Dye containing polarizing film

Details Dye containing polarizing film Dye containing polarizing film

1994-05-26

2001-05-22

Einsmann, Margaret (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Drawing or stretching of preform with dyeing, process or...

C008S641000, C008S506000, C008S685000, C008S687000, C427S163100, C252S585000

Reexamination Certificate

active

06235064

ABSTRACT:

This invention relates to a polarizing film containing dyestuffs.
Currently, polarizing films are generally prepared by incorporating iodine or a dichromatic dye as a polarizing element into a polyvinyl alcohol film which has been oriented by stretching, or a polyene film which has been prepared by dehydrochlorinating a polyvinyl chloride film or dehydrating a polyvinyl alcohol film to produce polyene and orientating the film.
Among those, iodine-containing polarizing films are good in early stage polarizing activities, but poor in the durability to water and heat. Thus, the films have some drawbacks in the lowered polarizing activities after having been used for a certain period of time at high temperatures under highly humid conditions. Several methods for improving the durability have been proposed, in which the film is treated with formalin or an aqueous boric acid solution, or a polymer film having a low moisture permeability is employed as a protecting film, but these methods are not yet fully satisfactory.
A dye-containing polarizing films using a dichromatic dye as a polarizing element is better in the durability to water and heat than iodine-containing polarizing film, but poor in the polarizing activities.
The dichromatic dye-containing polarizing film of neutral color is prepared by incorporating two or more kinds of dichromatic dyes into a polymer film and then orientating the film. If light breaks through two said polarizing films, which are superposed on each other so that those orientation directions meet at right angles (crossed state), at a specific wavelength within the visible radiation wavelength region, particularly from 400 to 700 nm, color of a liquid crystal display using the two polarizing films often changes from the color that the display should have at a dark state.
In order to prevent the color change of the display due to the light breaking through the films at a specific wave length, the light transmittance of the polarizing films at crossed state (cross light transmittance) must be lowered over the visible radiation wavelength region, particularly from 400 to 700 nm.
An object of the present invention is to provide a polarizing film of neutral color which is prepared by incorporating two or more kinds of dichromatic dyes into a film and then orientating the film, through which no light breaks at crossed state within the visible radiation wavelength region, particularly from 400 to 700 nm and which is excellent in the polarizing activities as well as the durability to water and heat.
The present inventors have extensively studied to accomplish the object, have found a polarizing film of neutral color containing specific dyes exhibits excellent properties for this object, and, as a result, have attained to the present invention.
The present invention provides a dye-containing polarizing film comprising, in the film substrate at least one kind of disazo dyes represented by the following formula (I) in the form of the free acid
wherein Me is a transition metal selected from copper, nickel, zinc and iron, A
1
is a phenyl or naphthyl group which may be substituted, B
1
is a 1-naphthol or 2-naphthol residue which may be substituted and in which its hydroxy group is adjacent to the azo group and is linked with the transition metal Me to form the complex, and R
1
is a lower alkoxy; and at least two dyes selected from a group consisting of [A], [B] and [C] described bellow.
[A] A group consisting of disazo dyes represented by the following formula (II) in the form of free acid
wherein Me is a transition metal selected from copper, nichel, zinc and iron, A
2
is a phenyl or naphthyl group which may be substituted, B
2
is a 1-naphthol or 2-naphthol residue which may be substituted and in which the hydroxy group is adjacent to the azo group and is linked with the transition metal Me to form the complex, and R
2
is hydrogen, a lower alkyl or sulfo group or an amino group which may be substituted.
[B] A group consisting of trisazo dyes represented by the following formula (III) in the form of free acid
wherein A
3
and B
3
are same or different and are phenyl or naphthyl groups which may be substituted, R
3
is hydrogen, a lower alkyl, lower alkoxy or sulfo group or an amino group which may be substituted, R
4
is a hydrogen, a hydroxy or lower alkoxy group, and m is 0 or 1; and copper complex salts thereof.
[C] A group consisting of C.I. Direct Yellow 12, C.I. Direct Yellow 28, C.I. Direct Yellow 44, C.I. Direct Orange 26, C.I. Direct Orange 39, C.I. Direct Orange 107, C.I. Direct Red 2, C.I. Direct Red 31, C.I. Direct Red 79, C.I. Direct Red 81, and C.I. Direct Red 247.
As mentioned above, the dye-containing polarizing film of the present invention contains the disazo dye represented by the formula (I) and at least two kinds of dyes selected from the group consisting of [A], [B] and [C].
As the latter, as long as being selected from the group consisting of [A], [B] and [C], any combinations of the dyes can be employed. For example, all of the dyes may be selected only from [A]. Likewise, all of the dyes may be selected only from [B] or only from [C] and a combination of dyes from different groups can also be employed.
The polarizing film described above has neutral color and is characterized in that it causes no light to break through the films at the dark state over the visible radiation wavelength region, particularly from 400 to 700 nm, has excellent polarizing activities and causes no discoloration and deterioration of polarizing activities under high temperature and high humid condition.
Preferable examples of the polarizing film include a film which contains a kind of the disazo dye represented by the formula (I) and two kinds of dyes selected from the group [C]; a film which contains a kind of the disazo dye represented by the formula (I), a kind of dye selected from the group [A] and two kind of dye selected from the group [C] and a film which contains a kind of the disazo dye represented by the formula (I), a kind of dye selected from the group [B] and a kind of dye selected from the group [C].
As the disazo dyes represented by the formula (I) or the formula (II), the copper complex salt thereof are preferably used. Namely, Me in the formula (I) and the formula (II) are preferably copper.
In the formula (I) and (II), A
1
and A
2
may be same or different and are phenyl or naphthyl groups which may be substituted. The substituent of the phenyl group includes, for example, sulfo, sulfamoyl, nitro, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, carboxy, halogen and unsubstituted, monosubstituted or disubstituted amino. The substituent of the amino includes, for examples, C
1-4
alkyl which is unsubstituted or substituted by hydroxy, cyano or the like, and C
1-4
alkylcarbonyl. As the phenyl denoted by A
1
or A
2
, preferable is phenyl which is substituted by one or two substituents selected from sulfo, sulfamoyl, nitro, methyl, ethyl, methoxy, ethoxy, carboxy, chlorine and unsubstituted or substituted amino. As the phenyl group particularly preferable is sulfophenyl.
The substituent of the naphthyl denoted A
1
or A
2
includes, for example, sulfo and hydroxy. Among the naphthyl, preferable is the naphthyl substituted by 1-3 sulfo groups, and particularly preferable is mono- or disulfonaphthyl.
In the formula (I) and (II), B
1
and B
2
are same or different and are 1-naphthol or 2-naphthol residues which may be substituted. Among them preferable is 1-naphthol which may be substituted.
The substitutent of the 1- or 2-naphthol includes, for example, sulfo, hydroxy and substituted and unsubstituted amino, provided that the hydroxy does not substitute adjacent to the azo group. Substituted amino may be either mono- or disubstituted and the substituent of the amino includes, for example, C
1-4
alkyl, C
1-4
alkylcarbonyl, carbamoyl, sulfamoyl, unsubstituted o

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