JP4335620B2 - Optically anisotropic layer, retardation plate, circularly polarizing plate, and image display device - Google Patents

Description

  The present invention relates to an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystalline compound and a polymer, and a retardation plate having the optically anisotropic layer. The present invention also relates to a retardation plate having two or more optically anisotropic layers and no alignment film layer provided between the two optically anisotropic layers. Further, the present invention relates to a circularly polarizing plate or an image display device using these retardation plates.

  A retardation plate made of an optically anisotropic material is a necessary material in an LCD display device. When a desired optical performance cannot be achieved with one kind of material, a plurality of optical materials may be used. For example, a λ / 4 plate is used in a reflective liquid crystal display device, but in such a wavelength range of R, G, and B, a broadband in which the phase difference of the λ / 4 plate is 1/4 of the wavelength. However, it is difficult to satisfy such optical performance with a single material, and λ / 2 plates and λ / 4 plates are used. Each of these materials has a thickness of several tens of μm or more, and they are used by being bonded with an adhesive or the like. Further, Patent Document 1 discloses a technique for producing a broadband λ / 4 plate by laminating two optically anisotropic layers made of a liquid crystalline compound on a long support. Also, Patent Document 2 discloses a technique for laminating layers obtained by immobilizing a liquid crystal compound. In these optical materials, an alignment film layer is separately formed between the layers obtained by immobilizing the liquid crystal compound, and in such a lamination method, it is necessary to apply an alignment film therefor before applying the liquid crystal compound. There is. That is, in order to fix the alignment of the liquid crystal compound and form one optically anisotropic layer, the alignment film and the liquid crystal compound must be applied at least once. For this reason, the manufacturing cost is increased, and a cheaper manufacturing technique is demanded. Furthermore, as the number of times of application increases, the probability of product failure due to application or liquid crystal compound alignment defects often increases, and as a result, the yield of the phase difference plate deteriorates. Therefore, it is required to reduce the number of coatings from the viewpoint of improving the yield at the time of manufacture.

On the other hand, Patent Document 3 describes a technique in which a surfactant is added for the purpose of controlling the tilt alignment on the air interface side of the liquid crystal composition, and the surface layer is formed by shifting to the air interface side. However, this patent document does not mention a technique for rubbing the surface layer on the air interface side to form an optically anisotropic layer made of a polymerizable liquid crystal composition. Patent Documents 4 and 5 disclose a technique in which a surfactant is added to the polymerizable liquid crystal composition as a leveling agent to smooth the surface of the formed film. These documents describe that the leveling agent can reduce optical unevenness due to film thickness unevenness by reducing the surface tension of the liquid crystal composition. However, these documents do not mention a technique for further forming an optically anisotropic layer made of a polymerizable liquid crystal composition on an optically anisotropic layer formed of a polymerizable liquid crystal composition. We made one optically anisotropic layer made of a polymerizable liquid crystal compound using the leveling agent described in Patent Document 5, and rubbed the surface, and then formed another optically anisotropic layer. Attempted to form. However, the surface of the first layer is sticky, the leveling agent is transferred to the rubbing cloth, and when the second optically anisotropic layer is applied, the lower layer is poorly wetted, so that the second layer is repelled. It has become clear that there is a problem that the orientation of the functional compound is insufficient.
JP 2001-4837 A US Pat. No. 6,160,597 JP 2000-105315 A JP-A-11-148080 JP-A-8-231958

  The problem to be solved by the present invention is that the surface is not sticky, the additive does not transfer even if the surface is rubbed with a cloth, etc., and the surface can be directly rubbed, and a composition containing a liquid crystalline compound An object of the present invention is to provide an optically anisotropic layer capable of forming an optically anisotropic layer made of another liquid crystalline compound directly on its surface without causing poor coating such as repellency when an object is applied. Another object of the present invention is to provide a retardation plate that can be produced by a simple production method with few coating steps and has few defects due to repellency, orientation failure, and the like. Another object of the present invention is to provide a method for producing a retardation plate that is simple and has a low occurrence frequency of defects such as repellency and orientation failure. Furthermore, an object of the present invention is to provide an optically anisotropic layer, a phase difference plate, and a circularly polarizing plate that contribute to reducing manufacturing costs and improving image display characteristics, and to provide an image display device having excellent display characteristics. It is to be.

The above problems have been achieved by the following means.
[1] An optically anisotropic layer formed from a liquid crystal composition containing a liquid crystalline compound and a polymer and subjected to an oxidative surface treatment.
[2] The optically anisotropic layer according to [1], wherein the oxidative surface treatment is a corona discharge treatment or a plasma treatment.
[3] The optically anisotropic layer according to [1] or [2], wherein a δa value of the polymer is smaller than a δa value of the liquid crystalline compound.
[4] The optically anisotropic layer according to any one of [1] to [3], wherein the polymer includes at least a repeating unit represented by the following general formula (I).

(R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ² represents a carboxyl group, an ester group, an amide group, a hydroxyl group, an alkoxy group, an acyloxy group, a carbamoyl group, a substituted or unsubstituted aryl group. Or a substituted or unsubstituted heterocyclic group.)
[5] The optically anisotropic layer according to any one of [1] to [4], wherein the polymer includes a repeating unit having a crosslinkable group.
[6] The optically anisotropic layer according to any one of [1] to [5], wherein the surface energy is increased by 5 mN / m or more from the surface energy before the oxidative surface treatment.
[7] The optically anisotropic layer according to any one of [1] to [5], wherein the surface energy is increased to 45 mN / m or more by the oxidative surface treatment.
[8] A retardation plate having the first optical anisotropic layer according to any one of [1] to [7] on a support.
[9] A second optical anisotropic layer adjacent to the first optical anisotropic layer is provided, and an alignment film layer is substantially interposed between the first and second optical anisotropic layers. The retardation plate according to [8], which does not have.
[10] The first optically anisotropic layer is closer to the transparent support than the second optically anisotropic layer, and the slow axis of the first optically anisotropic layer is The angle formed by the slow axis of the second optical anisotropic layer is substantially 60 °, and the phase difference at one wavelength of 550 nm of the first and second optical anisotropic layers is substantially The phase difference plate according to [9], in which the phase difference at the other wavelength of 550 nm is substantially π / 2.
[11] An optically anisotropic layer having the retardation plate according to [9] or [10] and a polarizing film and having a phase difference of π at a wavelength of 550 nm is an optically anisotropic layer having a phase difference of π / 2. Compared with the isotropic layer, the angle between the transmission axis of the polarized light of the polarizing film and the slow axis of the optically anisotropic layer having a phase difference of π is substantially 15 as compared to the polarizing layer. A circularly polarizing plate that is ° or 75 °.
[12] A step of oxidatively treating the surface of the first optically anisotropic layer formed from the composition containing the liquid crystalline compound and the polymer, and the oxidatively treated surface containing the liquid crystalline compound. And a step of forming a second optically anisotropic layer by applying a composition. A method for producing a retardation plate having first and second optically anisotropic layers.
[13] An image display device comprising the retardation plate according to any one of [8] to [10], the circularly polarizing plate according to [11], or the retardation plate produced by the production method according to [12]. .
[14] An optically anisotropic layer containing a polymer of a polymerizable liquid crystalline compound and a polymer on a transparent support, and the optically anisotropic layer is subjected to an oxidative surface treatment. Phase difference plate.

  In this specification, “substantially no alignment film” means that a film formed only for functioning as an alignment film is not included. Even when the surface of the lower layer contributes to the alignment of the liquid crystalline compound of the upper layer, unless the lower layer is formed only for use as an alignment film, It is included in the present invention. Further, “substantially” with respect to an angle means that the angle is within a range of an exact angle of less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °. Further, the “slow axis” means a direction in which the refractive index is maximized.

  According to the present invention, it is possible to provide a retardation plate that can be produced by a simple production method with few coating steps and has few defects due to repellency, orientation failure, and the like. In addition, according to the present invention, it is possible to provide a method for producing a retardation plate that is simple and has a low frequency of occurrence of defects such as repellency and orientation failure. Furthermore, according to the present invention, it is possible to provide an optically anisotropic layer, a phase difference plate, a circularly polarizing plate, and an image display device excellent in display characteristics, which contribute to reduction of manufacturing costs and improvement of image display characteristics. it can.

BEST MODE FOR CARRYING OUT THE INVENTION

  The optically anisotropic layer of the present invention can be used as a constituent member of a retardation plate. The retardation plate including the optically anisotropic layer of the present invention can be applied to various liquid crystal display devices (for example, a reflection type liquid crystal display device, a TN type liquid crystal display device, an STN type liquid crystal display device, a VA type liquid crystal display device, and an IPS). It can be used as an optically anisotropic material used for a liquid crystal display device), and can be suitably used particularly for a λ / 4 plate in a reflective liquid crystal display device. In particular, a λ / 2 plate having a broadband λ / 4 plate having a phase difference of ¼ of the wavelength in any wavelength region of R, G, and B (the phase difference at a wavelength of 550 nm is substantially reduced). Suitable for a retardation plate in which two layers of an optically anisotropic layer shifted by π and a λ / 4 plate (an optically anisotropic layer having a phase difference of substantially π / 2 at a wavelength of 550 nm) are bonded together. Can be used for In the retardation plate of this aspect, the optically anisotropic layer of the present invention may be either a λ / 4 plate or a λ / 2 plate.

  The retardation plate including the optically anisotropic layer of the present invention may be used as a circularly polarizing plate combined with a linearly polarizing film, and can be incorporated in a liquid crystal display device as a circularly polarizing plate. The position of the linearly polarizing film is not particularly limited. However, in the case where the linearly polarizing film is bonded to the retardation plate in which the λ / 4 plate and the λ / 2 plate are laminated, the position of the linearly polarizing film is more than that of the λ / 4 plate. It is preferable that the λ / 2 plate be positioned close to the λ / 2 plate, and the slow axis of the λ / 2 plate and the transmission axis of the linearly polarizing film be substantially 15 ° or 75 ° and bonded together. Two types of preferred circularly polarizing plate embodiments are shown in FIG. A circularly polarizing plate 06 in FIG. 1A includes a support body 02, an optically anisotropic layer 03 (first optically anisotropic layer) of the present invention that functions as a λ / 2 plate, and a first layer that functions as a λ / 4 plate. A retardation plate 05 comprising two optically anisotropic layers 04 and a linearly polarizing film 01 bonded to the back surface of the support body 02 of the retardation plate 05. 1B functions as a transparent support 02, the optical anisotropy 04 (first optical anisotropic layer) of the present invention that functions as a λ / 4 plate, and a λ / 2 plate. A retardation plate 05 ′ having a second optical anisotropic layer 03 and a linearly polarizing film 01 bonded to the surface of the second optical anisotropic layer 03 of the retardation plate 05 ′. In the circularly polarizing plate shown in FIGS. 1A and 1B, it is preferable that the slow axes of the λ / 2 plate and the λ / 4 plate substantially intersect at 60 °.

  The optically anisotropic layer of the present invention has a non-sticky surface, and even when it is rubbed with a cloth, the components in the layer are not transferred to the cloth. Therefore, the rubbing process can be performed directly. For example, when producing the circularly polarizing plate 06 of FIG. 1A, first, the optically anisotropic layer 03 of the present invention functioning as a λ / 2 plate is formed on the transparent support 02, and then directly rubbed on the surface thereof. Processing can be performed. Furthermore, a composition containing a liquid crystal compound is applied to the rubbing surface to form an optically anisotropic layer 04 that functions as a λ / 4 plate, and finally a linearly polarizing film 01 is bonded. A circularly polarizing plate 06 can be produced. Similarly, the circularly polarizing plate 06 ′ of FIG. 1B can be directly rubbed without forming an alignment film on the surface of the optically anisotropic layer 04 to form the optically anisotropic layer 03. Conventionally, in order to produce a circularly polarizing plate having the configuration shown in FIG. 1, a λ / 2 plate and a λ / 4 plate are bonded together via an adhesive layer, or a λ / 2 plate or a λ / 4 plate is used. After the lower layer was formed, an alignment film layer was formed on the surface, and then the upper λ / 4 plate had to be formed. If the optically anisotropic layer of the present invention is used, the process for producing the retardation plate and the circularly polarizing plate can be simplified without going through a step of separately forming an alignment film and a step of bonding via an adhesive layer.

  When surface energy is increased by performing oxidative surface treatment on the surface of a substrate or alignment film, the wettability of a liquid crystal layer or the like applied thereon is improved. As described in JP-A-90365, an optical anisotropy is formed by applying an oxidative surface treatment to an optically anisotropic layer formed from a liquid crystal composition containing a liquid crystalline compound and a polymer. It was unexpected that the orientation of the layer could be controlled.

  Hereinafter, details of the liquid crystal compounds (hereinafter also referred to as liquid crystal molecules) and polymers used for the production of the optically anisotropic layer of the present invention will be described.

1. The liquid crystalline compound is preferably a rod-like liquid crystalline molecule or a discotic liquid crystalline molecule, and more preferably a rod-like 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.

(1) Rod-like liquid crystalline molecules As rod-like liquid crystalline molecules, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines , Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. In addition to the above low-molecular liquid crystalline molecules, high-molecular liquid crystalline molecules can also be used.

  It is more preferable to fix the orientation of the rod-like liquid crystalline molecules by polymerization, and examples of the polymerizable rod-like liquid crystalline molecules include those described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648 and 5,770,107, WO 95/22586, 95/24455, 97/97. No. 0600, No. 98/23580, No. 98/52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and Japanese Patent Application No. 2001-64627 These compounds can be used. More preferably, it is a compound represented by the following general formula (II).

Formula (II)
^{Q 1 -L 1 -Cy 1 -L 2} - (Cy 2 -L 3) n -Cy 3 -L 4 -Q 2
In the formula, Q ¹ and Q ² are each independently a polymerizable group, L ¹ and L ⁴ are each independently a divalent linking group, and L ² and L ³ are each independently a single bond or a divalent group. It is a linking group, Cy ¹ , Cy ² and Cy ³ are divalent cyclic groups, and n is 0, 1 or 2.

In the formula (II), the polymerizable group represented by Q ¹ and Q ² is preferably a functional group capable of addition polymerization reaction or condensation polymerization reaction. Examples of preferred polymerizable groups are shown below.

In formula (II), L ¹ and L ⁴ are each independently a divalent linking group. L ¹ and L ⁴ are each independently selected from the group consisting of —O—, —S—, —CO—, —NR ²¹ —, a divalent chain group, a divalent cyclic group, and combinations thereof. A valent linking group is preferred. R ²¹ is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom, preferably an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and preferably a methyl group, an ethyl group, or a hydrogen atom. More preferably, it is a hydrogen atom. Below, -O -, - S -, - CO -, - NR 21 -, showing an example of the divalent linking group of a combination of a divalent chain group and divalent cyclic group. Here, the left side is coupled to Q ¹ or Q ² and the right side is coupled to Cy ¹ or Cy ³ .

L-1: —CO—O—divalent chain group —O—
L-2: -CO-O-divalent chain group -O-CO-
L-3: —CO—O—divalent chain group —O—CO—O—
L-4: -CO-O-divalent chain group -O-divalent cyclic group-
L-5: -CO-O-divalent chain group -O-divalent cyclic group -CO-O-
L-6: -CO-O-divalent chain group -O-divalent cyclic group -O-CO-
L-7: -CO-O-divalent chain group-O-divalent cyclic group-divalent chain group-
L-8: -CO-O-divalent chain group -O-divalent cyclic group -divalent chain group -CO-O-
L-9: -CO-O-divalent chain group -O-divalent cyclic group -divalent chain group -O-CO-
L-10: —CO—O—divalent chain group—O—CO—divalent cyclic group—
L-11: -CO-O-divalent chain group -O-CO-divalent cyclic group -CO-O-
L-12: -CO-O-divalent chain group -O-CO-divalent cyclic group -O-CO-
L-13: —CO—O—Divalent chain group—O—CO—Divalent cyclic group—Divalent chain group—
L-14: -CO-O-divalent chain group -O-CO-divalent cyclic group -divalent chain group -CO-O-
L-15: -CO-O-divalent chain group-O-CO-divalent cyclic group-divalent chain group-O-CO-
L-16: —CO—O—divalent chain group—O—CO—O—divalent cyclic group—
L-17: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -CO-O-
L-18: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -O-CO-
L-19: —CO—O—Divalent chain group—O—CO—O—Divalent cyclic group—Divalent chain group—
L-20: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -divalent chain group -CO-O-
L-21: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -divalent chain group -O-CO-

In the formula (II), the divalent chain group means an alkylene group, a substituted alkylene group, an alkenylene group, a substituted alkenylene group, an alkynylene group, or a substituted alkynylene group. An alkylene group, a substituted alkylene group, an alkenylene group and a substituted alkenylene group are preferred, and an alkylene group and an alkenylene group are more preferred.
The alkylene group may have a branch. The alkylene group preferably has 1 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkylene part of the substituted alkylene group is the same as the above alkylene group. Examples of the substituent include a halogen atom.
The alkenylene group may have a branch. The alkenylene group preferably has 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkenylene part of the substituted alkenylene group is the same as the above alkenylene group. Examples of the substituent include a halogen atom.
The alkynylene group may have a branch. The alkynylene group preferably has 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkynylene part of the substituted alkynylene group is the same as the above alkynylene group. Examples of the substituent include a halogen atom.

  Specific examples of the divalent chain group include ethylene, trimethylene, 1,2-propylene, tetramethylene, 2-methyl-tetramethylene, pentamethylene, hexamethylene, octamethylene, 2-butenylene, 2-butynylene and the like. Can be mentioned.

In formula (II), the definition and examples of the divalent cyclic group are the same as those of Cy ¹ , Cy ² and Cy ³ described later.

In the formula (II), L ² and L ³ are each independently a single bond or a divalent linking group. L ² and L ³ are each independently selected from the group consisting of —O—, —S—, —CO—, —NR ²² —, a divalent chain group, a divalent cyclic group, and combinations thereof. A valent linking group or a single bond is preferred. R ²² has the same meaning as R ²¹ above. The divalent chain group and divalent cyclic group, the same meanings as those described in L ¹ and L ^4.

In the formula (II), n is 0, 1 or 2. When n is 2, two L ³ may be the same or different, and two Cy ² may be the same or different. n is preferably 1 or 2, and more preferably 1.

In the formula (II), Cy ¹ , Cy ² and Cy ³ are each independently a divalent cyclic group. The ring contained in the cyclic group is preferably a 5-membered ring, a 6-membered ring or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring, and most preferably a 6-membered ring. The ring contained in the cyclic group may be a condensed ring. However, it is more preferably a monocycle than a condensed ring.
The ring contained in the cyclic group represented by Cy ¹ , Cy ² and Cy ³ may be any of an aromatic ring, an aliphatic ring, and a heterocyclic ring. Examples of the aromatic ring include a benzene ring and a naphthalene ring. Examples of the aliphatic ring include a cyclohexane ring. Examples of the heterocyclic ring include a pyridine ring and a pyrimidine ring.
As the cyclic group having a benzene ring, 1,4-phenylene is preferable. As the cyclic group having a naphthalene ring, naphthalene-1,5-diyl and naphthalene-2,6-diyl are preferable. The cyclic group having a cyclohexane ring is preferably 1,4-cyclohexylene. As the cyclic group having a pyridine ring, pyridine-2,5-diyl is preferable. The cyclic group having a pyrimidine ring is preferably pyrimidine-2,5-diyl.
These cyclic groups may have a substituent. Examples of the substituent include a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 5 carbon atoms, a halogen-substituted alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. , An alkylthio group having 1 to 5 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a carbamoyl group, and an alkyl-substituted carbamoyl group having 2 to 6 carbon atoms And an acylamino group having 2 to 6 carbon atoms.

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

(2) Discotic liquid crystalline molecules Discotic liquid crystalline molecules can be obtained from various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); Quarterly Chemical Review, No. 22, Chemistry of Liquid Crystal, 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).

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

  In the formula (III), the divalent linking group (L) 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 (L) 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 (L) 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 (L) 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.
L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-

L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AL-AR-O-AL-O-CO-
L17: -O-CO-AR-O-AL-CO-
L18: -O-CO-AR-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-CO-
L20: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L21: -S-AL-
L22: -S-AL-O-
L23: -S-AL-O-CO-
L24: -S-AL-S-AL-
L25: -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 (III), 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 L 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.

2. Polymer contained in liquid crystal composition The polymer used for forming the optically anisotropic layer of the present invention smoothes the surface when the liquid crystal composition is coated on a support to form an optically anisotropic layer. It has a leveling function and a function of moving to the air interface side of the optically anisotropic layer to form a surface concentrated layer containing a large amount of polymer. In the present invention, by forming an optically anisotropic layer from a composition containing a liquid crystal compound and a polymer, surface stickiness can be suppressed, and the surface can be directly rubbed without forming an alignment film. In addition, by performing oxidative surface treatment, the surface energy is improved, and occurrence of coating defects such as repelling is reduced in the coating process when the upper layer is formed. As a result, a laminated body of optically anisotropic layers can be stably produced by a simple method, which contributes to an improvement in the productivity of retardation plates and circularly polarizing plates. When the polymer has a polar group (however, it only needs to be present after the oxidative surface treatment, and is preferably generated during the oxidative surface treatment), the surface stickiness can be further suppressed, Furthermore, since stable application | coating becomes possible, without generating a repellency etc., productivity improves more. By selecting a polymer having good dissolution resistance with respect to the liquid crystal compound or coating solvent used in combination, the interaction with the liquid crystal compound can be increased, and the alignment film function can be remarkably improved.

  From the above viewpoint, the polymer used for the production of the optically anisotropic layer of the present invention preferably has higher hydrophobicity than the liquid crystal compound used in order to form a leveling function and form a surface concentrated layer. Further, when the polymer itself has liquid crystallinity, the affinity with the liquid crystal compound is increased and mixing becomes easy. In this case, the surface concentrated layer can be formed by greatly increasing the hydrophobicity of the polymer, but the polymer itself preferably has no liquid crystallinity.

The hydrophilicity / hydrophobicity of the polymer and the liquid crystal compound used in the present invention can be predicted from the compound structure using various methods, and a log P value, an I / O value, an SP value, and the like can be used. Among these, non-dispersion of the SP value calculated by the method of Hoy et al. (See VAN KREVELEN, DW, “PROPERITES OF POLYMERS (ED.3)” ELSEVIER publication (1990)) by the inventors' investigation. It was found that the leveling function expression ability and the surface concentrated layer forming ability of the polarity conversion polymer of the present invention can be estimated by obtaining the force component (referred to as δa value in the present invention). The δa value was calculated by Equation (1) using the three-dimensional SP values (δd, δp, δh) calculated by the method of Hoy et al. In the case of a copolymer composed of a plurality of repeating units, the sum of the square values (δd ² , δp ² , δh ² ) of the three-dimensional SP values for each repeating unit is multiplied by the volume fraction for each repeating unit. The square value (δd ² , δp ² , δh ² ) of the three-dimensional SP value of the copolymer was calculated, and the δa value of the copolymer was determined by substituting this into equation (1).
δa = (δp ² + δh ² ) ^0.5 formula (1)

The δa value of the polymer used in the present invention is, for example, a small value when it has a substituent such as a fluorine atom which is a hydrophobic atomic group or trifluoromethyl, and conversely, a water-soluble substituent, For example, when it has a hydroxy group, a carboxy group, an amide group or the like in the side chain, it takes a large value. In the present application, the value of δa is preferably smaller than the δa value of the liquid crystal compound used together in order to form the leveling function and form the surface concentrated layer. Furthermore, it is preferable that the difference is somewhat large, and it is preferable that a value obtained by subtracting the δa value of the polymer from the δa value of the liquid crystal compound is positively large. The preferred range of the value obtained by subtracting the δa value of the polymer of the present invention from the δa value of the liquid crystal compound depends on the type and molecular weight of the liquid crystal compound used and the polymer of the present invention, and the temperature and time during the alignment treatment to be heated if necessary. However, ^0.5 to 20 MPa ^0.5 is preferable, 2.0 to 20 MPa ^0.5 is more preferable, and 5.0 to 20 MPa ^0.5 is most preferable.

  The polymer used in the present invention is preferably a polymer capable of generating a polar group in its molecule by oxidative surface treatment. Preferred examples of the polar group mentioned here include acidic groups such as carboxyl group (carboxylic acid), sulfo group (sulfonic acid) and phosphonic acid, and basic groups such as hydroxyl group, mercapto group and amino group. Among these, a carboxyl group and a hydroxyl group are particularly preferable. However, in order to adjust the δa value of the polymer, a repeating unit containing these polar groups (for example, acrylic acid, methacrylic acid, hydroxyethyl acrylate, etc.) may be included in advance, and the content is 0.00. 1-20 mol% is preferable, More preferably, it is 1-10 mol%.

  The polymer preferably includes a polymer having a carbon-carbon bond as a main chain, a polymer containing a hetero atom (oxygen, nitrogen, sulfur, phosphorus, etc.) in the main chain, and a polymer containing silicon in the main chain (poly Siloxane etc.) are preferred, and preferred side chains to be substituted on these main chain skeletons are hydrogen atom, substituted or unsubstituted aliphatic hydrocarbon group, halogen (fluorine atom, chlorine atom, bromine atom etc.), carboxyl group, Examples include ester groups, amide groups, hydroxyl groups, ether groups, acyloxy groups, carbamoyl groups, substituted or unsubstituted aryl groups, and heterocyclic groups.

  Moreover, the more preferable aspect of the said polymer contains the repeating unit represented by the following general formula (I).

In the general formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (eg, a methyl group), and preferably represents a hydrogen atom or a methyl group. In the formula, R ² represents a carboxyl group, an ester group (—CO ₂ R ³ ), an amide group (—CONHR ⁴ ), a hydroxyl group, an ether group (—OR ⁵ ), an acyloxy group (—OCOR ⁶ ), a carbamoyloxy (— Represents an OCONHR ⁷ ) group, a substituted or unsubstituted aryl group or a heterocyclic group. The substituents R ^{3 to} R ⁷ contained in R ² are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms (for example, methyl group, ethyl group, n-butyl group, 2-hydroxyethyl group, 2 , 2,2-trifluoroethyl group, C ₆ F ₁₃ CH ₂ CH ₂ —, trimethylsilylmethyl group, cyclohexyl group, etc.), substituted or unsubstituted aryl groups having 6 to 20 carbon atoms (for example, phenyl group, etc.), and A heterocyclic group (for example, a pyridyl group, an imidazolyl group, etc.) is represented. Moreover, the repeating unit which 2 or more types of repeating units represented by the said general formula (I) mutually connected may be included.

  Although the preferable specific example of the repeating unit of the polymer used for this invention below is shown, this invention is not limited to these.

  The polymer preferably further has a crosslinkable group. In the process of forming an optically anisotropic layer using a polymer having a crosslinkable group, by cross-linking the crosslinkable group, the surface stickiness is suppressed, and the liquid crystalline compound and the coating solvent to be used are resistant to dissolution. This is preferable because the effect of imparting is often enhanced. The crosslinkable group possessed by the polymer may be any of addition, condensation, and substitution reactive groups, and any crosslinkable group can be used without particular limitation. On the other hand, as described above, as the liquid crystalline compound used together with the polymer, those having an ethylenically unsaturated group such as an acryloyl group and a methacryloyl group are used. Is preferably immobilized. Therefore, since the crosslinking of the polymer can be promoted together with the immobilization of the liquid crystalline compound, the polymer preferably has a crosslinking group that can be crosslinked by ultraviolet irradiation. Preferred examples of reactions that can be crosslinked by ultraviolet irradiation include ring-opening polymerization reactions of heterocyclic compounds such as epoxy rings and oxetane rings combined with compounds that generate cations by ultraviolet irradiation, and compounds that generate radicals by ultraviolet irradiation 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 about the introduction method of the crosslinkable group in the said polymer.

  Although the preferable specific example of the repeating unit containing a crosslinkable group is shown below, this invention is not limited to these.

  The polymer can be synthesized by any one of addition, condensation and substitution reactions, or a combination thereof. Although there is no restriction | limiting in particular, It is simple and preferable to synthesize | combine using the radical polymerization reaction of the ethylenically unsaturated compound corresponding to the repeating unit represented by general formula (I). On the other hand, when the polymer used in the present invention has a repeating unit substituted with a crosslinkable group, (a) rather than synthesizing by a method of directly introducing an ethylenically unsaturated group by polymerizing the corresponding monomer (b) It is preferable to synthesize by a technique of introducing an ethylenically unsaturated group into a polymer obtained by polymerizing a monomer having an arbitrary functional group by a polymer reaction. Available polymer reactions include: I) For example, after forming a polymer containing a functional group obtained by precuring an ethylenically unsaturated group, such as removing hydrochloric acid from a 2-chloroethyl group, functional group conversion (desorption) A method of deriving an ethylenically unsaturated group by a separation reaction, an oxidation reaction, a reduction reaction, a deprotection reaction, etc.); and II) formation of a polymer containing any functional group, followed by bond formation 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”). These methods I) and II) may be performed in combination. As used herein, the “bond formation reaction” 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.

  A preferable ratio in the case where a repeating unit substituted with a crosslinkable group is contained in the polymer is 1% by mass to 80% by mass, more preferably 3% by mass to 60% by mass, and particularly preferably 5% by mass to 40% by mass. It is below mass%.

  A preferred molecular weight range of the polymer used in the present invention is 1,000 to 1,000,000, more preferably 3,000 to 200,000 in terms of weight average molecular weight. Most preferably, it is 5000 or more and 100,000 or less.

  Although the preferable example of the polymer used for this invention below is shown in Table 1, this invention is not limited to this. In addition, the repeating unit represented by the general formula (I) given above as a specific example and the repeating unit containing a crosslinkable substituent are represented by the numbers of the specific examples given above, and the copolymer composition ratio is expressed by mass%. It was added in.

  The synthesis of the polymer used in the present invention can be easily obtained by applying a known method (for example, Experimental Chemistry Course, Vol. 28, Polymer Synthesis, edited by The Chemical Society of Japan, Maruzen). Although the specific synthesis example of the polymer used for this invention is described below, it is not limited to this.

Synthesis Example of (P-1) Into a 1000 mL three-necked flask, 2-butanone (250 ml) was placed and heated to 60 ° C. while flowing nitrogen at a flow rate of 35 ml / min. To the initiator (AIBN: 2, 2′- A solution of azobisisobutyronitrile, 0.45 g) in 2-butanone (10 ml) was added. Immediately thereafter, a mixed solution of butyl methacrylate (23.0 g, 161.7 mmol) and methacryloxyethyl-3-chloropropionate (14.8 g, 67.3 mmol) 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 (1/1: 3 L), and the precipitated polymer was taken out by suction filtration and further dried. The obtained polymer residue was 33 g. After the obtained polymer residue was dissolved in 2-butanone (250 ml), triethylamine (10 ml) was added and stirred at room temperature for 1 hour to form an acrylate group by dehydrochlorination, and then water (250 ml) was added. The hydrochloride of triethylamine was removed by performing a liquid separation operation. The 2-butanone solution is again slowly poured into stirred hexane / ethyl acetate (1/1: 3 L), and the precipitated polymer is removed by suction filtration and further used for drying. 25 g of polymer (P-1) was obtained. From the ¹ H-NMR spectrum of the obtained polymer, the polymer (P-1) has a composition in which the repeating units (K-3) and (A-1) have a molar ratio of 71/29 and a mass ratio of 65/35. It was confirmed that it was configured.

  The preferable content of the polymer in the composition used when forming the optically anisotropic layer of the present invention is preferably 0.01 to 20% by mass relative to the total mass of the liquid crystalline compound, and 0.1 to 10%. % By mass is more preferable, and 0.5 to 5% by mass is particularly preferable. Moreover, multiple types of polymers may be included simultaneously.

3. Oxidative surface treatment The optically anisotropic layer of the present invention is characterized by being subjected to an oxidative surface treatment. Examples of the oxidative surface treatment that can be used in the present invention include corona treatment, plasma treatment (for example, low-temperature glow discharge treatment), flame treatment, and the like. Corona discharge treatment and plasma treatment are preferred, and corona treatment is most preferred. The method of oxidative surface treatment varies depending on the type of treatment. In the case of corona treatment, an object (for example, liquid crystallinity) at a speed of 0.5 to 20 m / min. The polymer is preferably subjected to surface treatment by passing it through a corona treatment device comprising a high-frequency generator or the like while transporting a polymer film having a composition containing a compound and a polymer coated on the surface. In the case of plasma treatment, it is preferable to generate plasma by glow discharge under normal temperature, low pressure (10 torr or less), air or oxygen atmosphere, and perform surface treatment for about 0.5 to 10 minutes. The conditions for oxidative surface treatment should avoid excessive conditions that would damage the support or optically anisotropic layer after treatment, but the type and material of the object to be treated ( For example, it can be arbitrarily set according to the type and thickness of the support material), the type of liquid crystalline compound and polymer used for forming the optically anisotropic layer, and the treatment time.

  In the optically anisotropic layer of the present invention, the surface energy is preferably increased by 5 mN / m or more, more preferably 10 mN / m or more, more preferably 15 mN / m than the surface energy before the oxidative surface treatment. More preferably, it is increased by at least / m. As the surface energy of the optically anisotropic layer of the present invention is higher, a coating liquid containing a liquid crystalline compound can be more stably applied to the surface, and the surface energy after the oxidative surface treatment is 45 mN / m. Preferably, it is 50 mN / m or more, and more preferably 55 mN / m or more. On the other hand, when the surface energy is less than 45 mN / m, depending on the type of the solvent of the coating solution and the liquid crystal compound, when applied to the surface of the optically anisotropic layer of the present invention, coating failure such as repelling occurs. In some cases, the upper optically anisotropic layer in contact with the optically anisotropic layer of the present invention cannot be stably produced. Therefore, it is preferable to select the conditions for the oxidative surface treatment and the type of polymer used so that the surface energy is further increased. The upper limit of the surface energy is not particularly limited, but in general, the surface energy is about 70 mN / m for oxidative surface treatment that does not damage the optically anisotropic layer or the support. It becomes the following.

4). Retardation plate (1) configuration and production method The retardation plate of the present invention has the optically anisotropic layer of the present invention. The optically anisotropic layer of the present invention contains a liquid crystal compound such as a rod-like liquid crystal molecule or a discotic liquid crystal molecule and a polymer, and a coating liquid containing a polymerizable initiator and other additives as required. It can be produced by coating on the surface (preferably provided with an alignment film) and aligning, fixing, and oxidatively treating the liquid crystalline compound. In FIG. 2, sectional drawing of an example of the optically anisotropic layer of this invention formed on the transparent support body is shown typically. FIG. 2 is also a schematic cross-sectional view of an example of the single-layer retardation plate of the present invention. In FIG. 2, the optically anisotropic layer 15 of the present invention is formed on a support 11 (such as triacetyl cellulose) provided with an alignment film 12 (such as polyvinyl alcohol). The optically anisotropic layer 15 of the present invention is composed of a layer 13 fixed in a state where a liquid crystal compound is oriented in the layer, and a layer 14 in which a phase-separated polymer is concentrated on the surface thereof. In the coating solution, the liquid crystalline compound and the polymer are mixed, but in the process of forming a layer by coating on the support and then drying, the polymer is liquid crystalline compound due to the difference in both hydrophilicity and hydrophobicity. Phase separation and transfer to the air interface to form a polymer concentrated layer 14. On the other hand, the liquid crystalline compound is aligned by a rubbing treatment or the like applied to the surface of the alignment film 12, polymerized by irradiation with ultraviolet rays or the like, fixed to the alignment, and becomes a layer 13. When the polymer has a crosslinkable group, it is preferable that the polymer in the polymer concentrated layer 14 be cross-linked by UV irradiation because the polymer in the polymer concentrated layer 14 is not dissolved in the layer 13 to disturb the phase separation structure. However, FIG. 2 is merely a schematic illustration of an example of the optically anisotropic layer of the present invention, in which the interface between the layer 13 and the layer 14 is unclear, or the polymer is dissolved in the layer 13. The embodiment and the embodiment in which the liquid crystal compound is dissolved in the layer 14 are not excluded from the present invention.

  FIG. 3 shows a schematic cross-sectional view of an example of an embodiment in which an optically anisotropic layer is further formed on the optically anisotropic layer of the present invention shown in FIG. FIG. 3 is also a schematic cross-sectional view of an example of the laminated retardation plate of the present invention. In FIG. 3, the optical anisotropic layer 16 is formed on the surface of the optical anisotropic layer 15 of FIG. By subjecting the polymer concentrated layer 14 to surface oxidative surface treatment, the surface energy of the polymer concentrated layer 14 is increased, and coating defects such as repelling occur when a coating liquid containing a liquid crystal compound is applied. And the optically anisotropic layer 16 can be stably formed. Further, by rubbing the surface of the polymer concentrated layer 14, it can function as an alignment film when the optically anisotropic layer 16 is formed. In the above description, the oxidative surface treatment is performed before the rubbing treatment. However, the oxidative surface treatment may be performed after the rubbing treatment.

  FIG. 3 is also a schematic cross-sectional view of one embodiment of the laminated retardation plate of the present invention. By using one of the optically anisotropic layers 15 and 16 as a λ / 4 plate and the other as a λ / 2 plate, the above-described broadband λ / 4 plate can be configured. In this embodiment, it is preferable that the slow axis of the optically anisotropic layer 16 intersects the slow axis of the optically anisotropic layer 15 substantially at 60 °. The slow axis of the optically anisotropic layer 16 can be adjusted in the direction of rubbing treatment applied to the surface of the polymer condensation layer 14.

  Details of the production method of the present invention will be described below.

(A) Application of liquid crystal composition For the preparation of the coating liquid, a solvent may be used, and an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Of these, alkyl halides, esters and ketones are preferred. Two or more organic solvents may be used in combination. 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.

(B) Fixation of liquid crystal It is preferable to fix the aligned liquid crystalline molecules while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group (P, Q ¹ or Q ² ) introduced into the liquid crystal molecule. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is 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. It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules. 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 is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

(C) Support When using the retardation plate of the present invention without removing the support, it is preferable to use a polymer film that is transparent, has a small optical anisotropy, and has a 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 or rectangular sheet-like shape, and the roll-like transparent support is used to laminate the optically anisotropic layer and then cut into a required size. preferable. 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 the adhesion between the transparent support and the layer (adhesive layer, alignment film or optically anisotropic layer) provided on the transparent support, surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet light ( UV) treatment, flame treatment). An adhesive layer (undercoat layer) may be provided on the transparent support.

(D) Alignment control of liquid crystal (d) -1 Alignment film An alignment film is preferably used in order to align the liquid crystalline compound on the support. The alignment film may be an organic compound (for example, ω-triconic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroup, or Langmuir-Blodgett method (LB film). , Dioctadecyldimethylammonium chloride, methyl stearylate, etc.). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. An alignment film formed by a polymer rubbing treatment is particularly preferred. The rubbing process is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.

  The rod-like liquid crystalline molecules can be oriented substantially horizontally (average inclination angle in the range of 0 to 30 degrees) with respect to the coating plane, or can be substantially oblique (average inclination angle in the range of 30 to 70 degrees). Orientation can be oriented substantially vertically (average tilt angle in the range of 50 to 90 degrees), or hybrid orientation (for example, horizontal to vertical) in which the tilt angle continuously changes in the same layer. By selecting the type of polymer used for the alignment film, the alignment of the rod-like liquid crystalline molecules (especially the inclination angle of the alignment film interface) can be controlled. In the present invention, the alignment films used for each are expressed as a horizontal alignment film, an oblique alignment film, and a vertical alignment film. In addition, an alignment film capable of aligning rod-like liquid crystalline molecules in a direction (mainly orthogonal direction) substantially different from the rubbing direction in the horizontal alignment film is particularly expressed as an orthogonal alignment film.

  Discotic liquid crystalline molecules can be aligned substantially horizontally (average tilt angle in the range of 0 to 30 degrees) with the discotic core surface approximately parallel to the coating plane by using a horizontal alignment film. Yes, it can be substantially obliquely (average inclination angle in the range of 30 to 70 degrees) by using the oblique alignment film and the vertical alignment film, and substantially vertical (average inclination angle in the range of 50 to 90 degrees). ), And hybrid orientation (for example, horizontal to vertical) in which the tilt angle continuously changes in the same layer is also possible. On the other hand, when the orthogonal alignment film is used, the discotic core surface can be aligned approximately perpendicular to the coating plane and orthogonal to the rubbing direction. In any case, an alignment film can be appropriately selected according to a desired alignment direction.

  Specific types of polymers used for the alignment film are described in various literatures on liquid crystal cells or optical compensation sheets, and can be appropriately selected according to a desired alignment method and use form. In the present invention, it is particularly preferable to use a polyvinyl alcohol derivative or a polyacrylic acid derivative having a polymerizable group because the adhesion between the liquid crystal compound and the transparent support can be improved. JP-A-9-152509, JP-A-2002-62427, JP-A-9-152509, JP-A-9-152509, JP-A-9-152509, Compounds described in Kaikai 2002-90545, JP-A-2002-9836, etc. can be used.

  The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm. In addition, after aligning the liquid crystalline compound using the alignment film, the liquid crystalline compound is fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is polymer film (or transparent support) It may be transferred onto the body). The liquid crystal compound in which the alignment state is fixed can maintain the alignment state without an alignment film. Therefore, in the retardation plate of the present invention, the alignment film is not essential (although essential in the production of the retardation plate).

(D) -2 Alignment control agent Even if the alignment of the liquid crystalline compound is substantially horizontal on the alignment film side, the alignment is performed with an inclination angle on the air interface side, so that optical unevenness often occurs. The polymer of the present invention also has an effect of suppressing the optical unevenness, but the optical unevenness can be further eliminated by adding a certain additive, and such an additive is subsequently used as an orientation control agent. Called. As the orientation control agent, preferably, a low molecular orientation control agent in which a fluorine alkyl group, a long-chain alkyl group or an aryl group is substituted on the trihydroxybenzene skeleton or triazine skeleton, and a polymer orientation control agent such as polypropylene oxide or polymelamine Can be preferably used. Specific examples of the low molecular orientation control agent include the following D-1.

  The addition amount of the alignment control agent is preferably 0.05 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 0.1-5 mass%.

(2) Specific Example of Retardation Plate The retardation plate of the present invention can have a plurality of layers in which the orientation of the liquid crystal compound is fixed. As an example of such a phase difference plate, Japanese Patent Application Laid-Open Nos. 2001-4837, 2001-21720, and 2000-206331 disclose broadband λ / 4 plate technology. In the following, embodiments of the invention in the broadband λ / 4 plate will be described, but the present invention is not limited to the λ / 4 plate.

(A) Broadband λ / 4 plate The wideband λ / 4 specifically refers to a retardation value / wavelength value measured at wavelengths of 450 nm, 550 nm, and 650 nm, all in the range of 0.2 to 0.3. Means that The retardation value / wavelength value is preferably in the range of 0.21 to 0.29, and more preferably in the range of 0.22 to 0.28.
When a polarizing film, a polarizer having a phase difference of π, and a polarizer having a phase difference of π / 2 are used, circularly polarized light can be approximately achieved in a wide wavelength region. Japanese Patent Application Laid-Open No. 10-68816 describes an explanation using a Poincare sphere regarding achievement of circularly polarized light. Each polarizer (optically anisotropic layer or birefringent film) only needs to achieve a phase difference of substantially π or π / 2 at a specific wavelength. However, it is preferable that a phase difference of π or π / 2 is achieved at 550 nm, which is a substantially intermediate wavelength in the visible region. In order to achieve the phase difference π at the specific wavelength (λ), the retardation value of the polarizer measured at the specific wavelength (λ) may be adjusted to λ / 2. In order to achieve the phase difference π / 2 at the specific wavelength (λ), the retardation value of the polarizer measured at the specific wavelength (λ) may be adjusted to λ / 4.

  When the specific wavelength (λ) is 550 nm, the retardation value measured at a wavelength of 550 nm of the optically anisotropic layer used as a polarizer having a phase difference π is preferably 200 to 290 nm, and preferably 210 to 280 nm. More preferred. When the specific wavelength (λ) is 550 nm, the retardation value measured at a wavelength of 550 nm of the optically anisotropic layer used as a polarizer having a phase difference of π / 2 is preferably 100 to 145 nm, and preferably 110 to 140 nm. It is more preferable.

The retardation value means an in-plane retardation value for light incident from the normal direction of the optically anisotropic layer. Specifically, it is a value defined by the following formula.
Retardation value (Re) = (nx−ny) × d
Where nx and ny are the in-plane main refractive indices of the optically anisotropic layer, and d is the thickness (nm) of the optically anisotropic layer.

  When producing a broadband λ / 4 plate, the crossing angle between a layer having a phase difference of π and a layer having a phase difference of π / 2 is important, and is preferably 60 ° ± 10, and 60 ° ± 5. More preferably. When a circularly polarizing plate is produced from a broadband λ / 4 and a polarizing plate or a polarizing film, a polarizing plate (or a polarizing film), a layer having a phase difference of π, and a layer having a phase difference of π / 2 are stacked in this order. The slow axis of the layer having a phase difference of π from the polarization transmission axis of the polarizing plate (or polarizing film) is preferably 15 ° ± 5, more preferably 15 ° ± 3. . A generally available long polarizing plate has a polarization absorption axis in the long longitudinal direction and a polarization transmission axis in a direction perpendicular thereto. Therefore, when a circularly polarizing plate is formed from a polarizing plate and a broadband λ / 4 plate, it is preferable that the layer having a phase of π is substantially 75 ° with respect to the longitudinal direction of the support. Japanese Patent Application Laid-Open No. 2002-86554 discloses a polarizing plate technique in which the absorption axis of polarized light is substantially 45 ° with respect to the longitudinal direction. In the case of such a polarizing plate, the slow axis of the layer having a phase of π is preferably 15 ° or 75 ° with respect to the polarization absorption axis.

(B) Method for Producing Broadband λ / 4 Plate In the present invention, when producing the broadband λ / 4 plate, it is preferable to produce it by the following procedures (1) to (6).
(1) An alignment film layer is provided on a transparent support.
(2) The alignment film layer is rubbed.
(3) A composition containing a liquid crystal compound and a polymer is applied onto the rubbed alignment layer.
(4) If necessary, heat treatment is performed, the orientation of the liquid crystal compound is fixed, and the layer is fixed by irradiation with ultraviolet rays, followed by oxidative surface treatment, and the first optical anisotropic layer (phase is either π or π / 2) Form).
(5) The first optically anisotropic layer is rubbed so as to cross 60 ° with the slow axis of the first optically anisotropic layer.
(6) A second optical anisotropic layer is formed.

  When the retardation plate of the present invention has a plurality of layers in which the orientation of the liquid crystal compound is fixed, it is essential that the polymer of the present invention is added to the liquid crystal composition used for at least one layer. , May be added to all layers. On the layer using the polymer of the present invention, it is possible to form a layer in which the orientation of another liquid crystal compound is fixed without using an orientation film. Also, when the polymer of the present invention is used for the uppermost layer, the surface after immobilization is not sticky, and even if the surface is rubbed with a cloth or the like, it may be advantageous. Not required.

5. Circularly Polarizing Plate The retardation plate of the present invention is a λ / 4 plate used in a reflective liquid crystal display device, a λ / 4 plate used for a pickup for writing on an optical disk, or λ / used as an antireflection film. The four plates can be used particularly advantageously. The λ / 4 plate is generally used as a circularly polarizing plate combined with a polarizing film. Therefore, if it is configured as a circularly polarizing plate in which a retardation plate and a polarizing film are combined, it can be easily incorporated into a device for use such as a reflective liquid crystal display device. 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. A polarizing film generally has protective films on both sides. However, when the retardation plate of the present invention is used, the optically anisotropic layer itself or the transparent support can function as a protective film on one side of the polarizing film. When a protective film is used separately from the transparent support, it is preferable to use a cellulose ester film having high optical isotropy, particularly a triacetyl cellulose film, as the protective film.

[Example 1]
(1) Production of single-layer retardation plate 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. A diluted solution of the alignment film (polymer having the following structural formula) was continuously applied to one side of the transparent support to form a film having a thickness of 0.5 μm. Subsequently, a rubbing process was continuously performed in the direction of 30 ° on the left hand side with respect to the longitudinal direction of the transparent support to produce an alignment film.

On the rubbed surface of the alignment film, a coating solution having the following composition is continuously applied using a bar coater, dried and heated (alignment aging), and further irradiated with ultraviolet rays to form an optically anisotropic layer (A). Then, a single layer retardation plate 101 was produced. The optically anisotropic layer had a slow axis in the direction of 30 ° to the left hand with respect to the longitudinal direction of the transparent support. In addition, the film thickness of the optically anisotropic layer (A) was adjusted to have a retardation value (Re550) at 550 nm of 265 nm, and was about 2.4 μm.
───────────────────────────────
Optically anisotropic layer (A) coating composition ───────────────────────────────
The following rod-like liquid crystalline compound I-1) 14.5 mass ratio The following sensitizer 0.15 mass ratio The following photoinitiator 0.25 mass ratio The polymer of the present invention (P-1: δa value = 12. 7MPa ^0.5 )
0.30 mass ratio Methyl ethyl ketone 84.8 mass ratio ─────────────────────────────────

(2) Oxidative surface treatment The single-layer retardation plate 101 produced above is passed through a corona discharge treatment apparatus (manufactured by BETAPHONE) at 25 ° C. under an atmospheric atmosphere of 1 atm at a conveyance speed of 3 m / min. The surface was subjected to corona treatment to complete the optically anisotropic layer of the present invention.

(3) Production of laminated retardation plate (λ / 4 plate) The single-layer retardation plate produced above has a right-handed 60 ° with respect to the slow axis of the optically anisotropic layer (A) and is in the longitudinal direction. The rubbing process was continuously performed so that the right hand was 30 °. On the rubbing surface, a coating solution having the following composition is continuously applied using a bar coater, dried and heated (orientation aging), and further irradiated with ultraviolet rays to give an optical anisotropy of 1.2 μm in thickness. The layer (B) was formed, and the laminated phase difference plate 201 was produced.
────────────────────────────────
Optically anisotropic layer (B) coating composition ─────────────────────────────────
Rod-like liquid crystalline compound of Example 1 13.0 mass ratio Sensitizer of Example 1 0.10 mass ratio Photopolymerization initiator of Example 1 0.39 mass ratio Methyl ethyl ketone 86.5 mass ratio Orientation controller D-1 0.01 mass ratio ────────────────────────────────

(4) Production of 45 ° Polarizing Plate A polarizing plate was produced by the method described in Example 2 of JP-A-2002-86554. The absorption axis direction of the obtained polarizing plate was inclined 45 ° with respect to the longitudinal direction. The polarizing plate had a transmittance at 550 nm of 43.7% and a polarization degree of 99.97%. Further, as shown in FIG. 8 of JP-A-2002-86554, when cut into a size of 310 × 233 mm, a polarizing plate having an absorption efficiency of 91.5% and an inclination angle of 45 ° with respect to the side was obtained.

(5) Preparation of Circular Polarizing Plate Next, the PVA film part in which iodine of the 45 ° polarizing plate prepared above was immersed was used as a cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd., product number TD80UL, retardation value 3.0 nm). ), An antiglare antireflection film having a saponified support (triacetylcellulose) side was bonded to one side. On the other side, the saponification treatment of the laminated retardation plate 201 prepared above was saponified, and a PVA (Kuraray PVA-117H) 3% aqueous solution was bonded as an adhesive, and further at 80 ° C. It dried and the circularly-polarizing plate 301 was produced. At this time, the polarizing film and the retardation film were bonded so that the longitudinal directions thereof coincided to produce a circularly polarizing plate.

[Examples 2 to 4 (present invention)]
Single-layer retardation plates 102 to 104 were prepared in the same manner as in Example 1 except that the polymer used in the optically anisotropic layer (A) in Example 1 was changed to the compounds shown in Table 2, and the same After performing corona treatment under conditions, laminated phase difference plates 202 to 204 were produced. In addition, circularly polarizing plates 302 to 304 were produced by the same method as in Example 1 using the laminated retardation plates 202 to 204.

Example 5 (Invention)
The single-layer retardation plate 101 produced in Example 1 was placed on a plate in a radio frequency (RF) plasma generator (SAMCO, BP-1), and 0.5 torr while flowing argon gas at a flow rate of 20 ml / min. The plasma was generated by increasing the RF power to 50 W, and then plasma treatment was performed for 1 minute. Using this single-layer retardation plate, a laminated retardation plate 205 and a circularly polarizing plate 305 were produced in the same manner as in Example 1.

[Comparative Examples 1 and 2]
A laminated retardation plate 206 and a circularly polarizing plate 306 were produced in the same manner as in Example 1 except that the polymer used in the optically anisotropic layer (A) of Example 1 was not added. Moreover, in Example 1, the laminated phase difference plate 207 and the circularly-polarizing plate 307 were produced by the completely same method except not performing a corona treatment.

The retardation plate and the circularly polarizing plate were evaluated by the following methods, and the results are shown in Table 3.
(I) Surface energy before and after corona treatment of the single layer retardation plate The surface energy of the single layer retardation plate was determined from the contact angle between water and diiodomethane.
(Ii) Evaluation of orientation state and orientation defect of laminated phase difference plate The laminated phase difference plate before making it into a circularly polarizing plate was observed under a polarizing microscope, and the orientation state and orientation defect were evaluated. The alignment state was visually evaluated using an optical microscope to determine whether the optically anisotropic layer (B) is aligned in the rubbing direction. Further, the number of point defects was evaluated for the alignment defects. In addition, the number of point defects described the average value of 1.0 mm < ² > range.
(Iii) Evaluation of repellency of laminated phase difference plate After the production of the laminated phase difference plate, the optically anisotropic layer (B) is poorly wet with respect to the single-layer phase difference plate surface, and the optically anisotropic layer (B) is applied. In some cases, non-removed portions (repels) were observed in the form of dots having a diameter of 1 mm or less. The number of these spotted repellents per 25 cm ² was visually evaluated.
(Iv) Evaluation of Adhesiveness of Laminated Retardation Plate After creating a laminated retardation plate, its surface was scratched with a metal fitting to evaluate the ease of peeling of the optically anisotropic layer (B) from the optically anisotropic layer (A). . 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.
(V) Evaluation of image display performance of circularly polarizing plate Remove the upper part including the circularly polarizing plate part except the liquid crystal cell of Sharp's Zaurus MI-E1, paste the circularly polarizing plate prepared above, The displayed state was visually observed.

  From the results shown in Table 3, when forming the lower optically anisotropic layer (A), any of the retardation plates of Examples 1 to 5 produced by using a polymer and performing a corona treatment or a plasma treatment was used. There was no repellency, and the image display performance of the circularly polarizing plate was all good. On the other hand, in Comparative Example 1 in which no polymer was added to the liquid crystal composition for forming the optically anisotropic layer (A), there was no polymer that could be an alignment film on the surface of the optically anisotropic layer (A). Even when the treatment and rubbing were performed, the liquid crystal of the optically anisotropic layer (B) could not be aligned, and as a result, a circularly polarizing plate giving good image display performance could not be obtained. Further, in Comparative Example 2 in which no oxidative surface treatment was applied even when a polymer was added to the liquid crystal composition of the optically anisotropic layer (A), a hydrophobic polymer was formed on the surface of the optically anisotropic layer (A). Therefore, a circularly polarizing plate that gives extremely good wettability and gives good image display performance could not be obtained. A retardation plate and a circularly polarizing plate were prepared in the same manner as in Example 1 except that PVA having a higher δa value than that of the rod-like liquid crystal used was added instead of P-1, and the PVA had optical anisotropy. Since it was difficult to localize on the surface of the layer (A), the remarkable improvement like Examples 1-5 was not seen. From these results, as in the present invention, a hydrophobic polymer having a δa value smaller than that of the liquid crystal compound is added to the liquid crystal composition of the optically anisotropic layer (A), and the surface after coating is treated as an oxidative surface. By processing, the wettability is improved, and the optically anisotropic layer (B) can be stably formed without repelling the coating liquid of the upper optically anisotropic layer (B). As a result, good image display performance The circularly-polarizing plate which gives can be produced.

It is a cross-sectional schematic diagram of embodiment of the circularly-polarizing plate of this invention. It is a cross-sectional schematic diagram of the single layer type phase difference plate of this invention. It is a cross-sectional schematic diagram of the laminated retardation plate of the present invention.

Explanation of symbols

01 Linear polarizing film 02 Support body 03 λ / 2 plate 04 λ / 4 plate 05,05 ′ Broadband λ / 4 plate 06,06 ′ Circularly polarizing plate 11 Support body 12 Alignment film 13 Aligned and fixed liquid crystal layer 14 Polymer Condensed layer 15 Optically anisotropic layer of the present invention 16 Optically anisotropic layer

Claims (7)

A step of oxidatively treating the surface of the first optically anisotropic layer formed from a composition containing a liquid crystalline compound and a polymer, and a composition containing a liquid crystalline compound on the oxidatively treated surface. A method of producing a retardation plate having first and second optically anisotropic layers, the method comprising: applying and forming a second optically anisotropic layer. The method according to claim 1, wherein the oxidative surface treatment is a corona discharge treatment or a plasma treatment. The method according to claim 1 or 2, wherein a δa value of the polymer is smaller than a δa value of the liquid crystal compound. The method according to any one of claims 1 to 3, wherein the polymer contains at least a repeating unit represented by the following general formula (I).

(R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ² represents a carboxyl group, an ester group, an amide group, a hydroxyl group, an alkoxy group, an acyloxy group, a carbamoyl group, a substituted or unsubstituted aryl group. Or a substituted or unsubstituted heterocyclic group.) The method according to claim 1, wherein the polymer includes a repeating unit having a crosslinkable group. Surface energy, The method according to any one of claims 1 to 5, it increases the oxidative surface treatment prior to surface energy than 5 mN / m or more. Surface energy, The method according to any one of the oxidative surface treatment by 45 mN / m or more to increase that Ru claims 1-5.

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