CN1803979A - Method for preparing polymer dispersed liquid crystal film - Google Patents
Method for preparing polymer dispersed liquid crystal film Download PDFInfo
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- CN1803979A CN1803979A CN 200510130659 CN200510130659A CN1803979A CN 1803979 A CN1803979 A CN 1803979A CN 200510130659 CN200510130659 CN 200510130659 CN 200510130659 A CN200510130659 A CN 200510130659A CN 1803979 A CN1803979 A CN 1803979A
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Abstract
The provided preparation method for polymer dispersed liquid crystal film comprises: mixing the organic polymonomer with secondary cross-linking capacity and the liquid crystal by mass ratio as 50%:50%~10%:90%; adding light initiator and thermal initiator to stir and coat between two tin indium oxide conductive films; radiating with UV light for 1-30min at -10~50Deg to promote cross-linking reaction of light cross-linking groups and form macro molecular network; heating to 50-200Deg and holding for cross-linking reaction of thermal cross-linking groups; finally, natural cooling. This invention improves product stability and electric-photo property.
Description
Technical Field
The invention belongs to the field of liquid crystal and correlation, and particularly provides a preparation method of a polymer dispersed liquid crystal film.
Background
Polymer Dispersed Liquid Crystal (PDLC) films are recently developed flat panel display devices capable of displaying information. The PDLC film is a novel light control film, small molecular liquid crystal is dispersed in a polymer matrix in a droplet form, and the film can present two different optical states of transmission and scattering under the action of an external field (such as an alternating current electric field, a thermal field and the like). Because the PDLC film does not need a polaroid and does not need a more complex process preparation process like distortion and super-distortion, the PDLC film has the advantages of high display brightness, simple manufacture and low manufacturing cost, and has wide application prospect.
However, the PDLC has a slow response speed, a low contrast ratio, and a contradiction between a driving voltage and a contrast ratio (i.e., a high driving voltage due to an increase in the film thickness to improve the contrast ratio), and thus has a limitation in its application field due to factors such as a retardation of transmittance. Many researchers are working on improving these electro-optic properties, such as adding fluorinated polymers to PDLC or selecting the optimal structure of liquid crystal droplets. Experiments show that the main factors causing the slow response are the strong interaction between the liquid crystal droplets and the polymer matrix thereof and the interaction between the liquid crystal droplets, the polymer serving as the matrix is very important for the electro-optical characteristics of the PDLC, and the selection of a proper polymer can reduce the interaction with the liquid crystal droplets, stabilize the orientation of the droplets, improve the thermal stability, reduce the response time, enhance the scattering intensity and the like.
There are two main classes of materials for PDLC preparation: the thermosetting epoxy resin is used as a matrix, the polyacrylate or polymethacrylate is used as a matrix, the acrylate monomersare most applied, the monomers can be directly polymerized under the irradiation of light, and the polymerization is easier in the presence of a photoinitiator and a photosensitizer.
The chemical structure, molecular weight, compatibility with liquid crystal, etc. of the polymerized monomer are the main parameters for selecting the high polymer for preparing the PDLC material. Generally, a polymer is composed of linear molecular chains, and the viscosity thereof rapidly increases as the molecular chains grow. The literature, "One-step synthesis of hydrogenated polymers" (Coatings Tech, 1995, 67: 849) has conducted preliminary studies on the addition of functional groups to polymers. According to the document "synthesis of multifunctional acrylated polyesters and their photocuring" (thermosetting resins, 2003, 1, 18: 1-4), polyfunctional monomers are very compatible when blended with other polymers, and the more hydroxyl groups the higher the viscosity of the monomer, due to the formation of molecular hydrogen bonds. Such hydroxyl-containing polymers have been used in the coating field and have not been used in the preparation of PDLC. The research shows that the monomer has good polymerization effect.
Generally, the photosensitive wave bands of different photosensitive groups in a polymerized monomer are different, and the same photosensitive group also has different photosensitive wave bands according to different selected photoinitiators. Such as alkyl vinyl ketone, vinyl bromide and the like, can absorb light with the wavelength of more than 300nm to be directly dissociated into free radicals, and then the polymerization is initiated by the free radicals; when styrene, methyl methacrylate, acrylonitrile and other monomers are irradiated with light having a wavelength of less than 300nm, they can be only slowly photopolymerized. Currently, only a few unsaturated monomers absorb light in the 250nm to 500nm range, and most monomers must be photopolymerized using a photoinitiator or photosensitizer.
Many of the characteristic groups can undergo thermal polymerization under certain conditions, such as the polymerization of isocyanates and hydroxyl groups:
according to the mechanism, the photopolymerizable compound is selected as a polymerization monomer, and researches show that the stability and the electro-optic characteristic of the PDLC film can be effectively improved by adding a special functional group.
Disclosure of Invention
The invention aims to provide a preparation method of a polymer dispersed liquid crystal film, which is characterized in that organic compounds containing different crosslinking groups are used as polymerization monomers for preparing the polymer dispersed liquid crystal film, and the groups are subjected to secondary crosslinking under different conditions to improve the stability of a polymerization network, so that the electro-optic characteristics of the polymer dispersed liquid crystal film are improved.
The invention takes an organic compound with secondary crosslinking capability as a polymerization monomer to prepare a Polymer Dispersed Liquid Crystal (PDLC) film, and the polymerization monomer simultaneously contains a photo-crosslinking group and a thermal-crosslinking group. Mixing a polymerization monomer and liquid crystal according to the mass ratio of 50 percent to 50-10 percent to 90 percent, adding a photoinitiator and a thermal initiator (the adding amount of the photoinitiator and the thermal initiator is 0.1-10 percent of the mass of the polymerization monomer), uniformly stirring, and coating between two indium tin oxide conductive films; irradiating the monomers for 1 to 30 minutes at the temperature of between 10 ℃ below zero and 50 ℃ by using ultraviolet light to enable the molecules with photo-crosslinking groups in the polymerized monomers to generate crosslinking reaction to form a polymer network; and then heating to 50-200 ℃, preserving the heat for 2-50 hours to enable the heat-crosslinkable groups on the polymer network to perform a crosslinking reaction, and naturally cooling to obtain the polymer dispersed liquid crystal film.
The polymerized monomer with the secondary crosslinking capability is an organic compound containing both a photocrosslinking group and a thermal crosslinking group in a molecule, or a mixture of the organic compound containing the photocrosslinking group in the molecule and the organic compound containing the thermal crosslinking group in the molecule. The photocrosslinking group is typically an unsaturated double bond; the thermal crosslinking group is hydroxyl, amino, isocyanate group or epoxy group.
The invention has the advantages that: the secondary crosslinking of special groups in the monomer is utilized to increase a crosslinking network, improve the stability of a polymerization network and the associativity with a matrix, and further improve the stability and the electro-optical characteristics of the polymer dispersed liquid crystal film.
Drawings
FIG. 1 is an electro-optic characteristic curve obtained by applying a voltage of 70V to the polymer-dispersed liquid crystal film obtained in example 1. It can be seen from the curve that the film has a lower onset and saturation voltage, and a higher contrast and steepness.
FIG. 2 is a scanning electron micrograph (1000) of a polymer dispersed liquid crystal film obtained in example 1, from which it can be seen that the polymer dispersed liquid crystal film is stable and has excellent electro-optic properties, and the polymer dispersed liquid crystal film has a structure in which the polymer dispersed liquid crystal film is uniform and has a small mesh size of only a few micrometers.
FIG. 3 is an electro-optic characteristic curve obtained by applying a voltage of 70V to the polymer-dispersed liquid crystal film obtained in example 2.
FIG. 4 is a scanning electron micrograph (1000) of a polymerized network obtained after the polymer-dispersed liquid crystal film obtained in example 2 is peeled and the liquid crystal is washed away.
FIG. 5 is an electro-optic characteristic curve obtained by applying a voltage of 70V to the polymer-dispersed liquid crystal film obtained in example 3.
FIG. 6 is a scanning electron micrograph (1000) of a polymerized network obtained by peeling off a polymer-dispersed liquid crystal film obtained in example 3 and washing off the liquid crystal.
FIG. 7 is an electro-optic characteristic curve obtained by applying a voltage of 70V to the polymer-dispersed liquid crystal film obtained in example 4.
FIG. 8 is a scanning electron micrograph (1000) of a polymer network obtained by peeling off a polymer-dispersed liquid crystal film obtained in example 4 and washing off the liquid crystal.
Detailed Description
Examples 1
Adding 5 wt.% of butylene glycol acrylate into hydroxypropyl acrylate (with the purity of more than 99%) containing-OH groups, mixing a mixed monomer with liquid crystal (SLC7011-100, produced by Ikec corporation) according to the mass ratio of 20% to 80%, adding benzoin dimethyl ether and hexyl diisocyanate whichare 5% of the mass of the mixed monomer, uniformly stirring, coating the mixture between two indium tin oxide films, irradiating the mixture for 10 minutes at 10 ℃ by using 365nm ultraviolet light to photopolymerize double bonds in the monomer, heating the mixture to 120 ℃ and preserving the heat for 4 hours to thermally crosslink-OH groups to obtain a polymer dispersed liquid crystal film. The film has good stability, good folding property and good bonding property with the indium tin oxide film. The electro-optical performance curve of the film measured by a liquid crystal comprehensive parameter instrument is shown in figure 1. The picture of the monomer polymerization network under a scanning electron microscope is shown in figure 2. the-OH thermal polymerization effectively improves the electro-optical characteristics of the polymer dispersed liquid crystal film.
EXAMPLES example 2
Adding 5 wt.% of butylene glycol acrylate into hydroxypropyl acrylate (with the purity of more than 99%) containing-OH groups, mixing a mixed monomer with liquid crystal (SLC7011-100, produced by Ikec corporation) according to the mass ratio of 10% to 90%, adding benzoin dimethyl ether and hexyl diisocyanate which are 5% of the mass of the mixed monomer, uniformly stirring, coating the mixture between two indium tin oxide films, irradiating the mixture for 10 minutes at 14 ℃ by using 365nm ultraviolet light to photopolymerize double bonds in the monomer, heating the mixture to 120 ℃ and preserving the heat for 4 hours to thermally crosslink-OH groups to obtain a polymer dispersed liquid crystal film. The electro-optical properties of the film measured by a liquid crystal comprehensive parameter instrument are shown in FIG. 3. The picture of the monomer polymerization network under a scanning electron microscope is shown in FIG. 4.
EXAMPLE 3
Adding 5 wt.% ofbutylene glycol acrylate into hydroxypropyl acrylate (with the purity of more than 99%) containing-OH groups, mixing a mixed monomer with liquid crystal (SLC7011-100, produced by Ikec corporation) according to the mass ratio of 50% to 50%, adding benzoin dimethyl ether and hexyl diisocyanate which are 5% of the mass of the mixed monomer, uniformly stirring, coating the mixture between two indium tin oxide films, irradiating the mixture for 10 minutes at 0 ℃ by using 365nm ultraviolet light to photopolymerize double bonds in the monomer, heating the mixture to 120 ℃ and preserving the heat for 4 hours to thermally crosslink-OH groups to obtain a polymer dispersed liquid crystal film. The electro-optical properties of the film measured by a liquid crystal comprehensive parameter instrument are shown in FIG. 5. The image of the monomer polymerization network under a scanning electron microscope is shown in FIG. 6.
EXAMPLE 4
Adding 5 wt.% of epoxy resin into butanediol acrylate, mixing a mixed monomer and liquid crystal according to the mass ratio of 20% to 80%, adding benzoin dimethyl ether and ethylenediamine which are 5% of the mass of the mixed monomer, uniformly stirring, coating between two indium tin oxide films, irradiating for 5 minutes at 14 ℃, using 365nm ultraviolet light to polymerize double bonds in the monomer, heating to 60 ℃, preserving heat for 5 hours, and thermally crosslinking the epoxy resin to prepare the polymer dispersed liquid crystal film. The electro-optical performance curve is shown in fig. 7. The picture of the monomer polymerization network under a scanning electron microscope is shown in FIG. 8.
Claims (2)
1. A method of making a polymer-dispersed liquid crystal film, comprising: mixing an organic compound with secondary crosslinking capacity serving as a polymerization monomer with liquid crystal according to the mass ratio of 50 percent to 50-10 percent to 90 percent, adding a photoinitiator and a thermal initiator, wherein the adding amount of the photoinitiator and the thermal initiator is 0.1-10 percent of the mass of the monomer, uniformly stirring, and coating the mixture between two indium tin oxide conductive films; irradiating the polymer monomer for 1 to 30 minutes at the temperature of between 10 ℃ below zero and 50 ℃ by using ultraviolet light to enable the molecules with photo-crosslinking groups in the polymer monomer to generate crosslinking reaction to form a polymer network; and then heating to 50-200 ℃, preserving the heat for 2-50 hours to enable the thermal crosslinking groups on the polymer network to perform crosslinking reaction, and naturally cooling to obtain the polymer dispersed liquid crystal film.
2. The method of claim 1, wherein: the polymerized monomer is an organic compound containing both a photocrosslinking group and a thermal crosslinking group in a molecule, or a mixture of the organic compound containing the photocrosslinking group in the molecule and the organic compound containing the thermal crosslinking group in the molecule; the photo-crosslinking group is an unsaturated double bond; the thermal crosslinking group is hydroxyl, amino, isocyanate group or epoxy group.
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| CN 200510130659 CN1803979A (en) | 2005-12-20 | 2005-12-20 | Method for preparing polymer dispersed liquid crystal film |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101225308B (en) * | 2007-09-17 | 2010-10-27 | 北京科技大学 | Method for preparing polymer dispersion liquid crystal material by ultraviolet-heating step-polymerization process |
| CN102220139A (en) * | 2011-04-21 | 2011-10-19 | 北京科技大学 | Method for preparing PDLC (Polymer Dispersed Liquid Crystal) by epoxy resin ultraviolet photoinduced cationic polymerization |
| CN102707482A (en) * | 2012-05-31 | 2012-10-03 | 京东方科技集团股份有限公司 | Negative polymer dispersed liquid crystal film, liquid crystal panel and liquid crystal display |
| CN102955277A (en) * | 2012-11-07 | 2013-03-06 | 北京三五九投资有限公司 | Method for enhancing contrast of polymer dispersed liquid crystal (PDLC) display |
| CN103602338A (en) * | 2013-11-20 | 2014-02-26 | 华映视讯（吴江）有限公司 | Manufacture method of polymer dispersing type liquid crystal |
| CN105291532A (en) * | 2015-10-29 | 2016-02-03 | 广州市华惠材料科技有限公司 | Preparation technique for novel SPD (Surge Protective Device) membrane material |
| US9284489B2 (en) | 2013-11-07 | 2016-03-15 | Chunghwa Picture Tubes, Ltd. | Method of manufacturing polymer dispersed liquid crystal |
| CN109721709A (en) * | 2018-12-26 | 2019-05-07 | 北京大学 | A method of polymer stabilized nematic liquid crystals film is prepared based on epoxy monomer photocuring |
| CN110989236A (en) * | 2019-12-20 | 2020-04-10 | 哈尔滨工业大学 | Method for preparing flexible trans-polymer dispersed liquid crystal film by utilizing photoetching technology |
| CN115595001A (en) * | 2022-09-09 | 2023-01-13 | 杭州光粒科技有限公司（Cn） | Photosensitive polymer composition, preparation method thereof and holographic diffraction grating element |
-
2005
- 2005-12-20 CN CN 200510130659 patent/CN1803979A/en active Pending
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101225308B (en) * | 2007-09-17 | 2010-10-27 | 北京科技大学 | Method for preparing polymer dispersion liquid crystal material by ultraviolet-heating step-polymerization process |
| CN102220139A (en) * | 2011-04-21 | 2011-10-19 | 北京科技大学 | Method for preparing PDLC (Polymer Dispersed Liquid Crystal) by epoxy resin ultraviolet photoinduced cationic polymerization |
| WO2013177893A1 (en) * | 2012-05-31 | 2013-12-05 | 京东方科技集团股份有限公司 | Reflective polymer dispersed liquid crystal film, liquid crystal panel and liquid crystal display |
| CN102707482A (en) * | 2012-05-31 | 2012-10-03 | 京东方科技集团股份有限公司 | Negative polymer dispersed liquid crystal film, liquid crystal panel and liquid crystal display |
| CN102955277B (en) * | 2012-11-07 | 2014-11-19 | 北京三五九投资有限公司 | Method for enhancing contrast of polymer dispersed liquid crystal (PDLC) display |
| CN102955277A (en) * | 2012-11-07 | 2013-03-06 | 北京三五九投资有限公司 | Method for enhancing contrast of polymer dispersed liquid crystal (PDLC) display |
| US9284489B2 (en) | 2013-11-07 | 2016-03-15 | Chunghwa Picture Tubes, Ltd. | Method of manufacturing polymer dispersed liquid crystal |
| CN103602338A (en) * | 2013-11-20 | 2014-02-26 | 华映视讯（吴江）有限公司 | Manufacture method of polymer dispersing type liquid crystal |
| CN103602338B (en) * | 2013-11-20 | 2016-02-03 | 华映视讯（吴江）有限公司 | The manufacture method of polymer dispersion type liquid crystal |
| CN105291532A (en) * | 2015-10-29 | 2016-02-03 | 广州市华惠材料科技有限公司 | Preparation technique for novel SPD (Surge Protective Device) membrane material |
| CN109721709A (en) * | 2018-12-26 | 2019-05-07 | 北京大学 | A method of polymer stabilized nematic liquid crystals film is prepared based on epoxy monomer photocuring |
| CN110989236A (en) * | 2019-12-20 | 2020-04-10 | 哈尔滨工业大学 | Method for preparing flexible trans-polymer dispersed liquid crystal film by utilizing photoetching technology |
| CN115595001A (en) * | 2022-09-09 | 2023-01-13 | 杭州光粒科技有限公司（Cn） | Photosensitive polymer composition, preparation method thereof and holographic diffraction grating element |
| CN115595001B (en) * | 2022-09-09 | 2024-01-09 | 杭州光粒科技有限公司 | Photosensitive polymer composition, preparation method thereof and holographic diffraction grating element |
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