Release agent and preparation method thereof, release coating and optical release film

Abstract

The invention discloses a release agent and a preparation method thereof, a release coating and an optical release film, and relates to the technical field of release films, and the preparation method of the release agent comprises the following steps: mixing cellulose ester and an organic solvent to obtain a first solution; adding a basic catalyst and an isocyanate monomer into the first solution to obtain a reaction solution; pouring the reaction liquid into deionized water, and separating out a white fibrous solid; and purifying and drying the white fibrous solid to obtain the release agent. According to the polaroid release film, the demolding performance of the polaroid release film is improved.

Description

Technical Field

[0001] The present application relates to the technical field of release films, and in particular to a release agent and a preparation method thereof, a release coating, and an optical release film. Background Art

[0002] Polarizer release film is a core material in display panel manufacturing. It is responsible for protecting the polarizer's pressure-sensitive adhesive layer before lamination, ensuring that it is not damaged during the LCD (Liquid Crystal Display) lamination process, while effectively preventing the generation of lamination bubbles. It is crucial to improving the display effect of the display panel. Among many materials, polyester film is an ideal choice for polarizer release film due to its unique performance advantages. Polyester films such as polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, dimensional stability, flatness, heat resistance and chemical resistance. At the same time, they have excellent optical properties and are extremely cost-effective. Therefore, they are widely used in the field of display panel manufacturing.

[0003] However, due to the insufficient demoulding properties of polyester film for various resins and adhesives, problems such as demoulding difficulty, uneven film peeling, and residues may easily occur in actual applications. This has, to a certain extent, limited the widespread application of polyester film in the field of polarizer release films.

[0004] The above content is only used to assist in understanding the technical solution of this application and does not constitute an admission that the above content is prior art. Summary of the Invention

[0005] The main purpose of this application is to provide a release agent and its preparation method, a release coating, and an optical release film, aiming to improve the release properties of the polarizer release film.

[0006] To achieve the above-mentioned purpose, the present invention provides a release agent having a structure shown in formula (1):

[0007]

[0008] Wherein, 50≤m≤600, R1, R2 and R3 are selected from: H, COC a H 2a+1 (1≤a≤5) and CONHC b H 2b+1 Any one of (6≤b≤30);

[0009] The substitution degree of H is A, COC a H 2a+1 The degree of substitution is B, CONHC b H 2b+1The degree of substitution is C, and the degree of substitution of the group in the release agent satisfies: 2.90≤B+C≤3.0 or 0.05≤C / (A+B+C)≤1.0.

[0010] In addition, to achieve the above-mentioned purpose, the present invention also provides a method for preparing a release agent, which is used to prepare the release agent as described above, comprising the following steps:

[0011] mixing cellulose ester and an organic solvent to obtain a first solution;

[0012] adding an alkaline catalyst and an isocyanate monomer to the first solution to obtain a reaction solution;

[0013] The reaction solution was poured into deionized water to precipitate a white fibrous solid;

[0014] The white fibrous solid is purified and dried to obtain a release agent.

[0015] In one embodiment, the mass ratio between the cellulose ester and the organic solvent is (1-20):(1-4);

[0016] and / or, the hydroxyl content of the cellulose ester is 10 to 90%;

[0017] and / or, the molar ratio between the isocyanate monomer and the cellulose ester is (0.5-15):1;

[0018] And / or, the molar ratio between the isocyanate monomer and the alkaline catalyst is (0.5-4):1.

[0019] In one embodiment, the reaction solution is obtained by reacting at a reaction temperature of 10 to 120° C. and a reaction time of 0.5 to 48 hours.

[0020] In one embodiment, the isocyanate monomer comprises at least one of the compounds represented by formula (2):

[0021]

[0022] Wherein, R4 is selected from the general formula C n H 2n+1 Any group, wherein n is an integer of 3 to 36.

[0023] In one embodiment, the alkaline catalyst comprises at least one of the compounds represented by formula (3):

[0024]

[0025] Wherein, R5 and R6 are selected from the general formula C n H 2n+1Any group in (0≤n≤5), R7 is selected from H or N-(CH3)2.

[0026] In addition, to achieve the above-mentioned purpose, an embodiment of the present application also proposes a release coating, which includes: a release agent, a cross-linking agent, a water-dispersible resin and a water-soluble resin, wherein the release agent is the release agent as described above.

[0027] In one embodiment, the release coating comprises: 5 to 95 wt.% of a release agent, 5 to 90 wt.% of a cross-linking agent, 1 to 80 wt.% of a water-dispersible resin, and 1 to 50 wt.% of a water-soluble resin.

[0028] In one embodiment, the cross-linking agent is an isocyanate cross-linking agent, including at least one of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane, lysine diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, 4-toluene diisocyanate, 2,6-toluene diisocyanate, and 4,4'-diphenylmethane diisocyanate.

[0029] And / or, the water-dispersible resin includes: a copolyester resin having an aromatic ring structure;

[0030] And / or, the water-soluble resin includes: polyvinyl alcohol.

[0031] In addition, to achieve the above-mentioned purpose, an embodiment of the present application also proposes an optical release film, which includes: a polymer film layer and a release coating provided on at least one side of the polymer film layer, wherein the release coating is the release coating as described above.

[0032] One or more technical solutions proposed in the embodiments of the present application have at least the following technical effects: providing a release agent, which is composed of a sugar ring structure of cellulose ester grafted with a long-chain alkane molecule. Since the release agent contains the sugar ring structure of cellulose ester, the release coating prepared by applying the release agent has excellent transparency, which greatly meets the transparency requirements of the optical release film further prepared by applying the release coating. Furthermore, the sugar ring structure of cellulose ester has hydroxyl sites, so long-chain alkane molecules can be grafted. This enables the release agent to be closely arranged on the surface of the polymer film layer (for example, polyester film) based on the unique extended chain configuration of the long-chain alkane molecules during actual application, forming a dense lubricating layer; thereby helping to reduce the actual contact area between the final product (for example, the optical release film) and the pressure-sensitive adhesive layer protecting the polarizer, reduce the adhesion between them, and improve the demolding properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the method for preparing a release agent involved in the embodiment of the present application.

[0034] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0036] The following detailed description of the embodiments of the present application is appropriately referred to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0037] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0041] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0042] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] To make the above-mentioned objects, features and advantages of the present application more clearly understood, the technical solutions of the present application are further described below with reference to the accompanying drawings and embodiments. However, the present application is not limited to the embodiments listed, but also includes any other known modifications within the scope of the rights claimed in the present application.

[0044] The term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present application. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0045] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0046] In conventional technology, polyester film has insufficient demoulding properties for various resins and adhesives, which leads to problems such as demoulding difficulty, uneven film peeling, and residue in actual applications. This has, to a certain extent, limited the widespread application of polyester film in the field of polarizer release films. In order to improve the demoulding performance, conventional methods often apply a silicon-containing release coating on the surface of the polyester film, but this type of substance can easily contaminate the polarizer and affect the display effect. At the same time, since organic solvents may remain on the surface of the release coating or penetrate into the interior of the polarizer during the volatilization process, causing contamination to the polarizer, the coating liquid that forms the release coating should also not contain organic solvents.

[0047] The embodiments of the present application provide a solution, specifically, a release agent is provided, which is composed of a sugar ring structure of cellulose ester grafted with a long-chain alkane molecule. Since the release agent contains the sugar ring structure of cellulose ester, the release coating prepared by applying the release agent has excellent transparency, which greatly meets the transparency requirements of the optical release film further prepared by applying the release coating. Furthermore, the sugar ring structure of cellulose ester has a hydroxyl site, so long-chain alkane molecules can be grafted. This allows the release agent to be closely arranged on the surface of the base film (for example, polyester film) based on the unique extended chain configuration of the long-chain alkane molecules during actual application, forming a dense lubricating layer; thereby helping to reduce the actual contact area between the final product (for example, optical release film) and the pressure-sensitive adhesive layer protecting the polarizer, reduce the adhesion between them, and improve the demolding properties.

[0048] The first aspect of the embodiment of the present application provides a release agent, which has a structure shown in formula (1):

[0049]

[0050] Wherein, 50≤m≤600, R1, R2 and R3 are selected from: H, COC a H 2a+1 (1≤a≤5) and CONHC b H 2b+1 Any one of (6≤b≤30);

[0051] The substitution degree of H is A, COC a H 2a+1 The degree of substitution is B, CONHC b H 2b+1 The degree of substitution is C, and the degree of substitution of the group in the release agent satisfies: 2.90≤B+C≤3.0 or 0.05≤C / (A+B+C)≤1.0.

[0052] CONHC b H 2b+1 It can be grafted into the sugar ring structure of cellulose ester by synthesis, and COC aH 2a+1 Derived from cellulose esters.

[0053] It should be understood that by adjusting the length and degree of substitution of the long-chain alkane, the structure of the release agent can be regulated, thereby regulating the release properties of the release coating and optical release film obtained by applying the release agent; wherein, if the length of the long-chain alkane molecule is too short (i.e., the degree of substitution is low), it is difficult to effectively reduce the surface energy of the release agent, and thus it is difficult to achieve a good demoulding effect. If the length of the long-chain alkane molecule is too long (i.e., the degree of substitution is high), the grafting rate of the long-chain alkane molecule will be reduced. When the polymerization degree of the release agent is too small, it means that the sugar ring structure segment of the cellulose ester is short, which may cause the interaction force between the release agent molecules to be weakened, making the release agent layer not strong enough or easy to be destroyed. If the polymerization degree is too large, it means that the sugar ring structure segment of the cellulose ester is long, which may cause the interaction force between the release agent molecules to be too strong, the fluidity becomes poor, and it is not conducive to uniform coverage, making it difficult for the coating liquid prepared by applying the release agent to be evenly distributed on the surface of the film layer or to form an overly thick lubricating layer.

[0054] The second aspect of the present invention provides a method for preparing a release agent, referring to Figure 1 , the release agent preparation method comprises the following steps:

[0055] Step S10, mixing cellulose ester and an organic solvent to obtain a first solution;

[0056] In a feasible embodiment, cellulose ester and an organic solvent are uniformly mixed to prepare a colorless and transparent first solution.

[0057] In one feasible embodiment, the mass ratio between cellulose ester and organic solvent is (1-20):(1-4); for example, the mass ratio between cellulose ester and organic solvent is 1:1, 1:2, 1:3, 1:4, 4:1, 6:1, 12:1, 16:1, 20:1, etc.

[0058] Illustratively, the organic solvent includes at least one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, dichloromethane, chloroform, and an ionic liquid.

[0059] In one embodiment, the hydroxyl content of the cellulose ester is 10% to 90%; for example, the hydroxyl content of the cellulose ester is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc. The hydroxyl content is 100% when all hydroxyl groups are free. If the hydroxyl content is too high, the cellulose ester will have poor solubility and may also result in the release agent containing a large number of residual hydroxyl groups, affecting the release force. If the hydroxyl content is too low, there will be fewer hydroxyl groups available for substitution reactions, making it difficult to prepare a release agent polymer with satisfactory performance.

[0060] Preferably, the hydroxyl content of the cellulose ester is 20 to 70%.

[0061] Step S20, adding an alkaline catalyst and an isocyanate monomer to the first solution to obtain a reaction solution;

[0062] In one feasible embodiment, an alkaline catalyst and an isocyanate monomer are sequentially added to the first solution, and the reaction is allowed to proceed at a certain temperature for a period of time to obtain a viscous reaction solution. The isocyanate (-NCO) group in the isocyanate monomer is highly reactive and can react with the hydroxyl groups in the cellulose ester, thereby grafting long-chain alkane molecules onto the sugar ring structure of the cellulose ester. The alkaline catalyst consumes the HCl produced by acylation, maintaining the pH of the reaction system and promoting the reaction in the forward direction.

[0063] In one embodiment, the molar ratio of the isocyanate monomer to the cellulose ester is (0.5-15):1. For example, the molar ratio of the isocyanate monomer to the cellulose ester is 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, 15:1, etc. By controlling the molar ratio of the isocyanate monomer to the cellulose ester, the length and degree of substitution of the long-chain alkane in the prepared release agent polymer can be controlled.

[0064] In one possible embodiment, the molar ratio between the isocyanate monomer and the alkaline catalyst is (0.5-4): 1. For example, the molar ratio between the isocyanate monomer and the alkaline catalyst is 0.5:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, etc.

[0065] In one possible embodiment, the isocyanate monomer comprises at least one of the compounds represented by formula (2):

[0066]

[0067] Wherein, R4 is selected from the general formula C n H 2n+1 Any group, wherein n is an integer of 3 to 36.

[0068] In one possible embodiment, the basic catalyst comprises at least one of the compounds represented by formula (3):

[0069]

[0070] Wherein, R5 and R6 are selected from the general formula C n H 2n+1 Any group in (0≤n≤5), R7 is selected from H or N-(CH3)2.

[0071] In one feasible embodiment, the reaction solution is reacted at a reaction temperature of 10 to 120° C. and a reaction time of 0.5 to 48 hours to obtain the product. For example, the reaction solution is reacted at a reaction temperature of 10° C., 20° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90° C., 100° C., 110° C., 120° C., etc. For example, the reaction solution is reacted at a reaction time of 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 46 h, 47 h, 48 h, etc. to obtain the product.

[0072] Step S30, pouring the reaction solution into deionized water to precipitate a white fibrous solid;

[0073] In one feasible embodiment, the reaction solution is poured into a large amount of deionized water. Due to the change in solvent polarity and the difference in solubility, the reaction product will precipitate from the solution. At the same time, since the reaction product has a cross-linked structure, a fibrous solid will be formed, thereby obtaining a white fibrous solid.

[0074] Step S40: purify and dry the white fibrous solid to obtain a release agent.

[0075] In one possible embodiment, the release agent polymer is prepared by removing impurities and moisture from the reaction product (ie, white fibrous solid) through multiple purification and drying steps.

[0076] In this embodiment, a release agent polymer composed of a sugar ring structure of cellulose ester grafted with a long-chain alkane molecule is prepared. Since the release agent contains the sugar ring structure of cellulose ester, the release coating prepared by applying the release agent has excellent transparency, which greatly meets the transparency requirements of the optical release film further prepared by applying the release coating. Furthermore, the sugar ring structure of cellulose ester has hydroxyl sites, so long-chain alkane molecules can be grafted. This allows the release agent to be closely arranged on the surface of the base film (for example, polyester film) based on the unique extended chain configuration of the long-chain alkane molecules during actual application, forming a dense lubricating layer; thereby helping to reduce the actual contact area between the final product (for example, optical release film) and the pressure-sensitive adhesive layer protecting the polarizer, reduce the adhesion between them, and improve the demolding properties.

[0077] A third aspect of the present application provides a release coating, comprising: a release agent, a cross-linking agent, a water-dispersible resin, and a water-soluble resin, wherein the release agent has a structure shown in formula (1):

[0078]

[0079] Wherein, 50≤m≤600, R1, R2 and R3 are selected from: H, COC a H 2a+1 (1≤a≤5) and CONHC b H 2b+1 Any one of (6≤b≤30);

[0080] The substitution degree of H is A, COC a H 2a+1 The degree of substitution is B, CONHC b H 2b+1 The degree of substitution is C, and the degree of substitution of the group in the release agent satisfies: 2.90≤B+C≤3.0 or 0.05≤C / (A+B+C)≤1.0.

[0081] In one possible embodiment, the release coating comprises: 5 to 95 wt.% of a release agent, 5 to 90 wt.% of a cross-linking agent, 1 to 80 wt.% of a water-dispersible resin, and 1 to 50 wt.% of a water-soluble resin.

[0082] Exemplarily, the release agent content of the release coating is: 5wt.%, 10wt.%, 15wt.%, 20wt.%, 25wt.%, 30wt.%, 35wt.%, 40wt.%, 45wt.%, 50wt.%, 55wt.%, 60wt.%, 65wt.%, 70wt.%, 75wt.%, 80wt.%, 85wt.%, 90wt.%, 95wt.%, etc. The release agent contains the sugar ring structure of cellulose ester, which makes the release coating have excellent transparency, greatly meeting the transparency requirements of the optical release film further prepared by applying the release coating. Furthermore, the sugar ring structure of the cellulose ester of the release agent is grafted with long-chain alkane molecules, so that the release coating can be closely arranged on the surface of the base film (for example, a polyester film) to form a dense lubricating layer, and helps to reduce the actual contact area between the final product (for example, the optical release film) and the pressure-sensitive adhesive layer protecting the polarizer, reduce the adhesion between them, and improve the demolding property.

[0083] Preferably, the release coating contains a release agent in an amount of 20 to 80 wt.%.

[0084] Exemplary crosslinker content in the release coating is 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, etc. The crosslinker promotes crosslinking reactions between resin molecules in the release coating, thereby improving the coating's strength, heat resistance, and chemical resistance. The crosslinking reaction forms chemical bonds between resin molecules, making the coating more stable.

[0085] Preferably, the crosslinking agent content of the release coating is 20 to 80 wt.%.

[0086] Exemplary water-dispersible resin contents in the release coating include 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, and 80 wt.%. The water-dispersible resin forms a stable dispersion in water, facilitating uniform coating of the release coating solution on the substrate. The resin molecules cross-link during the drying process, forming a film with sufficient strength and toughness.

[0087] Preferably, the water-dispersible resin content of the release coating is 5 to 50 wt.%.

[0088] For example, the water-soluble resin content of the release coating is 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, etc. The water-soluble resin forms a uniform film with good transparency and gloss during the drying process. It also enhances the adhesion, flexibility, and impact resistance of the coating, improving its overall performance.

[0089] Preferably, the water-soluble resin content of the release coating is 5 to 40 wt.%.

[0090] In one embodiment, the crosslinking agent is an isocyanate crosslinking agent, including at least one of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane, lysine diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, 4-toluene diisocyanate, 2,6-toluene diisocyanate, and 4,4'-diphenylmethane diisocyanate. The addition of an isocyanate crosslinking agent can improve the adhesion between the release coating and the base film.

[0091] In one possible embodiment, the water-dispersible resin includes a copolyester resin having an aromatic ring structure.

[0092] For example, the water-dispersible resin can be a resin obtained by condensation polymerization of an aromatic dicarboxylic acid and a polyol, or a polycarboxylic acid and an aromatic diol. The addition of a water-dispersible polyester can improve the leveling of the release coating solution on the base film and enhance the adhesion between the release coating and the base film.

[0093] Illustratively, the water-dispersible resin includes at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, unsaturated polyester resin, aromatic polyester polyol, and polyarylate.

[0094] In one possible embodiment, the water-soluble resin includes polyvinyl alcohol.

[0095] For example, the degree of polymerization of polyvinyl alcohol may be 200 to 3000, and the degree of saponification may be 50 to 99 mol%.

[0096] Preferably, the saponification degree of the polyvinyl alcohol is 70 to 90 mol%.

[0097] In one feasible embodiment, a method for preparing a release coating is provided, comprising: dispersing a release agent in deionized water to prepare an aqueous dispersion of the release agent; mixing a water-soluble resin, a cross-linking agent, a water-dispersible resin, a release agent, and water to form a coating liquid, wherein an aqueous dispersion of the water-dispersible resin, a water-soluble resin solution, and an aqueous dispersion of the release agent can be prepared first, and then the components are mixed; applying the coating liquid to the surface of a base film, and heat-treating it at 40 to 250° C. to obtain a release coating.

[0098] A fourth aspect of an embodiment of the present application provides an optical release film, comprising: a polymer film layer and a release coating layer provided on at least one side of the polymer film layer.

[0099] The release coating comprises: a release agent, a cross-linking agent, a water-dispersible resin and a water-soluble resin, wherein the release agent has a structure shown in formula (1):

[0100]

[0101] Wherein, 50≤m≤600, R1, R2 and R3 are selected from: H, COC a H 2a+1 (1≤a≤5) and CONHC b H 2b+1 Any one of (6≤b≤30);

[0102] The substitution degree of H is A, COC a H 2a+1 The degree of substitution is B, CONHC b H 2b+1 The degree of substitution is C, and the degree of substitution of the group in the release agent satisfies: 2.90≤B+C≤3.0 or 0.05≤C / (A+B+C)≤1.0.

[0103] In one feasible embodiment, a method for preparing an optical release film is provided, comprising:

[0104] Step A10, dispersing the release agent in deionized water to prepare a release agent aqueous dispersion;

[0105] Step A20: Mixing a water-soluble resin, a crosslinking agent, a water-dispersible resin, a release agent, and water to form a coating solution. The coating solution may be prepared by first preparing a water-dispersible resin aqueous dispersion, a water-soluble resin solution, and a release agent aqueous dispersion, and then mixing the components.

[0106] In step A30, the coating liquid is coated on the surface of the polymer film (ie, the base film), and heat-treated at 40-250° C. to obtain an optical release film.

[0107] Exemplarily, the polymer film may be a polyester film.

[0108] In order to make the details and operations of the above embodiments of the present application clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the embodiments of the present application, the above technical solutions are illustrated by multiple embodiments below.

[0109] Example 1

[0110] (1) mixing cellulose acetate having a hydroxyl content of 58% and acetone to obtain a first solution, wherein the mass ratio of the cellulose acetate to the acetone is 6:1;

[0111] (2) adding pyridine (alkaline catalyst) and octadecyl isocyanate to the first solution, reacting at 80° C. for 6 hours to obtain a reaction solution, wherein the molar ratio of the alkaline catalyst, octadecyl isocyanate, and cellulose acetate is 1.2:1.2:1;

[0112] (3) The reaction solution was poured into deionized water to precipitate a white fibrous solid;

[0113] (4) purifying and drying the white fibrous solid to obtain a release agent;

[0114] (5) Polyvinyl alcohol (water-soluble resin), tetramethylene diisocyanate (crosslinking agent), polyethylene terephthalate (water-dispersible resin) 、 The release agent and water are mixed to form a coating liquid with a solid content of 2 wt.%;

[0115] (6) The coating liquid is applied to a polymer film layer (PET), and then heat-treated at 140° C. for 2 min to prepare an optical release film, wherein the mass ratio of the release agent, water-dispersible resin, crosslinking agent, and polyvinyl alcohol in the release coating after drying is 4:2.5:3:0.5.

[0116] Example 2

[0117] The experimental steps are the same as those in Example 1, except that:

[0118] The molar ratio of the alkaline catalyst, octadecyl isocyanate and cellulose acetate in step (2) is 1.5:1.5:1.

[0119] Example 3

[0120] The experimental steps are the same as those in Example 1, except that:

[0121] The molar ratio of the alkaline catalyst, octadecyl isocyanate and cellulose acetate in step (2) is 2:2:1.

[0122] Example 4

[0123] The experimental steps are the same as those in Example 1, except that:

[0124] The molar ratio of the alkaline catalyst, octadecyl isocyanate and cellulose acetate in step (2) is 2.5:2.5:1.

[0125] Example 5

[0126] The experimental steps are the same as those in Example 1, except that:

[0127] The molar ratio of the alkaline catalyst, octadecyl isocyanate and cellulose acetate in step (2) is 3:3:1.

[0128] Example 6

[0129] The experimental steps are the same as those in Example 1, except that:

[0130] The molar ratio of the alkaline catalyst, octadecyl isocyanate and cellulose acetate in step (2) is 4:4:1.

[0131] Example 7

[0132] The experimental steps are the same as those in Example 1, except that:

[0133] The isocyanate monomer in step (2) is dodecyl isocyanate.

[0134] Example 8

[0135] The experimental steps are the same as those in Example 1, except that:

[0136] The isocyanate monomer in step (2) is tetradecyl isocyanate.

[0137] Example 9

[0138] The experimental steps are the same as those in Example 1, except that:

[0139] In step (2), the isocyanate monomer is hexadecyl isocyanate.

[0140] Example 10

[0141] The experimental steps are the same as those in Example 1, except that:

[0142] The isocyanate monomer in step (2) is eicosyl isocyanate.

[0143] Comparative Example 1

[0144] The experimental steps are the same as those in Example 1, except that:

[0145] The coating liquid was prepared by directly using cellulose acetate as a release agent.

[0146] The optical release films of Examples 1 to 10 and Comparative Example 1 were subjected to performance tests, including:

[0147] (1) Transmittance and haze test:

[0148] The transmittance and haze of the film after the second heat treatment were tested using a transmittance and haze meter.

[0149] (2) Release film peeling force test:

[0150] Cut a 25mm wide and 200mm long release film sample. Use a 2kg rubber roller to press the adhesive tape back and forth on the coating surface. Measure the peel force after standing at room temperature for 1 hour. The peel force is tested using a universal testing machine with a peel angle of 180° and a tensile rate of 300mm / min.

[0151] The experimental results are shown in Table 1 below:

[0152] Table 1:

[0153] Test Group Light transmittance (%) Haze (%) Peel force (N / mm) Example 1 90.4 1.1 0.101 Example 2 90.4 1.0 0.091 Example 3 89.5 1.2 0.082 Example 4 89.6 0.94 0.047 Example 5 89.4 0.93 0.029 Example 6 89.7 0.98 0.035 Example 7 89.9 1.4 0.167 Example 8 89.8 1.2 0.153 Example 9 89.6 1.3 0.146 Example 10 89.3 1.1 0.106 Comparative Example 1 88.7 1.5 3.12

[0154] The test results of Examples 1 to 10 and Comparative Example 1 indicate that the optical release films prepared in Examples 1 to 10 of the present application all exhibit good light transmittance, low haze, and high clarity. Furthermore, compared to the optical release film in Comparative Example 1, the optical release films prepared in the Examples of the present application exhibit better demolding properties.

[0155] The above are only preferred embodiments of the present application and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of the present invention.

Claims

1. A release agent, characterized in that The release agent has a structure shown in formula (1): Wherein, 50≤m≤600, R1, R2 and R3 are selected from: H, COC a H 2a+1 (1≤a≤5) and CONHC b H 2b+1 Any one of (6≤b≤30); The substitution degree of H is A, COC a H 2a+1 The degree of substitution is B, CONHC b H 2b+1 The degree of substitution is C, and the degree of substitution of the group in the release agent satisfies: 2.90≤B+C≤3.0 or 0.05≤C / (A+B+C)≤1.

0.

2. A method for preparing a release agent, characterized in that: The method for preparing a release agent is applied to prepare the release agent as claimed in claim 1, comprising the following steps: Mixing cellulose ester and an organic solvent to obtain a first solution; adding an alkaline catalyst and an isocyanate monomer to the first solution to obtain a reaction solution; The reaction solution was poured into deionized water to precipitate a white fibrous solid; The white fibrous solid is purified and dried to obtain a release agent.

3. The method for preparing a release agent according to claim 2, wherein: The mass ratio between the cellulose ester and the organic solvent is (1-20):(1-4); and / or, the cellulose ester has a hydroxyl content of 10 to 90%; and / or, the molar ratio between the isocyanate monomer and the cellulose ester is (0.5-15):1; And / or, the molar ratio between the isocyanate monomer and the alkaline catalyst is (0.5-4):

1.

4. The method for preparing a release agent according to claim 2, wherein: The reaction liquid is obtained by reacting at a reaction temperature of 10 to 120° C. and a reaction time of 0.5 to 48 hours.

5. The method for preparing a release agent according to claim 2, wherein: The isocyanate monomer comprises at least one of the compounds represented by formula (2): Wherein R4 is selected from the general formula C n H 2n+1 Any group, wherein n is an integer of 3 to 36.

6. The method for preparing a release agent according to claim 2, characterized in that: The alkaline catalyst comprises at least one of the compounds represented by formula (3): Wherein, R5 and R6 are selected from the general formula C n H 2n+1 Any group among (0≤n≤5), R7 is selected from H or N-(CH3)2.

7. A release coating, characterized in that: The release coating comprises: a release agent, a cross-linking agent, a water-dispersible resin and a water-soluble resin, wherein the release agent is the release agent according to claim 1, or a release agent prepared by the release agent preparation method according to any one of claims 2 to 6.

8. The release coating according to claim 7, characterized in that: The release coating comprises: 5 to 95 wt.% of a release agent, 5 to 90 wt.% of a cross-linking agent, 1 to 80 wt.% of a water-dispersible resin and 1 to 50 wt.% of a water-soluble resin.

9. The release coating according to claim 7, characterized in that: The cross-linking agent is an isocyanate cross-linking agent, including at least one of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane, lysine diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, 4-toluene diisocyanate, 2,6-toluene diisocyanate and 4,4'-diphenylmethane diisocyanate; And / or, the water-dispersible resin comprises: a copolyester resin having an aromatic ring structure; And / or, the water-soluble resin includes: polyvinyl alcohol.

10. An optical release film, characterized in that: The optical release film comprises: a polymer film layer and a release coating disposed on at least one side of the polymer film layer, wherein the release coating is the release coating according to any one of claims 7 to 9.

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