Low dielectric constant uv-curable silicone compositions with tricyclic epoxy-functional cyclohexanes

Abstract

A UV-curable silicone composition comprises the following components: (a) a triepoxy-functionalized cyclohexane 3,3',3"-(cyclohexane-1,2,4-triyltris(ethane-2,1-diyl))tri(1-(2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl)-1,1,3,3-tetramethyldisiloxane); (b) a monoepoxy-functionalized siloxane; and (c) 0.3 to 1.5 weight percent of a photoacid generator; wherein the weight ratio of component (a) to component (b) is in the range of 30 / 70 to 70 / 30, and the combined weight of components (a) and (b) is in the range of 95.0 to 99.5 weight percent, wherein the weight percent is relative to the weight of the UV-curable silicone composition.

Description

Technical Field

[0001] This invention relates to UV-curable organosilicon compositions that achieve particularly low dielectric constants due to the presence of triepoxide-functionalized cyclohexane. Background Technology

[0002] Organosilicon compositions that can be cured into low dielectric constant (low Dk) polysiloxanes can be used in organic light-emitting diode (OLED) applications. Low Dk polysiloxanes can be used as encapsulating agents, for example, in multilayer OLED products. The low Dk property is ideal for improving touch sensitivity by reducing the parasitic capacitance of OLED products. Therefore, reducing the Dk of polysiloxanes suitable for OLED product manufacturing is particularly desirable.

[0003] One method for reducing density (Dk) in materials is to introduce pores into the material. For example, US7485362 discloses a nanoporous substrate of an organic resin functionalized by thermal decomposition at 120°C and higher temperatures. Polymer Chemistry, Vol. 3, No. 2, pp. 369-376 (2012) discloses a low-Dk material of poly(p-phenylenebenzobisoxazole) (“PPBO”) films, which incorporate pores in the PPBO film through thermal decomposition of the tert-butoxycarbonyl moiety at approximately 200°C. While introducing pores into polymer materials can reduce Dk, methods that introduce pores at temperatures above 100°C are not suitable for OLED manufacturing because such high temperatures could damage other parts of the OLED article.

[0004] Ideally, a silicone composition should be determined that is UV-curable and achieves a Dk value below 2.80, preferably 2.75 or less. Furthermore, it is ideal to achieve these Dk values ​​without the need for pore-forming agents, especially those requiring heating to above 100°C to form pores. It would be even more desirable if the silicone composition has a viscosity of 25 mPa·s or less at 40°C, or even more ideally at 25°C, allowing it to be readily inkjet printed onto a substrate. Summary of the Invention

[0005] This invention provides a solution to the problem of identifying silicone compositions that are UV-curable and achieve a Dk value below 2.80, and even 2.75 or less. Furthermore, this invention achieves such a Dk value without the need for pore-forming agents, especially those requiring heating to above 100°C to form pores. The silicone composition can even have a viscosity of 25 mPa·s or less at 40°C, or even 25°C, allowing for convenient inkjet printing. Simultaneously, the composition can be free of organic solvents and / or pore-forming agents.

[0006] This invention relates to the discovery that tricyclic cyclohexanes, when mixed in a weight ratio ranging from 70 / 30 to 30 / 70, can be combined with monocyclic cyclohexanes to achieve a Dk value below 2.80. The tricyclic cyclohexanes have an average structure (I).

[0007] (I)

[0008] In a first aspect, the present invention is a UV-curable silicone composition comprising: (a) a triepoxide-functionalized cyclohexane having an average structure (I); (b) a monoepoxide-functionalized siloxane; and (c) 0.3 to 1.5 weight percent of a photoacid generator; wherein the weight ratio of component (a) to component (b) is in the range of 30 / 70 to 70 / 30, and the combined weight of components (a) and (b) is in the range of 95.0 to 99.5 weight percent, wherein the weight percent is relative to the weight of the UV-curable silicone composition.

[0009] In a second aspect, the present invention is a method for curing a UV-curable silicone composition of the first aspect, the method comprising the steps of: (a) combining the components of the UV-curable silicone composition together to form the UV-curable silicone composition; (b) disposing the UV-curable silicone composition on a substrate; and (c) exposing the UV-curable silicone composition disposed on the substrate to ultraviolet light.

[0010] In a third aspect, the present invention is an article comprising a substrate having thereon disposed of the UV-curable silicone composition of the first aspect.

[0011] The compositions of the present invention can be used to prepare low-Dk compositions and coatings on substrates. Detailed Implementation

[0012] Products identified by their trade names refer to compositions available under those trade names as of the priority date of this document.

[0013] "Multiple" means two or more. "And / or" means "and, or as an alternative." Unless otherwise specified, all ranges include the endpoints.

[0014] Unless otherwise stated, weight % (wt%) in this document is relative to the weight of the composition.

[0015] "Solvent" refers to a non-polymerizable organic material that has a boiling point of 120°C or lower at a pressure of 101 kPa.

[0016] Using an AR2000ex rheometer from TA Instruments, with a 40 mm diameter aluminum plate and 100s... -1 The shear rate was used to determine the viscosity, in mPa*s, of the UV-curable silicone composition at 25°C and / or 40°C. Data were collected at a ramp rate of 3°C / min within a temperature ramp from 20°C to 50°C, and values ​​at 25°C and / or 40°C were reported.

[0017] In a first aspect, the present invention is a UV-curable silicone composition. In this aspect, the silicone composition is curable upon exposure to UV light. The composition may be curable upon exposure to other forms or frequencies of radiation, as long as it is curable upon exposure to UV light. The UV-curable silicone composition comprises the following components: (a) a triepoxide-functionalized cyclohexane; (b) a monoepoxide-functionalized siloxane; and (c) a photoacid generator (PAG). The UV-curable silicone composition may contain or not contain a pore-forming agent and / or an organic solvent.

[0018] (a) Tricyclic oxide functionalized cyclohexane

[0019] This invention comprises triepoxide-functionalized cyclohexane having an average structure (I):

[0020] (I)

[0021] Tricyclic oxygen-functionalized cyclohexane, also known as 3,3',3"-(cyclohexane-124-triyltris(ethane-2,1-diyl)tris(1,(2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl)-1,1,3,3-tetramethyldisiloxane), can be prepared as described in the Examples section below.

[0022] (b) Monocyclic epoxy functional siloxanes

[0023] Within the widest scope of this invention, a monoepoxy-functionalized siloxane can be any type of epoxy-functionalized siloxane. Ideally, a monoepoxy-functionalized siloxane is a linear siloxane. When the epoxy-functionalized siloxane is linear, ideally, the epoxy functional group is at one end of the siloxane (i.e., the epoxy is the "terminal" functional group). A monoepoxy-functionalized siloxane can also be an epoxy-functionalized trisiloxane.

[0024] Within the broadest scope of this invention, the epoxy functional group can be any epoxy group. Ideally, the epoxy group in the epoxy functional group is separated from the siloxane to which the functional group is attached by a carbon atom or a chain of carbon atoms. Ideally, each epoxy functional group is a [2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl] group having the following structure, where the dashed line represents the bond with the silicon atom of the functionalized siloxane:

[0025]

[0026] A suitable monocyclic epoxy-functionalized siloxane is 1,1,1,3,5,5,5-heptamethyl-3-[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]trisiloxane:

[0027] .

[0028] The weight ratio of tricyclic cyclohexane (component (a)) to monocyclic siloxane (component (b)) is in the range of 30 / 70 to 70 / 30, preferably in the range of 50 / 50 to 70 / 30. Preferably, the weight ratio of component (a) to component (b) is in the range of 50 / 50 to 70 / 30, and may be in the range of 60 / 40 to 70 / 30, or even 70 / 30. The range of 50 / 50 to 70 / 30 is preferred because this makes the UV-curable silicone composition more likely to have a viscosity of less than 25 mPa·s at 40°C, which makes it easy to inkjet print using a slightly heated inkjet nozzle. When the ratio reaches the range of 60 / 40 to 50 / 50, the UV-curable silicone composition has a viscosity of less than 25 mPa*s at 25°C and 40°C, which makes it easy to perform inkjet printing without heating the inkjet nozzle.

[0029] In addition, the combined weight of components (a) and (b) is in the range of 95.0 to 99.5% by weight, and may be 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more, or even 99.2% by weight or more, while typically 99.5% by weight or less, or even 99.26% by weight or less, where the weight percentage is relative to the weight of the UV-curable silicone composition.

[0030] (c) Photoacid generator (PAG)

[0031] PAG becomes acidic upon exposure to light and is therefore used as a photoinitiator for acid-catalyzed reactions. PAG typically becomes acidic by dissociating to form strong acids or by dissociating protons upon exposure to light. A common type of PAG includes triphenylsulfonium salts. Examples of PAG include: 4-isopropyl-4'-methyldiphenyliodonium tetra(pentafluorophenyl)borate, bis(4-dodecylphenyl)iodonium hexafluoroantimonate; (p-dodecylphenyl)(p-methylphenyl)iodonium hexafluoroantimonate; (p-isopropylphenyl)(p-methylphenyl)iodonium tetra(pentafluorophenyl)borate; diphenyliodonium nitrate, diphenyliodonium hexafluorophosphate, (4-fluorophenyl)diphenylsulfonium trifluoromethanesulfonate, N-hydroxynaphthalimide trifluoromethanesulfonate, (4-Iodophenyl)diphenylsulfonium trifluoromethanesulfonate, (4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, (4-phenoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, triarylsulfonium hexafluorophosphate, triphenylsulfonium perfluoro-1-butanesulfonate, triphenylsulfonium trifluoromethanesulfonate, tri(4-tert-butylphenyl)sulfonium perfluoro-1-butanesulfonate, bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate, and bis(4-tert-butylphenyl)iodonium p-toluenesulfonate.

[0032] The concentration of PAG in the UV-curable silicone composition is 0.3% by weight or higher, and can be 0.4% by weight or higher, 0.5% by weight or higher, 0.6% by weight or higher, or even 0.7% by weight or higher, and is also typically 2% by weight or lower, 1.5% by weight or lower, 1% by weight or lower, 0.9% by weight or lower, 0.8% by weight or lower, 0.75% by weight or lower, or even 0.7% by weight or lower, where the weight percentage is relative to the weight of the UV-curable silicone composition.

[0033] Optional components

[0034] In addition to components (a)-(c), the UV-curable silicone composition may also contain optional components. For example, the UV-curable silicone composition may contain any optional component selected from sensitizers, wetting agents (surfactants), and solvents, or any combination of more than one optional component. The UV-curable silicone composition may also be free of any one or any combination of optional components other than components (a)-(c).

[0035] Sensitizers can be used to help absorb UV light and accelerate the release of PAG acids—essentially, to improve the light efficiency of the composition. Examples of suitable sensitizers include any one or any combination of more than one thioxanthone and / or substituted thioxanthone materials. Suitable sensitizers include 2-isopropylthioxanthone (CAS#5495-84-1). The concentration of the sensitizer in the UV-curable epoxy composition is 0% by weight or higher, and can be 0.01% by weight or higher, 0.03% by weight or higher, 0.05% by weight or higher, 0.10% by weight or higher, or even 0.15% by weight or higher, while typically 0.20% by weight or lower, 0.15% by weight or lower, 0.10% by weight or lower, 0.05% by weight or lower, or even 0.04% by weight or lower, where the weight percentage is based on the weight of the UV-curable silicone composition.

[0036] Wetting agents can be used to reduce the surface tension of formulations, thereby promoting spread of the formulation onto the substrate. Examples of suitable wetting agents include polyether-modified siloxane surfactants, such as those marketed under the trade name BYK. ™ Those available for 378, and those under the brand name BYK ™ 354, BYK ™ 390, BYK ™ 352, BYK ™ 359, BYK ™ 350, BYK ™ 355, BYK ™ 356 and BYK ™ All of those available for purchase under 359N are available from BYK-Chemie GmbH (BYK is a trademark of BYK-Chemie GmbH).

[0037] Solvents can be used to reduce the viscosity of UV-curable silicone compositions to facilitate deposition at lower temperatures, and are particularly useful for spin coating onto substrates. However, solvents can be undesirable residual components in the cured coating of UV-curable silicone compositions. Therefore, UV-curable silicone compositions typically contain 10% by weight or less, even 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.5% by weight or less of organic solvents, or may even contain no organic solvents (or even any solvent).

[0038] Method for curing UV-curable silicone compositions

[0039] In a second aspect, the present invention is a method for curing the UV-curable silicone composition of the first aspect of the present invention.

[0040] The method of the present invention includes the following steps: (a) combining the components of a UV-curable silicone composition to form a UV-curable silicone composition; (b) depositing the UV-curable silicone composition onto a substrate; and (c) exposing the UV-curable silicone composition deposited on the substrate to ultraviolet light.

[0041] Within the broadest scope of this invention, step (b) can be performed by any means. However, step (b) is typically performed by inkjet printing or spin-coating a UV-curable silicone composition onto a substrate. Step (b) is ideally performed at a temperature in the range of 25 to 60°C, preferably in the range of 25 to 40°C, more preferably in the range of 25 to 30°C, and can be performed at approximately 25°C. To achieve a sufficiently low viscosity of the UV-curable silicone composition for deposition (typically 25 mPa*s or less), it may be necessary to heat the UV-curable silicone composition to a temperature above 25°C and / or include a solvent in the UV-curable silicone composition. Ideally, the UV-curable silicone composition has a viscosity of 25 mPa*s or less at 25°C, therefore the method can be performed with a solvent-free UV-curable silicone composition, and step (b) does not require heating to a temperature above 25°C.

[0042] Ideally, the UV-curable silicone composition is deposited onto the substrate before or during step (b). For example, it is ideal to form a film of the UV-curable silicone composition on the substrate prior to curing. The substrate may be a single composition or may include multiple components (e.g., an electronic circuit board).

[0043] Articles containing cured UV-curable silicone compositions

[0044] In a third aspect, the present invention is an article comprising the UV-curable silicone composition of the first aspect, preferably a cured UV-curable silicone composition of the first aspect. The cured UV-curable silicone composition of the first aspect can be obtained by curing the UV-curable silicone composition according to the method of the second aspect of the present invention.

[0045] The article may contain only a cured, UV-curable silicone composition. Alternatively, the article may contain a combination of the cured, UV-curable silicone composition and other elements to form the article. For example, the article may contain a cured, UV-curable silicone composition coated on a substrate. An ideal article is an organic light-emitting diode (OLED) containing a cured, UV-curable silicone composition as an encapsulating layer in the OLED. The encapsulating layer of the OLED covers the light-emitting layer of the OLED.

[0046] Example

[0047] Table 1 lists the materials used in this section for sample preparation.

[0048] Table 1

[0049]

[0050] 3,3',3"-(cyclohexane-1,2,4-triyltris(ethane-2,1-diyl)tris(1,(2-(7-oxabicyclo[4.1.0]) Synthesis of (hept-3-yl)ethyl)-1,1,3,3-tetramethyldisiloxane

[0051] Step 1. Preparation of SiH conversion agent

[0052] 20 g of toluene, 0.52 g of 2,6-di-tert-butyl-4-((dimethylamino)methyl)phenol inhibitor (Millipore-Sigma), 67.03 g of 1,1,3,3-tetramethyldisiloxane (Millipore-Sigma), and 0.15 g of Karstedt catalyst were added to a 500 mL three-necked flask equipped with a nitrogen inlet. The mixture was heated to 55 °C for 30 minutes. Then, 12.4 g of 3-vinyl-7-oxabicyclo[4.1.0]heptane (also known as 1,2-epoxy-4-vinylcyclohexane, from Alfa Chemistry) was added over 30 minutes. The mixture was maintained at 55 °C for three hours. 1,1,3,3-tetramethyldisiloxane and toluene were removed using a rotary evaporator. The Karstedt catalyst was removed using a silica column. The product was further stripped using a rotary evaporator at 30 °C for one hour. Gas chromatography-mass spectrometry analysis showed that the purity of the obtained SiH conversion agent was >98%. The structure of the SiH conversion agent is as follows:

[0053]

[0054] Step 2. The reaction forms the final product.

[0055] 20 g of toluene, 1.5 g of 1,2,4-trivinylcyclohexane (from TCI), and 30 mg of Karstedt catalyst were added to a 100 mL three-necked flask equipped with a nitrogen inlet. The mixture was heated to 78 °C over 30 minutes, avoiding any temperature jumps in the initial minutes. 8 g of SiH conversion agent was gradually added over 30 minutes, and the mixture was then maintained at 78 °C for 4 hours. Toluene was removed by rotary evaporation at 30 °C. The Karstedt catalyst was removed using a silica column. The product was further stripped using a rotary evaporator at 30 °C for one hour to obtain the final product. The purity of the product was greater than 95% as determined by liquid chromatography-mass spectrometry.

[0056] Synthesis of 1,1,1,3,5,5,5-heptamethyl-3-[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]trisiloxane

[0057] 133.6 g of 1,1,1,3,5,5,5-heptamethyltrisiloxane (Millipore Sigma), 0.01 g of Karstedt catalyst (Millipore Sigma), and 0.034 g of 2,6-di-tert-butyl-4-methylphenol (Fisher Scientific) were placed in a three-necked flask. The flask was repeatedly purged with nitrogen to obtain an inert atmosphere. 80.72 g of vinylcyclohexene monooxide (BOCSciences) was added dropwise to the flask at 100°C over a period of 110 minutes. The contents of the flask were heated to 110°C for several hours. Volatile components were removed under vacuum to obtain a pale yellow oil with a viscosity of 7 mPa·s (94% yield, 195.35 g). 13 C and 29 Si NMR spectroscopy characterization of the products.

[0058] Sample preparation and characterization

[0059] Samples were prepared using the formulations in Table 2, where the values ​​for each component of each sample are in grams (g). All components of the sample formulations were mixed together and then spin-coated onto a fluorine-doped tin oxide (FTO) glass substrate (50 mm × 50 mm) at 1000 rpm for 20 seconds. The coating was cured by exposing it to UV light at a wavelength of 365 nm, where the exposure corresponds to an energy of 2 joules per square centimeter.

[0060] Dk evaluation technology

[0061] The dielectric constant (Dk) of each cured sample was measured using the following Dk evaluation technique. The Dk value of a material depends on the method used to measure it. The Dk evaluation technique of this invention utilizes a method of directly attaching an aluminum electrode to the cured silicone material, which has proven to be more reproducible (+ / - 0.02) than other methods using aluminum electrodes attached to the cured silicone material via an oil film. Dk values ​​from the two different techniques differ slightly and cannot be directly compared.

[0062] The thickness of the spin-coated, cured film was measured using a Filmetrics F50 film thickness measurement instrument, employing light wavelengths fixed in the range of 832.6 nm to 958.667 nm. The measurement was performed at 85 points on the sample, excluding a 3 mm edge region (sample width = 50 mm, sample height = 40 mm). The thickness in the measurement area should be 8 μm ± 80%.

[0063] A 13 mm diameter aluminum electrode was deposited on the sample at a location with a diameter of 13 mm and a uniform thickness (thickness variation less than 0.2 μm from mapping assessment).

[0064] The capacitance between the aluminum electrode and the FTO glass substrate was measured using an Agilent E4980A LCR instrument at 100 Hz and 1 volt, with a 13 mm diameter electrode. The Dk of the cured silicone film was calculated using the following equations and values:

[0065] C=εS / d

[0066] Where "C" is the capacitance of the membrane, and ε is the dielectric constant, where ε = ε₀ε r Where ε0 is the permittivity of vacuum, and ε r Let Dk be the area of ​​the electrode, S be the area of ​​the electrode, and d be the thickness of the cured silicone film.

[0067] Sample viscosity

[0068] Using an AR2000ex rheometer from TA Instruments, with a 40 mm diameter aluminum plate and 100s... -1 The shear rate was measured, and the viscosity of the samples in mPa*s was determined at 25°C and 40°C. Data were collected at an ramp rate of 3°C / min within a temperature ramp from 20°C to 50°C, and the values ​​at 25°C and 40°C were reported.

[0069] Table 2

[0070]

[0071] Sample A illustrates the use of a single epoxy-functionalized siloxane to produce an uncured formulation.

[0072] Samples B and C demonstrate formulations that produce films with a Dk greater than 2.8 when used alone or in combination with monoepoxy functional siloxanes.

[0073] Sample D indicates that the use of only tri-epoxyfunctionalized cyclohexane resulted in a formulation with an undesirable high viscosity value and a Dk value of 2.80 or higher during curing.

[0074] Samples 1-3 illustrate embodiments of the invention and reveal that they have ideal viscosity values ​​and Dk values ​​of less than 2.80 and even 2.75 or lower for the cured formulation.

Claims

1. A UV-curable silicone composition comprising the following components: (a) Tricyclic hexane with average structure (I): (I) (b) monocyclic epoxy-functionalized siloxanes; and (c) 0.3 to 1.5% by weight of photoacid generator; The weight ratio of component (a) to component (b) is in the range of 30 / 70 to 70 / 30, and the combined weight of components (a) and (b) is in the range of 95.0 to 99.5% by weight, wherein the weight percentage is relative to the weight of the UV-curable silicone composition.

2. The UV-curable silicone composition according to claim 1, wherein the UV-curable silicone composition further comprises a sensitizer.

3. The UV-curable organosilicon composition according to claim 1 or claim 2, wherein the monoepoxy-functionalized siloxane is an epoxy-functionalized trisiloxane.

4. The UV-curable organosilicon composition according to claim 3, wherein the epoxy group on the monoepoxy functional siloxane is a [2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl] group.

5. The UV-curable organosilicon composition according to claim 4, wherein the monoepoxy functional siloxane is 1,1,1,3,5,5,5-heptamethyl-3-[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]trisiloxane.

6. The UV-curable silicone composition according to any of the preceding claims, wherein the weight ratio of component (a) to component (b) is in the range of 50 / 50 to 70 / 30.

7. A method for curing a UV-curable silicone composition according to any one of the preceding claims, the method comprising the following steps: (a) Combining the components of the UV-curable silicone composition to form the UV-curable silicone composition; (b) The UV-curable silicone composition is disposed on a substrate; as well as (c) Expose the UV-curable silicone composition disposed on the substrate to ultraviolet light.

8. The method of claim 7, wherein step (b) is performed by inkjet printing or spin coating the composition onto the substrate.

9. An article comprising a substrate having thereon disposed of a UV-curable silicone composition according to any one of claims 1 to 6.

10. The article of claim 9, wherein the UV-curable silicone composition is in a cured state.

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