JP5523657B2 - Stabilized liquid crystal material and liquid crystal element using the same - Google Patents

Description

  The present invention is used for display elements represented by TN (twisted nematic) type liquid crystal elements, STN (super twisted nematic) type liquid crystal elements, FLCD (ferroelectric liquid crystal display), and PDLC (polymer dispersed liquid crystal) type liquid crystal elements. The present invention relates to a liquid crystal material stabilization method, a liquid crystal material stabilized by using the stabilization method, and a liquid crystal element using these liquid crystal materials.

In recent years, with the progress of the information society, various display elements have become increasingly important as one of the man-machine interfaces. Under such circumstances, flat displays, in particular liquid crystal displays (LCDs), are rapidly spreading due to their features such as thinness, light weight, low voltage driving, and low power consumption. As the name suggests, a liquid crystal display uses a liquid crystal composition in its display portion, and the liquid crystal composition can be said to be a component constituting the core of a liquid crystal display.
The liquid crystal composition is composed of an organic compound. The fact that this is incorporated into a precision electrical product requires the liquid crystal composition to: The liquid crystal composition has stability capable of withstanding the harsh conditions of the manufacturing process of the liquid crystal display, and in order for the manufactured liquid crystal display to stably exhibit its excellent performance over a long period of time, the liquid crystal composition It is also necessary for the product to have long-term stability in which the physical properties do not change during the period of use. That is, the liquid crystal composition must withstand heat of 100 ° C. or higher in the manufacturing process of the liquid crystal display for several hours, and further needs to be stable over a period of use ranging from several thousand hours to tens of thousands of hours. This condition is very severe for the liquid crystal composition which is an organic compound, and even if it has excellent characteristics, this stability condition cannot be satisfied. Therefore, a liquid crystal compound that can actually be used for a liquid crystal display. Is limited.
On the other hand, with the advent of the information society, high performance of liquid crystal display elements has become indispensable. For example, liquid crystal materials with excellent refractive index anisotropy are required for high speed liquid crystal display elements. For example, in Japanese Patent Laid-Open No. 7-53417,

Various liquid crystal compounds have been found.

  However, no effective method has been found so far for a method for stabilizing various liquid crystal compounds or mixtures thereof accompanying the improvement in performance of liquid crystal display elements.

As a result of intensive studies on a method for stabilizing a liquid crystal compound or a mixture thereof suitable for a liquid crystal material having excellent refractive index anisotropy, the present inventors have found that an antioxidant and / or a light stabilizer are effective. As a result, the present invention has been completed.
That is, the following general formula (1)

[Wherein M and N are each independently

Z ¹ and Z ² each independently represent a single bond, —O—, —CH ₂ CH ₂ —, —COO— or —OCO—, and each of X ¹ , X ² , X ³ , X ⁴ , Y ¹ , Y ² , Y ³ and Y ⁴ each independently represent CH, CF or N, W is a single bond, —CH ₂ CH ₂ —, —CF ₂ CF ₂ —, —CF ₂ CH ₂ —, —CH ₂ CF ₂ —

Where L is

A, b, c or d represents 0 or 1, and R represents a hydrogen atom, a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a monofluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a mono It represents trifluoromethoxy group, cyano group, C ₁ -C ₁₂ alkyl group, C ₁ -C ₁₂ alkoxy group, a C ₂ -C ₁₂ alkenyl group or C ₂ -C ₁₂ alkoxyalkyl an alkyl group, R 'is an illustrates an optically active non Hitoshi C ₁ may contain a carbon -C ₁₂ alkyl group, C ₁ -C ₁₂ alkoxy group, a C ₂ -C ₁₂ alkenyl group or C ₂ -C ₁₂ alkoxyalkyl group. When W is a single bond, R ′ may be a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a monofluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a monofluoromethoxy group, or a cyano group. ]
A method for stabilizing a liquid crystal material, comprising mixing at least one kind of an antioxidant and / or a composition containing at least one kind of a compound represented by the formula: Provided are a liquid crystal material stabilized by use, and a liquid crystal element in which the liquid crystal material is sandwiched between a pair of electrode plates.
The present invention is described in detail below.

BEST MODE FOR CARRYING OUT THE INVENTION

  In the present invention, the content of the antioxidant and / or the light stabilizer in the liquid crystal material is 0.001 to 5% by weight.

Examples of the antioxidant in the present invention, phenolic antioxidants, phosphite-based antioxidant, phospho Na Ito antioxidant, sulfur antioxidant and the like, and the light stabilizer, hindered amine light stabilizer Agents, benzophenone light stabilizers, triazole light stabilizers, nickel quenchers and the like.

Although it does not specifically limit as a phenolic antioxidant in this invention, The compound which has the following structure as a partial structure is illustrated.
Formula 1

[Wherein, R ¹ and R ² each independently represents a hydrogen atom or an alkyl group. ]
As a preferable specific example,
2,6-di-t-butyl-4-methylphenol,
Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate,
2,2′-methylenebis (6-tert-butyl-4-methylphenol),
2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate,
2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate,
4,4′-butylidenebis (6-tert-butyl-3-methylphenol),
3,9′-bis [2- {3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxa Spiro [5/5] Undecane,
2- (3,5-di-t-butyl-4-hydroxyanilino) -4,6-bis (n-octylthio) -1,3,5-triazine,
2,2′-ethylidenebis (4,6-di-t-butylphenol),
2,2'-ethylidenebis (4-sec-butyl-6-t-butylphenol),

2,2′-thiobis (6-tert-butyl-3-methylphenol),
1,1,3-tris (5-t-butyl-4-hydroxy-2-methylphenyl) butane,
Bis [2-t-butyl-4-methyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) phenyl] terephthalate,
Tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane,
2,2′-thiodiethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate],
Triethylene glycol bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate],
1,6-hexanediol bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate],
1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate,
1,3,5-tris [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} ethyl] isocyanurate,
1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate,
Examples include 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene.

In the present invention, the sulfur-based antioxidant is not particularly limited, and examples thereof include compounds of the following formulas 2 and 3.
Formula 2

^{_{S- (CH 2 CH 2 -COOR 3}} ) 2 ( Equation 2)
[Wherein R ³ represents an alkyl group, preferably a C ₁₂ -C ₁₈ alkyl group. ]
Formula 3

[Wherein, R ⁴ represents an alkyl group, preferably a C ₁₂ alkyl group. ]
As a preferable specific example,
Dilauryl 3,3′-thiodipropionate,
Dimyristyl 3,3'-thiodipropionate,
Distearyl 3,3′-thiodipropionate,
And tetrakis (3-laurylthiopropionyloxymethyl) methane.
Further, as the phosphite-based antioxidant and phospho Na Ito antioxidants in the present invention, but it is not limited to, Formula 4 or a compound of formula 9 below are exemplified.
Formula 4
P- (OR ⁵ ) ₃ (Formula 4)
[Wherein, R ⁵ represents an optionally substituted alkyl group or aryl group. ]
Equation 5 and Equation 6

Wherein, R ⁶ represents a optionally substituted alkyl group or an aryl group, R ^7, R ⁸ and R ⁹ each independently represent a hydrogen atom or a C ₁ -C ₈ alkyl group, R ¹⁰ Represents a fluorine atom or an alkyl group, and X represents a single bond, an oxygen atom or a nitrogen atom. ]

[Wherein, R ¹¹ and R ¹² each independently represent a hydrogen atom or an alkyl group, and R ¹³ represents a hydrogen atom or an alkyl group. However, when R ¹³ is a hydrogen atom,

Resonance structure exists and is a phosphinate compound. ]
As a preferable specific example,
Tris (nonylphenyl) phosphite,
Tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) 4,4′-biphenylenediphosphonite,
Bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite,
Bis (2,6-di-t-butylphenyl) pentaerythritol diphosphite ,
Distearyl pentaerythritol diphosphite,
Phenyl diisooctyl phosphite,
Phenyl diisodecyl phosphite,
Phenyl di (tridecyl) phosphite,
Diphenyl isooctyl phosphite,
Diphenyl isodecyl phosphite,
Diphenyl tridecyl phosphite,
4,4′-isopropylidenebis (phenyldialkyl phosphite),
2,2'-methylenebis (4,6-di-t-butylphenyl) octyl phosphite,
Examples include 2,2′-ethylidenebis (4,6-di-t-butylphenyl) fluorophosphonite.
Although it does not specifically limit as a hindered amine light stabilizer in this invention, The compound which has the following structure as a partial structure is illustrated.
Equation 10

As a preferable specific example,
Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate,
Bis (N-methyl-2,2,6,6-tetramethyl-4-piperidyl) sebacate,
N, N′bis (2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine,
2-methyl-2- (2,2,6,6-tetramethyl-4-piperidyl) amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide,
Tetrakis (2,2,6,6-tetramethyl-4-piperidyl) (1,2,3,4-butanetetracarboxylate,
Poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl ) Imino} hexamethyl {(2,2,6,6-tetramethyl-4-piperidyl) imino}],
Poly [(6-morpholino-1,3,5-triazine-2,4-diyl) {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethine {(2,2,6,6 -Tetramethyl-4-piperidyl) imino}],
A polycondensate of dimethyl succinate and 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine,
N, N′4,7-tetrakis [4,6-bis {N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino} -1,3,5-triazine- 2-yl] -4,7-diazadecane-1,10-diamine and the like.
In the present invention, the benzophenone light stabilizer is not particularly limited, and examples thereof include compounds having the following structure as a partial structure.
Equation 11

  Specific examples include 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone.

In the present invention, the triazole light stabilizer is not particularly limited, and examples thereof include compounds having the following structure as a partial structure.
Formula 12

Specific examples include 2- (2-hydroxy-5-methoxyphenyl) benzotriazole, 2- (2-hydroxy-3,5-t-butylphenyl) benzotriazole and the like.
In the present invention, the nickel-based quencher is not particularly limited, and examples of the basic skeleton include organic nickel, and specific examples include nickel dibutyldithiocarbamate.

Examples of the liquid crystal material include an alkyl group which may be fluorine-substituted, an alkenyl group which may be fluorine-substituted, an alkynyl group which may be fluorine-substituted, an alkoxy group which may be fluorine-substituted, and a fluorine-substituted material. Biphenyl, phenylcyclohexane, tolan, stilbene or terphenyl, or a mixture thereof, which may have an alkoxyalkyl group, fluorine atom or cyano group as a substituent, may be mentioned. .
Furthermore, the following compounds can be exemplified.

R is a hydrogen atom, a fluorine atom, a trifluoromethyl group, difluoromethyl group, a monofluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a mono trifluoromethoxy group, cyano group, C ₁ -C ₁₂ alkyl group, C ₁ ~ C ₁₂ alkoxy group, a C ₂ -C ₁₂ alkenyl group or C ₂ -C ₁₂ alkoxyalkyl an alkyl group, R 'is an C ₁ -C ₁₂ alkyl group, C ₁ -C ₁₂ alkoxy group, C ₂ -C ₁₂ alkenyl group Or a C _{2 to} C ₁₂ alkoxyalkyl group, and W represents a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a monofluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a monofluoromethoxy group in the case of a single bond. Or a cyano group may be sufficient. Moreover, the aromatic ring of the said compound may be substituted by the fluorine atom. ]

[Effect of the invention]
The present invention is used for display elements represented by TN (twisted nematic) type liquid crystal elements, STN (super twisted nematic) type liquid crystal elements, FLCD (ferroelectric liquid crystal display), and PDLC (polymer dispersed liquid crystal) type liquid crystal elements. It is useful as a method for stabilizing a liquid crystal composition. In addition, a stabilized liquid crystal composition using the stabilization method and a liquid crystal element using the liquid crystal composition can be provided.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
In Examples 1 to 2, 2% by weight of an antioxidant was added to a liquid crystal compound, and after performing a heat resistance test (150 ° C., 2 hours) in the dark in the air, liquid chromatography (column SUMPAX QSDA-212 6 mmπX15 cm , 254 nm, MeC Resolution).

Example 1
To 50 mg of 4- (4-pentylcyclohexyl) benzonitrile (5PCH), 2 parts of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, which is a phenolic antioxidant, are added. A heat resistance test (150 ° C., 2 hours) was performed in the dark in the air, and the recovery rate was determined by liquid chromatography. As a comparison, the same test was performed without adding an antioxidant. The results are shown in Table 1.

Example 2
To 50 mg of 4-pentyl-cyanobiphenyl (5CB), 2 wt% of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, which is a phenolic antioxidant, was added. The heat resistance test (150 ° C., 2 hours) was performed in the air in the dark, and was determined by liquid chromatography. As a comparison, the same test was performed without adding an antioxidant. The results are shown in Table 2.

Examples 3-6
2% by weight of an antioxidant was added to 50 mg of 4- (4-propylcyclohexyl) benzonitrile (3PCH), and a heat resistance test (150 ° C., 2 hours) was performed in the dark in the air, and obtained by liquid chromatography. . As a comparison, the same test was performed without adding an antioxidant. The results are shown in Table 3. Moreover, the liquid chromatogram of Example 5 and a comparative example is shown in FIG.1 and FIG.2.

Antioxidant A: Dimyristyl 3,3′-thiodipropionate B: Tris (nonylphenyl) phosphite (phosphate antioxidant) 2% by weight
C / D: 2,6-di-t-butyl-4-methylphenol (phenolic antioxidant 1 wt% / tris (2,4-di-t-butylphenyl) phosphite (phosphoric acid antioxidant) 1% by weight
C / B: 2,6-di-t-butyl-4-methylphenol (phenolic antioxidant 1% by weight / tris (nonylphenyl) phosphite (phosphoric acid antioxidant) 1% by weight

Example 7
To 4-pentyl-cyanobiphenyl (5CB) (300 mg), 0.2% by weight of hindered amine benzoate bis (N-methyl-2,2,6,6-tetramethyl-4-piperidine) sebacate was added. This was put into a sample tube, irradiated with light by a light resistance tester SUNTESTER XF-180 manufactured by Shimadzu Corporation for 16 hours, and the recovery rate was determined by liquid chromatography. As a comparison, the same test was performed without adding a light stabilizer. The results are shown in Table 4.

The liquid chromatogram obtained in Example 5 is shown. The liquid chromatogram of the comparative example of Examples 3-6 is shown.

Claims (4)

The following general formula (1)

[Wherein, M and N are each independently

The stands, Z ¹ and Z ² represents a single ^{binding, X 1, X 2, X} 3, X 4, Y 1, Y 2, Y 3 and Y ⁴ represent CH, W is Tan'yui case the stands, L is

A represents 1; b, c or d represents 0 or 1; R represents a C _{1 to} C ₁₂ alkyl group, a C _{1 to} C ₁₂ alkoxy group, a C _{2 to} C ₁₂ alkenyl group, or C _2. represents -C ₁₂ alkoxyalkyl an alkyl group, R 'is an off Tsu atom, a trifluoromethyl group, Application Benefits trifluoromethoxy group or a cyano group. And a liquid crystal composition comprising at least one compound represented by formula (1) or at least one compound represented by formula (1) (wherein the compound represented by formula (1)) the liquid crystal composition does not contain an epoxy resin), the light stabilizer is characterized by mixing at least one, wherein the light stabilizer is bis (2,2,6,6-tetramethyl-4-piperidyl) Said process, which is sebacate or bis (N-methyl-2,2,6,6-tetramethyl-4-piperidyl) sebacate . The method of claim 1, wherein the light stabilizer is bis (N-methyl-2,2,6,6-tetramethyl-4-piperidine) sebacate. The method according to claim 1 or 2 , further comprising mixing at least one antioxidant. The method according to claim 3 , wherein the antioxidant is a phenol-based antioxidant, a phosphite-based antioxidant, a phosphite-based antioxidant, or a sulfur-based antioxidant.

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