A method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film

Abstract

The present application relates to the technical field of volume holographic thin film waveguide production, and specifically to a method for processing a resin substrate for volume holographic liquid crystal polymer film transfer. The processing method specifically comprises: after ozone cleaning and UV cleaning of the surface of the resin substrate coated with a functional coating, spin coating a mixed monomer treatment liquid comprising trimethylolpropane allyl ether and trimethylolpropane diallyl ether on the surface of the resin substrate to form a hydrophilic group substrate; further spin coating or scraping an acrylic ester glue on the surface of the hydrophilic group substrate, and performing a UV curing treatment. The present application adopts a polymer synthesis method to modify the surface of the resin substrate through hydrogen bonding, and completely changes the surface of the resin substrate after curing, thereby facilitating the attachment of the acrylic ester glue.

Description

Technical Field

[0001] The present application relates to the technical field of volume holographic thin film waveguide production, and in particular to a method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film. Background Art

[0002] Polarization volume grating (PVG) is a new type of holographic grating that produces periodic refractive index variations by periodically rotating the optical axis of liquid crystal molecules. Compared to traditional volume gratings, PVGs offer higher refractive index modulation and a wider response bandwidth, addressing the limited field of view (FOV) of traditional gratings and making them more suitable for near-eye display waveguides. PVGs also possess polarization sensitivity, which is lacking in traditional gratings, ensuring high transmittance at wide FOVs. They can also be customized in small or large sizes depending on the application, expanding the application range of optical waveguide coupling components. PVG technology, with its exceptional wide-angle Bragg diffraction properties and excellent polarization response, has made significant progress in recent research and development. It not only provides a wider field of view for lightweight waveguide display systems but also introduces new design dimensions and application potential to the field of lightweight optical displays.

[0003] Lightweight optical waveguide technology currently relies on glass as its substrate. High-density, brittle glass adds extra weight and unavoidable safety risks to glasses, making the use of safe and reliable resin lenses a must for lightweight optical waveguides. Currently, the development of diffractive optical waveguides based on wafer-level resin substrates has been hindered by the inherent surface tension of the resin, making it difficult for photoresist to adhere properly. Therefore, the resin substrate surface must be modified.

[0004] Typically, wafer-level resin surfaces are coated with coatings such as hardening agents and antireflection films. These coatings enhance the optical performance and structural stability of the resin substrate, but they also increase the surface tension of the resin itself, making it difficult for the photoresist to adhere. Therefore, the resin surface requires further treatment to improve its surface properties.

[0005] Currently, existing technologies use traditional methods such as plasma cleaning and glass cleaning to remove oxides from the surface of resin substrates, thereby achieving a smooth and clean surface. However, this method is ineffective and does not directly address the surface tension of the resin surface itself. While the addition of leveling agents can improve surface properties to a certain extent, the addition of solvents can also easily damage the surface of the resin substrate, thereby affecting optical performance. Summary of the Invention

[0006] The present application provides a method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film.

[0007] Typically, the surface of the resin substrate wafer / flexible PI film cannot reach the surface tension required for liquid crystal film transfer after ozone cleaning and UV cleaning to remove surface oxides. The treatment method of this application can improve the surface performance of the resin substrate, successfully enhance the wetting ability of the glue on the surface of the resin substrate, and will not affect the optical effect of the volume holographic waveguide, thereby successfully realizing the transfer of the liquid crystal molecular film onto the resin substrate.

[0008] In a first aspect, the present application provides a method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film, which adopts the following technical solution:

[0009] A method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film, the method specifically comprising:

[0010] After ozone cleaning and UV cleaning are performed on the surface of the resin substrate coated with the functional coating, a mixed monomer treatment liquid including trimethylolpropane allyl ether and trimethylolpropane diallyl ether is spin-coated on the surface of the resin substrate to form a hydrophilic group substrate; acrylic glue is further spin-coated or scraped on the surface of the hydrophilic group substrate, and UV curing treatment is performed.

[0011] The surface treatment method of the resin substrate provided in the present application is specifically as follows: after ozone cleaning and UV cleaning of the surface-modified resin substrate, a layer of mixed monomer treatment liquid including trimethylolpropane allyl ether and trimethylolpropane diallyl ether is spin-coated on the surface of the resin substrate at a rotation speed of more than 6000 r / min to ensure that the thickness of the formed hydrophilic group substrate is less than 100 nm, and then thermally cured in a vacuum oven. After taking out, a layer of UV glue is spin-coated / scraped.

[0012] Optionally, in the mixed monomer treatment liquid, the weight portion of trimethylolpropane allyl ether is 30-50 parts, and the weight portion of trimethylolpropane diallyl ether is 45-65 parts.

[0013] In a specific embodiment, the weight parts of the trimethylolpropane allyl ether are 30 parts, 35 parts, 40 parts, 45 parts, or 50 parts.

[0014] In some specific embodiments, the weight proportion of the trimethylolpropane allyl ether is 30-35 parts, 30-40 parts, 30-45 parts, 35-40 parts, 35-45 parts, 35-50 parts, 40-45 parts, 40-50 parts, or 45-50 parts.

[0015] In a specific embodiment, the weight parts of trimethylolpropane diallyl ether are 45 parts, 50 parts, 55 parts, 60 parts, or 65 parts.

[0016] In some specific embodiments, the weight proportion of the trimethylolpropane diallyl ether is 45-50 parts, 45-55 parts, 45-60 parts, 50-55 parts, 50-60 parts, 50-65 parts, 55-60 parts, 55-65 parts, or 60-65 parts.

[0017] Optionally, the mixed monomer treatment solution further comprises a thermal initiator and a solvent; the weight portion of the thermal initiator is 1.5-2.5 parts, and the weight portion of the solvent is 2-4 parts.

[0018] In a specific embodiment, the weight proportion of the thermal initiator is 1.5 parts, 2 parts, or 2.5 parts.

[0019] In some specific embodiments, the weight portion of the thermal initiator is 1.5-2 parts or 2-2.5 parts.

[0020] In a specific embodiment, the weight parts of the solvent are 2 parts, 3 parts, or 4 parts.

[0021] In some specific embodiments, the weight portion of the solvent is 2-3 parts or 3-4 parts.

[0022] Optionally, the spin coating speed of the mixed monomer treatment liquid is greater than 6000 r / min.

[0023] By controlling the spin coating speed to above 6000 r / min, the thickness of the hydrophilic group substrate can be ensured to be less than 100 nm.

[0024] Optionally, the thermal initiator is azobisisobutyronitrile.

[0025] Azobisisobutyronitrile acts as a free radical initiator, generating methylene radicals in the subsequent heating step, which initiate the monomers to form cross-linked polymers.

[0026] Optionally, the solvent is propylene glycol methyl ether acetate.

[0027] Optionally, after the spin coating of the mixed monomer treatment solution is completed, thermal curing is performed to form a hydrophilic group substrate; the thermal curing temperature is 70-90° C. and the time is 1-5 hours.

[0028] Alternatively, the heat curing process can be completed in a vacuum chamber.

[0029] Optionally, the acrylic glue is any one or more of Norland 61, Norland 68, Norland 71, Norland 72, Norland 83H, and Norland 165H.

[0030] Optionally, the acrylic glue has a thickness of 10-20 μm.

[0031] Optionally, the energy of the UV curing treatment is 3-10J.

[0032] Optionally, the resin substrate is made of any one of epoxy resin, polycarbonate, polymethyl methacrylate, polyethylene terephthalate and polyimide.

[0033] Optionally, the resin substrate has a thickness of 100-200 μm.

[0034] Optionally, the functional coating includes any one or more of a hardening coating, an anti-reflective coating, an anti-fouling coating, and an antistatic coating.

[0035] A hardening coating, also known as a wear-resistant coating, is formed using a hardening fluid. The resin substrate surface is relatively soft and susceptible to mechanical damage. A hardening coating can increase the hardness and wear resistance of the resin substrate surface, preventing scratches and wear, and extending service life.

[0036] Antireflection coatings, also known as anti-reflective coatings or reduced-reflection coatings, are used to optimize optical performance by reducing light reflection from the resin substrate surface and increasing light transmittance. The resin substrate surface reflects some incident light, resulting in reduced transmittance and glare.

[0037] Antifouling coatings are also known as hydrophobic coatings or easy-to-clean coatings. Resin substrates are easily contaminated by fingerprints, dust, and other debris. Antifouling coatings maintain the hydrophobic and oleophobic properties of the resin substrate, preventing stains from adhering, keeping it clean, and reducing cleaning frequency.

[0038] Antistatic coating is also known as antistatic coating. Resin substrates are prone to static electricity, which attracts dust and particles, affecting appearance and performance. Antistatic coating can reduce surface static electricity accumulation and prevent dust absorption.

[0039] After the resin substrate is treated by the method provided in this application, it can be used for volume holographic liquid crystal polymer film transfer. The transfer process is as follows:

[0040] (1) Applying the liquid crystal grating: Apply the prepared liquid crystal grating on the UV glue, solidify the glue by ultraviolet irradiation, and initially combine the liquid crystal grating with the resin substrate.

[0041] (2) Ultrasonic cleaning: Place the resin substrate (resin wafer device) with the liquid crystal grating in an ultrasonic cleaning machine filled with a mixed solvent and ultrasonicate for 2-3 minutes. Under the action of ultrasound, the glass substrate of the liquid crystal grating will separate on its own, while the liquid crystal grating will remain on the UV adhesive, completing the transfer and achieving the separation between the liquid crystal polymer film and the glass substrate.

[0042] (3) Removal of the photo-oriented film: Use a blended solvent (such as N-methylpyrrolidone, butyl acetate, etc.) to remove the photo-oriented film and further clean the surface.

[0043] The blending solvent is any two or more of N-methylpyrrolidone, tetrahydrofuran, N,N-dimethylformamide, butyl acetate, and ethyl acetate. Preferably, the blending solvent comprises 40-60 parts N-methylpyrrolidone and 40-60 parts butyl acetate. Ultrasonic treatment is employed during the process at a frequency of 40,000 Hz for 2-4 minutes.

[0044] In summary, this application includes at least one of the following beneficial technical effects:

[0045] This application discloses a method for processing a resin substrate for transferring volume holographic liquid crystal polymer films. The core technology involves spin-coating a mixed monomer treatment solution consisting of trimethylolpropane allyl ether and trimethylolpropane diallyl ether onto the surface of a resin wafer (resin substrate). Using polymer synthesis methods, the surface of the resin substrate is modified through hydrogen bonding. After curing, the surface of the resin substrate is completely altered, facilitating the adhesion of acrylic adhesives.

[0046] The resin substrate treated with the method provided in this application was used for volume holographic liquid crystal polymer film transfer, with a transfer yield of 90%. However, the resin substrate not treated with the method provided in this application was used for volume holographic liquid crystal polymer film transfer, with a transfer yield of 0%. DETAILED DESCRIPTION

[0047] Before describing the embodiments of the present application in detail, it should be understood that the terminology used herein is only for the purpose of describing particular embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the term belongs.

[0048] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of this application, unless otherwise specified, "plurality" means two or more.

[0049] The endpoints of the ranges and any values ​​disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0050] In this application, the term "comprise" or "include" is an open expression, that is, it includes the content specified in this application, but does not exclude other aspects of the content.

[0051] The present application provides a method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film.

[0052] The treatment method specifically includes: after ozone cleaning and UV cleaning of the surface of the resin substrate coated with the functional coating, spin coating a mixed monomer treatment liquid including trimethylolpropane allyl ether and trimethylolpropane diallyl ether on the surface of the resin substrate to form a hydrophilic group substrate; further spin coating or scraping acrylic glue on the surface of the hydrophilic group substrate, and performing UV curing treatment.

[0053] The preparation process of the mixed monomer treatment liquid is as follows: the monomer, initiator and solvent are mixed in proportion, stirred at 40°C for 1 hour by a magnetic stirrer, filtered with a 2μm polytetrafluoroethylene filter element, and then subjected to ultrasonic degassing treatment for 10 minutes to obtain the mixed monomer treatment liquid.

[0054] To make the purpose, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be understood as limiting this application.

[0055] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0056] The present application is further described in detail below in conjunction with the examples and test results.

[0057] Example 1

[0058] This embodiment provides a method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film.

[0059] The processing method specifically includes the following steps:

[0060] (1) Ozone cleaning and UV cleaning of the surface of a resin wafer (polycarbonate, 150 μm thick) coated with a hardened coating.

[0061] (2) The cleaned resin substrate surface was spin-coated with a mixed monomer treatment solution at a speed of 7000 r / min and thermally cured at a temperature of 80°C for 3 hours to form a hydrophilic group substrate. The addition of each component in the mixed monomer treatment solution is shown in Table 1.

[0062] The preparation process of the mixed monomer treatment liquid is as follows: trimethylolpropane allyl ether, trimethylolpropane diallyl ether, azobisisobutyronitrile and propylene glycol methyl ether acetate are mixed in proportion, stirred at 40°C for 1 hour with a magnetic stirrer, filtered with a 2μm polytetrafluoroethylene filter element, and then subjected to ultrasonic degassing treatment for 10 minutes to obtain the mixed monomer treatment liquid.

[0063] (3) Norland 61 was further spin-coated on the surface of the hydrophilic group substrate with a thickness of 15 μm, and then UV-cured with an energy of 5 J.

[0064] Example 2-17

[0065] Examples 2-17 each provide a method for treating a resin substrate for transferring a volume holographic liquid crystal polymer film. The difference between these examples and Example 1 lies in the addition of the components to the mixed monomer treatment solution, as detailed in Table 1. The remaining processing steps remain the same as in Example 1.

[0066] Comparative Example

[0067] Comparative Example 1

[0068] Comparative Example 1 provides a method for treating a resin substrate, which differs from Example 1 in that the mixed monomer treatment solution is not spin-coated, and the remaining treatment steps are consistent with those of Example 1.

[0069] Table 1 Addition of components in the mixed monomer treatment solution

[0070]

[0071] Test results

[0072] The resin substrates treated by the treatment methods provided in the above embodiments and comparative examples were used for transferring volume holographic liquid crystal polymer films, and the transfer yield was calculated.

[0073] Transfer yield (%) = number of successful transfers / total number of transfers × 100%.

[0074] The transfer process is as follows:

[0075] (1) Applying the liquid crystal grating: Apply the prepared liquid crystal grating on the UV glue, solidify the glue by ultraviolet irradiation, and initially combine the liquid crystal grating with the resin substrate.

[0076] (2) Ultrasonic cleaning: Place the resin substrate (resin wafer device) with the liquid crystal grating in an ultrasonic cleaning machine filled with a mixed solvent and ultrasonicate for 2-3 minutes. Under the action of ultrasound, the glass substrate of the liquid crystal grating will separate on its own, while the liquid crystal grating will remain on the UV adhesive, completing the transfer and achieving the separation between the liquid crystal polymer film and the glass substrate.

[0077] (3) Removal of the photo-aligned film: Use a blended solvent (N-methylpyrrolidone and butyl acetate, volume ratio 1:1) to remove the photo-aligned film and further clean the surface. Ultrasonic treatment is used during the process, with an ultrasonic frequency of 40,000 Hz and a duration of 2-4 minutes.

[0078] The results are shown in Table 1.

[0079] As shown in Table 1, the resin substrate treated with the method provided in this application was used for volume holographic liquid crystal polymer film transfer with a transfer yield of 90%. However, the resin substrate not treated with the method provided in this application was used for volume holographic liquid crystal polymer film transfer with a transfer yield of 0%.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for processing a resin substrate for transferring a volume holographic liquid crystal polymer film, characterized in that: The treatment method specifically includes: after ozone cleaning and UV cleaning of the surface of the resin substrate coated with the functional coating, spin coating the surface of the resin substrate with a mixed monomer treatment liquid including trimethylolpropane allyl ether and trimethylolpropane diallyl ether to form a hydrophilic group substrate; spin coating or scraping acrylic glue on the surface of the hydrophilic group substrate, and performing UV curing treatment.

2. The processing method according to claim 1, characterized in that In the mixed monomer treatment liquid, the weight portion of trimethylolpropane allyl ether is 30-50 parts, and the weight portion of trimethylolpropane diallyl ether is 45-65 parts.

3. The processing method according to claim 1, characterized in that The mixed monomer treatment solution further comprises a thermal initiator and a solvent; the weight portion of the thermal initiator is 1.5-2.5 parts, and the weight portion of the solvent is 2-4 parts.

4. The processing method according to claim 3, characterized in that The thermal initiator is azobisisobutyronitrile.

5. The processing method according to claim 4, characterized in that: The solvent is propylene glycol methyl ether acetate.

6. The processing method according to claim 1, characterized in that The spin coating speed of the mixed monomer treatment liquid is greater than 6000 r / min.

7. The processing method according to claim 1, characterized in that After the spin coating of the mixed monomer treatment solution is completed, thermal curing is performed to form a hydrophilic group substrate; the thermal curing temperature is 70-90° C. and the time is 1-5 hours.

8. The processing method according to claim 1, characterized in that The acrylic glue is any one or more of Norland 61, Norland 68, Norland 71, Norland 72, Norland 83H, and Norland 165H.

9. The processing method according to claim 8, characterized in that: The thickness of the acrylic glue is 10-20 μm.

10. The processing method according to claim 8, characterized in that: The energy of the ultraviolet curing treatment is 3-10J.

11. The processing method according to claim 1, characterized in that: The resin substrate is made of any one of epoxy resin, polycarbonate, polymethyl methacrylate, polyethylene terephthalate and polyimide.

12. The processing method according to claim 1, characterized in that: The thickness of the resin substrate is 100-200 μm.

13. The processing method according to claim 1, characterized in that: The functional coating includes any one or more of a hardening coating, an anti-reflection coating, an anti-fouling coating, and an antistatic coating.

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