TAC substrate, method for processing TAC substrate, and antireflection film

Abstract

The invention discloses a TAC base material, a TAC base material processing method and an anti-reflection film, and the TAC base material processing method comprises the following steps: taking the TAC base material, and carrying out microwave drying on the TAC base material. The microwave dehydration method is used for treating the TAC base material, microwaves penetrate through the base material, water molecules are subjected to high-frequency vibration to generate heat, dehydration is uniform, the dehydration speed is high, the water content of the TAC base material can be reduced to be smaller than or equal to 3.5%, and the optical uniformity of the TAC anti-reflection film is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of TAC substrate processing technology, specifically relating to a TAC substrate, a TAC substrate processing method, and an anti-reflective film. Background Technology

[0002] Anti-reflective coatings, also known as anti-reflective coatings or AR films, utilize the principle of optical interference to reduce light reflection and increase transmittance. Their main function is to reduce interface reflectivity, allowing light to penetrate the material more efficiently rather than being reflected. Anti-reflective coatings are typically fabricated by depositing multiple layers onto a substrate, with TAC (triacetate cellulose) being a suitable substrate.

[0003] Existing TAC substrates have a high moisture content, which easily releases gas during the coating process, affecting the uniformity of the coating and resulting in significantly poor coating uniformity and reduced adhesion. To reduce the moisture content of TAC substrates, the conventional treatment method is to remove moisture from the TAC substrate using a low-temperature curing method, but this method is time-consuming and inefficient. Summary of the Invention

[0004] The purpose of this invention is to provide a TAC substrate, a method for processing the TAC substrate, and an anti-reflective film. This processing method can efficiently and quickly remove most of the moisture in the TAC substrate and effectively improve the optical uniformity of the anti-reflective film.

[0005] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0006] A method for processing a TAC substrate, the method comprising the following steps:

[0007] Take the TAC substrate and microwave dry it.

[0008] In one or more embodiments of the present invention, the microwave drying frequency is 915MHz-2450MHz and the time is less than or equal to 1min.

[0009] In one or more embodiments of the present invention, the microwave drying frequency is 2000MHz-2450MHz and the time is 40s-60s.

[0010] In one or more embodiments of the present invention, the thickness of the TAC substrate is 30μm-250μm.

[0011] In one or more embodiments of the present invention, the TAC substrate is pre-dried at a temperature of 40°C-60°C for 10-15 days.

[0012] In one or more embodiments of the present invention, the TAC substrate is pre-dried at a temperature of 45°C-50°C for 10-12 days.

[0013] In one or more embodiments of the present invention, the TAC substrate, after being microwave dried, has a moisture content of less than or equal to 3.5%.

[0014] Another specific embodiment of the present invention provides the following technical solution:

[0015] A TAC substrate, wherein the TAC substrate is obtained by the above-described processing method.

[0016] Another specific embodiment of the present invention provides the following technical solution:

[0017] An anti-reflective film includes a substrate layer and an anti-reflective coating stacked sequentially, wherein the substrate layer is a TAC substrate obtained by the above-described processing method.

[0018] Compared with the prior art, the present invention uses microwave dehydration to treat TAC substrate. Microwaves penetrate the substrate, causing water molecules to vibrate at high frequency and generate heat, resulting in uniform dehydration. The dehydration speed is fast and can reduce the moisture content of TAC substrate to ≤3.5%, significantly improving the optical uniformity of TAC antireflective film. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the antireflective film in one embodiment of the present invention;

[0021] Figure 2 This is a reflection curve diagram of an antireflective film made using the original substrate in one embodiment of the present invention;

[0022] Figure 3 The image shows the reflection curve of the antireflective film made using the TAC substrate in Comparative Example 2 in one embodiment of the present invention.

[0023] Figure 4 This is a reflection curve of the antireflective film made using the TAC substrate in Example 2 in one embodiment of the present invention;

[0024] Figure 5 This is a reflection curve of the antireflective film made using the TAC substrate in Example 4 in one embodiment of the present invention.

[0025] Explanation of key figure labels:

[0026] 1. Substrate layer; 21. Lower hardening layer; 22. Upper hardening layer; 3. Underlying silicon oxide layer; 4. High-refractive-index niobium oxide layer; 5. Low-refractive-index silicon oxide layer; 6. AF layer. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0028] A specific embodiment of the present invention provides a method for processing TAC substrate, comprising the following steps: taking TAC substrate and microwaving the TAC substrate.

[0029] Specifically, the TAC substrate has a large number of polar groups on its molecular chain, such as incompletely esterified hydroxyl groups (-OH) and acetate groups (-OOCCH3). The hydroxyl group is a strong hydrophilic group that can bind tightly with water molecules through hydrogen bonds, which is equivalent to actively "adsorbing" water. At the same time, the TAC molecular chain has low regularity and large intermolecular gaps, which also provides space for water molecules to penetrate and remain.

[0030] TAC antireflective film is made by coating a hardened layer onto a TAC substrate and then depositing an AR layer. The AR layer is mainly composed of a high-refractive-index niobium oxide (Nb2O5) layer and a low-refractive-index silicon dioxide (SiO2) layer. Because TAC antireflective film has low reflectivity, with an average reflectivity of ≤0.5% in the visible light band 400-700nm, the film-forming atmosphere has a significant impact on the film thickness and optical uniformity, and a stable film-forming atmosphere is crucial.

[0031] AR (antireflective coating) is mostly an inorganic oxide (such as SiO2, TiO2) film layer, which relies on "vacuum coating" to achieve a tight bond with the substrate. The residual moisture in TAC will damage the film layer performance from both the coating process and long-term use, and has a great impact on the uniformity of AR film.

[0032] Currently, the conventional treatment method for TAC substrates is low-temperature curing, which is time-consuming and, because heat is transferred from the outside in, leads to surface hardening, making it difficult to remove internal moisture and easily resulting in a "dry outside, wet inside" problem. This invention uses microwave drying to remove moisture from TAC substrates. During the process, microwaves penetrate the substrate. While TAC substrates themselves have weak microwave absorption, the water molecules within the substrate are polar molecules that rapidly rotate and collide with the high-frequency changes in the microwave electric field. This high-speed movement of the water molecules generates frictional heat, causing the moisture inside the TAC substrate to heat up directly, reaching its boiling point in a short time. The heated moisture vaporizes into water vapor, which, driven by the concentration difference within the substrate, diffuses from the inside to the surface and eventually escapes into the surrounding environment, achieving rapid dehydration and precise control of moisture content.

[0033] Furthermore, the microwave drying frequency is 915MHz-2450MHz, and the time is less than or equal to 1min. Preferably, the microwave drying frequency is 2000MHz-2450MHz, and the time is 40s-60s.

[0034] Specifically, by treating the TAC substrate with microwaves of an appropriate frequency for a certain period of time, the moisture content of the TAC substrate can be reduced to ≤3.5% in a short time. If the treatment time is too long, it can easily lead to problems such as catalysis and yellowing of the TAC substrate, affecting subsequent coating processes.

[0035] Furthermore, the thickness of the TAC substrate is 30μm-250μm. Within this thickness range, the moisture content of the TAC substrate can be reduced to the required level within 1 minute under microwave treatment at frequencies of 915MHz-2450MHz.

[0036] Furthermore, the TAC substrate is pre-dried at a temperature of 40℃-60℃ for 10-15 days, preferably at a temperature of 45℃-50℃ for 10-12 days.

[0037] Specifically, a drying process is performed before microwave drying to prevent the TAC substrate from absorbing further moisture during storage, thereby improving the dehydration efficiency. Simultaneously, the drying process removes some moisture, reducing the microwave dehydration load and preventing shrinkage and deformation of the substrate due to a sudden drop in moisture content.

[0038] Another specific embodiment of the present invention provides a TAC substrate, which is obtained by the above-described TAC substrate processing method.

[0039] Another specific embodiment of the present invention provides an anti-reflective film, comprising a substrate layer and an anti-reflective coating layer stacked sequentially, wherein the substrate layer is a TAC substrate obtained by the above-described processing method.

[0040] Specifically, the TAC substrate is directly used to prepare the antireflective film after microwave drying to prevent it from reabsorbing moisture during storage and affecting the uniformity of the coating. The treated TAC substrate has a moisture content of less than or equal to 3.5%, which can significantly improve the optical uniformity of the antireflective film when used to prepare it.

[0041] Furthermore, the antireflective film is prepared as follows: A 30μm-250μm TAC substrate is used. An upper hardening layer with a thickness of 40nm-320nm and a lower hardening layer with a thickness of 0.3μm-3.9μm are coated on both sides of the TAC substrate using a coating process. Both the upper and lower hardening layers are formed using an acrylic resin coating solution. After coating, a 30μm-188μm high-temperature protective film (such as a PET film) is laminated onto the lower hardening layer to ensure the protection of the film surface appearance and the stability of the coating during the magnetron sputtering deposition process. A base silicon oxide (SiO2) layer (1nm-30nm thick) is deposited on the hardened layer using a magnetron sputtering process. A high-refractive-index niobium oxide (Nb2O5) layer (5nm-150nm thick) is deposited on the silicon oxide (SiO2) layer. A low-refractive-index silicon oxide (SiO2) layer (1nm-30nm thick) is deposited on the niobium oxide (Nb2O5) layer. A high-refractive-index niobium oxide (Nb2O5) layer (5nm-150nm thick) is deposited on the silicon oxide (SiO2) layer. A low-refractive-index silicon oxide (SiO2) layer (5nm-120nm thick) is deposited on the niobium oxide (Nb2O5) layer.

[0042] The gas used for bombarding the target material in the above magnetron sputtering process is argon, and the target material reaction gas is a mixture of argon and oxygen. After the magnetron sputtering is completed, an AF layer (anti-fingerprint liquid, perfluorocyclic ether, 2nm-80nm) is coated on the surface to resist oil stains, fingerprints, and scratches. After the AF coating is applied, the overall optics are tested. Finally, after baking the film in an oven for a few minutes, it is left to stand for 48 hours to stabilize the AF coating.

[0043] The present invention will be further described in detail below with reference to specific embodiments.

[0044] Example 1

[0045] The method for processing the TAC substrate in this embodiment is as follows:

[0046] Take a 60μm thick TAC substrate, first place it in a curing chamber and dry it at 50℃ for 240h, then use a 2450MHz microwave to dry it for 10s.

[0047] Example 2

[0048] The method for processing the TAC substrate in this embodiment is as follows:

[0049] Take a 60μm thick TAC substrate, first place it in a curing chamber and dry it at 50℃ for 240h, then use a 2450MHz microwave to dry it for 20s.

[0050] Example 3

[0051] The method for processing the TAC substrate in this embodiment is as follows:

[0052] Take a 60μm thick TAC substrate, first place it in a curing chamber and dry it at 50℃ for 240h, then use a 2450MHz microwave to dry it for 30s.

[0053] Example 4

[0054] The method for processing the TAC substrate in this embodiment is as follows:

[0055] Take a 60μm thick TAC substrate, first place it in a curing chamber and dry it at 50℃ for 240h, then use a 2450MHz microwave to dry it for 40s.

[0056] Comparative Example 1

[0057] The treatment method for the TAC substrate in this comparative example is as follows:

[0058] Take a 60μm thick TAC substrate and dry it in a curing room at 50℃ for 120h.

[0059] Comparative Example 2

[0060] The treatment method for the TAC substrate in this comparative example is as follows:

[0061] Take a 60μm thick TAC substrate and dry it in a curing room at 50℃ for 240h.

[0062] Using an ST-110A moisture analyzer with a high-efficiency halogen lamp heating device mounted on a precision electromagnetic force sensor, the moisture content of the TAC substrate in each embodiment and comparative example was tested by rapid heating and evaporation using the halogen lamp. Simultaneously, the moisture content of the untreated raw substrate was tested using a rapid heating mode at a fixed time of 8 minutes and a temperature of 150°C. To ensure experimental accuracy, all test samples were 5.00 g.

[0063] Table 1. Moisture content of TAC substrates in each embodiment and comparative example

[0064]

[0065] As shown in Table 1, the original substrate had a moisture content of approximately 5% without treatment. Even after 10 days of hot air drying in a curing chamber, the moisture content remained as high as 4.11%, indicating both time-consuming and inefficient processes. However, the substrate sample treated with curing followed by microwave treatment showed a significant reduction in moisture content. After 10 seconds of microwave dehydration, the moisture content was only 2.36%, and it continued to decrease with increasing microwave treatment time, reaching only 0.41% after 40 seconds. This dehydration efficiency far exceeded that of the original process, demonstrating that the treatment method in this invention can rapidly dehydrate TAC substrates and precisely control their moisture content.

[0066] Antireflective films were prepared using untreated raw substrates, the TAC substrate from Comparative Example 2, the TAC substrate from Example 2, and the TAC substrate from Example 4. The structures of the antireflective films are as follows: Figure 1 As shown, the substrate layer 1 has a thickness of 60 μm. An upper hardening layer 22 and a lower hardening layer 21 are respectively disposed on both sides of the substrate layer 1. The upper hardening layer 22 has a thickness of 200 nm, and the lower hardening layer 21 has a thickness of 2 μm. On the upper hardening layer 22, a 10 nm thick base silicon oxide layer 3, an 80 nm thick high-refractive-index niobium oxide layer 4, a 10 nm thick low-refractive-index silicon oxide layer 5, an 80 nm thick high-refractive-index niobium oxide layer 4, a 60 nm thick low-refractive-index silicon oxide layer 5, and a 5 nm thick AF layer 6 are sequentially disposed. OCA optical adhesive is applied to the back of the antireflective film, which is then bonded to a black acrylic sheet. After bonding, the film is degassed using a degassing machine. After degassing, the surface is wiped clean, and the reflection is measured using an Olympus reflectometer. Ten points are tested for each sample. The reflection curves of each antireflective film are shown below. Figures 2-5 As shown, Figures 2-5 In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents reflectivity (%).

[0067] Depend on Figures 2-5 As can be seen, the antireflective film obtained by microwave treatment of TAC substrate followed by AR layer deposition has a uniform and stable reflection curve, which is significantly better than the antireflective film made using TAC substrate in Comparative Example 2. This indicates that the reduction of water content in TAC substrate greatly improves the uniformity of antireflective film.

[0068] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from the spirit or essential characteristics of this disclosure. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this disclosure.

[0069] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for processing a TAC substrate, characterized in that, The processing method for the TAC substrate includes the following steps: Take the TAC substrate and microwave dry it.

2. The method for processing TAC substrate according to claim 1, characterized in that, The microwave drying frequency is 915MHz-2450MHz, and the time is less than or equal to 1min.

3. The method for processing TAC substrate according to claim 2, characterized in that, The microwave drying frequency is 2000MHz-2450MHz, and the time is 40s-60s.

4. The method for processing TAC substrate according to claim 1, characterized in that, The thickness of the TAC substrate is 30μm-250μm.

5. The method for processing TAC substrate according to claim 1, characterized in that, The TAC substrate is pre-dried at a temperature of 40℃-60℃ for 10-15 days.

6. The method for processing TAC substrate according to claim 5, characterized in that, The TAC substrate is pre-dried at a temperature of 45℃-50℃ for 10-12 days.

7. The method for processing TAC substrate according to claim 1, characterized in that, The TAC substrate, after being microwave dried, has a moisture content of less than or equal to 3.5%.

8. A TAC substrate, characterized in that, The TAC substrate is obtained by the processing method described in claim 1.

9. An anti-reflective film, characterized in that, It includes a substrate layer and an anti-reflective coating stacked sequentially, wherein the substrate layer is a TAC substrate obtained by the processing method described in claim 1.

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