Release coating agent and release film for OCA (optical clear adhesive) and application of release coating agent and release film

Abstract

The invention belongs to the field of manufacturing and application of OCA optical cement, and particularly relates to a release coating agent for the OCA optical cement, a release film and application of the release coating agent and the release film. The release coating agent comprises a vinyl-terminated silicone oil main agent, a hydrogen-containing silicone oil cross-linking agent, an anchoring agent, a platinum catalyst and a solvent; any one or two of the vinyl-terminated silicone oil main agent and the hydrogen-containing silicone oil cross-linking agent is / are grafted with a functional group with a cross-linking delaying effect; and the viscosity of the release coating agent is 100 to 150mpa. S. The vinyl-terminated silicone oil and / or the hydrogen-containing silicone oil are / is subjected to graft modification, compared with additional single addition of an inhibitor, a catalyst does not need to be additionally added to affect the residual adhesion rate of the release film, meanwhile, the cross-linking reaction occurrence rate at the normal temperature can be effectively reduced, the viscosity of the release coating agent is kept within the range of 100-150 mpa.s, and the release coating agent has the advantages of being good in adhesion property, good in stability and the like. The release film has the advantages of high flatness, high release force stability, high aging residual adhesion rate and excellent thickness stability, and is suitable for OCA (optical clear adhesive) coating and laminating processes.

Description

Technical Field

[0001] The present invention belongs to the field of manufacturing and application of OCA optical adhesives, and specifically relates to a release coating, and in particular to a release coating, a release film and applications thereof for OCA optical adhesives. Background Art

[0002] OCA optical adhesive is a double-sided tape made of optical acrylic pressure-sensitive adhesive without a backing material and with release films attached to the top and bottom. It has the characteristics of high light transmittance (total light transmittance ≥ 99%), weather resistance, high flatness, high cleanliness and strong adhesion. As an adhesive, it is widely used in the field of touch display. The release film for OCA is a key material for the production of OCA optical adhesive, and its performance directly affects the optical properties and processing performance of the final product. The release film for OCA usually uses BOPET film as the base material. A release coating with an easy-to-peel release effect is coated on its surface through a precision coating process (including roller coating, slit coating or spraying, etc.), and is formed into a dense release layer through UV curing or high-temperature curing. The release coating can be oxygen-containing silane, fluorine-containing silicone, long-chain alkane, modified acrylic resin, etc.

[0003] Due to the high flatness and transmittance requirements of OCA optical adhesives, the release films used for lamination also require high flatness and stable release force. To achieve these technical indicators, the current OCA release film process shows two major development trends: first, high coating weight control, with mainstream coating thicknesses increasing to the 0.1-0.5μm range, ensuring performance stability by increasing the thickness of the functional layer; second, low-temperature, rapid-cure systems, using excess catalyst to accelerate silicone oil crosslinking. The curing mechanism of conventional release coatings is based on the hydrosilylation reaction, which is essentially the selective addition of siloxanes containing unsaturated bonds (C=C, C=O, C=N) to silicon-hydrogen bonds in the presence of a catalyst. Platinum catalysts are the preferred choice due to their high reactivity, stability, selectivity, and low toxicity.

[0004] However, adding excessive catalyst to the release coating can easily cause it to crosslink prematurely, resulting in the formation of grains, crystal nuclei, gels, etc., which increases the viscosity of the release coating beyond the conventional viscosity range of 100~150mPa.s. After coating on the substrate, problems such as uneven coating thickness, coating surface defects, decreased bonding strength with the substrate, and poor release force stability will occur. To address these issues, publication number CN107722864B discloses a release film with medium release force and high residual adhesion. The release film comprises a film substrate and a release layer. The release layer comprises 45-65 parts of liquid silicone resin, 45-25 parts of vinyl silicone oil, 5-25 parts of hydrogenated silicone oil, 0.1-0.3 parts of a catalyst, 0.005-0.02 parts of an inhibitor, 0.05-0.10 parts of a tackifier, and 300-400 parts of an organic solvent. The liquid silicone resin is a mixture of methyl vinyl MQ silicone resin and methyl vinyl silicone oil dissolved in a mass ratio of 0.05-0.15:1 at a temperature of 100-150°C. The catalyst is a platinum chelate complex, the inhibitor is an acetylenic alcohol compound, and the tackifier is a silane coupling agent containing a hydroxyl, methoxy, or ethoxy group. The above solution delays the crosslinking reaction by adding an inhibitor to the release coating.

[0005] However, by adding the inhibitor to delay the cross-linking reaction and prevent the viscosity of the release coating from exceeding 100-150 mPa.s, the final product OCA release film may have a problem of reduced residual adhesion. Summary of the Invention

[0006] The present invention provides a release coating agent, a release film and applications thereof for OCA optical adhesive, which can control the viscosity of the release coating agent within the range of 100-150 MPa.s and ensure a high residual adhesion rate of the release film for the finished OCA product.

[0007] The first aspect of the present invention provides a release coating for OCA optical adhesive, the release coating comprising a vinyl-terminated silicone oil main agent, a hydrogen-containing silicone oil cross-linking agent, an anchoring agent, a platinum catalyst and a solvent, wherein either one or both of the vinyl-terminated silicone oil main agent and the hydrogen-containing silicone oil cross-linking agent are grafted with a functional group having a delayed cross-linking effect; the viscosity of the release coating is 100~150mPa.s.

[0008] As mentioned in the background art, in the prior art, inhibitors are added to the release coating to delay the occurrence of the cross-linking reaction. However, this method has the problem of a decrease in the residual adhesion rate of the release film for the finished OCA. The inventor speculates that this may be because in the prior art method of delaying the cross-linking reaction by adding inhibitors, a corresponding amount of platinum catalyst needs to be added to compensate for the loss of catalytic activity, and the inhibitor itself and the excess reaction residues of the added surplus platinum catalyst will form migratory impurities, thereby affecting the residual adhesion rate of the release film for the finished OCA. If the amount of platinum catalyst used is not increased to compensate for the loss of catalytic activity, the cross-linking reaction between the vinyl-terminated silicone oil main agent and the hydrogen-containing silicone oil cross-linking agent will be affected, resulting in the release force of the release coating formed by the release coating, especially the release force of the release coating formed by the release coating after continuous coating for 2 hours increases.

[0009] Compared with the prior art solution of adding an inhibitor externally, the solution of the present invention directly grafts the inhibitor functional groups onto a vinyl-terminated silicone oil or a hydrogenated silicone oil crosslinker, thereby reducing the molecular occupancy effect. This eliminates the need for an additional platinum catalyst and prevents the generation of migratory impurities formed by the inhibitor itself and excess reaction residues of the added platinum catalyst. This ensures that the viscosity of the release coating is within the range of 100 to 150 MPa.s, while ensuring that the release coating formed after the release coating is applied to the substrate has a high residual adhesion rate.

[0010] In a specific embodiment, the functional group having a cross-linking delaying effect grafted onto the vinyl-terminated silicone oil main agent is a propargyl group. The acetylene bond contained in the vinyl-terminated silicone oil grafted with the propargyl group forms a stable complex with platinum, inhibiting overactivation of the catalyst and delaying the rate of the cross-linking reaction.

[0011] In one embodiment, the grafting rate of the propargyl functional groups in the propargyl-grafted vinyl-terminated silicone oil is ≥95%. A grafting rate below 95% can affect the efficiency of the formation of a stable complex between the acetylenic bond and the platinum catalyst, thereby reducing the inhibitory effect. The grafting rate is controlled by monitoring the vinyl conversion rate using H NMR, and the reaction is terminated when the desired grafting rate is reached.

[0012] In one specific embodiment, the raw materials for the propargyl-grafted vinyl-terminated silicone oil include 100 parts by weight of vinyl-terminated silicone oil, 5-7 parts by weight of propargyltrimethoxysilane, and 0.02-0.04 parts by weight of a platinum catalyst. This raw material composition is only one embodiment, and the raw material content can be adjusted to ultimately achieve a grafting rate of ≥95%.

[0013] In one embodiment, the vinyl content of the vinyl-terminated silicone oil is 0.15-1 mol%, more preferably 0.45-0.5 mol%. The viscosity and crosslink density of vinyl-terminated silicone oil within this range are more suitable for use as a release coating agent. A low vinyl content results in a low crosslink density, affecting the residual adhesion of the release coating; a high vinyl content results in an excessively high crosslink density, affecting the stability of the release force of the release coating.

[0014] In one embodiment, the preparation method of vinyl-terminated silicone oil grafted with propargyl is as follows:

[0015] ①. Mix vinyl-terminated silicone oil and propargyltrimethoxysilane under nitrogen protection and heat to 60-65°C;

[0016] ②. Add platinum catalyst, maintain stirring at 60-65°C for 6 hours, and monitor the vinyl conversion by ¹H NMR to control the propargyl grafting rate;

[0017] ③. Remove low-boiling substances under reduced pressure to obtain vinyl-terminated silicone oil with a side-chain propargyl functional group and a viscosity of 4000-20000 mPa·s.

[0018] In a specific embodiment, the functional group having the cross-linking inhibiting effect grafted onto the hydrogenated silicone oil cross-linker is a thioether group. The sulfur atom contained in the thioether-grafted hydrogenated silicone oil coordinates with platinum to form a reversible complex, thereby inhibiting overactivation of the catalyst and slowing down the rate of the cross-linking reaction.

[0019] In one embodiment, the grafting rate of the sulfide functional groups in the sulfide-grafted hydrogen-containing silicone oil is ≥90%, preferably >95%. When the grafting rate of the sulfide groups is less than 90%, the reversible coordination reaction between the sulfide functional groups and platinum will be affected, thereby reducing the inhibitory effect. The grafting rate is measured by real-time monitoring of the characteristic peak of the silicon-hydrogen bond (2150 cm -1 ) intensity changes and terminates the reaction when the desired grafting rate is reached.

[0020] In one specific embodiment, the raw materials for the sulfide-grafted hydrogenated silicone oil include 100 parts by weight of hydrogenated silicone oil, 8-12 parts by weight of mercaptopropyltrimethoxysilane, 0.05-0.1 parts by weight of a platinum catalyst, and 200-300 parts by weight of anhydrous toluene. This raw material composition is only one embodiment, and the raw material content can be adjusted to achieve a grafting rate of ≥90%.

[0021] In a specific embodiment, the hydrogen content of the hydrogen-containing silicone oil is 0.75±0.05% by mass.

[0022] In one embodiment, the preparation method of the sulfide-grafted hydrogen-containing silicone oil is:

[0023] ① Dehydration of the system: Add hydrogenated silicone oil and toluene to the flask, adjust the solid content of the reaction system to 30-40 wt%, bubble nitrogen for 30 minutes to replace the oxygen in the system, raise the temperature to 75-80°C, and remove trace water by vacuum distillation (until the Karl Fischer titrator shows <50 ppm);

[0024] ②, Raw material mixing: Cool to 55-60 ° C, add mercaptopropyltrimethoxysilane, maintain nitrogen protection, stir at 200-300 rpm, and mix for 15 minutes;

[0025] ③ Catalytic reaction: Add platinum catalyst (diluted to 1 ± 0.1 wt% solution with toluene) dropwise, control the dropping speed so that the system temperature does not exceed 65 ° C; heat to 70 ± 2 ° C, and react at constant temperature for 6-8 hours. Monitor the characteristic peak of silicon-hydrogen bond (2150 cm) by FTIR in real time. -1 ) intensity changes to control the grafting rate of sulfide groups;

[0026] ④. Termination and post-treatment: After the reaction is completed, cool to 40±2°C, add 0.5 parts of activated carbon to adsorb the residual catalyst, stir for 1 hour and filter, and remove toluene from the filtrate by rotary evaporation (60°C, -0.095 MPa) to obtain a light yellow transparent liquid, which is sulfide-grafted hydrogenated silicone oil.

[0027] In one embodiment, the anchoring agent can be an organosilicon compound, such as an organosiloxane compound containing vinyl and epoxy groups; or a polymeric anchoring agent composed of an oligomeric alkenylsiloxane and / or a high molecular weight epoxypolysiloxane. The anchoring agent can react with the crosslinking agent and interact with the substrate, thereby improving the adhesion of the release coating to the substrate while not affecting the release force and stability of the release coating formed by the release coating.

[0028] In a specific embodiment, the anchoring agent is one or both of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane.

[0029] In one specific embodiment, the platinum catalyst is a platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane complex solution.

[0030] In a specific embodiment, the solvent is three or more of ethyl acetate, heptane, butyl acetate, toluene, xylene, butanone, and isopropanol.

[0031] In a specific embodiment, the solvent is heptane, toluene, butanone, or isopropyl alcohol, which has suitable surface energy, solvency, and leveling properties.

[0032] In a specific embodiment, the solvent is ethyl acetate, xylene, or isopropyl alcohol, which has suitable surface energy, solvency, and leveling properties.

[0033] In one embodiment, the release coating exhibits a thickness variation of less than 25% between the initial coating thickness and the coating thickness two hours after application on a BOPET film. By directly grafting inhibitor functional groups onto a vinyl-terminated silicone oil or hydrogenated silicone oil crosslinker to adjust the release coating's viscosity, the thickness variation between the initial coating thickness and the coating thickness two hours after application can be reduced to less than 25%, resulting in excellent thickness stability for the release coating.

[0034] In one embodiment, the release coating comprises 100 parts by weight of a vinyl-terminated silicone oil base, 0.5-2 parts by weight of a hydrogenated silicone oil crosslinker, 0.2-1 parts by weight of an anchoring agent, 0.05-0.1 parts by weight of a platinum catalyst, and 300-400 parts by weight of a solvent. This composition ratio is only one embodiment, and those skilled in the art can adjust the raw material content based on this, combined with adjustments to process conditions, to meet the performance requirements of the release coating.

[0035] The present invention also provides a method for preparing the above-mentioned release coating, comprising: uniformly dispersing a vinyl-terminated silicone oil main agent and a solvent by high-speed stirring in a high-shear disperser at a rotation speed of 250-300 rpm for 10-12 minutes; then slowly adding a solvent-dispersed hydrogenated silicone oil crosslinker, a solvent-dispersed anchoring agent, and a solvent-dispersed platinum catalyst in sequence; and after replenishing the remaining mixed solvent, maintaining the rotation speed and continuing stirring for 5-6 minutes to prepare the release coating to be applied. The viscosity of the release coating can be maintained within the range of 100-150 mPa.s.

[0036] A second aspect of the present invention provides a release film comprising a substrate layer and a release coating layer, wherein the release coating layer is formed from the aforementioned release coating agent. Specifically, the release coating agent is applied to one or both sides of the substrate layer using a coating method such as micro-dimpled, multi-roll, or slit coating, and then cured in an oven at a high temperature of 90-140°C.

[0037] A third aspect of the present invention provides an application of the above-mentioned release film, which can be used in the OCA optical adhesive coating and bonding process, and has high flatness, high release force stability, high residual adhesion rate and excellent thickness stability.

[0038] By implementing the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention grafts and modifies the vinyl-terminated silicone oil main agent and / or the hydrogen-containing silicone oil cross-linking agent. Compared with the additional addition of inhibitors, no additional catalyst is required, thereby avoiding the influence of the migration of the inhibitors and the added additional catalyst on the residual adhesion rate of the release film. At the same time, it can effectively reduce the cross-linking reaction rate at room temperature, so that the viscosity of the release coating is maintained in the range of 100~150mPa.s, so as to form a release film with high flatness, high release force stability, high residual adhesion rate and excellent thickness stability, which is suitable for OCA optical adhesive coating and bonding processes. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below through specific examples.

[0041] It should be noted that the following implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned implementation cases, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

[0042] Overall embodiment

[0043] A release coating for OCA optical adhesive comprises a vinyl-terminated silicone oil main agent, a hydrogenated silicone oil cross-linking agent, an anchoring agent, a platinum catalyst and a solvent.

[0044] The main agent of vinyl-terminated silicone oil is grafted with propargyl groups. The grafting method is as follows:

[0045] S1. Place vinyl-terminated silicone oil with a vinyl content of 0.45 mol% in a reaction vessel under a nitrogen atmosphere, add propargyltrimethoxysilane, stir evenly, and then heat to 60°C.

[0046] S2. Add a platinum catalyst to the reaction vessel and react at 60°C for 6 hours. Monitor the vinyl conversion by ¹H NMR to control the propargyl grafting rate.

[0047] S3. Reduce the pressure to -0.03-0.05 MPa to remove low-boiling substances, and obtain a vinyl-terminated silicone oil with a side-chain propargyl grafted functional group, with a viscosity of 4000-20000 mPa·s.

[0048] The hydrogenated silicone oil crosslinker is grafted with a sulfide group, and the grafting method is as follows:

[0049] ① Dehydration of the system: Add 0.70% hydrogen-containing silicone oil and anhydrous toluene to the reaction vessel, adjust the solid content of the reaction system to about 30 wt%, bubble nitrogen for 30 minutes to replace the oxygen in the system, heat to 80°C, and remove trace water by vacuum distillation (until the Karl Fischer titrator shows <50 ppm);

[0050] ②, Raw material mixing: Cool to 60 ° C, add mercaptopropyltrimethoxysilane, maintain nitrogen protection, stir at a speed of 200-300 rpm, and mix for 15 minutes;

[0051] ③ Catalytic reaction: Add platinum catalyst (diluted to 1 wt% solution with toluene) dropwise, control the dropping speed so that the system temperature does not exceed 65°C; raise the temperature to 70±2°C, and react at constant temperature for 6-8 hours. Monitor the characteristic peak of silicon-hydrogen bond (2150cm) by FTIR in real time. -1 ) intensity changes to control the grafting rate of sulfide groups.

[0052] ④. Termination and post-treatment: After the reaction is completed, cool to 40°C, add activated carbon to adsorb the residual catalyst, stir for 1 hour and filter, remove toluene by rotary evaporation (60°C, -0.095 MPa), and obtain a light yellow transparent liquid, which is the sulfide-grafted hydrogenated silicone oil.

[0053] The preparation method of the release coating is as follows:

[0054] 100 parts by weight of the vinyl-terminated silicone oil main agent and 400 parts by weight of the solvent are uniformly dispersed by high-speed stirring in a high-shear disperser at a speed of 250-300 rpm for 10-12 minutes. Then, the solvent-dispersed hydrogenated silicone oil crosslinker, the solvent-dispersed anchoring agent, and the solvent-dispersed platinum catalyst are slowly added in sequence. After the remaining mixed solvent is replenished, the speed is maintained and stirring is continued for 5-6 minutes to prepare the release coating.

[0055] The solvents used are:

[0056] Solvent 1: Ethyl acetate: xylene: isopropanol = 20:4:1. (Used in Examples 1-9, Examples 14-19, and Comparative Examples 1-4)

[0057] Solvent 2: Toluene:Butanone = 1:1. (Used in Example 10)

[0058] Solvent 3: Heptane: Toluene: Butanone: Isopropanol = 6:4:4:1. (Used in Example 11)

[0059] Solvent 4: Ethyl acetate: xylene: isopropanol = 20:4:3. (Used in Example 12)

[0060] Solvent 5: Ethyl acetate: xylene: isopropanol = 20:4:5. (Used in Example 13)

[0061] Each specific embodiment is based on the general embodiment, and the amount of each component is adjusted. Please refer to the following Table 1 for details.

[0062] Table 1 Composition and content of raw materials in each embodiment and comparative example

[0063] Among them, in Examples 14-16 and Comparative Examples 1-4, the hydrogenated silicone oil crosslinking agent is hydrogenated silicone oil that has not been grafted modified; in Examples 17-19 and Comparative Examples 1-4, the vinyl-terminated silicone oil main agent is vinyl-terminated silicone oil that has not been grafted modified.

[0064] Comparative Example 5:

[0065] Preparation of liquid silicone resin (Scheme of Example c in CN107722864B)

[0066] A methyl vinyl MQ silicone resin with a relative molecular weight between 17000 and 19000 and M / Q=1.2 and a terminal methyl vinyl silicone oil with a viscosity of 500 mPa.s (25°C), a vinyl molar percentage of 0.2%, and a volatility of ≤1.5 at 200°C are mixed and stirred in a mass ratio of 0.1:1 at a temperature of 130°C and a stirring speed of 1000 rpm for 1 hour to obtain a liquid silicone resin with a viscosity of 2500-3000 mPas (25°C).

[0067] Preparation of release coating:

[0068] Add 49.85 parts of liquid silicone resin, 35 parts of vinyl-terminated silicone oil, 0.15 parts of platinum catalyst, 0.008 parts of ethynylcyclohexanol, 0.05 parts of dimethyldiethoxysilane and 400 parts of toluene into the reactor, stir and mix them evenly at a speed of 400-450rpm / 60min, then add 19.95 parts of hydrogenated silicone oil, stir and mix them evenly at 800-850rpm / 60min to obtain a coating liquid with a viscosity of 50-105mpas. Among them, the viscosity of the vinyl-terminated silicone oil is 800mPa.s (25℃), the molar percentage of vinyl is 0.45%,

[0069] The volatile matter at 200℃ is ≤1.5; the viscosity of hydrogen-containing silicone oil is 200mpas and the hydrogen molar ratio is 0.20%.

[0070] Application Examples

[0071] Release films were prepared using the release coatings obtained in the above examples and comparative examples.

[0072] The preparation method of the release film is as follows:

[0073] Take BOPET film as the substrate layer, evenly apply the above-prepared release coating on the surface of the substrate layer, and dry and cure it at 90-140°C for 2-15 minutes (select appropriate curing conditions according to the specific release coating) to form a release coating to obtain a release film.

[0074] The relevant properties of the release coating are tested. The test items and test methods are as follows:

[0075] Coating Appearance: Observe the coating surface of the release film with the naked eye at a 45° angle against the light. The evaluation criteria are: Level 1: No obvious coating lines under strong light; Level 2: Visible coating lines under strong light but not in diffuse light indoors; Level 3: Obvious coating lines visible in diffuse light indoors.

[0076] Release coating viscosity: Tested using a spindle viscometer.

[0077] Release coating viscosity after 2 hours: After the coating liquid is prepared, simulate the normal production cycle for 2 hours and then take a sample for testing using a rotor viscometer.

[0078] Room-temperature release force: Using a tesa 7475 test tape with release coating, apply three cycles of pressure using a 2kg standard roller. Allow to rest at room temperature for 20 minutes. Then peel at an 180° angle at a speed of 300 mm / min. Test three strips of the release film, left, center, and right across its width. The average value is the room-temperature release force.

[0079] Aged release force: Using a tesa 7475 test tape and release coating, apply three cycles of pressure using a 2kg standard roller. Place the tape in a 70°C oven for 20 hours, remove it, and allow it to rest at room temperature for 4 hours. Then, peel it at an 180° angle at a speed of 300 mm / min. Three strips (left, center, and right) of the release film were tested, and the average value was used as the aged release force.

[0080] 7475 Aging Residual Adhesion: Apply a 7475 test tape, peeled from the aged release tape, to a mirror-finished steel plate. Roll the tape back and forth three times using a 2kg standard roller. After 20 minutes, test the tape's peel strength against the mirror-finished steel plate. Simultaneously, apply a new 7475 test tape to the mirror-finished steel plate and test its peel strength, serving as a blank. The aging residual adhesion is calculated by dividing the aged peel strength by the blank's peel strength times 100%. The three data sets are grouped together and the average is calculated.

[0081] The test results are shown in Table 2.

[0082] Table 2 Test results

[0083] As can be seen from the results in Table 2, in Examples 1-13, both the vinyl-terminated silicone oil main agent and the hydrogenated silicone oil crosslinker were graft-modified. The resulting release coatings had a viscosity of approximately 112 mPa.s upon completion and approximately 125 mPa.s after 2 hours. The aging residual adhesion rates upon completion all reached 99%, and the aging residual adhesion rates after 2 hours were also above 95%, with most stabilizing at 99%. The coating appearances all showed Grade 1, reaching an excellent grade. Furthermore, the release force was also of appropriate magnitude. The thickness change rate between the initial coating thickness and the coating thickness after 2 hours was <10%.

[0084] In Examples 14-16, the vinyl-terminated silicone oil main agent was graft-modified with propargyl groups, while the hydrogenated silicone oil crosslinker was not graft-modified. The results showed that the viscosity of the resulting release coatings was stable at around 112 mPa.s upon formulation, but after 2 hours, the viscosity increased significantly compared to Examples 1-13, as evidenced by visible coating lines under strong light after 2 hours. The residual adhesion rate reached 99% both upon formulation and after 2 hours of aging. The thickness change between the initial coating thickness and the coating thickness after 2 hours was less than 25%.

[0085] In Examples 17-19, the hydrogenated silicone oil crosslinker was graft-modified with a thioether group, while the vinyl-terminated silicone oil main agent was not graft-modified. The results showed that the viscosity of the resulting release coatings was stable at around 112 mPa.s upon formulation, but after 2 hours, the viscosity increased significantly compared to Examples 1-13, as evidenced by visible coating lines under strong light after 2 hours. The residual adhesion rate reached 99% both upon formulation and after 2 hours of aging. The thickness change between the initial coating thickness and the coating thickness after 2 hours was less than 25%.

[0086] In Comparative Examples 1-4, neither the vinyl-terminated silicone oil main agent nor the hydrogenated silicone oil crosslinker was grafted. The results of Comparative Example 1 showed a significant increase in coating viscosity after 2 hours, resulting in increased coating thickness, a significant decrease in release force, a decrease in aging residual adhesion, and a deterioration in coating appearance. Comparative Examples 2-4, based on Comparative Example 1, added inhibitors, using varying inhibitor and catalyst contents. The results showed that while viscosity stability was effectively controlled and the viscosity increase after 2 hours was minimal, the release force and aging release force were improved, and the aging residual adhesion was significantly reduced.

[0087] Comparative Example 5 is a release coating disclosed in the prior art. Compared with the various embodiments, the viscosity of the coating solution increased significantly after 2 hours, resulting in a decrease in the aging residual adhesion rate, a serious loss of control of the coating thickness, and a deterioration in the coating appearance.

Claims

1. A release coating for OCA optical adhesive, characterized in that: The release coating comprises a vinyl-terminated silicone oil main agent, a hydrogen-containing silicone oil cross-linking agent, an anchoring agent, a platinum catalyst and a solvent, wherein either one or both of the vinyl-terminated silicone oil main agent and the hydrogen-containing silicone oil cross-linking agent are grafted with a functional group having a delayed cross-linking effect; and the viscosity of the release coating is 100-150 mPa.s.

2. The release coating according to claim 1, characterized in that The functional group grafted to the vinyl-terminated silicone oil main agent is a propargyl group.

3. The release coating according to claim 2, characterized in that The grafting rate of the propargyl functional group is ≥95%.

4. The release coating according to claim 1, wherein The functional group grafted with the hydrogenated silicone oil crosslinking agent is a thioether group.

5. The release coating according to claim 4, characterized in that The grafting rate of the thioether functional group is ≥90%.

6. The release coating according to claim 1, characterized in that The solvent is three or more of ethyl acetate, heptane, butyl acetate, toluene, xylene, butanone, and isopropyl alcohol.

7. The release coating according to claim 1, characterized in that The release coating agent is coated on the BOPET film, and the thickness change rate between the initial coating thickness and the coating thickness 2 hours later is less than 25%.

8. The release coating according to any one of claims 1 to 7, characterized in that: The invention comprises 100 parts by weight of a vinyl-terminated silicone oil main agent, 0.5-2 parts by weight of a hydrogenated silicone oil crosslinking agent, 0.2-1 parts by weight of an anchoring agent, 0.05-0.1 parts by weight of a platinum catalyst and 300-400 parts by weight of a solvent.

9. A release film, characterized in that: The invention comprises a substrate layer and a release coating layer, wherein the release coating layer is formed by the release coating agent according to any one of claims 1 to 8.

10. The use of a release film according to claim 9, characterized in that: Used for coating and bonding processes of OCA optical adhesive.

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