JP4335714B2 - Retardation plate manufacturing method, retardation plate, and image display device - Google Patents

Description

  The present invention relates to a method for producing a retardation plate using a liquid crystalline polymer, a retardation plate, and an image display device using the retardation plate.

  A liquid crystal display device usually includes a liquid crystal cell, a polarizing element, and a retardation plate. In a transmissive liquid crystal display device, usually, two polarizing elements are arranged on both sides of a liquid crystal cell, and one or two retardation plates are arranged between the liquid crystal cell and the polarizing element. In a reflection type liquid crystal display device, usually, a reflection plate, a liquid crystal cell, a single phase difference plate, and a single polarizing element are arranged in this order. A liquid crystal cell usually consists of a rod-like liquid crystalline molecular layer, two substrates for encapsulating it, an electrode layer for applying voltage to the rod-like liquid crystalline molecules, and an alignment film layer for controlling the orientation of the rod-like liquid crystalline molecules. Become. The liquid crystal cell is different in the alignment state of rod-like liquid crystal molecules. As for the transmissive type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystals), OCB (Optically Compensatory B) Twisted Nematic), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and reflection type are TN, HAN (Hybrid Aligned Nematic), and GH (Guest).

  The phase difference plate is used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As the retardation film, a stretched birefringent polymer film has been conventionally used. It has been proposed to use a retardation plate having an optically anisotropic layer formed of liquid crystalline molecules on a transparent support instead of the retardation plate made of a stretched birefringent film. Since liquid crystal molecules have various alignment forms, it has become possible to realize optical properties that cannot be obtained with conventional stretched birefringent polymer films by using liquid crystal molecules. When liquid crystalline molecules are used, various retardation plates having optical properties corresponding to various display modes of the liquid crystal cell can be manufactured. In fact, liquid crystal molecules corresponding to various display modes are used. A phase difference plate has already been proposed.

  Incidentally, rod-like liquid crystal molecules or discotic liquid crystal molecules are generally used for the production of such a retardation plate. Further, liquid crystal molecules include not only low molecules but also various polymers, and it is known that liquid crystal polymers can take various alignment forms as well as low molecules (for example, patent documents). 1). Usually, a retardation plate produced using liquid crystalline molecules is provided with an alignment film for regulating the orientation of liquid crystalline molecules on a transparent support, and a composition containing liquid crystalline molecules on the alignment film. Is applied to form an optically anisotropic layer. The alignment film is usually formed by applying a coating solution containing a polymer and rubbing the surface of the formed coating layer. Thus, conventionally, when producing a retardation plate, in order to form one optically anisotropic layer, both the step of forming an alignment film and the step of forming an optically anisotropic layer are applied. It was necessary.

  In addition, a liquid crystal alignment control method has been proposed, in which an alignment film made of a liquid crystal polymer film is formed, and the liquid crystal polymer film is heated at a predetermined temperature (see Patent Document 2). . However, with this method, the liquid crystalline polymer can be oriented only so that the slow axis is parallel to the rubbing direction, and cannot be oriented so that it is perpendicular to the rubbing direction. It was. Patent Document 2 describes that a liquid crystalline polymer film can be used as a liquid crystal alignment film for a liquid crystal cell, but there is no mention of using it as an optically anisotropic layer of a retardation plate. . Further, a rod-like liquid crystal is usually used for the liquid crystal cell, and therefore, Patent Document 2 describes nothing about using the liquid crystalline polymer film as an alignment film of a discotic liquid crystalline compound. There is no suggestion.

JP 2002-66433 A Japanese Patent Laid-Open No. 5-181141

  An object of the present invention is to provide a simple method for producing a retardation plate. Another object of the present invention is to provide a retardation plate having an optically anisotropic layer formed from discotic liquid crystalline molecules, which can be easily produced. It is another object of the present invention to provide a retardation plate that can be easily manufactured and contributes to an improvement in display characteristics of an image display apparatus, and an image display apparatus with improved display characteristics.

Means for solving the above problems are as follows.
[1] A method for producing a retardation plate having one or more optically anisotropic layers, wherein an optically anisotropic material is prepared by aligning a liquid crystalline polymer having at least one crosslinkable group without using an alignment film. A method for producing a retardation plate, including forming a functional layer.
[2] A step of aligning the surface of the layer formed of the liquid crystalline polymer, a step of aligning the liquid crystalline polymer by phase transition to a liquid crystal phase, and fixing the alignment of the liquid crystal phase. And a step of forming an optically anisotropic layer.
[3] The method for producing a retardation plate according to [2], wherein the orientation axis is formed by a rubbing process.
[4] A composition containing at least a discotic liquid crystalline molecule is applied to the surface of the optically anisotropic layer, the discotic liquid crystalline molecule is aligned on the optically anisotropic layer, and the discotic The method for producing a retardation plate according to [2] or [3], further comprising a step of fixing liquid crystalline molecules in the alignment state and further forming an optically anisotropic layer.
[5] Any one of [1] to [4], in which the liquid crystalline polymer is aligned so that the slow axis of the optically anisotropic layer is substantially perpendicular to the longitudinal direction of the transparent support. A method for producing a retardation plate.
[6] The liquid crystalline polymer has a rod-like liquid crystalline skeleton in a side chain, a hydrogen bonding group, and an aromatic ring in a linking group portion connecting the side chain and the main chain. 5] The method for producing a retardation plate according to any one of 5).

[7] A retardation plate produced by the method for producing a retardation plate according to any one of [1] to [6].
[8] A liquid crystalline polymer layer containing an aligned and fixed liquid crystalline polymer on a transparent support, and is laminated in contact with the surface of the liquid crystalline polymer layer. A retardation plate having an optically anisotropic layer containing a fixed discotic liquid crystal molecule.
[9] The position of [8], wherein the liquid crystalline polymer has a rod-like liquid crystalline skeleton in a side chain, a hydrogen bonding group, and an aromatic ring in a linking group portion connecting the side chain and the main chain. Phase difference plate.
[10] The retardation plate of [8] or [9], wherein a slow axis of the optically anisotropic layer is substantially parallel to a slow axis of the liquid crystalline polymer layer.
[11] The retardation plate according to any one of [8] to [10], wherein in the optically anisotropic layer, discotic liquid crystalline molecules are aligned substantially perpendicular to the surface of the transparent support.
[12] The phase difference plate according to any one of [8] to [11], wherein the thickness of the liquid crystalline polymer layer is 1/10 or less of the thickness of the optically anisotropic layer.
[13] An image display device comprising a liquid crystal cell and at least one retardation plate of any one of [7] to [12], wherein the retardation plate is an optical compensation sheet for the liquid crystal cell.
[14] The image display device according to [13], wherein the liquid crystal cell is an IPS (In-Plane Switching) mode liquid crystal cell.

In the present specification, “vertical alignment” for the discotic liquid crystalline molecules means a state in which the discotic liquid crystalline molecules are aligned with their disk surfaces substantially perpendicular to the layer plane. In addition, “substantially vertical” and “substantially orthogonal” are both 90 ° ±
“Substantially parallel” is used to include a width of about 5 °, and “substantially parallel” is used to include a width of about 0 ° ± 5 °. Further, in this specification, the “slow axis” of the optically anisotropic layer means the direction having the highest refractive index in the layer plane.

  In the present invention, by using a liquid crystalline polymer, a method for producing a retardation plate, which conventionally requires at least two steps (an alignment film forming step and an optically anisotropic layer forming step), is produced in one step. It is possible. As a result, the manufacturing process of the retardation plate can be simplified. Furthermore, when an optically anisotropic layer is formed using a liquid crystalline polymer having a specific structure, the optically anisotropic layer also functions as an alignment film. The disc surface of the discotic liquid crystal molecules and the rubbing direction can be easily orientated substantially non-uniformly and substantially perpendicular to the plane. In addition, the retardation plate having an optically anisotropic layer containing a liquid crystalline compound fixed in the alignment state contributes to improvement of display characteristics of the image display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
First, the manufacturing method of the phase difference plate of this invention is demonstrated using drawing. FIG. 1 is a view schematically showing an example of a method for producing a retardation plate of the present invention. First, a transparent support 11 is prepared (FIG. 1 (a)), and then a composition such as a coating liquid containing a liquid crystalline polymer is applied directly to the surface of the transparent support to improve the liquid crystallinity. A molecular layer 12 is formed (FIG. 1B). When an alignment process such as a rubbing axis is formed on the surface 12a of the liquid crystalline polymer layer 12 to form an alignment axis such as a rubbing axis, the liquid crystalline polymer can be aligned in a direction determined by the alignment axis. Thereafter, for example, by heating to a temperature at which the liquid crystalline polymer transitions to the liquid crystal phase and causing the liquid crystalline polymer to transition to the liquid crystal phase, the liquid crystalline polymer is aligned in the direction determined by the alignment axis. Next, the liquid crystalline polymer is fixed in the alignment state to form an optically anisotropic layer 12 ′ (FIG. 1 (c)). Through the steps (a) to (c), the first retardation plate 13 having the optically anisotropic layer 12 ′ on the transparent support is obtained. Further, by forming an optically anisotropic layer 14 formed of a liquid crystalline molecule, preferably a discotic liquid crystalline molecule, on the surface 12a of the optically anisotropic layer 12 ′ of the retardation plate 13, the second A phase difference plate is obtained (FIG. 1 (d)). For example, when a coating liquid containing liquid crystalline molecules is applied to the surface of the optically anisotropic layer 12 ′, the long axis of the liquid crystalline compound molecules is the length of the liquid crystalline polymer of the optically anisotropic layer 12 ′. The orientation tends to be parallel to the axis (however, when the side chain includes a liquid crystal skeleton). By fixing in the alignment state, the optically anisotropic layer 14 can be formed without using an alignment film separately.

The alignment state of the liquid crystalline polymer and the discotic liquid crystalline molecule in the manufacturing process will be described with reference to FIGS.
FIG. 2 is a diagram schematically showing an example of an alignment state when a liquid crystalline polymer 02 having a main chain 04 and a side chain 03 having a rod-like liquid crystalline skeleton is used. For example, a liquid crystalline polymer layer is formed on the transparent support 11 and the surface thereof is rubbed to form a rubbing axis 16 (alignment axis) parallel to the longitudinal direction. When transitioned to a phase, the liquid crystalline polymer 02 is oriented with its main chain 04 parallel to the rubbing axis 16. The side chain 03 including the rod-like liquid crystalline skeleton in the liquid crystalline polymer may be arranged in parallel to the rubbing axis 16 as shown in FIG. 2A, or as shown in FIG. In some cases, the rubbing shaft 16 is arranged vertically. Which alignment state is taken is determined by the structure of the liquid crystalline polymer.

  FIG. 3 is a diagram schematically showing an example of the alignment state when the discotic liquid crystalline molecules are aligned on the surface of each layer of FIGS. 2 (a) and 2 (b). As described above, when a coating liquid containing a low-molecular liquid crystalline compound is applied on the layer 12 ′ made of the aligned liquid crystalline polymer, the molecules of the liquid crystalline compound have their long axis aligned with the liquid crystalline polymer. There is a tendency to align with the long axis of the liquid crystal skeleton. For example, when the discotic liquid crystal molecules 05 are aligned on the surface of the layer 12 ′ made of the liquid crystal polymer in the alignment state shown in FIG. 2A, the disk surface is horizontal to the rubbing axis 16. And oriented perpendicular to the layer plane. On the other hand, when the discotic liquid crystalline molecules 05 are aligned on the surface of the layer 12 ′ made of the liquid crystalline polymer in the alignment state shown in FIG. 2B, the disc surface is perpendicular to the rubbing axis 16. And perpendicular to the layer plane.

  A phase difference plate having an optically anisotropic layer in which discotic liquid crystal compound molecules are oriented substantially perpendicularly to the layer plane is used for an image display device, particularly an IPS mode image display device. It is useful for optical compensation and contributes to improvement of display characteristics. In particular, conventionally, it has been difficult to align the discotic liquid crystal molecules shown in FIG. 3B with the disc surface and the rubbing axis orthogonal to each other and perpendicular to the alignment film plane without unevenness. However, by utilizing the method for producing a retardation plate of the present invention, the discotic liquid crystal molecules can be stably aligned in such a state. Furthermore, since the tilt angle of the disk surface with respect to the layer plane can be adjusted by combining with an orientation control agent described later, a retardation plate having desired optical characteristics useful for optical compensation of liquid crystal cells in various modes. Can be easily manufactured.

  Further, if the production method of the present invention is used, as shown in FIG. 4, an optically anisotropic layer composed of a liquid crystalline polymer continuously on a long support, and discotic liquid crystalline molecules In the case of forming an optically anisotropic layer comprising the above, the liquid crystalline polymer and the discotic liquid crystalline molecule can be uniformly aligned in the above-mentioned various alignment states without unevenness. It contributes to the improvement.

  In the above example, the rubbing process has been described as an example of the alignment process applied to the liquid crystalline polymer layer, but other alignment processes can be used. For example, when the alignment treatment is performed by applying an electric field or a magnetic field, or by light irradiation, the direction in which the energy is supplied becomes the alignment axis that determines the alignment of the liquid crystalline polymer. In the above example, an example of a polymer having a liquid crystal skeleton in the side chain is given as the liquid crystalline polymer. However, the present invention is not limited to this, and the liquid crystal polymer may include a liquid crystal skeleton in the main chain. Good.

  In the present specification, a retardation plate (13 in FIG. 1) having a polymer liquid crystal layer formed of a transparent support and a liquid crystalline polymer is referred to as a “first retardation plate”, A retardation plate (15 in FIG. 1) having an optically anisotropic layer formed of liquid crystalline molecules on the retardation plate is referred to as a “second retardation plate”.

  Hereinafter, materials such as a liquid crystalline polymer that can be used in the production of the first retardation plate of the present invention and the production method of the first retardation plate will be sequentially described. Next, materials such as a low-molecular liquid crystal compound and the second retardation plate, which are used for producing an optically anisotropic layer formed on the first retardation plate, will be described.

1. 1. Method for producing first retardation plate using liquid crystalline polymer 1-1. Liquid Crystalline Polymer The liquid crystalline polymer that can be used in the present invention has a skeleton exhibiting at least one liquid crystallinity in the side chain or main chain of the structural unit forming the polymer. The skeleton exhibiting liquid crystallinity may be a rod-like liquid crystalline skeleton or a discotic liquid crystalline skeleton, but preferably contains a rod-like liquid crystalline skeleton.

(1). Structural units containing a liquid crystalline skeleton Among the liquid crystalline skeletons, the rod-like liquid crystalline skeleton includes azomethine skeleton, azoxy skeleton, cyanobiphenyl skeleton, cyanophenyl ester skeleton, benzoic acid ester skeleton, cyclohexanecarboxylic acid phenyl ester skeleton, and cyanophenylcyclohexane. A skeleton, a cyano-substituted phenylpyrimidine skeleton, an alkoxy-substituted phenylpyrimidine skeleton, a phenyldioxane skeleton, a tolan skeleton and an alkenylcyclohexylbenzonitrile skeleton are preferably used. Further, examples of the discotic liquid crystalline skeleton include a triphenylene skeleton and a triazine skeleton. Further, a polymerizable group may be substituted on these liquid crystalline skeletons.

More preferably, the structural unit of the liquid crystal polymer having a liquid crystalline skeleton is a structural unit in which the above skeleton is substituted on the side chain, and the main chain skeleton in that case is a hydrocarbon polymer (for example, polyethylene, polypropylene, Polybutadiene, polystyrene, polymaleimide, polyacrylic acid, polyacrylate, polyacrylamide, polyacrylanilide, etc.), polyether, polyester, polycarbonate, polyamide, polyamic acid, polyimide, polyurethane, and polyureido. Is preferred.
More preferably, the main chain skeleton of the liquid crystalline polymer is a hydrocarbon polymer, polycarbonate, polyamic acid, and polyimide.

  Preferred specific examples of the structural unit containing a liquid crystalline skeleton contained in the liquid crystalline polymer used in the present invention are shown below.

(2) Constituent unit not containing liquid crystalline skeleton The liquid crystalline polymer of the present invention may be a homopolymer consisting of only one of the constituent units having the liquid crystalline skeleton, or two or more of these constituent units, or It may be a copolymer of one or more of these structural units and one or more of the structural units not containing a liquid crystalline skeleton. The constitutional unit not containing a liquid crystalline skeleton is not particularly limited, but preferred copolymer constitutional units include, for example, hydrocarbon polymers (eg, polyethylene, polypropylene, polystyrene, polymaleimide, polyacrylic acid, polyacrylic). Acid esters, polyacrylamides, polyacrylanilides, etc.), polyethers, polyesters, polycarbonates, polyamides, polyamic acids, polyimides, polyurethanes, and polyureides, which may be the same as the structural unit containing a liquid crystalline skeleton. preferable.

  Specific examples of structural units that do not contain a liquid crystalline skeleton are shown below, but the present invention is not limited to the following specific examples.

  When the liquid crystalline polymer of the present invention is a copolymer of the structural unit containing the liquid crystalline skeleton and the structural unit not containing, the content of the structural unit containing the liquid crystalline skeleton is 10% by mass or more and 100%. Less than mass% is preferable, More preferably, it is 30 mass%-90 mass%, More preferably, it is 50 mass%-80 mass%.

(3) Structural Unit Containing Crosslinkable Group It is preferable that the liquid crystalline polymer used in the present invention further includes a structural unit having a crosslinkable group. By using a liquid crystalline polymer having a crosslinkable group, it becomes easy to fix the liquid crystalline polymer layer after alignment, and details will be given below. Also in the case of forming an optically anisotropic layer of a compound, it is often preferable that adhesion between the liquid crystalline polymer layer and the optically anisotropic layer can be improved. The crosslinkable group contained in the liquid crystalline polymer can be used without particular limitation, such as addition, condensation, and substitution reactive groups. On the other hand, the optically anisotropic layer formed on the liquid crystalline polymer layer uses a liquid crystal material having an ethylenically unsaturated group such as an acryloyl group or a methacryloyl group, and in the presence of a radical photopolymerization initiator. The liquid crystalline polymer layer that also functions as an alignment film for the optically anisotropic layer is preferably formed by being fixed by irradiation. It preferably consists of molecules. As a preferred example of a reaction that can be cross-linked by UV irradiation, a ring-opening polymerization reaction of a heterocyclic compound such as an epoxy ring or an oxetane ring that uses a compound that generates a cation by UV irradiation, and a compound that generates a radical by UV irradiation And a radical polymerization reaction of a compound having an ethylenically unsaturated group. Among these, the most preferable crosslinkable group contained in the polymer is an ethylenically unsaturated group (for example, acryloyl group, methacryloyl group, styryl group, etc.). Moreover, there is no restriction | limiting in particular as a method of introduce | transducing the crosslinkable group into the said polymer for alignment films.

  Although the preferable specific example of the structural unit containing a crosslinkable group is shown below, this invention is not limited at all by the following specific examples.

  The liquid crystalline polymer used in the present invention can be produced by various methods such as addition, condensation, and substitution reaction. In order to include a structural unit having a crosslinkable group in the liquid crystalline polymer, (a) a corresponding monomer (that is, a monomer having a substituent that becomes a crosslinkable group) is polymerized to directly form an ethylenically unsaturated group. A method of introducing; or (b) a method of introducing an ethylenically unsaturated group into a polymer obtained by polymerizing a monomer having an arbitrary functional group by a polymer reaction. The polymer reaction includes the following: I) For example, after a polymer containing a functional group obtained by precuring an ethylenically unsaturated group that removes hydrochloric acid from a 2-chloroethyl group is generated, functional group conversion (elimination reaction, oxidation) A method of deriving an ethylenically unsaturated group by a reaction, a reduction reaction, a deprotection reaction, etc.); and II) after forming a polymer containing any functional group, a bond formation reaction proceeds with the functional group in the polymer. And a method of reacting a compound having both a functional group capable of forming a covalent bond and an ethylenically unsaturated group (hereinafter referred to as “reactive monomer”). Further, the polymer may be synthesized by combining the methods I) and II). The bond formation reaction referred to here can be used without particular limitation as long as it is a reaction that forms a covalent bond in the bond formation reaction generally used in the field of organic synthesis. On the other hand, the ethylenically unsaturated group contained in the polymer may be thermally polymerized and gelled during the reaction, so that the reaction proceeds at the lowest possible temperature (preferably 60 ° C. or less, particularly preferably room temperature or less). Is preferred. A catalyst may be used for the purpose of promoting the progress of the reaction, and a polymerization inhibitor may be used for the purpose of suppressing gelation.

  The liquid crystalline polymer of the present invention preferably contains 0.1% by mass to 60% by mass, more preferably 0.3% by mass to 50% by mass of a structural unit having a crosslinkable group, and 0.5% More preferably, the content is from 40% by mass to 40% by mass.

(4) Physical properties of liquid crystalline polymer The preferred molecular weight range of the liquid crystalline polymer is 1,000 to 1,000,000, more preferably 2000 to 200,000 in terms of weight average molecular weight. Most preferably, it is 3000-100,000.

  The temperature range showing the liquid crystal phase of the liquid crystalline polymer is preferably 20 ° C. to 300 ° C., more preferably 50 ° C. to 250 ° C., and still more preferably 80 ° C. to 200 ° C. It is. However, unlike a low-molecular liquid crystal compound, a liquid crystalline polymer tends to spread in the temperature lowering process once the layer transitions to the liquid crystal layer during the temperature rising process, preferably at room temperature (15 ° C. to 25 ° C.). It is preferable that the liquid crystal state is maintained even when the pressure is returned to.

(5) Specific Examples of Liquid Crystalline Polymers Preferred examples of the liquid crystalline polymer used in the present invention are shown in Table 1 below, but the present invention is not limited to the following specific examples. The structural unit containing a liquid crystalline skeleton, the structural unit not containing a liquid crystalline skeleton, and the structural unit containing a crosslinkable substituent are indicated by the numbers of the specific examples described above, and the copolymer composition ratio is added in mass%. did.

  The liquid crystalline polymer has a rod-like liquid crystalline skeleton in the side chain, a hydrogen bonding group (for example, —COOH, etc.), and an aromatic ring in a linking group portion connecting the side chain and the main chain. Since the liquid crystalline polymer tends to be aligned in the state schematically shown in FIG. 2 (b), the discotic liquid crystalline molecule is schematically shown in FIG. 3 (b) on the surface. Can be stably oriented in the state shown in FIG.

(6) Synthesis Method of Liquid Crystalline Polymer The synthesis of the liquid crystal polymer of the present invention can be easily produced by applying a known method. Specific synthesis examples of the liquid crystalline polymer that can be used in the present invention are described below, but the synthesis examples of the liquid crystalline polymer that can be used in the present invention are not limited thereto.

Synthesis Example of (AL-1 and AL-2) Mesylate obtained by methanesulfonylation of hydroxybutyl acrylate and I-1 easily obtained from cyanobiphenyl and acrylic acid were mixed at a mass ratio of 8: 2, and methyl ethyl ketone was obtained. A solution was made. To a 1000 mL three-necked flask was charged 2-butanone (250 ml) and heated to 60 ° C. while flowing nitrogen at a flow rate of 35 ml / min, and the initiator (AIBN: 2,2′-azobisisobutyronitrile, 0 .35 g) of 2-butanone (10 ml) was added. Immediately thereafter, a methyl ethyl ketone solution of the monomer (total molar amount: 0.25 mol) was added dropwise over 2 hours. After completion of the dropwise addition, a 2-butanone (10 ml) solution of an initiator (AIBN: 2,2′-azobisisobutyronitrile, 0.45 g) was added again, and the mixture was reacted at the same temperature for 4 hours. Thereafter, the reaction system was returned to room temperature, and then slowly poured into stirred hexane / ethyl acetate (2/1: 2.5 L), and the precipitated polymer was taken out by suction filtration and further dried. The obtained polymer residue was 28 g. By drying this polymer, 20 g of a liquid crystal alignment film (AL-1) used in the present invention was obtained. ¹ H-N. M.M. From R, it was confirmed that the repeating unit (I-1) and (II-1) of the polymer (AL-1) was composed of a composition having a molar ratio of 80/20 in terms of mass ratio.

  Furthermore, 5 mol% of glycidyl methacrylate was reacted in N, N-dimethylacetamide with respect to the obtained AL-1, and the reaction solution was poured into water and then dried to obtain AL-2. The ratio of I-1, II-1, and A-16 constituting AL-2 was confirmed by 1H-NMR.

1-2. Support The retardation plate of the present invention has a support. The support is not necessarily the same as the support used at the time of production, and after the layer made of the liquid crystalline polymer is produced, it may be transferred from the temporary support used at the production to another support. . It is preferable to use a polymer film that is transparent and has small optical anisotropy and small wavelength dispersion as the support. Here, that the support is transparent means that the light transmittance is 80% or more. Specifically, the small chromatic dispersion means that the ratio of Re400 / Re700 is preferably less than 1.2. Specifically, the small optical anisotropy means that in-plane retardation (Re) is preferably 20 nm or less, and more preferably 10 nm or less. The transparent support preferably has a roll-like long rolled sheet as shown in FIG. 4 or a rectangular sheet-like shape, and the long transparent support is used for liquid crystallinity. It is preferable to laminate a polymer layer, and further an optically anisotropic layer thereon, and then cut it into a required size. Examples of the polymer include cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate and polymethacrylate. Cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. The polymer film is preferably formed by a solvent cast method. The thickness of the transparent support is preferably 20 to 500 μm, and more preferably 50 to 200 μm. In order to improve adhesion between the transparent support and the liquid crystalline polymer layer provided on it, surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) is performed on the transparent support. May be. An adhesive layer (undercoat layer) may be provided on the transparent support.

1-3. Formation of Liquid Crystalline Polymer Layer The liquid crystalline polymer layer is prepared by applying a coating solution prepared by dissolving the liquid crystalline polymer in a solvent to the surface of the transparent support, and applying the coating solution at 25 ° C to 13 ° C. It can be produced by removing the solvent contained therein by drying. Moreover, although it can also form by vapor deposition if possible, formation by application | coating is more preferable. When the optically anisotropic layer is formed thereon, the thickness of the liquid crystalline polymer layer thus formed is preferably 0.01 to 5 μm, and 0.05 to 2 μm. Is more preferable. On the other hand, when the layer made of a liquid crystalline polymer is provided with sufficient optical compensation capability and the first retardation plate is used as an optical compensation sheet of an image display device, the thickness of the layer made of the liquid crystalline polymer is: It is preferable that it is 0.1-20 micrometers, and it is more preferable that it is 0.5-10 micrometers.

  Examples of the solvent used for the preparation of the coating liquid for forming the liquid crystalline polymer layer include water, alcohols (for example, methanol, ethanol, isopropanol), and amides (for example, N, N-dimethylformamide). , Acetonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and the like, preferably water, alcohols and a mixed solvent thereof. The concentration of the alignment film polymer in the coating solution is preferably 0.1% by mass to 40% by mass, more preferably 0.5% by mass to 20% by mass, and 2% by mass to 10% by mass. % Is more preferable. The viscosity of the coating solution is preferably 0.1 cp to 100 cp, and more preferably 0.5 cp to 50 cp.

  In addition to the liquid crystalline polymer, additives may be appropriately added to the coating solution. For example, when the liquid crystalline polymer is difficult to dissolve in a water-soluble solvent, a basic compound (eg, sodium hydroxide, lithium hydroxide, triethylamine, etc.) or an acidic compound (eg, hydrochloric acid, acetic acid, succinic acid, etc.) ) May be added to promote dissolution.

1-4. Alignment and immobilization of liquid crystalline polymer layer (1) Providing orientation The liquid crystalline polymer layer formed by the above method has an alignment surface such as rubbing treatment in order to align the liquid crystalline polymer. It is preferable that an alignment axis for aligning the liquid crystal is formed by the treatment. The rubbing treatment can be performed by rubbing the surface of the liquid crystalline polymer layer several times with paper or cloth in a certain direction (usually the longitudinal direction). As a method other than the rubbing treatment, liquid crystal alignment can be imparted by applying an electric field, applying a magnetic field, or irradiating light. As a method for imparting liquid crystal orientation, rubbing treatment is particularly preferable.

(2) Alignment and Immobilization of Liquid Crystalline Polymer Next, after forming an alignment axis on the surface of the liquid crystalline polymer layer by an alignment treatment, the liquid crystalline polymer is aligned. For example, the alignment can be performed by raising the temperature to a temperature range in which the liquid crystalline polymer layer exhibits liquid crystallinity. Thereafter, the optically anisotropic layer can be formed by fixing the alignment state. When the liquid crystalline polymer contains a structural unit having a crosslinkable group, it is preferable to fix the alignment by light irradiation or the like after aligning the entire layer. Further, even a liquid crystalline polymer containing no crosslinkable group may be immobilized while maintaining the alignment state once formed even when the temperature is lowered to room temperature. In this manner, an optically anisotropic layer made of a liquid crystalline polymer can be formed without using an alignment film.

The first retardation plate having a support and an optically anisotropic layer made of a liquid crystalline polymer produced as described above can be used for various applications including an optical compensation sheet. Furthermore, another optically anisotropic layer can be formed on the first retardation plate to form the second retardation plate, and can be used for various applications.
2. Second retardation plate On the layer of the first retardation plate, which is composed of a liquid crystal polymer whose orientation is fixed (hereinafter sometimes referred to as a “first optical anisotropic layer”), it is further lowered. An optically anisotropic layer formed of a molecular liquid crystal compound (hereinafter sometimes referred to as “second optically anisotropic layer”) may be formed. As described above, when a low-molecular liquid crystal compound is applied to the surface of the first optical anisotropic layer, the molecules of the liquid crystalline compound are determined by the orientation of the liquid crystalline polymer in the optical anisotropic layer. Oriented in the specified direction. By fixing the liquid crystal molecules in the alignment state and forming the optically anisotropic layer, the second retardation plate can be produced.
Hereinafter, a discotic liquid crystalline compound necessary for forming the second retardation plate and a method for producing the retardation plate will be described in detail.

2-1. Second optically anisotropic layer The second optically anisotropic layer formed on the first optically anisotropic layer is composed of a liquid crystalline compound, preferably a discotic liquid crystalline compound, and optionally polymerizable. A coating liquid containing an initiator and other additives is applied to the surface of the first optically anisotropic layer, preferably the alignment treatment surface, and the liquid crystal compound molecules are aligned and fixed. Can do. After aligning and fixing the molecules of the liquid crystal compound, the support may be peeled off.
Hereinafter, the method for forming the second optically anisotropic layer and the discotic liquid crystalline compound used therein will be described in detail.

(1) Forming method The optically anisotropic layer is formed on the support as described above, and the orientation-fixed coating solution prepared by dissolving in a solvent capable of dissolving the discotic liquid crystalline compound. In addition, it can be produced by coating on the liquid crystalline polymer layer of the present invention. Further, if possible, formation by vapor deposition may be used, but formation by coating is preferably used. Examples of the coating method include known coating methods such as curtain coating, dip coating, spin coating, printing coating, spray coating, slot coating, roll coating, slide coating, blade coating, gravure coating, and wire bar method. Next, the solvent used at 25 ° C. to 130 ° C. is dried, and at the same time, the liquid crystalline compound is oriented, and further fixed by ultraviolet irradiation or the like as required, thereby forming an optically anisotropic layer of the liquid crystalline compound. . It is preferable to use ultraviolet rays for light irradiation for polymerization. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer thus formed varies depending on the optimum retardation value depending on the application such as optical compensation, but is preferably 0.1 to 10 μm, preferably 0.5 to 5 μm. More preferably. The thickness ratio between the first optical anisotropic layer made of a liquid crystalline polymer and the second optical anisotropic layer made of a discotic liquid crystalline molecule is the first optical anisotropic layer. Is preferably ½ or less, more preferably 1/10 or less of the thickness of the second optically anisotropic layer. When the thickness ratio is within the above range, the optical characteristics of the second optically anisotropic layer are mainly reflected. Therefore, a liquid crystal cell mode (for example, IPS mode) in which a uniaxial retardation plate is particularly suitable as an optical compensation film. Preferred).

(2) Material used for forming optically anisotropic layer The material used for the new optically anisotropic layer necessary for the second retardation plate is mainly a liquid crystalline compound and an orientation for controlling the orientation. It consists of a control agent, additives such as a polymerization initiator for fixing the orientation, and a solvent capable of dissolving them. These details are described below.

(A) Liquid crystalline compound It is preferable to use a discotic liquid crystalline molecule as the liquid crystalline molecule. The liquid crystalline molecules are preferably substantially uniformly aligned, more preferably fixed in a substantially uniformly aligned state, and the liquid crystalline molecules are fixed by a polymerization reaction. Is most preferred.

  Discotic liquid crystalline molecules are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am.Chem.Soc., Vol.116, page 2655 (1994)). The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Accordingly, the discotic liquid crystalline molecule having a polymerizable group is preferably a compound represented by the following formula (III).

(III) D (-MP) _n
Where D is a discotic core; L is a divalent linking group; P is a polymerizable group; and n is an integer from 4 to 12. Examples of the discotic core (D) of the formula (III) are shown below. In each of the following examples, MP (or PM) means a combination of a divalent linking group (M) and a polymerizable group (P).

  In the formula (III), the divalent linking group (M) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. A divalent linking group is preferred. The divalent linking group (M) is a combination of at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -CO-, -NH-, -O-, and -S-. More preferably, it is a group. The divalent linking group (M) is most preferably a group obtained by combining at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -CO- and -O-. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms in the arylene group is preferably 6-10. The alkylene group, alkenylene group and arylene group may have a substituent (eg, alkyl group, halogen atom, cyano, alkoxy group, acyloxy group).

Examples of the divalent linking group (M) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (P). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group.
M1: -AL-CO-O-AL-
M2: -AL-CO-O-AL-O-
M3: -AL-CO-O-AL-O-AL-
M4: -AL-CO-O-AL-O-CO-
M5: -CO-AR-O-AL-
M6: -CO-AR-O-AL-O-
M7: -CO-AR-O-AL-O-CO-
M8: -CO-NH-AL-
M9: -NH-AL-O-
M10: —NH—AL—O—CO—

M11: -O-AL-
M12: -O-AL-O-
M13: -O-AL-O-CO-
M14: -O-AL-O-CO-NH-AL-
M15: -O-AL-S-AL-
M16: -O-CO-AL-AR-O-AL-O-CO-
M17: -O-CO-AR-O-AL-CO-
M18: -O-CO-AR-O-AL-O-CO-
M19: -O-CO-AR-O-AL-O-AL-O-CO-
M20: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
M21: -S-AL-
M22: -S-AL-O-
M23: -S-AL-O-CO-
M24: -S-AL-S-AL-
M25: -S-AR-AL-

  The polymerizable group (P) of the formula (III) is determined according to the type of polymerization reaction. Examples of the polymerizable group (P) are shown below.

  The polymerizable group (P) is preferably an unsaturated polymerizable group (P1, P2, P3, P7, P8, P15, P16, P17) or an epoxy group (P6, P18). More preferably, it is most preferably an ethylenically unsaturated polymerizable group (P1, P7, P8, P15, P16, P17). In formula (II), n is an integer of 4-12. A specific number is determined according to the type of discotic core (D). In addition, although the combination of several M and P may differ, it is preferable that it is the same. Two or more kinds of discotic liquid crystalline molecules (for example, a molecule having an asymmetric carbon atom in a divalent linking group and a molecule not having it) may be used in combination.

  Examples of the polymerizable liquid crystal compound represented by the formula (III) are shown below. The present invention is not limited to these.

(B) Coating liquid additive In the coating liquid for forming the second optically anisotropic layer, a photopolymerization initiator and a photosensitizer are used for fixing the aligned liquid crystal compound by photopolymerization. It is preferable to be added. In addition to the photopolymerization initiator, additives may be added as appropriate, and examples thereof include a plasticizer, a monomer, a surfactant, a cellulose ester, an alignment controller, and a chiral agent. Hereinafter, the photopolymerization initiator, the photosensitizer, and the alignment controller will be described in detail.

(B) -1 Photopolymerization initiator and photosensitizer It is preferable that the liquid crystalline molecule is fixed while maintaining the alignment state, and the fixing is carried out by a polymerizable group (general formula (III) introduced into the liquid crystalline molecule. It is preferable to carry out the polymerization reaction represented by P). The purpose of fixation is to develop and stabilize the desired optical anisotropy, and as a result, the liquid crystallinity may be lost. For that purpose, it is preferable to contain a polymerization initiator in the coating solution. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator, a photopolymerization reaction using a photopolymerization initiator, and EB curing using an electron beam. Of these, photopolymerization (photocuring) and EB curing are preferred. Examples of polymerization initiators that generate radicals by the action of light include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α -Combination of hydrocarbon-substituted aromatic acyloin compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), triarylimidazole dimer and p-aminophenyl ketone (Described in US Pat. No. 3,549,367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (described in US Pat. No. 4,221,970), acetophenone compounds Ben Preferred are zoin ether compounds, benzyl compounds, benzophenone compounds, thioxanthone compounds, and the like. Examples of the acetophenone compound include 2,2-diethoxyacetophenone, 2-hydroxymethyl-1-phenylpropan-1-one, 4′-isopropyl-2-hydroxy-2-methyl-propiophenone, 2-hydroxy -2-methyl-propiophenone, p-dimethylaminoacetone, p-tert-butyldichloroacetophenone, p-tert-butyltrichloroacetophenone, p-azidobenzalacetophenone and the like. Examples of the benzyl compound include benzyl, benzyl dimethyl ketal, benzyl-β-methoxyethyl acetal, 1-hydroxycyclohexyl phenyl ketone and the like. Examples of benzoin ether compounds include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-n-propyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, and benzoin isobutyl ether. Examples of the benzophenone compound include benzophenone, methyl o-benzoylbenzoate, Michler's ketone, 4,4′-bisdiethylaminobenzophenone, 4,4′-dichlorobenzophenone, and the like. Examples of the thioxanthone compound include thioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, and the like. Among such photosensitive radical polymerization initiators composed of aromatic ketones, acetophenone compounds and benzyl compounds are particularly preferable in terms of curing characteristics, storage stability, odor, and the like. The photosensitive radical polymerization initiators composed of these aromatic ketones can be used alone or in combination of two or more according to the desired performance. In addition to a polymerization initiator, a sensitizer may be used for the purpose of increasing sensitivity. Examples of the sensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, thioxanthone and the like.

  Multiple photopolymerization initiators may be combined, and the amount used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.05 to 5% by mass, based on the solid content of the coating solution. It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.

(B) -2 Orientation Control Agent In addition to the photopolymerization initiator, an additive may be appropriately added to the coating liquid for forming the second optically anisotropic layer. For example, a plasticizer, a monomer, a surfactant, a cellulose ester, an alignment controller, a chiral agent, and the like can be given. The orientation control agent will be described in detail below. The alignment control agent in the present invention is added to the liquid crystal compound coating solution, and after application, the liquid crystal compound layer is unevenly distributed on the surface of the liquid crystal compound layer, that is, on the air interface side. Represents a compound capable of controlling Depending on the structure of this alignment control agent, the liquid crystal compound can be aligned substantially vertically on the air interface side, or conversely horizontally aligned, but in the present invention, the discotic liquid crystal compound is aligned on the air interface side. Additives that are oriented substantially vertically are preferred. For example, in the case of a discotic liquid crystalline compound, a compound represented by the following general formula (V) described in JP-A No. 2000-344734 and the like can be mentioned.
General formula (V)
(Hb−) _m L (−Bu) _n
In the formula, Hb is a fluorine-substituted alkyl group having 1 to 40 carbon atoms, a fluorine-substituted aryl group having 6 to 40 carbon atoms, an alkyl group having 6 to 60 carbon atoms, and 1 to 60 carbon atoms. A hydrophobic group selected from the group consisting of alkyl-substituted oligosiloxanoxy groups, Bu is a group having an excluded volume effect containing at least two cyclic structures, L is a (m + n) -valent linking group, m and n are each independently an integer of 1 to 12.

  The alignment controller represented by the general formula (V) is preferably a low molecular alignment controller in which a trihydroxybenzene skeleton and a triazine skeleton are substituted with a fluorine alkyl group, a long-chain alkyl group, or an aryl group. Specific examples of the alignment control agent for vertically aligning the discotic liquid crystal on the air interface side include, for example, the following D-1 and the like, and D-2 and the like as the alignment control agent for horizontally aligning. Can be mentioned.

  In addition, the alignment controller may be a polymer compound as shown below. The polymer alignment control agent added may be a polymer that can be dissolved in the liquid crystal layer coating solution. An example of a preferred polymer alignment controller is shown below.

Polypropylene oxide polytetramethylene oxide poly-ε-caprolactone poly-ε-caprolactone diol poly-ε-caprolactone triol polyvinyl acetate polymelamine poly (ethylene adipate)
Poly (1,4-butylene adipate)
Poly (1,4-butylene glutarate)
Poly (1,2-butylene glycol)
Poly (1,4-butylene succinate)
Poly (1,4-butylene terephthalate)
polyethylene terephthalate)
Poly (2-methyl-1,3-propylene adipate)
Poly (2-methyl-1,3-propylene glutarate)
Poly (neopentyl glycol adipate)
Poly (neopentyl glycol sebacate)
Poly (1,3-propylene adipate)
Poly (1,3-propylene glutarate)
Polyvinyl butyral polyvinyl formal polyvinyl acetal polyvinyl propanal polyvinyl hexanal polyvinyl pyrrolidone polyacrylic acid ester polymethacrylic acid ester poly (3-hydroxybutyric acid)

  Further, a polymer containing a structural unit composed of a monomer having at least one fluorinated alkyl group is more preferably used. For example, the following polymer D-3 is preferably used.

  The addition amount of the alignment control agent is preferably 0.05% by mass to 10% by mass with respect to the liquid crystal compound in the liquid crystal composition to which the control agent is added. More preferably, it is 0.1 mass%-5 mass%.

(C) Coating solvent As a solvent used for preparing the coating liquid for forming the optically anisotropic layer, an organic solvent is preferable. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, toluene, hexane) alkyl halides (eg, Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, 2-butanone, methyl isobutyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane), and the like . Of these, alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

  The solid content concentration of the liquid crystal compound and other additives in the coating solution is preferably 0.1% by mass to 60% by mass, more preferably 0.5% by mass to 50% by mass, and 2% by mass to 40% by mass. % Is more preferable. The viscosity of the coating solution is preferably 0.01 cp to 100 cp, and more preferably 0.1 cp to 50 cp.

  The retardation plate of the present invention is used for various applications. It can be used as a polarizing plate by being laminated with an optical compensation sheet of a liquid crystal display device, a linearly polarizing film or a transparent protective film.

4). Polarizing plate It is preferable when a linear polarizing film or a transparent protective film is bonded to the retardation plate of the present invention to form a polarizing plate, and then used for an actual liquid crystal display element. Hereinafter, the polarizing film and the transparent protective film will be described.

(1) Polarizing film Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The transmission axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. When the discotic liquid crystalline compound is used for the optically anisotropic layer, the transmission axis of the polarizing film is arranged so as to be substantially parallel to the surface of the discotic liquid crystalline molecule on the alignment film side. . When a rod-like liquid crystalline compound is used, the transmission axis of the polarizing film is arranged so as to be substantially parallel to the long axis direction (slow axis) of the rod-like liquid crystalline molecule. Usually, it is preferable to bond to the support side of the retardation plate, but if necessary, it may be bonded to the optically anisotropic layer side.

(2) Transparent protective film It is preferable that a transparent polymer film is used as a transparent protective film on the optically anisotropic layer side of the retardation plate. That the protective film is transparent means that the light transmittance is 80% or more. As the transparent protective film, generally a cellulose ester film, preferably a triacetyl cellulose film is used. The cellulose ester film is preferably formed by a solvent cast method. The thickness of the transparent protective film is preferably 20 to 500 μm, and more preferably 50 to 200 μm.

5. Liquid Crystal Display Device The retardation plate of the present invention can be used for a liquid crystal display device having liquid crystal cells of various display modes. As described above, the retardation plate of the present invention is useful as an optical compensation sheet that contributes to improving the display characteristics of a liquid crystal cell. As for the optical compensation sheet having an optically anisotropic layer made of liquid crystalline molecules, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal Bend), OCB (Optically Compensatory Bend) Super Twisted Nematic), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), reflection type is TN, HAN (Hybrid Aligned Nematic), G . The retardation plate and polarizing plate obtained by the present invention can be applied to various liquid crystal display modes depending on the alignment state. For example, a retardation plate having an optically anisotropic layer formed of a liquid crystalline polymer on a transparent support and the liquid crystalline polymer being in the orientation state shown in FIG. 2B is a transmission type VA. It can be suitably used for the mode. Further, for example, a first optically anisotropic layer formed from a liquid crystalline polymer on a transparent support and a second optically anisotropic layer formed from a discotic liquid crystalline molecule are provided. As shown in FIG. 3B, a retardation plate in which tick liquid crystalline molecules are vertically aligned from the alignment film side to the air interface side can be suitably used for a transmission type IPS mode.

The present invention will be described more specifically with reference to the following examples. The materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.
[Example 1: Production of first retardation plate]
(1) Formation of liquid crystalline polymer film An optically isotropic triacetylcellulose film having a thickness of 100 μm, a width of 150 mm, and a length of 200 m was used as a transparent support. Liquid crystalline polymer (Exemplary Compound No. AL-1) is diluted to 4% by mass in a water / methanol mixture, equimolar triethylamine is added as a neutralizing agent for acrylic acid, and the coating solution is prepared. did. This coating solution was continuously applied to one side of the transparent support, and the coating layer was heated at 120 ° C. for 2 minutes and dried to form a liquid crystalline polymer film E-101 having a thickness of 1 μm.

(2) Formation of optically anisotropic layer The E-101 was continuously rubbed in the longitudinal direction (transport direction) of the transparent support. Furthermore, this layer was heated for 1 minute at 135 ° C., which is 5 ° C. higher than the temperature at which the liquid crystalline polymer AL-1 is phase-transduced into the nematic phase, to align the liquid crystalline polymer layer. Thus, retardation plate RL-101 was produced.

(3) Evaluation of alignment state and alignment defect of first retardation plate As a result of visual evaluation of the alignment state using an optical microscope, the liquid crystalline polymer AL-1 has a side chain having a substituent of a liquid crystalline skeleton. It was confirmed that the film was oriented in parallel with the rubbing direction (longitudinal direction of the retardation plate). Furthermore, as a result of examining the number of alignment defects generated in the optically anisotropic layer made of a liquid crystalline polymer by observing with an optical microscope, the number of point defects (average value in the range of 1.0 mm ² ) is 1.0 mm. It was 20 or less in ² ranges.

(4) Evaluation of adhesion After the retardation plate was prepared, its surface was scratched with a metal fitting, and the ease of peeling of the optically anisotropic layer from the support was evaluated. As evaluation criteria, evaluation was made in three stages: A: not peeled off at all, B: peeled off a little, and C: easy to peel off.

[Example 2]
In the method for producing a retardation plate shown in Example 1, the liquid crystalline polymer AL-1 of the present invention was changed to AL-2, AL-3, and AL-5 shown in Table 2 below. In addition, the retardation plates RL-102, 103, and 104 were respectively added in the same manner as in Example 1 except that the polymerization initiator was added to the coating solution, applied, and then fixed by light irradiation after orientation. Produced.
About these phase difference plates, similarly to phase difference plate RL-101, the alignment state was observed, the number of alignment defects was examined, and the adhesiveness was evaluated. The results are summarized in the following table.

  When the orientation state of the liquid crystalline polymer in the optically anisotropic layer was observed, the retardation plates RL-103 and 104 using AL-3 and AL-5 were on the side containing the liquid crystalline skeleton of the liquid crystalline polymer. The chains were perpendicular to the rubbing direction as shown in FIG. 2 (b). Moreover, the adhesiveness of the film was greatly improved by incorporating a photocrosslinkable site into the liquid crystalline polymer and photopolymerizing and fixing after orientation.

[Example 3: Evaluation of optical compensation function of first retardation plate]
A roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizing film. A roll-shaped phase difference plate (RL-103) in which a saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is saponified on one surface of the polarizing film. The transparent support was continuously bonded to produce polarizing plate HL-103. As a result of visually observing the state in which the produced deflection plate was attached to the transmission type VA liquid crystal cell and the human image was displayed, an image without unevenness was obtained.
Thus, by using a liquid crystalline polymer, it was possible to form an optically anisotropic layer without an alignment film. In addition, a retardation plate having an optically anisotropic layer made of an aligned liquid crystalline polymer contributes to improvement of display characteristics of a VA mode liquid crystal cell, and is useful as an optical compensation sheet.

[Example 4: Production of second retardation plate]
(1) Production of first retardation plate In the formation of the liquid crystalline polymer film described in Example 1, the concentration of the water / methanol mixed liquid of the liquid crystalline polymer (Exemplary Compound No. AL-1) was set to 0. A first retardation plate RL-101 ′ was produced in the same manner as in Example 1 except that the content was changed to 4% by mass. The thickness of the optically anisotropic layer on this retardation plate was 0.1 μm.

(2) Formation of optically anisotropic layer On the 1st phase difference plate R-101 'produced above, the coating liquid of the following composition was continuously apply | coated using the bar-coater. The coating layer was heated at 100 ° C. for 1 minute to align the discotic liquid crystalline molecules. The discotic liquid crystalline molecules were polymerized by irradiating with 600 mj / cm ² of ultraviolet rays at that temperature for 4 seconds to fix the alignment state. Thus, the optically anisotropic layer was formed, and the second retardation plate RL-201 of the present invention was produced. When in-plane retardation (Re) at a wavelength of 550 nm was measured using an ellipsometer (M-150, manufactured by JASCO Corporation), Re was 100 nm.

────────────────────────────────────
Optically anisotropic layer (A) coating solution composition ─────────────────────────────────────
The following discotic liquid crystal compound III-1 14.5 mass%
The following sensitizer 0.15% by mass
0.45% by mass of the following photopolymerization initiator
Following orientation control agent D-3 0.10 mass%
Methyl ethyl ketone 84.7% by mass
────────────────────────────────────

(3) Evaluation of alignment state and alignment defect of retardation plate As a result of visual evaluation of the alignment state of discotic liquid crystalline molecules in the optically anisotropic layer of the prepared retardation plate using an optical microscope, discotic liquid crystal It was confirmed that the sex molecules were fixed in the orientation state shown in FIG. That is, in the produced optically anisotropic layer 14, the discotic liquid crystal molecules 05 are parallel to the angle formed by the disc surface of the molecule and the rubbing direction (longitudinal direction of the retardation plate) and with respect to the layer plane. It was confirmed that it was fixed in a vertically orthogonal orientation state. 5, (a) a side view is a sectional view as seen from a in FIG. 4, (b) a front view is a sectional view as seen from b in FIG. 4, and FIG. The meaning of each symbol is the same as the meaning of each symbol in FIG. The same applies to FIG. 6 described later.
Further, 10 the number of alignment defects generated in the optical anisotropic layer 14 results were examined in an optical microscope, (average of 1.0 mm ² range) number of point defects is 1.0 mm ² range It was the following.

(4) Evaluation of adhesion After the retardation plate was produced, its surface was scratched with a metal fitting, and the ease of peeling of the optically anisotropic layer (B) from the optically anisotropic layer (A) was evaluated. As evaluation criteria, A: not peeled off at all, B: peeled off slightly, and C: easy to peel off. As a result, R-201 was at the B level.

2. Production of Polarizing Plate A rolled polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizing film. A roll phase difference plate (RL-201) having a saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) on one surface of the polarizing film and a saponified surface on the other surface. The transparent support was continuously bonded to produce polarizing plate HL-201. As a result of visually observing the state in which the produced deflecting plate was attached to the transmissive liquid crystal cell for IPS and the human image was displayed, an image without unevenness was obtained.

[Example 5]
In the method for producing the second retardation plate shown in Example 4, the liquid crystalline polymer AL-1 of the present invention was prepared as AL-2, AL-3, and AL-5 shown in Table 2 below. The second retardation plates RL-202, 203, and 204 of the present invention were respectively produced in the same manner as in Example 4 except that each of them was changed.

When the orientation state of the discotic liquid crystalline molecules in the optically anisotropic layer was observed in the same manner as described above for the produced retardation plate, the orientation of the discotic liquid crystalline molecules in the retardation plate RL-202 was RL-101. The orientation was as shown in FIG. On the other hand, the orientation of the discotic liquid crystalline molecules in the case of using RL-203 and 204 is such that the discotic liquid crystalline molecules 05 are aligned with the disc surface of the molecule and the rubbing direction (of the retardation plate) as shown in FIG. It was confirmed that the substrate was fixed in a state in which the angle formed with the longitudinal direction was perpendicular to the substrate plane and perpendicular to the substrate plane.
Table 2 below shows the number of orientation defects obtained in the same manner as described above and the evaluation results of the adhesion of these prepared retardation plates.

  Further, the polarizing plates HL-202, 203 and HL are the same as in Example 4 except that the retardation plate RL-201 used in Example 4 is replaced with retardation plates RL-202, 203 and 204, respectively. -204 were prepared respectively. About these produced polarizing plates, image display performance was evaluated similarly to the above. The results are shown in Table 3.

  In this way, by using a layer made of oriented liquid crystalline polymer as an alignment film, the slow axis of the discotic liquid crystalline compound is parallel to the slow axis of the liquid crystalline polymer and perpendicular to the substrate. Could be oriented. Furthermore, by using a liquid crystalline polymer that can be aligned in a direction perpendicular to the rubbing direction as in the present invention, the discotic liquid crystalline molecules that have been difficult to obtain with conventional alignment films can be made substantially perpendicular to the discotic liquid crystal. It was found that a retardation plate in which the surface of the functional molecule and the rubbing direction are oriented substantially orthogonally can be obtained. Moreover, the polarizing plate which gives favorable image display performance as a result was able to be obtained.

It is a schematic diagram which shows roughly an example of the manufacturing method of the phase difference plate of this invention. It is the figure which showed typically an example of the orientation state with respect to the rubbing direction of a liquid crystalline polymer. It is the figure which showed typically an example of the orientation state of a discotic liquid crystalline molecule. It is a perspective view of an example of the support body which can be used for this invention. It is the (a) side surface schematic diagram and (b) front schematic diagram of the phase difference plate of an Example. It is the (a) side surface schematic diagram and (b) front surface schematic diagram of the phase difference plate of another Example.

Explanation of symbols

02 Liquid crystalline polymer 03 Side chain having liquid crystal skeleton of liquid crystalline polymer 04 Main chain of liquid crystalline polymer 05 Discotic liquid crystalline molecule 11 Support 12 Liquid crystalline polymer layer 12 ', 12 "From liquid crystalline polymer Formed optically anisotropic layer 13, 13 ′ first retardation plate 14, 14 ′ Optically anisotropic layer formed from discotic liquid crystalline molecules 15, 15 ′ Second retardation plate 16 Rubbing axis ( Orientation axis)

Claims (10)

Without using an alignment film, at least by orienting the liquid crystalline polymer having one crosslinking groups, including to form an optically anisotropic layer, a retardation plate having one or more optically anisotropic layers A manufacturing method of
A step of aligning the surface of the layer formed from the liquid crystalline polymer, a step of aligning the liquid crystalline polymer by phase transition to a liquid crystal phase, and fixing the alignment of the liquid crystal phase to obtain an optical difference. A method for producing a retardation plate, comprising a step of forming an isotropic layer. The method for producing a retardation plate according to claim 1 , wherein an alignment axis is formed by a rubbing process in the alignment process. A composition containing at least a discotic liquid crystalline molecule is applied to the surface of the optically anisotropic layer, and the discotic liquid crystalline molecule is aligned on the optically anisotropic layer, whereby the discotic liquid crystalline molecule is aligned. were fixed in the alignment state, further a method for manufacturing a retardation film according to claim 1 or 2 comprising the step of forming an optically anisotropic layer. The slow axis of the optically anisotropic layer, the transparent support so as to be substantially perpendicular to the longitudinal direction, according to any one of claims 1 to 3 for orienting the liquid crystalline polymer A method for producing a retardation film. A liquid crystalline polymer layer containing an oriented and fixed liquid crystalline polymer is laminated on the transparent support in contact with the surface of the liquid crystalline polymer layer, and oriented and fixed. a retardation plate having an optically anisotropic layer containing a discotic liquid crystal molecules,
A phase difference plate, wherein the liquid crystalline polymer has a rod-like liquid crystalline skeleton in a side chain, a hydrogen bonding group, and an aromatic ring in a linking group portion connecting the side chain and the main chain. The retardation plate according to claim 5 , wherein a slow axis of the optically anisotropic layer is substantially parallel to a slow axis of the liquid crystalline polymer layer. The phase difference plate according to claim 5 or 6 , wherein in the optically anisotropic layer, discotic liquid crystalline molecules are aligned substantially perpendicularly to the surface of the transparent support. The retardation plate according to any one of claims 5 to 7 , wherein a thickness of the liquid crystalline polymer layer is 1/10 or less of a thickness of the optically anisotropic layer. An image display device comprising at least one liquid crystal cell and the retardation plate according to claim 5 , wherein the retardation plate is an optical compensation sheet of the liquid crystal cell. The image display device according to claim 9 , wherein the liquid crystal cell is an IPS (In-Plane Switching) mode liquid crystal cell.

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