Processing method of resin substrate for volume holographic liquid crystal polymer film transfer printing

Abstract

The invention relates to the technical field of volume holographic thin film waveguide manufacturing, in particular to a processing method of a resin substrate for volume holographic liquid crystal polymer film transfer printing. The treatment method specifically comprises the following steps: carrying out ozone cleaning and ultraviolet cleaning on the surface of a resin substrate coated with a functional coating, and spin-coating the surface of the resin substrate with a mixed monomer treatment liquid containing trimethylolpropane allyl ether and trimethylolpropane diallyl ether to form a hydrophilic group substrate; and further spin-coating or blade-coating acrylic ester glue on the surface of the hydrophilic group substrate, and carrying out ultraviolet curing treatment. The surface of the resin substrate is modified through hydrogen-bond interaction by adopting a polymer synthesis method, the surface of the resin substrate is completely changed after curing, and adhesion of acrylate glue is facilitated.

Description

Technical Field

[0001] This application relates to the technical field of fabricating volume holographic thin film waveguides, and particularly relates to a method for treating a resin substrate for transferring a volume holographic liquid crystal polymer film. Background Art

[0002] A polarization volume grating (PVG) is a new type of holographic grating that generates periodic refractive index changes by periodically rotating the optical axis of liquid crystal molecules. Compared with traditional volume gratings, PVG has a higher refractive index modulation and a wider response bandwidth, solves the problem of limited field of view (FOV) of traditional gratings, and is more suitable for the field of near-eye display optical waveguides. PVG also has polarization sensitivity that traditional gratings lack, ensuring high transmittance at a large field of view, and can be customized in small or large sizes according to the application field, expanding the application range of optical waveguide coupling elements. With its excellent large-angle Bragg diffraction characteristics and good polarization response characteristics, PVG technology has made remarkable progress in recent research and development. It not only provides a wider field of view display range for lightweight waveguide display systems, but also brings new design dimensions and application potential to the field of lightweight optical displays.

[0003] Currently, lightweight optical waveguide technologies all use glass as the substrate material. The high-density and brittle glass material brings additional weight and inevitable safety risks to the glasses themselves. Therefore, using resin lenses with high safety and reliability has become the only way for lightweight optical waveguides. Currently, for the development of diffractive optical waveguides based on wafer-level resin substrates, due to the surface tension of the resin surface itself, it is very difficult for photoresist materials to adhere well. Therefore, the surface of the resin substrate needs to be modified.

[0004] Generally, coatings such as hardening liquid and antireflection film are applied to the wafer-level resin surface. These coatings improve the optical performance and structural stability of the resin substrate, but increase the surface tension of the resin itself, posing great difficulties for the adhesion of photoresist. Therefore, the resin surface needs to be further treated to improve its surface properties.

[0005] Currently, existing technologies use traditional methods such as plasma cleaning and glass cleaning to remove oxides on the surface of the resin substrate to achieve a flat and clean surface. However, the actual effect of this method is poor and cannot directly solve the problem of the surface tension of the resin surface itself. Although the scheme of adding a leveling agent can improve the surface properties to a certain extent, the addition of solvents is also likely to damage the surface of the resin substrate, thus affecting the optical performance. Summary of the Invention

[0006] This application provides a method for treating a resin substrate for transferring a volume holographic liquid crystal polymer film.

[0007] Generally, after the surface of the resin substrate wafer / flexible PI film is subjected to ozone cleaning and ultraviolet cleaning to remove surface oxides, the surface tension required for the transfer of the liquid crystal film cannot be achieved. Through the treatment method of the present application, the surface performance of the resin substrate can be improved, the wetting ability of the glue on the resin substrate surface can be successfully enhanced, and the optical effect of the volume holographic waveguide will not be affected, thus successfully realizing the transfer of the liquid crystal molecular film on the resin substrate.

[0008] In a first aspect, the present application provides a treatment method for a resin substrate for transferring a volume holographic liquid crystal polymer film, adopting the following technical solution: A treatment method for a resin substrate for transferring a volume holographic liquid crystal polymer film, the treatment method specifically includes: After ozone cleaning and ultraviolet cleaning the surface of the resin substrate coated with a functional coating, spin-coat a mixed monomer treatment solution including trimethylolpropane allyl ether and trimethylolpropane diallyl ether on the surface of the resin substrate to form a hydrophilic group substrate; further spin-coat or scrape-coat an acrylate glue on the surface of the hydrophilic group substrate, and perform ultraviolet curing treatment.

[0009] The treatment method for the surface of the resin substrate provided by the present application is specifically: after ozone cleaning and ultraviolet cleaning the resin substrate subjected to surface modification treatment, spin-coat a layer of mixed monomer treatment solution including trimethylolpropane allyl ether and trimethylolpropane diallyl ether on the resin substrate surface, with 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, cure it in a vacuum oven, and then spin-coat / scrape-coat a layer of UV glue after taking it out.

[0010] Optionally, in the mixed monomer treatment solution, the weight part of trimethylolpropane allyl ether is 30 - 50 parts, and the weight part of trimethylolpropane diallyl ether is 45 - 65 parts.

[0011] In a specific embodiment, the weight part of trimethylolpropane allyl ether is 30 parts, 35 parts, 40 parts, 45 parts, 50 parts.

[0012] In some specific embodiments, the weight part of 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, 45 - 50 parts.

[0013] In a specific embodiment, the weight part of trimethylolpropane diallyl ether is 45 parts, 50 parts, 55 parts, 60 parts, 65 parts.

[0014] In some specific embodiments, the weight parts of the trimethylolpropane diallyl ether are 45 - 50 parts, 45 - 55 parts, 45 - 60 parts, 50 - 55 parts, 50 - 60 parts, 50 - 65 parts, 55 - 60 parts, 55 - 65 parts, 60 - 65 parts.

[0015] Optionally, the mixed monomer treatment liquid further includes a thermal initiator and a solvent; the weight parts of the thermal initiator are 1.5 - 2.5 parts, and the weight parts of the solvent are 2 - 4 parts.

[0016] In one specific embodiment, the weight parts of the thermal initiator are 1.5 parts, 2 parts, 2.5 parts.

[0017] In some specific embodiments, the weight parts of the thermal initiator are 1.5 - 2 parts, 2 - 2.5 parts.

[0018] In one specific embodiment, the weight parts of the solvent are 2 parts, 3 parts, 4 parts.

[0019] In some specific embodiments, the weight parts of the solvent are 2 - 3 parts, 3 - 4 parts.

[0020] Optionally, the spin - coating speed of the mixed monomer treatment liquid is greater than 6000 r / min.

[0021] Controlling the spin - coating speed above 6000 r / min can ensure that the thickness of the hydrophilic group substrate is less than 100 nm.

[0022] Optionally, the thermal initiator is azobisisobutyronitrile.

[0023] As a free - radical initiator, azobisisobutyronitrile generates methylene free radicals in the subsequent heating process, initiating the monomers to form cross - linked polymers.

[0024] Optionally, the solvent is propylene glycol monomethyl ether acetate.

[0025] Optionally, after the spin - coating of the mixed monomer treatment liquid is completed, thermal curing is carried out to form a hydrophilic group substrate; the temperature of thermal curing is 70 - 90 °C, and the time is 1 - 5 h.

[0026] Optionally, the thermal curing process can be completed in a vacuum chamber.

[0027] Optionally, the acrylate glue is any one or more of Norland61, Norland68, Norland71, Norland72, Norland83H, Norland165H.

[0028] Optionally, the thickness of the acrylate glue is 10 - 20 μm.

[0029] Optionally, the energy of the ultraviolet curing treatment is 3 - 10 J.

[0030] Optionally, the material of the resin substrate is any one of epoxy resin, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, and polyimide.

[0031] Optionally, the thickness of the resin substrate is 100 - 200 μm.

[0032] Optionally, the functional coating includes any one or more of a hardening coating, an anti-reflection coating, an anti-fouling coating, and an anti-static coating.

[0033] A hardening coating, also known as an abrasion-resistant coating, is formed using a hardening solution. The surface of the resin substrate is relatively soft and vulnerable to mechanical damage. The hardening coating can improve the hardness and abrasion resistance of the resin substrate surface, prevent scratching and wear, and extend the service life.

[0034] An anti-reflection film is also known as an anti-reflection coating or a reduction-reflection film. The surface of the resin substrate will reflect part of the incident light, resulting in reduced light transmittance and glare problems. The anti-reflection coating can optimize the optical performance, reduce the reflection of light on the resin substrate surface, and improve the light transmittance.

[0035] An anti-fouling coating is also known as a hydrophobic coating or an easy-to-clean coating. The surface of the resin substrate is prone to fingerprints, dust, etc. The anti-fouling coating can keep the resin substrate surface hydrophobic and oleophobic, prevent stains from adhering, keep it clean, and reduce the cleaning frequency.

[0036] An anti-static coating is also known as an anti-static coating. The surface of the resin substrate is prone to static electricity, which can adsorb dust and particles, affecting the appearance and performance. The anti-static coating can reduce the surface static electricity accumulation and prevent dust adsorption.

[0037] After the resin substrate is processed by the treatment method provided in this application, it can be used for the transfer of a volume holographic liquid crystal polymer film. The transfer process is as follows: (1) Affix the liquid crystal grating: Affix the prepared liquid crystal grating on the UV glue, and cure the glue by ultraviolet irradiation to preliminarily bond the liquid crystal grating to the resin substrate.

[0038] (2) Ultrasonic cleaning: Place the resin substrate (resin wafer device) with the affixed liquid crystal grating in an ultrasonic cleaner filled with a mixed solvent and ultrasonicate for 2 - 3 min. Under the action of ultrasonic waves, the glass substrate of the liquid crystal grating will separate by itself, and the liquid crystal grating will remain on the UV glue, completing the transfer and realizing the separation between the liquid crystal polymer film and the glass substrate.

[0039] (3) Remove the photo-alignment film: Use a blend solvent (such as N-methylpyrrolidone, butyl acetate, etc.) to remove the photo-alignment film and further clean the surface.

[0040] The blend solvent is any two or more of N-methylpyrrolidone, tetrahydrofuran, N,N-dimethylformamide, butyl acetate, and ethyl acetate. Preferably, the blend solvent includes: 40-60 parts of N-methylpyrrolidone and 40-60 parts of butyl acetate. Ultrasonic treatment is adopted during the process, with the ultrasonic frequency at 40000 Hz and the time at 2-4 min.

[0041] In summary, this application includes at least one of the following beneficial technical effects: This application discloses a method for treating a resin substrate for volume holographic liquid crystal polymer film transfer. The core technology lies in spin-coating a mixed monomer treatment solution including trimethylolpropane allyl ether and trimethylolpropane diallyl ether on the surface of a resin wafer (resin substrate). The surface of the resin substrate is modified by hydrogen bonding using a polymer synthesis method, and after curing, the surface of the resin substrate is completely changed, facilitating the adhesion of acrylate glue.

[0042] The resin substrate treated by the method provided in this application is used for volume holographic liquid crystal polymer film transfer, and the transfer yield is 90%. While the resin substrate not treated by the method provided in this application is used for volume holographic liquid crystal polymer film transfer, the transfer yield is 0%. Detailed Description of the Invention

[0043] Before describing the embodiments of this application in detail, it should be understood that the terms used herein are only for the purpose of describing specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this term belongs.

[0044] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of this application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0045] In this application, the endpoints and any values within the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0046] In this application, the term "comprising" or "including" is an open expression, that is, it includes the content specified in this application, but does not exclude other aspects of the content.

[0047] This application provides a method for treating a resin substrate for transfer of a volume holographic liquid crystal polymer film.

[0048] The treatment method specifically includes: after ozone cleaning and ultraviolet cleaning the surface of the resin substrate coated with a functional coating, spin-coating a mixed monomer treatment solution 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 knife-coating an acrylate glue on the surface of the hydrophilic group substrate, and performing ultraviolet curing treatment.

[0049] Among them, the preparation process of the mixed monomer treatment solution is as follows: Mix the monomer, initiator and solvent in proportion, stir with a magnetic stirrer at 40 °C for 1 h, then filter with a 2-μm polytetrafluoroethylene filter element, and then perform ultrasonic degassing treatment for 10 min to obtain the mixed monomer treatment solution.

[0050] 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 creative efforts belong to the scope protected by this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as a limitation to this application.

[0051] For those not specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product specifications are followed. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0052] The following further describes this application in detail in conjunction with the embodiments and test results.

[0053] Example 1

[0054] This embodiment provides a method for treating a resin substrate for transfer of a volume holographic liquid crystal polymer film.

[0055] The treatment method specifically includes the following steps: (1) Ozone clean and ultraviolet clean the surface of a resin wafer (polycarbonate, thickness 150 μm) coated with a hardening coating, (2) Spin-coat the mixed monomer treatment solution on the surface of the cleaned resin substrate at a spin-coating speed of 7000 r / min, perform thermal curing, the temperature of thermal curing is 80 °C, and the time is 3 h to form a hydrophilic group substrate. Among them, the addition of each component in the mixed monomer treatment solution is specifically shown in Table 1.

[0056] Among them, 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. After stirring with a magnetic stirrer at 40 °C for 1 h, it is then filtered through a 2-μm polytetrafluoroethylene filter element, and then subjected to ultrasonic degassing treatment for 10 min to obtain the mixed monomer treatment liquid.

[0057] (3)Further spin-coat Norland 61 on the surface of the hydrophilic group substrate with a thickness of 15 μm, and perform ultraviolet curing treatment with an energy of 5 J.

[0058] Example 2-17 Examples 2-17 respectively provide a treatment method for a resin substrate for body holographic liquid crystal polymer film transfer. The differences between the above examples and Example 1 are as follows: The addition of each component in the mixed monomer treatment liquid is specifically as shown in Table 1, and the remaining treatment steps are the same as those in Example 1.

[0059] Comparative Example Comparative Example 1 Comparative Example 1 provides a treatment method for a resin substrate. The difference between it and Example 1 is that the mixed monomer treatment liquid is not spin-coated, and the remaining treatment steps are the same as those in Example 1.

[0060] Table 1 Addition of each component in the mixed monomer treatment liquid

[0061] Detection Results The resin substrates treated by the treatment methods provided in the above examples and comparative examples were respectively used for body holographic liquid crystal polymer film transfer, and the transfer yield was calculated.

[0062] Transfer yield (%) = Number of successful transfers / Total number of transfers × 100%.

[0063] The transfer process is as follows: (1)Applying the liquid crystal grating: The prepared liquid crystal grating is applied on the UV glue, and the glue is cured by ultraviolet irradiation to preliminarily bond the liquid crystal grating to the resin substrate.

[0064] (2)Ultrasonic cleaning: The resin substrate (resin wafer device) with the liquid crystal grating applied is placed in an ultrasonic cleaning machine filled with a mixed solvent and ultrasonically cleaned for 2-3 min. Under the action of ultrasonic waves, the glass substrate of the liquid crystal grating will separate by itself, and the liquid crystal grating will remain on the UV glue to complete the transfer and realize the separation between the liquid crystal polymer film and the glass substrate.

[0065] (3) Remove the photo-aligned film: Use a blended solvent (volume ratio of N-methylpyrrolidone to butyl acetate is 1:1) to remove the photo-aligned film and further clean the surface. Ultrasonic treatment is adopted during the process, with the ultrasonic frequency at 40000 Hz and the time at 2 - 4 min.

[0066] The results are shown in Table 1.

[0067] As can be seen from Table 1, the resin substrate treated by the method provided in this application is used for volume holographic liquid crystal polymer film transfer, and the transfer yield is 90%. While the resin substrate not treated by the method provided in this application is used for volume holographic liquid crystal polymer film transfer, the transfer yield is 0%.

[0068] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this 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 a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of this application.

Claims

1. A processing method for a resin substrate used in transfer of a volume holographic liquid crystal polymer film, characterized in that, The described processing method specifically includes: after ozone cleaning and ultraviolet cleaning the surface of the resin substrate coated with a functional coating, spin-coating a mixed monomer treatment solution 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 doctor-blading an acrylate glue on the surface of the hydrophilic group substrate and performing ultraviolet curing treatment.

2. The processing method according to claim 1, wherein In the described mixed monomer treatment solution, the weight parts of trimethylolpropane allyl ether are 30 - 50 parts, and the weight parts of trimethylolpropane diallyl ether are 45 - 65 parts.

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

4. The processing method according to claim 3, wherein The thermal initiator is azobisisobutyronitrile; Optionally, the solvent is propylene glycol monomethyl ether acetate.

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

6. The processing method according to claim 1, wherein After completing the spin-coating of the mixed monomer treatment solution, thermal curing is performed to form a hydrophilic group substrate; the temperature of thermal curing is 70 - 90 °C, and the time is 1 - 5 h.

7. The processing method according to claim 1, characterized in that The acrylate glue is any one or more of Norland61, Norland68, Norland71, Norland72, Norland83H, Norland165H; Optionally, the thickness of the acrylate glue is 10 - 20 μm; Optionally, the energy of the ultraviolet curing treatment is 3 - 10 J.

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

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

10. The processing method according to claim 1, wherein The functional coating includes any one or more of a hardening coating, an antireflection coating, an antifouling coating, and an antistatic coating.

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