DE102013022162A1 - Optical filter - Google Patents

Abstract

The present invention relates to an optical filter, a method for producing an optical filter, and the use of the filter according to the invention.

Description

The present invention relates to an optical filter, a method for producing an optical filter, and the use of the filter according to the invention.

Most available filters and filter systems, which are used in the field of cameras, mobile phones, o. A. WLP (wafer-level packaging) -based electronics are used based on inorganic systems. The aim of such systems is i. d. R. The realization of a specification-accurate transmission curve, for example. A steep edge in the range of 650 nm. Frequently, so-called blue glass is used, d. H. an optical glass, for example, a fluorophosphate glass to which coloring glass components such as CuO have been added. Further, layers containing inorganic constituents or multilayer systems are used. With the use of blue glass one is limited with very good optical properties with regard to some things: on the one hand the glass is only conditionally corrosion-resistant, on the other hand glass thicknesses of less than 300 μm are difficult to realize due to the brittleness of the material or their production is associated with high costs , In addition, the coefficient of thermal expansion (CTE) of the glass limits further processing by some bonding techniques, such as wafer-level packaging (WLP), which are standard in microelectronics. Multilayers or layers of inorganic particles have the problem that the optical properties are not adequately fulfilled, and in particle-filled systems a large spread (haze) often occurs which causes undesired optical effects, i.e., haze. H. optical losses in the form of transmission degradation and image degradation produced.

The so-called "haze" or "haze value" (also opacity, turbidity) is an optical parameter for describing the scattering behavior of a material, in particular for the turbidity of transparent samples. The value describes the proportion of transmitted light that is scattered forward by the irradiated sample. Thus, the Haze value quantifies the influence of particles in the surface or structure that interfere with the clear view. These particles can either be deliberately introduced or derived from material defects. The method for measuring the Haze value is described in the Standard ASTM D 1003 described. The standard requires the measurement of four spectra. For each spectrum the light transmittance is calculated. The four transmittances are charged to the% Haze value.

Multi-layer systems or interference filters with good optical properties are today a standard in such filters. Since the light is not absorbed in these layers, multiple reflections occur in the filter, which become so-called "ghost images". Only by an optical absorption in layers or in the substrate, these ghost images can be avoided. On the other hand, multi-layer systems that have the desired filter function with steep edges are very expensive and therefore not suitable for implementation.

Furthermore, there are now plastic-based films on the market, which have good optical properties at low cost. However, the optical properties or the stability of the film deteriorate during stress tests such as temperature and climate exposure, resistance to chemicals such as isopropanol and are therefore not suitable for WLP processes.

Coatings of polyurethane (PU) are known in the art. In WO 2007/025011 A1 Scratch protective coatings for mobile phone displays and other display components are described, these layers may be uncolored or tinted. There is no indication as to how and with what selection criteria this coloration can be produced and how intense the tinting can be, wherein the system described has no filter function in the sense of a targeted optical design.

In WO 2012/031837 A1 For example, a PU-based coating system is described for display areas on smooth transparent molded articles having a visible transmission of from 1 to 20% which are color stable to 150 ° C, which does not lower the impact / flexural strength of the substrate, and is sufficiently opaque Illuminate LEDs and other components of the display. Thus, the systems described here are not suitable for use in the field of filter systems for microelectronics / optics and processes such as WLP, since at least in the short term temperatures of> 250 ° C are reached.

Thus, the object of the present invention is to provide a filter which can be produced inexpensively in small thicknesses and with good optical filter properties, for example homogeneity and haze. The filter should also be sufficiently mechanically and thermally stable and have good chemical and environmental resistance.

The above object is achieved by the embodiments of the present invention described in the claims.

In particular, an optical filter is provided which is a substrate 2 and a filter layer on at least one side of the substrate 3 comprising, wherein the filter layer 3 comprises a matrix containing at least one organic dye dissolved in the matrix.

The filter according to the invention comprises a substrate and at least one filter layer. The filter layer comprises a matrix and at least one dye incorporated into the matrix.

The figures show:

1 shows a schematic illustration of a variant of the filter according to the invention 1 , On the substrate 2 is at least one filter layer 3 applied. Optionally, anti-reflective coatings can be provided on the top and / or bottom 4 respectively. 4 ' be upset. Furthermore, an intermediate layer 5 for example, to improve the adhesion of the filter layer 3 between substrate 2 and filter layer 3 be upset. The layers 4 . 4 ' and or 5 Optionally, they may further have a function of fine tuning the optical properties of the filters, for example, they may have an IR blocking function.

2 shows schematically an embodiment of the coating method according to the invention.

3 shows a transmission curve of a filter according to the invention according to Example 1 and the definitions of the passband and stopband of the filter including the 1-50 values.

4 and 5 show transmission curves of inventive filter according to Examples 2 and 3.

6 shows the result of a homogeneity measurement of a filter according to Example 1, ie transmission curves measured at four different locations on the filter. The curves are exactly superimposed, the filter thus has a high optical homogeneity.

7 shows the comparison of transmission curves of filters with filter layers, which were applied on the one hand with spin-coating (solid line), on the other hand with screen printing (dotted curve). The transmission in the passage region of the filter layer applied by means of spin coating is significantly better than that of the screen applied by means of screen printing.

8th shows the comparison of transmission curves of filters with filter layers, which were applied with different spin-coating parameters. Although both curves are better than the layer applied by means of screen printing, a further improvement in the transmission curve can be achieved by adapting the spin-coating parameters.

The filter according to the invention has good optical properties.

The filters according to the invention have a surprisingly low dispersion or a surprisingly low haze compared with filters of the prior art. The Haze value of the filter is preferably less than 10%, more preferably less than 5%, more preferably less than 3%, most preferably less than 1%. The haze value is preferably determined using a device of the device designation Hazeguard Plus from Byk.

Further, they have less roughness than prior art filters, thereby providing low-scattering layers. In particular, the roughness of the filter layer R _{a is} less than 0.5 μm, in particular less than 0.3 μm and preferably less than 0.001 μm, which is comparable to the roughness of the uncoated substrate.

3 shows the inventive definition of passband as well as the T ₅₀ values for a bandpass filter. The filter according to the invention is characterized by the transmission in the so-called pass band (pass band) and the transmission in the stop band. Under the passband according to the invention the range between T ₅₀ I and T ₅₀ II understood. The passband should have the highest possible transmission. In particular, the transmission within the passband should be at least partially, ie for a wavelength range lying in the passband, at least 70%, preferably at most 80%, more preferably at least 85%. Under the blocking area is according to the invention the area according to T ₅₀ II understood. According to a like in 3 shown variant may connect to the stopband another area with high transmission. In such a variant, a third value T ₅₀ III can still be specified for characterizing the curve. The stopband should have the lowest possible transmission. In particular, the transmission within the passband should be at least partially, ie for a wavelength range lying in the stopband, at most 40%, preferably at most 30%, more preferably at most 25%. The average transmission in the blocking region is preferably at most 50%, preferably at most 40%, more preferably at most 30%. The value T ₅₀ describes a wavelength at which the value of 50% transmission is exceeded. For filters, this value is entered before entering the transmission range, here designated T ₅₀ I, and after exiting the transmission range, here designated T ₅₀ II. T ₅₀ II according to the invention at the same time the entry into the restricted area, T ₅₀ III, the entry into a further passband. So-called long-pass and short-pass filters have only a T ₅₀ value between the blocking and the passband.

Furthermore, the width of the passband at which the transmission is more than 70%, 80% or 85% should be as large as possible.

According to a variant of the invention, the filter according to the invention is a blue filter or an NIR-cut filter. The region with a transmission of more than 70%, preferably more than 85%, then preferably starts at a wavelength of 460 nm, preferably 450 nm, more preferably 440 nm and / or ends preferably at the earliest at 540 nm, preferably 550 nm, more preferably at 560 nm. In particular, the T ₅₀ II should be at 650 nm +/- 30 nm, the average transmission in the range from 450 to 550 nm at 87% (+/- 5%) and the width of the wavelength range around T ₅₀ II from a transmission of 70% to a transmission of 30% at most 80 nm (+/- 10 nm) (measure of the steepness of the band edge) amount.

The filter layer 3 preferably has a layer thickness of at least 0.1 .mu.m, more preferably at least 0.5 .mu.m, more preferably at least 1 .mu.m, according to specific embodiments at least 2 microns. The layer thickness is preferably at most 15 μm, more preferably at most 12 μm, according to a variant at most 10 μm. According to specific embodiments, larger layer thicknesses of, for example, at most 20 μm or at most 100 μm may also be preferred.

The filter according to the invention has a thickness of preferably at most 2 mm, more preferably at most 1 mm and / or at least 0.1 mm. According to a variant of the invention, filters which have a thickness of less than 0.1 mm, for example filters with a layer thickness of 0.05 mm or 0.025 mm, can also be provided as substrates when thin glass glasses are used as substrates. According to this variant also has the filter layer 3 only a very small thickness of at most 10 microns or at most 5 microns on.

The filter layer has a homogeneity of the layer thickness over the entire coating area of preferably at least 15%, more preferably at least 10%, and most preferably at least 5%. This homogeneity of the layer thickness is preferred in the finished filter, however, in the production of filters over wafers over the entire wafer surface, i. H. reached on an area with a diameter of 8 or 12 inches or even 16 inches. According to the invention, the term "filter" may include both the singulated filter and a wafer for producing filters.

Due to the great homogeneity of the layer thickness of the filter layer, the filter according to the invention has a good optical homogeneity, in particular a wavelength deviation at T ₅₀ II of preferably at most 5%, preferably at most 3%, more preferably at most 1%.

The filter according to the invention also has excellent mechanical properties, in particular with regard to adhesive strength and abrasion resistance according to MIL-C-48497.

The adhesive strength is determined by a so-called adhesive tape test (application of the adhesive tape, such as Tesafilm, and slow removal over the corner). Preferably, less than 10% of the test area, preferably less than 2%, dissolves in this test, more preferably no separation takes place.

The abrasion resistance is determined by a so-called scrubbing test with a so-called "cheese cloth" (see Definition cheese cloth according to US Federal Standard CCC-C-440 ) with a run of 500 g and 50 strokes. Preferably, the filters of the invention pass this test without degrading the optical properties.

The filter has good chemical resistance (eg to water, isoprop, ethanol) and high climate (according to MIL-C-675A: 95% RH at 49 ° C 24 h) and long-term stability (according to MIL-STD). 810C) with consistent absorption properties.

The term "constant absorption properties" means that the change in the transmission in the passband and stopband before and after the load test is at most +/- 5%. By contrast, a significant change in the absorption properties is understood as meaning a change in the transmission of more than +/- 10%, in particular more than +/- 5%.

For long-term stability is also tested by the following methods: (i) temperature-humidity test: 1000 h at 85 ° C and 85% rel. LF and (ii) cyclic wet heat test: from -20 to 65 ° C at 90% rel. LF a temperature ramp of <1 ° C / min and 14 repetitions. Preferably, the filters of the invention pass this test without degrading the optical properties.

Variants of the filter according to the invention have a high temperature stability, d. H. the filter may be heated for a period of time of up to 10 minutes to a temperature in the range of 220 to 270 ° C with constant absorption properties, as defined above. In particular, due to the use of the thermally stable matrix, there is no significant change in the transmission or there is no additional absorption, for example due to the yellowing of the matrix material due to organic decomposition reactions.

The "relevant wavelength range" according to the invention is understood in particular to mean the wavelength range from 405 to 700 nm, preferably from 400 to 800 nm, according to an embodiment of 400 to 2500 nm. According to certain embodiments, the relevant wavelength range may begin at 300 nm, 330 nm, 350 nm, 380 or 400 nm, provided the substrate and matrix have sufficient transparency in the UV range. Furthermore, the upper limit of the relevant wavelength range may be 2400 nm, 1500 nm, 1000 nm, or 800 nm, if this is sufficient for the intended application.

The filter according to the invention can simultaneously be used as a carrier or substrate for electronic components, ie. H. serve as a circuit board. Circuit boards are made of electrically insulating material with adhering, conductive connections (conductors). As an insulating material, the filter according to the invention can also be used as a substrate. The tracks may be etched from a thin metallic layer, or patterned by a photolithography process using lift-off technology. Typically, copper or silver or gold layers are used as a conductive material, which usually still have a (metallic) adhesion promoter layer. This may, for example, consist of titanium, with a number of further adhesion promoter layers being known. A buffer layer known as a solder mask in the printed circuit board industry can be used to expose areas in which the printed conductors can be contacted. From these exposed metallic surfaces, soldering points ("bumps") are set, which later in the soldering process make the contacts to the CMOS chip or the printed circuit board. The components are contacted with it electrically. At the same time they can also be mechanically held by the contacts. Larger components can also be attached to the printed circuit board using cable ties, adhesive or screwed connections. Due to the thermal load in the soldering process, the filter layer must have a temperature stability in order to be able to be heated to the temperature required for soldering, at least for a short time.

The substrate is preferably optically inactive in the relevant wavelength range, ie transparent and has a transmission of at least 85%, preferably at least 90%, more preferably at least 91%, the maximum transmission due to the reflection at the two substrate surfaces with the refractive index n _d of circa 1.5 without additional antireflection coating is limited to approximately 92%. In addition, the substrate should have a thermal resistance of preferably at least 300 ° C, more preferably at least 400 ° C.

As a material for the substrate for the filter according to the invention glass, glass ceramic, crystals and optoceramics in question, with glass substrates, more preferably thin glass substrates are preferred

According to one embodiment, transparent glasses (eg, borosilicate glass, soda-lime glass, alumosilicate glass, alkaline-earth silicate glass, quartz glass, or alkali-free glasses) may be used, which may be rolled or floated, or by (e.g. EP 1 414 762 B1 described) can be made of drawing methods such as the downdraw or updraw processes or an overflow fusion method. For glasses that due to their manufacturing process only in larger thicknesses, eg. B. greater than 1 mm can be produced by mechanical processing by grinding, lapping and / or polishing or a Wiederziehverfahren a suitably thin substrate can be produced.

According to a variant are used as substrate thin glasses, d. H. Glasses with a thickness of 100 μm to 2 mm, or thin glasses, d. H. Glasses with a thickness of 25 microns to 100 microns, used. For example, the glasses marketed by SCHOTT AG under the names AF32, D263, B270 are suitable for such thin glasses

An optical glass, such as those offered by SCHOTT AG under the name PSK glasses, BASF glasses, LAF glasses, LASF glasses, BK glasses or LF glasses, may also be used as the substrate.

According to a further particular embodiment, a transparent ceramic, in particular an optoceramic is used.

As crystalline substrates according to another embodiment, for example, calcium fluoride or sapphire can be used.

For subsequent processes, such as wafer level packaging, the coefficient of thermal expansion of the filter may be of great importance. Here, the filter according to the invention has the advantage over glassbulk or plastic solutions that the expansion coefficient is essentially determined by the glass substrate used and can be adapted to the respective connection partners, such as, for example, silicon. In this case, substrates with a thermal expansion coefficient CTE or α (20, 300) in the range of 3 to 9.4 10 ^-6 K ^{-1 are} preferred.

In a particular embodiment, a biased substrate is used. The bias voltage can be induced chemically or thermally.

As the substrate, a glass having absorbing properties can also be used. The absorption properties of such a glass can be used to fine tune the transmission profile of the filter.

The matrix contains at least one dye which is dissolved in the matrix, i. H. in the preparation of the coating solution or the paint production shows no permanent streaking and allows a homogeneously colored matrix. The dye (s) should also be sufficiently strong in color and thermally stable enough to withstand the stress of crosslinking the binder system and later use.

According to a preferred embodiment, such an organic dye is soluble in a common solvent.

According to one variant of the invention, preference is given to dyes which are permanently thermally stable up to at least 140.degree. C. and withstand short-term exposure to temperatures of from 150.degree. C. to 300.degree. C., preferably from 200 to 270.degree. The term "permanent" is understood to mean a period of more than 60 minutes, preferably at least 100 hours. The term "short-term" means a period of at most 60 minutes, preferably at most 30 minutes.

Suitable dyes are preferably organic dyes which are selected from the group consisting of azo dyes, polymethine dyes, cyanine dyes, triphenylmethane dyes, carbonyl dyes: anthraquinones, indigo, porphyrins and phthalocyanines, with phthalocyanines and porphyrins are preferred.

Depending on the relevant wavelength range, a dye with suitable absorption properties is selected. For the production of a blue filter or an IR cut filter blue-green dyes can be used.

Phthalocyanines (Tetrabenzotetraazaporphyrine) are characterized by high chemical and thermal stability. According to the invention, phthalocyanines having different central atoms can be used, for example Pb, Zn, Al, Ga, Si, Ti, Cu or V. A pigment which does not contain this central atom appears turquoise (Pigment Blue 16) and can also be used.

Porphyrins are organic chemical dyes consisting of four pyrrole rings (tetrapyrrole) which are cyclically linked by four methine groups. The simplest representative is porphin.

Of the blue-green dyes, preference is given to those whose transmission maximum lies in the range from 550 to 750 nm, more preferably in the range from 650 to 750 nm. Particular preference is given to using iron cyan complexes, indanthrone, indigo, pthalocyanines with Cu, Zn or V as the central atom , preferably the β-form of the phthalocyanines, for example of the Kupfephthalocyanins (z. B. Orasol ^® as Orasol Blue GN, Orasol Blue 94416, Orasol Blue 94416), vanadium or zinc phthalocyanines (eg. B. Epolight ^®), chromium chelates , preferably Cr ³⁺ with ligands from the azo and Azomethinreihen z. Heliogen Blue 23050, Heliogen Blue 23080, Corimax Blue, Kremer Pigmente and Marabu Glasfarben ,.

Preferably, the Epolight dyes of Epolin, d. H. the group of NIR dyes of 700 nm, 800 nm, 900 nm, 1000 nm NIR Absorbing Dyes (such as 700A, 700B, 714A, 720B, 721A, 728A), phthalocyanines with different central atom (such as Pb, Zn, Al, Ga, Si, Ti, Cu, and others) from, for example, Sigma Aldrich and QCR Solutions Corp. also the group of visible range 400 nm, 500 nm, 600 nm Visible Absorbing Dyes can be used.

In addition to the dyes already mentioned, especially those of high interest which block in the IR range> 600 nm. For this purpose, in particular dyes of the group tetrakis (alkyl) ammonium salts, in particular dyes of the group tetrakis (alkyl) ammonium bromide, or chloride particularly preferably in the straight-chain version with n ≥ 4, and symmetrical cyanines suitable with n ≥ 5, described by: N ^⊕ (- (CH ₂ ) _n -CH ₃ ) ₄ Br ^- Tetrakis (alkyl) ammonium bromide (CH ₃ ) ₂ N- (CH = CH) _n-1 -CH = N ^⊕ (CH ₃ ) ₂ Cyanine

In the invention, one or a combination of two or more of the above-mentioned dyes may be used in the matrix.

As a further embodiment, absorbing dyes may be used in the red region of the spectrum.

In addition, dyes can be used which have a suitable absorption spectrum for green contrast filters or gray filters.

In addition to the above-mentioned soluble dyes, fine-scale pigments according to the invention, i. H. not soluble in the solvents or coating solutions soluble dyes are incorporated into the matrix. In particular, if necessary, with a mixture of one or more dyes with pigments, one possibility may be to adjust the fine adjustment of the desired transmission profile in the relevant wavelength range.

For example, to block well IR light in the range> 750 nm, ie a transmission <20% in this wavelength range, are, for example, CuO or Cu ₃ (PO) ₄ compounds or salts.

Suitable in principle are all pigments which have no or no excessive dispersion.

The finer the pigments, the less the scatter. With particle sizes> 1 μm, a scattering of 5 to 40% usually occurs in the wavelength range from 400 to 750 nm, so that such pigments are not preferred according to the invention.

When using pigments with particle sizes below 1 μm, so-called nanopigments, the scattering can be reduced to less than 6% (0.1-6%), in particular to 4-5%. When dispersing these nanopigments, it should be noted that they must be finely dispersed in order to prevent agglomeration, which is possible, for example, by means of a three-roll mill or ultrasound treatment.

These absorption pigments are preferably present in nanoscale form with a primary particle diameter of 2 to 5000 nm, preferably 8 to 1000 nm, very particularly 10 to 500 nm. Primary particles are generally understood as meaning the particles in the unagglomerated state. Particle diameters can be determined by small angle scattering (SAXS), dynamic light scattering (DLS) and / or Fraunhofer diffraction.

At least one dye as described above is dissolved in the matrix. The matrix preferably consists of a so-called binder. As binders, on the one hand, it is possible to use compounds which already have the properties required for layer formation, for example plastics or polymers having a sufficient polymer weight. As a further variant, the matrix may be formed in situ after coating of the substrate by crosslinking and / or polymerization reactions.

As the binder, polyurethane resins, sol-gel compounds, hybrid polymers, silicones (organic and / or inorganic crosslinking), phenolic resins, epoxies, polyamides, polyimide, EVA (ethylene-vinyl acetate), and polyester resins and mixtures thereof can be used.

Various thermoplastics can be used as plastic layers, such as cyclo-olefin copolymer COC, ionomers, polyamide PA, polyethylene terephthalate PET, polybutylene terephthalate PBT, polyether ketone PEK, polyoxymethylene POM, acrylate-based systems, polymethylmethacrylate and / or polystyrene PS, which are characterized by their high chemical and distinguish mechanical stability.

Of the polyester resins, so-called UP resins, d. H. unsaturated polyester resins, preferred. Depending on the reaction with acids or alcohols soft or hard plastic layers can be produced.

Alkyd resins can be processed with various film formers such as epoxy resins or phenolic resins. Use for paint synthesis, yes after solvents can be prepared low or higher viscosity paints.

When using EVA it is preferred that the polyolefin content (i.e., the ethylene content) has a content of at most 5%, otherwise coating by spin-coating is made difficult by the high viscosity of the binder solution. Suitable solvents for EVA are toluene, benzene and xylene.

According to a variant of the invention, sol-gel compounds or polyurethane resins are preferred.

In the case of sol-gel compounds, the coating composition comprises in particular sol-gel precursors of silicon, titanium, zirconium, aluminum, zinc, magnesium, calcium, tin or mixtures thereof. Most preferably, the sol-gel precursors are Si (ORx) Ry, Ti (ORx) Ry, Zr (ORx) Ry, Al (ORx) Ry, Zn (ORx) Ry, Mg (ORx) Ry, Ca (ORx) Ry and Sn (ORx) Ry.

Therein Rx is preferably hydrogen, alkyl, allyl or aryl and / or Ry = epoxy, methacrylate, acrylate, vinyl, allyl, amino, thiol, alkyl or aryl. The indices x and y are 4 in total, d. H. x + y = 4.

Preferably, the coating composition comprises a UV curable and / or thermally curable hybrid polymer hydrolyzed and condensed alkoxysilane precursor, especially glycidyloxypropyltriethoxysilane (GPTES) and / or methacryloxypropyltrimethoxysilane. These may also be functionalized with polysiloxanes. Preference is given to using methyl- and / or phenyl-functionalized polysiloxanes. Thus, the sol-gel layer on the substrate preferably comprises the reaction products of sol-gel precursors described herein with polysiloxanes described herein.

In another embodiment, the binder composition comprises a polyurethane resin formed by reacting a polyisocyanate component with a polyol component. By polyisocyanates are meant organic compounds containing two or more isocyanate groups (-N = C = O). Polyols are understood as meaning organic compounds which contain two or more hydroxyl groups (-OH). Reaction of polyisocyanates and polyols produces straight-chain or branched polyurethanes:

• – aromatischen Isocyanaten, z. B. 2,4-Toluylendiisocyanat (TDI), 4,4'-Diphenylmethandiisocyanat (MDI),
• – cycloaliphatischen und araliphatischen Isocyanaten, z. B. Isophorondiisocyanat (IPDI), 2,4-Methylcyclohexyldiisocyanat (HTDI), Xylylendiisocyanat (XDI),
• – aliphatischen Isocyanaten, z. B. Hexamethylendiisocyanat (HDI), Trimethylhexamethylendiisocyanat (TMDI) oder 1,4-Cyclohexyldiisocyanat (CHDI),

Depending on the application, the following polyisocyanates can be used according to the invention:

• - aromatic isocyanates, eg. 2,4-tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI),
• - Cycloaliphatic and araliphatic isocyanates, eg. Isophorone diisocyanate (IPDI), 2,4-methylcyclohexyl diisocyanate (HTDI), xylylene diisocyanate (XDI),
• - aliphatic isocyanates, eg. Hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI) or 1,4-cyclohexyl diisocyanate (CHDI),

With aliphatic isocyanates, especially with HDI, polyurethanes can be produced with excellent thermal stability, which decompose only at 210 to 270 ° C. The thermal stability of polyurethane layers of aliphatic isocyanates is therefore sufficient for use as filter systems, which are usually introduced via WLP (wafer-level packaging) processes in the component, since here for a short time temperatures of 260 ° C for a period of about 10 minutes, preferably less than 5 minutes occur. In the field of application, for example, in camera modules, however, only temperatures significantly <150 ° C come into play.

Instead of monomeric polyisocyanates and polymers of the corresponding monomers may preferably be used, for. B. their dimers, trimers, oligomers or higher polymers. It is also possible to use polyhydric alcohols such as biurets, isocyanurates or adducts of trimethylolpropane or similar compounds which, by enlarging the molecular weight, convert the monomers into less volatile and thus easier-to-handle components.

Also preferred are blocked polyisocyanates (so-called Einbrennurethanharze, EBU resins) in which the highly reactive isocyanate groups are reversibly blocked by so-called blocking agents. A blocked polyisocyanate cleaves at elevated temperature, the blocking agent to release the reactive isocyanate, so that the crosslinking reaction must be started by thermal treatment. Suitable blocking agents are, in addition to alcohols and phenols, other Brönsted acids (proton donors, compounds with acidic hydrogen) such as thio alcohols, thiophenols, oximes, hydroxamic acid esters, amines, amides, imides, lactams or dicarbonyl compounds and in particular ε-caprolactam, butanone oxime, dimethylpyrazole, diisopropylamine and malonic acid esters such as B. diethyl malonate. While it is possible to formulate coatings with butanone oxime-blocked HDI, which already cure at 140 to 180 ° C. (5-60 min), somewhat higher temperatures are necessary for crosslinking with ε-caprolactam-blocked HDI (160-240 ° C., 5-60 min). Since crosslinking releases the blocking agent and malonic acid diethyl ester and ε-caprolactam have less critical classification as hazardous substance compared with butanone oxime, aliphatic polyisocyanates blocked with malonic acid ester or with ε-caprolactam are preferred. Butanone oxime, ε-caprolactam and most other blocking agents escape during crosslinking to a considerable extent from the paint film and are removed with the exhaust air flow of the dryer from the paint. This shifts the reaction equilibrium from the side of the starting components to the side of the polyurethane.

Examples of suitable blocked aliphatic polymers of polyisocyanates are, for. As the Desmodur ^® grades from Bayer MaterialScience, for example Desmodur ^® BL 3175 SN and Desmodur® BL 3272 MPA.

From the content of blocked isocyanate groups, the equivalent weight can be calculated. If the average NCO functionality of the blocked polyisocyanates is known, the average molecular weight can be determined therefrom. NCO functionality is the number of blocked and optionally free NCO groups per molecule. For suitable EBU resins, the NCO functionality is ≥ 2, especially 2.5-6, more preferably 2.8-4.2. However, resins having more than 6 blocked isocyanate groups per molecule are also suitable, though not preferred.

The average molecular weight of preferred polymers of blocked polyisocyanates is 800-2000 g / mol. However, polyisocyanates with molecular weights of 2000-10000 g / mol may also be suitable. The average molecular weights may, for. B. via a GPC measurement (gel permeation chromatography) can be determined.

In principle, all compounds which contain a reactive (acidic) hydrogen atom can serve as reactants for a polyisocyanate. By the reaction of the isocyanate groups with compounds containing reactive hydrogen atoms, polyaddition forms the polyurethane.

The properties of the polyurethane depend not only on the isocyanate component, but also on the chosen H-acidic compound.

Polyols, in particular polyester polyols and polyether polyols are suitable, since mechanically and chemically very stable coatings can be obtained with these components. Particularly suitable are polyester polyols, in particular branched polyester polyols having a high hydroxyl group content (preferably three or more hydroxyl groups per molecule, corresponding to an OH content of 2-8 wt .-%, in particular 3-6 wt .-%) and an average molecular weight in the range of 1000-2000 g / mol proved. These polyols lead via their hydroxyl groups to strongly crosslinked polyurethane films, so that particularly hard, scratch-resistant and chemically resistant layers can be produced. The more the polyesterpolyols are branched and the more hydroxyl groups they have, the more crosslinked the polyurethane formed is.

Examples of suitable polyester polyols are the Desmophen ^® grades of Bayer MaterialScience Desmophen ^® 651 MPA Desmophen ^® 680 BA and Desmophen ^® 670th

The molecular structure of most commercially available polyester polyols and also the above-mentioned Desmophen ^® grades can not be specified exactly, since a polymer mixture is obtained in the production rule. However, the properties of the polyester polyols can be reproducibly adjusted by the reaction procedure, the products being characterized by the hydroxyl content (OH number), the average molecular weight, their density and the viscosity. The average OH functionality is determined by the choice of starting components.

The control and knowledge of the hydroxyl content (OH content) of the polyol component (H-acid or hydroxyl component) and the knowledge of the content of blocked isocyanate groups (NCO content) of the polyisocyanate component are important because, theoretically, maximum crosslinking The coating is carried out only when using the same stoichiometric amounts of isocyanate and hydroxyl component, if the stoichiometric ratio of isocyanate to hydroxyl component is therefore 1: 1 according to the following reaction equation:

The maximum crosslink density theoretically achievable at the stoichiometric ratio of 1: 1 is decisive for the properties of the coating (adhesion, scratch resistance, flexibility, chemical and thermal resistance). Isocyanate and hydroxyl components should therefore be present in the polyurethane system in the stoichiometric ratio of 1: 1. The quantities required for this purpose can be calculated using the equivalent weight.

The reduction of the polyisocyanate portion (undercrosslinking) results in more flexible coatings with less mechanical and chemical stability and is therefore not preferred. The increase in the polyisocyanate content (over-crosslinking) increases the crosslinking density because the excess isocyanate groups react with atmospheric moisture to form urea groups. The use of polyisocyanate to polyol in the equivalent ratios of 1.1: 1 to 2: 1 may therefore be useful to increase the scratch resistance or adhesion to the substrate on the hardness of the coating. Since the secondary reaction with water is also made possible by other factors, such as the water content of the solvent or the residual moisture of the substrate, which deprives the system of isocyanate groups which are then no longer available for reaction with the hydroxy groups of the polyol component, equivalent Ratios of polyisocyanate to polyol component in the order of 1.1: 1 to 2: 1, in particular from 1.2: 1 to 1.5: 1, preferably.

Of course, various H-acid compounds can be combined, for. As polyester polyols with silicone or epoxy resins, in particular to adapt the film properties with respect to specific requirements.

The thermal curing of the applied polyurethane system is carried out by heating to 150 ° C-260 ° C, in particular by heating to 170-210 ° C for a period of 10-120 min, in particular from 60-90 min. Curing time of 45 minutes at 180 ° C. shows no chemical resistance to isopropanol and does not pass the adhesive tape test, whereas curing at the same temperature of> 60 minutes results in that both tests are passed. The heating on the one hand evaporates the solvent from the paint and on the other hand deblocks the isocyanate component so that the crosslinking reaction with the H-acidic component (eg polyester polyol) takes place and a solid film forms. Higher temperatures than 210 ° C are usually not used for a longer curing (> 30 min), since the polyurethane formed can decompose from 200 ° C. The decomposition causes a slight browning of the coating, which is generally undesirable.

The required reaction temperature depends, inter alia, quite significantly on the blocking agent with which the isocyanate component is blocked. Thus, in the case of isocyanates blocked with butanone oxime, 140-180 ° C. suffice to initiate the crosslinking, whereas in the case of isocyanates blocked with ε-caprolactam, 160-240 ° C. are necessary. The time necessary for sufficient crosslinking depends on the choice of the isocyanate component and the H-acid compound (polyester polyol). It can be shortened significantly (to a few minutes) by catalysts, eg. B. by tertiary amines, but especially by metal-containing catalysts, eg. Zn, Co, Fe, Sn (IV), Sb and Sn (II) salts. Particularly suitable catalysts are tin (IV) alkoxylates such. As dibutyltin dilaurate and tetra (2-ethylhexyl) titanate, zinc or cobalt naphthenate. The catalyst or catalyst mixture is added in an amount of 0.05-1% by weight (based on the color paste).

• (1) Herstellung Bindersystem: Lösen des Binders (eine oder zwei Komponenten) im Lösungsmittel;
• (2) Herstellung des Lackes durch Lösen des Farbstoffes und ggf. Dispergieren der Pigmente im Bindersystem sowie ggf. weitere Zusatzstoffe;
• (2) ggf. Entlüften des Lacks;
• (3) ggf. Substratreinigung;
• (4) ggf. Aufbringen einer Zwischenschicht;
• (5) Aufbringen des Lacks beispielsweise durch Spin-coating;
• (6) ggf. Vortrocknung des Lacks (sogenanntes „soft-bake”);
• (7) Trocknung thermische und/oder UV-Härtung des Lacks;
• (8) ggf. Aufbringen weiterer Schichten.

A method for producing the filter preferably comprises the following steps:

• (1) Preparation of binder system: dissolving the binder (one or two components) in the solvent;
• (2) preparation of the paint by dissolving the dye and, if appropriate, dispersing the pigments in the binder system and optionally further additives;
• (2) if necessary, bleeding the paint;
• (3) if necessary, substrate cleaning;
• (4) optionally applying an intermediate layer;
• (5) application of the paint, for example by spin-coating;
• (6) if necessary predrying of the varnish (so-called "soft-bake");
• (7) drying thermal and / or UV curing of the varnish;
• (8) optionally applying further layers.

By "drying" is understood according to the invention that the binder is transferred substantially without chemical reaction in the filter layer, d. H. that only volatile constituents are removed from the coating solution.

The production of the filter layer preferably comprises the step of preparing a coating solution. To prepare the coating solution or the paint, at least one dye and binder or a binder system are dissolved in a solvent. The coating solution is applied to the substrate and cured.

The binder can serve as a solvent for the dye. If the viscosity of the binder is insufficient, a solvent may be added. Solvents ensure in particular that the paint can be influenced in its viscosity and processability. By adding solvents, the filter layer can be applied in a coating process, wherein the amount of the solvent or the viscosity of the coating solution significantly influences the resulting layer thickness. It should be noted that the design and condition of the film surface may also depend on the solvents used. Solvents with very high evaporation rates, ie high vapor pressure, are less suitable because it can lead to the formation of a skin on the surface. As a result, the flow behavior changes, there may be hydrodynamic instabilities, which ultimately lead to the formation of lateral coating structures, which emanate star-shaped from the center of rotation. Furthermore, hygroscopic solvents are not suitable, although they attract water from the environment, but are themselves not miscible with this. Then it can come to demixing effects, which also causes lateral structures. Therefore, solvents having a vapor pressure <120 hPa (at standard conditions: 20 ° C.) are preferred, particularly preferably <60 hPa, in order to ensure good processability.

Preferred solvents are alcohols, ethers and mixtures thereof. Preference is given to n-butyl acetate, carbitol, carbitol acetate, butylcarbitol acetate, ethyl acetate, methanol, ethanol, 1-propanol, dimethylformamide (DMF), ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, tripropylene glycol monomethyl ether, dichloromethane, 1,2,3-trichloropropane, cyclohexane, tetrahydrofuran, Hydroxy-4-methyl-2-pentanone, ethyl methyl ketone, cyclohexanone and mixtures thereof.

For the preparation of thin polymer films for a spin-coating process, 1,2,3-trichloropropane (2.8 hPa vapor pressure at 20 ° C.) or cyclohexanone (4.55 hPa vapor pressure at 20 ° C.) are used according to the prior art. or DMF (3.77 hPa vapor pressure at 20 ° C) is preferably used. As a rule, between 10 and 30% based on the total mass of the coating solution is used.

Surprisingly, however, it has been found that a mixture of at least one solvent with a low vapor pressure <2 hPas (under normal conditions) with at least one solvent with a high vapor pressure> 100 hPas also showed good results.

The coating solution may be further added additives such as adhesion promoters, defoamers, flow control additives, levelers, deaerators, slip additives, Substratnetadditive, wetting and dispersing additives, rheology additives, radiation-curing and antiblocking (UV blocker) additives. These additives may constitute up to 5% by weight, preferably up to 2% by weight of the coating solution. They can be obtained commercially, for example, from TEGO (EVONIK) and are known to the person skilled in the art as typical paint additives.

In particular, they are pure and or organically modified low molecular weight polysiloxanes and or organic polymers and or fluorine-functionalized polymers and or polyether-modified and or polysiloxanes and or polyacrylates and or basic and acidic fatty acid derivatives.

Many organic dyes have the disadvantage that, despite the desired transmission behavior and possibly also high temperature stability, they are not stable to UV radiation. For this reason, in a further embodiment, so-called. Anti-blocking additives can be added to increase the UV stability. The effect of such blocking additives is due to the deactivation of free radicals and are generally referred to as HALS ("hindered amine light stabilizers") and are chemically usually derivatives of TMP (2,2,6,6-tetramethylpiperidine).

Depending on the coating method, it is also possible to add various leveling agents, for example PEG, BYK 302, BYK 306, TEGO Wet or TEGO Rad products, in order to achieve homogeneous layer thicknesses. In particular, when coating non-smooth, uneven surfaces, a wetting agent / leveling agent is added, which ensures a homogeneous running of the layer despite the unevenness. For spin coating, preference is given to solvents which permit good wetting of the surface and are suitable for additionally using additives such as leveling agents and wetting aids; these may be, for example, ethyl methyl ketone or butyl carbitol acetate.

If the binder system is too liquid for the coating process and the solvent content can not be further reduced, the viscosity can be increased by adding rheological additives. Otherwise, depending on the spin coating parameters chosen, the paint would become too thin and not sufficiently absorb the filter layer.

Typically, thickening, i. H. the viscosity can be increased by adding resins such as polyacrylates, polysiloxanes, thixotropic acrylic resins and isocyanate- or urethane-thixotropic alkyd resins, or by reducing the solvent content. Waxes such as hydrogenated castor oil or polyolefin waxes are also suitable or associative thickeners such as associative acrylate thickeners, hydrophobically modified cellulose ethers, hydrophobically modified etherurethanes ("polyurethane thickeners"), hydrophobically modified polyethers or modified ureas. When selecting the thickening agent, however, it must be ensured that the color film is to be further coated, for example. In this case, in particular waxes are not suitable as thickeners.

In addition, so-called. Hardener z. B. be added to increase the layer hardness / scratch resistance, such as nanoparticles, bis-epoxides.

The preferred weight percentages of the various components of the coating solutions for applying filter layers to substrates depend on the binder used.

In particular, a viscosity suitable for the coating process is set. For a spin-coating process, it is preferable to adjust the viscosity of the binder mixture to at most 100 mPas, preferably at most 50 mPas, particularly preferably at most 20 mPas.

In the following tables, preferred weight proportions of the components of coating solutions are exemplified for a polyurethane system and GPTES. Proportions in% by weight PU system solvent dye additives Prefers 22-99 1-80 <10 <10 more preferred 41-90 2-60 <5 <5 particularly preferred 60-80 20-35 <1 < Proportions in% by weight GPTES solvent dye additives Prefers 22-99 1-80 <10 <10 more preferred 30-80 30-60 <5 <5 particularly preferred 40-60 40-50 <2 <1

The proportion of dye necessary to achieve the desired transmission in the coating depends on the layer thickness of the coating and, depending on the layer thickness, is 0.1-45% by weight (based on the cured coating). The dye content corresponds to a binder content of 55-99.9 wt .-%. At higher layer thicknesses, lower dye contents than at low layer thicknesses are necessary in order to achieve the desired wavelength-dependent absorption and thus a reduction in transmission. In addition, by changing the concentration, the steepness of the band edge of the filter can also be influenced, since saturation effects occur at higher concentrations. This can be utilized for the purposeful adjustment of the shape of the band edge of the filter. Dye fractions of more than 45% by weight are not preferred since the scratch and adhesion strength would then no longer be sufficient.

In a dried and cured filter layer, the mass ratio of dye to binder 1 is 200: 1 to 50: 1, preferably 175: 1 to 60: 1, most preferably 150: 1 to 100: 1.

In a dried and cured filter layer, the mass ratio of dye to binder 2 is 100: 1 to 3: 1, preferably 50: 1 to 5: 1, most preferably 40: 1 to 25: 1.

All components, the matrix, the dyes and the functional additives are homogenized, preferably by means of Dispermat (Ultraturax) or three-roll mill.

The finished paint can be pressure filtered to remove lint, dust or other particles from the raw materials or in the manufacturing process. Alternatively, the paint can be filtered through an ultrafine filter prior to coating.

The coating can take place in one or more layers, with a single-layer coating being preferred.

In a specific embodiment, the filter layer is only locally structured or cut out or applied to the substrate. Preferably, however, the substrate is coated over its entire surface.

The coating of the substrate can be carried out by spin coating, spraying, dipping, pouring, brushing, screen printing, pad printing, ink jet printing, off-set printing, roll coating, or other methods known to those skilled in the art. For these coating methods, the viscosity of the color matrix must be adapted to the processability.

According to the invention, a spin-coating method or spin-coating method or a spin-coating method is preferred, since with such a method very homogeneous filter layers can be applied.

For spin coating, all materials in solution are suitable. The substrate is fixed on a turntable, the so-called chuck, usually by means of vacuum suction at the bottom. With a metering device above the center of the substrate, the desired amount of the solution is applied.

• 1. Schritt Verteilung der Beschichtungslösung, charakteristisch sind hier moderate Beschleunigung und Drehzahlen, üblicherweise im Bereich 200–2000 rpm, jedoch abhängig von dem verwendeten Spin-Coater;
• 2. Schritt Beschichtung, hier werden mittlere bis hohe Drehzahlen benötigt, um das Substrat gleichmäßig zu beschichten, üblicherweise im Bereich 1000–10000 rpm, jedoch abhängig von dem verwendeten Spin-Coater;
• 3. Schritt Abschleudern von überschüssigem Material, wobei hohe Drehzahlen notwendig sind, typischerweise > 2000 rpm, jedoch abhängig von dem verwendeten Spin-Coater.

The spin-coating process is divided into three steps:

• 1st step distribution of the coating solution, characteristic here are moderate acceleration and speeds, usually in the range 200-2000 rpm, but depending on the spin coater used;
• 2nd step coating, here medium to high speeds are required to evenly coat the substrate, usually in the range 1000-10000 rpm, but depending on the spin coater used;
• Step 3 Spinning off excess material, where high speeds are required, typically> 2000 rpm, depending on the spin coater used.

In order to obtain a solid layer, it is necessary to remove the solvent. Part of the solvent volatilizes already during spin-coating. The removal of the solvent can be accelerated by a heated chuck or by subsequent heating on a "Hotplate" (annealing, also called Soft Bake). Advantages of this treatment are that with moderate temperatures the soft bake prevents the solvent from generating bubbles in the layer, as is often the case with rapid heating. Furthermore, the layer becomes "dust-dry", i. H. Dust and suspended particles are essentially no longer adhering to the surface, so that contamination can be removed more easily.

For spin coating, in particular a solvent, such as, for example, ketones or acetates, is preferred, which permits good wetting of the surface and is suitable for additionally using additives such as leveling agents and wetting aids

After coating, the color layers are thermally cured if necessary and / or UV cured. The layers are preferably baked at temperatures> 150 ° C., preferably> 170 ° C. For this standard equipment can be used, in the case of UV curing or combination of UV curing with thermal curing, for example, conventional UV surface radiators can be used, preferably microwave excited electrodeless surface radiator UV lamps, more preferably UV LEDs.

For a high quality of the filters, in addition to the already mentioned low roughness and the low scattering it is further important that a smooth film forms and that the cured coating does not contain coarse, opaque particles, impurities or the like (eg dust, lint , Grains with a size of over 200 microns, in particular 0.3-1.5 mm). Due to this requirement, care must be taken to ensure clean production during the production of filter layers of excellent quality. Ideally, it is produced under clean room conditions (cleanroom class <10000).

Filter can also do more than one filter layer 3 exhibit. According to such a variant of the invention have further filter layers 3 ' preferably other absorption properties, ie for example absorption bands at different wavelengths.

One or more filter layers 3 ' can on the bottom of the substrate 2 between substrate 2 and layer 4 ' or on top of the substrate below or below the filter layer 3 be arranged. This variant is opposite to a variant in which in a filter layer 3 more than one dye is included, in cases where undesirable optical effects are caused by interactions of the dye molecules. Since the filter layers according to the invention can have a high homogeneity of the layer thickness, filters with two or more filter layers also have very good to sufficient optical homogeneity.

Furthermore, the filter according to the invention can transmissive multilayer layers 4 . 4 ' us 5 include. Multilayer coatings typically include sequences of high and low refractive index layers of nitrides, oxides, oxynitrides of metals, or mixtures thereof, and may be applied to the filter by, for example, PVD techniques such as sputtering, evaporation, etc., or PECVD.

By way of example, electromagnetic radiation in the infrared range above 650 nm to 1000 nm, preferably up to 1200 nm, can be largely reflected or blocked by such a transmission-modifying multilayer layer, and thus the blocking range of, for example, the in 3 shown filters are extended in the direction of longer wavelengths. In the prior art, such reflective multilayer films are used as the only layer which influences IR radiation. Due to the scattered light generated by the reflection, however, so-called ghost images usually form. Surprisingly, no ghosting occurs even with the combination of the filter layers according to this invention with such multilayer coatings. It is believed that the absorbing layers absorb the stray light generated by the multilayer layers through the filter layer.

The design of the multilayer films, when used in conjunction with the organic filter layer, may be adapted such that the combined wavelength-dependent transmission of the entire filter meets the desired specification. Particularly critical here is the value T ₅₀ II, which is regarded as a central component of the optical specification. The absorption edge of the multilayer layer at short wavelengths must be shifted to longer wavelengths. For the example of a blue glass filter, this absorption edge T ₅₀ II is, for example, 630 nm. This absorption edge is already realized essentially by the absorption of the organic filter layer, so that the multilayer layer should have a high transmission above 80% in order to achieve the total transmission. This allows a more tolerant design of the multilayer layer, in which, for example, a less steep edge and a lower transmission suppression is sufficient to achieve the total transmission. Overall, this combination can be used to produce technically simpler and thus more cost-effective multilayer coatings. The design of such multilayer coatings is well known to those skilled in the art and can be performed well using optical layer design software such as TFCalc from Software Spectra Inc. In order to include the effect of the organic filter layer, the transmission and reflection of the organic filter layer can be converted into the optical constants of a substrate glass and thus taken into account in the layer design. The person skilled in the art is aware of how the optical transmission and reflection of the organic filter curve are converted, for example, into the Sellmeyer coefficients used by a program such as TFCalc. The adaptation of the multilayer layer design is done by adjusting the number and thickness of the individual layers.

Preferably, reflections on the front and back of the filter, respectively, are achieved by the application of anti-reflection coatings 4 . 4 ' prevents or reduces, so that the total transmission in the optical range increases significantly. Here more than 6% transmission gain in the absorption-free wavelength range can be achieved. Also, such anti-reflection coatings are usually multilayer films as described above. By appropriate layer design, the antireflection function can be combined with the function of extending the stop band as described above in a multilayer layer.

Furthermore, adhesion promoters may be applied between substrate and filter layer or filter system, preferably inorganic adhesion promoters, such as porous SiO ₂ layers, for example by means of pyrolysis (for example flame treatment with HMDSO) or SolGel processes, particularly preferably organic adhesion promoters consisting of hexamethyldisilazane (US Pat. HMDS), epoxy, methacrylate, acrylate, amino, vinyl, and thiol groups are applied in a highly diluted alcoholic solution or by a CVD method.

Optionally, additional functional layers, such as scratch-resistant layers, anticorrosive layers, smoothing layers Easy to Clean layers u. v. m. also be applied to the filter layer or the filter layer system or the substrate surface opposite the filter layer or the filter layer system, or a combination of these described layers and their arrangements.

The present invention further relates to the use of the filter according to the invention. In particular, the filter can be used as a filter element in the beam path of optically sensitive semiconductor detectors, for example a CMOS (Complementary Metal Oxide Semiconductor) sensor or CCD (Charge Coupled Device) sensor. Such semiconductor detectors are used, for example, as image sensors in digital cameras or video cameras or in spectroscopy.

The method according to the invention makes it possible to produce very homogeneous filter layers even on larger surfaces. Thus, the filters or wafers according to the invention for the production of filters are also suitable for use in wafer-level packaging (WLP) processes. The substrate ( 2 ), hereinafter "glass wafer", in such a case does not have the dimensions of a single filter, but the dimension of a wafer on which a plurality of filter elements is provided. In WLP processes, the semiconductor wafers with the optically active sensors and a glass wafer ( 2 ) Filter layer ( 3 ) mounted directly above one another, with distances between glass surface and semiconductor chip of less than 1 mm, so that the optical beam path from the light source via the filter ( 1 ) falls on the sensor. When mounting the glass wafers over the sensor chip seals can be applied at the same time, so that the sensor chip is hermetically protected from the environment. The assembly can be done either by gluing processes, or by a soldering process in which either a metallic seal by a low-melting solder or a glassy compound is realized by a low-melting glass solder. Typically, for such processes, a glass wafer ( 1 ), whose thermal expansion coefficient is in the range of the expansion coefficient of the silicon chip. As an example of a suitable Glassubtrat the glass AF32 (SCHOTT AG) can be used, with a thermal expansion of 3.2 10 ^-6 K ^-1 particularly well adapted to the silicon substrate. In adhesive processes, the thermal expansion coefficient is less critical, so that glasses with higher expansion coefficients, such as the glass D263eco (SCHOTT AG) with a thermal expansion coefficient of 7.2 10 ^-6 K ^-1 can be used. The big advantage of the WLP process is that the wafer-shaped filter and filter are connected together before being separated into individual chips.

The present invention thus further relates to a glass wafer on which a plurality of the filters according to the invention is provided and which is the same as in 1 for the filter according to the invention described construction. Such a glass wafer may have a diameter of, for example, 8 or 12 inches.

According to another embodiment, the CMOS sensor can be controlled by "pick-and-place" processes with the filter (FIG. 3 ) are brought together. Here, the CMOS sensor by similar bonding and soldering processes as described above through the filter ( 3 ) hermetically sealed and protected. The separation of the CMOS chips and glass wafers before mounting allows a further product variant in which the filter ( 3 ) and the CMOS chip have different sizes.

As described above, heat-resistant variants of the filter according to the invention are suitable for use as a substrate for printed circuit boards. Thus, in addition to the optical filter effect, electrically conductive, structured electrodes can also be applied outside the optical beam path in order to contact the CMOS chip and / or the contacts of an electrical circuit board. According to specific embodiments, the contacts of the CMOS chip on the front side as well as the contacts of an electrical circuit board located below the CMOS chip can be contacted by the electrically conductive conductor tracks and an electrical connection can be established. In these cases, the sizes of the glass chip differ from the size of the silicon chip because the tracks are geometrically extended beyond the silicon chip to allow external bonding.

The above invention will be further explained by examples below, but is not limited to the embodiments described in the examples.

Examples

Inventive filters were prepared according to the conditions given in Table 1. 0.5 to 0.7 mm thick glass wafers from AF32 or D263 (SCHOTT AG) served as the substrate. Table 1:

Table 2 summarizes the properties of the filters produced according to the invention. TABLE 2 properties Example 1 Ex. 2 Example 3 Example 4 Example 5 layer thickness + + + + + adhesiveness + O + O + Chemical resistance + O + O O air resistance + + + + + Haze + + + + + homogeneity + + + + + temperature stability + + + + + transmission properties + - + + + absorption properties + - + + + The following legend applies: + O - layer thickness <10% deviation 10-15% deviation > 15% deviation adhesiveness no replacement Replacement <2% of the test area Replacement> 2% of the test area Chemical resistance no replacement // transmission change <5% Replacement <2% of the test area // 5-10% Replacement <2% of the test area //> 10% air resistance Deviation in transmission <5% 5-10% > 10% Haze <4% 4-8% > 8 Homogeneity over the wafer surface Deviation in transmission <5% 5-10% > 10% temperature stability Deviation in transmission <5% 5-10% > 10% Band edge T ₅₀ (at 650 nm) <25 nm 25-40 nm > 40 nm

Example 5

The coating solution of Example 1 was applied to the substrate by a screen printing method. The transmission curve is in 7 compared to a filter applied by a spin-coating method.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2007/025011 A1 [0006]
• WO 2012/031837 A1 [0007]
• EP 1414762 B1 [0041]

Cited non-patent literature

• Standard ASTM D 1003 [0003]
• Standard CCC-C-440 [0032]

Claims (15)

Optical filter comprising a substrate ( 2 ) and on at least one side of the substrate a filter layer ( 3 ), wherein the filter layer ( 3 ) comprises a matrix containing at least one organic dye dissolved in the matrix. An optical filter according to claim 1, wherein the filter layer ( 3 ) is applied by a spin-coating method. Optical filter according to one of the preceding claims, wherein the filter has an optical homogeneity, in particular a wavelength deviation at T ₅₀ II of preferably at most 5%, preferably at most 3%, more preferably at most 1%. Optical filter according to one of the preceding claims, wherein the substrate ( 2 ) comprises a glass, preferably a thin glass or thin glass, and wherein the substrate ( 2 ) has a transmission of at least 85%, preferably of at least 90%, more preferably of at least 91% in the spectral range from 400 nm to 800 nm. Optical filter according to one of the preceding claims, wherein the filter layer ( 3 ) has a thickness of at most 100 μm, more preferably at most 20 μm, and most preferably at most 15 μm. Optical filter according to one of the preceding claims, wherein the filter has a thickness of at most 2 mm, preferably at most 1 mm and / or at least 0.1 mm. Optical filter according to one of the preceding claims, wherein the filter has a haze value of less than 10%, preferably less than 5%, more preferably less than 3%, most preferably less than 1%. Optical filter according to one of the preceding claims, wherein the filter in the stop band of 650 nm to 700 nm has an average transmission of not more than 50%, preferably not more than 40%, particularly preferably not more than 30%. Optical filter according to one of the preceding claims, wherein the filter comprises at least one further layer, which lowers the transmission in the IR range, and wherein this layer is used as multilayer layer ( 4 . 4 ' . 5 ) and / or further filter layer ( 3 ' ) is trained. Optical filter according to one of the preceding claims, wherein the filter on the upper and / or lower surface an antireflective coating ( 4 . 4 ' ), preferably a multilayer layer. An optical filter according to any one of the preceding claims, wherein the substrate is a wafer. Process for producing an optical filter according to one of Claims 1 to 11, comprising the following steps: - Preparation binder system: Dissolve the binder (one or two components) in the solvent - Preparation of the paint by dissolving the dye and optionally dispersing the pigments in the binder system; if necessary further additives - Application of the paint by a coating method, preferably by spin-coating; - "drying" and / or thermal and / or UV curing of the filter layer. Use of an optical filter according to one of claims 1 to 11 as a filter element in the beam path of optically sensitive semiconductor detectors, for example a CMOS sensor. Use of an optical filter according to one of claims 1 to 11 in digital cameras, video cameras or spectroscopes. Use of an optical filter according to claim 11 in a WLP process.

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