Method for producing a thin film of a cured silicone rubber

Abstract

The present invention provides a method for efficiently producing a thin film of a silicone rubber cured product, which does not substantially release an organic solvent having a large environmental load and causing atmospheric pollution, which is harmful to the human body, to the surroundings, and which reduces surface pinholes that cause deterioration of physical properties, the thin film having a maximum film thickness of 5.5 μm. The method for efficiently producing a thin film of a silicone rubber cured product is a method in which a gravure roll having a surface with a concave-convex pattern and having a concave portion with a line number per unit length of at least 200 lines / inch, coats and transfers an addition-curable liquid silicone rubber coating liquid, which is substantially free of an organic solvent and has a maximum viscosity of 75 Pa-s at 25°C, to a substrate through the concave portion, and crosslinks and cures the addition-curable liquid silicone rubber coating liquid transferred and coated onto the substrate by heating, ultraviolet irradiation, and / or electron beam irradiation, thereby producing a thin film of a silicone rubber cured product having a maximum thickness of 5.5 μm.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a cured silicone rubber film, and the cured silicone rubber film thereof. The method involves preparing a film-forming coating liquid composed of an addition-curable liquid silicone rubber composition without substantially using organic solvents for dilution, transferring the coating liquid onto a substrate using a gravure roller, and crosslinking and curing the resulting coating film to manufacture a cured silicone rubber film. Background Technology

[0002] Cured silicone rubber is a rubber-like elastomer obtained by three-dimensional cross-linking and curing dimethyl polysiloxane, a polymer with excellent heat resistance, gas permeability and biocompatibility. After thin film formation, cured silicone rubber is expected to be used in a wide range of applications, such as cosmetics, biochemical applications such as cell culture containers, medical applications such as wound covering materials, and gas separation membranes such as CO2 and N2 separation membranes.

[0003] Previously, the method for forming a film from a cured silicone rubber was as follows: a non-crosslinked addition-curing liquid silicone rubber composition containing a liquid dimethyl polysiloxane having at least a plurality of vinyl groups in the molecule, a liquid methyl hydropolysiloxane having at least a plurality of hydrosilane groups (SiH groups) in the molecule, and a platinum catalyst was diluted with organic solvents such as hexane, toluene, and cyclic siloxanes to prepare a coating liquid. The coating liquid was then applied to a substrate by gravure coating or spin coating. The organic solvent was evaporated and removed, and the film was cured by heating and ultraviolet irradiation (Non-Patent Literature 1).

[0004] Typically, to obtain a silicone rubber cured film with a maximum thickness of 5.5 μm via spin coating, the following method is used: the addition-curing liquid silicone rubber composition is diluted with an organic solvent to prepare a coating liquid with lower viscosity, which is then spin-coated to form a film and allowed to crosslink and cure. The film thickness that can be formed by spin coating depends on the viscosity of the addition-curing liquid silicone rubber composition and the spin coater's rotation speed; the higher the viscosity and the lower the rotation speed, the thicker the film becomes. However, even when using a vinyl-containing liquid dimethyl polysiloxane with a relatively low molecular weight and low viscosity, and setting the spin coater's rotation speed to a high value, it is usually difficult to form a film with a maximum thickness of 5.5 μm in spin coating without dilution with an organic solvent. In recent years, although ultra-high-speed spin coaters with a maximum rotation speed of 60,000 rpm are available on the market, the faster the rotation speed, the more the dimethyl polysiloxane chains will align radially and cure, resulting in uneven strain and physical properties of the film, making it impossible to obtain a homogeneous silicone rubber cured film.

[0005] Furthermore, the molecular weight of the vinyl-containing liquid dimethyl polysiloxane in the coating solution significantly affects the physical properties of the cured silicone rubber film. The elongation of the crosslinked cured silicone rubber depends on the chain length of the dimethyl polysiloxane between the crosslinking points; the larger the chain length between these points, the greater the elongation tends to be. Silicone rubber cured products obtained from low-molecular-weight and low-viscosity vinyl-containing liquid dimethyl polysiloxanes exhibit poor stretchability and brittleness due to the small chain length between these crosslinking points, and are therefore unsuitable. Therefore, the conventional method involves diluting a relatively high-molecular-weight and high-viscosity vinyl-containing liquid dimethyl polysiloxane with an organic solvent, applying the reduced-viscosity coating solution using gravure coating or spin coating, evaporating and removing the organic solvent, and then allowing it to crosslink and cure into a film.

[0006] On the other hand, green chemistry, aimed at reducing environmental impact, has received increasing attention in recent years, with a strong desire to avoid the use of organic solvents that cause air pollution. Furthermore, organic solvents are generally harmful to human health. Therefore, in health products, cosmetics, and medical devices where safety is paramount, even if organic solvents have been removed during the manufacturing process, it is still necessary to evaluate the residual organic solvent levels in the final product, which can increase manufacturing costs.

[0007] Volatile low molecular weight cyclic siloxanes, such as octamethylcyclotetrasiloxane, used as organic solvents, are non-toxic and highly safe for humans. They are commonly used in cosmetics and to dilute relatively high molecular weight liquid dimethyl polysiloxanes containing vinyl groups. However, once released into the aquatic environment, they are difficult to decompose and will adsorb onto the mud at the bottom of the water and remain for a long time, posing a high risk of environmental pollution. In recent years, they have been added to the 19th batch of SVHCs in the REACH regulation.

[0008] Furthermore, when manufacturing cured silicone rubber films using addition-curing liquid silicone rubber coating solutions diluted with organic solvents, there is a problem that pinholes can easily form in the cured silicone rubber films when the organic solvent is evaporated and removed. Specifically, after the addition-curing liquid silicone rubber coating solution diluted with organic solvent is applied to the substrate, if the coating film is being film-formed simultaneously with the evaporation of the organic solvent before or during cross-linking and curing, pinholes can form as the organic solvent evaporates from the coating film. This can lead to a decrease in the barrier properties of the film or become the starting point for film breakage, thus posing a risk of deterioration in the physical properties of the film. Cured silicone rubber films are expected to be used in cell culture containers and gas separation membranes due to their gas permeability; however, especially in these applications, the presence of pinholes can lead to leakage of liquid and gas, thus significantly impairing the functionality of the product. Existing technical documents Non-patent literature

[0009] Non-patent literature 1: Sho Mihara, Shinji Takeoka, "Preparation and characterization of highly elongated polydimethylsiloxane nanosheets", Polym. Adv. Technol., 33, p.1180-1189 (2022). Summary of the Invention Technical problems to be solved

[0010] This invention was made to solve the above-mentioned problems, and its purpose is to provide a method for efficiently manufacturing a silicone rubber cured film with a maximum film thickness of 5.5 μm, and the silicone rubber cured film, wherein the method substantially does not release organic solvents that have a high environmental impact, cause air pollution and are therefore harmful to human health, and reduces pinholes on the surface that cause physical property degradation. means of solving technical problems

[0011] Through repeated and in-depth research, the inventors discovered that, without substantially using organic solvents for dilution, a coating liquid for forming an addition-curing liquid silicone rubber composition can be prepared. This coating liquid is then scraped onto the recess of a specific gravure roller with an uneven surface, forming a coating film on a substrate by transferring the non-crosslinked addition-curing liquid silicone rubber coating liquid, which is substantially free of organic solvents. This coating film can then be heated, irradiated with ultraviolet light, and / or irradiated with an electron beam to crosslink and cure it. This method can efficiently produce a silicone rubber cured film that substantially does not release organic solvents into the environment and has a low number of pinholes on its surface, thus completing the present invention.

[0012] A method for manufacturing a silicone rubber cured film to achieve the above objectives involves using an addition-curing liquid silicone rubber coating liquid containing a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in its molecule, a liquid methylhydropolysiloxane having at least a plurality of hydrosilane groups in its molecule, and a platinum catalyst solution and / or suspension, and substantially free of organic solvents. The addition-curing liquid silicone rubber coating liquid is scraped onto the recesses of an embossed pattern on the surface of a gravure roller, transferred, and coated onto a substrate to form a coated film. Then, the coated film is subjected to… Heating, ultraviolet irradiation, and / or electron beam irradiation are used to crosslink and cure the liquid dimethyl polysiloxane and the liquid methyl hydrogen polysiloxane; the maximum viscosity of the addition-curing liquid silicone rubber coating liquid at 25°C is set to 75 Pa·s, and the embossed pattern has the recesses formed by lines arranged obliquely on the outer periphery of the gravure roller, and the number of lines per unit length parallel to the rotation axis of the gravure roller is at least 200 lines / inch, thereby making the thickness of the film a maximum of 5.5 μm.

[0013] Optionally, the method for manufacturing the silicone rubber cured film involves forming a water-soluble sacrificial layer on the substrate, transferring and coating the addition-curing liquid silicone rubber coating liquid onto the water-soluble sacrificial layer to form a coating film, and then cross-linking and curing the coating film to form a silicone rubber cured film.

[0014] Optionally, in the method for manufacturing the silicone rubber cured film, the water-soluble sacrificial layer on which the silicone rubber cured film is formed is further peeled off from the substrate, and then the water-soluble sacrificial layer is dissolved to separate the silicone rubber cured film.

[0015] Optionally, in the method for manufacturing the silicone rubber cured film, the depth of the recess is set to 5–40 μm.

[0016] Optionally, in the method for manufacturing the cured silicone rubber film, the maximum content of organic solvent in the addition-curing liquid silicone rubber coating liquid is adjusted to 1% by mass.

[0017] Optionally, in the method for manufacturing the cured silicone rubber film, the addition-curing liquid silicone rubber coating liquid does not contain organic solvents other than those in the platinum catalyst solution and / or suspension.

[0018] The method for manufacturing the silicone rubber cured film may optionally use, as the liquid dimethyl polysiloxane, a linear dimethyl polysiloxane having vinyl groups bonded to silicon atoms at both ends of the molecular chain, and as the liquid methyl hydrogen polysiloxane, a linear methyl hydrogen polysiloxane having multiple hydrogen atoms bonded to silicon atoms at the non-terminal ends of the molecular chain.

[0019] The method for manufacturing the silicone rubber cured film may optionally use a dimethyl polysiloxane whose molecular chain is capped at both ends by dimethylvinylsiloxy groups as the liquid dimethyl polysiloxane, or a dimethylsiloxane-methylhydrosiloxane copolymer whose molecular chain is capped at both ends by trimethylsiloxy groups as the liquid methylhydrosiloxane.

[0020] Optionally, in the method for manufacturing the cured silicone rubber film, the addition-curing liquid silicone rubber coating liquid further contains dimethyl polysiloxane raw rubber having at least a plurality of vinyl groups in its molecule.

[0021] Optionally, in the method for manufacturing the silicone rubber cured film, the number of lines per unit length is set to 200 to 250 lines per inch.

[0022] Optionally, in the method for manufacturing the cured silicone rubber film, the viscosity of the addition-curing liquid silicone rubber coating liquid at 25°C is set to 1–75 Pa·s.

[0023] The silicone rubber cured film, completed to achieve the above objectives, is a cross-linked cured product of a transfer coating film made from an addition-curing liquid silicone rubber coating liquid. The addition-curing liquid silicone rubber coating liquid comprises a liquid dimethyl polysiloxane having at least a plurality of vinyl groups in its molecules, a liquid methylhydropolysiloxane having at least a plurality of hydrosilane groups in its molecules and which is cross-linked therewith, and a platinum catalyst solution and / or suspension, and substantially contains no organic solvents, having a maximum viscosity of 75 Pa·s at 25°C. The silicone rubber cured film is a cross-linked cured product of the transfer coating film formed by the coating liquid from the recesses of the raised pattern, wherein the raised pattern has recesses formed by lines arranged obliquely on the outer periphery of the gravure roller, and the number of lines per unit length parallel to the rotation axis of the gravure roller is at least 200 lines / inch, and the thickness of the silicone rubber cured film is at most 5.5 μm.

[0024] In the silicone rubber cured film, the cross-linked cured material may optionally be a separation layer separated from the water-soluble sacrificial layer.

[0025] Optionally, in the cured silicone rubber film, the number of pinholes with a diameter of at least 1 μm present in a surface with an area of ​​20 mm × 20 mm is less than 7.

[0026] Optionally, in the cured silicone rubber film, the addition reaction curable liquid silicone rubber coating liquid does not contain organic solvents except for the organic solvents in the platinum catalyst solution and / or suspension, and the maximum content of organic solvents is 1% by mass.

[0027] Optionally, the thickness of the cured silicone rubber film is 0.2 to 5.5 μm, the number of pinholes is less than 5, the tensile strength is at least 0.6 MPa, and the elongation is at least 35%. Invention Effects

[0028] The method for manufacturing a silicone rubber cured film according to the present invention can efficiently produce a silicone rubber cured film with a maximum thickness of 5.5 μm that does not substantially release environmentally hazardous organic solvents that cause air pollution and are harmful to human health, and reduces surface pinholes that lead to physical property degradation. The fewer surface pinholes in this silicone rubber cured film, which can reduce barrier properties and become the starting point for film damage, reduce the risk of physical property degradation. Detailed Implementation

[0029] The following describes in detail the methods for implementing the present invention, but the scope of the present invention is not limited to these embodiments.

[0030] The method for manufacturing the silicone rubber cured film of the present invention is as follows: using an addition-curing liquid silicone rubber composition comprising a reactive dimethyl polysiloxane component capable of constructing a three-dimensional crosslinked structure, a liquid dimethyl polysiloxane having at least a plurality of vinyl groups bonded to silicon atoms as a main agent, a liquid methyl hydropolysiloxane having at least a plurality of hydrosilane groups as a crosslinking agent, and a platinum catalyst solution and / or suspension, and obtaining a silicone rubber elastomer by crosslinking and curing it by heating, ultraviolet irradiation, etc., substantially free of organic solvents; even if the platinum catalyst solution and / or suspension contained in the composition contain trace amounts of organic solvents, it is not necessary to dilute it with other organic solvents to prepare a coating liquid for film formation; using a specific gravure roller with an embossed pattern on the surface, the substantially solvent-free coating liquid is transferred onto a substrate, and then subjected to heating, ultraviolet irradiation and / or electron beam irradiation to crosslink and cure it to obtain a silicone rubber cured film.

[0031] In order to obtain a film by uniformly coating a substantially solvent-free coating liquid containing a vinyl-containing liquid dimethyl polysiloxane with relatively high viscosity onto a substrate without substantially diluting it with organic solvents other than trace amounts of organic solvents in the platinum catalyst solution and / or suspension, gravure coating is selected as the coating method in this invention.

[0032] Furthermore, in this invention, "substantially free of organic solvents," "substantially not using organic solvents for dilution," and "substantially solvent-free" mean that the maximum content of organic solvents in the coating liquid is 1% by mass, particularly 0.5% by mass, and particularly 0.1% by mass. Additionally, in this invention, "film" refers to a film with a maximum thickness of 5.5 μm.

[0033] Compared to spin coating, gravure coating allows for the uniform and thin application of high-viscosity coating liquids. Furthermore, gravure coating is essentially a method where a gravure roller continuously scrapes and transfers the coating liquid onto the substrate, making it highly efficient and suitable for mass production.

[0034] In gravure coating, a small-diameter gravure roller is used, rotating while in contact with the coating liquid at a certain rotational speed, and having various fine embossed patterns engraved or formed on its surface. Depending on the embossed pattern on its surface, this gravure roller can be categorized as follows: a so-called oblique-line type gravure roller with recesses formed by obliquely arranged lines on its outer periphery; a so-called pyramid-type gravure roller with recesses formed by longitudinally and transversely arranged quadrangular pyramidal grooves on its outer periphery; a so-called grid-type gravure roller with recesses formed by quadrangular prism-shaped grooves; a so-called frustum-shaped gravure roller with recesses formed by quadrangular truncated pyramidal grooves; and a so-called tortoise-shell type gravure roller with recesses formed by hexagonal pyramidal, hexagonal prismal, or hexagonal truncated pyramidal grooves.

[0035] Depending on the depth of the recesses in the raised and recessed patterns formed on the surface of the gravure roller, the recesses of the gravure roller, which rotates at a certain speed while in contact with the coating liquid, scrape up and carry a predetermined amount of coating liquid. Excess coating liquid is scraped off by a doctor blade before being transferred to the substrate. Furthermore, the coating liquid scraped up to the recesses of the raised and recessed patterns is transferred and coated onto the substrate according to the depth of the recesses on the gravure roller.

[0036] The finer the raised or recessed pattern engraved or formed on the surface of the gravure roller, the more lines and grooves per unit length parallel to the rotation axis of the gravure roller will be, and the shallower the recess will be. Therefore, less coating liquid is transferred to the substrate, and a thinner film-like coating film can be transferred onto the substrate.

[0037] Furthermore, when using pyramid-shaped, grid-shaped, platform-shaped, or tortoise-shell-shaped gravure rollers as gravure rollers, the recesses of the grooves forming the raised and recessed patterns are independent. This results in the coating liquid, once scraped up into the recesses, not flowing smoothly and failing to level, leading to problems with easy transfer of the printing pattern. In contrast, the oblique-line gravure roller, with its spirally connected lines arranged obliquely on its outer periphery, allows the scraped coating liquid to flow easily along the recesses, facilitating leveling and making printing easier. Therefore, the oblique-line gravure roller is selected as the gravure roller in the manufacturing method of the present invention.

[0038] When using a slanted gravure roller as the gravure roller, in order to manufacture a silicone rubber cured film with a maximum thickness of 5.5 μm, the number of lines per unit length parallel to the rotation axis of the gravure roller needs to be set to at least 200 lines / inch, preferably 200 to 250 lines / inch. If this number of lines is less than 200 lines / inch, too much coating liquid will be scraped up to the recesses of the embossed pattern, thus making it impossible to achieve a maximum silicone rubber cured film thickness of 5.5 μm.

[0039] Furthermore, for coating liquids with relatively high viscosity, such as 70 Pa·s or higher at 25°C, using a slanted gravure roller with a high line count, such as 250 lines / inch, would result in excessive viscosity and coating difficulties. Therefore, for coating liquids with relatively high viscosity, it is desirable to use a slanted gravure roller with a relatively low line count, preferably 200 lines / inch or higher but less than 250 lines / inch, and more preferably 200 to 230 lines / inch. Specifically, for coating liquids with a viscosity of 70 Pa·s or higher at 25°C, it is desirable not to use a slanted gravure roller with a line count of 250 lines / inch.

[0040] The depth of the recess in this invention is not particularly limited, but from the viewpoint of manufacturing a silicone rubber cured film with a maximum thickness of 5.5 μm, especially 0.2 to 3 μm, especially 0.3 to 2 μm, the depth of the recess is generally preferably set to 5 to 40 μm, more preferably about 7 to 30 μm.

[0041] Regarding the diameter of the gravure roller, the greater the number of lines in a slanted gravure roller, the less coating liquid is carried in the concave portion of the roller, posing a risk of the coating liquid solidifying on the roller during the coating process. Therefore, it is desirable for the gravure roller to have the smallest possible diameter. In this invention, the diameter of the gravure roller is preferably about 20 to 40 mm.

[0042] Regarding the rotation speed of the gravure roller, increasing the rotation speed increases the contact area between the coating liquid and the substrate, resulting in an increase in the coating amount and film thickness. Therefore, when aiming for thin film formation, it is necessary to reduce the rotation speed to a certain extent. However, if the rotation speed is too low, the contact area between the coating liquid and the substrate will decrease, leading to insufficient coating amount and the risk of uneven coating and scratches. In this invention, the rotation speed of the gravure roller is preferably about 3 to 30 rpm.

[0043] The liquid dimethyl polysiloxane that serves as the main agent of the addition-curing liquid silicone rubber coating liquid and has at least a plurality of vinyl groups in its molecule is a linear or branched dimethyl polysiloxane that has at least 2, typically 2 to 50, preferably 2 to 20, and more preferably 2 to 10 vinyl groups in its molecule; and is liquid at room temperature of 1 to 30°C. The main chain portion is basically composed of the repetition of dimethylsiloxane units ((CH3)2SiO units). Typically, the two ends of the molecular chain are end-capped with trimethylsiloxy, dimethylvinylsiloxy, divinylmethylsiloxy, trivinylsiloxy, vinylphenylmethylsiloxy, etc., which are linear liquid dimethyl polysiloxanes. However, it can also be a branched liquid dimethyl polysiloxane in which a portion of the siloxane structure constituting the molecular chain contains a branched structure. The vinyl group can be bonded to silicon atoms at one or both ends of the molecular chain, or it can be bonded to silicon atoms in the middle of the molecular chain, i.e., at non-terminal silicon atoms. However, it is preferred to have a vinyl group containing at least silicon atoms bonded to both ends of the molecular chain. In this case, the vinyl group can exist only at the two ends of the molecular chain, or it can exist simultaneously at both ends of the molecular chain and at non-terminal silicon atoms.

[0044] Examples of liquid dimethyl polysiloxanes having at least a plurality of vinyl groups in the molecule include: dimethyl polysiloxanes with two ends of the molecular chain capped by dimethylvinylsiloxy groups, dimethyl polysiloxanes with two ends of the molecular chain capped by divinylmethylsiloxy groups, dimethyl polysiloxanes with two ends of the molecular chain capped by trivinylsiloxy groups, dimethyl polysiloxanes with two ends of the molecular chain capped by vinylphenylmethylsiloxy groups, dimethyl siloxane-methyl vinyl siloxane copolymers with two ends of the molecular chain capped by trimethylsiloxy groups, dimethyl siloxane-methyl vinyl siloxane copolymers with two ends of the molecular chain capped by dimethylvinylsiloxy groups, dimethyl siloxane-methyl vinyl siloxane copolymers with two ends of the molecular chain capped by divinylmethylsiloxy groups, dimethyl siloxane-methyl vinyl siloxane copolymers with two ends of the molecular chain capped by trivinylsiloxy groups, and dimethyl siloxane-methyl vinyl siloxane copolymers with two ends of the molecular chain capped by vinylphenylmethylsiloxy groups, etc.

[0045] The degree of polymerization, which is the number of repeating siloxane units constituting the main chain of the vinyl-containing liquid dimethyl polysiloxane, is optionally typically 20 to 2000, preferably about 80 to 1000; the number average molecular weight is optionally typically 1500 to 150000, preferably about 6000 to 75000. Furthermore, the viscosity of the vinyl-containing liquid dimethyl polysiloxane is optionally typically 100 to 100000 mPa·s at 25°C, preferably about 500 to 50000 mPa·s.

[0046] Typically, the molecular weight of the vinyl-containing liquid dimethyl polysiloxane, the degree of polymerization (degree of polymerization) of the repeating siloxane units constituting the main chain, can be determined. This is used as the number-average molecular weight or weight-average molecular weight, and the number-average degree of polymerization or weight-average degree of polymerization, converted from polystyrene in gel permeation chromatography analysis using toluene or similar developing solvents. Furthermore, viscosity can usually be measured at 25°C using a rotational viscometer, such as a BL-type, BH-type, BS-type, cone-plate type, or rheometer.

[0047] Examples of vinyl-containing liquid dimethyl polysiloxanes include: DMS-V03, DMS-V21, DMS-V31, DMS-V41, DMS-V46, and DMS-V52 (all trade names from Gelest Corporation). These vinyl-containing liquid dimethyl polysiloxanes can be used alone or in combination of two or more types.

[0048] The crosslinking agent used as the addition-curing liquid silicone rubber coating liquid is a liquid methylhydropolysiloxane having at least a plurality of hydrosilicone groups in its molecule. It typically has 2 to 200 groups per molecule, preferably 3 to 150 groups, and more preferably 4 to 100 hydrosilicone groups. It is a linear, cyclic, or branched liquid methylhydropolysiloxane. The hydrosilicone groups in the molecule are crosslinked by the addition reaction of the vinyl group in the vinyl-containing liquid dimethyl polysiloxane with hydrosilylation, thereby curing the addition-curing liquid silicone rubber composition used as the coating liquid.

[0049] This hydrosilane-containing liquid methylhydropolysiloxane is suitable as a substance that is liquid at room temperature, with a degree of polymerization of 2 to 200 siloxane units per molecule, particularly 3 to 150, particularly about 4 to 100, and a number average molecular weight of 150 to 15,000, particularly 300 to 10,000, particularly about 500 to 7,500. Alternatively, the hydrosilane group may be located at one or both ends of the molecular chain, or at any of the non-ends of the molecular chain, or both. Furthermore, the viscosity of this hydrosilane-containing liquid methylhydropolysiloxane is, optionally, typically 0.5 to 1000 mPa·s at 25°C, preferably about 5 to 500 mPa·s.

[0050] Examples of such liquid methylhydropolysiloxanes include: 1,3-dihydro-1,1,3,3-tetramethyldisiloxane, 1,5-dihydro-1,1,3,3,5,5-hexamethyltrisiloxane, 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasiloxane, 1,3,5,7,9-pentahydro-1,3,5,7,9-pentamethylcyclopentasiloxane, and other methylhydrocyclic siloxane oligomers; and branched siloxane oligomers such as tris(dimethylhydrosiloxy)methylsilane. Methylhydropolysiloxane with both ends of the molecular chain capped by trimethylsiloxy groups; dimethylsiloxane-methylhydrosiloxane copolymer with both ends of the molecular chain capped by trimethylsiloxy groups; dimethylpolysiloxane with both ends of the molecular chain capped by dimethylhydrosiloxy groups; methylhydropolysiloxane with both ends of the molecular chain capped by dimethylhydrosiloxy groups; dimethylsiloxane-methylhydrosiloxane copolymer with both ends of the molecular chain capped by dimethylhydrosiloxy groups; dimethylhydrosiloxane-methylhydrosiloxane copolymer with both ends of the molecular chain capped by dimethylhydrosiloxy groups; dimethylhydrosiloxy units (H(CH3)2SiO) 1 / 2 ) and SiO 4 / 2 The unit structure optionally, or arbitrarily, includes a trimethylsiloxy unit ((CH3)3SiO2). 1 / 2 ), dimethylsiloxane unit ((CH3)2SiO 2 / 2 ), methylhydrosiloxane unit (H(CH3)SiO) 2 / 2 ), Hydrogen silsesquioxane unit (HSiO) 3 / 2 ) and / or methylsilsesquioxane units ((CH3)SiO 3 / 2 Liquid methylhydropolysiloxanes with a three-dimensional network structure, etc.

[0051] Examples of such liquid methylhydropolysiloxanes include DMS-H03 and HMS-301 (trade names from Gelest Corporation). These liquid methylhydropolysiloxanes containing hydrosilicone groups can be used alone or in combination of two or more types.

[0052] Regarding the amount of the hydrosilicone-containing liquid methylhydropolysiloxane, the molar ratio of the hydrosilicone group in the hydrosilicone-containing liquid methylhydropolysiloxane to the vinyl group in the vinyl-containing liquid dimethylpolysiloxane is 1 to 30, and particularly preferably 1 to 15.

[0053] The addition-curing liquid silicone rubber coating liquid contains a platinum catalyst solution and / or suspension as a catalyst for promoting the hydrosilylation addition reaction between the vinyl groups in the aforementioned vinyl-containing liquid dimethyl polysiloxane and the hydrosilyl groups in the aforementioned hydrosilyl-containing liquid methyl hydropolysiloxane.

[0054] The platinum catalyst can be any known platinum catalyst used to promote the hydrosilylation addition reaction, such as platinum, platinum chloride, platinum chloride acid, platinum chloride salt, platinum chloride acid, or platinum chloride salt, and complexes of low-molecular-weight siloxanes containing vinyl groups, such as 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane. To ensure the shelf life of the coating liquid, a complex with a structure obtained by chelation with a low-molecular-weight siloxane containing vinyl groups that has a curing delay effect is preferred. In particular, when the coating liquid is heated and the curing reaction begins, a platinum or platinum compound complex of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane or 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane is desirable.

[0055] The amount of platinum catalyst solution and / or suspension may optionally be the so-called catalyst amount, but calculated based on the mass of platinum atoms contained in the platinum catalyst solution and / or suspension, relative to the mass of the aforementioned vinyl-containing liquid dimethyl polysiloxane, is typically 1 to 1000 ppm, preferably about 2 to 500 ppm.

[0056] Since the amount of this platinum catalyst is trace, from an operational perspective, it is preferable to dissolve and / or suspend it in organic solvents such as hexane, toluene, lower alcohols, higher alcohols, and organosilicon compounds. The platinum atom content in the solution and / or suspension is preferably about 2-5% by mass (based on the mass of platinum atoms).

[0057] Furthermore, the amount of platinum catalyst solution and / or suspension used is the so-called catalyst amount, and the amount of organic solvent contained in the platinum catalyst solution and / or suspension is also trace. Therefore, when the addition-curing liquid silicone rubber coating liquid is crosslinked and cured, since the evaporation of the organic solvent is negligible, the organic solvent in the platinum catalyst solution and / or suspension does not substantially affect the physical properties of the silicone rubber cured film manufactured by the method of manufacturing silicone rubber cured film of the present invention, especially the surface physical properties such as the number of pores on the surface.

[0058] In the method for manufacturing the cured silicone rubber film, the addition-curing liquid silicone rubber coating liquid used may, in addition to the aforementioned vinyl-containing liquid dimethyl polysiloxane, the aforementioned hydrosilyl-containing methyl hydropolysiloxane, the aforementioned platinum catalyst solution and / or suspension, add, without impairing the purpose and effect of the present invention, a linear dimethyl polysiloxane without functional groups participating in the hydrosilylation addition reaction, i.e., so-called non-functional dimethyl silicone oil, as a plasticizer. Furthermore, for reinforcement, fillers such as silica-based fillers, non-functional silicone resins without functional groups participating in the hydrosilylation addition reaction, dyes, pigments, etc., may also be added.

[0059] Furthermore, in order to improve the mechanical and physical properties of the silicone rubber cured film manufactured by this method, such as tensile strength and elongation, a raw dimethyl polysiloxane containing at least a plurality of vinyl groups may be added to the addition-curing liquid silicone rubber coating liquid. This raw dimethyl polysiloxane is typically non-flowing and solid at room temperature. The molecular structure of this vinyl-containing raw dimethyl polysiloxane can be the same as that of the vinyl-containing liquid dimethyl polysiloxane, but the degree of polymerization of this vinyl-containing raw dimethyl polysiloxane is typically at least 5000, preferably about 6000 to 20000, and the number average molecular weight is at least 370000, preferably about 450000 to 1500000.

[0060] The vinyl-containing dimethyl polysiloxane raw rubber can typically be formulated in an amount of up to 10% by mass, preferably up to about 6% by mass, relative to the addition-curing liquid silicone rubber coating liquid. When formulated, it can typically be set to at least 0.1% by mass, preferably at least 1% by mass.

[0061] From the viewpoint of manufacturing a silicone rubber cured film with a maximum thickness of 5.5 μm, particularly 0.2–3 μm, and especially 0.3–2 μm, the addition-curing liquid silicone rubber coating solution requires a maximum viscosity of 75 Pa·s at 25°C, preferably typically 1–75 Pa·s, particularly 2–72 Pa·s, and especially 2–65 Pa·s. If the viscosity of the coating solution at 25°C exceeds 75 Pa·s, the viscosity is too high to be easily transferred using the gravure roller, or the thickness of the coated film becomes too large, making it impossible to manufacture a silicone rubber cured film with a maximum thickness of 5.5 μm. Furthermore, if the viscosity of the coating solution is too low, the obtained silicone rubber cured film may become brittle, its physical properties may deteriorate, and it may be difficult to separate the silicone rubber cured film from the substrate.

[0062] Furthermore, for coating liquids with relatively high viscosity, such as those with a viscosity of 70 Pa·s or higher at 25°C, using a high-line-count slanted gravure roller (e.g., 250 lines / inch) can lead to excessively high viscosity and difficulty in coating. Therefore, when using coating liquids with relatively high viscosity, it is desirable to use a slanted gravure roller with a line count of less than 250 lines / inch, preferably 200 lines / inch or higher but less than 250 lines / inch, and more preferably 200 to 230 lines / inch. Specifically, for coating liquids with a viscosity of 70 Pa·s or higher at 25°C, it is desirable not to use a slanted gravure roller with a line count of 250 lines / inch.

[0063] This addition-curing liquid silicone rubber coating liquid can be prepared by uniformly mixing the vinyl-containing liquid dimethyl polysiloxane, the hydrosilyl-containing liquid methylhydropolysiloxane, and a platinum catalyst solution and / or suspension using conventional methods. However, to prevent crosslinking and curing caused by the hydrosilylation addition reaction between the vinyl-containing liquid dimethyl polysiloxane and the hydrosilyl-containing liquid methylhydropolysiloxane during mixing and stirring, it is desirable to rapidly mix the components at a low temperature below 0°C to a room temperature below 30°C to prepare the coating liquid. If necessary, a planetary mixer or other stirring device can also be used.

[0064] The prepared addition-curing liquid silicone rubber coating liquid is scraped onto the substrate by a gravure roller that rotates at a certain rotational speed and contacts the coating liquid to form a coating film. The coating film is then subjected to heating, ultraviolet irradiation and / or electron beam irradiation to crosslink and cure the vinyl-containing liquid dimethyl polysiloxane and the hydrosilyl-containing liquid methyl hydropolysiloxane in the coating liquid, thereby enabling the manufacture of the silicone rubber cured film of the present invention.

[0065] The raw materials for this substrate can be selected from glass, plastic, metal, ceramic, rubber, cloth, paper, etc.

[0066] A silicone rubber cured film can be obtained by crosslinking and curing a coating film formed on a substrate through heating, ultraviolet irradiation, and / or electron beam irradiation using conventional methods to promote the hydrosilylation addition reaction. For example, when heating, it is typically carried out at 80–150°C, preferably 100–130°C, for 0.5–120 minutes, preferably about 3–60 minutes, to achieve crosslinking and curing. After crosslinking and curing, the film can be peeled off from the substrate, but from the viewpoint of cooling and physical property stability, it is desirable to allow it to stand for about 24 hours after crosslinking and curing.

[0067] Alternatively, the substrate may have a water-soluble sacrificial layer on its surface, composed of a water-soluble thermoplastic resin such as polyvinyl alcohol. If the substrate has a water-soluble sacrificial layer on its surface, the water-soluble sacrificial layer on which the cross-linked cured silicone rubber film is formed and laminated can be peeled off from the substrate as described above. Then, the water-soluble sacrificial layer can be dissolved in water or the like to separate the cured silicone rubber film. The water-soluble sacrificial layer can be any substance soluble in water or the like, and materials other than water-soluble thermoplastic resins can be used; for example, starch can be used instead. The material of the water-soluble sacrificial layer can be appropriately selected based on cost, solubility in water, and wettability with the cured silicone rubber film.

[0068] The thickness of the water-soluble sacrificial layer is preferably 1 μm or more, and more preferably 3 μm or more. A thicker water-soluble sacrificial layer makes it easier to peel off from the substrate, but the dissolution time becomes longer. Typically, a maximum thickness of approximately 30 μm for the water-soluble sacrificial layer is sufficient.

[0069] The silicone rubber cured film of the present invention is a cross-linked cured product on a substrate, or a cross-linked cured product separated from a substrate. It is formed by using a specific oblique-line gravure roller with an embossed pattern on the surface, as described above, to transfer an addition-curing liquid silicone rubber coating liquid containing a reactive dimethyl polysiloxane component capable of constructing a three-dimensional cross-linked structure, namely, the above-mentioned vinyl-containing liquid dimethyl polysiloxane as the main agent, the above-mentioned hydrosilicone-containing liquid methylhydropolysiloxane as the cross-linking agent, and the above-mentioned platinum catalyst solution and / or suspension, with a maximum viscosity of 75 Pa·s at 25°C, which is substantially undiluted with organic solvents, onto a substrate, and then heating, irradiating with ultraviolet light and / or electron beam irradiation to achieve cross-linking and curing.

[0070] The thickness of the cured silicone rubber film is a maximum of 5.5 μm, typically 0.2–5.5 μm, especially 0.2–3 μm, and particularly 0.3–2 μm. Since there is virtually no evaporation of organic solvents during the crosslinking and curing of the coated film, the number of pinholes on the surface is reduced.

[0071] The number of pinholes with a diameter of at least 1 μm present in the silicone rubber cured film, for example, within a surface area of ​​20 mm × 20 mm, is typically less than 7, preferably less than 5.

[0072] The number of pinholes on the surface of the cured silicone rubber film can be assessed by, for example, cutting the cured silicone rubber film into 20mm × 20mm pieces and observing and evaluating its surface using a scanning electron microscope. Furthermore, the diameter of these pinholes is typically a maximum of 10μm, but preferably about 3μm.

[0073] The cured silicone rubber film can be configured to have a tensile strength of at least 0.6 MPa, particularly about 0.65 to 5.0 MPa, and an elongation of at least 35%, particularly about 35 to 350%.

[0074] The cured silicone rubber film has fewer pinholes on the surface that lead to decreased barrier properties and become the starting point for film damage, thus reducing the risk of physical property degradation. Example

[0075] The following describes examples of hydrophilic treatment methods using the present invention and comparative examples of methods not using the present invention.

[0076] The following components are used in the preparation of addition-curing liquid silicone rubber coating liquid. [Liquid dimethyl polysiloxane containing vinyl groups] DMS-V31: A dimethyl polysiloxane with dimethyl vinylsiloxy groups at both ends of its molecular chain (Gelest trade name, viscosity 1000 mPa·s, degree of polymerization 380, molecular weight 28000, vinyl concentration 0.0071 mol / 100g). DMS-V41: A dimethyl polysiloxane with dimethyl vinylsiloxy groups at both ends of its molecular chain (Gelest trade name, viscosity 10000 mPa·s, degree of polymerization 850, molecular weight 62,700, vinyl concentration 0.0032 mol / 100g). DMS-V46: A dimethyl polysiloxane with dimethyl vinylsiloxy groups at both ends of its molecular chain (Gelest trade name, viscosity 60000 mPa·s, degree of polymerization 1,580, molecular weight 117000, vinyl concentration 0.0017 mol / 100g). DMS-V52: Dimethyl polysiloxane with dimethyl vinylsiloxy groups at both ends of its molecular chain (Gelest trade name, viscosity 165000 mPa·s, degree of polymerization 2090, molecular weight 155000, vinyl concentration 0.0013 mol / 100g). [Liquid methylhydropolysiloxane containing hydrosilicone groups] HMS-301: A dimethylsiloxane-methylhydrosiloxane copolymer with trimethylsiloxy groups at both ends of the molecular chain (Gelest trade name, viscosity approximately 35 mPa·s, degree of polymerization approximately 26, molecular weight 2000, methylhydrosiloxane unit content relative to the total dimethylsiloxane and methylhydrosiloxane units in the main chain is approximately 24 mol%, hydrosilane concentration 0.30 mol / 100g). [Platinum catalyst solution] SIP6829.2: A solution of a tetravinylcyclotetrasiloxane complex of platinum carbonyl (Gelest trade name, solvent tetravinylcyclotetrasiloxane, platinum atom concentration in the solution approximately 2.1% by mass, specific gravity approximately 1%) [Dimethyl polysiloxane raw rubber containing vinyl groups] PDMS110-8: A dimethylsiloxane-methylvinylsiloxane copolymer with trimethylsiloxy groups at both ends of the molecular chain (DJSilicone trade name, degree of polymerization 6000-10800, molecular weight 450000-800000, vinyl content approximately 2 mol%, vinyl concentration approximately 0.027 mol / 100g).

[0077] In addition, the viscosity of each of the above liquid components was measured using a rotational viscometer at 25°C, and the molecular weight and degree of polymerization were converted from the number-average molecular weight and number-average degree of polymerization of polystyrene in gel permeation chromatography analysis using toluene as the developing solvent.

[0078] (Example 1) [Film formation of a polyvinyl alcohol water-soluble sacrificial layer obtained by gravure coating] Polyvinyl alcohol (molecular weight 22000, saponification degree 86.5-89%, manufactured by Kanto Chemical Co., Ltd.) was dissolved in ion-exchanged water by heating to prepare a 10% by mass solution. Then, a PET film (Lumirror L-25T60, manufactured by TORAY Co., Ltd.) was placed on a MICROGRAVURE coating machine (manufactured by Yasuie Seiki Co., Ltd.), and the 10% by mass polyvinyl alcohol aqueous solution was coated while being heated and dried at 120°C, thereby forming a water-soluble sacrificial film with a thickness of 10 μm onto the PET film. At this time, the film feed speed was 0.2 m / min, and the gravure roller rotation speed was 30 rpm.

[0079] [Film formation of addition-curing liquid silicone rubber coating liquid obtained by gravure coating] An addition-curing liquid silicone rubber coating liquid, prepared by uniformly mixing the components shown in Table 1 below, was applied to a PET film laminated with a polyvinyl alcohol water-soluble sacrificial layer using a MICROGRAVURE coating machine (manufactured by Yasuie Seiki Co., Ltd.). The coated film was then heated to crosslink and cure, thus producing a cured silicone rubber film. The heating temperature was 120°C, the film feed speed was 0.2 m / min, and the gravure roller rotation speed was 3 rpm. Hot air at 120°C was applied to the coated film for approximately 1 minute to induce partial crosslinking, followed by heating at 120°C for 1 hour to fully cure the coating film. The gravure roller used was a 20 mm diameter gravure roller (oblique-line type gravure roller) with recesses formed by obliquely arranged lines on its outer periphery, and the number of lines per unit length parallel to the rotation axis of the gravure roller (hereinafter referred to as the line count) was 250 lines / inch. In addition, the viscosity of each coating liquid was measured using a rotational viscometer (TV-25, manufactured by Toki Sangyo Co., Ltd.) at 25°C with a rotational speed of 1 rpm and a measurement time of 1 minute. The thickness, tensile strength, and elongation at break of the obtained silicone rubber cured films were measured using the methods described below, as shown in Table 1.

[0080] [Measurement of film thickness] Four masking tapes were adhered as a frame to the outermost layer of the three-layer structure of silicone rubber cured film / polyvinyl alcohol water-soluble sacrificial layer / PET film, i.e., the surface of the silicone rubber cured film. This frame was then peeled off, thereby separating the two-layer structure composed of the silicone rubber cured film / polyvinyl alcohol water-soluble sacrificial layer. The two layers were then washed with hot water at 40°C for 10 minutes, followed by washing with deionized water to dissolve the polyvinyl alcohol water-soluble sacrificial layer, thus separating the silicone rubber cured film. The separated silicone rubber cured film was then adhered to a 20mm × 20mm square silicon wafer (manufactured by KST, SEIREN Co., Ltd.), allowed to air dry, and its thickness was measured using a Dektak-XT-S stylus analysis system (manufactured by Bruker).

[0081] [Measurement of mechanical and physical properties] A sample of the cured silicone rubber film, separated using the same method as the film thickness measurement, was adhered to a glass tube with an inner diameter of 7.0 mm and fixed in a fixture. 100 μL of ion-exchanged water was dropped onto the adhered cured silicone rubber film, and the resulting deformation was photographed. The stress applied to the cured silicone rubber film was calculated using equation (1) below, and the strain of the cured silicone rubber film was calculated using equation (2) below. A stress-strain curve was then plotted. The maximum stress of the cured silicone rubber film until fracture was recorded as the fracture strength in the stress-strain curve. Furthermore, the strain at fracture was recorded as the elongation at fracture. Each sample was measured three times, and the average value of the fracture strength and the elongation at fracture was presented as the result. Formula 1 σ: stress P: Pressure generated by the dripping of water a: tube inner diameter d: Deflection of the cured silicone rubber film t: Thickness of the cured silicone rubber film Formula 2 ε: strain s: The outline length of the silicone rubber cured film after water is added. s0: The outline length of the cured silicone rubber film before water is added.

[0082] (Examples 2 and 3, Reference Example 1, Comparative Example 1) Except for changing the components used in preparing the addition-curing liquid silicone rubber coating liquid in Example 1 to those shown in Table 1 below, a silicone rubber cured film was manufactured according to the same method as in Example 1, and evaluated according to the same method (Example 2, Reference Example 1, Comparative Example 1). In Example 3, except that the gravure roller was changed to a gravure roller with a line count of 200 lines / inch, a silicone rubber cured film was manufactured according to the same method as in Reference Example 1, and evaluated according to the same method. The results are shown in Table 1.

[0083] (Example 4, Comparative Examples 2 and 3) Except that the gravure roller used in Example 1 for transferring and coating the addition-curing liquid silicone rubber coating liquid was changed to a gravure roller with a line count of 150, 180, or 200 lines per inch, silicone rubber cured films were manufactured according to the same method as in Example 1, and the thickness was evaluated using the same method. The results are shown in Table 2 below. In addition, for comparison, the results of Example 1 are also listed in Table 2.

[0084] (Examples 5-7) Except for the components used in Example 1 for preparing the addition-curing liquid silicone rubber coating liquid, which were further formulated with the components shown in Table 3 below, the cured silicone rubber film was manufactured according to the same method as in Example 1, and evaluated according to the same method. The results are shown in Table 3.

[0085] (Compare Examples 4 and 5) Except for the addition of the organic solvents shown in Table 4 below to the components used in Example 1 for preparing the addition-curing liquid silicone rubber coating liquid, the cured silicone rubber film was manufactured according to the same method as in Example 1, and the thickness was evaluated in the same manner. In Comparative Example 5, except that the gravure roller was replaced with a gravure roller with a line count of 180 lines / inch, the cured silicone rubber film was manufactured according to the same method as in Example 1, and the thickness was evaluated in the same manner. Furthermore, the number of pinholes on the surface of the cured silicone rubber films obtained in Example 1 and Comparative Examples 4 and 5 was measured according to the method shown below. The results are shown in Table 4 below. Additionally, for comparison purposes, the results of Example 1 are also listed in Table 4.

[0086] [Measurement of the number of pinholes on the surface] The three-layer structure consisting of a silicone rubber cured film, a polyvinyl alcohol water-soluble sacrificial layer, and a PET film was cut into 20mm × 20mm pieces. After performing a gold sputtering treatment on the surface for 1 minute, the surface was observed using a scanning electron microscope VE-9800 (manufactured by KEYENCE Co., Ltd.) at a magnification of 40 to 1000x, and the number of pinholes with a diameter of 1μm or larger on the surface of the silicone rubber cured film was measured.

[0087] (Comparative Examples 6-9) Using the addition-curing liquid silicone rubber coating liquid prepared in Example 1, a coating and film formation process based on spin coating was performed under the following conditions to attempt to manufacture a silicone rubber cured film. The results are shown in Table 5 below.

[0088] Film formation of addition-curing liquid silicone rubber coating liquid using spin coating method A glass plate was mounted on a spin coater (MS-B200, manufactured by MIKASA Co., Ltd.), and the PET film with the polyvinyl alcohol water-soluble sacrificial layer laminated thereon was fixed on it with double-sided tape. Then, 0.5 mL of each of the coating solutions prepared by uniformly mixing the components shown in Table 3 below was added dropwise to the PET film with the polyvinyl alcohol water-soluble sacrificial layer laminated thereon, and spin-coating was performed for 20 seconds at rotation speeds of 4000, 5000, 6000, and 7000 rpm, respectively. Then, the addition-curing liquid silicone rubber coating film was cross-linked and cured by standing in an oven heated to 120°C for 10 minutes.

[0089] Table 1 The Influence of Vinyl-Containing Liquid Dimethyl Polysiloxanes with Different Degrees of Polymerization on the Viscosity of Coating Solution, Thickness of Cured Silicone Rubber Film, and Physical Properties H / V : The molar ratio (mol / mol) of hydrosilicone groups in hydrosilicone-containing liquid methylhydrosiloxanes to vinyl groups in vinyl-containing liquid dimethylpolysiloxanes. Pt quantity The mass ratio (ppm) of platinum atoms in the platinum catalyst solution to vinyl-containing liquid dimethyl polysiloxane.

[0090] Based on the results in Table 1, it can be confirmed that in Examples 1 and 2, by using a slanted gravure roller with a line count of 250 lines / inch to transfer an addition-curing liquid silicone rubber coating solution that has not been diluted with an organic solvent, a silicone rubber cured film with a thickness of less than 5.5 μm can be produced. Furthermore, when using a gravure roller with the same line count, there is a tendency for the thickness of the resulting silicone rubber cured film to be thinner as the viscosity of the addition-curing liquid silicone rubber coating solution increases. It was confirmed that in Reference Example 1, although the slanted gravure roller with a line count of 250 lines / inch could not perform coating due to the excessively high viscosity of the coating solution, Example 3, which used a slanted gravure roller with a line count of 200 lines / inch, still achieved a silicone rubber cured film with a thickness of less than 5.5 μm, even when using the same coating solution as Reference Example 1.

[0091] Furthermore, in Comparative Example 1, if the viscosity is too high, it is impossible to use a slanted gravure roller with a line count of 250 lines per inch to transfer the addition-curing liquid silicone rubber coating liquid that has not been diluted with organic solvent.

[0092] In addition, although an attempt was made to manufacture a silicone rubber cured film using a vinyl-containing liquid dimethyl polysiloxane with a lower molecular weight (lower degree of polymerization) than DMS-V31, the silicone rubber cured film after film formation was brittle and had poor physical properties, making it impossible to separate the film from the three-layer structure of silicone rubber cured film / polyvinyl alcohol water-soluble sacrificial layer / PET film and measure the film thickness.

[0093] Table 2 The Influence of Different Line Counts on the Thickness of Cured Silicone Rubber Films

[0094] Based on the results in Table 2, it can be confirmed that in Examples 4 and 1, by using slanted gravure rollers with line counts of 200 and 250 lines / inch respectively, and transferring the addition-curing liquid silicone rubber coating liquid without dilution with organic solvent, silicone rubber cured films with a thickness of less than 5.5 μm can be produced. Furthermore, when using addition-curing liquid silicone rubber coating liquids of the same composition, there is a tendency that the higher the line count of the slanted gravure roller, the thinner the resulting silicone rubber cured film becomes. Additionally, in Comparative Examples 2 and 3, when using slanted gravure rollers with line counts of 150 and 180 lines / inch, it was not possible to produce silicone rubber cured films with a maximum thickness of 5.5 μm.

[0095] Table 3 The effect of incorporating vinyl dimethyl polysiloxane-containing raw rubber into addition-curing liquid silicone rubber coating liquid on the viscosity of the coating liquid, the thickness of the cured silicone rubber film, and its physical properties.

[0096] Based on the results in Table 3, it can be confirmed that in Examples 5-7, by adding a small amount of vinyl-containing dimethyl polysiloxane raw rubber, up to 10% by mass, to an addition-curing liquid silicone rubber coating liquid containing vinyl-containing liquid dimethyl polysiloxane, hydrosilicone-containing liquid methyl hydropolysiloxane, and a platinum catalyst solution, the thickness of the resulting cured silicone rubber film tends to decrease. In addition, the physical properties (tensile strength, elongation) of the resulting cured silicone rubber film are improved.

[0097] Table 4 The effect of organic solvent dilution on the number of pinholes in addition-curing liquid silicone rubber coating solutions

[0098] According to the results in Table 4, when comparing the silicone rubber cured film obtained in Example 1 by transferring the addition-curing liquid silicone rubber coating liquid without dilution with organic solvent using a slanted gravure roller, with the silicone rubber cured films obtained in Comparative Examples 4 and 5 by transferring the addition-curing liquid silicone rubber coating liquid with reduced viscosity by dilution with organic solvent using a slanted gravure roller, the number of pinholes on the surface of the silicone rubber cured film is significantly reduced, whether comparing films obtained by transferring using a slanted gravure roller with the same line count or films with the same thickness.

[0099] Table 5 Effect of spin coating on the thickness of cured silicone rubber films

[0100] According to the results in Table 5, although in Comparative Examples 6 to 9, an addition-curing liquid silicone rubber coating liquid that was not diluted with an organic solvent was used to form a silicone rubber cured film by spin coating, it was not possible to produce a silicone rubber cured film with a maximum thickness of 5.5 μm within the spin coating speed range of 1000 to 7000 rpm (limit value). Industrial applicability

[0101] The method for manufacturing a silicone rubber cured film according to the present invention can efficiently produce a silicone rubber cured film that does not release environmentally hazardous organic solvents that cause air pollution and are harmful to human health. Furthermore, it significantly reduces surface pinholes that would otherwise degrade physical properties. This method is expected to be suitable for a wide range of applications, including cosmetics, biochemical applications such as cell culture containers, medical applications such as wound dressing materials, and gas separation membranes. The silicone rubber cured film of the present invention reduces surface pinholes, making it suitable for a wide range of applications, including cosmetics, biochemical applications such as cell culture containers, medical applications such as wound dressing materials, and gas separation membranes.

Claims

1. A method for manufacturing a silicone rubber cured film, characterized in that: Using an addition-curing liquid silicone rubber coating liquid comprising a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in its molecule, a liquid methylhydropolysiloxane having at least a plurality of hydrosilane groups in its molecule, and a platinum catalyst solution and / or suspension, and substantially free of organic solvents, the addition-curing liquid silicone rubber coating liquid is scraped onto the recesses of an embossed pattern on the surface of a gravure roller, transferred and coated onto a substrate to form a coating film. The coating film is then heated, irradiated with ultraviolet light, and / or irradiated with an electron beam to crosslink and cure the liquid dimethylpolysiloxane and the liquid methylhydropolysiloxane. The film thickness is maximized to 5.5 μm by setting the maximum viscosity of the addition-curing liquid silicone rubber coating liquid at 25°C to 75 Pa·s, by having the embossed pattern comprised of recesses formed by lines arranged obliquely on the outer periphery of the gravure roller, and by having at least 200 lines / inch per unit length parallel to the rotation axis of the gravure roller.

2. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: A water-soluble sacrificial layer is formed on the substrate, and the addition-curing liquid silicone rubber coating liquid is transferred and coated on the water-soluble sacrificial layer to form a coating film. The coating film is then cross-linked and cured to form a silicone rubber cured film.

3. The method for manufacturing a silicone rubber cured film according to claim 2, characterized in that: The water-soluble sacrificial layer on which the silicone rubber cured film is formed is further peeled off from the substrate, and then the water-soluble sacrificial layer is dissolved to separate the silicone rubber cured film.

4. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: The depth of the recess is set to 5–40 μm.

5. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: The maximum content of organic solvent in the addition-curing liquid silicone rubber coating liquid is adjusted to 1% by mass.

6. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: The addition-curing liquid silicone rubber coating liquid does not contain any organic solvents other than those in the platinum catalyst solution and / or suspension.

7. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: As the liquid dimethyl polysiloxane, a linear dimethyl polysiloxane with vinyl groups bonded to silicon atoms at both ends of the molecular chain is used; as the liquid methyl hydrogen polysiloxane, a linear methyl hydrogen polysiloxane with multiple hydrogen atoms bonded to silicon atoms at the non-terminal ends of the molecular chain is used.

8. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: As the liquid dimethyl polysiloxane, a dimethyl polysiloxane with both ends of the molecular chain capped by dimethylvinylsiloxy groups is used; as the liquid methylhydropolysiloxane, a dimethylsiloxane-methylhydrosiloxane copolymer with both ends of the molecular chain capped by trimethylsiloxy groups is used.

9. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: The addition-curing liquid silicone rubber coating liquid also contains dimethyl polysiloxane raw rubber having at least a plurality of vinyl groups in its molecule.

10. The method for manufacturing a silicone rubber cured film according to claim 1, characterized in that: The number of lines per unit length is set to 200-250 lines per inch.

11. The method for manufacturing a silicone rubber cured film according to any one of claims 1 to 10, characterized in that: The viscosity of the addition-curing liquid silicone rubber coating liquid at 25°C is set to 1–75 Pa·s.

12. A silicone rubber cured film, characterized in that: The cured silicone rubber film is a cross-linked cured product of a transfer coating film made from an addition-curing liquid silicone rubber coating liquid. The addition-curing liquid silicone rubber coating liquid comprises a liquid dimethyl polysiloxane having at least a plurality of vinyl groups in its molecule, a liquid methyl hydropolysiloxane having at least a plurality of hydrosilane groups in its molecule and which is cross-linked therewith, and a platinum catalyst solution and / or suspension, and is substantially free of organic solvents, with a maximum viscosity of 75 Pa·s at 25°C. The cured silicone rubber film is a cross-linked cured product of the transfer coating film formed by the coating liquid from the recesses of an embossed pattern, wherein the embossed pattern has recesses formed by lines arranged obliquely on the outer periphery of the gravure roller, and the number of lines per unit length parallel to the rotation axis of the gravure roller is at least 200 lines / inch. The maximum thickness of the cured silicone rubber film is 5.5 μm.

13. The silicone rubber cured film according to claim 12, characterized in that: The cross-linked cured product is a separation layer separated from the water-soluble sacrificial layer.

14. The silicone rubber cured film according to claim 12, characterized in that: The number of pinholes with a diameter of at least 1 μm that exist within a surface with an area of ​​20 mm × 20 mm is less than 7.

15. The silicone rubber cured film according to claim 12, characterized in that: The addition-curing liquid silicone rubber coating liquid contains no organic solvents other than the organic solvents in the platinum catalyst solution and / or suspension, and the maximum content of organic solvents is 1% by mass.

16. The silicone rubber cured film according to any one of claims 12 to 15, characterized in that: The thickness is 0.2 to 5.5 μm, the number of pinholes is less than 5, the breaking strength is at least 0.6 MPa, and the elongation is at least 35%.

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