CS273273B1 - Silver glass paste suitable for resistance strips formation by silk-screen printing technique - Google Patents

Abstract

Application of resistance strips on glass is usually carried out by a silk-screen printing technique using pastes containing silver and zinc with subsequent firing. Layers formed by pastes containing zinc need to be subsequently plated with silver. Existing methods are labour intensive and the formed layers are not very resistant to abrasion. The silver paste according to this invention eliminates these disadvantages. By mass it contains 50 to 75 parts powdered silver with maximum particle size of 8 micrometers, 0.04 to 0.2 parts rhodium mercaptide, 3.5 to 6 parts fluxing agent composed of 85.2 % by weight lead oxide, 5.2 % by weight silicon oxide and 9.6 % by weight boric oxide and with a maximum particle size of 4 micrometers, 0.4 to 0.75 parts rheological additive on a base of hydrogenated castor oil, 1.0 to 3.9 parts ethyl cellulose, 8.6 to 10.2 parts terpineol and 9.3 to 31.5 parts butyl diglycol.

Description

BACKGROUND OF THE INVENTION The present invention relates to a silver paste suitable for forming resistive strips by screen printing techniques. Silver screen printing pastes are designed for printing electrically heated glasses with the possibility of obtaining an adjustable electrical resistance of the resulting layer by mixing them. The method of depositing resistance strips on glass is usually carried out by screen printing technique using silver or zinc containing pastes and subsequent firing.

The layers made with zinc-containing pastes must then be electroplated with silver. The process is laborious, the layers formed are sensitive to abrasion and the adhesion of the lead and tin solder connectors is insufficient. The layers produced by the silver pastes used so far do not need to be strengthened, but still have some disadvantages, such as high sensitivity to lead, tin and silver solders, resulting in reduced adhesion of soldered connectors, high mechanical aggressiveness of the pastes to the sieves used. resulting in their low lifetime. There are also often unsuitable rheological properties of the pastes which result in silver sedimentation and therefore limited shelf life and imprecision of the printing, which is manifested by the flow of printed tapes before firing.

The closest to the proposed solution is MS. Author's Certificate No. 225 253 Degussa NSR glass pane resistance paste. Silver paste according to MS. No. 225 253 shows printing inaccuracies manifested by the flow of printed strips before firing, limited shelf life due to silver powder sedimentation, low and varying adhesion of the printed strips to glass and low brazing resistance.

Degussa pastes exhibit increased mechanical aggressiveness to the fabrics of the printing screen and adhere to and clog their eyes, resulting in reduced screen life and difficult cleaning.

The above-mentioned drawbacks are remedied substantially by the paste according to the invention, which comprises 50 to 75 parts by weight of silver powder with a maximum particle size of 8 µm, 0.04 to 0.2 parts of rhodium mercaptide, 3.5 to 6 parts of flux of 85.2 wt. % lead oxide PbO, 5.2 wt. % SiO ₂ and 9.6 wt. boron trioxide Β ₂ θ3 ^{with a} maximum particle size of 4 pia, as well as 0.4 to 0.75 parts of hydrogenated castor oil based rheological additive, 1.0 to 3.9 parts of ethylcellulose, 8.6 to 10.2 parts of terpineol and 9 3 to 31.5 parts of butyldiglycol.

The raw materials are weighed, homogenized with a planetary kneader and rubbed on a three-roller to form a viscous, highly thixotropic light gray paste suitable for screen printing of conductive strips on glass. The coated glass sheet is then baked at a temperature of 500 to 700 ° C, whereby a thermo-chemical reaction causes the paste-formed layer to adhere to the glass and form resistance strips.

The paste according to the invention exhibits better printing properties over the above pastes, which increases the life of the screen and makes it easier and faster to clean.

Example 1

In the mixture resulting from stirring 8.6 parts by weight. terpineol and 9.36 parts by weight. butyldiglycol dissolves under constant stirring, preferably at a temperature of 70 to 80 c 1 part by weight. ethylcellulose (Ethocel 100). 75 parts by weight are added to the binder thus formed in a planetary mixer with stirring. powdered silver with a maximum particle size of 8 µm (measured with the Mikrovideomat MV 2 image analyzer), 6 parts by mass. % flux of 85.2 wt. % lead oxide PbO, 5.2 wt. SiO ₂ , 9.6 wt.% boron oxide B ₂ ° 3, ^{with a} maximum particle size of 4 µm, 0.4 parts by weight of SiO ₂ ; Thiomenene and 0.04 parts by weight rhodium mercaptide to form a light gray paste. After thorough mixing, the resulting paste is further homogenized, preferably on a friction roller, to form a viscous, highly thixotropic paste suitable for applying resistive strips to the glass by screen printing techniques.

and

Example 2

In the mixture resulting from the mixing of 10.2 parts of terpineol and 31.5 parts by weight. butyldiglycol dissolves 3.9 parts by weight, preferably with stirring at 70-80 ° C. ethylcellulose (Etocel 100). 50 parts by weight are added to the binder thus formed in a planetary mixer with stirring. silver powder with a maximum particle size of 8 µm, 3.5 parts by weight. % flux of 85.2 wt. % lead oxide PbO, 5.2 wt. % SiO2, 9.6 wt. boron trioxide BgO4, P3e ^< 3 ^em ground to a maximum particle size of 4 pra, 0.75 parts by weight. Thixomene and 0.2 parts by weight rhodium mercaptide to form a light gray paste. After thorough mixing, the resulting paste is further homogenized preferably on a three-roll friction roller to form a highly thixotropic paste suitable for applying resistive tapes to a screen printing technique.

Example 3

In the mixture resulting from stirring 10.2 parts by weight. terpineol and 11.24 parts by weight. butyldiglycol is dissolved with stirring, preferably at a temperature of 70-80 ° C, 1 part by weight. ethylcellulose (Ethocel 100). 71 parts by weight are added to the binder thus formed in a planetary mixer with stirring. silver powder with a maximum particle size of 8 µm, 6.0 parts by weight. % flux of 85.2 wt. % lead oxide PbO, 5.2 wt. % SiO2 and 9.6 wt. Boron oxide Pre-ground to a maximum particle size of 4 µm,

0.4 parts by weight Thixcin R and 0.16 parts by weight. rhodium mercaptide to form a light gray paste. After thorough mixing, the resulting paste is further homogenized, preferably on a three-roll friction roller, to give a viscous, highly thixotropic paste suitable for applying resistive strips to the glass by a screen printing technique.

In the examples, Cincin R and / or Cinomen mentioned are rheological additives based on hydrogenated castor oil.

Claims (1)

Silver glass paste suitable for forming resistive strips by the screen printing technique, characterized in that it contains 50 to 75 parts by weight of silver powder with a maximum particle size of 8 µm, 0.04 to 0.2 parts of rhodium mercaptide, 3.5 to 6 parts % flux of 85.2 wt. % lead oxide PbO, 5.2 wt. % SiO2, 9.6 wt. boron trioxide B ₂ ° 3 ^{and with a} maximum particle size of 4 µm, 0.4 to 0.75 parts of Theological Additive based on hydrogenated castor oil, 1.0 to 3.9 parts of ethyl cellulose, 8.6 to 10.2 parts of terpienol and 9 3 to 31.5 parts of butyldiglycol.