JPS62100460A - Method of chemically strengthening float glass - Google Patents

Abstract

PURPOSE:To obtain the titled glass having excellent properties in flatness, surface compressive stress and rupture strength and useful to the substrate of an electronic material such as an optical disc substrate, etc., by dipping the float glass with a molten tin which is maintained at a prescribed temp. and then by strengthening chemically the treated float glass, thereby preventing a generation of the warpage of the floating glass. CONSTITUTION:The plate such as the float glass produced and treated according to a float glass process, is dipped with a molten tin which is maintained at a temp. of 400-650 deg.C for 0.05-50hr., or a surface of said float glass which is not contacted with the molten metal, is treated by making a contact with said molten tin, cooled slowly, and washed followed by strengthening the obtd. float glass according to a conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application and packaging] The present invention applies glass produced by a float method, particularly soda-lime float glass, to substrates for electronic materials, particularly glass substrates for original disks, etc. Regarding chemical strengthening methods.

The present invention is applicable not only to scales for displays and disc substrates, but also to thin, large-area architectural and vehicle window glasses, as well as various molded products using sheet glass, cooking glass products, and various other products. It is widely used as substrates for air equipment.

[Conventional technology]

Float glass has smoothness, flatness, and thickness uniformity compared to so-called ordinary plate glass, so it is widely used in the field of electronic materials, such as liquid crystal and plasma displays, in addition to packaging for buildings and vehicles. It's getting worse.

Furthermore, as a recent trend, thin glass sheets with a thickness of 41,111 mm or less are gaining popularity, and as the thickness decreases, it is desired that the strength will be improved.

It is reasonable to apply a chemical strengthening method by alkali ion replacement to effectively strengthen thin glass, but if the chemical strengthening method is directly applied to float glass, the glass will warp (for example, IEII thickness 0.4~
1.31uI (7500m diameter), which impairs the flatness required for optical disk substrates (for example, 1
It was not possible to obtain a diameter of 0.2Q/15001 or less with a thickness of 1 m.

The cause of the warpage is presumed to be due to the influence of molten metal, typically Sn, penetrating into the contact glass during float molding of the glass, but no innovative solution to this warpage has been found. For example, grinding the Sn-infiltrated surface of glass,
Although alkali ion replacement treatment is carried out after polishing, the Sn diffusion depth on the contact glass surface of the Sn nucleus is 10 to 20 μm, and this method requires grinding and polishing. This process is not only complicated, but also involves problems in grinding and polishing, which can cause cracks and defects in the glass, and is also expensive.

Therefore, in the above-mentioned method, float glass was not used for the original disk substrate or the like.

In addition, for example, Japanese Patent Publication No. 17765/1983 discloses a method that attempts to carry out pre-treatment during chemical strengthening, and in the examples of this publication, NaNO and K
A method is described in which a pre-treatment is carried out in a mixed salt solution consisting of NO, for general chemical strengthening, and a method is disclosed in which the strength of the glass article is increased to E7.

[Problem that the invention seeks to solve]

As mentioned above, when chemically strengthening float glass, unless the molten metal contact surface is ground and polished to remove the 8n diffusion layer, or in the preliminary treatment described in Japanese Patent Publication No. 17765/1980, 70- It is impossible to prevent the occurrence of warping of glass.

[Failure to solve the problem]

The present invention has been made in view of the conventional drawbacks, and when chemically strengthening float glass, Na ions are formed between the molten metal contact surface and the molten metal non-contact surface where the float glass is in its original state. This provides a universal method that can solve the problem of warping by performing a chemical strengthening treatment after a balancing process.

That is, the present invention provides float glass i 400-65
After immersion treatment in molten tin maintained at a temperature range of 0°C for 0.05 to 50 hours or contact treatment of the molten metal non-contact side of the glass and the acetic acid molten tin surface, chemical strengthening is performed. I'll go.

Here, when the temperature of molten tin is 400°C, it does not affect both the molten metal contact and non-contact surfaces of the float glass, and there is almost no effect of molten tin in a part of Table 1 of the above, and there is no difference between both sides. It does not shrink and is not effective in preventing warping during chemical strengthening, preferably at 450°C or higher. Also 650℃
If the temperature exceeds the temperature, the temperature approaches the softening temperature of the glass itself, which tends to cause deformation, and if the glass is kept immersed for a long time, a cloudy phenomenon will occur on the second side of the glass, and although the difference in influence of Na ions, etc. on both sides will be reduced, other drawbacks will occur. The temperature is preferably 600°C or lower.

On the other hand, in the above-mentioned immersion or contact treatment, the degree of warping changes depending on the temperature of the molten tin and the immersion or contact time, and the treatment time can be arbitrarily selected from 0.05 to 50 hours depending on the treatment temperature.

0.05 hours, preferably 0.1 hours or more,
=5- The reason why the treatment temperature is 650° C. or less and the treatment time is 50 hours or less, preferably 40 hours or less is not only from an economical point of view but also to prevent changes in the glass surface from progressing too much.

For the immersion treatment, the glass is fixed in molten tin with a holder and immersed, and for the contact treatment, the glass is brought into contact with the bath molten tin surface in a floating state with the non-contact side of the glass facing downward. However, it goes without saying that any method other than these may be used as long as it can achieve the present invention.

In addition, when carrying out the above-mentioned immersion or contact treatment, it will be more effective if the glass is preheated, and after the immersion or contact treatment, it is subjected to slow cooling such as step cooling, and then washed.

In addition, as the six vessels for the 1'M tin bath, for example, lfl may be used.The six vessels should be sealed tightly, and nitrogen (Nm) or hydrogen (H,) should be added to the space inside the vessel to prevent oxidation of the molten tin. must be inserted and kept in a reducing atmosphere.

Furthermore, for the chemical strengthening treatment, commonly used known treatment methods can be applied.

[Effect]

As mentioned above, the method of chemically strengthening float glass of the present invention requires a unique pre-treatment to be performed, including the problem that as the thickness of the float glass decreases from about 4W, sufficient strengthening cannot be achieved using the air-cooling strengthening method. This solves the problem of warpage in float glass by reducing it to a value close to that of raw glass (no subsequent bending processing). Therefore, it eliminates the need for grinding and polishing and improves the characteristics of narrow surface roughness, surface parallelism, and smoothness. Because float glass can be chemically strengthened, thinner, relatively bulky, and strong float glass has been used for many purposes. , we have found a solution to this problem, which can improve the precision of the shape of molded products, etc., and prevent warping, as well as displays, etc.
It also satisfies the disk specifications such as a diameter of 2 m/300 og or less, and has a % copying system that greatly improves yield.

〔Example〕

The present invention will be explained in detail below.

Examples 1 to 7 As a glass 24i plate, the plate thickness is approximately 1.0g and the size is rare +)5
00×300 g of float glass and molten tin were respectively immersed at the temperature and time shown in SL and subjected to ordinary chemical strengthening treatment using potassium nitrate to prepare samples.

For these samples, the amount of warpage is I) KKTAK
The chemical reinforcement (six-face pressure assembly stress value) was measured using a six-time stress meter.

The warp it is shown in 6l.

Comparative Example 1 A sample of the same float glass as in Example was chemically strengthened without being treated with molten tin, but under the same conditions as above.

The amount of warpage and the optical surface compressive stress value were measured using the same equipment as in the example.

The amount of warpage is shown in 11.

Comparative Example 2 The same float glass as in the example was used as a sample (green plate), and the amount of warpage was measured using the same equipment as in the example.

The results are shown in Isa I.

Comparison? 1J 5-6 Using the same glass and molten tin as in the example, the immersion treatment was carried out at the temperature and time shown in pi, and the rest was carried out in the same manner as in the example, and the amount of warpage is shown in Table 1.

The margin table below shows the amount of warpage of 1 μm and 5 samples, and the negative value indicates that the side in contact with the molten metal surface is convex.

It should be noted that almost the same results were obtained by the above-mentioned contact treatment.

〔Effect of the invention〕

A comparison including the embodiment of the present invention described above and the conventional method? As is clear from 61 shown in comparison, conventional chemical strengthening only or immersion or contact treatment at a temperature below the lower limit of the present invention is chemical strengthening after contact treatment. The amount of warpage is ten times greater than that of a cod ridge, and with the present invention, the warpage can be reduced to a value close to that of a raw board, and in some cases can be made smaller than that of a raw board, and the effect is remarkable.

Regarding the degree of chemical strengthening, even when the present invention is implemented, there is almost no difference between the molten metal contact surface and the non-contact surface of the 70-glass plate. Surface compressive stress value is 2200
~5500 kf/cyA, and the bending fracture strength is 42
00 to 6000 Ail/(:llI), and the same level of reinforcement as the conventional method can be obtained.

Furthermore, the compression stress from the surface is 20 to 50%.
μm has been determined, and the product satisfies the specifications in the field of electronic materials.

Furthermore, within the scope of the present invention, a short immersion or contact treatment time is sufficient as long as the immersion or contact treatment temperature is high, and the amount of warpage can be arbitrarily selected depending on the specifications. ) The depth from the surface of the moon is increased to make the warped salmon 0.2. /300■ If you wish, you can freely choose and achieve the desired length.

As described above, the present invention solves the problem of nine warps that have not been solved conventionally in the chemical strengthening of float glass.
The central advantage is that thin float glass can be used for electronic packaging, especially for wide packaging such as optical disk substrates and architectural applications.

Claims (1)

[Claims] When chemically strengthening processed plate-like glass manufactured by the float method, the holding temperature is 400 to 650°C.
The chemistry of float glass, characterized in that the glass is immersed in molten tin for 0.05 to 50 hours, or the molten tin is brought into contact with the molten metal non-contact surface of the glass, and then chemically strengthened. Strengthening method.