KR20050073460A - Processe for preparing retarders - Google Patents

Abstract

A novel process for preparing a rolled- up retarder comprising a transparent substrate and two or more optically- anisotropic layers respectively formed of a composition comprising a liquid-crystalline compound on or above one surface thereof. The process comprises steps for preparing plural optically anisotropic layers while keeping a long substrate unrolled and a step of rolling up the long substrate after forming all of optically-anisotropic layers thereon.

Description

Retarder Manufacturing Process {PROCESSE FOR PREPARING RETARDERS}

Technical Field

The present invention relates to a process for producing a retarder having at least two optically anisotropic layers each formed of a composition comprising a liquid crystal compound. The present invention also relates to a retarder manufactured by the process, in particular a retarder which can be used as a quarter wave plate in a reflective liquid crystal display device, a write pickup for an optical disk or an antireflection film.

Related technology

Retarders, particularly quarter-wave (λ / 4) plates, can be used for various purposes and have already been used in practice. JP-A-1998-68816 and JP-A-1998-90521 ("JPA" means "Unexamined Japanese Patent Application") for lambda / 4 retardation over a wide range of wavelengths It is described that a quarter wave plate having) can be produced by stacking two sheets of optically anisotropic polymer films. In addition, JP-A-2000-206331, JP-A-2001-4837, JP-A-2001-21720, and JP-A-2001-91741 have lambda / 4 litres for a wide range of wavelengths. It is described that a quarter wave plate having a date can be produced by laminating two or more optically anisotropic layers each formed of a liquid crystal compound.

The former method cuts the two polymer films at an angle and sticks the obtained chips to each other in order to adjust the optical orientation (optical axis and retardation axis) of the two polymer films to obtain the desired optical properties. )Should be. This process misaligns the shafts, lowering the quality of the product, lowering the yield, increasing the manufacturing cost, and causing the product to deteriorate due to contamination. In addition, the polymer film is inherently disadvantageous in accurately adjusting the retardation value required for the λ / 4 waveplate.

On the other hand, the latter method, which is advantageous for easily providing a broadband? / 4 plate, requires an alignment layer for the production of an optically anisotropic layer formed of aligned liquid crystal molecules. The necessity of manufacturing the alignment layer increases the manufacturing cost. In addition, in the case of manufacturing a quarter wave plate including two optically anisotropic layers each formed of aligned liquid crystal molecules, an upper optically anisotropic layer is prepared substantially without forming an alignment layer on the surface of the lower optically anisotropic layer. It is known that the alignment layer must be formed every time an optically anisotropic layer formed of aligned liquid crystal molecules is formed by decreasing the uniformity and accuracy of the liquid crystal alignment and increasing the defects in the alignment.

Summary of the invention

One object of the present invention is to produce a retarder comprising at least two optically anisotropic layers each formed of a process that solves the above problems, more specifically, aligned liquid crystal molecules, and the uniformity and accuracy of liquid crystal alignment. It is possible to improve the process, and to provide a process that lowers the disadvantages of alignment and manufacturing costs.

In one aspect, the invention comprises a transparent substrate and at least two optically anisotropic layers each formed of a composition comprising a liquid crystal compound on or on one surface of the transparent substrate,

A process for producing a rolled retarder comprising forming an alignment layer on a surface of a transparent substrate having a longitudinal direction under continuous feeding along a longitudinal direction, the method comprising:

(a) rubbing the surface of the alignment layer or the surface of the layer formed on or over the alignment 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 a transparent substrate having two optically anisotropic layers thereon, to provide a rolled retarder manufacturing process.

As in an embodiment of the present invention, at least one of the steps (a) is a step of rubbing the surface of the optically anisotropic layer comprising the modified polyvinyl alcohol having a hydrocarbon group containing 9 or less carbon atoms; The liquid crystal compound used in at least one of the steps (b) is a rod-like liquid crystal compound having a polymerizable group; And a discotic liquid crystal compound having a polymerizable group, wherein the liquid crystal compound used in at least one of the steps (b) is provided.

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

In this specification, the expression “substantially” with respect to an angle means that the angle is in the range of the correct angle ± 5 °. Preferably, the difference with the correct angle is ± 4 ° or less, more preferably ± 3 ° or less. In this specification, the expression “uniform alignment” is used not only for exactly uniform alignment, but also for any alignment having an average tilt angle in the range of 0 to 40 °. In this specification, the expression "vertical alignment" is used not only for exactly vertical alignment, but also for any alignment having an average tilt angle in the range of 50 to 90 degrees. As used herein, the term "delay axis" means the direction representing the maximum index of refraction.

Brief description of the drawings

1 is a schematic diagram showing a process flow of a method of manufacturing a wave plate of the present invention.

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

3 is a schematic diagram of an exemplary circular polarizer plate utilizing the waveplate of the present invention.

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

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

6 is a schematic view showing an exemplary layer configuration of the circular polarizing plate of the present invention.

7 is a schematic view showing another exemplary layer configuration of the circular polarizing plate of the present invention.

FIG. 8 is a schematic plan sectional view showing a circular polarizer plate prepared in Example 2. FIG.

Example

[Retarder manufacturing process]

An exemplary retarder manufacturing process of the present invention is shown in FIG. 1 schematically illustrates an exemplary retarder fabrication process with two optically anisotropic layers.

First, the long and transparent substrate shown in FIG. 1 is continuously supplied, and a coating liquid for forming an alignment layer containing 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 alignment layer 2 is rubbed using 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 depending on the surface properties of the alignment layer 2 and the rubbing direction. Subsequently, the liquid crystal molecules of the layer 4 'are fixed in an aligned state by polymerizing or the like under heat irradiation and / or active radiation to form an optically anisotropic layer 4 (step (c)). Steps (a) to (c) are repeated to form the optically anisotropic layer 5. Thus, a retarder comprising two optically anisotropic layers can be produced continuously. After forming the optically anisotropic layer 5, the substrate with two optically anisotropic layers on top can be rolled, stored, transported, and cut into various shapes to target application.

An exemplary retarder manufacturing process with two optically anisotropic layers is shown schematically in FIG. 1, but repeating steps (a) to (c) n times (n is an integer of 2 or more, the same below), n It is also possible to produce a retarder having an optically anisotropic layer of layers. By leaving the retarder unrolled and not forming the optically anisotropic layer, i.e. not carrying out step (e), the present invention provides a method for the separation between adjacent optically anisotropic layers (in FIG. Even when no alignment layer is formed between the layers 5), a retarder including a plurality of optically anisotropic layers each formed of liquid crystal molecules aligned with high accuracy, uniformity and few alignment defects can be produced. Therefore, this can omit the step of forming the alignment layer between the optically anisotropic layers, thereby making the manufacturing cost low.

In the present invention, the conditions and materials applied in the first to nth steps (a) to (c) are selectable in an independent manner. For example, the direction of rubbing performed in the plurality of steps (a), or the species of the liquid crystal compound used in the plurality of steps (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. It is preferable that the wavelength dispersion of a transparent substrate is small, and more specifically, it is more preferable that the ratio of Re400 / Re700 is 1.2 or less. Moreover, it is preferable that a transparent substrate has small optical anisotropy, More specifically, it is preferable that in-plane retardation Re is 20 nm or less, and it is more preferable that it is 10 nm or less.

It is preferable that a transparent substrate consists of a polymer film. Examples of available polymers include cellulose esters, polycarbonates, polysulfones, polyether sulfones, polyacrylates, and polymethacrylates. Of these, cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. In particular, when using triacetyl cellulose, it is preferable that the compound has an acetylation degree of 60.25 to 61.50. It is preferable to form a polymer film by the solvent cast method.

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

[Sorting layer]

In the present invention, an alignment layer is formed on the substrate while continuously transporting the long substrate along the longitudinal direction. The alignment layer has a function of aligning the liquid crystal molecules applied to the surface in a predetermined alignment. Alignment layers prepared by rubbing the surface of layers formed of organic compounds, preferably polymers, can be used in the present invention. The species of the polymer constituting the alignment layer is determined in accordance with the preferred alignment of the liquid crystal molecules (in particular, the average tilt angle).

In order to uniformly align the liquid crystal molecules, an alignment layer formed of a polymer should be used so that its surface energy is not lowered. Such alignment layers have generally been used. Preferably, examples of the polymer used in such an alignment layer include polyvinyl alcohol, polyimide derivatives, and nylon.

In order to improve the adhesiveness with the liquid crystal compound layer formed in the upper part, it is preferable that the alignment layer has a polymerizable group. A polymerizable group can be introduce | transduced in the side chain shape of a repeating unit, or the substituent shape of a 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 an alignment layer is disclosed in JP-A-1997-152509.

It is preferable that it is 0.01-5 micrometers, and, as for the thickness of an alignment layer, it is more preferable that it is 0.05-3 micrometers.

[Rubber processing]

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) can be rubbed.

The rubbing treatment can be performed by rubbing the surface of the layer several times with paper or cloth along a predetermined direction. The alignment of the liquid crystal molecules can be previously determined in the rubbing direction. The rubbing treatment can be performed along a direction of a predetermined angle with respect to the longitudinal direction of the long substrate. The rubbing is preferably performed in a direction parallel to the longitudinal direction or along an angle in the range of -45 ° to + 45 ° with respect to the longitudinal direction.

Rubbing can be performed by a method selected from various known rubbing methods, and it is preferable to use one or more rubbing rolls. For example, the rubbing roll is arranged in contact with the surface of the layer formed on or above the elongated substrate, and the elongated substrate is rotated while being transported along the longitudinal direction, so that the layer along the predetermined direction by the direction of rotation of the rubbing roll. Rub the surface. The device used for rubbing preferably has a mechanism capable of freely adjusting the angle between the rubbing roll and the direction of movement of the end. The rubbing roll described herein refers to a roll having an appropriate rubbing cloth material on its surface.

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

[Optical anisotropic layer containing liquid crystal compound]

The liquid crystal compound used in step (b) is preferably a rod type liquid crystal compound or a disk type liquid crystal compound, and more preferably a rod type liquid crystal compound having a polymerizable group or a disk type liquid crystal compound having a polymerizable group.

Examples of the rod-shaped liquid crystal compound include azomethine, azoxy, cyanobiphenyl, cyanobiphenyl ester, benzoic acid ester, cyclohexanecarboxylic acid phenyl ester, cyanophenylcyclohexane, cyano substituted phenylpyrimidine, alkoxy substituted phenyl Pyrimidine, phenyl dioxane, tolan, and alkenylcyclohexyl benzonitrile. Not only the low molecular weight liquid crystal compound as mentioned above but also a high molecular weight liquid crystal compound can be used. Preferably, the rod-like liquid crystal compound represented by Formula (I) is used.

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 a divalent linking group in which at least one of L ³ and L ⁴ represents —O—CO—O—; A ¹ and A ² each represent a C2-20 spacer group; M represents a mesogenic group.

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

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

L ¹ , L ² , L ³ , and L ⁴ , respectively The divalent bond represented is -O-, -S-, -CO-, -NR ^2- , -CO-O-, -O-CO-O-, -CO-NR ^2- , NR ² -CO-, It is preferably one 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 groups).

Among the groups represented by the combination of Q ¹ and L ¹ or the 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) -CO-O-, with a more preferred example being 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 oxygen atoms or sulfur atoms not adjacent to each other. The spacer group may have a substituent and more particularly may be substituted with halogen atoms (boron, chlorine, bromine), cyano, methyl, or ethyl.

The mesogenic group represented by M can be selected from known mesogenic groups. Preferable examples thereof are shown below by formula (II).

Formula (II)

-(-W ¹ -L ⁵ ) _n -W ^2-

In the formula (II), W ¹ and W ² each represent a divalent arylcyclic group, a divalent aromatic group, or a divalent heterocyclic group. L ⁵ is a single bond or a bonding group. Examples of the linking group represented by L ⁵ include —CH ₂ —O— and —O—CH ₂ — which are detailed examples represented by L ¹ to L ⁴ in the 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-2,5-diyl, and Pyridazine-3,6-diyl. 1,4-cyclohexanediyl may be present in the form of one of trans- and cis-isomers, and any mixture of any mixing ratio may be used in the present invention. The trans shape is more preferable. W ¹ and W ² may independently have a substituent, and specific examples of the substituents include halogen atoms (fluorine, chlorine, bromine, iodine), cyano, C 1-10 alkyl groups (eg, methyl, ethyl, propyl) , C1-10 alkoxy group (eg methoxy, ethoxy), C1-10 acyl group (eg formyl, acetyl), C1-10 alkoxycarbonyl group (eg methoxycarbonyl , Ethoxycarbonyl), C1-10 acyloxy groups (eg, acetyloxy, propionyloxy), nitro, trifluoromethyl, and difluoromethyl.

Although the preferable example of the mesogenic group represented by said Formula (II) is shown below, a mesogenic group is not restrict | limited to this example. Mesogenic groups can be substituted with any of the above substituents.

Although the specific example of the compound represented by Formula (I) is shown below, this invention is not limited to this. The compound represented by formula (I) can be prepared by the process described in JP-A-1999-513019.

Various discotic liquid crystal compounds can be used in the present invention as liquid crystal compounds. Preferably, the discotic liquid crystal compound is aligned vertically, ie at an inclination angle in the range of 50 to 90 ° with respect to the film plane. Examples of discotic liquid crystal compounds include benzene derivatives described in "Mol. Cryst., Vol. 71, p. 111 (1981), C. Destrade et al."; Turuxic acid derivatives described in "Mol. Cryst., Vol. 122, p. 141 (1985), C, Destrade et al." And "Physics lett. A, vol. 78, p. 82 (1990)"; Cyclohexane derivatives described in Angew. Chem., Vol. 96, p. 70 (1984), B. Kohne et al .; And J. Chem. Commun., P. 1974 (1985), M. Lehn et al. And “J. Am. Chem. Soc., Vol. 116, p. 2655 (1994), J. Zhang et al. Cyclic aza crowns or phenyl acetylene.

After the liquid crystal compound used to prepare the optically anisotropic layer is contained in the optically anisotropic layer, there is no need to maintain the liquid crystal degree. For example, when a low molecular weight liquid crystal compound having a reactor initialized by light and / or heat is used to prepare an optically anisotropic layer, the crosslinking reaction or polymerization reaction of the compound is performed after initialization to light and / or heat, thereby To form. The polymerized compound or crosslinked compound may no longer exhibit liquid crystallinity. Polymerization of discotic liquid crystal compounds is described in JP-A-1996-27284.

Preferably, the discotic liquid crystal molecules have a polymerizable group which is fixed by the polymerization thereof. However, when the polymerizable group is directly bonded to the disc-shaped core, it becomes difficult to maintain alignment during the polymerization reaction. Thus, preferably, the discotic liquid crystal compound comprises a bonding group between the disc-shaped core and the polymerizable group. That is, preferably, the discotic liquid crystal compound is represented by the following formula (III).

Formula (III)

D- (LP) _n

In the formula, D is a disc-shaped core, L is a divalent bonding group, P is a polymerizable group, and n represents an integer of 4 to 12. Preferred examples of the disc-shaped core "D", the divalent linking group "L", and the polymerizable group "P" are Examples (D1) to (D15) and Examples (D) described in JP-A-2001-4837, respectively. Same as L1) to (L25) and Examples (P1) to (P18).

In the optically anisotropic layer, these liquid crystal molecules are aligned in substantially the same manner, more preferably in substantially the same alignment, and most preferably in a polymerization reaction. In the case of using a rod-like liquid crystal compound having a polymerizable group, it is preferable to fix the rod-shaped molecules while maintaining a substantially uniform alignment. The expression "substantially uniform" as described herein means that the inclination angle between the long axial direction of the rod-shaped molecules and the plane of the optically anisotropic layer is within the range of 0 to 40 degrees. In addition, the rod-like liquid crystal molecules are aligned inclined, or the tilt angle is changed in steps, that is, hybrid alignment. Preferably, the average angle of inclination is within the range of 0 to 40 degrees even under oblique alignment and hybrid alignment.

In the case of using a disc-shaped liquid crystal compound having a polymerizable group, it is preferable to fix the compound while maintaining a substantially vertical alignment. The expression "substantially perpendicular" here means that the angle of inclination between the disk surface and the plane of the optically anisotropic layer is within the range of 50 to 90 degrees. The disc-shaped liquid crystal molecules are aligned obliquely, or the tilt angle is changed in steps, that is, hybrid alignment. Preferably, the average tilt angle is within the range of 50 to 90 ° even under tilt alignment and hybrid alignment.

In the present invention, steps (a) to (c) are repeated n times (n is an integer of 2 or more) to form n layers of optically anisotropic layers, and the first to (n-1) th steps (a) Each optically anisotropic layer formed through steps (c) through (c) preferably serves as an alignment layer of the optically anisotropic layer formed through n steps (a) through (c). If the lower optically anisotropic layer functions as an alignment layer of the upper optically anisotropic layer formed thereon, the modified polyvinyl alcohol having a hydrocarbon group containing 9 or less carbon atoms in combination with the liquid crystal compound in step (b) It is preferable to use the composition to form an optically anisotropic layer in step (c) and to rub the surface of the optically anisotropic layer thus formed in subsequent step (a).

Next, the modified polyvinyl alcohol which has a hydrocarbon group containing 9 or less carbon atoms which can be used for combination with a liquid crystal compound is described in detail.

Modified polyvinyl alcohol represented by formula (PX) is preferable.

Expression (PX)

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

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

Preferred "HyD" which is a repeating unit having a hydrocarbon group of 9 or less carbon atoms is represented by the formula (HyD-I) or (HyD-II).

In the formula, L ¹ is a divalent bonding 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 single bond or a divalent bond group 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. The detailed example of the coupling group formed by the said combination is shown below.

L1: -O-CO-

L2: -O-CO-alkylene-O-

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

L4: -O-CO-alkylene-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-

Detailed examples of "HyD" are 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 polymer may be used in the combination.

Detailed examples of the polymers are shown below, but the polymers that can be used in the present invention are not limited to these examples.

The amount of the modified polyvinyl alcohol of the optically anisotropic layer is preferably in the range of 0.05 to 10 wt%, 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 isocyanate or formyl at the terminal. Detailed examples of the condensing agent are shown below, but the condensing agent which can be used in the present invention is not limited to these examples.

Poly (1,4-butane diol), isophorone diisocyanate ends

Poly (1,4-butane diol), tolylene 2,4-diisocyanate ends

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

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

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 coating liquid comprising a liquid crystal compound and, if necessary, the modified polyvinyl alcohol, a polymerization initiator or other additives listed below, which is dissolved therein to the rubbed surface. Preferably, an organic solvent is used to prepare a coating liquid. Examples of organic solvents include, but are not limited to, amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg For example, benzene, hexane), alkyl halides (eg chloroform, dichloromethane), esters (eg methyl acetate, butyl acetate), ketones (eg acetone, methyl ethyl ketone), and ethers (eg Tetrahydrofuran, 1,2-dimethoxyethane). Of these, alkyl halides and ketones are preferred. Two or more organic solvents may be mixed. The coating liquid may be coated by any known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, and die coating method).

[Fix alignment of liquid crystal molecules]

In step (C), the coating solution applied to the rubbed surface is solidified to form an optically anisotropic layer. The liquid crystal molecules may be aligned in an alignment state predetermined by the characteristics of the alignment layer and the rubbing direction. It is preferable to form an optically anisotropic layer by fixing liquid crystal molecules and maintaining this alignment state. Preferably, the immobilization is embodied in the polymerization reaction of the polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes thermal polymerization using a thermal polymerization initiator to advance the polymerization reaction under heat exposure and photopolymerization using a photopolymerization initiator to advance the polymerization reaction under activating radiation, which is more preferable. Examples of photopolymerization initiators include a-carbonyl compounds (described in US Pat. Nos. 23,677, 173 and 2367670), acyloin ethers (described in US Pat. No. 244882), a-hydrocarbon substituted aromatic acyls Phosphorus compounds (described in US Pat. No. 2722512), polynuclear quinone compounds (described in US Pat. Nos. 3046127 and 2951758), triarylimidazole dimers, and p-aminophenylketones (US patents). Combinations of No. 3549367, acridine and phenazine compounds (described in Japanese Patent Application Laid-Open No. 60-105667, and US Pat. No. 4239850), and oxadiazole compounds (US patents) No. 4212970).

The amount of photopolymerization initiator to be 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 UV light. The irradiation energy is more preferably it is 20 mJ / cm ² to 50 J / cm ² is preferable, and 100 to 800 mJ / cm ^2. Irradiation under heating can accelerate the photopolymerization reaction.

It is preferable that it is 0.1-10 micrometers, and, as for the thickness of an optically anisotropic layer, it is more preferable that it is 0.5-5 micrometers.

[Optical Characteristics of Retarder]

It is preferable that the optically anisotropic layer formed in this step ensures a phase difference of substantially p or p / 2 at a particular wavelength. The phase difference of p at a specific wavelength λ can be obtained by adjusting the retardation value of the optically anisotropic layer measured at the specific wavelength λ to λ / 2, and the phase difference of p / 2 is specified to the specific wavelength λ to λ. It can be obtained by adjusting the retardation value of the optically anisotropic layer measured at / 4. If the retarder comprises two optically anisotropic layers, at 550 nm, the wavelength substantially in the center of the visible region, one of the two layers produces a phase difference of p and the other layer is p / 2 It is preferable to generate the phase difference of. In an exemplary case of repeating steps (a) to (c) twice to form two optically anisotropic layers, the retardation value measured at 550 nm of one optically anisotropic layer (first optically anisotropic layer) is Preferably it is 240-290 nm, More preferably, it is 250-280 nm, The retardation value measured at 550 nm of another optically anisotropic layer (2nd optically anisotropic layer), Preferably it is 110-145 nm, More preferable Preferably from 120 to 140 nm.

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

Retardation value (Re) = (nx-ny) × d

Here, nx and ny represent the in-plane main refractive index of an optically anisotropic layer, and d represents the thickness (nm) of an optically anisotropic layer.

The thickness of the optically anisotropic layer can be arbitrarily determined as long as the layer can exhibit the desired retardation value. The retarder comprises both optically anisotropic layers formed of the same species of uniformly aligned rod-like liquid crystal compounds, one of which produces a phase difference of p and the other of which produces a phase difference of p / 2 In an exemplary case, it is preferred that the thickness of the optically anisotropic layer producing a phase difference of p is twice the thickness of the optically anisotropic layer producing a 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 0.1-10 micrometers, preferably 0.2-8 micrometers, and 0.5-5 micrometers. It is more preferable that is.

[Configuration of Retarder]

Fig. 2 is a schematic diagram showing a typical configuration of the retarder of the present invention, which includes two optically anisotropic layers formed of a composition containing a rod-like liquid crystal compound. As shown in FIG. 2, the basic retarder includes an elongate transparent substrate S, a first optically anisotropic layer A, and a second optically anisotropic layer B. FIG. 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 retardation axis a of the first optically anisotropic layer A intersect at 30 degrees. The retardation axis b of the second optically anisotropic layer B and the retardation axis a of the first optically anisotropic layer A intersect at 60 degrees. Each of the first optically anisotropic layer (A) and the second optically anisotropic layer (B) shown in FIG. 1 contains rod-like liquid crystal molecules c1 and c2. The rod-like liquid crystal molecules c1 and c2 are aligned uniformly. The longitudinal axes of the rod-like liquid crystal molecules c1 and c2 correspond to the delay axes a and b of the optically anisotropic layer.

An exemplary configuration of a retarder in which an optically anisotropic layer A (phase difference = p) is disposed adjacent to the transparent substrate S and an optically anisotropic layer B (phase difference = p / 2) is disposed on the outside is shown in FIG. Although shown for convenience, the position of the optically anisotropic layer (A) and the optically anisotropic layer (B) can also be changed. However, a more preferable configuration is such that the optically anisotropic layer A (phase difference = p) is disposed adjacent to the transparent substrate S and the optically anisotropic layer B (phase difference = p / 2) is disposed on the outside.

[Circular Polarizer]

The retarder of the present invention is advantageous when applied to a quarter wave plate used for a reflective liquid crystal display device, a write pickup for an optical disk, or an antireflection film. Generally, a quarter wave plate is formed as a circular polarizing plate such as a combination with a linear polarizing film. Therefore, the quarter wave plate formed of a circular polarizing plate such as that combined with a linear polarizing film can be easily combined with a device such as a reflective liquid crystal display device. Examples of the linear polarizing film include an iodine-containing linear polarizing film, a dye-containing linear polarizing film using a dichroic dye, and a poly-ene-containing linear polarizing film. Generally, an iodine containing linear polarizing film and dye containing linear polarizing film can be manufactured using a poly (vinyl alcohol) type film.

[Configuration of Circular Polarizer]

FIG. 3 is a schematic diagram showing a typical configuration of a circular polarizing plate including the retarder of the present invention shown in FIG. 2 including two optically anisotropic layers formed in a composition containing a rod-type liquid crystal compound. The circular polarizing plate shown in FIG. 3 includes the transparent substrate S shown in FIG. 2, the first optically anisotropic layer A, and the second optically anisotropic layer B, and further includes a linear polarizing film P. FIG. . The polarization transparent axis p of the linear polarizing film P and the longitudinal direction s of the transparent substrate S intersect at 45 °, and the retardation axis a of the first optically anisotropic layer A and the polarization transparent axis (p) intersects by 15 °, and similarly as shown in Fig. 2, the retardation axis a of the first optically anisotropic layer A and the retardation axis b of the second optically anisotropic layer B are 60 °. To cross. 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. The rod-like liquid crystal molecules c1 and c2 are aligned uniformly. The longitudinal axes of the rod-shaped liquid crystal molecules c1 and c2 correspond to the in-plane retardation axes a and b of the optically anisotropic layers A and B.

There is no particular limitation on the linear polarizing film to be combined with the retarder of the present invention, and examples that can be used include iodine-containing linear polarizing films, dye-containing linear polarizing films using dichroic dyes, and poly-ene-containing linear polarizing light. It includes a film. Generally, an iodine containing linear polarizing film and dye containing linear polarizing film can be manufactured using a poly (vinyl alcohol) type film. Preferably, the linear polarizing film is stacked with the retarder of the present invention to align its transparent axis inclined at 45 ° away from the longitudinal direction of the transparent substrate of the retarder. If a linear polarizing film having a polarized transparent axis inclined at 45 ° spaced from the longitudinal direction of the transparent substrate (hereinafter, simply referred to as "45 ° linear polarizing film"), the stacking angle no longer needs to be adjusted. Production of the circular polarizing plate 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 ° away from the longitudinal direction of the transparent substrate, thereby successfully producing a 45 ° linear polarizing film. can do. With reference to the conditions described in paragraphs [0009] to [0045] of JP-A-2002-86554, available device structure, and the like, the film is drawn in a direction inclined at 45 ° to the longitudinal direction of the film, A linear polarizing film can be manufactured.

The polymer film to be stretched in the present invention is not particularly limited, and a film including any suitable thermoplastic polymer is available. Examples of polymers include polyvinyl alcohol (PVA), polycarbonates, cellulose acylates, and polysulons. It is preferable to use PVA as a polymer. Generally, PVA is obtained by saponifying polyvinyl acetate, but PVA may include any component copolymerizable with vinyl acetate, such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. It is also possible to use modified PVA containing acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group and the like.

Although the saponification degree of PVA is not specifically limited, It is preferable to adjust in 80-100 mol% from the viewpoint of solubility etc., and it is more preferable to adjust in 90-100 mol%. Although the polymerization degree of PVA is not specifically limited, It is preferable to adjust in the range of 1,000-10,000, and it is more preferable to adjust in the range of 1,500-5,000.

PVA can be dyed to produce a linear polarizing film, and this dyeing process can proceed by adsorption from vapor phase or liquid phase. In one exemplary process of liquid phase adsorption with iodine, the PVA film is immersed in an aqueous iodine-potassium iodide solution for absorption. It is preferable that content of iodine-potassium iodide is 0.1-20g / L and 1-100g / L, respectively, and it is preferable that the weight ratio of iodine-potassium iodide is in the range of 1-100. It is preferable that dyeing time is 30 to 5,000 second, and it is preferable that solution temperature exists in the range of 5-50 degreeC. The dyeing method is not limited to immersion, but any method such as coating or spraying of iodine or dye solution is possible. The dyeing process can be carried out before or after the stretching process, but it is particularly advantageous to dye before stretching since the film is easily stretched if the film is properly expanded.

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. It is preferred that these dyes are water soluble, but are not limited thereto. It is also preferred that such dichroic dyes have hydrophilic substituent groups introduced therein, such as sulfonic acid groups, amino groups, and hydroxyl groups. Detailed 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, these include JP-A-1989-161202, JP-A-1989-172906, JP-A-1989-172907, JP-A-1989-183602, JP-A-1989- 248105, JP-A-1989-265205 and JP-A-1995-261024. Such dichroic molecules are used in the form of free acids, alkali metal salts, ammonium salts or amine salts. Two or more of these dichroic molecules are mixed to successfully produce polarizing plates having various shapes. A mixture or compound (dye) of various dichroic molecules, which is contained in a polarizing plate element or a polarizing plate and when its transparent axis is normally crossed with respect to each other, has a high polarization and a single plate shape. It is preferable because it has a transmittance.

In the stretching of PVA for producing a linear polarizing film, it is preferable to add an additive to crosslink the PVA. In particular, when using the oblique stretching process of the present invention, if the PVA film does not have enough curl at the exit of the stretching process, the orientation direction of the PVA may be misaligned due to an unstable process, and thus before or during the stretching process. It is preferable to contain the crosslinker in the PVA film by dipping or coating such crosslinker solution. The crosslinking agent disclosed in US Pat. No. 232897 can be used in the present invention, most preferably bromic acid.

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

The 45 ° linear polarizing film produced by stretching the film in a direction inclined at 45 ° with respect to the longitudinal direction of the film can be configured as a polarizing plate without deformation and can be used as the retarder of the present invention, but on one side or both sides thereof. It is more preferable to use as a polarizing plate after laminating | stacking a protective film.

There is no particular limitation on the species of the protective film, and available examples thereof include cellulose esters such as cellulose acetate, cellulose acetate butylate, and cellulose propionate; Polycarbonates; Polyolefins; polystyrene; And polyesters. However, since the linearly polarized light converts into circularly polarized light due to the inclination misalignment between the alignment axis and the transparent axis of the protective film, the retardation value of the protective film exceeding a specific value is not preferable. It is preferable that the retardation value of a protective film is small, It is common that it is 10 nm or less at 632.8 nm, and it is more preferable that it is 5 nm or less. In particular, cellulose triacetate is preferred as the polymer constituting the protective film having such a low retardation value. Preferably, polyolefins such as ZEONEX and ZEONOR (trade name, manufactured by ZEON Japan), and ARTON (trade name, manufactured by JSR Japan) are used. Other available examples include the non-birefringent optical resin materials described in JP-A-1996-110402 and JP-A-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 solution of PVA resin (including PVA modified with acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group, etc.) and aqueous boron compound solution PVA resin is preferable among these. It is preferable that the thickness of the dried layer of an adhesive exists in the range of 0.01-10 micrometers, and it is more preferable to exist in the range which is 0.05-5 micrometers.

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

Exemplary known punching patterns of polarizing plates and exemplary punching patterns of the present invention of polarizing plates 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, corresponding to the longitudinal direction 72. On the other hand, as shown in Fig. 5, the polarizing plate of the present invention has a polarization absorbing axis 81, i.e., a stretching axis, inclined at 45 DEG apart from the longitudinal direction 82, and the inclination angle is combined with the liquid crystal cell of the LCD. In accordance with the angle between the absorption axis of the polarizing plate and the longitudinal or transverse direction of the liquid crystal cell itself, it is no longer necessary to obliquely punch the film in the punching process. As can be clearly seen from Fig. 5, since the cutting line for manufacturing the polarizing plate of the present invention extends in a straight line along the longitudinal direction, the polarizing plate can be manufactured by slitting along the longitudinal direction rather than punching, It is also advantageous in securing excellent productivity.

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

Generally, a linear polarizing film has a protective film on both surfaces thereof. In the present invention, the retarder of the present invention can function as a protective film on one side of the linear polarizing film. When manufacturing a circular polarizing plate using a 45 degree linear polarizing film, the circular polarizing plate of a right direction and a left direction can be manufactured easily by the selective method of changing a stacking method.

[Configuration of Circular Polarizer]

6 shows a schematic view of one embodiment of the circular polarizing plate of the present invention.

The circular polarizing plate shown in FIG. 6 is formed and 45 degree linear polarizing film P and the protective film G are stacked on the retarder of this invention. The retarder comprises optically anisotropic layers A and B (shown as a single layer in the figure) and a transparent substrate S. Stacking the retarder with a 45 ° linear polarizing film P, the surface of the transparent substrate S having the optically anisotropic layers A and B on which the opposite surface is formed on the surface of the 45 ° linear polarizing film P Place in contact with In this configuration, the retarder also functions as a protective film for the 45 ° linear polarizing film P. Fig. 6 also shows the mutual relationship between the longitudinal direction s of the transparent substrate S, the retardation axes a and b of the optically anisotropic layers A and B, and the transparent axis p of the 45 ° linear polarizing film P. Represents a relationship.

When the circular polarizing plate shown in Fig. 6 is bonded to the display device, the protective film P side faces the display surface side (arrows in the drawing indicate the viewing direction). Circularly polarized light obtained with the configuration shown in FIG. 6 is right polarized light. Light comes out of the direction shown by the arrow in FIG. 6, passes through linearly polarizing film P and optically anisotropic layers A and B in order, and exits to right polarization.

Another exemplary configuration of the circular polarizing plate of the present invention is shown in FIG. In the circular polarizing plate illustrated in FIG. 7, the positions of the protective film G and the retarder previously shown in FIG. 6 are changed from each other, and the protective film G, the 45 ° linear polarizing film P, the transparent substrate S, And the optically anisotropic layers A and B are stacked in this order upwards. The circular polarizer configured in this way may emit left polarized light.

As can be clearly seen from the above, the right polarization and the left polarization can be selectively obtained by changing the top and bottom of the stacking when combining the protective film G and the retarder to the 45 ° linear polarizing film P.

When using a protective film other than a transparent substrate, it is preferable that a protective film is comprised from the cellulose ester film which has high optical anisotropy, and it is especially preferable to consist of a triacetyl cellulose film.

Specifically, a wide range of λ / 4 that can be obtained using the polarizing plate and the retarder of the present invention has all the values of the retardation value / wavelength measured at 450 nm, 550 nm, and 650 nm in the range of 0.2 to 0.3 It means to be within. 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, still more 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 is explained in more detail with reference to the following detailed examples in the following paragraphs. Any materials, reagents, fees, and operations may be modified without departing from the spirit of the invention. Therefore, the scope of the present invention is not limited to the following examples.

Example 1

An optically anisotropic triacetyl cellulose film of 80 micrometers in thickness, 680 mm in width, and 500 m in length, having an acetylation degree of 60.9 ± 0.2% and a retardation value of 6.0 nm, was used as the transparent substrate. Both surfaces of the transparent substrate were saponified, and on one surface thereof, a coating liquid "A" adjusted to pH 4 to 5 with NH ₄ OH was continuously applied and dried to prepare an alignment layer, which was 1 micrometer thick. A layer was formed. In addition, the layer was continuously rubbed at an angle of 30 ° with respect to the longitudinal direction of the transparent substrate. Thus, an alignment layer was prepared.

Composition of Coating Liquid "A"

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

Water 72.6 wt%

Methanol 23.3 wt%

Glutalaldehyde 0.2 wt%

A coating liquid prepared according to the following composition was applied to the surface of the alignment layer continuously using a bar coater, dried, heated (complete alignment), and irradiated with UV radiation, thereby providing a 2.1 micrometer-thick optically anisotropic layer. (A) was formed. It was confirmed that the optically anisotropic layer A had a retardation axis in a direction inclined at 30 ° with respect to the longitudinal direction of the transparent substrate, and had a retardation value of 259 nm at 550 nm (Re 550).

Composition of the coating liquid of the optically anisotropic layer (A)

Rod type liquid crystal compound 38.1 wt%

(Example Compound I-2)

The following photosensitizer (A): 0.38 wt%

The following photopolymerization initiator (B): 1.14 wt%

0.19 wt% of Exemplary Compounds (PX-9) herein

Glutalaldehyde 0.04 wt%

Methyl Ethyl Ketone 60.1 wt%

Thereafter, the optically anisotropic layer A thus obtained was prepared at -60 ° with respect to its retardation axis and -30 ° with respect to its longitudinal axis while keeping the film unrolled after preparing the optically anisotropic layer A. Rubbing was continued continuously in the inclined direction.

A coating liquid prepared according to the following composition was continuously applied to the surface of the alignment layer using a bar coater, dried, heated (complete alignment), and irradiated with UV radiation to obtain an optically anisotropic layer (B) having a thickness of 1.0 micrometer. Formed. Thus, a retarder (λ / 4 plate) was produced. The average retardation value at 550 nm (Re 550) was found to be 136 nm. The angle between the longitudinal direction of the transparent substrate and the retardation axis of the optically anisotropic layer (B) is shown in Table 1 below.

Composition of Coating Liquid of Optically Anisotropic Layer (B)

Rod-type liquid crystal compound 38.4 wt%

(Example Compound I-2)

0.38 wt% of the photosensitizer (A)

1.15 wt% of the photopolymerization initiator (B)

0.06 wt% of following alignment regulator (C)

Methyl ethyl ketone 60.0 wt%

Comparative Example 1

In the process of Example 1, each substrate was rolled once after forming an optically anisotropic layer (A) thereon, and for the times listed in Table 1, under conditions of 60% RH (relative humidity), 25 ° C. Under rolled condition. Thereafter, the surface of the optically anisotropic layer (A) was rubbed similarly as in Example 1; An optically anisotropic layer (B) was then formed by coating to form respective retarders corresponding to Comparative Examples 1-3. The angle between the longitudinal direction of each transparent substrate of the sample and the retardation axis of the optically anisotropic layer (B) is shown in Table 1.

From the results shown in Table 1, after the optically anisotropic layer (A) showed a slight change in the in-plane angle between the longitudinal direction of the transparent substrate and the retardation axis of the optically anisotropic layer (B), the sample was left unrolled. This confirmed that the liquid crystal compounds were uniformly aligned while maintaining the ideal value. This demonstrates the effect of the present invention.

After forming the optically anisotropic layer (A), when the coating liquid "A" for forming the alignment layer was applied to the surface of the layer (A), a layer having a thickness of 1 micrometer was formed. Thereafter, the coating liquid of layer (B) was applied to the rubbing surface of the alignment layer similarly to that described in Comparative Examples 1 to 3 to form an optically anisotropic layer (B). No changes as shown in Table 1 were observed, which resulted in the same results as in Example 1 at the in-plane angle between the longitudinal direction of the transparent substrate and the retardation axis of the optically anisotropic layer (B). This is due to the fact that the angular change after storage in the rolled state shown in Table 1 does not form the alignment layer on the optically anisotropic layer (A), and is seen when the alignment layer is not formed between 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 iodine and 4.0 g / L potassium iodide at 25 ° C. for 240 seconds, then immersed in 10 g / L aqueous boric acid solution at 25 ° C. for 60 seconds, JP- It was introduced into a tenter stretching machine constructed as shown in Fig. 2 of A-2002-86554 and stretched 5.3 times. Thereafter, the tenter was bent from the stretching direction, as shown in FIG. 2 of JP-A-2002-86554, kept at a constant width, the film was dried under shrinkage in an 80 ° C. environment, and then released from the tenter. The water content of the PVA film before extending | stretching and after drying confirmed that it was 31% and 1.5%, respectively.

The difference in the movement speed of the left tenter clip and the right tenter clip was found to be 0.05% or less, and the angle between the center line of the film to be introduced and the center line of the film to be sent to the next process was 46 °. It was confirmed that | L1-L2 | and W were both 0.7 m in the relationship of | L1-L2 | = W. It was confirmed that the actual stretching direction (Ax-Cx) at the exit of the tenter was inclined at 45 ° away from the center line 22 of the film to be sent to the next process. No wrinkles or deformations of the film were observed at the exit of the tenter.

The film was a saponified cellulose triacetate film (FUJITACK, Fuji Photo Film Co., Ltd., manufactured, retardation value) using 3% aqueous PVA (PVA-117H, manufactured by Kuraray Co., Ltd.) as an adhesive. 3.0 nm), and dried at 80 ° C., to obtain a polarizing plate having an effective width of 650 nm.

It was confirmed that the obtained polarizing plate had an absorption axis inclined at 45 ° spaced from its longitudinal direction. It was confirmed that the transmittance at 550 nm and the degree of polarization of the obtained polarizing plate were 43.7% and 99.97%, respectively. As shown in FIG. 5, the film was cut to a size of 310 × 233 nm to successfully obtain a polarizing plate having an absorption axis tilted at 45 ° with an area efficiency of 91.5%.

Next, as shown in FIG. 8, the retarder 96 prepared in Example 1 was laminated on one surface of the iodine-containing linear polarizing film 91 prepared above, and the anti-glare was prevented on the opposite surface. Another circular polarizing plate 92 was prepared by laminating an antireflection film. Other polarizing plates 93 to 95 were similarly manufactured except that the retarders prepared in Comparative Examples 1 to 3 were used in place of the retarder 96, respectively. In all the manufacturing processes of such a circular polarizing plate, the linear polarizing film and the retarder were laminated | stacked on each other, and each longitudinal direction was confirmed.

Each of the circularly polarizing plates 92 to 95 thus obtained was irradiated with light (450 nm, 550 nm, and 650 nm) from the saponified anti-glare antireflection film 97 side, and the retardation value of the transmitted light (retardation value: Re) was measured at any 20 points within an area of 650 nm wide and 1,000 nm long, with the range of change being indicated by the maximum and minimum values. The results are shown in Table 2.

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

Example 3: Fabrication of Reflective Liquid Crystal Display Device

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

The visual evaluation of the reflective liquid crystal display device thus obtained found that the faded gray was displayed in any mode among white display, black display, and midtone display without showing color.

Next, the contrast ratio according to the reflection luminance was measured using a viewing angle measuring instrument (EZcontrast160D, manufactured by Eldim SA, France). The 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 producing a retarder comprising two or more optically anisotropic layers each formed of aligned liquid crystal molecules with little or no defect in alignment.

Claims (6)

A transparent substrate, and two or more optically anisotropic layers each formed in a composition comprising a liquid crystal compound on or on one surface of the transparent substrate, A process for manufacturing a rolled retarder comprising forming an alignment layer on a surface of the transparent substrate having a longitudinal direction under continuous feeding along a longitudinal direction, the method comprising: (a) rubbing the surface of the alignment layer or the surface of a layer formed on or over the alignment 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 steps (a) to (c) one or more times while keeping the substrate unrolled; And (e) rolling the transparent substrate having the two optically anisotropic layers thereon. The method of claim 1, Wherein at least one of the steps (a) is rubbing a surface of the optically anisotropic layer comprising a modified polyvinyl alcohol having a hydrocarbon group containing 9 or less carbon atoms. The method of claim 2, The modified polyvinyl alcohol, Formula (PX):-(VAl) _x- (HyD) _y- (VAc) _z- Is indicated by Wherein "Val" is a vinyl alcohol repeating unit, "HyD" is a repeating unit having a hydrocarbon group of 9 carbon atoms or less, and "VAc" is a vinyl acetate repeating unit; wherein 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 any one of claims 1 to 3, And wherein said liquid crystal compound used in at least one of said steps (b) is a rod-like liquid crystal compound having a polymerizable group. The method according to any one of claims 1 to 3, And wherein said liquid crystal compound used in at least one of said steps (b) is a discotic liquid crystal compound having a polymerizable group. The retarder manufactured by the process as described in any one of Claims 1-5.