CN113265219B - UV adhesive for PDLC electrochromic film and preparation method thereof - Google Patents
UV adhesive for PDLC electrochromic film and preparation method thereof Download PDFInfo
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- C09J163/00—Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
- C09J163/10—Epoxy resins modified by unsaturated compounds
Abstract
The application belongs to the technical field of PDLC (polymer dispersed liquid crystal) dimming films, and particularly relates to a UV (ultraviolet) adhesive for a PDLC electrochromic film and a preparation method thereof. The UV adhesive for the PDLC electrochromic film comprises, by weight, 50-70 parts of liquid crystal monomers, 5-15 parts of dye liquid crystals, 8-12 parts of acrylate oligomers, 5-8 parts of modified epoxy acrylate oligomers, 5-15 parts of acrylate monomers, 0.4-0.6 part of photoinitiators, 0.5-0.8 part of bridging agents and 3-4 parts of emulsifiers. The UV adhesive for the PDLC electrochromic film, which is prepared by the application, improves the switching liquid crystal rotation efficiency of the UV adhesive for the PDLC electrochromic film, and is not easy to change and transparent in folding, bending or high temperature, low in use voltage, high in haze in power-off and low in haze in power-on.
Description
Technical Field
The application belongs to the technical field of PDLC (polymer dispersed liquid crystal) dimming films, and particularly relates to a UV (ultraviolet) adhesive for a PDLC electrochromic film and a preparation method thereof.
Background
With the development of new display technologies, the display technologies are required to have high brightness, high contrast, high resolution, large display capacity, full color display, low voltage driving, low power consumption display, and the like, and have the advantages of high reliability, long service life, thinness, lightness, and the like. The PDLC film is a polymer dispersed liquid crystal film, the transparency of the PDLC functional film is adjusted by voltage, the conversion between a transparent state and a non-transparent state is realized, and the PDLC film has the characteristics of intelligent dimming, convenience in use and the like, and has an unlimited application prospect.
The PDLC electrochromic film realizes the on-state and the off-state of the PDLC electrochromic film by using a liquid crystal monomer mixture in the UV adhesive. When no external voltage is applied, a regular electric field cannot be formed between the films, the optical axis orientation of the liquid crystal particles is random and is in a disordered state, incident light is strongly scattered, and the film is opaque or semitransparent. After the external voltage is applied, the optical axes of the liquid crystal particles are arranged perpendicular to the surface of the film, the incident light cannot be scattered, and the film is transparent. The dye liquid crystal realizes color change, and the color is changed into colorless and transparent.
The main factor influencing the performance of the UV adhesive for the PDLC electrochromic film is the state of the liquid crystal monomer mixture during curing of components such as acrylic esters. In the existing UV adhesive for the PDLC electrochromic film, a liquid crystal monomer mixture is directly mixed with components such as acrylate, so that the liquid crystal monomer mixture is distributed in a continuous phase island manner when the components such as acrylate are cured, namely, a continuous liquid drop structure is formed. The continuous phase island distribution hardly enables the PDLC electrochromic film to be made into pixel points with basic image display requirements by using the UV adhesive, and the rotation efficiency of the switching liquid crystal is low.
In view of the above technical defects, the applicant believes that it is urgently needed to develop a preparation method of a UV adhesive for a PDLC electrochromic film, so that liquid crystal monomer mixtures can form microcapsules with consistent sizes when acrylate oligomers are cured, and the rotation efficiency of switching liquid crystals is improved.
Disclosure of Invention
In order to improve the switching liquid crystal rotation efficiency of the UV adhesive for the PDLC electrochromic film, the application provides the UV adhesive for the PDLC electrochromic film and a preparation method thereof.
In a first aspect, the application provides a UV adhesive for a PDLC electrochromic film, which adopts the following technical scheme: the UV adhesive for the PDLC electrochromic film comprises, by weight, 50-70 parts of liquid crystal monomers, 5-15 parts of dye liquid crystals, 8-12 parts of acrylate oligomers, 5-8 parts of modified epoxy acrylate oligomers, 5-15 parts of acrylate monomers, 0.4-0.6 part of photoinitiators, 0.5-0.8 part of bridging agents and 3-4 parts of emulsifiers.
By adopting the technical scheme, under the combined action of the acrylate oligomer and the emulsifier, the liquid crystal monomer and the dye liquid crystal can be separated out in a phase separation manner under the low-temperature placing environment, the acrylate oligomer flows to the surfaces of the liquid crystal monomer and the dye liquid crystal to wrap the separated liquid crystal monomer and the dye liquid crystal, the liquid crystal monomer and the dye liquid crystal form microcapsules in the curing shrinkage process of the acrylate oligomer instead of a continuous liquid drop structure, and the microcapsules can be formed into pixel points with basic requirements for image display, so that the driving voltage is reduced, and the rotation efficiency of the switching liquid crystal is improved. Meanwhile, the self-made acrylate oligomer greatly improves the stripping force of the UV adhesive for the PDLC electrochromic film, can also adjust the solubility of the liquid crystal monomer and the dye liquid crystal, and adjust the droplet distribution and the diameter of the precipitated liquid crystal monomer and the dye liquid crystal, is more beneficial to forming microcapsules with consistent sizes, and can also adjust the refractive index difference between the precipitated liquid crystal monomer and the dye liquid crystal before and after power failure, so that the switching liquid crystal rotation efficiency of the UV adhesive for the PDLC electrochromic film is improved, namely, the UV adhesive has low light transmittance and high haze in a power failure state, and has high light transmittance and low haze in a power on state. In addition, due to the addition of the dye liquid crystal, the UV adhesive for the PDLC electrochromic film can be reversibly switched from power-off blue to power-on transparent colorless, and the cycle frequency can reach 10 ten thousand times.
Preferably, the acrylate oligomer is prepared by a solvent-free radiation curing copolymerization method; the preparation monomer of the acrylate oligomer comprises isooctyl acrylate, isobornyl acrylate, cyclohexyl acrylate and methacrylic acid; the mass ratio of the isooctyl acrylate, isobornyl acrylate, cyclohexyl acrylate and methacrylic acid is (2.5-3.5) to (1.2-1.8) to (1) to (0.4-0.6).
By adopting the technical scheme, the acrylate oligomer prepared by a solvent-free radiation curing copolymerization method is controlled to have the mass ratio of isooctyl acrylate, isobornyl acrylate, cyclohexyl acrylate and methacrylic acid of (2.5-3.5) to (1.2-1.8) to 1 to (0.4-0.6), so that the number average molecular weight of the acrylate oligomer is 15-20 ten thousand, the activity is higher, the crosslinking density is higher, the stripping force of the UV adhesive for the PDLC electrochromic film is improved, the viscosity of the acrylate oligomer can be reduced, the solubility of the liquid crystal monomer and the dye liquid crystal is adjusted, the separation of the liquid crystal monomer and the dye liquid crystal is facilitated, the acrylate oligomer can flow to the surfaces of the liquid crystal monomer and the dye liquid crystal, the formation of microcapsules is facilitated, and the optical performance of the UV adhesive for the PDLC electrochromic film is improved.
Herein, the number average molecular weight of the acrylate oligomer is 15 to 20 ten thousand.
In the present application, the number average molecular weight of the modified epoxy acrylate oligomer is 10000 to 15000.
Preferably, the modified epoxy acrylate oligomer is a fatty acid modified epoxy acrylate oligomer.
By adopting the technical scheme, the adhesive force and flexibility of the UV adhesive are improved by the fatty acid modified epoxy acrylate oligomer, so that the stripping force of the UV adhesive for the PDLC electrochromic film is improved.
Preferably, the acrylate monomer comprises a bisphenol A acrylate monomer, a hydroxyl acrylate monomer and a long-chain acrylate monomer, and the mass ratio of the bisphenol A acrylate monomer to the hydroxyl acrylate monomer to the long-chain acrylate monomer is 1 (2-3) to 1.2-1.6.
By adopting the technical scheme, the voltage and the refractive index of a system can be better adjusted by matching the bisphenol A type acrylate monomer, the hydroxyl acrylate monomer and the long-chain acrylate monomer, and the adhesion of the UV adhesive for the PDLC electrochromic film is further improved.
Preferably, the number of carbon atoms of the long-chain acrylate monomer is 17.
By adopting the technical scheme, the long-chain acrylate monomer with the carbon atom number of 17 is more beneficial to coaction with the fatty acid modified epoxy acrylate oligomer, and is more beneficial to adjusting the refractive index difference between the liquid crystal monomer and the dye liquid crystal before and after power failure, so that the UV adhesive for the PDLC electrochromic film has low light transmittance and high haze in the power failure state, and the UV adhesive for the PDLC electrochromic film has high light transmittance and low haze in the power failure state. Meanwhile, the adhesive property of the UV adhesive for the PDLC electrochromic film is further improved.
Preferably, the hydroxy acrylate monomers include 4-hydroxy butyl acrylate and hydroxypropyl methacrylate; the mass ratio of the 4-hydroxy butyl acrylate to the hydroxypropyl methacrylate is 1 (1.5-2.5).
By adopting the technical scheme, the 4-hydroxy butyl acrylate and the hydroxypropyl methacrylate are compounded, so that the reactive diluent has the effect of an active diluent, the refractive index difference of the UV adhesive before and after power failure is better adjusted, the light transmittance of the UV adhesive for the PDLC electrochromic film is low and the haze of the UV adhesive is high in a power failure state, and the light transmittance of the UV adhesive for the PDLC electrochromic film is high and the haze of the UV adhesive is low in a power failure state. Meanwhile, the 4-hydroxy butyl acrylate and the hydroxypropyl methacrylate also have a crosslinking effect, and the 4-hydroxy butyl acrylate, the hydroxypropyl methacrylate and the bridging agent act together, so that the UV curing effect is further improved, the stability of the microcapsule is improved, and the stripping force of the UV adhesive for the PDLC electrochromic film is further improved.
In the present application, the bisphenol A type acrylate monomers include, but are not limited to, miramer m2101, american chemical chemistry.
Preferably, the emulsifier is sorbitan trioleate.
By adopting the technical scheme, the sorbitan trioleate enables the distribution and the diameter of the micro-droplets of the separated liquid crystal monomer and the dye liquid crystal to be more uniform, so that the refractive indexes of the separated liquid crystal monomer and the dye liquid crystal can be more favorably adjusted.
In this application, the liquid crystal monomer includes, but is not limited to, one or more of bicyclohexane, trans-4- (3, 4-difluorophenyl) -4' -vinylbicyclohexane, 4- (difluoro (4- (4-propylcyclohexyl) phenyl) methoxy) -2,3',4',5' -tetrafluorobiphenyl, 4-ethyl-2 ',3' -difluoro-4 "-propyl-1, 1',4',1' -terphenyl, 1, 3-difluoro-5- { [4- (trans-4-propylcyclohexyl) phenyl ] ethynyl } benzene, and 4-cyano-3, 5-difluorophenyl 4- (3-butenyl) -benzoate.
In the present application, the photoinitiator includes, but is not limited to, 2,2-dimethoxy-2-phenylacetophenone and/or diphenyl- (2,4,6-trimethylbenzoyl) oxyphosphorus.
In the present application, the bridging agent includes, but is not limited to, trimethylolpropane trimethacrylate and/or oxetanyl methacrylate.
In a second aspect, the application provides a preparation method of a UV adhesive for a PDLC electrochromic film, which adopts the following technical scheme:
a preparation method of a UV adhesive for a PDLC electrochromic film comprises the following steps:
s1, low-temperature phase splitting: uniformly mixing a liquid crystal monomer, dye liquid crystal, acrylate oligomer, half of photoinitiator and emulsifier, and standing at 5-10 ℃ until phase separation is achieved to obtain a phase substance;
s2, low-pressure curing: curing the phase-separated substance obtained in the step S1 under a low-pressure mercury lamp in the stirring process until the acrylate oligomer wraps the liquid crystal monomer and the dye liquid crystal to obtain a microcapsule;
and S3, adding the modified epoxy acrylate oligomer, the acrylate monomer and the bridging agent into the microcapsule obtained in the step S2, uniformly mixing, adding the photoinitiator with the residual mass, and mixing to obtain the UV adhesive for the PDLC electrochromic film.
By adopting the technical scheme, the liquid crystal monomer and the dye liquid crystal are subjected to phase separation at the temperature of 5-10 ℃, and the acrylate oligomer flows to the surfaces of the liquid crystal monomer and the dye liquid crystal; then, curing at low pressure, wherein the acrylate oligomer wraps the liquid crystal monomer and the dye liquid crystal to form microcapsules, and the liquid crystal monomer and the dye liquid crystal form microcapsules in the curing shrinkage process; and finally, mixing the microcapsule, the modified epoxy acrylate oligomer, the acrylate monomer, the bridging agent and the photoinitiator to obtain the UV adhesive for the PDLC electrochromic film, wherein the switching liquid crystal has high rotation efficiency.
Preferably, in the step S2, the light intensity consumption of the low-pressure mercury lamp is 15-25mW/cm 2 。
By adopting the technical scheme, the low-pressure curing condition is controlled, the wrapping effect of the acrylate oligomer on the liquid crystal monomer and the dye liquid crystal is better controlled, the micro-droplets are narrow in distribution and uniform in diameter, and the micro-capsules with the same size are more favorably formed.
In summary, the present application has the following beneficial effects:
1. under the low-temperature placing environment, the acrylate oligomer, the liquid crystal monomer and the dye liquid crystal are separated out, the acrylate oligomer flows to the surfaces of the liquid crystal monomer and the dye liquid crystal to wrap the separated liquid crystal monomer and the dye liquid crystal, the liquid crystal monomer and the dye liquid crystal form microcapsules in the curing and shrinking process of the acrylate oligomer instead of a one-piece continuous liquid drop structure, and the microcapsules can be formed into pixel points basically required for displaying, so that the driving voltage is reduced, and the rotation efficiency of the switching liquid crystal is improved. The UV adhesive for the PDLC electrochromic film, which is prepared by the application, improves the switching liquid crystal rotation efficiency of the UV adhesive for the PDLC electrochromic film, and is not easy to change and transparent in folding, bending or high temperature, high in haze in power-off and low in haze in power-on.
2. The acrylate oligomer prepared by the solvent-free radiation curing copolymerization method of isooctyl acrylate, isobornyl acrylate, cyclohexyl acrylate and methacrylic acid has high activity and crosslinking density, improves the stripping force of the UV adhesive for the PDLC electrochromic film, and is favorable for the acrylate oligomer to flow to the surfaces of a liquid crystal monomer and dye liquid crystal, so that microcapsules can be formed, and the optical performance of the UV adhesive for the PDLC electrochromic film is improved.
3. According to the application, the bisphenol A acrylate monomer, the hydroxy acrylate monomer and the long-chain acrylate monomer are matched, so that the voltage and the refractive index of a system can be better adjusted, and the adhesive property of the UV adhesive for the PDLC electrochromic film is improved.
4. The long-chain acrylate monomer with the carbon atom number of 17 is adopted, so that the long-chain acrylate monomer can better interact with the fatty acid modified epoxy acrylate oligomer, the refractive index difference of the UV adhesive for the PDLC electrochromic film before and after power failure can be adjusted, and the bonding performance of the UV adhesive for the PDLC electrochromic film is improved.
Detailed Description
The present application will be described in further detail with reference to examples.
The raw materials used in the present application are commercially available, and if not otherwise specified, the raw materials not mentioned in the preparation examples, examples and comparative examples of the present application are purchased from national drug group chemical agents limited.
Preparation example
Preparation examples 1 to 3 provide an acrylate oligomer, and the following description will be made by taking preparation example 1 as an example.
The acrylate oligomer provided in preparation example 1 was prepared by the following steps:
(1) 5g of isooctyl acrylate (CAS No. 103-11-7), 2.4g of isobornyl acrylate (CAS No. 5888-33-5) and 2g of cyclohexyl acrylate (CAS No. 3066-71-5) were mixed, 0.8g of methacrylic acid (CAS No. 79-41-4) was added dropwise, after mixing, 0.05g of photoinitiator BP (CAS No. 119-61-9) and 0.02g of t-dodecyl mercaptan (CAS No. 25103-58-6) were added, and N was added 2 Reacting for 0.5h at 80 ℃ after 30min to obtain a prepolymer;
(2) Mixing 20g of isooctyl acrylate, 9.6g of isobornyl acrylate and 8g of cyclohexyl acrylate, dropwise adding 3.2g of methacrylic acid, and mixing with 0.12g of photoinitiator BP and 0.06g of tert-dodecyl mercaptan to obtain a mixture;
(3) And (3) dropwise adding the mixture to the prepolymer, reacting at 80 ℃ for 1h after the dropwise adding is finished, and placing under a 750W ultraviolet lamp for 5min at a position of 15cm after the reaction is finished to obtain the acrylate oligomer.
Preparation examples 2 to 3 differ from the preparation examples only in that: the preparation monomers of the acrylate oligomer have different mass, and are shown in table 1.
Table 1 preparation examples 1-3 quality of preparation monomers for acrylate oligomer
Preparation of comparative example
Comparative example 1 was prepared, differing from preparation example 1 only in that: the mass of methacrylic acid in the step (1) was 0.4g, and the mass of methacrylic acid in the step (2) was 1.6g.
Comparative example 2 was prepared, differing from preparation example 1 only in that: the mass of isobornyl acrylate in the above (1) was 1.2g, and the mass of isobornyl acrylate in the above step (2) was 4.8g.
Comparative example 3 was prepared, differing from preparation example 1 only in that: the mass of isobornyl acrylate in the above (1) was 4.8g, and the mass of isobornyl acrylate in the above step (2) was 19.2g.
The number average molecular weights of the acrylate oligomers provided in preparation examples 1 to 3 and preparation comparative examples 1 to 3 were measured by gel permeation chromatography GPC, and the results are shown in Table 2.
TABLE 2 number average molecular weight test results for acrylate oligomers
| Acrylate oligomer | Number average molecular weight |
| Preparation example 1 | 158700 |
| Preparation example 2 | 192100 |
| Preparation example 3 | 179600 |
| Preparation of comparative example 1 | 146900 |
| Preparation of comparative example 2 | 137400 |
| Preparation of comparative example 3 | 217800 |
Examples
Examples 1 to 24 provide a UV adhesive for PDLC electrochromic films, and the following description will be made by taking example 1 as an example.
The preparation steps of the UV adhesive for the PDLC electrochromic film provided in embodiment 1 are as follows:
s1, low-temperature phase splitting: uniformly mixing 5g of liquid crystal monomer, 0.5g of dye liquid crystal, 0.8g of acrylate oligomer, 0.02g of photoinitiator and 0.3g of emulsifier, standing at 5 ℃ until the liquid crystal monomer and the dye liquid crystal are separated out, and carrying out phase separation to obtain a phase substance;
s2, low-pressure curing: stirring the phase-separated substance obtained in the step S1 at the speed of 200rpm, and placing under a low-pressure mercury lamp (the light intensity consumption of the low-pressure mercury lamp is 15 mW/cm) 2 The wavelength of UV light is 220 nm) until the acrylate oligomer wraps the liquid crystal monomer and the dye liquid crystal, and microcapsules are obtained;
s3, adding 0.5g of modified epoxy acrylate oligomer, 0.5g of acrylate monomer, 0.02g of photoinitiator and 0.05g of bridging agent into the microcapsule in the step S2, uniformly mixing, then adding the rest 0.02g of photoinitiator, and uniformly mixing to obtain the UV adhesive for the PDLC electrochromic film;
wherein the liquid crystal monomer is prepared from bicyclohexane (CAS No. 92-51-3), trans-4- (3, 4-difluorophenyl) -4 '-vinyl bicyclohexane (CAS No. 142400-92-8), and 4- (difluoro (4- (4-propylcyclohexyl) phenyl) methoxy) -2,3',4',5' -tetrafluorobiphenyl (molecular formula C) 28 H 26 F 6 O, structural formula
) 4-ethyl-2 ',3' -difluoro-4 "-propyl-1, 1',4',1' -terphenyl (CAS number 157248-25-4), 1, 3-difluoro-5- { [4- (trans-4-propylcyclohexyl) phenyl]Ethynyl } benzene (CAS No. 151105-71-4) and 4- (3-butenyl) -benzoic acid 4-cyano-3, 5-difluorophenyl ester (CAS No. 208528-35-2) in a mass ratio of 1;
the dye liquid crystal was purchased from Suzhou Hanlang photoelectricity, inc.;
the acrylate oligomer was derived from preparation example 1;
the modified epoxy acrylate oligomer is a modified bisphenol A epoxy acrylate oligomer with the brand number of KAYARAD R-190w and the number average molecular weight of 10000-15000 and is purchased from Japan chemical and pharmaceutical industry (tin-free) Co.Ltd;
the acrylate monomer is formed by mixing a bisphenol A type acrylate monomer, a hydroxyl acrylate monomer and a long-chain acrylate monomer according to a mass ratio of 1; the grade of the bisphenol A acrylate monomer is miramer m2101 which is purchased from American chemical; the hydroxyl acrylate monomer is hydroxypropyl methacrylate (CAS number 27813-02-1); the long-chain acrylate monomer is 2-methyl-2-tridecyl acrylate (CAS number 2495-25-2);
the photoinitiator is prepared by mixing 2, 2-dimethoxy-2-phenylacetophenone and diphenyl- (2, 4, 6-trimethylbenzoyl) oxyphosphorus according to the mass ratio of 1;
the bridging agent is formed by mixing trimethylolpropane trimethacrylate and methacrylic acid oxetanyl ester according to the mass ratio of 1;
the emulsifier is Tween-85 (CAS number 9005-70-3).
Examples 2-7, which differ from example 1 only in that: the quality of the raw materials for preparing the UV adhesive for the PDLC electrochromic film is different, and the raw materials are shown in Table 3.
Table 3 examples 1-7 quality of raw materials for preparation of UV adhesives for PDLC electrochromic films
Examples 8 to 11 differ from example 3 only in that: the preparation processes of the UV adhesive for the PDLC electrochromic film are different, and are specifically shown in Table 4.
Table 4 example 3, 8-11 preparation of UV adhesive for PDLC electrochromic films
Examples 12 to 13 differ from example 11 only in that: the acrylate oligomers were derived from different sources, as shown in Table 5.
Table 5 examples 11-13 sources of acrylate oligomers
| Examples | Example 11 | Example 12 | Example 13 |
| Sources of acrylate oligomers | Preparation example 1 | Preparation example 2 | Preparation example 3 |
Example 14, which differs from example 13 only in that: the modified epoxy acrylate oligomer is a fatty acid modified epoxy acrylate oligomer with the grade of CN151 and is purchased from sartomer.
Example 15, which differs from example 14 only in that: the mass ratio of the bisphenol A acrylate monomer to the hydroxy acrylate monomer to the long-chain acrylate monomer is 1.6.
Example 16, which differs from example 14 only in that: the mass ratio of the bisphenol A acrylate monomer to the hydroxy acrylate monomer to the long-chain acrylate monomer is 1.5.
Example 17 differs from example 16 only in that: the long-chain acrylate monomer is 2-methyl-2-heptadecyl acrylate (CAS number 6140-75-6).
Example 18, which differs from example 17 only in that: the hydroxyl acrylate monomer is prepared by mixing 4-hydroxyl butyl acrylate (CAS number 2478-10-6) and hydroxypropyl methacrylate according to the mass ratio of 1.5.
Example 19, which differs from example 18 only in that: the mass ratio of the 4-hydroxy butyl acrylate to the hydroxypropyl methacrylate is 1.
Example 20, which differs from example 18 only in that: the mass ratio of the 4-hydroxy butyl acrylate to the hydroxypropyl methacrylate is 1.
Example 21 differs from example 20 only in that: the emulsifier is Span-85 (CAS number 26266-58-0).
Examples 22 to 24 differ from example 1 only in that: the acrylate oligomers were derived from different sources, as shown in Table 6.
Table 6 examples 22-24 sources of acrylate oligomers
| Examples | Example 22 | Example 23 | Example 24 |
| Sources of acrylate oligomers | Preparation of comparative example 1 | Preparation of comparative example 2 | Preparation of comparative example 3 |
Comparative example
Comparative example 1, which differs from example 1 only in that: the PDLC electrochromic film is different in preparation method of the UV adhesive;
the UV adhesive for the PDLC electrochromic film provided by the comparative example 1 comprises the following preparation steps:
s1, uniformly mixing 5g of liquid crystal monomer and 0.5g of dye liquid crystal to obtain a liquid crystal mixture;
s2, uniformly mixing 0.8g of acrylate oligomer, 0.5g of modified epoxy acrylate oligomer, 0.5g of acrylate monomer, 0.05g of bridging agent and 0.3g of photoinitiator to obtain the UV adhesive for the PDLC electrochromic film.
Comparative example 2, which differs from example 1 only in that: the temperature of the S1 step in the preparation process of the UV adhesive for the PDLC electrochromic film is 15 ℃.
Comparative example 3, which differs from example 1 only in that: the acrylate oligomer is replaced by modified bisphenol A epoxy acrylate oligomer KAYARAD R-190w in equal mass.
Performance test
The PDLC electrochromic films described in examples 1-24 and comparative examples 1-3 were coated between two ITO conductor films (model No. KH150NMH2-50-U7/P125, purchased from Nippon Pond) with a UV adhesive (coating weight 5 mg/cm) 3 ) And curing the mixture for 5s (power supply power 30 KW) by using a UV point light source curing machine (365 nm, purchased from Shanghai Philippine industries, ltd.) to obtain the PDLC electrochromic film.
The following performance tests were performed on the PDLC electrochromic films obtained by applying example 1 and comparative example 1 of the present application.
1. Folding resistance: the PDLC electrochromic films corresponding to example 1 and comparative example 1 were folded in half (power-off), and whether the PDLC electrochromic films became transparent or not was observed, and the test results are shown in table 7.
2. Bending resistance: the PDLC electrochromic films corresponding to example 1 and comparative example 1 were bent by 90 ° (power-off), and whether the PDLC electrochromic films became transparent or not was observed, and the test results are shown in table 7.
3. High temperature resistance: the PDLC electrochromic films (power off) corresponding to example 1 and comparative example 1 were left at 120 ℃ for 1h, and whether the PDLC electrochromic films became transparent or not was observed, and the test results are shown in table 7.
TABLE 7 anti-folding and high-temperature resistance of example 1 and comparative example 1
| Performance of | Example 1 | Comparative example 1 |
| Resistance to doubling over | Is not transparent | Is transparent |
| Resistance to bending | Is not transparent | Is transparent |
| High temperature resistance | Is not transparent | Is transparent |
The present application is described in detail below with reference to the test data provided in table 7.
The PDLC electrochromic film corresponding to embodiment 1 of the present application is an adhesive containing liquid crystal microcapsules, and does not become transparent after being folded or bent, because the liquid crystal microcapsules have a certain resistance after being subjected to external stress, the arrangement of liquid crystal particles is not affected, the low haze after being folded is maintained, and the application of the PDLC electrochromic film on a curved surface device is greatly expanded. Meanwhile, the PDLC electrochromic film of the adhesive containing the liquid crystal microcapsule prepared in example 1 was not transparent even at a high temperature of 120 ℃. In contrast, the liquid crystal in the PDLC electrochromic film in comparative example 1 is easy to rotate and becomes transparent under external stress or high temperature conditions.
The following performance tests were performed on the PDLC electrochromic films obtained by applying examples 1 to 24 and comparative examples 1 to 3 of the present application.
4. Peeling force: the PDLC electrochromic films obtained in examples 1-24 and comparative examples 1-3 were tested for 180 DEG peel force using a peel force tester according to the method of GB/T7122-1996, and the test results are shown in Table 8.
5. Optical properties: the PDLC electrochromic films obtained in examples 1 to 24 and comparative examples 1 to 3 were measured for light transmittance and haze in the off state and light transmittance and haze in the on state (driving voltage of 23V) using an integrating sphere optical instrument, and the results of the measurements are shown in table 8.
TABLE 8 test results
The present application is described in detail below with reference to the test data provided in table 8.
According to the test data of the examples 1-7, the UV adhesive for PDLC electrochromic films prepared by the method has high mechanical property, and the 180-degree stripping force is greater than 20N; the transparent conductive film also has high optical performance, the transmittance is less than 60% and the haze is greater than 95% in the power-off state, the haze is not greater than 2.4% and the light transmittance is greater than 92% in the power-on state, the transparent colorless reversible conversion from power-off blue to power-on is realized, the driving voltage is 23V, and the electricity is saved.
From the test data of example 1 and comparative example 1 of the present application, it can be seen that the microcapsules without liquid crystal in comparative example 1 and the microcapsules with liquid crystal in example 1 have a haze of 96.2% when power is off and a haze of 2.2% when power is on (23V), so that the effects of opaque when power is off and transparent when power is on are achieved, the haze is greatly reduced when power is on, and the haze is improved when power is off.
From the test data of example 1 and comparative example 2 of the present application, it can be seen that the temperature of the S1 step in example 1 is 5 deg.c and the temperature of the S1 step in comparative example 2 is 15 deg.c, and the optical properties of comparative example 2 are significantly reduced compared to example 1. The optical performance of the PDLC electrochromic film is reduced because the phase separation effect of the liquid crystal monomer and the dye liquid crystal at 15 ℃ is poor and microcapsules cannot be well formed.
From the test data of example 1 and comparative example 3 herein, it can be seen that the mass replacement of the acrylate oligomer and the like of comparative example 3 with the modified epoxy acrylate oligomer reduced the 180 ° peel force of the PDLC electrochromic film by 10N compared to example 1.
From the test data of examples 1 and 22 to 24 of the present application and the test data of table 2, it can be seen that, compared to example 1, the content of methacrylic acid in example 22 is halved, the number average molecular weight of acrylate oligomer is less than 15 ten thousand, the 180 ° peel force of PDLC electrochromic film is reduced by 4N, and the optical properties are also reduced; example 23 the isobornyl acrylate content was halved, the number average molecular weight of the acrylate oligomer was less than 15 ten thousand, the 180 ° peel force of the PDLC electrochromic film was reduced by 7N, and the optical properties were also reduced to some extent; example 24, the isobornyl acrylate content was twice that of example 1, the number average molecular weight of the acrylate oligomer was greater than 20 ten thousand, the 180 ° peel force of the PDLC electrochromic film was reduced by 2N, and the optical properties were much reduced, because the too large number average molecular weight of the acrylate oligomer inhibited the flow of the acrylate oligomer to the surface of the liquid crystal monomer and dye liquid crystal, which was not conducive to the formation of uniform-sized microcapsules.
From the test data of examples 11 to 13 of the present application in combination with the test data of table 2, it can be seen that the number average molecular weight of the acrylate oligomer can be controlled to 15 to 20 ten thousand by controlling the mass ratio of isooctyl acrylate, isobornyl acrylate, cyclohexyl acrylate and methacrylic acid, thereby improving the peeling force and optical properties of the PDLC electrochromic film.
From the test data of examples 13 to 14 herein, it can be seen that the fatty acid-modified epoxy acrylate oligomer improves the peel force of the PDLC electrochromic film.
From the test data of the examples 14 to 16, it can be known that the mass ratio of the bisphenol A acrylate monomer to the hydroxy acrylate monomer to the long-chain acrylate monomer is controlled to be 1 (2-3) to (1.2-1.6), so that the voltage and the refractive index of the system can be better adjusted, the optical performance of the PDLC electrochromic film is improved, and the stripping force of the PDLC electrochromic film is improved.
From the test data of examples 16 to 17 of the present application, it can be seen that the long-chain acrylate monomer having 17 carbon atoms further improves the optical properties of the PDLC electrochromic film and improves the peeling force of the PDLC electrochromic film.
From the test data of examples 17 to 20 of the present application, it can be seen that the combination of 4-butylacrylate and hydroxypropyl methacrylate further improves the peeling force and optical properties of the PDLC electrochromic film.
The specific embodiments are only for explaining the present application and are not limiting to the present application, and those skilled in the art can make modifications to the embodiments without inventive contribution as required after reading the present specification, but all the embodiments are protected by patent law within the scope of the claims of the present application.
Claims (4)
1. The UV adhesive for the PDLC electrochromic film is characterized by comprising, by weight, 50-70 parts of liquid crystal monomer, 5-15 parts of dye liquid crystal, 8-12 parts of acrylate oligomer, 5-8 parts of modified epoxy acrylate oligomer, 5-15 parts of acrylate monomer, 0.4-0.6 part of photoinitiator, 0.5-0.8 part of bridging agent and 3-4 parts of emulsifier;
the acrylate oligomer is prepared by a solvent-free radiation curing copolymerization method; the preparation monomer of the acrylate oligomer comprises isooctyl acrylate, isobornyl acrylate, cyclohexyl acrylate and methacrylic acid; the mass ratio of the isooctyl acrylate, the isobornyl acrylate, the cyclohexyl acrylate and the methacrylic acid is (2.5-3.5): (1.2-1.8): 1: (0.4-0.6);
the number average molecular weight of the acrylate oligomer is 158700-192100;
the preparation method of the UV adhesive for the PDLC electrochromic film comprises the following steps:
s1, low-temperature phase splitting: uniformly mixing a liquid crystal monomer, dye liquid crystal, acrylate oligomer, half of photoinitiator and emulsifier, and stirring at 5-10 ℃ until phase separation is achieved to obtain a phase substance;
s2, low-pressure curing: curing the phase-separated substance obtained in the step S1 under a low-pressure mercury lamp in the stirring process until the acrylate oligomer wraps the liquid crystal monomer and the dye liquid crystal to obtain a liquid crystal microcapsule;
s3, adding the modified epoxy acrylate oligomer, the acrylate monomer and the bridging agent into the microcapsule obtained in the step S2, uniformly mixing, then adding the photoinitiator with the residual mass, and mixing to obtain the UV adhesive for the PDLC electrochromic film;
the modified epoxy acrylate oligomer is a fatty acid modified epoxy acrylate oligomer;
the acrylate monomer comprises a bisphenol A acrylate monomer, a hydroxyl acrylate monomer and a long-chain acrylate monomer, wherein the mass ratio of the bisphenol A acrylate monomer to the hydroxyl acrylate monomer to the long-chain acrylate monomer is 1 (2-3) to 1.2-1.6;
the number of carbon atoms of the long-chain acrylate monomer is 17;
the bridging agent is formed by mixing trimethylolpropane trimethacrylate and oxetanyl methacrylate according to the mass ratio of 1.
2. The UV adhesive for the PDLC electrochromic film according to claim 1, wherein the hydroxy acrylate monomer comprises 4-hydroxy butyl acrylate and hydroxypropyl methacrylate; the mass ratio of the 4-hydroxy butyl acrylate to the hydroxypropyl methacrylate is 1 (1.5-2.5).
3. The UV adhesive for PDLC electrochromic films according to any one of claims 1-2, wherein the emulsifier is sorbitan trioleate.
4. The method for preparing the UV adhesive for the PDLC electrochromic film according to claim 1, wherein in the step S2, the light intensity consumption of the low-pressure mercury lamp is 15-25mW/cm 2 。
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