RU2053533C1 - Electro-optic composite - Google Patents

Abstract

FIELD: electro-optic materials. SUBSTANCE: electro-optic composite is formed by copolymetacrilates and nematic liquid crystal, where polymeric component has to be triple copolymer on the base of alkylmetacrylates with number of carbon atoms in alkyl residue n being equal to 6 or 8, either 10. Metacrylate and 2-hydroxyethylmetakrylate - general formula 1 - where components relate as following (mass %) : copolymetacrylates of formula described - 40-60, and nematic liquid crystal - 60-44. Commercial mixture of liquid crystals is used as nematic liquid crystal, known as ЖК 1277, which has to be mixture of alkyl-and alkylxycianbiphylies with terpheniles. Large volume information may be recorded due to availability of great optical memory of electro-optic composite. The materials may be used in large capacity displays. Structure of relation is given in the description of the invention. EFFECT: improved efficiency. 2 tbl

Description

 The invention relates to electro-optical materials based on mixtures of nematic liquid crystals (LC) and polymers based on copolymethacrylates that change their optical properties (light scattering, transparency) when an electric field is applied.

In the initial state, such composites strongly scatter light and are opaque materials. After the application of an electric field, the films of the composites are clarified, since the refractive index of the polymer n _{n is} selected equal to the refractive index of an ordinary ray n _{o of the} oriented liquid crystal. The presence of optical memory allows the recording of large-volume information, which can be used in displays of large information capacity.

 Known electro-optical composites consisting of a polymer component (for example, polyvinyl acetate, polymethyl methacrylate, polyisopropene, etc.) and a nematic FA, the content of which is at least 50 wt. from the mixture.

 The disadvantage of these composites is the insignificant memory times from a few seconds to ten seconds for the best samples.

 The proposed composite eliminates this drawback and has a fairly high electro-optical characteristics determined by the molecular structure and composition of the polymer component.

(CH₂-

)_y (CH₂-

(I) а в качестве жидкого кристалла нематические ЖК (коммерческая смесь жидких кристаллов, известная под наименование ЖК 1277 и представляющая собой смесь алкил- и алкоксицианбифенилов с терфенилами) при следующем соотношении компонентов, мас.The proposed electro-optical composite consists of copolymethacrylates and a nematic liquid crystal, where the polymer component is a triple copolymer based on alkyl methacrylates (MA-n) with the number of carbon atoms in the alkyl residue n 6 or 8, or 10, methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate ( GEMA) general formula
- (CH ₂ -

(CH ₂ -

) _y (CH ₂ -

(I) and as a liquid crystal, nematic FAs (a commercial mixture of liquid crystals, known as LC 1277 and which is a mixture of alkyl- and alkoxycyanobiphenyls with terphenyls) in the following ratio of components, wt.

Copolymethacrylates
the specified formula 40-56
Liquid Crystal 60-44
Polymeric electro-optical materials are prepared in the form of films by pouring a solution of a polymer and a liquid crystal in chloroform onto a glass or polymer substrate with a conductive coating (IT coating), using a predetermined ratio of polymer liquid crystal and polymer concentration in the solution of 4-12 wt.

 PRI me R 1. Preparation of electro-optical material. To a solution of 0.56 g of the MA-8-MMA-HEMA copolymer in 7 ml of chloroform, 0.44 g of a liquid crystal is added and the mixture is stirred until complete dissolution. The prepared solution is applied to a glass substrate with a conductive coating and, after drying, is coated on top with a second glass plate with a conductive coating.

 PRI me R s 2-4. Samples of materials are prepared analogously to example 1.

 The copolymers of alkyl methacrylates (MA-n) with MMA and HEMA used to prepare the electro-optical composition are obtained by radical polymerization of the corresponding monomers.

 Obtaining a copolymer of MA-8 with MMA and HEMA.

Copolymerization MA-8 (1 mL, 5 mmol), MMA (7 ml, 66 mmol) and HEMA (2 mL, 16 mmol) in the presence of 0.015 g of azobisisobutyronitrile in benzene (25 mL) was carried out under argon at ⁶⁰ ° C for 24 hours. The copolymer is planted with petroleum ether. Yield 85%. The glass transition temperature of the copolymer is 87 ^° C. The characteristic viscosity is η 0.28 dl / g (25 ^° C, chloroform), polydispersity (M _w / M _n ) 3.1.

The obtained composites were measured off time τ _off depending on the duration of the electric pulse τ _and . The time τ _{off was} defined as the time during which the intensity of the optical response varied from 0.9 to 0.1 of the maximum transmittance of light.

Table 1 shows the times τ _off for the compositions with a sample thickness of 30 μm, an average capsule size of 2 μm and an electric pulse duration of 0.2-0.5 s at various electric field strengths. It can be seen that with an increase in the electric field strength, the _off time τ _off for all compositions increases and the optimal compositions with the largest optical memory have an LC concentration of 44 wt. with an electric pulse of 0.6 · 10 ⁵ V / m.

Table 2 shows the dependence of the off times τ _off for a composite containing 55 wt. LC, with an electric field strength of 0.45 · 10 ⁵ V / m of the duration of the electric pulse τ _and . It can be seen from Table 2 that, with an increase in the pulse duration, the turn-off times increase, reaching 100 s at τ _and 40 s. The data presented indicate that the compositions obtained have an extremely large memory.

Claims (1)

ELECTRO-OPTICAL COMPOSITION comprising copolymethacrylates and a nematic liquid crystal, characterized in that it contains copolymers of alkyl methacrylates with the number of carbon atoms in the alkyl residue n = 6, or 8, or 10 with methyl methacrylate and 2-hydroxyethyl methacrylate of the general formula

in the following ratio of components, wt.%:
Copolymethacrylates of the indicated formula - 40 - 56
Nematic liquid crystal - 60 - 44

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