A photochromic coating liquid and its preparation method

Abstract

This invention discloses a photochromic coating liquid and its preparation method, belonging to the field of polymer materials technology. The photochromic coating liquid comprises the following components: photochromic dye, polyacrylic acid polyol, polycarbonate polyol, polyether polyol, isocyanate curing agent, polymethylsiloxane, organic solvent, antioxidant, and light stabilizer. The photochromic dye includes one or more of spiropyran, spiroxazine, naphthopyran, and ursine anhydride compounds. The polymethylsiloxane is selected from polymethylsiloxanes with a molecular weight of 1000-3000 g / mol and functionalized at both ends with hydroxyl / amino groups. Compared with existing photochromic coating liquid formulations, the coating liquid of this invention introduces polymethylsiloxane, providing a favorable microenvironment for the photochromic dye, resulting in good color-changing depth and a faster fading rate in the coating. Furthermore, it also imparts strong adhesion and good surface hardness to the lens coating.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a photochromic coating liquid and its preparation method. Background Technology

[0002] Photochromism refers to the reversible change in the optical properties of a material under ultraviolet light irradiation. Photochromism can alter color and transmittance, and this change is reversible. Organic photochromic dyes are highly favored due to their diverse structures and rich colors, and have wide applications in information storage, optical lenses, textiles and clothing, and anti-counterfeiting printing. Currently, the most widely used organic photochromic dyes include spiropyran, spiroxazine, naphthopyran, naphthooxazine, and fumonisin anhydride.

[0003] Smart photochromic lenses are a typical example of the application of photochromic dyes. They can filter out ultraviolet light from sunlight, reducing the intensity of light reaching the eyes outdoors and making it more comfortable for wearers to see outdoors. Simultaneously, the reduction in ultraviolet radiation also protects the wearer's eye health. Early photochromic lenses were glass lenses using silver halide as the photochromic material. With the continuous advancement of science and technology, the vast majority of photochromic lenses now use organic photochromic dyes. Adding photochromic dyes to the polymer monomers of the lens substrate and then curing them creates smart photochromic lenses. This method is also known as substrate photochromism. However, due to the influence of polymer molecules and the polymerization environment, the photochromic dyes' color-changing / fading performance is limited when excited by ultraviolet light. They also suffer from drawbacks such as poor photostability, low photochromic response values, and insufficient thermal stability. Furthermore, the difference in thickness between the center and the periphery of the lens leads to color differences after the lens changes color. In recent years, new manufacturing processes for photochromic lenses have been developed. By coating a photochromic layer onto the lens surface, the shortcomings of uneven substrate color change and significant influence of the polymerization environment can be solved, and an ideal photochromic effect is expected to be achieved. However, existing photochromic coatings have certain shortcomings: (1) it is difficult to achieve a deep color change, the fading rate after color change is slow, and some base color remains for a long time; (2) the coating has poor adhesion and is easy to fall off the lens; (3) the coating is relatively thick and soft, and is prone to scratches. Therefore, it is crucial to develop a photochromic coating liquid with deep color change, fast fading, strong adhesion, and excellent mechanical properties. Summary of the Invention

[0004] To overcome the problems of existing photochromic coatings, this invention provides a photochromic coating liquid and its preparation method.

[0005] This invention provides a photochromic coating liquid, which is composed of photochromic dyes, organic prepolymers, isocyanate curing agents, polymethylsiloxane, organic solvents, coupling agents, and additives. The content of each component by mass fraction is as follows:

[0006] Photochromic dyes: 3-8%;

[0007] Organic prepolymer: 25-45%;

[0008] Isocyanate curing agent: 20-40%;

[0009] Polymethylsiloxane: 3-10%;

[0010] Organic solvents: 20-40%

[0011] Coupling agent: 2-6%;

[0012] Additives: 0.3-2%.

[0013] Furthermore, the photochromic dye includes one or more of spiropyran, spiroxazine, naphthopyran, and fumonisin compounds.

[0014] Furthermore, the organic prepolymer includes one or more of polymethacrylic acid polyols, polyether polyols, and polycarbonate polyols.

[0015] Furthermore, the isocyanate curing agent includes one or more of toluene diisocyanate curing agent, diphenylmethane-4,4'-diisocyanate curing agent, 1,6-hexane diisocyanate curing agent, isophthalimide diisocyanate curing agent, methylcyclohexyl diisocyanate curing agent, and isophorone diisocyanate curing agent.

[0016] Furthermore, the structural formula of the polymethylsiloxane is shown in Formula I below:

[0017]

[0018] R and R' are each independently selected from H or CH3, and each structural unit is independent of the others;

[0019] R1 and R2 are independently selected from (CH2) x OH or (CH2) x NH2, where x = 2 to 5.

[0020] Furthermore, the mutual independence means that R and R' in each structural unit can be the same or different.

[0021] Furthermore, the molecular weight of the polymethylsiloxane is 1000–3000 g / mol.

[0022] Furthermore, the organic solvent includes one or more of toluene, xylene, N-methylpyrrolidone, N-ethylpyrrolidone, propylene glycol methyl ether, diethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, ethyl acetate, and butyl acetate.

[0023] Furthermore, the coupling agent includes one or more of γ-aminopropyltriethoxysilane (APTES), γ-methacryloxypropyltrimethoxysilane (MPTS), γ-glycidoxypropyltrimethoxysilane (GPTMS), and vinyltrimethoxysilane (VTMS).

[0024] Furthermore, the additives include antioxidants, light stabilizers, or leveling agents.

[0025] Furthermore, antioxidants include hindered phenols, aromatic amines, nitrites, phosphates, or thiols.

[0026] Furthermore, light stabilizers include hindered amines, benzotriazoles, benzofuranones, benzophenones, or triazines.

[0027] Furthermore, leveling agents include polysiloxanes, acrylates, fluorocarbons, polyethers, or nonionic surfactants.

[0028] This invention also provides a method for preparing the photochromic coating liquid, the method comprising the following steps:

[0029] Photochromic dyes and auxiliaries are added to an organic solvent and dissolved thoroughly to form solution A. Then, organic prepolymer, isocyanate curing agent, methylsiloxane, and coupling agent are thoroughly mixed to form solution B. Finally, solution A is added to solution B and stirred. After filtration, the photochromic coating liquid is obtained.

[0030] Furthermore, the stirring temperature in the preparation method is 10–40°C, and the stirring time is 1–24 h.

[0031] The photochromic coating liquid provided by this invention and the photochromic coating liquid prepared according to the above preparation method are applied in the fields of coatings, information storage, optical lenses, textiles and clothing, and anti-counterfeiting printing.

[0032] Furthermore, the photochromic coating liquid is applied by means of spin coating, spray gun coating, or immersion coating to cover the surface of the article. After thermosetting, the coating thickness is controlled at 5-20 μm. A product with reversible photochromic effect can be obtained by ultraviolet irradiation.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention prepares a photochromic coating by adding a certain amount of organosiloxane to the main component polyurethane, and then crosslinks and modifies the polyurethane network during high-temperature curing, thereby enhancing the color-changing performance of the photochromic compound, greatly increasing the color-changing depth, accelerating the fading rate, and giving the coating excellent adhesion and mechanical strength.

[0035] The method for preparing the photochromic coating liquid of the present invention is simple and can be used for spin coating, spray coating and dip coating, making it easy to realize industrial application on photochromic lenses. Attached Figure Description

[0036] Figure 1 The image shows a comparison of the color change of the photochromic coating obtained in Example 1 of this invention on a lens before and after ultraviolet irradiation, and also shows traces of the adhesion test.

[0037] Figure 2 The adhesion test of the photochromic lens prepared in Example 1 is shown in the cross-cut adhesion test. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0039] The raw materials used in the examples and comparative examples are all commercially available products.

[0040] Example 1

[0041] Photochromic dyes and auxiliaries (antioxidants and light stabilizers) were dissolved in an organic solvent to form solution A. Organic prepolymers, isocyanate curing agents, methylsiloxanes, and coupling agents were thoroughly mixed to form solution B. Solution A was added to solution B and stirred at room temperature for 3 hours. The resulting photochromic coating liquid was obtained after filtration. The components and their contents are shown in Table 1 below.

[0042] Table 1

[0043]

[0044]

[0045] The structural formula of spiropyran is as follows: Formula II:

[0046]

[0047] The structural formula of polymethylsiloxane is shown in Formula III below:

[0048]

[0049] The method for preparing the photochromic coating lens is as follows:

[0050] First, the lens blank is washed and dried. After wetting the lens surface with N-methylpyrrolidone, the lens is fixed on a spin coater. 400 μL of photochromic coating liquid is added to the center of the lens and rotated at 500 rpm for 20 seconds, then at 1500 rpm for 30 seconds. Finally, the lens is dried and cured at 110°C for 2.5 hours to obtain a photochromic coated lens.

[0051] Example 2

[0052] The operation steps are the same as in Example 1, and the material composition is shown in Table 2 below. Finally, a photochromic coating and a photochromic coating lens are obtained.

[0053] Table 2

[0054] Spiropyran: 4g Polymethyl methacrylate polyol KN3210P: 16g N-Methylpyrrolidone: 20g Polycarbonate polyol PC-1122: 15g Antioxidant Zrganox-245: 0.5g Polyether polyol PTMEG2000: 5g Light stabilizer Tinuvin-144: 0.5g Isocyanate curing agent SBN70D: 30g Polymethylsiloxane M≈2000g / mol: 3g Coupling agent A-187: 3g

[0055] Example 3

[0056] The operation steps are the same as in Example 1, and the material composition is shown in Table 3 below. Finally, a photochromic coating and a photochromic coating lens are obtained.

[0057] Table 3

[0058] Spiropyran: 4g Polymethyl methacrylate polyol KN3210P: 16g N-Methylpyrrolidone: 20g Polycarbonate polyol PC-1122: 16g Antioxidant Zrganox-245: 0.5g Polyether polyol PTMEG2000: 5g Light stabilizer Tinuvin-144: 0.5g Isocyanate curing agent SBN70D: 30g Polymethylsiloxane M≈2000g / mol: 8g Coupling agent A-187: 3g

[0059] Example 4

[0060] The operation steps and the composition of each component are the same as in Example 1, except that the structural formula of polymethylsiloxane is adjusted as shown in Formula IV, and finally a photochromic coating and a photochromic coated lens are obtained.

[0061]

[0062] Example 5

[0063] The operation steps and the composition of each component are the same as in Example 1, except that the structural formula of polymethylsiloxane is adjusted as shown in Formula V, and finally a photochromic coating and a photochromic coated lens are obtained.

[0064]

[0065] Example 6

[0066] The operation steps and the composition of each component are the same as in Example 1, except that the molecular weight of polymethylsiloxane is adjusted to 1000 g / mol, and finally a photochromic coating and a photochromic coated lens are obtained.

[0067] Comparative Example 1

[0068] The preparation method of the photochromic coating in Example 1 is the same, except that polymethylsiloxane is not added.

[0069] Comparative Example 2

[0070] The preparation method of the photochromic coating in Example 1 is the same, except that polymethylsiloxane is replaced with small-molecule tetraethoxysilane.

[0071] Comparative Example 3

[0072] The preparation method of the photochromic coating in Example 1 is the same, except that the molecular weight of polymethylsiloxane is 4000 g / mol.

[0073] Comparative Example 4

[0074] The preparation method of the photochromic coating in Example 1 is the same, except that the polymethylsiloxane is replaced with an amino polymer, with the molecular formula shown in Formula VI below:

[0075]

[0076] Performance testing:

[0077] (1) Depth of color change: The transmittance of the lens after being exposed to ultraviolet light for 2 minutes is measured by an instrument and expressed as a percentage. The smaller the value, the deeper the color change.

[0078] (2) Fading rate: The time it takes for the color of a lens to fade from its darkest point back to half of its transmittance after the lens has been tinted, expressed in seconds;

[0079] (3) Adhesion: Tested using the cross-cut adhesion test (GB / T 9286-1998);

[0080] (4) Surface hardness: Tested using the pencil hardness test of GB 6739—86;

[0081] The test results are shown in Table 4 below:

[0082] Table 4. Performance comparison of photochromic coatings prepared in each embodiment and comparative example.

[0083] Example 1 17.2 52 5B 3H Example 2 18.5 55 5B 3H Example 3 18.8 48 5B 2H Example 4 16.6 57 5B 2H Example 5 19.0 60 4B 2H Example 6 18.3 54 5B 2H Comparative Example 1 20.1 127 4B H Comparative Example 2 28.6 115 3B HB Comparative Example 3 24.5 99 3B 2H Comparative Example 4 34.8 146 2B HB

[0084] As can be seen from Table 4, the color change depth of Examples 1 to 6 is less than 20%, the fading rate is less than 60s, the adhesion exceeds 4B grade, and the surface hardness is greater than 2H; while the other comparative examples are all inferior to the examples.

[0085] This invention illustrates a photochromic coating liquid and its preparation method through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of the claims of this invention.

Claims

1. A photochromic coating liquid, characterized in that, The coating liquid is composed of photochromic dyes, organic prepolymers, isocyanate curing agents, polymethylsiloxane, organic solvents, coupling agents, and additives. The content of each component by mass fraction is as follows: Photochromic dyes: 3~8%; Organic prepolymer: 25~45%; Isocyanate curing agent: 20~40%; Polymethylsiloxane: 3~10%; Organic solvents: 20~40% Coupling agent: 2-6%; Additives: 0.3~2%; The structural formula of the polymethylsiloxane is shown in Formula I below: Formula I R and R' are each independently selected from H or CH3, and each structural unit is independent of the others; R1 and R2 are independently selected from (CH2). x OH or (CH2) x NH2, where x = 2~5; The organic prepolymer includes at least one of polymethacrylic acid polyol, polyether polyol, and polycarbonate polyol; the molecular weight of the polymethylsiloxane is 1000~3000 g / mol.

2. The photochromic coating liquid according to claim 1, characterized in that, The photochromic dyes include one or more of spiropyran, spiroxazine, naphthopyran, and succinic anhydride compounds.

3. The photochromic coating liquid according to claim 1, characterized in that, The isocyanate curing agent includes at least one of toluene diisocyanate curing agent, diphenylmethane-4,4'-diisocyanate curing agent, 1,6-hexane diisocyanate curing agent, isophthalimide diisocyanate curing agent, methylcyclohexyl diisocyanate curing agent, or isophorone diisocyanate curing agent.

4. The photochromic coating liquid according to claim 1, characterized in that, The organic solvent includes one or more of toluene, xylene, N-methylpyrrolidone, N-ethylpyrrolidone, propylene glycol methyl ether, diethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, ethyl acetate, and butyl acetate.

5. The photochromic coating liquid according to claim 1, characterized in that, The coupling agent includes one or more of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, or vinyltrimethoxysilane.

6. The photochromic coating liquid according to claim 1, characterized in that, The additives include antioxidants, light stabilizers, or leveling agents; the antioxidants include hindered phenols, aromatic amines, nitrites, phosphate esters, or thiols; the light stabilizers include hindered amines, benzotriazoles, benzofuranones, benzophenones, or triazines; the leveling agents include polysiloxanes, acrylates, fluorocarbons, polyethers, or nonionic surfactants.

7. A method for preparing a photochromic coating liquid according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Photochromic dyes and auxiliaries are added to an organic solvent and fully dissolved to form solution A. Then, organic prepolymer, isocyanate curing agent, polymethylsiloxane, and coupling agent are fully mixed to form solution B. Finally, solution A is added to solution B and stirred. After filtration, the photochromic coating liquid is obtained.

8. The application of the photochromic coating liquid according to any one of claims 1 to 6 and / or the photochromic coating liquid prepared by the preparation method according to claim 7 in the fields of information storage, optical lenses, textiles and clothing, and anti-counterfeiting printing.

9. The application according to claim 8, characterized in that, The application involves applying a photochromic coating liquid to the surface of an object using methods including spin coating, spray gun coating, and immersion coating. After thermosetting, the coating thickness is controlled at 5~20μm, and a product with reversible photochromic effect can be obtained by irradiation with ultraviolet light.

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