JPS62100458A - Method for 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 in a (mixed) molten salt and then by strengthening chemically it, 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 salt contg. a Li ion (such as LiNO3 molten salt) or a mixed molten salt composed of >=2 kinds of said molten salt and the molten salt contg. a Na ion, etc., at a temp. of 350-650 deg.C for 0.01-50hr followed by strengthening the obtd. float glass according to a conventional method.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a glass manufactured by a float method.

In particular, the present invention relates to a method for chemically strengthening soda-lime-based float glass when it is applied as a substrate for electronic materials, particularly as a glass substrate for optical disks.

The present invention is applicable not only to scales used in display and disk substrates, but also to thin, large-area architectural and vehicle window glasses, various wooden molded products using float glass, glass products for stabilization, and various electronic products. Electrical equipment circuit boards etc. 1
Widely used.

[Conventional technology] Float glass has superior surface smoothness, flatness, and thickness uniformity compared to so-called ordinary plate glass, so it is used not only in the fields of architecture and vehicles, but also in the field of electronic materials, such as displays such as liquid crystals and plasma. It is becoming widely used.

Furthermore, as a recent trend, thin glass with a thickness of 4W+ or less is being used, and the thickness is becoming thinner.

Improvement in strength is desired.

It is well known that a chemical strengthening method using alkali ion substitution is applied to effectively strengthen thin glass. However, if the chemical strengthening method is applied directly to float glass, the glass will warp (for example, I 0.4-1.3g in weight
y'30-diameter), which impairs the flatness required for optical disk substrates (for example, 0.2
It was not possible to obtain a diameter of 300 mm or less.

It is presumed that the cause of the warpage is due to the influence of the molten excess volume (usually Fin) entering the contact glass surface during float molding of glass, but no innovative method for dealing with this warpage has been found. For example, an alkali ion replacement treatment is carried out after grinding and polishing the an infiltration surface of glass, but the Sn diffusion layer on the 8n contact glass surface is 10 to 20 μm, and the maximum thickness of this layer is grinding and polishing. This method not only requires a complicated process, but also has problems with the ωf grinding and grinding itself, which causes cracks and defects in the glass, and is also expensive. .

Therefore, in the method described in -1-, float glass was not used for optical disk substrates and the like.

For example, Japanese Patent Publication No. Sho 54-17765 discloses a method that requires preliminary treatment during chemical strengthening, and in the examples of this publication, a mixed salt consisting of Na, NOl, and NO kept at a constant temperature is used. A pre-treatment in a bath for conventional chemical strengthening is described, and a method for increasing the strength of glass articles is disclosed.

[Problems to be Solved by the Invention] As mentioned above, when chemically strengthening float glass, the surface in contact with molten metal is ground and polished.

Scraping without removing the Sn diffusion layer, and the above-mentioned
The pre-treatment described in Japanese Patent No. 4-17765 cannot prevent the float glass from warping.

[Means for solving problems]

The present invention has been made in view of the above drawbacks of the conventional technology, and when chemically strengthening float glass, Na ions are formed between the molten metal contact surface and the molten metal non-contact surface of the float glass as it is. After doing something like balancing.

The present invention provides a new method that can solve the problem that one warpage occurs due to chemical strengthening treatment.

That is, in the present invention, the float glass is 350 to 650
In a molten salt containing Li ions or a mixed molten salt of two or more types containing 111 ions and Na ions with a temperature range of 1.0 to 50 hours,
The percentage indicates chemical strengthening.

Here, when the temperature of the molten salt is lower than 350°C, it does not act on both surfaces of the float glass in contact with the molten metal and non-contact, and there is almost no diffusion of Li ions, etc. in the surface layer portions of both surfaces.
The gap on both sides has not narrowed.

It is not effective in preventing warping during chemical strengthening, and is preferably 400°C or higher. When the temperature exceeds 9,650℃, 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 glass surface. However, the temperature is preferably 600°C or lower.

On the other hand, in the above-mentioned immersion treatment, the amount of warpage changes depending on the temperature of the molten salt and the immersion time, and the amount of warpage varies depending on the treatment temperature.
It can be selected arbitrarily within the processing time. 0
．． 0.01 hour, preferably 0.065 hour or more is because the treatment temperature is 650°C or less, and 50 hours or less, preferably 0.065 hour or more is economical. In addition, this is to prevent further changes in the glass surface.

In addition, when carrying out the above-mentioned dipping treatment, it will be more effective if the glass is preheated, and after the dipping treatment, the glass is gradually cooled and then washed.

In addition, molten salt containing Li ions (, 2 and 1, for example.

Lithium nitrate, lithium nitrite, lithium sulfate.

Lithium phosphate or a mixed molten salt of these is used, and in addition, lithium phosphate containing Li ion and Na ion is used.
Other additives may be supplementarily used in the mixed molten salt of Class 11 or higher.

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

1. Effect J As mentioned above, 1. The chemical strengthening method for float glass of the present invention solves the problem of the problem that as the glass becomes thinner from about 4 cm, the air-cooling strengthening method cannot achieve sufficient strengthening. By applying this method, the warpage of float glass can be reduced to a value close to that of raw glass (no surface processing), and therefore the surface roughness can be improved to unilateral graininess and smoothness without the need for grinding or polishing. Because it can be chemically strengthened by taking advantage of these characteristics, float glass, which is thin, has a relatively large area, and is strong, is used for many purposes. As the need increases, we have found a solution to this problem, which can improve the precision of the shape of molded products, etc., and eliminates counterfeiting, as well as displays, etc.
It satisfies the disk specifications such as a diameter of 2 wm/300 trm or more, and has a t\i* that greatly improves the yield rate.

Furthermore, when a mixed molten salt of two or more types containing Ll ions and Na ions is used, the stability of the molten salt itself increases, and it is also preferable in terms of cost.

〔Example〕

The present invention will be explained in detail below.

Examples 1 to 9 As a glass substrate, the size is approximately 500aX with a 0 fin thickness.
Using lithium nitrate as a molten salt containing L1 ions, immersion treatment was carried out under the conditions of temperature and time shown in Table 5), and ordinary chemical strengthening treatment was carried out using potassium nitrate. , sample binding nine.

For these samples, the amount of warpage is r) J! K.T.A.
The degree of chemical strengthening (surface compressive stress flil: ) was measured using KIf (BT, a shape measuring instrument manufactured by OAN (USA)) and a surface stress measuring meter.

Table 1 shows the amount of warpage.

Comparative Example 1 The same float glass as in Example was used as a sample without being treated with the molten salt containing L1 ions, but chemically strengthened under the same conditions except for the same.

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

Table 1 shows the amount of warpage.

Using the same 70-gold glass as in Example 1 as a sample (raw board), the amount of warpage was measured using the same equipment as in Example [Also.

The results are shown in Table 1.

↓! ! (The same glass and molten salt as in Example 1 were used, and the immersion treatment was carried out at the temperature and time shown in Table 1.

The rest was the same as in Example, and the amount of reaction υ is shown in Table 1.

However, 1 warpage I is a measured value of 5 samples, and a negative value indicates that the side in contact with the molten metal surface is on the west side.

〔Effect of the invention〕

As is clear from Table 1, which shows a comparison of the above-described embodiment of the present invention and a comparative example including a conventional method.

Conventional chemical strengthening only or chemical strengthening after dipping treatment at a dipping treatment temperature below the lower limit of the present invention is several times that of raw board.
The amount of warpage is several tens of times greater, and if the present invention is used, the amount of warp per sheet will reach a value close to that of a raw board.

In some cases, it can be made smaller than raw boards, and the effect is remarkable.

Regarding chemically strengthened counterfeiting, even when the present invention is implemented, the molten metal Jl! #1 The optical surface compressive stress value is 25 with almost no difference on both the contact and non-contact surfaces.
00~3500 W-, 1 bending fracture strength is 4500
~b o o Okcq /-, and the same level of reinforcement as the conventional method can be obtained.

Furthermore, regarding the compressive stress layer from the surface, 20 to 30μ
m is obtained, which fully satisfies the specifications in the field of electronic materials1.Furthermore, it goes without saying that a short dipping time is sufficient as long as the dipping temperature is high within the scope of the present invention1.
The amount of warpage can also be selected arbitrarily depending on the specifications, and the depth from the surface of the compressive stress layer can be increased to reduce the amount of warpage.
Even when you want the amount to be within 0.2W1500■ length,
It is something that can be achieved by freely choosing [7].

As described above, the present invention solves problems that could not be solved conventionally in the chemical strengthening of float glass.
This has the remarkable effect that thin float glass can be used in a wide range of fields, from electronic materials, particularly optical disk substrates to architectural applications.

Claims (1)

[Claims] When chemically strengthening processed plate-like glass manufactured by the float method, the holding temperature is 350 to 650°C.
In a molten salt containing Li ions in the range of or in a mixed molten salt of two or more types containing Li ions and Na ions,
A method for chemically strengthening float glass, characterized in that the glass is immersed for 0.01 to 50 hours and then chemically strengthened.