Epoxy-functionalized polysiloxane composition

Abstract

The present invention relates to a composition comprising a DaTb-based resin, an epoxy-functionalized organosiloxane crosslinker, a photo acid generator, and an adhesion promoter of Formula 1: wherein a and b represent mole fractions of Da and Tb respectively; the DaTb-based resin is functionalized with C1-C6-alkyl groups; aryl groups; and epoxy-functionalized fragments; and the ratio of b:a is in the range of from 0.5:1 to 20:1; wherein each R is a C3-C12-alkyl anhydride group; the sum of m and n is in the range of from 1 to 4; and -DHx- is a mono- or diradical of the compound of Formula 2: The composition of the present invention is capable of forming thin cured coatings on substrates with excellent physical properties.

Description

[0001] Epoxy-functionalized Polysiloxane Composition

[0002] Background of the Invention

[0003] Silicones exhibit flexibility, processability, and thermal reliability, but low surface hardness and substrate adhesion. Epoxy resins, on the other hand, exhibit hardness and substrate adhesive strength, but suffer from poor flexibility and processability. For these reasons, silicone-epoxy hybrids have been developed to incorporate the advantages of silicones and epoxy resins. These hybrids are thermally- and UV-curable with acid generators such as photo acid and heat acid generators (PAGs and HAGs), and have demonstrated suitability for many applications that demand flexibility, high modulus, excellent hardness, and acceptable substrate adhesion, including electrical, electronic, and automotive applications.

[0004] A limitation of current silicone-epoxy hybrid coatings is their inadequate adhesive strength, especially when applied as micron-thick layers (-10-300 pm) to substrates. The ability to use thin coatings is crucial for applications in semiconductor packaging and thin film transistor (TFT) display modules, for example. It would therefore be desirable to find a way to improve adhesion strength for silicone-epoxy coatings using thin coatings.

[0005] Summary of the Invention

[0006] The present invention addresses a need in the art by providing a composition comprising a DaTb-based resin, an epoxy-functionalized organosiloxane crosslinker, a photo acid generator, and an adhesion promoter of Formula 1 :

[0007] Formula 1 wherein a and b represent mole fractions of D and T respectively; the DaTb-based resin is functionalized with Ci-Ce-alkyl groups; aryl groups; and epoxy-functionalized fragments; and the ratio of b:a is in the range of from 0.5:1 to 20:1; wherein each R is a Cs-Cn-alkyl anhydride group; the sum of m and n is in the range of from 1 to 4; and -DHX- is a mono- or diradical of the compound of Formula 2:

[0008] Formula 2 where x is from 3 to 10, and y is x - 3.

[0009] The silicone-epoxy hybrid containing composition of the present invention is capable forming thin coatings with excellent adhesion strength. Detailed Description of the Invention

[0010] The present invention is a composition comprising a DaTb-based resin, an epoxy-functionalized organosiloxane crosslinker, a photo acid generator, and an adhesion promoter of Formula 1 :

[0011] Formula 1 wherein a and b represent mole fractions of D and T, respectively; the DaTb-based resin is functionalized with Ci-Ce-alkyl groups; aryl groups; and epoxy-functionalized fragments; and the ratio of b:a is in the range of from 0.5:1 to 20:1; wherein each R is a Cs-Cn-alkyl anhydride group; the sum of m and n is in the range of from

[0012] 1 to 4; and -DHX- is a mono- or diradical of the compound of Formula 2:

[0013] Formula 2 where x is from 3 to 10, and y is x - 3.

[0014] As used herein, “DaTb-based resin” refers to a resin comprising the following units:

[0015]

[0016] Where each R1is independently Ci-Ce-alkyl, aryl, or an epoxy functionalized fragment.

[0017] Preferably, at least one of the R1groups is aryl and at least one of the R1groups is Ci-Ce-alkyl, more preferably methyl, ethyl, or n-propyl ; the mole fraction of the epoxy functionalized fragment in the resin is preferably in the range of from 0.02 to 0.30. Preferred aryl groups are phenyl groups and naphthyl groups, with phenyl groups being especially preferred aryl groups.

[0018] The DaTb-based resin may further comprise Mcand / or Qd units: where R2is Ci-Ce-alkyl and a + b + c + d = l. In one embodiment of the invention a + b > 0.5; in another embodiment; a + b > 0.8; in yet another embodiment; a + b > 0.9.

[0019] In another embodiment, the ratio of b: a is in the range of from 1:1 or from 1.5: 1, to 10:1 or to 5: 1.

[0020] As used herein, “epoxy functionalized fragment” refers to a C2-C12 hydrocarbyl or hydrocarbyl ether group connecting an oxirane group and a silicon atom. The hydrocarbyl group may be linear, branched, cyclic, or fused cyclic. Examples of suitable epoxy functionalized fragments include 2-(3,4-epoxycyclohexyl) ethyl, 3-glycidoxy propyl, and 3-epoxy propyl fragments, as illustrated: where the dotted lines represent the point of attachment to the silicon atom.

[0021] An example of a subclass of DaTt>-based resins is a resin of the formula DaTbTb ", where Da> is a Ci-Ce-alkylphenyl-functionalized D unit, preferably a methylphenyl D unit; Tb' is a Ci-Ce-alkyl functionalized T unit, preferably a methyl or ethyl functionalized T unit; and Tb" is an epoxy-functionalized T unit. The ratio of (b' + b'') / a' is preferably in the range of 1:1 or from 1.5:1, to 10: 1 or to 5:1.

[0022] The resin of formula DabTb" can be prepared by hydrolyzing under basic conditions a mixture of an epoxy-functionalized trimethoxysilane; a Ci-Ce-alkyl-functionalized trimethoxysilane such as methyltrimethoxysilane, ethyltrimethoxysilane, or n-propyltrimethoxysilane; and a phenyl-C i -Ce-alkyl-dimethoxysilane.

[0023] The weight average molecular weight of the DaTb-based resin is preferably in the range of from 1000 or from 2000 g / mole, to 10,000 or to 6000 g / mole, as measured by gel permeation chromatography as described below in the section labeled Weight Average Molecular Weight Determination. The concentration of the DaTb-based resin is preferably in the range of from 60 to 85 weight percent, based on the weight of the composition.

[0024] The epoxy-functionalized organosiloxane crosslinker is an organosiloxane that comprises two or more epoxy-functionalized fragments. An example of a class of epoxy functionalized crosslinkers is illustrated: where Ep is an epoxy functionalized fragment, and f is from 0 to 10. An example of a commercially available epoxy-functionalized organosiloxane crosslinker is 1 ,3-bis[2-(3,4- epoxycyclohexyl)ethyl]tetramethyldisiloxane (CAS: 18724-32-8, EP dimer): l ,3-bis[2-(3,4-epoxycyclohexyl)ethyl]tetramethyldisiloxane - EP dimer

[0025] The concentration of the epoxy-functionalized organosiloxane crosslinker is preferably in the range of from 5 or from 10 weight percent to 40 or to 30 weight percent, based on the weight of the composition.

[0026] Photo acid generators decompose under UV irradiation conditions to generate acids, which, in turn, catalyze the cure of the composition. Examples of suitable photo acid generators include sulfonium salts, iodonium salts, phosphonium salts, and diazonium salts of SbFe , AsFe , BF4 , B CfiFslC, HSOc, CIO4", an CF3SCX. An example of a commercially available photo acid generator is TR-PAG-21608 photo acid generator ((thiodi-4,l-phenylene)bis[bis(4- methylphenyl)-sulfonium bis[tetrakis(pentafluorophenyl)borate) CAS:875713-04-5:

[0027] TR-PAG-21608 photo acid generator

[0028] The concentration of the photo acid generator is preferably in the range of from 0.05 or from 0.1 to 2 or to 1 weight percent, based on the weight of the composition.

[0029] The adhesion promoter is a compound of Formula 1 :

[0030] Formula 1 where each R is a Cs-C -alkyl anhydride group. In one embodiment, m + n is in the range of 1 to 2;

[0031] -DHX- is a mono- or diradical of the compound of Formula 2:

[0032] Formula 2

[0033] In one embodiment, x is in the range of from 4 to 6. The concentration of the adhesion promoter is preferably in the range of from 0.01 or from 0.1 or from 0.5 weight percent to 5 or to 3 weight percent, based on the weight of the composition.

[0034] Examples of suitable anhydride substituents include succinic anhydride, maleic anhydride, and phthalic anhydride groups. Where the anhydride group is a succinic anhydride group, R is represented by the following fragment: where z is from 1 to 10, and where the dotted line represents the point of attachment to the DHXdiyl group.

[0035] DHXis represented by the compound of Formula 2. When x is 4, y is 1. Thus, DH4 is represented by the compound of Formula 2a:

[0036] Formula 2a

[0037] In one embodiment, R1is phenyl, m is 1, n is 1, y is 1, and z is 1. Accordingly, a possible configuration of a compound of the present invention is represented by Formula 3: It is understood that the R groups can be attached to any of the Si atoms of the DHXgroups and that the DHXgroups may be a blend of DHXgroups. For example, DHXmay be a mixture of DH4, DH5, and DH6. It is further understood that the compound of Formula 1 may comprise a blend of mono-, di-, tri-, and tetrasubstituted alkyl anhydride groups. In one embodiment, the compound of Formula 1 comprises a blend of mono- and disubstituted alkyl anhydride groups; i.e., m + n is in the range of 1 to 2.

[0038] The compound of Formula 1 (where m is 1 and n is 1) can be prepared in 2-steps, as illustrated: where Formula lois represented by the following formula:

[0039] Formula l0and Anh is an anhydride group. An example of a suitable acid catalyst is tris(pentafluorophenyl)borane (BCF).

[0040] The DaTb-based resin, the epoxy-functionalized organosiloxane crosslinker, the photo acid generator, and the adhesion promoter of Formula 1 preferably comprise at least 90 weight percent of the composition; the composition may further comprise one or more fillers such as crushed quartz, glass particles, glass beads, and fused or fumed silica.

[0041] A cured coated substrate is advantageously prepared by applying to a substrate a thin layer of the composition (20 pm to 300 pm), then subjecting the coating to a LED UV light source at room temperature.

[0042] It has been discovered that the thin coatings of UV-cured composition of the present invention provides excellent adhesion onto substrates such as glass.

[0043] Weight Average Molecular Weight Determination by Gel Permeation Chromatography

[0044] A Waters 2695 Separations module with a seal wash, a degasser, and a Waters 2414 Refractive Index detector was used to measure the weight average molecular weight (Mw) of a

[0045] DPho .34TEpo.i6TPro so resin. The resin sample was dissolved in THF (0.5 weight percent resin) and injected into a Styragel guard column (4.6 x 30 mm) connected to a series of three Styragel HR columns (7.8 x 300 mm, separation range from 100 g / mole to 4,000,000 g / mole). Polystyrene standards covering the molecular weight range of 580 g / mole to 2,610,000 g / mole were used. The flow rate of the sample through the columns was 1 mL / min, the injection volume was 100 pL, the eluent was HPLC grade THF, and the run time was 1 h. Mwof the resin was found to be -3000 g / mol. Examples

[0046] In the following examples, TEprefers to a T unit functionalized with a 2-(3,4-epoxycyclcohexyl) ethyl group, and TPrrefers to a T unit functionalized with an 77-propyl group; pbw refers to parts by weight.

[0047] Intermediate Example 1 - Preparation of Formula lo

[0048] A compound of Formula 2 (99.97 g, y is predominantly 1) in anhydrous toluene (49.97 g) were added to a N2 purged 1-L 3 -neck round bottom flask equipped with a thermocouple, an overhead stirrer, and a septum. The contents of the flask were stirred, then BCF catalyst solution (0.32 g, 1% wt.% in toluene) was added. Diphenyldisilanol (56.07 g) was added in 4 portions over the course of ~1.5 h while maintaining a reaction temperature < 30 °C. The contents were stirred for an additional 1.5 h after addition was complete. A clear solution was obtained and treated with 36 pL of phenyl acetylene before volatiles were removed in vacuo at 80 °C.

[0049] Intermediate Example 2 - Preparation of a Compound of Formula 3

[0050] The compound of Formula lo(81.0 g) was charged into a three-neck round bottom flask and heated to 75 °C under N2 with stirring. Karstedt’s catalyst (5 ppm) was added, followed by the gradual addition of an allyl succinic anhydride solution (29.0 g in 7 g toluene). The addition rate was controlled so that the reaction mixture temperature did not exceed 80 °C. After completion of the addition, the reaction mixture was stirred at 75 °C under N2 for additional 1 h before being allowed to cool to room temperature. 1-Ethynyl-l -cyclohexanol (0.43 g) was added to the mixture, after which time volatiles were removed in vacuo.

[0051] Masterbatch Preparations

[0052] A first Masterbatch 1 (MB1) was prepared by dissolving the DPho.34^0.16^0.50 resin (80 pbw) and EP dimer (20 pbw) in heptane. The heptane was then removed in vacuo.

[0053] Masterbatch 2 (MB2) was prepared by mixing PAG-21608 (10 pbw) with EP dimer (90 pbw). Example 1 - Preparation of Epoxy-Silicone Composition with Adhesion Promoter

[0054] A UV-curable epoxy- silicone hybrid composition containing adhesion promoter (Intermediate Example 2) was prepared by blending MB1 (94 pbw), MB2 (5 pbw), and Intermediate Example 2 (1 pbw). The blend was mixed at 1,500 rpm for 2 min in vacuo, then placed into 30-mL syringes and vacuum sealed. Essential properties (viscosity, cross hatch test) were measured, and samples were stored (-5 °C).

[0055] Comparative Example 2 - Preparation of Epoxy-Silicone Composition without Adhesion Promoter

[0056] The procedure for preparing the composition of Example 1 was followed except that no adhesion promoter was added.

[0057] Preparation and Testing of Coated Substrates

[0058] Samples were applied to glass at a coating thickness of 200-300 m, cured for 10 s using a Firejet FJ800 LED UV light source (365 nm at 5000 mJ / cm2UVA), then allowed to stand at room temperature for 20 min prior to testing.

[0059] ASTM D3359 was used to evaluate the adhesive strength of the cured coatings. The coating surface was cut into a lattice pattern with six longitudinal and six transverse cuts. Then, pressure sensitive tape was applied to the substrates and adhesion was evaluated and rated. The coating prepared from Example 1 had a classification rating of 4B, indicating < 5% removal of the coating. In contrast, the coating prepared from the comparative example showed nearly complete removal of the coating from the substrate. The results show the effectiveness of the adhesion promoter for thin coatings.

Claims

Claims:

1. A composition comprising a DaTb-based resin, an epoxy-functionalized organosiloxane crosslinker, a photo acid generator, and an adhesion promoter of Formula 1 :Formula 1 wherein a and b represent mole fractions of D and T respectively; the DaTb-based resin is functionalized with Ci-Ce-alkyl groups; aryl groups; and epoxy-functionalized fragments; and the ratio of b:a is in the range of from 0.5:1 to 20:1; wherein each R is a Cs-Cn-alkyl anhydride group; the sum of m and n is in the range of from 1 to 4; and -DHX- is a mono- or diradical of the compound of Formula 2:Formula 2 where x is from 3 to 10, and y is x - 3.

2. The composition of Claim 1 wherein x is in the range of from 4 to 6; m + n is in the range of from 1 to 2; and the ratio of b:a is in the range of from 1.1 to 10: 1; wherein, based on the weight of the composition, the concentration of the DaTb-based resin is in the range of from 60 to85 weight percent, the concentration of the epoxy-functionalized organosiloxane crosslinker is in the range of from 5 to 40 weight percent, the concentration of the photo acid generator is in the range of from 0.05 to 2 weight percent, and the concentration of the adhesion promoter of Formula 1 is in the range of from 0.01 to 5 weight percent.

3. The composition of Claim 2 where x is 4.

4. The composition of Claim 1 wherein the adhesion promoter is represented by the following Formula 3 :

5. The composition of Claim 2 wherein the mole fraction of the epoxy functionalized fragment in the resin is in the range of from 0.02 to 0.30.

6. The composition of Claim 5 wherein DaTt>-based resin comprises the following units:where each R1is independently Ci-Ce-alkyl, phenyl, or an epoxy functionalized fragment, wherein at least one of the R1groups is phenyl and at least one of the R1groups is methyl, ethyl, or n- ropyl; wherein a + b > 0.8.

7. The composition of Claim 2 wherein the DaTb-based resin is a resin of the formula Da'TbTb", where Da- is a Ci-Ce-alkylphenyl-functionalized D unit; T is a Ci-Ce-alkyl functionalized T unit; and Tb" is an epoxy-functionalized T unit, and wherein the mole fraction of the epoxy functionalized fragment in the epoxy-functionalized T unit is from 0.02 to 0.30.

8. The composition of Claim 7 wherein the ratio of (b' + b'') / a' is in the range of 1.5:1, to 5:1, wherein the epoxy functionalized fragment is a 2-(3,4-epoxycyclohexyl) ethyl, 3-glycidoxy propyl, or 3-epoxy propyl fragment; Da- is a methylphenyl-functionalized D unit; and Tb' is a methyl, ethyl, or n-propyl functionalized T unit.

9. The composition of any of Claims 1 to 8 wherein the epoxy-functionalized organosiloxane crosslinker is represented by the following formula:where Ep is an epoxy functionalized fragment, and f is from 0 to 10 the photo acid generator is a sulfonium salt, an iodonium salt, a phosphonium salt, or a diazonium salt of SbFd-, AsF6‘, BF4‘, B(C6F5)4 , HSO4 , ClOF, an CF3SO3.

10. The composition of Claim 9 wherein the photo acid generator is ((thiodi-4,1- phenylene)bis[bis(4-methylphenyl)-sulfonium bis[tetrakis(pentafluorophenyl)borate), and the epoxy-functionalized organosiloxane is l,3-bis[2-(3,4-epoxycyclohexyl) ethyl]tetramethyldisiloxane.

11. The composition of Claim 2 wherein the Mwof the DaTt>-based resin is in the range of 2000 g / mole to 6000 g / mole, as measured by gel permeation chromatography.

12. The composition of Claim 2 wherein the DaTb-based resin further comprises Mcand / or Qd units of the formulas:McQ where R2is Ci-Ce-alkyl and a + b + c + d = l.

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