JP2011032140A - Method for producing ion exchange treatment glass, method for producing chemically strengthened glass and ion exchange treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress quality deterioration of a glass product even if exchange frequency of a molten salt to ion exchange treatment amount is reduced when the glass product is produced by ion exchange treatment. <P>SOLUTION: Untreated glass containing Na and Li is subjected at least to a first ion exchange treatment process of being dipped in a first molten salt which contains Li and satisfies formula 1: C1(Li<SP>+</SP>)>C2(Li<SP>+</SP>)≥0 [wherein C1(Li<SP>+</SP>) denotes Li ion concentration (ppm) included in the first molten salt and C2(Li<SP>+</SP>) denotes Li ion concentration (ppm) included in the second molten salt], and a second ion exchange treatment process of being dipped in a second molten salt which contains Na and K and satisfies formula 1 to produce the ion exchange treatment glass. The method for producing chemically strengthened glass is provided by using the method for producing the ion exchange treatment glass and further an ion exchange treatment apparatus used for them is provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ion exchange treated glass production method, a chemically strengthened glass production method, and an ion exchange treatment apparatus.

  Ion exchange treatment in which glass containing alkali metal is immersed in molten salt to exchange ions in the glass is chemically strengthened by forming a compressive stress layer on the surface layer, such as for cover glass applications in mobile phone display parts. Mainly used to make glass. In addition, it is also used for producing glass optical components having a refractive index distribution.

  As an ion exchange treatment method for the purpose of producing chemically strengthened glass, alkali metal ions in the glass are exchanged for alkali metal ions having an ionic radius larger than the alkali metal ions, whereby a compression stress layer is formed on the surface layer of the glass. A method of forming is known. In this method, an ion exchange treatment is performed by immersing a glass to be subjected to a chemical strengthening treatment in a molten salt. As the molten salt, when the glass to be chemically strengthened contains Li ions or Na ions, a mixed molten salt containing sodium nitrate and potassium nitrate is often used. When ion exchange treatment is performed using this mixed molten salt, Li ions in the glass are ion-exchanged to Na ions in the molten salt, and Na ions in the glass are ion-exchanged to K ions in the molten salt.

  As a method for manufacturing various glass products using such ion exchange treatment, various techniques have been proposed according to the purpose. For example, in order to manufacture a chemically strengthened cover glass for a CCD camera by ion exchange treatment, a method has been proposed in which ion exchange is performed on a plate-like glass produced by an overflow downdraw method with a glass having a predetermined thermal expansion coefficient ( Patent Document 1). In this method, for example, a plate glass is immersed in molten potassium nitrate, and an ion exchange treatment is performed in which Na ions and Li ions in the glass are exchanged with K ions in the molten salt. In addition, a method for manufacturing glass for touch panel displays, cover glasses for mobile phones and solar cells, etc. by ion exchange treatment that replaces Na ions and Li ions in the glass with K ions in the molten salt is also proposed. (Patent Document 2).

  Moreover, in order to manufacture chemically strengthened glass that can be stably cut, a technique has been proposed in which a two-stage dipping treatment is performed when the glass is dipped in a molten salt for ion exchange treatment (Patent Document 3). . In this technique, the temperature of the molten salt for performing the second immersion treatment is controlled in the range of +20 degrees to +50 degrees with respect to the temperature of the molten salt for performing the first immersion treatment, and the second immersion treatment time Is controlled in the range of 10 minutes to 60 minutes to perform the ion exchange treatment. By controlling the temperature of the second molten salt and the immersion treatment time in this way, it is possible to achieve both the cutting property and strength of the chemically strengthened glass and to prevent the ion exchange solution from deteriorating. In this technique, the two ion exchange treatments are both performed using the same molten salt.

JP 2008-195602 A (Claim 1, paragraph number 0033, etc.) JP 2009-13052 A (Claims 8-11, paragraph number 0031, etc.) JP 2004-1359504 A (Claim 1, paragraph numbers 0016 to 0017, 0023 to 0027, etc.)

  When ion exchange treatment is performed by immersing glass in the molten salt as described above, the number of ions exchanged in the molten salt (ions originally contained in the glass) increases as the amount of ion exchange treatment increases. Thus, the composition of the molten salt deviates from the composition at the time of preparation (composition deteriorates). When ion exchange treatment is performed using a molten salt having such a deteriorated composition, for example, if the ion exchange treatment is intended for chemical strengthening, the melt having a deteriorated composition is compared with the case of using a fresh molten salt. When salt is used, quality deterioration such as a decrease in strength and dimensional change of chemically strengthened glass occurs.

  Therefore, when manufacturing various glass products such as chemically strengthened glass and optical parts using ion exchange treatment, the molten salt whose composition is deteriorated is replaced with a new molten salt before the quality of the glass product is deteriorated. There is a need. However, the greatest cost factor of glass products manufactured using ion exchange treatment is the frequency of exchange of molten salt. For this reason, from the viewpoint of cost, it is desirable that the exchange frequency of the molten salt with respect to the ion exchange processing amount is small.

  The present invention has been made in view of the above circumstances, and in the case of producing a glass product using an ion exchange treatment, the quality of the glass product is reduced even if the exchange frequency of the molten salt relative to the ion exchange treatment amount is reduced. It is an object of the present invention to provide an ion exchange treated glass production method capable of suppressing deterioration, a chemically strengthened glass production method using the same, and an ion exchange treatment apparatus used in these production methods.

The above-mentioned subject is achieved by the following present invention. That is, the ion-exchange-treated glass manufacturing method of the present invention is obtained by immersing an untreated glass containing Li ₂ O and Na ₂ O in a first molten salt containing Li ions and satisfying the following formula (1). After passing through the first ion exchange treatment step for performing the exchange treatment and the first ion exchange treatment step, the ions are immersed in a second molten salt containing Na ions and K ions and satisfying the following formula (1). A glass subjected to ion exchange treatment is manufactured by performing at least a second ion exchange treatment step for performing exchange treatment.
Formula (1) C1 (Li ⁺ )> C2 (Li ⁺ ) ≧ 0
[In Formula (1), C1 (Li ⁺ ) represents the Li ion concentration (ppm) contained in the first molten salt, and C2 (Li ⁺ ) is contained in the second molten salt. Represents Li ion concentration (ppm). ]

It is preferable that one embodiment of the method for producing ion-exchanged glass of the present invention satisfies the following formula (2) and the following formula (3).
Formula (1) C1 (Li ⁺ ) ≧ 500
Formula (2) 2000 ≧ C2 (Li ⁺ ) ≧ 0
[In Formula (2) and Formula (3), C1 (Li ⁺ ) and C2 (Li ⁺ ) are the same as C1 (Li ⁺ ) and C2 (Li ⁺ ) shown in Formula (1). ]

  In another embodiment of the method for producing ion-exchanged glass of the present invention, it is preferable that the first molten salt further contains Na ions and K ions in addition to Li ions.

  In another embodiment of the method for producing ion-exchanged glass of the present invention, the first molten salt is prepared by reusing the second molten salt whose composition has deteriorated by repeatedly performing the second ion-exchange step. It is preferable that the molten salt is used.

  The chemically tempered glass manufacturing method of the present invention is a chemically tempered glass manufacturing method using the ion exchange-treated glass manufacturing method of the present invention, wherein the shape of the untreated glass is plate-like, and the ion-exchanged glass is chemically tempered glass. It is preferable that

  In one embodiment of the method for producing chemically tempered glass of the present invention, the plate-like untreated glass is preferably a plate-like glass formed by a fusion down draw method.

  In another embodiment of the method for producing chemically tempered glass of the present invention, the chemically tempered glass is preferably used as a cover glass for a display of a mobile phone.

  The ion exchange treatment apparatus of the present invention comprises two or more tanks for holding a molten salt and a salt supply means for supplying a salt used for ion exchange treatment of untreated glass, and the two or more tanks are at one end. The molten salt is connected in series so that the molten salt can move from the arranged tank to the tank arranged at the other end, and the salt supply means is arranged so that the salt can be supplied to the tank arranged at one end. It is characterized by being.

  According to the present invention, when a glass product is manufactured using an ion exchange treatment, the quality of the glass product can be suppressed even if the molten salt exchange frequency with respect to the ion exchange treatment amount is reduced. It is possible to provide a method, a chemically tempered glass manufacturing method using the same, and an ion exchange treatment apparatus used in these manufacturing methods.

It is a schematic diagram which shows an example of the ion exchange processing apparatus used for the ion exchange processing glass manufacturing method of this embodiment. It is a schematic diagram which shows the other example of the ion exchange treatment apparatus used for the ion exchange treatment glass manufacturing method of this embodiment. It is a schematic diagram which shows the further another example of the ion exchange treatment apparatus used for the ion exchange treatment glass manufacturing method of this embodiment.

In the ion exchange-treated glass manufacturing method of this embodiment, an untreated glass containing Li ₂ O and Na ₂ O is immersed in a first molten salt containing Li ions and satisfying the following formula (1) to perform ion exchange. After the first ion exchange treatment step for performing the treatment and the first ion exchange treatment step, the ion exchange is performed by immersing in a second molten salt containing Na ions and K ions and satisfying the following formula (1) It is characterized by producing an ion-exchanged glass by passing through at least a second ion-exchange treatment process.
Formula (1) C1 (Li ⁺ )> C2 (Li ⁺ ) ≧ 0
Here, in formula (1), C1 (Li ⁺ ) represents the Li ion concentration (ppm) contained in the first molten salt, and C2 (Li ⁺ ) is contained in the second molten salt. The Li ion concentration (ppm) contained is expressed.

  According to the ion exchange treated glass production method of the present embodiment, when producing a glass product using the ion exchange treatment, the quality of the glass product is deteriorated even if the exchange frequency of the molten salt relative to the ion exchange treatment amount is reduced. Can be suppressed. The reason why such an effect is obtained is estimated by the inventors as follows.

  First, glass containing Li ions and Na ions as the target ions for ion exchange treatment, such as aluminosilicate glass, is subjected to ion exchange treatment, and these ions are exchanged for Na ions and K ions having a larger ion radius. In general, the immersion treatment is performed in a molten salt composed of potassium nitrate or a mixed salt of potassium nitrate and sodium nitrate. This immersion treatment is usually a one-step treatment except for a special case as exemplified in Patent Document 3.

And, when the ion exchange treatment is repeatedly performed using this molten salt, for example, focusing on Na ions in the glass, the composition of the molten salt is fresh at the initial stage when the ion exchange treatment is started. It can be said that the ion exchange reaction shown in Reaction 1 (fresh composition molten salt) is dominant. However, when the ion exchange treatment is repeated using the same molten salt, the Li ion concentration in the molten salt gradually increases due to the ion exchange of Li ions in the glass. And in the latter part of the ion exchange treatment in which the composition of the molten salt has deteriorated, it is presumed that the ion exchange reaction shown in the following reaction 2 (deteriorated composition molten salt) becomes relatively dominant. In addition, in the conventional typical ion exchange treatment as described above and the ion exchange treated glass manufacturing method of the present embodiment described later, as an actual problem, ion exchange between various ions other than reactions 1 and 2 is possible. It seems that it is happening. However, in the following description, for the convenience of simplifying the description and facilitating understanding, mainly, Na ions contained in the glass before ion exchange, Li ions introduced into the glass by ion exchange, and The description will be given focusing on Li ions and K ions in the molten salt.
Reaction 1 (fresh composition molten salt)
K ion (in molten salt) ⇔ Na ion (in glass)
・ Reaction 2 (deteriorated composition molten salt)
Li ion (in molten salt) ⇔ Na ion (in glass)

  In addition, about the point which reaction 2 becomes dominant in the latter stage of ion-exchange processing, the present inventors confirmed also from the principle confirmation experiment implemented without being caught by the presence or absence of quality degradation at the time of manufacture of chemically strengthened glass. ing. That is, when the present inventors repeatedly performed an ion exchange treatment on a glass containing Li ions and Na ions in a molten salt containing potassium nitrate and sodium nitrate, the glass is finally converted into a molten salt. It was confirmed that the glass was broken only by immersion. As a result of the reaction that Na ions in the glass are ion-exchanged to Li ions having a smaller ion radius than Na ions, the glass surface layer is not a compressive stress layer that improves mechanical strength, This is because it is considered that a tensile stress layer that deteriorates the mechanical strength is formed.

  However, in the ion exchange treatment glass manufacturing method of this embodiment, as described above, the first ion exchange treatment step and the second ion exchange treatment step are performed in this order. In the first ion exchange treatment step, the first molten salt having a relatively high Li ion concentration shown in Formula (1) is used. For this reason, reaction 2 is dominant in the first ion exchange treatment step. That is, Na ions in the glass are mainly exchanged for Li ions in the first molten salt. Subsequently, in the second ion exchange treatment step, a second molten salt having a relatively low Li ion concentration shown in Formula (1) is used. And the surface layer of the glass immediately before implementing the 2nd ion exchange treatment process is in the state where there were fewer Na ions and more Li ions than before implementation of the 1st ion exchange treatment process. . For this reason, in the second ion exchange treatment step, in addition to the ion exchange between Na ions and Li ions originally present in the glass and K ions in the second molten salt, in the first ion exchange treatment step, Ion exchange between Li ions newly introduced into the glass and K ions in the second molten salt is also promoted.

  Here, in the ion exchange treated glass manufacturing method of this embodiment, ions (introduced ions) introduced by ion exchange into the surface layer of the ion exchange treated glass finally obtained through two ion exchange treatment steps are ion exchange. The ion radius is larger than the ions (initial ions) contained in the surface layer of the glass before treatment. Considering only this point, the essential ion exchange treatment process is only the second ion exchange treatment process, as in the case of performing the ion exchange treatment in one stage in the past, and darely than the initial ion. It is considered that the first ion exchange treatment step of ion exchange treatment for ions having a small ion radius is unnecessary. However, the following merit is obtained by performing the first ion exchange treatment step before the second ion exchange treatment step.

  First, when the second ion exchange treatment step is repeatedly performed, the Li ion concentration of the second molten salt increases and eventually becomes unusable. On the other hand, the first molten salt used in the first ion exchange treatment step is the second molten salt used in the second ion exchange treatment step, as is apparent from the relationship of the Li ion concentration shown in Formula (1). Li ion concentration is relatively higher than the molten salt. The Li ion concentration of the second molten salt whose composition has deteriorated due to repeated use in the second ion exchange treatment step is suitable for use in the first ion exchange treatment step as the composition deterioration proceeds. It approaches the Li ion concentration of the first molten salt. For this reason, for the molten salt having a deteriorated composition that can no longer be used in the second ion exchange treatment step, the first molten salt for the first ion exchange treatment step can be easily adjusted by finely adjusting the Li ion concentration. Can be reused as

  Such a molten salt whose composition has deteriorated due to an increase in the Li ion concentration cannot be used and discarded because the quality cannot be ensured in the production of the target glass product by conventional ion exchange treatment. It will be disposed of. However, in the ion exchange treated glass manufacturing method of the present embodiment, as described above, the molten salt whose composition is deteriorated due to an increase in the concentration of Li ions in the second molten salt is used for the first ion exchange treatment step. It can be reused as the first molten salt. For this reason, when it sees as the whole ion exchange treatment process, the exchange frequency of the 1st molten salt per unit ion exchange treatment amount, such as the quantity equivalent to the glass for one lot, can be reduced.

  In addition, by performing the second ion exchange treatment step after the first ion exchange treatment step, even if the second ion exchange treatment step is repeatedly performed using the same second molten salt, it is finally obtained. It becomes easy to suppress the quality deterioration of the ion exchange processing glass obtained. That is, even if the composition of the second molten salt is deteriorated, the quality deterioration of the ion exchange treated glass accompanying this is unlikely to occur.

  The reason for this is estimated as follows. First, since a large ion (Na ion) in the surface layer of glass is exchanged for a small ion (Li ion) by the first ion exchange treatment step, the glass network structure on the surface layer of the glass has many gaps. For this reason, it is thought that the surface layer of the glass after the first ion exchange treatment step is in a state in which K ions introduced into the glass in the second ion exchange treatment step are easily diffused and moved.

  That is, as is clear from Fick's law, the diffusion of a substance is governed by the concentration gradient and the diffusion constant. For this reason, when the conventional ion exchange treatment is performed once and the ion exchange treated glass manufacturing method of the present embodiment is compared, ions that are interdiffusion phenomena between ions in the glass and ions in the molten salt When performing the exchange process, the point that the concentration gradient gradually decreases by repeating the ion exchange process (that is, the deterioration of the composition of the molten salt proceeds) is common. However, paying attention to the diffusion constant, the ion exchange treated glass manufacturing method of the present embodiment has a larger diffusion constant than the conventional one (that is, the gap in the glass network structure of the glass surface layer increases, It is considered that the resistance when K ions diffuse and move is reduced). From the above, it is presumed that the ion exchange process glass manufacturing method of the present embodiment is less susceptible to the influence of the deterioration of the composition of the second molten salt in the ion exchange treated glass manufacturing method of the present embodiment than in the conventional case. . Therefore, even if the composition of the second molten salt deteriorates as described above, it can be said that the quality deterioration of the ion-exchanged glass accompanying this is less likely to occur. In other words, in the same way as the conventional one-time treatment, the first ion exchange treatment step and the second ion exchange treatment step are performed in comparison with the case where only the second ion exchange treatment step is performed alone. It can be said that when the combination is carried out, the frequency of replacement of the second molten salt used in the second ion exchange treatment step can be further reduced in producing a glass product of a predetermined quality.

  Furthermore, from the mechanism as described above, in order to produce a glass product of the same quality using the second molten salt of the same composition, rather than performing only the second ion exchange treatment step alone, If the first ion exchange treatment step and the second ion exchange treatment step are performed in combination, the time required for the ion exchange treatment in the second ion exchange treatment step can be expected to be shorter.

-Molten salt-
Next, the detail of two types of molten salt used for the ion exchange processing glass manufacturing method of this embodiment is demonstrated. First, if the 1st molten salt used for the 1st ion exchange treatment process and the 2nd molten salt used for the 2nd ion exchange treatment satisfy the relation shown in a formula (1), The absolute value of the Li ion concentration is not particularly limited. However, it is particularly preferable that the first molten salt satisfies the following formula (2) and the second molten salt satisfies the following formula (3).
Formula (2) C1 (Li ⁺ ) ≧ 500
Formula (3) 2000 ≧ C2 (Li ⁺ ) ≧ 0
In the formulas (2) and (3), C1 (Li ⁺ ) and C2 (Li ⁺ ) are the same as C1 (Li ⁺ ) and C2 (Li ⁺ ) shown in the formula (1). However, in the overlapping range (500 ppm to 2000 ppm) of Formula (2) and Formula (3), C1 (Li ⁺ ) and C2 (Li ⁺ ) always satisfy the relationship shown in Formula (1).

The Li ion concentration C1 (Li ⁺ ) needs to satisfy the formula (1), and is preferably 500 ppm or more, more preferably 1000 ppm or more, as shown in the formula (2), and 2000 ppm or more. It is particularly preferred that By setting the Li ion concentration C1 (Li ⁺ ) to 500 ppm or more, the reaction of ion-exchange of Na ions contained in the surface layer of the glass with Li ions contained in the first molten salt becomes more dominant. As described above, even if the composition of the second molten salt is deteriorated, the quality of the ion exchange treated glass is prevented from being deteriorated, and the second ion exchange treatment is performed for producing a glass product of a predetermined quality. The exchange frequency of the 2nd molten salt used for a process can be decreased more.

The upper limit of the Li ion concentration C1 (Li ⁺ ) is not particularly limited, but when the concentration is too high, the tensile stress of the tensile stress layer formed on the surface layer of the glass tends to increase, and as a result, the glass breaks. It is likely to occur. Further, in order to avoid such breakage of the glass, it is necessary to control the ion exchange treatment time and the ion exchange temperature. However, since the concentration is too high, stable control may be difficult. From such a viewpoint, the upper limit of the Li ion concentration C1 (Li ⁺ ) is preferably set to 20000 ppm or less in practice, and preferably set to 15000 ppm or less.

  The alkali metal ions contained in the first molten salt may be only Li ions, but other alkali metals such as Na ions and K ions may be contained as alkali metals other than Li ions. Usually, it is preferable that Na ions and / or K ions are contained. In general, nitrate ions are used as counter ions of alkali metal ions.

The first molten salt may be formulated using a commercially available salt so as to have a predetermined composition satisfying the formula (2) in addition to the formula (1), but usually the cost is reduced. From the viewpoint, it is preferable to reuse the second molten salt whose composition has deteriorated by repeatedly performing the second ion exchange treatment step. In this case, in addition to the formula (1), more desirably, the Li ion concentration is finely adjusted by adding lithium nitrate so as to satisfy the formula (2). Molten salt can be formulated. Or you may reuse the molten salt which Li ion concentration fell by repeating and implementing a 1st ion exchange treatment process, and the composition deteriorated. Also in this case, the molten salt having a deteriorated composition can be regenerated by finely adjusting the Li ion concentration. Further, when the first ion exchange treatment step is repeatedly performed, the Li ion concentration C1 (Li ⁺ ) is always more desirable in addition to the formula (1) by sequentially monitoring the Li ion concentration of the first molten salt. If necessary, the Li ion concentration may be adjusted appropriately so as to satisfy Equation (2).

On the other hand, the second molten salt used in the second ion exchange treatment step contains Na ions and K ions. In addition to this, the Li ion concentration C2 (Li ⁺ ) needs to satisfy the formula (1), and is preferably 2000 ppm or less, more preferably 1000 ppm or less, as shown in the formula (3). It is preferably 500 ppm or less. By setting the Li ion concentration C2 (Li ⁺ ) to 2000 ppm or less, Na ions and Li ions contained in the surface layer of the glass that has finished the first ion exchange treatment step are larger than those contained in the second molten salt. It is possible to efficiently exchange ions with ions having an ionic radius (Na ions or K ions). For this reason, the ion exchange treatment glass which introduce | transduced the ion which has a larger ion radius than before implementing a two-stage ion exchange treatment to the surface layer of glass can be obtained. Therefore, for example, when the purpose is to manufacture chemically strengthened glass, a desired compressive stress layer can be more efficiently formed as an ion-exchanged layer (ion exchange layer) on the surface layer of the glass, and an optical element having a refractive index distribution. In the case of producing parts, a desired refractive index distribution layer can be more efficiently formed as an ion exchange layer on the surface of glass. In addition, the minimum of Li ion concentration C2 (Li ^<+> ) is 0 ppm.

  The second molten salt contains Na ions and K ions as alkali metal ions, and more preferably contains Li ions within the range satisfying Formula (3) in addition to Formula (1). May be. Moreover, alkali metal ions other than these may be contained. In general, nitrate ions are used as counter ions of alkali metal ions. Further, the concentration of Na ions and K ions can be appropriately selected according to the specifications of the glass product produced by the ion exchange treatment, the ion exchange treatment conditions, and the like. However, when nitrate is used, the content of sodium nitrate (that is, Na ion source) in the total molten salt is preferably in the range of about 10% by mass to 60% by mass, and potassium nitrate ( That is, the content of K ion source is preferably in the range of about 40% by mass to 90% by mass.

-Ion exchange treated glass manufacturing method and uses of ion exchange treated glass-
The use of the ion exchange treated glass production method of the present embodiment is not particularly limited as long as it is an application for producing various glass products utilizing ion exchange treatment. For example, it can be used as a chemically tempered glass manufacturing method or a glass optical component manufacturing method. Moreover, the shape and composition of the untreated glass used for the ion exchange treatment can be appropriately selected according to the target glass product. For example, when producing chemically strengthened glass, the shape of untreated glass is usually preferably a plate shape. Further, when producing a glass optical component, for example, when producing a gradient index optical fiber or rod, the shape of the untreated glass is preferably a fiber or rod, and the gradient index optical waveguide or micro When producing a lens, it is preferable to use a plate shape. The details of the composition of the untreated glass will be described later.

  Although it does not specifically limit as a use of the chemically strengthened glass produced using the ion exchange processing glass manufacturing method of this embodiment, Mechanical strengths, such as a surface scratch resistance and impact resistance, are mainly calculated | required as a glass substrate. It is suitable to use for a use. Examples of such applications include various display cover glasses used for electronic devices such as mobile phones, solar cell cover glasses, and touch panel display glasses. The chemically strengthened glass produced by using the method for producing ion-exchanged glass of the present embodiment can easily obtain mechanical strength suitable for use in the above-described applications, similarly to the conventional chemically strengthened glass. . For example, if the ion-exchange-treated glass manufacturing method of this embodiment is utilized, the chemically strengthened glass which has bending strength suitable for the said use (for example, about 500 MPa-2000 MPa by 3 point | piece bending strength) can be obtained easily.

-Untreated glass-
The untreated glass used in the ion exchange treatment the glass manufacturing method of the present embodiment, those containing Li 2 _O and Na 2 _O is used. Here, in this specification, “untreated glass” generally means that any ion exchange treatment is performed after the glass is melt-molded until the ion exchange treated glass production method of the present embodiment is performed. Means glass not made. However, in essence, “untreated glass” has a reaction in which Na ions in the glass are ion exchanged with Li ions in the first molten salt when the first ion exchange treatment step is performed. As long as it becomes dominant, other ion-exchange treatments may be performed in advance before the ion-exchange treatment glass manufacturing method of the present embodiment. And the ease of production and availability of untreated glass, and practical ion exchange treatment is possible in terms of technology and quality when a glass product is produced by the ion exchange treatment glass production method of the present embodiment. From a practical point of view, it is preferable to use glass that contains Li ₂ O in a range of 3% to 15% and Na ₂ O in a range of 3% to 20% by mass. A more preferred content, Li ₂ O is 4% to 10%, Na ₂ O is within the range of 4% to 12%. As such an untreated glass, a glass having a known composition excluding glass substantially free of alkali metals such as quartz and non-alkali glass can be used. Typically, aluminosilicate glass, aluminoborate glass, Examples include soda lime glass produced mainly by the float process.

  It does not specifically limit as a manufacturing method of untreated glass, A well-known glass manufacturing method can be utilized, for example, a float method, a fusion down draw method, a direct press method etc. can be utilized. In addition, which method is selected can be appropriately selected according to physical properties such as the melting temperature of the untreated glass, the shape of the untreated glass, the cost, and the like.

  In addition, when producing chemically tempered glass using glass of non-soda lime composition as untreated glass, such as aluminosilicate glass usually produced by other than the float process, as a method suitable for production of untreated glass, From a practical point of view such as mass productivity, the fusion down draw method or the direct press method may be mentioned. However, it is more preferable to select the fusion downdraw method among these glass production methods from the viewpoint of further shortening the treatment time during the ion exchange treatment.

  The reason for this is that, as shown in Table 1, when etching is performed using a glass substrate having the same aluminosilicate composition, the etching rate is higher than that of a glass substrate manufactured by the direct press method. It is mentioned that the produced glass substrate is about 1.4 times larger. That is, this result suggests that the fusion downdraw method is more likely to be rapidly cooled during glass production than the direct press method, and as a result, the density of the glass substrate is lower. Conceivable. As shown in Table 2, when the ion exchange treatment is performed using the glass substrate produced by both methods, the time required for forming the compressive stress layer having a thickness of 100 μm is 7.3 for the direct press method. Time is 2.5 hours in the fusion downdraw method. For reference, in the soda lime glass substrate, the time required for forming a similar compressive stress layer is about 16 to 24 hours. Considering these points, it is considered that the ion down treatment time can be shortened as a result of a decrease in the density of the glass substrate in the fusion downdraw method. Considering the above points, when chemically strengthened glass is produced using a glass substrate produced by the fusion downdraw method, the time required for the ion exchange treatment can be greatly shortened, and as a result, productivity can be greatly improved. Can do.

The etching conditions shown in Table 1 are as follows.
1) Etchant composition Sulfuric acid: hydrofluoric acid: water = 25: 15: 60 (mass ratio)
2) Etchant temperature 36 ° C
3) Etching method-Etching solution is applied by shower from the top of the glass substrate while swinging the glass substrate-Shower pressure: 0.25 MPa
-Etching solution application surface
Direct press molded product: Polished surface
Fusion Down Draw Molded Product: Molding Surface 4) Composition of Glass Substrate 63.5SiO ₂ -8.2 Al ₂ O ₃ -8.0 Li ₂ O-10.4Na ₂ O
−11.9ZrO ₂ (mass%)
5) Shape of glass substrate 40mm long x 40mm wide x 0.5mm thick

The ion exchange treatment conditions shown in Table 2 are as follows.
1) Molten salt composition Potassium nitrate: Sodium nitrate = 60: 40 (mass% ratio)
2) Molten salt temperature 360 ° C
3) Composition and shape of glass substrate Same as glass substrate used in experiment shown in Table 1

-Ion exchange treatment process-
Next, details of the specific implementation conditions of the first and second ion exchange treatment steps will be described except for the molten salt composition described above. About the temperature of the molten salt in the first and second ion exchange treatment steps, the immersion time of the untreated glass, the glass composition of the untreated glass to be used, the thickness of the ion exchange layer required for the target glass product, It can select suitably according to the composition etc. of the molten salt to be used. However, generally, the molten salt temperature in the first ion exchange treatment step can be in the range of about 300 to 450 degrees, and the molten salt temperature in the second ion exchange treatment step is 300 to 450 degrees. It can be in the range of about degrees. In general, the first ion exchange treatment step is preferably performed by immersing the glass only once in the first molten salt, but if necessary, the glass is immersed in two or more times. You may carry out by doing. In this case, the composition of the first molten salt used for each immersion treatment may be the same or different as long as the formula (1) is satisfied. This point is the same even when the second ion exchange treatment step is performed.

  Chemical strengthening with a compressive stress layer depth of about 20 μm to 150 μm using a soda lime glass substrate manufactured by a float method, an aluminosilicate glass substrate manufactured by a fusion down draw method, a direct press method, etc. In the case of producing glass, the molten salt temperature is preferably in the range of 300 to 450 degrees, more preferably in the range of 320 to 420 degrees in the first ion exchange treatment step, In the ion exchange treatment step, a range of 300 to 450 degrees is preferable, and a range of 320 to 420 degrees is more preferable. The immersion time is preferably in the range of 30 minutes to 1500 minutes in the first ion exchange treatment step, more preferably in the range of 120 minutes to 1200 minutes, and in the second ion exchange treatment step, The range is preferably 10 minutes to 1500 minutes, more preferably 20 minutes to 1000 minutes. By setting the molten salt temperature and the immersion time within the above ranges, the total time required for the ion exchange process can be shortened while preventing the glass substrate from being damaged during the ion exchange process and ensuring the yield. In addition, if necessary, in order to prevent the glass from being damaged by thermal shock due to rapid heating or rapid cooling before and after immersing the untreated glass in the molten salt or the glass after the first ion exchange treatment step, The glass may be preheated before dipping, or the glass may be slowly cooled at a constant cooling rate after the glass is pulled up from the molten salt.

-Ion exchange treatment device-
When the first and second ion exchange treatment steps are performed, at least one ion exchange treatment vessel (hereinafter, may be abbreviated as “treatment vessel”) corresponding to each step is used. When the composition of the molten salt used in these two treatment tanks deteriorates by repeating the ion exchange treatment, 1) exchange the molten salt in the treatment tank, or 2) change the composition of the molten salt in the treatment tank, In order to return to the initial composition, the missing components can be added. Using the first treatment tank (first ion exchange treatment tank) filled with the first molten salt and the second treatment tank (second ion exchange treatment tank) filled with the second molten salt, When implementing the ion-exchange-treated glass manufacturing method of embodiment, molten salt can be utilized as follows, for example. That is, after a predetermined amount of untreated glass has been subjected to ion exchange treatment, the molten salt in the first ion exchange treatment tank is discarded when the composition of the molten salt has deteriorated. Then, the molten salt in the second ion exchange treatment tank is transferred into the emptied first ion exchange treatment tank, and if necessary, in addition to the expression (1), more preferably the expression (2) is also satisfied. Thus, the concentration of Li ions is adjusted (all exchange method). The empty second ion exchange treatment tank is filled with a newly prepared second molten salt. Alternatively, after discarding a part of the molten salt in the first ion exchange treatment tank, transferring a part of the molten salt in the second ion exchange treatment tank to the first ion exchange treatment tank having a lowered water level, If necessary, the concentration of Li ions is adjusted so as to satisfy Equation (2) more desirably in addition to Equation (1). Moreover, in order to return the composition of the molten salt in the treatment tank to the initial composition in the second ion exchange treatment tank in which the water level has dropped, it is possible to add the missing component (partial exchange method). .

  Such a batch exchange system of molten salt can easily identify the timing of exchange of molten salt if the relationship of the degree of deterioration of the composition of the molten salt with respect to the amount of ion exchange is grasped. In this sense, management of the manufacturing process is easy. However, in the batch exchange system, the molten salt is exchanged after the composition of the molten salt has deteriorated to some extent with respect to the initial composition. For this reason, when ion exchange processing is performed for each of a plurality of glasses, that is, in units of lots, it is essentially difficult to avoid quality variations in units of lots. However, even if quality variation occurs in lot units, in the ion exchange treated glass manufacturing method of the present embodiment, as described above, when the second ion exchange treatment step is performed, the ion exchange treated glass is used. Is less susceptible to compositional deterioration of the second molten salt. For this reason, it is considered that the variation in quality between lots can be suppressed as compared with the conventional case, unless the timing of replacement of the molten salt is correct.

  FIG. 1 is a schematic diagram showing an example of an ion exchange treatment apparatus used in the ion exchange treatment glass manufacturing method of the present embodiment, and specifically shows an ion exchange treatment apparatus of a batch exchange type of molten salt. Is. The ion exchange treatment apparatus 1 shown in FIG. 1 has a first ion exchange treatment tank 10 and a second ion exchange treatment tank 12. When performing the ion exchange treatment, the first ion exchange treatment tank 10 is filled with the first molten salt 20, and the second ion exchange treatment tank 12 is filled with the second molten salt 22. These molten salts 20 and 22 are maintained at a predetermined temperature by a heater (not shown). In the ion exchange treatment, the untreated glass is immersed in the first molten salt 20 for a predetermined time, and then immersed in the second molten salt 22 for a predetermined time. After the ion exchange treatment, the salt adhering to the surface is washed with acid and water, and further post-processing such as cutting and polishing is performed as necessary.

  On the other hand, in order to further suppress the quality variation between lots, it is preferable to replace the molten salt not by the batch exchange method but by the continuous exchange method. Such a continuous exchange type ion exchange treatment apparatus includes two or more tanks for holding a molten salt, and a salt supply means for supplying a salt used for ion exchange treatment of untreated glass. The molten salt is connected in series so that the molten salt can move from the tank disposed at one end to the tank disposed at the other end, and the salt can be supplied to the tank disposed at one end. The thing by which the salt supply means is arrange | positioned is mentioned. In this case, in the molten salt flow direction, at least one tank located on the upstream side is used for the second ion exchange treatment step, and at least one tank located on the downstream side is used for the first ion exchange treatment step. In addition to the formula (1), the salt that satisfies the formula (3) is more preferably used as the salt supplied from the salt supply means. In addition, during the ion exchange treatment, it is preferable that the molten salt flow continuously or sequentially from the upstream side to the downstream side. In this case, as for the 2nd molten salt which satisfy | fills Formula (1) with low Li density | concentration in an upstream, Li ion density | concentration increases first by ion exchange with an untreated glass. Subsequently, the molten salt having an increased Li ion concentration is used as the first molten salt downstream for the implementation of the first ion exchange treatment step. However, there is usually a large difference in Li ion concentration between the first molten salt and the second molten salt. For this reason, as a result of using the second molten salt for ion exchange, it is often difficult to use the molten salt having an increased Li ion concentration downstream as it is and use it as the first molten salt. If this point is considered, the upstream tank (second ion exchange treatment tank) used in the second ion exchange treatment step and the downstream tank (first ion exchange treatment) used in the first ion exchange treatment step It is preferable to provide one or more tanks (adjustment tanks) mainly intended to adjust the Li ion concentration to a concentration suitable for use in the first ion exchange treatment step. In this case, the number of tanks constituting the ion exchange treatment apparatus is not particularly limited as long as it is 3 or more, but usually, the number of tanks is particularly preferably 3 from the viewpoint of simplifying the structure of the apparatus.

  Here, in the adjustment tank, after adjusting the concentration of Li ions of the molten salt flowing from the second ion exchange treatment tank on the upstream side to the expression (1), more preferably to satisfy the expression (3), This concentration-adjusted molten salt is allowed to flow to the first ion exchange treatment tank on the downstream side. As a method for adjusting the concentration of Li ions, addition of a salt containing Li such as lithium nitrate can be mentioned. Moreover, you may adjust the density | concentration of Li ion by ion exchange using the glass containing Li. In this case, for example, a process of immersing the untreated glass in the order of the adjustment tank, the first ion exchange treatment tank, and the second ion exchange treatment tank (Process A), or the first ion exchange treatment tank, the adjustment tank, A process (process B) in which immersion treatment is performed in the order of the second ion exchange treatment tank can be performed.

However, it is more preferable to execute the process A among the processes A and B. As shown below, the glass surface layer and molten salt Li ion concentration in each tank, when considering the qualitative changes required in carrying out the ion-exchange treated glass manufacturing method of the present embodiment, the process In A, it is easy to ensure a sufficient concentration gradient between the glass side and the molten salt side in both the adjustment tank and the first ion exchange treatment tank, whereas in Process B, in the adjustment tank, This is because there is a high possibility that it is difficult to ensure a sufficient concentration gradient between the molten salt side and the molten salt side. That is, in this case, since the concentration gradient between the glass side and the molten salt side is insufficient, it becomes difficult to move Li ions in the glass into the molten salt, and the molten salt in the adjustment tank is converted into the Li salt. This is because it is difficult to adjust the ion concentration so as to satisfy the formula (1) and supply it to the first ion exchange treatment tank on the downstream side.
<Qualitative change of Li ion concentration of glass surface layer and molten salt in Process A>
・ First ion exchange treatment (adjustment tank)
Glass side (small (initial concentration) → medium), molten salt side (medium → large)
・ Second ion exchange treatment (first ion exchange treatment tank)
Glass side (medium → large), molten salt side (large → medium)
・ The third ion exchange treatment (second ion exchange treatment tank)
Glass side (large → small), molten salt side (small (initial concentration) → medium)
<Qualitative change in Li ion concentration of glass surface layer and molten salt in Process B>
・ First ion exchange treatment (first ion exchange treatment tank)
Glass side (small (initial concentration) → medium), molten salt side (large → medium)
・ Second ion exchange treatment (adjustment tank)
Glass side (middle → large), molten salt side (middle → large)
・ The third ion exchange treatment (second ion exchange treatment tank)
Glass side (large → small), molten salt side (small (initial concentration) → medium)

  In addition, in the ion exchange treatment in the adjustment tank, the molten salt filled in the adjustment tank (hereinafter sometimes referred to as “adjusted molten salt”) is satisfied even if Expression (1) or Expression (2) is satisfied. It does not have to be. However, the Li ion concentration in the molten salt is set so that the reaction in which the Li ions in the molten salt are ion-exchanged with ions having a larger ion radius (such as Na ions) contained in the glass becomes dominant. There is a need.

  FIG. 2 is a schematic diagram showing an example of an ion exchange treatment apparatus used in the method for producing ion exchange treatment glass of the present embodiment, and specifically shows an ion exchange treatment apparatus of a system for continuously exchanging molten salt. Is. The ion exchange treatment device 2 shown in FIG. 2 includes a salt supply means 30, a first ion exchange treatment tank 32, an adjustment tank 34, and a second ion exchange treatment tank 36. The three tanks 32, 34, and 36 are arranged in the order of the first ion exchange treatment tank 32, the adjustment tank 34, and the second ion exchange treatment tank 36 from the right to the left in the drawing, and the second ion exchange A salt supply means 30 for supplying fresh salt to the second ion exchange treatment tank 36 is disposed on the side of the treatment tank 36 opposite to the side on which the adjustment tank 34 is disposed. In addition, a discharge pipe 40 is connected to the side of the first ion exchange treatment tank 32 opposite to the side where the adjustment tank 34 is disposed, and the first ion exchange treatment tank 32 and the adjustment tank 34 are connected by a connection pipe 42. The adjustment tank 34 and the second ion exchange treatment tank 36 are connected by a connection pipe 44. When performing the ion exchange treatment, the first molten salt 50A is placed in the first ion exchange treatment tank 32, the adjustment molten salt 50B is filled in the adjustment tank 34, and the second ion exchange treatment tank 36 is filled. Is filled with the second molten salt 50C. Here, the molten salt 50 (50A, 50B, 50C) is maintained at a predetermined temperature by a heater (not shown). In addition, the fresh salt supplied from the salt supply means 30 is a salt whose Li ion concentration is adjusted so as to satisfy the formula (1) (more desirably, so as to satisfy the formula (2)). In addition, the fresh salt may be in a solidified state upon supply or in a molten state. In addition, when it is desired to prevent a significant change in the temperature of the first molten salt 50C filled in the second ion exchange treatment tank 36, it is preferable that the fresh salt is supplied in a molten state.

  In the ion exchange treatment, when the ion exchange treatment is also performed using the adjusted molten salt 50B, the untreated glass is immersed in the adjusted molten salt 50B for a predetermined time, and then the first molten salt 50A is given a predetermined time. After being dipped and then dipped in the second molten salt 50C for a predetermined time (process A), or after the untreated glass has been dipped in the first molten salt 50A for a predetermined time, The adjustment molten salt 50B is immersed for a predetermined time, and then the second molten salt 50C is immersed for a predetermined time (process B). Further, when the ion exchange treatment is performed without using the adjusted molten salt 50B, the untreated glass is immersed in the first molten salt 50A for a predetermined time, and then immersed in the second molten salt 50C for a predetermined time. Processed (Process C).

  Further, the molten salt 50 is basically connected to the connection pipe 44 and the adjustment tank from the second ion exchange treatment tank 36 by the amount of fresh salt supplied from the salt supply means 30 to the second ion exchange treatment tank 36. 34, the connection pipe 42, the first ion exchange treatment tank 32, and the discharge pipe 40, and then sequentially move to a waste tank (not shown). The composition such as the Li ion concentration of the first molten salt 50A, the adjusted molten salt 50B, and the second molten salt 50C is the composition of the fresh salt supplied from the salt supply means 30, the supply amount per unit time, By appropriately adjusting the amount of ion exchange processing per unit time, etc., each is maintained substantially constant. Further, if necessary, a salt for supplying a salt having a predetermined composition to the adjustment tank 34 or the first ion exchange treatment tank 32 in order to finely adjust the composition deviation of the adjustment molten salt 50B or the second molten salt 50C. Supply means may be provided.

  In addition, the movement of the molten salt 50 is made to flow in a fixed direction by providing a one-way valve in each of the discharge pipe 40 and the connection pipes 42 and 44. The movement of the molten salt 50 can also be performed using a pump or the like. However, from the viewpoint that the configuration of the ion exchange treatment device 2 can be further simplified, the liquid level of the molten salt 50 filled in the first ion exchange treatment tank 32, the adjustment tank 34, and the second ion exchange treatment tank 36. The molten salt 50 may be moved by providing a difference in height.

  FIG. 3 is a schematic diagram showing an example of an ion exchange treatment apparatus used in the ion exchange treatment glass manufacturing method of the present embodiment, and in principle has the same configuration as the ion exchange treatment apparatus 2 shown in FIG. It is the figure shown about the ion exchange processing apparatus. Here, in FIG. 3, members having substantially the same functions and structures as those shown in FIG. In the ion exchange treatment device 3 shown in FIG. 3, the salt supply means 30, the first ion exchange treatment tank 32, the adjustment tank 34, and the second ion exchange treatment tank 36 are integrally configured, and the adjacent tanks are , Share a part of the wall that constitutes the tank. Moreover, the height of each tank 32,34,36 and the salt supply means 30 is set so that it may become high in order of the 1st ion exchange treatment tank 32, the adjustment tank 34, the 2nd ion exchange treatment tank 36, and the salt supply means 30. Has been.

  And the 1st molten salt 50A which became surplus in the 1st ion exchange processing tank 32 is discharged | emitted to the upper part of the wall surface on the opposite side to the side in which the adjustment tank 34 of the 1st ion exchange processing tank 32 was provided. Is provided on the side of the adjustment tank 34 on the side where the first ion exchange treatment tank 32 is provided, and the adjustment molten salt 50B surplus in the adjustment tank 34 is placed on the adjustment tank 34 side. Is provided in the second ion exchange treatment tank 36 at the upper part of the wall surface of the second ion exchange treatment tank 36 on the side where the adjustment tank 34 is provided. An opening 64 is provided for discharging the second molten salt 50C that has become surplus from the second ion exchange treatment tank 36 side to the adjustment tank 34 side. Furthermore, an opening 66 for supplying fresh salt to the second ion exchange treatment tank 36 is provided at the upper portion of the wall surface of the salt supply means 30 on the side where the second ion exchange treatment tank 36 is provided. . For this reason, in this ion exchange processing device 3, the molten salt 50 filled in each of the tanks 32, 34, 36 overflows corresponding to the amount of fresh salt supplied from the salt supply means 30. Thus, the molten salt 50 can automatically flow from the upstream tank 36 to the downstream tank 32. Accordingly, in order to move the molten salt 50 from the upstream tank 36 to the downstream tank 32, a pump, a connecting pipe and the like are not required, and the configuration of the ion exchange treatment apparatus can be further simplified.

As described above, the ion-exchange-treated glass manufacturing method of the present embodiment uses an untreated glass containing Li ₂ O and Na ₂ O to perform ion-exchange treatment with two types of molten salts satisfying the formula (1). The alkali metal ions (Li ions, Na ions) in the untreated glass are once exchanged for alkali metal ions having a smaller ion radius, and then the alkali metal ions originally contained in the untreated glass. The ion exchange is performed with alkali metal ions (Na ions, K ions) having a larger ionic radius than the above. However, the technical idea of the ion exchange treated glass production method of the present embodiment is that if the purpose is to produce a glass product in which alkali metal ions in the glass are finally exchanged for alkali metal ions having a larger ion radius, The present invention is applicable to ion exchange treatment between any alkali metal ion species.

For example, a first ion exchange treatment step in which an untreated glass containing at least Y ₂ O is immersed in a first molten salt containing X ions and satisfying the following formula (4) is ion exchange treated: After the first ion exchange treatment step, at least a second ion exchange treatment step in which ion exchange treatment is performed by immersing in a second molten salt containing Z ions and satisfying the following formula (4): By passing, the glass by which the ion exchange process was carried out can be manufactured.
Formula (4) C1 (X ⁺ )> C2 (X ⁺ ) ≧ 0
Here, in formula (4), C1 (X ⁺ ) represents the X ion concentration (ppm) contained in the first molten salt, and C2 (X ⁺ ) is contained in the second molten salt. Represents X ion concentration (ppm). X, Y and Z represent different types of alkali metals, and their ionic radii satisfy the relations X <Y and X <Z. Here, as the combination of (X, Y, Z), for example, (Li, Na, Tl), (Li, K, Tl), (Na, K, Tl), (Li, Na, Ag), ( Li, K, Ag) and the like.

  The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

(Untreated glass)
As the untreated glass used for the ion exchange treatment, the following plate-like glass having a length of 80 mm × width of 45 mm × thickness of 0.5 mm was prepared.
<Glass A>
・ Aluminosilicate glass substrate (HOYA, N5)
· Li ₂ O content (mass%): 8.0
· Na ₂ O content (wt%): 10.4
<Glass B>
_{· SiO 2 -Al 2 O 3 -CaO} -MgO-Li 2 O-Na 2 O -based glass substrate · Li ₂ O content (mass%): 3.0
· Na ₂ O content (wt%): 15.0
<Glass C>
_{· SiO 2 -Al 2 O 3 -ZnO} -MgO-Li 2 O-Na 2 O-K 2 O -based glass substrate · Li ₂ O content (wt%): 11.5
· Na ₂ O content (mass%): 7.0

Example 1
The ion exchange treatment apparatus 1 shown in FIG. 1 was used for the ion exchange treatment. In this ion exchange treatment, the first ion exchange treatment tank 10 is filled with 100 kg of the first molten salt 20,
The second ion exchange treatment tank 12 is filled with 100 kg of the second molten salt 22. The composition at the time of preparation of each molten salt is as shown in Table 3.

  In the ion exchange treatment, first, 500 pieces of glass A were set in a stainless steel substrate holder, and this was taken as one lot. Next, the glass A for one lot was immersed in the order of the first molten salt 20 and the second molten salt 22 in the order of temperature and immersion time shown in Table 3. And this ion exchange process was continuously implemented to the 100th lot, without exchanging the 1st molten salt 20 and the 2nd molten salt 22. FIG. For the glass after the ion exchange treatment, after acid washing and water washing, three samples are prepared for each of the first lot, the 20th lot, the 40th lot, the 60th lot, the 80th lot and the 100th lot. The three-point bending strength was taken out and the average value was obtained. The results are shown in Table 3.

-3 point bending strength
For the measurement of the three-point bending strength, a precision load measuring instrument (manufactured by Aiko Engineering, model 1311VRW) was used as a measuring instrument. In the measurement, two stainless rods (diameter 10 mm) were arranged in parallel at an interval of 50 mm, and then a glass sample was arranged on the two stainless rods. Next, a load was applied to the location of the glass sample located at the center of the two stainless steel bars, and measurement was performed. At this time, the head speed is set to 10 mm / min, and the initial load value of the bending strength is set to about 800 to 1000 MPa when the untreated glass is glass A (N5 substrate). In this case, the pressure was set to about 500 to 700 MPa. And in the case of a measurement, it implemented 3 times about the same kind of sample, and made the average value the 3-point bending strength. The evaluation criteria for the three-point bending strength shown in Table 3 are as follows.
A: Three-point bending strength S1 of ion-exchanged glass is 4 times or more of three-point bending strength S0 of untreated glass. O: S1 is three times or more and less than four times S2. Δ: S1 is 1 of S2. .5 times or more and less than 3 times x: S1 is less than 1.5 times S2

(Comparative Example 1)
In Example 1, using only the second ion exchange treatment tank 12 filled with the second molten salt 22 and performing the ion exchange treatment repeatedly under the conditions shown in Table 3, the same as in Example 1. Thus, an ion exchange treated sample was obtained. For these samples, the three-point bending strength was measured in the same manner as in Example 1. The ion exchange treatment was stopped at the 80th lot because the three-point bending strength significantly decreased.

(Examples 2-3)
Except that the kind of untreated glass and the ion exchange treatment conditions were changed as shown in Table 3, the first molten salt 20 and the second molten salt 22 were not exchanged, and 100 was obtained in the same manner as in Example 1. Ion exchange treatment was performed up to the lot. Table 3 shows the three-point bending strength of the obtained sample.

Example 4
The ion exchange treatment apparatus 3 shown in FIG. 3 was used for the ion exchange treatment. In this ion exchange treatment, the first ion exchange treatment tank 60 is filled with 100 kg of the first molten salt 50A, and the second ion exchange treatment tank 36 is filled with 100 kg of the second molten salt 50C. . The composition at the time of preparation of each molten salt is as shown in Table 3.

  And the ion exchange process was implemented for 100 lots continuously. At this time, fresh salt was appropriately supplied from the salt supply means 30 so that the Li ion concentration of the second molten salt 50C was within ± 10% of the value shown in Table 3. In addition, lithium nitrate is appropriately added to the adjusted molten salt 50B in the adjustment tank 34 so that the Li ion concentration of the first molten salt 50A is within ± 10% of the value shown in Table 3. The ion concentration was controlled.

(Examples 5-7)
In Example 1, an ion exchange treatment sample was obtained in the same manner as in Example 1 except that the ion exchange treatment conditions were changed to the conditions shown in Table 3 and the ion exchange treatment was performed. And about this sample, 3 point | piece bending strength was evaluated. The results are shown in Table 3.

  As is clear from the results of Example 1 and Comparative Example 1, although the total immersion time required for the ion exchange treatment is the same for both Example 1 and Comparative Example 1, it is compared with Example 1. In Example 1, the decrease in the three-point bending strength due to repeated ion exchange treatment was significant. The 100th lot of Example 1 and the 60th lot of Comparative Example 1 show almost the same three-point bending strength, but if this value is assumed to be the lowest quality standard line, In Example 1, it is understood that the molten salt needs to be exchanged around the 100th lot and in Comparative Example 1 around the 60th lot. However, in Example 1, when exchanging the molten salt, only the second molten salt needs to be completely exchanged. For the first molten salt, the second molten salt after 100 lots of ion exchange treatment is completed. It can be reused by adjusting the Li ion concentration. From the above, it was found that in Example 1, compared with Comparative Example 1, the desired quality can be maintained over a long period of time, and the molten salt replacement frequency can be reduced.

  Further, as apparent from the results shown in Examples 2 to 3, even when the kind of untreated glass is changed, the effect of sufficiently improving the mechanical strength of the glass is obtained up to the 100th lot as in Example 1. I found out that

  Further, as apparent from the results shown in Example 4, when ion exchange is performed while appropriately controlling the variation of the Li ion concentration so as to be within a predetermined range, the first lot to the 10th lot compared to Example 1. Up to the eyes, high mechanical strength could be obtained stably. Further, at the end of the 100th lot, the total amount of molten salt (waste salt) discharged from the opening 60 is about 55 kg, which is 0.55 kg in terms of consumption per lot. On the other hand, in the 100th lot in which the three-point bending strength has decreased in Example 1, the entire 100 kg of the first molten salt is discarded, and the second molten salt 100 kg is not discarded and the lithium nitrate is added. When the Li ion concentration is adjusted by addition and reused as the first molten salt, the consumption per lot is 1.0 kg. Further, in the case where the molten salt is completely exchanged in the 60th lot in which the three-point bending strength has decreased in Comparative Example 1, the consumption per lot is 1.67 Kg. From the above points, it was found that Example 4 consumed less molten salt per lot.

1, 2, 3 Ion exchange treatment apparatus 10 First ion exchange treatment tank 12 Second ion exchange treatment tank 20 First molten salt 22 Second molten salt 30 Salt supply means 32 First ion exchange treatment tank 34 Adjustment tank 36 Second ion exchange treatment tank 40 Discharge pipes 42, 44 Connecting pipe 50 Molten salt 50A First molten salt 50B Adjusted molten salt 50C Second molten salt 60, 62, 64, 66 Opening

Claims (8)

A first ion exchange treatment step of performing an ion exchange treatment by immersing an untreated glass containing Li ₂ O and Na ₂ O in a first molten salt containing Li ions and satisfying the following formula (1);
A second ion exchange treatment step of performing ion exchange treatment by immersing in a second molten salt containing Na ions and K ions and satisfying the following formula (1) after passing through the first ion exchange treatment step; The method of producing an ion exchange-treated glass, comprising producing an ion-exchanged glass by passing through at least.
Formula (1) C1 (Li ⁺ )> C2 (Li ⁺ ) ≧ 0
[In Formula (1), C1 (Li ⁺ ) represents the Li ion concentration (ppm) contained in the first molten salt, and C2 (Li ⁺ ) is contained in the second molten salt. Represents Li ion concentration (ppm). ] In the ion exchange processing glass manufacturing method of Claim 1,
An ion-exchanged glass manufacturing method characterized by satisfying the following formula (2) and the following formula (3):
Formula (2) C1 (Li ⁺ ) ≧ 500
Formula (3) 2000 ≧ C2 (Li ⁺ ) ≧ 0
[In Formula (2) and Formula (3), C1 (Li ⁺ ) and C2 (Li ⁺ ) are the same as C1 (Li ⁺ ) and C2 (Li ⁺ ) shown in Formula (1). ] In the ion exchange processing glass manufacturing method of Claim 1 or Claim 2,
Said 1st molten salt contains Na ion and K ion in addition to Li ion, The ion exchange processing glass manufacturing method characterized by the above-mentioned. In the ion exchange processing glass manufacturing method of any one of Claims 1-3,
The ion exchange treatment, wherein the first molten salt is a molten salt prepared by reusing the second molten salt whose composition has deteriorated by repeatedly performing the second ion exchange step. Glass manufacturing method. A chemically tempered glass manufacturing method using the ion exchange treated glass manufacturing method according to any one of claims 1 to 4,
The method for producing chemically tempered glass, wherein the untreated glass has a plate shape, and the ion-exchanged glass is chemically tempered glass. In the chemical tempered glass manufacturing method according to claim 5,
The method for producing chemically strengthened glass, wherein the plate-like untreated glass is a plate-like glass formed by a fusion downdraw method. In the chemical tempered glass manufacturing method according to claim 5 or 6,
A method for producing chemically tempered glass, wherein the chemically tempered glass is used as a cover glass for a display of a mobile phone. Two or more tanks holding molten salt;
A salt supply means for supplying a salt used for ion exchange treatment of untreated glass,
The two or more tanks are connected in series so that the molten salt can move from a tank disposed at one end to a tank disposed at the other end, and
An ion exchange treatment apparatus, wherein the salt supply means is arranged so that salt can be supplied to a tank arranged at the one end.

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