JP2008292978A - Retardation film and optical element, and method for manufacturing retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control wavelength dispersion characteristics of a refractive index and three-dimensional anisotropy in a retardation film at a low cost. <P>SOLUTION: The retardation film contains a liquid crystalline retardation material having a negative birefringence and a compound expressed by a formula. In the formula, X represents an alkyl group which can have a substituent, an alkoxy group which can have a substituent, an amino group which can have a substituent, a hydroxyl group, a cyano group or a halogen atom; n represents an integer of 0 to 5; Y represents a hydrogen atom or a cyano group; and Z represents a hydroxyl group, an alkoxy group which can have a substituent, or a halogen atom. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a retardation film used for a display or the like, an optical element having the retardation film, and a method for producing the retardation film.

  Various retardation films are used in flat panel displays such as liquid crystal displays. In particular, since a liquid crystal display is composed of a liquid crystal layer having an optical anisotropy and a polarizing plate, the liquid crystal display has a strong viewing angle dependency. It is desirable to precisely control the phase difference in the film thickness and the phase difference in the film thickness direction (see Non-Patent Document 1).

  The optical mechanism of the retardation film includes a birefringence type and a reflection type. For example, the former is a polymer with refractive index anisotropy provided by mechanical deformation / flow such as stretching or coating, or irradiation with polarized ultraviolet rays. Examples thereof include a film and a liquid crystal compound film. Examples of the latter include a Fresnel prism and a Mooney prism, but a birefringent type is often used industrially from the viewpoint of cost, simplicity of the optical system, and response to an increase in size.

  Among the birefringent retardation films, those using liquid crystal compounds can spontaneously control the refractive index anisotropy of the film depending on their molecular structure, and do not require precise process control. As such liquid crystal compounds, various liquid crystal compounds such as thermotropic liquid crystal compounds (see Non-Patent Document 2) and chromonic liquid crystal compounds (see Patent Document 1) have been proposed as retardation materials.

  A material having negative birefringence is said to be useful for compensating the viewing angle characteristics of a liquid crystal display (see Non-Patent Document 3). As liquid crystalline retardation materials having negative birefringence, for example, discotic liquid crystals are known in thermotropic liquid crystals, and chromonic liquid crystals are known in the lyotropic liquid crystals. Among them, the chromonic liquid crystal has a molecular structure in which a solvophilic functional group is bonded around a disc-shaped or strip-shaped mesogen as described in Non-Patent Document 4, and by controlling the molecular shape, Since the three-dimensional refractive index can be easily controlled, the process cost can be suppressed, which is suitable for a retardation material for liquid crystal displays.

  The mesogens of discotic liquid crystals and chromonic liquid crystals often comprise aromatic compounds such as benzene, naphthalene, triphenylene, and perylene; condensed polycyclic compounds such as pyridine, triazine, quinoline, and xanthone; Has a large absorption in the wavelength region close to the visible region. For this reason, the wavelength dependence of the phase difference in the visible light region monotonously decreases with respect to the wavelength, and the wavelength dependence tends to be strong. Therefore, it was not suitable for use as a so-called broadband retardation film.

  Until now, as a method for widening the retardation film, a method of laminating a plurality of retardation films (see Non-Patent Document 5) or a co-polymerization of monomer units having positive and negative molecular polarizability anisotropy is used. A method using coalescence (see Non-Patent Document 6) has been attempted.

International Publication No. 2002/048759 Pamphlet S. M. Kelly, "Flat Panel Displays-Advanced Organic Materials", The Royal Society of Chemistry, (2000) P. V. Witte, J. V. Harren, J. Tuijtelaars, S. Stallinga and J. Lub, Jpn. J. Appl. Phys. Vol. 38, 748-754, (1999) Toray Research Center "Frontiers in Liquid Crystal Display Material Development", P.240, (2006) A. S. Vasilevskaya, E. V. Generalova and A. S. Sonin, "Chromonic mesophases", Russian Chemical Reviews, 58 (9), 904, (1989). Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, "Optical Properties of Retardation Films for STN-LCDs", SID International Symposium, 1991, 739-742. Akihiko Uchiyama, “Chromatic dispersion control of birefringence in retardation film and its application to liquid crystal display”, Journal of the Japanese Liquid Crystal Society, vol.9, No.4, p.209, (2005)

  As described above, attempts to increase the bandwidth of the retardation film have been made in Non-Patent Document 5, Non-Patent Document 6, and the like. However, the lamination method described in Non-Patent Document 5 is not industrially useful because the process cost increases in addition to the material cost of a plurality of films. The copolymer method described in Non-Patent Document 6 is easy to control the wavelength dispersion characteristics, but it requires a complicated process to control the three-dimensional anisotropy of the refractive index. Lack of sex. That is, a retardation film capable of easily controlling the wavelength dispersion characteristic of refractive index and three-dimensional anisotropy at low cost has not been obtained so far.

  The present invention has been made in view of the above problems. That is, an object of the present invention is to control the wavelength dispersion characteristic of the refractive index and the three-dimensional anisotropy in the retardation film at low cost.

  As a result of intensive studies by the present inventors, it is possible to solve the above problems by incorporating a compound represented by the following formula (1) into a retardation film containing a liquid crystalline retardation material having negative birefringence. As a result, the present invention has been completed.

（式（１）中、Ｘは、置換基を有していてもよいアルキル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアミノ基、水酸基、シアノ基またはハロゲン原子である。ｎは、０以上５以下の整数である。Ｙは、水素原子またはシアノ基である。Ｚは、水酸基、置換基を有していてもよいアルコキシ基またはハロゲン原子である。） That is, the gist of the present invention resides in a retardation film comprising a liquid crystalline retardation material having negative birefringence and a compound represented by the following formula (1) (Claim 1).

(In the formula (1), X represents an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an amino group which may have a substituent, a hydroxyl group, and a cyano group. Or n is an integer of 0 to 5. Y is a hydrogen atom or a cyano group, and Z is a hydroxyl group, an optionally substituted alkoxy group or a halogen atom. .)

  The liquid crystalline retardation material is preferably a water-soluble compound exhibiting chromonic liquid crystal properties.

  Another subject matter of the present invention lies in an optical element comprising the retardation film (claim 3).

  Still another subject matter of the present invention is to produce a retardation film, characterized in that a film containing a liquid crystalline retardation material having negative birefringence is brought into contact with the compound represented by the above formula (1). It resides in a method (claim 4). In addition, it is preferable that the manufacturing method includes a wet film forming step of forming a liquid crystalline retardation material by a wet film forming method and an impregnation step of impregnating the compound represented by the above formula (1) into the film. (Claim 5).

  According to the present invention, the wavelength dispersion characteristic of the refractive index and the three-dimensional anisotropy in the retardation film can be controlled at low cost, and the broadband retardation plate having excellent performance and the retardation film are provided. An optical element can be obtained.

  Hereinafter, the present invention will be described in detail with reference to examples and embodiments. However, the present invention is not limited to the following examples and embodiments, and can be implemented with arbitrary modifications without departing from the gist of the present invention.

  The retardation film of the present invention comprises a liquid crystalline retardation material having negative birefringence (hereinafter sometimes referred to as “specific liquid crystalline retardation material”) and a compound represented by formula (1) described below (hereinafter referred to as “specific liquid crystalline retardation material”). (Sometimes referred to as a “specific compound”).

  In the following description, the specific compound will be described first, and then the specific liquid crystalline retardation material, the retardation film of the present invention, and the production method thereof will be described.

（式（１）中、Ｘは、置換基を有していてもよいアルキル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアミノ基、水酸基、シアノ基またはハロゲン原子である。ｎは、０以上５以下の整数である。Ｙは、水素原子またはシアノ基である。Ｚは、水酸基、置換基を有していてもよいアルコキシ基またはハロゲン原子である。） [1. Specific compound]
A specific compound is a compound which has a structure shown to following formula (1).

(In the formula (1), X represents an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an amino group which may have a substituent, a hydroxyl group, and a cyano group. Or n is an integer of 0 to 5. Y is a hydrogen atom or a cyano group, and Z is a hydroxyl group, an optionally substituted alkoxy group or a halogen atom. .)

(About X and n)
In formula (1), X is an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an amino group, a hydroxyl group, a cyano group or a halogen atom.

Examples of the alkyl group which may have a substituent include alkyl groups having usually 1 or more carbon atoms and usually 10 or less, preferably 3 or less.
Specific examples include a methyl group, an ethyl group, and a propyl group. Of these, a methyl group is preferred. The substitution position is preferably the 4-position where the molecular shape is a rod. Here, the 4-position refers to the 4-position when the position at which the group containing Y and Z is substituted with the benzene ring is the 1-position.

  The alkyl group may further have a substituent. Examples of the substituent include halogen atoms such as fluorine, chlorine and bromine. These substituents may have one, and may have two or more in arbitrary combinations and ratios.

Examples of the alkoxy group which may have a substituent include an alkoxy group having 1 or more carbon atoms and usually 10 or less, preferably 3 or less.
Specific examples include a methoxy group, an ethoxy group, and a propoxy group. Of these, a methoxy group is preferred. The substitution position is preferably the 4-position where the molecular shape is a rod. Here, the 4-position refers to the 4-position when the position at which the group containing Y and Z is substituted with the benzene ring is the 1-position.

  The alkoxy group may further have a substituent. Examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom and a bromine atom. These substituents may have one, and may have two or more in arbitrary combinations and ratios.

  Examples of the substituent of the amino group which may have a substituent include an alkyl group. These substituents may have one, and may have two or more in arbitrary combinations and ratios.

  Examples of the halogen atom include a chlorine atom, a bromine atom, and a fluorine atom. Of these, a chlorine atom is preferred.

  Among the above, X is preferably an alkyl group which may have a substituent or an alkoxy group which may have a substituent. Specifically, a methyl group or a methoxy group is preferable. This is because the UV absorption wavelength is appropriate and the solubility is good.

Moreover, in Formula (1), n is an integer of 0-5, and represents the number of X.
That is, the specific compound may not have X substituted on the aromatic ring of the basic skeleton, and may have one or a plurality of the above X (however, 5 or less). When n is 2 or more, all Xs may be the same, or two or more may be used in any combination and ratio.

  The number of substituents (that is, n) is arbitrary as long as the effect of the present invention is not significantly impaired as long as it is within the above-mentioned range, but is usually 0 or more, preferably 1 or more, and usually 5 or less, preferably 3 or less. Particularly preferably 1.

(About Y)
In formula (1), Y is a hydrogen atom or a cyano group, preferably a hydrogen atom.

(About Z)
In formula (1), Z is a hydroxyl group, an alkoxy group which may have a substituent, or a halogen atom.

Examples of the alkoxy group which may have a substituent include an alkyl group having usually 1 or more carbon atoms and usually 5 or less, preferably 3 or less.
Specific examples include methoxy group, ethoxy group, propoxy and the like. Of these, a methoxy group is preferred.

  The alkoxy group may further have a substituent. Examples of the substituent include halogen atoms such as fluorine, chlorine and bromine. These substituents may have one, and may have two or more in arbitrary combinations and ratios.

  Examples of the halogen atom include a chlorine atom, a bromine atom, and a fluorine atom. Of these, a chlorine atom is preferred.

  Among the above, as Z, a hydroxyl group is preferable. It is because it is excellent in solubility and orientation.

(Specific compound types)
If a specific compound is provided with the said structure, there will be no restriction | limiting unless the effect of this invention is impaired remarkably. Specific examples thereof include 4-methoxycinnamic acid and 4-hydroxycinnamic acid. This is because the UV absorption wavelength is appropriate and the solubility is good.

  As for the specific compound, only 1 type may be contained in the retardation film of this invention, and 2 or more types may be contained by arbitrary combinations and a ratio. The wavelength dispersion characteristic can be controlled by selecting a specific compound.

(Physical properties of specific compounds)
The molecular weight of the specific compound is usually 140 or more, preferably 150 or more, and usually 1000 or less, preferably 500 or less, more preferably 300 or less. If it exceeds this range, there is a possibility that the specific compound is difficult to impregnate the retardation film in the impregnation step described later.

  The specific compound is a compound exhibiting birefringence. In the present invention, a compound having birefringence opposite to that of the liquid crystalline retardation material is selected. Therefore, in the present invention, since the specific liquid crystalline retardation material has negative birefringence, a specific compound having positive birefringence is selected.

[2. Specific liquid crystalline retardation material]
The specific liquid crystal phase difference material is a material having nematic liquid crystal properties having negative birefringence. The specific liquid crystalline retardation material is preferably a compound having a high degree of long-range order with respect to the molecular orientation and exhibiting fluidity as a liquid.

  Specific liquid crystalline retardation materials include discotic liquid crystal compounds and chromonic liquid crystal compounds. Of these, chromonic liquid crystal compounds are preferred. This is because it is easy to control the three-dimensional anisotropy.

  Specific examples of the specific liquid crystalline retardation material include H. Mori, Y. Itoh, Y. Nishimura, T. Nakamura, and Y. Sinagawa, AM-LCD'96 / IDW'96 Proceedings of the Third International Display. Workshop, Kobe, Vol.1, p.189-191, (1996) and R. Hentschke, PJB Edwards, N. Boden, RJ Bushby, Macromol. Symp., 81, 361-367, (1994). Discotic liquid crystal compounds; water-soluble chromonic liquid crystal compounds described in JP-A-52-2541, JP-A-2001-515945, and WO 2002/048759.

  Specific examples of preferred ones include disodium cromoglycate (DSCG), cromoglycate compounds such as 7,7-chromoglycate, baflorin sodium salt, nafoxidine, acrinol, hexa-oxaalkyl-triphenylene. Etc.

  The anisotropic film material described in Japanese Patent Application No. 2006-335245 is also preferable. The anisotropic film material will be described in detail later.

The specific liquid crystalline retardation material is not limited to the above-described examples as long as the effects of the present invention are not significantly impaired, but the above-exemplified compounds are preferable. Moreover, you may use by only 1 type and may use 2 or more types by arbitrary combinations and a ratio.
In addition, if the specific liquid crystalline retardation material is a discotic liquid crystal compound, two or more kinds of chromonic liquid crystals may be used in combination if the discotic liquid crystal compounds are water-soluble chromonic liquid crystals.

(Physical properties of specific liquid crystalline retardation materials)
The maximum absorption wavelength of the specific liquid crystalline phase difference material is usually a wavelength of 420 nm or less, preferably a wavelength of 400 nm or less, more preferably a wavelength of 350 nm or less.
Above this range, there are cases where it absorbs visible light and is colored yellow, which is not preferable as a retardation material. In addition, the chromatic dispersion of the phase difference becomes steep, and chromatic dispersion control may be difficult.

The specific liquid crystalline retardation material is preferably water-soluble. When a water-soluble material is used, since the voids existing between the stacked molecular columns in the liquid crystalline retardation material become relatively large, it becomes easy to control the wavelength dispersion.
Here, “water-soluble” means that 0.1% by weight or more dissolves in distilled water.
Further, the molecular column refers to an aggregate in which flat molecules are laminated in almost parallel planes.

  The molecular weight of the specific liquid crystalline retardation material is not limited as long as the effects of the present invention are not significantly impaired, but is preferably 100 or more, more preferably 200 or more, and preferably 2000 or less, more preferably 1000 or less. Outside this range, the liquid crystallinity tends to be difficult to develop.

  As the specific liquid crystalline constant phase difference material, a material in which a large area is uniformly aligned by an external field such as a flow field or an electromagnetic field or contact with an aligned substrate is preferable. Further, a material whose refractive index for polarized light oscillating in the alignment direction is smaller than the refractive index in the direction perpendicular to the alignment is preferable.

  Furthermore, the specific liquid crystalline retardation material is preferably a material that can accurately and uniformly control the retardation within the film surface by appropriately controlling the film thickness and the degree of orientation. It is preferable that the control can be freely set in the order of the wavelength of visible light or a quarter thereof.

[3. Retardation film]
The retardation film of the present invention contains a specific liquid crystalline retardation material and a specific compound. The retardation film of the present invention may contain other compounds as long as the effects of the present invention are not significantly impaired.

The content of the specific liquid crystalline retardation material with respect to 100 parts by weight of the retardation film of the present invention depends on the desired wavelength dispersion and the birefringence of the specific liquid crystalline retardation material alone, preferably 30 parts by weight or more, Moreover, it is preferably 99 parts by weight or less.
In addition, when the retardation film of this invention contains two or more types of specific liquid crystalline phase difference materials, it is preferable that those total values exist in the said range.

The content of the specific compound relative to 100 parts by weight of the retardation film of the present invention depends on the desired wavelength dispersion and the birefringence of the specific liquid crystalline retardation material alone, but is usually 0.5 parts by weight or more, preferably 1 It is at least 5 parts by weight, more preferably at least 5 parts by weight, and usually at most 90 parts by weight, preferably at most 70 parts by weight, more preferably at most 50 parts by weight. Above this range, there is a possibility that the film will crack during manufacture. Further, if it falls below this range, there is a possibility that the chromatic dispersion control is insufficient.
In addition, when the retardation film of this invention contains two or more types of specific compounds, it is preferable that those total values exist in the said range.

  In the retardation film of the present invention, when the total weight of the specific compound and the specific liquid crystalline retardation material is 100 parts by weight, the weight of the specific compound is usually 1 part by weight or more, preferably 10 parts by weight or more, Moreover, it is 70 weight part or less normally, Preferably it is 50 weight part or less.

  The retardation film of the present invention may contain other compounds in addition to the specific liquid crystalline retardation material and the specific compound described above. For example, a surfactant added for improving wettability during film formation, a polymer compound for imparting strength of the film and its monomer, an initiator, or the like may be included. These compounds may be used alone or in combinations of two or more in any ratio.

  The thickness of the retardation film of the present invention is usually 0.5 μm or more, preferably 1 μm or more, more preferably 2 μm or more, and usually 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less. Above this range, orientation defects tend to occur. On the other hand, below this range, it tends to be difficult to maintain film thickness uniformity during production.

[4. Method for producing retardation film]
The method for producing a retardation film of the present invention can be achieved by bringing a film containing a specific liquid crystalline retardation material (hereinafter sometimes referred to as “specific retardation film” as appropriate) and a specific compound into contact with each other. It is not limited as long as the effect is not significantly impaired. For example, the specific compound may be dissolved in a solvent, and the specific retardation film may be immersed in the solution, or the solution may be applied to the specific retardation film. Further, other operations may be performed before, after, or during the contact between the specific retardation film and the specific compound.
Hereinafter, a typical method for producing a retardation film of the present invention will be described, but the present invention is not limited to the following unless the effects of the present invention are significantly impaired.

[4-1. Manufacturing method of specific retardation film]
As the specific retardation film, any known method may be used as long as the specific liquid crystalline retardation material can be formed into a film shape. However, in the present invention, it is preferable to obtain a film by a wet film-forming method using a solution or dispersion liquid (hereinafter sometimes simply referred to as “coating liquid”) containing a specific liquid crystalline retardation material. .

[4-1-1. Coating liquid]
The concentration of the specific liquid crystalline retardation material in the coating solution depends on the solubility of the specific liquid crystalline retardation material and the formation concentration of the supramolecular structure such as the chromonic liquid crystal state, but is usually 0.1% by weight or more, preferably Is 0.5% by weight or more, usually 50% by weight or less, preferably 30% by weight or less. Below this range, a uniform retardation film may not be formed. On the other hand, if it exceeds this range, the viscosity of the coating solution may increase, making it difficult to handle.

The coating liquid contains a solvent in addition to the specific liquid crystalline retardation material. The solvent may be selected in consideration of the operability of the coating liquid in the wet film forming method described later, the manifestation of the liquid crystal state of the specific liquid crystalline retardation material, and the like.
Examples of solvents are water, water-miscible organic solvents, or mixtures thereof.
Specific examples of water-miscible organic solvents include C1-C4 lower alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; glycols such as ethylene glycol and diethylene glycol; cellosolves such as methyl cellosolve and ethyl cellosolve And the like.
In addition, a solvent may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The coating liquid may contain other components in addition to the solvent. Moreover, these other components may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  Examples of other components include additives such as surfactants. The surfactant is used as necessary in order to improve the wettability to the substrate surface and the coating property when the coating liquid is applied to the substrate during the formation of the retardation film.

  As the surfactant, any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used. Moreover, surfactant may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The concentration of the surfactant in the coating solution is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably 0.05% by weight or more, and usually 0.5% by weight. % Or less, preferably 0.2% by weight or less.

The coating liquid can also contain other anisotropic materials in combination with the specific liquid crystalline retardation material. Examples thereof include chromonic liquid crystal compounds described in R. Hentschke, PJB Edwards, N. Boden, RJ Bushby, Macromol. Symp., 81, 361-367, (1994) and the like.
Specific examples of suitable ones include disodium cromoglycate (DSCG), 7,7-chromoglycate, baflorin sodium salt, nafoxidine, acrinol, hexa-oxaalkyl-triphenylene and the like. By using these compounds in combination, it is possible to produce a film whose optical anisotropy is precisely controlled.
In addition, said anisotropic material may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

[4-1-2. Wet film formation process]
The wet film forming step is a step of forming a liquid crystalline retardation material by a wet film forming method. Here, the wet film forming method is a process including a film forming process for forming the coating liquid and a drying process for removing the solvent. Another process may be performed between the film forming process and the drying process.

In the retardation film, the liquid crystalline retardation material is usually aligned in the film, but the alignment of the liquid crystalline retardation material may be performed in any of the film forming process and the drying process.
Specifically, a known method such as a method of forming a coating solution after forming the coating solution and drying and removing the solvent can be used. Hereinafter, this method will be described in more detail.

(Film formation process)
The film forming step is a step of forming a film by applying the coating liquid.
Here, a case where a retardation film is formed on a substrate such as a glass plate by a film forming process will be described as an example. Note that as long as film formation is possible, the film is not limited to a base material and can be formed on an arbitrary material.

Although there is no restriction | limiting in a base material, For example, glass, a triacetate, an acryl, polyester, a triacetyl cellulose, or a urethane type film etc. are mentioned.
Further, in order to control the orientation direction, the surface of the base material is aligned by a known method described in “Liquid Crystal Handbook” Maruzen Co., Ltd., issued October 30, 2000, pages 226 to 239 ”. An alignment treatment for forming a treatment layer may be performed.

There is no restriction | limiting in the specific method of apply | coating a coating liquid on a base material.
Specific examples of the coating method include “Yuji Harasaki,“ Coating Engineering ”, Asakura Shoten Co., Ltd., published on March 20, 1971, pages 253 to 277”, “supervised by Kunihiro Ichimura” Application ”CMC Publishing Co., Ltd., published March 3, 1998, pages 118 to 149” and the like, and “Harazaki Yuji“ Coating Method ”Tsuji Shoten, October 30, 1979 Issuer, page 3 (Table 1-2) and pages 6 to 154 ”, as well as spin coat method, spray coat method, bar coat method, roll coat method, blade coat method, Examples include a free span coating method and a die coating method.

The operating conditions for performing the coating are arbitrary, but control is performed so as to maintain a high-order molecular alignment state formed based on high chromonic liquid crystallinity due to self-organization of the liquid crystalline retardation material. Is preferred.
Specifically, the temperature at the time of application on the substrate is usually preferably 0 ° C. or higher, and is usually 80 ° C. or lower, and particularly preferably 40 ° C. or lower. Moreover, the humidity at the time of application is usually 10% RH or more, preferably 30% RH or more, and usually 80% RH or less.
Note that RH is an abbreviation for Relative humidity, and% RH is relative humidity.

(Drying process)
After the coating step, the solvent is dried and removed from the coating film formed on the substrate. At this time, it is preferable that the liquid crystal phase difference material is aligned with the removal of the solvent and exhibits chromonic liquid crystallinity.

The drying conditions are arbitrary, and may be natural drying, heat drying, reduced pressure drying, or a combination thereof, but higher-order molecular orientation formed based on high chromonic liquid crystallinity due to self-organization of liquid crystalline retardation material. It is preferable to control to maintain the state.
Specifically, the temperature during drying in the drying step is usually 0 ° C. or higher, preferably 10 ° C. or higher, and usually 120 ° C. or lower, particularly preferably 110 ° C. or lower. Further, the humidity during drying in the drying step is usually 10% RH or more, preferably 30% RH or more, and usually 90% RH or less. It is more preferable to avoid a rapid temperature rise when the temperature is raised during drying.

[4-1-3. Impregnation process]
The retardation film of the present invention is obtained by bringing the specific retardation film obtained above into contact with a specific compound and impregnating the specific compound in the film. This process is called an impregnation process.
The impregnation step may be performed any time after the wet film formation step. For example, another process may be performed between the wet film formation process and the impregnation process, or the impregnation process may be performed immediately after the wet film formation process.

  Further, the method for contacting the specific retardation film and the specific compound is not limited as long as the effects of the present invention are not significantly impaired. For example, the specific compound may be directly contacted with the specific retardation film, but a solution or dispersion containing the specific compound (hereinafter sometimes referred to as “specific compound composition”) is prepared and specified. A method of contacting with the retardation film is preferred. Hereinafter, the latter method will be described in detail.

(Specific compound composition)
The specific compound composition is obtained by dissolving or dispersing the specific compound in a solvent. As the solvent, it is preferable to select a solvent that does not dissolve the specific retardation film or cause cracks.
Specific examples of the solvent are largely different depending on whether the specific liquid crystalline phase difference material is a discotic liquid crystal or a chromonic liquid crystal, but if it is a chromonic liquid crystal, an alcohol such as isopropyl alcohol (IPA), n-butyl alcohol, n-hexyl alcohol, etc. Ketones such as acetone and methyl ethyl ketone (MEK); carbonates such as dimethyl carbonate, diethyl carbonate, and propylene carbonate; A solvent may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The content of the specific compound in the specific compound composition is usually 0.1% by weight or more, preferably 0.2% by weight or more, and usually 10% by weight or less, preferably 5% by weight or less. Below this range, the specific compound may not be sufficiently impregnated, and the effects of the present invention may not be sufficiently obtained. Moreover, when it exceeds this range, it tends to be necessary to perform a lot of cleaning.

  A specific compound may be used individually by 1 type, and may be used 2 or more types by arbitrary combinations and a ratio. Wavelength dispersion characteristics can be controlled by using two or more types in combination.

  The specific compound composition may contain a surfactant, a polymer compound for imparting the strength of the retardation film, a monomer, an initiator, and the like. These compounds may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

(Impregnation method)
After preparing the specific compound composition, the specific retardation film is brought into contact with the specific compound composition (that is, the specific compound).
For example, the specific retardation film may be immersed in the specific compound composition, the specific compound composition may be applied to the specific retardation film, or other methods may be used. Moreover, you may combine these methods arbitrarily.

  In the impregnation step, the mixing ratio of the specific liquid crystalline retardation material and the specific compound in the retardation film of the present invention is controlled by controlling the blending of the specific compound composition and the conditions such as the time and temperature of the impregnation step. It is possible to change. This makes it possible to control the wavelength dispersion characteristics of the refractive index and the optical characteristics such as three-dimensional anisotropy in the retardation film of the present invention.

  For example, when the impregnation step is performed by dipping, conditions such as temperature are not limited as long as the effects of the present invention are not significantly impaired.

  The time for immersing the specific retardation film in the specific compound composition is usually 1 second or longer, preferably 5 seconds or longer, and usually 10 minutes or shorter, preferably 5 minutes or shorter, more preferably 2 minutes or shorter. Above this range, the production time tends to be too long or the immersion bath has to be enlarged. Moreover, when less than this range, uniform immersion may become difficult.

  The temperature of the specific compound composition at the time of immersion is usually 0 ° C. or higher, preferably 10 ° C. or higher, more preferably 20 ° C. or higher, and usually 300 ° C. or lower, preferably 200 ° C. or lower, more preferably 100 ° C. or lower. . If it exceeds this range, the orientation of the retardation film may be disturbed. Further, if it falls below this range, condensation may occur on the film.

  In addition, for example, when the impregnation step is performed by coating, conditions such as temperature are not limited as long as the effects of the present invention are not significantly impaired.

  The temperature when the specific compound composition is applied to the specific retardation film is usually 0 ° C. or higher, preferably 10 ° C. or higher, more preferably 20 ° C. or higher, and usually 300 ° C. or lower, preferably 200 ° C. or lower, more preferably. Is 100 ° C. or lower. If it exceeds this range, the orientation of the retardation film may be disturbed. Further, if it falls below this range, condensation may occur on the film.

  The humidity when applying the specific compound composition to the specific retardation film is usually 10% RH or more, preferably 30% RH or more, and usually 90% RH or less.

  Although there is no restriction | limiting in the application method when apply | coating a specific compound composition to a specific phase difference film, For example, [4-1-2. It can be carried out by the method exemplified in the section of (Application process) in [Wet film-forming process] However, spray coating, blade coating, and the like are preferable. This is because the orientation of the specific liquid crystalline retardation material is hardly affected.

(Washing process)
After the impregnation step, the specific retardation film is preferably washed with a solvent. As the solvent used for the cleaning, a solvent that does not dissolve the specific retardation film or cause cracks is preferably selected. Specifically, the solvent of the specific compound composition is preferable. One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.

It is also preferable to dry after washing. Drying may be natural drying, heat drying, vacuum drying, or a combination thereof.
Specifically, the temperature during drying is usually 0 ° C. or higher, preferably 10 ° C. or higher, and usually 120 ° C. or lower, particularly preferably 110 ° C. or lower. Further, the humidity during drying is usually 10% RH or more, preferably 30% RH or more, and more preferably 80% RH or less. It is more preferable to avoid a rapid temperature rise when the temperature is raised during drying.

[5. Optical element]
The optical element of the present invention is an optical element provided with the above-described retardation film of the present invention. The optical element of the present invention may be an optical element composed only of the retardation film of the present invention, or may be provided with a member other than the retardation film. Usually, the retardation film of the present invention comprises a base material, and has a structure having a retardation film on the base material. In this case, the substrate including the base material is called an optical element.

  As a base material, what was illustrated as a base material with which the coating liquid containing the said liquid crystalline phase difference material is apply | coated is mentioned, for example.

  The optical element of the present invention may include one or more members other than the retardation film and the base material. When the example is given, a protective layer will be mentioned. This protective layer is a layer provided as needed when the mechanical strength of the retardation film is low. Although there is no restriction | limiting in the specific structure, For example, transparent polymer films, such as a triacetate, an acryl, polyester, a polyimide, a triacetyl cellulose, or a urethane type film, are laminated | stacked and formed.

  Furthermore, the optical element of the present invention is, for example, an adhesive layer, an antireflection layer, an alignment film, a layer having a function as a polarizing film, a layer having a function as a brightness enhancement film, or a layer having a function as a reflection film. In addition, a layer having various functions such as a layer having each optical function, such as a layer having a function as a transflective film and a layer having a function as a diffusion film, may be provided. In this case, the layers and films can be stacked by, for example, a wet film forming method. Moreover, you may laminate | stack the said layer and film | membrane in what order according to a use. When laminated in this way, the optical element of the present invention is configured as a laminate.

[6. Advantages of the present invention and mechanisms for obtaining the effects of the present invention]
According to the present invention, the wavelength dispersion characteristic of the refractive index and the three-dimensional anisotropy in the retardation film can be controlled. It is not clear why such an effect is obtained, but the inventors presume as follows.

  Specific compounds include liquid crystalline compounds and / or polymer liquid crystal precursors such as 4-methoxycinnamic acid and 4-hydroxycinnamic acid. Since the liquid crystals of these compounds exhibit positive birefringence, the specific compound is considered to be a compound having positive molecular polarizability anisotropy. On the other hand, the specific liquid crystalline retardation material is a compound having negative birefringence, that is, a compound having negative molecular polarizability anisotropy.

  In the specific retardation film, the liquid crystalline phase difference material (specific liquid crystalline phase difference material) having negative birefringence exists in the form of stacked molecular columns, and between the molecular columns, There are voids.

  Here, when the specific retardation film and the specific compound are brought into contact with each other, it is assumed that the specific compound penetrates into the film without disturbing the orientation of the specific liquid crystalline retardation material, and is in a state as shown in FIG. Is done.

FIG. 1 is a schematic view schematically showing the structure of the retardation film of the present invention.
In FIG. 1, a disk-shaped structure represents a specific liquid crystalline phase difference material. These specific liquid crystalline retardation materials are connected to form a molecular column. Moreover, the double arrow-shaped rod-shaped structure (white) represents the specific compound, and the direction of the double arrow represents the molecular polarizability anisotropy. The direction of the arrow (black) represents the molecular polarizability anisotropy of the specific liquid crystalline retardation material.

  From FIG. 1, it is estimated that the retardation film of the present invention is in a state where molecules having positive and negative molecular polarizability anisotropy are mixed. This state can be said to be a state similar to the copolymer described in Non-Patent Document 6 and composed of monomer units having positive and negative molecular polarizability anisotropy. Therefore, according to the present invention, it is considered that the wavelength dispersion characteristic of the retardation film can be easily controlled. Furthermore, since the specific liquid crystalline retardation material and the specific compound are mixed at the molecular level, it is presumed that a decrease in the transmittance of the specific retardation film can be avoided.

From the above, according to the present invention, the wavelength dispersion of the retardation film can be easily controlled at low cost. Furthermore, when a chromonic liquid crystal is used as the retardation film, the three-dimensional refractive index can be easily controlled. Therefore, the retardation film of the present invention exhibits excellent performance as a broadband retardation plate such as a liquid crystal display.
In addition, it is expected that the durability of the film is improved by filling the voids existing between the molecular columns in which the liquid crystalline retardation material is laminated with the specific compound.

[7. Anisotropic film materials]
The anisotropic film material described in Japanese Patent Application No. 2006-335245, which is suitably used as the liquid crystalline retardation material of the retardation film of the present invention, will be described below.

  The anisotropic film material described in the following Japanese Patent Application No. 2006-335245 can usually exhibit one or more of the advantages described below. That is, the following anisotropic film materials are stable to heat, acid, and alkali. Therefore, the anisotropic film material does not change with time during production and storage. Therefore, a transparent retardation film can be formed by using the anisotropic film material. Furthermore, since the anisotropic film material exhibits chromonic liquid crystallinity, it is possible to form an anisotropic film such as a retardation film that is uniform over a large area.

（式（２）において、Ｘ¹、Ｙ¹およびＺ¹は、それぞれ独立に、ＮＲ¹Ｒ²、ＳＲ³またはＯＲ⁴を表し、Ｒ¹〜Ｒ⁴は、それぞれ独立に、水素原子、置換基を有していてもよい炭素数１〜１８のアルキル基、置換基を有していてもよい炭素数２〜１８のアルケニル基、置換基を有していてもよい炭素数６〜１８の芳香族炭化水素基、置換基を有していてもよい炭素数３〜１２の脂環炭化水素基、または、置換基を有していてもよい炭素数３〜１８の複素環基を表す。また、Ｒ¹およびＲ²は結合してＮ原子とともに環を形成していてもよい。） The structure of the anisotropic film material is shown in the following formula (2).

In (Equation ^{(2), X 1, Y} 1 and Z ¹ each independently represents an NR ¹ R ^2, SR ³ or OR ^4, R ¹ ~R ⁴ are each independently a hydrogen atom, a substituent An optionally substituted alkyl group having 1 to 18 carbon atoms, an optionally substituted alkenyl group having 2 to 18 carbon atoms, and an optionally substituted fragrance having 6 to 18 carbon atoms. Represents an aromatic hydrocarbon group, an alicyclic hydrocarbon group having 3 to 12 carbon atoms which may have a substituent, or a heterocyclic group having 3 to 18 carbon atoms which may have a substituent. , R ¹ and R ² may combine to form a ring together with the N atom.)

  As in the formula (2), the anisotropic film material is a compound having a triazine ring. The anisotropic film material may have two or more triazine rings in one molecule, but preferably has only one triazine ring. That is, the anisotropic film material preferably has a monotriazine structure. This is because of high liquid crystallinity and ease of manufacture.

In the formula (2), X ¹ , Y ¹ and Z ¹ each independently represent NR ¹ R ² , SR ³ or OR ⁴ . Among them, X ¹ , Y ¹ and Z ¹ are preferably NR ¹ R ² independently from the viewpoint of the stability of the compound.
At this time, X ¹ , Y ¹ and Z ¹ may be the same or different.

In the formula (2), R ^{1 to} R ⁴ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 18 carbon atoms, or an optionally substituted carbon number. An alkenyl group having 2 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 3 to 12 carbon atoms which may have a substituent, or Represents a C3-C18 heterocyclic group which may have a substituent.
Hereinafter, groups constituting these R ^{1 to} R ⁴ will be described in detail.

When R ^{1 to} R ⁴ are an optionally substituted alkyl group having 1 to 18 carbon atoms, the lower limit of the carbon number of the alkyl group is 1 or more, and the upper limit is 18 or less. However, among these, 9 or less is preferable.

  Specific examples of the alkyl group having 1 to 18 carbon atoms include an optionally substituted methyl group such as a methyl group; an ethyl group, a 2-hydroxyethyl group, a 2-sulfoethyl group, a 2-carboxyethyl group, An optionally substituted ethyl group such as 2-cyanoethyl group; an optionally substituted propyl group such as n-propyl group, i-propyl group, 2,3-dihydroxypropyl group, 3-carboxypropyl group; n -An optionally substituted butyl group such as a butyl group; an optionally substituted hexyl group such as an n-hexyl group and a 2-ethylhexyl group; an optionally substituted octyl group such as an n-octyl group; n -Nonyl group which may be substituted, such as nonyl group; Dodecyl group which may be substituted, such as n-dodecyl group, etc. are mentioned.

  Among the specific examples of the alkyl group having 1 to 18 carbon atoms, preferred are methyl group, ethyl group, 2-hydroxyethyl group, 2-sulfoethyl group, 2-cyanoethyl group, n-propyl group, 2 , 3-dihydroxypropyl group, 3-carboxypropyl group, n-butyl group, n-hexyl group, n-octyl group and n-nonyl group.

  As a substituent which the said C1-C18 alkyl group may have, as long as the effect of this invention is not impaired remarkably, it is arbitrary, For example, a C1-C4 alkyl group, C1-C1 -4 alkoxy groups, hydroxyl groups, cyano groups, optionally substituted amino groups, optionally substituted carbamoyl groups, optionally substituted sulfamoyl groups, sulfo groups, carboxy groups and the like.

  Examples of the substituent of the amino group which may be substituted include, for example, an acyl group having 2 to 7 carbon atoms such as acetyl group and benzoyl group; methyl group, ethyl group, 2-hydroxyethyl group, butyl C1-C4 alkyl groups, such as group, etc. are mentioned. Moreover, as a substituent which the said carbamoyl group which may be substituted has, C1-C4 alkyl groups, such as a methyl group, an ethyl group, 2-hydroxyethyl group, a butyl group, etc. are mentioned. Furthermore, as a substituent which the said sulfamoyl group which may be substituted has, C1-C4 alkyl groups, such as a methyl group, an ethyl group, 2-hydroxyethyl group, a butyl group, etc. are mentioned.

  Moreover, the substituent mentioned above may comprise the single substituent which two or more substituents couple | bonded together by arbitrary combinations and ratios. Furthermore, the C1-C18 alkyl group may have only one substituent and may have two or more in arbitrary combinations and ratios.

When R ^{1 to} R ⁴ are an optionally substituted alkenyl group having 2 to 18 carbon atoms, the lower limit of the carbon number of the alkenyl group is 2 or more, and the upper limit is 18 or less. However, among these, 9 or less is preferable.

  Specific examples of the alkenyl group having 2 to 18 carbon atoms include a vinyl group, an allyl group, and a 2-methyl-1-propenyl group.

  Among the specific examples of the alkenyl group having 2 to 18 carbon atoms, preferred are a vinyl group and an allyl group.

The substituent that the alkenyl group having 2 to 18 carbon atoms may have is arbitrary as long as the effects of the present invention are not significantly impaired, and examples thereof include an alkyl group having 1 to 4 carbon atoms. .
In addition, the said substituent may comprise two or more substituents couple | bonded by arbitrary combinations and ratios, and may comprise the single substituent. Furthermore, the C2-C18 alkenyl group may have only one substituent and may have two or more in any combination and ratio.

When R ^{1 to} R ⁴ are an optionally substituted aromatic hydrocarbon group having 6 to 18 carbon atoms, the lower limit of the number of carbon atoms of the aromatic hydrocarbon group is 6 or more, The upper limit is 18 or less, with 14 or less being preferred.

  Specific examples of the aromatic hydrocarbon group having 6 to 18 carbon atoms include phenyl group, 3-cyanophenyl group, 4-cyanophenyl group, 3-carbamoylphenyl group, 4-carbamoylphenyl group, 4-sulfo group. Even if phenyl group, 4-carboxyphenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 3-acetylaminophenyl group, 4-acetylaminophenyl group, 2,5-dicarbamoylphenyl group, etc. are substituted Good phenyl group; 1-naphthyl group, 2-naphthyl group, 5-sulfo-2-naphthyl group, 6-sulfo-2-naphthyl group, 7-sulfo-2-naphthyl group, 6,8-disulfo-2-naphthyl And a naphthyl group which may be substituted such as a group.

  Among the specific examples of the aromatic hydrocarbon group having 6 to 18 carbon atoms, preferred are 3-cyanophenyl group, 3-carbamoylphenyl group, 4-sulfophenyl group, 4-carboxyphenyl group, 6 -Sulfo-2-naphthyl group, 6,8-disulfo-2-naphthyl group.

  The substituent that the aromatic hydrocarbon group having 6 to 18 carbon atoms may have is optional as long as the effect of the present invention is not significantly impaired, for example, an alkyl group having 1 to 4 carbon atoms, An alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, a cyano group, a nitro group, a halogen atom, an optionally substituted amino group, an optionally substituted carbamoyl group, an optionally substituted sulfamoyl group, a sulfo group, A carboxy group, a phosphate group, etc. are mentioned.

  In addition, examples of the substituent that the amino group that may be substituted include, the substituent that the carbamoyl group that may be substituted include, and the substituent that the sulfamoyl group that may be substituted include include. These are the same as those described above as the substituents that the alkyl group substituents having 1 to 18 carbon atoms may further have.

  Moreover, the substituent mentioned above may comprise the single substituent which two or more substituents couple | bonded together by arbitrary combinations and ratios. Furthermore, the C6-C18 aromatic hydrocarbon group may have only one substituent and may have two or more in any combination and ratio.

When R ^{1 to} R ⁴ are an alicyclic hydrocarbon group having 3 to 12 carbon atoms that may have a substituent, the lower limit of the carbon number of the alicyclic hydrocarbon group is 3 or more, 6 or more is preferable, and the upper limit is 12 or less.

  Specific examples of the alicyclic hydrocarbon group having 3 to 12 carbon atoms include a cyclohexyl group and a 4-carboxycyclohexyl group.

  Among the specific examples of the alicyclic hydrocarbon group having 3 to 12 carbon atoms, a 4-carboxycyclohexyl group is preferable.

  The substituent that the alicyclic hydrocarbon group having 3 to 12 carbon atoms may have is optional as long as the effect of the present invention is not significantly impaired, for example, an alkyl group having 1 to 4 carbon atoms, A C1-C4 alkoxy group, a carboxy group, etc. are mentioned.

  Moreover, the substituent mentioned above may comprise the single substituent which two or more substituents couple | bonded together by arbitrary combinations and ratios. Furthermore, the C3-C12 alicyclic hydrocarbon group may have only one substituent, and may have two or more in any combination and ratio.

When R ^{1 to} R ⁴ are an optionally substituted heterocyclic group having 3 to 18 carbon atoms, the lower limit of the number of carbon atoms in the heterocyclic group is 3 or more, and among these, 5 or more is preferable. In addition, the upper limit is 18 or less, with 14 or less being preferred.

  Specific examples of the heterocyclic group having 3 to 18 carbon atoms include pyridyl group, pyrimidyl group, quinolyl group, benzothiazolyl group, benzimidazolyl group, 1,3-dioxo-2,3-dihydro-1H-isoindole Examples include a -5-yl group and a 2-oxo-2,3-dihydro-1H-benzimidazole-5 group.

  Of the specific examples of the heterocyclic group having 3 to 18 carbon atoms, preferred are a pyridyl group, a benzothiazolyl group, a 1,3-dioxo-2,3-dihydro-1H-isoindol-5-yl group. 2-oxo-2,3-dihydro-1H-benzimidazole-5-group.

  The substituent that the heterocyclic group having 3 to 18 carbon atoms may have is optional as long as the effects of the present invention are not significantly impaired. For example, the alkyl group having 1 to 4 carbon atoms and the carbon number 1-4 alkoxy group, hydroxyl group, cyano group, nitro group, halogen atom, optionally substituted amino group, optionally substituted carbamoyl group, optionally substituted sulfamoyl group, sulfo group, carboxy group Etc.

  In addition, examples of the substituent that the amino group that may be substituted include, the substituent that the carbamoyl group that may be substituted include, and the substituent that the sulfamoyl group that may be substituted include include. These are the same as those described above as the substituents that the alkyl group substituents having 1 to 18 carbon atoms may further have.

  Moreover, the substituent mentioned above may comprise the single substituent which two or more substituents couple | bonded together by arbitrary combinations and ratios. Furthermore, the C3-C18 heterocyclic group may have only one substituent, and may have two or more in an arbitrary combination and ratio.

In the above formula (2), R ¹ and R ² may be bonded to form a ring together with the N atom. In this case, the structure of the ring formed is arbitrary as long as the effects of the present invention are not significantly impaired, and examples thereof include a piperidine ring, a piperazine ring, and a morpholine ring.

Among those described above, R ^{1 to} R ⁴ are preferably an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent.

Among the above-mentioned NR ¹ R ² , SR ³ and OR ⁴ , examples of suitable ones include 4-sulfophenylamino group, 4-carboxyphenylamino group, 6-sulfo-2-naphthyl group, 6,8. -Disulfo-2-naphthylamino group, 3-cyanophenylamino group, 3-carbamoylphenylamino group, phenoxy group, phenylthio group, 4-pyridylamino group, 2-oxo-2,3-dihydro-1H-benzimidazole-5 -An amino group etc. are mentioned.

（式（３）において、Ａｒ¹〜Ａｒ³は、それぞれ独立に、置換基を有していてもよい炭素数６〜１８の芳香族炭化水素基を表す。） Furthermore, among the compounds represented by the formula (2), the anisotropic film material is particularly preferably a compound represented by the following formula (3).

(In Formula (3), Ar < ¹ > -Ar < ³ > represents the C6-C18 aromatic hydrocarbon group which may have a substituent each independently.)

In the formula (3), the aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent and constitutes Ar ^{1 to} Ar ³ is R ^{1 to} R ⁴ in the formula (2). The same as the aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent described above. Therefore, the aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent and constitutes Ar ^{1 to} Ar ³ may have specific examples, preferred specific examples, preferred carbon numbers and the like. Good substituents are the same as in the case where each of R ^{1 to} R ⁴ is an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent.

  Further, when the anisotropic film material has an acid group, it may be used in the form of a free acid (free acid type), and a part of the acid group is in a salt form. There may be. Moreover, the salt type compound and the free acid type compound may be mixed in any combination and ratio. Furthermore, 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. As a salt type exchange method, a known method can be arbitrarily used, and examples thereof include the following methods 1) to 4).

1) A strong acid (such as hydrochloric acid) is mixed with the aqueous solution of the anisotropic membrane material obtained in the salt form, and the anisotropic membrane material is acidified in the form of a free acid. A method of neutralizing a dye acidic group with an alkaline solution (for example, an aqueous lithium hydroxide solution) and performing salt exchange.
2) A large excess of neutral salt (eg, lithium chloride) having the desired counter ion is mixed with the aqueous solution of the anisotropic membrane material obtained in the salt form, and salt exchange is performed in the form of a salting out cake. How to do.
3) The aqueous solution of the anisotropic membrane material obtained in the salt form is treated with a strongly acidic cation exchange resin, and the anisotropic membrane material is acidified in the form of a free acid. A method of neutralizing the acidic groups of the anisotropic membrane material and performing salt exchange with an alkaline solution (for example, an aqueous lithium hydroxide solution) containing
4) Salt exchange is performed by causing an aqueous solution of anisotropic membrane material obtained in salt form to act on a strongly acidic cation exchange resin that has been previously treated with an alkaline solution having a desired counter ion (for example, an aqueous lithium hydroxide solution). How to do.

Whether the acidic group of the anisotropic film material takes the free acid type or the salt type is usually determined by the pKa of the anisotropic film material and the pH of the aqueous solution of the anisotropic film material. Dependent.
Examples of the above salt types include salts of alkali metals such as Na, Li, and K; salts of ammonium optionally substituted with an alkyl group or hydroxyalkyl group; salts of organic amines, and the like. Examples of these organic amines include lower alkyl amines having 1 to 6 carbon atoms, hydroxy-substituted lower alkyl amines having 1 to 6 carbon atoms, and carboxy-substituted lower alkyl amines having 1 to 6 carbon atoms. The number of substituents possessed by the organic amine may be one or two or more. In addition, in the case of these salt types, the type is not limited to one type, and a plurality of types may be mixed in any combination and ratio.

  Preferred examples of the anisotropic film material are shown below. In addition, although all the following examples are represented in the form of a free acid, these may be a salt form.

  The molecular weight of the material for an anisotropic film is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 126 or more, preferably 200 or more, and usually 2000 or less, preferably 1000 or less. If the molecular weight is too large, the solubility may decrease.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and can be arbitrarily modified and implemented without departing from the gist of the present invention. . In the following description of the examples, “parts” means “parts by weight” unless otherwise specified.

[Evaluation methods]
In the following Examples (Examples 1 to 3) and Comparative Example (Comparative Example 1), various evaluations of the retardation film were performed as follows.

(1) Wavelength dispersion of retardation The retardation Re of the film with respect to incident light having a wavelength of 400 nm to 800 nm was measured using a RETS-100 manufactured by Otsuka Electronics. The numerical value (Re ratio) obtained by dividing the phase difference at each wavelength by the phase difference of 550 nm was plotted against the wavelength to evaluate chromatic dispersion.

(2) Positive / negative of birefringence According to the method described in Hiroya Ashiya “Introduction to Polarizing Microscopes for Polymer Materials” (2001 publication, Agne Technology Center), crossed Nicols of a polarizing microscope (Eclipse E600-POL manufactured by Nikon) Then, the positive / negative of birefringence was determined from the interference color change due to the insertion of the inspection plate.

[Example]
Example 1
In 76 parts of water, 24 parts of a lithium salt of a compound represented by the following formula (4) that has been desalted and purified as a liquid crystalline retardation material is stirred and dissolved, and then filtered to apply a specific liquid crystalline retardation material (pH = 9). A liquid was obtained.

  On the glass substrate (75 mm × 25 mm, thickness 1 mm), the coating solution is applied with an applicator having a gap of 4 μm (applicator manufactured by Horita Seisakusho Co., Ltd.) and then naturally dried to form a transparent film (specific liquid crystal properties). A film containing a retardation material was obtained.

Next, 1.3 parts by weight of a compound represented by the formula (5) below was stirred and dissolved in 98.7 parts by weight of isopropanol to obtain a composition containing the compound represented by the formula (5).

  A film containing the specific liquid crystalline retardation material was immersed in the composition for 1 minute, washed with isopropanol, and then blown and dried to obtain a retardation film.

  The obtained retardation film was transparent and had negative birefringence, and the retardation for incident light of 550 nm was 155 nm. The result is shown by a solid line in FIG. As shown in FIG. 2, the wavelength dispersion of the phase difference was gentle compared to the comparative example described later.

(Example 2)
0.5 parts by weight of the compound represented by the following formula (6) was dissolved by stirring in 99.5 parts by weight of dimethyl carbonate to obtain a composition containing the compound represented by the formula (6).

  Next, a film containing the specific liquid crystalline retardation material obtained in the same manner as in Example 1 was immersed in the composition for 1 minute, washed with dimethyl carbonate, and then blown and dried to obtain a retardation film. .

  The obtained retardation film was transparent and had negative birefringence, and the phase difference with respect to incident light of 550 nm was 183 nm. The result is shown by a solid line in FIG. The chromatic dispersion of the phase difference was almost constant as shown in FIG.

(Example 3)
0.5 parts by weight of the compound represented by the above formula (6) was stirred and dissolved in 99.5 parts by weight of diethyl carbonate to obtain a composition containing the compound represented by the formula (6). Next, a film containing the specific liquid crystalline retardation material obtained in the same manner as in Example 1 was immersed in the composition for 2 minutes, washed with dimethyl carbonate, and then blown and dried to obtain a retardation film. .

  The obtained retardation film was transparent and had negative birefringence, and the retardation for incident light of 550 nm was 201 nm. The results are shown in FIG. As shown in FIG. 3, the chromatic dispersion of the phase difference showed so-called reverse chromatic dispersion.

[Comparative example]
(Comparative Example 1)
A film containing the specific liquid crystalline retardation material was obtained in the same manner as in Example 1. The film was not brought into contact with the specific compound, and this was used as a retardation film.

  The obtained anisotropic film was transparent and had negative birefringence, and the phase difference with respect to incident light of 550 nm was 185 nm. The results are shown by broken lines in FIGS. As shown in FIGS. 2 and 3, the chromatic dispersion of the phase difference is monotonously decreased with respect to the wavelength, and the slope thereof is steep.

[Summary]
From Examples 1 to 3 and Comparative Example 1, it can be seen that by using the retardation film of the present invention, an anisotropic film in which the wavelength dispersion characteristic of the refractive index Re and the three-dimensional anisotropy are controlled can be provided.

  The present invention can be used in any field where a retardation film is used. Above all, not only liquid crystal displays and organic EL displays but also liquid crystal projectors and in-vehicle display panels are obtained because a retardation film that can control the wavelength dispersion characteristics and three-dimensional anisotropy of refractive index at low cost is obtained. In addition, it can be suitably used for applications such as flexible displays that require a low cost, thin and large area.

It is a figure which represents typically the structure of the phase difference film of this invention. It is a figure showing Re ratio with respect to each wavelength measured in Example 1 and Comparative Example 1 of this invention. It is a figure showing Re ratio with respect to each wavelength measured in Example 2, 3 and Comparative Example 1 of this invention.

Claims (5)

A retardation film comprising a liquid crystalline retardation material having negative birefringence and a compound represented by the following formula (1).

(In the formula (1), X represents an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an amino group which may have a substituent, a hydroxyl group, and a cyano group. Or n is an integer of 0 to 5. Y is a hydrogen atom or a cyano group, and Z is a hydroxyl group, an optionally substituted alkoxy group or a halogen atom. .) The retardation film according to claim 1, wherein the liquid crystalline retardation material is a water-soluble compound exhibiting chromonic liquid crystallinity. An optical element comprising the retardation film according to claim 1. A method for producing a retardation film, comprising contacting a film containing a liquid crystalline retardation material having negative birefringence with a compound represented by the following formula (1).

(In the formula (1), X represents an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an amino group which may have a substituent, a hydroxyl group, and a cyano group. Or n is an integer of 0 to 5. Y is a hydrogen atom or a cyano group, and Z is a hydroxyl group, an optionally substituted alkoxy group or a halogen atom. .) A wet film forming step of forming the liquid crystalline retardation material by a wet film forming method;
The method for producing a retardation film according to claim 4, wherein an impregnation step of impregnating the film with the compound represented by the formula (1) is performed.

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