CN1204066A - Method for preparing ferroelectric liquid crystal device with multi-domain structure - Google Patents

Abstract

The present invention belongs to the field of LC display technology. It relates to a preparation process of ferroelectric liquid crystal device with multi-domain structure. Said invention adopts organic semiconductor compound doping method to modify polymer orientation layer and improve its orientation capability. The doping compound is phthalocyanine or naphthalene phthalocyanine, and the doped mother body is polyimidic acid, and the doping mole ratio is 0.1 : 1-20 : 1. Said invention improves the ferroelectric crystal contrast and bistable memory property, and its liquid crystal initial arrangement possesses uniformly multi-domain structure, and has high stability. Said invention is simple in technological process, convenient in operation, can make large-scale production.

Description

The preparation method of ferroelectric liquid crystal device with multi-domain structure

The invention belongs to technical field of liquid crystal display, is a kind of ferroelectric liquid crystal device with multi-domain structure preparation method.

At present, liquid crystal display device has obtained widely utilizing in each possible application, and this comprises from simple timer, wrist-watch, game machine, to becoming increasingly complex and senior color TV, foldable computer display screen or the like.Correspondingly, also more and more higher to the requirement of high-quality liquid crystal display device.For satisfying this requirement, people have developed Active Matrix LCD At, the supertwist nematic liquid crystal shows that (STN-LCD), ferroelectric liquid crystals show a series of high quality lcd parts such as (FLCD).

Ferroelectric liquid crystal devices, the ferroelectric liquid crystal display of surface-stable pattern particularly, has quick response, the characteristics of bistable and memory, the FLCD of Yan Zhikaifaing compares with STN-LCD on its basis, has high density, large information capacity, high-contrast, the superiority that wide visual angle etc. are incomparable, not only can utilize it at a high speed, the characteristics development space photomodulator of bistable, be applied to the optical information processing of real-time image conversion, the virtual reality 3 D stereo shows, high-tech areas such as dull and stereotyped LCD TV of high-fidelity and optical computer, and can utilize its memory effect, bring into play the advantage that it fixedly shows not power consumption, in fixing display spare field, as the large screen projection outdoor advertising, supermarket electronics price list, the airport, the timetable at station, aspects such as person-to-person communication record are widely used.

Though FLCD is bigger than STN-LCD difficulty aspect manufacturing process, but there do not have tft liquid crystal to show to be complicated like that, thereby be expected to replace the flat-panel display device of other type, becomes the leading information media product of 21st century information society.But in concrete liquid crystal device development process, still exist many technical barriers, limit and slowed down further developing and using of FLCD.These technical barriers mainly comprise the desirable chiral smectic C acquisition of layer mutually, the assurance of bistable Memorability and the stability of device etc.

The desirable configuration of ferroelectric liquid crystals is to present the bookshelf-type structure mutually at chiral smectic C, and exists with the single domain form, but ferroelectric liquid crystal molecule often forms herringbone defective and zigzag defective after orientation, and this has reduced the electro-optical characteristic of device greatly.The surface charge that FLCD produces in the electric field switching process if can not in time be released, will produce polarization field at device inside, impel device that slow Henan and degeneration take place, and have influence on the bistable Memorability of device.In addition, it is more orderly that smectic C compares nematic phase, and the defective that obtains in initial orientation state is difficult to spontaneous healing, under the impact of electricity, light and machinery, all will form permanent impairment, directly has influence on the performance and the serviceable life of device.

Though the ferroelectric liquid crystals single domain can guarantee device and have good contrast that the even single domain orientation in big zone is difficult to obtain.Recently discover, apply low-frequency current field in the ferroelectric liquid crystals temperature-fall period, can obtain comparatively uniform ferroelectric liquid crystals multidomain and arrange, corresponding devices all is being improved aspect electro-optical characteristic and the bistable Memorability.But this method is owing to need be in temperature-fall period apply electric field to device one by one, and complex operation has increased difficulty and the running time on the manufacturing process, is unfavorable for the commercialization large-scale mass production.Therefore, adopt one with the liquid crystal production line is compatible mutually at present, need not apply electric field, and it is good to obtain electro-optical characteristic, the bistable Memorability improves, or even the ferroelectric liquid crystals multidomain orientation that device stability strengthens improves one's methods, and for applying of practicability production in enormous quantities, commercialization and the industrialization of device, has higher actual application value.

The object of the present invention is to provide a kind of orientation even, thereby can improve the preparation method of the ferroelectric liquid crystal device with multi-domain structure of contrast, bistable Memorability and stability.

Ferroelectric liquid crystals is in the device of low tilt angle polymkeric substance friction film orientation, lightning class or hair clip type defective in a zigzag often appears, neither belong to single domain, do not belong to even multidomain yet, and in the device of high tilt angle polymkeric substance friction film orientation, then be easy to occur unidirectional folded chevron,, also be difficult for forming ferroelectric multidomain even applying under the electric field.For not applying the uniform ferroelectric liquid crystals multidomain of acquisition under the electric field, the method that the present invention adopts organic semiconductor compound to mix is improved the capacity of orientation of alignment films by the modification to the polymer orientation layer, thereby obtains required ferroelectric liquid crystals multidomain orientation.Its step is as follows:

Soluble organic semiconductor compound phthalocyanine or naphthalene phthalocyanine are doped in the polyimide acid solution with 0.1: 1～20: 1 mol ratio, are spun on then on the electro-conductive glass substrate, preliminary drying obtains the doped polyimide film after imidization under 140～160 ℃ of high temperature.The conductive glass surface that is covered with rete is rubbed.Two through the electro-conductive glass substrate of similar friction treatment by the placement that superposes face-to-face of identical frictional direction, four limits are done at interval separately with polymer microbeads.Ferroelectric liquid crystals injects substrate gap under isotropic state, reduce to after the room temperature the substrate sealing, thereby form liquid crystal cell.Utilize this method, can body plan go out to have the ferroelectric liquid crystal devices that even multidomain is arranged, and corresponding devices has good contrast, bistable Memorability and stability.

Can be more specifically described as follows to the present invention:

The soluble organic semiconductor compound phthalocyanine or the naphthalene phthalocyanine of light, good thermal stability are doped in the polyimide acid solution with certain proportion.Polyimide acid drips of solution after mixing is added in the electro-conductive glass substrate surface, rotates on sol evenning machine, even glue speed is generally 2000～5000 rev/mins, and solution is spin-coated on the substrate, forms the oriented layer precursor.This precursor at high temperature after preliminary drying and imidization, obtains the doped polyimide film.The substrate that is covered with rete can adopt the velvet roll friction, friction force generally 1～50 gram force/centimetre.Through this friction process, obtain doped polymer friction orientation layer.Two orientation glass substrates that the above same process of warp obtains, according to the superimposed placement of direction that frictional direction is parallel to each other, wall is made with polymer microbeads in four limits, and uses the epoxy resin seal, leaves the sampling mouth simultaneously, utilizes capillary action to enter substrate gap.Selected ferroelectric liquid crystal material is by the ferroelectricity of schiff bases, non-schiff bases, azo, biphenyl and aromatic ester series and non-ferroelectric liquid crystal is mixed forms.Be to guarantee the homogeneity of ferroelectric liquid crystals orientation in the device, selected liquid crystal is preferably in has isotropy → phase sequence of chiral nematic phase → smectic A phase → chiral smectic C phase in the temperature-fall period.Treat that cooling and injection process finish, use epoxy resin sealing injection port equally, the body plan of such ferroelectric liquid crystals box finishes.With the ferroelectric liquid crystal devices of this method preparation, its liquid crystal initial arrangement is uniform multidomain, has improved the contrast and the bistable Memorability of ferroelectric liquid crystals, have good stability, can be used in enormous quantities, commercially produce, and technology is simple, easy to operate, be easy to apply.

The object lesson of this invention below will be described.

1: the four-tert-butyl group of example phthalocyanine tin is dissolved in the dimethylacetamide solution of polyimide acid with 0.5: 1 ratio of mol ratio.Drips of solution is added in indium tin oxide target (ITO) electro-conductive glass substrate surface, and with speed spin coating on sol evenning machine of 3,000 rev/mins, and meron is 150 ℃ of following preliminary dryings 1 hour, again 200 ℃ of following imidizations 2 hours.Glass substrate after the imidization 15 gram forces/centimetre velvet roll friction power under finish friction process.Press the superimposed placement of the identical direction of frictional direction through two substrates that same procedure is handled, and do at interval, all around with the fixing pre-envelope of epoxy resin with the polymer microbeads of diameter 2.0 μ m.After treating epoxy resin cure, ferroelectric liquid crystal material (SCE-13 of BDH) injects the gap of box from injection port under capillary action.Sample introduction is used the good injection port of epoxy resin sealing after finishing equally, and the body plan of ferroelectric liquid crystals box is finished like this.So the ferroelectric liquid crystal devices of body plan acquisition presents uniform ferroelectric liquid crystals multidomain in its initial orientation state.Device is at ± 20V, and contrast is 82: 1 under the square-wave voltage of 10Hz; At pulse width 1ms, the memory ratio under the bipolar pulse effect of cycle 20ms is 100: 1, reaches bistability completely.In addition, device is under the electric field on-off action or under the static placement, and multidomain structure is stable, tangible degeneration useless, and also electro-optical characteristic is constant, has stability preferably.

2: the four-tert-butyl group of example phthalocyanine tin is dissolved in the dimethylacetamide solution of polyimide acid with 0.5: 1 ratio of mol ratio.Drips of solution is added in ITO electro-conductive glass substrate surface, and with speed spin coating on sol evenning machine of 3,000 rev/mins, and meron is 150 ℃ of following preliminary dryings 1 hour, again 200 ℃ of following imidizations 2 hours.Glass substrate after the imidization 25 gram forces/centimetre velvet roll friction power under finish friction process.Press the superimposed placement of the identical direction of frictional direction through two substrates that same procedure is handled, and do at interval, all around with the fixing pre-envelope of epoxy resin with the polymer microbeads of diameter 2.0 μ m.After treating epoxy resin cure, ferroelectric liquid crystal material (SCE-13 of BDH) injects the gap of box from injection port under capillary action.Sample introduction is used the good injection port of epoxy resin sealing after finishing equally, and the body plan of ferroelectric liquid crystals box is finished like this.So the ferroelectric liquid crystal devices of body plan acquisition presents uniform ferroelectric liquid crystals multidomain in its initial orientation state.Device is at ± 20V, and contrast is 70: 1 under the square-wave voltage of 10Hz; At pulse width 1ms, the memory ratio under the bipolar pulse effect of cycle 20ms is 100: 1, reaches bistability completely.In addition, device is under the electric field on-off action or under the static placement, and multidomain structure is stable, tangible degeneration useless, and also electro-optical characteristic is constant, has stability preferably.

3: the four-tert-butyl group of example phthalocyanine tin is dissolved in the dimethylacetamide solution of polyimide acid with 1: 1 ratio of mol ratio.Drips of solution is added in ITO electro-conductive glass substrate surface, and with speed spin coating on sol evenning machine of 3,500 rev/mins, and meron is 150 ℃ of following preliminary dryings 1 hour, again 200 ℃ of following imidizations 2 hours.Glass substrate after the inferior acidylate 10 gram forces/centimetre velvet roll friction power under finish friction process.Press the superimposed placement of the identical direction of frictional direction through two substrates that same procedure is handled, and do at interval, all around with the fixing pre-envelope of epoxy resin with the polymer microbeads of diameter 2.0 μ m.After treating epoxy resin cure, ferroelectric liquid crystal material (CS-1024 of Chisso) injects the gap of box from injection port under capillary action.Sample introduction is used the good injection port of epoxy resin sealing after finishing equally, and the body plan of ferroelectric liquid crystals box is finished like this.So the ferroelectric liquid crystal devices of body plan acquisition presents uniform ferroelectric liquid crystals multidomain in its initial orientation state.Device is at ± 20V, and contrast is 84: 1 under the square-wave voltage of 10Hz; At pulse width 1ms, the memory ratio under the bipolar pulse effect of cycle 20ms is 100: 1, reaches bistability completely.In addition, device is under the electric field on-off action or under the static placement, and multidomain structure is stable, tangible degeneration useless, and also electro-optical characteristic is constant, has stability preferably.

In addition, the organic semiconductor dopant material that is adopted not only is confined to the phthalocyanine tin of the tert-butyl group, and is Cu for center coordination element, Ni, Vo, AlCl ₃, a series of side chains such as Si are phthalocyanine, the naphthalene phthalocyanine compound of the solubility of alkoxy, benzyloxy, and are effectively same in the acquisition of ferroelectric liquid crystals multidomain.Simultaneously, corresponding orientation effect is not only effective to liquid crystal material SCE-13 and Chisso CS-1024, and the mixed liquid crystal material of the commercializations such as ZLI-4237 of Merk is also had good orientation multidomain effect.

Claims (5)

1, a kind of preparation method of ferroelectric liquid crystal device with multi-domain structure, adopt the organic semiconductor compound doping method, improve the capacity of orientation of oriented layer by modification to the polymer orientation layer, it is characterized in that the organic compound that adopts is phthalocyanine or naphthalene phthalocyanine, be doped in the polyimide acid solution with 0.1: 1～20: 1 mol ratios, be spun on then on the electro-conductive glass substrate, preliminary drying under 140～160 ℃ of high temperature, after imidization, obtain the doped polyimide film, again the conductive glass surface that is covered with rete is rubbed, two through the electro-conductive glass substrate of similar processing procedure by the placement that superposes face-to-face of identical frictional direction, four limits are done at interval separately with polymer microbeads, ferroelectric liquid crystals injects substrate gap under isotropic state, reduce to after the room temperature the substrate sealing.

2, the preparation method of ferroelectric liquid crystal devices according to claim 1 is characterized in that the polyimide solution that mixes is spun on the glass substrate in the speed with 2000～5000 rev/mins on the sol evenning machine.

3, the preparation method of ferroelectric liquid crystal devices according to claim 2 is characterized in that the glass substrate that is covered with rete is adopted the velvet roll friction, friction force be 1～50 gram force/centimetre, obtain doped polymer friction orientation layer.

4, the preparation method of ferroelectric liquid crystal devices according to claim 3, the ferroelectric liquid crystal material that it is characterized in that injecting substrate is by the ferroelectricity of schiff bases, non-schiff bases, azo, biphenyl and aromatic ester series and non-ferroelectric liquid crystal is mixed forms.

5, the preparation method of ferroelectric liquid crystal devices according to claim 4 is characterized in that selected ferroelectric liquid crystals has the phase sequence of isotropy → chiral nematic phase → smectic A phase → chiral smectic C phase in temperature-fall period.