Patent Application
20190040250
The invention relates to an epoxy resin system, in particular a one-component epoxy resin system. Furthermore, the invention relates to the use of an epoxy resin system. Furthermore, the invention relates to an optoelectronic device. Furthermore, the invention relates to a process for producing an epoxy resin system.
In electronic devices, for example in optoelectronic devices such as light-emitting diodes and light modules, epoxy resins, thermoplastics and silicones are often used as mounting and housing materials, casting resins and/or as matrix materials for light conversion elements, reflection layers and optical filters, for example, as well as lens materials. Today, high-performance polymers, such as glass fiber reinforced thermoplastics, mainly based on polyphthalamide, silicones, moldable epoxy resin compounds (EMC) have proven their worth as housing materials. However, due to the processing and the size of the fillers used, it is not possible to produce housings with wall thicknesses of considerably less than 200 μm with these materials. Furthermore, these materials can be used under clean room conditions only to a limited extent because there are concerns about additives and processing aids containing siloxane and silicone.
An object to be solved by the invention is to provide an epoxy resin system with improved properties. In particular, the epoxy resin system can be used to provide or manufacture housings for optoelectronic devices with wall thicknesses of up to 80 μm. Furthermore, the epoxy resin system according to the invention can be used for high operating temperatures. A further object of the invention is to provide an optoelectronic device that has an epoxy resin system with the improved properties. Another object of the invention is to provide a cost-effective process for producing the epoxy resin system.
These objects are solved by an epoxy resin system according to independent claim 1. Advantageous embodiments and further developments of the invention are subject-matter of the dependent claims. Furthermore, these objects are solved by the use of an epoxy resin system according to claim 13. Furthermore, these objects are solved by an optoelectronic device according to claim 14. Furthermore, these objects are solved by a process for producing an epoxy resin system according to claim 15.
In at least one embodiment, the epoxy resin system comprises or consists of at least one inorganic filler, at least one cycloaliphatic epoxy resin, a polyvinyl butyrate and at least one cationic accelerator. The inorganic filler is particularly an oxide of a metal or semi-metal or a nitride of a metal or semi-metal. In particular, the inorganic filler has an upper grain size (dmax) of not more than 30 μm. The epoxy resin system is in particular a one-component system.
Epoxy resin is usually provided as a two-component system to be mixed by the user ready for use. The so-called “A-component” usually contains the epoxy resin, the so-called “B-component” the hardener, which is added to the resin in a predetermined mixing ratio. One-component system means here and in the following that the epoxy resin system is reactive and thermally cures and has no B-component. One-component systems are delivered ready for use and can be stored. A B-component is especially an organic substance such as a carboxylic anhydride. A carboxylic anhydride of the B-component together with an accelerator usually cross-links the A-component (corresponds to formulated epoxy resin). This cross-linking produces a duromer epoxy resin molding material. The carboxylic anhydride together with an accelerator can be described as a hardener.
According to at least one embodiment, the epoxy resin system comprises at least one inorganic filler or a mixture of several inorganic fillers. The inorganic filler is selected from the group comprising an oxide of a metal, an oxide of a semimetal, a nitride of a metal and a nitride of a semimetal. In particular, the inorganic filler is selected from the group comprising silicon dioxide, titanium dioxide, aluminium oxide and zirconium oxide.
In particular, silicon dioxide, which is preferably amorphous, is used as an inorganic filler. Silicon dioxide with the CAS number (Chemical Abstracts Service) 60676-86-0 is preferred.
According to at least one embodiment, the inorganic filler has a content between 50% by weight inclusive and 85% by weight inclusive, preferably between 60% by weight inclusive and 80% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the inorganic filler has a specific surface area of at least 2 g/m2 and at most 20 g/m2, in particular between 2 g/m2 inclusive and 10 g/m2 inclusive, preferably between 2 g/m2 inclusive and 8 g/m2 inclusive, particularly preferably between 2.2 g/m2 inclusive and 5.5 g/m2 inclusive.
In addition or alternatively, the inorganic filler may have a grain size value d50 of at least 0.5 μm and/or a maximum of 20 μm. In particular, the inorganic filler has a grain size value d50 between 2 μm and 10 μm, preferably between 2.5 μm and 4.4 μm.
Alternatively or additionally, the inorganic filler can have an upper grain size dmax of a maximum of 30 μm or 25 μm or 20 μm, in particular of a maximum of 16 μm, for example 12 μm.
The specific surface area can be determined by means of BET isotherm. Unless otherwise stated, the grain size value d50 is defined below as the value d50, which is defined in such a way that 50% of the material is below and/or 50% of the material is above this size or diameter in relation to the volume fraction. The grain size value can be determined by dynamic light scattering (DLS). The term upper grain size dmax is used here and in the following to describe an inorganic filler filled in as a particle, which has a maximum diameter as upper grain size. In other words, according to DLS (Dynamic Light Scattering) there are no inorganic fillers present in the epoxy resin system that are larger than the upper grain size.
According to at least one embodiment, the inorganic filler has a specific surface area of at least 2 g/m2 and at most 20 g/m2 and a grain size value d50 of at most 20 μm and an upper grain size dmax of at most 30 μm.
According to at least one embodiment, the epoxy resin system comprises at least one cycloaliphatic epoxy resin. An epoxy resin system with the CAS number 2386-87-0 is preferably used as the cycloaliphatic epoxy resin system.
According to at least one embodiment, the cycloaliphatic epoxy resin contains at least two epoxy functions.
According to at least one embodiment, the cycloaliphatic epoxy resin is selected from a group of compounds comprising 3,4-epoxycyclohexyl-methyl-3,4-epoxycyclohexyl carboxylate and poly [(2-oxiranyl)-1,2-cyclohexanediol]-2-ethyl-2-(hydroxymethyl)-1,3-propanediol ether. Preferably the cycloaliphatic epoxy resin is 3,4-epoxycyclohexyl-methyl-3,4-epoxycyclohexyl carboxylate or (bis(epoxycyclohexyl)methyl carboxylate) having the following structure (formula I):
In one embodiment, the epoxy resin system does not contain any aromatic epoxy resin. Preferably, the epoxy resin system does not contain an aromatic compound. Aromatic compound means that the corresponding compound contains at least one aromatic ring. Because the epoxy resin system has no aromatic epoxy resin, preferably no aromatic compound, the epoxy resin system is significantly more light-stable. This means that it is less susceptible to yellowing when exposed to radiation, for example in an optoelectronic device, such as a light-emitting diode (LED). Compared to epoxy resins based on bisphenol A, the light stability is increased.
According to at least one embodiment, the content of the cycloaliphatic epoxy resin is between 3% by weight inclusive and 50% by weight inclusive, preferably between 3% and 40% by weight, based on the total weight of the epoxy resin system.
According to at least one embodiment, titanium dioxide, TiO2, is used as the inorganic filler. In particular, rutile-type titanium dioxide is used. In particular, the titanium dioxide has a CAS number 13463-67-7, EINECS 236-675-5, color index CI77891 and/or pigment white 6 (77891).
According to at least one embodiment of the epoxy resin system, it contains a polyvinyl butyrate as a polymer additive. In particular, polyvinyl butyrate with CAS number 68648-78-2 is used.
Polyvinyl butyrate are available with different molecular weights and different degrees of acetalization (formula III). The epoxy resin system can comprise several polyvinyl butyrate with different molecular weights and/or different degrees of acetalization.
The arrangement of the acetal, acetyl and hydroxy groups shown in the structural unit of formula III is not to be regarded as fixed. Rather, a statistical distribution or arrangement of the acetal, acetyl and hydroxy groups may be present. For example, a structural section could look like this (formula V):
Polyvinyl butyrate shows sufficient solubility in the cycloaliphatic epoxy resin.
According to at least one embodiment, the polyvinyl butyrate has gas transition temperatures of 63 to 84° C. At room temperature, the polyvinyl butyrate is present as a solid.
In accordance with at least one embodiment, the polyvinyl butyrate has an average molecular weight of from 10,000 g/mol to 80,000 g/mol, preferably from 20,000 g/mol to 70000 g/mol, for example 30,000 g/mol or 600,000 g/mol. With the use of polyvinyl butyrate having such average molecular weights, epoxy resin systems are available which have reduced brittleness, lower susceptibility to cracking, and higher bond strength over conventional cycloaliphatic epoxy based epoxy resins.
In accordance with at least one embodiment, the polyvinyl butyrate is selected from a group consisting of PVB B 30 T, PVB B 30 M, PVB B 30 H, PVB B 30 S, PVB B 30 HH, PVB B 60 T, PVB B 60 M, PVB B 60 H, PVB B 60 S, PVB B 60 HH and combinations thereof. The compounds are different polyvinyl butyrate types from Kuraray. Here, the number “30” or “60” stands for the average molecular weight, which is about 30,000 g/mol or 60,000 g/mol. The suffixes “T, M, H, S and HH” are an indication of the degree of acetalization which increases in that order and thus “T” stands for a low and “HH” for the highest possible degree of acetalization.
Due to the amount and type of polyvinyl butyrate used, the elasticizing and thermomechanical properties, the adhesion and moisture absorption behavior as well as the resistance to environmental influences of the epoxy resin system can be controlled in a targeted manner.
According to at least one embodiment of the epoxy resin system, the polyvinyl butyrate has a content between 0.1% by weight inclusive and 10% by weight inclusive, preferably between 0.1% by weight and 3% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment of the epoxy resin system, the polyvinyl butyrate has a content between 0.1% by weight inclusive and 10% by weight inclusive, preferably between 0.1% by weight and 3% by weight inclusive, based on the total weight of the epoxy resin system.
The epoxy resin system has a cationic accelerator. The cationic accelerator may be present in a content between 0.1% by weight inclusive and 3% by weight inclusive, preferably between 0.1% by weight inclusive and 2% by weight inclusive, based on the total weight of the epoxy resin system. The accelerator cures the epoxy resin system when exposed to temperature by cross-linking the epoxy functions according to a cationic homopolymerization mechanism.
According to at least one embodiment, the cationic accelerator is a halonium and/or sulfonium salt, preferably a thiolanium salt. The cationic accelerator may contain complex anions such as BF4−, PF6−, AsF6− and/or SbF6−. In particular, the cationic accelerator is an S-benzylthiolanium hexafluoroantimonate having the following structural formula:
The cationic accelerator can be obtained from Sigma Aldrich as PI 55.
According to at least one embodiment of the epoxy resin system, it also comprises an alcohol. The alcohol may be polyhydric. The alcohol can be an aliphatic or cycloaliphatic alcohol. The alcohol may be selected from the group consisting of ethanol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, cyclohexanedimethanol, 2-ethyl-2-hydroxymethyl, 1,3-propanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, tripolyethylene glycol, monoalkyl ether, glycerol and isosorbite. In particular, the alcohol may be 1,2-propanediol, butanediol or trimethylolpropane. The rheological, mechanical and thermomechanical properties as well as the wetting and flow behavior of the epoxy resin system can be adapted to the desired application form of the epoxy resin system by adding the alcohol.
According to at least one embodiment, the epoxy resin system contains between 0.1% by weight inclusive or 3% by weight inclusive and 3% by weight or 10% by weight inclusive, preferably between 0.1% by weight inclusive and 5% by weight inclusive, based on the total weight of the epoxy resin system.
Alternatively or additionally, the epoxy resin system may contain further epoxy resins. Another epoxy resin can be, for example, epoxy phenol novolac and epoxy resol novalac. In particular, epoxy phenol novolac with CAS number 28064-14-4 is used. Epoxy phenol novolac may have the following structural formula with n preferably between 0.2 and 1.8:
According to at least one embodiment, the other epoxy resins have a content of the total weight of the epoxy resin system between 0% by weight inclusive and 10% by weight inclusive, preferably between 0% by weight inclusive and 5% by weight inclusive. The epoxy phenol novolac resins are known to experts and are therefore not explained here. Epoxy phenol novolac resins are available from DOW, for example, as DEN-types. Other epoxy resins are available, for example, from Huntsman with the type designations EPN and ECN.
In at least one embodiment, the epoxy resin system comprises other materials selected from the group consisting of reactive diluents, silane coupling agents, carbon black, titanium dioxide pigment, fumed silica, CaCO3, deaerators, degassing agents, levelling agents, release agents, light stabilizer, organic dyes, brighteners and fluorescent pigments for LED conversion. Furthermore, the epoxy resin system can contain pigments such as carbon black, titanium dioxide, aluminum oxide, calcium fluoride and/or phosphors.
The reactive diluent may comprise an epoxy resin or an epoxy resin compound with one or two epoxy functions. In particular, the reactive diluent is an aliphatic epoxy compound. The reactive diluent can influence the glass transition temperature and the viscosity of the epoxy resin system. For example, a glycidyl ether, such as hexadiol diglycidyl ether with CAS number 16096-31-4, can be chosen as a reactive diluent.
In particular, the reactive diluent has a content between 0% by weight and 10% by weight inclusive, preferably between 0% by weight and 5% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system can have a silane coupling agent. The silane coupling agent may contain between 0% by weight inclusive and 5% by weight inclusive, preferably between 0% by weight inclusive and 3% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system can comprise pigment carbon black. In particular, the content of pigment carbon black is between 0% by weight and 2% by weight inclusive, in particular between 0% by weight and 1% by weight inclusive based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system contains titanium dioxide pigment. In particular, the content of titanium dioxide pigment is between 0% by weight inclusive and 20% by weight inclusive, preferably between 0% by weight inclusive and 10% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system contains fumed silica, in particular with a content between 0% by weight and 3% by weight inclusive, preferably between 0% by weight and 2% by weight inclusive, based on the total weight of the epoxy resin system. Aerosil R202 or Aerosil 200 can be used as pyrogenic silicas.
According to at least one embodiment, the epoxy resin system can have a silicone-free deaerator and/or a degassing agent. The deaerators and/or degassing agent may contain organic fluorine compounds, esters or acrylates. For example, BYK-A555 can be used as a deaerator and/or degassing agent. Deaerators and/or a degassing agent are available from Evonik and BYK-Chemie as commercial products.
In particular, the deaerator and/or degassing agent has a content of between 0% by weight and 1% by weight inclusive, in particular between 0% by weight and 0.5% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system has a levelling agent. For example, products from the Modaflour series can be used as levelling agents. In particular, the levelling agent has a content of between 0% by weight and 1% by weight inclusive, preferably between 0% by weight and 0.5% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system contains release agents. Waxes of long-chain carboxylic acids can preferably be used as release agents. A carbon chain or a carboxylic acid with 12 to 30 carbon atoms is understood as long chain. For example, commercially available carnauba waxes or the hydrocarbon wax Baerolub L-KK from Baerloher can be used as release agents. In particular, the release agent contains between 0% by weight and 1% by weight inclusive, preferably between 0% by weight and 0.5% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system contains one or more light stabilizers. Products from the series with the trade names Tinnvin, Irgonor, Irgafos, Tinnvin234, Tinnvin123, Irgafos163 or IrganoxMD1024 can be used as light stabilizers and/or stabilizers. In particular, the light stabilizer has a content between 0% by weight and 1% by weight inclusive, preferably between 0% by weight and 0.5% by weight inclusive, based on the total weight of the epoxy resin system.
According to at least one embodiment, the epoxy resin system may contain optical brighteners and/or dyes. For example, the epoxy resin system may contain antrachinone dyes.
In particular, the organic dye and/or brightener has a content of between 0% by weight and 1% by weight inclusive, preferably between 0% by weight and 0.5% by weight inclusive, based on the total weight of the epoxy resin system.
For example, 1,3-di-tertiary butyl-4-hydroxyphenol can be used as a light stabilizer. Light stabilizers are also available under the trade name Tinuvin.
According to at least one embodiment, the epoxy resin system contains fluorescent pigments. Rare earth doped garnets, rare earth doped alkaline earth sulfides, rare earth doped thiogallates, rare earth doped aluminates, rare earth doped silicates such as orthosilicates or chlorosilicates, rare earth doped alkaline earth silicon nitrides, rare earth doped oxynitrides, rare earth doped aluminum oxynitrides, rare earth doped silicon nitrides and/or sialones can be selected as phosphors. Garnets such as yttrium alumininium oxide (YAG), yttrium gadolinium aluminium oxide, luthetium aluminium oxide (LuAG), gallium aluminium oxide and therbium aluminium oxide (TAG) can be used as phosphors. The phosphors can be doped with cerium ions, europium ions, terbium ions, praseodymium ions, samarium ions or manganese ions. In particular, the phosphor is designed to convert radiation of a certain wavelength into radiation of another, especially longer wavelength. These phosphors can also be referred to as converter materials. Preferably the fluorescent pigments or phosphors have a content between 0 and 30% by weight inclusive, preferably between 0% and 20% by weight inclusive, based on the total weight of the epoxy resin system.
In particular, the components silane coupling agent, fumed silica, deaerator, degassing agent, levelling agent, release agent, light stabilizer, organic dyes and/or brightener of the epoxy resin composition can also be described as resin additives. For fine adjustment to the respective specific application and use, the content of these resin additives in total is a maximum of 5% by weight.
According to at least one embodiment, the epoxy resin system comprises or consists of a cycloaliphatic epoxy resin, preferably with a content of 85% by weight, an epoxy phenol novolac with a content of preferably 10% by weight, an alcohol, preferably with a content of 1% by weight, polyvinyl butyrate, preferably with a content of 3% by weight, and a cationic accelerator, preferably with a content of 1% by weight. In particular, the epoxy resin system with such a composition has a refractive index of 1.5065 at 24° C. and a viscosity of 2900 mPas at 25° C.
In at least one embodiment, the epoxy resin system comprises or consists of a composition of a cycloaliphatic epoxy resin, preferably with a content of 95.5% by weight, an alcohol, preferably with a content of 1% by weight, a polyvinyl butyrate, preferably with a content of 2% by weight, and a cationic acceleration, preferably with a content of 1.5% by weight. Such an epoxy resin composition has a refractive index of 1.4960 at 25° C. and a viscosity of 1240 mPas at 25° C.
According to at least one embodiment, the epoxy resin composition comprises a cycloaliphatic epoxy resin, preferably with a content of 96.8% by weight, an alcohol, preferably with a content of 1% by weight, polyvinyl butyrate, preferably with a content of 1% by weight, and a cationic accelerator, preferably with a content of 1.2% by weight. The refractive index of such an epoxy resin composition is 1.4974 at 22° C. and viscosity is 609 mPas at 25° C.
The production of the epoxy resin system and/or the mixing in of resin additives or additives, such as pigments, can be carried out according to methods known to a skilled artisan. In a second process step, the inorganic filler, preferably amorphous silicon dioxide, and optionally pigments such as carbon black, titanium dioxide, aluminum oxide, calcium fluoride and/or phosphors are preferably added. Thermal curing can take place at a temperature above 120° C. using a cationic mechanism with a thiolanium salt as a cationic accelerator, which may comprise the complex anions mentioned above.
The inventors have recognized that the epoxy resin system described above has advantageous properties and is a one-component system. The epoxy resin composition can be stored at room temperature or especially in the refrigerator.
According to at least one embodiment, the epoxy resin system is storage stable at a temperature between 4° C. and 10° C. inclusive, in particular for at least six months.
According to at least one embodiment, the epoxy resin system is anhydride-free, silicone-free and/or siloxane-free. In particular, the epoxy resin system can be formulated silicone- and siloxane-free for critical cleanroom applications.
The epoxy resin system can have a low coefficient of thermal expansion. For example, with a filling degree of 65% by weight of inorganic filler, the epoxy resin system can have a thermal expansion coefficient (TMA, CTE, coefficient of thermal expansion) of 20 ppm/K.
The epoxy resin system can have a high glass transition temperature, especially a glass transition temperature of >200° C. (DMA).
The epoxy resin system can have a high short-term temperature resistance. This means that the epoxy resin system has a stability against the high temperatures of usually 260° C., in some cases up to 325° C., which are briefly reached during soldering. The weight loss of the epoxy resin masses at 300° C. with synthetic air as TGA medium (TGA, thermogravimetric analysis) with a heating rate of 10 K/min is <1%.
The epoxy resin system can be used in particular as a black and/or white adjusted surface with good light stability for optical applications.
According to at least one version, the epoxy resin system has a chlorine content of <100 ppm, especially <50 ppm, preferably <20 ppm.
In particular, the epoxy resin system has a low EHS (Environmental, Health and Safety) risk potential and can therefore be classified as less critical for people in occupational safety and the environment.
The epoxy resin system can be used in particular for further applications due to a wide rheology window. For example, the epoxy resin system can be used as housing material, mounting material, casting resin, matrix material for light conversion elements, reflection layers and optical filters or as lens material. In particular, the epoxy resin system can be used for thin-walled housings for optoelectronic devices, especially with wall thicknesses of <80 μm. Furthermore, the advantage of the epoxy resin system is that the production costs are lower compared to silicones and epoxy mold compounds.
The use of an epoxy resin system is also indicated. The above-mentioned epoxy resin system is preferably used for an optoelectronic device.
According to at least one design, the optoelectronic device is selected from a group comprising a luminescent diode, a photodiode, a phototransistor, a photo-array, an optical coupler, an SMD device and an SMD-capable device. The optoelectronic device can be used, for example, in the automotive sector and/or for outdoor applications.
An optoelectronic device is also specified. Preferably, the optoelectronic device has the epoxy resin system described above. All definitions and embodiments for the optoelectronic device apply as specified above for the epoxy resin and vice versa.
According to at least one embodiment, the optoelectronic device has an epoxy resin system. In particular, the epoxy resin system is shaped as a housing, reflection element, casting, conversion element and/or substrate.
The epoxy resin system is preferably shaped as the housing of the optoelectronic device. The housing may have a recess. A layer sequence or a semiconductor layer sequence of a semiconductor chip can be inserted in this recess. The semiconductor layer sequence of the semiconductor chip is preferably based on a III-V compound semiconductor material. The semiconductor material is preferably a nitride compound semiconductor material, such as AlnIn1-n-mGamN, InGaN, GaN or also a phosphide-compound semiconductor material, such as
AlnIn1-n-mGamP, where 0≤n≤is 1, 0≤m≤1 and n+m≤1, respectively. The semiconductor material can also be AlxGa1-xAs with 0≤x≤1. The semiconductor layer sequence can contain dopants and additional components. For simplicity's sake, however, only the essential components of the crystal lattice of the semiconductor layer sequence, i.e. Al, As, Ga, In, N or P, are given, even if these can be partially replaced and/or supplemented by small amounts of other substances.
According to at least one embodiment, the epoxy resin system is designed as a reflection element. The epoxy resin system can additionally contain scattering particles such as calcium fluoride and/or titanium dioxide.
According to at least one embodiment, the epoxy resin system is designed as a casting compound. The casting may additionally contain luminescent materials that are designed to convert the radiation emitted by a semiconductor layer sequence into radiation with a different wavelength. The phosphors can be homogeneously embedded as particles in the epoxy resin system.
According to at least one embodiment, the epoxy resin system is designed as a substrate. This substrate can be equipped with a semiconductor layer sequence for emitting radiation.
A process for the production of an epoxy resin system is also specified. The epoxy resin system described above is preferably produced using this process. All designs and definitions of the epoxy resin system also apply to the process for producing an epoxy resin system and vice versa.
According to at least one embodiment, the procedure comprises the following procedural steps:
A) providing a cycloaliphatic epoxy resin,
B) adding of polybuytl butyrate at a temperature between 50° C. inclusive and 80° C. inclusive,
C) adding a cationic accelerator at a maximum temperature of 45° C. to form a matrix,
D) mixing the matrix produced according to step C) with at least one inorganic filler which is an oxide or nitride of a metal or semimetal and
E) curing of the mixture produced in accordance with step D) at a temperature between 120° C. and 190° C. inclusive.
In particular, the viscosity of the liquid resin formulation is set as low as possible so that as much inorganic filler as possible can be achieved for the lowest possible thermal expansion (CTE), high mechanical rigidity and high thermal stability. On the one hand, the inorganic filler should be as fine as possible, but on the other hand, it should not be too small, as otherwise it will not be possible to achieve sufficiently high filling level during production. It can also inhibit resin application due to excessive viscosity or thixotropy. High filling level are desirable for the highest possible reliability and stability of the components. With the inorganic fillers present, in particular spherical amorphous silicon dioxide filler, with grain sizes d50 between 0.5 μm or 2 μm and 10 μm or 20 μm, preferably between 2 and 8 μm and an upper grain size of 30 μm, preferably 20 μm, high filling level of up to 80% by weight, preferably up to 75% by weight, can be achieved. The filler quantities in the resin are in particular 50 to 85% by weight, preferably 60 to 80% by weight. Depending on the level of filling, the application can be carried out by dispensing, jetting or molding (compression molding). Thus an epoxy resin system can be produced as housing material, as cover layer, as reflection layer, as underfiller, as conversion element.
Curing in step E) can preferably take place between 120° C. and 190° C., preferably between 140° C. and 180° C., for example two hours at 160° C.
A new one-component epoxy resin system can be provided that meets the technical LED requirements with regard to cost, processing and innovative thin-walled LED form. Dynamic-mechanical investigations on the cured molding materials show a glass transition temperature of >200° C. (DMA), exhibit good mechanical brittleness behavior for reliable LED products and have a thermal expansion coefficient of 20 ppm/K (TMA) at a filling level of 75% by weight.
Further advantages, advantageous embodiments and further developments result from the examples described below in connection with the figures.
In the examples and figures, similar, identical elements or elements having the same effect can each be provided with the same reference signs. The represented elements and their proportions among themselves are not to be regarded as true to scale. Rather, individual elements, such as layers, components, devices and regions, can be displayed excessively large for better displayability and/or better understanding.
The percentage shown in the table means, for example, that 99.4% of the particles of the inorganic filler F1 have a maximum upper grain size of 12 μm. Accordingly, 100% of the particles of inorganic filler F2 have a maximum upper grain size of 12 μm. Accordingly, 99.8% of the particles of the inorganic filler F3 have an upper grain size of 16 μm. The electrical conductivity κ of inorganic fillers F1 to F3 is between 3.1 and 6.6 μS/cm2.
1. 85% by weight cycloaliphatic epoxy resin,
2. 10% by weight of epoxy phenol novolac,
3. 1% alcohol by weight,
4. 3% by weight polyvinyl butyrate, and
5. 1% by weight cationic accelerator.
Epoxy resin composition 2, abbreviated as EH2, has the following composition:
1. 95.5% by weight cycloaliphatic epoxy resin,
2. 1% by weight alcohol,
3. 2% by weight polyvinyl butyrate, and
4. 1.5% by weight cationic accelerator.
The FTIR spectrum for EH1 (2-1) and EH2 (2-2) shows that a band is observed at 1726 cm−1. This band represents the cycloaliphatic epoxy resin. OH bands are also shown in the range greater than 3000 cm−1.
Examples A5 to A7 show an identical epoxy resin system EH2 with different inorganic fillers F1 to F3, whereby the content of the filler in the examples A5 to A7 is constant and is 75% by weight. The table shows that the type of filler has an influence on the thixotropy index TI. A7 with filler F3 has the lowest thixotropy index compared to design examples A5 and A6. Further the table in
1. 96.8% by weight cycloaliphatic epoxy resin,
2. 1% by weight alcohol,
3. 1% by weight polyvinyl butyrate, and
4. 1.2% by weight cationic accelerator.
The filler content m in % by weight varies between 60% by weight and 77% by weight. In accordance with
According to
According to
According to
The examples described in connection with the figures and the features thereof can also be combined with each other according to further examples, even if such combinations are not explicitly shown in the figures. Furthermore, the examples described in connection with the figures may have additional or alternative features according to the description in the general part.
The invention is not limited by the description based on the examples. Rather, the invention includes each new feature and each combination of features, which includes in particular each combination of features in the patent claims, even if this feature or this combination itself is not explicitly indicated in the patent claims or examples.
This patent application claims the priority of the German patent application 10 2016 102 685.9, the disclosure of which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 102 685.9 | Feb 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/053155 | 2/13/2017 | WO | 00 |
