JPH02179612A - High-polymer liquid crystal element - Google Patents

Abstract

PURPOSE:To stabilize the memory characteristic obtd. when the liquid crystal element is driven by an electric field and to form the element having the screen of a larger area by using a ferroelectric high-polymer liquid crystal or ferroelectric high-polymer liquid crystal compsn. having a specific melt viscosity as a display layer to be crimped between a pair of substrates. CONSTITUTION:The ferroelectric high-polymer liquid crystal or the liquid crystal compsn. contg. the ferroelectric high-polymer liquid crystal is used for the display layer and the melt viscosity at the isotropic phase transition point of the ferroelectric high-polymer liquid crystal or liquid crystal compsn. is specified to <=1X10<6>poise. Then, the element can be constituted without generating bubbles and spacings on the contact surfaces of the display layer and electrodes and without using high-resistance oriented films and, therefore, the inversion electric field generated when the polarization inversion current is blocked by the high-resistance oriented films is eliminated and the extremely stable memory characteristic is obtd. The modulus of bending elasticity of at least one of a pair of the substrates is preferably <=1,000kgmm<-2>.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a polymer liquid crystal element using a polymer liquid crystal having ferroelectric properties, and particularly relates to a polymer liquid crystal element adapted for display using memory properties. It is something.

[Prior Art] As a conventional liquid crystal element, for example, M-Shut (M,
5chadt) and Double Helfrich (W.

“Applied Physics Letters” by He1frich
tters'') Volume 1a, No. 4 (February 15, 1971
Voltage Dependant Optical Activities of Voltage Dependant Optical Activity
“A Twisted Nematic Liquid Crystal” (“Voltage Dependent 0pti
cal Activity of a Twisted
Nes+atic 1quid Crystal, al”
) shown in the twisted nematic
d nematic) using liquid crystals are known. This TN liquid crystal has a problem in that crosstalk occurs during time-division driving using a matrix electrode structure with high pixel density, so the number of pixels is limited.

Furthermore, its use as a display has been limited due to its slow electric field response and poor viewing angle characteristics. Further, there are problems in that the process of forming a thin film transistor in each pixel is extremely complicated, and it is difficult to create a large-area display element.

The use of a bistable liquid crystal element is one way to improve these drawbacks of conventional liquid crystal elements.

Clark (C1ark) and Lager (Lager)
wall) (Japanese Patent Application Laid-open No. 107-1983)
No. 216, U.S. Patent No. 4,367,924, etc.)
. As a liquid crystal having bistability, a ferroelectric liquid crystal having a chiral smectic C phase (Ss''C) or H phase (Sm''H) is generally used.

This ferroelectric liquid crystal (FLC) has a very fast response speed because it has spontaneous polarization, and can also develop a bistable state with memory properties. Furthermore, since it has excellent viewing angle characteristics, it is thought to be suitable as a material for large-capacity, large-area displays. but,
When actually forming a liquid crystal cell, it is difficult to monodomain over a wide area, and there are technical problems in creating a large screen display element.

To solve this problem, it has been reported that a ferroelectric smectic liquid crystal monodomain is created by an epitaxial method using interfacial energy. (U.S. Pat. No. 4,561,726) However, the monodomains obtained in this way are not inherently stable and are easily converted into multidomains by pressure or thermal stimulation, making it difficult to increase the area.

Specifically, there is a method of obtaining orientation by rubbing the surface of a polymer film of SiO2, polyimide, polyvinyl alcohol, or the like on a substrate forming a liquid crystal cell in one direction with a cloth or the like. In addition, SiO and other oxides,
Similar effects have also been obtained by oblique vapor deposition of fluoride or metals such as Au and Ai'. Epitaxial alignment using interfacial energy is also possible by surface treatments such as stretched polymer films and gratings.

As a mechanical processing method, it has also been reported that liquid crystal is sealed in a container with a thin gap and that shear is applied by shifting the substrates relative to each other to obtain orientation.

It has also been reported that liquid crystals can be aligned by using a magnetic field, an electric field, or an electromagnetic field caused by light as an external field.

[Problems to be Solved by the Invention] However, in the conventional example described above, when a method of controlling the interface using an alignment film or the like is used as a method of controlling the alignment of the ferroelectric liquid crystal, the alignment film becomes an insulating film, The polarization reversal current that occurs when the spontaneous polarization is reversed by an electric field is blocked by the alignment film, and it remains as a charge even after the electric field is removed, resulting in a reversal electric field that impedes memory performance. there were.

Furthermore, when using a method of controlling orientation using an external field such as an electric field, magnetic field, shear, etc., short circuits easily occur between the upper and lower electrodes because the distance between the upper and lower substrates with electrodes is extremely small, only a few square meters. However, it was difficult to increase the area.

The present invention has been made to improve the drawbacks of the prior art, and uses a ferroelectric polymer liquid crystal or ferroelectric polymer having a specific melt viscosity as a display layer sandwiched between a pair of substrates. The purpose of the present invention is to provide a polymer liquid crystal element that can obtain extremely stable memory properties when driven by an electric field by using a liquid crystal composition, and that can be made to have a large area without shorting even with an extremely thin film thickness. It is something.

[Means for Solving the Problems] That is, the present invention provides a polymer liquid crystal element in which a ferroelectric polymer liquid crystal is sandwiched between substrates having a pair of electrodes. The present invention is a polymeric liquid crystal device characterized in that a melt viscosity at a phase transition point is less than I x 10'poise.

The present invention also provides a polymer liquid crystal element comprising a ferroelectric polymer liquid crystal composition sandwiched between substrates having a pair of electrodes, in which melting at the isotropic phase transition point of the ferroelectric polymer liquid crystal composition is performed. The viscosity is l x 1 x 106 poise.
) is a polymer liquid crystal element characterized by the following.

The present invention will be explained in detail below.

According to the present invention, a ferroelectric polymer liquid crystal or a ferroelectric polymer liquid crystal composition containing the ferroelectric polymer liquid crystal (hereinafter referred to as a liquid crystal composition) is used in the display layer. By controlling the melt viscosity of the molecular liquid crystal or liquid crystal composition at the isotropic phase transition point to less than ix io'voice, bubbles and Since the device can be constructed without creating gaps and without using a high-resistance alignment film, it eliminates the inversion electric field caused by the polarization inversion current blocked by the high-resistance alignment film, making it extremely stable. This makes it possible to obtain memory properties. In addition, ferroelectric polymer liquid crystal has good film formability and good strength, so even if it is an extremely thin film, it maintains the film thickness and does not cause pinholes, so shorts between the upper and lower electrodes can be avoided. This allows a large area to be formed with a film thickness of JL11.

The ferroelectric polymer liquid crystal that can be used in the present invention preferably has a chiral smectic phase. More preferably Sac''' phase, SmH''
It has three phases: Sml'' phase, Sugly J' phase, and SmG'' phase.

Also, main chain type ferroelectric polymer liquid crystal.

Those having a side chain type or main chain-side chain type structure are used, and main chain type ferroelectric polymer liquid crystals include polyester, polyether, polyazomethine, polythioester, and polythioether. system.

Polysiloxane-based, polyamide-based, polyimide-based, etc. can be used. As the side chain type ferroelectric polymer liquid crystal, polymethacrylic, polyacrylic, polychloroacrylic, polyether, etc. can be used.

The main chain type, side chain type, and main chain-side chain type ferroelectric liquid crystal compounds may be used alone, or two or more of the same or different types of liquid crystal polymer compounds may be used as a mixture. Alternatively, a copolymerized product may be used.

Next, some specific examples of ferroelectric polymer liquid crystals that can be used in the present invention are shown below, but the present invention is not limited thereto.

m≧5 j2=1-2. ni=1~2゜j=0 or 1゜n=4~18゜m≧5 j=0 or l, m≧5 m≧5. n=4-18 j=0 or 1. m≧5 j=0 or l, m≧5 y=0.1 to 1.0 m=4 to 12. n≧3 first
Figures (a) and (b) show an example of the polymer liquid crystal element of the present invention, and Figure 1 (a) is a plan view of the polymer liquid crystal element of the present invention.
FIG. 1(b) is a cross-sectional view taken along line AA'.

In FIG. 1, the polymer liquid crystal device of the present invention consists of a pair of substrates 1. made of glass plates, plastic plates, etc. l'
are held at a predetermined distance by spacers 4, and this pair of substrates 1
. (electrode group) is formed in a predetermined pattern such as a strip pattern. Further, on the substrate 1', there are a plurality of transparent electrodes 2 intersecting with the transparent electrode 2 described above.
' (for example, an electrode group for applying a signal voltage in a matrix electrode structure) is formed. 3 is a display layer made of a ferroelectric polymer liquid crystal or a liquid crystal composition containing a ferroelectric polymer liquid crystal and a low molecular liquid crystal. The ferroelectric polymer liquid crystals may be used alone or in combination of two or more. Further, 7 and 8 indicate polarizing plates.

In the present invention, a liquid crystal composition containing a ferroelectric polymer liquid crystal and a low molecular liquid crystal can be used in the display layer. As the low molecular liquid crystal, a ferroelectric liquid crystal is preferably used, but a ferroelectric liquid crystal is also used. Ferroelectric liquid crystal may be omitted as long as it does not impair the properties of dielectric polymer liquid crystal 0 The content of low molecular liquid crystal in the mixture of ferroelectric polymer liquid crystal and low molecular liquid crystal is 60
If it exceeds 60% by weight, the film strength and film formability will be impaired, so it is not preferable, and more preferably 40% by weight.
% by weight or less.

Next, the structure of a specifically used low molecular weight liquid crystal is shown below, but it is not limited thereto.

P-decyloxybenzylidene-P'-amino-2-methylbutylcinnamate (DQBAMBC) P-hexyloxybenzylidene-P'-amino-2-chlorobropylcinnamate)-(HOBACPC) P-decyloxybenzylidene- P'-amino-2-methylbutyl-α-cyanocinnamate (DOBAMBCC) P-tetradecyloxybenzylidene-P'-amino-2-methylbutyl-α-cyanocinnamate (TDOBAMBCG) (2
-methylbutyl) ester P-octyloxybenzylidene-P'-amino-2-
Methylbutyl-α-chlorocinnamate (OOBAM
BCG)-4'-octylaniline (MBRA Oxybiphenyl-4-carboxylate P-octyloxybenzylidene-P'-amino-2-methylbutyl-α-methylcinnamate hexyloxyphenyl-4
-(2"-methylbutyl)biphenyl-4'-carboxylate 4-(2"-methylbutyl)phenyl-4-(
4'-Methylhexyl)biphenyl-4'-carboxylate 4-octyloxyphenyl-4-(2''-methylbutyl)biphenyl-4'-carboxylate 4-hexyloxyphenyl-4-(2''-methylbutyl)biphenyl -4'-carboxylate/Z, 4 -11+61; Example of liquid crystal compound exhibiting nonchiral smectic a=6
°b = 12 4'-n-nonyloxy-4-biphenylyl-4-cyanobenzoate isotropic phase → nematic → smectic C a = 8 °b = i.

4-n-hebutylphenyl-4-(4'-nitrobenzoyloxy)benzoate (DB?NO□) Isotropic phase→
Nematic → Smectic A 4-n-octylphenyl-4-(4'-nitrobenzoyloxy)benzoate (DB, N02) Isotropic phase order nematic Clasmectic A → Smectic C 4-n-Decylphenyl-4-(4'-nitrobenzoyl) Oxy)
Benzoate (OBl.N02) 4-n-nonyloxyphenyl-4-(4'-nitrobenzoyloxy)benzoate (DB9ONO2) Isotropic phase → Nematic ÷ Smectic A + Smectic C Isotropic phase → Nematic → Smectic A + Smectic C1 ~ Lance -4-(4″-
octyloxybenzoyloxy)-4'-cyanostilbene (T8) 2-(4'-n-pentylphenyl)
-5-(/I--n-pentyloxyphenyl)pyrimidine isotropic phase ÷ nematic → smectic A.

→ Smectic A2 → Nematic isotropic phase →・Smectic A → Smectic C → Smectic F → Smectic G CsHr + +N=CII+c H=N+c sll
+ +4-n-Pentylphenyl-4-(4'-cyanobenzoyloxy)benzoate (DBsCN) Terephthalylidene-bis-4-n-pentylaniline (TB
PA) Isotropic phase → Nematic → Smectic A Isotropic phase → Nematic ÷ Smectic A + Smectic C
→ Smectic F + Smectic G → Smectic H (
1) C, II9+N-(:H+CII-Nhaato(:Yama n-
c4119o +(:IImN+Cal!, t-nN
-Terephthalylidene-bis-4-n-butylaniline (
TBBA) N-(4'-n-butyloxybenzylidene)-octylaniline (408) 4-n Isotropic phase ÷ Nematic → Smectic A + Smectic C
→ Smectic G + Smectic H Isotropic phase → Smectic A → Smectic BCo II
r tOWCN n-C611+30 WCslll: +-n4-cyano-4'-n-octyloxybiphenyl (80CB) 4-n-hexyl-4'-n-hexyloxybiphenyl isotropic phase → smectic B + smectic E isotropic Phase → Nematic → Smectic A Ethyl-4-azobenzoate 4-n-hexyloxyphenyl-4'-n-octyloxybiphenyl-4-carboxylate Isotropic phase → Smectic A Isotropic phase → Nematic → Smectic A + Smectic C
÷Smectic B di-n-octyl-4°sylate 4''-terphenyl dicarpho 4-n-heptyloxyphenyl-4-n-decyloxybenzoate isotropic phase → smectic A → smectic C isotropic phase → smectic A → Smectic Cn-hexyl-4'-n-
Pentyloxybiphenyl-4-carboxylate (6
508G) 4-n-octyloxybenzoic acid Isotropic phase → Nematic → Smectic C Isotropic phase → Smectic A → Smectic B → Smectic E 4-n-hexyl-4'-n-decyloxyph,
Ninyl-4-carboxylate isotropic phase → smectic A → smectic C As mentioned above, methods for laminating ferroelectric polymer liquid crystal onto a substrate include a method of laminating ferroelectric polymer liquid crystal formed into a film, and a method of laminating ferroelectric polymer liquid crystal formed into a film, This can be carried out by a method of applying a ferroelectric polymer liquid crystal in a state, a method of sealing it into a cell using capillary action, a method of applying it in a solution state by spin cord or dipping, and drying it. Furthermore, liquid crystal compositions can also be laminated in a similar manner.

In this way, when the ferroelectric polymer liquid crystal or liquid crystal composition is laminated on the substrate, the melt viscosity at the isotropic phase transition point of the ferroelectric polymer liquid crystal or liquid crystal composition is
It is used at 1×106 poise or less.

For example, when applying the ferroelectric polymer liquid crystal of the present invention to one substrate, it is possible to dissolve it in a solvent and use it at a lower viscosity of 1 x 1 x 106 poise or less, or to apply it to the other substrate after drying. For adhesion, a melt viscosity at the isotropic phase transition point of I x 1×10 6 poise or less is required. For this purpose, the melt viscosity of the ferroelectric polymer liquid crystal film coated on one substrate is reduced to 1 x 10'Voice or less by heating it to a temperature above the phase transition point using a heating means such as a heat roller. By adhering the display layer and the electrode to the other substrate at a lower temperature, it is possible to prevent bubbles and gaps from forming on the contact surface between the display layer and the electrode.

If the melt viscosity at the isotropic phase transition point exceeds I x 10' poise, bubbles or gaps are likely to form between the electrode and the display layer of the ferroelectric polymer liquid crystal or liquid crystal composition, so it is preferable. do not have. More preferably, the melt viscosity is I
X 1×106 poise or less.

Furthermore, in the case where a pair of substrates used in the present invention are thermocompression bonded to a display layer of a ferroelectric polymer liquid crystal or a liquid crystal composition to form a hump liquid crystal element, the flexural modulus of at least one substrate is It is preferable that it is less than 100Kg■-''.If it exceeds 1000Kg■2, it will be difficult to make sufficient contact between the substrate and the display layer of ferroelectric polymer liquid crystal or liquid crystal composition during thermocompression bonding. Therefore, bubbles and gaps are likely to occur.

Examples of the substrate material include polyester film, polyether ether film, polyimide film, polyetherimide film, polyphenylene sulfide film, polycarbonate film, polyketone sulfide film, polyether sulfon film, and the like. The film used as the substrate material and the ferroelectric polymer liquid crystal or liquid crystal composition can be bonded together by thermocompression using a heat roll or the like.

The laminated ferroelectric polymer liquid crystal or liquid crystal composition needs to be subjected to an alignment treatment, and the alignment treatment may be performed without using an alignment film or with an alignment film.

As an orientation method that does not use an orientation film, when using a ferroelectric polymer liquid crystal or a liquid crystal composition formed into a film, -axis stretching, biaxial stretching, roll pressing, etc. are preferred.

In a molten state, good orientation can be obtained by applying shear in a temperature range showing a nematic phase, chiral nematic phase, smectic phase, chiral smectic phase, etc.

When encapsulated into a cell by capillary action, orientation is possible due to the flow of the injection.

When dissolved in a solvent and applied, after drying, shear orientation is performed by shearing the surface or by slightly moving it between the upper and lower substrates.

In addition, when using an alignment film, its electrical resistance value is l
It needs to be 10'Ω or less. More preferably, the electrode and the ferroelectric polymer liquid crystal or liquid crystal composition are directly laminated without using an alignment film and have a contact surface.

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

Example I 30x3 1.5 am thick with ITO transparent electrodes
A 20 wt% cyclohexanone solution (viscosity 10
00 cp) was applied by a spin code method, and after drying, a film thickness of 2 cp was obtained. This substrate is coated with 50% polyethylene terephthalate (PET) with an ITO transparent electrode.
(Bending elastic modulus 600 Kgm Garden-2) The film was laminated at 120°C using a hot roller.

Furthermore, good alignment was obtained when the glass substrate was slightly moved at 50° C. using a microgauge.

n=10 (I)0℃
35℃ 70℃-〉S■C''-〉SII8
-> Viscosity of l5O0 at 70°C 5 x 1 x 106 poise (Measured with rheometrics, rheometer - RMS800) An electric field of ±20V was applied to this cell, the electric field was removed, and observation with crossed nicols showed that the cell remained in good condition for over 30 minutes. Memory properties were obtained.

Example 2 ■ :lO with a thickness of 1.511111 provided with a TO transparent electrode
The following ferroelectric polymer liquid crystal compound (n) and low molecular weight ferroelectric liquid crystal (C3-1014
A film thickness of about 5 pots was obtained by roll-coating a mixture of 8:2 by weight (manufactured by Chisso Corporation) at 100°C.

A 501 PET film (flexural modulus of elasticity 600 Kg+*m-'') with ITO transparent polarization was laminated onto this substrate at 120° C. using a hot roller.

Further, when the film was oriented by passing through a heated roller at 60° C., good orientation was obtained.

n = 10 (■) 14℃
71°C SmC"->SmA->Iso.

Viscosity at 80℃ 1 x 1 x 106 poise ± to this cell
When an electric field of 20 V was applied, the electric field was removed, and crossed Nicol observation was performed, good memory properties were obtained for more than 5 minutes.

Comparative Example 1 After rubbing the glass substrate with ITO used in Example 1 on which a polyimide film with a thickness of 5,000 was formed, a ferroelectric polymer liquid crystal compound ( I) was applied. A cell was created by stacking the glass substrates together.

An electric field of ±30 V was applied to this cell, but no memory property was observed after the electric field was removed.

[Effects of the Invention] As explained above, according to the present invention, a ferroelectric polymer liquid crystal or a liquid crystal composition containing the ferroelectric polymer liquid crystal is used in the display layer. The melt viscosity at the isotropic phase transition point of the liquid crystal composition is I
By lowering the elastic modulus to 6 poise or less and by using a substrate with a low flexural modulus for at least one of the pair of substrates, bubbles and gaps can be prevented at the contact surface between the electrode and the display layer using the ferroelectric polymer liquid crystal or liquid crystal composition. It is possible to obtain extremely stable memory properties when driven by an electric field without causing any problems.

In addition, since the polymer liquid crystal element of the present invention uses ferroelectric polymer liquid crystal that has good film formability and good strength,
With extremely thin film thickness, it is possible to increase the area without short-circuiting, and good alignment can be obtained even when no alignment film is used, resulting in efficient production with high yield.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing an example of the polymer liquid crystal element of the present invention, and FIG. 1(b) is a sectional view taken along line AA'.

Claims (7)

[Claims] (1) In a polymer liquid crystal element formed by sandwiching a ferroelectric polymer liquid crystal between substrates having a pair of electrodes, the melt viscosity of the ferroelectric polymer liquid crystal at the isotropic phase transition point is 1×10
A polymer liquid crystal device characterized by having a poise of 6 poise or less. (2) The polymer liquid crystal device according to claim 1, wherein the bending elastic modulus of at least one of the pair of substrates is 1000 Kgmm^-^2 or less. (3) The polymer liquid crystal device according to claim 1, wherein the electrode and the ferroelectric polymer liquid crystal have a contact surface. (4) In a polymer liquid crystal element formed by sandwiching a ferroelectric polymer liquid crystal composition between substrates having a pair of electrodes, the melt viscosity of the ferroelectric polymer liquid crystal composition at the isotropic phase transition point is 1. 1. A polymer liquid crystal element characterized in that the poise is less than ×10^6 poise. (5) The polymer liquid crystal device according to claim 4, wherein the bending elastic modulus of at least one of the pair of substrates is 1000 Kgmm^-^2 or less. (6) The polymer liquid crystal device according to claim 4, wherein the electrode and the ferroelectric polymer liquid crystal composition have a contact surface. (7) The ferroelectric polymer liquid crystal composition is composed of a ferroelectric polymer liquid crystal and a low molecular liquid crystal, and the content of the low molecular liquid crystal is 6.
5. The polymer liquid crystal device according to claim 4, wherein the content is 0% by weight or less.