Curable silicone composition and cured product thereof

Abstract

[Problem] The present invention relates to: a curable silicone composition which is able to be configured to contain less or no solvent, and exhibits excellent transparency and excellent adhesion to a base material, while enabling the achievement of a low total haze value; and a cured product of this curable silicone composition. [Solution] A curable silicone composition which contains (A) 100 parts by mass of a chain organopolysiloxane that has an aliphatic unsaturated carbon-carbon bond-containing group, while having a siloxane polymerization degree within the range of from 10 to 1,000, (B) from 1 to 100 parts by mass of a chain organopolysiloxane that has an aliphatic unsaturated carbon-carbon bond-containing group, while having a siloxane polymerization degree within the range of from 1,001 to 10,000, (C) from 0 to 100 parts by mass of an organopolysiloxane resin that contains an M unit and a Q unit, (D) a polyorganohydrogen siloxane, and (E) a catalytic amount of a hydrosilylation catalyst, and which also contains (F) from 0 to 60 parts by mass of an organic solvent relative to a total of 100 parts by mass of the components (A) to (D); and a cured product of this curable silicone composition.

Description

[Technical Field]

[0001] The present invention relates to a curable silicone composition that can be used with little or no solvent, has excellent adhesion to substrates and transparency, and provides a low total haze value. The present invention also relates to a cured product obtained by curing the composition. [Background technology]

[0002] Compared to acrylic or rubber-based pressure-sensitive adhesive compositions, polysiloxane-based curable silicone compositions are superior in electrical insulation, heat resistance, cold resistance, and adhesion to various substrates, and are therefore used in heat-resistant adhesive tapes, electrically insulating adhesive tapes, heat-sealing tapes, plating masking tapes, etc. These polysiloxane-based curable silicone compositions are classified into addition reaction curing types, condensation reaction curing types, peroxide curing types, etc. depending on their curing mechanism. Addition reaction curing type pressure-sensitive adhesive compositions are widely used because they cure rapidly when left at room temperature or upon heating and do not produce by-products.

[0003] Taking advantage of the above-mentioned properties of polysiloxane-based curable silicone compositions and their ability to achieve high transparency when necessary, their application in advanced electronics materials such as smart devices and in the field of display elements has been explored in recent years. Such devices have a structure in which a film consisting of multiple layers, including an electrode layer and a display layer, is sandwiched between transparent substrates, and polysiloxane-based silicone curable compositions, which have excellent heat and cold resistance, are expected to be effective in protecting the electrode and display layers and improving adhesion between the layers, both in the products and in their manufacturing processes.

[0004] However, since polysiloxane-based curable silicone compositions are generally commercialized by dissolving them in organic solvents, their applications have been limited. In particular, in recent years, in light of the trend toward environmental regulations in various countries around the world, there has been a strong demand for the development of solvent-free or low-solvent polysiloxane-based curable silicone compositions. In addition, in the manufacturing process of electronic components, there has been a strong demand for curable silicone compositions that have further improved properties such as low solvent content, low haze, transparency, and easy removal after use. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4678471 [Patent Document 2] Patent No. 5338626 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-047310 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a curing-reactive silicone composition and a cured product thereof that have a viscosity that allows coating even with a low solvent content, have excellent curing properties, and form, through a curing reaction, a silicone cured product (particularly a cured product film) that has good adhesion to substrates, is highly transparent, has a low total haze value, and can be easily removed from the surface of a substrate after use. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into the above-mentioned problems and have arrived at the present invention. (A) 100 parts by mass of a linear or branched organopolysiloxane having at least two aliphatic unsaturated carbon-carbon bond-containing groups in the molecule and having a degree of siloxane polymerization in the range of 10 to 1,000; (B) a linear or branched organopolysiloxane having at least two aliphatic unsaturated carbon-carbon bond-containing groups in the molecule and having a degree of siloxane polymerization in the range of 1,001 to 10,000, in an amount of 1 to 100 parts by mass per 100 parts by mass of component (A); (C) RSiO in the molecule 1 / 2 (wherein R each independently represents a monovalent saturated organic group), and SiO 4 / 2 an organopolysiloxane resin containing siloxane units (Q units) represented by the formula: (D) polyorganohydrogensiloxane, and (E) Hydrosilylation reaction catalyst catalytic amount and (F) organic solvent, 0 to 60 parts by mass per 100 parts by mass of the total of the components (A) to (D) The object of the present invention is also achieved by a curable silicone composition comprising the following:

[0023] The object of the present invention is also achieved by a cured silicone product obtained by curing the curable silicone composition. [Effects of the Invention]

[0008] The curable silicone composition of the present invention has a viscosity that allows it to be applied even with a low solvent content, has excellent curing properties via a hydrosilylation reaction, and is capable of curing to form a silicone cured product (particularly a cured product film) layer that has practically sufficient adhesion to substrates, is highly transparent, has a low total haze value, and is easily removable from the surface of a substrate after use. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Curable Silicone Composition] First, we will explain the curable silicone composition of the present invention. This composition cures rapidly via a curing reaction that includes a hydrosilylation reaction, and forms an adhesive layer that has sufficient adhesion to substrates for practical use, is highly transparent, has a low total haze value, and is easily removable from the surface of the substrate after use.

[0010] Specifically, the curable silicone composition of the present invention contains the above components (A) to (E), and from the standpoint of ease of handling, may optionally further contain an organic solvent (F), and may also contain a cure retarder and other additives within the scope of the present invention. Each component is described below. Note that components (C) and (F) are optional components of the present composition, and their content in the composition may be zero.

[0011] [Component (A)] Component (A) is the main component (base polymer) of the composition, and is a linear or branched organopolysiloxane having at least two aliphatic unsaturated carbon-carbon bond-containing groups in the molecule and a degree of siloxane polymerization in the range of 10 to 1,000. Component (A) is a component that participates in the curing reaction together with components (B) and (D) in the hydrosilylation reaction. By using a specific amount of this component (A) together with component (B), the cured product obtained by curing the composition contains a certain amount of extended molecular chain structures, significantly improving the adhesive properties of the elastic adhesive member. Furthermore, because component (A) is a siloxane component with a relatively low degree of polymerization, adjusting the degree of polymerization of the siloxane makes it possible to adjust the viscosity and coatability of the composition without using large amounts of organic solvents while maintaining the strength of the silicone adhesive layer, thereby enabling the formation of a film of any desired thickness, from thin to thick. This component (A) may be a single organopolysiloxane or a mixture of two or more organopolysiloxanes.

[0012] The siloxane degree of polymerization of such organopolysiloxane as component (A) is in the range of 10 to 1,000, preferably 50 to 1,000, and even more preferably 100 to 1,000. Component (A) may be a mixture of (A1) an organopolysiloxane having a siloxane degree of polymerization of 10 to 1,000, preferably 50 to 1,000, and having aliphatic unsaturated carbon-carbon bond-containing groups only at both molecular chain terminals, and (A2) an organopolysiloxane having a siloxane degree of polymerization of 10 to 1,000, preferably 50 to 1,000, and having aliphatic unsaturated carbon-carbon bond-containing groups at both molecular chain terminals or in the side chain, and preferably an organopolysiloxane having a siloxane degree of polymerization of 31 to 1,000. If the degree of polymerization of the siloxane of component (A) exceeds the upper limit, the viscosity of the entire composition tends to increase, and coating may become difficult unless a large amount of organic solvent is used. On the other hand, if the degree of polymerization of the siloxane of component (A) is less than the lower limit, the curability and adhesion performance of the composition may decrease.

[0013] The organopolysiloxane of component (A) cures via a hydrosilylation reaction and therefore has at least two aliphatic unsaturated carbon-carbon bond-containing groups at the molecular chain terminals or side chains. Examples of such aliphatic unsaturated carbon-carbon bond-containing groups include alkenyl groups, alkenyloxyalkyl groups, acryloxyalkyl groups, and methacryloxyalkyl groups, with alkenyl groups being particularly preferred. Specific examples of alkenyl groups include vinyl groups, allyl groups, propenyl groups, butenyl groups, pentenyl groups, and hexenyl groups, with vinyl groups and hexenyl groups being particularly preferred. Furthermore, these aliphatic unsaturated carbon-carbon bond-containing groups are preferably bonded to silicon atoms.

[0014] The content of the aliphatic unsaturated carbon-carbon bond-containing group is preferably 0.001 to 10 mass%, more preferably 0.005 to 5.0 mass%, and more preferably 0.01 to 3.0 mass%, relative to the mass of component (A). In particular, the content of vinyl (CH2=CH-) moieties in the aliphatic unsaturated carbon-carbon bond-containing group (hereinafter referred to as "vinyl content") is preferably in the range of 0.005 to 10.0 mass%, and it is particularly preferred to use an organosiloxane in which the content is in the range of 0.005 to 5.0 mass%.

[0015] Component (A) may contain, as organic groups other than the aliphatic unsaturated carbon-carbon bond-containing groups, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl. From an industrial standpoint, the inclusion of a methyl group is particularly preferred. On the other hand, from the standpoints of improving the elongation, adhesion to substrates, and transparency of the cured product, particularly at high temperatures, and particularly reducing the haze value, methyl is preferred as the organic group other than the aliphatic unsaturated carbon-carbon bond-containing groups in component (A). It is also preferred that the content of aryl or aralkyl groups be less than 0.1 mol %, particularly 0.0 mol %, of all groups bonded to silicon atoms, so that the component is substantially free of aryl or aralkyl groups.

[0016] Component (A) may be a single component or a mixture of multiple components. However, from the viewpoint of the technical effects of the present invention, particularly the elongation of the cured product and the adhesion to the substrate, it is preferable to use a component (A) of the following type: (A1) a linear or branched organopolysiloxane having at least two aliphatic unsaturated carbon-carbon bond-containing groups only at both molecular chain terminals and having a degree of siloxane polymerization in the range of 10 to 1,000; and (A2) A linear or branched organopolysiloxane having at least one aliphatic unsaturated carbon-carbon bond-containing group at a site other than the molecular chain terminals and at least three aliphatic unsaturated carbon-carbon bond-containing groups within the molecule, and having a degree of siloxane polymerization in the range of 10 to 1,000. in a mass ratio of 30:70 to 70:30. Furthermore, these components (A1) and (A2) may also be, and preferably are, mixtures of two or more components differing in the degree of siloxane polymerization and / or the content of aliphatic unsaturated carbon-carbon bond-containing groups.

[0017] Component (A1) is a component that forms an elongated molecular chain structure through a chain extension reaction with other components during a hydrosilylation reaction, improving the elongation, flexibility, and adhesion to substrates of the cured reaction product. By using specific amounts of this component (A1), particularly with component (A2) having a low siloxane polymerization degree and component (B) having a high siloxane polymerization degree, the cured reaction product obtained by curing the composition contains a certain amount of elongated molecular chain structures, further improving the adhesion of the adhesive layer. Furthermore, because component (A1) itself does not have a particularly high degree of siloxane polymerization, the overall viscosity of the composition can be reduced, and practically sufficient coatability can be achieved even with a small amount of organic solvent used.

[0018] Such component (A1) includes compounds of the general formula: R a 3SiO(R 1 2SiO 2 / 2 ) m1 SiR a 3 However, component (A1) preferably contains a linear organopolysiloxane represented by the formula: 1 SiO 3 / 2 and branched siloxane units represented by 4 / 2 The organopolysiloxane may contain an average of 0 to 5 units selected from the group consisting of branched siloxane units represented by the following formula (1):

[0019] In the formula, each R 1 are each independently exemplified by an organic group other than an aliphatic unsaturated carbon-carbon bond-containing group. a is an aliphatic unsaturated carbon-carbon bond-containing group or R 1 and there are at least two Ra is an aliphatic unsaturated carbon-carbon bond-containing group, preferably an alkenyl group, more preferably a vinyl group or a hexenyl group. In the formula, the degree of siloxane polymerization, "m1+2," is preferably a number within the range of 10 to 950, more preferably a number within the range of 50 to 925, and particularly preferably a number within the range of 100 to 900. Note that "+2" is the sum of the siloxane units at both ends of the linear molecule, and further, R 1 SiO 3 / 2 and branched siloxane units represented by 4 / 2 The branched siloxane unit may contain a unit selected from the branched siloxane units represented by the formula: 1 SiO 3 / 2 For the branched siloxane unit represented by 4 / 2 For branched siloxane units represented by 1 3SiO 1 / 2 Units are added within the molecule to form the chain ends corresponding to the branched siloxane units.

[0020] In the above general formula, R at both ends a 3SiO 1 / 2 R in units a At least one of the R a is preferably an alkyl group, and from an industrial standpoint, is particularly preferably a methyl group. It is also preferred that component (A1) be substantially free of aryl or aralkyl groups.

[0021] Component (A2) possesses crosslinking reaction sites in its side chains during hydrosilylation reactions, forming crosslinked structures between siloxane units, imparting appropriate hardness to the cured product and improving adhesion to substrates. By using specific amounts of this component (A2), particularly in conjunction with component (A1) with a low siloxane polymerization degree and component (B) with a high siloxane polymerization degree, it is possible to adjust the crosslink density of the cured product obtained by curing the composition and the length of siloxane units between crosslinking points in the crosslinked product, thereby further improving the adhesion and removability of the adhesive layer. Like component (A1), component (A2) itself does not have a particularly high degree of siloxane polymerization, thereby reducing the overall viscosity of the composition and achieving practically sufficient coatability with minimal organic solvent usage.

[0022] Such component (A2) is preferably a compound represented by the general formula: R b 3SiO(R 1 2SiO 2 / 2 ) n1 (R 1 R 2 SiO 2 / 2 ) n2 SiR b 3 However, component (A2) is preferably a linear organopolysiloxane represented by the formula: 1 SiO 3 / 2 and branched siloxane units represented by 4 / 2 The organopolysiloxane may contain an average of 0 to 5 units selected from the group consisting of branched siloxane units represented by the following formula (1):

[0023] In the formula, each R 1 are independently an organic group other than an aliphatic unsaturated carbon-carbon bond-containing group, and each R 2 is an aliphatic unsaturated carbon-carbon bond-containing group. b is R 1 or R 2 However, if n2 is 2 or less, R b At least one of them is R 2 and there are at least three R2 Includes:

[0024] Since component (A2) has at least one aliphatic unsaturated carbon-carbon bond-containing group at a site other than the molecular chain terminals, the above n2 is a value of 1 or greater. Furthermore, the siloxane polymerization degree, "n1+n2+2" in the formula, is preferably a number within the range of 10 to 900, more preferably a number within the range of 15 to 800, and particularly preferably a number within the range of 15 to 750. Note that "+2" represents the sum of the siloxane units at both terminals of the linear molecule, and further, there are 0 to 5 R 1 SiO 3 / 2 and branched siloxane units represented by 4 / 2 The branched siloxane unit may contain a unit selected from the branched siloxane units represented by the formula: 1 SiO 3 / 2 For the branched siloxane unit represented by 4 / 2 For branched siloxane units represented by 1 3SiO 1 / 2 Units are added within the molecule to form the chain ends corresponding to the branched siloxane units.

[0025] In the above general formula, R at both ends a 3SiO 1 / 2 R in units a At least one of the R a is preferably an alkyl group, and from an industrial standpoint, is particularly preferably a methyl group. It is also preferred that component (A1) be substantially free of aryl or aralkyl groups.

[0026] As described above, component (A2) has crosslinking reactive groups in its siloxane side chains and is a component that imparts appropriate hardness to the cured product. In the present invention, when the distance between siloxane molecules between crosslinking points derived from component (A2), i.e., the degree of polymerization of siloxane between crosslinking points, is between 30 and 200, the adhesion of the cured reaction product to the substrate is improved.

[0027] Specifically, the average number of siloxane units between the two aliphatic unsaturated carbon-carbon bond-containing groups in component (A2) is preferably in the range of 30 to 200, and more preferably 40 to 170. In particular, component (A2) may be, and is preferably, a mixture of two or more organopolysiloxanes that do not have aliphatic unsaturated carbon-carbon bond-containing groups at the molecular chain terminals and that differ in the degree of siloxane polymerization and / or the content of aliphatic unsaturated carbon-carbon bond-containing groups / average number of siloxane units between the two aliphatic unsaturated carbon-carbon bond-containing groups. In the case of a linear polysiloxane, the average number of siloxane units between the two aliphatic unsaturated carbon-carbon bond-containing groups in component (A2) can be calculated by dividing the total number of siloxane units by the number of siloxane units containing an aliphatic unsaturated carbon-carbon bond-containing group such as a vinyl group.

[0028] Particularly preferably, component (A2) is a linear organopolysiloxane or mixture thereof in which the molecular chain terminals are blocked with siloxane units that do not contain an aliphatic unsaturated carbon-carbon bond-containing group such as a trimethylsiloxy group and the siloxane side chains have at least three aliphatic unsaturated carbon-carbon bond-containing groups, and the average number of siloxane units between the two aliphatic unsaturated carbon-carbon bond-containing groups in the siloxane side chain is preferably in the range of 30 to 200, more preferably 40 to 170. When component (A2) is a mixture of two types of linear organopolysiloxanes, the average number of siloxane units between the two aliphatic unsaturated carbon-carbon bond-containing groups in the siloxane side chain is preferably in the range of 30 to 200, more preferably 40 to 170, for each organopolysiloxane constituting the mixture and for the mixture as a whole.

[0029] Component (A) is preferably oily at room temperature, and has a viscosity of at least 10 mPa·s at 25° C. From the standpoint of the coatability of the curable silicone composition of the present invention, it is particularly preferable that the viscosity of component (A) be at least 1 mPa·s and no more than 10,000 mPa·s.

[0030] From the standpoint of preventing contact failure, it is preferable that volatile or low-molecular-weight siloxane oligomers (octamethyltetrasiloxane (D4), decamethylpentasiloxane (D5), etc.) be reduced or removed from component (A). The extent of this can be designed as desired, but it may be less than 1 mass% of the entire component (A), less than 0.1 mass% for each siloxane oligomer, or even reduced to near the detection limit, if necessary.

[0031] [(B) Component] Component (B) is a linear or branched organopolysiloxane that contains at least two aliphatic unsaturated carbon-carbon bond-containing groups within the molecule, and whose degree of siloxane polymerization is in the range of 1001 to 10000. Component (B) is a curable reactive component like component (A), but has a higher degree of polymerization and viscosity than component (A). Therefore, by using a certain amount of both components in combination, the overall viscosity of the curable silicone composition can be adjusted, improving coatability and increasing the strength of the cured product. Such component (B) includes compounds of the general formula: [ka] However, component (B) is preferably a linear organopolysiloxane represented by the formula: 1 SiO 3 / 2 or SiO 4 / 2 The organopolysiloxane may contain 0 to 5 branched siloxane units represented by the following formula, and may be a branched-chain organopolysiloxane.

[0032] In the formula, each R1 is independently exemplified by an organic group such as an aliphatic unsaturated carbon-carbon bond-containing group or an alkyl group. ais an organic group containing no aliphatic unsaturated carbon-carbon bond-containing group, or R1, and in one molecule, at least two R1s are aliphatic unsaturated carbon-carbon bond-containing groups, preferably alkenyl groups, more preferably vinyl groups or hexenyl groups. Furthermore, the degree of siloxane polymerization, "m+n" in the formula, is preferably a number within the range of 1,001 to 10,000, more preferably a number within the range of 2,000 to 10,000, and particularly preferably a number within the range of 2,000 to 8,000. Furthermore, within the range of 0 to 5, R 1 SiO 3 / 2 or SiO 4 / 2 It may contain a branched siloxane unit represented by the formula: 1 SiO 3 / 2 For the branched siloxane unit represented by 4 / 2 For branched siloxane units represented by 1 3SiO 1 / 2 Units are added within the molecule to form the chain ends corresponding to the branched siloxane units.

[0033] In the above general formula, R2 is an organic group that does not contain an aliphatic unsaturated carbon-carbon bond-containing group, and is preferably an alkyl group, with a methyl group being particularly preferred from an industrial standpoint. On the other hand, from the standpoints of improving the elongation, adhesion to substrates, and transparency of the cured product, particularly at high temperatures, and particularly reducing the haze value, a methyl group is preferred as the organic group other than the aliphatic unsaturated carbon-carbon bond-containing group in component (B), and the content of aryl or aralkyl groups is preferably less than 0.1 mol %, particularly 0.0 mol %, of all groups bonded to silicon atoms, so that the component is substantially free of aryl or aralkyl groups.

[0034] Component (B) is preferably in the form of a high-viscosity liquid or gum at room temperature. Specifically, component (B) may be, and is preferably, in the form of a crude rubber having a viscosity of 1,000,000 mPa·s or greater at 25°C or a plasticity measured according to the method specified in JIS K6249 (measured by applying a load of 1 kgf to a 4.2 g spherical sample at 25°C for 3 minutes, reading the thickness to the nearest 1 / 100 mm, and multiplying this value by 100) in the range of 50 to 200, more preferably in the range of 80 to 180.

[0035] From the standpoint of preventing contact failure, it is preferable that these alkenyl group-containing organopolysiloxanes have reduced or eliminated volatile or low-molecular-weight siloxane oligomers (octamethyltetrasiloxane (D4), decamethylpentasiloxane (D5), etc.) The extent of this can be designed as desired, but may be less than 1 mass% of the entire component (A), less than 0.1 mass% for each siloxane oligomer, or even reduced to near the detection limit, if necessary.

[0036] Component (B) adjusts the viscosity of the curable silicone composition of the present invention, improving its coatability, and also adjusts the strength and hardness of the cured product obtained by curing the composition, thereby imparting adhesion. Therefore, the amount of component (B) is preferably in the range of 1 to 100 parts by mass, more preferably 2.5 to 40 parts by mass, and particularly preferably 3.0 to 30 parts by mass, based on 100 parts by mass of component (A) in the composition. If the amount of component (B) is less than the lower limit, the viscosity of the composition of the present invention may be low and its adhesion may be insufficient. On the other hand, if the amount of component (B) is more than the upper limit, the viscosity of the curable silicone composition of the present invention may be excessively high, making it unsuitable for the above-mentioned applications.

[0037] When the total amount (=sum) of components (A) to (D), which form the solid content of the curable silicone composition of the present invention upon curing, including components (C) and (D) described below, is taken as 100 parts by mass, the total amount of components (A) and (B) is preferably in the range of 65 to 99 parts by mass.

[0038] [(C) component] Component (C) is an organopolysiloxane resin that optionally adjusts adhesion to the substrate. Depending on the amount of component (C), the hardness and adhesion of the cured product of the composition to the substrate can be adjusted. Specifically, when the content of component (C) is zero or a small amount, the cured product is flexible and exhibits low adhesion to the substrate surface. Even when exposed to high temperatures, the cured product can be easily removed from the substrate surface by interfacial peeling. On the other hand, as the content of component (C) increases, the adhesion of the cured product to the substrate surface tends to increase. Using more than 100 parts by weight of component (C) per 100 parts by weight of component (A) reduces the flexibility of the resulting cured product and forms a strong bond with the substrate surface, making removal from the substrate surface difficult, especially after exposure to high temperatures.

[0039] Component (C) has (a) R3SiO in the molecule. 1 / 2 (wherein R each independently represent a monovalent organic group), and (b) SiO 4 / 2 The organopolysiloxane resin contains siloxane units (Q units) represented by the following formula: The molar ratio of M units to Q units is preferably 0.5 to 2.0. If this molar ratio is less than 0.5, the adhesion of the cured product to the substrate may decrease, while if it is more than 2.0, the cohesive force of the substance that constitutes the adhesive layer decreases.

[0040] In particular, the molar ratio of (a) M units to (b) Q units is preferably in the range of 0.50:1.00 to 1.50:1.00, more preferably 0.55:1.00 to 1.20:1.00, and even more preferably 0.60:1.00 to 1.10:1.00. 29 It can be easily measured by Si nuclear magnetic resonance.

[0041] (C) Component has the general unit formula: (RSiO 1 / 2 ) a (SiO 4 / 2 ) b(wherein R are each independently a monovalent organic group, a and b are each a positive number, a+b=1, and a / b=0.5 to 1.5) is preferred.

[0042] The (C) component may be composed of only (a) M units and (b) Q units, but may also be composed of RSiO 2 / 2 Units (D units) and / or RSiO 3 / 2 In the formula, each R independently represents a monovalent organic group. The total content of (a) M units and (b) Q units in component (C) is preferably 50% by weight or more, more preferably 80% by weight or more, and particularly preferably 100% by weight.

[0043] The monovalent organic group is not particularly limited, but in view of its relationship with component (D), it is preferably an aliphatic unsaturated group containing no carbon-carbon bond.

[0044] Aliphatic unsaturated groups not containing a carbon-carbon bond include monovalent saturated hydrocarbon groups and oxygen atom-containing monovalent saturated hydrocarbon groups.

[0045] Suitable monovalent saturated hydrocarbon groups include, for example, substituted or unsubstituted monovalent saturated hydrocarbon groups having 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 6 carbon atoms.

[0046] Examples of unsubstituted monovalent saturated hydrocarbon groups having 1 to 12 carbon atoms include alkyl groups such as methyl, ethyl, propyl, pentyl, hexyl, and octyl; cycloalkyl groups such as cyclohexyl and cycloheptyl; aryl groups such as phenyl, tolyl, and xylyl; and aralkyl groups such as benzyl, α-methylstyryl, and 2-phenylethyl. Examples of substituted monovalent saturated hydrocarbon groups having 1 to 12 carbon atoms include these monovalent unsaturated hydrocarbon groups in which some of the hydrogen atoms have been substituted with halogen atoms (fluorine, chlorine, bromine, or iodine). Specific examples include fluorinated monovalent saturated hydrocarbon groups, such as perfluoroalkyl groups such as 3,3,3-trifluoropropyl, 4,4,5,5,5-pentafluorobutyl, and 3,3,4,4,5,5,6,6,6-nonafluorohexyl; and chlorinated monovalent saturated hydrocarbon groups, such as chloroalkyl groups such as 3-chloropropyl, and chlorophenyl groups such as dichlorophenyl.

[0047] The monovalent saturated hydrocarbon group is preferably a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms. A preferred example of the substituted or unsubstituted alkyl group having 1 to 12 carbon atoms is a methyl group. From the standpoint of reducing the haze value of the cured product, a methyl group is preferred as the monovalent organic group in component (C), and the content of aryl or aralkyl groups is preferably less than 0.1 mol %, and especially 0.0 mol %, based on the total group bonded to silicon atoms, so that the component is substantially free of aryl or aralkyl groups.

[0048] Examples of oxygen atom-containing monovalent saturated hydrocarbon groups include substituted or unsubstituted oxygen atom-containing monovalent saturated hydrocarbon groups having 2 to 12 carbon atoms.

[0049] Examples of the substituted or unsubstituted, oxygen atom-containing monovalent saturated hydrocarbon group having 1 to 12 carbon atoms include alkoxy groups having 1 to 12 carbon atoms.

[0050] Examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and an isopropoxy group.

[0051] [Reduction of hydroxyl groups or hydrolyzable groups] The hydrolyzable groups, such as hydroxyl or alkoxy groups, in component (C) are directly bonded to silicon in the T or Q units of the siloxane units in the resin structure and are derived from the silane raw material or are generated as a result of the hydrolysis of the silane. Therefore, the content of hydroxyl or hydrolyzable groups can be reduced by hydrolyzing the synthesized organopolysiloxane resin with a silylating agent such as trimethylsilane. This prevents the formation of organopolysiloxane resin structures with high molecular weights in the cured product, further improving the low-temperature curability of the composition and the storage modulus of the resulting cured product layer, and may result in good adhesion to substrates and improved removability from the substrate surface after exposure to high temperatures.

[0052] In the present invention, component (C) is represented by the general unit formula: (RSiO 1 / 2 ) a (SiO 4 / 2 ) b (wherein R are each independently a monovalent saturated organic group, a and b are each positive numbers, a+b=1, a / b=0.5 to 1.5), in which at least 90 mol % of R are preferably alkyl groups having 1 to 6 carbon atoms or phenyl groups, and it is particularly preferred that 95 to 100 mol % of R are methyl groups or phenyl groups. It is most preferred to use a resin (also known as an MQ resin) in which the content of hydroxyl groups or hydrolyzable groups in component (C) is in the range of 0 to 7 mol % relative to the total silicon (0.0 to 1.50 mass % as hydroxyl groups).

[0053] Examples of such component (C) include: (Me3SiO 1 / 2 ) 0.45 (SiO 4 / 2 ) 0.55 (HO 1 / 2 ) 0.05 (Me3SiO 1 / 2 ) 0.40 (SiO 4 / 2 ) 0.60 (HO 1 / 2 ) 0.10 (Me3SiO 1 / 2 ) 0.52 (SiO 4 / 2 ) 0.48 (HO 1 / 2 ) 0.01 (Me3SiO 1 / 2 ) 0.40 (Me2ViSiO 1 / 2 ) 0.05 (SiO 4 / 2 ) 0.55 (HO 1 / 2 ) 0.05 (Me3SiO 1 / 2 ) 0.45 (SiO 4 / 2 ) 0.55 (MeO 1 / 2 ) 0.10 (Me3SiO 1 / 2 ) 0.25 (Me2PhSiO 1 / 2 ) 0.20 (SiO 4 / 2 ) 0.55 (HO 1 / 2 ) 0.05 (Me3SiO 1 / 2 ) 0.40 (Me2SiO 2 / 2 ) 0.05 (SiO 4 / 2 ) 0.55 (HO 1 / 2 ) 0.05 (Me3SiO 1 / 2 ) 0.40 (MeSiO 3 / 2 ) 0.05 (SiO 4 / 2 ) 0.55 (HO 1 / 2 ) 0.05 (Me3SiO 1 / 2 ) 0.40 (Me2SiO 2 / 2 ) 0.05 (MeSiO 3 / 2 )0.05 (SiO 4 / 2 ) 0.50 (HO 1 / 2 ) 0.05 (Me: methyl group, Ph: phenyl group, MeO: methoxy group, HO: silicon-bonded hydroxyl group. To express the relative amount of hydroxyl groups to silicon atoms, the sum of the subscripts of the silicon-containing units is set to 1, (HO) 1 / 2 The unit subscript indicates the relative amount. From the standpoint of preventing contact failure, the amount of low molecular weight siloxane oligomers in component (C) may be reduced or eliminated.

[0054] In the present invention, particularly from the standpoint of improving low-temperature curability and the storage modulus and haze value of the cured product, it is preferable that low-molecular-weight, high-molecular-weight components (components that tend to aggregate into a gel, increase the haze value, and reduce low-temperature curability) have been removed from component (C) in advance. Specifically, a suitable example of component (C) in the present invention is an organopolysiloxane resin with a mass-average molecular weight in the range of 1,000 to 10,000, and the content of organopolysiloxane resins with molecular weights of 100,000 or more is 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably substantially 0% by mass, of the total. By using as component (C) a component that has a low molecular weight and, as described above, has a reduced number of hydroxyl groups or hydrolyzable groups, it is possible to prevent the presence or by-production of high molecular weight organopolysiloxane resin in the cured product, and it is possible to provide a curable silicone composition that has transparency and a low haze value, and in particular, even during curing or when exposed to high temperatures, high molecular weight organopolysiloxane resin is not produced in the system as a side reaction, thereby preventing changes in the storage modulus.As a result, it is possible to provide a cured product with greatly improved adhesion to substrates and removability.

[0055] Component (C) adjusts the storage modulus of the cured product obtained by curing the curable silicone composition of the present invention and imparts adhesion to the desired substrate, so its blending amount is in the range of 0 to 100 parts by mass, where 100 parts by mass of component (A) in the composition is taken as 100 parts by mass. At low blending amounts (including 0 parts by mass), the cured product has relatively weak adhesion to the substrate, and even when exposed to high temperatures, this adhesion does not change significantly, allowing it to be easily removed from the substrate surface. On the other hand, if the blending amount of component (C) exceeds the upper limit, the silicone curable composition of the present invention becomes too hard and may not be particularly suitable for the above-mentioned applications.

[0056] When the total amount (= sum) of components (A) to (D), which form the solid content of the curable silicone composition of the present invention upon curing, is taken as 100 parts by mass, the total amount of component (C) is preferably in the range of 0 to 40 parts by mass.

[0057] [(D) component] Component (D) is an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule. It functions as a crosslinker in the hydrosilylation reaction between components (A) and (B) and adjusts the hardness of the cured product depending on the amount added. By using this component (D) in a certain quantitative range relative to components (A) and (B), the curing reactivity of the entire composition is improved, achieving good curing characteristics and appropriate hardness (crosslink density), and the adhesion of the cured product and its removability after use can be designed within practically satisfactory ranges.

[0058] Component (D) may be at least one selected from cyclic organohydrogenpolysiloxanes having at least three silicon-bonded hydrogen atoms in the molecule and linear or branched organohydrogenpolysiloxanes having at least two silicon-bonded hydrogen atoms in the molecule, or may be a mixture of two or more of the above organohydrogenpolysiloxanes.

[0059] Examples of cyclic organohydrogenpolysiloxanes include those represented by the following formula: [(R 3 HSiO) m3 (R 3 2SiO) m4 ] Here, m3+m4 is a number ranging from 3 to 20, m3 is a number equal to or greater than 3, and m4 is a number equal to or greater than 0. R 3 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, excluding alkenyl groups, and R 2 Examples include groups similar to those shown below, and preferably a methyl group or a phenyl group.

[0060] The linear or branched organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in the molecule is an organohydrogenpolysiloxane such as a polyorganohydrogensiloxane or organohydrogensiloxane-diorganosiloxane copolymer having at least two silicon-bonded hydrogen atoms in the side chain portion and having the molecular chain terminals blocked with trialkylsiloxy groups, aryldialkylsiloxy groups, etc. The degree of polymerization of the siloxane is in the range of 5 to 500, preferably 5 to 200.

[0061] Specifically, the components (D) include 1,3,5,7-tetramethylcyclotetrasiloxane, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, 1-(3-glycidoxypropyl)-1,3,5,7-tetramethylcyclotetrasiloxane, 1,5-di(3-glycidoxypropyl)-1,3,5,7-tetramethylcyclotetrasiloxane, 1-(3-glycidoxypropyl)-5-trimethoxysilylethyl-1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogenpolysiloxane end-blocked with trimethylsiloxy groups at both molecular chain ends, and dimethylsiloxane-methylhydrogensiloxane copolymer end-blocked with trimethylsiloxy groups at both molecular chain ends. Examples include dimethylpolysiloxanes terminated at both molecular chain ends with dimethylhydrogensiloxy groups, methylhydrogensiloxane-diphenylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, methyltris(dimethylsiloxy)silane, tetrakis(dimethylsiloxysilane), methylhydrogenpolysiloxanes terminated at both molecular chain ends with trimethylsiloxy groups, methylhydrogensiloxane-dimethylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, and methylhydrogensiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups.

[0062] [SiH / Vi ratio in component (A) / component (B) and component (D)] In the composition of the present invention, the number of moles of silicon-bonded hydrogen atoms in components (A), (B), and (D) and the number of moles of aliphatic unsaturated carbon-carbon bonds such as alkenyl groups in components (A) and (B) in the entire composition are preferably in the range of 0.1 to 40, more preferably 0.5 to 30, and even more preferably 1.0 to 30. Within this range, the overall crosslink density can be appropriately adjusted, making it possible to exhibit the desired properties of storage modulus and adhesion of the cured product. On the other hand, if the SiH / Vi ratio is less than the lower limit, adhesive residue may remain when the cured product is adhered to a substrate, and if the SiH / Vi ratio exceeds the upper limit, the unreacted SiH groups may become excessive, resulting in unstable adhesion properties of the cured product.

[0063] When the total amount (= sum) of components (A) to (D) that form the solid content of the curable silicone composition of the present invention upon curing is taken as 100 parts by mass, the total amount of component (D) is preferably in the range of 0.01 to 15 parts by mass.

[0064] [(E) component] The curable silicone composition of the present invention contains a hydrosilylation catalyst as component (E). Examples of hydrosilylation catalysts include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts, with platinum-based catalysts being preferred because they significantly accelerate the curing of the composition. Examples of platinum-based catalysts include platinum fine powder, chloroplatinic acid, alcohol solutions of chloroplatinic acid, platinum-alkenylsiloxane complexes, platinum-olefin complexes, and platinum-carbonyl complexes, with platinum-alkenylsiloxane complexes being particularly preferred. Examples of this alkenylsiloxane include 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, alkenylsiloxanes in which some of the methyl groups of these alkenylsiloxanes have been substituted with groups selected from the group consisting of nitriles, amides, dioxolanes, and sulfolanes, ethyl groups, phenyl groups, etc., and alkenylsiloxanes in which the vinyl groups of these alkenylsiloxanes have been substituted with allyl groups, hexenyl groups, etc. In particular, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is preferred because the stability of this platinum-alkenylsiloxane complex is good, and it is preferably added in the form of an alkenylsiloxane solution. In addition, from the viewpoint of improving handling and workability and the pot life of the composition, these hydrosilylation catalysts may be hydrosilylation catalyst-containing thermoplastic resin fine particles, particularly thermoplastic resin fine particles containing a platinum-containing hydrosilylation catalyst, which are catalysts dispersed or encapsulated in a thermoplastic resin such as a silicone resin, a polycarbonate resin, or an acrylic resin. Non-platinum metal catalysts such as iron, ruthenium, or iron / cobalt may also be used as catalysts that promote the hydrosilylation reaction.

[0065] The thermoplastic resin microparticles containing a platinum-containing hydrosilylation catalyst that can be used in the present invention may be either microparticles in which a hydrosilylation catalyst such as a platinum-based catalyst is dissolved or dispersed in a thermoplastic resin, or microcapsule microparticles in which a hydrosilylation catalyst such as a platinum-based catalyst is contained as a core within a thermoplastic resin shell. The thermoplastic resin that constitutes the wall material preferably has a glass transition point (Tg) of 75°C or higher, more preferably 80°C or higher, and particularly preferably in the range of 80 to less than 250°C. Such thermoplastic resins may be used alone or in combination. The average particle size of the thermoplastic resin microparticles containing a hydrosilylation catalyst is not limited, but is preferably in the range of 0.1 to 500 μm, more preferably 0.3 to 100 μm.

[0066] In the present invention, the content of the hydrosilylation catalyst is not particularly limited, but is preferably within a range of 0.1 to 200 ppm of platinum-based metal relative to the total amount of solids in the composition, and may be within a range of 0.1 to 150 ppm, 0.1 to 100 ppm, or even 0.1 to 50 ppm. Here, the platinum-based metal refers to a Group VIII metal element consisting of platinum, rhodium, palladium, ruthenium, and iridium. For practical purposes, however, it is preferable that the content of platinum metal, excluding the ligands of the hydrosilylation catalyst, be within the above range. The solid content refers to the components (mainly the base resin, adhesion-imparting component, crosslinking agent, catalyst, and other non-volatile components) that form a cured layer when the curable silicone composition of the present invention is cured, but does not include volatile components such as solvents that volatilize during heat curing.

[0067] When the platinum-based metal content in the curable silicone composition of the present invention is 50 ppm or less (45 ppm or less, 35 ppm or less, 30 ppm or less, 25 ppm or less, or 20 ppm or less), discoloration or coloring of the transparent adhesive layer may be particularly suppressed after curing or when exposed to high-energy rays such as heat or ultraviolet light. On the other hand, from the standpoint of the curability of the organopolysiloxane composition, the platinum-based metal content should be 0.1 ppm or more, and a content below this lower limit may cause poor curing.

[0068] The curable silicone composition of the present invention may optionally contain a cure retarder. The cure retarder is incorporated to inhibit the crosslinking reaction between the aliphatic unsaturated carbon-carbon bond-containing groups and silicon-bonded hydrogen atoms in the composition, thereby extending the usable time at room temperature and improving storage stability. Therefore, in practice, it is a nearly essential component for the curable silicone composition of the present invention.

[0069] Specific examples of the cure retarder include acetylene compounds, enyne compounds, organic nitrogen compounds, organic phosphorus compounds, oxime compounds, and phosphorus compounds.Specific examples include alkyne alcohols such as 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-pentyn-3-ol, 1-ethynyl-1-cyclohexanol, and phenylbutynol; enyne compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-1-hexyn-3-yne; methylalkenylcyclosiloxanes such as 2-ethynyl-4-methyl-2-pentene, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane; and benzotriazole.

[0070] The phosphorus-containing hydrosilylation reaction retarder may be at least one selected from the group consisting of phosphine compounds, phosphoric acid compounds, phosphonic acid compounds, phosphine oxide compounds, phosphorous acid compounds, and phosphonous acid compounds, and examples thereof include the components described in JP 2007-308542 A, such as 1,3-bis(diphenylphosphino)propane.

[0071] From the standpoint of the curing behavior of the composition, it is preferable that the curable silicone composition of the present invention exhibits a viscosity increase of no more than 1.5 times after 8 hours at room temperature following preparation of the composition, and be curable at 80 to 200°C. Suppressed viscosity increase is important from the standpoints of handling, pot life, and post-curing properties, and curing at a high temperature above a certain level (80 to 200°C) ensures curability. Such a composition can be achieved by selecting an appropriate combination and blending amounts of the above-mentioned components, hydrosilylation catalyst, and cure retarder.

[0072] [(F) Organic Solvent and Low-Solvent / Solvent-Free Compositions] The curable silicone composition of the present invention has relatively low viscosity components, making it possible to design low-solvent or solvent-free compositions. Even compositions containing only a small amount of (F) organic solvent or substantially no organic solvent can achieve practically sufficient coatability. Specifically, the organic solvent content is preferably 0 to less than 60% by mass, less than 50% by mass, and substantially within the range of 0 to 30% by mass, based on 100 parts by mass of the total composition. On the other hand, the inclusion of a small amount of organic solvent is acceptable when it is necessary to improve the wettability of the composition to the substrate or when it is unavoidably included as a solvent accompanying component (B). The type and amount of organic solvent are adjusted taking into account factors such as coating workability, but from the perspective of designing a solvent-free composition, it is preferable to use as little as possible.

[0073] More specifically, when the total amount (= sum) of components (A) to (D), which form the solid content of the curable silicone composition of the present invention upon curing, is taken as 100 parts by mass, the total amount of component (F), which serves as a diluent, is preferably in the range of 0 to 25 parts by mass.

[0074] In the present invention, examples of the organic solvent (F) include aromatic hydrocarbon solvents such as toluene, xylene, and benzene; aliphatic hydrocarbon solvents such as heptane, hexane, octane, and isoparaffin; ester solvents such as ethyl acetate and isobutyl acetate; ether solvents such as diisopropyl ether and 1,4-dioxane; chlorinated aliphatic hydrocarbon solvents such as trichloroethylene, perchloroethylene, and methylene chloride; and volatile oils. Two or more of these may be combined depending on the wettability of the sheet-like substrate.

[0075] The curable silicone composition of the present invention may optionally contain components other than those described above, provided that the technical effects of the present invention are not impaired. For example, the composition may contain an adhesion promoter; a non-reactive organopolysiloxane such as polydimethylsiloxane or polydimethyldiphenylsiloxane; an antioxidant such as a phenol, quinone, amine, phosphorus, phosphite, sulfur, or thioether; a light stabilizer such as a triazole or benzophenone; a flame retardant such as a phosphate ester, halogen, phosphorus, or antimony; or one or more antistatic agents such as a cationic surfactant, anionic surfactant, or nonionic surfactant. In addition to these components, pigments, dyes, inorganic fine particles (reinforcing fillers, dielectric fillers, conductive fillers, thermally conductive fillers), etc. may also be optionally blended.

[0076] [(A') A chain organopolysiloxane that does not contain a carbon-carbon double bond-containing reactive group in the molecule] The curable silicone composition of the present invention can be blended with a non-reactive organopolysiloxane, such as polydimethylsiloxane or polydimethyldiphenylsiloxane, that does not contain any carbon-carbon double bond-containing reactive groups such as alkenyl groups, acrylic groups, or methacrylic groups. This may improve the loss factor (tan δ), storage modulus (G'), and loss modulus (G'') of the cured layer. For example, the use of a polydimethylsiloxane or polydimethyldiphenylsiloxane that has terminal hydroxyl groups can increase the loss factor of the cured layer, and such compositions are within the scope of the present invention.

[0077] [Viscosity of the entire composition] The curable silicone composition of the present invention has a viscosity of the entire composition at 25°C in the range of 1,000 to 300,000 mPa·s, preferably 5,000 to 50,000 mPa·s. In particular, when the content of organic solvent is 30 mass% or less per 100 parts by mass of the composition, the viscosity of the entire composition is preferably in the range of 5,000 to 300,000 mPa·s.

[0078] There are no particular limitations on the method for preparing the curable silicone composition of the present invention, and the composition can be prepared by mixing the components to homogeneity. If necessary, a small amount of organic solvent may be added, and the components may be mixed at a temperature of 0 to 200°C using a known stirrer or kneader.

[0079] The curable silicone composition of the present invention is applied to a substrate to form a coating film, which is then cured by heating at a temperature of 80 to 200° C., preferably 90 to 190° C. Examples of coating methods include gravure coating, offset coating, offset gravure, roll coating, reverse roll coating, air knife coating, curtain coating, and comma coating.

[0080] The curable silicone composition of the present invention may optionally contain components other than those described above, provided that the technical effects of the present invention are not impaired. For example, the composition may contain an adhesion promoter; a non-reactive organopolysiloxane such as polydimethylsiloxane or polydimethyldiphenylsiloxane; an antioxidant such as a phenol, quinone, amine, phosphorus, phosphite, sulfur, or thioether; a light stabilizer such as a triazole or benzophenone; a flame retardant such as a phosphate ester, halogen, phosphorus, or antimony; or one or more antistatic agents such as a cationic surfactant, anionic surfactant, or nonionic surfactant. In addition to these components, pigments, dyes, inorganic fine particles (reinforcing fillers, dielectric fillers, conductive fillers, thermally conductive fillers), etc. may also be optionally blended.

[0081] [(A') A chain organopolysiloxane that does not contain a carbon-carbon double bond-containing reactive group in the molecule] The curable silicone composition of the present invention can be blended with a non-reactive organopolysiloxane, such as polydimethylsiloxane or polydimethyldiphenylsiloxane, that does not contain any carbon-carbon double bond-containing reactive groups such as alkenyl groups, acrylic groups, or methacrylic groups. This may improve the loss factor (tan δ), storage modulus (G'), and loss modulus (G'') of the adhesive layer obtained by curing the curable silicone composition of the present invention. For example, the loss factor of the adhesive layer can be increased by using a polydimethylsiloxane or polydimethyldiphenylsiloxane that has terminal hydroxyl groups, and such compositions are within the scope of the present invention.

[0082] There are no particular limitations on the method for preparing the curable silicone composition of the present invention, and the composition can be prepared by mixing the components to homogeneity. A solvent may be added as necessary, and the components may be mixed at a temperature of 0 to 200°C using a known stirrer or kneader.

[0083] The organopolysiloxane composition of the present invention is applied to a substrate to form a coating film, which is then cured by heating at a temperature of 80 to 200° C., preferably at a temperature of 90 to 190° C. Examples of coating methods include gravure coating, offset coating, offset gravure, roll coating, reverse roll coating, air knife coating, curtain coating, and comma coating.

[0084] [Adhesion of the cured product] The curable silicone composition of the present invention is characterized by the fact that the cured layer obtained by curing the composition via a hydrosilylation reaction exhibits adhesiveness. The adhesive layer of the present invention has the above-mentioned structure and exhibits adhesive strength sufficient for practical use, so that it can be used as a substitute for known silicone pressure-sensitive adhesives, etc., as desired.

[0085] Specifically, it is possible to design a 40 μm thick adhesion layer obtained by curing the curable silicone composition of the present invention, with an adhesion strength to a SUS base measured at a tensile speed of 300 mm / min using the 180° peel test method according to JIS Z 0237, in the range of 100 to 2500 gf / inch, and preferably in the range of 500 to 2250 gf / inch. Note that the above thickness (40 μm) is the thickness of the cured layer itself, which serves as a standard for objectively defining the adhesion of the cured layer according to the present invention, and it goes without saying that the organopolysiloxane composition of the present invention can be used as a cured layer (cured adhesion layer) of any thickness, not just 40 μm.

[0086] [Use as an adhesive layer] The cured product of the present invention can be used particularly as an adhesion layer. Furthermore, in order to improve adhesion to an adherend, the surface of the adhesion layer or the substrate may be subjected to a surface treatment such as a primer treatment, a corona treatment, an etching treatment, or a plasma treatment. However, since the adhesion layer of the present invention has excellent adhesion to substrates such as display devices as described above, these steps may be added as necessary to further improve adhesion to the adherend, or these steps may be omitted to achieve higher production efficiency.

[0087] The curable silicone composition of the present invention can be coated onto a release liner and cured by heating under the above-mentioned temperature conditions. The release liner can then be peeled off and the composition can be attached to a film-like, tape-like, or sheet-like substrate (hereinafter referred to as "film-like substrate"). Alternatively, the composition can be coated onto a film-like substrate and cured by heating under the above-mentioned temperature conditions to form a cured adhesive layer on the surface of the substrate. Laminates having a cured layer, particularly a film-like cured layer, formed by curing the organopolysiloxane composition of the present invention on these film-like substrates can be used for adhesive tapes, detachable protective films, adhesive bandages, low-temperature supports, transfer films, labels, emblems, and decorative or explanatory signs. Furthermore, cured layers formed by curing the organopolysiloxane composition of the present invention can be used in the assembly of automobile parts, toys, electronic circuits, or keyboards. Alternatively, cured layers, particularly film-like adhesive layers, formed by curing the organopolysiloxane composition of the present invention can be used for the protection, construction, and use of laminated touch screens or flat panel displays.

[0088] Examples of substrates include paperboard, corrugated cardboard, clay-coated paper, polyolefin-laminated paper, especially polyethylene-laminated paper, synthetic resin films and sheets, natural fiber fabrics, synthetic fiber fabrics, artificial leather fabrics, and metal foils. Synthetic resin films and sheets are particularly preferred, and examples of synthetic resins include polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyethylene terephthalate, cyclopolyolefin, and nylon. When heat resistance is particularly required, films of heat-resistant synthetic resins such as polyimide, polyether ether ketone, polyethylene naphthalate (PEN), liquid crystal polyarylate, polyamide imide, and polyether sulfone are suitable. On the other hand, for applications requiring visibility, such as display devices, transparent substrates, specifically transparent materials such as polypropylene, polystyrene, polyvinylidene chloride, polycarbonate, polyethylene terephthalate, and PEN, are suitable.

[0089] The substrate is preferably in the form of a film or sheet. There are no particular limitations on its thickness, and it can be designed to a desired thickness depending on the application. Furthermore, to improve the adhesion between the support film and the cured adhesive layer, a support film that has been subjected to a primer treatment, corona treatment, etching treatment, or plasma treatment may be used. The surface of the film substrate opposite the cured layer / cured adhesive layer may also be subjected to a surface treatment such as scratch resistance, stain resistance, fingerprint resistance, anti-glare, anti-reflection, or anti-static treatment.

[0090] As a method for coating the substrate, gravure coating, offset coating, offset gravure, roll coating using an offset transfer roll coater or the like, reverse roll coating, air knife coating, curtain coating using a curtain flow coater or the like, comma coating, Mayer bar coating, and other known methods used for forming a cured layer can be used without any limitation.

[0091] The coating amount can be designed to a desired thickness depending on the application, such as a display device. For example, the thickness of the adhesive layer after curing is 1 to 1,000 μm, or may be 5 to 900 μm, or may be 10 to 800 μm, but is not limited to these.

[0092] The adhesive layer according to the present invention may be a single layer or a multilayer consisting of two or more adhesive layers, depending on the required properties. To form a multilayer adhesive layer, films prepared one by one may be laminated together, or a process of applying a curable silicone composition to a film substrate equipped with a release layer and then curing the composition may be carried out multiple times.

[0093] In addition to bonding or adhering between components, the adhesion layer according to the present invention may also serve as another functional layer selected from the group consisting of a dielectric layer, a conductive layer, a heat dissipation layer, an insulating layer, a reinforcing layer, etc. In particular, the curable silicone composition according to the present invention forms a cured adhesion layer that can be very easily removed from the surface of a substrate, making it extremely useful for temporary functional layers or for temporarily fixing functional layers that are intended to be attached or detached.

[0094] When the cured layer obtained by curing the curable silicone composition of the present invention is an adhesive layer, particularly an adhesive film, it is preferable to handle the cured layer as a laminate film in which it is releasably adhered to a film substrate provided with a release layer having release coating capability. The release layer is also called a release liner, separator, release layer, or release coating layer, and is preferably a release layer having release coating capability such as a silicone-based release agent, a fluorine-based release agent, an alkyd-based release agent, or a fluorosilicone-based release agent, or the substrate itself may form physical fine irregularities on the substrate surface or may be difficult to adhere to the adhesive layer of the present invention. In particular, in the laminate of the present invention, it is preferable to use a release layer obtained by curing a fluorosilicone-based release agent as the release layer.

[0095] The cured product obtained by curing the curable silicone composition of the present invention possesses both the viscoelasticity and adhesion described above, and also exhibits outstanding properties such as transparency and low haze, making it useful as an elastic adhesive layer for components of various electronic devices or electrical devices. It is particularly useful as an electronic material, display device component, or transducer component (including sensors, speakers, actuators, and generators), with the cured product being suitable for use as a component for electronic components or display devices. The cured product of the present invention may be either transparent or opaque. However, a film-shaped cured product, particularly a substantially transparent protective film, is suitable as a component for a display panel or display, and is particularly useful for so-called touch panel applications in which devices, particularly electronic devices, can be operated by touching the screen with a fingertip or the like. The cured product layer of the present invention may also be used as a film- or sheet-like component for sensors, speakers, actuators, etc., where transparency is not required and a certain degree of stretchability or flexibility is required for the adhesive layer itself.

[0096] [Use as adhesive tape] The article comprising a cured layer obtained by curing the curable silicone composition of the present invention may be an adhesive tape, particularly a protective tape intended to be attached and detached, and is characterized by comprising the adhesive layer described above and a sheet-like member made of a textile product such as the above-mentioned synthetic resin film / sheet, metal foil, woven fabric, nonwoven fabric, or paper. The type of such adhesive tape is not particularly limited, and examples include insulating tape, heat-resistant tape, solder masking tape, mica tape binder, temporary fixing tape (particularly including temporary fixing tape for silicone rubber parts, etc.), and splicing tape (particularly including splicing tape for silicone release paper).

[0097] In particular, the cured product, particularly the cured product layer, obtained by curing the curable silicone composition of the present invention can achieve high transparency and a low total haze value, and has sufficient adhesion to the substrate for practical use. Even when exposed to high temperatures, the adhesion properties and appearance of the adhesion layer remain stable, and the composition can be easily removed from the substrate surface after use. Therefore, the composition is particularly suitable for use as a functional film that is used temporarily and is intended to be attached and detached to display devices, semiconductors, etc.

[0098] [Laminate and adhesive sheet] A laminate having a cured adhesive layer formed by curing the curable silicone composition may be formed on the film-like substrate, and preferably, the film-like substrate may be provided with a release layer for the cured adhesive layer.

[0099] In the laminate, the sheet-like substrate preferably has at least one release layer, and the release layer is in contact with the cured adhesive layer. This allows the cured adhesive layer to be easily peeled off from the sheet-like substrate. The release agent contained in the release layer is not particularly limited, and examples thereof include the same release agents as those described above.

[0100] In particular, the laminate may be such that the adhesive layer separated from the film-like substrate can be handled alone, or the laminate may have two film-like substrates. in particular, Film-like substrate, a first release layer formed on the film-like substrate; an adhesive layer formed by applying the curable silicone composition onto the release layer and curing the composition; and a second release layer laminated on the adhesive layer; The present invention may be applicable to the above-described embodiments.

[0101] Similarly, the laminate of the above form may be formed, for example, by applying the curable silicone composition to one release layer formed on a film-like substrate and curing it to form an adhesive layer, and then laminating another release layer on the adhesive layer.

[0102] Alternatively, a laminate of the above form may be produced, for example, by sandwiching the curable silicone composition between a first film-like substrate and a second film-like substrate, forming the composition to a certain thickness with a press or roll while heating, and then curing the composition.

[0103] The first sheet substrate may have a first release layer, or the first sheet substrate itself may have release properties. Similarly, the second sheet substrate may have a second release layer, or the second sheet substrate itself may have release properties. When the first sheet substrate and / or the second sheet substrate have a first release layer and / or a second release layer, it is preferred that the cured adhesive layer contacts the first release layer and / or the second release layer.

[0104] Examples of sheet substrates having release properties include sheet substrates made of materials having release properties such as fluororesin films, and sheet substrates made of materials with no or low release properties such as polyolefin films to which release agents such as silicone, fluororesin, etc. On the other hand, examples of sheet substrates having a release layer include polyolefin films coated with release agents such as silicone, fluororesin, etc.

[0105] The laminate can be used, for example, by applying the cured adhesive layer to an adherend and then peeling the adhesive layer from the film-like substrate.

[0106] The thickness of the adhesive layer (cured adhesive layer) is preferably 5 to 10,000 μm, more preferably 10 μm or more or 8,000 μm or less, and even more preferably 20 μm or more or 5,000 μm.

[0107] [Display panel or display components] The cured product obtained by curing the curable silicone composition of the present invention can be used to protect, construct, and utilize laminated touch screens or flat panel displays, and the specific method of use thereof can be any known method for using adhesive layers (e.g., silicone PSAs, silicone adhesives, and silicone sealants) without any particular restrictions. [Industrial Applicability]

[0108] The uses of the curable silicone composition of the present invention and the cured product obtained by curing the composition are not limited to those disclosed above, and films comprising the cured product obtained by curing the composition can be used in various display devices for displaying characters, symbols, and images. The surface shape of such display devices may be curved or bent rather than flat, and examples include various flat panel displays (FPDs) as well as curved displays or curved transmission screens used in automobiles (including electric vehicles) and aircraft. Furthermore, these display devices may be equipped with a touch panel function that allows input operations by touching icons, notification displays, and operation buttons for executing functions or programs on the screen or display. Applicable devices include CRT displays, liquid crystal displays, plasma displays, organic electroluminescent displays, inorganic electroluminescent displays, LED displays, surface electrolytic displays (SEDs), field emission displays (FEDs), and other display devices, as well as touch panels using these. Furthermore, the cured product obtained by curing the composition has excellent adhesion to substrates and viscoelastic properties, and can therefore be used as film or sheet-like members that are transducer members (including those for sensors, speakers, actuators, and generators) such as membranes for speakers, and can also be used as sealing layers or adhesion layers for secondary batteries, fuel cells, or solar cell modules.

[0109] The cured adhesive produced by curing the curable silicone composition of the present invention is substantially transparent, does not suffer from problems of poor curing or reduced curing properties, and exhibits excellent adhesion to substrates for various display devices and the like.

[0110] The transparent film substrate having an adhesive layer of the present invention may be used for the purpose of preventing scratches, stains, fingerprints, static electricity, reflection, and peeping on the display surface. [Example]

[0111] (Examples 1 to 7, Comparative Examples 1 to 3) Examples and comparative examples of the present invention are described below. In each example, comparative example, and reference example, "cured" means that the respective composition was completely cured under the respective curing conditions.

[0112] (Preparation of Curable Reactive Silicone Composition) The curable silicone compositions shown in the examples and comparative examples were prepared using the components shown in Table 1. Note that all % in Table 1 is by mass.

[0113] (Measurement of molecular weight of organopolysiloxane component) Using a Waters gel permeation chromatograph (GPC) and tetrahydrofuran (THF) as a solvent, the weight average molecular weight (Mw) and number average molecular weight (Mn) of organopolysiloxane components such as organopolysiloxane resins were determined in terms of standard polystyrene. (membrane surface) Each composition was applied to a PET film (Toray Industries, Inc., product name: Lumirror (registered trademark) S10, thickness: 50 μm) to a thickness of 75 μm after curing and cured at 140°C for 2 minutes. After leaving for 1 day, the sample was cut into a width of 20 mm, and the adhesive layer surface was attached to a SUS plate (Partec) using a roller to prepare a test piece. After peeling, the film surface was observed, and compositions in which the adhesive layer (cured product) remained on the SUS plate were judged to have adhesive residue, while compositions in which no adhesive layer remained on the SUS plate were rated as "no adhesive residue." The results are shown in Table 1. (Adhesion to glass surface, removability) Each composition was applied to a PET film (manufactured by Toray Industries, Inc., product name: Lumirror (registered trademark) S10, thickness: 50 μm) to a cured thickness of 75 μm and cured at 140°C for 2 minutes. After leaving for 1 day, the sample was cut into a 20 mm width and the adhesive surface was attached to the fresh water surface of a float glass plate using a roller to prepare a test specimen. The test specimens were measured for adhesion strength (measurements at a 25 mm width were converted to gf / inch) using a 180° peel test method in accordance with JIS Z0237 using an Orientec RTC-1210 tensile tester at a pulling rate of 300 mm / min. Test specimens with an adhesion strength of 1 gf / 25 mm or greater were considered to have good adhesion, and are indicated in Table 1 as "Good adhesion." Furthermore, the test pieces were left attached to the glass and stored in an oven at 85°C for 4 hours, and the adhesion strength (measurements over a 25 mm width were converted to gf / inch) was measured at a pulling rate of 300 mm / min using an Orientec RTC-1210 tensile tester in accordance with JIS Z0237 using the 180° peel test method. Compared to the initial adhesion strength, samples that were in the range of 100% to 200% were rated as ◯, samples that were 200% to 300% were rated as △, and samples that were 300% or more were rated as ×. These results are shown as "removability" in Table 1. (Haze value) Each composition was coated onto a PET film (manufactured by Toray Industries, Inc., product name Lumirror (registered trademark) #10, thickness 50 μm, Lumirror #50) so that the thickness after curing was 75 μm, and cured for 2 minutes at 140° C. The cured film was measured with a haze meter, and samples with a haze value of less than 2.0 were rated as good, and samples with a haze value of 2.0 or more were rated as bad.

[0114] The materials of the curable organopolysiloxane composition are shown in Table 1. The viscosity or plasticity of each component was measured at room temperature by the following method. [viscosity] Viscosity (mPa·s) is a value measured using a rotational viscometer conforming to JIS K7117-1, and kinematic viscosity (mm 2 / s) is a value measured using an Ubbelohde viscometer in accordance with JIS Z8803. [Structural analysis of each silicone] The structures of the various silicones used in the examples were determined by measuring 29Si with a 500 MHz NMR spectrometer manufactured by Bruker. The following silicone components were used for each component in the table. The silicone resin of component C was prepared by mixing the other components A and B in advance and then distilling off the xylene under reduced pressure. (A1 component) Alkenyl group-containing polysiloxane (vinyl group content: 0.089% by mass) represented by the following formula: [ka] (A2-1 component) Alkenyl group-containing polysiloxane (vinyl group content: 0.49% by mass) represented by the following formula: [ka] (A2-2 component) Alkenyl group-containing polysiloxane (vinyl group content: 0.3% by mass) represented by the following formula: [ka] (B component) Vinyl-functional polydimethylsiloxane, gum-like (degree of polymerization 2000), vinyl group content 0.21% by weight (C component) (CH3)3SiO 1 / 2 Units and SiO 4 / 2 MQ silicone resin consisting of units and hydroxyl groups, weight average molecular weight (Mw) in polystyrene equivalent: 6500, OH content: 4.5 mol% (1.0 mass%), xylene solution (solid content: 70 mass%) (D1 component) Methylhydrogenpolysiloxane with both molecular chain ends blocked with trimethylsiloxy groups (viscosity at 25°C: 20 mm2 / s, SiH content: 1.59%) (D2 component) Dimethylsiloxane-methylhydrogensiloxane copolymer (mass average molecular weight 1600, SiH content 0.73% by mass) with both molecular chain ends capped with trimethylsiloxy groups (E component) Platinum catalyst: 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex (Amount that results in 40 ppm of platinum) (F component) Organic solvent: toluene (Cure retarder) 3-methyl-1-butyn-3-ol (abbreviated as "methylbutynol" in the table)

[0115] [Table 1] *% by mass of organic solvent (toluene) relative to 100 parts by mass of the sum of components A to D **Adhesion to glass surfaces ***Removability from glass surface after 48 hours at 85°C

[0116] [Summary] The curable silicone compositions of Examples 1 to 7, even though they were low-solvent compositions, had viscosities within a range sufficient for practical application, and the resulting adhesive layers were sufficiently excellent for practical use in terms of curability and adhesion / removability from the substrate.

[0117] On the other hand, if the amount of component (B) is too large, the cured product will not have a low haze value and will have insufficient removability after high-temperature storage, as in Comparative Examples 1 and 2. Furthermore, if component (B) is absent, the removability after high-temperature storage will be significantly impaired, as in Comparative Example 3.

Claims

1. (A) (A1) a linear or branched organopolysiloxane having at least two aliphatic unsaturated carbon-carbon bond-containing groups only at both molecular chain terminals and having a degree of siloxane polymerization in the range of 10 to 1,000; and (A2) A linear organopolysiloxane having at least one aliphatic unsaturated carbon-carbon bond-containing group at a position other than the molecular chain terminals and at least three aliphatic unsaturated carbon-carbon bond-containing groups within the molecule, with a siloxane degree of polymerization in the range of 10 to 1,000, and an average number of siloxane units between two aliphatic unsaturated carbon-carbon bond-containing groups in the component of 30 to 200. 100 parts by mass of a mixture containing these in a mass ratio of 30:70 to 70:30, (B) a linear or branched organopolysiloxane having at least two aliphatic unsaturated carbon-carbon bond-containing groups in the molecule and having a degree of siloxane polymerization in the range of 2,000 to 8,000, in an amount of 2.5 to 40 parts by mass per 100 parts by mass of component (A); (C) R in the molecule ３ SiO １／２ (wherein R each independently represent a monovalent saturated organic group), and a siloxane unit (M unit) represented by the formula: ４／２ an organopolysiloxane resin containing siloxane units (Q units) represented by the formula: (D) polyorganohydrogensiloxane, and (E) Hydrosilylation reaction catalyst, catalytic amount and (F) Organic solvent, 0 to 60 parts by mass per 100 parts by mass of the total of the components (A) to (D) A curable silicone composition comprising:

2. 2. The curable silicone composition according to claim 1, wherein the content of silicon-bonded aryl or aralkyl groups in the molecules of components (A) and (B) is less than 0.1 mol%, based on the total number of silicon-bonded groups in these components.

3. 3. The curable silicone composition according to claim 1, wherein component (C) is an organopolysiloxane resin having a mass-average molecular weight in the range of 1,000 to 10,000, and the content of organopolysiloxane resins having a molecular weight of 100,000 or greater is 1 mass% or less of the total organopolysiloxane resin.

4. 4. The curable silicone composition according to claim 1, wherein component (D) is a linear or branched organohydrogenpolysiloxane that has at least one silicon-bonded hydrogen atom at a position other than the molecular chain terminals, and the ratio of the number of moles of silicon-bonded hydrogen atoms in component (D) to the number of moles of aliphatic unsaturated carbon-carbon bond-containing groups in components (A) and (B) is in the range of 0.1 to 40.

5. The curable silicone composition according to any one of claims 1 to 4, wherein when the curable silicone composition is cured on a PET film to form a cured film having a thickness of 75 µm, the cured film has a total haze value of 2.0 or less.

6. A cured silicone product obtained by curing the curable silicone composition according to any one of claims 1 to 5.

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