JPH0721085B2 - Ferroelectric composite film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to a ferroelectric composite film. More specifically, it relates to a ferroelectric composite film containing a liquid crystal capable of forming a thermodynamically stable ferroelectric phase near room temperature and a thermoplastic resin.

“Prior Art” Smectic C liquid crystal composed of chiral molecules is known as liquid crystal exhibiting ferroelectricity. A typical ferroelectric liquid crystal that is a chiral smectic C liquid crystal is
p-decyloxybenzylidene-p'-amino-2-methylbutyl cinnamate (p-decyloxybenzylidene-
p'-amino-2-methylbutylcinnamate) (hereinafter referred to as "DOBAMBC").

The pitch of the spiral of the ferroelectric liquid crystal is usually about several microns, but when the thickness of the liquid crystal layer becomes thinner than the pitch of the spiral, the spiral structure is eliminated and the liquid crystal molecules are aligned in one direction. By applying a DC voltage to the liquid crystal in such a state, the direction of the dipole, that is, the direction of the liquid crystal molecules can be switched by the positive or negative polarity of the voltage. The time required for this switching is extremely short as compared with that of the nematic liquid crystal element which is most widely used as a liquid crystal display, and is 1 / 1,000,000.
Response times shorter than seconds are obtained. Even if the voltage application is turned off, the orientation of the liquid crystal molecules is maintained as it is, so that the bistable effect and the memory characteristic can be realized.

Such a chiral smectic C liquid crystal has excellent advantages not found in a nematic liquid crystal or a cholesteric liquid crystal, but has not been practically used so far. This is because no chiral smectic liquid crystal having a thermodynamically stable ferroelectric property near room temperature has been found, such as a nematic liquid crystal. For example, the above-mentioned DOBA MBC has a ferroelectric phase region of 64-92 ° C., which is considerably higher than room temperature.

On the other hand, an ester-based liquid crystal known as a kind of ferroelectric liquid crystal shows ferroelectricity at around room temperature, unlike DOBAMBC, but has a drawback that it is thermodynamically unstable.

“Problems that the Invention Attempted to Solve” Under the circumstances, the present inventors have conducted extensive studies to provide a composite film capable of forming a thermodynamically stable ferroelectric phase near room temperature, and as a result, It has been found that this object can be achieved by mixing a specific ester-based liquid crystal with a chiral smectic C liquid crystal typified by DOBAMBC, and further mixing this mixed liquid crystal with a thermoplastic resin to form a thin film. Has been completed.

"Means for Solving the Problem" The gist of the present invention is, therefore, that the thermoplastic resin (A), the azomethine-based liquid crystal group represented by the general formula I-1 or the general formula I-2, and the general formula II- 1 or general formula II-2
And a ferroelectric liquid crystal mixture (B) selected from at least two groups of the ester type liquid crystal group represented by the general formula III. .

General formula: [In the general formula I-1, A is hydrogen, a halogen atom, C
≡N- means an atom or group selected from a hydrocarbon group having 1 to 5 carbon atoms, B represents a halogen atom, an atom or group selected from a hydrocarbon group having 1 to 5 carbon atoms, and n represents 1 to
Represents an integer of 20. ] [In the general formula I-2, n represents an integer of 1 to 20,
m represents an integer of 1 to 15. ] [In the general formula II-1, n represents an integer of 1 to 15. ] [In the general formula II-2, n represents an integer of 1 to 15. ] [In General Formula III, X is CnH ₂ n ₊₁ O-, And n is an integer group of 1 to 20, Represents a group selected from, Y is represented by CmH ₂ m ₊ 1-, CmH ₂ m ₊₁ O-, and m is an integer group of 1 to 20, Represents a group selected from The present invention will be described in detail below.

The thermoplastic resin (A) contained in the composite film according to the present invention is
There is no particular limitation as long as it is compatible with the ferroelectric mixture (B). Specifically, polyvinyl chloride, polyvinyl bromide, polyvinyl fluoride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-vinylidene chloride copolymer Polymer, vinyl chloride-butadiene copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-styrene-acrylonitrile terpolymer, vinyl chloride-vinylidene chloride-vinyl acetate copolymer Halogenated vinyl polymers or copolymers such as polymer, polyvinylidene chloride, polytetrafluoroethylene, polytetrafluorochloroethylene, polyvinylidene fluoride; unsaturated alcohols such as polyvinyl alcohol, polyallyl alcohol, polyvinyl ether, polyallyl ether Or the weight of ether Polymers or copolymers of unsaturated carboxylic acids such as acrylic acid or methacrylic acid; unsaturated bonds in alcohol residues such as polyvinyl esters such as polyvinyl acetate and polyallyl esters such as polyphthalic acid Polymers or copolymers of those having: polyacrylic acid ester, polymethacrylic acid ester,
Polymers or copolymers of acid residues such as polymers of maleic acid esters or fumaric acid esters or those having unsaturated bonds in acid residues and alcohol residues; Polymers or copolymers of acrylonitrile or methacrylonitrile An unsaturated nitrile polymer or copolymer such as polyvinylidene cyanide, a polymer or copolymer of malononitrile or fumaronitrile; polystyrene, polyalphamethylstyrene, polyparamethylstyrene, styrene-alphamethylstyrene copolymer, styrene- Polymers or copolymers of aromatic vinyl compounds such as para-methylstyrene copolymer, polyvinylbenzene, polyhalogenated styrene, etc .; Poly (vinylpyridine), poly (N-vinylpyrrolidine), poly (N-vinylpyrrolidone), etc. Coalesce or copolymer; Polyester condensate such as polycarbonate, polyamide condensate such as nylon 6, nylon 6.6, etc .; Polymer or copolymer containing maleic anhydride, fumaric anhydride and its imidized product; polyamideimide, polyetherimide, polyimide,
Examples thereof include heat resistant organic polymers such as polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether sulfone and polyarylate. These examples are not meant to limit the invention.

The ferroelectric liquid crystal mixture (B) contained in the composite film according to the present invention is an azomethine-based liquid crystal group represented by the general formula I-1 or I-2 (hereinafter referred to as a group I) and a general formula.
Of the three liquid crystal groups of the azoxy-based liquid crystal group represented by II-1 or the general formula II-2 (hereinafter referred to as Group II) and the ester-based liquid crystal group represented by the general formula III (hereinafter referred to as Group III). It is a mixture of at least two liquid crystals selected from a group.

If you choose at least one from each group,
The above-mentioned drawbacks are exhibited, and the object of the present invention is not achieved. The object of the present invention is achieved by selecting at least one kind from each group and combining and mixing liquid crystals selected from at least two groups.

In the present invention, the azomethine series liquid crystal group means the above-mentioned general formula I
-1 or a liquid crystal represented by the general formula I-2. Specific examples thereof include the following compounds.

p-decyloxybenzylidene-p'-amino-2-methylbutyl cinnamate (DOMAMBC), p-hexyloxybenzylidene-p'-amino-2-
Chloro-α-propyl cinnamate (HOBACPC), p-octyloxybenzylidene-p'-amino-2-
Methyl butyl-α-chlorocinnamate (OOBAMBCC), o-hydroxy-p-3-methylheptoxybenzylidene-p′-aminooctylbenzene.

In the present invention, the azoxy-based liquid crystal group refers to the general formula II-
1 or a liquid crystal represented by the general formula II-2. Specific examples thereof include the following compounds.

4,4'-azoxycinnamic acid-2-methylbutyl ester, 4,4'-azoxyphenyl pentyl ether.

In the present invention, the ester-based liquid crystal group is defined by the general formula
Is a liquid crystal represented by. Specific examples thereof include the following compounds.

pn-hexyloxybenzic acid-p'-
(2-methylbutoxycarbonyl) phenyl ester, pn-octyloxybenzic acid-p'-
(2-Methylbutoxycarbonyl) phenyl ester, pn-nonanooxybenzoic acid-p '-(2
-Methylbutoxycarbonyl) phenyl ester, pn-decaoxybenzic acid-p '-(2-
Methylbutoxycarbonyl) phenyl ester, pn-dodecaoxybenzoic acid-p '-(2
-Methylbutoxycarbonyl) phenyl ester, pn-tetradecaoxybenzoic acid-p'-
(2-methylbutoxycarbonyl) phenyl ester, pn-hexadecaoxybenzoic acid-p'-
(2-Methylbutoxycarbonyl) phenyl ester.

The above examples of the compounds included in each liquid crystal group are not intended to limit the present invention to these examples.

According to the experiments of the present inventors, when combining liquid crystals selected from the three groups, if the proportion of the liquid crystal component in the smallest group is 20 mol% or more, the object of the present invention is effective. I found that I could achieve it.

To the liquid crystal mixture which is the component (B) of the present invention, a polar surfactant can be added to assist the alignment of liquid crystal molecules, and a dichroic dye can be added to display in color.

The mixing ratio of the thermoplastic resin (A) and the liquid crystal mixture (B) is preferably such that the ratio of the thermoplastic resin (A) is in the range of 20 to 60% by weight. When the content of the thermoplastic resin is less than 20% by weight, it becomes difficult to obtain a thin film from the composition of the present invention, and when it exceeds 60% by weight, a thin film forming a ferroelectric phase cannot be obtained, which is not preferable.

The ferroelectric thin film according to the present invention can be used in various forms such as a flat film, a spiral film and a hollow film. When it is used as a flat film, it is often used as an ultrathin film, and its performance can be sufficiently exhibited.

The ferroelectric thin film according to the present invention may be prepared by any method such as a dry / wet film forming method, a solution casting method, a solution coating method, and a water spreading method. In order to obtain a flat film-like ultra-thin film that exhibits sufficient performance, a mixture of the thermoplastic resin (A) and the liquid crystal mixture (B) is mixed with a good solvent of the thermoplastic resin (A) or a good solvent and a poor solvent. It is preferable to dissolve in a mixed solution of and to form a film by a solution casting method, a solution coating method, a water spreading method, or the like.

The ferroelectric thin film according to the present invention can be applied to electro-optical elements, large-sized liquid crystal displays, temperature sensors, liquid crystal optical shutters, optical modulators and the like.

"Effects of the Invention" The present invention has particularly remarkable effects as described below, and its industrial utility value is extremely large.

(1) The composite film according to the present invention forms a ferroelectric phase at around room temperature, and when used for display applications, excellent brightness is achieved. This is a remarkable effect that could not be achieved by the liquid crystal alone selected from the group I liquid crystal or the group II liquid crystal and the composite film containing the thermoplastic resin.

(2) The composite film containing the liquid crystal alone of group III and the thermoplastic resin has a strong tendency that the crystal structure of the liquid crystal changes due to a slight temperature change near room temperature, but the composite film according to the present invention is
It is thermodynamically stable near room temperature and has the property that the crystal structure does not easily change even with a slight temperature change. Further, the polarization reversal time at room temperature is short, which is suitable for applications such as switches.

"Examples" Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded.

Examples and Comparative Examples <Preparation of Ferroelectric Liquid Crystal Mixture> As liquid crystals, p-decyloxybenzylidene-p′-amino-2-methylbutyl cinnamate (DOBAMBC) belonging to Group I and p belonging to Group III are used. -N-dodecaoxybenzic acid-p '-(2-methylbutoxycarbonyl) phenyl ester (hereinafter referred to as "C- ₁₂ ") and DOBAMBC / C- ₁₂ in a molar ratio of 50/50. To obtain a mixed ferroelectric liquid crystal mixture.

<Mixing with thermoplastic resin> Only the above liquid crystal mixture (example) and DOBAMBC (comparative example)
Polyvinyl chloride (average degree of polymerization of 1,
050) powder was mixed with liquid crystal / polyvinyl chloride at a weight ratio of 70/30.

<Preparation of Thin Film> Each of the above two kinds of mixtures was dissolved in cyclohexanone to prepare a solution having a resin concentration of 10% by weight.

A drop of each of the above polymer solutions was gently dropped on the wall of the water surface in a water tank kept at 283K to form a thin film on the water surface, immediately scooped up, and vacuum dried at room temperature to obtain a film of about 30 nm (water surface). A developed film) was obtained. After 40 water-spreading membranes thus obtained were laminated on a Teflon plate, this film was fixed to a ring-shaped frame, then the frame was peeled off from the Teflon plate and treated at 333K for several minutes in a nitrogen atmosphere. Then, a film without wrinkles or sagging was prepared.

<Measurement of Switching Effect on Composite Membrane> The switching effect on the composite membrane was measured as follows.

Width of about 5 mm on each side of two slides
Then, aluminum was vacuum-deposited in a strip shape and used as an electrode. The composite membrane obtained above was sandwiched while the electrode surfaces were opposed to each other, and a test apparatus as shown in FIG. 1 as a schematic perspective view and in FIG. 2 as a longitudinal side view in the II-II portion of FIG. Prepared. The upper slide glass is omitted in FIGS. 1 and 2.

1 and 2, 1 is a slide glass,
2 and 3 are aluminum electrodes, 4 is a composite film, and 5 and 6 are lead wires, respectively.

A DC electric field was applied between both electrodes using the above test device, and the polarization change of the sample composite film due to the application of the DC electric field was determined by plotting it against the time after the electric field was applied.

FIG. 3 shows the electric field dependence of the polarization reversal time of 320 K for the composite film containing the liquid crystal mixture of DOBAMBC / C- ₁₂ at 50/50 (molar ratio), and FIG. 4 shows DOBAMBC for comparison. The field dependence of the polarization reversal time at 358K and 353K is shown for the composite film containing only Pd.

3 and 4 show that the composite membrane according to the invention has a short switching time even at low temperatures.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a test apparatus used for measuring a switching effect of a composite film, and FIG. 2 is a II-II of FIG.
It is a vertical side view in a part. FIGS. 3 and 4 show the electric field dependence of the polarization inversion time. FIG. 3 shows the example, and FIG. 4 shows the comparative example. In the figure, 1 is a slide glass, 2 and 3 are aluminum electrodes, 4 is a composite film, and 5 and 6 are lead wires, respectively.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09K 19/48 9279-4H G02F 1/137 500 9315-2K

Claims (4)

[Claims] 1. A thermoplastic resin (A), an azomethine-based liquid crystal group represented by the general formula I-1 or general formula I-2, and a general formula.
It contains a ferroelectric liquid crystal mixture (B) selected from at least two groups selected from the group consisting of the azoxy liquid crystal group represented by II-1 or the general formula II-2 and the ester liquid crystal group represented by the general formula III. A ferroelectric composite film characterized by the above. General formula: [In the general formula I-1, A is hydrogen, a halogen atom, C
≡N- means an atom or group selected from a hydrocarbon group having 1 to 5 carbon atoms, B represents a halogen atom, an atom or group selected from a hydrocarbon group having 1 to 5 carbon atoms, and n represents 1 to
Represents an integer of 20. ] [In the general formula I-2, n represents an integer of 1 to 20,
m represents an integer of 1 to 15. ] [In the general formula II-1, n represents an integer of 1 to 15. ] [In the general formula II-2, n represents an integer of 1 to 15. ] [In General Formula III, X is CnH ₂ n ₊₁ O-, And n is an integer group of 1 to 20, Represents a group selected from, Y is represented by CmH ₂ m ₊ 1-, CmH ₂ m ₊₁ O-, and m is an integer group of 1 to 20, Represents a group selected from ] 2. The liquid crystal of a plurality of groups contained in the liquid crystal mixture (B) has a ratio of the liquid crystal of the smallest group being 20 mol%.
It is above, The claim (1)
A ferroelectric composite film according to item. 3. A composite film containing a thermoplastic resin (A) and a liquid crystal mixture (B), wherein the ratio of the thermoplastic resin (A) is
20 to 60% by weight of the ferroelectric composite film according to any one of claims (1) and (2). 4. A composite film, which is dissolved in a good solvent of a thermoplastic resin (A) or a mixed solution of a good solvent and a poor solvent, and formed into a film from this solution. The ferroelectric composite film according to any one of items (1) to (3).