JP2013249222A - Chemically strengthened crystallized glass article and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemically strengthened crystallized glass article having high mechanical strength and excellent designability, and a method for producing the same.SOLUTION: A chemically strengthened crystallized glass article is obtained by depositing crystals of one or more selected from rutile (TiO), MgO-2TiOand zirconia (ZrO) and has a compressive stress layer formed on a surface thereof. Specifically, the article is made of crystallized glass comprising, in mass%, 40-60% of SiO, 0.5-10% of TiO+ZrO, 10-25% of AlO, 2-15% of BO, 2-20% of NaO+KO+LiO, and 0-20% of ZnO+MgO+CaO+BaO.

Description

  The present invention relates to a high-strength crystallized glass article suitable for housing decoration such as portable electronic devices and computers, and a method for producing the same.

Conventionally, air-cooled tempered soda-lime glass, air-cooled tempered borosilicate glass, and various types of ion-exchanged products have been used as high-strength glass. The air-cooled tempered glass is tempered by applying a compressive stress to the glass surface layer by blowing the cooling air at a high pressure after heating to a temperature equal to or higher than the softening point of the glass. On the other hand, the ion-exchanged product is usually soda-lime glass or borosilicate glass, but by immersing it in a molten salt heated to 500 ° C. or lower, it melts Na ⁺ ions having a small ion radius in the glass surface. The exchange reaction of alkali ions with K ⁺ ions having a large ionic radius in the salt (K ⁺ → Cs ⁺ , Li ⁺ → K ⁺ ) proceeds, the volume of the glass surface increases, and the compressive stress in the glass surface layer As a result, the mechanical strength of the glass plate is improved. As such an example, Patent Document 1 discloses an example of strengthening SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ based glass by ion exchange treatment. Patent Document 2 discloses an example of strengthening SiO ₂ —Al ₂ O ₃ —Li ₂ O-based glass by ion exchange treatment.

JP-A-10-182182 JP 2004-99370 A

  However, air-cooled tempered borosilicate glass and air-cooled tempered soda-lime glass are air-cooled at a temperature equal to or higher than the softening point of the glass in order to improve mechanical strength. A tempering treatment must be performed. As a result, the glass surface is wavy or the glass is warped, and the image is likely to be distorted. The effect differs depending on the expansion coefficient of the glass. In particular, since the expansion coefficient of borosilicate glass is low, the effect is small, and the strength is improved only about twice.

Conventional borosilicate glass and soda lime glass have low effects of strengthening by ion exchange treatment. The reason why the borosilicate glass cannot be sufficiently strengthened is that the content of Na ₂ O and other alkali components (Li, K, Cs) in the glass is low. Soda lime glass has a high content of Na ₂ O in the glass, but has a low ion diffusion coefficient due to a low content of Al ₂ O ₃ . For this reason, the rate of ion exchange on the glass surface is slow, and the exchange reaction of alkali ions is inferior. As a result, soda lime glass cannot be sufficiently strengthened. As a matter of course, these glasses are transparent because they are not crystallized glass, and are unsuitable for housing decorations such as portable electronic devices and computers. Furthermore, the strength is insufficient for these applications.

_{Further, SiO 2 -Al 2 O 3 -B} 2 O 3 based glass which is strengthened by ion exchange treatment described in Patent Document 1, for _Al 2 _{O 3} content and less than 5%, by ion-exchange process The degree of improvement in mechanical strength was small.

Furthermore, the SiO ₂ —Al ₂ O ₃ —Li ₂ O-based glass described in Patent Document 2 is a fire-resistant glass used for an opening with a transparent glass pursuing fire-proof performance, and is not a crystallized glass having design properties. It was unsuitable for the case decoration of portable electronic devices and computers.

  An object of the present invention is to provide a chemically strengthened crystallized glass article having high mechanical strength and excellent design, and a method for producing the same.

The chemically strengthened crystallized glass article of the present invention is formed by depositing one or more kinds of crystals selected from rutile (TiO ₂ ), MgO.2TiO ₂ , and zirconia (ZrO ₂ ), and a compressive stress layer is formed on the surface. It is characterized by.

In the present invention, by mass%, SiO ₂ 40-60%, TiO ₂ + ZrO ₂ 0.5-10%, Al ₂ O ₃ 10-25%, B ₂ O ₃ 2-15%, Na ₂ O + K ₂ O + Li ₂ O 2-20%, ZnO + MgO + CaO + BaO It is preferable to contain 0-20%. Here, “TiO ₂ + ZrO ₂ ” means the total content of TiO ₂ and ZrO ₂ . “Na ₂ O + K ₂ O + Li ₂ O” means the total content of Na ₂ O, K ₂ O and Li ₂ O. “ZnO + MgO + CaO + BaO” means the total content of ZnO, MgO, CaO and BaO.

According to the above structure, rutile _{(TiO 2), MgO · 2TiO} 2, and / or zirconia (ZrO ₂₎ can be easily precipitated. And since the content of Al ₂ O ₃ is large, the effect of improving the mechanical strength by the ion exchange treatment is increased.

  In the present invention, the volume ratio of the glass phase is preferably 70% or more.

  According to the said structure, the improvement effect of the mechanical strength by an ion exchange process becomes large.

  In the present invention, it is preferable that a compressive stress layer having a stress value of 300 MPa or more and a stress layer depth of 30 μm or more is formed. “Compressive stress value” and “depth of compressive stress layer” refer to values measured by microscopic laser Raman spectroscopy.

  According to the said structure, when used as a housing | casing of a portable electronic device, destruction by an injury etc. becomes difficult to occur.

In the method for producing a chemically strengthened crystallized glass article of the present invention, the raw materials are prepared so that one or more kinds of crystals selected from rutile (TiO ₂ ), MgO.2TiO ₂ , and zirconia (ZrO ₂ ) are deposited. A step of producing a crystalline glass body by melting and molding, a step of heat-treating the crystalline glass body to form a crystallized glass body, and a chemically strengthened crystallized glass article by ion exchange of the crystallized glass body And a step of.

In the chemically strengthened crystallized glass article of the present invention, crystals of rutile (TiO ₂ ), MgO.2TiO ₂ , and / or zirconia (ZrO ₂ ) are precipitated, and the appearance is opaque and ceramic. Therefore, it is excellent in design. Further, the mechanical strength is high due to the presence of the precipitated crystal and the compressive stress layer. Moreover, even if it breaks down, the cracks do not extend due to the presence of the precipitated crystals, so that the fragments are not shattered. Therefore, it is possible to reduce the risk that the user will be injured by fragments. Therefore, it is suitable as a casing member for electronic devices such as portable electronic devices and computers.

  Moreover, according to the method of the present invention, the above-described chemically strengthened crystallized glass article can be easily produced.

The chemically strengthened crystallized glass article of the present invention has precipitated one or more kinds of crystals selected from rutile (TiO ₂ ), MgO.2TiO ₂ and zirconia (ZrO ₂ ), and at least rutile, particularly rutile and zirconia. It is desirable that it is deposited. If rutile or MgO.2TiO ₂ is precipitated, the whiteness of the crystallized glass increases. Therefore, it is possible to reduce the amount of crystals to increase the proportion of the glass phase and to effectively exchange ions. Further, when zirconia is precipitated, the mechanical strength of the crystallized glass is increased. In the present invention, precipitation of crystals other than rutile (TiO ₂ ), MgO · 2TiO ₂ , and zirconia (ZrO ₂ ) (for example, garnite and forsterite) is not excluded. Further, rutile, MgO.2TiO ₂ , and zirconia do not necessarily need to be main crystals.

  The chemically strengthened crystallized glass of the present invention has a glass phase volume ratio of 70% or more (that is, a crystal phase volume ratio of 30% or less), particularly 75% or more (that is, a crystal phase volume ratio of 25% or less). Preferably there is. When the volume ratio of the glass phase is less than 75%, it is difficult to form a high compressive stress layer by the ion exchange process because the volume ratio of the glass phase to be subjected to the ion exchange process is small. Therefore, it is important that the crystallized glass has a glass phase volume ratio of 70% or more. In order to obtain characteristics such as mechanical strength and opacity, the volume ratio of the glass phase is 99% or less (that is, the volume ratio of the crystal phase is 1% or more), particularly 95% or less (that is, the volume ratio of the crystal phase is 5%). % Or more) is desirable.

  In the chemically strengthened crystallized glass of the present invention, the compressive stress value CS of the compressive stress layer formed on the surface thereof is preferably 300 MPa or more, particularly preferably 400 MPa or more, and the depth DOL of the compressive stress layer is 30 μm or more, In particular, it is preferably 35 μm or more. When the stress value of the compressive stress layer formed on the surface is less than 300 MPa, the strength tends to be insufficient as a housing decoration material for portable electronic devices and computers. Further, when the depth of the compressive stress layer is less than 30 μm, the strength is likely to be insufficiently maintained against damage when used as a housing decoration material for portable electronic devices and computers.

Further, the chemically strengthened crystallized glass article of the present invention has a strain point of 500 ° C. or higher, particularly 530 ° C. or higher, and a thermal expansion coefficient of 40 to 80 × 10 ⁻⁷ / K, particularly 60 to 75 × 10 at 30 to 380 ° C. ^A crystallized glass of ⁻⁷ / K is preferred because it has excellent thermal shock resistance and heat resistance and can withstand rapid heating and quenching during ion exchange treatment.

The composition of the chemically strengthened crystallized glass article of the present invention is not limited as long as it is a crystallized glass that precipitates rutile (TiO ₂ ), MgO.2TiO ₂ , and / or zirconia (ZrO ₂ ). In order to combine the properties of SiO ₂ 40-60%, TiO ₂ + ZrO ₂ 0.5-10%, Al ₂ O ₃ 10-25%, B ₂ O ₃ 2-15%, Na It is preferable to employ crystallized glass containing _{2 to} 20% of ₂ O + K ₂ O + Li ₂ O and 0 to 20% of ZnO + MgO + CaO + BaO. In the following description, “%” means mass% unless otherwise specified.

  The reason for limiting the composition of crystallized glass as described above is as follows.

SiO ₂ is a component that enhances chemical durability, and its content is preferably 40.0 to 60.0%, particularly preferably 42.0 to 58.0%. When the content of SiO ₂ is less than 40.0%, the weather resistance is remarkably deteriorated. On the other hand, when the content of SiO ₂ is more than 60.0%, melting of the glass tends to be difficult.

TiO ₂ and ZrO ₂ are essential components for precipitating rutile (TiO ₂ ), MgO · 2TiO ₂ and zirconia (ZrO ₂ ). The total content is preferably 0.5 to 10.0%, particularly preferably 1.0 to 5.0%. If the total content of TiO ₂ and ZrO ₂ is less than 0.5%, the amount of precipitated crystals decreases and the mechanical strength tends to decrease. On the other hand, the total content of TiO ₂ and ZrO ₂ is 10 When it is more than 0%, undissolved material is likely to be generated when the glass is melted. The content ratio of the TiO ₂ is 0.05 to 5.0%, particularly preferably 0.5 to 3.5%. The content of ZrO ₂ is preferably 0.05 to 5.0%, particularly preferably 0.2 to 3.0%.

Al ₂ O ₃ is a component that determines ion exchange performance, and its content is preferably 10.0 to 25.0%, particularly preferably 13.0 to 23.0%. When the content of Al ₂ O ₃ is less than 10.0%, the ion diffusion coefficient during the ion exchange treatment is lowered, the ion exchange rate is lowered, and the ion exchange property may be lowered. On the other hand, if the content of Al ₂ O ₃ is more than 25.0%, the solubility of the glass tends to deteriorate.

The total content of Na ₂ O, K ₂ O and Li ₂ O is preferably 2.0% to 20.0%, particularly 2.5 to 18.0%. When the total amount of these components is less than 2.0%, the melting property of the glass is inferior or the ion exchange property is lowered. On the other hand, when the total amount of these components is more than 20.0%, crystallization is difficult. Incidentally content of Na ₂ O is 2.0 to 15.0%, particularly preferably 5.0 to 12.0%. The content of K ₂ O is preferably 0.5 to 5.0%, particularly preferably 1.0 to 4.0%. The content of Li ₂ O is preferably 0 to 8.0%, particularly preferably 0.5 to 5.0%.

B ₂ O ₃ has an effect of improving the meltability of the glass and lowering the liquidus temperature, and its content is preferably 2.0 to 15.0%, particularly preferably 4.0 to 13.0%. . When the content of B ₂ O ₃ is less than 2.0%, not only the meltability of the glass is inferior, but also the liquidus temperature becomes high and the glass tends to be devitrified at the time of forming the original glass. On the other hand, when the content of B ₂ O ₃ is more than 15.0%, crystallization is difficult.

  The total content of ZnO, MgO, CaO and BaO is preferably 0 to 20.0%, particularly preferably 2.0 to 12.0%. These components can improve the meltability. The ZnO content is preferably 0 to 10%, particularly preferably 2.0 to 6.0%. The content of MgO is preferably 0 to 10%, particularly preferably 2.0 to 6.0%. The CaO content is preferably 0 to 5.0%, particularly preferably 0.1 to 1.0%. The BaO content is preferably 0 to 3.0%, particularly preferably 0.2 to 2.0%.

Further, CeO ₂ may be added although it is not an essential component. The CeO ₂ content is preferably 0 to 0.5%, particularly 0.05 to 0.5%, and more preferably 0.1 to 0.3%. CeO ₂ not only improves the solubility but also has an effect as an oxidant, suppresses the increase of Fe ²⁺ in the total Fe, which is an impurity, and increases the whiteness of the crystallized glass to make the color development vivid. . When the content of CeO ₂ is more than 0.5%, the coloring due to Ce ⁴⁺ becomes too strong, and the crystallized glass may be browned. If the CeO ₂ content is less than 0.01%, the above effect is difficult to obtain.

Further, although not an essential component, SO ₃ may be added. The content of SO ₃ is preferably 0 to 0.5%, particularly 0.02 to 0.5%, and more preferably 0.05 to 0.3%. SO ₃ can be added as bow glass. Effect of SO ₃ is to improve the solubility of the raw glass, it acts as an oxidizing agent in the same manner as CeO _2, the effect is remarkable by coexisting with CeO _2. If SO ₃ is more than 0.5%, different types of crystals may be precipitated and the surface quality of the crystallized glass may be deteriorated. If the content is less than 0.02%, the above effect is difficult to obtain.

The crystallized glass of the present invention contains colored oxides such as CoO, NiO, Fe ₂ O ₃ , MnO ₂ and Cr ₂ O ₃ up to 10.0% in addition to the components described above, so that the colored crystallized glass can be obtained. Is possible.

  Next, the manufacturing method of the chemically strengthened crystallized glass article of this invention is demonstrated.

First, a glass raw material is prepared so as to have a composition in which rutile (TiO ₂ ), MgO · 2TiO ₂ and / or zirconia (ZrO ₂ ) is precipitated. The raw material to be used is not limited to raw materials, and glass cullet can be used as necessary. Moreover, since the preferable composition of target glass overlaps with the above-mentioned content, description is omitted.

Next, the prepared raw material batch is melted at 1500 to 1600 ° C. and formed into a predetermined shape. In this way, a crystalline glass body capable of precipitating rutile (TiO ₂ ), MgO.2TiO ₂ and / or zirconia (ZrO ₂ ) upon heat treatment is obtained. For forming, a well-known forming method such as a float method, an overflow method, a downdraw method, a roll-out method, a mold press method or the like can be employed.

Next, the crystalline glass body is heat-treated at a temperature at which the glass has a viscosity of 10 ^4.5 to 10 ^5.5 dPa · s, whereby rutile (TiO ₂ ), MgO · 2TiO ₂ , zirconia (ZrO ₂ ) as precipitated crystals. ) To obtain a white or colored opaque crystallized glass body. These three types of crystals may be precipitated, but other crystals may be precipitated. Further, it is preferable to select the composition and adjust the heat treatment conditions so that the total amount of precipitated crystals is 1 to 25% (that is, the volume ratio of the glass phase is 75 to 99% by volume).

  Thereafter, the crystallized glass body is ion-exchanged to obtain a chemically strengthened crystallized glass article. In ion exchange, by bringing a crystallized glass body into contact with a molten salt adjusted to near the strain point temperature of crystallized glass, alkali ions (for example, Na ions and Li ions) in the surface glass phase are ionized more than that. Substitution with alkali ions having a large radius (for example, K ions). In this way, a compressive stress layer having a compressive stress value of 300 MPa or more and a compressive stress depth of 30 μm or more can be formed on the surface of the crystallized glass body.

  If necessary, before or after ion exchange, surface processing such as film deposition, machining such as cutting and drilling, and the like may be performed.

  Hereinafter, the high-strength crystallized glass article of the present invention will be described in detail based on examples. Table 1 shows Examples 1 and 2 and Comparative Examples 1 to 4.

  The crystallized glass article of Example 1 is a casing decoration material for portable electronic devices, computers, etc., and has dimensions of 90 mm on one side × 45 mm on the other side × 0.7 mm in thickness, and the volume ratio of the glass phase is 90. %, A compressive stress layer having a stress value of 700 MPa and a depth of 40 μm is formed on the free surface by ion exchange treatment.

  In the crystallized glass article of Example 2, the volume ratio of the glass phase is 85%, and a compressive stress layer having a stress value of 750 MPa and a depth of 45 μm is formed on the free surface by ion exchange treatment.

  The crystallized glass plates and transparent glass plates of Examples 1 and 2 and Comparative Examples 1 to 4 were produced as follows.

First, batch raw materials prepared so as to have the composition shown in the table are put into a melting kiln and melted at 1500 to 1600 ° C., and then the molten glass dough is roll-formed and then slowly cooled to 900 × 1200 × 7 mm. A glass plate was produced. Rutile and zirconia were precipitated by heat-treating this glass plate at 1050 ° C. at which the viscosity of the glass was 10 ^4.5 to 10 ^5.5 dPa · s.

  In Comparative Example 3, a soda-lime glass plate having a thickness of 1 mm, which is commercially available for general window glass, was used. In Comparative Example 4, a commercially available borosilicate glass plate having a thickness of 1 mm was used.

  Next, samples for measuring the thermal expansion coefficient, transition point, yield point, softening point, and strain point were cut out from these glass plates.

  Further, a sample for bending strength measurement of 4 mm short side × 50 mm long side × 1 mm thickness and a steel ball drop test sample of 50 mm × 50 mm × 1 mm are cut out, and the bending strength measurement sample and the steel ball drop test sample are The ion exchange treatment and the air cooling strengthening treatment were performed.

In Examples 1 and 2 and Comparative Examples 1 and 2, ion exchange treatment was performed by immersing the sample in KNO ₃ molten salt maintained at 500 ° C. near the strain point temperature of the crystallized glass for 24 hours. In Comparative Examples 3 and 4, the sample was placed in an electric furnace set at the same temperature as the softening point, held for 1 hour, then taken out, and blown with cooling air to perform air cooling strengthening treatment.

  The samples thus prepared were evaluated for thermal expansion coefficient, transition point, yield point, strain point, softening point, appearance quality, appearance color, bending strength before and after strengthening, and steel ball drop height. The results are shown in Table 1.

  The precipitated crystal seeds were confirmed by a powder X-ray diffraction method. The case where precipitation of rutile or zirconia was confirmed by this method was indicated by “◯”, and the case where no precipitation was confirmed was indicated by “−”. The amount of precipitated crystals was calculated from the crystal area ratio in the SEM photograph of the sample cross section.

  The stress value of the compressive stress layer was determined from the amount of peak movement of the Raman scattering peak by microscopic Raman spectroscopy. Similarly, the depth of the stress layer was determined by measuring Raman scattering from the surface by micro-Raman spectroscopy and measuring the depth at which peak movement does not occur.

  The appearance quality after the treatment was evaluated by visual observation, and the case where no distortion was observed in the image was “◯”, and the case where the image was distorted was “x”.

  The thermal expansion coefficient, transition point, and yield point were measured using a Dilatometer according to JIS R 3103-3: 2001. The softening point and strain point were measured by the fiber elongation method (JIS R 3103-2: 2001, ISO 7884-6: 1987).

  The bending strength was measured using a three-point load method according to ASTM C880-78. In addition, the steel ball drop test was based on JIS R 3206 “tempered glass” and dropped a 32.5 g steel ball to determine the height at which the specimen was damaged.

  Examples 1 and 2 of the present invention contain a lot of glass phase, and the ion exchange treatment makes the bending strength very high, the impact strength is strong, it is difficult to break, and the appearance quality after the ion exchange treatment is also high. There was no problem with no swell or warp. Moreover, since rutile was precipitated, an appearance with high whiteness could be obtained despite the small amount of crystals. In Example 2, zirconia was also precipitated, and a crystallized glass article having higher mechanical strength could be obtained.

  On the other hand, Comparative Examples 1 and 2 showed about 1.5 times the bending strength and the steel ball drop distance by ion exchange, but the effect of ion exchange was inferior to that of the Example and was easily damaged. In Comparative Examples 3 and 4, the air-cooling strengthening treatment increases the bending strength and the impact strength, but the appearance quality after the air-cooling strengthening treatment is poor and the image looks distorted. It was unsuitable as a case decoration.

  The chemically strengthened crystallized glass article of the present invention is suitable as a portable electronic device, an electronic device such as a computer, or other casing member. Moreover, it can be used suitably also for various uses other than the housing | casing in which high intensity | strength and design property are calculated | required.

Claims (5)

Chemically strengthened crystallization characterized in that one or more kinds of crystals selected from rutile (TiO ₂ ), MgO · 2TiO ₂ and zirconia (ZrO ₂ ) are deposited, and a compressive stress layer is formed on the surface. Glass articles. SiO ₂ 40-60%, TiO ₂ + ZrO ₂ 0.5-10%, Al ₂ O ₃ 10-25%, B ₂ O ₃ 2-15%, Na ₂ O + K ₂ O + Li ₂ O 2-20 %, ZnO + MgO + CaO + BaO 0-20% is contained, The chemically strengthened crystallized glass article of Claim 1 characterized by the above-mentioned.   The chemically strengthened crystallized glass article according to claim 1 or 2, wherein the volume ratio of the glass phase is 70% or more.   The tempered crystallized glass article according to any one of claims 1 to 3, wherein a compressive stress layer having a stress value of 300 MPa or more and a depth of the stress layer of 30 µm or more is formed. A raw material is prepared so as to have a composition in which one or more kinds of crystals selected from rutile (TiO ₂ ), MgO · 2TiO ₂ , and zirconia (ZrO ₂ ) are precipitated, and melted and molded to produce a crystalline glass body. A chemically strengthened crystal comprising: a step, a step of heat-treating the crystalline glass body to obtain a crystallized glass body, and a step of ion-exchanging the crystallized glass body to obtain a chemically strengthened crystallized glass article. A method for producing a vitrified glass article.