CURABLE POLYSILOXANE COMPOSITIONS AND OPTICALLY SMOOTH FILMS PREPARED THEREOF - Patent application

Abstract

The curable composition contains (a) 15 to 73 weight percent of a vinyl-functional M-capped aryl silsesquioxane resin; (b) 0.5 to 5 weight percent of a vinyl-functional disiloxane; (c) 2 to 25 weight percent of a silicon hydride-functional M-capped silsesquioxane resin; and (d) 1 to 10 parts by weight per million parts by weight of platinum from a platinum hydrosilylation catalyst, where the sum of the concentrations of (a) and (b) is at least 35 weight percent, the weight percentage values ​​being based on the weight of the curable composition, and the curable composition does not contain an acetylenic alcohol hydrosilylation inhibitor.

Description

[Technical field]

[0001] The present invention relates to curable polysiloxane compositions, methods for curing the curable polysiloxane compositions, particularly into optically smooth films, and optically smooth films made from the curable polysiloxane compositions. [Background technology]

[0002] Introduction Light guides are useful for directional transmission of light from a light emitter to a specific desired location. In contrast to lenses, which transmit light through the thickness dimension of the article, light guides are used by internally reflecting light within the light guide article as it guides the light to an edge of the light guide article and then transmits the light through the light guide through the length and / or width dimension of the article to the opposite edge of the light guide. Light guide articles have more stringent requirements for surface roughness and refractive index to maximize the light retained within the light guide article as it travels through the light guide. Surface roughness and insufficient refractive index can result in loss of light through the surface of the light guide as the light is internally reflected from the surface of the light guide as it travels through the light guide article. Light can be efficiently guided through a tortuous or complex path around other objects within the light guide and emitted at a desired location. Light guides are widely used in mobile phones, televisions, and display electronics.

[0003] Polymethylsiloxane is not a common light guide medium due to its high cost and low refractive index. Polymethylsiloxane typically has a refractive index of about 1.4, while more common light guide materials such as polycarbonate ("PC") and poly(methyl methacrylate) ("PMMA") typically have refractive indexes greater than 1.5, with refractive index values ​​measured using 589 nanometer wavelength light at 20 degrees Celsius. It is desirable for the material to have a refractive index greater than 1.50 to more efficiently translate light within the material as a light guide. However, it is also desirable to use polysiloxane materials as light guide media because of their known inherent stability, including thermal stability.

[0004] Certain light guide applications require the light guide to be a film having a thickness of approximately 25 to 500 micrometers. Examples of such applications include outdoor display electronics, front-lit electronic displays, aesthetic or ambient lighting, automotive accent lighting, and other applications where light must emanate from an area that is thin and / or flexible (i.e., a sheet of light). Such films present unique challenges. For example, the film must have opposing major surfaces that are optically smooth or where light may scatter from the light guide along surface roughness features. Surfaces with values ​​R of less than 25 nanometers are required. a A surface is "optically smooth" if it has a roughness characterized by "R a " is the arithmetic mean of the feature height encountered in any 1.0 millimeter long line on the surface, excluding areas that are intentionally roughened to diffuse light from the surface. Light guide films may contain intentionally roughened patterns, such as words or shapes, to diffuse light from the light guide, and they are not intentionally optically smooth. However, the remainder of the film must be optically smooth to minimize light diffusion from the major surface in areas other than the intentionally diffused areas.

[0005] Additionally, the film must cure to a sufficiently high modulus to be handleable, which is greater than 15 deciNewtons as measured by ASTM D5289-19a. * meters (dN * This means that the composition must be cured to a torque stiffness of greater than 100 kPa (m). Curable compositions suitable for preparing such films further desirably have a working time of at least 1 hour at 25 degrees Celsius (°C), where working time is the time required for the composition to double in viscosity. Summary of the Invention

[0006] The present invention provides a glass substrate having a refractive index of 1.50 or greater when measured at 20 degrees Celsius (°C) using 589 nanometer wavelength light, a thickness of 25 to 500 micrometers, and a surface roughness R of less than 25 nanometers. a value of 15dN * The present invention provides a solution to each of the problems discussed above by providing a curable polysiloxane composition that can be cast and cured into a film having a cured stiffness of greater than 100° C. Moreover, the curable composition is capable of forming such a film when cured in open air (with a major surface exposed to air) at temperatures in excess of 100° C. The curable composition also has a working time of at least 1 hour at 25° C.

[0007] This solution is the result of discovering a particular combination of polysiloxane materials that can be cast to form a film and then cured by hydrosilylation to obtain a film with the above-mentioned properties (the "target film"). It is known that the refractive index can be increased to values ​​above 1.50 by including aryl groups in the polysiloxane. However, during the discovery of the present invention, it was found that aryl-functional polysiloxanes can have problems curing into a film with an optically smooth major surface when cured at temperatures above 100° C. with the major surface exposed to air. The present invention is the result of discovering a particular composition that can be cured into an optically smooth major surface when exposed to air, while also achieving the other properties of the target film.

[0008] In a first aspect, the present invention provides a curable composition comprising: (a) 15 to 73 weight percent of a vinyl-functional M-capped aryl silsesquioxane resin having a weight average molecular weight in the range of 700 to 1900 daltons and having the following average chemical structure (I): (R3SiO 1 / 2 ) a (R'SiO 3 / 2 ) b ((ZO) x R'SiO (3-x / 2) ) z (I) wherein at least one R is a terminal alkenyl group having 1 to 8 carbon atoms, subscript x is independently selected at each occurrence from a value in the range of 0 to 2, subscript a is a value in the range of 0.15 to 0.35, subscript b is a value in the range of 0.65 to 0.85, subscript z is a value in the range of 0 to 0.10, and the sum of subscripts a, b, and z is 1.0; (b) 0.5 to 5 weight percent of a vinyl-functional disiloxane having a weight average molecular weight in the range of 250 to 500 daltons and having the following chemical structure (II): (R'R2SiO 1 / 2 )2(II) wherein at least one R is a terminal alkenyl group having 1 to 8 carbon atoms; (c) 2 to 25 weight percent of a silicon hydride functional M-capped silsesquioxane resin having a weight average molecular weight in the range of 500 to 1200 Daltons and having the following average chemical structure (III): (R”2HSiO 1 / 2 ) c (R'SiO 3 / 2 ) d ((ZO) x R'SiO (3-x / 2) ) z (III) wherein subscript x is independently selected at each occurrence from a value in the range of 0 to 2, subscript c has a value in the range of 0.5 to 0.7, subscript d has a value in the range of 0.3 to 0.5, subscript z is in the range of 0 to 0.10, and the sum of subscripts c, d, and z is 1.0; (d) 1 to 10 weight parts per million weight parts of platinum from a platinum hydrosilylation catalyst, based on the weight of the curable composition; Including, wherein R is, subject to the above qualifications, independently at each occurrence, selected from the group consisting of alkyl groups having 1 to 8 carbon atoms, and terminal alkenyl groups having 1 to 8 carbon atoms; R' is, independently at each occurrence, selected from aryl groups; R" is, independently at each occurrence, selected from alkyl groups having 1 to 8 carbon atoms; Z is, independently at each occurrence, selected from the group consisting of hydrogen, and alkyl groups, and R groups; the subscripts a-d and the subscript z refer to the molar ratio of corresponding siloxane units in a molecule containing siloxane units; the sum of the concentrations of (a) and (b) is at least 35 weight percent; the weight percent values ​​are based on the weight of the curable composition; the curable composition does not include an acetylenic alcohol hydrosilylation inhibitor. It is a curable composition.

[0009] In a second aspect, the invention is a method of curing the curable composition of the first aspect, comprising forming a film of the curable composition and then heating the film to a temperature greater than 100 degrees Celsius to form a cured polymer film.

[0010] In a third aspect, the invention is a cured polymer film comprising the cured polymer film of the composition of the first aspect.

[0011] In particular, transparent siloxane compositions are known in various compositions for filling mold voids or as coatings on semiconductor devices. However, these applications do not address the problem of achieving optically flat films of siloxane compositions, and do not identify compositions that can be used to make optically flat films, such as the target films described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Test methods refer to the test method most recent as of the priority date of this document unless a date is given with the test method number. Reference to a test method includes both a reference to the testing society and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International methods, EN refers to European Norm, DIN refers to Deutsches Institut fur Normung, ISO refers to the International Organization for Standards, and UL refers to the Underwriters Laboratory.

[0013] Products identified by trade names refer to compositions available under those trade names as of the priority date of this document.

[0014] "Plurality" means two or more. "And / or" means "and, or alternatively." All ranges are inclusive of the endpoints unless otherwise indicated.

[0015] "Alkyl" refers to a hydrocarbon group derivable from an alkane by removing a hydrogen atom. Alkyl can be straight-chained or branched.

[0016] "Molecular weight" refers to weight average molecular weight unless otherwise specified. Weight average molecular weight of polymers is determined by gel permeation chromatography (GPC) against polystyrene standards. Polymer samples for GPC analysis are prepared as dilute solutions in toluene and the solutions are filtered using 0.45 micrometer polytetrafluoroethylene filters prior to analysis. The eluents are passed through two Polymer Labs 5 micrometer mixed C columns maintained at 35°C using high pressure liquid chromatography (HPLC) grade tetrahydrofuran as the eluent.

[0017] "Refractive index" or "RI" is measured on the curable compositions using a Rudolph Research Analytical J257 Series Automatic Refractometer equipped with an artificial sapphire prism and a light emitting diode (LED) light source. The refractive index is measured using 589 nanometer light at 20°C. For the purposes of the compositions herein, the RI of the curable composition is assumed to be equivalent to the RI of the resulting cured polymer film made with the curable composition, so that the RI value of the cured film corresponds to the RI value of the curable composition used to make the cured polymer film. To actually measure the RI on the film, a Metricon Prism Coupler is used.

[0018] The "surface roughness" of a film is determined by the value "R a" which is the arithmetic mean of the feature height encountered in any 1.0 millimeter long line on the surface as assessed using a Zygo New View 7300 white light interferometer equipped with a 5x objective.

[0019] "Optically smooth" means a surface roughness R of less than 25 nanometers for any surface that is not intentionally roughened to diffuse light. a This refers to a film with a R value. a The values ​​correspond to the highest gloss standard for injection molded finishes of plastics from the Plastics Industry Association standard SPI A-1.

[0020] A "major surface" of a film refers to the surface having the largest planar surface area, where planar surface area refers to the surface area of ​​the surface projected onto a plane while ignoring surface texture. Films typically have opposing major surfaces separated by the thickness of the film.

[0021] "Edge" of a film refers to the outer limit of the film along the dimension of the film that joins opposing major surfaces of the film.

[0022] Determine the viscosity of the curable composition at 25° C. using a Brookfield DV-II cone on a plate viscometer (CPA-52Z - Brookfield) equipped with a 3° cone and revolutions per minute value such that the torque reading is 40-60% of the maximum torque value of the rheometer under the given settings.

[0023] In one aspect, the present invention is a curable composition. The curable composition can undergo a curing reaction that crosslinks the components of the curable composition. The present invention can be cured by a hydrosilylation reaction of a vinyl-functional M-capped aryl silsesquioxane resin, a vinyl-functional disiloxane, and a silicon hydride-functional M-capped silsesquioxane resin in the presence of a platinum hydrosilylation catalyst.

[0024] The vinyl-functional M-capped aryl silsesquioxane resin has the following average chemical structure (I): (R3SiO 1 / 2 ) a (R'SiO 3 / 2 ) b ((ZO) x R'SiO (3-x / 2) ) z (I) Where: R, independently at each occurrence, is selected from the group consisting of alkyl groups having 1 to 8 carbon atoms, and alkenyl groups having 1 to 8 carbon atoms. In the vinyl-functional M-capped aryl silsesquioxane resins, at least one R group, and preferably two or more R groups, is selected from a terminal alkenyl group having 1 to 8 carbon atoms. Preferably, the terminal alkenyl group of R is a vinyl ("Vi") group and the alkyl group is selected from methyl ("Me"), ethyl, and propyl groups.

[0025] R', independently at each occurrence, is selected from the group consisting of aryl groups, preferably phenyl ("Ph") groups and benzyl groups.

[0026] Z, independently at each occurrence, is selected from the group consisting of hydrogen and R groups, preferably hydrogen ("H"), methyl, and ethyl groups.

[0027] The subscript x is independently selected from the range of values ​​from 0 to 2 and may be 0, 1, or 2 at each occurrence.

[0028] The subscripts a, b, and z refer to the molar ratio of the corresponding siloxane units in the molecule containing the siloxane units, and the sum of a, b, and z is 1.0 in the chemical structure (I). The subscript a is a value in the range of 0.15 to 0.35, and can be 0.15 or more, 0.20 or more, 0.25 or more, or even 0.30 or more, while at the same time being 0.35 or less, 0.30 or less, 0.25 or less, or even 0.20 or less. The subscript b is a value in the range of 0.65 to 0.85, and can be 0.65 or more, 0.70 or more, 0.75 or more, or even 0.80 or more, while at the same time being 0.85 or less, 0.80 or less, 0.75 or less, or even 0.70 or less. The subscript z is a value in the range of 0 to 0.10, and can be greater than or equal to 0, and even greater than or equal to 0.05, while at the same time being less than or equal to 0.10 and less than or equal to 0.05.

[0029] Desirably, the vinyl-functional M-capped aryl silsesquioxane resin has the following chemical structure: (ViMe2SiO 1 / 2 ) a (PhSiO 3 / 2 ) b ((ZO) x PhSiO (3-x / 2) ) z .

[0030] The vinyl functional M-capped aryl silsesquioxane resin has a weight average molecular weight (Mw) in the range of 700 to 1900 Daltons (Da) and can have a Mw of 700 Da or more, 800 Da or more, 900 Da or more, 1000 Da or more, 1100 Da or more, 1200 Da or more, 1300 Da or more, 1400 Da or more, 1500 Da or more, 1600 Da or more, 1700 Da or more, or even 1800 Da or more, while at the same time having a Mw of 1900 Da or less, 1800 Da or less, 1700 Da or less, 1600 Da or less, 1500 Da or less, 1400 Da or less, 1300 Da or less, 1200 Da or less, 1100 Da or less, 1000 Da or less, 900 Da or less, or even or less. The copolymer may have a Mw of 1.0 or less.

[0031] The concentration of the vinyl-functional M-capped aryl silsesquioxane resin in the curable composition is in the range of 15 to 73 weight percent (wt%), and can be 15 wt% or more, 20 wt% or more, 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, 45 wt% or more, 50 wt% or more, 55 wt% or more, 60 wt% or more, or even 70 wt% or more, while at the same time being 73 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 30 wt% or less, 25 wt% or less, or even 20 wt% or less, based on the weight of the curable composition.

[0032] The vinyl-functional disiloxane has the following average chemical structure (II): (R'R2SiO 1 / 2 )2(II) where R and R' are as defined hereinabove, except that at least one R is a terminal alkenyl group having 1 to 8 carbon atoms. Desirably, the vinyl-functional disiloxane has the following chemical structure: (ViMePhSiO 1 / 2 )2.

[0033] The vinyl functional disiloxane has a Mw in the range of 250 to 500 Da, and can have a Mw of 250 Da or more, 300 Da or more, 350 Da or more, 400 Da or more, or even 450 Da or more, while at the same time having a Mw of 500 Da or less, 450 Da or less, 400 Da or less, 350 Da or less, or even 300 Da or less.

[0034] The concentration of the vinyl functional disiloxane in the curable composition, in weight percent based on the weight of the curable composition, can be in the range of 0.5 to 5 weight percent, and can be 0.5 weight percent or more, 1 weight percent or more, 2 weight percent or more, 3 weight percent or more, or even 4 weight percent or more, while at the same time being 5 weight percent or less, 4 weight percent or less, 3 weight percent or less, 2 weight percent or less, or even 1 weight percent or less, with the proviso that the combined concentration of the vinyl functional M capped aryl silsesquioxane resin and the vinyl functional disiloxane is 35 weight percent or more, based on the weight of the curable composition. The combined concentration of the vinyl-functional M-capped aryl silsesquioxane resin and the vinyl-functional disiloxane can be, for example, in the range of 35% to 78% by weight, or in other words 35% or more, 40% or more, 50% or more, 60% or more, or even 70% or more by weight, while at the same time being 78% or less, 75% or less, 70% or less, 65% or less, 60% or less, 50% or less, or even 40% or less by weight, based on the weight of the curable composition.

[0035] The silicon hydride functional M-capped silsesquioxane resin has the following average chemical structure (III): (R”2HSiO 1 / 2 ) c (R'SiO 3 / 2 ) d ((ZO) x R'SiO (3-x / 2) ) z (III) During the ceremony, R', Z, and the subscript z are as defined hereinabove, independently at each occurrence; R″, at each occurrence, is independently selected from the group consisting of alkyl groups having 1 to 8 carbon atoms, and can have 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, or even 6 or more, while simultaneously having 8 or less, 7 or less, 6 or less, 4 or less, 3 or less, or even 2 or less carbon atoms; The subscript x, at each occurrence, is independently selected from values ​​in the range of 0 to 2, and may be 0, 1, or 2; The subscript c has a value in the range of 0.5 to 0.7, and may be in the range of 0.6 to 0.7 or 0.5 to 0.6; The subscript d has a value in the range of 0.3 to 0.5, and may be in the range of 0.3 to 0.4 or 0.4 to 0.4; The sum of subscript c, subscript d, and subscript z is 1.0.

[0036] Desirably, the silicon hydride functional M-capped silsesquioxane resin has the following average chemical structure: (HMeSiO 1 / 2 ) c (PhSiO 3 / 2 ) d ((ZO) x PhSiO (3-x / 2) ) z .

[0037] The silicon hydride functional M-capped silsesquioxane resin has a Mw in the range of 500 to 1200 Da, and can be 500 Da or more, 600 Da or more, 700 Da or more, 800 Da or more, 900 Da or more, 1000 Da or more, or even 1100 Da or more, while simultaneously being 1200 Da or less, 1100 Da or less, 1000 Da or less, 900 Da or less, 800 Da or less, 700 Da or less, or even 600 Da or less.

[0038] The concentration of the silicon hydride functional M-capped silsesquioxane resin is in the range of 2-25 wt%, and can be, relative to the weight of the curable composition, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 10 wt% or more, 15 wt% or more, or even 20 wt% or more, while at the same time being 25 wt% or less, 20 wt% or less, 15 wt% or less, 10 wt% or less, or even 5 wt% or less.

[0039] The platinum hydrosilylation catalyst can be any one or a combination of more than one platinum-containing hydrosilylation catalyst. Platinum hydrosilylation catalysts include compounds and complexes such as platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Karstedt's catalyst), HPtCl, di-μ.-carbonyldi-.π.-cyclopentadienyldinickel, platinum-carbonyl complexes, platinum-divinyltetramethyldisiloxane complexes, platinum cyclovinylmethylsiloxane complexes, platinum acetylacetonate (acac), platinum black, and platinum compounds such as chloroplatinic acid, chloroplatinic acid hexahydrate, reaction products of chloroplatinic acid with monohydric alcohols, platinum bis(ethylacetoacetate), platinum bis(acetylacetonate), platinum dichloride, and complexes of platinum compounds with olefins or low molecular weight organopolysiloxanes, or platinum compounds microencapsulated in a matrix or core-shell structure. The platinum hydrosilylation catalyst may be part of a solution containing complexes of platinum with low molecular weight organopolysiloxanes, including 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes with platinum. These complexes may be microencapsulated in a resin matrix. The catalyst may be 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes with platinum.

[0040] The concentration of the platinum hydrosilylation catalyst is sufficient to obtain a platinum concentration in the range of 1 to 10 parts per million (ppm) by weight, which can be 1 ppm or more, 2 ppm or more, 3 ppm or more, 4 ppm or more, 5 ppm or more, 6 ppm or more, 7 ppm or more, 8 ppm or more, or even 9 ppm or more, while at the same time being 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, or even 2 ppm or less, in ppm based on the weight of the curable composition.

[0041] Optionally, the curable composition may further comprise a linear alkenyl-functional polyorganosiloxane having an average chemical structure (IV): (R3SiO 1 / 2 )e (R' (2-x) R” x SiO 2 / 2 ) f (IV) wherein each R, R', and R" is independently selected from the group definitions provided hereinabove; subscript x has an average value in the range of 0 to 1; subscript e has a value from 0.03 to 0.97, and can be 0.03 or more, 0.05 or more, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, 0.80 or more, or even 0.90 or more, while simultaneously being 0.97 or less, 0.95 or less, 0.90 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, 0.20 or less, or even 0.10 or less, and subscript f is selected such that the sum of subscript e and subscript f is 1.0.

[0042] Desirably, the linear alkenyl-functional polyorganosiloxane is selected from one or more components having a chemical structure within the following two structures: (ViMe2SiO 1 / 2 ) e (PhMeSiO 2 / 2 ) f where subscript e and subscript f are as defined hereinabove: (ViMe2SiO 1 / 2 )(Ph2SiO 2 / 2 )(ViMe2SiO 1 / 2 ).

[0043] The concentration of linear alkenyl functional polyorganosiloxane in the curable composition is in the range of 0-65 wt%, and can be, in weight percent based on the weight of the curable composition, 0 wt% or more, 10 wt% or more, 20 wt% or more, 30 wt% or more, 40 wt% or more, 50 wt% or more, or even 60 wt% or more, while at the same time being 65 wt% or less, 65 wt% or less, 55 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 25 wt% or less, 15 wt% or less, or even 5 wt% or less.

[0044] At the same time, the curable composition may optionally include a silylhydride-functional linear organosiloxane having the average chemical structure (V): (HR2SiO 1 / 2 )2(R'2SiO 2 / 2 ) (V) wherein R and R' are as described hereinabove and each occurrence is independent. Desirably, the silylhydride functional linear organosiloxane has the following chemical structure: (HMeSiO 1 / 2 )2(PhPhSiO 2 / 2 ).

[0045] The concentration of the silylhydride functional linear organosiloxane in the curable composition is in the range of 0-25 wt.%, and can be 0 wt.% or more, 10 wt.% or more, or even 20 wt.% or more, while at the same time being 25 wt.% or less, 15 wt.% or less, or even 5 wt.% or less, based on the weight of the curable composition.

[0046] Desirably, the curable composition has a molar ratio of silicon hydride functionality (SiH) to terminal alkenyl groups in the range of 0.8 to 3.0, which may be 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.6 or more, 1.8 or more, 2.0 or more, 2.2 or more, 2.4 or more, 2.6 or more, or even 2.8 or more, while at the same time desirably 3.0 or less, 2.9 or less, 2.7 or less, 2.5 or less, 2.3 or less, 2.1 or less, 1.9 or less, 1.7 or less, 1.5 or less, 1.3 or less, 1.1 or less, or even 1.0 or less. Proton nuclear magnetic resonance ( 1The molar ratio of SiH to terminal alkenyl groups is determined by H NMR spectroscopy. A known amount of sample is combined with a known amount of internal standard (1,4-dioxane) to prepare the analytical sample in deuterated chloroform. Spectra are collected using an Aligent 400-MR NMR instrument equipped with a 5 millimeter ONeNMR probe. Data are analyzed using MesReNova x64 software. The weight percentage of terminal alkenyl and SiH groups is calculated by integrating the relevant proton resonances against the proton resonances of the internal standard.

[0047] Desirably, the curable composition does not contain more than 3 mole percent (mol %), preferably 2 mol % or more, and even more preferably 1 mol % or more of siloxane molecules that contain epoxy-containing groups relative to the moles of silicon atoms in the siloxane molecules.

[0048] Desirably, the curable composition has a refractive index (RI) at 589 nanometers of 1.50 or greater, preferably greater than 1.50.

[0049] In another aspect, the present invention is a method of curing the curable composition of the present invention into a cured polymer film. The method includes forming a film of the curable composition and then heating the film to a temperature above 100 degrees Celsius (°C), preferably 120°C or higher, even more preferably 130°C or higher, to cure the film into a cured polymer film. The curable composition can be formed into a film by any method, such as spin-coating onto a substrate or casting into a film using a pull-down bar, doctor blade (or any knife blade), or slot die. For example, the curable composition can be spin-coated onto a silicon wafer, preferably an optically smooth silicon wafer. Alternatively, the curable composition can be placed onto a substrate, preferably an optically smooth substrate, where the film thickness is controlled by the physical offset of the slot die, or by passing the curable composition onto the substrate under the blade or knife, and the thickness is controlled by the gap between the blade or knife edge and the substrate.

[0050] The film thickness before and especially after curing is desirably in the range of 25 to 500 micrometers, and can be 25 micrometers or more, 50 micrometers or more, 75 micrometers or more, 100 micrometers or more, 150 micrometers or more, 200 micrometers or more, 250 micrometers or more, 300 micrometers or more, 350 micrometers or more, 400 micrometers or more, or even 450 micrometers or more, while at the same time desirably 500 micrometers or less, 475 micrometers or less, 425 micrometers or less, 375 micrometers or less, 325 micrometers or less, 275 micrometers or less, 225 micrometers or less, 175 micrometers or less, 125 micrometers or less, 75 micrometers or less, or even 50 micrometers or less. A handheld digital micrometer (Mitutoyo 547-526S) is used to determine the film thickness according to ASTM D1005 procedure C 6.3.6.

[0051] While one major surface of the film of the curable composition is in contact with the substrate surface, the opposite major surface can be exposed to air. Even when exposed to air, the exposed major surface of the film can be cured to an optically smooth surface. Furthermore, when cured on a substrate having an optically smooth surface, the resulting cured polymer film can have opposing major surfaces that are both optically smooth. In particular, intentional patterning can be imprinted or imparted to some or all of the major surfaces while retaining an optically smooth surface where no intentional patterning is present.

[0052] The cured polymer film has a resistance of 15 deciNewtons. * meters (dN * m) or more rigidity, * m or more, 25dN * m or more, 30dN * m or more, 35dN * m or more, 40dN * m or more, 45dN * m or more, 50dN * m or more, 55dN * m or more, 60dN * m or more, 65dN * m or more, 70dN * m or more, 75dN * m or more, 80dN * m or more, 85dN * m or even 90dN * m or more, while at the same time typically having a stiffness of 150 dN * m or less, 100dN * m or less, 75dN * m or less, or even 50dN * It has a rigidity of less than m.

[0053] The cured polymer film may be part of an article further comprising a light source coupled to the film so that the cured polymer film guides light to the edge of the film. The cured polymer film of the present invention is particularly useful as a light guide, where light is guided into the edge of the film and transmitted within the film to the other edge of the film and optionally out of the patterned portion of one or more major surfaces of the film. In such applications, the film is "coupled" with a light source that guides light to the edge of the film. Coupling can be by direct contact with the light emitting source or by indirect coupling via an optical fiber or other waveguiding material that transmits light from the light emitting source. EXAMPLES

[0054] Table 1 lists the materials for the following examples.

[0055] [Table 1]

[0056] The curable compositions are prepared by combining the composition components (amounts of components in grams) shown in the table below in a container, mixing by hand with a metal spatula, and then mixing with a speed mixer at 3500 revolutions per minute for 30 seconds. The RI of the curable compositions is determined. The working time of the curable compositions is also determined by first measuring the viscosity after preparation, followed by measurements every 15 minutes to determine the time it takes for the viscosity to double, which corresponds to the working time of the curable composition.

[0057] A film of the curable composition is prepared by depositing 2-4 grams of the curable composition onto an optically smooth silicon wafer (100 or 150 millimeter diameter Pure Wafer, boron doped silicone, experimental grade, 0.5 millimeter thick, root mean square surface roughness less than 1 nanometer) and then spin coating the curable composition onto the wafer using a Coast Effective Equipment spin coater at 500-1000 revolutions per minute for 60 seconds to achieve a uniform thin film 25-500 micrometers thick.

[0058] The film of the curable composition is cured by transferring the wafer containing the film onto a hot plate set at 130° C. in open air for 5 minutes, then allowing the cured film to cool. A handheld digital micrometer (Mitutoyo 547-526S) is used to determine the thickness of the cured film according to ASTM D1005 procedure C 6.3.6. The surface roughness of the exposed major surface is evaluated.

[0059] The following table provides recipes for the curable compositions and the characterization results of those curable compositions.

[0060] The compositions of the present invention have an RI of greater than 1.5 at 589 nanometers and an RI of less than 24 nanometers at their exposed cured surfaces. a value, and thickness of 25 to 500 micrometers and >15dN * The results demonstrate the ability to form cured polymer films with stiffness in excess of 1 mm and working times in excess of 1 hour.

[0061] Examples A-G demonstrate that without the silicon hydride functional M-capped silsesquioxane resin, the cured films exhibit unacceptable surface roughness.

[0062] Examples H-J show that a curable composition having less than 35% by weight of a combination of a vinyl-functional M-capped aryl silsesquioxane resin and a vinyl-functional disiloxane exhibits a 15dN *It is clear that this results in a cured film that does not achieve a stiffness of >100 mm.

[0063] Example K is 15 dN * It is shown that to achieve stiffness greater than m, greater than 1.9 wt. % of the silicon hydride functional M-capped silsesquioxane resin is required.

[0064] In Examples L and 1, the cured films had a strength of 15 dN * We demonstrate that to achieve stiffness greater than m, greater than 15 wt. % of the vinyl-functional M-capped aryl silsesquioxane resin is required.

[0065] Examples M-O and 9-11 demonstrate that in the absence of a vinyl-functional disiloxane component, the curable compositions have working times of less than 60 minutes.

[0066] Examples P and 12 demonstrate that the present invention must not include an acetylenic alcohol hydrosilylation inhibitor in order to achieve an optically smooth surface on the exposed cured film surface.

[0067] Examples 12-16 demonstrate that linear alkenyl-functional polyorganosiloxanes having alkylaryl or diaryl substituents on the polymer backbone can be used separately or as blends in compositions to provide desirable film properties.

[0068] Examples 1-16 are "optically clear". "Optical clarity" refers to a transmittance of greater than 80% for light at 400 nanometers (nm) and a transmittance of greater than 0.7, calculated by dividing the transmittance at 400 nm by the transmittance at 800 nm ("%T(400 / 800)"). Transmittance is measured over the wavelength range of 400-800 nm with an ultraviolet / visible (UV / Vis) dual beam spectrophotometer (Perkin Elmer Lambda 950) by the method of ASTM D1003. Samples for measuring transmittance are prepared by hand mixing the reactive composition precursors, then mixing in a speed mixer at 3500 revolutions per minute for 30 seconds and curing at 80°C for 12 hours. The samples are cured between glass slides to produce samples with optically smooth surfaces 10 millimeters thick.

[0069] For the examples, Example 4 has a percent transmittance (%T) at 400 nm of 85.1 and a %T(400 / 800) of 0.95; Example 8 has a percent transmittance (%T) at 400 nm of 86.7 and a %T(400 / 800) of 0.95; Example 10 has a percent transmittance (%T) at 400 nm of 87.9 and a %T(400 / 800) of 0.98; Example 13 has a percent transmittance (%T) at 400 nm of 87.9 and a %T(400 / 800) of 0.98; Example 14 has a percent transmission (%T) at 400 nm of 88.5 and a %T(400 / 800) of 0.98; Example 15 has a percent transmission (%T) at 400 nm of 89.0 and a %T(400 / 800) of 0.98; and Example 16 has a percent transmission (%T) at 400 nm of 88.0 and a %T(400 / 800) of 0.99.

[0070] [Table 2] No data - could not be characterized, cured too quickly before a film could be made.

[0071]

Table 3

Claims

1. 1. A curable composition comprising: (a) 15 to 73 weight percent of a vinyl-functional M-capped aryl silsesquioxane resin having a weight average molecular weight in the range of 700 to 1900 daltons and having the following average chemical structure (I): (R ３ SiO １／２ ) ａ (R'SiO ３／２ ) ｂ ((ZO) ｘ R'SiO （３－ｘ／２） ) ｚ (I) wherein at least one R is a terminal alkenyl group having 1 to 8 carbon atoms, subscript x is independently selected each time it occurs from a value in the range of 0 to 2, subscript a is a value in the range of 0.15 to 0.35, subscript b is a value in the range of 0.65 to 0.85, subscript z is a value in the range of 0 to 0.10, and the sum of subscripts a, b, and z is 1.0; (b) 0.5 to 5 weight percent of a vinyl-functional disiloxane having a weight average molecular weight in the range of 250 to 500 daltons and having the following chemical structure (II): (R'R ２ Yes １／２ ) ２ (II) wherein at least one R is a terminal alkenyl group having 1 to 8 carbon atoms; (c) 2 to 25 weight percent of a silicon hydride functional M-capped silsesquioxane resin having a weight average molecular weight in the range of 500 to 1200 daltons and having the following average chemical structure (III): (2” ２ 23iｯ １／２ ) ) ｃ (2'3i) ３／２ ) ) ｄ ((b) ｘ R'ｳiｯ （３－ｘ／２） ) ) ｚ (999) wherein subscript x is independently selected each time it appears from a value in the range of 0 to 2, subscript c has a value in the range of 0.5 to 0.7, subscript d has a value in the range of 0.3 to 0.5, subscript z is in the range of 0 to 0.10, and the sum of subscripts c, d, and z is 1.0; (d) 1 to 10 parts by weight per million parts by weight of platinum from a platinum hydrosilylation catalyst, based on the weight of the curable composition; Including, where: R is, subject to the above qualifications, independently each time it is mentioned, selected from the group consisting of alkyl groups having 1 to 8 carbon atoms, and terminal alkenyl groups having 1 to 8 carbon atoms; R' is, independently each time it is mentioned, selected from aryl groups; R" is, independently each time it is mentioned, selected from alkyl groups having 1 to 8 carbon atoms; Z is, independently each time it is mentioned, selected from the group consisting of hydrogen, and alkyl groups, and R groups; the subscripts a-d and subscript z refer to the molar ratio of corresponding siloxane units in molecules containing siloxane units; the sum of the concentrations of (a) and (b) is at least 35 weight percent; the weight percent values ​​are based on the weight of the curable composition; and the curable composition does not comprise an acetylenic alcohol hydrosilylation inhibitor.

2. the curable composition further comprises greater than 0 weight percent and at the same time less than or equal to 65 weight percent of a linear alkenyl-functional polyorganosiloxane having a weight average molecular weight in the range of 300 to 9000 Daltons and chemical structure (IV): (R ３ SiO １／２ ) ｅ (R’ （２－ｘ） R” ｘ SiO ２／２ ) ｆ (IV) In the formula, each (R ３ SiO １／２ 2. The curable composition of claim 1, wherein R is independently selected each time it appears from alkyl groups having 1 to 8 carbon atoms and terminal alkenyl groups, provided that at least one R in the ) unit is a terminal alkenyl group, R' is selected from aryl groups, R" is selected from alkyl groups having 1 to 8 carbon atoms, subscript x has an average value in the range of 0 to 1, subscript e has a value of 0.03 to 0.97, subscript e and subscript f are the molar ratio of associated siloxane units in said molecule containing siloxane units, the sum of the values ​​of subscript e and subscript f is 1.0, and weight percents are based on the weight of the curable composition.

3. the curable composition further comprises greater than 0 weight percent and at the same time less than or equal to 25 weight percent of a silylhydride-functional linear organosiloxane having a weight average molecular weight in the range of 250 to 500 Daltons and chemical structure (V): (HR ２ SiO １／２ ) ２ (R’ ２ SiO ２／２ ) (V) 2. The curable composition of claim 1, wherein R is, independently each occurrence, selected from alkyl groups having 1 to 8 carbon atoms, and R' is selected from aryl groups.

4. 2. The curable composition of claim 1, wherein the molar ratio of SiH to terminal alkenyl groups is in the range of 0.8 to 3.

0.

5. (i) Chemical structure (I) has the following chemical structure: (ViMe ２ SiO １／２ ) ａ (PhSiO ３／２ ) ｂ ((ZO) ｘ PhSiO （３－ｘ／２） ) ｚ ; (ii) Chemical structure (II) has the following chemical structure: (ViMePhSiO １／２ ) ２ ; (iii) Chemical structure (III) has the following chemical structure: (HMe ２ SiO １／２ ) ｃ (PhSiO ３／２ ) ｄ ((ZO) ｘ PhSiO （３－ｘ／２） ) ｚ ; (iv) Chemical structure (IV), when present, has the following chemical structure: ２ SiO １／２ ) ｅ (PhMeSiO ２／２ ) ｆ ; (v) Chemical structure (V), if present, has the following chemical structure: (HMe ２ SiO １／２ ) ２ (PhPhSiO ２／２ );and, 2. The curable composition of claim 1, wherein "Vi" refers to a vinyl group, "Ph" refers to a phenyl group, and "Me" refers to a methyl group.

6. 10. The curable composition of claim 1, wherein the curable composition does not contain more than 3 mole percent of siloxane molecules containing epoxy-containing groups relative to the moles of silicon atoms in the siloxane molecules.

7. 7. A method of curing the curable composition of any one of claims 1 to 6, comprising forming a film of the curable composition and then heating the film to a temperature greater than 100 degrees Celsius to form a cured polymer film.

8. A cured polymer film comprising a cured polymer film of the composition of any one of claims 1 to 6.

9. 10. The cured polymer film of claim 8, wherein the film has a refractive index of 1.50 or greater when measured using 589 nanometer wavelength light, a thickness in the range of 25 to 500 micrometers, and wherein the film has an optically smooth major surface.

10. 10. The cured polymer film of claim 8, further comprising a light source coupled to the film to direct light to an edge of the film.