JPH0466268B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a dichroic dye and a polarizing film using the same, and more particularly to a novel polarizing film particularly excellent in moisture resistance and heat resistance. [Prior Art] The polarizing film most commonly used today uses a polyvinyl alcohol resin as the film base material, which is coated with an iodine compound and/or a dye such as an acid dye or a direct dye having a selected structure. It has polarization properties using a colored substance. This type of polarizing film usually maintains its heat resistance by covering both sides of the film with a film-like material (hereinafter referred to as a protective film layer) that is moisture resistant and transparent on at least one side. That is, measures have been taken to obtain practical durability by covering the drawbacks of an internally polarizing film layer (hereinafter referred to as a polarizing element), which is inherently extremely poor in durability, with protective film layers on both sides. Polarizing films are already being used in large quantities as an important component of liquid crystal display elements, but as the field of use for liquid crystal display elements expands, the durability of the polarizing films used needs to be improved, especially in terms of moisture resistance and heat resistance. is strongly requested. Various proposals have been made to solve these demands, but these can be summarized into three methods. The first method uses a polarizer made from a combination of a conventional polyvinyl alcohol resin and a water-soluble dichroic dye, while the protective film layer is made of cellulose acetate resin or acrylic resin, which are more durable than polyvinyl alcohol. , polyester resin, polyurethane resin, etc. This method can significantly improve durability, but the polarizer has low moisture resistance and the polarizer base material is exposed at the cut portion of the polarizing film. There are limits to improving durability due to the low heat resistance of the resin itself.
The second method is to use a hydrophobic polymer film having a conjugated double bond in a polyene structure as a polarizing film, but although the moisture resistance is improved, there is a change in transmittance due to an increase in the polyene structure due to heat, etc. It has drawbacks such as a low degree of polarization, and has not yet been technically perfected. The third method is an attempt to obtain a polarizing film or polarizer by coloring a hydrophobic polymer represented by polyester, polyamide, etc. with a dichroic dye and stretching it, and the present invention is also basic. This method generally belongs to this method. According to the third method, fundamental problems such as moisture resistance and heat resistance can be solved in principle. However, in reality, there are few proposals for dichroic dyes that exhibit high dichroism in such hydrophobic polymers, and the reality is that the completion of polarizing film manufacturing technology using such methods is limited. Examples of known techniques for durable polarizing films include JP-A No. 57-84409 and JP-A No. 58-68008 by the present inventors. Both are applications of dichroic dyes developed for liquid crystals to polarizing films. [Problems to be solved by the invention] Immediately after production, this type of polarizing film may have polarizing performance comparable to that of conventional PVA-based polarizing films, etc.; When used, especially when used for a long time in a heated state, the polarization ability deteriorates significantly, causing a practical problem. The main reason for this is that dichroic dyes for liquid crystals are generally structurally selected to be dissolved in the liquid crystal material in as high a concentration as possible. However, it is thought that such dye molecules easily move due to thermal movement, especially when heated, and disturb their own arrangement in a hydrophobic resin film base material such as polyethylene terephthalate. In addition, in the manufacturing process of this type of polarizing film, a heat treatment process following the stretching process is usually used to prevent shrinkage of the film and to obtain dimensional stability. When using dyes that have extremely high solubility in hydrophobic base resins, such as dichroic dyes for liquid crystals, the degree of polarization may be quite high immediately after the stretching process, but during the heat treatment process There was a problem in that the degree of polarization decreased significantly after passing through this process.
Therefore, in order to obtain a polarizing film with a high degree of polarization, this kind of polarizing film cannot be heated to a sufficient degree for heat setting after stretching, so it is difficult to obtain sufficient dimensional stability. On the other hand, in order to obtain a product with dimensional stability and a stable degree of polarization, sufficient heat treatment must be performed after the stretching process, so a high degree of polarization is required. I could not find anything with this. An object of the present invention is to provide a novel dichroic dye that is suitable for coloring hydrophobic polymers and has excellent transparency, moisture resistance, and weather resistance. Another object of the present invention is to provide a novel polarizing film that uses a hydrophobic polymer as a film base material and contains the novel dichroic dye in an oriented manner. [Means for solving the problem] As a result of various studies to solve the problem, we have found the most important requirements for the dye used to solve the above problem in polarizing films using hydrophobic resin as the film base material. The inventors have discovered that the most important characteristic is to have high dichroism, and that they must also have certain pigment suitability, and have arrived at the present invention. The present invention is based on the general formula (), [In formula (), Y is an oxygen atom or a sulfur atom, and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ and X ₆ are hydrogen atoms, halogen atoms, hydroxy groups or carbon atoms
It is an amino group optionally substituted with ~3 alkyl groups, and Q is the formula (), or expression(), It is a monovalent group represented by Here the expression ()
Inside, R ₁ and R ₂ are a hydrogen atom, a halogen atom,
A methyl group or a methoxy group, m is 1, 2
or an integer of 3, where R ₃ is -COOH, -
COOR ₄ , −CONH ₂ , −CONHR ₄ , −OOCR ₄ , −
_NHCOR4 , -N= _NR4 ,

【formula】

[Formula] Ma Taha

〔Example〕

Hereinafter, representative examples of the dye of the present invention and a polarizing film using the dye will be specifically described with reference to Examples. Note that the degree of polarization in Examples is a value measured by the following method. In other words, the light transmittance (T ‖) at the maximum absorption wavelength in the visible region measured by placing two polarizing films on top of each other with their stretching directions as parallel as possible and placing them in the optical path of a spectrophotometer, and The degree of polarization (V) was calculated from the light transmittance (T ⊥) at the same wavelength, which was measured overlappingly so as to be perpendicular to each other, using the following formula. Example 1 (Table 1, dye synthesis of dye number 1) 2-amino-3,4-dihydroxy-1-nitro-anthraquinone 15 g, biphenyl-4,4'-
17 g of dicarboxylic acid monochloride and 1 g of zinc chloride were dissolved in 200 ml of orthodichlorobenzene at 70°C.
After stirring for an hour, the mixture was further stirred at 170 to 180°C for 10 hours, and after cooling, 100 ml of methanol was added, the precipitate was filtered, and the mass was washed with methanol and water. The resulting mass was dispersed in 500 ml of ethanol, and this was mixed with an aqueous solution containing 14.5 g of 60% sodium sulfide.
100 g was added, stirred under reflux for 10 hours, heated, washed with methanol and water, and dried.
18.1 g of crude pigment was obtained. After pulverization, soluble impurities were removed by Soxhlet extraction using acetone and dried to obtain a reddish-purple powdered pigment (Table 1, pigment number 1, mp>300°C). After heating 0.5 g of dye in 100 g of nitrobenzene,
It was left at 25°C for several hours. The upper light solution was slightly colored red, but most of the pigment had precipitated. The liquid crystal was heated to 90° C. in Liquid Crystal E-8 (trade name of biphenyl liquid crystal manufactured by BDH), but the liquid crystal was hardly colored. Next, 1 g of the same dye was uniformly mixed with 1 kg of polyethylene terephthalate resin pellets having an intrinsic viscosity of 0.7, and the mixture was melt-extruded at 280° C. to form a film.
The film was stretched 5 times in the longitudinal direction using a roll stretching machine to obtain a film-like test piece having a thickness of 80 μm. The dichroic ratio of the dye at the maximum absorption wavelength of 520 nm was 12.3. Example 2 Polyethylene terephthalate resin pellets 1Kg
After adding 2 g of the dye from Example 1 and mixing uniformly,
It was melt-extruded and formed into a film of approximately 200μ. This film was stretched 5 times in the transverse direction at 80°C using a tenter stretching machine and heat treated at 150°C for 1 minute. A clear red polarized film is obtained, and the maximum absorption wavelength is
The degree of polarization at 520 nm was excellent at 91%. This polarizing film was left for 500 hours at 80° C. and 90% relative humidity, but virtually no change in hue or decrease in the degree of polarization was observed. Also,
The shrinkage rate of the film was 1% or less in both the vertical and horizontal directions, and it had good dimensional stability. Example 3 (Table 1, dye synthesis of dye number 5) Biphenyl-4,4'-dicarboxylic acid monochloride in Example 1 was replaced with biphenyl-4,4'-dicarboxylic acid monochloride.
4'-(naphthalene-2,3-dicarboximide)
-4-Carboxylic acid chloride was used in the same manner, but a reddish-purple powdery pigment (Table 1, pigment number 5,
mp>300℃) was obtained. This dye also contains nitrobenzene and liquid crystal E-8.
On the other hand, it was almost insoluble, and the dichroic ratio of the dye in polyethylene terephthalate measured by the same method as in Example 1 was 11.2 (maximum absorption wavelength 520 nm). Example 4 Instead of the dye (number 1) in Example 2,
A bright red polarizing film was obtained in the same manner except that the dye of Example 3 was used. The degree of polarization is 90% (maximum absorption wavelength 520nm), and as a result of the durability test,
Substantially no decrease in the degree of polarization was observed, and it had good dimensional stability. Example 5 (Table 1, dye synthesis of dye number 21) 3-amino-1,2,5-trihydroxy-
4,8-dinitroanthraquinone 15g, 4'-
18 g of (5″-methyl-benzoxazolyl)-biphenyl-4-carboxylic acid chloride and 1 g of zinc chloride were reacted in 300 ml of nitrobenzene at 70°C for 1 hour and at 180°C for 10 hours, then cooled and 100 ml of methanol was added. The precipitate was filtered and washed with methanol and water.The resulting mass was dispersed in 1000 ml of ethanol and added with 24.3 mL of 60% sodium sulfide.
20 g of an aqueous solution containing g was added thereto, stirred under reflux for 10 hours, heated, washed with methanol and water, and dried. 17.6 g of crude pigment was obtained. After crushing,
Soluble impurities were removed by Soxhlet extraction using acetone to obtain a dark blue powdered dye (Table 1, dye number 21, mp>300°C). This dye also
N,N-dimethylformamide and liquid crystal ZLT
-1840 (trade name of phenylcyclohexane liquid crystal manufactured by Merck), and the dichroic ratio in polyethylene terephthalate was 12.1 (maximum absorption wavelength 615 nm). Example 6 A bright blue polarizing film was obtained in the same manner using the dye of Example 5 instead of the dye (number 1) in Example 2. The degree of polarization was 91%, and as a result of the durability test, virtually no decrease in the degree of polarization was observed, and it had good dimensional stability. Example 7 (Table 1, dye synthesis of dye number 27) 21 g of 1,4-diamino-anthraquinone-6-carboxylic acid chloride and 15 g of 3-amino-1,2-dihydroxyanthraquinone were added to nitrobenzene.
Heat in 300ml at 140℃ for 2 hours, cool, filter,
The nitrobenzene was washed with methanol and then water and the mass was dried. 600g of 90% sulfuric acid
After stirring at 105°C for 5 hours, it was poured into 500 g of ice water, filtered, and washed with 70% sulfuric acid.
The mass was boiled in 1000 ml of water, cooled, filtered, washed with water and dried to obtain a dark purple crystalline pigment (Table 1, pigment no.
27, mp>300℃). The dye was substantially insoluble in nitrobenzene and liquid crystal E-8, and the dichroic ratio in polyethylene terephthalate was 9.3 (maximum absorption wavelength 650 nm). Example 8 A green polarizing film was obtained in substantially the same manner as in Example 2, except that the dye of Example 7 was used instead of the dye (number 1) and nylon 6 was used instead of polyethylene terephthalate. The degree of polarization was 80% (maximum absorption wavelength 655 nm). Examples 9 to 34 Table 2 shows the dichroic ratios, polarization degrees, and hues of the colored polyethylene terephthalate films of the other dyes in Table 1.

【table】

[Table] Comparative Example 1 Same procedure as in Example 2 except that a dichroic dye for liquid crystals (Structural formula A: dichroic ratio 8 in polyethylene terephthalate) was used instead of dye (1). A blue polarizing film was obtained. maximum absorption wavelength
The degree of polarization at 640 nm was as low as 52%. However, in the manufacturing process of this film, if the heat treatment process after stretching is omitted, at the same wavelength, 78%
It was clear that the degree of polarization decreased significantly during the heat treatment process. In addition, the shrinkage rate of the film after heat treatment is less than 1% in both the vertical and horizontal directions, whereas the film without heat treatment shows a large shrinkage rate of 8% in the vertical direction and 15% in the horizontal direction.
It lacked dimensional stability. The solubility of dye A in liquid crystal E-8 (trade name of nematic liquid crystal manufactured by BDH Co., Ltd.) is about 2.0% by weight. Comparative Example 2 A red-orange polarizing film was obtained in the same manner as in Example 2, except that a dichroic dye for liquid crystals (structural formula B: dichroic ratio in polyethylene terephthalate: 8) was used instead of dye (1). The degree of polarization at the maximum absorption wavelength of 495 nm was as low as 47%. However, although the degree of polarization of the untreated film was high at 80%, the shrinkage rate was 6% in the vertical direction and 12% in the horizontal direction, and it lacked dimensional stability. The solubility of dye B in liquid crystal E-8 and nitrobenzene was about 1.0% by weight and about 0.6% by weight, respectively. Comparative Example 3 In place of the dye (1) in Example 2, the following structural formula C (dichroic ratio in polyethylene terephthalate
Polarizing films were prepared in the same manner except that dichroic dyes for liquid crystals of 7.5) and D (dichroic ratio 8.0) were used. This polarizing film and the polarizing films of Examples 2 and 6 were heated in an oven at 120° C. for 1000 hours. The degree of polarization of each polarizing film before and after the heating test is shown in Table 3, and the polarizing films using the dyes of Example 2 and Example 6 (numbers 1 and 21) are more stable than the comparative dyes C and D. It showed a polarizing property. The solubility of C and D in liquid crystal E-8 was 1.0% by weight and 1.0% by weight, respectively.

【table】

Claims (1)

[Claims] 1 General formula () [In formula (1), Y is an oxygen atom or a sulfur atom,
X ₁ , X ₂ , X ₃ , X ₄ , X ₅ and X ₆ are hydrogen atoms, halogen atoms, hydroxy groups, or have 1 to 3 carbon atoms
is an amino group optionally substituted with alkyl groups, Q is the formula (), or expression(), It is a monovalent group represented by Here the expression ()
where R ₁ and R ₂ are a hydrogen atom, a halogen atom, a methyl group or a methoxy group, m is an integer of 1, 2 or 3, and R ₃ is -COOH, -
COOR ₄ , −CONH ₂ , −CONHR ₄ , −OOCR ₄ , −
NHCOR ₄ , −N=NR ₄ , [formula] [formula] or [formula]. Here, R ₄ and ring A are R ₁ , R ₂ , -COOH and/or -
a phenyl group optionally substituted with COOCH ₃ ,
It is a biphenyl group or a naphthalene group. In formula (), X ₇ , X ₈ , X ₉ , X ₁₀ , X ₁₁ , X ₁₂ and
X ₁₃ is a hydrogen atom, a halogen atom, a hydroxy group, or an amino group optionally substituted with an alkyl group having 1 to 3 carbon atoms. However, X ₁ , X ₂ ,
When X ₃ , X ₄ , X ₅ and X ₆ are hydrogen at the same time, X ₇ ,
At least one of X ₈ , X ₉ , X ₁₀ , X ₁₁ , X ₁₂ and X ₁₃ is a hydroxy group. ] A dichroic dye characterized by being represented by: 2 General formula () in the hydrophobic polymer [In formula (1), Y is an oxygen atom or a sulfur atom,
X ₁ , X ₂ , X ₃ , X ₄ , X ₅ and X ₆ are hydrogen atoms, halogen atoms, hydroxy groups, or have 1 to 3 carbon atoms
is an amino group optionally substituted with alkyl groups, Q is the formula (), or expression(), It is a monovalent group represented by Here the expression ()
Among them, R ₁ and R ₂ are a hydrogen atom, a halogen atom, a methyl group or a methoxy group, m is an integer of 1, 2 or 3, and R ₃ is -COOH, -COOR ₄ ,
−CONH ₂ , −CONHR ₄ , −OOCR ₄ , −NHCOR ₄ ,
−N=NR ₄ , [formula] [formula] or [formula]. Here, R ₄ and ring A are R ₁ , R ₂ , -COOH and/or -
a phenyl group optionally substituted with COOCH ₃ ,
It is a biphenyl group or a naphthalene group. In formula (), X ₇ , X ₈ , X ₉ , X ₁₀ , X ₁₁ , X ₁₂ and
X ₁₃ is a hydrogen atom, a halogen atom, a hydroxy group, or an amino group optionally substituted with an alkyl group having 1 to 3 carbon atoms. However, X ₁ , X ₂ ,
When X ₃ , X ₄ , X ₅ and X ₆ are hydrogen at the same time, X ₇ ,
At least one of X ₈ , X ₉ , X ₁₀ , X ₁₁ , X ₁₂ and X ₁₃ is a hydroxy group.] A polarizing film containing an oriented dichroic dye represented by .