JPS62191449A - Chemically strengthened float glass - Google Patents

Abstract

PURPOSE:To impart a fine finish surface having a surface compressive stress value within the range of 25-100kg/mm<2> and an amount of warpage within the range of + or -0.4mu/cm to float glass produced by a floating method, by chemically toughening the float glass without surface grinding. CONSTITUTION:Float glass is produced by a floating method. A molten salt or mixed molten salt containing alkali ions, e.g. Na ion or Li ion, of the same kind as an alkali component in the glass composition is applied to the surfaces of the glass without surface grinding and the resultant coats are then treated at 350-650 deg.C for 0.01-100hr to carry out chemical strenghtening by a low-or high-temperature type ion exchange method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses glass produced by a float method, for example, soda-lime float glass having a thickness of 3 mm or less, to be used as a substrate for electronic materials, particularly for optical disks. The present invention relates to a chemically strengthened float glass having a high degree of reinforcement with a small surface area and good flatness, which can be applied as glass substrates for photomasks, various displays, device members, etc.

In addition to the above, the present invention also applies to thin, large-area architectural and vehicle window glasses, various molded products using float glass, cooking glass products, and substrates for various electronic and electrical devices, etc.
It is widely used.

[Conventional technology]

Float glass has superior surface smoothness, flatness, and thickness uniformity compared to various types of plate glass, so it is widely used in fields such as architecture and vehicles, as well as in the field of electronic materials, such as displays such as liquid crystals and plasma. It is being used.

Furthermore, as a recent trend, thin glass sheets with a thickness of 3 mm or less are gaining popularity, and as the thickness decreases, it is desired to improve the strength.

It is well known that in order to effectively strengthen thin glass, chemical strengthening methods such as low-temperature or high-temperature alkali ion substitution are applied. Reverse cracking occurs (for example, 0.4 to 1.3 wV/300 frr1n at approximately 11 thickness)
diameter), which impairs the flatness required for optical disk substrates, etc. (for example, 0.2wIV1 with a thickness of about 1fi)
500 wm diameter or less) could not be obtained.

The cause of the above warpage is presumed to be due to the influence of molten metal, usually sn, entering the contact glass surface during float molding of glass, but no innovative solution to this warpage has been found.

For example, the Bnn large surface of glass is ground and polished, and then subjected to alkali ion replacement treatment, but the Sn diffusion layer on the SnO contact glass surface is 0 to 20
p$υ, this layer requires grinding and polishing, and this method not only requires a complicated process, but also has problems with the grinding and polishing itself, which can cause cracks and defects in the glass, and is costly. The top is also expensive.

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

Examples of methods for chemically strengthening float glass include Japanese Patent Publication No. 43-11106 and Japanese Unexamined Patent Application Publication No. 58-115043, and examples of glass compositions that are not limited to float glass include: 5
←There is Publication No. 17765, etc., and Special Publication No. 11106, 1977.
The publication discloses forming a glass article whose surface is substantially stress-free but having a surface layer rich in elements that are in a chemically low valence state, and the surface of this article is subjected to straining of the glass. At a temperature close to or below the point, the glass is brought into contact with a substance capable of reacting with the elements in the lower valence state in the surface layer, and the elements in the lower valence state are converted into compounds of the elements in the higher valence state. Thus, a method for producing glass with enhanced breaking strength is described which forms a compressed layer on the surface of the glass, which is introduced onto the lower surface of the glass band in a float process which produces a band of glass on the surface of a molten tin bath. Since tin generally does not exhibit its highest valence and is thought to exist in the form of stannous oxide on the lower surface of the glass band, tin oxide vapor or the like is used to coat the upper surface of the glass band. The glass surface is treated by introducing the same concentration into both the upper and lower surfaces of the glass strip, and converting the stannous compound into a stannic compound using an oxidizing atmosphere or an oxidizing agent. It is disclosed that a compressed layer can be formed in the glass, resulting in a glass with enhanced fracture strength with less flattening.

Furthermore, in Japanese Patent Application Laid-Open No. 58-11500, the glass is precisely annealed for at least 2 hours from the annealing point to the strain point, and the residual strain at the center of the thickness of the glass is reduced to 5 μm.
b. An ion exchange method for plate glass is described in which the glass is subjected to ion exchange treatment, and in the example, float glass is precisely annealed according to the present invention, the upper and lower surfaces are polished to achieve flatness, and then this process is performed. It is disclosed that a glass substrate with little change in flatness can be obtained by chemically strengthening glass using a low-temperature ion exchange method.

Furthermore, Japanese Patent Publication No. 54-7765 discloses that the main alkali metal ions A in the glass article are replaced with alkali metal ions B having a larger ionic radius at a temperature lower than the strain point of the glass article. In the method for increasing the strength, first, as a preliminary treatment, the glass article is brought into contact with a salt containing alkali metal ions B and alkali metal ions A in a desired ratio P for a certain period of time at a temperature below its strain point,
Then, as a subsequent treatment, the salt is brought into contact with a salt containing a large amount of alkali metal ion B at a higher ratio Q than the ratio P under conditions that satisfy at least one of the following conditions: a temperature lower than the above temperature or a shorter treatment time. A method of treating glass articles is disclosed.

[Problem that the invention seeks to solve]

As mentioned above, when chemically strengthening float glass, the stannous oxide on both the upper and lower surfaces of the float glass band is made to have the same concentration as disclosed in the above-mentioned Japanese Patent Publication No. 11106/1983, and this stannous oxide is By converting tin to stannic oxide, even though flatness can be obtained, only a small surface compressive stress value can be obtained, and the fracture strength cannot necessarily be said to be sufficient. Since the surface compressive stress is extremely small, it can hardly be called chemically strengthened glass.As disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-115043, the surface of float glass, at least the surface in contact with molten tin, is ground and polished. However, unless the north diffusion layer is removed, it is not possible to prevent the occurrence of cracking in the glass and make it into the original chemically strengthened product. This float glass cannot be applied to substrates for optical disks, glass substrates for photomasks, various display device members, etc., or even if it can be applied, it is insufficient. If float glass is chemically strengthened using the method described above, the effect of eliminating warpage cannot be obtained. In other words, the warpage cannot be controlled even if the preceding and subsequent processes are performed.

[Means for solving problems]

The present invention was developed in view of the above-mentioned drawbacks of the conventional glass.However, if an attempt was made to take advantage of the unique fire-shaped surface of float glass without mechanical polishing, the degree of flatness and reinforcement would be severe, and it was not adopted. The present invention provides a chemically strengthened float glass that can be used satisfactorily in various fields.

That is, the present invention relates to float glass manufactured by a float method and chemically strengthened without surface polishing of a processed plate-like body, and the surface compressive stress value of the glass is 25 to I2.
okfttJ is a chemically strengthened float glass characterized by having a fire-shaped surface with a warping amount within ±0.4 μm1an.

Here, the surface compressive stress value is a value measured with a surface stress meter manufactured by Toshiba Glass.
The limit to v/1R1j is 25ky/-Mimizo,
If the tempered plate glass is not satisfied, for example, ball test,
The bending fracture strength is also low, making it difficult to be evaluated as chemically strengthened glass, and if it exceeds 120 kg/rlIi, the pretreatment time to correct the amount of shear will be long, which will increase the glass cost. However, there is a possibility that the quality of the flame-forming surface of the float glass may deteriorate, or for example, haze may appear, and it is difficult to control the amount of anti-silt using the present invention. Moreover, due to the increase in the amount of birefringence of the glass, it can no longer be used in some fields such as substrates for electronic materials.Furthermore, among the composition components of float glass, For example, it becomes necessary to significantly increase the amount of components that affect the surface compressive stress value, such as Nano, Ll, 0, or ZrO2, which causes practical problems such as extremely difficult manufacturing using the float glass method, and various problems arise. This is because failures occur. In addition, the preferable range for the surface compressive stress value is 35~''kg/yxa.On the other hand, the amount of warpage is DK
These are the values measured with KTAK (manufactured by 5LOAN), etc., and the reason why the amount of warpage was limited to within ±0.4 μm 1 an is that ± This is because if the thickness exceeds 0.4 μm or less, it cannot be used as a substrate for electronic materials, etc.

The preferred range for the amount of warpage is ±0.2μm1crn
Within Furthermore, the surface of the float glass is a type of large-scale polishing and has the best surface condition, so it can be made into a chemically strengthened article by taking advantage of this.

The compositional components of the float glass of the present invention include soda-lime-based, borosilicate-based, alumina-silicate-based glasses, etc., but there is no need to limit them as long as they can be manufactured by the float method, and soda lime is preferred. System float plate glass composition, i.e. 5in2 by weight%
6B-75%A15o@0~5%C! a05-15
% MgO0~5% Nano I o~2o%, O
Composed of 0 to 5% of components such as Fe2O3 and As2.
The composition includes O3, Tie, OeO@, and other trace components. It goes without saying that the processed plate-like body may be a flat plate or a bent plate, and includes various shapes.

There is no need to limit the thickness of the plate, but
3? Those with a diameter of less than a, especially those with a diameter of 2 or less are preferable and bring about remarkable effects.

Although the method for obtaining the chemically strengthened float glass of the present invention is not particularly limited, for example, the holding temperature of 350
0.5-10 in molten salt containing Na ions at ~650°C
After the immersion treatment for 0 hours, an inorganic salt containing Na ions, which is described in Japanese Patent Application No. 60-47368, is applied to the molten metal contact surface of the float glass at a temperature of 380 to 650°C. A method for chemically strengthening float glass, which is chemically strengthened after heat treatment for 0.1 to 70 hours at a holding temperature of 350 to 65, as described in Japanese Patent Application No. 60-240430.
0.01 to 50 in a molten salt containing Ll ions or a mixed molten salt containing Ll ions and Na ions at 0°C.
Method for chemically strengthening float glass after time immersion treatment, and L1 described in Japanese Patent Application No. 60-240431
Applying an ion-containing inorganic salt or a mixed inorganic salt containing L1 ions and Na ions to the molten metal contact surface of the float glass,
There is a method of chemically strengthening float glass, which is chemically strengthened after being treated at 380 to 650°C for 0.01 to 3 hours, and in particular, the glass composition is Using a molten salt or mixed molten salt containing the same type of alkali ion as the alkali component in the glass, for example, Na ion or L1 ion, either the front and back surfaces of the glass or only the surface in contact with molten tin during plate forming of the glass Another method is to chemically strengthen the material using a low-temperature or high-temperature ion conversion method after treatment at a temperature range of approximately 350 to 650°C for 0.01 to 100 hours by means such as vapor phase method, coating, dipping, or coating. preferable. It is particularly preferable to use a low-temperature ion exchange method, but it goes without saying that a high-temperature method may also be used depending on the case.

Note that the amount of deformation for bent plate glass is the amount of deformation obtained by measuring the deformation after chemical strengthening treatment using, for example, the standard shape of float glass after bending.

In addition, the amount of warpage is the measured value of the amount of warpage per arbitrary length of the plate-like body, or the converted value calculated by using the square of the diameter or length of the plate-like body as a proportional coefficient ( μm/cm
For example, if it is a disk-shaped board with a diameter of 30 cm, it is 30 cm.
Measure the amount of reaction υ of mfip, and the measured value is 0.2#I
If so, 0.2X (1/900): 0.00
022-/iki0.2 p m/c17! is adopted as the amount of warpage.

[For production]

As mentioned above, the chemically strengthened float glass of the present invention has a problem that arises due to chemical strengthening, including the problem that it is difficult to obtain an inexpensive tempered glass using the air-cooling strengthening method, especially as the plate thickness becomes thinner than about 3 mm. Regarding the problem of anti-oxidation in float glass, due to the difference in the depth of the tin diffusion layer and the amount of tin distribution on both the upper and lower surfaces that occur when forming the float glass, the potassium By focusing on the fact that there is a difference in the amount of ion substitution, as in the present invention, by controlling the diffusion of potassium ions on both the top and bottom surfaces of the glass, the surface treatment can reduce the amount of ions while providing a sufficient degree of reinforcement. It is possible to obtain the required chemically strengthened float glass product by controlling the values to be close to those of raw glass without polishing, and also to improve the original characteristics of float glass such as surface roughness, plane parallelism, and smoothness without polishing. With the growing demand for flat tempered glass that is thinner, has a relatively large area, has high strength, has a contoured precision shape that does not warp, and is highly smooth. We can provide a chemically strengthened float glass that meets this need, and can be used not only for displays, etc., but also for displays, etc., and has a tensile strength of 0.2rMV/300-
The following features satisfy the specifications of the disk substrate, can be widely adopted in various fields, and greatly improve the manufacturing yield.

〔Example〕

Examples of the present invention will be described below.

] 1% by weight Sin, 72.30%, Al, 0.1.70
%, Fe2O30, I 0%, Ca07.7o%, Mg
O175%, Na, OI 3. O0%, K2O1, O
0%Other composition plate thickness approx. 1. ]rrr! A disk-shaped float glass substrate with n of about 300 in diameter was used. First, the surface of the glass substrate was cleaned and set in a holder, and the substrate was gradually maintained at a temperature of about 550°C. After immersing the holder in a molten sodium nitrate bath for about 1 hour, the substrate was taken out from the bath and the surface of the substrate was washed and dried. Set the substrate on the holder again,
The holder is immersed in a potassium nitrate molten salt bath maintained at a temperature of about 490° C. for about 2.5 hours to exchange sodium ions and potassium ions in the glass substrate surface layer, and the glass substrate surface layer A compressive stress layer was formed on the glass, which was taken out from the front bath, washed and dried to obtain a chemically strengthened float glass substrate.

A large number of glass substrates thus obtained were examined for various properties. As a result, the degree of chemical strengthening was measured using a surface stress needle (manufactured by Toshiba Glass), and the surface compressive stress value was 70 to 80 kLyll. ) etc., the maximum value was 10-1 to +02
11m/Cm (-0,1~KJ:2gay'300m
diameter), and the bending fracture strength was 50 to 80 kII/m7 when measured using the concentric circle load bending method, and 1
Furthermore, the surface condition was observed under an optical microscope (x+OO) and was found to be almost the same as before treatment. The obtained chemically strengthened float glass disc-shaped substrate is warped,
It has good flatness and high strength with almost no ridges observed, and could be used as a high-density, high-precision optical disk glass substrate.

Example 2 5iO172,40% by weight, Alto, o, 15
96% Fe203o, o 9%, CaO3, 65%, M
g04.20%, Nano l 3. '80%, K2
Using a disk-shaped float glass substrate with a thickness of 1.3 m and a diameter of approximately 30 mm, the surface of the glass substrate is first cleaned, and the float glass plate is placed in a holder. The substrate is set with the molten tin contact surface facing downward, and the molten tin contact surface of the substrate is gradually immersed in the surface layer of a sodium nitrate molten salt bath maintained at a temperature of about 500°C. After processing for about 5 hours, the holder was taken out from the bath, and the surface of the substrate was washed and dried. The process for chemical strengthening was carried out in the same manner as in Example] to obtain a chemically strengthened float glass substrate.

As a result of examining various properties of a large number of glass substrates obtained in the same manner as in Example 1, the surface compressive stress value was found to be between 70 and 90? The maximum value of /rtL anti-shi amount is -0.1 to +0.2fi-
7cm (-0.1~+0.2Wm/300rrrm diameter), the bending fracture strength was 97mtc in the range of 55-80. Furthermore, the surface condition of both the front and back surfaces of the substrate remained unchanged, being almost the same as before treatment.

Adopted as an optical disk glass substrate as in Example 1,
It has excellent flatness and high strength, making it suitable for high-density and high-precision applications.

Furthermore, the surface compressive stress value is I 2 oky/rtt
In order to approach the value a, it can be achieved, for example, by increasing the amount of Nano component in the glass composition to about 15.00% by weight. Note that a negative value for the amount of reciprocity indicates that the side that contacts the molten metal surface is convex.

A conventional chemically strengthened glass substrate was obtained by using the same float glass as in Example 1 and chemically strengthening it without dipping it in sodium nitrate, with the other conditions being the same as in Example. Ta.

As a result of measurement using the same measuring equipment as in the example, the surface compressive stress value was 40~'' kg//la, and the maximum amount of warpage was 0.65~1.2 fi/c1n (0.65~1 .2
rrrrB/300 flies), bending fracture strength is 30-5
oky/, 4, and the surface condition was almost the same as in the example.

This conventional chemically strengthened glass substrate had a particularly large amount of warpage and could not be used as an optical disk substrate.

〔Effect of the invention〕

As is clear from the above-mentioned embodiments of the present invention and conventional examples, the present invention takes advantage of the good flatness of float glass by fire polishing, and reduces the amount of warpage to the extent that it can be said to have almost the same shape as a non-chemically strengthened article. It is a chemically strengthened float glass article with sufficient surface compressive stress value and bending fracture strength, so it can be used in fields where it has not been used conventionally. The depth of the compressive stress layer from the surface of the chemically strengthened float glass of the present invention is 20 μm as measured by KPMA.
m or higher, and 1), Kikan hardness, etc. are also improved.

It should be noted that plate glass manufactured by a plate forming method other than the float method has a narrow surface that is worse than that of float glass, and high-quality products may not be able to undergo optical surface polishing. The one is better than this.

As described above, the chemically strengthened float glass of the present invention solves the warpage that could not be solved with conventional chemically strengthened float glass products, and is a product with high strength and extremely good flatness and smoothness. Since it can be stably supplied as a low-cost, high-quality product, it has the potential to be used in the electronic materials field, especially in a wide range of fields from optical disk substrates, to vehicles to architecture, etc., including thin sheets. be.

Claims (1)

[Claims] Regarding float glass manufactured by the float method and chemically strengthened without surface polishing, the surface compressive stress value of the glass is 25 to 120 kg/mm^2, and the amount of warpage is within ±0.4 μm/cm. A chemically strengthened float glass characterized by having a fire-molded surface.