JP5499791B2 - Azo compound for anisotropic film, composition for anisotropic film, anisotropic film and polarizing element - Google Patents

Description

  The present invention relates to an azo compound exhibiting high dichroism useful for a polarizing plate provided in a display device such as a light control device, a liquid crystal device (LCD), and an organic electroluminescence device (OLED), and a compound containing the compound. The present invention relates to a composition for an isotropic film, an anisotropic film, and a polarizing element.

  LCDs use linearly polarizing plates and circularly polarizing plates to control optical rotation and birefringence in display. In the OLED, a circularly polarizing plate is used for preventing reflection of external light.

  Conventionally, iodine has been widely used as a dichroic substance in these polarizing plates (polarizing elements). However, since iodine has a high sublimation property, when used in a polarizing element, its heat resistance and light resistance are not sufficient. Further, the extinction color is deep blue, and it cannot be said to be an ideal achromatic polarizing element over the entire visible spectrum region.

  Therefore, a polarizing element using an organic compound as a dichroic material has been studied. However, these organic compounds have a problem that only a polarizing element having a degree of dichroism considerably inferior to that of iodine can be obtained.

  In an LCD that uses optical rotation and birefringence of light as a display principle, a polarizing element is an important component, and in recent years, a new polarizing element has been developed for the purpose of improving display performance and the like.

  One method is to dissolve or adsorb a dichroic organic compound (so-called dichroic dye) in a polymer material such as polyvinyl alcohol in the same way as a polarizing element containing iodine, and the film is oriented in one direction. A method of orienting a dichroic compound by stretching it into a film is mentioned. However, this method has a problem such that a process such as a stretching process is troublesome.

Therefore, other methods have recently attracted attention.
As this method, Non-Patent Document 1 forms a polarizing film (anisotropic film) by orienting a dichroic compound on a substrate such as glass or a transparent film by utilizing an intermolecular interaction of an organic compound. ing. However, it has been known that the method described in this document has a problem of heat resistance.

  Further, orienting the dichroic compound on the substrate such as glass or transparent film by utilizing the intermolecular interaction of the organic compound can be achieved by a wet film forming method. In addition to the high dichroism of the molecules used, this film is required to be a compound suitable for the wet film forming process. Examples of the process in the wet film forming method include a method of depositing and orienting a compound on a substrate and a method of controlling the orientation, and even a compound used for a polarizing element that has undergone the above-described conventional stretching treatment, Often not suitable for wet film formation.

  In Patent Documents 1 to 4, various materials suitable for the process of the wet film forming method have been proposed. However, even if these materials are suitable for the process, high polarization characteristics (extinction ratio) cannot be obtained. There was a problem.

In addition, as a material suitable for the process, Patent Document 4 discloses (chromogen) (SO ₃ M).
A dye represented by n has been proposed. However, in this document, achromatic color is expressed by combining several kinds of dichroic compounds, but when an anisotropic film is obtained by combining several kinds of dichroic compounds in this way, different molecules are mixed. There was a problem that molecular orientation was disturbed and it was difficult to obtain high dichroism.

  Furthermore, as a material suitable for the process, Patent Document 5 proposes a tetrakisazo dye for an anisotropic film having a naphthyl group having a specific structure at the terminal.

JP 2002-180052 A JP-T-2002-528758 JP 2002-338838 A JP-T 8-511109 JP 2005-255846 A

Dreyer, J.A. F., Journal de Physique, 1969, 4, 114., “Light Polarization From Films of Lyotropic Nematic Liquid Crystals”

The tetrakisazo dye described in Patent Document 5 having a naphthyl group having a specific structure at the end has been said to exhibit high dichroism when used in an anisotropic film. In order to obtain a sufficient dichroic ratio, there is still room for improvement including not only the terminal structure but also the structure of other sites.
It is an object of the present invention to provide a tetrakisazo type azo compound for use in an anisotropic film, which is an anisotropic film that exhibits high dichroism and a high degree of molecular orientation. .

As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a tetrakisazo type azo compound whose free acid form is represented by the following formula (1), thereby achieving high dichroism and high molecular orientation. The present inventors have found that a polarizing element comprising an anisotropic film that has a high degree of optical performance can be formed, and has reached the present invention.
That is, the present invention provides an anisotropic film azo compound characterized in that the form of the free acid is represented by the following formula (1), an anisotropic film composition containing the compound and a solvent, the compound And a polarizing element comprising the anisotropic film.

(In the above formula (1), R ¹ and R ² are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or an optionally substituted phenyl group. Represents
A represents the following formula (1-a) or (1-b),

(In the above formula (1-a) or (1-b), R ³ represents a hydrogen atom, a hydroxyl group, or an optionally substituted alkoxy group having 1 to 4 carbon atoms.)
C represents a 1,4-phenylene group which may have an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an acetylamino group as a substituent;
n represents 0 or 1. )

  By using the azo compound of the present invention, it is possible to provide an anisotropic film, particularly an anisotropic film formed by a wet film formation method, which exhibits high dichroism and a high degree of molecular orientation. In addition, a polarizing element including an anisotropic film having such characteristics can be used in various fields such as a light control element, a liquid crystal element, and an organic electroluminescence element.

Hereinafter, embodiments of the present invention will be described in detail.
The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not specified in these contents unless it exceeds the gist.

  The anisotropic film as used in the present invention has anisotropy in electromagnetic properties in any two directions selected from a total of three directions in the three-dimensional coordinate system of the film thickness direction and any two orthogonal in-plane directions. It is a membrane. Examples of electromagnetic properties include optical properties such as absorption and refraction, and electrical properties such as resistance and capacitance. Examples of the film having optical anisotropy such as absorption and refraction include a linearly polarizing film, a circularly polarizing film, a retardation film, and a conductive anisotropic film.

  The anisotropic film of the present invention is preferably used for a polarizing film, a retardation film, and a conductive anisotropic film, and more preferably used for a polarizing film.

  The azo compound for anisotropic film of the present invention is a compound also having a function as a so-called dye, and the anisotropic film containing the azo compound for anisotropic film of the present invention can also function as a dye film. Is. In addition, generally a pigment | dye here means the compound which has absorption in a visible light wavelength range.

In the present specification, “may have a substituent” means that one or more substituents may be present.
Further, in this specification, the term “carbon number” of a substituent represents the number of carbon atoms contained in the substituent, and when the substituent has a further substituent, In the case of “carbon number”, it means all the carbon numbers including the carbon number contained in the further substituent.

[Azo compound for anisotropic film]
The azo compound for anisotropic films of the present invention is characterized in that the form of the free acid is represented by the following formula (1).

(In the above formula (1), R ¹ and R ² are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or an optionally substituted phenyl group. Represents
A represents the following formula (1-a) or (1-b),

(In the above formula (1-a) or (1-b), R ³ represents a hydrogen atom, a hydroxyl group, or an optionally substituted alkoxy group having 1 to 4 carbon atoms.)
C represents a 1,4-phenylene group which may have an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an acetylamino group as a substituent;
n represents 0 or 1. )

The anisotropic film azo compound represented by the above formula (1) has a naphthyl group substituted with a sulfo group at a specific position at one end and an amino group NR ¹ R ² at the 7 position at the other end. One of the features is that it is a tetrakisazo compound having a substituted naphthyl group.
The compound of the present invention exhibits a neutral black color tone by having a naphthyl group substituted with an amino group NR ¹ R ^{2 at} the 7-position, and is therefore suitable for a visible light polarizer.

  In addition, since it is a tetrakisazo dye, the number of aromatic rings in the molecule is increased compared to a disazo compound or a trisazo compound having a naphthyl group having the same structure at the terminal, so that the π-π interaction that is a cause of molecular association is reduced. Strengthens and increases the degree of meeting. As a result, the concentration of transition to the lyotropic liquid crystal phase is low, which is suitable for the wet film-forming method described later, and the orientation of the obtained anisotropic film is also high. Furthermore, since the tetrakisazo compound has a larger molecular long-short axis ratio than the disazo compound and the trisazo compound, the molecular long axis is likely to be parallel to the film in an anisotropic film formed by a wet film-forming method. There are features. As a result, the absorption in the film thickness direction of the anisotropic film decreases, and the absorption in the parallel direction tends to increase. This characteristic has the advantage of improving the polarization performance for vertically incident polarized light, while reducing the polarization performance for obliquely incident polarized light.

In addition, a composition containing the compound of the present invention by a structure having a naphthyl group substituted with a sulfo group at a specific position at one end and a naphthyl group substituted with an amino group NR ¹ R ^{2 at the} other end at the other end In the product, it can be expected that the sulfo group and the amino group NR ¹ R ² interact well with each other sterically and form a high association state in the solution. Furthermore, due to this interaction, the molecules in the aggregate are stacked without shifting, so there is a great advantage that the alignment axis of the aggregate and the absorption axis of the azo compound do not shift.

Other combinations of molecular end substituents having such attractive interaction are conceivable. However, as a result of investigations by the present inventors, in particular, a naphthyl group substituted with an amino group NR ¹ R ^{2 at the} 7-position is terminated. In the tetrakisazo compound having, it became clear that the other end is preferably combined with a naphthyl group substituted with a sulfo group at the specific position represented by the formula (1-a) or (1-b).

  Furthermore, this azo compound for anisotropic films has another feature that it has a structure in which a naphthylene group-phenylene group-naphthylene group is linked inside the molecule. When a naphthylene group is introduced into the molecule, the π-π interaction for causing the association is strengthened, so that there is an advantage that the degree of association is increased and the orientation of the anisotropic film is increased. Further, when the naphthylene group is a 1,4-naphthylene group, there is an advantage that the main absorption absorption axis substantially parallel to the alignment axis in the aggregate and the molecular long axis of the azo compound is difficult to shift.

  For example, as described in Japanese Patent Application Laid-Open No. 2007-199333, etc., it is generally considered that the association of a compound composed of an aromatic ring is not easily stacked vertically but is easily stacked by shifting due to repulsive force of π electrons. Yes. However, as a result of the study by the present inventors, it has been found that if a 1,4-naphthylene group is present at the center of the molecule, the molecules are shifted in the minor axis direction, but the deviation in the major axis direction is rather suppressed. did. Since the absorption axis of the azo compound is almost parallel to the major axis of the molecule, surprisingly, the deviation in the minor axis direction is not significantly affected, and high polarization characteristics can be obtained. Further, when the 1,4-naphthylene group is substituted with a sulfo group, the aggregates are prevented from agglomerating due to hydrophobic bonds, and the long and slender aggregates are stably dispersed, so that the orientation of the anisotropic film is improved. It turned out to be very favorable in terms.

  Further, as a result of further detailed investigation, in the tetrakisazo compound, it is preferable to link three 1,4-naphthylene groups inside the molecule from the viewpoint of enhancing the associative property and orientation, but the polarization property of the secondary absorption of the azo compound. It was also found unfavorable from the viewpoint of When 1,4-naphthylene groups are linked side by side, the molecular plane of adjacent naphthylene groups is twisted, so that the absorption axis of secondary absorption deviates from the average molecular plane of one molecule. It was found that the dichroic ratio of the wavelength corresponding to the sub-absorption is lowered due to the deviation of the orientation axis and the absorption axis of the sub-absorption. Although there are a plurality of side absorptions of the tetrakisazo compound, the side absorption exists at a wavelength having a higher visibility than the main absorption, so that the polarization characteristics having a corrected visibility are greatly affected. In order to improve the dichroic ratio of side absorption at such a wavelength with high visibility, 1,4-naphthylene groups are not connected side by side but phenylene groups are inserted in between, and naphthylene groups-phenylene groups-naphthylene groups are connected. Most preferably, the structure is made to suppress the twist of molecules. That is, by having two naphthylene groups, the naphthylene groups attract each other and stabilize the layered state of the molecules at the time of association, and the phenylene group at the center of the molecule has a structure in which three naphthylene groups are linked. It is considered that the dichroic ratio (contrast) can be increased by suppressing the twist of the molecule compared to the one.

By having such a structure, for example, in an anisotropic film obtained by applying a composition containing the azo compound for anisotropic film of the present invention to a wet film forming method, the compound is very An anisotropic film that is oriented with high order and exhibits high dichroism can be provided.
Further, the azo compound for anisotropic film represented by the formula (1) of the present invention has absorption in the entire visible light wavelength region, and the anisotropic film using the compound becomes achromatic. Therefore, by using the azo compound for anisotropic film of the present invention, it is possible to form an achromatic anisotropic film having high anisotropy.

Hereinafter, the azo compound for anisotropic films represented by the formula (1) of the present invention will be described.
<A>
In the formula (1), A represents the following formula (1-a) or (1-b).

(In the above formula (1-a) or (1-b), R ³ represents a hydrogen atom, a hydroxyl group, or an optionally substituted alkoxy group having 1 to 4 carbon atoms.)
That is, A is a naphthyl group having a sulfo group substituted at a specific position and further having R ³ as another substituent.
R ³ represents a hydrogen atom, a hydroxyl group, or an alkoxy group having 1 to 4 carbon atoms which may have a substituent. Examples of the alkoxy group having 1 to 4 carbon atoms which may have a substituent include a methoxy group, an ethoxy group, and a (n) -butoxy group. Examples of the substituent that the alkoxy group may have include a hydroxyl group.
Among these, R ³ is preferably a hydrogen atom from the viewpoint of molecular planarity.

<C>
In said Formula (1), C represents the 1, 4- phenylene group which may have a C1-C4 alkyl group, a C1-C4 alkoxy group, or an acetylamino group as a substituent.
When C is a 1,4-phenylene group, there is an advantage that twisting in the molecule hardly occurs.
Examples of the alkyl group having 1 to 4 carbon atoms that the 1,4-phenylene group may have include a methyl group, an ethyl group, and a (n) -butyl group.
Examples of the alkoxy group having 1 to 4 carbon atoms that the 1,4-phenylene group may have include a methoxy group, an ethoxy group, and a (n) -butoxy group.
From the viewpoint of molecular planarity, the 1,4-phenylene group preferably has no substituent, or has one or two methyl, methoxy, or acetylamino groups as substituents.

<R ¹ and R ² >
In Formula (1), R ¹ and R ² are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or an optionally substituted phenyl group. Represents.
The alkyl group having 1 to 4 carbon atoms which may have a substituent usually has a total carbon number of 1 or more and 6 or less, preferably 4 or less. The phenyl group which may have a substituent has a total carbon number of usually 6 or more, usually 12 or less, preferably 10 or less, more preferably 8 or less.

Examples of the substituent that the alkyl group and the phenyl group may have include a hydroxyl group, a carboxy group, and a sulfo group.
In particular, when R ¹ and R ² are hydrogen atoms (NR ¹ R ² is an amino group), when R ¹ is a hydrogen atom and R ² is an alkyl group (NR ¹ R ² is an alkylamino group) And R ¹ is preferably a hydrogen atom and R ² is a phenyl group (NR ¹ R ² is a phenylamino group). However, from the viewpoint of easily exhibiting lyotropic liquid crystallinity, R ¹ Alternatively, R ² is preferably a hydrogen atom, an alkyl group having a carboxy group or a sulfo group, or a phenyl group having a carboxy group or a sulfo group. In particular, it is preferable that both R ¹ and R ² are hydrogen atoms from the viewpoint of easily exhibiting lyotropic liquid crystal properties at a relatively low concentration and excellent process suitability.

<N>
In the formula (1), n represents 0 or 1.

<Compound represented by Formula (2)>

(In the above formula (2), R ¹ , R ² , A, C and n have the same meanings as in the formula (1).)
The azo compound for an anisotropic film of the present invention is preferably a compound whose free acid form is represented by the following formula (2). That is, the substitution position of the sulfo group in the naphthylene group located between C and the terminal naphthyl group substituted with the amino group NR ¹ R ^{2 at} the 7-position is the 7-position from the viewpoint of fixing the rotational isomerism state of azo. Preferably there is. Further, from the viewpoint of suppressing aggregation of the aggregate, the substitution position of the sulfo group in the naphthylene group located between A and C is preferably 6th or 7th position.

<Molecular weight>
The molecular weight of the azo compound for an anisotropic film of the present invention (hereinafter sometimes referred to as “azo compound of the present invention”) in which the form of the free acid is represented by the formula (1) is 1000 or more in the form of the free acid. Is preferable, 2000 or less is preferable, and 1500 or less is more preferable.

<Water-soluble>
The azo compound of the present invention is usually a water-soluble compound.
The azo compound of the present invention has a solubility in water of preferably 0.1% by weight or more, more preferably 0.5% by weight or more at room temperature and normal pressure, specifically at 25 ° C. and 1 atm. preferable. Further, the solubility is preferably 50% by weight or less, and more preferably 40% by weight or less. For example, as will be described later, when an anisotropic film is produced, it is common to use water, a water-miscible organic solvent, or a mixture of water and a water-miscible organic solvent as the solvent. For this reason, if the solubility of the compound in water is too low, it may be difficult to use for such purposes. Conversely, from the viewpoint of forming a favorable association state of the compound, it may be preferable that the solubility in water is not too high.

<Salt>
The azo compound of the present invention may be used as it is in the free acid form (free acid form) as shown in the above formula (1), and a part of the acid group is in salt form. Also good. Further, a salt type compound and a free acid type compound may be mixed. Moreover, when it is obtained in a salt form at the time of production, it may be used as it is, or may be converted into a desired salt form (salt exchange). As the salt exchange method, a known method can be arbitrarily used, and examples thereof include the following methods.

1) A strong acid such as hydrochloric acid is added to an aqueous solution of an azo compound obtained in a salt form, the azo compound is acidified in the form of a free acid, and then an alkali solution having a desired counter ion (for example, an aqueous sodium hydroxide solution) , Neutralizing the acidic group of the compound with a lithium hydroxide aqueous solution and the like, and performing salt exchange.
2) A method of adding a large excess of a neutral salt (eg, sodium chloride, lithium chloride, etc.) having a desired counter ion to an aqueous solution of an azo compound obtained in a salt form, and performing salt exchange in the form of a salting out cake. .
3) The aqueous solution of the azo compound obtained in the salt form is treated with a strongly acidic cation exchange resin, and the azo compound is acidified in the form of a free acid, and then an alkaline solution having a desired counter ion (for example, water A method of neutralizing an acidic group of a compound with a sodium oxide aqueous solution, a lithium hydroxide aqueous solution, etc., and salt-exchange.
4) An aqueous solution of an azo compound obtained in a salt form is allowed to act on a strongly acidic cation exchange resin previously treated with an alkaline solution having a desired counter ion (for example, an aqueous solution of sodium hydroxide, an aqueous solution of lithium hydroxide). How to exchange.

  Whether the acidic group of the azo compound for an anisotropic film of the present invention is a free acid type or a salt type depends on the pKa of the compound and the pH of the compound solution. Therefore, the acidic group of the azo compound for anisotropic film of the present invention may be a free acid type, any salt type, or a mixture of free acid type and salt type or two or more types when there are two or more acidic groups. It can be various types such as a mixture of salt types. In particular, the acidic group of the azo compound in the anisotropic film includes a preferable pH of the composition for an anisotropic film described later and a dissociable salt to the substrate containing the azo compound for the anisotropic film. Under the influence of treatment with a solution or the like, the salt form may be different from that used in the step of producing the anisotropic film.

  Examples of the salt type include salts of alkali metals such as Na, Li, and K, ammonium salts that may be substituted with alkyl groups or hydroxyalkyl groups, and salts of organic amines.

Examples of the alkyl group or hydroxyalkyl group which may be a substituent of the ammonium salt include a lower alkyl group having 1 to 6 carbon atoms and a lower alkyl group having 1 to 6 carbon atoms which are hydroxy-substituted. .
Examples of organic amines include lower alkylamines having 1 to 6 carbon atoms (for example, methylamine, ethylamine, dimethylamine, trimethylamine, etc.), hydroxy-substituted lower alkylamines having 1 to 6 carbon atoms (for example, ethanolamine, Diethanolamine, triethanolamine and the like), carboxy-substituted lower alkylamines having 1 to 6 carbon atoms (for example, carboxymethylamine, carboxyethylamine, carboxypropylamine, dicarboxymethylamine and the like) and the like.
In the case of these salt types, the type is not limited to one type, and a plurality of types may be mixed. Moreover, multiple types may be mixed in one molecule of a compound, and multiple types may be mixed in the composition.

  The preferred type of the acidic group of the azo compound for anisotropic film of the present invention varies depending on the production process of the azo compound, the content of the composition for anisotropic film described later and the preferred pH, etc., but has high solubility in water. Is necessary (for example, when a high compound concentration is required in the composition for anisotropic film in order to develop a lyotropic liquid crystal phase), a lithium salt, an ammonium salt, a triethylamine salt, a water-soluble group is present. It is preferable to have one or more substituted organic amine salts or salts thereof. On the other hand, when low solubility in water is required (for example, when a low-viscosity anisotropic film composition containing a low concentration of an azo compound is required, or when the compound is removed from a compound solution in an azo compound production process, In the case where it is desired to precipitate, it is preferable that it is in a free acid form, or has at least one alkaline earth metal salt such as sodium salt, potassium salt, calcium salt, or these salts.

<Specific example>
Specific examples of the azo compound for an anisotropic film of the present invention include, but are not limited to, compounds having the structure shown below as the form of the free acid.

<Synthesis method>
The azo compound for anisotropic film of the present invention represented by the formula (1) can be produced according to a method known per se.
For example, the azo compound represented by the formula (1-2) can be produced according to the following steps (A) to (D).
(A) From 2-aminonaphthalene-5-sulfonic acid and 8-amino-2-naphthalenesulfonic acid (1,7-Cleves acid), a conventional method (for example, “New Dye Chemistry” written by Yutaka Hosoda (12, 1973)
The monoazo compound is produced through a diazotization and coupling process according to (published by Gihodo on May 21) (see page 396, page 409).
(B) The obtained monoazo compound is similarly diazotized by a conventional method, subjected to a coupling reaction with aniline-ω-methanesulfonic acid, and then subjected to an alkaline hydrolysis reaction to produce a disazo compound.
(C) The obtained disazo compound is similarly diazotized by a conventional method and subjected to a coupling reaction with 8-amino-2-naphthalenesulfonic acid (1,7-Cleves acid) to produce a trisazo compound.
(D) The resulting trisazo compound is similarly diazotized by a conventional method, subjected to a coupling reaction with 7-amino-1-naphthol-3,6-disulfonic acid (RR acid) and salted out with sodium chloride. The target azo compound represented by the formula (1-2) is obtained as a sodium salt.

The azo compound for an anisotropic film of the present invention is usually prepared as a composition for an anisotropic film which will be described later, and is suitably used for preparing an anisotropic film having high dichroism.
As a method for producing an anisotropic film using the azo compound for anisotropic film of the present invention, preferably, for example, the compound is dissolved in an appropriate solvent to form a film (for forming an anisotropic film). A composition (anisotropic film composition) was prepared, and this composition was used to form a film on the surface of various substrates such as a glass plate by a wet film formation method, and the compound contained in the composition was Examples of the method include orientation and lamination. An anisotropic film manufacturing method and a wet film forming method will be described in detail later.

  The azo compound represented by the formula (1) is excellent in associative property and can form a high lyotropic liquid crystal state. Therefore, it is particularly suitable as an azo compound for an anisotropic film formed by a wet film formation method, and since its dichroic ratio is high, a composition containing the compound is used for the production of an anisotropic film. Thus, an anisotropic film having high dichroism can be obtained.

  Below, the composition for anisotropic films containing the azo compound for anisotropic films of this invention is demonstrated. The composition for an anisotropic film of the present invention is a composition suitably used for producing an anisotropic film by a wet film forming method.

[Anisotropic film composition]
The composition for an anisotropic film of the present invention contains the azo compound for an anisotropic film of the present invention and a solvent, and the azo compound for an anisotropic film of the present invention is usually dissolved or dispersed in the solvent. It is.
In the anisotropic film composition of the present invention or in the anisotropic film of the present invention described in detail below, the azo compound for anisotropic film of the present invention can be used alone. The azo compound for anisotropic film of the present invention can be used in combination of two or more, or other dichroic substances can be used in combination. Furthermore, various compounding compounds, solvents, additives, and the like can be used in appropriate combination in order to give desired performance to the produced anisotropic film or to make a composition suitable for production.

<Compound compound>
In the composition for anisotropic film of the present invention, the color tone of the anisotropic film is adjusted, the associative property of the azo compound for the anisotropic film is improved, the durability of the anisotropic film is improved, and the defect For the purpose of reducing the above, a compounding compound may be used in combination with the azo compound for anisotropic film of the present invention.

  Preferable examples of the compound that can be used in combination with the azo compound of the present invention include azo compounds, anthraquinone compounds, amino acids, hydroxyamines, sugars and the like.

For example, C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 34, C.I. I. Direct Yellow 86, C.I. I. Direct Yellow 142, C.I. I. Direct Yellow 132, C.I. I. Acid
Yellow 25, C.I. I. Direct Orange 39, C.I. I. Direct Orange 72, C.I. I. Direct Orange 79, C.I. I. Acid Orange 28, C.I. I. Direct Red 39, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 83, C.I. I. Direct Red 89, C.I. I. Acid Red 37, C.I. I. Direct Violet 9, C.I. I. Direct Violet 35, C.I. I. Direct Violet 48, C.I. I. Direct Violet 57, C.I. I. Direct Blue 1, C.I. I. Direct Blue 67, C.I. I. Direct Blue 83, C.I. I. Direct Blue 90, C.I. I. Direct Green 42, C.I. I. Direct Green 51, C.I. I. Direct Green 59 etc. are mentioned.

Further, an anthraquinone compound may be blended according to the methods described in JP 2007-199333 A and JP 2008-101154 A. Furthermore, a method described in JP 2006-3864 A or a method described in JP 2006-323377 A may be used.

  In addition, as described in JP-A-2007-178993, a cation of 0.9 equivalents or more and 0.99 equivalents or less and a strong acidic anion of 0.02 equivalents or more and 0.1 or less with respect to the acidic group of the azo compound. The time required for the relaxation elastic modulus G to decrease to 1/10 of the temperature at 5 ° C. and 0.01 seconds after applying the strain is 0.1 by adding the equivalent or less. By setting it to 2 seconds or less, defects in the anisotropic film can be suppressed.

Since such a composition tends to lower the pH, a buffer substance may be further added as necessary for the purpose of preventing corrosion of the production apparatus. Examples of buffer substances include D.I. D. Perrin, B.H. Examples include weak acids and weak bases partially or wholly neutralized as described in Dempsey's "Selection and Application of Buffer", Kodansha Scientific (1981), and the like. Specific examples include phosphates, carbonates, organic acids, and the like, and examples of organic acids include malic acid, citric acid, oxalic acid, tartaric acid, amino acids, and the like. Of these, amino acids are preferably used because they promote the association of the azo compound for the anisotropic film and improve the orientation. In addition, an amino acid oligomer in which a plurality of amino acids are condensed is preferable because it also has a function as a rheology adjusting agent of the composition for anisotropic film, and an improvement in flow orientation can be expected by addition. When these buffer substances are used alone and crystallize on an anisotropic film, it is preferable to use a combination of a plurality of different buffer substances.
Furthermore, an ultraviolet absorber, a near infrared absorber, etc. can also be used in combination.

When the azo compound for anisotropic films of the present invention is used in combination with other compounds such as other dichroic substances and compounding compounds, the effects of the azo compound for anisotropic films of the present invention are sufficiently exerted. Therefore, the other combined compound is preferably 50% by weight or less, and more preferably 10% by weight or less based on the azo compound for anisotropic film of the present invention.
The pH of the anisotropic film composition thus obtained is usually about 2 to 10.

<Additives>
The composition for an anisotropic film of the present invention, for example, when used to apply to a substrate as a solution for forming an anisotropic film in a wet film forming method described later, wettability to the substrate, coating In order to improve property, additives, such as surfactant, can be added as needed. As the surfactant, any of anionic, cationic, and nonionic surfactants can be used. In addition to the above, known additives described in, for example, “Additives for Coating” (Edited by J. Bieleman, Willey-VCH, 2000) can be used. The concentration of the additive is sufficient to obtain the desired effect, and is an amount that does not inhibit the orientation of the azo compound for anisotropic film of the present invention and the compounding compound molecule used as necessary. The concentration in the composition for an isotropic film is usually more preferably 0.05% by weight or more and 0.5% by weight or less.

<Solvent>
As the solvent used in the composition for an anisotropic film of the present invention, water, a water-miscible organic solvent, or a mixture thereof is suitable. Specific examples of the organic solvent include alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin, and cellosolves such as methyl cellosolve and ethyl cellosolve. The mixed solvent is mentioned.

<Concentration>
The concentration in the case of dissolving the azo compound for anisotropic film of the present invention and other compounds such as the above-mentioned compounding compounds and additives used as necessary includes the solubility of these solutes and the lyotropic liquid crystal state. Although it depends on the formation concentration of the association state, it is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, preferably 30% by weight or less, more preferably 20% by weight or less.

[Anisotropic film]
The anisotropic film of the present invention is characterized by containing the azo compound for anisotropic film of the present invention. The anisotropic film is an anisotropic film formed by a wet film forming method. Usually, the anisotropic film of the present invention is obtained by depositing the anisotropic film composition of the present invention on a substrate by a wet film forming method.

  As described above, the azo compound for an anisotropic film of the present invention represented by the formula (1) can form a high lyotropic liquid crystal state and can exhibit a high-order molecular orientation state, and has a high dichroism. Can show gender. Therefore, the anisotropic film of the present invention containing such an azo compound for anisotropic film of the present invention is a useful film exhibiting high dichroism.

Although the anisotropic film of the present invention exhibits a high dichroic ratio, the dichroic ratio is preferably 8 or more, more preferably 12 or more, and particularly preferably 15 or more.
In particular, when used for a polarizing film, a film having a neutral color tone is preferable. In the L * a * b * color system, √ {(a ^* ) ² + (b ^* ) ² } ≦ 30, preferably √ {(a ^* ) ² + (b ^* ) ² } ≦ 10, more preferably √ {(a ^* ) ² + (b ^* ) ² } ≦ 5. Moreover, the higher the transmittance of the membrane, the better. Usually, it is 25% or more, preferably 35% or more, more preferably 40% or more, and particularly preferably 44% or more.
As the deflecting film, those satisfying both the above-described preferable ranges of hue and transmittance are particularly preferable, and such a deflecting film is preferably used as a display element, particularly as a polarizing element for a color display element.

<Method for producing anisotropic film>
In the present invention, an anisotropic film is produced by a wet film forming method. More preferably, it is produced by a wet film forming method using the composition for anisotropic film of the present invention.

<Wet deposition method>
The wet film-forming method referred to in the present invention is based on an anisotropic film compound through a process in which an anisotropic film composition is applied to various substrates such as a glass plate by some method and the solvent is dried. This is a method of orientation and lamination on a material. In the wet film formation method, when the composition itself containing a solvent is formed on a substrate, the compound itself self-associates in the composition or in the process of drying the solvent, thereby aligning in a small area. Happens. By applying an external field to this state, it is characterized in that an anisotropic film having desired performance is obtained by orienting in a certain direction in a macro region. This is different from the method based on the principle that a so-called polyvinyl alcohol (PVA) film or the like is dyed with a solution containing an anisotropic compound and stretched, and the compound is oriented only by a stretching process. Here, the external field includes the influence of the orientation treatment layer previously applied on the base material, shear force, magnetic field, and the like, and these may be used alone or in combination. Further, the process of forming the composition on the substrate, the process of aligning by applying an external field, and the process of drying the solvent may be performed sequentially or simultaneously.

Examples of the method for applying the anisotropic film composition on the substrate in the wet film forming method include a coating method, a dip coating method, an LB film forming method, and a known printing method. There is also a method of transferring the anisotropic film thus obtained to another substrate. Among these, in the present invention, it is preferable to use a coating method, and the coating method will be described in detail below.
The azo compound for an anisotropic film of the present invention can be in a state in which an aggregate is formed by a good intermolecular interaction such as a lyotropic liquid crystal state in the composition for an anisotropic film. Therefore, this was applied to a substrate such as glass or resin, a shearing force was applied at the same time or after application, or an orientation treatment layer was applied on the substrate in advance, and the influence was made. By drying the film, the azo compound for anisotropic film of the present invention and the compounding compound used as necessary can be oriented in a certain direction to obtain an excellent anisotropic film.

  As the substrate, a transparent material having a thickness of about 10 to 1500 μm made of glass, resin or the like is used. Examples of the resin include triacetate, acrylic resin, polyester resin, triacetyl cellulose, cycloolefin resin, and urethane resin.

  In order to control the orientation direction of the azo compound for an anisotropic film of the present invention in the composition for an anisotropic film and the aforementioned compounding compound molecule used as necessary, the surface of the base material is “ The alignment treatment layer may be applied by a known method described in “Liquid Crystal Handbook” (Maruzen Co., Ltd., issued on October 30, 2000), pages 226 to 239.

  As a method for applying the composition for an anisotropic film on a substrate, a conventionally known method may be used. For example, Yuji Harasaki "Coating Engineering" (Asakura Shoten Co., Ltd., issued on March 20, 1971) Pages 253 to 277 or “Creation and Application of Molecular Coordinating Materials” supervised by Kunihiro Ichimura (CMC Publishing Co., Ltd., published on March 3, 1998), pages 118 to 149, etc. For example, a spin coating method, a spray coating method, a bar coating method, a roll coating method, a blade coating method, a free span coating method, a die coating method and the like may be mentioned on a substrate that has been previously subjected to an alignment treatment.

  By applying a shearing force to the azo compound for an anisotropic film of the present invention in the anisotropic film composition coated on a substrate and the compounding compound used as necessary, the azo compound of the present invention And the above-mentioned compound for compounding etc. which are used as needed orientate in a fixed direction. A bar coating method, a roll coating method, a blade coating method, a free span coating method, a die coating method and the like are preferable because a shearing force can be applied simultaneously with application.

The temperature at the time of application of the anisotropic film composition to the substrate is preferably 0 ° C. or more and 80 ° C. or less, and the humidity is preferably about 10% RH or more and 80% RH or less.
The drying temperature is preferably 0 ° C. or more and 120 ° C. or less, and the humidity is preferably about 10% RH or more and 80% RH or less.

When forming an anisotropic film on a substrate by the above method, the thickness of the formed anisotropic film is usually a film thickness after drying, preferably 50 nm or more, more preferably 100 nm or more, preferably Is 50 μm or less, more preferably 1 μm or less.
The produced anisotropic film of the present invention preferably contains the compound of the present invention in a concentration in terms of free acid of 20% by weight or more, more preferably 30% by weight or more, and particularly preferably 40% by weight or more. To do. When there is little content of the compound of this invention, the orientation in a lyotropic liquid crystal state will become inadequate, and it may show the property which is not preferable as an anisotropic film | membrane.

The anisotropic film thus obtained may be insolubilized.
Insolubilization means a treatment step that suppresses elution of the compound from the film by reducing the solubility of the compound in the film, thereby increasing the stability of the film. For example, the difference in solubility depending on the salt form of the compound for anisotropic film of the present invention is as described above, and in this step, the treatment can be performed by utilizing such difference.
Specifically, for example, a process of replacing ions with a lower valence with ions with a higher valence (for example, replacing a monovalent ion with a multivalent ion). As such a treatment method, for example, known methods such as treatment steps described in Yutaka Hosoda, “Theoretical Manufacturing Dye Chemistry” (Gihodo, 1957), pages 435 to 437 are used. Preferably, the obtained anisotropic film is treated by a method described in JP-A No. 2007-241267, etc. to form a film that is insoluble in water, such as ease of post-processing and durability. It is preferable from the viewpoint.

  Since the anisotropic film manufactured by such a method may have low mechanical strength, a protective layer is provided as needed. This protective layer is formed by laminating an anisotropic film with a transparent polymer film such as triacetate, acrylic, polyester, polyimide, triacetyl cellulose, cycloolefin resin, or urethane film, and is practically used.

  In addition, when the anisotropic film of the present invention is used as a polarizing film or the like for various display elements such as LCDs and OLEDs, the film is formed directly on the electrode substrate or the like constituting these display elements. The base material made can be used as a constituent member of these display elements.

[Polarizing element]
The anisotropic film of the present invention functions as a polarizing film that obtains linearly polarized light, circularly polarized light, elliptically polarized light, etc. by utilizing the anisotropy of light absorption. By selecting a composition containing an azo compound for a film and the above-mentioned compounding dye used as necessary, it can be functionalized as various anisotropic films such as refractive anisotropy and conduction anisotropy. This type of polarizing element can be used for various applications.

  The polarizing element of the present invention is provided with the above-described anisotropic film of the present invention, but may be a polarizing element comprising only an anisotropic film, or an anisotropic film may be formed on a substrate. The polarizing element provided may be sufficient. In the present invention, a polarizing element comprising an anisotropic film on a substrate is referred to as a polarizing element including the substrate.

When the anisotropic film of the present invention is formed on a substrate and used as a polarizing element, it may be used only with the substrate and the formed anisotropic film, and in addition to the protective layer as described above, Layers with optical functions such as adhesive layer or antireflection layer, alignment film, retardation film function, brightness enhancement film function, reflection film function, transflective film function, diffusion film function, etc. For example, layers having various functions may be laminated by a wet film formation method or the like, and used as a laminate.
These layers having an optical function can be formed, for example, by the following method.

  The layer having a function as a retardation film is subjected to, for example, a stretching process described in JP-A-2-59703, JP-A-4-230704, or a process described in JP-A-7-230007. Or can be formed.

  The layer having a function as a brightness enhancement film may be formed by forming a fine hole by a method as described in, for example, Japanese Patent Application Laid-Open Nos. 2002-169025 and 2003-29030, or the center of selective reflection. It can be formed by overlapping two or more cholesteric liquid crystal layers having different wavelengths.

  The layer having a function as a reflective film or a transflective film can be formed using a metal thin film obtained by vapor deposition or sputtering. The layer having a function as a diffusion film can be formed by coating the protective layer with a resin solution containing fine particles.

  The layer having a function as a retardation film or an optical compensation film can be formed by applying and aligning a liquid crystal compound such as a discotic liquid crystal compound or a nematic liquid crystal compound.

The anisotropic film using the azo compound for anisotropic film of the present invention can be directly formed on a high heat-resistant substrate such as glass, and a high heat-resistant polarizing element can be obtained. Therefore, it can be suitably used not only for liquid crystal displays and organic electroluminescence displays, but also for applications requiring high heat resistance such as liquid crystal projectors and in-vehicle display panels.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the following description, “part” means “part by weight”.
In each of the following examples, the dichroic ratio, the single transmittance, and the contrast ratio of the anisotropic film are measured using a spectrophotometer in which a prism polarization element is disposed in the incident optical system and an integrating sphere is disposed in the light receiving system. The transmittance of the anisotropic film was measured using “SolidSpec3700” manufactured by Seisakusho Co., Ltd. and then calculated according to the following formula.

Dichroic ratio (D) = Az / Ay
Az = -log (Tz)
Ay = -log (Ty)
Tz: Transmittance for polarized light in the absorption axis direction of the anisotropic film
Ty: transmittance for polarized light in the direction of the polarization axis of the anisotropic film

    Single transmittance (Ts) = (Ty + Tz) / 2

Contrast ratio (C / R) = (Ty ² + Tz ² ) / (2Ty · TZ)

In addition, the main absorption wavelength was calculated | required as the longest wavelength in the wavelength range from 380 nm to 780 nm where Az becomes maximum. A plurality of sub-absorptions exist in the vicinity of between 400 and 550 nm, and are overlapped and cannot be separated. Therefore, the wavelength was determined as a wavelength at which Az is maximum below the main absorption wavelength.
Further, the single transmittance and contrast ratio corrected for visibility were calculated using the color matching function of the XYZ color system (CIE1931 standard color system) and the spectrum of the D65 light source.

[Example 1]
In 78.6 parts of water, 12 parts of 50 mol% lithium neutralized salt of the azo compound for anisotropic film of the present invention represented by formula (1-2), 0.4 part of lithium chloride, glycine 3 manufactured by Tokyo Chemical Industry Co., Ltd. Part and 6 parts of glycylglycylglycine manufactured by Tokyo Chemical Industry Co., Ltd. were stirred and dissolved, followed by filtration to remove insolubles, thereby obtaining an anisotropic film composition. On a glass substrate (150 mm × 75 mm, 1.1 mm thickness, about 80 nm polyimide alignment film that has been previously rubbed with a cloth) with a polyimide alignment film formed on the surface by spin coating, The above anisotropic film composition was applied with an applicator (manufactured by Horita Seisakusho) with a gap of 4 μm, and then naturally dried to obtain an anisotropic film.
For the obtained anisotropic film, the single transmittance, dichroic ratio, and contrast ratio at the main absorption wavelength and the sub-absorption wavelength were measured, and the single transmittance, dichroic ratio, and contrast ratio corrected for visibility were calculated. . The results are shown in Table 1 below. This anisotropic film had high polarization characteristics that can sufficiently function as a polarizing film.

[Example 2]
An anisotropic film was obtained in the same manner as in Example 1 except that the anisotropic film composition prepared in Example 1 was applied with an applicator (manufactured by Horita Seisakusho) with a gap of 2 μm.
For the obtained anisotropic film, the single transmittance, dichroic ratio, and contrast ratio at the main absorption wavelength and the sub-absorption wavelength were measured, and further, the single transmittance, dichroic ratio, and contrast ratio corrected for visibility were calculated. . The results are shown in Table 1 below. This anisotropic film had high polarization characteristics that can sufficiently function as a polarizing film.

[Comparative Example 1]
In 81.8 parts of water, 2 parts of a 100 mol% lithium neutralized salt of an azo compound represented by the following formula (I), 10 parts of a 50 mol% lithium neutralized salt of an azo compound represented by the following formula (I), chloride 0.2 parts of lithium, 2 parts of Tokyo Chemical Co., Ltd. glycine and 4 parts of Tokyo Chemical Industry Co., Ltd. glycylglycylglycine were added, stirred and dissolved, and then filtered to remove insolubles, thereby forming an anisotropic film. A composition was obtained.
An anisotropic film is produced in the same manner as in Example 1, and the single transmittance, dichroic ratio, and contrast ratio at the main absorption wavelength and the sub-absorption wavelength are measured, and further, the single transmittance and dichroic ratio with corrected visibility are corrected. The contrast ratio was calculated. The results are shown in Table 1 below. Compared to the anisotropic films of Examples 1 and 2, only low polarization characteristics were obtained.

[Comparative Example 2]
In 90.6 parts of water, 6.3 parts of 100 mol% lithium neutralized salt of an azo compound represented by the following formula (II), 2.1 parts of glycine manufactured by Tokyo Chemical Industry Co., Ltd., 1 part of glycylglycylglycine manufactured by Tokyo Chemical Industry Co., Ltd. Was added, and dissolved by stirring, followed by filtration to remove the insoluble matter, thereby obtaining an anisotropic film composition.
An anisotropic film is produced in the same manner as in Example 1, and the single transmittance, dichroic ratio, and contrast ratio at the main absorption wavelength and the sub-absorption wavelength are measured, and further, the single transmittance and dichroic ratio with corrected visibility are corrected. The contrast ratio was calculated. The results are shown in Table 1 below. Compared to the anisotropic films of Examples 1 and 2, only low polarization characteristics were obtained.

Claims (5)

An azo compound for anisotropic film, wherein the free acid is represented by the following formula (1).

(In the above formula (1), R ¹ and R ² are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or an optionally substituted phenyl group. Represents
A represents the following formula (1-a) or (1-b),

(In the above formula (1-a) or (1-b), R ³ represents a hydrogen atom, a hydroxyl group, or an optionally substituted alkoxy group having 1 to 4 carbon atoms.)
C represents a 1,4-phenylene group which may have an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an acetylamino group as a substituent;
n represents 0 or 1. )   The azo compound for anisotropic films according to claim 1, which is for wet film formation.   An anisotropic film composition comprising the azo compound for an anisotropic film according to claim 1 or 2 and a solvent.   An anisotropic film comprising the azo compound for an anisotropic film according to claim 1.   A polarizing element comprising the anisotropic film according to claim 4.