 seconds to 30 minutes.

After orientating a liquid crystal compound by heating, it is preferable to cool to the temperature below a glass transition temperature. The cooling method is not specifically limited, For example, what is necessary is just to take out from a heating atmosphere to room temperature. Forced cooling such as air cooling or water cooling may be performed.

By irradiating the liquid crystal layer with light, photocuring is performed in a state where the photopolymerizable liquid crystal compound (liquid crystal monomer) has liquid crystal regularity. The irradiated light may polymerize the photopolymerizable liquid crystal compound, and usually, ultraviolet light or visible light having a wavelength of 250 to 450 nm is used. When a liquid crystal composition contains a photoinitiator, what is necessary is just to select the light of the wavelength in which a photoinitiator has a sensitivity. As an irradiation light source, a low pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, LED, a black light, a chemical lamp, etc. are used. In order to promote the photocuring reaction, light irradiation is preferably performed in an atmosphere of an inert gas such as nitrogen gas.

What is necessary is just to adjust irradiation intensity|strength suitably according to the composition of a liquid crystal composition, the addition amount of a photoinitiator, etc. The irradiation energy (integrated irradiation light amount) is usually from 20 to a 10000mJ / cm ² degree, 50 ~ 5000mJ / cm ² are preferred, and more preferably 100 ~ 800mJ / cm ^2. In order to accelerate the photocuring reaction, light irradiation may be performed under heating conditions.

The polymer after photocuring the liquid crystal monomer is non-liquid crystalline, and transition of the liquid crystal phase, glass phase, and crystal phase does not occur due to temperature change. Therefore, in the liquid crystal layer photocured in a state in which the liquid crystal monomer is oriented in a predetermined direction, a change in molecular orientation due to temperature change is unlikely to occur. In addition, since the aligning liquid crystal layer has remarkably large birefringence as compared with a film containing a non-liquid crystal material, the thickness of the optically anisotropic element having a desired retardation can be remarkably reduced. What is necessary is just to set according to the retardation value etc. made into the objective, and, as for the thickness of an aligning liquid crystal layer, it is about 0.1-20 micrometers normally, 0.2-10 micrometers is preferable and 0.5-7 micrometers is more preferable.

Application of the liquid crystal composition on the film substrate, orientation of the liquid crystal compound by heating, and photocuring may be performed by a roll-to-roll system while conveying the elongate film substrate in the longitudinal direction. A long laminated optical film is obtained by forming an oriented liquid crystal layer on a film base material by a roll-to-roll system. A long laminated optical film may be wound up in roll shape, and it is good also as a wound body. 300 mm or more, 500 mm or more, 800 mm or more, or 1000 mm or more may be sufficient as the width|variety of a long laminated optical film. 10 m or more, 50 m or more, 100 m or more, 300 m or more, or 500 m or more may be sufficient as the length of a long laminated optical film.

As described above, in the laminated optical film of the present invention, the liquid crystal aligning layer 3 is in contact with the stretched film substrate 1, and the liquid crystal compound of the oriented liquid crystal layer 3 is caused by the orientation regulating force of the stretched film substrate 1 . It is oriented in the in-plane direction of the film base material 1 (homogeneous orientation). The extending direction of the film base material 1 and the orientation direction of the liquid crystal compound in the aligning liquid crystal layer 3 are non-parallel. Therefore, the slow axis direction of the film base material 1 and the slow axis direction of the aligning liquid crystal layer 3 are non-parallel.

The angle between the slow axis direction of the film base material 1 and the slow axis direction of the aligning liquid crystal layer 3 is, for example, 5 to 90°. The slow axis direction (θ) of the alignment liquid crystal layer 3 when the slow axis direction of the film substrate 1 is taken as a reference (0°) is 5° or more, 10° or more, 15° or more, 20° or more, 30 ° or more, or 40 degrees or more may be sufficient. θ may be 45°, may be larger than 45°, and may be 50° or more, 60° or more, or 70° or more. 90 degrees may be sufficient as (theta), and 85 degrees or less may be sufficient as it.

The film base material 1 is a stretched film, and can function as a retardation plate even independently. In the alignment liquid crystal layer 3, since the liquid crystal molecules are homogeneously aligned, it can function as a retardation plate as a single layer. When the slow axis direction of the film base material 1 and the slow axis direction of the aligning liquid crystal layer 3 are non-parallel, retardation of a laminated retardation plate is adjustable.

For example, when the front retardation of the film substrate 1 is greater than the front retardation of the liquid crystal alignment layer 3 and the slow axis direction of the film substrate 1 and the slow axis direction of the liquid crystal alignment layer 3 are perpendicular to each other, The front retardation of the laminated retardation plate becomes a value obtained by subtracting the front retardation of the alignment liquid crystal layer 3 from the front retardation of the film substrate 1 . By using such a characteristic, it is possible to adjust the wavelength dispersion of retardation of a laminated retardation plate. The wavelength dispersion of the front retardation of the retardation plate can be evaluated as a ratio Re(450)/Re(550) of the front retardation Re(450) at a wavelength of 450 nm to the front retardation Re(550) at a wavelength of 550 nm.

The front retardation of the film substrate 1 is larger than the front retardation of the alignment liquid crystal layer 3, and Re(450)/Re(550) of the film substrate 1 is Re(450) of the alignment liquid crystal layer 3 When smaller than /Re(550), it is possible to make Re(450)/Re(550) of a laminated optical film smaller than Re(450)/Re(550) in the case of the film base material 1 single-piece|unit. The slow axis direction of the film substrate 1 and the slow axis direction of the alignment liquid crystal layer 3 are not necessarily orthogonal, and when the angle θ is greater than 45°, It is possible to adjust the wavelength dispersion. When the wavelength dispersion of the laminated retardation plate is adjusted by subtraction, the angle θ between the slow axis direction of the film substrate 1 and the slow axis direction of the alignment liquid crystal layer 3 is preferably 50° or more, and 60° or more. More preferably, 70 degrees or more are still more preferable.

By using the 'subtraction' of the front retardation as described above, it is also possible to obtain a laminated retardation plate having Re(450)/Re(550) smaller than 1 and larger retardation as the wavelength is longer. Re(450)/Re(550) of the laminated retarder may be 0.75 to 0.99. Re(450)/Re(550) of the laminated retarder may be 0.95 or less, 0.92 or less, or 0.90 or less. Re(450)/Re(550) may be 0.80 or more. Re(450)/Re(550) of the retardation plate in which the retardation exhibits the ideal reverse wavelength dispersion is 0.82.

The wavelength dispersion of the single-piece retardation of the film substrate 1 is small (for example, Re(450)/Re(550) is 0.90 to 1.05), and Re(450)/Re(550) of the alignment liquid crystal layer is the film substrate In the case of being larger than Re(450)/Re(550) of Re(450)/Re(550), a laminated retarder having a small Re(450)/Re(550) is obtained.

Re(450)/Re(550) of the film base material 1 may be 0.95-1.03. As Re(450)/Re(550) of the alignment liquid crystal layer 3 is larger, the effect of adjusting wavelength dispersion by subtraction of front retardation becomes larger. Re(450)/Re(550) of the alignment liquid crystal layer 3 may be 1.05 or more, 1.08 or more, or 1.10 or more.

The front retardation of the laminated optical film may be appropriately set according to the purpose of use, and is, for example, about 10 to 500 nm. When the laminated optical film and the polarizer are laminated to form a circularly polarizing plate, Re (550) of the laminated optical film is preferably 90 to 180 nm, more preferably 110 to 160 nm, and still more preferably 120 to 150 nm.

[Application of alignment liquid crystal layer and laminated optical film]

The laminated optical film 10 in which the alignment liquid crystal layer 3 was provided in contact with the film base material 1 can be used as a laminated retardation plate as it is.

From the film base material 1 of the laminated optical film 10, the alignment liquid crystal layer 3 may be peeled and it may be transcribe|transferred to another base material. When peeling the oriented liquid crystal layer 3 from the elongate laminated optical film 10 and transcribe|transferring to another base material, you may carry out by a roll-to-roll system. Since the alignment liquid crystal layer 3 has a slow axis in a direction non-parallel to the longitudinal direction of the film base material, even when laminated with other base materials, it is applicable to adjustment of retardation wavelength dispersion, etc. Moreover, a circularly polarizing plate or an elliptically polarizing plate can also be formed by laminating|stacking an alignment liquid-crystal layer with a polarizer.

A polarizing plate may be formed by laminating|stacking a polarizer on one main surface or both main surfaces of a laminated optical film. 2 : is sectional drawing of the polarizing plate which laminated|stacked the polarizer on one main surface of the laminated optical film 10. As shown in FIG. In the polarizing plate 50 , a laminated optical film 10 is laminated on one main surface of the polarizer 20 with an adhesive layer 41 interposed therebetween. In FIG. 2 , the surface of the laminated optical film 10 on the side of the film substrate 1 is bonded to the polarizer 20 , but the surface on the side of the alignment liquid crystal layer 3 may be bonded to the polarizer 20 . In addition, another film may be laminated|stacked between the laminated optical film 10 and the polarizer 20.

A transparent film 30 as a polarizer protective film is bonded to the other main surface of the polarizer 20 via an adhesive layer 42 . In addition, as for the polarizing plate of this invention, the laminated|multilayer optical film 10 should just be laminated|stacked on one main surface of the polarizer 20, and you may abbreviate|omit the transparent film 30. Optical films other than a laminated optical film and a polarizer protective film may be laminated|stacked on the polarizing plate. As a specific example of an optical film, functional films, such as retardation film, a viewing angle expansion film, a viewing angle restriction|limiting (peep prevention) film, and a brightness|luminance improvement film, are mentioned. The adhesive layer and adhesive layer for bonding with an image display cell etc. may be laminated|stacked on a polarizing plate.

The laminated optical film and polarizing plate provided with an oriented liquid crystal layer can be used as an optical film for image display devices. For example, an image display apparatus is formed by arrange|positioning a polarizing plate provided with a laminated optical film or a laminated optical film on the surface of an image display cell.

In a liquid crystal display device, a retardation plate as an optical compensation film is disposed between an image display cell (liquid crystal cell) and a polarizer for the purpose of appropriately converting the polarization state of light emitted from the liquid crystal cell toward the viewer and improving the viewing angle characteristic. there may be cases In an organic EL display device, in order to suppress external light from being reflected by a metal electrode layer and visually recognized like a mirror surface, a quarter-wave plate may be disposed between a cell and a polarizing plate. Moreover, by arranging the quarter wave plate on the visual recognition side of the polarizing plate and making the emitted light circularly polarized light, an appropriate image display can be made visible even to a viewer wearing polarized sunglasses.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following examples.

[Example 1]

<Preparation of stretched film base material>

As a diol component, using a polycarbonate resin pellet containing isosorbide and 1,4-cyclohexanedimethanol in a molar ratio of 70:30, an unstretched film having a thickness of 100 μm was produced by melt extrusion. . Using a tenter stretching machine, it extended|stretched 1.6 times in the width direction at the extending|stretching temperature of 131 degreeC, and obtained the extending|stretching polycarbonate film A with which the width direction and the slow-axis direction correspond. The front retardation of this film at a wavelength of 590 nm was 360 nm.

<Preparation of orientation composition>

100 parts by weight of a photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase ('Paliocolor LC242' manufactured by BASF), 0.5 parts by weight of a surfactant ('BYK-361' manufactured by Bic Chemie), a photopolymerization initiator ('Irgacure 907' manufactured by BASF) ) 3 parts by weight and 200 parts by weight of toluene were mixed to prepare a liquid crystal composition solution A.

<Formation of alignment liquid crystal layer>

The liquid crystal composition A was apply|coated to said stretched polycarbonate film A with a bar coater, and after heating at 110 degreeC for 150 second, it cooled to room temperature. Then, ultraviolet-ray was irradiated in nitrogen atmosphere, photopolymerization was performed, and the oriented liquid crystal layer with a film thickness of 2.7 micrometers was formed.

[Example 2]

<Preparation of stretched film base material>

As a diol component, a polycarbonate resin pellet containing isosorbide and tricyclodecanedimethanol in a molar ratio of 70:30 was used to prepare an unstretched film having a thickness of 100 µm by melt extrusion. Using a roll stretching machine, free-end uniaxial stretching was performed at a length of 2.1 times in the longitudinal direction at a stretching temperature of 133° C., and the stretched polycarbonate film B in which the longitudinal direction and the slow axis direction coincide was obtained. The front retardation of this film at a wavelength of 590 nm was 360 nm.

<Formation of alignment liquid crystal layer>

Instead of the stretched polycarbonate film A, the above stretched polycarbonate film B was used. Other than that, it carried out similarly to Example 1, and formed the alignment liquid crystal layer on the stretched film base material.

[Comparative Example 1]

<Preparation of stretched film base material>

Using a linear motor-type tenter stretching machine capable of arbitrarily setting the moving speed of the clip, a norbornene-based resin film with a thickness of 80 μm (“Zeonoa Film” manufactured by Zeon Japan) was prepared so that the slow axis direction was 45° with respect to the conveying direction. It diagonally stretched, and the stretched norbornene film was obtained. The front retardation of this film at a wavelength of 590 nm was 69 nm.

<Preparation of alignment composition and formation of alignment liquid crystal layer>

Except having changed the solvent from toluene to methyl ethyl ketone, it carried out similarly to Example 1, and prepared the liquid-crystal composition solution B. On said stretched norbornene film, the liquid crystal composition B was apply|coated, and heating, cooling, and photopolymerization were performed similarly to Example 1, and the alignment liquid crystal layer was formed.

[evaluation]

For the measurement of the retardation and the slow axis direction, a polarization/retardation measurement system (manufactured by Axometrics, product name 'AxoScan') was used, and measurement was performed in an environment of 23°C. The retardation value is a measured value with a wavelength of 550 nm unless otherwise specified. For the measurement of the alignment liquid crystal layer (single body), the alignment liquid crystal layer was transcribed on the pressure-sensitive adhesive laying surface of the glass plate in which the pressure-sensitive adhesive was provided on the surface, and what peeled and removed the film base material was used as a retardation measurement sample.

<Orientation of liquid crystal layer>

The slow axis direction of the alignment liquid crystal layers of Examples 1 and 2 was 80° with respect to the slow axis direction of the film substrate. The sample was rotated in the range of -70° to +70° centered on the slow axis direction, and retardation per 10° was measured. The retardation was largely symmetrical. From these results, in Examples 1 and 2, it was confirmed that the alignment liquid crystal layer on the stretched film substrate was homogeneously oriented in the direction of 80° with respect to the slow axis of the film substrate.

The slow axis direction of the alignment liquid crystal layer of Comparative Example 1 was parallel to the slow axis direction of the film substrate (diagonally stretched film). Similarly to the above, when the sample was rotated in the range of -70° to +70° with respect to the slow axis direction and the retardation was measured, the positive and negative retardations were substantially symmetrical, so the film It was confirmed that the liquid crystal compound was homogeneously oriented in a direction parallel to the slow axis of the substrate.

<Wavelength dispersion of front retardation>

The front retardation Re (450) at a wavelength of 450 nm of the laminated retardation film of Example 1 is 118 nm, the front retardation Re (550) at a wavelength of 550 nm is 132 nm, Re (450) / Re (550) is 0.89, the reverse Wavelength dispersion characteristics were shown. Re (450) of the single-piece|unit of the stretched film base material (polycarbonate film A) of Example 1 is 372 nm, Re (550) is 362 nm, Re (450)/Re (550) is 1.02, and the slow axis direction on the stretched film base material It turns out that Re(450)/Re(550) became small by this 80 degree|times inclination and the oriented liquid crystal layer which is homogeneously oriented was formed. Similarly to Example 1, the laminated retardation film of Example 2 has a Re(450)/Re(550) of 0.89, and the slow axis direction is inclined by 80° on the stretched film base material (polycarbonate film B), and the orientation is homogeneous. Due to the formation of the liquid crystal layer, Re(450)/Re(550) became small.

1 Film substrate
3 alignment liquid crystal layer
10 laminated optical film
20 polarizer
30 transparent film
41, 42 adhesive layer
50 Polarizer

Claims (14)

A laminated optical film comprising an oriented liquid crystal layer in which a rod-shaped liquid crystal compound is homogeneously oriented on a film substrate, the laminated optical film comprising:
The film substrate is a polymer film stretched in at least one direction,
The film substrate and the alignment liquid crystal layer are in contact,
The laminated optical film in which the slow axis direction of the said film base material and the slow axis direction of the said aligning liquid crystal layer are non-parallel. According to claim 1,
The laminated optical film, wherein the film substrate comprises a polymer having an asymmetric carbon in the repeating unit of the main chain. 3. The method of claim 2,
The film substrate comprises an ester-based polymer having an ester bond,
The laminated optical film which contains the cyclic diol which has asymmetric carbon as a diol component of the said ester. 4. The method of claim 3,
The laminated optical film in which the cyclic diol containing the said asymmetric carbon contains 1 or more types selected from the group which consists of isosorbide, isomannide, and isoidide. 5. The method of claim 3 or 4,
The laminated optical film which further contains an alicyclic diol as a diol component of the said ester. 6. The method according to any one of claims 3 to 5,
The laminated optical film, wherein the ester-based polymer is polycarbonate. 7. The method according to any one of claims 1 to 6,
The laminated optical film, wherein the rod-shaped liquid crystal compound is a polymer of a photopolymerizable thermotropic liquid crystal compound. 8. The method according to any one of claims 1 to 7,
The laminated optical film whose ratio Re(450)/Re(550) of front retardation Re(450) in wavelength 450nm and front retardation Re(550) in wavelength 550nm is 0.75-0.99. 9. The method according to any one of claims 1 to 8,
Front retardation Re (550) at a wavelength of 550 nm of the film substrate is larger than front retardation Re (550) at a wavelength of 550 nm of the aligned liquid crystal layer,
The film substrate has a ratio Re (450)/Re (550) of front retardation Re (450) at a wavelength of 450 nm and front retardation Re (550) at a wavelength of 550 nm of 0.90 to 1.05,
The laminated optical film whose Re(450)/Re(550) of the said alignment liquid crystal layer is larger than Re(450)/Re(550) of the said film base material. 10. The method according to any one of claims 1 to 9,
The angle between the slow axis direction of the film substrate and the slow axis direction of the alignment liquid crystal layer is greater than 45°. The polarizing plate which laminated|stacked the laminated optical film in any one of Claims 1-10, and a polarizer. The image display apparatus which equips the surface of an image display cell with the laminated optical film in any one of Claims 1-10. As a manufacturing method of the laminated optical film in any one of Claims 1-10,
A liquid crystal composition containing a liquid crystal compound is applied on a film substrate,
The manufacturing method of the laminated optical film which heats the liquid-crystal composition on the said film base material, and orientates a liquid-crystal compound as a liquid-crystal state. 14. The method of claim 13,
The liquid crystal compound is a photopolymerizable liquid crystal monomer,
After aligning the photopolymerizable liquid crystal monomer on the film substrate, polymerization or crosslinking of the liquid crystal monomer by light irradiation, a method for producing a laminated optical film.

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