WO2007036194A1 - Epoxide resin system and moulding material produced from said epoxide resin system and opto-electronic component with said moulding material - Google Patents

Abstract

An embodiment of the invention relates to an epoxide resin system comprising an epoxide-containing A component that contains at least an cycloaliphatic or aliphatic epoxide resin which can be obtained by means of distillative cleaning. The B component is at least an acid anhydride from a cycloaliphatic and aliphatic carbon acid, at least an acid ester of the carbon acid, at least an organic Zink<SUP>2+</SUP> complex compound and at least a phosphororganic compound. Such epoxide resin systems and epoxide resin moulding materials produced therefrom have a greater resistance to yellowing.

Description

Epoxy resin system as well as from the EpoxidharzSystem manufacturable molding material and optoelectronic device with the molding material

From the publication DE-OS 26 42 465 a casting resin for potting optoelectronic components based on acid anhydride-curable epoxy compounds is known, the epoxy compound 3, 4-Epoxycyclohexylmethyl- (3, 4-epoxy) cyclohexane carboxylate, at least one carboxylic acid anhydride, Zinc octoate, a low molecular acid ester and an organic phosphorus compound. The inventors have found that moldings of such casting resin compositions show a strong yellowing at a temperature-aging of> 110 ⁰ C.

The object of the present invention is an epoxy resin system to provide a producible from the epoxy resin molding material and an optoelectronic device with the molding material, which is improved in terms of the above-mentioned disadvantages.

This object is achieved by the various embodiments of the invention. Advantageous embodiments of the epoxy resin system and the optoelectronic component are the subject of further claims.

One embodiment of the invention describes an epoxy resin system comprising an epoxide-containing A component and an acid anhydride-containing B component. The A component contains as the first epoxy component at least one epoxy resin which is selected from cycloaliphatic and aliphatic epoxy resins, which are obtainable by distillation purification. The B component comprises at least one acid anhydride selected from a cyclic aliphatic and aliphatic carboxylic acid, at least one acidic ester of the carboxylic acid, at least one organic zinc ²⁺ complex compound and at least one organophosphorus compound.

The inventors have found that the thermal yellowing stability of epoxy resin systems can surprisingly be improved by further purifying the cycloaliphatic and aliphatic epoxy resins from the corresponding, non-purified products by means of distillative purification. As part of systematic basic investigations, the inventors found that neither purified hardener and accelerator components of the B component of the epoxy resin systems nor washing the cycloaliphatic and aliphatic epoxy resins with water or cleaning these epoxy resins with activated carbon improves the thermal yellowing stability. The improved yellowing stability of the epoxy-containing A component of the epoxy resin systems also leads to curing of the epoxy resin system to epoxy molding materials, which also have improved thermal yellowing stability. The available by distillation purification cycloaliphatic and aliphatic epoxy resins generally have less impurities compared to the non-purified corresponding epoxy resins. These impurities may be selected from the oligomers of the cycloaliphatic and / or aliphatic epoxy resins, teilepoxidierten products of the respective epoxy resins and process chemicals, which were used during the synthesis of epoxy resins. A molding material which can be produced from such an epoxy resin system also has the same properties apart from the good thermal yellowing stability a good cracking and delamination behavior with a high glass transition temperature.

Furthermore, the epoxy resin according to a further embodiment of the invention may be substantially transparent, so that a producible from the Epoxiharzsystem Epoxidharzformstoff particularly for the encapsulation of optoelectronic devices or for the production of optical elements such. B. lenses is suitable. Substantially transparent means that a 1 mm thick sample of an epoxy resin molding material that can be produced from the epoxy resin system> 88% is transparent to radiation in the wavelength range of about 400 to 800 nm. Such measurements may be carried out in a manner known to those skilled in the art by means of a UV spectrometer.

Furthermore, the A component can also be solvent-free. This has the advantage that only components are present in the A component, which are incorporated as completely as possible into the molding material during the crosslinking - that is, do not migrate or wash out, with no solubilizing components being necessary.

Furthermore, it is possible to use embodiments of the epoxy resin systems according to the invention as Gießharzsysteme.

The first epoxide component of the A component selected from cycloaliphatic and aliphatic epoxy resins carries at least one, but preferably two or more epoxide functions. It is possible that these epoxy resins have no or only a very low absorption in the UV-VIS spectrum at wavelengths less than 400 nm, preferably between 300 and 400 nm. Furthermore, the first epoxy resin component of the A component can be selected from hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, diglycidyl ester of adipate and cyclohexane dimethylol diclycidyl ether, epoxycyclohexyl methyl -3 ', 4'-epoxy cyclohexyl carboxylate, diglycidyl ester of hexahydrophthalic acid and methylhexahydrophthalic acid, diglycidyl ethers of tricyclodecanedimethanol, bis (3,4-epoxycyclohexylmethyl) adipate, and reaction products of 1,4-cyclohexanedimethanol (available from Dow Chemical under the designation ERLX-4360) with methyl 3,4-epoxycyclohexanecarboxylate. 3, 4-epoxycyclohexyl-methyl-3 ', 4'-epoxy cyclohexyl carboxylate (available from Dow Chemicals under the name ERL-4221 D) has the following structure:

In such cycloaliphatic or aliphatic epoxy resin components, an improvement in the thermal yellowing stability after purification by distillation under reduced pressure and an inert gas atmosphere has been demonstrated or is to be expected in the case of distillative purification.

In a further embodiment of epoxy resin systems according to the invention, the at least one saturated Acid anhydride of the B component may be selected from hexahydrophthalic acid anhydride and methyl-hexahydrophthalic anhydride and mixtures thereof.

Such acid anhydride hardeners are particularly suitable for colorless, transparent epoxy resin systems which have good yellowing stability since these acid anhydrides are not aromatic but saturated and otherwise have no C-C double bonds.

Furthermore, the at least one acidic ester of the aliphatic or cycloaliphatic carboxylic acid can be obtained by reacting the carboxylic acid with a substoichiometric amount of at least one alcohol.

The alcohol may be selected from aliphatic, cycloaliphatic and branched mono- or polyfunctional alcohols and polyethers and glycol ethers, for example ethanol, 1, 2-propanediol, 1, 4-butanediol, 1,6-hexanediol, glycerol, dimethylolpropane, trimethylolpropane , Diethylene glycol, ω-diethylene glycol, tricyclodecanedimethylol and α-ω-dipropylene glycol.

The at least one acidic ester of the aliphatic or cycloaliphatic carboxylic acid can improve the curing behavior of the epoxy resin in terms of temperature-time behavior in certain embodiments of the invention and ensure increased compatibility of the individual hardener and accelerator components of the B component and a good storage behavior. Thus modified hardener components improve the thermomechanical behavior and reduce the brittleness of moldings produced therewith. Preferably, 5 to 30% by weight of the B component is composed the acidic ester of the aliphatic or cycloaliphatic carboxylic acid.

In another embodiment of the compound, as the at least one organic zinc ²⁺ complex compound as the accelerator component, zinc octoate is added directly to the B component. Zinc octoate includes 2-ethylhexanoic acid anions and zinc as a double-positive cation. Zinc octoate can serve as a reaction accelerator in the epoxy resin systems and allow rapid cure cycles. These advantages can be realized particularly well in the interaction of the zinc octoate with the acidic esters of the carboxylic acids and phosphorus-organic constituents. The zinc octoate content may be less than 10% by weight in the B component, with the zinc content of the zinc octoate preferably being greater than 18% by weight, preferably between 21.5 and 23.5% by weight. In further embodiments of the invention, the Zn content of the zinc accelerator, the organic zinc ²⁺ complex compound may also comprise at least 10 wt%, or preferably at least 20 wt%, most preferably 21.5 to 23.5 wt%.

Furthermore, the at least one organophosphorus compound can be selected from triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) 4,4'-biphenyl-diphosphonite , Tris (4'-n-nonylphenyl) phosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphonite and diphenyldecyl phosphite.

Such organophosphorus compounds are advantageously added in proportions <10% by weight of the B component "and can act, for example, as antioxidants and as reaction accelerators and likewise the viscosity of the Epoxy resin system and the thermomechanical behavior of moldings produced therewith advantageously influence.

Particularly advantageous is a B component which in addition to aliphatic and cycloaliphatic carboxylic acid anhydrides, for example hexahydrophthalic anhydride and / or methyl hexahydrophthalic anhydride, also an organophosphorus compound, for example triphenyl phosphite and the acidic ester of said carboxylic acid anhydrides and zinc octoate with a maximum proportion of 10 weight percent, preferably 3 to 7 percent by weight, since such B-components are solvent-free among other things and good compatibility of the individual components is ensured. Such a B-component allows particularly fast curing cycles in the minute range at temperatures of 130 ⁰ C to 200 ⁰ C, preferably 160 ° to 190 ⁰ C for a reel-to-reel production. To achieve the final properties so produced components can be post-cured.

In a further embodiment of the invention, the cycloaliphatic and aliphatic epoxy resins of the first epoxy component of the A component by means of distillative purification at temperatures of less than 25O ⁰ C at a pressure <10 mbar are available. Further preferred is a distillative purification at temperatures below 200 ⁰ C and pressures <1 mbar. It is particularly advantageous if the distillation is carried out under an inert gas atmosphere, for example nitrogen. In such distillation procedures, a relatively gentle distillative purification of the cycloaliphatic and aliphatic epoxy resins under reduced pressure is possible and the epoxide resins produced therewith are as little as possible thermally damaged. In a further embodiment of the invention, the cycloaliphatic and aliphatic epoxy resins of the first epoxy component of the A component may have a purity of at least 91% by weight. Such a first epoxy component is particularly suitable for epoxy resin systems and resulting epoxy resin moldings which are to have an increased yellowing stability. The purity of the cycloaliphatic and aliphatic epoxy resins of the first epoxide component of the A component is preferably from 91 to 97% by weight, preferably more than 95% by weight. The impurities may be selected, for example, from oligomeric reaction products of the respective cycloaliphatic and aliphatic epoxy resins, partially epoxidized products of these epoxy resins and process chemicals which were used during the synthesis of the epoxy resins. The purity of the cycloaliphatic and aliphatic epoxy resins could be detected, for example, by GPC, HPLC or GCMS methods.

In a further embodiment of epoxy resin systems according to the invention, non-aromatic epoxy resins as second epoxide component which are different from the first epoxy component of the A component are additionally present in the A component. Such non-aromatic epoxy resins may, for example, be selected from monofunctional and polyfunctional aliphatic alicyclic epoxy resins having oxirane groups, glycidyl ester compounds and glycidyl ether compounds of cycloaliphatic, aliphatic, alicyclic carboxylic anhydrides and carboxylic acids and glycidyl compounds of polyether polyols and polyester polyols. Such an epoxy resin may be, for example, glycidylated castor oil. The second For example, the epoxy component of the A component may serve to adjust the viscosity and to improve the thermomechanical properties and to adjust the glass transition temperatures. The inventors have recognized that the glass transition temperature of a molding material resulting from curing by the epoxy resin system is lower the more of this second epoxy component is added to the A component. The second epoxide component of the A component is advantageously added in concentrations of less than 30% by weight of the A component.

The non-aromatic epoxy resins of the second epoxy component of the A component can be selected, for example, from ce-.omega.-hexanediol diglycidyl ether, 1,4-butanediol dicyclodyl ether, glycidylated trimethylolpropane diglycidyl ether, 2-ethylhexyl diglycidyl ether and glycidylated castor oil ,

Conveniently, the non-aromatic epoxy resins of the second epoxy component are also obtainable by means of distillative purification. Such epoxy resin systems and epoxy resin molded articles made therefrom exhibit improved yellowing stability compared to the corresponding unpurified compositions.

In a further embodiment of an epoxy resin system according to the invention, at least one reaction product of bisphenol A and propylene oxide units of different length with diglycidyl ether functions in α / ω position may be present in the A component as the third epoxy resin component. Such a compound is available, for example, from Asahi Denka under the name EP-4005. The inventors have found that such compounds despite their aromatic structures do not lead to an unacceptable yellowing of these containing epoxy resin or epoxy resin molded therefrom. At the same time, however, these compounds can serve as flexibilizers for adjusting the thermomechanical properties of the molding materials and can be added in concentrations of <30% by weight of the A component. Epoxy resin systems according to the invention in further embodiments may, apart from this third epoxy resin component, comprise no further aromatic epoxy resin components.

In a further embodiment of an epoxy resin system according to the invention, more than 50% by weight of the A component consists of the cycloaliphatic and aliphatic epoxy resins as the first epoxide component.

In further embodiments of the epoxy resin systems, less than 30% by weight of the A component may consist of the non-aromatic epoxy resin of the second epoxy component.

In a further embodiment of an epoxy resin system according to the invention, more than 60% by weight of the B component consists of the at least one acid anhydride of the cycloaliphatic or aliphatic carboxylic acid or mixtures of both.

The A component may additionally contain light stabilizers, for example selected from sterically hindered amines, amine oxides and amine oxide derivatives, for example alkoxyamines and aminoethers. Furthermore, UV absorbers, which are for example selected from benzotriazole derivatives, triazines and benzoxazines in further Embodiments of epoxy resin systems according to the invention may be present.

Particularly preferred are, for example, amine oxide derivatives of the general formula

(R 1) (R 2) N-O-R 3,

wherein R ¹ and R ^{2 are} independently alkyl, aryl, or alkylaryl, together form a bivalent radical or together with the N-atom form a heterocyclic ring and R ^{3 is} the above-mentioned alkyl, aryl, alkylaryl or a cycloalkyl group. The group R ³ may have at least one oxygen atom in the chain or may also comprise a plurality of oxygen atoms and thus also, for example, ether groups or ester group. The light stabilizers can be present in concentrations of at most 5% by weight of the A component, preferably at most 2.5% by weight of the A component.

In the A component, in a further embodiment of epoxy resin systems according to the invention, at least one antioxidant may additionally be present which is selected from sterically hindered phenol, cresol, phosphite, phosphonite, thioester, tocopherol, 5,7-di-tert-butyl-3 - (3, 4-dimethylphenyl) -3H-benzofuran-2-one, 4,6-bis (octylthiomethyl) -o-cresol, 4-methoxy-phenol, 3-tert-butyl-4-hydroxyanisole and lactone -Links. The 5,7-di-tert-butyl-3- (3, 4-dimethylphenyl) -3H-benzofuran-2-one is available, for example, from Ciba Specialty under the designation HP136. These antioxidants can be used individually or in combinations of different antioxidants, for example in one portion of at most 5% by weight, preferably about a maximum of 2.5% by weight, may be present in the A component.

In a further embodiment of an epoxy resin system according to the invention, the A component may additionally contain phosphors for the production of luminescence conversion elements. Such luminescent substances are described for example in the utility model DE 297 24 382 Ul on page 3, lines 1 to 6, page 5, lines 9 to 26 and pages 6, lines 26 to page 7, line 7, the disclosure of which hereby by reference is recorded.

In further embodiments of an epoxy resin system, the mixing ratio is 100 parts A component to about 80 to 150 parts B component, with a mixing ratio of about 100 parts A component to about 100 to 130 parts B component being preferred. Such epoxy resin systems have a service life of at least 2 h at 25 ° C and allow a particularly good curing at the same time good thermomechanical stability and good yellowing stability.

In the A component, alcohols which are monohydric or polyhydric and may also comprise aliphatic, cycloaliphatic, polyether-polyester alcohols and alcohol ethers may furthermore be present. The alcohols are preferably selected from 3 (4), 8 (9) -bis (hydroxymethyl) -tricyclo [5.2.1. O ² ' ⁶ ] decane (= tricyclodecanedimethylol), α-ω-diethylene glycol and ce-ω-dipropylene glycol. Such alcohols can serve to improve the mechanical properties, which usually does not result in a significant deterioration of the moisture absorption. Often, a structural conditional Improvement in cracking behavior, for example, to observe a better solderability.

As further additives, deaerators, water repellents, adhesion promoters, internal release agents and brighteners may be present in particular embodiments of an epoxy resin system according to the invention and thus also in the epoxy resin molding materials obtainable therefrom. Furthermore, thixotropic agents may be added, for example finely divided, fumed silica, titanium dioxide and zirconium dioxides. Also possible is the use of dyes in the A component. Furthermore, diffuser pigments, for example CaF ₂ , BaSO ₄ , TiO ₂ and / or CaCO ₃ can be added to the A component. The A component may also contain, as further components, additives which are selected, for example, from fused silica, quartz flour, quartz, Al ₂ O ₃ , MgO, Y ₂ O ₃ , ZrO ₂ , CeO _x , TiO ₂ and ZnO and talc.

In the A component of further embodiments of an epoxy resin system of the invention, mono-, di- or trifunctionalized alkoxysilanes may also be present as adhesion promoters. In addition to the alkoxy groups (from C ₁ to C ₂₀ alcohols), these mono-, di- or trifunctionalized alkoxysilyles also have at least one maximum but three substituents with a functional group, for example a glycidyloxyalkyl group, a 0H group or an amine. Such an example of a coupling agent is, for example, 3-glycidyloxypropyltrimethoxysilane or 3-glycidyloxypropoyltriethoxysilane.

Epoxy resin moldings which are obtainable by means of curing of at least some embodiments of the epoxy resin systems according to the invention have a glass transition temperature of at least 125 ° C, preferably> 145 ° C. The epoxy resin systems and epoxy resin molding materials obtainable therefrom can be used for potting, covering, coating and as a mounting material for bonding electronic and optoelectronic components. Particularly suitable are such Epoxidharzformstoffe for optoelectronic devices in which high photochemical loads occur, such as UV emitters, light emitting diodes, photodiodes, phototransistors, photo arrays, optical couplers, optical transmitter-receiving components, optical fibers and lasers. Such photochemical loads occur, for example, amplified by radiation with wavelengths less than 500 nm. Electronic and optoelectronic components which comprise or are encapsulated with the epoxy resin moldings exhibit good stability against moisture and weathering and can also be used in the automotive sector. It is also possible to use the Epoxidharzformstoffe for outdoor applications.

The epoxy resin moldings can also be used for the production of optical components, for example lenses, prisms, windows, filters or light-guiding units, as well as for decorative purposes.

The subject matter of a further embodiment of the invention is also a process for producing an epoxy resin molding material in which the A and B components of an epoxy resin system are mixed together as mentioned above and the resulting mixture is cured. The curing can be carried out, for example, at temperatures above 100 ⁰ C for rapid processing at temperatures above 140 ⁰ C in the minute range. For example, at temperatures of about 140 ⁰ C. Cured for about 30 minutes or at temperatures above 16O ⁰ C at correspondingly shorter curing times. Improved molding properties of the Epoxidharzformstoffes be achieved by post-curing at temperatures greater than 125 ⁰ C. Post-curing under an inert gas atmosphere, for example under nitrogen, further improves the yellowing stability.

In the following, embodiments of the invention will be explained in more detail with reference to figures and examples.

Figure 1 shows a tabular comparative overview of various purified and non-purified cycloaliphatic epoxy resins.

Figures 2A and 2B show the glass transition temperatures Tg of a cured epoxy molding material according to an embodiment of the invention, depending on different curing conditions.

FIG. 3 shows the transparency of an epoxy resin molding material according to an embodiment of the invention as a function of the wavelength.

Figure 4 shows the UV-VIS shows characteristics of a cycloaliphatic epoxy resin which is purified by distillation, or was not cleaned after four weeks of thermal aging at 7O ⁰ C (10 mm cell).

An epoxy resin component A of an embodiment of the invention is generally composed as follows:

A preferred epoxy-containing A component as the first embodiment contains the following constituents:

Epoxy cyclohexyl methyl-1 ',> 90% by weight

A second exemplary embodiment describes a likewise preferred A component of an exemplary embodiment of an epoxy resin system according to the invention:

The A component of embodiment 2 is stable for storage for at least six months at room temperature and can be mixed and dosed bubble-free and homogeneously with a service life vgon min. 2h at 25 ° C with a hardener component, the B component. Component A shows a viscosity of 200 to 500 mPas (25 ⁰ C, 500 1 / sec), preferably 200 to 300 mPas. The viscosity increases after six months storage at room temperature from 215 mPas to 255 mPas. In the thermal resin aging, the viscosity after four weeks at 70 ⁰ C also increases only slightly from 270 to 280 mPas. With hexahydrophthalic anhydride based hardener glass transition temperatures of greater than 150 ⁰ C are achieved in the mixing ratio of 100: 104 to 100: 112 parts. In this composition range, the gel times be at 120 ⁰ C and 150 ⁰ C for 3 min 30 sec and 1 min, so that rapid Anhärtungen for fast production cycles can be performed.

Figures 2A and 2B show differential scanning calorimetry (DSC) results from hardness tests in which an epoxy resin component A according to the second embodiment was cured with a hexahydrophthalic anhydride based hardener at a mixing ratio A: B of 100: 112.

The column denoted by 13 of FIG. 2A designates the t-T profile (DSC isothermal), the column denoted by 14 designates the glass transition temperatures Tg resulting from the corresponding profile, and the column denoted by 15 denotes the calculated residual reaction in percent. It can be seen from FIG. 2A that, depending on the curing temperature and the curing time, the glass transition temperature of the resulting molding materials increases the longer and is cured at the higher temperatures.

In FIG. 2B, the column denoted by 16 designates the curing conditions (curing time and curing temperature), the post-hardening column denoted by 17 and the column denoted by 14 designates the glass transition temperature in ⁰ C of the resulting molded materials. This 2B it can be seen that can be achieved by very long subsequent hardening at high temperatures between about 150 ⁰ C to 160 ⁰ C improved glass transition temperatures, which are between 162 ° C and 166 ° C.

The epoxy resin moldings are colorless and transparent with high permeability in the visible range. After a short-term temperature load of 6 min at 290 ⁰ C, a slight yellowing of the molding material was observed. The molded materials show in the dynamic mechanical analysis at 1 Hz an E modulus at 2O ⁰ C and 100 ⁰ C of 3,300 MPa and 2,300 MPa, the linear thermal expansion coefficient between -50 ⁰ C and + 50 ⁰ C is 72 ppm / K , The Epoxidharzformstoffe all show a glass transition temperature greater than 150 ⁰ C. Thus potted Lumineszenzdioden are sufficiently cyclic (1000 x TC (temperature cycle): -40 ° C / + 100 ° C), sufficiently stable against soldering heat in wave soldering (5 x TTW (through the wave) 260 ⁰ C), stable in humidity (85 ⁰ C 85% RH 5 mA, hitherto 500 h) and yellow slightly after short-term temperature stress of 5 x Wellenlδten at 260 ⁰ C. in order potted components can below the predetermined quality requirements are economically prepared ,

FIG. 1 shows the chemical and physical properties of various cycloaliphatic epoxy resins which have been purified by distillation or have not been purified. The line marked 1 indicates the supplier, the line denoted by 2 the chemical name, line 3 the CAS number, line 4 shows the purity of the respective cycloaliphatic epoxy resins. The uppermost value in line 4 indicates the purity in percent by weight for the particular cycloaliphatic epoxy resin, the value in the middle of the weight fraction of monoepoxides and the lower value the proportion by weight of oligomers contained the respective cycloaliphatic epoxy resin. In line 5, the epoxy value is given in mol / 100 g. Line 6 indicates the color value (APHA max). In line 7, the viscosity in mPas at 25 ⁰ C is given. The refractive index n _D at 25 ^° C. is indicated in line 8 and in line 9 the density is given in kg / dm ³ . The pour point as far as determined is listed in line 10. Line 11 indicates the flash point in ⁰ C determined according to the ASTM D93 standard (Penski-Martens). The storage stability at 25 ^° C. in months is indicated in the last line 12. The column marked ERL-4221 on the left indicates the properties of an epoxy resin obtained from Dow Chemical which was not purified by distillation, the next column being designated ERL-4221 E indicates the chemical and physical properties of the corresponding epoxy-based epoxy resin after purification with water , ERL-4221 D and ERL-4241 (Opto) characterize the same cycloaliphatic epoxy resins from Dow obtained by distillative purification. EP 4085 S refers to the chemical and physical properties of a 1, 4-Cyclohexandimethyloldiglycidylethers which may also be part of the first component of the A component.

It can be seen from the table of FIG. 1 that the distillatively purified ERI-4221 (the columns denoted D and Opto, respectively) have a greater purity of 91 to 91% by weight, compared to a lower purity of 82 to 89% by weight for that purified ERL-4221 or water-purified ERL-4221 E. At the same time, the products obtained by means of distillative purification have fewer oligomers of the particular cycloaliphatic epoxy resin, namely less than 4% by weight in comparison with the by distillation purified products containing 8 to 13% by weight of soluble oligomers. Furthermore, the viscosity of the distillatively purified products is lower with simultaneously increased epoxy value. It is noteworthy and important in this context that products purified by distillation continue to have a lower color number (APHA max).

FIG. 3 shows the transparency of an epoxy resin molding material obtained by curing the epoxy resin component of the second embodiment with a hexahydrophthalic anhydride-based hardener. The curve denoted by 20 indicates the transmission behavior in% as a function of the wavelength in nm. Measured on a Perkin Elmar Lamda 2 spectrometer, wherein the sample had a layer thickness of 0.8 mm. It can be seen from the figure that from a wavelength of about 400 nm to more than 750 nm, a transmission greater than 88% can be observed with the epoxy resin molding material. This is thus particularly suitable for use in optoelectronic components and optical elements such as lenses and windows.

FIG. 4 shows the UV-VTS characteristics of a distillatively purified cycloaliphatic epoxy resin (curve designated 40: ERL-4221 Opto) in comparison to the corresponding UV-VIS characteristics of the same non-distillatively purified epoxy resin (curve designated 30: ERL-4221 Standard quality). The appropriate UV-VIS characteristics were after four weeks of thermal aging at 7O ⁰ C by means of a Perkin Elmar determined Lamda 2 spectrophotometer and a 10 mm cuvette at room temperature. It can be clearly seen that the non-distillatively purified cycloaliphatic epoxy resin has a higher Yellowing shows as the corresponding distillatively purified product.

Comparative Example

An epoxy resin molding material was prepared by curing an A component consisting of non-distillatively purified ERL-4221 in an amount of 94.986% by weight, trimethylolpropane in a proportion of 4.750% by weight, Tego-DF48 as a silicone-based internal release agent in a proportion of 0, 25% by weight and masterbatch 09 as optical brightener with a fraction of 0.014% by weight were obtained with a methylhexahydrophthalic anhydride-based hardener. In this epoxy resin molded thermal aging is after six weeks of aging at 120 ⁰ C in air as a spectroscopic color locus 17.3. This means a very high thermal yellowing. The radiation-induced yellowing determined by UV aging in air (area radiator type F (intensity 4.3 mW / cm ² 'dose 2592 kJ / cm ² with UVB filter from Linos Photonics GmbH) is only 0.25 Yellowing of such an epoxy resin molding material very low.

Distillatively purified aliphatic and / or cycloaliphatic epoxy resins are, above all, able to improve the thermal yellowing stability of the abovementioned epoxy resin molding material. This can be demonstrated by the fact that an epoxy resin molding produced by curing an A-component according to the second embodiment already mentioned above and a hardener component B based on methylhexahydrophthalic anhydride shows a substantially increased thermal yellowing stability. The decrease of the light intensity I _v in an LED with a GaN chip as a measure of the yellowing stability after 500 h at 85 ° C and 30 mΑ is about 30%. An epoxy resin molding material based on bisphenol A epoxy resin without distillatively purified cycloaliphatic components shows in comparative and simultaneously performed aging tests a total LED yellowing, which is characterized by a decrease in the light intensity I _v of about 65%. This result indicates a significant improvement in the yellowing stability as the sum of thermo-oxidative and photochemical component yellowing compared to conventional epoxy resin molding materials. Components that contribute to photochemical yellowing are the wavelength of the light, the intensity and the radiation dose.

Claims

claims 1. Epoxy resin system containing the following components: an epoxy-containing A component comprising, as the first epoxy component, at least one epoxy resin selected from cycloaliphatic and aliphatic epoxy resins obtainable by means of distillative purification, and a B component comprising a) at least one acid anhydride selected from at least one acid anhydride of a cycloaliphatic and aliphatic, saturated carboxylic acid and mixtures thereof, b) at least one acidic ester of the carboxylic acid, c) at least one organic Zn ²⁺ complex compound, and d) At least one organophosphorus compound. 2. Epoxy resin system according to the preceding claim, in which the first epoxide component of the A component is selected from hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, diglycidyl ester of adipate and cyclohexane dimethyl diglycidyl ether, 3,4-epoxycyclohexyl methyl-3 ', 4' - epoxy cyclohexyl carboxylate, diglycidyl esters of hexahydrophthalic acid and methylhexahydrophthalic acid, diglycidyl ethers of tricyclodecanedimethanol, bis (3,4-epoxycyclohexylmethyl) adipate and a reaction product of 1,4-cyclohexanedimethanol and methyl 3,4-epoxycyclohexanecarboxylate. 3. Epoxy resin system according to one of the preceding claims, - In which the first epoxy component of the A component is 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxy cyclohexyl carboxylate. 4. Epoxy resin system according to one of the preceding claims, in which the at least one acid anhydride of the B component is selected from hexahydrophthalic anhydride and methyl-hexahydrophthalic anhydride. 5. Epoxy resin system according to one of the preceding claims, in which the at least one acidic ester of an aliphatic or cycloaliphatic carboxylic acid of the B component is obtainable by reacting the carboxylic acid with a substoichiometric amount of at least one alcohol. 6. Epoxy resin system according to one of the preceding claims, in which the at least one organic Zn ²⁺ complex compound of the B component is zinc octoate. 7. Epoxy resin system according to one of the preceding claims, in which the at least one organophosphorus compound is selected from triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) 4,4'-biphenyl- diphosphonite, tris (4'-n-nonylphenyl) phosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphonite and diphenyldecylphosphite. 8. Epoxy resin system according to one of the preceding claims, - In which the cycloaliphatic and aliphatic epoxy resins of the first epoxy component of the A component by means of distillative purification at temperatures of <250 ⁰ C at a pressure of <lMmbar are available. 9. Epoxy resin system according to one of the preceding claims, - In which the cycloaliphatic and aliphatic epoxy resins of the first epoxy component of the A component have a purity of at least 91% by weight. 10. Epoxy resin system according to one of the preceding claims, - In which in the A-component additionally non-aromatic epoxy resins are present as the second epoxy component, which are different from the first epoxy component. 11. Epoxy resin system according to the preceding claim, in which the non-aromatic epoxy resins of the second epoxide component are selected from monofunctional and polyfunctional aliphatic, alicyclic epoxy resins with oxirane groups, Glycidyl ester compounds of cycloaliphatic, aliphatic, alicyclic carboxylic anhydrides and carboxylic acids and glycidyl compounds of polyether polyols and polyester polyols. 12. Epoxy resin system according to the preceding claim, - In which the non-aromatic epoxy resins of the second epoxy component are selected from α-ω-hexanediol diglycidyl ether, 1, 4-butanediol diglycidyl ether, glycidylated trimethylol propane diglycidyl ether, 2-ethyl-hexyl diglycidyl ether and glycidylated castor oil. 13. Epoxy resin system according to one of claims 10 to 12, - Wherein the non-aromatic epoxy resins of the second epoxy component are obtainable by distillation purification. 14. Epoxy resin system according to one of the preceding claims, - In the A component as the third epoxy resin at least one reaction product of bisphenol A and different lengths of propylene oxide units with diglycidyl ether functions in alpha / omega position is present. 15. Epoxidharzsytem according to any one of the preceding claims, - In which more than 50% by weight of the A component of the cycloaliphatic and aliphatic epoxy resins as the first epoxy component. 16. Epoxidharzsytem according to any one of the preceding claims, - In which less than 30% by weight of the A component consists of the non-aromatic epoxy resin of the second epoxy component. 17. Epoxy resin system according to one of the preceding claims, - In which more than 60% by weight of the B component consists of at least one cycloaliphatic or aliphatic carboxylic acid. 18. Epoxy resin system according to one of the preceding claims, in which less than 10% by weight of the B component consists of the at least one organic Zn ²⁺ complex compound. 19. Epoxy resin system according to one of the preceding claims, in which the B component comprises zinc octoate having a Zn content of about 21.5 to 23.5% by weight. 20. Epoxy resin system according to one of the preceding claims, - In which less than 10% by weight of the B component of the at least one organophosphorus compound. 21. Epoxy resin system according to one of the preceding claims, - wherein the A component additionally contains light stabilizers selected from sterically hindered amines, amine oxides and UV absorbers. 22. Epoxy resin system according to one of the preceding claims, wherein the A component additionally contains antioxidants selected from sterically hindered phenol, cresol, phosphite, phosphonite, thioester, tocopherol, 5,7-di-tert-butyl-3- (3,4-dimethylphenyl) -3H- benzofuran-2-one (HP136), 4,6-bis (octylthiomethyl) -o-cresol, 4-methoxy-phenol, 3-tert, -butyl-4-hydroxyanisole and lactone compounds. 23. Epoxy resin system according to one of claims 21 or 22, - wherein the light stabilizers or antioxidants are at most 5% by weight of the A component. 24. Epoxy resin system according to one of the preceding claims, - wherein the A component additionally contains Lumineszenzkonversionsstoffe. 25. Epoxy resin system according to one of the preceding claims, - wherein the mixing ratio is 100 parts A component to 80 to 140 parts B component. 26. Epoxy resin system according to one of the preceding claims, additionally in the A-component containing alcohols selected from 3 (4), 8 (9) -bis (hydroxymethyl) -tricyclo [5.2.1. O ² ' ⁶ ] decane, α-ω-diethylene glycol and α-ω-dipropylene glycol. 27. Epoxidharzformstoff, prepared by curing an epoxy resin system according to any one of the preceding claims with a glass transition temperature of at least 125 ⁰ C. 28. An optoelectronic component having a radiation path in the component and arranged for the transparent radiation encapsulation comprising an epoxy resin molding according to the preceding claim. 29. An optoelectronic component according to the preceding claim designed as a light-emitting diode, optical receiving component, optical coupler, optical transmitter-receiving component, or optical waveguide. 30. Optoelectronic component according to the preceding claim with a working wavelength> 360 nm. 31. Use of an epoxy resin molding material according to claim 27 for the encapsulation or assembly of optoelectronic components. 32. Optical component obtainable by curing an epoxy resin system according to one of the preceding claims 1 to 26. 33. Optical component according to the preceding claim, comprising a lens, prism, window, filter or unit. 34. A process for producing an epoxy resin molding material wherein the A and B components of an epoxy resin system according to any one of claims 1 to 26 are mixed together and the resulting mixture is cured. 35. Epoxy resin system containing the following components: an epoxy-containing A component comprising at least one epoxy resin selected from at least one cycloaliphatic and aliphatic epoxy resin containing less than 9% by weight of impurities, and a B component comprising a. at least one acid anhydride selected from at least one cycloaliphatic or aliphatic carboxylic acid, b. at least one acidic ester of the cycloaliphatic or aliphatic carboxylic acid, c. At least one organic Zn ²⁺ complex compound, and d. At least one organophosphorus compound. 36. Epoxy resin system according to the preceding claim, - In which the impurities are selected from the oligomers of the cycloaliphatic and / or aliphatic epoxy resin, teilepoxidierten products of the epoxy resin and process chemicals. 37. Epoxy resin system according to one of claims 1 to 26, wherein about 5 to 30% by weight of the B component consists of the at least one acidic ester of the carboxylic acid. 38. Epoxy resin system according to one of claims 1 to 26 or 37, - In which less than 30% by weight of the A component of the at least one reaction product of bisphenol A and different lengths of propylene oxide units with diglycidyl ether functions in alpha / omega position as a third epoxy resin component. 39. A method for encapsulating optical components in which in a reel-to-reel production on a band arranged optical components with an epoxy resin system according to one of claims 1 to 26, or 35 to 38 are cast. 40. Use of an epoxy resin system according to any one of claims 1 to 26, or 35 to 38 for the production of SMT-compatible components for use in the automotive sector. 41. Use of an epoxy resin system according to any one of claims 1 to 26, or 35 to 38 as a coating of optical elements, such as radiation-emitting semiconductor diodes, photo arrays, optical couplers, optical transceiver components or as a protective coating of solar cells and sealing applications in photovoltaics. 42. Use of an epoxy resin system according to any one of claims 1 to 26, or 35 to 38 as an adhesive or underfiller of optical components and elements such as prisms, mirrors, filters, beam splitters and collimators.