UV-curable organopolysiloxane composition and its uses

Abstract

[Problem] To provide a curable composition, particularly an ultraviolet-curable composition, that contains silicon atoms, yields a cured product having a low refractive index, and has excellent workability when applied to a substrate. [Solution] This ultraviolet-curable composition is characterized by including (A) an organopolysiloxane that has at least two alkenyl group-containing groups in each molecule thereof and at least three silicon atoms per molecule, (B) an organopolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule thereof, and (C) a photoactive hydrosilylation catalyst. The ultraviolet-curable composition is also characterized by not including any organic solvents, by the overall viscosity of the composition as measured at 25ºC using an E-type viscometer being 80 mPa•s or less, and by the refractive index of a cured product thereof as measured at 25ºC and a wavelength of 589 nm after curing being 1.45 or less.

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet-curable organopolysiloxane composition containing an organopolysiloxane that can be cured by chemical rays, such as ultraviolet light or electron beams, and more particularly to an ultraviolet-curable organopolysiloxane composition from which the resulting cured product has a low refractive index and excellent coatability. The curable organopolysiloxane composition of the present invention has a low refractive index of 1.45 or less and is suitable as an insulating material for electronic and electrical devices, and especially as a coating agent. Furthermore, it has excellent coatability and excellent wettability to substrates and is useful as an inkjet printing material. [Background technology]

[0002] Due to their high heat resistance and excellent chemical stability, silicone resins have been used as coatings, potting agents, and insulating materials for electronic and electrical devices. Among silicone resins, UV-curable silicone compositions have also been reported.

[0003] Touch panels are used in a variety of display devices, including mobile devices, industrial equipment, and car navigation systems. To improve their detection sensitivity, it is necessary to suppress electrical interference from light-emitting elements such as light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), and an insulating layer is usually placed between the light-emitting element and the touchscreen.

[0004] On the other hand, thin display devices such as OLEDs have a structure in which many functional thin layers are stacked. In recent years, research has begun on improving the overall brightness of the display device by combining layers with high and low refractive indices and stacking them on the touchscreen layer. In addition, inkjet printing has been adopted as a processing method for organic layers to improve productivity. Therefore, there is a need for materials that can be processed by inkjet printing for the insulating layer mentioned above.

[0005] Japanese Patent Publication No. 2019-73588 discloses a photocurable resin composition comprising an unsaturated bond-containing aromatic compound and a compound having a mercapto group, while Japanese Patent Publication No. 2020-26515 discloses a photocurable resin composition mainly composed of an unsaturated bond-containing naphthalene compound. Both compositions can be applied by inkjet printing, and are characterized by having a high refractive index of 1.60 or higher for their cured products.

[0006] On the other hand, Japanese Patent Publication No. 6200591 discloses an inkjet coating encapsulant for electronic devices comprising a UV-curable functional group-containing polysiloxane silicone and a specific curable compound, while Japanese Patent Application Publication No. 2019-189844 discloses a photocurable resin composition for electronic devices comprising a polyfunctional cationic polymerizable compound and a specific monofunctional cationic polymerizable compound. Although these patent documents do not describe the refractive index of the compositions after curing, calculating the refractive index based on the monomer structure in the curable composition yields a value of 1.48 or higher in both cases. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-73588 [Patent Document 2] Japanese Patent Publication No. 2020-26515 [Patent Document 3] Patent No. 6200591 [Patent Document 4] Japanese Patent Publication No. 2019-189844 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, several UV-curable organopolysiloxane compositions are known, but there is still a need for UV-curable compositions whose cured product has a low refractive index of 1.45 or less, as well as excellent workability for application to a substrate, particularly low viscosity. The present invention aims to provide a curable composition containing silicon atoms, particularly a UV-curable composition, in which the cured product has a low refractive index and excellent workability when applied to a substrate. [Means for solving the problem]

[0009] The present invention was completed by discovering that it is possible to design the components of an ultraviolet-curable organopolysiloxane composition such that the viscosity of the entire composition, measured at 25°C using an E-type viscometer, is 80 mPa·s or less, without containing an organic solvent in the composition, by using (A) an organopolysiloxane having two or more alkenyl group-containing groups in one molecule and three or more silicon atoms per molecule, (B) an organopolysiloxane having two or more silicon-bonded hydrogen atoms in one molecule, and (C) a photoactive hydrosilylation reaction catalyst, and that the curable composition has excellent workability such as coatability, and the refractive index of the cured product, measured at 25°C and a wavelength of 589 nm, can be reduced to 1.45 or less.

[0010] The UV-curable organopolysiloxane composition of the present invention, (A) Organopolysiloxanes having two or more alkenyl group-containing groups in one molecule and three or more silicon atoms per molecule, (B) Organopolysiloxanes having two or more silicon-bonded hydrogen atoms in one molecule, and (C) The composition contains a photoactive hydrosilylation reaction catalyst, does not contain an organic solvent, has a total viscosity of 80 mPa·s or less measured at 25°C using an E-type viscometer, and has a refractive index of 1.45 or less measured at 25°C and a wavelength of 589 nm after curing.

[0011] In the ultraviolet-curable composition of the present invention, it is preferable that the above component (A) contains an organopolysiloxane having two or more alkenyl group-containing groups in one molecule and three or more silicon atoms per molecule, the viscosity of which is measured at 25°C using an E-type viscometer is 60 mPa·s or less.

[0012] The ultraviolet-curable composition of the present invention preferably contains, as component (A), an organopolysiloxane having two or more alkenyl group-containing groups in one molecule and three silicon atoms per molecule, with a viscosity of 10 mPa·s or less as measured at 25°C using an E-type viscometer.

[0013] The above component (A) preferably contains an organopolysiloxane having alkenyl group-containing groups at both ends.

[0014] It is preferable that the organopolysiloxane having an alkenyl group, which is component (A) above, has an average of 4 or more silicon atoms per molecule.

[0015] It is preferable that all silicon-bonded organic groups other than the alkenyl group-containing groups in the organopolysiloxane of component (A) and all silicon-bonded organic groups other than the silicon-bonded hydrogen atoms in the organopolysiloxane having silicon-bonded hydrogen atoms of component (B) are substantially methyl groups. "All silicon-bonded organic groups are substantially methyl groups" means that 95% or more, preferably 97% or more, more preferably 99% or more, and most preferably 100% of all silicon-bonded organic groups in the organopolysiloxane are methyl groups. The proportion of methyl groups among all silicon-bonded organic groups other than alkenyl groups is, for example, 1 These values ​​are either measured by 1H-NMR spectroscopy or calculated based on the amount of organic groups contained in the raw materials used to produce organopolysiloxanes.

[0016] The UV-curable composition of the present invention preferably has a total viscosity of 5 to 60 mPa·s as measured at 25°C.

[0017] The UV-curable composition of the present invention preferably has a total viscosity of 10 to 30 mPa·s as measured at 25°C.

[0018] In the ultraviolet-curable composition of the present invention, it is preferable that the content of organopolysiloxane having an alkenyl group and a boiling point of 200°C or less at 1013.25 hectopascals is less than 1% by mass of the total composition, preferably less than 0.1% by mass.

[0019] In the UV-curable composition of the present invention, it is preferable that the photoactive hydrosilylation reaction catalyst, which is component (C), is an unsubstituted or alkyl-substituted cyclopentadienyltrialkylplatinum complex.

[0020] The UV-curable composition of the present invention is suitable for use as an insulating coating agent, and therefore, the present invention provides an insulating coating agent comprising the above UV-curable organopolysiloxane composition.

[0021] The present invention also provides a method for using the cured product of the above-mentioned UV-curable organopolysiloxane composition as an insulating coating agent.

[0022] The present invention also provides a display device, such as a liquid crystal display or an organic EL display, which includes a layer made of a cured product of the above-mentioned ultraviolet-curable organopolysiloxane composition. [Effects of the Invention]

[0023] The UV-curable polyorganosiloxane composition of the present invention has low viscosity even without the use of organic solvents, excellent coatability on substrates, good curability, and the refractive index of the cured product formed when the composition hardens is 1.45 or less. [Modes for carrying out the invention]

[0024] First, the UV-curable polyorganosiloxane composition of the present invention (hereinafter also simply referred to as the curable composition or UV-curable composition) will be described in detail. The curable composition of the present invention, (A) Organopolysiloxanes having two or more alkenyl group-containing groups in one molecule and three or more silicon atoms per molecule, (B) Organopolysiloxanes having two or more silicon-bonded hydrogen atoms in one molecule, and (C) comprises a photoactive hydrosilylation reaction catalyst, The curable composition is characterized by not containing organic solvents as a component, having a viscosity of 80 mPa·s or less measured at 25°C using an E-type viscometer, and having a refractive index of 1.45 or less measured at 25°C and a wavelength of 589 nm in the cured product obtained by curing the curable composition.

[0025] The UV-curable composition of the present invention contains a photoactive hydrosilylation catalyst, and when exposed to so-called chemical light, such as ultraviolet light, the catalyst becomes active as a hydrosilylation catalyst. As a result, crosslinking occurs through an addition reaction between the alkenyl group of component (A) and the silicon-bonded hydrogen atom (Si-H), i.e., the hydrosilyl group, of component (B), and thus the composition hardens.

[0026] The components (A), (B), (C), and other optional components constituting the curable composition of the present invention will be described below.

[0027] <Component (A): An organopolysiloxane having two or more alkenyl-containing groups in one molecule and three or more silicon atoms per molecule>

[0028] Component (A) is an organopolysiloxane having an alkenyl-containing group, i.e., a curing-reactive group containing a carbon-carbon double bond, wherein the carbon-carbon double bond can react with a SiH group by hydrosilylation, and is not limited to an alkenyl-containing group of a specific chemical structure. The alkenyl-containing group is preferably a terminal alkenyl group, and examples include, but is not limited to, alkenyl groups having 2 to 20 carbon atoms such as vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, and 4-vinylphenyl group. The alkenyl-containing group is preferably a group selected from vinyl group, allyl group, and hexenyl group, and is particularly preferably a vinyl group. The organopolysiloxane of component (A) is preferably a linear, branched, cyclic, or resinous (network-like) organopolysiloxane having an average of two or more alkenyl-containing groups per molecule and three or more silicon atoms per molecule, preferably an average of four or more silicon atoms per molecule, and is particularly preferably a linear or branched organopolysiloxane. One such organopolysiloxane having alkenyl-containing groups can be used, or two or more selected from the group consisting of linear, branched, cyclic, and resinous (network-like) organopolysiloxanes can be used in combination. Particularly, it is preferable to use only one or two or more linear organopolysiloxanes, or a combination of a linear organopolysiloxane and a branched organopolysiloxane as component (A).

[0029] The organopolysiloxane of component (A) is preferably one or more selected from the group consisting of linear organopolysiloxanes having alkenyl-containing groups at both ends of the molecule and branched organopolysiloxanes having alkenyl-containing groups at the ends of the molecule.

[0030] The organopolysiloxane, which is component (A), may contain groups selected from the group consisting of monovalent hydrocarbon groups, hydroxyl groups, and alkoxy groups that do not have a carbon-carbon double bond in their molecule, in addition to groups containing a carbon-carbon double bond. Monovalent hydrocarbon groups include unsubstituted monovalent hydrocarbon groups and fluorine-substituted monovalent hydrocarbon groups. Unsubstituted or fluorine-substituted monovalent hydrocarbon groups are preferably groups selected from unsubstituted or fluorine-substituted alkyl, cycloalkyl, arylalkyl, and aryl groups having 1 to 20 carbon atoms. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, pentyl, and octyl groups, with methyl groups being particularly preferred. Examples of cycloalkyl groups include cyclopentyl and cyclohexyl. Examples of arylalkyl groups include benzyl and phenylethyl groups. Examples of aryl groups include phenyl and naphthyl groups. Examples of fluorine-substituted monovalent hydrocarbon groups include 3,3,3-trifluoropropyl and 3,3,4,4,5,5,6,6,6-nonafluorohexyl groups. The 3,3,3-trifluoropropyl group is preferred as the fluorine-substituted monovalent hydrocarbon group.

[0031] The organopolysiloxane of component (A) preferably has substantially methyl groups among its silicon-bonded organic groups other than the alkenyl-containing groups. That is, preferably 95% or more, preferably 97% or more, more preferably 99% or more, and most preferably 100% of the silicon-bonded organic groups other than the alkenyl-containing groups are methyl groups. Therefore, the most preferred embodiment of component (A) is an organopolysiloxane having a vinyl group as the alkenyl-containing group and substantially methyl groups among its silicon-bonded organic groups other than the vinyl group, preferably one or more selected from the group consisting of linear organopolysiloxanes and branched organopolysiloxanes. In this case as well, the vinyl group is preferably located at the end of the organopolysiloxane molecule.

[0032] The organopolysiloxane of component (A) has the above-mentioned alkenyl group-containing group and has three or more silicon atoms per molecule. Preferably, the organopolysiloxane of component (A) has an average of four or more silicon atoms per molecule. On the other hand, siloxane compounds with fewer than three silicon atoms, such as organodisiloxanes, are components whose boiling point is 200°C or lower at 1013.25 hectopascals. Even if such components have low viscosity, they may inhibit the hydrosilylation reaction between the alkenyl group-containing organopolysiloxane and the silicon-bonded hydrogen atom (SiH group), and the inclusion of such components may prevent the achievement of the UV-curable composition targeted by the present invention.

[0033] In particular, the organopolysiloxane component (A) used in the curable composition of the present invention preferably contains less than 1% by mass, preferably less than 0.1% by mass, of the total mass of the curable composition, and is especially preferably below the detection limit of analytical instruments such as gas chromatography. In order to achieve UV curability of the entire composition, it is particularly preferable that the composition substantially does not contain organopolysiloxanes with fewer than 3 silicon atoms per molecule, such as the organodisiloxane mentioned above, and with a boiling point of 200°C or less at 1013.25 hectopascals. If such components are included, UV curability of the composition of the present invention may not be achieved.

[0034] From the standpoint of achieving low viscosity for the entire composition, the organopolysiloxane of component (A) has three or more silicon atoms per molecule, and its viscosity, as measured at 25°C using an E-type viscometer, is preferably 60 mPa·s or less, more preferably 30 mPa·s, and particularly preferably 10 mPa·s or less. In this case, when two or more organopolysiloxanes are used in combination as component (A), it is preferable that the entire component (A) has the above viscosity.

[0035] Preferably, component (A) is the following average compositional formula (1): R 11 a R 12 b SiO (4-a―b) / 2 (1) It may be an organopolysiloxane represented by the formula, or a mixture of two or more thereof. In the formula, R 11 is the above alkenyl-containing group, R 12 is a group selected from the group consisting of a monovalent hydrocarbon group other than an alkenyl-containing group, a hydroxyl group, and an alkoxy group, a and b are numbers satisfying the following conditions: 1 ≤ a + b ≤ 3 and 0.001 ≤ a / (a + b) ≤ 0.33, preferably numbers satisfying the following conditions: 1.5 ≤ a + b ≤ 2.5 and 0.005 ≤ a / (a + b) ≤ 0.2. This is because when a + b is not less than the lower limit of the above range, the flexibility of the cured product can be increased, while when it is not more than the upper limit of the above range, the toughness of the cured product can be increased. When a / (a + b) is not less than the lower limit of the above range, the viscosity of the curable composition can be designed to be low, while when it is not more than the upper limit of the above range, the toughness of the cured product can be increased. R 11 The alkenyl-containing group that can be represented is not particularly limited as long as its carbon-carbon double bond can react with the SiH group by a hydrosilylation reaction. The alkenyl-containing group is particularly preferably a terminal alkenyl group. For example, alkenyl groups having 2 to 20 carbon atoms such as vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, and 4-vinylphenyl group can be mentioned, but are not limited thereto. The alkenyl-containing group is particularly preferably a group selected from vinyl group, allyl group, and hexenyl group, and particularly preferably a vinyl group. R 12Other monovalent hydrocarbon groups that can be represented include unsubstituted monovalent hydrocarbon groups and fluorine-substituted monovalent hydrocarbon groups. Unsubstituted or fluorine-substituted monovalent hydrocarbon groups are preferably selected from unsubstituted or fluorine-substituted alkyl, cycloalkyl, arylalkyl, and aryl groups having 1 to 20 carbon atoms. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, pentyl, and octyl groups, with methyl groups being particularly preferred. Examples of cycloalkyl groups include cyclopentyl and cyclohexyl. Examples of arylalkyl groups include benzyl and phenylethyl groups. Examples of aryl groups include phenyl and naphthyl groups. Examples of fluorine-substituted monovalent hydrocarbon groups include 3,3,3-trifluoropropyl and 3,3,4,4,5,5,6,6,6-nonafluorohexyl groups. 3,3,3-trifluoropropyl is a preferred fluorine-substituted monovalent hydrocarbon group. Therefore, in equation (1), R 11 is a vinyl group, R 12 It is most preferable that the group is a methyl group. However, the organopolysiloxane represented by average composition formula (1) has two or more alkenyl-containing groups in one molecule. The organopolysiloxane represented by average composition formula (1) is preferably one or more selected from the group consisting of linear organopolysiloxanes and branched organopolysiloxanes. Furthermore, it is particularly preferable that the alkenyl-containing groups are located at the molecular ends.

[0036] Examples of linear organopolysiloxanes having an alkenyl group that can be used as component (A) include organopolysiloxanes represented by the following formula (2). [ka] In the formula, R 1 and R 6These are the same or different C2-C12 alkenyl groups (terminal alkenyl groups), and examples include vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups. Due to their high reactivity to hydrosilylation reactions, vinyl, allyl, 5-hexenyl, and 7-octenyl groups are preferred, and vinyl groups are particularly preferred. R 2 , R 3 , R 4 , and R 5 Each of these groups is independently a monovalent hydrocarbon group other than an alkenyl group, for example, an unsubstituted or fluorine-substituted monovalent alkyl group having 1 to 12 carbon atoms, selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, 3-chloropropyl, and 3,3,3-trifluoropropyl, with methyl being particularly preferred. In the formula, m and n are numbers that satisfy 0 ≤ m < 50, 0 ≤ n < 5, and 1 ≤ m + n < 50. Note that when m + n = 1 or greater, the organopolysiloxane represented by the above formula has three or more silicon atoms per molecule.

[0037] A particularly preferred component (A) is the following general formula (3): Me2ViSiO(Me2SiO) a SiMe2Vi (3) Examples include one or a mixture of two or more organopolysiloxanes represented by the formula. In the formula, Me and Vi represent a methyl group and a vinyl group, respectively, and a is preferably an integer of 1 or more such that the viscosity of the organopolysiloxane of formula (3) at 25°C is 1000 mPa·s or less, preferably 500 mPa·s or less, more preferably 100 mPa·s or less, particularly preferably 60 mPa·s or less, and most preferably 10 mPa·s or less. The lower limit of viscosity is not limited, but is generally 2 mPa·s or more.

[0038] The organopolysiloxane having a branched alkenyl group that can be used as component (A) is given by the following average unit formula (4): (R 21 SiO 3 / 2 ) o (R 22 2SiO 2 / 2 ) p (R 23 3SiO 1 / 2 ) q (SiO 4 / 2 ) r (XO 1 / 2 ) s (4) It is preferable that the organopolysiloxane is represented by . In the above formula, R 21 , R 22 , and R 23 R is a group selected from the group consisting of alkenyl groups and monovalent hydrocarbon groups that do not have a carbon-carbon double bond, and X is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 21 , R 22 , and R 23 Some of these are alkenyl groups, and in particular, R 23 3SiO 1 / 2 R on the siloxane unit represented by 23 Preferably, at least a portion of it is an alkenyl group.

[0039] In the above formula, it is preferable that (o+r) is a positive number, p is 0 or a positive number, q is a positive number, s is 0 or a positive number, and p / (o+r) is a number in the range of 0 to 500, q / (o+r) is a number in the range of 2 to 5, (o+r) / (o+p+q+r) is a number in the range of 0.001 to 0.7, and s / (o+p+q+r) is a number in the range of 0 to 0.4.

[0040] As the branched organopolysiloxane having the alkenyl-containing group described above, it is preferable to use an organopolysiloxane selected from the group consisting of terminally dimethylvinylsilyl-bound branched trifunctional polydimethylsiloxane and terminally dimethylvinylsilyl-bound branched tetrafunctional polydimethylsiloxane, and it is preferable to use terminally dimethylvinylsilyl-bound branched tetrafunctional polydimethylsiloxane. As these trifunctional polydimethylsiloxanes, for example, they have an average of one T unit in their molecule, i.e., the R of formula (4) above. 21 SiO 3 / 2 It has one unit, and the rest are in M ​​units, that is, R in equation (4). 23 3SiO 1 / 2 The unit, or M unit and D unit, that is, R in equation (4). 22 2SiO 2 / 2 Examples include organopolysiloxanes composed of units. Furthermore, as a tetrafunctional polydimethylsiloxane, for example, it may have an average of one Q unit within its molecule, i.e., SiO in formula (4) above. 4 / 2 Examples of organopolysiloxanes include those having one unit and the rest being M units, or M units and D units.

[0041] The branched organopolysiloxane used as component (A) is preferably one that has an average of 3 to 500 silicon atoms per molecule, preferably 3 to 100, more preferably 3 to 50, and most preferably 3 to 10 silicon atoms.

[0042] Branched organopolysiloxanes containing alkenyl groups have a viscosity at 25°C that is preferably 1000 mPa·s or less, more preferably 500 mPa·s or less, and particularly preferably 300 mPa·s or less. The lower limit of viscosity is not limited, but is generally 5 mPa·s or higher.

[0043] In the curable composition of the present invention, component (A) is preferably a linear organopolysiloxane having alkenyl-containing groups only at both ends of the molecular chain, a branched organopolysiloxane having alkenyl-containing groups only at the ends of the molecular chain, or a combination of the two. It is particularly preferable that component (A) includes a linear organopolysiloxane having alkenyl-containing groups at both ends.

[0044] The organopolysiloxane used as component (A) has a viscosity of preferably 60 mPa·s or less, and more preferably 10 mPa·s or less, as measured at 25°C. When two or more organopolysiloxanes are used in combination as component (A), each component may have a viscosity of 60 mPa·s at 25°C. However, even if the viscosity of some components is greater than this value, it is sufficient to include organopolysiloxanes with lower viscosity so that the overall viscosity of component (A) is 60 mPa·s or less, preferably 10 mPa·s or less. For example, even if component (A) includes a component with a viscosity exceeding 1000 mPa·s as part of it, the overall viscosity of component (A) can be achieved if the viscosity of the other components is sufficiently low.

[0045] Specific examples of organopolysiloxanes used as component (A) include, but are not limited to, the following. Polydimethylsiloxane with dimethylvinylsilyl groups sealed at both ends (viscosity of 2-1000 mPa·s at 25°C) Terminally dimethylvinylsilyl group-sealed branched trifunctional polydimethylsiloxane (viscosity of 2-1000 mPa·s at 25°C) Terminally dimethylvinylsilyl group-sealed branched tetrafunctional polydimethylsiloxane (viscosity of 2-1000 mPa·s at 25°C)

[0046] <Component (B): Organopolysiloxane having two or more silicon-bonded hydrogen atoms in one molecule> Component (B) is an organopolysiloxane having an average of two or more silicon-bonded hydrogen atoms (Si-H) per molecule that can form a bond with component (A) through a hydrosilylation reaction.

[0047] Component (B), an organopolysiloxane having silicon-bonded hydrogen atoms (hereinafter also referred to as organohydrogenpolysiloxane), has on average two or more silicon-bonded hydrogen atoms per molecule and functions as a crosslinking agent that forms a crosslink with component (A), which has an alkenyl group, through a hydrosilylation reaction.

[0048] Component (B) can be one or more selected from the group consisting of linear organohydrogenpolysiloxanes and branched or resinous organohydrogensiloxanes. Such organohydrogenpolysiloxanes are well-known compounds in the art.

[0049] Examples of linear organohydrogenpolysiloxanes that can be used as component (B) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, tetrakis(dimethylhydrogensiloxy)silane, methylhydrogenpolysiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain, and dimethylsiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain. Examples of suitable copolymers include, but are not limited to, methylhydrogensiloxane copolymers, dimethylpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane copolymers with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, methylhydrogensiloxane-diphenylsiloxane copolymers with trimethylsiloxy groups sealed at both ends of the molecular chain, and methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymers with trimethylsiloxy groups sealed at both ends of the molecular chain. These can be used individually or in combination of two or more. As the compound used as component (B) of the present invention, organohydrogenpolysiloxanes in which the proportion of methyl groups in the silicon atom-bonded organic groups is 80% or more, preferably 90% or more, are preferred. Organohydrogenpolysiloxanes in which substantially all of the silicon atom-bonded organic groups are methyl groups are most preferred.

[0050] Examples of branched-chain or resinous organohydrogenpolysiloxanes that can be used as component (B) include hydrolysis condensates of trimethoxysilane, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and (C6H5)SiO 3 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2Units and (C6H5)SiO 3 / 2 Examples of resinous organohydrogenpolysiloxanes include copolymers consisting of units and, and mixtures of two or more selected from these. Further examples of resinous organohydrogenpolysiloxanes include at least SiO 4 / 2 Units (Q units) and R 31 SiO 3 / 2 Units (T units), and include branched siloxane units selected from the group consisting of R 31 3SiO 1 / 2 Units (M units), R 31 2HSiO 1 / 2 Units (M H Units), and optionally R 31 2SiO 2 / 2 Units (D units), R 31 HSiO 1 / 2 Units (D H Units), and are composed of M H MQ type, M H Q type, M H MT type, M H T type, M H MQT type, M H QT type, M H MDQ type, M H MDD H Q type, M H DQ type, M H DD H Q type, M H MDT type, M H MDD H T type, M H DT type, M<{ H DD H T type, M H MDQT type, M H MDD H QT type, M H DQT type, M H DD H QT type, and one or more organohydrogenpolysiloxane resins can be mentioned. These can be used alone or in combination of two or more. In addition, in the above formulas, R 31 is independently a methyl group or a phenyl group. R 31 is preferably a methyl group.

[0051] The branched or resinous organohydrogenpolysiloxane that can be used as component (B) may contain small amounts of silanol groups and alkoxysilyl groups that do not affect the hydrosilylation reaction. Here, "small amount" refers to a number less than 5% of the total number of substituents, including hydrogen atoms on the silicon atoms.

[0052] Furthermore, as component (B), any one of the linear, branched, and resinous organohydrogenpolysiloxanes described above may be used, or two or more may be used in any combination.

[0053] As component (B) of the present invention, it is preferable to use an organohydrogenpolysiloxane in which the hydrogen group concentration of the SiH group is 0.1 to 10% by mass, preferably 0.1 to 5% by mass, and most preferably 0.1 to 3% by mass.

[0054] The viscosity of component (B) is preferably 2 mPa·s to 100 mPa·s at 25°C, but any organohydrogenpolysiloxane of any viscosity can be used as long as the viscosity of the curable composition of the present invention, when combined with components (A) and (C), is 80 mPa·s or less when measured with an E-type viscometer at 25°C.

[0055] In the curable composition of the present invention, the content of component (B) is preferably in an amount such that the amount of silicon-bonded hydrogen atoms in component (B) is in the range of 0.1 to 5.0 moles per mole of carbon-carbon double bonds in component (A) in the composition, more preferably in the range of 0.2 to 5.0 moles, and particularly preferably in the range of 0.5 to 2 moles. By keeping the amount of silicon-bonded hydrogen atoms in component (B) within the above range, a curable composition with good curability and excellent physical properties of the cured product can be obtained. However, this does not preclude designing the amount of component (B) used in this curable composition so that the amount of silicon-bonded hydrogen atoms in component (B) is 10 moles or more per mole of carbon-carbon double bonds in component (A).

[0056] <Component (C): Photoactive hydrosilylation reaction catalyst> Component (C) is a photoactive hydrosilylation reaction catalyst for imparting the property of curing to the curable composition of the present invention by irradiation with chemical light, such as ultraviolet light.

[0057] Component (C) is not particularly limited as long as it is a compound that becomes active as a hydrosilylation reaction catalyst when irradiated with ultraviolet light, but it is preferable to use a photoactive platinum complex. Specific examples of photoactive platinum complexes include (methylcyclopentadienyl)trimethylplatinum(IV), (cyclopentadienyl)trimethylplatinum(IV), (1,2,3,4,5-pentamethylcyclopentadienyl)trimethylplatinum(IV), (cyclopentadienyl)dimethylethylplatinum(IV), (cyclopentadienyl)dimethylacetylplatinum(IV), (trimethylsilylcyclopentadienyl)trimethylplatinum(IV), (methoxycarbonylcyclopentadienyl)trimethylplatinum(IV), (dimethylphenylsilylcyclopentadienyl)trimethylplatinum(IV), (1,5-cyclooctadiene)dimethylplatinum(II), (1,5-cyclooctadiene)diphenylplatinum(II), (1,5-cyclooctadiene Examples include (2,5-norbornadiene)dimethylplatinum(II), (2,5-norbornadiene)dichloroplatinum(II), trimethyl(acetylacetonato)platinum(IV), trimethyl(3,5-heptanedione)platinum(IV), trimethyl(methylacetoacetate)platinum(IV), bis(2,4-pentanedionato)platinum(II), bis(2,4-hexanedionato)platinum(II), bis(2,4-heptanedionato)platinum(II), bis(3,5-heptanedionato)platinum(II), bis(1-phenyl-1,3-butanedionato)platinum(II), bis(1,3-diphenyl-1,3-propanedionato)platinum(II), and bis(hexafluoroacetylacetonato)platinum(II).

[0058] As component (C), cyclopentadienyltrialkylplatinum complexes and derivatives thereof in which the cyclopentadienyl ligand is alkyl-substituted are particularly preferred, with (methylcyclopentadienyl)trimethylplatinum(IV) being preferred in terms of versatility and availability. As component (C), bis(2,4-pentanedionato)platinum(II) is also preferred in terms of versatility and availability.

[0059] The amount of component (C) used is sufficient to increase the curing rate of the UV-curable composition of the present invention to a desired degree, preferably an amount such that the amount of platinum group metal atoms in the compound of component (C) is in the range of 1 to 500 ppm by mass, and more preferably an amount in the range of 10 to 300 ppm, relative to the UV-curable composition.

[0060] The curable composition of the present invention may or may not contain a hydrosilylation reaction inhibitor along with the photoactive hydrosilylation reaction catalyst of component (C) described above. Hydrosilylation reaction inhibitors are usually added to curable compositions to improve the pot life of the curable composition and to obtain a stable curable composition. However, in the curable composition of the present invention, a hydrosilylation reaction inhibitor may not be added in order to prevent the curing time of the curable composition from being delayed. However, a hydrosilylation reaction inhibitor may be added to the composition in order to extend the pot life of the curable composition. Hydrosilylation reaction inhibitors are well known in the art, and specific examples include alkyne alcohols such as 1-ethynylcyclohexane-1-ol, 2-methyl-3-butyne-2-ol, 3,5-dimethyl-1-hexyne-3-ol, and 2-phenyl-3-butyne-2-ol; enyne compounds such as 3-methyl-3-penten-1-yine and 3,5-dimethyl-3-hexen-1-yine; methylalkenylsiloxane oligomers such as 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane; alkyneoxysilanes such as dimethylbis(1,1-dimethyl-2-propyneoxy)silane and methylvinylbis(1,1-dimethyl-2-propyneoxy)silane, and triallyl isocyanurate compounds. When a hydrosilylation reaction inhibitor is used in the UV-curable composition of the present invention, the content of the hydrosilylation reaction inhibitor in the curable composition is not particularly limited, but it is preferably in the range of 0.0001 to 5 parts by mass, 0.01 to 5 parts by mass, or 0.01 to 3 parts by mass per 100 parts by mass of the total of components (A) to (C).

[0061] <UV-curable organopolysiloxane composition> The UV-curable organopolysiloxane composition of the present invention contains the above-mentioned components (A), (B), and (C) as essential components, does not contain organic solvents, and is characterized in that the viscosity of the entire composition, as measured at 25°C using an E-type viscometer, is 80 mPa·s or less, preferably 30 mPa·s or less, and in particular, it is preferable that the viscosity of the entire composition is in the viscosity range of 10 to 80 mPa·s, more preferably 10 to 30 mPa·s, and even more preferably 10 to 20 mPa·s. There is no lower limit to the viscosity, but it is generally 3 mPa·s or more. In this specification, "does not contain organic solvents" means that the content of organic solvents is less than 0.05% by mass of the entire composition, and preferably below the analytical limit using an analytical method such as gas chromatography. In the present invention, the viscosity of the desired composition can be achieved without using organic solvents by adjusting the molecular structure and molecular weight of components (A) and (B).

[0062] The cured product obtained from the curable composition of the present invention can be designed to have desired physical properties and curing speed, and the viscosity of the curable composition can be designed to have desired values, depending on the molecular chain length of component (A), the number of UV-reactive functional groups per molecule, the position of UV-reactive functional groups within the molecule, and the molecular structure. Furthermore, the cured product obtained by curing the curable composition of the present invention is also included in the scope of the present invention. Moreover, the shape of the cured product obtained from the composition of the present invention is not particularly limited, and may be a thin film coating layer, a molded product such as a sheet, or it may be injected into a specific area in an uncured state and cured to form a filler, or it may be used as a sealing material or intermediate layer for laminates or display devices, etc. The cured product obtained from the composition of the present invention is particularly preferably in the form of a thin film coating layer, and is particularly preferably an insulating coating layer.

[0063] The curable composition of the present invention is suitable for use as a coating agent or potting agent, particularly as an insulating coating agent or potting agent for electronic and electrical devices.

[0064] If desired, the cured product obtained by curing the curable composition of the present invention can be designed to have a relative permittivity of less than 3.0, less than 2.8, etc., and the curable composition of the present invention can also be used to form a coating layer having a low relative permittivity.

[0065] When the curable composition of the present invention is used as a coating agent, in order for the composition to have suitable fluidity and workability for application to a substrate, the viscosity of the entire composition is preferably 80 mPa·s or less, more preferably 5 to 60 mPa·s, and even more preferably 10 to 30 mPa·s at 25°C, as measured using an E-type viscometer. To adjust the viscosity of the entire curable composition to a desired viscosity, compounds having appropriate viscosities can be used as components so that the viscosity of the entire composition has the desired viscosity.

[0066] [Component (D)] When the UV-curable organopolysiloxane composition of the present invention is applied to a substrate surface as a coating agent by any method, in order to improve the wettability of the composition to the substrate and form a defect-free coating film, a component (D) selected from the following can be added to the composition of the present invention which contains the above-mentioned components. It is particularly preferable to use an inkjet printing method as a method for coating the substrate with the composition of the present invention. Therefore, component (D) is a component that improves the wettability of the UV-curable organopolysiloxane composition of the present invention to the substrate and significantly improves the inkjet printing characteristics in particular. Component (D) is at least one compound selected from the group consisting of (D1), (D2), and (D3) below.

[0067] (i) Component (D1) Component (D1) is a nonionic surfactant that does not contain silicon atoms and is not acrylic-based, i.e., a non-acrylic nonionic surfactant. Non-acrylic means that the surfactant does not have a (meth)acrylate group in its molecule. Examples of surfactants that can be used as component (D1) include organic nonionic surfactants such as glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, alkyl glycosides, and acetylene glycol polyethers, as well as fluorine-based nonionic surfactants, and one or more of these can be used in combination. Specific examples of component (D1) include the Emulgen series and Leodol series from Kao Corporation, the Surfinol 400 series from Evonik Industries, and the Orfin E series from Nisshin Chemical Industry Co., Ltd. as organic nonionic surfactants, and the FC-4400 series from 3M and the Megafac 550 and 560 series from DIC Corporation as fluorine-based nonionic surfactants. Among these, the Surfinol 400 series and Orphine E series, which are alquinol polyethers, are particularly preferred.

[0068] (ii) Component (D2) is a nonionic surfactant containing silicon atoms and having an HLB value of 4 or less. Here, the HLB value is a value that represents the degree of affinity of the surfactant to water and organic compounds, and here the HLB value is the value defined by the Griffin method (20 × sum of the formula weights of the hydrophilic parts / molecular weight). Silicone polyethers having polyether as the hydrophilic part, glycerol silicones having (di)glycerol derivatives as the hydrophilic part, and carbinol silicones having hydroxyethoxy groups as the hydrophilic part are known as silicon-containing nonionic surfactants. Among these surfactants, it is preferable to use those with an HLB value of 4 or less, that is, those with a mass fraction of the hydrophilic part of 20% by mass or less, in the composition of the present invention. Among these, carbinol silicone is particularly preferred.

[0069] (iii) Component (D3) is a silicone oil with a viscosity of 90 mPa·s or less at 25°C. Examples of silicone oils include terminally trimethylsilyl-polydimethylsiloxane, terminally dimethylvinylsilyl-polydimethylsiloxane, terminally trimethylsilyl-dimethylsiloxy / methylvinylsiloxy copolymer, terminally dimethylvinylsilyl-dimethylsiloxy / methylvinylsiloxy copolymer, terminally trimethylsilyl-dimethylsiloxy / methylphenylsiloxy copolymer, terminally trimethylsilyl-dimethylsiloxy / diphenylsiloxy copolymer, terminally dimethylvinylsilyl-dimethylsiloxy / methylphenylsiloxy copolymer, terminally dimethylvinylsilyl-dimethylsiloxy / diphenylsiloxy copolymer, etc., but terminally trimethylsilyl-polydimethylsiloxane and terminally dimethylvinylsilyl-polydimethylsiloxane can be used. The preferred viscosity range for the silicone oil is 2 to 50 mPa·s, a more preferred range is 2 to 30 mPa·s, and an even more preferred range is 5 to 20 mPa·s. The viscosity values ​​here were measured at 25°C using the rotational viscometer described in the examples.

[0070] The components (D1) to (D3) described above can be used individually or in combination of two or more. The amount of component (D) to be blended into the curable composition is not particularly limited, but it is preferable that the sum of components (D1) to (D3) (collectively referred to as component (D)) is 0.05% by mass or more and 1% by mass or less, relative to the total amount of components (A) and (B) described above, which is 100% by mass. If the amount of component (D) is less than 0.05% by mass relative to the total amount of components (A) and (B) which is 100% by mass, the effect of improving the wettability of the curable composition to the substrate may not be sufficiently obtained, and if the amount of component (C) exceeds 1% by mass relative to the total amount of components (A) and (B) which is 100% by mass, there is a risk that component (C) may bleed out from the cured product after curing.

[0071] It is preferable to use component (D) as component (D3) silicone oil alone, or component (D3) in combination with one or more components selected from the group consisting of components (D1) and components (D2), and it is particularly preferable to use component (D3) alone as component (D).

[0072] <Other additives> In addition to the above components, further additives may be added to the curable composition of the present invention as desired. Examples of additives are, but are not limited to, those listed below.

[0073] [Adhesion-enhancing agent] The composition of the present invention may contain an adhesion promoter to improve adhesion and bonding to the substrate in contact with the composition. When the curable composition of the present invention is used in applications requiring adhesion or bonding to a substrate, such as coatings and sealants, it is preferable to add an adhesion promoter to the curable composition of the present invention. Any known adhesion promoter can be used as this adhesion promoter, as long as it does not inhibit the curing reaction of the composition of the present invention.

[0074] Examples of adhesion promoters that can be used in the present invention include organosilanes having a trialkoxysiloxy group (e.g., trimethoxysiloxy group, triethoxysiloxy group) or a trialkoxysilylalkyl group (e.g., trimethoxysilylethyl group, triethoxysilylethyl group) and a hydrosilyl group or alkenyl group (e.g., vinyl group, allyl group), or organosiloxane oligomers having a linear, branched, or cyclic structure with approximately 4 to 20 silicon atoms; organosiloxanes having a trialkoxysiloxy group or a trialkoxysilylalkyl group and a methacryloxyalkyl group (e.g., 3-methacryloxypropyl group). Organosilane oligomers having linear, branched, or cyclic structures with approximately 4 to 20 silicon atoms; organosilanes or organosiloxane oligomers having linear, branched, or cyclic structures with approximately 4 to 20 silicon atoms, possessing a trialkoxysiloxy group or trialkoxysilyl alkyl group and an epoxy group-bonded alkyl group (e.g., 3-glycidoxypropyl group, 4-glycidoxybutyl group, 2-(3,4-epoxycyclohexyl)ethyl group, 3-(3,4-epoxycyclohexyl)propyl group); organic compounds having two or more trialkoxysilyl groups (e.g., trimethoxyyl group, triethoxysilyl group);Examples include reaction products of aminoalkyltrialkoxysilanes and epoxy-bonded alkyltrialkoxysilanes, and epoxy-containing ethyl polysilicates. Specifically, these include vinyltrimethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, hydrogentriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 1,6-bis(trimethoxy) Examples include silyl)hexane, 1,6-bis(triethoxysilyl)hexane, 1,3-bis[2-(trimethoxysilyl)ethyl]-1,1,3,3-tetramethyldisiloxane, reaction products of 3-glycidoxypropyltriethoxysilane and 3-aminopropyltriethoxysilane, condensation products of silanol-blocked methylvinylsiloxane oligomer and 3-glycidoxypropyltrimethoxysilane, condensation products of silanol-blocked methylvinylsiloxane oligomer and 3-methacryloxypropyltriethoxysilane, and tris(3-trimethoxysilylpropyl)isocyanurate.

[0075] The amount of adhesion promoter added to the curable composition of the present invention is not particularly limited, but it is preferable that the amount is in the range of 0.01 to 5 parts by mass, or 0.01 to 2 parts by mass, based on 100 parts by mass of the total of components (A) and (B), in order to avoid promoting the curing properties of the curable composition or discoloration of the cured product.

[0076] [Other additives] In addition to the adhesion-imparting agent described above, or in place of the adhesion-imparting agent, other additives may be added to the composition of the present invention as desired. Examples of additives that can be used include leveling agents, silane coupling agents not listed above as adhesion-imparting agents, ultraviolet absorbers, antioxidants, polymerization inhibitors, and fillers (functional fillers such as reinforcing fillers, insulating fillers, and thermally conductive fillers). Appropriate additives may be added to the composition of the present invention as needed. Furthermore, a thixotropic agent may be added to the composition of the present invention as needed, particularly when used as a potting agent or sealing material.

[0077] [Refractive index of the cured product of the curable composition of the present invention] The cured product obtained from the UV-curable organopolysiloxane composition of the present invention can have a low refractive index, which is 1.45 or less, preferably 1.42 or less, when measured at 25°C and a wavelength of 589 nm.

[0078] This composition can be prepared by uniformly mixing components (A) to (C), and optionally component (D) and other arbitrary components. When preparing this composition, the components can be mixed at room temperature using various stirrers or kneaders, and may be mixed under heating if necessary. Furthermore, there are no restrictions on the order in which the components are added; they can be mixed in any order.

[0079] Furthermore, this composition can be a one-component composition in which all components are blended in the same container, or it can be a multi-component composition such as a two-component composition that is mixed at the time of use, taking into consideration storage stability. In particular, when it is a two-component composition, it is preferable to have a first liquid containing part of component (A) and the catalyst component (C), and a second liquid containing part of component (A) and component (B). Component (D) and other optional components may be included in either liquid, but it is preferable to include the hydrosilylation reaction inhibitor in the second liquid containing component (B) from the viewpoint of reaction activity when mixed.

[0080] This composition can be cured in a relatively low temperature range, including room temperature (for example, 15 to 80°C), after irradiation with high-energy rays such as ultraviolet light. The curing reaction of this composition can be adjusted to a desired rate by controlling the concentration of the catalyst metal in component (C) and the type and amount of the aforementioned hydrosilylation reaction inhibitor.

[0081] [Application] The UV-curable organopolysiloxane composition of the present invention can be cured not only by ultraviolet light but also by electron beam, which is also one aspect of the present invention.

[0082] The curable composition of the present invention has low viscosity and is particularly useful as a material for forming insulating layers in various articles, especially electronic and electrical devices. The curable composition of the present invention can form an insulating layer by coating it onto a substrate or by sandwiching it between two substrates, at least one of which is made of a material that allows ultraviolet light or electron beams to pass through, and curing the composition by irradiating it with ultraviolet light or electron beams. In this case, a pattern can be formed when coating the substrate with the composition of the present invention and then curing the composition, or the composition can be coated onto a substrate and cured by irradiation with ultraviolet light or electron beams, leaving cured and uncured portions, and then the uncured portions can be removed with a solvent to form an insulating layer with a desired pattern. In particular, when the cured layer according to the present invention is an insulating layer, it can be designed to have a low relative permittivity of less than 3.0.

[0083] The curable composition of the present invention is particularly suitable as a material for forming an insulating layer in display devices such as touch panels and displays, due to the good transparency of the cured product obtained therefrom. In this case, the insulating layer may form any desired pattern as described above, if necessary. Therefore, a display device such as a touch panel or display, which includes an insulating layer obtained by curing the ultraviolet-curable organopolysiloxane composition of the present invention, is also one embodiment of the present invention.

[0084] Furthermore, the curable composition of the present invention can be used to coat an article and then cure it to form an insulating coating layer (insulating film). Therefore, the composition of the present invention can be used as an insulating coating agent. In addition, the cured product formed by curing the curable composition of the present invention can also be used as an insulating coating layer.

[0085] The insulating film formed from the curable composition of the present invention can be used in a variety of applications. In particular, it can be used as a component of electronic devices or as a material used in the manufacturing process of electronic devices. Electronic devices include electronic equipment such as semiconductor devices and magnetic recording heads. For example, the curable composition of the present invention can be used as an insulating film for semiconductor devices such as LSIs, system LSIs, DRAMs, SDRAMs, RDRAMs, D-RDRAMs, and multi-chip module multilayer wiring boards, as well as as an interlayer insulating film for semiconductors, an etching stopper film, a surface protective film, a buffer coat film, a passivation film in LSIs, a cover coat for flexible copper-clad boards, a solder resist film, and a surface protective film for optical devices.

[0086] Furthermore, in addition to being used as a coating agent, the UV-curable composition of the present invention is also suitable for use as a potting agent, particularly as an insulating potting agent for electronic and electrical devices.

[0087] The composition of the present invention can be used in particular as a material for forming a coating layer on a substrate surface using an inkjet printing method, in which case it is particularly preferable that the composition of the present invention contains the above-described component (D).

[0088] The present invention will be further described below based on examples, but the present invention is not limited to the following examples. [Examples]

[0089] The UV-curable organopolysiloxane composition and its cured product of the present invention will be described in detail with reference to examples. Furthermore, the measurements and evaluations in the examples and comparative examples were carried out as follows.

[0090] [Viscosity of organopolysiloxanes and curable organopolysiloxane compositions] The viscosity (mPa·s) at 25°C was measured using a rotational viscometer (VISCONIC EMD, E-type viscometer, manufactured by Tokimec Co., Ltd.).

[0091] [Preparation of curable organopolysiloxane compositions] The quantities of each material listed in Table 1 below were placed in a brown plastic container and thoroughly mixed using a planetary mixer to prepare a curable organopolysiloxane composition.

[0092] [Evaluation of curability of curable organopolysiloxane compositions and preparation of cured products] Approximately 0.2 g of a curable organopolysiloxane composition was injected between two glass substrates separated by a 0.18 mm thick spacer. LED light with a wavelength of 365 nm was then shone through one of the glass substrates at a stepwise rate up to a maximum of 4000 mJ / cm². 2 The energy level (mJ / cm²) is measured when the curable composition is irradiated up to the specified energy level and solidified. 2 The amount of ultraviolet irradiation required for curing was used to evaluate the curability of the composition. Under these irradiation conditions, plate-shaped organopolysiloxane cured materials with sides of 30 mm and a thickness of 0.18 mm were fabricated.

[0093] [Appearance of cured products obtained from curable organopolysiloxane compositions] The appearance of the polysiloxane cured products prepared using the above method was visually evaluated.

[0094] [Refractive index of cured products obtained from curable organopolysiloxane compositions] The refractive index (nD) of the cured material at 25°C was measured using a digital refractometer (ATAGO Corporation, RX-7000α).

[0095] [Examples and Comparative Examples] Using the components listed below, UV-curable organopolysiloxane compositions with the compositions (parts by mass) shown in Table 1 were prepared. (A1) Polydimethylsiloxane with dimethylvinylsilyl groups sealed at both ends. Viscosity: 60 mPa·s (A2) Polydimethylsiloxane with dimethylvinylsilyl groups sealed at both ends. Viscosity: 6 mPa·s (A3) End-terminated dimethylvinylsilyl polydimethylsiloxane. Viscosity: 350 mPa·s (A4) Terminally dimethylvinylsilyl group sealed branched tetrafunctional polydimethylsiloxane. Viscosity: 200 mPa·s (A5) 1,3-Divinyl-1,1,3,3-Tetramethyldisiloxane. Viscosity: 0.7 mPa·s (B1) MQ resin having dimethylhydrogensiloxy groups with a hydrogen group concentration of 1.2%. (B2) A polymethylhydrogensiloxane with a hydrogen group concentration of 1.6% and trimethylsilyl groups blocked at both ends. (C) Catalyst masterbatch consisting of the following components (C):(C1) / (A2)=5 / 95(mass ratio) (C1): Trimethylmethylcyclopentadienyl platinum

[0096] [Table 1]

[0097] As shown in Table 1, the UV-curable organopolysiloxane compositions of the present invention (Examples 1-11) have a viscosity suitable for application to substrates as a coating agent at 25°C, and exhibit particularly excellent coatability by inkjet printing. Furthermore, the cured product obtained by UV irradiation is transparent and has a low refractive index. Therefore, by forming a structure in combination with a layer made of a high refractive index material, an improvement in light extraction efficiency can be expected. On the other hand, in compositions that do not have the desired viscosity (Comparative Example 1) and compositions that contain a component (A5) having two silicon atoms per molecule even with low viscosity (Comparative Example 2), the overall viscosity of the composition is suppressed, but there are problems such as poor inkjet printing characteristics or poor curability, and sufficient UV curability cannot be achieved. [Industrial applicability]

[0098] The UV-curable organopolysiloxane composition of the present invention is particularly suitable for the above-mentioned applications, especially as a material for forming insulating layers in display devices such as touch panels and displays. The present invention encompasses the following aspects. [1] (A) Organopolysiloxanes having two or more alkenyl group-containing groups in one molecule and three or more silicon atoms per molecule, (B) Organopolysiloxanes having two or more silicon-bonded hydrogen atoms in one molecule, and (C) An ultraviolet-curable organopolysiloxane composition characterized by containing a photoactive hydrosilylation reaction catalyst, not containing an organic solvent in the composition, having a total viscosity of 80 mPa·s or less measured at 25°C using an E-type viscometer, and having a refractive index of 1.45 or less measured at 25°C and a wavelength of 589 nm in the cured product. [2] The ultraviolet-curable organopolysiloxane composition according to Embodiment 1, characterized in that it contains, as component (A), an organopolysiloxane having two or more alkenyl group-containing groups in one molecule, the viscosity of which is measured at 25°C using an E-type viscometer to 60 mPa·s or less. [3] The ultraviolet-curable organopolysiloxane composition according to embodiment 1 or 2, characterized in that component (A) contains an organopolysiloxane having two or more alkenyl group-containing groups in one molecule, the viscosity of which is measured at 25°C using an E-type viscometer to 10 mPa·s or less. [4] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 3, characterized in that it contains an organopolysiloxane having alkenyl group-containing groups at both ends as component (A). [5] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 4, characterized in that the organopolysiloxane having two or more alkenyl group-containing groups in one molecule of component (A) has an average of four or more silicon atoms per molecule. [6] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 5, wherein the alkenyl group-containing group of component (A) and the silicon atom-bonded organic groups other than silicon-bonded hydrogen atoms of component (B) are substantially methyl groups only. [7] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 6, wherein the viscosity of the entire composition measured at 25°C is 5 to 60 mPa·s. [8] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 7, wherein the viscosity of the entire composition measured at 25°C is 10 to 30 mPa·s. [9] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 8, wherein the content of an organopolysiloxane having an alkenyl group and a boiling point of 200°C or less at 1013.25 hectopascals is less than 1% by mass of the total composition.

[10] An ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 9, wherein component (C) is an unsubstituted or alkyl-substituted cyclopentadienyltrialkylplatinum complex.

[11] An insulating coating agent comprising the ultraviolet-curable organopolysiloxane composition described in any one of embodiments 1 to 10.

[12] A method for using a cured product of an ultraviolet-curable organopolysiloxane composition described in any one of embodiments 1 to 10 as an insulating coating layer.

[13] A display device comprising a layer made of a cured product of an ultraviolet-curable organopolysiloxane composition according to any one of embodiments 1 to 10.

Claims

1. (A) Organopolysiloxanes having two or more alkenyl group-containing groups in one molecule and three or more silicon atoms per molecule, (B) Organopolysiloxanes having two or more silicon-bonded hydrogen atoms in one molecule, and (C) The composition contains a photoactive hydrosilylation reaction catalyst and does not contain any organic solvents. The viscosity of the entire composition, measured at 25°C using an E-type viscometer, is 80 mPa·s or less, and the refractive index of the cured product, measured at 25°C and a wavelength of 589 nm, is 1.45 or less. Component (A) includes an organopolysiloxane having a viscosity of 10 mPa·s or less as measured at 25°C using an E-type viscometer, and having alkenyl group-containing groups at both ends, with two or more alkenyl group-containing groups in one molecule. A UV-curable organopolysiloxane composition comprising a polymethylhydrogensiloxane with trimethylsilyl group blockade at both ends as component (B).

2. The ultraviolet-curable organopolysiloxane composition according to claim 1, characterized in that it contains, as component (A), an organopolysiloxane having two or more alkenyl group-containing groups in one molecule, the viscosity of which is measured at 25°C using an E-type viscometer to 60 mPa·s or less.

3. The ultraviolet-curable organopolysiloxane composition according to claim 1 or 2, characterized in that the organopolysiloxane having two or more alkenyl group-containing groups in one molecule of component (A) has an average of four or more silicon atoms per molecule.

4. The ultraviolet-curable organopolysiloxane composition according to any one of claims 1 to 3, wherein the alkenyl group-containing group of component (A) and the silicon atom-bonded organic groups other than silicon-bonded hydrogen atoms of component (B) are substantially methyl groups only.

5. The UV-curable organopolysiloxane composition according to any one of claims 1 to 4, wherein the viscosity of the entire composition measured at 25°C is 5 to 60 mPa·s.

6. The UV-curable organopolysiloxane composition according to any one of claims 1 to 5, wherein the viscosity of the entire composition measured at 25°C is 10 to 30 mPa·s.

7. The ultraviolet-curable organopolysiloxane composition according to any one of claims 1 to 6, wherein the content of an organopolysiloxane having an alkenyl group and a boiling point of 200°C or less at 1013.25 hectopascals is less than 1% by mass of the total composition.

8. The UV-curable organopolysiloxane composition according to any one of claims 1 to 7, wherein component (C) is an unsubstituted or alkyl-substituted cyclopentadienyltrialkylplatinum complex.

9. An insulating coating agent comprising the ultraviolet-curable organopolysiloxane composition according to any one of claims 1 to 8.

10. A method for using a cured product of an ultraviolet-curable organopolysiloxane composition according to any one of claims 1 to 8 as an insulating coating layer.

11. A display device comprising a layer made of a cured product of an ultraviolet-curable organopolysiloxane composition according to any one of claims 1 to 8.

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