Organic compounds -- part of the class 532-570 series – Organic compounds – Azo
Reexamination Certificate
2000-12-15
2001-08-21
Powers, Fiona T. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Azo
C534S829000, C252S585000, C359S491010
Reexamination Certificate
active
06277966
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to azo-compounds useful as dyes, particularly as yellow dyes for polarizing films. The present invention also relates to polarizing films containing the azo-compound.
Polarizing films are produced by causing a polarizing film base, such as a stretch-oriented polyvinyl alcohol film or a polyene film which is produced by dehydrochlorination of a polyvinyl chloride film or dehydration of a polyvinyl alcohol film to form a polyene followed by an orientation of them, to contain iodine or a dichroic dye as a polarizing element. Among them, Iodine-based polarizing films are superior in the early polarizing performance. However, they have problems that they are inferior in durability against heat or water and thus their performance is lowered under high temperature-high humidity conditions In order to improve such durability, a method which include a treatment with an aqueous solution containing formaldehyde or boric acid, a method in which a high molecular film with a low permeability to water vapor is used as a protective film and other methods have been proposed. These methods, however, are not satisfactory.
On the other hand, while dye-based polarizing films in which a dichroic dye is used as a polarizing element are superior in durability against heat and water as compared to iodine polarizing films. However, they are generally inferior in early polarizing performance. Therefore, in order to improve the polarizing performance of dye-based polarizing films, various studies have been conducted on dyes to be used. For example, JP-A-1-172906 describes a polarizing film using a specific azo-compound as a yellow dye. The above polarizing film containing such an azo-compound, however, has not fully met the demands of consumers.
An object of the present invention is to provide yellow compounds suitable for the production of polarizing films having high performance. Another object of the present invention is to provide polarizing Elms with high performance, particularly polarizing films with high performance for liquid crystal projectors, using these compounds.
The present inventors have conducted studies to develop compounds which are good in dyeing ability in the production of polarizing films, which are excellent in polarizing performance and which are excellent in durability and light fastness under high temperature-high humidity conditions, when used as dyes for polarizing films. In addition, they have also conducted studies to develop compounds suitable for dyes which cover a region of comparatively short wavelength of 400 to 500 nm and are used in polarizing films produced by adsorbing two kinds or more of dichroic dyes on a high molecular film and orientating the film. As the result, they have found that specific azo-compounds are suitable for attaining the above objects Thus, the present invention was completed.
SUMMARY OF THE INVENTION
The present invention provides an azo-compound, free acid form of which is represented by the following formula
wherein A and B represent, independently with each other, a phenyl having one or two groups selected from sulfo and carboxyl or a naphthyl having 1 to 3 sulfo;
R
1
, R
2
, R
3
, R
4
, R
5
and R
6
represent, independently with each other, hydrogen, lower alkyl or lower alkoxy: and
X represents —N═N— or —NHCO—.
In addition, the present invention provides a dye-based polarizing film containing said azo-compound in a polarizing film base.
MODE FOR CARRYING OUT THE INVENTION
In the formula (I), A and B may be same to or different from each other, and are phenyl or naphthyl. The phenyl is substituted with one or two groups selected from sulfo and carboxyl. The naphthyl has 1 to 3 sulfo groups. Examples of the phenyl represented by A or B include 2-, 3- or 4-sulfophenyl, 2-, 3- or 4-carboxyphenyl, 2,4- or 2, 5-disulfophenyl, 3,5-dicarboxyphenyl and 2-carboxy-4- or 5-sulfophenyl. Examples of the naphthyl represented by A or B include 5-, 6-, 7- or 8-sulfo-2-naphthyl, 4-, 5-, 6- or 7-sulfo-1-naphthyl, 6,8-, 4,8-, 5,7- or 3,6-disulfo-2-naphthyl, 3,6- or 4,6-disulfo-1-naphthyl and 3,6,8- or 4,6,8-trisulfo-2-naphthyl.
Among the phenyl represented by A and B, monosulfophenyl having one sulfo is preferred. Among the naphthyl, disulfonaphthyl having two sulfo groups, in particular disulfo-2-naphthyl, is preferred.
R
1
, R
2
, R
3
, R
4
, R
5
and R
6
represent lower alkyl or lower alkoxy. R
1
, R
2
, R
3
, R
4
, R
5
and R
6
may be same to or different from each other. The lower alkyl and lower alkoxy here may have about 1 to 4 carbon atoms, respectively Specific examples of the lower alkyl include methyl, ethyl and propyl. Specific examples of the lower alkoxy include methoxy, ethoxy and propoxy. As a group represented by R
1
, R
2
, R
3
, R
4
, R
5
or R
6
, hydrogen, methyl or methoxy is preferred from the viewpoint of dichroism.
The azo-compound represented by the formula (I) can be produced, for example, by a process described below. Thus, an aromatic amine compound represented by the following formula (II):
NH
2
—B (II)
wherein B has the same meaning as above,
is first reacted with phenyl chlorocarbonate according to the conventional method to give a carbamate compound represented by the following formula (III):
wherein B has the same meaning as above. Then, the carbameate compound thus obtained is reacted with an azo-intermediate compound represented by the following formula (IV):
wherein A, X, R
1
, R
2
, R
3
, R
4
, R
5
and R
6
have the same meaning as above,
at 20 to 60° C. in an aqueous solvent to obtain an azo-compound of the formula (I).
The azo-intermediate compound of the formula (IV) can be produced by repeating the conventional coupling reaction on an aniline compound or a naphthylamine compound which may have a substituent such as those represented by R
1
, R
2
, R
3
, R
4
, R
5
or R
6
, amino, sulfo and carboxyl.
The azo-compound represented by the formula (I) obtained in this manner may exist either in the form of the free acid or in the form of a salt. Examples of the salt include alkali metal salts such as lithium salt, sodium salt and potassium salt; ammonium salt; organic amine salts such as ethanolamine salt and alkylamine salts. On using the compound In a polarizing film base, the compound in the form of a sodium salts is usually preferred.
When a polarizing film is produced by causing a polarizing film base to contain the azo-compound represented by the formula (I), modification of hue or improvement of polarizing performance can be effected by co-using another organic dye. The organic dye used in this case may be any dye insofar as it has a high dichroic property. For producing a polarizing film suitable for liquid crystal projectors, a dye superior in light fastness is preferably selected.
The dye polarizing film of the present Invention can be produced by causing a high molecular film as a polarizing film base to contain a dichroic dye comprising a compound of the formula (I) according to the known method. The dichroic dye may further comprise another organic dye, as described above. Examples of the high molecular film include those made of polyvinyl alcohol resin, polyvinyl acetate resin, ethylene/vinyl acetate (EVA) resin, nylon resin and polyester resin. Examples of the polyvinyl alcohol resin here include polyvinyl alcohol itself which is a partial or complete hydrolysis product of polyvinyl acetate, and saponification products of copolymers of vinyl acetate and another polymerizable monomer, such as saponified EVA resin. Examples of said another polymerizable monomer include olefins such as ethylene and propylene, unsaturated carboxylic acid such as crotonic acid, acrylic acid, methacrylic acid and maleic acid, unsaturated sulfonic acids, and vinyl ethers. Further, polyvinyl formal and polyvinyl acetal which are modification product of polyvinyl alcohol with an aldehyde, can be included in the polyvinyl alcohol resin. As the polarizing film base, films derived from a polyvinyl alcohol compound, particularly polyvinyl alcohol film, are
Hayashi Narutoshi
Kayane Yutaka
Taguma Akihiro
Powers Fiona T.
Stevens Davis Miller & Mosher L.L.P.
SumitomoChemical Company, Ltd.
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