Polyimide optical material with high refractive index and preparation method thereof

Abstract

The present invention relates to the technical field of materials, and particularly discloses a high refractive index polyimide optical material and a preparation method thereof, the high refractive index polyimide optical material comprises: a diamine component, the diamine component comprises 30-70 mol% of a sulfur-containing heterocyclic diamine selected from at least one of 4, 5-thiazolidine-2-thiol diamine, 1, 3, 4-thiazolidinedithiol diamine and 2-methylthiopyrimidine-4, 6-diamine, and the diamine component comprises at least one of 4, 5-thiazolidine-2-thiol diamine, 1, 3, 4-thiazolidinedithiol diamine, 1, 3, 4-thiazolidinedithiol diamine and 2-methylthiopyrimidine-4, 6-diamine; 5-40 mol% of a diamine monomer containing a tertiary amino group; 0 to 65 mol% of an aromatic or aliphatic diamine; the dianhydride component comprises at least one sulfur-containing dianhydride monomer, and the sulfur-containing dianhydride monomer contains a sulfur sulfuryl (-SO2-) or thioether bond (-S-) structural unit; according to the present invention, the synergistic combination of sulfur-containing heterocyclic diamine and tertiary amino-containing diamine is introduced, and the structural design of sulfur-containing dianhydride is matched, such that the electron cloud density and the molecular polarization are improved at the molecular level;

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of materials, and particularly relates to a high-refractive-index polyimide optical material and a preparation method thereof. BACKGROUND

[0002] The polyimide material is widely applied in the fields of aerospace, electronic industry, flexible circuit substrate, etc. due to its excellent thermal stability, mechanical strength, chemical corrosion resistance and dimensional stability. The refractive index of the traditional PI optical material is generally low, and there is significant C-H / N-H bond vibration absorption in the near-infrared band, resulting in insufficient infrared transmittance. In order to improve the refractive index, the prior art mainly adopts two types of ways: one is to introduce high-molar-polarization-group into the PI main chain to improve the refractive index by using the high electron polarization of sulfur atom; and the other is to add high-refractive-index nanoparticles or titanium dioxide to improve the dispersibility by surface amine functionalization.

[0003] The sulfur-containing monomer can improve the refractive index, but the rigidity of the molecular chain is enhanced, resulting in intensified charge transfer complex effect, and the visible light transmittance is significantly reduced. The introduction of fluorine-containing groups or alicyclic structures can inhibit the CTC and improve the light transmittance, but the low polarization of fluorine atom leads to the decrease of the refractive index, which restricts the application of the PI material in high-end optical devices. SUMMARY

[0004] The application aims to provide a high-refractive-index polyimide optical material and a preparation method thereof to solve the problems in the background.

[0005] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0006] The high-refractive-index polyimide optical material is prepared by polymerization reaction of raw materials containing the following monomers:

[0007] The diamine component includes 30-70 mol% of sulfur-containing heterocyclic diamine selected from at least one of 4,5-dihydrothiazole-2-thiol diamine, 1,3,4-thiazolidine dithiol diamine and 2-methylthiopyrimidine-4,6-diamine;

[0008] 5-40 mol% of a diamine monomer containing a tertiary amino group;

[0009] 0-65 mol% of an aromatic or aliphatic diamine;

[0010] The dianhydride component contains at least one sulfur-containing dianhydride monomer containing a sulfur sulfone group (-SO2-) or a thioether bond (-S-) structural unit.

[0011] Preferably, R1 and R2 in the diamine monomer containing a tertiary amino group are independently selected from methyl, ethyl or benzyl.

[0012] Preferably, the tertiary amino group-containing diamine monomer is N-methyl-bis(4- aminophenyl)amine or N,N'-dimethyl-3,5-diaminobenzylamine.

[0013] A method for preparing the high-refractive-index polyimide optical material according to any one of the preceding items, characterized by comprising the following steps:

[0014] (1) dissolving a diamine component in a polar aprotic solvent under an inert atmosphere;

[0015] (2) adding a dianhydride component in batches and reacting at -10°C to 30°C for 2-24 hours to obtain a polyamic acid solution;

[0016] (3) adding a chemical dehydrating agent and a catalyst to the polyamic acid solution and performing chemical imidization at 40-100°C for 4-12 hours;

[0017] (4) pouring the reaction solution into a precipitating agent, collecting the precipitate and drying to obtain a polyimide solid.

[0018] Preferably, the chemical dehydrating agent in step (3) is acetic anhydride, and the catalyst is pyridine or triethylamine, and the molar ratio of the dehydrating agent to the amic acid unit is 1.5-3.0:1.

[0019] Preferably, the imidization reaction in step (3) adopts a stepwise temperature rising procedure: first reacting at 40-60°C for 2 hours, and then rising the temperature to 70-100°C for 4-8 hours.

[0020] Preferably, the polar aprotic solvent is at least one selected from N-methylpyrrolidone, N,N-dimethylacetamide or dimethyl sulfoxide.

[0021] Preferably, the solid content of the solution in step (1) is controlled at 15-30 wt%.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) By introducing the synergistic combination of sulfur-containing heterocyclic diamine and tertiary amino group-containing diamine, and matching the structure design of sulfur-containing dianhydride, the electron cloud density and molecular polarization are improved at the molecular level, and compared with traditional aromatic polyimide, the refractive index and light transmittance are better, and the thermal stability and molecular chain regularity are maintained.

[0024] (2) The chemical imidization process is used to replace the conventional thermal cyclization method, and the molecular chain is controlled to be closed under mild reaction conditions, and through the synergistic effect of the dehydrating agent and the catalyst, the problems of sulfur bond rupture and molecular weight distribution deterioration caused by high temperature are effectively inhibited, and the uniformity and film forming quality of the material are improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Process flow diagram of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0027] Embodiment one:

[0028] Please refer to Figure 1 As shown in the figure, the high-refractive polyimide optical material is prepared by polymerization reaction from raw materials containing the following monomers:

[0029] Diamine component: 45 mol% of 4,5-dihydrothiazole-2-thiol diamine, 25 mol% of N-methyl-bis(4-aminophenyl) amine (containing tertiary amino diamine), and 30 mol% of 4,4'-diamino diphenyl ether;

[0030] Dianhydride component: 100 mol% of 4,4'-bis(3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride (containing sulfide bond).

[0031] A method for preparing any of the above high-refractive polyimide optical materials, comprising the following steps:

[0032] (1) Dissolve the total diamine (0.05 mol) in 120 mL of NMP under nitrogen protection, and stir until completely dissolved (solid content 25 wt%);

[0033] (2) Add an equimolar amount of dianhydride (0.05 mol) in batches, control the temperature at 0±5℃ for 6 hours, and obtain a light yellow polyamic acid solution;

[0034] (3) Add dehydrating agent acetic anhydride (0.15 mol) and catalyst pyridine (0.05 mol), heat to 50℃ for 3 hours, and then heat to 85℃ for 5 hours;

[0035] (4) Drop the viscous reaction liquid into a mixture of ethanol / water (1:1) as a precipitating agent, collect the fibrous precipitate by filtration, wash it with ethanol and deionized water for 3 times in turn, and vacuum dry at 120℃ for 24 hours to obtain a golden yellow polyimide solid.

[0036] Embodiment two:

[0037] The difference from Example One is that the diamine component is 35 mol% 1,3,4-thiazolidine dithiol diamine, 40 mol% 2-methylthiopyrimidine-4,6-diamine, and 25 mol% N,N'-dimethyl-3,5-diaminobenzylamine;

[0038] The dianhydride component is 100 mol% 2,2'-bis(3,4-dicarboxyphenyl) sulfone dianhydride;

[0039] The reaction temperature of Step 2 is 15°C, and the time is 8 hours; Step 3 uses gradient heating: 45°C (2h)→65°C (2h)→90°C (4h); and the precipitating agent is replaced with methanol.

[0040] Example Three:

[0041] The difference from Example One is that the total amount of sulfur-containing heterocyclic diamine is 60 mol% (1:1 mixture of 4,5-dihydrothiazole-2-thiol diamine and 1,3,4-thiazolidine dithiol diamine), the amount of tertiary amino diamine is 10 mol% (N-methyl-bis(4-aminophenyl)amine), and the amount of other diamine is 30 mol% (p-phenylenediamine).

[0042] The dianhydride is 4,4'-dicarboxy diphenyl sulfone dianhydride;

[0043] The chemical imidization temperature is 60°C for 10 hours; and the proportion of the dehydrating agent is 2.2:1 of acetic anhydride to amide acid units.

[0044]

[0045] Comparative Example One:

[0046] The difference from Example One is that the diamine component is 100 mol% 4,4'-diaminodiphenylmethane (a conventional aromatic diamine without sulfur elements), with the molecular formula H2N-C6H4-CH2-C5H4-NH2.

[0047] The dianhydride component is 100 mol% pyromellitic dianhydride (PMDA, without sulfur structure), with the molecular formula C 10 H2O5;

[0048] The preparation process replicates the chemical imidization process of Example 1 (same solvent, temperature, and dehydrating agent proportion);

[0049] The product obtained in Comparative Comparative Example One is compared with Example One, and the specific data are as follows:

[0050] Performance parameters Comparative Example 1 Example 1 Difference amplitude Refractive index (633 nm) 1.635 1.712 ↓11.3％ Transmittance (450 nm) 85％ 89％ ↓4.7％ Sulfur element content 0 wt% 12.7 wt% /

[0051] As can be seen from the above, the reason for the significant decrease in the refractive index is the molar polarizability of sulfur atoms (about 10.3 cm 3 / mol) is much higher than carbon (1.76 cm 3 / mol), the absence of sulfur element in Comparative Example 1 leads to the decrease of the overall electron density of the material;

[0052] The sulfur-containing heterocycle (such as thiazole, thiazolidine) has a high planar rigid structure. In the comparative group, the proportion of flexible -CH2- bond is too high, which weakens the molecular packing density.

[0053] Comparative Example Two:

[0054] The difference from Example One is that after synthesizing the polyamic acid solution, it is cast into a film (thickness 100 μm); in the oven, the temperature is raised in stages: 80℃ / 1h→150℃ / 1h→280℃ / 2h (thermal imidization); no precipitation redissolution step;

[0055] The product obtained in Comparative Example Two is compared with Example One, and the specific data are as follows:

[0056]

[0057] As can be seen from the above, the advantage of chemical imidization is that the chemical method (acetic anhydride / pyridine) achieves >99% ring closure rate in solution; the thermal method is limited by diffusion in the solid phase, and the ring closure rate is only 92-95% (verified by FTIR);

[0058] Thermal imidization requires high temperature of 280℃, which initiates main chain scission (TGA-MS detects SO2 release), and the chemical method completes the reaction at ≤100℃, preserving the integrity of the -S- bond;

[0059] Solution phase reaction avoids local stress concentration and eliminates microcracks.

[0060] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high refractive index polyimide optical material, characterized by, Prepared by polymerization of a starting material comprising: a diamine component comprising 30-70 mol% of a sulfur-containing heterocyclic diamine selected from at least one of 4,5-dihydrothiazole-2-thiol diamine, 1,3,4-thiazolidine dithiol diamine, 2-methylthiopyrimidine-4,6-diamine; 5-40 mol% of a tertiary amino group-containing diamine monomer; 0-65 mol% of an aromatic or aliphatic diamine; a dianhydride component comprising at least one sulfur-containing dianhydride monomer containing a sulfone group (-SO2-) or a thioether bond (-S-) structural unit.

2. The high refractive index polyimide optical material according to claim 1, and a method for preparing the same, wherein: R1, R2 in the tertiary amino group-containing diamine monomer are independently selected from methyl, ethyl or benzyl.

3. The high refractive index polyimide optical material according to claim 1, and a method for preparing the same, wherein: The tertiary amino group-containing diamine monomer is N-methyl-bis(4-aminophenyl)amine or N,N'-dimethyl-3,5-diaminobenzylamine.

4. The high refractive index polyimide optical material according to claim 1, and a method for preparing the same, wherein: The sulfur-containing dianhydride is selected from bis(3,4-dicarboxyphenyl)thioether dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, 2,2'-bis(3,4-dicarboxyphenyl) sulfone dianhydride, 4,4'-dicarboxy diphenyl sulfone dianhydride.

5. A method of producing the high refractive index polyimide optical material according to any one of claims 1 to 4, characterized by, Comprising the following steps: (1) dissolving the diamine component in a polar aprotic solvent under an inert atmosphere; (2) adding the dianhydride component in batches, and reacting at -10°C to 30°C for 2-24 hours to obtain a polyamic acid solution; (3) adding a chemical dehydrating agent and a catalyst to the polyamic acid solution, and performing chemical imidization at 40-100°C for 4-12 hours; (4) pouring the reaction solution into a precipitating agent, collecting the precipitate and drying to obtain a polyimide solid.

6. The method for preparing the high refractive index polyimide optical material according to claim 1, characterized in that: The chemical dehydrating agent in step (3) is acetic anhydride, and the catalyst is pyridine or triethylamine, and the molar ratio of the dehydrating agent to the amic acid unit is 1.5-3.0:

1.

7. The method for preparing the high refractive index polyimide optical material according to claim 1, characterized in that: The imidization reaction in step (3) uses a stepwise temperature rising program: first at 40-60°C for 2 hours, then at 70-100°C for 4-8 hours.

8. The method for preparing the high refractive index polyimide optical material according to claim 1, characterized in that: The polar aprotic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide or dimethyl sulfoxide.

9. The method for preparing the high refractive index polyimide optical material according to claim 1, characterized in that: The solid content of the solution in step (1) is controlled at 15-30 wt%.

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