DE102013022162B4 - Optical filter, process for its manufacture and its use - Google Patents

Abstract

Optical filter, comprising a substrate (2) and a filter layer (3) on at least one side of the substrate, the filter layer (3) comprising a homogeneously colored matrix which contains at least one organic dye dissolved in the matrix, the matrix being a sol -Gel compound or a polyurethane resin, wherein the organic dye is selected from the group of phthalocyanines, wherein the filter is thermally stable for a short period at temperatures of 220 to 270 ° C and permanently up to at least 140 ° C, which is the filter is an IR-cut filter in which a pass band with a transmission of more than 70% begins at the latest at a wavelength of 460 nm and ends at 540 nm at the earliest and a blocking range begins at 650 nm +/- 30 nm, where entry into the restricted area is indicated by T50II.

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 of the available filters and filter systems, which are used in the field of cameras, mobile phones, or other WLP (wafer-level packaging) -based electronics, are based on inorganic systems. The aim of such systems is usually the realization of a specification-precise transmission curve, e.g. a steep edge in the range of 650 nm. Often so-called blue glass is used, i.e. an optical glass, for example a fluorophosphate glass, to which coloring glass components such as CuO have been added. Layers which contain inorganic constituents or multilayer systems are also used. When using blue glass you are limited with very good optical properties with regard to some things: on the one hand, the glass is only corrosion-resistant to a limited extent, on the other hand, glass thicknesses of less than 300 µm are difficult to achieve due to the brittleness of the material and their production is associated with high costs . In addition, the coefficient of thermal expansion (CTE) of the glass restricts further processing through some bonding processes, such as "Wafer-Level-Packaging" (WLP), which are standard processes in microelectronics. Multiple layers or layers with inorganic particles have the problem that the optical properties are only inadequately met and, in particle-filled systems, there is often strong scattering (haze), which produces undesired optical effects, ie optical losses in the form of reduced transmission and image deterioration .

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 the transmitted light that is scattered forward by the irradiated sample. The haze value thus quantifies the influence of particles in the surface or structure that interfere with the clear view. These particles can either have been deliberately introduced or come from material defects. The method for measuring the haze value is described in the ASTM D 1003 standard. The standard requires the measurement of four spectra. The light transmittance is calculated for each spectrum. The four degrees of transmission are offset against the% haze value.

Multi-layer systems or interference filters with good optical properties are now 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”. These ghost images can only be avoided through optical absorption in layers or in the substrate. On the other hand, multi-layer systems that have the desired filter function with steep edges are very cost-intensive and therefore not suitable for implementation.

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

Coatings made of polyurethane (PU) are known in the prior art. In WO 2007/025011 A1 scratch protection layers for mobile phone displays and other display components are described, whereby these layers can be uncolored or tinted. There is no indication of how and according to which selection criteria this coloration can be generated and how intense the tint can be, the system described not having a filter function in the sense of a targeted optical design.

In WO 2012/031837 A1 PU-based coating systems for display areas on smooth, transparent moldings with a transmission in the visible range of 1 to 20% are described, which are color-stable up to 150 ° C, do not reduce the impact / flexural strength of the substrate, and are sufficiently opaque to display illuminated displays and cover up other components of the display. The systems described here are therefore not suitable for use in the field of filter systems for microelectronics / optics and processes such as WLP, since temperatures of> 250 ° C are reached here, at least for a short time.

The DE 10 2010 045 149 A1 describes a colored coating based on polyurethane for display areas of plastic, glass or glass ceramic molded bodies (eg cooking surfaces or control surfaces of household appliances). The coating is sufficiently transparent for illuminated displays and sufficiently opaque to cover the illuminated displays and other components when not in use. Blocked polyisocyanates are used as binders for the paint layer. Suitable colorants must be based on the requirements only be stable up to 100 ° C during later use. For this purpose, a number of inorganic pigments and organic colorants (pigments and dyes) are named with which layers of color can be created that should be as uniformly transparent as possible over the entire visible spectrum. This document teaches the production of a coloring layer which is as uniformly permeable as possible for all wavelengths of the visible spectrum, but with overall low transmission values (in the examples <20%) and not the production of an optical filter.

The US 2004/0102548 A1 discloses a blue colored filter for liquid crystal displays and imaging sensors (particularly for CCD sensors and CMOS sensors). It comprises a substrate and a layer of an alkali-soluble resin and a dye, the dye being a phthalocyanine component. To improve the poor solubility of this dye, special modifications to the basic dye structure are proposed which have a positive effect on the dissolution behavior. Resins which are soluble in alkaline media are described as binders for the dye component of the filter. The organic polymers disclosed here are compounds that have a lower temperature stability (briefly a maximum of 200 ° C.). The filters produced in this way are therefore not suitable for use in the field of filter systems for microelectronics / optics and processes such as WLP. A structured color filter and not an optical filter with a homogeneous filter layer is disclosed.

In the DE 10 2011 009 235 A1 describes a strength-increasing coating for glass or glass ceramic moldings which is based on blocked polyisocyanates as binders. In order to prevent the view into a cooktop or behind a control panel, it is taught that the polyurethane system must be colored in such a way that the transmission for visible light is in the range from 0 to 2%, in particular between 0.1 and 1%. A number of inorganic and organic colorants (pigments and dyes) are named for this. A colored coating of a substrate is disclosed, which leads to a desired low transmission (below 2% for wavelengths in the range of visible light), and no optical filter.

In the DE 10 2011 050 870 A1 a transparent, colored glass ceramic is disclosed, on which a colored layer is applied, which acts as a light compensation filter. The starting point is that the colored glass ceramic results in an undesirable change in the color of the light emitted by a light source (eg a commercially available LED) arranged below the glass ceramic. With an adapted color layer applied to the glass ceramic, it is possible to compensate for the shift in the original color location of the illuminant or to shift it to a desired color location. A corresponding transmission curve, which results from the transmission curves of the substrate (colored glass ceramic) and the color layer, is decisive for the overall impression desired in terms of color. There are no special requirements for the optical quality (homogeneity, transmission spectrum) of the color layer produced. The coated glass ceramic substrates produced are not suitable as optical filters for use in the field of filter systems for microelectronics / optics and processes such as WLP.

The object of the present invention is thus 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 climatic 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 comprises a substrate and a filter layer on at least one side of the substrate, the filter layer comprising a homogeneously colored matrix which contains at least one organic dye dissolved in the matrix. The matrix here comprises a sol-gel compound or a polyurethane resin, and the organic dye is selected from the group of phthalocyanines. The filter is thermally stable for a short period of time at temperatures of 220 to 270 ° C and permanently up to at least 140 ° C. The filter is an IR-cut filter in which a transmission range with a transmission of more than 70% begins at the latest at a wavelength of 460 nm and ends at 540 nm at the earliest and a blocking range (T ₅₀ II) at 650 nm +/- 30 nm begins.

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.

• 1 zeigt eine schematische Abbildung einer Variante des erfindungsgemäßen Filters 1. Auf dem Substrat 2 ist zumindest eine Filterschicht 3 aufgebracht. Optional können auf der Oberseite und/oder der Unterseite Antireflexbeschichtungen 4 bzw. 4' aufgebracht sein. Ferner kann eine Zwischenschicht 5 beispielsweise zur Verbesserung der Haftfestigkeit der Filterschicht 3 zwischen Substrat 2 und Filterschicht 3 aufgebracht sein. Die Schichten 4, 4' und/oder 5 können optional ferner eine Funktion zur Feineinstellung der optischen Eigenschaften der Filter aufweisen, beispielsweise können sie eine im IR-blockierende Funktion aufweisen.
• 2 zeigt schematisch eine vorteilhafte Ausführungsform des erfindungsgemäßen Beschichtungsverfahrens.
• 3 zeigt eine Transmissionskurve eines erfindungsgemäßen Filters gemäß Beispiel 1 sowie die Definitionen von Durchlass- und Sperrbereich des Filters einschließlich der T₅₀ Werte.
• 4 und 5 zeigen Transmissionskurven erfindungsgemäßer Filter gemäß Beispielen 2 und 3.
• 6 zeigt das Ergebnis einer Homogenitätsmessung des Filters gemäß Beispiel 1, d.h. Transmissionskurven gemessen an vier verschiedenen Stellen auf dem Filter. Die Kurven liegen exakt übereinander, der Filter weist somit eine hohe optische Homogenität auf.
• 7 zeigt den Vergleich von Transmissionskurven vorteilhafter Varianten erfindungsgemäßer Filter mit Filterschichten, welche zum einen mit Spin-coating (durchgezogene Linie), zum anderen mit Siebdruck (gepunktete Kurve) aufgebracht wurden. Die Transmission im Durchlassbereich der mittels Spin-coating aufgebrachten Filterschicht ist deutlich besser als die der mittels Siebdruck aufgebrachten Schicht.
• 8 zeigt den Vergleich von Transmissionskurven vorteilhafter Varianten erfindungsgemäßer Filter mit Filterschichten, welche mit unterschiedlichen Spin-coating-Parametern aufgebracht wurden. Zwar sind beide Kurven besser als die mittels Siebdruck aufgebrachte Schicht, jedoch lässt sich durch Anpassung der Spin-coating-Parameter eine weitere Verbesserung der Transmissionskurve erreichen.

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 upset. Optionally, anti-reflective coatings can be used on the top and / or the bottom 4th or. 4 ' be upset. Furthermore, an intermediate layer 5 for example to improve the adhesive strength of the filter layer 3 between substrate 2 and filter layer 3 be upset. The layers 4th , 4 ' and or 5 can optionally also have a function for fine adjustment of the optical properties of the filters, for example they can have an IR-blocking function.
• 2 shows schematically an advantageous 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 pass band and stop band of the filter including the T ₅₀ values.
• 4th and 5 show transmission curves of filters according to the invention according to Examples 2 and 3.
• 6th shows the result of a homogeneity measurement of the filter according to Example 1, ie transmission curves measured at four different points on the filter. The curves are exactly on top of each other, so the filter has a high optical homogeneity.
• 7th shows the comparison of transmission curves of advantageous variants of filters according to the invention with filter layers which were applied on the one hand with spin coating (solid line) and on the other hand with screen printing (dotted curve). The transmission in the transmission range of the filter layer applied by means of spin coating is significantly better than that of the layer applied by means of screen printing.
• 8th shows the comparison of transmission curves of advantageous variants of filters according to the invention with filter layers which were applied with different spin-coating parameters. Although both curves are better than the layer applied by screen printing, a further improvement in the transmission curve can be achieved by adjusting the spin coating parameters.

The filter according to the invention has good optical properties.

The filters according to the invention have a surprisingly low scatter 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%, very particularly preferably less than 1%. The haze value is preferably determined with a measuring device with the device name Hazeguard Plus from Byk.

Furthermore, they have a lower roughness than filters of the prior art, as a result of which layers with low scattering are obtained. 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 definition according to the invention of the pass band or stop band and the T ₅₀ values for a bandpass filter. The filter according to the invention is characterized by the transmission in the so-called pass range (pass range) and the transmission in the blocking range. According to the invention, the transmission range is understood to mean the range between T ₅₀ I and T ₅₀ II. The pass band should have the highest possible transmission. In particular, the transmission within the transmission range should be at least partially, ie for a wavelength range lying in the transmission range, at least 70%, preferably at least 80%, more preferably at least 85%. According to the invention, the blocked range is understood to mean the range according to T ₅₀ II. According to a like in 3 The variant shown can be followed by a further area with high transmission. In such a variant, a third value T ₅₀ III can also be specified to characterize the curve. The blocking area should have the lowest possible transmission. In particular, the transmission within the blocking range should be at least partially, ie for a wavelength range lying in the blocking range, at most 40%, preferably at most 30%, more preferably at most 25%. The average transmission in the blocking range 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. In the case of filters, this value is passed through before entering the transmission range, here referred to as T ₅₀ I, and after leaving the transmission range, here referred to as T ₅₀ II. According to the invention, T ₅₀ II simultaneously denotes entry into the restricted area, T ₅₀ III denotes entry into a further passage area. So-called long-pass and short-pass filters only have a T ₅₀ value between the stop and pass band.

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

According to the invention, the filter according to the invention is a blue filter or a NIR cut filter. The range with a transmission of more than 70%, preferably more than 85%, then begins at a wavelength of 460 nm, preferably 450 nm, more preferably 440 nm and ends 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 mean transmission in the range from 450 to 550 nm should be 87% (+/- 5%), and the width of the wavelength range around T ₅₀ ll from a transmission of 70% to a transmission of 30% should be at most 80 nm ( +/- 10 nm) (measure of the steepness of the strip edge).

The filter layer 3 preferably has a layer thickness of at least 0.1 μm, more preferably at least 0.5 μm, more preferably at least 1 μm, according to special embodiments at least 2 μm. The layer thickness is preferably at most 15 μm, more preferably at most 12 μm, according to one variant at most 10 μm. According to special embodiments, greater layer thicknesses of, for example, at most 20 μm or at most 100 μm can 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, when using extremely thin glasses as substrates, filters with a thickness of less than 0.1 mm can also be provided, for example filters with a layer thickness of 0.05 mm or 0.025 mm. According to this variant, the filter layer also has 3 only a very small thickness of at most 10 µm or at most 5 µm.

The filter layer has a homogeneity of the layer thickness over the entire coating surface, the deviation preferably being at most 15%, more preferably at most 10% and most preferably at most 5%. This homogeneity of the layer thickness is preferably achieved in the finished filter, but in the manufacture of filters over wafers on the entire wafer surface, i.e. on an area with a diameter of 8 or 12 inches or even 16 inches. According to the invention, the term “filter” can include both the separated filter and a wafer for the production of filters.

Due to the great homogeneity of the layer thickness of the filter layer, the filter according to the invention has 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 what is known as an adhesive tape test (application of the adhesive tape, such as, for example, scotch tape, and slow peeling over the corner). Preferably, less than 10% of the test area dissolves in this test, preferably less than 2%, more preferably no detachment takes place.

The abrasion resistance is determined by a so-called scrubbing test with a so-called "cheese cloth" (see definition of cheese cloth according to US Federal Standard CCC-C-440) with an application of 500 g and 50 strokes. The filters according to the invention preferably pass this test without any deterioration in the optical properties.

The filter has a good chemical resistance (e.g. to water, isopropanol, ethanol) and a high climate (according to MIL-C-675A: 95% rel. Humidity at 49 ° C 24 h) and long-term resistance (according to MIL-STD- 810C) with constant absorption properties.

The term “constant absorption properties” means that the change in transmission in the pass and stop areas before and after the stress test is a maximum of +/- 5%. By contrast, a significant change in the absorption properties is understood to mean a change in transmission of more than +/- 10%, in particular more than +/- 5%.

For long-term stability, the following methods are also tested: (i) Temperature-humidity test: 1000h at 85 ° C and 85% rel. LF and (ii) cyclic humid heat test: from -20 to 65 ° C at 90% rel. LF a temperature ramp of <1 ° C / min and 14 repetitions. The filters according to the invention preferably pass this test without any deterioration in the optical properties.

A filter according to the invention has a high temperature stability, ie the filter can be heated for a period of up to 10 minutes to a temperature in the range from 220 to 270 ° C. with constant absorption properties, as defined above. In particular, because of 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.

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

The filter according to the invention can simultaneously serve as a carrier or substrate for electronic components, i.e. as a printed circuit board. Circuit boards consist of electrically insulating material with conductive connections (conductor tracks) adhering to them. As an insulating material, the filter according to the invention can also be used as a substrate. The conductor tracks can be etched from a thin metallic layer or structured by a photolithography process using lift-off technology. Typically, copper or silver or gold layers are used as conductive material, which mostly also have a (metallic) adhesion promoter layer. This can consist of titanium, for example, a number of further adhesion promoter layers being known. A buffer layer, known as a solder mask in the circuit board industry, can be used to expose areas in which contact can be made with the conductor tracks. Soldering points ("bumps") are placed on these exposed metallic surfaces, which later make the contacts to the CMOS chip or the circuit board in the soldering process. The components are thus electrically contacted. At the same time, they can also be held mechanically by the contacts. Larger components can also be attached to the circuit board with cable ties, glue or screw connections. Due to the thermal load in the soldering process, the filter layer must have 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 ineffective 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 on the two substrate surfaces with the refractive index n _d of 1.5 is limited to approx. 92% without an additional anti-reflective layer. In addition, the substrate should have a thermal resistance of preferably at least 300 ° C, more preferably at least 400 ° C.

As the material for the substrate for the filter according to the invention, glass, glass ceramic, crystals and optoceramics come into consideration, with glass substrates, more preferably thin glass substrates, being preferred.

According to one embodiment, transparent glasses (for example borosilicate glass, soda-lime glass, aluminosilicate glass, alkaline earth silicate glass, quartz glass or alkali-free glasses) are used, which can be rolled or floated or through (such as in EP 1 414 762 B1 described) drawing processes such as the downdraw or updraw processes or an overflow fusion process can be produced. In the case of glasses, which due to their manufacturing process can only be manufactured in greater thicknesses, eg greater than 1 mm, a suitably thin substrate can be manufactured by mechanical processing with grinding, lapping and / or polishing processes or a redrawing process.

According to a variant, thin glasses, i.e. glasses with a thickness of 100 µm to 2 mm, or extremely thin glasses, i.e. glasses with a thickness of 25 µm to 100 µm, are used as the substrate. The glasses sold by SCHOTT AG under the names AF32, D263, B270, for example, are suitable for such thin glasses.

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

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

Calcium fluoride or sapphire, for example, can be used as crystalline substrates according to a further embodiment.

For subsequent processes, such as wafer-level packaging, the thermal expansion coefficient of the filter can be of great importance. Here the filter according to the invention has the advantage over glass bulk or plastic solutions that the expansion coefficient is essentially determined by the glass substrate used and can be adapted to the respective connection partner, such as silicon. Substrates with a coefficient of thermal expansion CTE or α (20.300) in the range from 3 to 9.4 10 ^-6 K ^{-1 are} preferred.

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

A glass with absorbent properties can also be used as the substrate. 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.e. does not show any permanent streaking during the production of the coating solution or the paint production and enables a homogeneously colored matrix. The dye or dyes should also have a sufficiently strong color and be thermally stable enough to withstand the stresses during crosslinking of the binder system and during later use.

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

According to the invention, dyes which are permanently thermally stable up to at least 140.degree. C. and withstand brief temperature loads of 150.degree. C. to 300.degree. C., preferably 200 to 270.degree. C., are preferred. The term “permanent” is understood to mean a period of more than 60 minutes, preferably at least 100 hours, and the term “short-term” a period of at most 60 minutes, preferably at most 30 minutes.

According to the invention, the organic dye is selected from the group of phthalocyanines.

Organic dyes selected from the group consisting of azo dyes, polymethine dyes, cyanine dyes, triphenylmethane dyes, carbonyl dyes: anthraquinones, indigo and porphyrins can also be used as dyes.

Depending on the relevant wavelength range, a dye with suitable absorption properties is selected. Blue-green dyes are used to manufacture a blue filter or an IR cut filter.

Phthalocyanines (Tetrabenzotetraazaporphyrine) are characterized by high chemical and thermal stability. According to the invention, phthalocyanines with 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 that consist of four pyrrole rings (tetrapyrrole) that are cyclically linked by four methine groups. The simplest representative is porphine.

Of the blue-green dyes, preference is given to those whose absorption maximum is in the range from 550 to 750 nm, particularly preferably in the range from 650 to 750 nm. Iron cyan complexes, indanthrone, indigo, pthalocyanines with Cu, Zn or V as the central atom are specifically used , preferably the β form of phthalocyanines, for example copper phthalocyanine (e.g. Orasol®, such as Orasol Blue GN, Orasol Blue 94416, Orasol Blue 94416), vanadium or zinc phthalocyanines (e.g. Epolight®), chromium chelates, preferably Cr ³⁺ with Ligands from the azo and azomethine series, for example Heliogen blue 23050, Heliogen blue 23080, Corimax Blue, from Kremer Pigments and Marabu Glass Paints.

The Epolight dyes from Epolin, ie 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 can preferably be used different central atom (such as Pb, Zn, Al, Ga, Si, Ti, Cu, and others) for example from Sigma Aldrich and from QCR Solutions Corp. also the group of the visible range 400 nm, 500 nm, 600 nm Visible Absorbing Dyes can be used.

In addition to the dyes already mentioned, those that block in the IR range> 600 nm are also of particular interest. For this purpose, dyes of the group tetrakis (alkyl) ammonium salts, in particular dyes of the group tetrakis (alkyl) ammonium bromide, or chloride, particularly preferably in a straight-chain version with n ≥ 4, and symmetrical cyanines suitable with n ≥ 5, are 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 cyanines

According to the invention, one or a combination of two or more of the aforementioned dyes can be used in the matrix.

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

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, i.e. dyes that are not soluble in the solvents or coating solutions used, can be incorporated into the matrix according to the invention. In particular, if necessary, a mixture of one or more dyes with pigments can be a way of fine-tuning the desired transmission curve in the relevant wavelength range.

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

In principle, all pigments which have no or not too high a scatter are suitable.

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

When using pigments with grain sizes below 1 µm, so-called nanopigments, the scatter 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 have to be finely dispersed in order to prevent agglomeration, which is possible, for example, using a three-roller mill or ultrasonic treatment.

These absorption pigments are preferably 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 to mean 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. On the one hand, compounds can be used as binders which already have the properties required for layer formation, for example plastics or polymers with a sufficient polymer weight. As a further variant, the matrix can be formed in situ by crosslinking and / or polymerization reactions after the substrate has been coated.

According to the invention, the matrix comprises a sol-gel compound or a polyurethane resin.

Hybrid polymers, silicones (organic and / or inorganic crosslinking), phenolic resins, epoxides, polyamides, polyimide, EVA (ethylene vinyl acetate) and polyester resins and mixtures thereof can also be used as binders.

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, polymethyl methacrylate and / or polystyrene PS, which are characterized by their high chemical properties and mechanical stability.

Of the polyester resins, so-called UP resins, i.e. unsaturated polyester resins, are 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, depending on the solvent, low or high viscosity paints can be produced.

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

According to the invention, sol-gel compounds or polyurethane resins are used.

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. The sol-gel precursors Si (ORx) Ry, Ti (ORx) Ry, Zr (ORx) Ry, AI (ORx) Ry, Zn (ORx) Ry, Mg (ORx) Ry, Ca (ORx) are very particularly preferred Ry and Sn (ORx) Ry.

Therein, Rx = hydrogen, alkyl, allyl or aryl and / or Ry = epoxy, methacrylate, acrylate, vinyl, allyl, amino, thiol, alkyl or aryl. The indices x and y are the sum 4th , i.e. x + y = 4.

The coating composition preferably comprises a UV-curable and / or thermally curable hybrid polymer, hydrolyzed and condensed alkoxysilane precursor, in particular glycidyloxypropyltriethoxysilane (GPTES) and / or methacryloxypropyltrimethoxysilane. These can also be functionalized with polysiloxanes. Methyl- and / or phenyl-functionalized polysiloxanes are preferably used. The sol-gel layer on the substrate thus preferably comprises the reaction products of the sol-gel precursors described herein with the polysiloxanes described herein.

In a further embodiment, the binder composition comprises a polyurethane resin which is formed by the reaction of a polyisocyanate component with a polyol component. Polyisocyanates are understood to mean organic compounds which contain two or more isocyanate groups (-N = C = O). Polyols are understood to mean organic compounds which contain two or more hydroxyl groups (—OH). The reaction of polyisocyanates and polyols produces straight-chain or branched polyurethanes:

• - aromatische Isocyanate, z.B. 2,4-Toluylendiisocyanat (TDI), 4,4'-Diphenylmethandiisocyanat (MDI),
• - cycloaliphatische und araliphatische Isocyanate, z.B. Isophorondiisocyanat (IPDI), 2,4-Methylcyclohexyldiisocyanat (HTDI), Xylylendiisocyanat (XDI),
• - aliphatische Isocyanate, z.B. Hexamethylendiisocyanat (HDI), Trimethylhexamethylendiisocyanat (TMDI) oder 1,4-Cyclohexyldiisocyanat (CHDI),

According to the invention, the following polyisocyanates can be used depending on the application:

• - aromatic isocyanates, e.g. 2,4-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI),
• - cycloaliphatic and araliphatic isocyanates, e.g. isophorone diisocyanate (IPDI), 2,4-methylcyclohexyl diisocyanate (HTDI), xylylene diisocyanate (XDI),
• - aliphatic isocyanates, e.g. hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI) or 1,4-cyclohexyl diisocyanate (CHDI),

With aliphatic isocyanates, in particular with HDI, polyurethanes with excellent thermal stability can be produced, which only decompose at 210 to 270 ° C. The thermal stability of polyurethane layers made from aliphatic isocyanates is therefore sufficient for use as filter systems, which are usually introduced into the component via WLP (wafer-level packaging) processes, since here brief temperatures of 260 ° C for a period of about 10 min, preferably less than 5 min occur. In the area of application, e.g. in camera modules, only temperatures well below 150 ° C come into play.

Instead of monomeric polyisocyanates, it is also possible with preference to use polymers of the corresponding monomers, for example their dimers, trimers, oligomers or higher polymers. Furthermore, polyhydric alcohols such as biurets, isocyanurates or adducts with trimethylolpropane or similar compounds can be used, which convert the monomers into less volatile and therefore easier to handle components by enlarging their molecules.

Blocked polyisocyanates (so-called stoving urethane resins, EBU resins) in which the highly reactive isocyanate groups are reversibly blocked by so-called blocking agents are also preferred. A blocked polyisocyanate splits off the blocking agent at an elevated temperature, releasing the reactive isocyanate, so that the crosslinking reaction has to be started by thermal treatment. In addition to alcohols and phenols, other Bronsted acids (proton donors, compounds with acidic hydrogen) such as thioalcohols, thiophenols, oximes, hydroxamic acid esters, amines, amides, imides, lactams or dicarbonyl compounds and in particular ε-caprolactam, butanone oxime, dimethylpyrazole and, diisopropylamine, are suitable as blocking agents such as diethyl malonate. While HDI blocked with butanone oxime can be used to formulate coatings that cure at 140 to 180 ° C (5 - 60 min), HDI blocked with ε-caprolactam requires slightly higher temperatures for crosslinking (160 - 240 ° C, 5 - 60 min). Since the blocking agent is released during crosslinking and diethyl malonate is not classified as hazardous and ε-caprolactam is less critical than butanone oxime, aliphatic polyisocyanates blocked with malonic acid ester or ε-caprolactam are preferred. Butanone oxime, ε-caprolactam and most of the other blocking agents escape to a large extent from the paint film during crosslinking and are removed from the paint with the exhaust air flow from the dryer. 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 include the Desmodur ^® grades from Bayer Material Science, for example, Desmodur ^® BL 3175 SN and Desmodur ^® BL 3272 MPA.

The equivalent weight can be calculated from the content of blocked isocyanate groups. If the average NCO functionality of the blocked polyisocyanates is known, the average molecular weight can be determined from it. NCO functionality means the number of blocked and optionally free NCO groups per molecule. In the case of suitable EBU resins, the NCO functionality is 2, in particular 2.5-6, particularly preferably 2.8-4.2. However, resins with more than 6 blocked isocyanate groups per molecule are also suitable, although not preferred.

The average molecular weight of preferred polymers of blocked polyisocyanates is 800-2000 g / mol. However, polyisocyanates with molecular weights of 2000-10,000 g / mol can also be suitable. The average molecular weights can be, for. B. be determined via a GPC measurement (gel permeation chromatography).

In principle, all compounds which contain a reactive (acidic) hydrogen atom can serve as reactants for a polyisocyanate. The polyurethane is formed through polyaddition through the reaction of the isocyanate groups with compounds that contain reactive hydrogen atoms.

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

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

Examples of suitable polyester polyols are the Desmophen® grades from Bayer Material Science Desmophen® 651 MPA, Desmophen® 680 BA and Desmophen® 670.

The molecular structure of most of the commercially available polyester polyols and also of the Desmophen ^® types mentioned above cannot be specified precisely because a polymer mixture is usually obtained during production. The properties of the polyester polyols can, however, be adjusted reproducibly by the conduct of the reaction, the products being characterizable 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 the starting components.

The control and knowledge of the hydroxyl content (OH content) of the polyol component (H-acidic 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 of the Coating is only carried out when the same stoichiometric amounts of isocyanate and hydroxyl components are used, if the stoichiometric ratio of isocyanate to hydroxyl components is 1: 1 according to the following reaction equation:

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

The reduction of the polyisocyanate content (under-crosslinking) leads to more flexible coatings with lower mechanical and chemical stability and is therefore not preferred. Increasing the polyisocyanate content (overcrosslinking) increases the crosslinking density because the excess isocyanate groups react with atmospheric moisture to form urea groups. The use of polyisocyanate to polyol components in the equivalent ratios of 1.1: 1 to 2: 1 can therefore make sense in order to increase the scratch resistance or the adhesion to the substrate via the hardness of the coating. Since the side 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, whereby isocyanate groups are withdrawn from the system, which are then no longer available for a reaction with the hydroxyl groups of the polyol component, equivalent Ratios of polyisocyanate to polyol component of the order of magnitude from 1.1: 1 to 2: 1, in particular from 1.2: 1 to 1.5: 1, are preferred.

Of course, various H-acidic compounds can also be combined, e.g. polyester polyols with silicone or epoxy resins, in particular to adapt the film properties to specific requirements.

The applied polyurethane system is thermally cured by heating to 150-260 ° C., in particular by heating to 170-210 ° C. for a period of 10-120 min, in particular 60-90 min. The hardening time is for the adhesive strength and chemical resistance is essential, e.g. curing for 45 minutes at 180 ° C shows no chemical resistance to isopropanol and does not pass the adhesive tape test, while curing at the same temperature for> 60 minutes results in both tests being passed. When heated, the solvent evaporates from the paint and the isocyanate component is deblocked, so that the crosslinking reaction with the H-acidic component (e.g. polyester polyol) takes place and a solid film is formed. Temperatures higher than 210 ° C are generally not used for longer curing (> 30 min), since the polyurethane formed can decompose from 200 ° C. The decomposition causes a slight brown coloration of the coating, which is usually undesirable.

The required reaction temperature depends largely on the blocking agent with which the isocyanate component is blocked. For isocyanates that are blocked with butanone oxime, 140-180 ° C are sufficient to set the crosslinking in motion, while for isocyanates that are blocked with ε-caprolactam, 160-240 ° C are necessary. The time required for adequate crosslinking depends on the selection of the isocyanate component and the H-acidic compound (polyester polyol). It can be shortened considerably (to a few minutes) using catalysts, for example tertiary amines, but especially metal-containing catalysts, for example 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 the catalyst mixture are added in an amount of 0.05-1% by weight (based on the color paste).

The above-mentioned object is also achieved by a method according to claim 12 for producing an optical filter according to the invention.

• (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;
• (3) ggf. Entlüften des Lacks;
• (4) ggf. Substratreinigung;
• (5) ggf. Aufbringen einer Zwischenschicht;
• (6) Aufbringen des Lacks beispielsweise durch Spin-coating;
• (7) ggf. Vortrocknung des Lacks (sogenanntes „soft-bake“);
• (8) Trocknung und/oder thermische und/oder UV-Härtung des Lacks;
• (9) ggf. Aufbringen weiterer Schichten.

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

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

According to the invention, “drying” is understood to mean that the binder is transferred into the filter layer essentially without a chemical reaction, i.e. that only volatile components are removed from the coating solution.

The production of the filter layer preferably comprises the step of producing a coating solution. To produce the coating solution or the lacquer, 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 can be added. Solvents in particular ensure that the viscosity and workability of the paint can be influenced. By adding solvents, the filter layer can be applied in a coating process, the amount of solvent or the viscosity of the coating solution having a decisive influence on the resulting layer thickness. It should be noted that the formation and nature of the film surface can also depend on the solvents used. Solvents with very high evaporation rates, i.e. high vapor pressure, are less suitable because a skin can develop on the surface. This changes the flow behavior, hydrodynamic instabilities can occur, which ultimately lead to the formation of lateral coating structures that start in a star shape from the center of rotation. Furthermore, hygroscopic solvents are not suitable which, although they attract water from the environment, are not themselves miscible with it. This can lead to segregation effects, which also causes lateral structures. Solvents with a vapor pressure of <120 hPa (under standard conditions: 20 ° C.) are therefore 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, butyl carbitol 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, 4-hydroxy -4-methyl-2-pentanone, ethyl methyl ketone, cyclohexanone and mixtures thereof are used.

For the production 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 state of the 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 are used.

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

Further additives, such as adhesion promoters, defoamers, leveling additives, leveling agents, deaerators, sliding additives, substrate additives, wetting and dispersing additives, rheology additives, radiation-curing and antiblocking (UV blocker) additives can be added to the coating solution. These additives can make up 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. They are generally referred to as HALS ("Hindered Amine Light Stabilizers") and are usually chemically derived from TMP (2,2,6,6-tetramethylpiperidine).

Depending on the coating process, different leveling agents can also be added, 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 that the layer runs homogeneously despite the unevenness. For spin-coating, solvents are preferred which allow good wetting of the surface and are suitable for using additional additives such as leveling agents and wetting aids, these can 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 cannot be further reduced, the viscosity can be increased by adding rheological additives. Otherwise, depending on the selected spin coating parameters, the lacquer would become too thin and the filter layer would not absorb sufficiently.

Typically, thickening, i.e. increasing the viscosity, can be achieved by adding resins such as polyacrylates, polysiloxanes, thixotropic acrylic resins and isocyanate- or urethanthixotropic 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 ether urethanes (“polyurethane thickeners”), hydrophobically modified polyethers or modified ureas. When selecting the thickening agent, however, it is important to ensure that the paint film should be coated further, for example. In this case, waxes in particular are unsuitable as thickeners.

In addition, so-called hardeners can be added, e.g. to increase the layer hardness / scratch resistance, for example nanoparticles, bis-epoxides.

The preferred proportions by weight of the various constituents 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 preferred 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 proportions by weight of the constituents of coating solutions are given by way of example 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 that is 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). A binder content of 55 - 99.9% by weight corresponds to the dye content. In the case of higher layer thicknesses, lower dye proportions are necessary than in the case of lower layer thicknesses in order to achieve the desired wavelength-dependent absorption and thus a reduction in transmission. 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 used to specifically adjust the shape of the band edge of the filter. Dye proportions of more than 45% by weight are not preferred, since the scratch and adhesive strength would then no longer be sufficient.

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

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

All components, the matrix, the dyes and the functional additives are homogenized, preferably using a Dispermat (Ultraturax) or three-roller mill.

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

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

In a special embodiment, the filter layer is only locally structured or recessed or applied to the substrate. However, the substrate is preferably coated over the entire area.

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

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

All materials in solution are suitable for spin coating. The substrate is fixed on a turntable, the so-called chuck, usually by means of vacuum suction on the underside. The desired amount of the solution is applied with a metering device over the center of the substrate.

1. 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. 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. 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:

1. 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;
2. 2nd step coating, here medium to high speeds are required in order to coat the substrate evenly, usually in the range 1000-10000 rpm, but depending on the spin coater used;
3. 3rd step Throwing off excess material, which requires high speeds, typically> 2000 rpm, but depending on the spin coater used.

In order to obtain a solid layer, it is necessary to remove the solvent. Part of the solvent evaporates when it is spun on. The removal of the solvent can be forced by a heated chuck or by subsequent heating on a "hotplate" (tempering, also called soft bake). The advantages of this treatment are based on the fact that moderate temperatures in the Soft Bake prevent the solvent from creating bubbles in the layer, as is often the case with rapid heating. Furthermore, the layer becomes "dust-dry", i.e. dust and suspended particles essentially no longer adhere to the surface, so that contamination can be removed more easily.

For spin-coating, a solvent such as ketones or acetates is particularly preferred, which allows good wetting of the surface and is suitable for using additional additives such as leveling agents and wetting aids

After coating, the layers of paint are thermally cured and / or UV cured if necessary. The layers are preferably baked at temperatures> 150.degree. C., preferably> 170.degree. Standard equipment can be used for this, in the case of UV curing or a combination of UV curing with thermal curing, for example, conventional UV surface emitters can be used, preferably microwave-excited, electrodeless surface emitter UV lamps, particularly preferably UV LEDs.

In addition to the already mentioned low roughness and low scattering, it is also important for a high quality filter that a smooth film is formed and that the cured coating does not contain any coarse, opaque particles, impurities or the like (e.g. dust, lint, grains with a size of over 200 µm, in particular 0.3-1.5 mm). Due to this requirement, care must be taken to ensure cleanliness in production when producing filter sheets of excellent quality. Ideally, production takes place under clean room conditions (clean room class <10000).

The filter can also have more than one filter layer 3 exhibit. According to such a variant of the invention, further filter layers have 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 shift 4 ' or on top of the substrate below or above the filter layer 3 be arranged. This variant is compared to a variant in which in a filter layer 3 more than one dye is contained, preferably in cases when the interaction of the dye molecules leads to undesirable optical effects. Since the filter layers according to the invention can have a high degree of homogeneity in terms of 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 have transmission-changing multilayer layers 4th , 4 ' and 5 include. Multilayer layers usually comprise sequences of high and low refractive index layers made of nitrides, oxides, oxynitrides of metals or mixtures thereof and can be applied to the filter, for example, by PVD processes such as sputtering, vapor deposition, etc. or PECVD processes.

For 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-changing multilayer layer, and thus the blocking range, for example of the in 3 The filter shown can be extended in the direction of longer wavelengths. In the prior art, such reflective multilayer layers are used as the only layer influencing IR radiation. However, due to the scattered light generated by the reflection, so-called ghost images usually occur. Surprisingly, even with the combination of the filter layers according to this invention with such multilayer layers, no ghost images occur. It is assumed that the scattered light produced by the multilayer layers is absorbed by the filter layer.

The design of the multilayer layers when used in conjunction with the organic filter layer can be adapted in such a way that the combined wavelength-dependent transmission of the entire filter corresponds to the desired specification. The value T ₅₀ II, which is a central component of the optical specification, is particularly critical. The absorption edge of the multilayer layer at short wavelengths must be shifted towards 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 essentially realized by the absorption of the organic filter layer, so that the multilayer layer here should have a high transmission above 80% in order to achieve the total transmission. This enables a more tolerant design of the multilayer layer, in which, for example, a less steep flank and lower transmission suppression are sufficient to achieve the overall transmission. Overall, this combination enables technically simpler and therefore more cost-effective multilayer layers to be produced. The design of such multilayer layers is known to the person skilled in the art and can easily be carried out with the aid of 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 knows how the optical transmission and reflection of the organic filter curve are converted, for example, into the Sellmeyer coefficients that a program such as TFCalc uses. The adaptation of the multilayer layer design is done by adapting the number and thickness of the individual layers.

Preferably, reflections on the front and back of the filter are caused by the application of anti-reflective coatings 4th , 4 ' prevented or reduced, so that the total transmission in the optical range increases noticeably. Here, more than 6% transmission gain can be achieved in the absorption-free wavelength range. Such anti-reflective coatings are generally also multilayer layers as described above. By means of a suitable layer design, the anti-reflective function can be combined with the function of expanding the restricted area, as described above, in a multilayer layer.

Furthermore, adhesion promoters can be applied between the substrate and the filter layer or filter system, preferably inorganic adhesion promoters such as porous SiO ₂ layers, for example applied by means of a pyrolysis (e.g. flame treatment with HMDSO) or SolGel process, particularly preferably organic adhesion promoters consisting of hexamethyldisilazane ( HMDS), epoxy, methacrylate, acrylate, amino, vinyl and thiol groups in a very dilute alcoholic solution or applied by a CVD process.

If necessary, additional functional layers, such as scratch protection layers, corrosion protection layers, smoothing layers, easy to clean layers and much more can also be applied to the filter layer or the filter layer system or to 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 also 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.

With the method according to the invention, very homogeneous filter layers can also be produced over larger areas. The filters or wafers according to the invention are thus also suitable for the production of filters for use in wafer-level packaging (WLP) processes. The substrate 2 , hereinafter “glass wafer”, does not have the dimensions of an individual filter in such a case, but the dimensions 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 with filter layer 3 Mounted directly one above the other, with gaps between the glass surface and the semiconductor chip of less than 1mm, so that the optical beam path from the light source over the filter 1 falls on the sensor. When assembling 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 is realized by a low-melting solder or a glass-like connection by a low-melting glass solder. A glass wafer is typically used for such processes 1 used, whose thermal expansion coefficient is in the range of the expansion coefficient of the silicon chip. As an example of a suitable glass substrate, the glass AF32 (SCHOTT AG) can be used, which has a thermal expansion of 3.2 10 ^-6 K ^{-1 is} particularly well adapted to the silicon substrate. The coefficient of thermal expansion is less critical in bonding processes, so that glasses with higher coefficients of expansion, such as D263eco glass (SCHOTT AG) with a coefficient of thermal expansion of 7.2 10 ^-6 K ^-1 , can also be used. The great advantage of the WLP process is based on the fact that the filter and sensor are connected to one another in wafer form and are only then 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 are provided and which are the same as in FIG 1 has the structure described for the filter according to the invention. Such a glass wafer can have a diameter of, for example, 8 or 12 inches.

According to a further embodiment, the CMOS sensor can be processed with the filter ( 3 ) are brought together. The CMOS sensor can be glued and soldered processes similar to those described above through the filter ( 3 ) hermetically sealed and protected. The separation of the CMOS chips and glass wafers before assembly enables 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. 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 special embodiments, both the contacts of the CMOS chip on the front side and the contacts of an electrical circuit board located below the CMOS chip can be contacted through the electrically conductive conductor tracks and an electrical connection can be established. In these cases, the size of the glass chip differs from the size of the silicon chip, since the conductor tracks are geometrically guided beyond the silicon chip in order to enable contact to be made outside.

The present invention is explained in more detail below by means of examples, but is not restricted to the embodiments described in the examples.

Examples

Filters according to the invention were produced according to the conditions given in Table 1. Glass wafers made of AF32 or D263 (SCHOTT AG) with a thickness of 0.5 to 0.7 mm were used as the substrate. Table 1: Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Binder component Desmodur ^® BL 3175 SN / Desmophen® 651 MPA GPTES Desmodur ^® BL 3175 SN / Desmophen® 670 Desmodur ^® BL 3272 MPA / Desmophen® 680 BA Desmodur ^® BL 3272 MPA / Desmophen® 651 MPA Weight of binder [% by weight] 70.67 51.82 70.67 70.67 70.67 Solvent (LM) Alkyl ketone alcohol Alkyl ketone Alkyl ketone Alkyl ketone Weight of LM [wt .-% 1 28.27 46.63 28.27 28.27 28.27 dye Phthalocyanine Phthalocyanine Phthalocyanine + porphyrin Phthalocyanine + tetrakis ammonium Phthalocyanine + copper (II) acetylacetonate Weight of dye [% by weight] 0.56 1.55 0.56 + 0.35 0.56 0.56 + 0.56 Additives Acrylated polysiloxanes none Acrylated polysiloxanes Acrylated polysiloxanes Acrylated polysiloxanes Weight of additives [% by weight] 0.50 0.50 0.50 0.50 Manufacturing Spin coating conditions Step 1: 800 rpm / 10s Step1: 200 rpm / 5s Step1: 800 rpm / 10s Step1: 800 rpm / 10s Step 1: 800 rpm / 10s Step 2: 1500 rpm 20s Step 2: 500 rpm 5s Step 2: 1500 rpm 20s Step 2: 1500 rpm 20s Step 2: 1500 rpm 20s Step 3: 4000rpm 10s Step 3: 1000 rpm 10s Step 3: 4000 rpm 10s Step 3: 4000 rpm 10s Step 3: 4000 rpm 10s Temp./duration curing 180 ° C 70min 200 ° C 60min 180 ° C 70min 180 ° C 60min 180 ° C 50min

Table 2 summarizes the properties of the filters according to the invention produced. Table 2: characteristics Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Layer thickness + + + + + Adhesive strength + O + O + Chemical resistance + O + O O Climate resistance + + + + + Haze + + + + + homogeneity + + + + + Temperature stability + + + + + Transmission properties + - + + + Absorption properties + - + + +

The following legend applies: + O - Layer thickness <10% deviation 10-15% deviation > 15% deviation Adhesive strength no replacement Detachment <2% of the test area Detachment> 2% of the test area Chemical resistance no detachment // change in transmission <5% Detachment <2% of the test area // 5-10% Detachment <2% of the test area //> 10% Climate resistance Deviation in transmission <5% 5-10% > 10% Haze <4% 4-8% > 8 Homogeneity over the wafer area 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 from Example 1 was applied to the substrate by a screen printing method. The transmission curve is in 7th compared to a filter applied with a spin-coating process.

Claims (15)

Optical filter, comprising a substrate (2) and a filter layer (3) on at least one side of the substrate, the filter layer (3) comprising a homogeneously colored matrix which contains at least one organic dye dissolved in the matrix, the matrix being a sol -Gel compound or a polyurethane resin, wherein the organic dye is selected from the group of phthalocyanines, wherein the filter is thermally stable for a short period at temperatures of 220 to 270 ° C and permanently up to at least 140 ° C, which is the filter is an IR-cut filter in which a pass band with a transmission of more than 70% begins at the latest at a wavelength of 460 nm and ends at 540 nm at the earliest and a blocking range begins at 650 nm +/- 30 nm, where entry into the restricted area is indicated by T ₅₀ II. Optical filter after Claim 1 , wherein the filter layer (3) is applied by a spin-coating process. Optical filter according to one of the preceding claims, wherein the filter has an optical homogeneity, the wavelength deviation at T ₅₀ II in measurements of transmission curves at different points on the filter being at most 5%. Optical filter according to one of the preceding claims, wherein the substrate (2) comprises a glass and wherein the substrate (2) has a transmission of at least 85% 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. Optical filter according to one of the preceding claims, wherein the filter has a thickness of at most 2 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%. Optical filter according to one of the preceding claims, the filter having an average transmission of a maximum of 50% in the blocking range from 650 nm to 700 nm. 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 formed as a multilayer layer (4, 4 ', 5) and / or further filter layer (3') is. Optical filter according to one of the preceding claims, wherein the filter comprises an anti-reflective coating (4, 4 ') on the upper and / or lower surface. An optical filter according to any one of the preceding claims, wherein the substrate is a wafer. Method for manufacturing an optical filter according to one of the Claims 1 to 11 , comprising the following steps: - Preparation of a binder system: dissolving a binder in a solvent, the binder comprising a sol-gel compound or a polyurethane resin, preparation of a coating solution by dissolving a dye in the binder system, the dye being selected from the group of phthalocyanines; Applying the coating solution to a substrate by a coating process; Drying of the coating solution by removing volatile constituents and / or thermal and / or UV curing of the coating solution, whereby a filter layer is formed which comprises a homogeneously colored matrix. Use of an optical filter according to one of the 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 the Claims 1 to 11 in digital cameras, video cameras or in spectroscopy. Using an optical filter after Claim 11 in a WLP process in which a semiconductor wafer with an optically active sensor and an optical filter in the form of a wafer are mounted directly on top of each other and connected to one another and only then are separated into individual chips.

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