UV stabilization optical nanoimprint lithography resin

Abstract

SOLUTION: To provide a UV stabilization optical nanoimprint lithography (P-NIL) resin, wherein the P-NIL resin includes an organic binder, titanium oxide (TiO2) inorganic nanoparticles dispersed in the P-NIL resin, and a photoinitiator for polymerization of acrylate; the organic binder is selected from the group consisting of an acrylate monomer component, an acrylate oligomer polymerizable component and an acrylated polymer, the titanium oxide inorganic nanoparticles have a coating on the titanium oxide particles, or one or more plurality of metal oxides added into the titanium oxide particles, and the metal oxide is selected from the group consisting of SiO2, Al2O3, ZrO2, SnO2, and NiO; and P-NIL resin may contain a radical scavenger selected from the group consisting of an HALS system, an ascorbic acid system, and a hydroquinone system, and may contain an adhesion accelerator for acrylate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] (Reference to Related Applications) This application claims priority based on U.S. Provisional Patent Application No. 63 / 608,629, filed on December 11, 2023.

[0002] The present invention generally relates to nanoimprint lithography, and more particularly to resins used in nanoimprint lithography.

Background Art

[0003] Imprint lithography is a method for economically embossing a structure on a hard substrate used in mass-producing optical components, optoelectronic components, or electronic components including nanometer-sized structures. When the structure is on the micrometer scale or nanometer scale, the terms microimprint lithography or nanoimprint lithography are used. In the case of curing by UV photolysis, the terms photo-nanoimprint lithography, or P-NIL, or UV-NIL have been used in place of 2P (photopolymer) that was more commonly used in the past.

[0004] In one form of NIL, an imprint resin, which is a curable resin, is applied to a pattern or mold, and the resin is polymerized and cured by heat or photolysis. If the material with the transferred shape is peeled off from the mold, the mold can be reused. Generally, the NIL technique is expected to achieve cost reduction, cycle time shortening, and yield improvement in the manufacturing process of sub-micrometer components of small devices. Photo-nanoimprint lithography (P-NIL) or UV nanoimprint lithography (UV-NIL) can be said to be a cost-effective processing method used in mass-producing optical components, optoelectronic components, or electronic components including nanometer-sized structures.

[0005] In general P-NIL processing, a liquid resin is coated or applied onto a substrate such as glass or silicon. This resin may contain a solvent. When the resin contains a solvent, the solvent is removed by heating the resin on the substrate. A stamp or master template containing nanostructured features is pressed onto the resin, and then the resin is cured by photolysis using ultraviolet (UV), heat, or visible light. After the stamp is removed, the embossed product is completed. For P-NIL or 2P resins, high tensile strength and stiffness are important mechanical properties. Also, for P-NIL resins, lack of shrinkage during and in the cured state is an important property.

[0006] The P-NIL technique can be used for the manufacture of photonic and optical applications such as diffusers for controlling the phase of transmitted light and diffractive optical elements (DOEs) including waveguides. In these applications, the refractive index (RI) of the resist is an important consideration. In the optical field, the refractive index of a material represents how fast light passes through that material.

[0007] High refractive index (high RI) materials are employed in personal devices for augmented reality (AR), virtual reality (VR), or mixed reality (MR), and optical applications such as lenses and waveguides. By increasing the refractive index, the field of view can be expanded and high refractive index glass can be realized. By the NIL technique using a resin matched to the high refractive index of the glass or substrate, structures can be embossed onto the high refractive index glass to prevent reflection. UV-curable P-NIL has the economic advantage of a fast UV-curing process and is a commonly used method.

[0008] Generally, a high refractive index NIL resin is a hybrid resin of a polymerizable organic component and a high refractive index inorganic filler. The inorganic filler is composed of nanoparticles of a high refractive index metal oxide covered with an organic layer to prevent aggregation. Generally, as the metal oxide, titanium dioxide (TiO2) that does not absorb light in the visible region and has an essentially high refractive index in the range of 2.7 to 2.9 at 589 nm due to its crystal structure is used.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The drawback of TiO2 in P-NIL resin is that it acts as a photocatalyst by UV light, absorbs UV light, and generates reactive oxygen species (ROS) in the presence of oxygen to deteriorate the organic components in the medium. When the polymer film and the organic capping material deteriorate, yellowing of the film, loss of integrity of the polymer network, and decrease in refractive index, which are considered to be due to aggregation of nanoparticles, occur. Degradation by UV can progress very rapidly, and some TiO2-containing P-NIL resins are virtually destroyed within hours even under relatively mild UV stress conditions used in the method according to the ASTM standard for evaluating the UV stability of plastics in sunlight.

[0010] Thus, a P-NIL resin with high refractive index and UV stability that does not deteriorate even when exposed to sunlight is desired.

Means for Solving the Problems

[0011] In one embodiment, a UV-stabilized photo-nanoimprint lithography (P-NIL) resin is disclosed. The P-NIL resin includes an organic binder, titanium oxide inorganic nanoparticles dispersed in the P-NIL resin, and a photoinitiator for acrylate polymerization. The organic binder is selected from the group consisting of an acrylate monomer component and an acrylate oligomer polymerizable component. The titanium oxide inorganic nanoparticles have one or more metal oxides coated on the titanium oxide particles or added to the titanium oxide particles, and the metal oxides are selected from the group consisting of SiO2, Al2O3, ZrO2, SnO2, and NiO. The P-NIL resin may include a radical scavenger selected from the group consisting of HALS-based, ascorbic acid-based, and hydroquinone-based, and may also include an adhesion promoter for acrylate.

[0012] In another embodiment, a photo-nanoimprint lithography (P-NIL) resin is disclosed. The resin includes a polymerizable organic component, nanoparticles containing titanium oxide or titanium oxide, and a photoinitiator for curing the polymerizable organic component. The nanoparticles are modified with one or more additional metal oxides selected from the group consisting of SiO2, Al2O3, ZrO2, SnO2, and NiO.

[0013] Also disclosed is a method for processing a high-resolution nanometer structure using a UV-stabilized photo-nanoimprint lithography (P-NIL) resin. The method includes providing a P-NIL resin comprising a polymerizable organic component, titanium oxide nanoparticles modified with one or more additional metal oxides selected from the group consisting of SiO2, Al2O3, ZrO2, SnO2, and NiO, and a photoinitiator; applying the resin onto a substrate; pressing a mold including a nanometer-sized structure against the resin; curing the resin using ultraviolet (UV) light; and removing the mold to impart a nanometer-sized structure to the cured resin.

Brief Description of the Drawings

[0014]

Figure 1

[0015] Here, reference is made to the P-NIL process shown in the drawings, particularly FIG. 1. In this specification, a photo-nanoimprint lithography (P-NIL) resin 100 having a high refractive index and high mechanical performance used in photo-nanoimprint lithography (P-NIL) or UV nanoimprint lithography, and a method of formulating the P-NIL resin 100 for P-NIL applications are disclosed. The P-NIL resin 100 can be a high refractive index organic / inorganic resin used for P-NIL applications. Further, the P-NIL resin 100 can have a refractive index (RI) substantially higher than that of conventional organic resins and exhibit acceptable mechanical or toughness performance characteristics. The P-NIL resin 100 can be configured to be suitable for use in photonic and optical applications such as optical diffusers and waveguides, as well as in AR / VR / MR devices.

[0016] As shown in FIG. 1, the P-NIL process is carried out using the P-NIL resin 100 disclosed herein. When carrying out the P-NIL process, as shown in FIG. 1(a), the P-NIL resin 100 is supplied or “coated” onto the substrate 102 via a coating device 104. The P-NIL resin 100 may contain any solvent. When the P-NIL resin 100 contains a solvent, as shown in FIG. 1(b), after coating the P-NIL resin 100 onto the substrate 102, heat 106 can be applied thereto to evaporate the solvent, thereby removing the solvent. This is a technique generally known in the art. Next, as shown in FIGS. 1(c) to 1(d), a stamp 108 called a pattern is pressed against the P-NIL resin 100. The stamp 108 can include a nanometer structure 110 that is embossed on the P-NIL resin 100. As shown in FIG. 1(d), the P-NIL resin 100 can be cured by photolysis 112 using UV light or visible light. Finally, as shown in FIG. 1(e), the stamp 108 is removed, whereby a transferred nanometer structure 110 is provided on the cured P-NIL resin 100.

[0017] In one embodiment, the P-NIL resin 100 is composed of an organic compound or an organic binder and inorganic nanoparticles being mixed in a pre-polymerized liquid medium. The P-NIL resin 100 containing both an organic compound and inorganic nanoparticles can be used at room temperature in the P-NIL technology, maintain a high refractive index value, and maintain excellent mechanical properties, for example, at the glass transition point. By improving the refractive index of the P-NIL resin 100, miniaturization of devices in photonic and optical applications such as optical diffusers, waveguides, and optical elements for AR / VR / MR applications becomes possible.

[0018] The organic compound can be selected from the group consisting of acrylate monomers, oligomers, and acrylated polymers having an RI value greater than 1.4 at 589 nm.

[0019] The inorganic nanoparticles of P-NIL resin 100 are nanometer-sized particles of titanium oxide (titania, TiO2) that have been changed so that the oxidation effect by the photocatalyst is suppressed. In order to avoid light scattering and maintain the transparency of the formulation, it is desirable that these particles have a size of 50 nm or less, or 30 nm or less, and a high refractive index of 1.6 or more at 589 nm.

[0020] In conventional titanium oxide (TiO2), the oxidation effect by the photocatalyst is suppressed by adding another metal oxide or a mixture of metal oxides to titanium oxide (TiO2). Usable metal oxides include silicon dioxide (SiO2), aluminum oxide (Al2O3), stannic oxide (SnO2), nickel oxide (NiO), zirconium oxide (ZrO2), and the like. These metal oxides prevent oxygen from reaching the photoactivated TiO2 particles and inactivate the photoactivated TiO2, thereby suppressing the generation of reactive oxygen species. Then, by a method generally known in the art, the changed TiO2 particles are capped with an organic capping agent to promote dispersion and suppress aggregation.

[0021] Furthermore, P-NIL resin 100 may contain an antioxidant that removes reactive oxygen species. Examples of antioxidants that can be incorporated into P-NIL resin 100 include hindered amine light stabilizers (HALS) such as commercially available Tinuvin (registered trademark) products, hydroquinone-based compounds, ascorbic acid, and related hydroxy compounds. By removing a small amount of reactive oxygen species with these agents, the lifespan of the high refractive index film after curing can be further extended.

[0022] By further adding a monomer, an oligomer, and an additive to the P-NIL resin 100, an appropriate viscosity can be maintained when transferring the master or working stamp used in P-NIL applications to the P-NIL resin 100. The acrylate monomers and oligomers used in these resins are selected to maintain appropriate fluidity for P-NIL applications so that the P-NIL resin 100 can be poured into the working stamp by capillary action. The UV catalyst used in the P-NIL resin 100 may be a commercially available UV catalyst, and such a UV catalyst is designed to cause a radical reaction by irradiating UV-A light from a mercury lamp or UV from 320 nm to 405 nm from an LED.

[0023] Example

[0024] In one embodiment of the formulation, an acrylate-based resin containing a mixture of acrylate monomers and oligomers, a Tinovin® HALS antioxidant, a radical initiator, and an adhesion promoter is mixed with titanium oxide nanoparticles containing tin oxide and zirconium oxide in an amount such that the refractive index of the cured film at 589 nm is 1.71. (Formulation A)

[0025] In another embodiment of the formulation, an acrylate-based resin containing a mixture of acrylate monomers and oligomers, a Tinovin® HALS antioxidant, a radical initiator, and an adhesion promoter is mixed with titanium oxide nanoparticles containing aluminum oxide and zirconium oxide in an amount such that the refractive index of the cured film at 589 nm is 1.76. (Formulation B)

[0026] In yet another embodiment of the formulation, an acrylate-based resin containing a mixture of acrylate monomers and oligomers, a Tinovin® HALS antioxidant, a radical initiator, and an adhesion promoter is mixed with titanium oxide nanoparticles containing tin oxide and zirconium oxide in an amount such that the refractive index of the cured film at 589 nm is 1.79. (Formulation C)

[0027] In yet another embodiment of the formulation, an acrylate resin containing a mixture of acrylate monomers and oligomers, a HALS antioxidant of Tinovin®, a radical initiator, and an adhesion promoter is mixed with titanium oxide nanoparticles containing tin oxide and aluminum oxide in an amount such that the refractive index of the cured film at 589 nm is 1.83. (Formulation D)

[0028] In yet another embodiment of the formulation, an acrylate resin containing a mixture of acrylate monomers and oligomers, a HALS antioxidant of Tinovin®, a radical initiator, and an adhesion promoter is mixed with titanium oxide nanoparticles containing tin oxide and zirconium oxide in an amount such that the refractive index of the cured film at 589 nm is 1.85. (Formulation E)

[0029] In yet another embodiment of the formulation, an acrylate resin containing a mixture of acrylate monomers and oligomers, a HALS antioxidant of Tinovin®, a radical initiator, and an adhesion promoter is mixed with titanium oxide nanoparticles containing tin oxide and zirconium oxide in an amount such that the refractive index of the cured film at 589 nm is 1.93. (Formulation F)

[0030] For comparison, formulations (Formulations X1 and X2) using TiO2 nanoparticles without additional metal oxides were prepared. These were formulated in the same manner as Formulations A - F with respect to the acrylate resin and initiator, except that no metal oxide was added.

[0031] Results

[0032] The UV stability of the formulation was evaluated by measuring the refractive index of a cured film with a thickness of 0.8 to 2.0 microns coated on glass. The film was exposed to UV light in a Q-Sun (registered trademark) xenon arc tester (Q-Lab Corporation) using a DaylightQ filter that generates an irradiance spectrum corresponding to outdoor sunlight. The conditions employed were 0.35 W / (m 2 ·nm) at 340 nm and 45 °C. The evaluation criterion for the destruction of the high refractive index film by UV is a decrease in the refractive index of 0.05 RI units at 589 nm. For example, if the initial refractive index of the high refractive index film at 589 nm was 1.75, a decrease in the refractive index of the film to 1.70 or less is classified as destruction. From a practical perspective, this level of refractive index decrease corresponds to a film that is judged unacceptable in the initial structure of the device. The table presents the results of the UV stability test.

[0033] The film of formulation X1 containing titanium oxide nanoparticles at a low concentration was destroyed within 2 days after irradiation. The film of formulation X2 containing titanium oxide nanoparticles at a higher concentration was destroyed within 1 day after irradiation. The films of formulations containing titanium oxide nanoparticles with added metal oxides were much more stable to irradiation than those without added metal oxides and HALS agents. Films (A, B) with a low titanium oxide content showed good stability even after 10 days of irradiation. Films (C, D) with a medium titanium oxide content showed stability for several days. Films (D, E) with a high titanium oxide content showed stability for about 2 days.

[0034] Table showing the results of UV irradiation of a P-NIL formulation coated on glass ab TIFF2025102700000002.tif155156

[0035] (Industrial Applicability) The present invention provides a method for processing high-resolution nanometer structures using a UV-stabilized photo-nanoimprint lithography (P-NIL) resin. This method can be industrially applied in various fields where nanofabrication is required, such as the manufacture of optical devices, augmented reality, virtual reality, mixed reality, semiconductor processing, biotechnology, and the like. According to the method of the present invention, by using a P-NIL resin comprising a polymerizable organic component, titanium oxide nanoparticles modified with one or more additional metal oxides selected from the group consisting of SiO2, Al2O3, ZrO2, SnO2, and NiO, and a photoinitiator, it becomes possible to create high-resolution nanoscale structures with excellent optical and mechanical properties.

[0036] The method according to the present invention comprises the steps of coating this resin on a substrate, pressing a mold containing a nanometer-sized structure against the resin, curing the resin using ultraviolet light, and removing the mold to impart a high-resolution nanometer structure to the cured resin. In the curing process, UV-A light from an LED light source is used, and the curing process may be performed in a nitrogen atmosphere or an inert atmosphere to reduce oxygen inhibition.

[0037] The method according to the present invention is useful in the manufacture of optical devices and can be employed, for example, in the manufacture of photonic devices such as optical waveguides, diffusers, and lenses. In photonic devices, precise nanoscale structures are required to control the transmission and refraction of light. The titanium oxide nanoparticles modified with the above-described metal oxides can reduce degradation by photocatalysis and improve the lifespan and optical performance of the processed structure. In the technical fields of augmented reality, virtual reality, and mixed reality, a P-NIL resin having a high refractive index and UV stability is an ideal material for manufacturing lightweight and compact optical components that improve the field of view and optical clarity.

[0038] By using a transparent mold, the irradiation of ultraviolet rays becomes uniform, and it becomes possible to accurately reproduce a nanostructure while minimizing defects. In addition, by curing the resin under a nitrogen atmosphere or an inert atmosphere, oxygen inhibition is prevented, so that it can polymerize firmly and a mechanically stable product can be manufactured. Furthermore, by using a UV-A LED light source, the curing time can be shortened while accurately controlling the photopolymerization process, so that the energy consumption can be reduced and the efficiency can be improved. The versatility of the method according to the present invention, the adaptability to various substrates, and the compatibility with advanced manufacturing technologies indicate that the industrial applicability of the present invention is extremely high, enabling technological progress in various fields.

Claims

1. A UV-stabilized photo-nanoimprint lithography (P-NIL) resin comprising: an organic binder; The titanium oxide (TiO ２ ) inorganic nanoparticles dispersed in the P-NIL resin, and a photoinitiator for polymerization of acrylate; wherein the organic binder is selected from the group consisting of an acrylate monomer component, an acrylate oligomer polymerizable component, and an acrylated polymer. The titanium oxide inorganic nanoparticles have one or more metal oxides coated on the titanium oxide particles or added to the titanium oxide particles, and the metal oxide is SiO ２ , Al ２ O ３ , ZrO ２ , SnO ２ , selected from the group consisting of NiO The UV-stabilized photo-nanoimprint lithography (P-NIL) resin is characterized by the above.

2. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, further comprising a radical scavenger selected from the group consisting of HALS-based, ascorbic acid-based, and hydroquinone-based radical scavengers. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin is characterized by the above.

3. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, further comprising an adhesion promoter for acrylate. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin is characterized by the above.

4. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, further comprising a radical scavenger selected from the group consisting of hindered amine light stabilizers (HALS), ascorbic acid compounds, and hydroquinone derivatives. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin is characterized by the above.

5. The titanium oxide nanoparticles are coated with ２ SiO ２ and ZrO. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, is characterized by the above.

6. The average size of the nanoparticles is less than 50 nm. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, is characterized by the above.

7. The refractive index of the polymerizable organic component is greater than 1.4 at 589 nm. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, is characterized by the above.

8. The refractive index of the cured resin is greater than 1.7 at 589 nm. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, is characterized by the above.

9. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, further comprising an adhesion promoter selected from silane-based adhesion promoters. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin is characterized by the above.

10. The photoinitiator is selected to be activated by UV-A light of 320 - 400 nm. The UV-stabilized photo-nanoimprint lithography (P-NIL) resin according to claim 1, is characterized by the above.

11. A photo-nanoimprint lithography (P-NIL) resin comprising: a polymerizable organic component; Titanium oxide, or SiO ２ , Al ２ O ３ , ZrO ２ , SnO ２ nanoparticles having titanium oxide modified with one or more additional metal oxides selected from the group consisting of NiO, and a photoinitiator for curing the polymerizable organic component; wherein A photo-nanoimprint lithography (P-NIL) resin, characterized by the following.

12. The nanoparticles are covered with an organic coating to prevent aggregation. The photo-nanoimprint lithography (P-NIL) resin according to claim 11, characterized by the above.

13. The titanium oxide nanoparticles are modified by a combination of one or more additional metal oxides. The photo-nanoimprint lithography (P-NIL) resin according to claim 11, characterized by the above.

14. The resin further contains an additive for adjusting the viscosity, improving the transfer performance. The photo-nanoimprint lithography (P-NIL) resin according to claim 11, characterized by the above.

15. The polymerizable organic component is composed of a mixture of acrylate monomers and oligomers. The photo-nanoimprint lithography (P-NIL) resin according to claim 11, characterized by the above.

16. The photoinitiator is sensitive to UV-A light and visible light. The photo-nanoimprint lithography (P-NIL) resin according to claim 11, characterized by the above.

17. The cured resin is suitable for optical waveguides and augmented reality devices. The photo-nanoimprint lithography (P-NIL) resin according to claim 11, characterized by the above.

18. A method for processing high-resolution nanometer structures using a UV-stabilized photo-nanoimprint lithography (P-NIL) resin, comprising: A P-NIL resin comprising a coincident organic component and titanium oxide nanoparticles modified with one or more additional metal oxides selected from the group consisting of SiO ２ , Al ２ O ３ , ZrO ２ , SnO ２ , NiO, and a photoinitiator is provided. Coating the resin on a substrate; Pressing a mold containing nanometer-sized structures against the resin; Curing the resin using ultraviolet (UV) light; Removing the mold to impart nanometer-sized structures to the cured resin. The method is characterized by comprising the above steps.

19. The method further comprises adding an additional component to the P-NIL resin, The component is selected from the group consisting of radical scavengers, adhesion promoters, and polymerizable organic compounds having a refractive index greater than 1.4 at 589 nm. The refractive index of the cured resin is greater than 1.7 at 589 nm. The method according to claim 18, characterized by the above.

20. Adjusting the average diameter of the nanoparticles to be less than 50 nm to minimize light scattering and enhance optical transparency. The method according to claim 19, characterized by the above.

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