Patent Description:
A curable silicone composition having good optical transparency and high elongation property is utilized as an adhesive or pressure sensitive adhesive. Especially, a photocurable silicone composition enabling relatively low curing temperature such as less than <NUM> is mainly used for an optical display because thermally instable components like liquid crystalline, OLED, touch panel, and cover lens are needed to use the image display unit.

Patent Document <NUM> proposes an ultraviolet radiation-curable silicone composition comprising: a straight-chain organopolysiloxane having an aliphatic unsaturated group; an organopolysiloxane having a silicon atom-bonded mercaptoalkyl group; an acylphosphine oxide-based photoreaction initiator; and acetophenone and/or propiophenone.

However, such an ultraviolet radiation-curable silicone composition has a problem of poor deep curability by ultraviolet radiation and insufficient curing, and a problem of occurrence of coloring and haze caused by exposure of the silicone cured product to high temperature or high humidity conditions.

Patent Document <NUM> proposes a photocurable silicone composition comprising: an organopolysiloxane having at least one aryl group having from <NUM> to <NUM> carbons and at least one alkenyl group having from <NUM> to <NUM> carbons in a molecule, an organic compound having at least two ether bonds and at least one aliphatic carbon-carbon double bond in a molecule, a compound having at least two thiol groups in a molecule, a photoradical initiator having a phosphorus atom, and a hindered phenol compound. The photocurable silicone composition cures by irradiation with an active energy ray to form a cured product that suppresses reduction in transmittance due to coloring and haze even when being left in high temperature/high humidity conditions.

However, such a photocurable silicone composition has a problem that, exhibiting excellent resistance to light, and poor curability by LED lamp with wide UV-Visible range (<NUM> - <NUM>) as well as metal-halide lamp.

Also known is Patent Document <NUM> that discloses a photocurable composition comprising a vinyl-polysiloxane, a polysiloxane comprising at least two thiol groups and a photoradical initiator being diphenyl(<NUM>,<NUM>,<NUM>-trimethylbenzoyl)phosphine oxide; this composition is used for LEDs.

An object of the present invention is to provide a photocurable silicone composition that exhibits excellent curability by LED lamp with wide UV-Visible range as well as metal-halide lamp, and cures to form a cured product exhibiting excellent resistance to light. Another object of the present invention is to provide a cured product exhibiting excellent resistance to light.

The photocurable silicone composition of the present invention comprises:.

In various embodiments, R<NUM>, R<NUM> and R<NUM> in component (D) are hydrogen atoms and R<NUM>, R<NUM>, R<NUM> and R<NUM> in component (D) are hydrogen atoms or alkyl groups having from <NUM> to <NUM> carbons.

In various embodiments, R<NUM> in component (D) is a group represented by the following general formula:.

wherein, R<NUM> is a linear or branched alkyl group having from <NUM> to <NUM> carbons.

In various embodiments, component (D) is an hydroxyphenyl triazine compound selected from a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
, and mixtures thereof. For example, component (D) may comprise just one, or two or more of the aforementioned compounds.

The cured product of the present invention is obtained by irradiating the photocurable silicone composition described above with light. In various embodiments, the cured product is laminated between same or different substrates, and especially, between same or different substrates in an optical device.

The photocurable silicone composition of the present invention exhibits excellent curability by LED lamp with wide UV-Visible range as well as metal-halide lamp, and cures to form a cure product exhibiting excellent resistance to light. Furthermore, the cured product of the present invention exhibits excellent resistance to light.

The terms "comprising" or "comprise" are used herein in their broadest sense to mean and encompass the notions of "including," "include," "consist(ing) essentially of," and "consist(ing) of. The use of "for example," "e.g.," "such as," and "including" to list illustrative examples does not limit to only the listed examples. Thus, "for example" or "such as" means "for example, but not limited to" or "such as, but not limited to" and encompasses other similar or equivalent examples. The term "about" as used herein serves to reasonably encompass or describe minor variations in numerical values measured by instrumental analysis or as a result of sample handling. Such minor variations may be in the order of ±<NUM>-<NUM>, ±<NUM>-<NUM>, ±<NUM>-<NUM>, or ±<NUM>-<NUM>, % of the numerical values. Further, the term "about" applies to both numerical values when associated with a range of values. Moreover, the term "about" may apply to numerical values even when not explicitly stated.

Generally, as used herein a hyphen "-" or dash "-" in a range of values is "to" or "through"; a ">" is "above" or "greater-than"; a "≥" is "at least" or "greater-than or equal to"; a "<" is "below" or "less-than"; and a "≤" is "at most" or "less-than or equal to.

It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

Component (A) is a base compound of the present composition and is an organopolysiloxane represented by the average composition formula:.

In the formula, R<NUM> is an alkenyl group having from <NUM> to <NUM> carbons, and examples thereof include vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, and dodecenyl group. Among these, vinyl group and hexenyl group are preferred.

In the formula, R<NUM> is an alkyl group having from <NUM> to <NUM> carbons, an aryl group having from <NUM> to <NUM> carbons, or an aralkyl group having from <NUM> to <NUM> carbons. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, and dodecyl group. Among these, methyl group is preferred. Examples of the aryl group include phenyl group, tolyl group, naphthyl group, and biphenyl group. Among these, phenyl group is preferred. Examples of the aralkyl group include phenylmethyl group, <NUM>-phenylethyl group, <NUM>-phenylethyl group, and <NUM>-phenylpropyl group. Among these, <NUM>-phenylethyl group and <NUM>-phenylpropyl group are preferred. In component (A), at least <NUM> mol% of R<NUM> in a molecule are the aryl groups or the aralkyl groups.

Furthermore, in the formula, "a" and "b" are positive numbers satisfying: <NUM> ≤ a + b ≤ <NUM>, and preferably <NUM> ≤ a + b ≤ <NUM>, and satisfying: <NUM> ≤ a/(a + b) ≤ <NUM>, and preferably <NUM> ≤ a/(a + b) ≤ <NUM>.

The state of component (A) at <NUM> is not limited and is preferably a liquid. The viscosity at <NUM> of component (A) is not limited; however, the viscosity is preferably in a range of <NUM> to <NUM>,<NUM>,<NUM> mPa·s. Note that in the present specification, viscosity is the value measured using a type B viscometer according to ASTM D <NUM> at <NUM> ± <NUM>.

Component (A) may be one type of organopolysiloxane that satisfies the average composition formula above or may be a mixture of at least two types of organopolysiloxanes that satisfy the average composition formula above. Examples of such component (A) include organopolysiloxanes represented by the following "average composition formulas: average formulas". Note that, in the formulas, "Me", "Vi", "Hex", "Ph", "Phe", and "Php" respectively indicate methyl group, vinyl group, hexenyl group, phenyl group, <NUM>-phenylethyl group, and <NUM>-phenylpropyl group.

Component (B) is a curing agent of the present composition and is a compound having at least two thiol groups in a molecule. Component (B) is not limited as long as the component has sufficient solubility in component (A).

Examples of such component (B) include o-, m-, or p-xylenedithiol, ethyleneglycol bisthioglycolate, butanediol bisthioglycolate, hexanediol bisthioglycolate, ethyleneglycol bis(<NUM>-thiopropionate), butanediol bis(<NUM>-thiopropionate), trimethylolpropane tris(<NUM>-thiopropionate), pentaerythritol tetrakis(<NUM>-thiopropionate), trihydroxyethyl triisocyanuric acid tris(<NUM>-thiopropionate), and organopolysiloxanes substituted with a mercapto group.

The content of component (B) is an amount such that the amount of the thiol groups provided by the present component is in a range of from <NUM> to <NUM> mol, or optionally in a range of <NUM> to <NUM> mol, per <NUM> mol of the total alkenyl groups in component (A). This is because, when the content of component (B) is within the range described above, mechanical strength of the resulting cured product increases.

Component (C) is a component to initiate photocuring reaction of the present composition, and is a photoradical initiator containing a phosphorus atom. Examples of such component (C) include diphenyl(<NUM>,<NUM>,<NUM>-trimethylbenzoyl) phosphine oxide (trade name: TPO, manufactured by BASF), ethyl(<NUM>,<NUM>,<NUM>-trimethylbenzoyl) phenyl phosphonate (trade name: TPO-L, manufactured by BASF), and bis(<NUM>,<NUM>,<NUM>-trimethylbenzoyl) phenyl phosphine oxide (trade name: IRGACURE <NUM>, manufactured by BASF).

The content of component (C) is in a range of from <NUM> to <NUM> parts by mass, optionally in a range of from <NUM> to <NUM> parts by mass, or optionally in a range of from <NUM> to <NUM> parts by mass, per <NUM> parts by mass of component (A). This is because, when the content of component (C) is within the range described above, curing efficiently proceeds to form a cured product having excellent heat resistance and light resistance.

Component (D) is a hydroxyphenyl triazine compound represented by the following general formula:
<CHM>.

In the formula, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> are the same or different, and are groups selected from hydrogen atoms, hydroxy groups or alkyl groups having from <NUM> to <NUM> carbons. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, and dodecyl group. Among these, methyl group is preferred. Among these, R<NUM>, R<NUM> and R<NUM> are preferably hydrogen atoms and R<NUM>, R<NUM>, R<NUM> and R<NUM> are preferably hydrogen atoms or alkyl groups having from <NUM> to <NUM> carbons.

In the formula, R<NUM> is a linear or branched alkyl group having from <NUM> to <NUM> carbons or a group represented by the following general formula:.

Among these, R<NUM> is preferably the group represented by the following general formula:.

Examples of the alkyl group for R<NUM> include hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, and dodecyl group.

In the formula, R<NUM> is a linear or branched alkyl group having from <NUM> to <NUM> carbons. Examples of the alkyl group for R<NUM> include hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, and dodecyl group.

Examples of such component (D) include a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
a hydroxyphenyl triazine compound represented by the following formula:
<CHM>
and mixtures thereof.

The content of component (D) is in a range of from <NUM> to <NUM> parts by mass, optionally in a range of from <NUM> to <NUM> parts by mass, or optionally in a range of from in a range of from <NUM> to <NUM> parts by mass, per <NUM> parts by mass of component (A). This is because, when the content of component (D) is within the range described above, curability of the composition by LED lamp increases.

The present composition comprises component (A) to component (D) described above; however, to impart heat resistance to a cured product of the present composition, (E) a hindered phenol compound is preferably contained. Examples of such component (E) include pentaerythritol tetrakis[<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionate], thiodiethylene bis[<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionate], octadecyl-<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionate, <NUM>,<NUM>-dimethyl-<NUM>-(<NUM>-methylpentadecyl)phenol, diethyl[<NUM>,<NUM>-bis(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)methyl}phosphonate, <NUM><NUM>',<NUM>",<NUM>,<NUM>',<NUM>"-hexane-tert-butyl-<NUM>-a,a',a"-(mesitylene-<NUM>,<NUM>,<NUM>-tolyl)tri-p-cresol, <NUM>,<NUM>-bis(octylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[<NUM>-(<NUM>-tert-butyl-<NUM>-hydroxy-m-tolyl)propionate], and hexamethylene bis[<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionate].

The content of component (E) is not limited; however, the content is preferably in a range of <NUM> to <NUM> part by mass, and preferably in a range of <NUM> to <NUM> parts by mass, per <NUM> parts by mass of component (A). This is because, when the content of component (E) is within the range described above, change in viscosity of the composition prior to the photocuring is small and a cured product having excellent heat resistance and light resistance is obtained.

The present composition may further contain, as an optional component, to enhance storage stability in a light-shielded condition of the present composition, (F) a radical scavenger other than component (E) is preferably contained. Examples of such component (F) include hindered amines, such as N,N',N",N‴-tetrakis(<NUM>,<NUM>-bis(butyl-(N-methyl-<NUM>,<NUM>,<NUM>,<NUM>-tetramethylpiperidin-<NUM>-yl)amino)-triazin-<NUM>-yl)-<NUM>,<NUM>-diazadecane-<NUM>,<NUM>-diamine, bis(<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentamethyl-<NUM>-piperidyl)[[<NUM>,<NUM>-bis(<NUM>,<NUM>-dimethylethyl)-<NUM>-hydroxyphenyl]methyl]butylmalonate, methyl-<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentamethyl-<NUM>-piperidylsebacate, bis(<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-piperidyl)sebacate, bis(<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentamethyl-<NUM>-piperidyl)sebacate, and <NUM>-acetyl-<NUM>-dodecyl-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>-triazaspiro[<NUM>]decane-<NUM>,<NUM>-dione; quinones or phenols, such as methylhydroquinone, <NUM>,<NUM>-naphthoquinone, <NUM>-methoxynaphthol, tert-butylhydroquinone, benzoquinone, pyrogallol, and phenothiazine.

The content of component (F) is not limited; however, the content is preferably in a range of <NUM> to <NUM> part by mass, optionally <NUM> to <NUM> parts by mass, or optionally <NUM> to <NUM> parts by mass, per <NUM> parts by mass of component (A). This is because, when the content of component (F) is within the range described above, a cured product having excellent heat resistance and light resistance is obtained.

The present composition may further contain, as an optional component, (G) an organic compound having at least two ether bonds and at least one aliphatic carbon-carbon double bond in a molecule. The group having an aliphatic carbon-carbon double bond in component (G) is not limited, and examples thereof include an alkenyl group, an acryloyl group, and a methacryloyl group. Among these, an acryloyl group or a methacryloyl group is preferred. Furthermore, the state of component (G) at <NUM> is not limited and is preferably a liquid. The viscosity at <NUM> of component (G) is not limited; however, the viscosity is preferably in a range of <NUM> to <NUM> mPa s.

Examples of such component (G) include phenoxy diethylene glycol acrylate, phenoxy tetraethylene glycol acrylate, methoxy triethylene glycol acrylate, methoxy nonaethylene glycol acrylate, methoxy polyethylene glycol acrylate, ethoxy diethylene glycol acrylate, ethoxyethoxyethyl acrylate, nonylphenoxy tetraethylene glycol acrylate, nonylphenoxy octaethylene glycol acrylate, nonylphenoxy dipropylene glycol acrylate, methoxy diethylene glycol methacrylate, methoxy polyethylene glycol methacrylate, polyethylene glycol methacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, bisphenol diethylene glycol diacrylate, bisphenol A triethylene glycol diacrylate, tetraethylene glycol diacrylate, bisphenol A polyethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, bisphenol A diethylene glycol dimethacrylate, bisphenol A triethylene glycol dimethacrylate, bisphenol A tetraethylene glycol dimethacrylate, bisphenol A polyethylene glycol dimethacrylate, triethylene glycol divinyl ether, tripropylene glycol divinyl ether, polyethylene glycol monoallyl ether, methoxy polyethylene glycol allyl ether, propylene glycol allyl ether, butoxy polyethylene glycol/propylene glycol allyl ether, polyethylene glycol diallyl ether, polypropylene glycol diallyl ether, trimethylolpropane triallyl ether, trimethylolpropane diallyl ether, pentaerythritol tetraallyl ether, and pentaerythritol triallyl ether.

The content of component (G) is not limited, however, it is preferably in a range of <NUM> to <NUM> parts by mass, or optionally in a range of <NUM> to <NUM> parts by mass, per <NUM> parts by mass of component (A). This is because, when the content of component (G) is greater than or equal to the lower limit of the range described above, reduction in transmittance of the cured product at a high temperature/high humidity becomes small. On the other hand, when the content is less than or equal to the upper limit of the range described above, change in hardness of the cured product at a high temperature is made small and coloring is reduced.

The present composition may further contain, as an optional component, (H) an organic compound having at least one aliphatic carbon-carbon double bond in a molecule other than component (A) and component (G) described above; an adhesion-imparting agent; an inorganic filler, such as silica, titanium oxide, glass, alumina, or zinc oxide; an organic resin fine powder of polymethacrylate resin, silicone resin, or the like; as well as a pigment or a fluorescent substance, as long as the object of the present invention is not impaired.

Component (H) is not limited as long as a component is an organic compound having at least one aliphatic carbon-carbon double bond in a molecule and is preferably a liquid at <NUM>. The viscosity at <NUM> of component (H) is not limited; however, the viscosity is preferably in a range of <NUM> to <NUM> mPa s.

Examples of such component (H) include methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, lauryl acrylate, stearyl acrylate, isodecyl acrylate, triacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, phenoxyethyl acrylate, tetrahydrofuran acrylate, benzyl acrylate, o-phenylphenol ethoxyethyl acrylate, <NUM>-ethylhexyl acrylate, hexane diol diacrylate, nonane diol diacrylate, <NUM>-propenoic acid octahydro-<NUM>,<NUM>-methano-<NUM>-inden-<NUM>-yl ester, decyl vinyl ether, <NUM>-ethylhexyl vinyl ether, <NUM>-octene, <NUM>-decene, <NUM>-dodecene, <NUM>-tetradecene, <NUM>-hexadecene, allyl methacrylate, divinyl sulfone, <NUM>-methacryloxypropyltrimethoxysilane, and <NUM>-acryloxypropyltrimethoxysilane.

Furthermore, examples the adhesion-imparting agent include silane compounds, such as <NUM>-glycidoxypropyltrimethoxysilane, <NUM>-(<NUM>,<NUM>-epoxycyclohexyl)ethyltrimethoxysilane, and <NUM>-methacryloxy propyltrimethoxysilane; siloxane compounds having at least one of silicon atom-bonded alkenyl groups and/or silicon atom-bonded hydrogen atoms, and at least one silicon atom-bonded alkoxy group in a molecule; mixtures of a silane compound or siloxane compound having at least one silicon atom-bonded alkoxy group and a siloxane compound having at least one silicon atom-bonded hydroxy group and at least one silicon atom-bonded alkenyl group in a molecule; methyl polysilicate, ethyl polysilicate, and epoxy group-containing ethyl polysilicate. The content of the adhesion-imparting agent is not limited; however, the content is preferably in a range of <NUM> to <NUM> parts by mass per <NUM> parts by mass of component (A).

The viscosity at <NUM> of the present composition is not limited; however, the viscosity is preferably in a range of <NUM> to <NUM>,<NUM> mPa s, or optionally in a range of <NUM> to <NUM>,<NUM> mPa s. This is because, when the viscosity of the present composition is greater than or equal to the lower limit of the range described above, a cured product having high mechanical strength can be obtained. On the other hand, when the viscosity is less than or equal to the upper limit of the range described above, excellent coatability/workability of the resulting composition is achieved and formation of a void in the cured product is avoided.

The cured product of the present invention is obtained by irradiating the photocurable silicone composition described above with light. Examples of the light used to cure the present composition include ultraviolet light and visible light; however, the light with a wavelength in a range of <NUM> to <NUM> is preferred. This is because excellent curability is achieved, and the cured product is not decomposed by the light.

The cured product is typically optically transparent. This is because when the cured product is preferably used for an optical device or an image display, optical transparency is desired for high performance. The form of the cured product is not limited and may be in a sheet, film, or block form. The cured product may be combined with various substrates. The cured product is typically laminated between same or different substrates, and especially, between same or different substrates in an optical device.

The state of the cured product is not limited, but it is preferably an elastomer or gel. The hardness is preferably in a range of <NUM> to <NUM>, or optionally in a range of <NUM> to <NUM>, in Shore OO Hardness. This is because when the cure product is within the range described above, good cohesive strength against deformation and good flexibility against material fracture are obtained. Note that in the present specification, Shore OO Hardness is the value measured using a type OO hardness according to ASTM D <NUM> at <NUM> ± <NUM>.

A method of producing the cured product is not limited, but it is exemplified by a method comprising the following steps:.

In the step i-<NUM>, the photocurable silicone composition is applied on the surface of substrates blocking the light (for example, a black-color substrate). Examples of a coating method include a slit coating, a roll coating, a spin coating, a screen printing, or the like. A thickness of the photocurable silicone composition is not limited, but it is preferably in a range of from <NUM> to <NUM>,<NUM>, optionally in a range of from <NUM> to <NUM>, or optionally in a range of from <NUM> to <NUM>. Then, the transparent substrate having the light shielding portion is laminated on the surface of the photocurable silicone composition as prepared above. Laminating can be carried out either in the air or in vacuum. In order to prevent air bubbles generated during the laminating, it is preferable to laminate in vacuum. Also, laminating can be carried out under pressure, by a press or the like.

In the step i-<NUM>, for curing the transparent area, the ultraviolet-curing is conducted by ultraviolet irradiation. For example, low pressure, high pressure or ultrahigh pressure mercury lamp, metal halide lamp, (pulse) xenon lamp, or an electrodeless lamp is useful as an UV lamp. Irradiation dose is preferably in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>, or optionally in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>.

Due to the light shielding portion of the transparent substrate, light cannot be penetrated, and uncured photocurable silicone composition is present at the bottom of the light shielding portion. For curing the light-shielding portion, the side curing is conducted by UV LED (light emitting diode) lamp. Typical wavelengths of UV LED lamp are <NUM>, <NUM>, <NUM> and <NUM>. Preferably, <NUM> and <NUM> are generally used. Irradiance is preferably in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>, or optionally in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>. The irradiation time is preferably in a range of from <NUM> to <NUM> seconds, or optionally in a range of from <NUM> to <NUM> seconds. The term "uncured" denote the state where there is flowable under <NUM> environment.

Another method of producing the cured product may comprise the following steps:.

In the step ii-<NUM>, the photocurable silicone composition is applied on the surface of substrate. Examples of coating methods include the method mentioned above. A thickness of the photocurable silicone composition is not limited, but it is preferably in a range of from <NUM> to <NUM>,<NUM>, optionally in a range of from <NUM> to <NUM>, or optionally in a range of from <NUM> to <NUM>.

In the step ii-<NUM>, the applied photocurable silicone composition is partially cured by UV LED lamp to form unflowable and less-cured layer. The term "less-cured" denotes the state where there is no flowable at <NUM>, but not fully crosslinked network (the state having middle physical properties between liquid and fully cured products). The ultraviolet-curing is conducted by ultraviolet irradiation, ultraviolet to does not matter source if the lamp for irradiating light rays near ultraviolet. Typically, to control cure rate precisely, UV LED lamp is generally used. Typical wavelengths of UV LED lamp are <NUM>, <NUM>, <NUM> and <NUM>. Preferably, <NUM> and <NUM> are generally used. Irradiation dose is preferably in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>, or optionally in a range of from <NUM> to <NUM> mJ/cm<NUM>. The irradiation of ultraviolet rays is usually in the air, the upper surface of the coating side (usually the atmosphere preferably irradiated from the surface). If need to prevent surface oxygen inhibition, the photocurable silicone composition may be irradiated with ultraviolet rays in an environment of a gas which does not cause curing inhibition such as nitrogen and carbon dioxide.

In the step ii-<NUM>, the transparent substrate with the light shielding portion is applied on the surface of the coated photocurable silicone composition as prepared in above. Laminating can be carried out either in the air and in vacuum. In order to prevent air bubbles generated during the laminating, it is preferable to laminate in vacuum. Also, laminating can be carried out under pressure, by a press or the like.

In the step ii-<NUM>, for curing the transparent area, the ultraviolet-curing is conducted by ultraviolet irradiation. For example, low pressure, high pressure or ultrahigh pressure mercury lamp, metal halide lamp, (pulse) xenon lamp, or an electrodeless lamp is useful as an UV lamp. Irradiation dose is preferably in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>, or optionally in a range of from <NUM> to <NUM>,<NUM> mJ/cm<NUM>.

The cured product is useful as laminates in an optical device or an image display. The optical device is, for example, an optical semiconductor device. Examples of the optical semiconductor device include a light emitting diode (LED), a photocoupler, and a CCD. Moreover, a light emitting diode (LED) element and a solid-state image sensor are illustrated as an optical semiconductor element. In particular, even in the case of collectively sealing a so-called micro LED (mini LED) having a structure in which a large number of small LED elements are disposed on a substrate, the photocurable silicone composition of the present invention can be suitably used. At this time, the refractive index of the cured product may be adjusted as desired by selecting the type of functional group such as the content of aryl group. Furthermore, since the photocurable silicone composition of the present invention is excellent in heat resistance and moisture resistance, it is hard to cause a decrease in transparency and hardly causes turbidity. Therefore, there is an advantage that the light extraction efficiency of the optical semiconductor device including the Micro LED can be maintained well.

The photocurable silicone composition and the cured product of the present invention will now be described in detail using Practical Examples and Comparative Examples. Note that, in the formulas, "Me", "Ph", and "Vi" respectively indicates methyl group, phenyl group, and vinyl group. The characteristics of the photocurable silicone composition and the cured product thereof were measured as follows.

Viscosity at <NUM> ± <NUM> was measured by using a type B viscometer (Brookfield LVF Type Rotational Viscometer with using Spindle #<NUM> at <NUM> rpm) according to ASTM D <NUM> "Standard Test Methods for Viscosity of Adhesive".

The photocurable silicone composition was poured into a mold having a depression of a predetermined shape, and ultraviolet rays were irradiated from the upper liquid surface with a high pressure mercury lamp so that the cumulative irradiation amount was <NUM>,<NUM> mJ/cm<NUM>. The hardness of the obtained cured product was measured by a type OO durometer hardness tester according to the method specified by ASTM D <NUM>-<NUM>.

The transmittance and yellow index of the plate-like cured product having a thickness of <NUM> cured as described above were measured by the method specified in ASTM D <NUM> (UV-Visible spectrometer). The yellow index (YI) was measured in the same manner as above by ASTM D1925 (spectrophotometer, CM-3600A).

The resistance to light fatigue was determined by means of a QUV Accelerated Weathering Tester (Q-Panel Co. , Cleveland, Ohio) equipped with UVA-<NUM> lamps calibrated to <NUM> W/m<NUM>/nm (ASTM G154 CYCLE <NUM>). The plate-like cured product having a thickness of <NUM> cured as described above was irradiated in the QUV Accelerated Weathering Tester for a series of <NUM> hours per a cycle consisting of <NUM> hours of irradiation at the temperature of <NUM> and <NUM> hours of darkness (condensation) at a temperature of <NUM>. Subsequently, the plate-like cured product was held for <NUM> cycles (<NUM> days) and the yellow index (YI) were measured in the same manner as above.

The photocurable silicone composition was poured into a mold composed of two black plates with a thickness of <NUM>, wherein the plates were separated by a spacer with a thickness of <NUM>. Ultraviolet light at a UV illuminance of <NUM> mW/cm<NUM> was irradiated for <NUM> and <NUM> seconds from the upper liquid surface with a <NUM> LED lamp (FIREJET™ FJ100). Then, ultraviolet light at a UV illuminance of <NUM> mW/cm<NUM> was irradiated for <NUM> and <NUM> seconds from the upper liquid surface with a <NUM> LED lamp (FIREJET™ FJ100). After irradiation, the specimen was disassembled and the length (cm) of the portion losing fluidity by curing was measured.

Photocurable silicone compositions were prepared by a planetary centrifugal vacuum mixer (Thinky mixer) from the following components using the composition (parts by mass) shown in Table <NUM>. Note that the photocurable silicone compositions of Practical Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> were prepared to provide <NUM> moles of thiol groups in component (b1) with regard to <NUM> mole of total aliphatic carbon-carbon double bonds in components (a1) and (a2). The properties of this photocurable silicone compositions and cured product thereof are shown in Table <NUM>.

The following organopolysiloxanes were used as component (A).

The following organic compounds were used as component (B). (b1): trimethylolpropane tris(<NUM>-thiopropionate).

The following photoradical initiator was used as component (C). (c1): ethyl (<NUM>,<NUM>,<NUM>-trimethylbenzoyl) phenyl phosphinate.

The following hydroxyphenyl triazine compounds were used as component (D).

The following hydroxyphenyl triazine compounds were used as comparison of component (D).

Comparative Example <NUM>, due to lack of triazine additives, showed severe yellowing/browning during QUV aging test. The yellow index increased from <NUM> to <NUM>. While, Practical Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM>, because of addition of triazine additives, showed good optical stability during QUV aging test. It revealed that these additives effectively stabilized cured products of photocurable silicone compositions under light irradiation condition. By the way, at the same time, these additives diminished the deep cure property due to high absorption at the range of UVA and UVB region as the transmittance were summarized in Table <NUM>. Among them, it was revealed that specific hydroxyphenyl triazine compounds such as components (d1) and (d2) in Practical Examples <NUM> and <NUM>, respectively, showed superior deep cure property compared to other hydroxylphenyl triazine compounds such as components (d3), (d4) and (d5) in Comparative Example <NUM>, <NUM> and <NUM>, respectively.

Photocurable silicone compositions were prepared by a planetary centrifugal vacuum mixer (Thinky mixer) from the above components using the composition (parts by mass) shown in Table <NUM>. Note that the photocurable silicone compositions of Practical Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> were prepared to provide <NUM> moles of thiol groups in component (b1) with regard to <NUM> mole of total aliphatic carbon-carbon double bonds in components (a1) and (a2). The properties of this photocurable silicone compositions and cured product thereof are shown in Table <NUM>.

Practical Examples <NUM>-<NUM> and Comparative Example <NUM>-<NUM> contained <NUM> ppb of component (c1). In Practical Examples <NUM>-<NUM> and Example <NUM>, the amount of component (d1) was varied from <NUM> to <NUM>. As the content of component (d1) decreased, more yellowing appeared after QUV aging test. As the content of component (d1) increased, a slight negative impact appeared on deep cure property and initial yellowing. The preferred content of component (d1) seems to be less than <NUM> ppb and higher than <NUM> ppb (mass) of the composition. The most favorable range is <NUM> to <NUM> ppb (mass) of the composition. While, Comparative Example <NUM>-<NUM>, in which component (d4) was used instead of component (d1), showed poor side cure property.

Photocurable silicone compositions were prepared by a planetary centrifugal vacuum mixer (Thinky mixer) from the above components and the following components using the composition (parts by mass) shown in Table <NUM>. Note that the photocurable silicone compositions of Practical Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> were prepared to provide <NUM> moles of thiol groups in component (b1) with regard to <NUM> mole of total aliphatic carbon-carbon double bonds in components (a1) and (a2). The properties of this photocurable silicone compositions and cured product thereof are shown in Table <NUM>.

The following photoradical initiators were used as component (C).

The following photoinitiators were used as comparison of component (C).

The phosphorous containing photoinitiators as shown in Practical Examples <NUM>-<NUM> showed superior deep cure property compared to Comparative Examples <NUM>-<NUM> containing simple phenyl ketone-type photoinitiators. As the amount of photoinitiator increases to <NUM> ppb, more severe yellowing appeared. The content is preferably < <NUM> ppb, more preferably <<NUM> of the composition.

Photocurable silicone compositions were prepared by a planetary centrifugal vacuum mixer (Thinky mixer) from the above components and the following components using the composition (parts by mass) shown in Table <NUM>. Note that the photocurable silicone compositions of Comparative Examples <NUM>-<NUM> were prepared to provide <NUM> moles of thiol groups in component (b1) with regard to <NUM> mole of total aliphatic carbon-carbon double bonds in components (a1) and (a2). The properties of this photocurable silicone compositions and cured product thereof are shown in Table <NUM>.

All Comparative Examples <NUM>-<NUM>, because of including component (d4), showed poor deep cure property.

Claim 1:
A photocurable silicone composition comprising:
(A) <NUM> parts by mass of an organopolysiloxane represented by the following average composition formula:

        R<NUM>aR<NUM>bSiO(<NUM>-a-b)/<NUM>

wherein, R<NUM> is an alkenyl group having from <NUM> to <NUM> carbons, R<NUM> is an alkyl group having from <NUM> to <NUM> carbons, an aryl group having from <NUM> to <NUM> carbons, or an aralkyl group having from <NUM> to <NUM> carbons; provided that, at least <NUM> mol% of R<NUM> in a molecule are the aryl groups or the aralkyl groups; and "a" and "b" are positive numbers satisfying: <NUM> ≤ a + b ≤ <NUM> and <NUM> ≤ a/(a + b) ≤ <NUM>;
(B) a compound having at least two thiol groups in a molecule, in an amount that the amount of the thiol groups in the present component is in a range of from <NUM> to <NUM> mol per <NUM> mol of the total alkenyl groups in component (A);
(C) from <NUM> to <NUM> parts by mass of a photoradical initiator having a phosphorus atom; and
(D) from <NUM> to <NUM> parts by mass of a hydroxyphenyl triazine compound represented by the following general formula:
<CHM>
wherein, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> are the same or different, and are groups selected from hydrogen atoms, hydroxy groups or alkyl groups having from <NUM> to <NUM> carbons, R<NUM> is a linear or branched alkyl group having from <NUM> to <NUM> carbons or a group represented by the following general formula:

        -CH<NUM>CH(OH)CH<NUM>OR<NUM>

wherein, R<NUM> is a linear or branched alkyl group having from <NUM> to <NUM> carbons.