DE2010920B2 - Composition for coating a substrate with an inorganic material - Google Patents

Description

represents in which η is an integer greater than 1 and R is an alkyl with up to 6 carbon atoms means the «-polystyrene has a molecular weight below 1000 and pyrolyzes at a temperature below the melting temperature of the inorganic material.

2. Composition according to claim 1, characterized in that the inorganic material Glass, copper, gold, silver, nickel or platinum

3. Composition according to claim 2, characterized in that the glass consists of about 70-80% by weight of PbO, about 16-8% by weight of ZnO, 10-7% by weight of B ₂ Oj, 1 -4% by weight SiO ₂ , 0-1% by weight BiO and 0-1% by weight SnO ₂ .

4. Composition according to claim 1-3, characterized in that the solvent from monocyclic or bicyclic terpenes or mixtures thereof.

5. Use of the composition according to claims 1-4 for coating a substrate, wherein the substrate is first heated to a temperature sufficient to produce the binder and optionally to remove the solvent, and then further heating to the inorganic To melt painterly.

The invention relates to a composition for coating a substrate with an inorganic one Material according to the preamble of claim 1.

One such composition is disclosed in US Pat. No. 11,513, US Pat. No. 2,386,634 and US Pat. No. 2,461,878 described.

There, a polystyrene is used as the base material in which the inorganic material is dispersed used, which decomposes when exposed to heat into monomers, which are highly volatile. After Heat treatment of the substrate coated with the composition thus remains on the the latter only the finely ground inorganic material, which by melting into a coherent coating can be converted.

These compositions are compared to an even older state of the art in which the Base material, in which the inorganic material is dispersed, for covering the substrate with inorganic material is carbonized and the carbon thus obtained is burned with oxygen, represents a significant advance as fewer carbon residues remain on the substrate, which can lead to a only irregularly formed layer of inorganic Material lead.

But it has been found that the compositions according to US-PS 23 11513, 23 86 634 and 24 61 878 for various applications where the substrate is very free of carbon are not yet entirely satisfactory.

Such use cases are in particular that Application of solder glass layers to electronic components, application of conductor tracks insulating substrates and the production of decorative surface layers. Contains solder glass in larger ones Amounts of lead oxide, which in the presence of carbon at the melting temperature sometimes turns into metallic Lead is reduced. This metallic lead then gives the solder glass layer an electrical conductivity, which is not wanted. In the case of conductor tracks, the electrical resistance is unfavorable due to carbon residues and not reproducibly influenced, while with decorative layers there are small residual impurities Plastic impress the aesthetic impression.

In US-PS 23 28 101 is also a composition for coating a substrate with a metal, which is a pyrolyzable compound of the metal and a solvent for this compound comprises such compositions but have the disadvantage that local changes in the viscosity of the when the solvent evaporates Composition occur, which can lead to wrinkles or wrinkles (orange peel effect, fish eyes) can lead, especially with smooth surfaces of the substrate.

It is also known (DE-AS 12 91434), Coating substrates directly with polystyrene containing dispersed inorganic material, including the Polystyrene is melted so that it can flow freely. After resolidification, the polystyrene forms together with the dispersed inorganic material a layer on the substrate. Such layers are suitable for marking streets »; areas or as Reflective layers from traffic signs. But you can not use layers of solder glass or of highly conductive layers Apply metal.

The present invention is intended to provide a composition according to the preamble of claim 1 be developed in such a way that no carbon residues are left during the thermal decomposition of the polystyrene remain.

This task is based on the prior art considered in the preamble of claim 1 solved according to the invention with the features specified in the characterizing part of claim 1.

The composition according to the invention can not only be converted into a very pure layer of the inorganic material on the substrate by the action of heat, it also has a fairly constant viscosity when heated to the pyrolysis temperature. The "-polystyrene used in the invention is liquid from room temperature up to about 300 ⁰ C, ie

remains in a liquid state until pyrolysis. Simultaneously the κ-polystyrenes have a low vapor pressure.

As alkyl groups mil; up to 6 carbon atoms can, for. B. the methyl, ethyl, propyl, butyl, isobuty!, isopropyl, Pentyl-isopentyl, necpentyl and the hexyl group be used.

The composition according to the invention can be applied to a substrate with any desired geometry will. Unlike the known compositions, however, the one according to the invention also works properly when applied to smooth surfaces, e.g. B. on a glass plate. To improve the adhesion of the layer the surface of the substrate can also have notches, depressions or other irregularities be provided.

The ratio between the α-polystyrene and the dispersed inorganic material can be within can be varied over a wide range to bring the viscosity of the composition to a desired one Value to enter & n. The composition according to the invention can for this purpose between about 90 and down to about 2% by weight of the -polystyrene and accordingly contain about 10 to about 98 weight percent of the dispersed inorganic material. Depending on the The viscosity of the composition can be adjusted by spraying on, spraying, dipping, screen printing. Extrusion or application with a blade or squeegee can be applied.

The composition according to the invention is also particularly suitable for applying dielectric and electrical layers in electronic components and gas discharge displays with storage capacity. These have a dielectric layer on the electrodes, on which the in the event of a discharge accumulate electrical charges. Conductor tracks on insulating substrates can also be used the composition according to the invention produce clean and reproducible.

Thick coatings can easily be obtained by making a first layer of the applies the composition according to the invention to the substrate and dries and this process several Male, e.g. B. 2- to 8 χ repeated until the desired total thickness is reached, which z. B. 0.1 to 0.5 mm can be. The overall coating obtained in this way, which consists of a plurality of dried individual layers is then heated in one or more ovens, so that the «polystyrene pyrolyzes and the Inorganic material melts. With such coatings, the coating is best dried by radiant heat, e.g. B. by infrared rays. This ensures that the top of the radiation exposed part of the coating dries without melting the inorganic material.

The temperature at which the inorganic material is to be melted or sintered together must be heated depends on this material and the intended use for the coated substrate away. For example, the surface roughness of a surface coating constituting a glaze depends on the length of time required for melting or sintering.

In the composition according to the invention, the size of the particles of the inorganic Materials vary within wide limits, from very fine to quite coarse. The smaller the diameter of the particles is, the larger is the total surface to be wetted and the more liquid -polystyrene has to be be used.

The composition of the invention can be applied to a substrate made of any magnetic or non-magnetic material, including glass, ceramic, glass-ceramic, metal, Metal oxides, carbon, plastic and combinations of these materials such as e.g. B. Ceramic / metal materials (Cermet). If a substrate made of plastic is used, the plastic must of course be used for the

ίο converting the composition into a layer can withstand the inorganic material. Such plastics are z. B. the high temperature resistant Polyaromatic materials.

Advantageous further developments of the invention are specified in the subclaims.

If the inorganic material is a crystallizable soldering glass with a composition according to claim 3, the coated substrate can then be soldered to another object. In this case, the soldering glass coating is first melted on the substrate at a temperature which is below the crystallization temperature of the soldering glass. The coated substrate is then reheated and the vitreous soldering glass coating is then crystallized in the subsequent soldering step. Such a connection of two glass parts using a composition according to claim 3 is particularly advantageous in the production of gas discharge display panels in which two spaced glass cover plates, which are held at a distance by an intermediate frame, have to be sealed gas-tight along their edge.
If, according to claim 4, a monocyclic

r> cal or bicyclic terpene or a mixture of such terpenes is used as a solvent, see above you can also use the amount of solvent added to determine the viscosity of the composition influence. The composition then contains about

• to 90 down to about 2% by weight of «polystyrene and Solvent and correspondingly 10 to about 98 wt .-% of the inorganic material. The weight ratio of solvent to -polystyrene is in the range from about 5: 1 to 1:10, especially 1: 1. You get

π so on the one hand compositions with so small Viscosity that they can still be sprayed, and on the other hand compositions with the consistency a paste or a putty.

From the terpenes, which boiling points up to about

μ 300 ⁰ C, terpenes with a low boiling point are preferred, that is, those with a boiling point of less than 230 ⁰ C, preferably less than 200 ⁰ C. Monocyclic terpenes that can be used include dipentene, para-cymene, «terpinene, para Menthenes,

<-> Para-menthans, terpinolene, 2,4 (8) -para-menthadiene, Thymol, limonene, pulegon, menthol, -terpineol, 0-terpineol, cis-l, 8-terpin hydrate and anethole. At Bicyclic terpenes may be mentioned: -pinene, 0-pinene, camphene, camphor, fenchone, sabinol and bornylene.

bo As embodiments of the present invention the following compositions are described in more detail.

These compositions contain poly («- methyl) styrenes, which hereafter with A and B

b5 and with these! properties in trade are available. Such -polystyrenes can also be easily produced.

Table I.

clear as water clear as water 0.85 0.85 150-300 150-300 1.01 1.04 1.008 1.039 100-200 700-1000 166 182 182 207 28-32 18-20 1.5 « 1.57

P Physical properties of the commercially available poly (a-methyl) styrenes A and B;

j?; i property

ti polystyrene A polystyrene B

; fi; : ^? work

f? i color (iodine standard)

/ Boiling range (5% -90%)

ΐ £ at 5 mm Hg, {' C)

'>" Density at 60 C, (g / cm ³ )

Density at 25 C, (g / cm ³ )

Viscosity at 60 °, (cps)

Flash point, ("C)

Focus, (C)

Volatility - 100 hours

at 100 C, (%)
Refractive index at 60 ° C

Acid number <0.1 <0.1

Iodine number <4.0 <4.0

Dielectric constant

at 1 kHz 2.56 2.60
Dielectric dissipation factor

at 1 kHz 0.0001 0.0005

Viscosity at 60 C, (cps) 100-200 700-1000

^{B e} ' ^s P' ^e '' of the liquid poly (a-methyl) styrene dispersed.

50 g of a glass fruct with 733% by weight of PbO, 13.4% by weight. The inorganic material consisted of about 95% by weight of B ₂ O ₃ and 13.3% by weight of SiO ₂ with a% by weight of glass and about 5% by weight

Particle sizes of no more than 0.02 mm were used in glass-ceramic. 74% by weight of the particles had one

50 g of the liquid poly («- methyl) styrene A dispersed. Diameter not exceeding 0.02 mm, the rest of the

A 0.38 mm thick layer of this composition particles had a diameter of up to approximately 0.15 mm.

The glass consisted of 537% by weight of JIiO ₂ , 0.15% by weight of glass substrate, was applied to the surface of a surface of 127 × 165: 6.4 mm. 4 ", Na ₂ O, 71.0 wt% PbO, 123 wt% ZnO, 7.78

The coated substrate was then 2 to 4 hours wt. O / o B ₂ O ₃ , 0.06 wt.% K ₂ 0.0.18 wt.% BaO, 1.17

heated to 621 ° C., and a readily transparent% by weight of Al ₂ O ₃ , 0.23% by weight of Li ₂ O was obtained.

dielectric layer with a thickness of about 0.05 mm. The solvent mixture consisted of 55 to 60

The surface wt .-% terpineol, 17 to 22 wt .-% ß-terpineol, 20% obtained after the heat treatment layer was characterized by unusually good smoothness w% by weight other), tertiary alcohols with boiling points

the end. in the range of a-terpineol and 3% by weight

. in terpene hydrocarbons and cineole. At normal

Example pressure, the solvent mixture had a boiling point

Was prepared eini composition corresponding to the temperature of 220 ⁰ C, a density of 0.939 g / cm ', a of Example I corresponded, except that 30 g of the r. Refractive index of 1.482, a flash point (

Glass frit and 70 g of the polystyrene A were used. agrees in the open crucible to Cleveland) of

However, the surface layer was not as smooth as 88 ° C and a Kauri-butanol solution value of over

in example I. 500.

. · Ι in The composition given above was ^{applied to substrates in the Bels} P ^lel '"μ. Screen printing process

600 g of finely ground inorganic material complete burnout and baking of the assemblies in 50 g of a mixed solvent and 50 g of sediment was obtained at about 300 ^° C.

Claims (1)

Patent claims: 1. 'Composition for coating a substrate with an inorganic material, wherein the inorganic material is dispersed in a polystyrene and optionally in a solvent is, characterized in that the polystyrene is an α-polystyrene of the general formula