JPH02272089A - Ferroelectric polymeric liquid crystal and display element containing the same - Google Patents

Abstract

PURPOSE:To provide the subject liquid crystal capable of performing switching operation at a high speed and composed of a copolymer of a dye monomer containing a dichromatic dye as a polymerizable monomer structure and a polymerizable mesogen monomer capable of exhibiting chiral smectic phase. CONSTITUTION:The objective liquid crystal is composed of a copolymer of (A) a dye monomer (e.g. the monomer of formula I) containing a dichromatic dye as a polymerizable monomer structure and (B) a polymerizable mesogen monomer (e.g. the monomer of formula II) capable of exhibiting chiral smectic phase. The amounts of the components A and B are adjusted to give a molar fraction of the component A of preferably 0.05-0.3. The number-average molecular weight of the above copolymer is preferably 5,000-100,000.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ferroelectric polymer liquid crystal that can be used as a display/recording material and a display element using the same.

[Prior Art] In recent years, polymeric liquid crystal materials have attracted attention as high aging materials in display elements. The reasons for this are that polymeric liquid crystal materials can be easily made into thin films, can be made into large areas, can be controlled in orientation by stretching, and can be fixed in structure at temperatures below the glass transition point. Examples include having characteristics such as being certain.

In addition, as a method for producing a polymer having a mesogen group, 1
For example, it is described in West German Patent Publication No. 2831909. Furthermore, regarding a method of driving a polymer liquid crystal by an electric field, US Pat. No. 42,394:15 and the like are known.

On the other hand, polymer liquid crystals containing dyes are known.6 For example, in a system where polymer liquid crystals and guest molecules such as dyes are made compatible, by aligning the guest molecules in the alignment direction of the liquid crystals, polymer liquid crystals can be There are known means to improve the functionality of

Furthermore, in order to increase the concentration of dye contained in polymeric liquid crystal, a method of copolymerizing a polymerizable dye monomer and a polymerizable mesogen monomer is disclosed in JP-A-58-176205. There is. It is stated that the dye-containing polymer liquid crystal obtained by this method can be used for electro-optical applications such as guest-host display.

[Problems to be Solved by the Invention] However, in the dye-containing polymer liquid crystal in the above-mentioned conventional example, the electric field response is based on a method that utilizes dielectric constant anisotropy. Depending on whether the sign of the rate anisotropy is positive or negative, some types change the alignment state of polymer liquid crystals from vertical to horizontal alignment, or from horizontal to vertical. It has the disadvantage of slow response speed.

The present invention has been made to improve the drawbacks of the prior art, and provides a ferroelectric polymer liquid crystal containing a dichroic dye in the side chain that can perform high-speed switching, and a ferroelectric polymer liquid crystal containing the dichroic dye in the side chain. The purpose of the present invention is to provide a display element using the following methods.

[Means for Solving the Problems] and [Operations] The present inventors have conducted intensive research to solve the drawbacks of the above-mentioned conventional examples, and as a result, the present inventors have found that five dichromatic liquid crystals are incorporated into polymeric liquid crystals having ferroelectric properties. By using a guest-host ferroelectric polymer liquid crystal into which a dichroic dye is introduced by copolymerization or substitution reaction, the reversal of the spontaneous polarization of one ferroelectric dust molecule liquid crystal is used, and the dichroic dye is produced together with the liquid crystal molecule. The present invention was completed by discovering that it is possible to switch molecules at high speed.

That is, the present invention provides a dye monomer in which a dichroic dye has a polymerizable monomer structure, and! A ferroelectric polymer liquid crystal characterized by being composed of a copolymer with a mesogen monomer having the ability to express a chiral smectioic phase capable of i-merging, and a uniaxially aligned ferroelectric polymer liquid crystal. is sandwiched between a pair of substrates having electrodes, and is characterized by comprising an analyzer whose vibration axis coincides with the alignment direction.

The present invention also provides a ferroelectric polymer liquid crystal characterized in that a dichroic dye and a mesogen capable of expressing a chiral smectic phase are introduced into a polymer compound by a substitution reaction, and the ferroelectric polymer liquid crystal. This display element comprises a uniaxially aligned molecular liquid crystal sandwiched between a pair of substrates having electrodes, and is equipped with an analyzer whose vibration axis coincides with the alignment direction.

Furthermore, the present invention uniaxially aligns at least two kinds of ferroelectric polymer liquid crystals selected from the above-mentioned ferroelectric polymer liquid crystals, each of which contains dichroic dyes having different absorption bands. A display element comprising a pair of electrodes sandwiched between a pair of electrodes and laminated with an insulating layer interposed therebetween so that the alignment directions match, and an analyzer whose vibration axis coincides with the alignment direction. .

The present invention will be explained in detail below.

In the present invention, the method of introducing a dichroic dye into a ferroelectric polymer liquid crystal is to form a dichroic dye into a polymerizable monomer structure, which has the ability to exhibit ferroelectricity that can be polymerized, that is, a chiral smectic phase. A method of copolymerizing a dye-containing ferroelectric polymer liquid crystal with ferroelectricity by copolymerizing it with a mesogen monomer having an expression phase, or a method of copolymerizing a dye-containing ferroelectric polymer liquid crystal with a dichroic dye and the ability to express ferroelectricity, that is, the ability to express chiral smectic phase. A method of introducing a mesogen having a compound into a polymer compound by a substitution reaction can be mentioned.

Here, the mesogen monomer having the ability to express ferroelectricity, that is, the ability to express chiral smectic phase, means a monomer having a mesogen that exhibits ferroelectricity, that is, chiral smectic phase, when polymerized alone. Specifically, the following structural formulas (1)-(
Examples include compounds represented by 6), but are not limited to these.

Further, as for the type of the two-polymer main chain, acrylic type and siloxane type can also be used.

C11, -CII CHt -C11 Wheat CH, - (:H J = 1 to 2. = 1 to 2゜n = 4 to 18゜j = 0 or 1 CH□-C) 1 1' = 1 to 2. ni=1~2. n=4-18゜j=o or 1 C1l□-CH These mesogen monomers and polymerizable dye monomers are:
It combines a commonly used host-guest dichroic dye with an alkyl spacer of an appropriate length to form a polymerizable monomer structure. Specifically, it has the following structural formula (7).
) to (13), but are not limited thereto.

f=1~2. = 1~2゜j=o or 1 C11, -CI+ n=4~18゜CH, -CH 4≦n≦18゜l≦m≦10 ffi=1-2. k=1~2. n=4~18゜j=0 or l C) 1m-C1 4≦m≦18 C1!2 Deep CH R3 False-■ or -C11゜2≦m≦18 4≦mfk18 4≦m≦18 8.0 R2R,=-1 or -C11°R,=alkyl group having 3 to 18 carbon atoms 2≦m≦18R.

ll2-C R, = -II or -CH4 4≦m≦18 \ CH.

When copolymerizing a dye monomer with the above-mentioned dichroic dye having a polymerizable monomer structure and a mesogen monomer having the ability to express a chiral smectioic phase that can be pentapolymerized, the dye monomer It is desirable that the mole fraction of the dye is in the range of 0.01 to 0.50, preferably 0.05 to 0.30@4 or less than 0.01 because the dye concentration is low. Since no optical density can be obtained, it cannot be practically used for guest-host display devices. Also, the 2 mole fraction is 0.
If it exceeds 50, the dye concentration is too high and a ferroelectric liquid crystal phase or liquid crystal phase may not be formed.

In addition, the copolymerization reactions between dye monomers and mesogen monomers are radical polymerization and cationic polymerization. This can be carried out by anionic polymerization, chain transfer polymerization, or the like.

In addition, the copolymer has a number average molecular weight of 1.000 to 50o.
, ooo, preferably 5,000 to 100. A value in the range of 00 is desirable.

Next, another ferroelectric polymer liquid crystal of the present invention is made of a polymer compound in which a dichroic dye and a mesogen capable of expressing a chiral smectic phase are introduced by substitution reaction.

A method of introducing a mesogen of a ferroelectric polymer liquid crystal and a dichroic dye into a polymer compound by a substitution reaction is described in "Journal of Polymer Science, Journal of Polymer Chemistry Edition".
polymer 5science, Polymer
Chemistry Ed, ) J Volume 19,
The method described on page 1427 (1981) can be used. That is, in the polymer represented by the following formula (I), -←C1l□-C(R,) +-(
I)n/\x (wherein, R1 is)1 or C)11, X is 011. -O
R,, R2 represents an alkyl group having 1 to 18 carbon atoms)
Esterification, transesterification, etc. can be carried out by known means, and a mesogen capable of expressing a dichroic dye and a chiral smectic phase of a ferroelectric polymer liquid crystal can be introduced via a suitable spacer.

Specifically, the mesogen group having the ability to express a chiral smectic phase and those used as dichroic dyes have the above-mentioned structural formulas (1) to (6) and structural formulas (7) to (13).
Among those represented by , those corresponding to a spacer and a dye residue, and a spacer and a mesogen residue can be mentioned.

When a dichroic dye and a mesogen having chiral smectic phase expression are introduced into a polymer compound, the molar fraction of the dichroic dye is 0. O1-0.5, preferably 0.
It is desirable that it be in the range of 0.05 to 0.30. If the molar fraction is less than 0.01, sufficient optical density cannot be obtained due to the low concentration of the dye, and it cannot be practically used for guest-host display devices. If it exceeds 5, the dye concentration may be too high and a ferroelectric liquid crystal phase or liquid crystal phase may not be formed.

In addition, the obtained polymer has a number average molecular weight of 1.000 to
5002 units 00. Preferably 5,000 to 1 mouth o, oo
.

It is desirable that it falls within the range of .

In order to widen the temperature range of the ferroelectric phase of the ferroelectric polymer liquid crystal of the present invention obtained as explained above, an appropriate amount of low-molecular ferroelectric liquid crystal or high-molecular ferroelectric liquid crystal was blended. In addition, when a low-molecular ferroelectric liquid crystal is blended, an effect of reducing the response speed can also be obtained. However, the amount of low-molecular ferroelectric liquid crystal added must be within a range that maintains good film-forming property, which is a characteristic of polymer liquid crystal.

Further, the ferroelectric polymer liquid crystal of the present invention can be easily formed into a film, and a uniaxially oriented state can be obtained by stretching the film. In addition to such stretching treatment, the substrate is subjected to orientation treatment, as is used for ordinary low-molecular-weight liquid crystals, and then ferroelectric polymer liquid crystal is applied to the substrate, and the liquid crystal is made into an actual image state. A uniaxially oriented state can also be easily obtained by slow cooling.

Next, 2, the above uniaxially aligned ferroelectric polymer liquid crystal of the present invention is sandwiched between a pair of substrates having two electrodes, and an analyzer whose vibration axis coincides with the -axis alignment direction is provided. Display elements can also be formed.

In addition, dichroism is obtained by mutually containing at least two or more types selected from ferroelectric polymer liquid crystals in which dichroic dyes are introduced into polymer liquid crystals having ferroelectric properties by copolymerization or substitution reaction. Ferroelectric polymer liquid crystals with different absorption bands of dyes are uniaxially aligned, and each oriented ferroelectric polymer liquid crystal is sandwiched between a pair of electrodes so that the alignment directions are aligned through an insulating layer. A display element can be formed by laminating an analyzer in which the vibration axis coincides with the -axis orientation direction.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Liquid crystalline monomer represented by the following structural formula (14) 0.8
g, and 0.15 g of a monomer having a dichroic dye represented by the following structural formula (15) to 25 g of benzene! and azobisisobutyronitrile (^1BN) was added as an initiator and placed in a 5 glass ampoule.

Next, the reaction solution was frozen with liquid nitrogen, and after degassing under reduced pressure, the upper part of the ampoule was melted and polymerized at 60° C. for 48 hours. The obtained reaction product was reprecipitated with methanol to obtain an acrylic main chain copolymer [A].

C) 1m-CH copolymer [A] CIl, -CH (Dissolved in CDC1'3, from the intensity ratio of the aromatic ring proton of 7 to 9 pp- and the methyl proton of 1 to 1.:l I) plm, ( +4) formula seven-piece unit 88 anus 2%,
The monomer uni-cito 12 OP% of the formula (15) was determined. ) Also, the phase transition point of this copolymer is I)S(: M
The results were as follows.

The copolymer thus obtained was formed into a film with a thickness of 5 kg, and the film was placed between two glass substrates on which transparent electrodes were adhered and polyimide rubbed as an alignment film was provided. They were sandwiched together with a spacer made of a 3tA polyethylene terephthalate film and pressed together while maintaining the temperature at 90°C. Thereafter, a uniaxially oriented cell was obtained by slowly cooling to room temperature.

Light is applied from the back of the uniaxially oriented cell obtained in this way,
The vibration axis is 30V through one analyzer that matches the orientation direction.
When the optical response was observed when a 5 Hz alternating current electric field was applied, a change in good contrast between colorless and blue colors was observed at a response speed of 150 m5ec.

Example 2 0.85 g of an acrylic ester copolymer represented by the following structural formula (16) was dissolved in 50 mj of dry benzene with triethylamine, and a two-color copolymer represented by the following structural formula (17) was dissolved therein. A solution prepared by dissolving 0.1.5 g of a coloring matter in 10 mj of dry benzene was added dropwise at room temperature with stirring, and the mixture was reacted for 6 hours.

The obtained reaction product was reprecipitated with methanol to form a copolymer [B
] was obtained.

C)(.

The phase transition point of this copolymer [B] is determined by DSCI,
It was as follows.

In the same manner as in Example 1, this copolymer was sandwiched between two glass substrates using a polyethylene terephthalate film as a spacer, and the copolymer was press-bonded while maintaining the temperature at 90°C. Thereafter, it was slowly cooled to room temperature to obtain a uniaxially oriented cell.

In the same manner as in Example 1, the optical response when an alternating current electric field of :lOV, 5 fiz was applied was determined. I observed good switching between colorless and several colors, or a response speed of LQQ m5ec.

Example 3 After forming a film from the molten state of the ferroelectric polymer liquid crystal obtained in Example 1 and Example 2, it was -axially stretched in a temperature range showing the SmA phase to a thickness of 5- A uniaxially oriented film was obtained. These two films were sandwiched between a pair of polyethylene films each having a transparent electrode attached thereto, and stacked so that the orientation directions matched. 2 layers of layers l. 2 is the polymer liquid crystal layer obtained in Example 1.2, respectively.

Using a polarizing microscope equipped with a hot stage, an electric field was applied to each of the 0 layers 1 and 2 of the 0 layer 1 and 2 whose orientation state was observed using a single analyzer aligned in the vibrational orientation direction. When switching to one of the bistable states of
The observed color was colorless. Next, when a reverse electric field is applied to only layer 1, a blue display is obtained, and when a reverse electric field is applied only to layer 2, a yellow display is obtained. Multi-color display is possible in stacked cells such as 0 or more. Something has been confirmed.

[Effects of the Invention] As explained above, according to the ferroelectric polymer liquid crystal of the present invention, dichroic dye molecules can be introduced into the polymer liquid crystal without destroying the ferroelectric liquid crystal phase. .

In addition, in display elements using the ferroelectric polymer liquid crystal of the present invention, it has become clear that switching occurs due to polarization reversal and rotation speed of the dye molecules or the polymer liquid crystal. switching is now possible.

Claims (7)

[Claims] (1) A strong dye monomer comprising a dichroic dye having a polymerizable monomer structure and a mesogen monomer having the ability to form a polymerizable chiral smectic phase. Dielectric polymer liquid crystal. (2) An analyzer comprising a uniaxially aligned ferroelectric polymer liquid crystal according to claim 1 sandwiched between a pair of substrates having electrodes, and whose vibration axis coincides with the alignment direction. A display element characterized by: (3) The display element according to claim 2, wherein the uniaxial alignment of the ferroelectric polymer liquid crystal is performed by stretching. (4) A ferroelectric polymer liquid crystal characterized in that a dichroic dye and a mesogen capable of expressing a chiral smectic phase are introduced into a polymer compound by a substitution reaction. (5) An analyzer comprising a uniaxially aligned ferroelectric polymer liquid crystal according to claim 4 sandwiched between a pair of substrates having electrodes, and whose vibration axis coincides with the alignment direction. A display element characterized by: (6) The display element according to claim 5, wherein the uniaxial alignment of the ferroelectric polymer liquid crystal is performed by stretching. (7) Uniaxial alignment of at least two ferroelectric polymer liquid crystals selected from the ferroelectric polymer liquid crystals according to claims 1 and 4, which are mutually contained and have dichroic dyes with different absorption bands. each of which is sandwiched between a pair of electrodes, and is laminated with an insulating layer interposed therebetween so that the orientation directions match, and is characterized by being equipped with an analyzer whose vibration axis coincides with the orientation direction. display element.