JPS6065746A - Manufacture of glass plate for transparent electrode - Google Patents

Abstract

PURPOSE:To prevent the dissolution of alkali metal ion from the substrate glass of a transparent electrode having transparent electrically conductive film on the surface, by substituting the alkali metal ion with a specific alkali metal ion. CONSTITUTION:The alkali metal ion in the surface layer of a glass substrate is substituted with other alkali metal ion having larger ionic radius. For example, a soda-lime glass is immersed in a molten potassium nitrate at about 400-450 deg.C for a long period (i.e. about 30min - several 10hr) to effect the substitution of the Na ion with K ion at the surface of the glass. The dissolution of the alkali metal ion from the glass can be remarkably suppressed by this process, and a glass plate giving a liquid crystal display panel and solar cell, etc. having stable property can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing a glass plate for a transparent electrode, particularly a transparent electrode formed by forming a transparent conductive film on the surface of a glass substrate.
The present invention relates to a method of manufacturing a glass plate for a transparent electrode that can maintain its function as a transparent electrode for a long period of time by preventing alkaline components in the glass from eluting or penetrating into the transparent conductive film.

Today, soda lime glass or borosilicate glass is used as substrate glass for liquid crystal display panels, solar cells, etc., but if used as is without surface treatment,
Alkaline components, which are normally contained in substrate glass in the form of oxides ranging from several percent to more than ten percent, are eluted from the glass surface and enter the transparent conductive film (indium oxide, tin oxide, or a mixture thereof, etc.) formed on the glass surface. Furthermore, there is a problem that the function of the transparent conductive film is deteriorated.

For this reason, the surface of the glass substrate is usually coated with a silicon oxide film for the purpose of preventing elution of alkaline components.

Methods such as vacuum evaporation, spunter method, OVD method, and dip coating method are often used to coat the glass surface with a silicon oxide film, but these methods require equipment and ancillary equipment. Since it is expensive, the cost required for coating with silicon oxide is high, and the effect of preventing the elution of alkaline components from glass is not necessarily satisfactory.

The present inventors have conducted extensive research into preventing the elution of alkali components from the glass substrate, and have found that by replacing the alkali metal ions in the glass surface layer with alkali metal ions having a larger ionic radius in advance, the elution of alkali components from the glass can be prevented. It has been found that the elution of alkali metal ions can be significantly suppressed. In addition, the present inventors believe that in order to fully exhibit the effects of the present invention, it is necessary to perform subsequent thermal treatments on the glass substrate, such as during the deposition of a transparent conductive film or during cell sealing after liquid crystal injection in a liquid crystal display panel. It was also found that the temperature needs to be kept below 250°C. This is because when the temperature of the glass substrate exceeds 2SO''C, the stability of the substituted alkali metal ions deteriorates and they begin to elute from the glass surface, causing the same adverse effects as the original alkali metal ions.

The reason why the elution of alkali metal ions is prevented by the above method is that the alkali metal ions in the surface layer are replaced with alkali metal ions having a larger ionic radius in the temperature range that does not exceed the transition humidity of the glass. ,
It is assumed that this is because compressive stress occurs in the surface layer of the glass plate at room temperature after ion exchange, and due to the influence of this compressive stress, the alkali metal ions on the glass plate surface are in a state where it is difficult to move compared to the normal state. be done.

Regarding the method of replacing the alkali metal ions on the glass surface with alkali metal ions having a larger ionic radius, the glass is usually immersed in an alkali metal nitrate melt heated to qoo/-ttso℃ for a long time (30 minutes to several IO hours). ) The method of immersion is often used.

Examples of the present invention will be described below in comparison with conventional methods.

Here, as a method for evaluating the performance deterioration of transparent electrodes, liquid crystal display panels, and solar cells due to alkaline elution from the glass substrate surface, we will use a method for evaluating the amount of free alkali on the glass substrate surface (surface electrical resistivity, water wetness, etc.). This is because it is estimated that the higher the amount of free alkali on the substrate surface, the faster the performance deterioration as a transparent electrode will occur.As an evaluation value, as the amount of free alkali increases, the electrical resistivity of the substrate surface The surface resistivity is the resistivity between two opposing sides of a square on a plane, and is usually expressed in ohms, and is a value that does not depend on the size of the sides.

Example IO x IO (Cm), thick omm soda lime glass (glass composition analysis value Na2O/3,10%, 200
．． 79% + MgO4', 03%, Ca07. ．．
27%, Aj+203/, 73%, 5i0272
．． 1% each weight%), 30 sheets of borosilicate glass (glass composition Na2O3, 1%, 'N200.'1% B2O3
/, 2.9%rA12032.2%, 5i02zaO,S
% each weight %) were prepared. Of these, for soda lime glass, 6 pieces each (110VD method, (2
)Subaku-tsu-tsu-method C3) Tire furnace (In dipping 1, a silicon oxide coating with a thickness of about 2000 mm was formed on the surface of each layer.Each formation condition is shown below.

(1) In the case of the CVD method, the lip material vapor is a mixture of monosilane (SiH4) and nitrogen gas (N2).
It was formed by spraying with a nozzle onto the soda lime glass shown in c.

(2) In the case of the Spanku method, the degree of vacuum is 3 x 10 TOrr.
The target was quartz glass, and a silicon oxide coating was formed on soda lime glass at a substrate temperature of 100''C.

(3) In the case of the immersion method, a silanol alfur solution (manufactured by Tokyo Ohka Co., Ltd., trade name: 0hka Goat Diffus)
Soda lime glass was applied by dip coating on ion-8source), then calcined for 10 minutes at iso°C, then heated to soo°C.
A silicon oxide coating was formed by baking for 30 minutes.

Of the remaining 12 pieces (2 sets of 6 pieces) of soda lime glass, one set was not subjected to any special treatment.

The last pair was immersed in a potassium nitrate melt at 10°C for 20 hours to remove sodium ions on the glass surface with potassium ions.

Two glasses were taken from each of the six sets (six glasses for each set) prepared and adjusted as described above, and after alcohol cleaning and pure water ultrasonic cleaning, the surface DC electrical resistivity (Ω) and water wetting angle were determined. (degrees) was measured.

These samples were then heated at 750° C. for 10 minutes, and after cooling, the surface resistivity and wetting angle were measured again.

Furthermore, for the remaining 1 glass in each group, after cleaning in the same manner as above, 2 glasses for each 2 glasses! ;O”C,3!;60 at 0℃
After cooling, one of the two sheets was measured for surface DC electrical resistivity, and the remaining one was measured for water wetting angle.

The results obtained in the above experiments are summarized in Tables 1 and 2. From the same table, the glass surface in which sodium is replaced with potassium according to the present invention is the best among the conventional methods under heat treatment conditions below 2Sθ℃ (room temperature, /!; O"C, l!; 0"C). Compared to the sputtered 5102 film, the surface DC electrical resistivity and water wetting angle are both larger.
It can be seen that compared to the conventional method, the amount of free alkali on the surface is smaller, that is, a glass substrate with less performance deterioration is provided.

Furthermore, as can be seen from Tables 1 and 2, the effects of the present invention are lost when the heat treatment temperature exceeds 330°C.

As seen in the above embodiments, the present invention makes it possible to produce a glass plate for transparent electrodes with a small amount of free alkali on the surface without forming a 5i02 film or the like.

In addition, the above example was a case in which sodium ions in the surface layer of ordinary glass (glass in which alkali metal ions such as sodium and potassium coexist and contain far more sodium than potassium) were replaced with potassium ions. ,
A similar effect can be obtained even when the alkali metal ions (lithium or sodium ions) inherent in the glass surface layer are replaced with alkali metal ions (potassium, rubidium, cesium, etc.) having a larger ionic radius.

Furthermore, although the above explanation describes a method for producing glass for a substrate with a small amount of free alkali, the substrate temperature is set to 2! ;
It is possible to form a conductive coating (a film of indium oxide, tin oxide, or a mixture thereof) while keeping the temperature below O'C, and the invention described above (as a method for manufacturing a glass plate for transparent electrodes) is useful. It shows something.

Claims (3)

[Claims] (1) A method for producing a glass plate for a transparent electrode with low 4-alkali elution, characterized by replacing alkali metal ions in the surface layer of the glass with alkali metal ions having a larger ionic radius. (2) The method for producing a glass plate for a transparent electrode according to claim 1, wherein the ion substitution is performed at a temperature lower than the glass transition temperature. (3) The method for manufacturing a glass plate for a transparent electrode according to claim 1 or 2, wherein the ion replacement is to replace sodium ions with potassium ions.