Photosensitive polyurethane film with surface relief grating pattern and preparation method and application thereof

Abstract

The application relates to the field of optical encryption technology, and discloses a photosensitive polyurethane film with a surface relief grating pattern and a preparation method and application thereof, which comprises the following steps: under ice bath and inert atmosphere, first, toluene diisocyanate and a dihydropyridine photosensitizer monomer are added into a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide, then 1,4-dibutanol is added dropwise; the ice bath is removed, and the reaction is carried out at a temperature of room temperature to 60 DEG C to obtain a photosensitive polyurethane solution; the photosensitive polyurethane solution is spin-coated on a substrate and dried to obtain a photosensitive polyurethane film; and a designed mask plate is exposed on the surface of the photosensitive polyurethane film. In the application, the non-covalent interaction difference of the polymer-dihydropyridine / pyridine part can be constructed to realize effective surface patterning, and the optical anti-counterfeiting technology is combined to realize the generation of a two-dimensional ordered grating-like wrinkle structure with a sinusoidal phase on the surface of the polyurethane film through a wrinkling mode, so that pattern anti-counterfeiting is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical encryption technology, and in particular to a photosensitive polyurethane film with a surface relief grating pattern and a preparation method and application thereof. BACKGROUND

[0002] The surface structuring of light-induced dihydropyridine unit-containing films allows the creation of complex surface relief patterns with varying heights, which are difficult to form using traditional lithographic tools. A variety of grating patterns can be combined to create pixels with wide color gamut structural colors and bright grating structures on the film surface. As long as the material behavior is linear, this multiple patterning method can be used to create any Fourier optical surface, creating the potential for complex 3D surface relief with nanometer precision.

[0003] Previous studies have focused on building supramolecular hierarchical structures. Chinese Patent CN111845148A discloses an optical anti-counterfeiting element and a method for making the same, and Chinese Patent CN103576216A discloses an optical anti-counterfeiting element and an anti-counterfeiting product using the same, the preparation of which requires multiple surfaces (substrate, plating layer, and absorbing layer) to achieve iridescent structural color. Although there are currently a variety of techniques and methods for manufacturing wrinkle structures with different morphologies, developing a technique that can manufacture ordered and controllable one-dimensional or two-dimensional wrinkle structures on a large area of a polymer surface is still a major challenge. Among them, controlling the stress distribution state (size and direction) of the film surface during the wrinkle process of the film is particularly important for the final wrinkle structure morphology. SUMMARY

[0004] The present application addresses the problems in the current research field of polymer surface wrinkling, such as narrow selection range of polymer types, single method of wrinkle structure manufacturing, difficulty in controlling stress distribution state (size and direction) during the polymer surface wrinkling process, difficulty in manufacturing large-area ordered structures, and narrow application range of wrinkle structures in information recording and signal transmission fields. Based on the development direction of new polymer materials and new wrinkle structure manufacturing technologies, the present application proposes a strategy of combining photolithography technology and residual solvent directional diffusion technology to construct periodic wrinkle patterns (grating patterns) with precise aspect ratio wrinkles on a photosensitive polyurethane film by controlling the stress distribution state. This strategy can be regarded as a method of achieving new micro-patterning on the film surface, and the present application can freely encode the surface properties of the polymer film at room temperature. The present application combines optical anti-counterfeiting technology to achieve the generation of two-dimensional ordered grating-like wrinkle structures with sinusoidal phase on the surface of the polyurethane film by wrinkling, and in the visible light range, specific encrypted information (such as text, graphics, letters, etc.) can be successfully written using simple optical diffraction principles.

[0005] To achieve the above object, the application provides a preparation method of a photosensitive polyurethane film with a surface relief grating pattern, which comprises the following steps:

[0006] S1, under ice water bath and inert atmosphere, first, toluene diisocyanate and dihydropyridine photosensitizer monomer of formula (1) are mixed in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=1:0-4:1, v / v), stirring reaction (the time is preferably 0.5-3h), then 1,4-dibutanol is added dropwise;

[0007]

[0008] S2, the ice water bath in step S1 is removed, and the reaction system is reacted at room temperature to 60 DEG C to obtain a photosensitive polyurethane solution;

[0009] S3, the photosensitive polyurethane solution is spin-coated on a substrate, and dried to obtain a photosensitive polyurethane film with a thickness of 3-30 microns;

[0010] S4, using a UV exposure machine, a mask plate with a preset grating pattern is exposed on the surface of the photosensitive polyurethane film, and then the exposed photosensitive polyurethane film is immersed in an ethanol solution for development operation, so that the exposed area forms a relief grating pattern with a grating structure corresponding to the preset grating pattern, that is, a photosensitive polyurethane film with a surface relief grating pattern is obtained.

[0011] As a further preferred technical solution of the application, in step S1, the molar ratio of toluene diisocyanate and dihydropyridine photosensitizer monomer is 10-20:1, and the molar ratio of the amount of 1,4-dibutanol added dropwise to dihydropyridine photosensitizer monomer is 10-20:1.

[0012] As a further preferred technical solution of the application, in step S2, first, stirring reaction is carried out at room temperature for 8-24h, then heating reaction is carried out at 40 DEG C for 8-24h, and finally heating reaction is carried out at 60 DEG C for 8-24h.

[0013] As a further preferred technical solution of the application, in step S3, the spin coating program is 500-3500r spin coating for 10-30s.

[0014] As a further preferred technical solution of the application, in step S4, a direct writing exposure mode is used to expose the mask plate on the surface of the photosensitive polyurethane film, and the exposure parameters are as follows: the exposure wavelength is 365nm, the exposure time is 15-300s, and the power is 3-30w.

[0015] As a further preferred technical solution of the present application, the relief grating pattern is composed of a grating line group of periodically arranged grating lines with a line width of 1-10 microns and a period of 2-20 microns.

[0016] As a further preferred technical solution of the present application, the grating line group is composed of one convex grating line and one concave grating line, and the line width of the convex grating line and the concave grating line is 1-10 microns, and the adjacent convex grating line and concave grating line form a grating line group of a two-dimensional concave-convex structure with a depth difference of less than or equal to 100 nm.

[0017] According to another aspect of the present application, the present application also provides a photosensitive polyurethane film with a surface relief grating pattern, which is prepared by the above method.

[0018] According to another aspect of the present application, the present application also provides the use of a photosensitive polyurethane film with a surface relief grating pattern as an anti-counterfeiting label in pattern anti-counterfeiting.

[0019] The above technical solution of the present application can achieve the following beneficial effects:

[0020] 1) The present application effectively expands the photo-induced surface relief grating (SRG) material. So far, research has focused on building supramolecular hierarchical structures, while in the present application, the difference in non-covalent interaction of the polymer-dihydropyridine / pyridine moiety can be constructed to achieve effective surface patterning;

[0021] 2) The film with a surface having a grating pattern of the present application has a specific pattern made on the film surface for anti-counterfeiting, which can achieve the characteristics of anti-counterfeiting specificity, easy interpretation, etc. In addition, the developing method uses non-toxic and low-hazard anhydrous ethanol immersion, which is green and environmentally friendly, and the immersion time only needs 3-30 seconds, which is simple to operate and efficient;

[0022] 3) The present application can be adjusted by the content of photosensitive monomer and the content of chain extender to achieve a more optimal ratio of SRG formation. These irreversible mechanical changes of the polymer in the photosensitive polyurethane are further utilized in many studies on hardness, stiffness, creep elastic modulus and creep coefficient.

[0023] 4) The present application can freely code the surface properties of the polyurethane film at room temperature, and combines optical anti-counterfeiting technology to realize the generation of a two-dimensional ordered grating-like wrinkle structure with a sinusoidal phase on the surface of the polyurethane film through wrinkling, and successfully writes specific encrypted information (such as words, graphics, letters, etc.) in the visible light range using simple optical diffraction principles, thereby realizing relief grating patterning for pattern anti-counterfeiting. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Figure 1 It is the mass spectrometry diagram of the pyridine structure formed after the ultraviolet light irradiation dehydration of the dihydropyridine photosensitizer monomer (DHPDO).

[0026] Figure 2 It is the POM diagram of the local surface relief grating of the thin film sample obtained in Example 1.

[0027] Figure 3 It is the AFM diagram of the surface relief grating formed on the thin film sample obtained in Example 1, where (a) is the two-dimensional plan view of AFM, (b) is the three-dimensional stereogram of AFM, and (c) is the concave-convex grating diagram of AFM.

[0028] Figure 4 It is the physical display diagram of the thin film sample obtained in Example 1. (a) is the iridescence diagram of the inner frame of the character "回" in the anti-counterfeiting pattern, and (b) is the iridescence diagram of the outer frame of the character "回" in the anti-counterfeiting pattern.

[0029] The realization of the object, functional features and advantages of the present invention will be further described in conjunction with the embodiments and referring to the accompanying drawings. Specific Embodiments

[0030] The specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0031] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0032] The dihydropyridine photosensitizer monomer provided by the present invention has the following molecular structural formula:

[0033]

[0034] This photosensitizer monomer can be synthesized through the following route:

[0035]

[0036] In a specific embodiment, its synthesis method is as follows:

[0037] (1) Synthesis of the compound dihydropyridine photosensitizer monomer (NDHP)

[0038] A1. Weigh 5-hydroxy-2-nitrobenzaldehyde 16.712 g (10 mmol, 1 eq) into a suitable amount of ethanol to form a homogeneous solution, and then add trifluoroacetic acid 27 ml (3.5 mmol, 3 eq) under stirring at 0°C ice water bath;

[0039] A2. Measure 150 ml of anhydrous ethanol to dissolve 3-amino methyl crotonate 34.54 g (30 mmol, 3 eq), and then gradually add the anhydrous ethanol solution (150 ml) containing 3-amino methyl crotonate into the solution of A1 under stirring at 0°C ice water bath, and react for 8 h under stirring at 0°C ice water bath;

[0040] A3. After the reaction is completed, add a large amount of deionized water to precipitate, filter, heat the cut-off material with a small amount of ethanol to dissolve, and recrystallize to obtain the purified target product NDHP, and then dry and weigh (the yield is 70%).

[0041] (2) Synthesis of intermediate A

[0042] B1. Dissolve 3,5-dibromophenol (10.00 g, 39.70 mmol) and 1,4-dihalobutane (3 eq, 59.55 mmol) in 100 mL of acetone, and add K2CO3 (16.46 g, 119.09 mmol), and reflux at 80°C under inert gas atmosphere for 48 h, wherein the halogen atom of 1,4-dihalobutane is Br, and of course, it can also be Cl or I;

[0043] B2. After the reaction is completed, cool the reaction solution to room temperature, wash with petroleum ether, and purify by silica gel column chromatography under reduced pressure to obtain intermediate A (x is Br) in the form of a colorless transparent liquid (the yield is 90%).

[0044] (3) Synthesis of intermediate B

[0045] C1. Dissolve NDHP (3.15 g, 8.70 mmol) in acetone (150 mL), and add K2CO3 (10.81 g, 78.33 mmol), and then add intermediate A (1 eq, 26.11 mmol) into the reaction system under stirring at 80°C under inert gas atmosphere; reflux and stir for 36 h under inert gas atmosphere;

[0046] C2. After the reaction is completed, wash with petroleum ether, and purify by silica gel column chromatography to obtain intermediate B (x is Br) in the form of a light yellow solid (the yield is 60%).

[0047] (4) Synthesis of dihydropyridine photosensitizer monomer (DHPDO)

[0048] D1. In an inert gas glove box, intermediate B (1 eq, 19.83 mmol) was dissolved in tetrahydrofuran (100 mL) to obtain a homogeneous solution, and then 2M K2CO3 aqueous solution (70 mL) and 4-hydroxymethylphenylboronic acid (5.71 g, 49.58 mmol) were added;

[0049] D2. A catalytic amount of tetrakis(triphenylphosphine)palladium(0) (Pd[P(C6H5)3]4)) (0.02 eq, 0.397 mmol) was quickly added to the above solution, and the mixture was stirred under reflux for 72 h under an inert gas atmosphere;

[0050] D3. After the reaction was completed, the oil after washing with petroleum ether was dissolved in a small amount of methanol solution, and the product was purified by using a large amount of deionized water to obtain a novel hydroxyl-containing dihydropyridine photosensitizer (DHPDO) (yield 76%).

[0051] The dihydropyridine photosensitizer monomer is based on the ultraviolet light sensitivity of the dihydropyridine unit, and its structure can undergo intramolecular dehydration under ultraviolet light, thereby realizing its photosensitivity. The photosensitivity of DHPDO can be verified by mass spectrometry, as shown in Figure 1 Based on this property, the present application proposes a photosensitive polyurethane film with a surface relief grating pattern prepared by using the dihydropyridine photosensitizer monomer as a raw material, which can be used as a security label to achieve pattern security. In order to further understand the technical solutions of the present application by those skilled in the art, the technical solutions of the present application are further described in detail through specific examples.

[0052] Example 1:

[0053] (1) Toluene diisocyanate TDI (16.8 mmol) was injected into a magnetic stirring inert gas atmosphere container, and stirred at 0°C under ice water bath conditions for 10-60 min;

[0054] (2) In an inert atmosphere glove box, the weighed dihydropyridine photosensitizer monomer DHPDO (1 mmol) was dissolved in a mixed solvent of anhydrous grade N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO (DMF:DMSO = 4:1, v / v);

[0055] (3) Under the ice water bath conditions at 0°C, the solution of dihydropyridine photosensitizer monomer DHPDO in step (2) was added dropwise to the toluene diisocyanate solution in step (1), and stirred under ice water bath for 0.5-3.5 h;

[0056] (4) ice bath conditions under drop injection 15mmol 1, 4-dibutanol BDO, then remove the ice bath, room temperature stirring reaction 8~24h, 40℃ heating reaction 8~24h, 60℃ heating reaction 8~24h, finally get photosensitive polyurethane solution;

[0057] (5) 2.5x2.5 glass base after UV 15min is placed on the spin coater, 50uL photosensitive polyurethane solution is taken and spin coated on the glass substrate, the spin coating procedure is 3500r spin coating 30s, post drying, the photosensitive polyurethane film with a thickness of 30μm is obtained.

[0058] (5) using direct writing exposure mode, the mask plate is exposed on the surface of the photosensitive polyurethane film, the exposure parameters are as follows: the exposure wavelength is 365nm, the exposure time is 15~100s, and the power is 3~30w; the template adopts a "hui" shaped grating stripe pattern, which includes an inner frame grating line group and an outer frame grating line group, the stripes of the inner frame grating line group and the outer frame grating line group are inclined at an angle of 15 degrees, and both the inner frame grating line group and the outer frame grating line group are composed of periodic arrangement of grating lines with a line width of 5μm and a period of 10μm.

[0059] (6) the exposed photosensitive polyurethane film is immersed in ethanol solution for development operation, and the surface relief grating encryption "hui" shaped pattern is formed after blowing dry, that is, the film with the surface having the grating encryption pattern is obtained. Due to the certain inclination angle between the inner and outer frame stripes, different pattern effects are achieved at different observation angles.

[0060] Figure 2 The surface relief grating POM map of the film sample obtained in example 1 is shown in the figure, and it can be seen from the figure that the grating line group is formed on the surface of the film substrate in a periodic arrangement.

[0061] Figure 3 The AFM map of the surface relief grating formed on the film sample obtained in example 1 is shown in the figure, and it can be seen from the figure that the convex height, i.e. the peak height, is 15.7nm, the concave part, i.e. the valley, is 13.7nm, the total height difference of the grating is 29.4nm, and the natural light visible iridescent structural color can be formed by the grating.

[0062] Figure 4 The real object display map of the photosensitive polyurethane film of the present embodiment at different viewing angles is shown in the figure, by adjusting the angle, the inner frame of the "hui" shaped pattern is displayed, then by adjusting the film inclination angle to about 15 degrees to one side, the outer frame of the "hui" shaped pattern is displayed, and the inner frame is hidden.

[0063] When the stress of the ultraviolet light irradiation area of the photosensitive polyurethane film reaches a certain critical value due to the formation of hydrogen bonds, mechanical instability occurs on the surface of the film, which in turn induces the film to undergo buckling deformation. The film that only undergoes ultraviolet exposure treatment in a local area shrinks in volume due to the new intermolecular forces generated in the irradiation area, which in turn causes the unexposed part around it to swell to a certain extent. This result correspondingly causes the contracted exposed area to have a greater modulus than the unexposed area in the swollen state, which can be derived from the modulus difference in the AFM test. It can be applied to the anti-fake signature in banknotes to realize the visible observation of the rainbow structural color under natural light.

[0064] Although the specific embodiments of the present application are described above, those skilled in the art should understand that these are only illustrative, and various changes or modifications can be made to the present embodiments without departing from the principles and essence of the present application, and the protection scope of the present application is only limited by the appended claims.

Claims

1. A method for producing a photosensitive polyurethane film with a surface relief grating pattern, characterized by, The method comprises the following steps: S1, under ice water bath and inert atmosphere, first toluene diisocyanate and the following formula (1) structure of dihydropyridine photosensitizer monomer is added in the mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide, after stirring reaction is completed, 1, 4-dibutanol is added dropwise; （1）； S2, remove the ice water bath in step S1, the reaction system is reacted at room temperature to 60 ℃, and a photosensitive polyurethane solution is obtained; S3, the photosensitive polyurethane solution is spin coated on the substrate, dried, and a photosensitive polyurethane film is obtained; S4, using ultraviolet exposure machine, the mask plate with preset grating pattern is exposed on the surface of the photosensitive polyurethane film, then the exposed photosensitive polyurethane film is immersed in anhydrous ethanol for development operation, so that the exposed area forms a relief grating pattern with the grating structure corresponding to the preset grating pattern, that is, a photosensitive polyurethane film with surface relief grating pattern is obtained.

2. The method for preparing a photosensitive polyurethane film with a surface embossed grating pattern according to claim 1, characterized in that, In step S1, the molar ratio of toluene diisocyanate and dihydropyridine photosensitizer monomer is 10-20:1, and the molar ratio of the amount of 1, 4-dibutanol added to dihydropyridine photosensitizer monomer is 10-20:

1.

3. The method for preparing a photosensitive polyurethane film with a surface relief grating pattern according to claim 1, characterized in that, In step S2, first, the reaction is stirred at room temperature for 8-24 h, then heated at 40 ℃ for 8-24 h, and finally heated at 60 ℃ for 8-24 h.

4. The method for preparing a photosensitive polyurethane film with a surface embossed grating pattern according to claim 1, characterized in that, In step S3, the spin coating program is 500-3500 r spin coating for 10-30 s.

5. The method for preparing a photosensitive polyurethane film with a surface relief grating pattern according to claim 1, characterized in that, In step S3, a glass substrate is used, and the glass substrate is irradiated with ultraviolet light for 15 min before spin coating.

6. The method for preparing a photosensitive polyurethane film with a surface relief grating pattern according to claim 1, characterized in that, In step S4, a direct writing exposure mode is used to expose the mask plate on the surface of the photosensitive polyurethane film, and the exposure parameters are as follows: the exposure wavelength is 365 nm, the exposure time is 15-300 s, and the power is 3-30 w.

7. Process for the production of a photosensitive polyurethane film with a surface relief grating pattern according to any one of claims 1 to 6, characterized in that, The relief grating pattern is composed of a grating line group composed of periodically arranged grating lines with a line width of 1-10 μm and a period of 2-20 μm.

8. The method for preparing a photosensitive polyurethane film with a surface relief grating pattern according to claim 7, characterized in that, The grating line group is composed of a convex grating line and a concave grating line, and the line width of the convex grating line and the concave grating line is 1-10 μm, and the adjacent convex grating line and concave grating line form a two-dimensional concave-convex structure grating line group with a depth difference less than or equal to 100 nm.

9. A photosensitive polyurethane film with a surface relief grating pattern, prepared by the method of any one of claims 1-7.

10. The use of the photosensitive polyurethane film with a surface relief grating pattern of claim 9 as an anti-counterfeiting label in pattern anti-counterfeiting.

Images