Glass frits for ion-exchangeable glasses

Abstract

Strengthened glass substrates with glass fits and methods for forming the same are disclosed. According to one embodiment, the present invention provides a glass frit with a coefficient of thermal expansion less than or equal to the coefficient of thermal expansion of the glass substrate where it is going to be painted. The glass frit of the present invention has similar ion exchange properties to the glass substrate that is going to be used to paint with the glass frit allowing the glass substrate to be ion-exchanged. The glass frit of the present invention is mixed with an organic carrier.

Claims

1. A glass substrate, comprising: a sintered glass frit on at least a portion of at least one surface of said glass substrate; wherein the sintered glass frit is formed from a glass frit paste comprising: a glass frit composition, the composition comprising the following components in weight percent: TABLE-US-00003 Component % SiO.sub.2 50-60 Al.sub.2O.sub.3 15-20 CaO 3-5 Fe.sub.2O.sub.3 1-2 Na.sub.2O 10-13 MgO 3.5-4.sup.  K.sub.2O .sup. 3-3.5 P.sub.2O.sub.5 .sup. 0-0.5 TiO.sub.2 .sup. 0-0.5 BaO less than or equal to 0.2 MnO .sup. 0-0.5 SnO.sub.2  0.2-0.4; and an organic carrier; wherein the glass frit composition has a coefficient of thermal expansion less than or equal to that of the glass substrate; and wherein the entire glass substrate, including the at least a portion where the sintered glass frit is placed, is ion exchanged.

2. The glass substrate of claim 1, wherein the proportion of glass frit composition to organic carrier is greater than 60:40.

3. The glass substrate of claim 1, wherein the ion-exchanged glass substrate has a depth of layer greater than or equal to 10 μm and a compressive stress greater than or equal to 400 Mpa.

4. A method for forming a glass frit on an ion exchangeable glass substrate, the method comprising: providing a glass frit composition, wherein said glass composition has a coefficient of thermal expansion less than or equal to that of the glass substrate; milling the glass frit composition to provide a powder composition; mixing said powder composition with an organic carrier, so that a glass frit paste is obtained; applying the glass frit paste on at least a portion of at least one surface of said glass substrate; heating the glass substrate having said glass frit paste thereon in a furnace to a temperature so that, after heating, the glass frit is sintered and bonded to the glass substrate; and subjecting the glass substrate having the sintered glass frit to an ion-exchange process; wherein the glass frit composition comprises the following components in weight percent: TABLE-US-00004 Component % SiO.sub.2 50-60 Al.sub.2O.sub.3 15-20 CaO 3-5 Fe.sub.2O.sub.3 1-2 NaO 10-13 MgO 3.5-4   K.sub.2O   3-3.5 P.sub.2O.sub.5   0-0.5 TiO.sub.2   0-0.5 BaO less than or equal to 0.2 MnO   0-0.5 SnO.sub.2  0.2-0.4.

5. The method of claim 4, further comprising, between the step of heating the glass substrate in a furnace and the step of subjecting the glass substrate to an ion-exchange process, the step of: cooling the glass substrate having the sintered glass frit.

6. The method of claim 4, wherein the provided powder composition has an average particle size in the range of about 5 μm to 300 μm.

7. The method of claim 4, wherein the proportion of powder composition to organic carrier is greater than 60:40.

8. The method of claim 4, wherein the ion-exchanged glass substrate has a depth of layer greater than or equal to 10 μm and a compressive stress greater than or equal to 400 Mpa.

9. The glass substrate of claim 1, wherein the proportion of glass frit composition to organic carrier is about 70:30.

10. The method of claim 4, wherein the provided powder composition has an average particle size in the range of about 10 μm to 200 μm.

11. The method of claim 4, wherein the proportion of powder composition to organic carrier is about 70:30.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For the purposes of illustration, there are forms shown in the drawings that are presently preferred, it is understood, however, that the embodiments disclosed and discussed herein are not limited to the precise arrangements and instrumentalities shown.

(2) FIG. 1 shows a glass substrate having applied a glass frit on its perimeter according to one or more embodiments shown and described herein.

(3) FIG. 2 schematically depicts a partial cross section of the strengthened glass substrate of FIG. 1.

(4) FIG. 3 graphically depicts the viscosity as a function of temperatures between two glass frits and two commercially available specialty glass in an exemplary glass frit composition.

DETAILED DESCRIPTION OF THE INVENTION

(5) According to the foregoing, the present invention consists in the design of ion exchangeable or chemical tempered color frits for the automobile glazing industry. Currently ion exchangeable glass are being used in the automobile industry as a way to minimize weight and improve mechanical performance; however, these glass cannot be painted with existent paint frits because the ion exchange process is blocked by the paint, thus reducing the compressive stresses to zero, weakening the glass perimeter. The present invention allows the glass to be painted and then be subject to an ion exchange process in the same bath of salt used for the glass substrate.

(6) The prior art shows that when ion exchangeable glass are used in the automobile industry, the glass is first curved, and then ion exchanged, leaving the glass without paint. For other applications where the glass is flat, organic paint can be used. Such types of paints are more expensive and might require additional processes to cure the paint.

(7) Glass substrates 12, such as automotive glazing and cover glass for electronic devices, may include a glass frit 10 applied to one or more surfaces of the glass substrate (FIGS. 1 and 2). The glass frit 10 may be used to conceal various electrical components that are attached to the glass substrate 12 or which may otherwise be visible through the glass substrate 12. The glass frit 10 is usually applied to the glass substrate 12 and then fired to sinter the glass frit 10 and to bond the glass frit 10 to the glass substrate 12. Conventional glass frits 10 for such applications generally have relatively high softening points and glass transition temperatures and, as such, require relatively high firing temperatures (600° C. to 700° C.) for relatively short periods of time.

(8) The glass frits 10 of the present invention are milled in powder in ranges of particles which allow to be mixed with an organic carrier. Afterwards, the powdered glass is mixed with the organic carrier and mixed in proportions such that they can be made in different proportions. In various embodiments of the invention, the proportion of ground glass to organic carrier is greater than or equal to 60:40, and preferably about 70:30.

(9) The organic carrier which is not part of the invention could be a mixture of pine oil with ethyl cellulose (or any other suitable material). Said material is like a paint or a varnish that mixes a specific proportion to form a paste. The paste is then impregnated on at least a portion of one or more surfaces of the glass substrate 12 by different means, for example by screen printing or spray or any other impregnation method on the glass, without limitation by similar deposition techniques.

(10) After impregnating the paint on the glass substrate 12, the paint is dried, binders are burned out, and then fully vitrified. While the figures depicts the paste as being deposited on the perimeter edge of the glass substrate 12, it should be understood that the paste may be applied to various locations on the surfaces of the glass substrate 12 or even on the edges of the glass substrate 12.

EXAMPLE 1

(11) Table 2 shows the compositions of two black frits developed for two commercially available specialty glass.

(12) TABLE-US-00002 TABLE 2 Compositions of two black frits Oxide AGP-1 AGP-2 SiO.sub.2 57.3% 58.4% Al.sub.2O.sub.3 18.0% 17.6% CaO 3.8% 3.0% Fe.sub.2O.sub.3 1.4% 1.1% Na.sub.2O 10.4% 11.2% MgO 3.7% 3.7% K.sub.2O 3.4% 3.4% P.sub.2O.sub.5 0.3% 0.2% TiO.sub.2 0.4% 0.3% Cl 0.1% 0.1% SO.sub.3 0.1% 0.1% BaO 0.2% 0.2% Cs.sub.2O 0.1% 0.1% MnO 0.1% 0.1% SnO.sub.2 0.3% 0.4% TOTAL 99.7% 99.8%

(13) Both compositions (AGP1 and AGP2) can be ion exchanged in a potassium bath. The viscosity curves are shown in FIG. 3 wherein AGP1 and AGP2 glass have viscosity properties similar to both specialty glass.

(14) It must be understood that this invention is not limited to the embodiments described and illustrated above. A person skilled in the art will understand that numerous variations and/or modifications can be carried out that do not depart from the spirit of the invention, which is only defined by the following claims.