Use of a nitride barrier for avoiding silver migration into glass

0001The present invention relates to the field of the metallization glass substrates especially for the manufacture of flat panel displays of viewing. This metallization is used to form arrays of electrodes. These electrodes are opaque, they are generally made of silver.

0002So far, the metallization of glass substrates for the dense electrode arrays, of not less than 500 micrometers was carried out under vacuum by sputtering or vaporization. Layer is deposited relatively thick, of a few micrometers and duration the deposition vacuum chamber is relatively long. The cost of such metallized substrates is high and the cost increases rapidly with the surface of the substrates.

0003New methods of metallization, cheaper were explored; these include of silver paste layers photogravure photosensitive or not. This method is not compatible with a use on the front face of a display panel as it occurs a yellow coloring in the glass substrate.

0004Indeed, an area under the electrode, and extending on either side of the electrode about 30 to 50 microns is colored in yellow Because of the distribution of money in the glass.

0005The light received by an observer from a part of the light produced by the electric discharge within the panel which is transmitted through the glass substrate and on the other hand, of the reflected light by the electrodes. It is in diffusion zones that fate more Much of the light perceived by the observer.

0006This coloring in the manner of a yellow filter, greatly degrades colorimetry of the color display panel. It is therefore not desirable that the perceived light is filtered in yellow.

0007The present invention aims to remove this yellow coloration avoiding the diffusion of silver into the glass without degrading much adhesion and chemical stability of the plating.

0008For this the present invention relates to the use of a nitride barrier to prevent the diffusion of silver into a substrate of glass.

0009The nitride may be for example a titanium nitride, a nitride boron, silicon nitride. titanium nitride gives results very satisfactory from the standpoint transparency.

0010The nitride based barrier can be deposited by sputtering cathode, vacuum evaporation or PECVD (for naming English Plasma Enhanced Chemical Vapor Deposition), for example.

0011Thick upper barrier about 50 nanometers is effective in stopping the spread of money.

0012The present invention will be better understood using the following description illustrated by the single figure which shows in section cross the glass substrate, the barrier and deposit based on silver.

0013The known method of deposition of electrodes photoengraving Silver generating a yellow coloring comprises the following steps.

0014Is deposited on a glass substrate by screen printing and then drying a dough based photosensitive silver or not. When the dough base Money is not sensitive it is covered with a layer of resin photosensitive.

0015then exposing the deposit based on silver, optionally covered with resin to ultraviolet light through a mask and then it develops all. This is followed by a baking of the substrate silver at a temperature between about 540 ° C and 600 ° C. This baking operation causes the distribution of money in the glass substrate and the appearance of a very troublesome yellow color if the substrate glass is the front face of a display panel. this coloration appears even for low concentrations of silver.

0016A yellow colored glass substrate with money passes 54% of the emitted red light, 59% for hundred of the emitted green light and 12% of the emitted blue light.

0017The present invention consists in using a barrier 2 based on nitride interposed between the glass substrate 1 and 3 to deposit money base to prevent the yellow coloring of the glass caused by the spread of Money in the glass. The single figure shows a section of the arrangement of layers on the glass substrate 1.

0018This barrier 2 The nitride is effective even after baking the deposit 3 based on silver to temperatures above 580 ° C.

0019The barrier 2 The nitride may be deposited on the substrate 1 glass, for example by sputtering or evaporation under empty. A deposit by a chemical process, driven by a plasma, and known under the English term PECVD (Plasma Enhanced Chemical Vapor for Deposition) is also possible. The PECVD technique allows the production a uniform deposit.

0020Titanium nitride gives very good results. Indeed, in presence of silver, titanium nitride which is gray in color becomes much clearer, which provides the application as front face of a display panel, well-transparent areas.

0021Other metal is of course usable in particular silicon or boron. A mixture of nitrides may also be used.

0022A barrier 2 having a thickness greater than about 50 nanometers is sufficient to prevent yellowing.

0023The glass substrate 1 may, for example, be soda-lime type (Known in the literature as the Anglo-Saxon name float glass). This substrate 1 may be optionally annealed, polished or shaped. Other types of glass dishes can of course be used, for example, Type borosilicate or aluminosilicate.

0024Deposit 3 based on silver can be achieved in conventional manner by screen printing and photoengraving then be subjected to baking at a temperature greater than 400 ° as previously described.

0025The thickness of the deposit 3 based on silver may be about 7 micrometers. Usually the thickness of the deposit is based on silver between 3 to 12 micrometers.