Method for producing silicone rubber cured product thin film

Abstract

Provided is a method for efficiently producing a silicone rubber cured product thin film that has a thickness of at most 5.5 μm, that has less surface pinholes causing a deterioration in the physical properties, and that substantially does not release an organic solvent that has a large environmental load, causes air pollution, and is harmful to the human body.　This method for efficiently producing a silicone rubber cured product thin film involves crosslinking and curing, through heating, UV irradiation, and / or electron beam irradiation, a liquid addition-curable silicone rubber coating liquid that has a viscosity of at most 75 Pa·s at 25°C, that is substantially free of an organic solvent, and that has been transferred and applied to a substrate by means of recessed portions of a gravure roll which has a projection / recess pattern in the surface and in which the number of lines of the recessed portions per unit length is at least 200 lines / inch, to produce a silicone rubber cured product thin film having a thickness of at most 5.5 μm.

Description

Method for producing thin films of cured silicone rubber

[0001] The present invention relates to a method for producing a thin film of cured silicone rubber by preparing a film-forming coating liquid from an addition-curable liquid silicone rubber composition without substantially diluting it with an organic solvent, and then transfer-coating the coating liquid onto a substrate with a gravure roll to form a coating film, which is then crosslinked and cured, and to this thin film of cured silicone rubber.

[0002] Cured silicone rubber is a rubber-like elastic material formed by three-dimensional crosslinking and curing of dimethylpolysiloxane, a polymer with excellent heat resistance, gas permeability, and biocompatibility. Thin-film cured silicone rubber is widely used in cosmetics, biochemistry applications such as cell culture vessels, medical applications such as wound dressings, and CO2 treatments. ２ and N ２ It is expected to be used in a wide range of applications, including gas separation membranes.

[0003] Conventionally, a method for forming a thin film of a cured silicone rubber has been used in which an uncrosslinked, addition-curable liquid silicone rubber composition containing a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in the molecule, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups (SiH groups) in the molecule, and a platinum-based catalyst is diluted with an organic solvent such as hexane, toluene, or a cyclic siloxane to prepare a coating liquid, which is then applied to a substrate by gravure coating or spin coating, after which the organic solvent is removed by volatilization, and the coating is then cured by heating or ultraviolet irradiation to form a film (Non-Patent Document 1).

[0004] Typically, to obtain a thin film of cured silicone rubber up to 5.5 μm thick by spin coating, the addition-curable liquid silicone rubber composition is diluted with an organic solvent to prepare a low-viscosity coating solution, which is then spin-coated to form a film and then crosslinked and cured. The thickness of the film that can be formed by spin coating depends on the viscosity of the addition-curable liquid silicone rubber composition and the rotation speed of the spin coater; the higher the viscosity and the lower the rotation speed, the thicker the film. However, even if a relatively low-molecular-weight, low-viscosity vinyl-containing liquid dimethylpolysiloxane is used and the rotation speed of the spin coater is increased, it is usually difficult to form a film up to 5.5 μm thick using spin coating without dilution with an organic solvent. In recent years, ultra-high-speed spin coaters with rotation speeds of up to 60,000 rpm have been commercially available. However, the faster the rotation speed, the more radially aligned the dimethylpolysiloxane chains become during curing, resulting in distortion of the film and variations in physical properties, making it difficult to obtain a homogeneous cured silicone rubber thin film.

[0005] Furthermore, the molecular weight of the vinyl-containing liquid dimethylpolysiloxane in the coating solution significantly affects the physical properties of the cured silicone rubber thin film. The elongation of the cured silicone rubber after crosslinking depends on the dimethylpolysiloxane chain length between crosslinks, with the longer the chain length between crosslinks, the greater the elongation tends to be. Cured silicone rubber obtained from low-molecular-weight, low-viscosity vinyl-containing liquid dimethylpolysiloxanes has a short chain length between crosslinks, making it difficult to elongate and brittle, making it undesirable. Therefore, conventionally, a relatively high-molecular-weight, high-viscosity vinyl-containing liquid dimethylpolysiloxane is diluted with an organic solvent to reduce the viscosity of the coating solution, which is then applied by gravure coating or spin coating, followed by volatilizing and removing the organic solvent, followed by crosslinking and curing to form a thin film.

[0006] Meanwhile, in recent years, green chemistry, which aims to reduce environmental impact, has been gaining attention, and it is desirable to avoid the use of organic solvents, which cause air pollution, as much as possible. Furthermore, organic solvents are generally harmful to the human body. Therefore, even if organic solvents are removed during the manufacturing process, it is necessary to evaluate the residual amount of organic solvents in the final product, which increases manufacturing costs.

[0007] Volatile low-molecular-weight cyclic siloxanes such as octamethylcyclotetrasiloxane, which are used as organic solvents, are non-toxic and highly safe for humans, and are often used in cosmetics to dilute relatively high-molecular-weight vinyl-containing liquid dimethylpolysiloxanes. However, once released into the aquatic environment, they are difficult to decompose and tend to adsorb to mud on the bottom of the water and remain there for long periods of time, posing a high risk of environmental pollution. In recent years, they have been added to the SVHCs of the REACH Regulation 19th Edition.

[0008] Furthermore, when producing a cured silicone rubber thin film using an addition-curable liquid silicone rubber coating solution diluted with an organic solvent, there is also the problem that pinholes are likely to occur in the cured silicone rubber thin film when the organic solvent is volatilized and removed. That is, after applying an addition-curable liquid silicone rubber coating solution diluted with an organic solvent to a substrate, before or during crosslinking and curing the coating film, as the organic solvent volatilizes and the coating film forms, pinholes may form as the organic solvent volatilizes from the coating film, which may reduce the barrier properties of the film or serve as the starting point for fracture when the film ruptures, resulting in concerns about deterioration of the film's physical properties. Due to their gas permeability, cured silicone rubber thin films are expected to be used as cell culture vessels and gas separation membranes. However, when used as cell culture vessels or gas separation membranes, the presence of pinholes can cause liquid or gas leakage, significantly impairing the functionality of the product.

[0009] Sho Mihara, Shinji Takeoka, “Preparation and characterization of highly elongated polydimethylsiloxane “nanosheets”, Polym. Adv. Technol. , 33, p. 1180-1189 (2022).

[0010] The present invention has been made to solve the above-mentioned problems, and has as its object to provide a method for efficiently producing a thin film of cured silicone rubber up to 5.5 μm thick, which does not substantially release into the surrounding area organic solvents that have a large environmental impact, cause air pollution, and are harmful to humans, and which has reduced surface pinholes that cause deterioration of physical properties, and to provide such a thin film of cured silicone rubber.

[0011] As a result of extensive investigation, the present inventors discovered that it is possible to efficiently produce a thin film of cured silicone rubber with a minimal number of pinholes on its surface by preparing a film-forming coating liquid of an addition-curable liquid silicone rubber composition without substantially diluting it with an organic solvent, scraping the coating liquid into the recesses of a specific gravure roll with an uneven surface, and transfer-coating the uncrosslinked addition-curable liquid silicone rubber coating liquid that is substantially free of organic solvent onto a substrate, and then crosslinking and curing the coating film by heating, irradiating with ultraviolet light and / or irradiating with an electron beam, without substantially releasing organic solvent into the surroundings. This discovery led to the completion of the present invention.

[0012] The method for producing a cured silicone rubber thin film, which has been devised to achieve the above object, comprises: a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in the molecule, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups in the molecule, and a platinum catalyst solution and / or suspension; an addition-curable liquid silicone rubber coating liquid that is substantially free of organic solvents; the liquid dimethylpolysiloxane having at least a plurality of vinyl groups in the molecule, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups in the molecule, and a platinum catalyst solution and / or suspension; the liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups in the molecule; the addition-curable liquid silicone rubber coating liquid that is substantially free of organic solvents ... and curing the liquid dimethylpolysiloxane and the liquid methylhydrogenpolysiloxane by crosslinking the liquid dimethylpolysiloxane and the liquid methylhydrogenpolysiloxane. The viscosity of the addition-curable liquid silicone rubber coating liquid at 25°C is set to a maximum of 75 Pa s, and the concave-convex pattern has recesses consisting of lines arranged diagonally on the outer periphery of the gravure roll, and the number of lines per unit length parallel to the rotation axis of the gravure roll is at least 200 lines / inch, thereby achieving a maximum thickness of the thin film of 5.5 μm.

[0013] This method for producing a cured silicone rubber thin film may involve forming a water-soluble sacrificial layer on the substrate, transferring and applying the addition-curable liquid silicone rubber coating liquid onto the sacrificial layer to form a coating film, and then crosslinking and curing the coating film to form a cured silicone rubber thin film.

[0014] This method for producing a cured silicone rubber thin film may further include peeling the water-soluble sacrificial layer on which the cured silicone rubber thin film has been formed from the substrate, and then dissolving the water-soluble sacrificial layer to isolate the cured silicone rubber thin film.

[0015] This method for producing a thin film of cured silicone rubber may also be such that the depth of the recesses is 5 to 40 μm.

[0016] This method for producing a cured silicone rubber thin film may also involve adjusting the content of organic solvent in the addition-curable liquid silicone rubber coating solution to a maximum of 1% by mass.

[0017] In this method for producing a thin film of cured silicone rubber, the addition-curable liquid silicone rubber coating solution does not need to contain any organic solvent other than the organic solvent in the platinum catalyst solution and / or suspension.

[0018] This method for producing a cured silicone rubber thin film may use, as the liquid dimethylpolysiloxane, a linear dimethylpolysiloxane having vinyl groups bonded to silicon atoms at both molecular chain terminals, and as the liquid methylhydrogenpolysiloxane, a linear methylhydrogenpolysiloxane having a plurality of hydrogen atoms bonded to silicon atoms not at the terminals of the molecular chain.

[0019] This method for producing a cured silicone rubber thin film may use, as the liquid dimethylpolysiloxane, a dimethylpolysiloxane whose molecular chain ends are capped with vinyldimethylsiloxy groups at both molecular chain ends, and may use, as the liquid methylhydrogenpolysiloxane, a dimethylsiloxane-methylhydrogensiloxane copolymer whose molecular chain ends are capped with trimethylsiloxy groups at both molecular chain ends.

[0020] In this method for producing a thin film of cured silicone rubber, the addition-curable liquid silicone rubber coating solution may further contain a dimethylpolysiloxane raw rubber having at least a plurality of vinyl groups in the molecule.

[0021] This method for producing a thin film of cured silicone rubber may be such that the number of lines per unit length is 200 to 250 lines / inch.

[0022] This method for producing a thin film of cured silicone rubber may be such that the viscosity of the addition-curable liquid silicone rubber coating liquid at 25°C is 1 to 75 Pa·s.

[0023] The cured silicone rubber thin film achieved in order to achieve the above object is a cured silicone rubber thin film which is a crosslinked and cured product of a transfer-coated film of an addition-curable liquid silicone rubber coating fluid which contains a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in its molecule, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups in its molecule which crosslink and cure thereto, and a platinum catalyst solution and / or suspension, and which is substantially free of organic solvents and has a viscosity of up to 75 Pa s at 25°C, and in which the crosslinked and cured product of the transfer-coated film of the coating fluid is formed from the recesses of an uneven pattern which has lines arranged diagonally on the outer periphery of a gravure roll, and in which the number of lines per unit length parallel to the rotation axis of the gravure roll is at least 200 lines / inch, and the thickness of the transfer-coated film is up to 5.5 μm.

[0024] In this cured silicone rubber thin film, the cross-linked cured product may be an isolation layer from the water-soluble sacrificial layer.

[0025] This cured silicone rubber thin film may have less than seven pinholes with a diameter of at least 1 μm within a surface area of ​​20 mm×20 mm.

[0026] In this cured silicone rubber thin film, the addition reaction curable liquid silicone rubber coating liquid may contain no organic solvent other than the organic solvent in the platinum catalyst solution and / or suspension, and the organic solvent content may be up to 1 mass %.

[0027] This cured silicone rubber thin film may have a thickness of 0.2 to 5.5 μm, the number of pinholes may be less than 5, a breaking strength of at least 0.6 MPa, and an elongation of at least 35%.

[0028] The method for producing a cured silicone rubber thin film of the present invention makes it possible to efficiently produce a cured silicone rubber thin film up to 5.5 μm thick, with substantially no release of organic solvents into the surrounding area, which have a large environmental impact and are a cause of air pollution and are harmful to humans, and with reduced surface pinholes that can cause deterioration of physical properties.This cured silicone rubber thin film has fewer surface pinholes that can reduce barrier properties and lead to film breakdown, reducing the risk of deterioration of physical properties.

[0029] Hereinafter, embodiments for carrying out the present invention will be described in detail, but the scope of the present invention is not limited to these embodiments.

[0030] The method for producing a cured silicone rubber thin film of the present invention uses an addition-curable liquid silicone rubber composition that is substantially free of organic solvents and that crosslinks and cures to form a silicone rubber elastomer by heating, ultraviolet irradiation, or the like, and contains a liquid dimethylpolysiloxane having at least a plurality of vinyl groups bonded to silicon atoms as the reactive dimethylpolysiloxane component capable of constructing a three-dimensional crosslinked structure, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups per molecule as the crosslinking agent, and a platinum catalyst solution and / or suspension. Even if the platinum catalyst solution and / or suspension contained in trace amounts in this composition contains a trace amount of organic solvent, it is prepared as a coating liquid for film formation without dilution with any other organic solvent, and this substantially solvent-free coating liquid is transfer-coated onto a substrate using a specific gravure roll having a concave-convex pattern on its surface, and the resulting coating is crosslinked and cured by heating, ultraviolet irradiation, and / or electron beam irradiation to obtain a cured silicone rubber thin film.

[0031] In the present invention, gravure coating is selected as the coating method in order to obtain a thin film by uniformly applying a substantially solvent-free coating liquid containing a relatively high viscosity vinyl group-containing liquid dimethylpolysiloxane onto a substrate without any substantial dilution with any organic solvent other than the trace amounts of organic solvent in the platinum catalyst solution and / or suspension.

[0032] In the present invention, "substantially free of organic solvents," "not substantially diluted with organic solvents," and "substantially solvent-free" mean that the content of organic solvent in the coating liquid is at most 1 mass %, particularly at most 0.5 mass %, and especially at most 0.1 mass %. Furthermore, in the present invention, a "thin film" means a film having a thickness of at most 5.5 μm.

[0033] Gravure coating allows for a more uniform and thin coating of a highly viscous coating liquid than spin coating, and is efficient and suitable for mass production because it essentially involves a gravure roll continuously scraping and transferring the coating liquid onto the substrate.

[0034] The gravure coating method uses a small-diameter gravure roll, which rotates in contact with the coating liquid at a constant rotation speed and has various fine concave-convex patterns engraved or molded on its surface. The gravure roll includes a so-called oblique gravure roll having concave portions consisting of diagonally arranged lines on the outer periphery, a so-called pyramid gravure roll having concave portions consisting of square pyramidal cells arranged vertically and horizontally on the outer periphery, a so-called lattice gravure roll having concave portions consisting of square prism-shaped cells, a so-called trapezoid gravure roll having concave portions consisting of square truncated pyramidal cells, and a so-called tortoiseshell gravure roll having concave portions consisting of hexagonal pyramidal, hexagonal prism-shaped, or hexagonal truncated pyramidal cells.

[0035] The concave portions of the gravure roll rotate at a constant rotation speed while in contact with the coating liquid, and scrape up and support a predetermined amount of coating liquid according to the depth of the concave portions of the concave-convex pattern formed on the surface of the gravure roll. Excess coating liquid is then scraped off with a doctor blade before being transferred to the substrate. The coating liquid scraped up into the concave portions of the concave-convex pattern according to the depth of the concave portions of the gravure roll is then transferred and coated onto the substrate.

[0036] The finer the concave-convex pattern engraved or molded on the surface of the gravure roll, the greater the number of lines or cells per unit length parallel to the rotation axis of the gravure roll, and accordingly the depth of the recesses becomes shallower, so that the amount of coating liquid transferred to the substrate decreases, and a thinner coating film can be transferred and coated onto the substrate.

[0037] When a pyramidal gravure roll, a lattice gravure roll, a trapezoidal gravure roll, or a tortoiseshell gravure roll is used as the gravure roll, the recesses, which are the cells of the uneven pattern, are independent of each other, so that the coating liquid scraped up into the recesses does not easily flow, making it difficult for the coating liquid to be smoothed and making it easy for the printing pattern to be transferred. On the other hand, with an oblique gravure roll, the lines arranged obliquely on the outer periphery are connected in a spiral, so that the scraped up coating liquid easily flows along the recesses, which make it easy for the coating liquid to be smoothed and making it difficult for the printing pattern to be transferred. Therefore, in the manufacturing method of the present invention, an oblique gravure roll is selected as the gravure roll.

[0038] When using an oblique gravure roll as the gravure roll, in order to produce a thin film of cured silicone rubber with a maximum thickness of 5.5 μm, the number of lines per unit length parallel to the rotation axis of the gravure roll must be 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 into the recesses of the uneven pattern, making it impossible to produce a thin film of cured silicone rubber with a maximum thickness of 5.5 μm.

[0039] For a coating liquid having a relatively high viscosity of 70 Pa s or more at 25°C, using an oblique gravure roll with a large number of lines, for example 250 lines / inch, may result in the viscosity being too high and coating may be difficult, so for a coating liquid with a relatively high viscosity, it is desirable to use an oblique gravure roll with a relatively small number of lines, less than 250 lines / inch, preferably 200 lines / inch or more but less than 250 lines / inch, more preferably 200 to 230 lines / inch. Specifically, it is desirable not to use an oblique gravure roll with 250 lines / inch for a coating liquid having a viscosity of 70 Pa s or more at 25°C.

[0040] In the present invention, there are no particular restrictions on the depth of the recesses. However, from the perspective of producing a thin film of cured silicone rubber having a thickness of up to 5.5 μm, particularly 0.2 to 3 μm, and especially 0.3 to 2 μm, it is generally preferable that the depth of the recesses be approximately 5 to 40 μm, and especially 7 to 30 μm.

[0041] Regarding the diameter of the gravure roll, the larger the number of lines on the oblique gravure roll, the smaller the amount of coating liquid carried in the recesses of the gravure roll, which may lead to the coating liquid hardening on the gravure roll during coating. Therefore, it is desirable that the gravure roll have as small a diameter as possible. In the present invention, the diameter of the gravure roll is preferably about 20 to 40 mm.

[0042] Regarding the rotation speed of the gravure roll, increasing the rotation speed increases the contact area between the coating liquid and the substrate, which results in an increase in the amount of coating applied to the substrate and a tendency for the film thickness to increase. Therefore, if the goal is to reduce the film thickness, it is necessary to reduce the rotation speed to a certain extent, but if the rotation speed is reduced too much, the contact area between the coating liquid and the substrate will decrease, resulting in an excessively small amount of coating applied to the substrate, which may result in uneven coating or blurring. In the present invention, the rotation speed of the gravure roll is preferably about 3 to 30 rpm.

[0043] The liquid dimethylpolysiloxane having at least a plurality of vinyl groups per molecule, which is the main component of this addition-curable liquid silicone rubber coating fluid, is a linear or branched dimethylpolysiloxane that is liquid at room temperature of 1 to 30°C and has at least two, usually 2 to 50, preferably 2 to 20, and more preferably 2 to 10 vinyl groups per molecule, and whose main chain is essentially composed of dimethylsiloxane units ((CH ３ ) ２ Generally, the dimethylpolysiloxane is a linear liquid dimethylpolysiloxane consisting of repeating units of SiO units, with both molecular chain terminals blocked with triorganosiloxy groups such as trimethylsiloxy, vinyldimethylsiloxy, divinylmethylsiloxy, trivinylsiloxy, or vinylphenylmethylsiloxy. However, it may also be a branched-chain siloxane structure containing a branched structure as part of the siloxane structure constituting the molecular chain. The vinyl group may be bonded to a silicon atom at one or both molecular chain terminals, or to a silicon atom at a non-terminal end of the molecular chain, i.e., in the middle of the molecular chain. However, it is preferable that the vinyl group contains a vinyl group bonded to a silicon atom at at least both molecular chain terminals. In this case, the vinyl group may be present only at both molecular chain terminals, or at both molecular chain terminals and non-terminal end.

[0044] Examples of liquid dimethylpolysiloxanes having at least a plurality of vinyl groups in the molecule include dimethylpolysiloxanes terminally capped with vinyldimethylsiloxy groups, dimethylpolysiloxanes terminally capped with divinylmethylsiloxy groups, dimethylpolysiloxanes terminally capped with trivinylsiloxy groups, dimethylpolysiloxanes terminally capped with vinylphenylmethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with vinyldimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with divinylmethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with trivinylsiloxy groups, and dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with vinylphenylmethylsiloxy groups.

[0045] The degree of polymerization, which is the number of repeating siloxane units constituting the main chain of this vinyl group-containing liquid dimethylpolysiloxane, is usually 20 to 2,000, preferably about 80 to 1,000, and the number average molecular weight is usually 1,500 to 150,000, preferably about 6,000 to 75,000. The viscosity of this vinyl group-containing liquid dimethylpolysiloxane at 25°C is usually 100 to 100,000 mPa·s, preferably about 500 to 50,000 mPa·s.

[0046] The molecular weight of this vinyl group-containing liquid dimethylpolysiloxane and the degree of polymerization, which is the number of repeating siloxane units constituting the main chain, can usually be determined as the polystyrene-equivalent number-average molecular weight or weight-average molecular weight and number-average degree of polymerization, etc., in gel permeation chromatography analysis using toluene or the like as a developing solvent. The viscosity can usually be measured at 25°C using a rotational viscometer such as a BL-type, BH-type, BS-type, or cone-plate type rheometer.

[0047] Examples of such vinyl group-containing liquid dimethylpolysiloxanes include DMS-V03, DMS-V21, DMS-V31, DMS-V41, DMS-V46, and DMS-V52 (all of which are product names of Gelest Co., Ltd.) These vinyl group-containing liquid dimethylpolysiloxanes may be used alone or in combination of two or more types.

[0048] The liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups per molecule, which serves as the crosslinking agent for this addition-curable liquid silicone rubber coating fluid, is a linear, cyclic, or branched liquid methylhydrogenpolysiloxane having at least two, usually 2 to 200, preferably 3 to 150, and more preferably 4 to 100, hydrosilyl groups per molecule, and the hydrosilyl groups in the molecule crosslink via a hydrosilylation addition reaction with the vinyl groups in the vinyl-group-containing liquid dimethylpolysiloxane, thereby curing the addition-reaction-curable liquid silicone rubber composition that is the coating fluid.

[0049] The hydrosilyl group-containing liquid methylhydrogenpolysiloxane is preferably a liquid at room temperature, having a degree of polymerization (the number of siloxane units per molecule) of 2 to 200, preferably 3 to 150, and more preferably 4 to 100, and a number average molecular weight of 150 to 15,000, preferably 300 to 10,000, and more preferably 500 to 7,500. The hydrosilyl groups may be located at one or both ends of the molecular chain, or at non-terminal positions, or may be located at both ends. The viscosity of the hydrosilyl group-containing liquid methylhydrogenpolysiloxane at 25°C is typically 0.5 to 1,000 mPa·s, preferably about 5 to 500 mPa·s.

[0050] Examples of such liquid methylhydrogenpolysiloxanes include methylhydrogen cyclic siloxane oligomers such as 1,3-dihydrogen-1,1,3,3-tetramethyldisiloxane, 1,5-dihydrogen-1,1,3,3,5,5-hexamethyltrisiloxane, 1,3,5,7-tetrahydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, and 1,3,5,7,9-pentahydrogen-1,3,5,7,9-pentamethylcyclopentasiloxane; and derivatives such as tris(dimethylhydrogensiloxy)methylsilane. Branched chain siloxane oligomer, methylhydrogenpolysiloxane terminated at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer terminated at both molecular chain terminals with trimethylsiloxy groups, dimethylpolysiloxane terminated at both molecular chain terminals with dimethylhydrogensiloxy groups, methylhydrogenpolysiloxane terminated at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer terminated at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylhydrogensiloxy unit (H(CH ３ ) ２ SiO １／２ ) and SiO ４／２ units, optionally containing trimethylsiloxy units ((CH ３ ) ３ SiO １／２ ), dimethylsiloxane units ((CH ３) ２ SiO ２／２ ), methylhydrogensiloxane unit (H(CH ３ ) SiO ２／２ ), hydrogen silsesquioxane unit (HSiO ３／２ ) and / or methylsilsesquioxane units ((CH ３ ) SiO ３／２ ) and a liquid methylhydrogenpolysiloxane having a three-dimensional network structure which may contain the same.

[0051] Examples of such liquid methylhydrogenpolysiloxanes include DMS-H03 and HMS-301 (both product names of Gelest Co., Ltd.) These hydrosilyl group-containing liquid methylhydrogenpolysiloxanes may be used alone or in combination of two or more types.

[0052] The amount of hydrosilyl group-containing liquid methylhydrogenpolysiloxane blended is preferably such that the molar ratio of hydrosilyl groups in the hydrosilyl group-containing liquid methylhydrogenpolysiloxane to vinyl groups in the vinyl group-containing liquid dimethylpolysiloxane is 1 to 30, and particularly 1 to 15.

[0053] This addition-curable liquid silicone rubber coating fluid contains a platinum catalyst solution and / or suspension as a catalyst for promoting the hydrosilylation addition reaction between the vinyl groups in the vinyl group-containing liquid dimethylpolysiloxane and the hydrosilyl groups in the hydrosilyl group-containing liquid methylhydrogenpolysiloxane.

[0054] Here, the platinum catalyst may be any known platinum catalyst for promoting a hydrosilylation addition reaction, such as platinum, platinum chloride, chloroplatinic acid, chloroplatinate salts, and complexes of chloroplatinic acid or chloroplatinate salts with vinyl group-containing low molecular weight siloxanes such as 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane. Among these, complexes having a structure chelated with a vinyl group-containing low molecular weight siloxane or the like that has a cure retarding effect are preferred in order to ensure the pot life of the coating liquid. In particular, when the curing reaction is initiated by heating the coating liquid, a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex or a 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane complex of platinum or a platinum compound is desirable.

[0055] The amount of platinum catalyst solution and / or suspension to be blended may be a so-called catalytic amount, which may be typically 1 to 1,000 ppm, and preferably 2 to 500 ppm, in terms of the mass of platinum atoms contained in the platinum catalyst solution and / or suspension relative to the mass of the vinyl group-containing liquid dimethylpolysiloxane.

[0056] Since the amount of the platinum catalyst to be added is very small, from the viewpoint of ease of handling and workability, it is preferable to use the platinum catalyst by dissolving and / or suspending it in an organic solvent such as hexane, toluene, a lower alcohol, a higher alcohol, a silicone-based solvent, etc. In this case, the content of platinum atoms in the solution and / or suspension is preferably about 2 to 5 mass % in terms of the mass of platinum atoms.

[0057] The amount of platinum catalyst solution and / or suspension blended is a so-called catalytic amount, and the amount of organic solvent contained in this platinum catalyst solution and / or suspension is also very small. Therefore, when the addition-curable liquid silicone rubber coating liquid is crosslinked and cured, the amount of organic solvent that volatilizes is negligibly small, so the organic solvent in the platinum catalyst solution and / or suspension does not substantially affect the physical properties of the cured silicone rubber thin film produced by the method of the present invention for producing a cured silicone rubber thin film, in particular surface physical properties such as the number of surface pores.

[0058] In addition to the vinyl group-containing liquid dimethylpolysiloxane, the hydrosilyl group-containing methylhydrogenpolysiloxane, and the platinum catalyst solution and / or suspension, the addition-curable liquid silicone rubber coating liquid used in this method for producing a thin film of cured silicone rubber may contain, as a plasticizer, so-called non-functional dimethylsilicone oil, which is a relatively low molecular weight, non-volatile linear dimethylpolysiloxane that does not contain functional groups involved in the hydrosilylation addition reaction, within a range that does not impair the objects and effects of the present invention.Furthermore, for reinforcement, fillers such as silica-based fillers and non-functional silicone resins that do not contain functional groups involved in the hydrosilylation addition reaction, as well as colorants such as dyes and pigments, may also be added.

[0059] Furthermore, in order to improve the mechanical properties such as breaking strength and elongation of the cured silicone rubber thin film produced by this method for producing a cured silicone rubber thin film, it is also possible to add to this addition-curable liquid silicone rubber coating liquid a dimethylpolysiloxane raw rubber, which is typically a non-fluid, solid, ultra-high molecular weight dimethylpolysiloxane having at least multiple vinyl groups per molecule. The molecular structure of this vinyl group-containing dimethylpolysiloxane raw rubber can be similar to that of the vinyl group-containing liquid dimethylpolysiloxane described above, but the degree of polymerization of this vinyl group-containing dimethylpolysiloxane raw rubber is typically at least 5,000, preferably about 6,000 to 20,000, and the number average molecular weight is at least 370,000, preferably about 450,000 to 1,500,000.

[0060] The vinyl group-containing dimethylpolysiloxane raw rubber can be blended into the addition-curable liquid silicone rubber coating solution in an amount of typically up to 10% by weight, preferably up to 6% by weight, and when blended, typically at least 0.1% by weight, preferably at least 1% by weight.

[0061] From the viewpoint of producing a cured silicone rubber thin film having a maximum thickness of 5.5 μm, particularly 0.2 to 3 μm, and especially 0.3 to 2 μm, this addition-curable liquid silicone rubber coating fluid must have a maximum viscosity of 75 Pa·s at 25°C, and typically 1 to 75 Pa·s, particularly 2 to 72 Pa·s, and especially 2 to 65 Pa·s is preferred. If the viscosity of this coating fluid at 25°C exceeds 75 Pa·s, the viscosity will be too high, making transfer coating with the gravure roll difficult, or the thickness of the applied coating film will be too large, making it impossible to produce a cured silicone rubber thin film having a maximum thickness of 5.5 μm. On the other hand, if the viscosity of this coating fluid is too low, the resulting cured silicone rubber thin film may be brittle and have poor physical properties, and it may be difficult to isolate this cured silicone rubber thin film from the substrate.

[0062] In addition, when a coating liquid has a relatively high viscosity of 70 Pa s or more at 25°C, using an oblique gravure roll with a large number of lines, for example 250 lines / inch, may result in coating being difficult due to the excessive viscosity, so when using a coating liquid with a relatively high viscosity, it is desirable to use an oblique gravure roll with a relatively small number of lines, such as less than 250 lines / inch, preferably 200 lines / inch or more but less than 250 lines / inch, more preferably 200 to 230 lines / inch. Specifically, it is desirable not to use an oblique gravure roll with 250 lines / inch for a coating liquid with a viscosity of 70 Pa s or more at 25°C.

[0063] This addition-curable liquid silicone rubber coating fluid can be prepared by uniformly mixing the vinyl group-containing liquid dimethylpolysiloxane, hydrosilyl group-containing liquid methylhydrogenpolysiloxane, and platinum catalyst solution and / or suspension in a conventional manner, but to prevent crosslinking and curing due to the progress of a hydrosilylation addition reaction between the vinyl group-containing liquid dimethylpolysiloxane and the hydrosilyl group-containing liquid methylhydrogenpolysiloxane during mixing and stirring, it is desirable to prepare the coating fluid by quickly mixing the components at a temperature from a low temperature of 0° C. or below to room temperature below 30° C. If necessary, a stirring device such as a planetary stirrer may be used.

[0064] The prepared addition-curable liquid silicone rubber coating fluid is scraped up into the recesses of the gravure roll described above, which rotates at a constant rotational speed while in contact with the coating fluid, and then transferred and coated onto a substrate to form a coating film. The coating film is then heated, irradiated with ultraviolet light and / or electron beams to crosslink and cure the vinyl group-containing liquid dimethylpolysiloxane and hydrosilyl group-containing liquid methylhydrogenpolysiloxane in the coating fluid, thereby producing the cured silicone rubber thin film of the present invention.

[0065] The material of the substrate can be selected from glass, plastic, metal, ceramic, rubber, cloth, paper, and the like.

[0066] The coating film formed on the substrate can be crosslinked and cured by heating, ultraviolet irradiation, and / or electron beam irradiation according to standard methods for promoting the hydrosilylation addition reaction, to obtain a thin film of cured silicone rubber. For example, when heating, crosslinking and curing can be achieved by heating typically at 80 to 150°C, preferably 100 to 130°C, for typically 0.5 to 120 minutes, preferably 3 to 60 minutes. After crosslinking and curing, the film can be peeled off from the substrate, but from the standpoint of cooling and maintaining stable physical properties, it is desirable to leave it to stand for approximately 24 hours after crosslinking and curing.

[0067] The substrate may have a water-soluble sacrificial layer on its surface, made 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 crosslinked and cured silicone rubber thin film is formed and laminated as described above can be peeled off from the substrate, and then the water-soluble sacrificial layer can be dissolved in water or the like to isolate the cured silicone rubber thin film. Materials other than water-soluble thermoplastic resins can also be used for the water-soluble sacrificial layer, as long as they are soluble in water or the like; for example, starch can be used as a substitute. The material for the water-soluble sacrificial layer can be selected appropriately based on factors such as cost, solubility in water or the like, and wettability with the cured silicone rubber thin film.

[0068] The thickness of the water-soluble sacrificial layer is preferably 1 μm or more, and more preferably 3 μm or more. The thicker the water-soluble sacrificial layer, the easier it is to peel it off from the substrate, but the longer it takes to dissolve. The thickness of the water-soluble sacrificial layer is usually about 30 μm at most.

[0069] The cured silicone rubber thin film of the present invention is a crosslinked and cured product on a substrate, or a crosslinked and cured product isolated from the substrate, obtained by transfer-coating an addition-curable liquid silicone rubber coating liquid that is not substantially diluted with an organic solvent and has a maximum viscosity of 75 Pa s at 25°C onto a substrate using a specific oblique gravure roll having a concave-convex pattern on its surface as described above, and then crosslinking and curing the resulting coating by heating, ultraviolet irradiation, and / or electron beam irradiation. The silicone rubber thin film is a crosslinked and cured product on a substrate, or a crosslinked and cured product isolated from the substrate. The silicone rubber thin film contains a reactive dimethylpolysiloxane component capable of constructing a three-dimensional crosslinked structure, the main component being the vinyl group-containing liquid dimethylpolysiloxane described above, the hydrosilyl group-containing liquid methylhydrogenpolysiloxane described above as a crosslinking agent, and the platinum catalyst solution and / or suspension described above.

[0070] This thin film of cured silicone rubber has a thickness of up to 5.5 μm, usually 0.2 to 5.5 μm, particularly 0.2 to 3 μm, and especially 0.3 to 2 μm, and since the organic solvent is not substantially volatilized when the coating film is crosslinked and cured, pinholes on the surface are reduced.

[0071] This cured silicone rubber thin film has, for example, a surface area of ​​20 mm x 20 mm in which the number of pinholes with a diameter of at least 1 μm is usually less than 7, and preferably less than 5.

[0072] The number of pinholes on the surface of the cured silicone rubber thin film can be evaluated, for example, by cutting a 20 mm × 20 mm piece of the formed cured silicone rubber thin film and observing its surface with a scanning electron microscope. The diameter of the pinholes should generally be a maximum of 10 μm, preferably about 3 μm.

[0073] This thin film of cured silicone rubber typically has a breaking strength of at least 0.6 MPa, and particularly about 0.65 to 5.0 MPa, and typically has an elongation of at least 35%, and particularly about 35 to 350%.

[0074] This cured silicone rubber thin film has fewer pinholes on the surface, which can reduce barrier properties and lead to film breakdown, and reduces the risk of deterioration in physical properties.

[0075] Examples of the hydrophilic treatment method to which the present invention is applied and comparative examples to which the present invention is not applied will be described below.

[0076] The following components were used to prepare the addition-curable liquid silicone rubber coating fluid. [Vinyl-containing liquid dimethylpolysiloxanes] DMS-V31: dimethylpolysiloxane terminated at both molecular chain ends with vinyldimethylsiloxy groups (product name of Gelest, viscosity 1,000 mPa·s, degree of polymerization 380, molecular weight 28,000, vinyl group concentration 0.0071 mol / 100 g) DMS-V41: dimethylpolysiloxane terminated at both molecular chain ends with vinyldimethylsiloxy groups (product name of Gelest, viscosity 10,000 mPa·s, degree of polymerization 850, molecular weight 62,700, vinyl group concentration 0.0032 mol / 100 g) DMS-V46: Dimethylpolysiloxane terminated at both molecular chain ends with vinyldimethylsiloxy groups (product name of Gelest, viscosity 60,000 mPa·s, degree of polymerization 1,580, molecular weight 117,000, vinyl group concentration 0.0017 mol / 100 g) DMS-V52: Dimethylpolysiloxane terminated at both molecular chain ends with vinyldimethylsiloxy groups (product name of Gelest, viscosity 165,000 mPa·s, degree of polymerization 2,090, molecular weight 155,000, vinyl group concentration 0.0013 mol / 100 g) [hydrosilyl group-containing liquid methylhydrogenpolysiloxane] HMS-301: Dimethylsiloxane-methylhydrogensiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups (Gelest product name, viscosity approximately 35 mPa·s, degree of polymerization approximately 26, molecular weight 2,000, content of methylhydrogensiloxane units relative to the total of dimethylsiloxane units and methylhydrogensiloxane units in the main chain approximately 24 mol%, hydrosilyl group concentration 0.30 mol / 100 g) [Platinum catalyst solution] SIP6829.2: Platinum carbonyl tetravinylcyclotetrasiloxane complex solution (Gelest product name, solvent tetravinylcyclotetrasiloxane, platinum atom concentration in platinum catalyst solution approximately 2.1 mass%, specific gravity approximately 1) [Vinyl group-containing dimethylpolysiloxane raw rubber] PDMS110-8: dimethylsiloxane-methylvinylsiloxane copolymer with both ends of the molecular chain blocked by trimethylsiloxy groups (trade name of DJ Silicone, degree of polymerization 6,000 to 10,800, molecular weight 450,000 to 800,000, vinyl group content approximately 2 mol%, vinyl group concentration approximately 0.027 mol / 100 g)

[0077] The viscosity of each of the liquid components is a value measured at 25°C using a rotational viscometer, and the molecular weight and degree of polymerization are the number average molecular weight and number average degree of polymerization in terms of polystyrene determined by gel permeation chromatography analysis using toluene as a developing solvent.

[0078] Example 1 [Formation of a Water-Soluble Polyvinyl Alcohol Sacrificial Layer by Gravure Coating] Polyvinyl alcohol (molecular weight 22,000, degree of saponification 86.5-89%, manufactured by Kanto Chemical Co., Inc.) was heated and dissolved in ion-exchanged water to a concentration of 10% by mass. Next, a PET film (Lumirror L-25T60, manufactured by Toray Industries, Inc.) was placed in a microgravure coater (manufactured by Yasui Seiki Co., Ltd.), and the 10% by mass aqueous polyvinyl alcohol solution was coated onto the PET film while heating and drying at 120°C, forming a water-soluble sacrificial film with a thickness of 10 μm. The film feed rate was 0.2 m / min, and the gravure roll rotation speed was 30 rpm.

[0079] [Formation of an Addition-Curable Liquid Silicone Rubber Coating by Gravure Coating] The addition-curable liquid silicone rubber coating solution was prepared by uniformly mixing the components shown in Table 1 below. The coating was applied to a PET film laminated with the above-prepared water-soluble polyvinyl alcohol sacrificial layer using a microgravure coater (manufactured by Yasui Seiki Co., Ltd.). The coating was then heated to crosslink and harden to produce a thin film of cured silicone rubber. The heating temperature was 120°C, the film feed rate was 0.2 m / min, and the gravure roll rotation rate was 3 rpm. The coating was partially crosslinked by exposing it to 120°C hot air for approximately 1 minute, and then heated at 120°C for 1 hour to fully harden the coating. The gravure roll used was a 20 mm diameter gravure roll (diagonal gravure roll) with recesses consisting of diagonally arranged lines on its outer periphery. The number of lines per unit length parallel to the gravure roll's rotation axis (hereinafter referred to as the number of lines) was 250 lines / inch. The viscosity of each coating liquid prepared was measured using a rotational viscometer (TV-25, manufactured by Toki Sangyo Co., Ltd.) at 25°C at a rotation speed of 1 rpm for a measurement time of 1 minute. The thickness, breaking strength, and elongation at break of the obtained cured silicone rubber thin films were measured using the methods described below, and are shown in Table 1.

[0080] [Film Thickness Measurement] Four pieces of masking tape were attached to the surface of the cured silicone rubber thin film, which was the outermost layer of a three-layer structure consisting of a cured silicone rubber thin film, a water-soluble polyvinyl alcohol sacrificial layer, and a PET film, to form a frame. The two-layer structure consisting of the cured silicone rubber thin film and the water-soluble polyvinyl alcohol sacrificial layer was then peeled off. The two-layer structure was then washed with hot water at 40°C for 10 minutes, and then washed with ion-exchanged water to dissolve the water-soluble polyvinyl alcohol sacrificial layer from the two-layer structure, thereby isolating the cured silicone rubber thin film. The isolated cured silicone rubber thin film was attached to a silicon wafer (KST, manufactured by Seiren Co., Ltd.) cut into 20 mm x 20 mm squares and allowed to dry naturally. The thickness of the cured silicone rubber thin film was then measured using a Dektak-XT-S stylus profiling system (manufactured by Bruker).

[0081] [Measurement of Mechanical Properties] A sample of the cured silicone rubber thin film isolated in the same manner as in the film thickness measurement was attached to a glass tube with an inner diameter of 7.0 mm and fixed to a jig. 100 μL of ion-exchanged water was dropped onto the attached cured silicone rubber thin film, and the resulting deformation of the cured silicone rubber thin film was photographed with a camera. The stress applied to the cured silicone rubber thin film was calculated using the following formula (1), and the strain of the cured silicone rubber thin film was calculated using the following formula (2), and the results were plotted as stress-strain curves. The maximum stress until the cured silicone rubber thin film broke on this stress-strain curve was recorded as the breaking strength. In addition, the strain at which the cured silicone rubber thin film broke was recorded as the breaking elongation. Measurements were performed three times for each sample, and the average values ​​of the breaking strength and breaking elongation were reported as results.

[0082] (Examples 2 and 3, Reference Example 1, Comparative Example 1) A cured silicone rubber thin film was produced and evaluated in the same manner as in Example 1, except that the components used to prepare the addition-curable liquid silicone rubber coating solution in Example 1 were changed to those shown in Table 1 below (Example 2, Reference Example 1, Comparative Example 1). In Example 3, a cured silicone rubber thin film was produced and evaluated in the same manner as in Reference Example 1, except that the gravure roll was changed to a gravure roll with a line count of 200 lines / inch. The results are shown in Table 1.

[0083] (Example 4, Comparative Examples 2 and 3) Thin films of cured silicone rubber were produced in the same manner as in Example 1, except that the gravure roll used for transfer coating of the addition-curable liquid silicone rubber coating liquid in Example 1 was changed to a gravure roll with a line count of 150, 180, or 200 lines / inch, and the thickness was evaluated in the same manner. The results are shown in Table 2 below. For comparison, the results of Example 1 are also shown in Table 2.

[0084] Examples 5 to 7 Cured silicone rubber thin films were produced and evaluated in the same manner as in Example 1, except that the components shown in Table 3 below were further blended in addition to the components used to prepare the addition-curable liquid silicone rubber coating fluid in Example 1. The results are shown in Table 3.

[0085] Comparative Examples 4 and 5 A cured silicone rubber thin film was produced in the same manner as in Example 1, except that the components used to prepare the addition-curable liquid silicone rubber coating solution in Example 1 were further diluted with the organic solvent shown in Table 4 below, and the thickness was evaluated in the same manner. In Comparative Example 5, a cured silicone rubber thin film was produced in the same manner as in Example 1, except that the gravure roll was changed to a gravure roll with a line count of 180 lines / inch, and the thickness was evaluated in the same manner. In addition, the number of pinholes on the surface of the cured silicone rubber thin films produced in Example 1 and Comparative Examples 4 and 5 was measured using the method described below. The results are shown in Table 4 below. For comparison, the results of Example 1 are also listed in Table 4.

[0086] [Measurement of the number of pinholes on the surface] A three-layer structure consisting of a cured silicone rubber thin film / aqueous polyvinyl alcohol sacrificial layer / PET film was cut into a piece of 20 mm x 20 mm, and the surface was subjected to a gold sputtering treatment for 1 minute. The surface was then observed at a magnification of 40 to 1,000 times using a scanning electron microscope VE-9800 (manufactured by Keyence Corporation), and the number of pinholes with a diameter of 1 μm or more on the surface of the cured silicone rubber thin film was measured.

[0087] Comparative Examples 6 to 9 The addition-curable liquid silicone rubber coating solution prepared in Example 1 was used to apply and form a film by spin coating under the conditions shown below in an attempt to produce a thin film of cured silicone rubber. The results are shown in Table 5 below.

[0088] [Formation of Addition-Curable Liquid Silicone Rubber Coating Solution by Spin Coating] A glass plate was mounted on a spin coater (MS-B200, manufactured by Mikasa Co., Ltd.), and the PET film with the above-prepared water-soluble polyvinyl alcohol sacrificial layer laminated thereon was fixed with double-sided tape. Subsequently, 0.5 mL of each coating solution prepared by uniformly mixing the components shown in Table 3 below was added dropwise to the PET film with the above-prepared water-soluble polyvinyl alcohol sacrificial layer laminated thereon, and spin-coated for 20 seconds at rotation speeds of 4,000, 5,000, 6,000, and 7,000 rpm. The applied addition-curable liquid silicone rubber coating was then allowed to stand in an oven heated to 120°C for 10 minutes to crosslink and cure.

[0089]

[0090] The results in Table 1 confirm that in Examples 1 and 2, a cured silicone rubber thin film having a thickness of 5.5 μm or less could be produced by transferring an addition-curable liquid silicone rubber coating liquid undiluted with an organic solvent using a 250 line / inch oblique gravure roll. Furthermore, when a gravure roll with the same line count was used, the thickness of the formed cured silicone rubber thin film tended to decrease as the viscosity of the addition-curable liquid silicone rubber coating liquid increased. In Reference Example 1, the viscosity of the coating liquid was too high to coat using a 250 line / inch oblique gravure roll. However, in Example 3, where a 200 line / inch oblique gravure roll was used, it was confirmed that a cured silicone rubber thin film having a thickness of 5.5 μm or less could be produced using the same coating liquid as in Reference Example 1.

[0091] Furthermore, in Comparative Example 1, when the viscosity was too high, it was not possible to transfer the addition-curable liquid silicone rubber coating liquid that was not diluted with an organic solvent using a diagonal gravure roll with a line count of 250 lines / inch.

[0092] An attempt was made to produce a similar cured silicone rubber thin film using a vinyl group-containing liquid dimethylpolysiloxane with a lower molecular weight (lower degree of polymerization) than DMS-V31, but the formed cured silicone rubber thin film was brittle and had poor physical properties, and it was not possible to isolate this thin film from the three-layer structure of cured silicone rubber thin film / water-soluble polyvinyl alcohol sacrificial layer / PET film to measure the film thickness.

[0093]

[0094] The results in Table 2 confirm that in Examples 4 and 1, a cured silicone rubber thin film with a thickness of 5.5 μm or less could be produced by transferring an addition-curable liquid silicone rubber coating liquid undiluted with an organic solvent using a diagonal gravure roll with a line count of 200 or 250 lines / inch, respectively. Furthermore, when an addition-curable liquid silicone rubber coating liquid of the same composition was used, the thickness of the cured silicone rubber thin film tended to decrease as the line count of the diagonal gravure roll increased. In Comparative Examples 2 and 3, when diagonal gravure rolls with a line count of 150 or 180 lines / inch were used, it was not possible to produce a cured silicone rubber thin film with a maximum thickness of 5.5 μm.

[0095]

[0096] The results in Table 3 confirm that in Examples 5 to 7, by adding a small amount of vinyl group-containing dimethylpolysiloxane crude rubber, up to a maximum of 10 mass %, to an addition-curable liquid silicone rubber coating fluid containing a vinyl group-containing liquid dimethylpolysiloxane, a hydrosilyl group-containing liquid methylhydrogenpolysiloxane, and a platinum catalyst solution, the thickness of the formed cured silicone rubber thin film tends to decrease, and the physical properties (breaking strength, elongation) of the formed cured silicone rubber thin film are improved.

[0097]

[0098] The results in Table 4 show that the thin film of cured silicone rubber produced in Example 1 by transferring, with a hatched gravure roll, an addition-curable liquid silicone rubber coating liquid that was not diluted with an organic solvent, had a significantly reduced number of pinholes on the surface of the thin film of cured silicone rubber when compared with the thin films of cured silicone rubber produced in Comparative Examples 4 and 5 by transferring, with a hatched gravure roll, an addition-curable liquid silicone rubber coating liquid that had been diluted with an organic solvent to reduce its viscosity, even when comparing films produced by transferring with a hatched gravure roll having the same number of lines, and even when comparing films of cured silicone rubber having similar thicknesses.

[0099]

[0100] The results in Table 5 show that in Comparative Examples 6 to 9, an addition-curable liquid silicone rubber coating solution that was not diluted with an organic solvent was used to attempt to produce a thin film of cured silicone rubber by spin coating, but it was not possible to produce a thin film of cured silicone rubber with a maximum thickness of 5.5 μm when the spin coater rotation speed was in the range of 1,000 to 7,000 rpm (limit value).

[0101] The method for producing a cured silicone rubber thin film of the present invention makes it possible to efficiently produce a cured silicone rubber thin film that is expected to be applicable to a wide range of applications, such as cosmetics, biochemistry applications such as cell culture vessels, medical applications such as wound dressings, and gas separation membranes, without substantially releasing organic solvents into the surrounding area that have a large environmental impact, are a cause of air pollution, and are harmful to the human body, and with surface pinholes that cause deterioration of physical properties greatly reduced.The cured silicone rubber thin film of the present invention has reduced surface porosity and is applicable to a wide range of applications, such as cosmetics, biochemistry applications such as cell culture vessels, medical applications such as wound dressings, and gas separation membranes.

Claims

1. An addition-curable liquid silicone rubber coating liquid containing a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in the molecule, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups in the molecule, and a platinum catalyst solution and / or suspension, and substantially free of organic solvents, is scraped up into the recesses of a concave-convex pattern on the surface of a gravure roll, transferred onto a substrate, and coated to form a coating film, and then the coating film is heated, irradiated with ultraviolet light, and / or irradiated with an electron beam to combine the liquid dimethylpolysiloxane and the liquid methylhydrogenpolysiloxane. and a method for producing a cured silicone rubber thin film, in which an addition-curable liquid silicone rubber coating solution is crosslinked with an alkylene polysiloxane and cured, the method comprising: setting the viscosity of the addition-curable liquid silicone rubber coating solution at 25°C to a maximum of 75 Pa s; and forming the concave-convex pattern on the outer periphery of the gravure roll, the concave portions being formed of lines arranged diagonally on the outer periphery of the gravure roll, and the number of lines per unit length parallel to the rotation axis of the gravure roll being at least 200 lines / inch, thereby achieving a maximum thickness of the thin film of 5.5 μm.

2. The method for producing a thin film of cured silicone rubber according to claim 1, characterized in that a water-soluble sacrificial layer is formed on the substrate, the addition-curable liquid silicone rubber coating liquid is transferred and applied onto the sacrificial layer to form a coating film, and the coating film is crosslinked and cured to form a thin film of cured silicone rubber.

3. The method for producing a cured silicone rubber thin film described in claim 2, further comprising peeling the water-soluble sacrificial layer on which the cured silicone rubber thin film has been formed from the substrate, and then dissolving the water-soluble sacrificial layer to isolate the cured silicone rubber thin film.

4. The method for producing a thin film of cured silicone rubber according to claim 1, wherein the depth of the recesses is set to 5 to 40 μm.

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

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

7. A method for producing a thin film of cured silicone rubber as described in claim 1, characterized in that the liquid dimethylpolysiloxane is a linear dimethylpolysiloxane having vinyl groups bonded to silicon atoms at both ends of the molecular chain, and the liquid methylhydrogenpolysiloxane is a linear methylhydrogenpolysiloxane having multiple hydrogen atoms bonded to silicon atoms not at the ends of the molecular chain.

8. A method for producing a thin film of cured silicone rubber as described in claim 1, characterized in that the liquid dimethylpolysiloxane is a dimethylpolysiloxane blocked at both molecular chain ends with vinyldimethylsiloxy groups, and the liquid methylhydrogenpolysiloxane is a dimethylsiloxane-methylhydrogensiloxane copolymer blocked at both molecular chain ends with trimethylsiloxy groups.

9. A method for producing a thin film of cured silicone rubber according to claim 1, characterized in that the addition-curing liquid silicone rubber coating liquid further contains a dimethylpolysiloxane raw rubber having at least a plurality of vinyl groups in the molecule.

10. The method for producing a thin film of cured silicone rubber according to claim 1, wherein the number of lines per unit length is 200 to 250 lines / inch.

11. A method for producing a thin film of cured silicone rubber 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 1 to 75 Pa·s.

12. A cured silicone rubber thin film that is a crosslinked and cured product of a transfer-coated film of an addition-curable liquid silicone rubber coating liquid that contains a liquid dimethylpolysiloxane having at least a plurality of vinyl groups in the molecule, a liquid methylhydrogenpolysiloxane having at least a plurality of hydrosilyl groups in the molecule that crosslink and cure thereto, and a platinum catalyst solution and / or suspension, and that is substantially free of organic solvents and has a maximum viscosity of 75 Pa·s at 25°C, the cured silicone rubber thin film being a crosslinked and cured product of a transfer-coated film of the coating liquid from the recesses of an uneven pattern that has lines arranged diagonally on the outer periphery of a gravure roll, and the number of lines per unit length parallel to the rotation axis of the gravure roll is at least 200 lines / inch, and the cured silicone rubber thin film is characterized in that it has a maximum thickness of 5.5 μm.

13. The cured silicone rubber thin film according to claim 12, wherein the cross-linked cured product is an isolation layer from a water-soluble sacrificial layer.

14. A thin film of cured silicone rubber according to claim 12, characterized in that the number of pinholes having a diameter of at least 1 μm present within a surface area of ​​20 mm × 20 mm is less than 7.

15. A cured silicone rubber thin film as described in claim 12, characterized in that the addition-curable liquid silicone rubber coating liquid does not contain any organic solvent other than the organic solvent in the platinum catalyst solution and / or suspension, and the organic solvent content is a maximum of 1 mass%.

16. A thin film of cured silicone rubber 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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