Schiff base material, preparation method thereof and bulk three-dimensional display system

Abstract

The invention provides a Schiff base material of which the molecular structural formula is shown in the specification, and the Schiff base material has ultrafast reversible photochromic characteristic, can emit light at a light source intersection under the combined action of a photochromic light source and a ketone tautomer fluorescence excitation light source, and is a light-emitting material adaptable to three-dimensional display application. The photochromic property of the Schiff base material is stable and not prone to failure, the Schiff base material is high in transparency and light in color in media such as solutions, epoxy resin and polymethyl methacrylate, display patterns are not shielded, and the Schiff base material is high in practical value in in-vivo three-dimensional display application. The invention also provides a preparation method of the Schiff base material and a bulk three-dimensional display system containing the Schiff base material.

Description

TECHNICAL FIELD

[0001] The present application relates to a Schiff base material and a preparation method thereof, and a volume three-dimensional display system comprising the Schiff base material. BACKGROUND

[0002] As a three-dimensional display technology, the volume three-dimensional display technology is a technology for reproducing image information in a real three-dimensional space with width, height and depth. The displayed three-dimensional object has both psychological depth and physical depth, and multiple observers can directly observe the three-dimensional object from multiple angles without using any auxiliary equipment, which is the latest research direction in computer stereoscopic vision systems. The basic unit of volume three-dimensional display is voxel, which is the most basic unit for displaying three-dimensional images, just like pixels in two-dimensional display. The more voxels activated in the three-dimensional space at the same time, the more details and better effect of the three-dimensional image. The principle of volume three-dimensional imaging is based on a special luminescent material. When two light beams intersect at a point inside the luminescent material, a voxel in three-dimensional space is generated. When the light beams move quickly, multiple intersection points are formed in three-dimensional space, thereby forming a three-dimensional pattern composed of multiple voxel points. Developing a luminescent material with better performance for application in volume three-dimensional display technology has always been the focus of research. SUMMARY

[0003] In view of this, the first aspect of the present application provides a Schiff base material, and the molecular structure formula is:

[0004]

[0005] The Schiff base material provided by the present application is a new type of photochromic material, which has superfast reversible photochromic properties.

[0006] The second aspect of the present application provides a volume three-dimensional display system, comprising the above-mentioned Schiff base material.

[0007] The Schiff base material has superfast reversible photochromic properties. Under the joint action of the light source for photochromism and the fluorescent excitation light source for the keto tautomer, the Schiff base material can emit light at the intersection of the light source, and is an excellent luminescent material suitable for volume three-dimensional display applications. The photochromic properties of the Schiff base material are stable and not easy to fail. In solutions, epoxy resins, polymethyl methacrylate and other media, the Schiff base material has high transparency, light color and does not block the display pattern, and has high practical value in volume three-dimensional display applications.

[0008] The third aspect of the present application provides a preparation method of a Schiff base material, comprising:

[0009] Step S1: reacting 3-(trifluoromethyl)salicylaldehyde and 1,4-phenylenedimethylamine to obtain an intermediate product, which is

[0010] Step S2: reacting 4-methoxysalicylaldehyde and the intermediate product to obtain the target product, which is

[0011]

[0012] The Schiff base material provided in the application is simple to synthesize, has low raw material cost, and has a green and environmentally friendly production route, and can be produced on a large scale. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The nuclear magnetic hydrogen spectrum of the Schiff base material of Example 1 of the application.

[0014] Figure 2 The absorption spectrum of the Schiff base material of Example 1 of the application.

[0015] Figure 3 The application of the Schiff base material of Example 1 of the application in a body three-dimensional display system Figure 1 .

[0016] Figure 4 The application of the Schiff base material of Example 1 of the application in a body three-dimensional display system Figure 2 .

[0017] Explanation of main element symbols:

[0018] Body three-dimensional display system 100, 200

[0019] Imaging space 10

[0020] Container 30

[0021] First excitation light 21

[0022] Second excitation light 22 DETAILED DESCRIPTION

[0023] The embodiments of the application will be described below with reference to the accompanying drawings. The data range involved in the application should include the end value if not otherwise specified.

[0024] Photochromic Schiff base salicylidene aniline and its related compounds have great application potential in many fields, such as optical information storage, molecular memory switch, etc., and have attracted extensive research in the scientific community. Salicylaldehyde azine is a salicylidene aniline, and belongs to the smallest symmetrical aromatic Schiff base (having two hydrogen bond centers) in the salicylidene aniline family. Salicylaldehyde azine has very strong intramolecular hydrogen bonds, and is arranged in a face-to-face stacking in the crystal, so that the molecular structure thereof is almost planar, which is also the reason for its thermochromic property. At present, there are few reports about the properties of solid-state salicylaldehyde azine. There are even fewer reports about the properties of salicylaldehyde azine in solution, which, like all other Schiff bases, can reveal the photochromic behavior in the solution state. In acetonitrile solution, the ground state lifetime of the trans-keto tautomer is nearly two orders of magnitude shorter than that of other aromatic Schiff bases. The unsymmetrical double Schiff base material derived from salicylaldehyde azine has rich groups, and can provide more functions for the photochromic Schiff base.

[0025] The unsymmetrical double Schiff base material derived from salicylaldehyde azine has rich groups, and can provide more functions for the photochromic Schiff base. The unsymmetrical double Schiff base material has both the advantage of short lifetime of the trans-keto tautomer in solution and the stable photochromic property. Under light stimulation, the Schiff base material undergoes ultrafast interconversion between enol form and keto form, accompanied by displacement of the absorption spectrum, so that the solution of the Schiff base material can emit light at the intersection of a light source capable of causing photochromism and a fluorescence excitation light source capable of generating keto tautomer, and the interconversion process is reversible under the action of heat. Therefore, the material having the reversible light switching property is extremely advantageous in the application of active light-emitting three-dimensional display technology.

[0026] The application provides a novel Schiff base material, which is an unsymmetrical double Schiff base material, and the molecular structure formula is as follows:

[0027]

[0028] The molecular structure formula is the structure formula of the Schiff base material in a natural state. Please refer to Figure 2 As can be seen from the absorption spectrum, the Schiff base material provided by the application has relatively strong light absorption in the ultraviolet region with a wavelength of 300 nm-410 nm, and weak light absorption in the region with a wavelength of 410 nm-480 nm.

[0029] Based on the principle of excited state proton transfer, the Schiff base material can quickly convert from enol form (initial state) to keto form isomer under ultraviolet light (ultraviolet light with a wavelength of 350 nm-410 nm), and the keto form will convert into the enol form of the Schiff base material at room temperature after ultraviolet light irradiation, that is, the enol form and the keto form are interconverted, and the reaction formula is as follows.

[0030]

[0031] Another beam of visible light (blue light with a wavelength of 440nm-470nm) intersects with the ultraviolet light, exciting the ketone isomer to produce a voxel point to emit light; when a plurality of voxel points array, a three-dimensional image is displayed inside the Schiff base material. The speed of the voxel point generation and disappearance of the Schiff base material is less than the limit resolution of the human eye, the response speed is fast, and dynamic refreshing of the three-dimensional image can be realized.

[0032] The application also provides a preparation method of the Schiff base material, comprising steps S1 to S2.

[0033] Step S1: reacting 3-(trifluoromethyl)salicylaldehyde and 1,4-phenylenedimethylamine to obtain an intermediate product, and the molecular structural formula of the intermediate product is:

[0034] Step S1 specifically comprises: dissolving 3-(trifluoromethyl)salicylaldehyde and 1,4-phenylenedimethylamine in organic solutions respectively to prepare solutions, then slowly adding the solution of 3-(trifluoromethyl)salicylaldehyde to the solution of 1,4-phenylenedimethylamine, keeping the reaction solution at 70-80°C and stirring, refluxing for a certain time, for example, 2-4h, obtaining the solution of the intermediate product, removing part of the solvent from the solution of the intermediate product by rotary evaporation, cooling to 0°C to precipitate crystals, filtering, washing, and recrystallizing to obtain the intermediate product.

[0035] The organic solvent used in step S1 is selected from at least one of dimethyl sulfoxide, dimethyl formamide, acetonitrile, methanol, ethanol, tetrahydrofuran, toluene, and dichloroethane.

[0036] The reaction formula of step S1 is as follows.

[0037]

[0038] Step S2: reacting 4-methoxysalicylaldehyde and the intermediate product to obtain a target product, and the target product is

[0039]

[0040] Step S2 specifically comprises: dissolving 4-methoxysalicylaldehyde and the intermediate product in organic solvents respectively to prepare solutions, then slowly adding the solution of 4-methoxysalicylaldehyde to the solution of the intermediate product, keeping the reaction solution at 70-80°C and stirring, refluxing for a certain time, for example, 2-4h, and obtaining the target product by recrystallization.

[0041] The organic solvent used in step S2 is selected from at least one of dimethyl sulfoxide, dimethyl formamide, acetonitrile, methanol, ethanol, tetrahydrofuran, toluene, dichloroethane.

[0042] The reaction formula of this step S2 is as follows.

[0043]

[0044] In this preparation method, the molar ratio of the three reaction materials 3-(trifluoromethyl)salicylaldehyde, 1,4-phenylenedimethylamine and 4-methoxysalicylaldehyde is 1:(1-1.2):(0.9-1.1).

[0045] Referring to Figure 3 The present application also provides a volume three-dimensional display system 100 comprising the Schiff base material described above. The Schiff base material is dispersed in a transparent medium to form a transparent mixture as shown in Figure 3 The medium is a liquid solvent, which can be selected from at least one of acetonitrile, dimethyl sulfoxide, N,N-dimethyl formamide, ethanol, ethyl acetate and tetrahydrofuran. Since the medium is a liquid solvent, the mixture as a solution needs to be placed in a transparent container 30. In some embodiments, the container 30 can be a quartz container. In the mixture, the mass ratio of the Schiff base material to the medium is 1:(5000-100000).

[0046] The volume three-dimensional display system 100 further comprises an excitation light source for irradiating the imaging space 10, which comprises a first excitation light 21 and a second excitation light 22. The first excitation light 21 is ultraviolet light with a wavelength of 350-410 nm, and the second excitation light 22 is blue light with a wavelength of 440-470 nm. The two light sources intersect at a point in the imaging space 10 to generate a luminescent voxel. By controlling the scanning path and scanning speed of the first excitation light 21 and the second excitation light 22 respectively, a plurality of intersection points can be formed in the imaging space 10 to constitute a three-dimensional image display. Irradiation of the first excitation light 21 can promote the Schiff base material to undergo a photochromic reaction by intramolecular excited-state proton transfer process to generate a transformation of enol form structure to keto tautomer. Irradiation of the second excitation light 22 can promote the keto tautomer of the Schiff base material to emit fluorescence.

[0047] Referring to Figure 4 The present application also provides a volume three-dimensional display system 200 comprising the Schiff base material described above. Unlike the volume three-dimensional display system 100, the medium in the volume three-dimensional display system 200 is a solid resin material. The resin material can be selected from at least one of epoxy resin and polymethyl methacrylate.

[0048] The Schiff base material of the present application is an asymmetric double Schiff base material, which has superfast reversible photochromic characteristics. Under the joint action of a light source capable of causing the Schiff base material to produce photochromism and a fluorescence excitation light source capable of causing the Schiff base material to produce a ketone form tautomer, the Schiff base material can produce light at the intersection of the light sources, and is an excellent light-emitting material suitable for three-dimensional display applications. The photochromic characteristics of the asymmetric double Schiff base material are stable and not prone to failure. In organic solutions, epoxy resins, polymethyl methacrylate and other media, the transparency is high, the color is light, and the display pattern is not blocked, and the practical value in three-dimensional display applications is high.

[0049] The Schiff base material of the present application can be converted into an isomer under the irradiation of a second excitation light, and the isomer produces stimulated light under the irradiation of a first excitation light. The overall response speed is fast, and the Schiff base material can be applied to various application scenarios, such as two-dimensional display devices, three-dimensional display devices, light-controlled switch elements, or multiple light-emitting anti-counterfeiting materials.

[0050] The preparation of the Schiff base material is specifically described below through Examples 1 and 2.

[0051] Example 1

[0052] The preparation steps of the Schiff base material of Example 1 are as follows:

[0053] (1) Under stirring at 78°C, anhydrous ethanol solution containing 2.00 g of 3-(trifluoromethyl) salicylaldehyde was slowly added dropwise to an anhydrous ethanol solution containing 1.50 g of 1,4-xylylenediamine, and refluxed for 3 h to obtain an intermediate product through recrystallization.

[0054] (2) Under stirring at 78°C, anhydrous ethanol solution containing 1.00 g of 4-methoxysalicylaldehyde was slowly added dropwise to an anhydrous ethanol solution containing 2.00 g of the intermediate product, and refluxed for 3 h to obtain the target product, the Schiff base material, through recrystallization.

[0055] Example 2

[0056] The preparation steps of the Schiff base material of Example 2 are as follows:

[0057] (1) Under stirring at 78°C, anhydrous ethanol solution containing 2.00 g of 3-(trifluoromethyl) salicylaldehyde was slowly added dropwise to an anhydrous ethanol solution containing 1.65 g of 1,4-xylylenediamine, and refluxed for 3 h to obtain an intermediate product through recrystallization.

[0058] (2) Under stirring at 78°C, anhydrous ethanol solution containing 1.10 g of 4-methoxysalicylaldehyde was slowly added dropwise to an anhydrous ethanol solution containing 2.00 g of the intermediate product, and refluxed for 3 h to obtain the target product through recrystallization.

[0059] Example 3

[0060] The preparation steps of the Schiff base material of Example 3 are as follows:

[0061] (1) Anhydrous ethanol solution containing 2.00 g of 3-(trifluoromethyl)salicylaldehyde was slowly added dropwise to anhydrous ethanol solution dissolving 1.65 g of 1,4-phenylenedimethylamine under stirring at 72°C, and refluxed for 4 h to obtain an intermediate product by recrystallization.

[0062] (2) Anhydrous ethanol solution containing 1.10 g of 4-methoxysalicylaldehyde was slowly added dropwise to anhydrous ethanol solution containing 2.00 g of the intermediate product under stirring at 72°C, and refluxed for 4 h to obtain the target product by recrystallization.

[0063] Application Example 1

[0064] The application experiment of the Schiff base material in three-dimensional display in vivo is as follows:

[0065] The Schiff base material prepared in Example 1 was dissolved and dispersed in dimethyl sulfoxide to obtain a liquid transparent mixture 1, and the concentration of the Schiff base material in the mixture 1 was 0.05 mg / mL.

[0066] Application Example 2

[0067] The Schiff base material prepared in Example 2 was dissolved and dispersed in epoxy resin to obtain a solid transparent mixture 2, and the concentration of the Schiff base material in the mixture 2 was 0.02 mg / mL.

[0068] The structure of the product Schiff base material of Example 1 was characterized by nuclear magnetic hydrogen spectrum, and the results are as follows Figure 1 , and the nuclear magnetic hydrogen spectrum of the target product is as follows, wherein: 1 HNMR (400 MHz, DMSO-d6) δ 3.82 (3H, s), 4.75 (2H, s), 4.82 (2H, s), 6.43 (1H, dd, J = 1.5, 0.5 Hz), 6.91 (1H, dd, J = 7.7, 1.5 Hz), 7.13-7.32 (5H, 7.15 (dd, J = 7.9, 1.3 Hz), 7.30 (ddd, J = 8.1, 1.0, 0.5 Hz), 7.30 (ddd, J = 8.1, 1.0, 0.5 Hz)), 7.40-7.60 (2H, 7.45 (dd, J = 7.9, 7.5 Hz), 7.52 (dd, J = 7.5, 1.3 Hz)), 7.62 (1H, dd, J = 7.7, 0.5 Hz), 8.21-8.35 (2H, 8.27 (s), 8.32 (s)). According to the position (chemical shift) and area (number of hydrogen atoms) of the peaks, the Figure 1 Figure 1 ​The peak of hydrogen in the spectrum corresponds to the hydrogen-containing functional group in the molecular structure of the Schiff base material, which verifies that the Schiff base material with the molecular structure is formed.

[0069] Figure 2 The ultraviolet-visible absorption spectrum of the Schiff base material prepared in Example 1 shows that the Schiff base material absorbs light with a wavelength of 300-410 nm. According to the absorption spectrum of the Schiff base material, and by performing a continuous adjustable laser test, it is found that the Schiff base material prepared in the present application is suitable for using ultraviolet light with a wavelength of 350 nm-410 nm as a light source for producing photochromism, and blue light with a wavelength of 440-470 nm as a fluorescent excitation light source for the ketone form tautomer. Figure 2

[0070] The light sources with wavelengths of 365 nm and 450 nm respectively excite the mixture 1, and the intersection point emits light. The computer controls the scanning path and scanning speed of the two light sources respectively, so that the three-dimensional display is completed.

[0071] The light sources with wavelengths of 405 nm and 450 nm respectively excite the mixture 2, and the intersection point emits light. The computer controls the scanning path and scanning speed of the two light sources respectively, so that the three-dimensional display is completed.

[0072] The Schiff base material provided in the present application is a new type of photochromic material, which is simple to synthesize, has low raw material cost, and has a green and environmentally friendly production route, and can be produced on a large scale. The Schiff base material has superfast reversible photochromic properties, and under the joint action of a light source for photochromism and a fluorescent excitation light source for the ketone form tautomer, the Schiff base material can emit light at the intersection of the light sources, and is an excellent light-emitting material suitable for three-dimensional display applications. The photochromic properties of the Schiff base material are stable and not easy to fail, and the Schiff base material has high transparency and light color in a solution, an epoxy resin, polymethyl methacrylate and other media, and does not block the display pattern, so the practical value of the Schiff base material in three-dimensional display applications is high.

[0073] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit the present application. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.​

Claims

1. A Schiff base material characterized in that, The molecular structural formula of the Schiff base material is:

2. A volumetric three-dimensional display system, characterized by The Schiff base material, and a molecular structural formula of the Schiff base material is:

3. The volumetric three-dimensional display system of claim 2, wherein, The Schiff base material is dispersed in a medium to form a transparent mixture, the medium is a transparent solvent or a transparent resin, and the mixture is used as an imaging space of the volumetric display system.

4. The volumetric three-dimensional display system of claim 3, wherein, The transparent solvent is at least one selected from acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, ethanol, ethyl acetate and tetrahydrofuran.

5. The volumetric three-dimensional display system of claim 3, wherein, The transparent resin is at least one selected from epoxy resin and polymethyl methacrylate.

6. The volumetric three-dimensional display system of claim 3, wherein, The mass ratio of the Schiff base material to the medium is 1:(5000-100000).

7. The volumetric three-dimensional display system of claim 3, wherein, The volumetric display system further comprises an excitation light source for emitting excitation light for irradiating the imaging space, and the excitation light comprises ultraviolet light with a wavelength of 350-410 nm and blue light with a wavelength of 440-470 nm.

8. A method of preparing a Schiff base material, characterized by, Comprising: Step S1: reacting 3-(trifluoromethyl)salicylaldehyde and 1,4-benzenedimethylamine to obtain an intermediate product, the intermediate product is Step S2: reacting 4-methoxysalicylaldehyde and the intermediate product to obtain a target product, the target product is 9. The method of claim 8, wherein the Schiff base material is prepared by the reaction of a compound of formula (I) with a compound of formula (II) ###00003### (I) (II) in the presence of a base. The step S1 specifically comprises: dissolving the 3-(trifluoromethyl)salicylaldehyde and the 1,4-benzenedimethylamine in organic solutions respectively to prepare solutions, then slowly adding the 3-(trifluoromethyl)salicylaldehyde solution into the 1,4-benzenedimethylamine solution, keeping the reaction solution at 70-80°C and stirring, refluxing for a certain time, and then recrystallizing the obtained solution to obtain the intermediate product; The step S2 specifically comprises: dissolving the 4-methoxysalicylaldehyde and the intermediate product in organic solutions respectively to prepare solutions, then slowly adding the 4-methoxysalicylaldehyde solution into the intermediate product solution, keeping the reaction solution at 70-80°C and stirring, refluxing for a certain time, and then recrystallizing the obtained solution to obtain the target product.

10. The method of claim 8, wherein the Schiff base material is prepared by the reaction of a primary amine and an aldehyde or ketone. The molar ratio of the 3-(trifluoromethyl)salicylaldehyde, the 1,4-benzenedimethylamine and the 4-methoxysalicylaldehyde is 1:(1-1.2):(0.9-1.1).

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