JP2024517119A - Silicone pressure sensitive adhesives and compositions and methods for their preparation and use in flexible displays - Patents.com - Google Patents

Abstract

Silicone pressure sensitive adhesives are prepared by curing a hydrosilylation reaction curable composition. Silicone pressure sensitive adhesives adhere to silicone elastomers and are useful in the preparation of components for flexible displays.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
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FIELD OF THEINVENTION
SILICONE PRESSURE SENSITIVE ADHESIVES AND METHODS FOR PREPARATION AND USE THEREOF FIELD OF THEINVENTION The present invention relates to silicone pressure sensitive adhesives and methods for their preparation and use. In particular, the present invention relates to hydrosilylation curable compositions that cure to form silicone pressure sensitive adhesives suitable for use in flexible displays.

Introduction Flexible displays have been developed that can be deformed, for example, by bending, folding, rolling, coiling, or stretching. Flexible displays can be deformed according to the needs of consumers or the usage of the flexible display. Typically, the various components of the display are made of multiple layers, and when the flexible display is deformed, it is important that the layers are adhered to each other and are not damaged, which would cause the components to fail.

A variety of silicone elastomers, including liquid silicone rubbers (LSR) and high consistency rubbers (HCR), can be useful in forming the different layers in flexible displays. Commercially available LSRs include SILASTIC™ 9202-50 LSR, SILASTIC™ LCF 3760, and SILASTIC™ LCF 3600. Optical LSRs include SILASTIC™ MS-1001, MS-1002, MS-1003, MS-4001, MS-4002, and MS-4007, which are moldable optical silicone elastomers, and SYLGARD™ 182, 184, and 186, which are also optical silicone elastomers. Commercially available HCRs include XIAMETER™ RBB-2030-40EN, XIAMETER™ RBB-6660-60EN, XIAMETER™ RBB-2002-30 Base, XIAMETER™ RBB-2004-60, and XIAMETER™ RBB-2220-70. Filled silicone elastomers such as DOWSIL™ VE-8001 flexible silicone adhesive are also suitable. All these silicone elastomers are commercially available from Dow Silicones Corporation of Midland, Michigan, USA.

However, silicone elastomers as described above can suffer from the drawback of being difficult to adhere to other layers in a flexible display. Thus, there is an industrial need for silicone pressure sensitive adhesives that can adhere to silicone elastomers and do not cause failures in flexible displays.

The hydrosilylation reaction curable composition can form a silicone pressure sensitive adhesive. Methods for making the composition and methods for fabricating articles using the composition are provided. The articles can include components of flexible displays.

A partial cross-sectional view of a part 100 of a flexible display is shown.

Reference numeral 100: Part of a flexible display component 101: Substrate 101b: Surface of substrate 101 102: Silicone pressure sensitive adhesive 102a: Surface of silicone pressure sensitive adhesive 102 102b: Opposite surface of silicone pressure sensitive adhesive 102 103: Silicone elastomer 103a: Surface of silicone elastomer 103

The hydrosilylation reaction curable composition for forming a silicone pressure sensitive adhesive comprises
(A) a polydiorganosiloxane gum component,
38.7% to 48.1% by weight, based on the combined weight of starting materials (A) through (F), of (A-1) an aliphatically unsaturated polydiorganosiloxane gum of the unit formula (R ^M ₂ R ^U SiO _1/2 ) ₂ (R ^M ₂ SiO _2/2 ) _a , where each R ^M is an independently selected monovalent hydrocarbon radical of 1 to 30 carbon atoms free of aliphatic unsaturation and each R ^U is an independently selected monovalent aliphatically unsaturated hydrocarbon radical of 2 to 30 carbon atoms, and the subscript a has a value sufficient to impart to the polydiorganosiloxane gum a plasticity of 20 mils (0.51 mm) to 80 mils (2.03 mm); and 0 to <1.2% by weight of (A-2) an aliphatically unsaturated polydiorganosiloxane gum of the unit formula ((HO)R ^M ₂ SiO _1/2 ) ₂ (R ^M ₂ SiO _2/2 ) _a′ , where each R ^M is an independently selected monovalent hydrocarbon radical of 1 to 30 carbon atoms free of aliphatic unsaturation and each subscript a′ has a value sufficient to impart to the polydiorganosiloxane gum a plasticity of 20 mils (0.51 mm) to 80 mils (2.03 mm);
provided that the weight ratio of the aliphatic unsaturated polydiorganosiloxane gum (A-1) to the hydroxyl-terminated polydiorganosiloxane gum (A-2) {(A-1):(A-2) ratio} is ≧32.5:1;
(B) a polyorganosilicate resin component,
42.4% to 50.9% by weight, based on the combined weight of the starting materials (A)-(F), of a capped resin having (B-1) a unit of the formula: (R ^M ₃ SiO _1/2 ) _z (SiO _4/2 ) _o Z _p , where Z is a hydrolyzable group, subscript p is from 0 to a value sufficient to provide the capped resin with a hydrolyzable group content of up to 2%, subscripts z and o have values such that z>4, o>1, and the quantity (z+o) has a value sufficient to provide the capped resin with a number average molecular weight of from 500 g/mol to 2,700 g/mol; and 0 to 1.5% by weight, based on the combined weight of the starting materials (A)-(F), of a capped resin having (B-2) a unit of the formula (R ^M ₃ SiO _1/2 ) _z' (SiO _4/2 ) _o' Z _p' uncapped resin, wherein subscript p' has a value sufficient to provide the uncapped resin with a hydrolyzable group content of >3% to 10%, subscripts z' and o' have values such that z'>4, o'>1, and the quantity (z'+o') has a value sufficient to provide the uncapped resin with a number average molecular weight of 500 g/mol to 5,000 g/mol; (B-1) the capped resin and (B-2) the uncapped resin are present in a combined amount of 42.4% to 52.4% by weight based on the combined weight of the starting materials (A) through (F);
a polyorganosilicate resin component, wherein (A) the polydiorganosiloxane gum component and (B) the polyorganosilicate resin component are present in a weight ratio of (B):(A) (resin:gum ratio) <1.4:1;
0.01% to 5% by weight, based on the total weight of the starting materials (A) to (F), of (C) a hydrosilylation reaction catalyst;
(D) Unit formula: ( _RM2SiO2/2 ⁾ _{e ( HRMSiO2} ^/ ₂ ) _f ( _RM2HSiO1 ^/ ₂ ) _g ( ^RM3SiO1 / ₂ ) (D) a polyorganohydrogensiloxane of formula _(h) , wherein subscript e≧0, subscript f≧0, the quantity (e+f) is 4 to 500, subscript g is 0, 1, or 2, subscript h is 0, 1, or 2, the quantity (g+h)=2, and the quantity (f+g)≧3, wherein (D) the polyorganohydrogensiloxane is present in an amount sufficient to provide a molar ratio of silicon-bonded hydrogen atoms to aliphatically unsaturated hydrocarbon groups of the (A) polydiorganosiloxane gum {(D):(A) ratio} of from 22.0:1 to 57.8:1;
0.05% to 4.65% by weight (E) of a trialkyl borate, based on the total weight of the starting materials (A) to (F);
0% to 5% by weight (F) of a hydrosilylation reaction inhibitor, based on the combined weight of the starting materials (A)-(F);
>0 wt. % to 90 wt. % of (G) a solvent, based on the combined weight of all starting materials in the composition;
and (H) 0 to 5 weight percent of an adhesion promoter, based on the combined weight of the starting materials (A) through (F).

(A) Polydiorganosiloxane Gum Component The hydrosilylation reaction curable composition comprises (A) a polydiorganosiloxane gum component. The polydiorganosiloxane gum component comprises (A-1) an aliphatically unsaturated polydiorganosiloxane gum and (A-2) a hydroxyl-terminated polydiorganosiloxane gum.

The starting material (A-1), an aliphatically unsaturated polydiorganosiloxane gum, has the unit formula: (R ^M ₂ R ^U SiO _1/2 ) ₂ (R ^M ₂ SiO _2/2 ) _a , where each R ^M is an independently selected monovalent hydrocarbon radical of 1 to 30 carbon atoms free of aliphatic unsaturation, each R ^U is an independently selected monovalent aliphatically unsaturated hydrocarbon radical of 2 to 30 carbon atoms, and the subscript a has a value sufficient to impart to the (A-1) aliphatically unsaturated polydiorganosiloxane gum a plasticity of from 20 mils (0.51 mm) to 80 mils (0.203 mm), alternatively from 30 mils (0.76 mm) to 70 mils (1.78 mm), alternatively from 55 mils (1.40 mm) to 65 mils (1.65 mm), which plasticity is in accordance with ASTM D926 by applying a 1 kg load to a spherical sample weighing 4.2 g for 3 minutes at 25° C., the results are measured in 1/1000 inch (mils), and the procedure is based on ASTM D926.

In unit formula (A-1), each R ^M is an independently selected monovalent hydrocarbon group of 1 to 30 carbon atoms free of aliphatic unsaturation. Alternatively, each R ^M may have 1 to 12 carbon atoms, alternatively 1 to 6 carbon atoms. Suitable monovalent hydrocarbon groups for R ^M are exemplified by alkyl groups and aromatic groups such as aryl and aralkyl groups. "Alkyl" means a cyclic, branched or unbranched saturated monovalent hydrocarbon group. Alkyl is exemplified by, but is not limited to, methyl, ethyl, propyl (e.g., isopropyl and/or n-propyl), butyl (e.g., isobutyl, n-butyl, tert-butyl and/or sec-butyl), pentyl (e.g., isopentyl, neopentyl and/or tert-pentyl), hexyl, heptyl, octyl, nonyl, and decyl, as well as branched alkyl groups of 6 or more carbon atoms and cyclic alkyl groups such as cyclopentyl and cyclohexyl. "Aryl" means a fully unsaturated cyclic hydrocarbon group. Aryl includes, but is not limited to, cyclopentadienyl, phenyl, anthracenyl, and naphthyl. Monocyclic aryl groups can have 5 to 9 carbon atoms, alternatively 6 to 7 carbon atoms, alternatively 5 to 6 carbon atoms. Polycyclic aryl groups can have 10 to 17 carbon atoms, alternatively 10 to 14 carbon atoms, alternatively 12 to 14 carbon atoms. "Aralkyl" means an alkyl group having a pendant and/or terminal aryl group, or an aryl group having a pendant alkyl group. Exemplary aralkyl groups include tolyl, xylyl, benzyl, phenylethyl, phenylpropyl, and phenylbutyl. Alternatively, each R ^M may be independently selected from the group consisting of alkyl and aryl. Alternatively, each R ^M may be independently selected from methyl and phenyl. Alternatively, each R ^M may be alkyl. Alternatively, each R ^M may be methyl.

In unit formula (A-1), each R ^{1 U} is an independently selected monovalent aliphatically unsaturated hydrocarbon group of 2 to 30 carbon atoms. Alternatively, each R 1 ^U may have 2 to 12 carbon atoms, alternatively 2 to 6 carbon atoms. Suitable monovalent aliphatically unsaturated hydrocarbon groups include alkenyl and alkynyl groups. "Alkenyl" means a branched or unbranched monovalent hydrocarbon group having one or more carbon-carbon double bonds. Suitable alkenyl groups are exemplified by vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl (including branched and linear isomers of 3 to 7 carbon atoms); and cyclohexenyl. "Alkynyl" means a branched or unbranched monovalent hydrocarbon group having one or more carbon-carbon triple bonds. Suitable alkynyl groups are exemplified by ethynyl, propynyl, and butynyl (including branched and linear isomers of 2 to 4 carbon atoms). Alternatively, each R 1 ^U may be an alkenyl, such as vinyl, allyl, or hexenyl.

Polydiorganosiloxane gums are known in the art and can be prepared by methods such as hydrolysis and condensation of the corresponding organohalosilanes or equilibration of cyclic polydiorganosiloxanes. Examples of polydiorganosiloxane gums suitable for use in the hydrosilylation reaction curable compositions are:
i) dimethylvinylsiloxy-terminated polydimethylsiloxane;
ii) dimethylvinylsiloxy-terminated poly(dimethylsiloxane/methylphenyl)siloxane;
iii) dimethylvinylsiloxy-terminated poly(dimethylsiloxane/diphenyl)siloxane;
iv) phenyl, methyl, vinyl-siloxy terminated polydimethylsiloxanes;
v) dimethylhexenylsiloxy-terminated polydimethylsiloxane;
vi) dimethylhexenyl-siloxy terminated poly(dimethylsiloxane/methylphenyl)siloxane;
vii) dimethylvinylsiloxy-terminated poly(dimethylsiloxane/diphenyl)siloxane;
viii) a combination of two or more of i)-vii). Alternatively, the polydiorganosiloxane gum is exemplified by i) a dimethylvinylsiloxy-terminated polydimethylsiloxane;
v) dimethylhexenylsiloxy terminated polydimethylsiloxane, and a combination of i) and v).

The starting material (A-1), the aliphatically unsaturated polydiorganosiloxane gum, is present in the hydrosilylation reaction curable composition in an amount of at least 38.7% by weight, alternatively at least 40% by weight, alternatively at least 42% by weight, alternatively at least 44% by weight, based on the combined weight of the starting materials (A)-(F), while the amount may be up to 48.1% by weight, alternatively up to 47% by weight, alternatively up to 46% by weight. Alternatively, the amount of (A-1) the aliphatically unsaturated polydiorganosiloxane gum may be 37.8% to 48.1% by weight, alternatively 38.7% to 48.1% by weight, alternatively 42% to 45% by weight, based on the combined weight of the starting materials (A)-(F).

In addition to the (A-1) aliphatically unsaturated polydiorganosiloxane gum, the starting (A) polydiorganosiloxane component may optionally further comprise (A-2) a hydroxyl terminated polydiorganosiloxane gum of the unit formula: (R ^M ₂ R ^U SiO _1/2 ) ₂ (R ^M ₂ SiO _2/2 ) _a ', where R ^M and R ^U are as defined above and the subscript a' has a value sufficient to impart to the (A-2) hydroxyl terminated polydiorganosiloxane gum a plasticity of from 20 mils (0.51 mm) to 80 mils (2.03 mm), alternatively from 30 mils (0.76 mm) to 70 mils (1.78 mm), alternatively from 45 mils (1.14 mm) to 65 mils (1.65 mm), which plasticity is in accordance with ASTM D926 by applying a 1 kg load to a spherical sample weighing 4.2 g for 3 minutes at 25° C., the results are measured in 1/1000 inch (mils), and the procedure is based on ASTM D926.

Hydroxyl-terminated polydiorganosiloxane gums suitable for use as starting materials (A-2) are known in the art and can be prepared by methods such as hydrolysis and condensation of the corresponding organohalosilanes or equilibration of cyclic polydiorganosiloxanes. Examples of hydroxyl-terminated polydiorganosiloxane gums suitable for use as starting materials (A-2) in the hydrosilylation reaction curable compositions are:
i) bis-hydroxyl terminated polydimethylsiloxane;
ii) bis-hydroxyl terminated poly(dimethylsiloxane/methylphenylsiloxane);
iii) bis-hydroxyl terminated poly(dimethylsiloxane/diphenylsiloxane);
iv) phenyl, methyl, hydroxyl-siloxy terminated polydimethylsiloxanes;
v) a combination of two or more of i) through iv). Alternatively, the starting material (A-2) comprises a bis-hydroxyl terminated polydimethylsiloxane.

The starting material (A-2) hydroxyl-terminated polydiorganosiloxane gum is present in the hydrosilylation reaction curable composition in an amount of 0% to <1.2% by weight, based on the combined weight of the starting materials (A)-(F). Alternatively, the (A-2) hydroxyl-terminated polydiorganosiloxane gum may be present in an amount of at least 0.1% by weight, alternatively at least 0.13% by weight, while the amount may be up to 1.1% by weight, alternatively up to 1.06% by weight, on the same basis.

When starting material (A-2) is present, (A-1) the aliphatically unsaturated polydiorganosiloxane gum and (A-2) the bis-hydroxyl terminated polydiorganosiloxane may be present in amounts such that the weight ratio (A-1):(A-2) may be ≧32.5:1. Alternatively, the weight ratio (A-1):(A-2) may alternatively be at least 35:1, alternatively at least 37:1, while at the same time, when (A-2) the hydroxyl terminated polydiorganosiloxane gum is present, the weight ratio (A-1):(A-2) may be up to 50:1, alternatively up to 48:1, alternatively up to 47:1. Alternatively, the ratio (A-1):(A-2) may be from 32.5:1 to 45.3:1.

(B) Polyorganosilicate Resin Component The hydrosilylation reaction curable composition further comprises starting material (B), a polyorganosilicate resin component, which includes (B-1) a capped resin and (B-2) an uncapped resin. A polyorganosilicate resin comprising monofunctional units ("M" units) of the formula R ^M ₃ SiO _1/2 , where R ^M is as defined above, and tetrafunctional silicate units ("Q" units) of the formula SiO _4/2 . Alternatively, at least one third, or at least two thirds, of the R ^M groups are alkyl groups (e.g., methyl groups). Alternatively, the M units may be exemplified by (Me ₃ SiO _1/2 ) and (Me ₂ PhSiO _1/2 ). Polyorganosilicate resins are soluble in solvents such as those listed below exemplified by liquid hydrocarbons such as benzene, toluene, xylene, and heptane, or in liquid organosilicon compounds such as low viscosity linear and cyclic polydiorganosiloxanes.

When prepared, the polyorganosilicate resin comprises M and Q units as described above, and the polyorganosiloxane further comprises units having silicon-bonded hydroxyl groups, and may comprise a neopentamer of the formula Si(OsiR ^M ₃ ) ₄ , where R ^M is as described above, for example, the neopentamer may be tetrakis(trimethylsiloxy)silane. ²⁹ Si NMR spectroscopy can be used to measure the hydroxyl content and molar ratio of M and Q units, which is expressed as {M(resin)}/{Q(resin)}, where the M and Q units are removed from the neopentamer. The M:Q ratio represents the molar ratio of the total number of triorganosiloxy groups (M units) in the resinous portion of the polyorganosilicate resin to the total number of silicate groups (Q units) in the resinous portion. The M:Q ratio may be from 0.5:1 to 1.5:1.

The Mn of the polyorganosilicate resins varies depending on various factors, including the type of hydrocarbon group represented by R ^M present. The Mn of the polyorganosilicate resins refers to the number average molecular weight measured using GPC when the peak representing the neopentamer is excluded from the measurement. The Mn of the polyorganosilicate resins is from 500 g/mol to 5,000 g/mol, alternatively from 2,500 g/mol to 5,000 g/mol, alternatively from 2,700 g/mol to 4,900 g/mol, alternatively from 2,700 g/mol to 4,700 g/mol. A suitable GPC test method for measuring Mn is disclosed in U.S. Pat. No. 9,593,209, column 31, Reference Example 1.

No. 8,580,073 (column 3, line 5 to column 4, line 31) and U.S. Patent Application Publication No. 2016/0376482 (paragraphs [0023] to [0026]) are incorporated herein by reference for disclosing MQ resins, which are suitable polyorganosilicate resins for use in the hydrosilylation reaction curable compositions described herein. The polyorganosilicate resins can be prepared by any suitable method, such as cohydrolysis of the corresponding silanes or a silica hydrosol capping method. The polyorganosilicate resins can be prepared by a silica hydrosol capping process, such as those disclosed in U.S. Patent No. 2,676,182 to Daudt et al., U.S. Patent No. 4,611,042 to Rivers-Farrell et al., and U.S. Patent No. 4,774,310 to Butler et al. The method of Daudt et al. involves reacting a silica hydrosol with a hydrolyzable triorganosilane such as trimethylchlorosilane, a siloxane such as hexamethyldisiloxane, or a mixture thereof under acidic conditions and recovering a copolymer having M and Q units. The resulting copolymer generally contains 2 to 5 weight percent hydroxyl groups.

The intermediates used to prepare the polyorganosilicate resins can be triorganosilanes and silanes or alkali metal silicates containing four hydrolyzable substituents. The triorganosilanes can have the formula R ^M ₃ SiX ¹ , where R ^M is as above, and X ¹ represents a hydrolyzable substituent such as halogen, alkoxy, acyloxy, hydroxyl, oximo, or ketoximo, or a hydrolyzable substituent such as halogen, alkoxy, or hydroxyl. The silanes with four hydrolyzable substituents can have the formula SiX ² ₄ , where each X ² is a halogen, alkoxy, or hydroxyl. Suitable alkali metal silicates include sodium silicates.

The polyorganosilicate resins prepared as described above are uncapped resins, which typically contain silicon-bonded hydroxyl groups, i.e., of the formula HOSi _3/2 and/or HOR ^M ₂ SiO _1/2 . The polyorganosilicate resins may contain >3% to 10% silicon-bonded hydroxyl groups as measured by NMR spectroscopy. In certain applications, it may be desirable for the amount of silicon-bonded hydroxyl groups to be ≦2%, alternatively <0.7%, alternatively less than 0.3%, alternatively less than 1%, alternatively 0.3% to 2%. The silicon-bonded hydroxyl groups formed during the preparation of the polyorganosilicate resins can be converted to trihydrocarbon siloxane groups or different hydrolyzable groups by reacting the silicone resin with a silane, disiloxane or disilazane containing the appropriate end group, in a process known as capping. The silane containing hydrolyzable groups may be added in a molar excess over the amount required to react with the silicon-bonded hydroxyl groups in the polyorganosilicate resin.

If the polyorganosilicate resin is a capped resin, the capped resin may contain 2% or less of units represented by the formula HOSiO3 _/2 and/or HOR ^M2SiO1 _{/ 2} , where R ^M is as defined above, alternatively 0.7% or less, alternatively 0.3% or less, alternatively 0.3% to 0.8%. The concentration of silanol groups present in the polyorganosiloxane can be measured using NMR spectroscopy as described above.

Thus, the polyorganosilicate resin component includes (B-1) a capped resin as described above, and (B-2) an uncapped resin as described above. _The capped resin may have the unit formula: (R ^M SiO _1/2 ) _z (SiO _4/2 ) _o Z _p , where R ^M is as defined above, the subscripts z and o have values such that o>1 and subscript z>4, the quantity (o+z) has a value sufficient to give the capped resin an Mn as described above (e.g., from 500 g/mol to 5,000 g/mol, alternatively from 1,000 g/mol to 4,700 g/mol, alternatively from 2,900 g/mol to 4,700 g/mol, alternatively from 2,900 g/mol to 4,100 g/mol), and the subscript p has a value sufficient to give the capped resin a hydrolyzable group content as described above (e.g., from 0 to 2%, alternatively from 0 to 0.7%, alternatively from 0 to 0.3%). The starting material (B-1) capped resin may be present in an amount of 42.4% to 50.9% by weight based on the combined weight of the starting materials (A) through (F). Alternatively, the (B-1) capped resin may be present in an amount of 44% to 48% by weight, or alternatively 44.7% to 47.4% by weight on the same basis.

The starting material (B-2), the uncapped resin, may have the unit formula (R ^M ₃ SiO _1/2 ) _z' (SiO _4/2 ) _o' Z _p' , where R ^M is as described above, the subscripts z' and o' have values such that o'>1 and subscript z'>4, the quantity (o'+z') has a value sufficient to give the capped resin an Mn as described above (e.g., from 500 g/mol to 5,000 g/mol, alternatively from 1,000 g/mol to 4,700 g/mol, alternatively from 2,700 g/mol to 4,700 g/mol, alternatively from 2,700 g/mol to 4,100 g/mol), and the subscript p' has a value sufficient to give the capped resin a hydrolyzable group content as described above (e.g., >3% to 10%). The starting material (B-2) uncapped resin is optional and the amount may be 0. Alternatively, if used, the (B-2) uncapped resin may be present in an amount of >0% to 1.5% by weight, alternatively 1.25% to 1.45% by weight, alternatively 1.26% to 1.42% by weight, based on the combined weight of the starting materials (A) through (F).

The hydrosilylation reaction curable composition includes a (B) polyorganosilicate resin content in an amount of 42.4% to 52.4% by weight, alternatively 43.7% to 52.3% by weight, and alternatively 46.2% to 48.8% by weight, based on the total weight of the starting materials (A)-(F) (e.g., the combined amount of (B-1) capped resin and (B-2) uncapped resin, based on the total weight of all starting materials in the hydrosilylation reaction curable composition, excluding solvent). When (B-2) uncapped resin is present, the amount of capped resin and uncapped resin in the starting material (B) may be sufficient to provide a weight ratio of uncapped resin:capped resin {i.e., the (B-2):(B-1) ratio} of 0.028:1 to 0.0.032:1, alternatively 0.029:1 to 0.031:1, alternatively 0.03. Alternatively, the (B-2):(B-1) ratio may be at least 0.028, alternatively at least 0.029, while at the same time the (B-2):(B-1) ratio may be at most 0.032, alternatively at most 0.031. Alternatively, the (B-2):(B-1) ratio may be 0.03:1.

The starting (A) polydiorganosiloxane gum component and the starting (B) polyorganosilicate resin component may be present in the hydrosilylation reaction curable composition in an amount sufficient to provide a weight ratio of the (B) polyorganosilicate resin component to the (A) polydiorganosiloxane gum component {i.e., the (B):(A) ratio} of <1.4:1. Alternatively, the (B):(A) ratio may be at least 0.75:1, alternatively at least 0.88:1, alternatively 1:09, while at the same time the (B):(A) ratio may be at most <1.4:1, alternatively at most 1.31:1, alternatively at most 1.13:1. Alternatively, the (B):(A) ratio may be from 1.0:1 to 2.0:1, alternatively from 1.8:1 to 1.9:1.

(C) Hydrosilylation Reaction Catalyst The starting material (C) in the hydrosilylation reaction curable composition is a hydrosilylation reaction catalyst. Hydrosilylation reaction catalysts are known in the art and are commercially available. Hydrosilylation reaction catalysts include platinum group metal catalysts. Such hydrosilylation reaction catalysts can be (C-1) a metal selected from platinum, rhodium, ruthenium, palladium, osmium, and iridium; alternatively, the metal can be platinum. Alternatively, the hydrosilylation reaction catalyst may be (C-2) a compound of such a metal, for example, chloridetris(triphenylphosphane)rhodium(I) (Wilkinson's catalyst), a rhodium diphosphine chelate such as [1,2-bis(diphenylphosphino)ethane]dichlorodirhodium or [1,2-bis(diethylphospino)ethane]dichlorodirhodium, chloroplatinic acid (Speier's catalyst), chloroplatinic acid hexahydrate, or platinum dichloride. Alternatively, the hydrosilylation reaction catalyst may be (C-3) a complex of a platinum group metal compound with an alkenyl-functional organopolysiloxane oligomer, or (C-4) a platinum group metal compound microencapsulated in a matrix or core-shell type structure. Complexes of platinum alkenyl-functional organopolysiloxane oligomers include platinum complexes of 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane (Karstedt's catalyst). Alternatively, the hydrosilylation catalyst may comprise a complex microencapsulated in a (C-5) resin matrix. Exemplary hydrosilylation reaction catalysts are described in U.S. Pat. Nos. 2,823,218 to Speier, 3,159,601 to Ashby, 3,220,972 to Lamoreaux, 3,296,291 to Chalk et al., 3,419,593 to Willing, 3,516,946 to Modic, 3,715,334 to Karstedt, 3,814 to Karstedt, and 3,972 to Karstedt. No. 3,928,629 to Chandra, No. 3,989,668 to Lee et al., No. 4,766,176 to Lee et al., No. 4,784,879 to Lee et al., No. 5,017,654 to Togashi, No. 5,036,117 to Chung et al., and No. 5,175,325 to Brown, as well as European Patent No. 0 347 895(A) to Togashi et al. Hydrosilylation catalysts are commercially available, for example, SYL-OFF™ 4000 Catalyst and SYL-OFF™ 2700 are available from Dow Silicones Corporation.

The amount of hydrosilylation catalyst used herein will vary depending on various factors, such as the selection of the starting materials (D) polyorganohydrogensiloxane and (A) polydiorganosiloxane gum components and their respective silicon-bonded hydrogen atom (SiH) and aliphatically unsaturated group contents, and the platinum group metal content in the selected catalyst, but the amount of hydrosilylation catalyst is sufficient to catalyze the hydrosilylation reaction of SiH with aliphatically unsaturated groups, or the amount of catalyst is sufficient to provide 1 ppm to 6,000 ppm of platinum group metal, or 1 ppm to 1,000 ppm, or 1 ppm to 100 ppm of platinum group metal, based on the total weight of the starting materials containing silicon-bonded hydrogen atoms and aliphatically unsaturated hydrocarbon groups, on the same basis. Alternatively, when the hydrosilylation catalyst comprises a platinum-organosiloxane complex, the amount of the hydrosilylation catalyst may be 0.01% to 5% by weight, based on the combined weight of the starting materials (A) to (F).

(D) Polyorganohydrogensiloxane Starting material (D) in the hydrosilylation reaction curable composition is a polyorganohydrogensiloxane of the unit formula: (R ^M ₂ SiO _2/2 ) _e (HR ^M SiO _2/2 ) _f (R ^M ₂ HSiO _1/2 ) _g (R ^M ₃ SiO _1/2 ) _h , where R ^M is as defined above, subscript e ≧ 0, subscript f ≧ 0, the quantity (e+f) is 4-500, subscript g is 0, 1, or 2, subscript h is 0, 1, or 2, the quantity (g+h)=2, and the quantity (f+g) ≧ 3. Alternatively, the quantity (f+g) may be sufficient to provide the polyorganohydrogensiloxane with a silicon-bonded hydrogen content of from 0.5% to 2%, alternatively from 0.6% to 1.5%, where the silicon-bonded hydrogen (Si—H) content of the polyorganohydrogensiloxane can be determined using quantitative infrared analysis according to ASTM E168.

Suitable polyorganohydrogensiloxanes are
(D-1) bis-dimethylhydrogensiloxy-terminated poly(dimethyl/methylhydrogen)siloxane,
(D-2) bis-dimethylhydrogensiloxy-terminated polymethylhydrogensiloxane,
(D-3) bis-trimethylsiloxy-terminated poly(dimethyl/methylhydrogen)siloxane,
(D-4) bis-trimethylsiloxy terminated polymethylhydrogensiloxanes, and (D-5) combinations of two or more of (D-1), (D-2), (D-3), and (D-4). Methods for preparing polyorganohydrogensiloxanes, such as the hydrolysis and condensation of organohydridohalosilanes, are known in the art, see, for example, U.S. Patent No. 3,957,713 to Jeram et al. and U.S. Patent No. 4,329,273 to Hardman et al. Polyorganohydrogensiloxanes can also be prepared as described, for example, in U.S. Patent No. 2,823,218 to Speier et al., which discloses organohydrogensiloxane oligomers and linear polymers such as 1,1,1,3,3-pentamethyldisiloxane, bis-trimethylsiloxy terminated polymethylhydrogensiloxane homopolymer, bis-trimethylsiloxy terminated poly(dimethyl/methylhydrogen)siloxane copolymer, and cyclic polymethylhydrogensiloxane. Polyorganohydrogensiloxanes are also commercially available, for example, from Gelest, Inc. (Morrisville, Pennsylvania, USA), for example, HMS-H271, HMS-071, HMS-993, HMS-301, HMS-301 R, HMS-031, HMS-991, HMS-992, HMS-993, HMS-082, HMS-151, HMS-013, HMS-053, HAM-301, HPM-502, and HMS-HM271.

The amount of polyorganohydrogensiloxane in the hydrosilylation reaction curable composition is 0.1% to 5% based on the combined weight of starting materials (A)-(F). Alternatively, the amount of polyorganohydrogensiloxane in the hydrosilylation reaction curable composition may be at least 0.1%, alternatively at least 0.25%, alternatively at least 0.3%, while the amount may be up to 5%, alternatively up to 2.5%, alternatively up to 1.5%, alternatively up to 1%, on the same basis.

The ratio of silicon-bonded hydrogen to aliphatically unsaturated groups is important when relying on a hydrosilylation curing process. Generally, this is determined by calculating the total weight percent of aliphatically unsaturated groups (e.g., vinyl [V]) in the composition and the total weight percent of silicon-bonded hydrogen [H] in the composition, where the molecular weight of hydrogen is 1 and the molecular weight of vinyl is 27, the molar ratio of silicon-bonded hydrogen to vinyl is 27 [H]/[V]. The starting materials (A) polydiorganosiloxane gum component and (D) polyorganohydrogensiloxane may be present in the hydrosilylation reaction curable composition in an amount sufficient to provide a molar ratio of silicon-bonded hydrogen atoms to aliphatically unsaturated hydrocarbon groups {(D):(A) ratio} of at least 22.0:1, alternatively at least 28.7:1, while the ratio may be up to 57.8:1, alternatively up to 57.6:1. Alternatively, the (D):(A) ratio may be from 22.0:1 to 57.8:1, alternatively from 22.0:1 to 57.6:1, alternatively from 57.5:1 to 57.6:1.

(E) Trialkyl Borate The starting material (E) in the hydrosilylation reaction curable composition is a trialkyl borate of the formula R ^A ₃ B, where each R ^A is an independently selected alkyl group of 1 to 30 carbon atoms, alternatively 1 to 12 carbon atoms, alternatively 1 to 6 carbon atoms. The alkyl group may be methyl, ethyl, propyl (e.g., isopropyl or n-propyl), butyl (e.g., isobutyl, n-butyl, tert-butyl, or sec-butyl), pentyl (e.g., isopentyl, neopentyl, or tert-pentyl), hexyl, a branched alkyl group of 6 carbon atoms, or a cyclic alkyl group such as cyclopentyl or cyclohexyl. Examples of suitable trialkyl borates include trimethyl borate, triethyl borate, tributyl borate, and combinations of two or more thereof. Alternatively, the trialkyl borate may be triethyl borate.

Trialkyl borates are known in the art and can be prepared by known methods, such as those described in U.S. Patent No. 3,020,308 to Stange. Trialkyl borates are also commercially available, for example, triethyl borate is available from Meryer (Shanghai) Chemical Technology Co., Ltd., and trialkyl borate additives for silicone compositions are also known in the art, for example, DOWSIL™ 7429 PSA Additive available from Dow Silicones Corporation.

The amount of (E) trialkyl borate added to the hydrosilylation curable composition is 0.1% to 4.65% by weight based on the total weight of the starting materials (A) to (F). Alternatively, the amount of (E) trialkyl borate may be at least 0.1%, alternatively at least 0.5%, alternatively at least 0.8%, while the amount may be up to 4.65%, alternatively up to 4.64%, alternatively up to 4.63%, alternatively up to 4.2%, alternatively up to 4.13% by weight on the same basis. Alternatively, the amount of (E) trialkyl borate may be 4.63% to 4.65%, alternatively up to 4.64% by weight on the same basis.

(F) Hydrosilylation Reaction Inhibitors Starting material (F) is an optional hydrosilylation reaction inhibitor (inhibitor) that can be used to alter the rate of the hydrosilylation reaction compared to a composition containing the same starting material except for the inhibitor. Starting material (F) may be selected from the group consisting of (F-1) acetylenic alcohols, (F-2) silylated acetylenic alcohols, (F-3) ene-yne compounds, (F-4) triazoles, (F-5) phosphines, (F-6) mercaptans, (F-7) hydrazines, (F-8) amines, (F-9) fumarates, (F-10) maleates, (F-11) ethers, (F-12) carbon monoxide, (F-13) alkenyl-functional siloxane oligomers, and (F-14) combinations of two or more thereof. Alternatively, the hydrosilylation reaction inhibitor may be selected from the group consisting of (F-1) acetylenic alcohols, (F-2) silylated acetylenic alcohols, (F-9) fumarates, (F-10) maleates, (F-13) carbon monoxide, (F-14) combinations of two or more thereof.

Acetylenic alcohols are exemplified by 3,5-dimethyl-1-hexyn-3-ol, 1-butyn-3-ol, 1-propyn-3-ol, 2-methyl-3-butyn-2-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3-phenyl-1-butyn-3-ol, 4-ethyl-1-octyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, and 1-ethynyl-1-cyclohexanol, and combinations thereof. Acetylenic alcohols are known in the art and are commercially available from a variety of sources, see, for example, U.S. Patent No. 3,445,420 to Kookootsedes et al. Alternatively, the inhibitor may be a silylated acetylenic compound. Without wishing to be bound by theory, it is believed that the addition of the silylated acetylenic compound reduces the yellowing of the reaction products prepared from the hydrosilylation reaction as compared to reaction products from the hydrosilylation of starting materials that do not contain the silylated acetylenic compound or that contain an organic acetylenic alcohol inhibitor such as those described above. The silylated acetylene compounds are (3-methyl-1-butyn-3-oxy)trimethylsilane, ((1,1-dimethyl-2-propynyl)oxy)trimethylsilane, bis(3-methyl-1-butyn-3-oxy)dimethylsilane, bis(3-methyl-1-butyn-3-oxy)silanemethylvinylsilane, bis((1,1-dimethyl-2-propynyl)oxy)dimethylsilane, methyl(tris(1,1-dimethyl-2-propynyloxy))silane, methyl(tris(3-methyl-1-butyn-3-oxy))silane, (3-methyl-1-butyn-3-oxy)dimethylphenylsilane, (3-methyl-1-butyn-3-oxy)dimethylhexenylsilane, (3-methyl-1-butyn-3-oxy)triethylsilane, bis(3-methyl-1- silane, (3,5-dimethyl-1-hexyne-3-oxy)trimethylsilane, (3-phenyl-1-butyne-3-oxy)diphenylmethylsilane, (3-phenyl-1-butyne-3-oxy)dimethylphenylsilane, (3-phenyl-1-butyne-3-oxy)dimethylvinylsilane, (3-phenyl-1-butyne-3-oxy)dimethylhexenylsilane, (cyclohexyl-1-ethyne-1-oxy)dimethylhexenylsilane, (cyclohexyl-1-ethyne-1-oxy)dimethylvinylsilane, (cyclohexyl-1-ethyne-1-oxy)diphenylmethylsilane, (cyclohexyl-1-ethyne-1-oxy)trimethylsilane, and combinations thereof. The silylated acetylenic compounds useful as inhibitors herein can be prepared by methods known in the art, for example, U.S. Patent No. 6,677,407 to Bilgrien et al. discloses silylation of the above acetylenic alcohols by reaction with chlorosilanes in the presence of an acid acceptor.

Alternatively, the inhibitor may be an ene-yne compound, such as 3-methyl-3-penten-1-yne, 3,5-dimethyl-3-hexen-1-yne, and combinations thereof. Alternatively, the inhibitor may include a triazole, exemplified by benzotriazole. Alternatively, the inhibitor may include a phosphine. Alternatively, the inhibitor may include a mercaptan. Alternatively, the inhibitor may include a hydrazine. Alternatively, the inhibitor may include an amine. The amine is exemplified by tetramethylethylenediamine, 3-dimethylamino-1-propyne, n-methylpropargylamine, propargylamine, 1-ethynylcyclohexylamine, or combinations thereof. Alternatively, the inhibitor may include a fumarate. Fumarates include dialkyl fumarates, such as diethyl fumarate, dialkenyl fumarates, such as diallyl fumarate, and dialkoxyalkyl fumarates, such as bis-(methoxymethyl)ethyl fumarate. Alternatively, the inhibitor may include a maleate. Maleates include dialkyl maleates such as diethyl maleate, dialkenyl maleates such as diallyl maleate, and dialkoxyalkyl maleates such as bis-(methoxymethyl)ethyl maleate. Alternatively, the inhibitor may include an ether.

Alternatively, the inhibitor may include carbon monoxide. Alternatively, the inhibitor may include an alkenyl-functional siloxane oligomer, which may be cyclic or linear, such as methylvinylcyclosiloxane, exemplified by 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane, 1,3-divinyl-1,3-diphenyl-1,3-dimethyldisiloxane, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, and combinations of two or more thereof. Compounds useful as inhibitors as described above are commercially available, for example, from Sigma-Aldrich Inc. or Gelest, Inc., and are known in the art, see, for example, U.S. Patent No. 3,989,667 to Lee et al. Suitable inhibitors for use herein are exemplified by those described as Stabilizer E in paragraphs [0148] to [0165] of U.S. Patent Application Publication No. 20007/0099007.

The amount of inhibitor will vary depending on a variety of factors, such as the desired pot life, whether the composition is a one-part or multi-part composition, the particular inhibitor used, and the selection and amount of (C) hydrosilylation reaction catalyst. However, if present, the amount of (F) inhibitor may range from 0% to 5%, alternatively 0% to 1%, alternatively 0.001% to 1%, alternatively 0.01% to 0.5%, alternatively 0.0025% to 0.025%, based on the combined weight of the starting materials (A)-(F) in the hydrosilylation reaction curable composition.

(G) Solvent The hydrosilylation reaction curable composition further comprises a solvent as a starting material (G). The solvent may be an organic solvent such as a hydrocarbon, a ketone, an acetate, an ether, and/or a cyclic siloxane having an average degree of polymerization of 3 to 10. A suitable hydrocarbon for the solvent may be (G-1) an aromatic hydrocarbon such as benzene, benzene, toluene, or xylene, (G-2) an aliphatic hydrocarbon such as hexane, heptane, octane, or isoparaffin, or (G-3) a combination thereof. Alternatively, the solvent may be a glycol ether such as propylene glycol methyl ether, dipropylene glycol methyl ether, or propylene glycol n-butyl ether. Suitable ketones include acetone, methyl ethyl ketone, or methyl isobutyl ketone. Suitable acetates include ethyl acetate or isobutyl acetate. Suitable ethers include diisopropyl ether or 1,4-dioxane. Suitable cyclic siloxanes having a degree of polymerization of 3 to 10, alternatively 3 to 6, include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and/or decamethylcyclopentasiloxane. Alternatively, the solvent may be selected from the group consisting of benzene, toluene, xylene, heptane, ethylbenzene, ethyl acetate, and combinations of two or more thereof.

The amount of solvent will vary depending on various factors such as the type of solvent selected and the amount and type of other starting materials selected for the hydrosilylation reaction curable composition. However, the amount of solvent may range from >0% to 90%, alternatively 0% to 60%, alternatively 20 to 60%, alternatively 45% to 65%, alternatively 50% to 60%, based on the combined weight of all starting materials in the hydrosilylation reaction curable composition. The solvent may be added during the preparation of the hydrosilylation reaction curable composition, for example, to aid in the mixing and delivery of one or more of the starting materials described above. All or a portion of the solvent may be added with one or more of the other starting materials. For example, the polyorganosilicate resin and/or the hydrosilylation reaction catalyst may be dissolved in a solvent prior to combining with the other starting materials in the hydrosilylation reaction curable composition. All or a portion of the solvent may be optionally removed after preparation of the hydrosilylation reaction curable composition.

(H) Anchorage Additive The starting material (H) in the hydrosilylation reaction curable composition is an anchorage additive. Without wishing to be bound by theory, it is believed that the anchorage additive facilitates bonding to a substrate by a silicone pressure sensitive adhesive prepared by curing the hydrosilylation reaction curable composition described herein.

Suitable fixing additives for the starting material (H) include silane coupling agents such as methyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, bis(trimethoxysilyl)propane, and bis(trimethoxysilylhexane, as well as mixtures or reaction mixtures of such silane coupling agents. Alternatively, the fixing additive may be tetramethoxysilane, tetraethoxysilane, dimethyldimethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, or 3-methacryloxypropyltrimethoxysilane.

Other suitable adhesion promoters are exemplified by reaction products of vinyl alkoxysilanes with epoxy-functional alkoxysilanes; reaction products of vinyl alkoxysilanes with epoxy-functional alkoxysilanes; and combinations (e.g., physical blends and/or reaction products) of polyorganosiloxanes having at least one aliphatically unsaturated hydrocarbon group and at least one hydrolyzable group per molecule with epoxy-functional alkoxysilanes (e.g., a combination of a hydroxy-terminated vinyl-functional polydimethylsiloxane with glycidoxypropyltrimethoxysilane).

Exemplary fixing additives are known in the art and are disclosed, for example, in U.S. Pat. No. 9,562,149, U.S. Patent Application Publication No. 2003/0088042, U.S. Patent Application Publication No. 2004/0254274, U.S. Patent Application Publication No. 2005/0038188, U.S. Patent Application Publication No. 2012/0328863 at paragraph [0091], and U.S. Patent Application Publication No. 2017/0233612 at paragraph [0041], and European Patent No. 0 556 023. Fixing additives are commercially available. For example, SYL-OFF™ 9250, SYL-OFF™ 9176, SYL-OFF™ 297, and SYL-OFF™ 397 are available from Dow Silicones Corporation, Midland, Michigan, USA. Other exemplary adhesion promoters include (G-1) vinyltriacetoxysilane, (G-2) glycidoxypropyltrimethoxysilane, and (G-3) a combination of (G-1) and (G-2). The combination (G-3) may be a mixture and/or a reaction product.

The amount of the fixative additive will vary depending on various factors, such as the type of substrate to which the silicone pressure sensitive adhesive is to be adhered. However, if present, the amount of fixative additive may be from 0.5 to 5%, alternatively from 0.5% to 3%, alternatively from 0.5% to 2.5%, based on the combined weight of all starting materials, excluding solvent, in the hydrosilylation reaction curable composition.

Methods for Making the Hydrosilylation Reaction Curable Composition The hydrosilylation reaction curable composition can be prepared by a process that includes combining all of the starting materials described above in any convenient manner, such as by mixing at ambient or elevated temperature. The hydrosilylation reaction inhibitor may be added prior to the hydrosilylation reaction catalyst, for example, when the hydrosilylation reaction curable composition is prepared at elevated temperature and/or when the hydrosilylation reaction curable composition is prepared as a one-part composition.

The method may further include delivering one or more starting materials (e.g., a hydrosilylation reaction catalyst and/or a polyorganosilicate resin) in a solvent, which may be dissolved in the solvent when combined with one or more other starting materials in the hydrosilylation reaction curable composition. Those skilled in the art will appreciate that if it is desired that the resulting hydrosilylation reaction curable composition be solvent-free (i.e., free of solvent or may contain trace amounts of residual solvent from the delivery of the starting materials), the solvent may be removed after mixing two or more of the starting materials, in which case no solvent is intentionally added to the hydrosilylation reaction curable composition.

Alternatively, the hydrosilylation reaction curable composition may be prepared as a multi-part composition, e.g., where the hydrosilylation reaction curable composition is stored for an extended period of time prior to use, e.g., up to 6 hours prior to application of the hydrosilylation reaction curable composition to an optical silicone elastomer or other substrate. In a multi-part composition, the hydrosilylation reaction catalyst is stored in a separate part from any starting material having silicon-bonded hydrogen atoms, e.g., polyorganohydrogensiloxane, and the parts are combined immediately prior to use of the hydrosilylation reaction curable composition.

For example, the multi-part composition may be prepared by combining starting materials including a polydiorganosiloxane gum component, a polyorganohydrogensiloxane, and optionally at least some of the other starting materials described above (other than the hydrosilylation reaction catalyst) by any convenient method, such as mixing, to form a base. The curing agent may be prepared by combining starting materials including a polydiorganosiloxane gum, a hydrosilylation reaction catalyst, and optionally at least some of the other starting materials described above (other than the polyorganohydrogensiloxane) by any convenient method, such as mixing. The starting materials may be mixed at ambient or elevated temperatures. The hydrosilylation reaction inhibitor may be included in one or more of the base, the curing agent part, or a separate additive part. The polyorganosilicate resin may be added to the base, the curing agent part, or a separate additive part. Alternatively, the polyorganosiloxane resin may be added to the base. A solvent may be added to the base. Alternatively, some or all of the starting materials, including the polyorganosilicate resin, and the solvent may be added in a separate additive part. When using a two-part composition, the weight ratio of the amount of base part to the amount of hardener part may range from 1:1 to 10:1. The hydrosilylation reaction curable composition will cure by a hydrosilylation reaction to form a silicone pressure sensitive adhesive.

Method of Use The above method may further include one or more additional steps. The hydrosilylation reaction curable composition prepared as above may be used to form an adhesive article, such as a silicone pressure-sensitive adhesive, on a substrate, which is prepared by curing the above hydrosilylation reaction curable composition.Therefore, the method may further include applying the hydrosilylation reaction curable composition to a substrate.

Applying the hydrosilylation reaction curable composition to a substrate can be carried out by any convenient means. For example, the hydrosilylation reaction curable composition can be applied to a substrate by a gravure coater, a comma coater, an offset coater, an offset gravure coater, a roller coater, a reverse roller coater, an air knife coater, or a curtain coater.

The substrate may be any material capable of withstanding the curing conditions (described below) used to cure the hydrosilylation reaction curable composition to form a silicone pressure sensitive adhesive on the substrate. For example, any substrate capable of withstanding heat treatment at temperatures of 120° C. or higher, or even 150° C., is suitable. Examples of suitable materials for such substrates include polymeric films and/or foams, which may include polyimide (PI), polyetheretherketone (PEEK), polyethylene naphthalate (PEN), liquid crystal polyarylate, polyamideimide (PAI), polyether sulfide (PES), polyethylene terephthalate (PET), polycarbonate (PC), polymethylmethacrylate (PMMA), thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), polyethylene (PE), or polypropylene (PP). Alternatively, the substrate can be glass. Alternatively, the substrate can be a release liner, for example, when the silicone pressure sensitive adhesive is used in a dry casting process. The thickness of the substrate is not critical, but the thickness can be from 5 μm to 300 μm, or from 10 μm to 200 μm. Alternatively, the substrate can be selected from the group consisting of PE, PU, TPE, TPU, and silicone elastomers.

Liquid silicone rubber (LSR) and high viscosity rubber (HCR) can be used for the silicone elastomer. The silicone elastomer can be selected based on the application in the flexible display device, i.e., the part of the flexible display device being fabricated.

For example, optical silicone elastomers (optical LSRs) are known in the art and are described, for example, in U.S. Patent No. 8,859,693 to Hasegawa et al. and U.S. Patent No. 8,853,332 to Akitomo et al. Optical LSRs are commercially available. For example, optical LSRs include SILASTIC™ MS-1001, MS-1002, MS-1003, MS-4001, MS-4002, and MS-4007, which are moldable optical silicone elastomers, and SYLGARD™ 182, 184, and 186, which are other optical silicone elastomers, all of which are commercially available from Dow Silicones Corporation. These LSRs are suitable for fabricating optical components in flexible displays.

Alternatively, when the component of the flexible display being fabricated is a lens (frame) component, an LSR such as SILASTIC™ 9202-50 LSR, SILASTIC™ LCF 3760, and SILASTIC™ LCF 3600, or an HCR such as XIAMETER™ RBB-2030-40EN, XIAMETER™ RBB-6660-60EN, XIAMETER™ RBB-2002-30 Base, XIAMETER™ RBB-2004-60, or XIAMETER™ RBB-2220-70 may be used.

Alternatively, when the part of the flexible display being fabricated is a hinge part, a filled silicone elastomer such as DOWSIL™ VE-8001 flexible silicone adhesive can be used. All silicone elastomer brands DOWSIL™, SILASTIC™, SYLGARD™, and XIAMETER™ are commercially available from Dow Silicones Corporation.

To improve bonding of the silicone pressure sensitive adhesive to a substrate, the method of forming the adhesive article may optionally further include treating the substrate prior to applying the hydrosilylation reaction curable composition. Treating the substrate may be carried out by any convenient technique, such as applying a primer or subjecting the substrate to a corona discharge treatment, etching, or plasma treatment prior to applying the hydrosilylation reaction curable composition to the substrate.

The methods described herein may optionally further include applying a removable release liner to the silicone pressure sensitive adhesive on the side opposite the substrate, for example to protect the silicone pressure sensitive adhesive prior to use of the adhesive article. The release liner may be applied before, during, or after curing of the hydrosilylation reaction curable composition. The adhesive article may be a component for use in a flexible display device, such as an optical component, a lens (frame) component, or a hinge component.

Use of Silicone Pressure Sensitive Adhesives in Components of Flexible Displays Figure 1 shows a partial cross-sectional view of a flexible display component (100). The component (100) comprises a silicone pressure sensitive adhesive (102) having a surface (102a) and an opposing surface (102b). The opposing surface (102b) of the silicone pressure sensitive adhesive (102) adheres to a surface (103a) of a silicone elastomer (103) with a peel adhesion of >400 g/inch as measured by the test method described in the Examples below. The silicone pressure sensitive adhesive (102) may have a thickness of 10 μm to 200 μm. The silicone pressure sensitive adhesive (102) is adhered to a substrate (101) having a surface (101a) and an opposing surface (101b). The surface (102a) of the silicone pressure sensitive adhesive (102) is in contact with the opposing surface (101b) of the substrate (101). The substrate (101) may be selected from the group consisting of PE, PU, TPU, TPE and silicone elastomer (which may be the same or different from the silicone elastomer (103)) and may have a thickness of 10 μm to 200 μm. The silicone elastomer (103) may be HCR as described above.

The hydrosilylation reaction curable composition and method described above can be used to manufacture flexible display components (100) by wet casting. For example, the hydrosilylation reaction curable composition can be applied to the opposite surface (101b) of the substrate (101) and cured to form a silicone pressure sensitive adhesive (102). Alternatively, the hydrosilylation reaction curable composition described herein can be applied to the surface (103a) of a silicone elastomer (103) and cured to form a silicone pressure sensitive adhesive (102). Alternatively, the hydrosilylation reaction curable composition can be applied to the surface of a release liner and cured to form a silicone pressure sensitive adhesive (102). The silicone elastomer (103) can then be contacted with the opposite surface (102b) of the silicone pressure sensitive adhesive (102), and the substrate (101) can be contacted with the surface (102a) of the silicone pressure sensitive adhesive (102). Pressure may be applied to bond the layers of substrate (101), silicone pressure sensitive adhesive (102), and silicone elastomer (103) together.

The following examples are provided to illustrate the invention to one of ordinary skill in the art and should not be construed as limiting the invention as claimed. The starting materials used herein are listed in Table 1.

In Table 1, DOWSIL™, SILASTIC™, and SYL-OFF™ brand starting materials were commercially available from Dow Silicones Corporation.

In this Reference Example 1, a sample of a hydrosilylation reaction curable composition was prepared as follows using the starting materials and amounts shown in Table 2 below. Amounts are in parts by weight unless otherwise specified. The starting material (A) polydiorganosiloxane gum component and the starting material (B) polyorganosilicate resin component were dissolved in (G) solvent with mixing until the resulting mixture was homogenous. Next, the starting material (F) hydrosilylation reaction inhibitor was thoroughly blended into the above mixture. Next, the starting material (E) trialkyl borate was thoroughly blended into the above mixture. Next, the starting material (D) polyorganohydrogensiloxane was thoroughly blended into the above mixture. Next, optionally, the starting material (H) fixative additive (if used) was thoroughly blended into the above mixture. Finally, the starting material (C) hydrosilylation reaction catalyst was added and mixed until homogenous. All starting materials were mixed at RT. The starting materials and their amounts (by weight) are shown in Tables 2 and 3 below.

The hydrosilylation reaction curable compositions in Tables 2 and 3 contained small amounts of residual solvent 1 that were incorporated with the starting material.

Prior to coating the hydrosilylation reaction curable composition on the substrate, DOWSIL™ 7499 PSA Primer was coated on the substrate at a thickness sufficient to provide a dry coat weight of 0.20 gsm after heating in an oven at 120° C. for 0.5 minutes. The primer layer on the substrate provided sufficient bonding between the substrate and the cured silicone pressure sensitive adhesive. In this Reference Example 2, the hydrosilylation reaction curable composition was coated on the substrate and cured according to the following procedure. Each sample prepared as above was applied on a 50 μm thick PET film at a thickness sufficient to provide a dry coat weight of 50 μm after heating in an oven at 140° C. for 2 minutes.

The resulting tape samples were applied to substrates with the silicone pressure sensitive adhesive in contact with the substrate. The substrates were SUS and Si Rubber A, and after contacting the silicone pressure sensitive adhesive with the substrate, the samples were held at RT for 20 minutes before testing. This test was repeated, but the samples were held at 70°C for 1 day before testing.

In this Reference Example 3, samples prepared as described in Reference Example 2 were tested as follows. Each tape sample prepared as above was tested for adhesion to SUS and Si Rubber A substrates by peeling each tape from the substrate and determining if there was any silicone pressure sensitive adhesive transferred from the PET film onto the substrate. An adhesion/peel tester AR-1500 was used. Each PET sheet was 1 inch wide. The peel speed and peel angle were 0.3 m/min and 180°, respectively. The units were grams/in. The results are shown in Tables 6 and 7 below.

The test method for adhesive strength to SUS refers to the test standard ASTM D3330.
The stainless steel plate is cleaned with a solvent. A tape sample (1 inch wide) is applied to the stainless steel plate. It is rolled twice in each direction at a speed of 10 mm/sec using a standard 2 kg test roller. After a rest time of 20 minutes, the sample is peeled from the plate using an AR-1500 at a peel angle of 180° and a speed of 300 mm/min.

The adhesion test method to silicone rubber A refers to test standard ASTM D3330. The silicone rubber sheet is cleaned with a solvent. A tape sample (1 inch, 25.4 mm wide) is applied to the silicone rubber sheet. Roll twice in each direction at a speed of 10 mm/sec with a standard 2 kg test roller. After a dwell time of 20 minutes, the sample is peeled from the silicone rubber sheet using an AR-1500 at a peel angle of 180° and a speed of 300 mm/min.

Adhesion to silicone rubber (70°C-1 day) test method refers to test standard ASTM D3330. Clean the silicone rubber sheet with a solvent. Apply a tape sample (1 inch, 25.4 mm wide) to the silicone rubber sheet. Roll twice in each direction with a standard 2 kg test roller at a speed of 10 mm/sec. After aging the sample at 70°C for 1 day (24 hours), peel the sample from the silicone rubber sheet using an AR-1500 with a peel angle of 180° and a speed of 300 mm/min.

The test method for rheological data (Tg, G' at -20°C, 25°C and 100°C) refers to test standard ASTM D4440-15.
Cured pure silicone pressure sensitive adhesive films (without substrate) with thicknesses of 0.5 mm to 1.5 mm, respectively, were prepared on 8 mm diameter parallel plates of a rheometer (either TA DHR-2 or ARES-G2) for rheological property testing. The loss modulus G'' and storage modulus G' at different temperatures (i.e., 200°C to -80°C) were measured by a temperature ramp program using oscillatory mode at 1 Hz and a cooling rate of 3°C/min at 0.25% strain. tan δ was calculated by G''/G'. The glass transition temperature was defined as the temperature at the peak point of tan δ.
The results are shown in Tables 6 and 7 below.

INDUSTRIAL APPLICABILITY The above examples show that hydrosilylation reaction curable compositions can be prepared that cure to form silicone pressure sensitive adhesives with desirable adhesion properties of >300 g/in to stainless steel, >400 g/in to silicone rubber at RT, and >1000 g/in to silicone rubber after aging the silicone pressure sensitive adhesive on the silicone rubber at 70° C. for 1 day. The high adhesion makes the bond between the silicone pressure sensitive adhesive and the substrate (adherend) strong enough to resist delamination over repeated deformation tests of flexible displays (e.g., by folding, bending, rolling, or stretching tests). The silicone pressure sensitive adhesive can also have a Tg≦0° C., a G′<300 kPa at −20° C., a G′<0.1 100 kPa at 25° C., and a G′<100 kPa at 100° C. The low Tg and low G' over a wide temperature range make the silicone pressure sensitive adhesive suitable for use over a wide temperature range with low stress on other layers during repeated deformation tests (e.g., folding, bending, rolling, and stretching tests). This combination of properties makes the silicone pressure sensitive adhesive suitable for use in the fabrication of multi-layer components of flexible displays, particularly optical components, lens (frame) attachment layers, silicone hinges, and bonding layers. Due to the excellent ability of silicone elastomers to withstand repeated deformation tests (e.g., folding, bending, rolling, and stretching), the combination of silicone pressure sensitive adhesives and silicone elastomers makes the articles described herein suitable for use in flexible displays with excellent reliability tests such as folding, bending, rolling, and stretching.

Definitions and Use of Terms All amounts, ratios, and percentages are by weight unless otherwise specified. The Summary and Abstract are incorporated herein by reference. Unless otherwise specified by the context of the specification, the articles "a,""an," and "the" each refer to one or more. The transitional phrases "comprising,""consisting essentially of," and "consisting of" are used as set forth in Sections §2111.03 I., II., and III of the Manual of Patent Examinng Procedure Ninth Edition, Revision 08.2017, Last Revised January 2018. The use of "for example,""eg,""suchas," and "including" to list examples does not limit the examples listed. 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. Abbreviations used herein have the definitions in Table 8.

The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of terms of description rather than of limitation. With respect to any Markush group on which the description of an individual feature or aspect herein relies, different, unusual and/or unexpected results may result from each element of the respective Markush group, independent of all other Markush group elements. Each element of the Markush group may be relied upon individually and/or in combination in specific embodiments within the scope of the appended claims, providing sufficient support.

Moreover, any ranges and subranges relied upon in describing the present invention are understood to be independently and inclusively within the scope of the appended claims and to describe and contemplate the entire range encompassing all and/or partial values therein, even if the entire and/or partial values are not expressly set forth herein. Those skilled in the art will readily recognize that the recited ranges and subranges fully describe and enable various embodiments of the present invention, and that such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and any other subranges contained within the range. As merely an example, the range "0.1 to 4.65" may be further delineated into a lower third, i.e., 0.1 to 1.5, a middle third, i.e., 1.76 to 3.1, and an upper third, i.e., 3.2 to 4.65; or the range "0.1 to 4.65" includes the subranges "0.1 to 4.2," "4.1 to 4.65," and "4.63 to 4.65," each of which individually and collectively are within the scope of the appended claims and may be relied upon individually and/or collectively to provide appropriate justification for particular embodiments within the scope of the appended claims. In addition, with respect to words defining or modifying a range, such as "at least," "greater than," "less than," "less than," etc., such words should be understood to include subranges and/or upper or lower limits.

Claims (15)

1. A hydrosilylation reaction curable composition for forming a silicone pressure sensitive adhesive, said composition comprising:
(A) a polydiorganosiloxane gum component,
38.7% to 48.1% by weight, based on the combined weight of starting materials (A)-(F), of (A-1) an aliphatically unsaturated polydiorganosiloxane gum of the formula (R ^M ₂ R ^U SiO _1/2 ) ₂ (R ^M ₂ SiO _2/2 ) _a , where each R ^M is an independently selected monovalent hydrocarbon radical of 1 to 30 carbon atoms free of aliphatic unsaturation and each R ^U is an independently selected monovalent aliphatically unsaturated hydrocarbon radical of 2 to 30 carbon atoms, subscript a having a value sufficient to impart to said polydiorganosiloxane gum a plasticity of 20 mils (0.51 mm) to 80 mils (2.03 mm), and the plasticity is within the range of 0.01 to 0.02 mm as measured by ASTM A1234. and 0 to <1.2 weight % (A-2) of a hydroxyl-terminated polydiorganosiloxane gum of the unit formula ((HO)RM2SiO1 _/ 2) ₂ ( _RM2SiO2 / ₂ ) _a' , where each R ^M is an independently selected monovalent hydrocarbon radical of 1 to 30 carbon atoms free of aliphatic unsaturation and each subscript a' has a value sufficient to impart a plasticity of 20 ^mils ( _0.51 ^mm ) to 80 mils (2.03 mm) to said polydiorganosiloxane gum,
provided that the weight ratio of (A-1) said aliphatically unsaturated polydiorganosiloxane gum to (A-2) said hydroxyl-terminated polydiorganosiloxane gum {(A-1):(A-2) ratio} is ≧32.5:1;
(B) a polyorganosilicate resin component,
a capped resin having 42.4% to 50.9% by weight, based on the combined weight of starting materials (A)-(F), of a (B-1) unit of the formula: (R ^M ₃ SiO _1/2 ) _z (SiO _4/2 ) _o Z _p , where Z is a hydrolyzable group, subscript p is from 0 to a value sufficient to provide said capped resin with a hydrolyzable group content of up to 2%, subscripts z and o have values such that z>4, o>1, and the quantity (z+o) has a value sufficient to provide said capped resin with a number average molecular weight of 500 ^g _/ mol _{to 5,000} g _/ mol; _and an uncapped resin of _{formula p'} , where subscript p' has a value sufficient to provide said uncapped resin with a hydrolyzable group content of >3% to 10%, subscripts z' and o' have values such that z'>4, o'>1, and the quantity (z'+o') has a value sufficient to provide said uncapped resin with a number average molecular weight of 500 g/mol to 5,000 g/mol; (B-1) said capped resin and (B-2) said uncapped resin are present in a combined amount of 42.4% to 52.4% by weight, based on the combined weight of starting materials (A)-(F);
(A) said polydiorganosiloxane gum component and (B) said polyorganosilicate resin component are present in a weight ratio of (B):(A) (resin:gum ratio)<1.4:1;
0.01% to 5% by weight, based on the total weight of the starting materials (A) to (F), of (C) a hydrosilylation reaction catalyst;
(D) Unit formula: ( _RM2SiO2/2 ⁾ _{e ( HRMSiO2} ^/ ₂ ) _f ( _RM2HSiO1 ^/ ₂ ) _g ( ^RM3SiO1 / ₂ ) (D) a polyorganohydrogensiloxane of formula _(h) , wherein subscript e≧0, subscript f≧0, the quantity (e+f) is 4 to 500, subscript g is 0, 1, or 2, subscript h is 0, 1, or 2, the quantity (g+h)=2, and the quantity (f+g)≧3, wherein said polyorganohydrogensiloxane is present in an amount sufficient to provide a molar ratio of silicon-bonded hydrogen atoms to aliphatically unsaturated hydrocarbon groups of (A) said polydiorganosiloxane gum component {(D):(A) ratio} of from 22.0:1 to 57.8:1;
0.05% to 4.8% by weight of (E) a trialkyl borate, based on the total weight of the starting materials (A) to (F);
0% to 5% by weight (F) of a hydrosilylation reaction inhibitor, based on the combined weight of the starting materials (A)-(F);
>0 wt. % to 90 wt. % of (G) a solvent, based on the combined weight of all starting materials in the composition;
and (H) 0 to 5 weight percent of an anchoring additive, based on the total weight of the starting materials (A) through (F). 10. The composition of claim 1, wherein in (A) said polydiorganosiloxane gum component, each R ^M is an independently selected alkyl group of 1 to 6 carbon atoms, each R ^U is independently selected from the group consisting of vinyl, allyl, and hexenyl, subscript a is sufficient to provide (A-1) said aliphatically unsaturated polydiorganosiloxane gum with a number average molecular weight of 500,000 g/mole to 1,000,000 g/mole, and subscript a' is sufficient to provide (A-2) said hydroxyl terminated polydiorganosiloxane gum with a number average molecular weight of 200,000 g/mole to 1,000,000 g/mole. 2. The composition of claim 1, wherein in (B) the polyorganosilicate resin component, each R ^M is an independently selected alkyl group of 1 to 6 carbon atoms, each Z is OH, and the quantity (z+o) has a value sufficient to provide (B-1) the capped resin having a number average molecular weight of 2,900 g/mol to 4,100 g/mol. (C) The composition of claim 1, wherein the hydrosilylation reaction catalyst comprises a Karstedt catalyst. (D) The composition of claim 1, wherein in the polyorganohydrogensiloxane, each R ^M is an independently selected alkyl group of 1 to 6 carbon atoms, subscript g=0, and subscript h=2. (E) The composition of claim 1, wherein the trialkyl borate comprises triethyl borate. The composition of any one of claims 1 to 6, wherein the composition is a multi-part composition comprising a base and a hardener part, the base comprising starting materials A) and C), the hardener part comprising starting materials A) and D), and the composition further comprising starting materials B), E), and F) in one or more of the base, the hardener part, or a separate additional part. 1. A wet casting method comprising the steps of:
1) applying a composition according to any one of claims 1 to 6 to a substrate;
2) curing the composition to form the silicone pressure sensitive adhesive on the substrate. 1. A dry casting method comprising the steps of:
1) applying a composition according to any one of claims 1 to 6 to a release liner;
2) curing the composition to form the silicone pressure sensitive adhesive on the release liner; and
3) applying the silicone pressure sensitive adhesive to a substrate. The method according to claim 8 or 9, wherein the substrate is a silicone elastomer. An article prepared by the method according to any one of claims 8 to 10. The article of claim 11, wherein the article is part of a foldable organic light emitting diode display. The article of claim 12, wherein the article is a lens (frame) mounting part. The article of claim 12, wherein the article comprises a hinge and a bonding layer. A component of a foldable display device, comprising:
I) a silicone elastomer layer;
II) a silicone pressure sensitive adhesive layer adhered to said silicone elastomer layer, said silicone pressure sensitive adhesive layer being the product of a composition according to any one of claims 1 to 6.