A uv protection film for surface of polymer transparent member and its preparation method and application

Abstract

The application belongs to the technical field of functional materials, and particularly relates to a polymer transparent piece surface ultraviolet protection film and a preparation method thereof. The polymer transparent piece surface ultraviolet protection film is formed in an alternating stacking mode of low-refractive-index layer material and high-refractive-index layer material. The application first proposes to use one-dimensional photonic crystals for polymer transparent piece surface ultraviolet protection, and successfully constructs a one-dimensional photonic crystal multilayer film represented by organic silicon / TiO2 on a polycarbonate surface through an alternating spin coating method. Ultraviolet cutoff and high visible light transmission are realized by using selective reflection of the photonic crystal, and the application can be well applied to polymer transparent piece surface ultraviolet protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of functional materials, and particularly relates to a polymer transparent piece surface ultraviolet protection film and a preparation method and application thereof. BACKGROUND

[0002] Transparent polymer materials represented by polycarbonate (PC) have been widely used in various fields of life such as transportation and building due to their light weight, easy molding processing, good impact resistance and optical properties, and they also play an important role in national strategic fields such as aerospace and national defense. However, transparent polymer materials themselves do not have the performance of resisting ultraviolet radiation, and in the process of outdoor service, they are easily affected by ultraviolet rays in sunlight, which can cause the decline of mechanical properties and optical properties, which greatly limits the application of transparent polymer materials in harsh environments such as strong ultraviolet radiation.

[0003] Traditional measures for resisting ultraviolet radiation of transparent polymers are mainly based on the absorption of ultraviolet rays by specific materials, and a film layer with ultraviolet shielding function is constructed on the surface, such as organic absorbing materials using specific groups for resonance absorption effect of ultraviolet rays, and inorganic oxides using intrinsic absorption of ultraviolet rays. However, the secondary effects such as photocatalytic degradation caused by these materials in absorbing ultraviolet rays cannot be avoided. Therefore, it is of great significance to develop a new type of non-absorbing ultraviolet protection film. SUMMARY

[0004] In order to realize the ultraviolet protection performance of transparent polymers and break through the limitations of traditional absorbing ultraviolet protection film, the present application provides a new type of reflective polymer surface ultraviolet protection film and a preparation method thereof.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A polymer transparent piece surface ultraviolet protection film, the film is formed in an alternating stacking manner of low refractive index layer material and high refractive index layer material.

[0007] Further, the low refractive index layer material is silicone (Silicone), the high refractive index layer material is TiO2, and the base transparent piece is polycarbonate (PC).

[0008] The film is formed in an alternating stacking manner of silicone layer and TiO2 layer.

[0009] Each completion of an alternating stacking of one layer of silicone sol and one layer of TiO2 sol is regarded as one cycle, and the cycle is 4 or 5.

[0010] The application further provides a preparation method of the polymer transparent piece surface ultraviolet protection film, and sols of low refractive index layer material and high refractive index layer material are coated on the surface of the polymer transparent piece in sequence to make the two sols be deposited alternately.

[0011] The sol is coated on the surface of the polymer transparent piece by preferably using a spin coating method, the spin coating speed is 5000 rpm-7000 rpm, and the spin coating time is 30 s-50 s.

[0012] The curing condition for coating the first layer of silicone sol on the surface of the polymer transparent piece is to be heated to 70-90 ℃ and maintained for 20-30 min, and then cooled to 50 ℃; the curing condition for each layer of sol after being coated is to be cured at 40-60 ℃ for 30 min.

[0013] Preferably, the curing condition for coating the first layer of silicone sol on the surface of the polymer transparent piece is to be heated to 80 ℃ and maintained for 20 min, and then cooled to 50 ℃; the curing condition for each layer of sol after being coated is to be cured at 50 ℃ for 30 min.

[0014] Specifically, the preparation of the low refractive index material (silicone) sol in the method is as follows:

[0015] The water bath temperature is set to 28 ℃, 20 mL of isopropyl alcohol is added into a three-necked flask, then 32 mL of methyl trimethoxysilane is added, after stirring for 10 min, 28 mL of deionized water is added dropwise, and then stirring and reaction is conducted for 10 min, 1 mL of glacial acetic acid is added dropwise, stirring and reaction is conducted for 30 min, 5.46 mL of GPTMS is added, stirring and reaction is conducted for 10 min, finally, 73 μL of hydrochloric acid is added, and the reaction is stopped after 48 h. Then, the water bath is aged at 28 ℃ for 18 h, and then 640 μL of tetrabutylammonium hydroxide (TBAOH) curing agent is added, and stirring and reaction is conducted for 20 min.

[0016] The preparation of the high refractive index layer material (TiO2) sol is as follows:

[0017] 7 mL of isopropyl alcohol and 5 mL of tetrabutyl titanate are sequentially added into a 50 mL beaker, after stirring for 10 min, a mixture of 0.5 mL of deionized water, 40 μL of concentrated hydrochloric acid (37%) and 8 mL of isopropyl alcohol is added into the beaker at a rate of 1 drop / s, and stirring and reaction is conducted at 25 ℃ water bath for 2 h.

[0018] Specifically, the TiO2 sol is diluted to 1.5 wt% with anhydrous ethanol, the silicone sol is diluted to 1.5 wt%, then the silicone sol is deposited on a pre-processed PC board by using a spin coater, and then the TiO2 sol is deposited, and the two sols are deposited alternately. The anhydrous ethanol can also be replaced by methanol or isopropyl alcohol.

[0019] The ultraviolet protection film has good application in ultraviolet protection of the surface of the transparent member.

[0020] The application alternately spin-coats a low refractive index material and a high refractive index material on the surface of a polymer to form a photonic crystal periodic structure, to obtain a one-dimensional photonic crystal (1DPhC) structure, and to construct a high-stability reflective ultraviolet cut-off film with high ultraviolet reflectivity and high visible light transmittance. The film has good ultraviolet shielding performance, good environmental stability and good solvent resistance, and can not only meet the ultraviolet protection requirements of general transparent polymers, but also can be applied to extreme space environments.

[0021] The most basic feature of the one-dimensional photonic crystal (1DPhC) structure is a photonic band gap, and light of a corresponding wavelength in the photonic band gap cannot pass through. The main factors affecting the photonic band gap structure of the photonic crystal include the Bragg stack number (period number), the refractive index, and the light wave incidence angle. The Bragg formula can be used to calculate the photonic band gap position (reflection peak) of the 1DPhC, and the expression is as follows:

[0022]

[0023]

[0024]

[0025]

[0026] In the formula, m represents the diffraction order, λ represents the wavelength of the reflected light, n eff represents the effective refractive index of the 1DPhC, θ represents the incidence angle, n s , n H , and n L represent the refractive indices of the three materials of the substrate, the high refractive index layer, and the low refractive index layer, respectively, d H and d L represent the film thicknesses of the continuous high and low refractive index medium materials, respectively, N represents the Bragg stack number, and R represents the reflection intensity. Figure 1

[0027] By using the formula (1.1), the reflection center can be adjusted to the ultraviolet region by controlling the total thickness of the high and low refractive index layers, while ensuring the smooth passage of visible light, as shown in Figure 2 and Figure 5 (a).

[0028] ​Currently, the UV protective film layer for the surface of transparent polymer is mostly limited to the absorption type film layer. The one-dimensional photonic crystal concept is introduced into the UV irradiation protection in the application, which makes up for the defects of the absorption type UV protective film. Meanwhile, the performance of the selected medium material is also beneficial, such as the low refractive index material organic silicon forms a crosslinked network structure in the curing process, which can maintain good optical performance and also achieve excellent mechanical properties, such as certain wear resistance and solvent barrier performance, realize multifunctionality, and can be widely applied in various fields.

[0029] Compared with the prior art, the application has the following advantages:

[0030] The application first proposes to use one-dimensional photonic crystals for the UV protection of the surface of polymer transparent parts, and successfully constructs a one-dimensional photonic crystal multilayer film represented by organic silicon / TiO2 on the surface of polycarbonate through an alternating spin coating method, realizes UV cutoff and high visible light transmission by using the selective reflection of the photonic crystal, and can be well applied to the UV protection of the surface of polymer transparent parts. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a schematic diagram of the reflection principle of the photonic crystal;

[0032] Figure 2 It is a schematic diagram of the selective reflection of the high-UV reflection-high-visible light transmission photonic crystal;

[0033] Figure 3 It is the reflection spectrum of organic silicon / TiO2 with different cycle numbers (3, 4, 5);

[0034] Figure 4 It is the reflection spectrum of the organic silicon / TiO2 1DPhC obtained at different spin coating speeds;

[0035] Figure 5 It is the (a) reflection spectrum and transmission spectrum of the UV protective film on the PC surface obtained in Example 1; (b) the refractive index-wavelength curve diagram of organic silicon and TiO2; (c) the schematic diagram of the surface roughness; (d) the cross-sectional morphology diagram;

[0036] Figure 6 It is the difference of the absorbance at 400 nm of PC and the reflection type UV cutoff film (a) (Example 1) and (b) the yellowing index after different UVB irradiation times;

[0037] Figure 7(a) is the reflectance spectra of PC and organic silicon / TiO2 1DPhC / PC before and after 100 times of rubbing, and the inset is a schematic diagram of paper tape rubbing; (b) is the change of haze of PC and organic silicon / TiO2 1DPhC / PC before and after 100 times of rubbing; (c) and (d) are the surface topography of PC and organic silicon / TiO2 1DPhC / PC after 100 times of rubbing test, respectively.

[0038] Figure 8 (a) and (b) are the reflectance spectra (a) and transmittance spectra (b) of organic silicon / TiO2 1DPhC / PC before and after 100 cycles of acetone wiping, and the inset in (b) is a photograph of the sample of organic silicon / TiO2 1DPhC / PC before and after 100 cycles of acetone wiping; (c) is the transmittance spectra of PC with different acetone wiping cycles; (d) is the change of haze value of PC and organic silicon / TiO2 1DPhC / PC with different acetone wiping cycles, and the inset is a photograph of the sample of PC before and after 100 cycles of acetone wiping. DETAILED DESCRIPTION

[0039] The technical solutions of the present application are described below with specific examples, but the protection scope of the present application is not limited thereto:

[0040] Example 1

[0041] A UV protective film on the surface of a polymer transparent piece is prepared by the following steps:

[0042] S1 Preparation of low-refractive-index material organic silicon sol:

[0043] A water bath is set to 28℃, 20mL of isopropyl alcohol is added to a three-necked flask, then 32mL of methyltrimethoxysilane is added, after stirring for 10min, 28mL of deionized water is added dropwise, and stirring is continued for 10min, 1mL of glacial acetic acid is added dropwise, and stirring is continued for 30min, 5.46mL of GPTMS is added, and stirring is continued for 10min; finally, 73μL of hydrochloric acid is added, and the reaction is stopped after 48h. Then the water bath is aged at 28℃ for 18h, and then 640μL of tetrabutylammonium hydroxide (TBAOH) curing agent is added, and stirring is continued for 20min.

[0044] S2 Preparation of high-refractive-index layer material TiO2 sol:

[0045] 7mL of isopropyl alcohol and 5mL of tetrabutyl titanate are sequentially added to a 50mL beaker, after stirring for 10min, a mixture of 0.5mL of deionized water, 40μL of concentrated hydrochloric acid (37%) and 8mL of isopropyl alcohol is added to the beaker at a rate of 1 drop / s, and the reaction is carried out in a 25℃ water bath for 2h.

[0046] S3 Preparation of a reflective UV protective film:

[0047] TiO2 sol was diluted to 1.5wt% with anhydrous ethanol, and organosilica sol was diluted to 1.5wt% for later use. Then, using a spin coater, the organosilica sol was deposited on a pre-treated PC board, followed by the TiO2 sol, alternating between the two. The required spin coating speed was 5000 rpm, and the spin coating time was 50 seconds. The first organosilica layer was cured by heating the oven to 80°C and holding it for 20 minutes, then cooling it to 50°C. Each subsequent layer was cured at 50°C for 30 minutes. This process was repeated until four cycles were completed.

[0048] At the same time, the number of cycles in step S3 in the above embodiment is changed to 3 and 5 respectively, and the rest is the same as in embodiment 1.

[0049] Figure 3 The reflectance spectra for stacking periods of 3, 4, and 5, respectively, are shown in the embodiment of the present invention. As can be seen, the reflectance in the ultraviolet region increases with increasing period number, while the visible light band is not significantly affected. When the period number is greater than 3, a significant ultraviolet reflection effect is observed.

[0050] Figure 4 The reflectance spectra of the multilayer film obtained at different spin coating speeds for a 4-period stacking process in the present invention are shown in the figure. As can be seen from the figure, within the spin coating speed range of 5000 rpm to 7000 rpm, the reflectance spectrum shifts to the blue as the spin coating speed increases. This is because increasing the spin coating speed reduces the overall film thickness and the central reflection wavelength, but the strong reflection region remains in the ultraviolet range.

[0051] Figure 5 The corresponding graphs of the 4-period UV protective film on the PC surface obtained by spin coating at a speed of 5000 rpm in this Example 1: (a) reflection spectrum and transmission spectrum; (b) refractive index-wavelength curve of silicone and TiO2; (c) surface roughness schematic diagram; (d) cross-sectional morphology diagram.

[0052] like Figure 5 As shown in (a), the reflective UV cutoff film of the present invention has a high reflectivity of 83% and a high transmittance of more than 85% of visible light. In the wavelength range of 290 to 1000 nm, the average refractive index of the organic silicon film layer is about 1.46, and the average refractive index of the TiO2 layer is about 2.05. Figure 5 As shown in (b), there is a large refractive index difference between the two (Δn>0.59), and only a small number of layers are needed to achieve high reflectivity of 1DPhC multilayer film. Figure 5 (c) It can be seen that there are no obvious protrusions or large particles on the surface of the reflective UV cutoff film, and the surface roughness is very small (Rq = 0.44nm). Figure 5(d) It can be seen that the interfacial boundary between different unit layers of the reflective ultraviolet cut-off film is uniform, smooth and continuous, which can effectively reduce the scattering effect on light waves and ensure strong reflection between the interfaces of the multilayer film.

[0053] Performance measurement

[0054] 1. Perform ultraviolet protection performance measurement: test the absorbance and yellowness factor of PC and reflective ultraviolet cut-off film / PC (Example 1) at 400 nm, respectively, to explore the aging degradation.

[0055] From Figure 6 (a) and (b), it can be seen that the absorbance and yellowness index of PC at 400 nm increase rapidly with the extension of UVB irradiation time, and show approximately the same change curve. This is because under the condition of UVB irradiation, PC will degrade, and with the increase of irradiation time, the degree of degradation is greater, the content of chromogenic group is more, and the absorbance and yellowness factor at 400 nm increase more obviously. For PC protected by the reflective ultraviolet cut-off film in this example, the increase rate of its absorbance value and yellowness index value is much lower than that of pure PC, which shows that the reflective ultraviolet cut-off film has good ultraviolet protection performance.

[0056] 2. Abrasion resistance

[0057] The reflective ultraviolet cut-off film of Example 1 of the present application was subjected to paper tape friction test, and the results are shown in Figure 7 From Figure 7 (a) and (b), it can be seen that the reflective ultraviolet cut-off film has no obvious change in reflectivity and haze after 100 times of paper tape friction. The haze of PC increases from 0.34% to 12.24% after 100 times of friction. In addition, Figure 7 (c) and (d) can see the difference in surface morphology of PC and PC protected by reflective ultraviolet cut-off film after 100 times of paper tape friction. The number of scratches on the surface of PC protected by reflective ultraviolet cut-off film after 100 times of friction is significantly less than that of PC, which shows that the reflective ultraviolet cut-off film has certain enhancement on the abrasion resistance of the substrate.

[0058] 3. Solvent barrier performance

[0059] Since PC is prone to acetone-induced crystallization, acetone is used as the solvent for solvent barrier test. Figure 8 (a) and (b) are the reflectance spectrum and transmittance spectrum of PC sample (Example 1) protected by reflective ultraviolet cut-off film before and after 100 times of acetone wiping, respectively. It can be seen that after 100 times of acetone wiping, the reflectivity, light transmittance and sample physical insert of the sample have almost no change. However, from Figure 8As can be seen from (c) and (d), after 100 times of acetone wiping, the transmittance of the PC is reduced to below 60%, the haze is increased to 92.51%, and the transparency of the PC physical drawing is obviously reduced. It can be seen that the prepared reflective ultraviolet cutoff film has good solvent blocking effect.

Claims

1. A UV protective film on the surface of a polymer transparent part, characterized in that: The film is formed by alternating stacking of low-refractive-index layer materials and high-refractive-index layer materials; the low-refractive-index layer material is an organic silica sol material; the high-refractive-index layer material is a TiO2 sol material; each layer of the organic silica sol and the layer of the TiO2 sol alternately stacked is considered a cycle, and the cycle of the alternating stacking is 4 or 5; The organosilica sol is obtained by the following method: Set the water bath temperature to 28 °C, add methyltrimethoxysilane to isopropanol, stir, add deionized water dropwise, stir and react for 10 min, add glacial acetic acid dropwise, stir and react for 30 min, add GPTMS, stir and react for 10 min; finally, add hydrochloric acid, and stop the reaction after 48 h; then age in a water bath at 28 °C for 18 h, then add tetrabutylammonium hydroxide curing agent, and stir and react for 20 min.

2. The UV protective film for the surface of a transparent polymer part according to claim 1, wherein: The polymer transparent part is polycarbonate.

3. The method for preparing the ultraviolet protective film on the surface of a polymer transparent part according to claim 1 or 2, characterized in that: A low-refractive-index layer material sol and a high-refractive-index layer material sol are sequentially coated on the surface of the polymer transparent member, so that the two sols are deposited alternately.

4. The method for preparing a UV protective film on the surface of a polymer transparent part according to claim 3, wherein: The curing conditions for coating the first layer of organosilicon sol on the surface of the polymer transparent part are to raise the temperature to 70~90℃ and maintain it for 20~30 minutes, and then cool it down to 50℃; the curing conditions for each subsequent layer of sol are to cure at 40~60℃ for 30 minutes.

5. The method for preparing a UV protective film on the surface of a polymer transparent part according to claim 3, wherein: The sol is coated on the surface of the polymer transparent part by spin coating, with a spin coating speed of 5000 rpm to 7000 rpm and a spin coating time of 30s to 50s.

6. The method for preparing a UV protective film on the surface of a polymer transparent part according to claim 3, wherein: The low-refractive-index material organic silicon sol and the high-refractive-index material TiO2 sol are diluted with organic solvents to a mass concentration of 1.0-2.0%.

7. The method for preparing a UV protective film on the surface of a polymer transparent part according to claim 6, wherein: The sol was diluted with ethanol to a mass concentration of 1.5%.

8. Use of the UV protection film according to any one of claims 1 to 7 for UV protection on the surface of a transparent part.

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