Radiation curable polyorganosiloxane resin – linear copolymer composition and methods for preparation and use thereof

Abstract

A radiation curable polyorganosiloxane resin – linear copolymer composition includes (A) an alkenyl-, aryl- functional resin linear polyorganosiloxane block copolymer, (B) a mercapto- functional crosslinker, and (C) a photoradical initiator. The composition may further include (D) a stabilizer, (E) an adhesion promoter, or both. The composition may be used to encapsulate (opto)electronic devices, such as light emitting diodes.

Description

RADIATION CURABLE POLYORGANOSILOXANE RESIN - LINEAR COPOLYMER COMPOSITION AND METHODS FOR PREPARATION AND USE THEREOFCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 567485 filed on March 20, 2024 under 35 U.S.C. §1 19 (e). U.S. Provisional Patent Application Serial No. 63 / 567485 is hereby incorporated by reference.FIELD

[0002] This invention relates to a radiation curable polyorganosiloxane resin - linear copolymer composition and methods for preparation and use of the composition. More particularly, the composition can be used in a low temperature process to encapsulate (opto)electronic devices, such as mini and micro LED arrays.INTRODUCTION

[0003] The mini and micro light emitting diode (LED) market is rapidly growing due in part to use in displays and automotive applications. Mini LED arrays are useful as backlighting panels for standard liquid crystalline displays and improve brightness, contrast and black levels. Micro LEDs refer to tiny LEDs that are used directly as the pixels in a display, specifically combining red, green and blue LED dots. Both technologies require an encapsulant to both protect the fragile LEDs and improve light extraction by replacing air with a silicone interlayer.

[0004] Encapsulating compositions have historically been applied to LED components by a liquid injection molding process. More recently, hot-melt systems have been found to be more desirable for their advantages over liquid injection molding systems. Such advantages include facile coverage of large areas, process simplicity in that there is no need for a dam to prevent overflow, and improved productivity and re- workability.

[0005] However, certain hotmelt film technologies employing hydrosilylation reaction cure may require high temperature (> 80 °C) for a thermal triggering mechanism to make the material flowable, and the material may need even higher temperature (100 °C) and long time (typically, > 1 hour) for curing, after platinum catalysts are activated by UV irradiation. Unfortunately, some display designs incorporate temperature sensitive materials that cannot be exposed to high temperatures for long times without compromising their function. Therefore, to protect temperature sensitive materials and increase manufacturing efficiency to meet the increasing need for (opto)electronic devices such as mini and micro LED devices, there is an industry need to identify an encapsulating technology that does not require the temperature or time of hydrosilylation curing systems.SUMMARY

[0006] A radiation curable polyorganosiloxane resin - linear copolymer composition comprises: (A) an alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer; (B) an organic mercapto-functional crosslinker; and (C) a photoinitiator. Methods for making and using the composition for encapsulation are provided. An encapsulated article may be prepared from the composition.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 describes an exemplary encapsulation process using the radiation curable polyorganosiloxane resin - linear copolymer composition (composition). In step 1) the composition (in the form of a solid film, 101) is placed on a substrate 102 having features (such as LEDs) on its surface. In step 2) the composition 101 is formed over at least a portion of the substrate 102 while the composition 101 becomes flowable by heating (optionally with vacuum lamination), thereby encapsulating the features. In step 3) the composition 101 is cured to form an encapsulant 103 on the substrate 102 by a technique comprising exposure to ultraviolet radiation.DETAILED DESCRIPTION

[0008] The radiation curable polyorganosiloxane resin - linear copolymer composition (composition) introduced above comprises: (A) an alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer; (B) an organic mercapto-functional crosslinker; and (C) a photoinitiator. The composition may optionally further comprise an additional starting material selected from the group consisting of (D) a stabilizer, (E) an adhesion promoter, (F) a solvent, and a combination of two or more thereof.(A) Alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer

[0009] The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer, introduced above, comprises linear blocks and non - linear blocks. Each linear block comprises 10 to 500 disiloxy units of formula (R2R3SiO2 / 2), wherein each R2and each R3is an independently selected monovalent hydrocarbyl group of 1 to 30 carbon atoms. Each non - linear block has a molecular weight of at least 500 g / mol. The non - linear blocks comprise trisiloxy units and hydrolyzable groups; and the non - linear blocks further comprise alkenyl and aryl groups bonded to silicon atoms. At least 30 mol % of the non - linear blocks may be crosslinked with each other, and each linear block is linked to at least one non - linear block. The copolymer may have a Mw of at least 20,000 g / mol measured by GPC according to the following test method. Samples for GPC analysis are prepared in certified ACS grade toluene at 1% concentration, filtered through a 0.45 pm PTFE syringe filter, and analyzed against polystyrene standards. The relative calibration (3rdorder fit) used for molecular weight determination was based on 12 polystyrene standards ranging in molecular weights from 580Daltons to 906,600 Daltons. The chromatographic apparatus was a Viscotek GPC Max equipped with a vacuum degasser, a Viscotek VE3580 RI detector and two (300 mm x 7.5 mm) Polymer Laboratories mixed C columns (molecular weight separation range of 200 to 3,000,000) preceded by a guard column. Separations were performed using certified grade THF programmed to flow at 1.0 ml / min, injection volume was set at 100 pL and columns and detector were heated at 35 °C. Data collection was 45 minutes. Malvern OMNISEC 5.02 was used for data collection and Malvern OMNISEC 5.12 was used for data reduction. A total of 17 PS linear narrow molecular weight standards from Agilent having Mp values from 4,000 to 0.58 kg / mol were used for conventional molecular weight calibration. A 3rdorder polynomial was used for calibration curve fitting. Thus, all molecular weight averages, distributions and references to molecular weight provided in this report are PS equivalent values and only RI was used for molecular weight calculation.

[0010] Linear polyorganosiloxanes typically comprise mostly D units, which results in polydiorganosiloxanes that are fluids of varying viscosity, depending on the DP, indicated by the number of D units in the polydiorganosiloxanes. Linear polydiorganosiloxanes typically have Tg lower than 25 °C, alternatively lower than 0 °C, and alternatively lower than -20 °C.

[0011] “Resin” polysiloxane results when a majority of the siloxy units are T, Q, or both units. When T siloxy units are predominant, the resulting polysiloxane can be referred to as a “silsesquioxane resin”. When Q units are predominant, the resulting polysiloxane can be referred to as a silicate. Increasing the amount of T and / or Q siloxy units (relative to amount of M and / or D units) typically results in polysiloxanes having increasing hardness and / or glass like properties. “Resin” polysiloxanes thus have higher Tg values than linear polydiorganosiloxanes, for example resin polysiloxanes often have Tg values greater than 30 °C, alternatively greater than 40 °C, and alternatively greater than 50 °C. Alternatively up to 100 °C, alternatively up to 80 °C, alternatively up to 70 °C, and alternatively 50 °C to 100 °C.

[0012] As used herein, “resin - linear polyorganosiloxane block copolymer” refers to polyorganosiloxanes containing polydiorganosiloxane blocks comprising, alternatively consisting essentially of, alternatively consisting of, D units in combination with resin blocks comprising T units. The resin - linear polyorganosiloxane block copolymer is a block copolymer (not a random copolymer). D units are bonded together to form polymeric polydiorganosiloxane chains having 10 to 500 D units, referred to herein as linear blocks. The T units are primarily bonded to each other to form branched polymeric chains, and these are included in the non - linear blocks. A significant number of these non - linear blocks may aggregate to form nano-domains when solid forms of the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer are provided. The disiloxy units of formula (R2R3SiO2 / 2)that are arranged in linear blocks have an average of 10 to 500 units of formula (R2R3SiO2 / 2) per linear block. Alternatively, each linear block may have an average of at least 10, alternatively at least 50, alternatively at least 100, alternatively at least 150, and alternatively at least 200 disiloxy units; while at the same time each linear block may have up to 500, alternatively up to 400, alternatively up to 300, and alternatively up to 200, disiloxy units per linear block. Alternatively, each linear block may have 100 to 150 disiloxy units, alternatively 1 15 to 125 disiloxy units, alternatively 90 to 170 disiloxy units. The linear blocks are covalently bonded to the non - linear blocks.

[0013] The trisiloxy units are arranged in the non - linear blocks. The non - linear blocks each have a molecular weight of at least 500 g / mol, alternatively 500 g / mol to 4,000 g / mol per block. Alternatively, each non - linear block may have a Mn of at least 500 g / mol, alternatively at least 1,000 g / mol, alternatively at least 1,500 g / mol; while at the same time each non - linear block may have a Mn of up to 4,000 g / mol, alternatively up to 3,000 g / mol; alternatively up to 2,500 g / mol; alternatively up to 2,000 g / mol; and alternatively up to 1,500 g / mol.

[0014] The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may further comprise hydrolyzable groups in the non - linear blocks. The hydrolyzable groups may have formula (ZO1 / 2), wherein each Z is independently selected from H or a monovalent hydrocarbyl group of 1 to 30 carbon atoms. Alternatively, the monovalent hydrocarbyl group for Z may be an alkyl group, such as an alkyl group of 1 to 6 carbon atoms, alternatively 1 to 4 carbon atoms, alternatively 1 to 2 carbon atoms, and alternatively methyl. Alternatively, each Z may be H. The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may comprise up to 50 mol % of the hydrolyzable groups, alternatively at least 0.5 mol%, alternatively at least 1 mol%, alternatively at least 5 mol %, alternatively at least 10 mol%, and alternatively at least 15 mol%; while at the same time the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may comprise up to 50 mol %, alternatively up to 35 mol %, alternatively up to 30 mol%, alternatively up to 25 mol%, and alternatively up to 20 mol % of the hydrolyzable groups.

[0015] The hydrolyzable groups may allow the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer to further react or cure or to crosslink. Crosslinking of the non - linear blocks may be accomplished via a variety of chemical mechanisms and / or moieties. For example, crosslinking of the non - linear blocks within the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may result from condensation of residual silanol and / or alkoxy groups present in the non - linear blocks. At least 30% of the non - linear blocks in the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may be crosslinked with each other, alternatively at least 40%, alternatively at least 50%, alternatively atleast 60%, alternatively at least 70%, and alternatively at least 80%. Alternatively, 30% to 80% of the non - linear blocks may be crosslinked with each other, alternatively 30% to 70%, alternatively 30% to 60%, alternatively 30% to 40%, and alternatively 30% to 40% of the non - linear blocks are crosslinked with each other.

[0016] The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have a Mw of 20,000 g / mol to 500,000 g / mol. Alternatively, the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have a Mw of at least 20,000 g / mol, alternatively at least 40,000 g / mol, alternatively at least 50,000 g / mol, alternatively at least 60,000 g / mol, alternatively at least 70,000 g / mol, and alternatively at least 80,000 g / mol; while at the same time Mw may be up to 500,000 g / mol, alternatively up to 450,000 g / mol, alternatively up to 400,000 g / mol, alternatively up to 350,000 g / mol, alternatively up to 300,000 g / mol; alternatively up to 250,000 g / mol; alternatively up to 200,000 g / mol; alternatively up to 150,000 g / mol and alternatively up to 100,000 g / mol. Alternatively, the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have a Mn of 15,000 to 50,000 g / mol. Alternatively, the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have a Mw of 25,000 g / mol to 400,000 g / mol, alternatively 30,000 g / mol to 300,000 g / mol, alternatively 35,000 g / mol to 200,000 g / mol, alternatively 40,000 g / mol to 100,000 g / mol, alternatively 45,000 g / mol to 75,000 g / mol, and alternatively 49,000 to 74,000 g / mol. Alternatively, the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have Mn of at least 15,000 g / mol, alternatively at least 20,000 g / mol; while at the same time Mn may be up to 50,000 g / mol, alternatively up to 30,00 g / mol, alternatively up to 25,000 g / mol. Mw and Mn may be measured by GPC, using the test method provided above.

[0017] The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may be isolated in a solid form, for example, by casting a film of a solution of the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer in an organic solvent (e.g., benzene, toluene, xylene, or a combination thereof) and allowing the solvent to evaporate. The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may be provided in a solution in an organic solvent in an amount of 50% to 80%, alternatively 60% to 80%, copolymer solids with the balance being organic solvent in the solution. The solution may be cast as a film and then dried to remove the solvent and form a solid, and the non - linear blocks may further aggregate together to form nano - domains. As used herein, “predominately aggregated” means the majority of the non - linear blocks are found in certain regions of the solid composition, referred to herein as “nano - domains”. The nano - domains refer to phase regions within the solid alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer that are phase separated and possess at least one dimension sized from 1 nm to 100nm. The nano - domains may vary in shape, providing at least one dimension of the nano - domains is sized from 1 to 100 nm. The nano - domains may be regularly or irregularly shaped, alternatively spherical, tubular, or lamellar shaped. Alternatively, the solid alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may contain a first phase and an incompatible second phase, the first phase containing predominantly the linear block and the second phase containing predominantly the non - linear block, the non - linear blocks being sufficiently aggregated into nano - domains that are incompatible with the first phase.

[0018] The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have, per molecule, at least one alkenyl group (R1) as described and exemplified below. Each alkenyl group is covalently bonded to a silicon atom. The alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer may have an alkenyl group content of 0.5 mol % to 5 mol %, alternatively 0.5 mol % to 4.5 mol%, alternatively 0.8 mol % to 4 mol %, alternatively 1 mol % to 4 mol %, alternatively 1 mol% to 3 mol %, and alternatively 2 mol % to 3 mol %.

[0019] The alkenyl group (R1) described herein may have 2 to 20 carbon atoms, alternatively 2 to 12 carbon atoms, alternatively 2 to 10 carbon atoms, alternatively 2 to 8 carbon atoms, and alternatively 2 to 6 carbon atoms. The alkenyl group may have terminal alkenyl functionality,R1may be independently selected from the group consisting of vinyl, allyl, and hexenyl. Alternatively, each R1may be independently selected from the group consisting of vinyl and allyl. Alternatively, each R1may be independently selected from the group consisting of vinyl and hexenyl. Alternatively, each R1may be vinyl.

[0020] In addition to the alkenyl groups, the monovalent hydrocarbyl groups (e.g. , R2and R3) in the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer may be selected from alkyl groups and aryl groups. Suitable alkyl groups may be linear, branched, cyclic, or combinations of two or more thereof. The alkyl groups may have 1 to 30 carbon atoms, alternatively 1 to 20 carbon atoms, alternatively 1 to 10 carbon atoms, alternatively 1 to 6 carbon atoms, and alternatively 1 to 4 carbon atoms. The alkyl groups are exemplified by methyl, ethyl, propyl (including n-propyl and / or isopropyl), butyl (including n-butyl, tert-butyl, sec-butyl, and / or isobutyl); pentyl, hexyl, heptyl, octyl, decyl, dodecyl, undecyl, and octadecyl (and branched isomers having 5 to 30 carbon atoms), and the alkyl groups are further exemplified by cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Alternatively, the alkyl group may be selected from the group consisting of methyl, ethyl, propyl and butyl; alternatively methyl, ethyl, and propyl; alternatively methyl and ethyl. Alternatively,each alkyl group may be methyl. Alternatively, in the linear block comprising units of formula (R2R3SiO2 / 2), each R2and each R3may be alkyl, and alternatively each R2and each R3may be methyl.

[0021] Suitable aryl groups for may have 6 to 30 carbon atoms, alternatively 6 to 20 carbon atoms, alternatively 6 to 12 carbon atoms. The aryl groups may be monocyclic or polycyclic and may have pendant hydrocarbyl groups. For example, the aryl groups include phenyl, tolyl, xylyl, and naphthyl and further include aralkyl groups such as benzyl, 1-phenylethyl and 2- phenylethyl. Alternatively, the aryl groups may be monocyclic, such as phenyl, tolyl, or benzyl; and alternatively each aryl group may be phenyl.

[0022] Examples of alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymers are known in the art and may be made by known methods, such as those disclosed inUS Patents 9765192 to Horstman, et al. and 10793681 to Swier, et al., both of which are hereby incorporated by reference.

[0023] Alternatively, the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer used herein may comprise at least one of units of formula (I) and units of formula(II), wherein formulaformula (II) is, wherein R1is the alkenyl group as described above, R4is the aryl group as described above, and R2and R3are each independently selected alkyl groups, as described above. In formula (II), R5and R6represent monovalent hydrocarbyl groups of 1 to 30 carbon atoms, which may be alkyl, alkenyl or aryl groups as described above. Alternatively, R5may be an alkyl group. Alternatively, R6may be an alkenyl group or aryl group, alternatively an aryl group. Alternatively, in formulas (I) and (II), each R1may be vinyl, each R2may be methyl, each R3may be methyl, each R4may be phenyl, each R5may be methyl, and each R6may bevinyl or phenyl, alternatively phenyl. Alternatively, the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer may have units of formula (I) linking the linear and non - linear blocks.

[0024] Alternatively, the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer comprising units of formula (I) and / or formula (II) may comprise 20 mole% to 60 mole% of T‘"ylunits of formula (R4SiCh / 2), where R4is the aryl group as described above; alternatively at least 25 mole%, alternatively at least 28 mole%; alternatively no more than 55 mole%, alternatively no more than 52 mole%.

[0025] Alternatively, the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer comprising units of formula (I) and / or formula (II) may comprise 0.5 mole% to 4.5 mole% Talkenylunits of formula ( R Si O3 / 2 ) : alternatively at least 0.8 mole%, alternatively at least 1.0 mole%; alternatively no more than 4 mole%, alternatively no more than 3 mole%, alternatively no more than 2.5 mole%. Alternatively, the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer comprising units of formula (I) and / or formula (II) may comprise 40 mole% to 80 mole% difunctional siloxy units of formula (R2R3SiO2 / 2) units; alternatively at least 45 mole%, alternatively at least 48 mole%; alternatively no more than 75 mole%, alternatively no more than 72 mole%. Alternatively, the T"'ylunits are arranged in a non-linear block, having a molecular weight of at least 500 g / mole. Alternatively, the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer has a weightaverage molecular weight of at least 20,000 g / mole. Alternatively, at least 50 mole% of the units having alkenyl groups are present as T units, alternatively at least 60 mole%, alternatively at least 70 mole%, alternatively at least 80 mole%, alternatively at least 90 mole%.

[0026] Structural analysis, e.g.. determination of the average number of difunctional siloxane units in the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer described above may be performed by29Si NMR as follows: 5 g of an alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer as described above was mixed with 1 ml Debenzene for NMR characterization. The29Si NMR spectra of each product were collected by a Bruker 600 MHz NMR instrument (NS = 256, dl = 60).

[0027] The amount of starting material (A) in the composition may be 85% to 99%, based on combined weights of all starting materials in the composition, excluding solvent, if used. Alternatively, the amount of starting material (A) may be at least 85%, alternatively at least 86%, alternatively at least 87%, alternatively at least 88%, alternatively at least 89%, and alternatively at least 90%; while at the same time the amount of starting material (A) may be up to 99%, alternatively up to 98%, alternatively up to 97.5%, alternatively up to 97%, and alternatively up to 96%, on the same basis.(B) Organic mercapto-functional crosslinker

[0028] Starting material (B) is an organic mercapto- functional crosslinker having at least 2, alternatively 2 to 4, mercapto- functional groups per molecule. The organic mercapto- functional crosslinker may be selected from the group consisting of compounds having formula (B-I), formula (B-II), and a combination thereof, wherein: formula (B-I) is R’mCX(4-m), wherein each R’ is an independently selected alkyl group of 1 to 20 carbon atoms, subscript m is an integer with a value of 2, 3, or 4, and each X is independently a mercapto-functional group of formulasubscript p is an integer with a value of 0 or1 ; and formula (B-II) is X’-R”-X’, wherein R” is an alkylene group of 1 to 20 carbon atoms, andX’ is a mercapto-functional group with a formula selected fromsubscript p is an integer with a value of 0 or 1.Alternatively, in formula (B-I), R’ may be methyl, ethyl, propyl or butyl; alternatively methyl or ethyl. Alternatively, in formula (B-I), subscript m may be 3 or 4. Examples of compounds of formula (B-I) include Trimethylolpropane Tris(3-mercaptopropionate) (CAS# 33007-83-92) and Pentaerythritol tetrakis(3-mercaptopropionate) (CAS# 7575-23-7), both of which are commercially available from TCI America. Alternatively in formula (B-II), R” may be an alkylene group of 2 to 16 carbon atoms, alternatively 4 to 14, carbon atoms, alternatively 6 to 12 carbon atoms, and alternatively 8 to 10 carbon atoms. Examples of compounds of formula (B- II) include 3,6-Dioxa-l,8-octanedithiol (CAS# 14970-87-7), ethylene bis(thioglycolate) (CAS# 123-81-9); 1,4-Butanediol Bis(thioglycolate) (CAS# 10193-95-0), hexanediol bis(thioglycolate), ethylene glycol bis(3-mercaptopropionate) (CAS#22504-50-3), and 1 ,4-butanediol bis(3- mercaptopropionate) (CAS# 92140-97-1), which are also available from TCI America or Alpha Chemical. Other examples of organic mercapto-functional crosslinkers for starting material (B) are disclosed, for example, in US Patent 10604653 at col. 5, lines 13 - 22, and include o-, m-, or p-xylenedithiol.

[0029] The amount of (B) the organic mercapto-functional crosslinker in the composition depends on various factors including the amount and selections of starting materials (A) and (C),and whether any of additional starting materials (D), (E), and / or (F) are present, however, the amount of (B) the organic mercapto- functional crosslinker may be 0.5% to 14.9%.Alternatively, the amount of starting material (B) may be at least 1%, alternatively at least 1.5%, alternatively at least 2%, alternatively at least 3%, alternatively at least 4%, and alternatively at least 5%; while at the same time the amount of starting material (B) may be up to 14.9%, alternatively up to 14%, alternatively up to 13%, alternatively up to 12%, alternatively up to 11%, and alternatively up to 10.5%, based on combined weights of all starting materials in the composition, excluding solvent, if used.(C) Photoradical initiator

[0030] Starting material (C) in the composition is a photoradical initiator. Suitable photoradical initiators include ultraviolet (UV) initiators such benzophenone and benzophenone derivatives, acetophenone and acetophenone derivatives, benzoin and its alkyl esters, and phosphine oxide derivatives. Suitable commercially available photoinitiators include 2,6-bis(4- azido benzylidene)cyclohexanone; 2,6-bis(4-azido benzylidene)-4-methylcyclohexanone; 1- hydroxy-cyclohexyl-phenyl-ketone (CAS# 947-19-3, available under the name OMNIRAD™ 184); 2-methyl-l-[4-(methylthio)phenyl]-2-morpholinopropane-l-one (CAS# 718-10-5, available under the name OMNIRAD™ 907); 2-hydroxy-2-methyl-l-phenyl-propane-l-one (CAS# 7473-98-5, available under the name OMNIRAD™ 1173); a mixed initiator of 50% benzophenone (CAS# 119-61-9) and 50% of OMNIRAD™ 184C (the mixed initiator available under the name OMNIRAD™ 500); a mixed initiator of 20% of OMNIRAD™ 184C and 80% of OMNIRAD™ 1173 (the mixed initiator available under the name OMNIRAD™ 1000); l-[4- (2-hydroxyethoxyl)-phenyl]-2-hydroxy-2-methylpropanone (CAS# 106797-53-9 available under the name OMNIRAD™ 2959); methylbenzoylformate (CAS# 152-55-0, available under the name OMNIRAD™ MBF); 2,2-dimethoxy-2-phenylacetophenone (CAS# 24650-42-8, available under the name OMNIRAD™ BDK); 2-benzyl-2-(dimethylamino)-4’- morpholinobutyrophenone (CAS# 119313-12-1 available under the name OMNIRAD™ 369); diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide (CAS# 75980-60-8, available under the name OMNIRAD™ TPO); ethyl (2,4,6-trimethylbenzoyl) phenyl phosphinate (CAS# 84434-11-7, available under the name OMNIRAD™ TPO-L); and a combination of two or more thereof.The photoradical initiators with the OMNIRAD™ brands are commercially available from IGM Resins B.V., Netherlands. Other photoradical initiators are commercially available from other sources, and are as described, for example, in PCT Patent Publication WO2024039544 and US Patent 11827799.

[0031] The amount of (C) the photoradical initiator in the composition depends on various factors including the types and amounts of starting materials (A) and (B) and whether any ofadditional starting materials (D) and / or (E) are present, however, the amount of starting material(C) may be 0.1% to 10% based on combined weights of all starting materials in the composition, excluding solvent, if used. Alternatively, the amount of starting material (C) may be at least 0.1%, alternatively at least 0.2%, alternatively at least 0.3%, alternatively at least 0.4%, and alternatively at least 0.5%; while at the same time the amount of starting material (C) may be up to 10%, alternatively up to 7.5%, alternatively up to 5%, alternatively up to 2.5%, alternatively up to 1%, and alternatively up to 5%, on the same basis.(D) Stabilizer

[0032] Optionally, the composition may further comprise (D) an ultraviolet stabilizer. Ultraviolet stabilizers are radical scavengers, which can extend the storage stability of the composition by inhibiting curing until intentionally exposing the composition to UV radiation. Ultraviolet stabilizers include phenolic compounds such as 4-methoxyphenol (MEHQ, methyl ether of hydroquinone), hydroquinone, 2-methylhydroquinone, 2-t-butylhydroquinone, t-butyl catechol, butylated hydroxy toluene, and butylated hydroxy anisole. Other types of ultraviolet stabilizers include phenothiazine and anaerobic inhibitors such as NPAL type inhibitors (tris-(N- nitroso-N-phenylhydroxylamine) aluminum salt) available from Albemarle Corporation.

[0033] Alternatively, the stabilizer used herein may be an inhibitor comprising a manganese ion source and a phenolic compound. The manganese ion source used herein may be a manganese (III) compound or a manganese (II) compound. Alternatively, the manganese ion source may be a manganese (II) compound. Suitable manganese compounds include manganese (II) acetate, manganese (II) nitrite, manganese (II) propionate, manganese (II) oxide, manganese (II) hydroxide, manganese (II) chloride, manganese (II) phosphate, manganese (II) perchlorate, hydrates thereof (e.g., manganese (II) tetrahydrate) and combinations thereof. Alternatively, the manganese ion source may comprise manganese (II) acetate or manganese (II) tetrahydrate, or a combination thereof. Suitable manganese ion sources are commercially available from Millipore Sigma of St. Louis, Missouri, USA, Fisher Scientific of Waltham, Massachusetts, USA, and City Chemical LLC of Connecticut, USA. The amount of manganese ion source depends on various factors including the selections and amounts of starting materials used herein, and the time and temperature for heating. However the amount of manganese ion source may be 0.1 ppm to 5,000 ppm, alternatively 0.1 ppm to 1,000 ppm, based on combined weights of all starting materials in the composition, excluding solvent, if used. Alternatively, the amount of the manganese ion source may be > 0 ppm, alternatively at least 0.1 ppm, alternatively at least 0.5 ppm, alternatively at least 1 ppm, alternatively at least 1.5 ppm; while at the same time, the amount of manganese ion source may be up to 5,000 ppm, alternatively up to 1,000 ppm, alternatively up to 100 ppm, alternatively up to 10 ppm, alternatively up to 5 ppm, alternativelyup to 4 ppm, and alternatively up to 3 ppm, and alternatively up to 2 ppm, on the same basis.

[0034] The phenolic compound used herein has one or more phenolic groups per molecule. Suitable phenolic compounds include hydroquinone (HQ), dihydroxybenzene (catechol), resorcinol, dihydroxyxylene, methoxyphenols such as guaiacol, p-methoxyphenol (also called methyl ether of hydroquinone or MeHQ), tert-butyl hydroquinone (tBuHQ), pyrogallol, methylpyrogallol, cresol, phenol, xylenols, and combinations thereof. Alternatively, the phenolic compound may be selected from the group consisting of HQ, MeHQ, tBuHQ, and a combination of two or more thereof. Suitable phenolic compounds are commercially available, e.g., from Millipore Sigma of St. Louis, Missouri, USA. The amount of phenolic compound source depends on various factors including the selections and amounts of starting materials used in the composition, however the amount may be 5 ppm to 5,000 ppm based on combined weights of all starting materials in the composition, excluding solvent, if used. Alternatively, the amount of the phenolic compound may be at least 5 ppm, alternatively at least 50 ppm, alternatively at least 100 ppm, alternatively at least 150 ppm; while at the same time, the amount of phenolic compound may be up to 500 ppm, alternatively up to 400 ppm, alternatively up to 350 ppm, and alternatively up to 320 ppm, on the same basis.

[0035] Alternatively, the amount of ultraviolet stabilizer in the composition may be 0% or more, alternatively 0.1% or more, alternatively 0.5% or more, alternatively 1.0% or more, and alternatively 1.5% or more; while at the same time the amount of the stabilizer may be 2.0% or less, alternatively 1.5% or less, alternatively 1.0% or less, and alternatively 0.5% or less, each based on combined weights of all starting materials in the composition.(E) Adhesion Promoter

[0036] Optionally, the composition may further comprise (E) an adhesion promoter. Suitable adhesion promoters include organosilicon compounds having at least one silicon-bonded alkoxy group per molecule. This alkoxy group is exemplified by a methoxy group, an ethoxy group, a propoxy group, a butoxy group, or a methoxyethoxy group. Alternatively, the alkoxy group may be a methoxy group. Moreover, silicon-bonded groups other than alkoxy groups in the organosilicon compound are exemplified by halogen-substituted or unsubstituted monovalent hydrocarbon groups such as alkyl groups, alkenyl groups, aryl groups, aralkyl groups, halogenated alkyl groups, halogenated aryl groups, and halogenated aralkyl group; epoxy functional groups exemplified by glycidoxyalkyl groups such a 3-glycidoxypropyl group, and a 4-glycidoxybutyl group; epoxycyclohexylalkyl groups such as a 2-(3,4-epoxycyclohexyl)ethyl group and a 3-(3,4-epoxycyclohexyl)propyl group; and epoxyalkyl groups such as a 3,4- epoxybutyl group, and a 7,8-epoxyoctyl group; (meth)acrylic group containing monovalent organic groups such as a 3-methacryloxy ropyl group; and a hydrogen atom. The adhesionpromoter may contain a group that can react with the alkenyl groups of starting material (A). For example, the adhesion promoter may contain a silicon-bonded hydrogen atom. Moreover, due to the ability to impart good adhesion to various types of substrates, the adhesion promoter may have at least one epoxy-functional group per molecule. This type of adhesion promoter is exemplified by organosilane compounds, organosiloxane oligomers, and alkyl silicates. The molecular structure of the organosiloxane oligomer or alkyl silicate is exemplified by linear, partially branched linear, branched chain, cyclic, and net-shaped structures. Linear, branched chain, and net shaped structures are particularly preferred. The adhesion promoter is exemplified by silane compounds such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, and 3 -methacryloxypropyltrimethoxy silane; siloxane compounds having at least one each of silicon-bonded alkenyl groups or silicon-bonded hydrogen atoms and silicon- bonded alkoxy groups in a molecule: mixtures of a silane compound or siloxane compound having at least one silicon-bonded alkoxy group and a siloxane compound having at least one silicon-bonded hydroxyl group and at least one silicon-bonded alkenyl group in a molecule; and methyl polysilicate, ethyl polysilicate, and epoxy group-containing ethyl polysilicate. The adhesion promoter may be a low- viscosity liquid, and its viscosity is not particularly limited but may be 1 milliPascal (mPa) to 500 mPa at 25 °C.

[0037] The amount of (E) the adhesion promoter in the composition may be 0% or more, alternatively 0.1%, alternatively 0.5% or more, alternatively 1.0% or more, and alternatively 1.5% or more; while at the same time the amount of adhesion promoter may be 2.0% or less, alternatively 1.5% or less, alternatively 1.0% or less, and alternatively 0.5% or less, each based on combined weights of all starting materials in the composition.(F) Solvent

[0038] Optionally, the composition may further comprise (F) a solvent. Suitable solvents are those which can dissolve starting materials (A), (B), and / or (C). Typically, starting material (A) may be prepared in a solvent, such as an aromatic hydrocarbon exemplified by benzene, toluene, xylene or combinations thereof; an aliphatic hydrocarbon such as hexane, heptane, octane, or a combination thereof, or a combination of an aromatic hydrocarbon and an aliphatic hydrocarbon. The solvent may be used to facilitate mixing of the starting materials described above, and may optionally be removed from the composition after mixing. For example, the composition may be prepared in a method comprising: mixing starting materials (A), (B), (C), and when present (D), (E), and (F) at RT or with heating. Alternatively, one or more of starting materials (A), (B), (C), (D), and / or (E) may be dissolved in (F) the solvent before mixing with the other starting materials. For example, starting material (A) the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer may be dissolved in (F) the solvent before mixing with startingmaterials (B) and (C), and when present starting materials (D) and (E). The method for preparing the composition may further comprise removing all or a portion of (F) the solvent after mixing, thereby rendering the composition non-flowable at 25 °C.

[0039] Notably, the composition of the present invention can be free of hydrosilylation reaction catalysts such as platinum catalysts. As such, the composition can be free of platinum, which can be desirable to avoid yellowing of the composition and / or a cured product of the composition, and to keep costs lower than systems that require platinum catalysts.

[0040] The present composition may be non-flowable at 25 °C and may have a viscosity of 5,000 Pa-s or less, and alternatively 1,000 Pa-s or less, at 120 °C. For purposes of this application “non-flowable” means not flowing when no load is applied, and indicates the condition at lower than the softening point measured by a testing method for the softening point by the Ring-and-ball method of a hot melt adhesive agent stipulated in JIS K 6863-1994, “Testing methods for the softening point of hot melt adhesives”. That is, in order to be non- flowable at 25 °C, the softening point of the composition needs to be higher than 25 °C. This is because excellent shape retention properties are achieved at the temperature if the composition is non-flowable at 25° C. Furthermore, if the melt viscosity at 120 °C is 5,000 Pa- s or less, processing into various forms is facilitated. Since the present composition is non-flowable at 25 °C, the present composition can be processed into various forms, and for example, can be made into a film having a thickness of 5 pm to 5 mm. Examples of the radiation used to cure the composition include ultraviolet, however, electron beam and / or radial ray may alternatively be used. Examples of devices that emit the ultraviolet radiation include high-pressure mercury lamps, medium-pressure mercury lamps, and ultraviolet LEDs.

[0041] The cured product of the present invention is obtained by irradiating the composition described above. A cured product having a form of the composition before curing can be obtained if the irradiation is performed at a temperature that the present composition does not exhibit flowability. The form of this cured product is not limited; however, the form may be a film.Method of Producin a Film

[0042] The method of producing a film of the present invention may comprise: sandwiching the composition described above in between two releasable transparent films, forming the composition to a fixed thickness, and then irradiating the composition.

[0043] Sandwiching the composition between the films may be performed by any convenient means, such as depositing the composition on a surface of a first film, removing (F) the solvent, when present, and then placing a second film on a surface of the composition opposite the surface of the first film. Alternatively, the composition (without solvent) may be placed betweenthe films and then formed to the fixed thickness by thermal compression or a heating roller.

[0044] The irradiation may be performed through a transparent film, or the composition may be directly irradiated after one or both transparent film(s) described above are removed. The releasable transparent film that can be used in this method include a transparent film in which the releasability is exhibited by itself and a transparent film obtained by adding or applying a releasing agent to a transparent film having low releasability. Examples of the transparent film having releasability include polyacrylate resin films or polyolefin resin films that are grafted with silicone, and fluorinated polyolefin resin films. Examples of the transparent film, to which a releasing agent is added or applied, include polyester resin films, polyolefin resin films, and polyethylene terephthalate films.

[0045] This invention further relates to a process for using the composition described herein as a curable coating on a substrate. The process comprises the steps of softening the composition by heating, thereby forming a softened composition, and forming the softened composition over at least a portion of a substrate. Forming may be performed by any convenient means, such as vacuum lamination. The process can further comprise exposing the composition to ultraviolet radiation to cure the composition.

[0046] Alternatively, the composition may be used to form an encapsulant for light emitting diodes. In such an application, the process is as described above and the substrate over which the composition is formed comprises light emitting diodes. The composition covers the light emitting diodes thereby encapsulating them and then the composition is cured by exposure to UV radiation.

[0047] The present invention further comprises an article comprising the composition (or cured product thereof forming an encapsulant) covering at least a portion of a surface of a substrate. Desirably, the substrate, and most desirably the portion of the substrate covered by the composition (or encapsulant), may comprise light emitting diodes.EXAMPLES

[0048] The following examples are provided to illustrate the invention to one skilled in the art and are not to be construed to limit the scope of the invention set forth in the claims. Starting materials used in these examples are summarized below in Table 1.Table 1 - Starting Materials

[0049] In Table 1, 3,6-Dioxa-l,8-octanedithiol (Xlinker 1) had formula:Trimethylolpropane Tris(3-mercaptopropionate) (Xlinker 2) had formula:Pentaerythritol tetrakis(3- mercaptopropionate) (Xlinker 3) had formula:

[0050] As used in the following examples, ETFE film refers to Chemours Tefzel™ ETFE films.

[0051] In this Synthesis Example 1, Silanol-terminated PDMS with DP=80 was prepared as follows: 1,500.0 g of starting XIAMETER™ PMX-0156 were added into a 2L 3-neck round bottom flask equipped with a PTFE stir paddle and a thermocouple, leaving one neck open while purging with nitrogen gas at a flow rate of 1 .5 standard cubic feet per hour. 0.515 g of 3% potassium hydroxide solution were added to the flask at 90 °C. After 3 hours and 50 min at 90 °C, were added 1.62 g of 2.5% aqueous phosphoric acid solution. The solution was cooled to 25 °C and purged with nitrogen gas overnight to remove water. The resulting material was filtered through a nylon filter (0.45 pm) to obtain PDMS 1 (a bis-silanol-terminated polydimethylsiloxane).29Si NMR confirmed that PDMS 1 had a DP of 80.

[0052] In this Synthesis Example 2, alkenyl-, aryl- functional resin-linear polyorganosiloxane block copolymer RL1 was prepared as follows: A IL four-neck round bottom flask equipped with a thermal couple, Teflon stir paddle, and a Dean Stark apparatus attached to a water-cooled condenser was loaded with 217 Flake (90.0 g), toluene (240.8 g) and an amount of toluene equal to the volume of the Dean Stark apparatus. Then, an inert gas blanket was applied. The mixture was refluxed for 30 min to remove water present in the mixture.

[0053] Meanwhile, diacetoxysilane terminated PDMS was prepared by adding vinyltriacetoxysilane (VTA, 8.50 g) and XIAMETER™ OFS-1579 (3.45 g) to a mixture of toluene (59.2 g) and bis-silanol terminated PDMS (110.0 g, dp=63) in a 500 ml round bottom flask. The mixture was stirred at room temperature for 1 hr. Diacetoxysilane-terminated PDMS was prepared and was quickly added to the flask containing the 217 Flake at 106 °C. Then, the reaction mixture was refluxed for 2 hours. Then, the reaction mixture was cooled to 106 °C and XIAMETER™ OFS-1579 (6.14 g) was added. After 1 hr of reflux, the reaction temperature was cooled to 90 °C and deionized water (28.2 g) was added. Water and acetic acid by-product were removed by azeotropic distillation. The step of addition and removal of water was repeated one more time. Then, volatiles were removed to make a concentrated solution (100.0 g of volatiles were removed). The step of addition and removal of water was repeated three times. A translucent solution was obtained after fdtration. This sample contained an alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer labelled RL1.

[0054] In this Synthesis Example 3, alkenyl-, aryl- functional resin- linear polyorganosiloxane block copolymer RL2 was prepared as follows: A 3L four-neck round bottom flask equipped with a thermal couple, Teflon stir paddle, and a Dean Stark apparatus attached to a water-cooled condenser was loaded with 217 Flake (270.0 g), toluene (722.3 g) and an amount of toluene equal to the volume of the Dean Stark apparatus. Then, an inert gas blanket was applied. Themixture was refluxed for 30 min to remove water present in the mixture.

[0055] Meanwhile, diacetoxysilane terminated PDMS was prepared by adding vinyltriacetoxysilane (VTA, 25.50 g) and XIAMETER™ OFS-1579 (10.36g) to a mixture of toluene (177.7 g) and bis-silanol-terminated PDMS (330.0g, dp=63) in a 500 ml round bottom flask. Then, the mixture was stirred at room temperature for 1 hr. Diacetoxysilane-terminated PDMS was prepared and was quickly added to the flask containing 217 Flake at 106 °C. Then, the reaction mixture was refluxed for 2 hours. After the reaction mixture was cooled to 90 °C, deionized water (56.0 g) was added. Water and acetic acid by-product were removed by azeotropic distillation. The step of addition and removal of water was repeated one more time. Then, volatiles were removed to make a concentrated solution (300.0 g of volatiles were removed). The step of addition and removal of water was repeated three times. A translucent solution was obtained after filtration. This sample contained an alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer labelled RL2.

[0056] In this Synthesis Example 4, an alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer RL3 was prepared as follows: A I L four-neck round bottom flask equipped with a thermal couple, Teflon stir paddle, and a Dean Stark apparatus attached to a water-cooled condenser was loaded with 217 Flake (90.0 g), toluene (240.8 g) and an amount of toluene equal to the volume of the Dean Stark apparatus. Then, an inert gas blanket was applied. The mixture was refluxed for 30 min to remove water present in the mixture.

[0057] Meanwhile, diacetoxysilane terminated PDMS was prepared by adding vinyltriacetoxysilane (VTA, 9.44 g) to a mixture of toluene (59.2 g) and PDMS 1 (prepared as described in Synthesis Example 1, above) (110.0 g, DP=80) in a 500 ml round bottom flask. Then, the mixture was stirred at room temperature for 1 hr. Diacetoxysilane-terminated PDMS was prepared and was quickly added to the flask containing 217 Flake at 106 °C. Then, the reaction mixture was refluxed for 2 hours. After the reaction mixture was cooled to 106 °C, XIAMETER™ OFS-1579 (4.60 g) was added. Then, the mixture was refluxed for 1 hour. The reaction mixture was cooled to room temperature and deionized water (21.8 g) was added. Water and acetic acid byproduct were removed by azeotropic distillation. The step of addition and removal of water treatment was repeated. Then, volatiles (100 g) were removed to make a concentrated solution. The step of addition and removal of water treatment was repeated three times. A translucent solution was obtained after filtration. This sample contained an alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer labelled RL3.

[0058] In this Synthesis Example 5, a (comparative) resin - linear polyorganosiloxane block copolymer (without alkenyl groups) RL4 was synthesized as follows:A IL four-neck round bottom flask equipped with a thermal couple, Teflon stir paddle, and aDean Stark apparatus attached to a water-cooled condenser was loaded with 217 Flake (90.0 g), toluene (240.8 g) and an amount of toluene equal to the volume of the Dean Stark apparatus. Then, an inert gas blanket was applied. The mixture was refluxed for 30 min to remove water present in the mixture.

[0059] Meanwhile, diacetoxysilane terminated PDMS was prepared by adding XIAMETER™ OFS-1579 (1 1 .78 g) to a mixture of toluene (59.3 g) and bis-silanol-terminated PDMS (1 10.0 g, dp=63) in a 500 ml round bottom flask. Then, a mixture was stirred at room temperature for 1 hr. Diacetoxysilane-terminated PDMS prepared was quickly added to the flask containing 217 Flake at 106 °C. Then, the reaction mixture was refluxed for 2 hours. The reaction mixture was cooled to room temperature and deionized water (18.7 g) was added. Water and acetic acid by-product were removed by azeotropic distillation. The step of addition and removal of water was repeated. Then, volatiles were removed to make a concentrated solution. The step of addition and removal of water was repeated three times. A transparent solution was obtained after filtration. This sample contained a resin - linear polyorganosiloxane block copolymer labelled RL4.

[0060] The resin - linear polyorganosiloxane block copolymers prepared as described above are summarized below in Table 2.Table 2 - Ph T-PDMS RL copolymers used in this invention and information

[0061] The samples of RL1, RL2, RL3, and RL4 (toluene solutions of resin - linear polyorganosiloxane block copolymers) prepared as described above were used in preparation of curable compositions and films thereof (SHFs), as follows: The toluene solution of resin - linear polyorganosiloxane block copolymer, organic mercapto- functional crosslinker, and photoradical initiator were placed in a dental cup and uniformly mixed in a dental mixer. The composition prepared was coated on an ETFE film to prepare 200 mm thick film and dried at 70 °C for 1 hr. The starting materials and amounts in each composition are shown below in Tables 3 and 4.

[0062] Viscoelastic Properties of Uncured Compositions were evaluated as follows: Viscoelastic properties such as complex viscosity, storage modulus and Tan (5) of uncured SHFs were determined by rotational rheometer (ARES-G2 from TA instrument). Viscoelastic profiles were obtained with 25 mm parallel plates using 1 mm thickness samples. After the samples were loaded onto the parallel plate, samples were equilibrated at 20 °C for 5 min. Then, the temperature was ramped up to 120 °C with a rate of 3 °C / min.

[0063] The Curing Procedure for the films was as follows: UV irradiation was conducted by UVitron SkyRay with Raven at 365 nm. After a SHF on an ETFE film was prepared, another ETFE film was placed on top of the SHF. The SHF sandwiched between ETFE fdms was placed in an UV chamber. Then, UV ray at 365 nm was irradiated (250 mW for 16 seconds). After flipping side, another UV ray was irradiated. Total dosage was 8 J / cm2(each side 4 J / cm2).

[0064] Determination of Gel Percentage was performed as follows on the cured films described above. First, a known amount of cured SHF sample (1.0 g) was placed in a 40 ml dental cup. Next, 15.0 g of toluene was added to the cup containing the SHF sample, and the cup was shaken for 1 hour. After decanting toluene solution from the dental cup, the undissolved sample was transferred to an aluminum pan. The sample was dried at 120 °C for 2 hours. The dried sample was thein weighed. “Curability” was determined by gel percentage experiments described below. “Good curability” means cured percentage after UV irradiation was > 50%.

[0065] Determination of Total Transmittance (%T) was evaluated as follows: %T was obtained by Haze Gard Plus using ASTM D1003 method.

[0066] The test results of each sample are shown below in Tables 3 and 4.Table 3 - Comparative Examples

[0067] In Table 3, ND means non -detectable. The data in Table 3 show that the composition did not cure under the conditions tested when the resin - linear polyorganosiloxane block copolymer did not have alkenyl groups (Comparative Example 1, CE.l). The composition alsodid not cure under the conditions tested when the photoradical initiator was omitted, in CE.2. The composition also did not cure under the conditions tested when the crosslinker was omitted or contained insufficient mercapto-functional groups (CE.3 and CE.4). CE.5 showed that when a polydiorganosiloxane gum was used instead of an alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer, the composition was flowable at 25 °C and had insufficient complex viscosity properties for the present application. CE.6 showed that when too much crosslinker was used, the composition was flowable at 25 °C and had insufficient complex viscosity properties for the present application.Table 4 - Working Examples

[0068] The data in Table 4 show that curable silicone compositions that are non-flowable at 25 °C and that have complex viscosity ratio at 25 °C and 120 °C (T]*at25°c / T|*at i2o°c) > 20,alternatively > 100 can be prepared using the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer in the compositions described herein. Furthermore, these radiation curable polyorganosiloxane resin - linear copolymer composition have storage modulus at 25 °C > 0.01 MPa, alternatively > 0.1 MPa and tan (5) < 5.0, alternatively < 2.0, at 25 °C, as measured using the test methods described above. These curable silicone compositions are curable to form cured products useful as encapsulants with good optical transparency (> 94%, alternatively > 95%, up to 100%) with good curability (with gel % > 67%) measured using the test methods described above. Working Examples 1, 2, and 3 show that different mercapto- functional crosslinkers can be used. Working Example 4 shows that the compositions herein are curable even at low photoradical initiator loading. Working Examples 5 and 6 show varying amounts of crosslinker can be used in the compositions herein.

[0069] Due to the firm solid character of SHFs prepared from the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymers at room temperature, the inventors were concerned that efficiency of UV curing would be limited by slow diffusion rate. However, the inventors surprisingly found that UV irradiation at equal to or less than 25 °C for less than 1 minute provided cured films.INDUSTRIAL APPLICABILITY

[0070] In the (opto)electronics industry, there a need for encapsulants that can be made from curable compositions that cure at < 25 °C and in a short time (i.e., less than 5 minutes and alternatively less than 1 minute of UV irradiation) to increase productivity and protect fragile (opto)electronic display components. Curing technologies in silicones are often based on hydrosilylation cure, which requires high temperature and / or long curing time. Therefore, the present radiation curable polyorganosiloxane resin - linear copolymer composition, which is curable at < 25 °C with short curing time is desirable to meet this need. The present radiation curable polyorganosiloxane resin - linear copolymer composition may be non-flowable at 25 °C. The radiation curable polyorganosiloxane resin - linear copolymer composition may have a complex viscosity at 120 °C is 5,000 Pa s or less, wherein a ratio of complex viscosity at 25 °C and complex viscosity at 120 °C (r|*at 25°c / r|*at i2o°c) is greater or equal to 20, alternatively greater than or equal to 100. The radiation curable polyorganosiloxane resin - linear copolymer composition may also have a storage modulus at 25 °C > 0.01 MPa, alternatively > 0.1 MPa and Tan (5) < 5.0 at 25 °C, alternatively < 2.0 at 25 °C, and alternatively < 1.0 at 25 °C measured according to the test methods described above.DEFINITIONS AND USAGE OF TERMS

[0071] All amounts, ratios, and percentages are by weight unless otherwise indicated by the context of the specification. The articles ‘a’, ‘an’, and ‘the’ each refer to one or more, unlessotherwise indicated by the context of specification. The singular includes the plural unless otherwise indicated by the context of the specification. The SUMMARY and ABSTRACT are hereby incorporated by reference. The amounts of all starting materials in a composition total 100%. The transitional phrases “comprising”, “consisting essentially of’, and “consisting of” are used as described in the Manual of Patent Examining Procedure Ninth Edition, Revision 08.2017, Last Revised January 2018 at section §211 1 .03 I., II., and III. 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 disclosure of ranges includes the range itself and also anything subsumed therein, as well as endpoints. Similarly, the disclosure of Markush groups includes the entire group and also any individual members and subgroups subsumed therein. For example, disclosure of the Markush group a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, includes the member alkyl individually; the subgroup alkyl and aryl; and any other individual member and subgroup subsumed therein. Any feature or aspect of the invention may be used in combination with any other feature or aspect recited herein. Abbreviations are as defined below in Table 7.Table 7 - AbbreviationsEmbodiments of the Invention

[0072] In a first embodiment of the invention, an encapsulation process comprises:1) heating a radiation curable polyorganosiloxane resin - linear copolymer composition, wherein the radiation curable polyorganosiloxane resin - linear copolymer composition comprises85 weight parts to 99 weight parts of (A) an alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer, wherein the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer comprises linear blocks and non - linear blocks, wherein each linear block independently comprises 10 to 500 disiloxy units of formula (R2R3SiO2 / 2), wherein each R2and each R3is an independently selected monovalent hydrocarbyl group of 1 to 30 carbon atoms;each non - linear block has a number average molecular weight of at least 500 g / mol, the non - linear blocks comprise trisiloxy units and hydrolyzable groups, and wherein the non - linear blocks further comprise alkenyl groups bonded and aryl groups bonded to silicon atoms; at least 30 mol % of the non - linear blocks are crosslinked with each other, each linear block is linked to at least one non - linear block, and the copolymer has a weight average molecular weight of at least 20,000 g / mol measured by gel permeation chromatography;0.5 weight part to 14.9 weight parts of (B) an organic mercapto- functional crosslinker having at least two mercapto - functional groups per molecule; and0.1 weight part to 10 weight parts of (C) a photoinitiator, thereby forming a flowable composition;2) forming the flowable composition on a substrate, and3) irradiating the composition with ultraviolet radiation, thereby curing the composition to form an encapsulant on the substrate.

[0073] In a second embodiment, the process of the first embodiment further comprises producing a solid film of the radiation curable polyorganosiloxane resin - linear copolymer composition before step 1).

[0074] In a third embodiment, in the process of the first embodiment or the second embodiment step 2) comprises vacuum lamination.

[0075] In a fourth embodiment, in the process of any one of the first to third embodiments, a plurality of features are on the substrate, and the features are encapsulated in step 3).

[0076] In a fifth embodiment, in the process of the fourth embodiment, the features comprise light emitting diodes.

[0077] In a sixth embodiment, in the process of any one of the first to fifth embodiments, all steps of the process are performed at a temperature < 80 °C.

[0078] In a seventh embodiment, in the process of any one of the first to sixth embodiments, the radiation curable polyorganosiloxane resin - linear copolymer composition further comprises an additional starting material selected from the group consisting of (D) a stabilizer, (E) an adhesion promoter, (F) a solvent, and a combination of two or more thereof.

[0079] In an eighth embodiment, the process of the seventh embodiment further comprises dissolving (A) the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer in (F) the solvent, mixing starting materials (A), (B), (C), (F), and optionally one or both of (D) and (E), and thereafter removing (F) the solvent, thereby forming the radiation curablepolyorganosiloxane resin - linear copolymer composition before step 1).

[0080] In a ninth embodiment, in the process of any one of the first to eighth embodiments, in(A) the alkenyl-, aryl- functional polyorganosiloxane resin - linear copolymer each linear block is linked to at least one non - linear block via a moiety of formula, wherein each dashed line represents a covalent bond to another silicon atom in the molecule; R1is an alkenyl group of 2 to 20 carbon atoms, each R2is an independently selected alkyl group of 1 to 20 carbon atoms, each R3is an independently selected alkyl group of 1 to 20 carbon atoms, and R4is an aryl group of 6 to 20 carbon atoms.

[0081] In a tenth embodiment, in the process of the ninth embodiment, in (A) the alkenyl-, aryl- functional polyorganosiloxane resin - linear copolymer, each R1is vinyl, each R2is methyl, each R3is methyl, and each R4is phenyl.

[0082] In an eleventh embodiment, in the process of any one of the first to tenth embodiments, (A) the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer has a Mw of 20,000 g / mol to 500,000 g / mol and an alkenyl content of 0.5 mol% to 5 mol%.

[0083] In a twelfth embodiment, in the process of any one of the first to eleventh embodiments, in (A) the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer, each non - linear block has a number average molecular weight of 500 to 4,000 g / mol.

[0084] In a thirteenth embodiment, in the process of any one of the first to twelfth embodiments, (B) the organic mercapto- functional crosslinker is selected from compounds having formula (B-I), formula (B-II), and a combination thereof, wherein: formula (B-I) is R’mCX(4-m), wherein subscript m is an integer with a value of 2, 3, or 4; each R’ is an independently selected alkyl group of 1 to 20 carbon atoms, each X’ is a mercapto-functional group of formulawherein subscript p is an integer with a value of 0 or 1 ; and formula (B-II) is X’-R”-X’, whereinR” is an alkylene group of 1 to 20 carbon atoms, and each X’ is a mercapto-functional group with a formula selected fromwherein subscript p is an integer with a value of 0 or 1.

[0085] In a fourteenth embodiment, in the process of any one of the first to thirteenth embodiments, (B) the organic mercapto- functional crosslinker is selected from the group consisting of: 3,6-Dioxa-l,8-octanedithiol; Trimethylolpropane Tris(3-mercaptopropionate); Pentaerythritol tetrakis(3-mercaptopropionate); and a combination of two or more thereof.

[0086] In a fifteenth embodiment, in the process of any one of the first to fourteenth embodiments, (C) the photoradical initiator is selected from the group consisting of: 2,4,6- trimethylbenzoyl-diphenyl phosphine oxide; ethyl (2,4,6-trimethylbenzoyl)-phenyl phosphinate; and a combination thereof.

[0087] In a sixteenth embodiment, an article is prepared by the process of any one of the first to fourteenth embodiments..

[0088] In a seventeenth embodiment, the article of the sixteenth embodiment comprises an encapsulant covering LEDs on the substrate.

Claims

CLAIMS:

1. A radiation curable polyorganosiloxane resin - linear copolymer composition comprising:85 weight parts to 99 weight parts of (A) an alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer, wherein the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer comprises linear blocks and non - linear blocks, wherein each linear block independently comprises 10 to 500 disiloxy units of formula (R2R3SiO2 / 2), wherein each R2and each R3is an independently selected monovalent hydrocarbyl group of 1 to 30 carbon atoms; each non - linear block has a number average molecular weight of at least 500 g / mol, the non - linear blocks comprise trisiloxy units and hydrolyzable groups, and wherein the non - linear blocks further comprise alkenyl groups bonded and aryl groups bonded to silicon atoms; at least 30 mol % of the non - linear blocks are crosslinked with each other, each linear block is linked to at least one non - linear block, and the copolymer has a weight average molecular weight of at least 20,000 g / mol measured by gel permeation chromatography;0.5 weight part to 14.9 weight parts of (B) an organic mercapto- functional crosslinker having at least two mercapto - functional groups per molecule; and0.1 weight part to 10 weight parts of (C) a photoinitiator.

2. The composition of claim 1, further comprising an additional starting material selected from the group consisting of (D) a stabilizer, (E) an adhesion promoter, (F) a solvent, and a combination of two or more thereof.

3. The composition of claim 1 or claim 2, wherein each linear block is linked to at least one non- linear block in (A) the alkenyl-, aryl- functional polyorganosiloxane resin - linear block copolymer via a moiety of formula, wherein each dashed line represents a covalent bond to another silicon atom in the molecule; R1is an alkenyl group of 2 to 20 carbon atoms, each R2is an independently selected alkyl group of 1 to 20 carbon atoms, eachR3is an independently selected alkyl group of 1 to 20 carbon atoms, and R4is an aryl group of 6 to 20 carbon atoms.

4. The composition of any one of claims 1 to 3, wherein (A) the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer has a Mw of 20,000 g / mol to 500,000 g / mol and an alkenyl content of 0.5 mol% to 5 mol%; and in (A) the alkenyl-, aryl- functional resin - linear polyorganosiloxane block copolymer, each non - linear block has a number average molecular weight of 500 to 4,000 g / mol.

5. The composition of claim 3, wherein each R1is vinyl, each R2is methyl, each R3is methyl, and each R4is phenyl.

6. The composition of any one of claims 1 to 5, wherein (B) the organic mercapto- functional crosslinker is selected from compounds having formula (B-I), formula (B-II), and a combination thereof, wherein: formula (B-I) is R’111CX(4-m), wherein subscript m is an integer with a value of 2, 3, or 4; each R’ is an independently selected alkyl group of 1 to 20 carbon atoms, each X’ is a mercapto-functional group of formulawherein subscript p is an integer with a value of 0 or 1 ; and formula (B-II) is X’-R”-X’, whereinR” is an alkylene group of 1 to 20 carbon atoms, and each X’ is a mercapto-functional group with a formula selected fromwherein subscript p is an integer with a value of 0 or 1.

7. The composition of claim 6, wherein (B) the organic mercapto- functional crosslinker is selected from the group consisting of: 3,6-Dioxa-l,8-octanedithiol; Trimethylolpropane Tris(3-mercaptopropionate); Pentaerythritol tetrakis(3-mercaptopropionate); and a combination of two or more thereof.

8. The composition of any one of claims 1 to 7, wherein (C) the photoradical initiator is selected from the group consisting of: 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide; ethyl (2,4,6- trimethylbenzoy])-phenyl phosphinate; and a combination thereof.

9. An encapsulation process, wherein the process comprises:1) heating the composition of any one of claims 1 to 8, thereby forming a flowable composition,2) forming the flowable composition on a substrate, and3) irradiating the composition with ultraviolet radiation, thereby curing the composition to form an encapsulant on the substrate.

10. The process of claim 9, further comprising producing a film of the composition before step 1).

11. The process of claim 9 or claim 10, wherein step 2) comprises vacuum lamination.

12. The process of any one of claims 9 to 11, wherein the substrate comprises light emitting diodes.

13. The process of any one of claims 9 to 12, wherein all steps of the process are performed at a temperature < 80 °C.

14. An article prepared by the process of any one of claims 9 to 13.

15. An article comprising the composition of any one of claims 1 to 8 encapsulating at least a portion of a substrate.

Images