KR100970355B1 - Process for preparing retarders - Google Patents

Abstract

A new process for producing a rolled retarder comprising a transparent substrate and two or more optically anisotropic layers each formed on or on a surface of the transparent substrate with a composition comprising a liquid crystal compound.

Comprising the steps of: preparing a plurality of optically anisotropic layers while keeping the long substrate unrolled; and rolling the substrate after forming all the optically anisotropic layers on the long substrate.

A transparent substrate, an optically anisotropic layer, a liquid crystal compound,

Description

PROCESS FOR PREPARING RETARDERS [0002]

Technical field

The present invention relates to a process for producing a retarder having two or more optically anisotropic layers each formed of a composition containing a liquid crystal compound. Further, the present invention relates to a retardation plate which can be used as a 1/4 wavelength plate for a retardation plate manufactured by the process, particularly a reflection type liquid crystal display device, a writing pickup for an optical disk, or an antireflection film.

Related Technology

A retarder, especially a quarter wavelength (lambda / 4) plate, can be used for various purposes and is already in actual use. JPA-1998-68816 and JPA-1998-90521 ("JPA" means "unexamined Japanese patent application") discloses a 1 / It is described that a four-wavelength plate can be produced by laminating two sheets of an optically anisotropic polymer film. In JPA-2000-206331, JPA-2001-4837, JPA-2001-21720, and JPA-2001-91741, a 1/4 wave plate having? / 4 retardation over a wide wavelength range , And laminating two or more optically anisotropic layers each formed of a liquid crystal compound.

The former method involves cutting two polymer films at a predetermined angle in order to adjust the optical orientation (optical axis and slow axis) of the two polymer films to obtain the desired optical properties, . Such processes degrade the quality of the product by misaligning the axes, lowering the yield, increasing the manufacturing cost, and causing deterioration of the product due to contamination. Further, the polymer film is inherently disadvantageous in accurately adjusting the retardation value required for the? / 4 wave plate.

On the other hand, the latter method, which is advantageous in easily providing a broad band? / 4 plate, requires an orientation layer in the production of an optically anisotropic layer formed of oriented liquid crystal molecules. The need for orientation layer production increases manufacturing costs. Further, when a 1/4 wave plate including two optically-anisotropic layers each formed of aligned liquid crystal molecules is manufactured, an upper optically-anisotropic layer is produced without forming an orientation layer on the surface of the lower optically-anisotropic layer, It is known that the alignment layer must be formed every time when the uniformity and accuracy of the liquid crystal alignment are lowered and defects on the orientation are increased to form the optically anisotropic layer formed of aligned liquid crystal molecules.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method capable of solving the above problems, more particularly to a retardation plate comprising two or more optically anisotropic layers respectively formed of aligned liquid crystal molecules, And to provide a method for lowering the disadvantages of double boosting and manufacturing cost.

In one aspect, the present invention provides a liquid crystal display comprising a transparent substrate and two or more optically anisotropic layers each formed of a liquid crystal compound-containing composition on or on one surface of the transparent substrate,

And forming an orientation layer on the surface of the transparent substrate having the longitudinal direction under continuous feeding along the longitudinal direction, the method comprising the steps of:

(a) rubbing the surface of the orientation layer or the surface of the layer formed on or above the orientation layer;

(b) applying a composition comprising a liquid crystal compound to the rubbed surface;

(c) solidifying the composition applied to the rubbed surface in step (b) to form an optically anisotropic layer;

(d) repeating steps (a) to (c) one or more times while keeping the substrate unrolled; And

(e) rolling the transparent substrate having two optically anisotropic layers on top thereof.

As in an embodiment of the present invention, at least one step (a) includes rubbing the surface of an optically anisotropic layer comprising a modified polyvinyl alcohol having a hydrocarbon group containing not more than 9 carbon atoms; Wherein the liquid crystal compound used in the at least one step (b) is a rod-like liquid crystal compound having a polymerizable group; And the liquid crystal compound used in the at least one step (b) is a discotic liquid crystal compound having a polymerizable group.

In another aspect, the present invention provides a retarder produced by the above method.

In this specification, the expression "substantially" in relation to the angle means that the angle is in the range of the correct angle of 5 [deg.]. Preferably, the difference from the correct angle is +/- 4 DEG or less, more preferably +/- 3 DEG or less. In this specification, the expression "uniform orientation " is used not only for precise uniform orientation, but also for any orientation having an average tilt angle in the range of 0 to 40 degrees. As used herein, the expression "vertical orientation" is used not only for precise vertical orientation, but also for any orientation having an average tilt angle in the range of 50 to 90 degrees. In the present specification, the term "slow axis" means a direction indicating the maximum refractive index.

Brief Description of Drawings

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic view showing a process flow of a method of manufacturing a wave plate of the present invention. FIG.

2 is a schematic view of an exemplary wave plate of the present invention.

3 is a schematic view of an exemplary circular polarizer using the wavelength plate of the present invention.

4 is a schematic plan view showing an exemplary punching process for manufacturing a conventional polarizing plate.

FIG. 5 is a schematic plan view showing an exemplary punching process for producing a 45 ° polarizing plate used in the present invention. FIG.

6 is a schematic view showing an exemplary layer structure of the circular polarizer of the present invention.

7 is a schematic view showing another exemplary layer structure of the circular polarizer of the present invention.

8 is a schematic plan sectional view showing the circular polarizer produced in Example 2. Fig.

Example

[Phase difference plate manufacturing process]

An exemplary phase difference plate manufacturing process of the present invention is shown in Fig. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically depicts an exemplary phase difference plate manufacturing process with two optically anisotropic layers.

First, a long transparent substrate showing that portion is continuously fed in Fig. 1, and a coating solution for forming an alignment layer containing a modified polyvinyl alcohol or the like is applied to the surface of the transparent substrate 1 to form an alignment layer 2 (Step (1)). Next, the surface of the orientation layer 2 is rubbed with a rubbing roll or the like (step (a)). A coating liquid containing a liquid crystal compound is applied to the rubbed surface to form a layer 4 '(step (b)). The liquid crystal molecules of the layer 4 'are aligned in a predetermined alignment state according to the surface characteristics of the alignment layer 2 and the rubbing direction. Subsequently, the optically anisotropic layer 4 is formed by fixing the liquid crystal molecules of the layer 4 'in an alignment state by polymerizing or the like under heat and / or actinic irradiation (step (c)). The steps (a) to (c) are repeated to form the optically anisotropic layer 5. Thus, a retardation plate including two optically anisotropic layers can be continuously produced. After forming the optically anisotropic layer 5, the substrate having two optically anisotropic layers on top is rolled, stored, transported, and cut into various shapes, and provided for use.

Although an exemplary retardation plate manufacturing process with two optically anisotropic layers is shown schematically in Fig. 1, repeating steps (a) through (c) n times, where n is an integer of 2 or greater, It is also possible to produce a retardation plate having an optically anisotropic layer of a layer. By leaving the retarder plate unrolled, i. E. By not performing step (e), until the optically anisotropic layer is completely formed, Layer 5), it is possible to manufacture a retarder comprising a plurality of optically anisotropic layers respectively formed of liquid crystal molecules aligned with high accuracy and uniformity and few alignment defects. Therefore, it is possible to omit the step of forming the orientation layer between the optically anisotropic layers, thereby making it possible to lower the manufacturing cost.

In the present invention, the conditions and materials applied to the first to n-th steps (a) to (c) can be selected in an independent manner. For example, the direction of the rubbing performed in the plurality of steps (a), or the species of the liquid crystal compound used in the plurality of the step (b) may be the same or different from each other.

Next, each step, various members, and materials used in the present invention will be described in detail.

[Transparent Substrate]

A transparent substrate is used in the present invention. Here, the transparent substrate refers to a substrate having a light transmittance of 80% or more. The wavelength dispersion of the transparent substrate is preferably small, and more specifically, the ratio of Re400 / Re700 is more preferably 1.2 or less. Further, it is preferable that the transparent substrate has small optical anisotropy, and more specifically, the in-plane retardation (Re) is preferably 20 nm or less, more preferably 10 nm or less.

The transparent substrate is preferably composed of a polymer film. Examples of polymers that can be used include cellulose esters, polycarbonates, polysulfones, polyether sulfone, polyacrylates, and polymethacrylates. Of these, cellulose esters are preferred, acetylcellulose is more preferred, and triacetylcellulose is most preferred. Particularly, when triacetyl cellulose is used, it is preferable that the compound has an acetylation degree of 60.25 to 61.50. The polymer film is preferably formed by a solvent cast method.

In the present invention, a substrate having a longitudinal axis is used. The substrate may be a rolled shape. The coating liquid forming the optically anisotropic layer is continuously applied to the surface of the long substrate. After forming all the optically anisotropic layers on top of it, it is desirable to cut the substrate into pieces of the required size. The thickness of the transparent substrate is preferably 20 to 500 micrometers, more preferably 40 to 200 micrometers. In order to improve the adhesion between the transparent substrate and the layer formed thereon (adhesive layer, uniform orientation layer, vertical orientation layer, or optically anisotropic layer), the transparent substrate is subjected to surface treatment (e.g., glow discharge treatment , Corona discharge treatment, ultraviolet (UV) treatment, flame treatment, saponification), or an adhesive layer (undercoat layer) can be provided on a transparent substrate. Saponification is preferable as the surface treatment.

[Orientation Layer]

In the present invention, an orientation layer is formed on a substrate while continuously transporting the substrate along the longitudinal direction. The alignment layer has a function of aligning the liquid crystal molecules coated on the surface in a predetermined orientation. An oriented layer prepared by rubbing the surface of a layer formed of an organic compound, preferably a polymer, may be used in the present invention. The kind of the polymer constituting the alignment layer is determined according to the preferred orientation of the liquid crystal molecules (in particular, the average inclination angle).

In order to uniformly orient the liquid crystal molecules, the alignment layer formed of a polymer which does not lower the surface energy of the alignment layer should be used. This orientation layer was generally used. Preferably, examples of polymers used in this orientation layer include polyvinyl alcohol, polyimide derivatives, and nylon.

It is preferable that the alignment layer has a polymerizable group in order to improve the adhesiveness with the liquid crystal compound layer formed thereon. The polymerizable group may be introduced in the form of a side chain of the repeating unit or a substituent of the cyclic group. It is preferable to use an alignment layer capable of forming a chemical bond with the liquid crystal compound at the interface, and such alignment layer is disclosed in JPA-1997-152509.

The thickness of the orientation layer is preferably 0.01 to 5 micrometers, more preferably 0.05 to 3 micrometers.

[Rubbing Treatment]

In step (a), the alignment layer formed on the transparent substrate is rubbed. The surface of the optically anisotropic layer formed in steps (a) to (c) may be rubbed.

The rubbing treatment can be carried out by rubbing the surface of the layer several times along a certain direction with a paper or cloth. The orientation of the liquid crystal molecules can be determined in advance in the rubbing direction. The rubbing treatment can be performed along the direction of a predetermined angle with respect to the longitudinal direction of the long substrate. It is preferable that the rubbing is performed along the direction parallel to the longitudinal direction or along the direction of the angle within the range of -45 to +45 relative to the longitudinal direction.

Rubbing can be performed by a method selected from various known rubbing methods, and it is preferable to use at least one rubbing roll. For example, a rubbing roll may be arranged on a long substrate or in contact with the surface of a layer formed thereon, and the long substrate may be rotated while being transported along the longitudinal direction, The surface of the substrate is rubbed. The apparatus used for rubbing preferably has a mechanism capable of freely adjusting the angle between the rubbing roll and the moving direction of the stage. The rubbing roll described herein refers to a roll having an appropriate rubbing cloth material on the surface.

Next, a composition containing the liquid crystal compound is applied to the rubbed surface (step (b)) and the composition is cured to form an optically anisotropic layer (step (c)).

[Optically Anisotropic Layer Containing Liquid Crystal Compound]

The liquid crystal compound used in the step (b) is preferably a rod-like liquid crystal compound or a disc-shaped liquid crystal compound, more preferably a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group.

Examples of rod-like liquid crystal compounds include azomethine, azoxy, cyanobiphenyl, cyanobiphenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl ester, cyanophenylcyclohexane, cyano-substituted phenylpyrimidines, alkoxy-substituted Phenyl pyrimidine, phenyl dioxane, tolane, and alkenyl cyclohexyl benzonitrile. Not only low molecular weight liquid crystal compounds as described above but also high molecular weight liquid crystal compounds can be used. Preferably, the rod-shaped liquid crystal compound represented by the formula (I) is used.

In formula (I)

Q ¹ -L ¹ -A ¹ -L ³ -ML ⁴ -A ² -L ² -Q ²

In formula (I), Q ¹ and Q ² each represent a polymerizable group; L ¹ , L ² , L ³ and L ⁴ each represent a single bond or at least one of L ³ and L ⁴ represents a divalent linking group represented by -O-CO-O-; A ¹ and A ² each represent a C2-20 spacer group; M represents a mesogen group.

The polymerizable rod-like liquid crystal compound represented by formula (I) is described in detail.

In the formula (I), Q ¹ and Q ² each represent a polymerizable group. The polymerizable group may be addition polymerization (ring-opening polymerization) or condensation polymerization may be possible. Preferably, Q ¹ and Q ² represent groups capable of addition polymerization or condensation polymerization, respectively. Examples of the polymerizable group are shown below.

L ¹ , L ² , L ³ , and L ⁴ The divalent linking group represented is preferably -O-, -S-, -CO-, -NR ² -, -CO-O-, -O-CO-O-, -CO-NR ² -, NR ² -CO-, A group selected from the group consisting of -O-CO-, -O-CO-NR ² -, -NR ² -CO-O-, -NR ² -CO-NR ² - and a single bond. R ² represents a C 1-7 alkyl group or a hydrogen atom. At least one of L ³ and L ⁴ represents -O-CO-O- (carbonate group).

Among the groups represented by a combination of Q ¹ and L ¹ or a combination of Q ² and L ² , preferred examples are CH ₂ ═CH-CO-O-, CH ₂ ═C (CH ₃ ) -CO-O-, and CH ₂ = C (C1) comprises a -CO-O-, and more preferable example is _{CH 2 = CH-CO-O-} .

A ¹ and A ² each represent a C2-20 spacer group, preferably a C2-12 aliphatic group, more preferably an alkylene group. The spacer group is preferably a chain group and may include an oxygen atom or a sulfur atom not adjacent to each other. The spacer group may have a substituent, and more specifically, may be substituted with a halogen atom (boron, chlorine, bromine), cyano, methyl, or ethyl.

The mesogen group represented by M may be selected from known mesogen groups. A preferred example thereof is represented by the following formula (II).

The formula (II)

- (- W ¹ - L ⁵ ) _n --W ² -

In formula (II), W ¹ and W ² each represent a divalent aryl cyclic group, a divalent aromatic group or a divalent heterocyclic group. L ⁵ is a single bond or a linking group. Examples of the linking group represented by L ⁵ include -CH ₂ -O- and -O-CH ₂ - which are specific examples represented by L ¹ to L ⁴ in the above formula (I). "n" is an integer of 1, 2, or 3.

Examples of W ¹ and W ² are cyclohexane-1,4-diyl, 1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 1,3,4-thiadiazole 2,5-diyl, 1,3,4-oxathiadiazole-2,5-diyl, naphthalene-2,6-diyl, naphthalene-1,5-diyl, thiophene- Pyridazine-3,6-diyl. 1,4-cyclohexanediyl can be present as a trans- and cis- stereoisomer, and any mixture of any of its stereoisomers and any mixture ratio can be used in the present invention. And a transformer shape is more preferable. W ¹ and W ² may independently have a substituent and specific examples of the substituent include a halogen atom (fluorine, chlorine, bromine, iodine), cyano, a C1-10 alkyl group (for example, methyl, ethyl, A C1-10 alkoxy group (e.g., methoxy, ethoxy), a C1-10 acyl group (for example, formyl, acetyl), a C1-10 alkoxycarbonyl group (for example, methoxycarbonyl, ethoxy Carbonyl), a C1-10 acyloxy group (e.g., acetyloxy, propionyloxy), nitro, trifluoromethyl, and difluoromethyl.

Preferable examples of the mesogen group represented by the above formula (II) are shown below, but the mesogen group is not limited to this example. The mesogen group may be substituted with any of the substituents described above.

Specific examples of the compound represented by formula (I) are shown below, but the present invention is not limited thereto. The compound represented by formula (I) can be prepared by the process described in JPA-1999-513019.

A variety of discotic liquid crystal compounds can be used in the present invention as liquid crystal compounds. Preferably, the discotic liquid crystal compound is oriented vertically, that is, at an oblique angle in the range of 50 to 90 degrees with respect to the film surface. Examples of discotic liquid crystal compounds include benzene derivatives described in " Mol. Cryst., Vol. 71, p. 111 (1981), C. Destrade et al. A truxane derivative as described in "Mol. Cryst., Vol. 122, 141 (1985), C, Destrade et al." And "Physics Lett., Vol. Chem., Vol. 96, 70 (1984), B. Kohne et al., "Cyclohexane derivatives; And M. Zhang et al., "J. Chem. Commun., 1974 (1985), M. Lehn et al." And J. Am. Chem. Soc., Vol. Cyclic azela-crown or phenylacetylene.

The liquid crystal compound used for preparing the optically anisotropic layer does not need to maintain the liquid crystal degree after being contained in the optically anisotropic layer. For example, when a low molecular weight liquid crystal compound having a light and / or heat-initiated reactor is used to produce an optically anisotropic layer, the cross-linking reaction or polymerization reaction of the compound is performed after initiation by light and / or heat, . The polymerized or crosslinked compound may no longer exhibit liquid crystallinity. The polymerization of discotic liquid crystal compounds is described in JPA-1996-27284.

Preferably, the discotic liquid crystal molecule has a polymerizable group fixed by its polymerization. However, when the polymerizable group directly bonds to the disc-shaped core, it becomes difficult to maintain the orientation during the polymerization reaction. Therefore, preferably, the discotic liquid crystal compound comprises a linking group between the discotic core and the polymerizable group. That is, the discotic liquid crystal compound is preferably represented by the following formula (III).

The formula (III)

D- (LP) _n

In the formula, D represents a disk-shaped core, L represents a divalent linking group, P represents a polymerizable group, and n represents an integer of 4 to 12. Preferred examples of the disk-shaped core "D", the divalent linking group "L" and the polymerizable group "P" are Examples D1 to D15 described in JPA-2001-4837, (L25), and Examples (P1) to (P18).

In the optically anisotropic layer, these liquid crystal molecules are oriented in substantially the same way, more preferably in substantially the same orientation manner, most preferably in a polymerization reaction. When a rod-like liquid crystal compound having a polymerizable group is used, it is preferable to fix the rod-like molecules while maintaining a substantially uniform orientation. As used herein, the expression "substantially uniform" means that the tilt angle between the long axis direction of the rod-shaped molecule and the surface of the optically anisotropic layer is within the range of 0 to 40 degrees. In addition, the rod-like liquid crystal molecules are oriented so as to be inclined or the inclination angle is changed stepwise, that is, in the hybrid orientation. Preferably, the average tilt angle is in the range of 0 to 40 degrees even under the oblique and hybrid orientations.

When a disk-shaped liquid crystal compound having a polymerizable group is used, it is preferable to fix the compound while maintaining a substantially perpendicular orientation. Here, the expression "substantially perpendicular" means that the inclination angle between the disk surface and the surface of the optically anisotropic layer is within a range of 50 to 90 degrees. The disk-shaped liquid crystal molecules are oriented so as to be inclined or the inclination angle is changed stepwise, that is, hybrid alignment. Preferably, the average tilt angle is within the range of 50 to 90 degrees even under the oblique and hybrid orientations.

In the present invention, the steps (a) to (c) are repeated n times (n is an integer of 2 or more) to form an optically anisotropic layer of n layers, and the first to (n-1) ) To (c) preferably functions as an orientation layer of the optically anisotropic layer formed through n steps (a) to (c). When the lower optically-anisotropic layer functions as an orientation layer of the upper optically-anisotropic layer formed thereon, a composition comprising a modified polyvinyl alcohol having a hydrocarbon group containing not more than 9 carbon atoms together with the liquid crystal compound is used in step (b) To form an optically anisotropic layer in step (c), and to rub the surface of the thus formed optically anisotropic layer in the subsequent step (a).

Next, the modified polyvinyl alcohol having a hydrocarbon group containing not more than 9 carbon atoms which can be used together with the liquid crystal compound will be described in detail.

The modified polyvinyl alcohol represented by the formula (PX) is preferred.

The formula (PX)

- (VAl) _x- (HyD) _y- (VAc) _z -

In the formula (PX), "VAl" is a vinyl alcohol-based repeating unit, "HyD" is a repeating unit having a hydrocarbon group of 9 or less carbon atoms, "VAc" is a vinyl acetate-based repeating unit; x is from 20 to 95 wt%, preferably from 25 to 95 wt%; y is from 2 to 98 wt%, preferably from 10 to 80 wt%; And z is 0 to 30 wt%, preferably 2 to 20 wt%. "Hydrocarbon group" can be used for any aliphatic group, any aromatic group, and combinations thereof. The aliphatic group may have a circular, linear or branched chain structure. Preferably, the aliphatic group is an alkyl group (including a cycloalkyl group) or an alkenyl group (including a cycloalkenyl group). The hydrocarbon group may have one or more substituents. The number of carbon atoms contained in the hydrocarbon group is 1 to 9, preferably 1 to 8.

(HyD-I) or (HyD-II), which is a repeating unit having a hydrocarbon group of 9 or less carbon atoms.

Wherein L ¹ is a divalent linking group selected from the group consisting of -O-, -CO-, -SO ₂ -, -NH-, an alkylene group, an arylene group and any combination thereof; L ² is a divalent linking group or a single bond selected from the group consisting of -O-, -CO-, -SO ₂ -, -NH-, an alkylene group, an arylene group and any combination thereof; R ¹ and R ² each represent a hydrocarbon group of 9 or less carbon atoms. A detailed example of the connector formed by the above combination is shown below.

L1 is -O-CO-

L2: -O-CO-alkylene-O-

L3: -O-CO-alkylene-CO-NH-

L4: -O-alkylene-CO- -NH-SO ₂ - arylene -O-

L5: -arylene-NH-CO-

L6: -arylene-CO-O-

L7: -arylene-CO-NH-

L8: -arylene-O-

L9: -O-CO-NH-arylene-NH-CO-

A detailed example of "HyD" is shown below.

The polymer used as an additive in the present invention preferably has a degree of polymerization of 200 to 5,000 (more preferably 300 to 3,000) and a molecular weight of 9,000 to 200,000 (more preferably 13,000 to 130,000). Two or more species of polymers may be used in combination.

Detailed examples of the polymer are shown below, but the polymers usable in the present invention are not limited to these examples.

The amount of the modified polyvinyl alcohol in the optically anisotropic layer is preferably in the range of 0.05 to 10 wt%, and more preferably in the range of 0.1 to 5 wt%, based on the weight of the liquid crystal compound.

Modified polyvinyl alcohol can be used in combination with one or more condensing agents. Preferably, the condensing agent is a compound having an isocyanate or formyl at the terminal. Although a detailed example of the condensing agent is shown below, the condensing agent usable in the present invention is not limited to these examples.

Poly (1,4-butanediol), isophorone diisocyanate terminal

Poly (1,4-butanediol), tolylene 2,4-diisocyanate terminal

Poly (ethylene adipate), tolylene 2,4-diisocyanate terminal

Poly (propylene glycol) tolylene 2,4-diisocyanate terminal

1,6-Diisocyanate Hexane

1,8-diisocyanate octane

1,12-diisocyanate decane

Isophorone isocyanate

Glyoxal

In step (b), it is preferable to apply a composition such as a liquid crystal compound and, if necessary, a coating liquid containing the above-mentioned modified polyvinyl alcohol, the polymerization initiator or other additives listed below dissolved therein to the rubbed surface. Preferably, an organic solvent is used to prepare the coating solution. Examples of organic solvents include amides (e.g., N, N-dimethylformamide), sulfoxides (e.g., dimethylsulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons Such as benzene, hexane, alkyl halides such as chloroform, dichloromethane, esters such as methyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, For example, tetrahydrofuran, 1,2-dimethoxyethane). Of these, alkyl halides and ketones are preferred. Two or more organic solvents may be mixed. Coding of the coating solution can be carried out by any known method (for example, extrusion coating method, direct gravure coating method, reverse gravure coating method, and die coating method).

[Fixed alignment state of liquid crystal molecules]

In step (C), the coating liquid applied to the rubbed surface is solidified to form an optically anisotropic layer. The liquid crystal molecules can be aligned in a predetermined alignment state by the characteristics of the alignment layer and the rubbing direction. It is preferable to fix the liquid crystal molecules and form the optically anisotropic layer while maintaining this alignment state. Preferably, the immobilization is realized by a polymerization reaction of the polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes thermal polymerization using a thermal polymerization initiator and photopolymerization using a photopolymerization initiator so as to proceed the polymerization reaction under active radiation so that the polymerization reaction proceeds under heat exposure, and the latter is more preferable. Examples of the photopolymerization initiator include a-carbonyl compounds (described in U.S. Patent Nos. 2367661 and 2367670), acyloin ethers (described in U.S. Patent No. 244882), a-hydrocarbon-substituted aromatic acyl (Described in U.S. Patent No. 2722512), polynuclear quinone compounds (described in U.S. Patent Nos. 3046127 and 2951758), triarylimidazole dimers and p-aminophenyl ketones No. 3549367), acridine and phenazine compounds (described in Japanese Patent Application Laid-open No. 60-105667 and US Patent No. 4239850), and oxadiazole compounds No. 4212970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20 wt%, more preferably 0.5 to 5 wt%, depending on the solidification in the coating solution. Preferably, the irradiation for polymerizing the liquid crystal molecules is an UV ray. The irradiation energy is preferably 20 mJ / cm ² to 50 J / cm ² , more preferably 100 to 800 mJ / cm ² . And then irradiated under heating to accelerate the photopolymerization reaction.

The thickness of the optically anisotropic layer is preferably 0.1 to 10 micrometers, more preferably 0.5 to 5 micrometers.

[Optical properties of retarder]

It is preferable that the optically anisotropic layer formed in the above-mentioned step secures a phase difference of substantially p or p / 2 at a specific wavelength. The phase difference of p at a specific wavelength (?) Can be obtained by adjusting the retardation value of the optically anisotropic layer measured at specific wavelengths (?) To? / 2, and the phase difference of p / 2 can be obtained from specific wavelengths / 4 < / RTI > by adjusting the retardation value of the optically anisotropic layer. When the phase difference plate comprises two optically anisotropic layers, at 550 nm, which is approximately the wavelength in the center of the visible light region, one of the two layers produces a phase difference of p and the other produces a phase difference of p / 2 It is preferable to generate a phase difference. In an exemplary case where steps (a) to (c) are repeated twice to form two optically-anisotropic layers, one optically-anisotropic layer (first optically-anisotropic layer) (Second optically anisotropic layer) has a retardation value of 240 to 290 nm, more preferably 250 to 280 nm, and the other optically anisotropic layer (second optically anisotropic layer) has a retardation value of preferably 110 to 145 nm, And has a retardation value of 120 to 140 nm.

Here, the retardation value means an in-plane retardation value defined for the light incident from the direction of the normal line on the optically anisotropic layer, and more specifically, represented by the following formula.

The retardation value Re = (nx - ny) xd

Herein, nx and ny represent principal in-plane refractive indices of the optically anisotropic layer, and d represents the thickness (nm) of the optically anisotropic layer.

The thickness of the optically anisotropic layer can be arbitrarily determined as long as the layer can exhibit a desired retardation value. An example in which both retarder plates comprise two optically anisotropic layers formed of the same species of homogeneously oriented rod-like liquid crystal compound, one of which produces a phase difference of p and the other produces a phase difference of p / 2 It is preferable that the thickness of the optically anisotropic layer which produces the phase difference of p is twice the thickness of the optically anisotropic layer which produces the phase difference of p / 2. Although the preferred range for the thickness of each optically anisotropic layer may vary depending on the species of liquid crystal compound used, it is generally from 0.1 to 10 micrometers, preferably from 0.2 to 8 micrometers, more preferably from 0.5 to 5 micrometers Is more preferable.

[Configuration of retardation plate]

2 is a schematic view showing a typical configuration of a retardation film of the present invention, including two optically anisotropic layers formed in a composition including a rod-like liquid crystal compound. As shown in Fig. 2, the basic retardation plate includes a long transparent substrate S, a first optically-anisotropic layer A, and a second optically-anisotropic layer B. The first optically-anisotropic layer (A) produces a phase difference of p, and the second optically-anisotropic layer (B) produces a phase difference of p / 2. The longitudinal direction of the transparent substrate S and the slow axis (a) of the first optically anisotropic layer (A) cross at 30 degrees. The slow axis (b) of the second optically anisotropic layer (B) and the slow axis (a) of the first optically anisotropic layer (A) cross at 60 degrees. Each of the first optically-anisotropic layer (A) and the second optically-anisotropic layer (B) shown in Fig. 2 contains rod-shaped liquid crystal molecules (c1 and c2). Thereby uniformly orienting the rod-like liquid crystal molecules (c1 and c2). The longitudinal axes of the rod-like liquid crystal molecules (c1 and c2) correspond to the slow axes (a and b) of the optically anisotropic layer.

An exemplary configuration of a retardation plate in which an optically anisotropic layer A (phase difference = p) is disposed adjacent to the transparent substrate S and an optically anisotropic layer B (retardation = p / 2) The position of the optically anisotropic layer (A) and the optically anisotropic layer (B) may be changed. However, a more preferable configuration is the same as placing the optically anisotropic layer A (phase difference = p) adjacent to the transparent substrate S and placing the optically anisotropic layer B (phase difference = p / 2) on the outside.

[Circular Polarizer]

The retardation film of the present invention is advantageous when applied to a 1/4 wavelength plate used for a reflective liquid crystal display device, a write pickup for an optical disk, or an antireflection film. Generally, a 1/4 wavelength plate is formed as a circular polarizer plate such as a linear polarizer film combined with the linear polarizer film. Therefore, a 1/4 wave plate formed of a circularly polarizing plate such as that combined with a linear polarizing film can be easily coupled to a device such as a reflective liquid crystal display device. Examples of linear polarizing films include iodine-containing linear polarizing films, dye-containing linear polarizing films using dichroic dyes, and poly-ene containing linear polarizing films. Generally, an iodine-containing linear polarizing film and a dye-containing linear polarizing film can be produced by using a poly (vinyl alcohol) -based film.

[Configuration of Circular Polarizer]

Fig. 3 is a schematic view showing a typical configuration of a circular polarizer including the retardation plate of the present invention shown in Fig. 2 including two optically anisotropic layers formed of a composition containing a rod-like liquid crystal compound. Fig. 3 includes a transparent substrate S, a first optically-anisotropic layer (A), and a second optically-anisotropic layer (B) shown in Fig. 2 and further includes a linear polarizing film (P) . The longitudinal direction s of the polarizing transparent axis p of the linear polarizing film P and the longitudinal direction s of the transparent substrate S intersect at 45 degrees and the slow axis a of the first optically anisotropic layer A, (a) of the first optically anisotropic layer (A) and the slow axis (b) of the second optically-anisotropic layer (B) intersect at 60 degrees . In addition, each of the first optically-anisotropic layer (A) and the second optically anisotropic layer (B) shown in Fig. 3 contains rod-like liquid crystal molecules (c1 and c2). Thereby uniformly orienting the rod-like liquid crystal molecules (c1 and c2). The longitudinal axes of the rod-like liquid crystal molecules (c1 and c2) correspond to the in-plane slow axes (a and b) of the optically anisotropic layers (A and B).

The linear polarizing film to be combined with the retardation film of the present invention is not particularly limited, and examples thereof include iodine-containing linear polarizing films, dye-containing linear polarizing films using dichroic dyes, and poly-ene- Film. Generally, an iodine-containing linear polarizing film and a dye-containing linear polarizing film can be produced by using a poly (vinyl alcohol) -based film. Preferably, a linear polarizing film is laminated with the retardation plate of the present invention to orient its transparent axis, which is inclined at 45 [deg.] Away from the longitudinal direction of the transparent substrate of the retardation plate. When a linear polarizing film (hereinafter simply referred to as "45 linear polarizing film") having a polarizing transparent axis inclined at 45 degrees apart from the longitudinal direction of the transparent substrate is used, there is no need to further adjust the laminating angle, The production of the circular polarizer of the invention becomes easy. Since the transparent axis of the linear polarizing film formed of the stretched film substantially coincides with the stretching direction, the film is stretched in a direction inclined at 45 DEG apart from the longitudinal direction of the transparent substrate to successfully produce a 45 DEG linear polarizing film can do. With reference to the conditions described in paragraphs [0009] to [0045] of JPA-2002-86554, the usable device structure, and the like, the film is stretched in a direction inclined at 45 ° with respect to the longitudinal direction of the film, A film can be produced.

The polymer film stretched in the present invention is not particularly limited, and any suitable thermoplastic polymer-containing film is usable. Examples of polymers include polyvinyl alcohol (PVA), polycarbonate, cellulose acylate, and polysulfone. PVA is preferably used as the polymer. Generally, although PVA is obtained by saponifying polyvinyl acetate, PVA may include any component capable of copolymerizing with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. It is also possible to use a modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group and the like.

Although the degree of saponification of PVA is not particularly limited, it is preferably adjusted within a range of 80 to 100 mol%, more preferably within a range of 90 to 100 mol% from the viewpoint of solubility and the like. The degree of polymerization of PVA is not particularly limited, but is preferably adjusted within the range of 1,000 to 10,000, more preferably within the range of 1,500 to 5,000.

PVA can be dyed to produce linear polarizing films, which can proceed by adsorption from a vapor phase or a liquid phase. In one exemplary process of liquid adsorption using iodine, the PVA film is immersed in an aqueous iodide-potassium iodide solution and adsorbed. The content of iodine and potassium iodide is preferably in the range of 0.1 to 20 g / L and 1 to 100 g / L, respectively, and the weight ratio of iodine and potassium iodide is preferably in the range of 1 to 100. The dyeing time is preferably 30 to 5,000 seconds, and the solution temperature is preferably in the range of 5 to 50 DEG C. The dyeing method is not limited to the dipping method, and any method such as coating or spraying of the iodine or dye solution is also possible. The dyeing step can be carried out before or after the stretching step, but it is particularly advantageous to dye it before stretching because the stretching becomes easy when the film expands appropriately.

In addition to iodine, it is also preferable to use a dichroic dye for dyeing. Specific examples of dichroic dyes include dye compounds such as azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. While these dyes are preferably water soluble, they are not limited thereto. It is also preferable that such a dichroic dye has a hydrophilic substituent such as a sulfonic acid group, an amino group, and a hydroxyl group introduced therein. Specific examples of dichroic dyes include C.I. Direct Yellow 12, C.I. Direct Orange 39, C.I. Direct Orange 72, C.I. Direct Red 39, C.I. Direct Red 79, C.I. Direct Red 81, C.I. Direct Red 83, C.I. Direct Red 89, C.I. Direct Violet 48, C.I. Direct Blue 67, C.I. Direct Blue 90, C.I. Direct Green 59, C.I. Acid Red 37, which are used in JPA-1989-161202, JPA-1989-172906, JPA-1989-172907, JPA-1989-183602, JPA-1989-248105, JPA-1989-265205, JPA-1995-261024. Such dichroic molecules are used in the form of free acids, alkali metal salts, ammonium salts or amine salts. Two or more such dichroic molecules are mixed to successfully produce a polarizing plate having various colors. A mixture or compound (dyestuff) of various dichroic molecules designed to exhibit a black color, when contained in a polarizing element or a polarizing plate, and when its transparent axis is orthogonal to each other, has a high transmittance in a high polarization and single plate form .

In the stretching of the PVA producing a linear polarizing film, it is preferable to add additives to crosslink the PVA. In particular, when the oblique stretching process of the present invention is used, if the PVA film is not sufficiently cured at the exit of the stretching process, the orientation direction of the PVA can be misoriented due to the unstable process, It is preferable that the crosslinking agent is contained in the PVA film by dip coating or coating of such a crosslinking agent solution. Crosslinking agents disclosed in US Reissue Patent No. 232897 can be used in the present invention, and it is most preferable to use bromic acid.

Also preferably, a so-called polyvinylene-based linear polarizing film, which can be thought of as belonging to a conjugated double bond of the poly-ene structure obtained by removing the chlorine of PVA and poly (vinyl chloride) and dehydrating it, The stretching process can be applied to manufacture.

The 45 占 linear polarizing film prepared by stretching the film in a direction inclined at 45 占 with respect to the longitudinal direction of the film can be configured as a polarizing plate without any modification and can be used as a retardation plate of the present invention, And it is more preferable to use them as a polarizing plate after laminating a protective film on both sides.

There are no particular restrictions on the type of protective film, examples of which are available are cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate; Polycarbonate; Polyolefin; polystyrene; And polyesters. However, since linear polarized light is converted into circularly polarized light due to the inclined misalignment between the orientation axis of the protective film and the transparent axis, the retardation value of the protective film exceeding a specific value is not preferable. The retardation value of the protective film is preferably small, and is generally 10 nm or less at 632.8 nm, and more preferably 5 nm or less. In particular, cellulose triacetate is preferable as a polymer constituting a protective film having such a low retardation value. Preferably, polyolefins such as ZEONEX and ZEONOR (trade name, manufactured by ZEON Corporation of Japan) and ARTON (trade name, manufactured by JSR Corporation of Japan) are used. Other examples of usable examples include the non-birefringent optical resin materials described in JPA-1996-110402 and JPA-1999-293116.

The pressure-sensitive adhesive which can be used between the linear polarizing film and the protective layer is not particularly limited, but a PVA resin (containing a modified PVA with an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc.) and a solution of an aqueous boron compound Among them, PVA resin is preferable. The thickness of the dried layer of the pressure-sensitive adhesive is preferably in the range of 0.01 to 10 micrometers, more preferably in the range of 0.05 to 5 micrometers.

The thickness of the film before stretching is not particularly limited, but is preferably 1 micrometer to 1 mm, more preferably 20 to 200 micrometers from the viewpoint of stability of film retention and uniformity of stretching.

Exemplary conventional punching patterns of the polarizing plate and exemplary punching patterns of the polarizing plate of the present invention are shown in Figs. 4 and 5, respectively. As shown in Fig. 4, the known polarizing plate has an absorption axis 71, that is, a stretching axis, which coincides with the longitudinal direction 72. Fig. 5, the polarizing plate of the present invention has a polarization absorption axis 81, that is, a stretching axis, which is inclined at 45 degrees apart from the longitudinal direction 82, The angle between the absorption axis of the polarizing plate and the liquid crystal cell itself or between the longitudinal direction and the lateral direction of the liquid crystal cell itself does not need to be obliquely punched in the punching step. 5, since the cutting line for producing the polarizing plate of the present invention extends straight along the longitudinal direction, it is possible to manufacture the polarizing plate by slitting along the longitudinal direction rather than punching Which is advantageous in that it secures excellent productivity.

Preferably, the polarizing plate used in the present invention has high transmittance and high degree of polarization in terms of enhancing the contrast of the liquid crystal display device. The transmittance is preferably 30% or more at 550 nm, and more preferably 40% or more. The degree of polarization is preferably 95.0% or more at 550 nm, more preferably 99% or more, and still more preferably 99.9% or more.

Generally, a linear polarizing film has a protective film on both surfaces thereof. In the present invention, the retardation film of the present invention can function as a protective film on one side of the linear polarizing film. When the circular polarizer is manufactured by using a 45 占 linear polarizing film, the circular polarizer in the rightward direction and the leftward direction can be easily manufactured by a selective method by changing the lamination method.

[Configuration of Circular Polarizer]

6 shows a schematic view of an embodiment of the circular polarizer of the present invention.

The circular polarizer shown in Fig. 6 is configured to laminate a 45-degree linear polarizing film (P) and a protective film (G) on the retarder of the present invention. The retardation plate comprises optically anisotropic layers A and B (represented by a single layer in the figure) and a transparent substrate S. The retardation plate is laminated with a 45 DEG linear polarizing film P to form a 45 DEG linear polarizing film P on the surface of the transparent substrate S opposite to the surface having the optically anisotropic layers A and B formed thereon, As shown in FIG. In this configuration, the retarder also functions as a protective film for the 45 DEG linear polarizing film (P). 6 shows the relationship between the longitudinal direction s of the transparent substrate S, the slow axes a and b of the optically anisotropic layers A and B and the transparent axis p of the 45 占 linear polarizing film P .

When the circular polarizer shown in Fig. 6 is coupled to the display device, the protective film G side faces the display surface side (arrows in the drawing indicate the viewing direction). The circularly polarized light obtained with the configuration shown in Fig. 6 is right-handed. The light exits from the direction indicated by the arrow in Fig. 6, passes through the linear polarizing film P and the optically anisotropic layers A and B in turn, and exits to the right polarized light.

Another exemplary configuration of the circular polarizer of the present invention is shown in Fig. 7, the positions of the protective film G and the retardation plate shown in Fig. 6 are changed from each other so that the protective film G, the 45-degree linear polarizing film P, the transparent substrate S, And the optically anisotropic layers (A, B) are stacked in this order upward. The circular polarizer thus configured can emit left-polarized light.

As is apparent from the above, right polarization and left polarization can be selectively obtained by changing the top and bottom of the laminate when the protective film (G) and the retarder are bonded to the 45 ° linear polarizer film (P).

When a protective film is used in addition to the transparent substrate, the protective film is preferably composed of a cellulose ester film having high optical anisotropy, and particularly preferably composed of a triacetylcellulose film.

In detail, a wide? / 4 obtainable by using the polarizing plate and the retarder of the present invention is such that all values of the retardation value / wavelength measured at 450 nm, 550 nm and 650 nm are in the range of 0.2 to 0.3 . ≪ / RTI > The value of the retardation value / wavelength is preferably in the range of 0.21 to 0.29, more preferably in the range of 0.22 to 0.28, further preferably in the range of 0.23 to 0.27, and most preferably in the range of 0.24 to 0.26 .

Example

The present invention will now be described in more detail with reference to the detailed examples in the following paragraphs. Any material, reagent, utilization ratio, and operation may be suitably modified without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[Example 1]

An optically anisotropic triacetylcellulose film with a thickness of 80 micrometers, a width of 680 mm, and a length of 500 m, having an acetylation degree of 60.9 ± 0.2% and a retardation value of 6.0 nm, was used as a transparent substrate. Both surfaces of the transparent substrate were saponified, and on one surface thereof, a coating solution "A" prepared by adjusting the pH to 4 to 5 with NH ₄ OH to prepare an orientation layer was successively applied and dried to form a 1 micrometer- . The layer was continuously rubbed at an angle of 30 DEG with respect to the longitudinal direction of the transparent substrate. Thus, an orientation layer was produced.

Composition of coating liquid "A"

The following modified poly (vinyl alcohol): 4 wt%

Water 72.6 wt%

Methanol 23.3 wt%

Glutaraldehyde 0.2 wt%

The coating liquid prepared according to the following composition was continuously applied to the surface of the orientation layer by using a bar coater, dried, heated (completed orientation), and irradiated with UV radiation to form a 2.1-micrometer-thick optically anisotropic layer (A). It was found that the optically anisotropic layer (A) had a slow axis in a direction inclined at 30 DEG to the longitudinal direction of the transparent substrate and had a retardation value of 259 nm at 550 nm (Re 550).

Composition of coating liquid of optically anisotropic layer (A)

The rod-shaped liquid crystal compound 38.1 wt%

(Exemplary Compound I-2)

The following photoresist (A): 0.38 wt%

The following photopolymerization initiator (B): 1.14 wt%

An exemplary compound (PX-9) in this disclosure is 0.19 wt%

Glutaraldehyde 0.04 wt%

Methyl ethyl ketone 60.1 wt%

Thereafter, while the optically anisotropic layer (A) was produced, the optically anisotropic layer (A) thus obtained was kept at -60 deg. Relative to its slow axis and at -30 deg. Relative to the longitudinal direction And rubbed continuously in an oblique direction.

The coating liquid prepared according to the following composition was continuously applied to the surface of the orientation layer using a bar coater, dried, heated (completed orientation), and irradiated with UV radiation to form an optically anisotropic layer (B) . Thus, a retardation plate (? / 4 plate) was produced. The average retardation value at 550 nm (Re 550) was found to be 136 nm. An angle between the longitudinal direction of the transparent substrate and the slow axis of the optically anisotropic layer (B) is shown in Table 1 below.

Composition of coating liquid of optically anisotropic layer (B)

The rod-shaped liquid crystal compound 38.4 wt%

(Exemplary Compound I-2)

0.38 wt% of the photosensitive agent (A)

1.15 wt% of the photopolymerization initiator (B)

0.06 wt% of the following alignment agent (C)

Methyl ethyl ketone 60.0 wt%

[Comparative Example 1]

In the process of Example 1, each of the substrates was rolled once after forming the optically anisotropic layer (A) on the top thereof, and then subjected to the conditions of 60% RH (relative humidity), 25 DEG C To maintain the rolled state. Thereafter, the surface of the optically anisotropic layer (A) was rubbed similarly as in Example 1; Then, an optically anisotropic layer (B) was formed by coating, and respective retardation plates corresponding to Comparative Examples 1 to 3 were formed. The angles between the longitudinal direction of each of the transparent substrates and the slow axis of the optically anisotropic layer (B) are shown in Table 1.

From the results shown in Table 1, it can be seen that the sample kept in the unrolled state after the formation of the optically anisotropic layer (A) has a smaller change in the in-plane angle between the longitudinal direction of the transparent substrate and the slow axis of the optically anisotropic layer , Indicating that the liquid crystal compound is uniformly oriented while maintaining an ideal value. This proves the effect of the present invention.

After forming the optically anisotropic layer (A), the coating solution "A" was applied to the surface of the layer (A) to form an orientation layer, thereby forming a layer having a thickness of 1 micrometer. Thereafter, the optically anisotropic layer (B) was formed by applying the coating liquid to the rubbing surface of the alignment layer for the optically anisotropic layer (B) similarly to those described in Comparative Examples 1 to 3. No change as shown in Table 1, which gives the same result as in Example 1, was observed at an in-plane angle between the longitudinal direction of the transparent substrate and the slow axis of the optically anisotropic layer (B). This is because the angle change after storing in the rolled state shown in Table 1 is due to the fact that the orientation layer is not formed on the optically anisotropic layer (A), and when the orientation layer is not formed between the two optically anisotropic layers It clearly shows that the invention is effective.

[Example 2]

The PVA film was immersed in an aqueous solution containing 2.0 g / L of iodine and 4.0 g / L of potassium iodide at 25 DEG C for 240 seconds and immersed in a 10 g / L aqueous boric acid solution at 25 DEG C for 60 seconds, Was introduced into a tenter stretcher constructed as shown in Fig. 2 of 2002-86554, and stretched 5.3 times. Thereafter, as shown in Fig. 2 of JPA-2002-86554, the tenter was bent from the stretching direction and then kept at a constant width, and the film was dried under shrinkage of the 80 DEG C atmosphere, and then released from the tenter. The moisture content of the PVA film before and after the stretching was found to be 31% and 1.5%, respectively.

The difference between the moving speed of the left tenter clip and the right tenter clip was found to be less than 0.05% and the angle between the center line of the film to be introduced and the center line of the film to be fed to the next process was 46 °. In the relationship of | L1-L2 | = W, | L1-L2 | and W were all found to be 0.7 m. The substantial stretching direction Ax-Cx at the exit of the tenter was found to be inclined at 45 [deg.] Away from the center line 22 of the film to be fed to the next process. No wrinkles or deformation of the film were observed at the exit of the tenter.

A saponified cellulose triacetate film (FUJITACK, manufactured by Fuji Photo Film Co., Ltd., retardation value = 3.0) was prepared using a solution of 3% aqueous PVA (PVA-117H, manufactured by Kuraray Co., nm) and the film were further combined and dried at 80 DEG C to obtain a polarizing plate having an effective width of 650 nm.

It was found that the obtained polarizing plate had an absorption axis inclined at 45 DEG away from its longitudinal direction. It was found that the transmittance at 550 nm and the obtained polarization degree of the polarizing plate were 43.7% and 99.97%, respectively. As shown in Fig. 5, the film was cut into a size of 310 x 233 nm to successfully obtain a polarizing plate having an absorption axis inclined at 45 [deg.] With an area efficiency of 91.5%.

Next, as shown in Fig. 8, the retardation plate 96 prepared in Example 1 was laminated on one surface of the iodine-containing linear polarizing film 91 prepared above, and the saponified anti-glare film 91 An antireflection film was laminated to prepare another circular polarizer plate 92. [ Other polarizing plates 93 to 95 were similarly prepared, except that the retardation plates prepared in Comparative Examples 1 to 3 were used in place of the retardation plates 96, respectively. In all the manufacturing processes of such a circular polarizing plate, the linear polarizing film and the retarder were laminated to each other to align their longitudinal directions.

Each of the circular polarizers 92 to 95 thus obtained was irradiated with light (450 nm, 550 nm, and 650 nm) from the saponified antiglare antireflection film 97 side and the retardation value (retardation value: Re) were measured at arbitrary 20 points within the range of 650 nm width and 1,000 nm length, and the range of change was expressed by the maximum value and the minimum value. The results are shown in Table 2.

As shown in Table 2, the process of the present invention is successful in producing circular polarizers with very small in-plane Re variations.

[Example 3: Production of reflection type liquid crystal display device]

The polarizing plate and the retarder were removed from a commercial reflection type liquid crystal display device ("Color Zaurus MI-310", manufactured by SHARP Corporation of Japan), and the circular polarizer plate 92 prepared in Example 2 was attached instead.

The visual evaluation of the thus obtained reflective type liquid crystal display device revealed that the blurred gray is displayed in any mode among the white display, the black display, and the mid-tone display without color hue.

Next, the contrast ratio according to the reflection luminance was measured using a viewing angle measuring instrument (EZcontrast 160D, manufactured by Eldim SA of France). A contrast ratio measured on the front side was found to be practically sufficient 10.

Industrial availability

The present invention can contribute to lowering the manufacturing cost of manufacturing a retarder comprising two or more optically anisotropic layers each formed of aligned liquid crystal molecules with few defects in alignment.

Claims (6)

1. A method for producing a rolled retarder comprising a transparent substrate and two or more optically anisotropic layers each formed of a composition containing a liquid crystal compound on or on one surface of the transparent substrate, Forming an alignment layer on a surface of the transparent substrate while continuously supplying a transparent substrate having a longitudinal direction along the longitudinal direction, (a) rubbing the surface of the orientation layer or the surface of the layer formed on or above the orientation layer; (b) applying a composition comprising the liquid crystal compound to the rubbed surface; (c) solidifying the composition applied to the rubbed surface in step (b) to form an optically anisotropic layer; (d) repeating the steps (a) to (c) one or more times while keeping the substrate unrolled; And (e) rolling the transparent substrate having the at least two optically anisotropic layers thereon, The step of rubbing the surface of the optically anisotropic layer comprising a modified polyvinyl alcohol having a hydrocarbon group containing at least 9 carbon atoms at least once in the step (a). delete The method according to claim 1, In the modified polyvinyl alcohol, (PX): - (VAl) _x- (HyD) _y- (VAc) _z- Lt; / RTI > Here, "VAl" is a vinyl alcohol repeating unit, "HyD" is a repeating unit having a hydrocarbon group of 9 or less carbon atoms, "VAc" x is from 20 to 95 wt%, y is from 2 to 98 wt%, and z is from 0 to 30 wt%. The method according to claim 1 or 3, Wherein the liquid crystal compound used in at least one of the steps (b) is a rod-like liquid crystal compound having a polymerizable group. The method according to claim 1 or 3, Wherein the liquid crystal compound used in at least one of the steps (b) is a discotic liquid crystal compound having a polymerizable group. A retarder produced by the method described in claim 1 or 3.

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