JP7149595B2 - glass and crystallized glass - Google Patents

Description

The present invention relates to glass and crystallized glass.

In recent years, in mobile devices such as smartphones and tablet terminals, glass has been used not only for the front display but also for the back cover and housing itself from the viewpoint of compatibility with contactless charging and/or from the viewpoint of design. It's becoming commonplace. In addition, there is an increasing demand for glass materials for such applications to have high strength and a high degree of freedom in shape (can be molded into complicated shapes).

Here, as a method of manufacturing a member having a complicated shape such as a housing of a mobile device using a glass material, there is a direct press method (hereinafter sometimes referred to as “DP”). This DP is a method in which a low-viscosity glass melt is directly received in a mold and pressed, and has the advantage of being able to produce a glass member at a relatively low cost.

On the other hand, various reports have so far been made on high-strength glass.
For example, Patent Literature 1 discloses tempered glass having a surface compressive stress of 300 MPa or more, in which the component composition is optimized.
Further, Patent Document 2 discloses that a glass-ceramic containing a lithium disilicate crystalline phase and a β-spodumene crystalline phase in a predetermined ratio can have high mechanical strength.
Furthermore, Patent Literature 3 discloses a glass-ceramic material containing lithium metasilicate (Li ₂ SiO ₃ ) as a main crystal, with an optimized component composition. It is reported that this glass-ceramic material is easy to machine as it is, but can be converted into a glass-ceramic product with excellent mechanical properties by heat treatment.

JP 2018-104285 A Japanese Patent Publication No. 2016-529201 JP-A-2005-053776

However, the tempered glass described in Patent Document 1 and the glass ceramic described in Patent Document 2 tend to have a high melt viscosity. Therefore, in order to fabricate a member from these materials by DP, it is necessary to heat them to an extremely high temperature, which is disadvantageous in terms of production cost and durability of molding equipment. The material described in Patent Document 3 also cannot be said to have a sufficiently low viscosity when converted into a melt, and there is room for improvement in terms of further reducing the viscosity of the melt.
In addition, the material described in Patent Document 3 does not take into consideration the formation of a compressive stress layer by ion exchange (chemical strengthening), so the ion exchangeability is low and the strength is insufficient.

In addition, members such as back covers and housings of mobile devices are required to be uniformly opaque so that the internal structure cannot be seen. In this regard, since the tempered glass described in Patent Document 1 is a transparent body, in order to use it for the above-mentioned member, it is necessary to separately perform opacification treatment such as surface coating, which increases the manufacturing process and manufacturing cost. bring. On the other hand, members such as front displays of mobile devices are required to be transparent. Cannot be used for parts.

Under these circumstances, a highly adaptable glass that can be easily converted into a crystallized glass and that can be provided with desired properties as it is (in an uncrystallized state) or crystallized. Material development is desired.

Therefore, according to the present invention, the viscosity of the melt is sufficiently low, and high-strength and uniform crystallized glass can be formed by crystallization treatment. To provide glass which effectively exhibits high strength by ion exchange (chemical strengthening) even in the state of glass. Another object of the present invention is to provide a homogeneous, high-strength crystallized glass that can be formed from the glass described above.

As a result of intensive studies to achieve the above object, the present inventors have found that the lithium silicate-based glass contains predetermined amounts of B ₂ O ₃ , P ₂ O ₅ and Na ₂ O, and also contains Al ₂ O ₃ . It has been found that a glass that satisfies the above purpose can be obtained by containing a small amount of SiO ₂ and Li ₂ O within a predetermined range. By subjecting such glass to a crystallization treatment, Li ₂ Si ₂ O ₅ crystals exhibiting high strength can be homogeneously precipitated.

That is, the glass of the present invention is
In mol% of oxide conversion,
SiO ₂ : 50% or more and 70% or less,
B ₂ O ₃ : more than 0% and 15% or less,
P ₂ O ₅ : more than 0% and 2% or less,
Al ₂ O ₃ : more than 0% and 0.5% or less,
Li ₂ O: 25% or more and 35% or less,
Na ₂ O: more than 0% and 10% or less,
K ₂ O: 0% or more and 5% or less,
TiO ₂ : 0% or more and 10% or less, ZrO ₂ : 0% or more and 10% or less, and having a composition in which the total of SiO ₂ and Li ₂ O is 95% or less. Such glass has a sufficiently low viscosity when melted, and can form a high-strength and uniform crystallized glass by crystallization treatment. Even in a state, it effectively exhibits high strength by ion exchange (chemical strengthening).

The glass of the present invention preferably has a viscosity of 100 dPa·s or less at 1200°C.

The glass of the present invention preferably has a compressive stress layer on its surface.

The glass of the present invention preferably has a three-point bending strength of 400 MPa or more as measured according to JIS R1601:2008.

Further, the crystallized glass of the present invention is
In mol% of oxide conversion,
SiO ₂ : 50% or more and 70% or less,
B ₂ O ₃ : more than 0% and 15% or less,
P ₂ O ₅ : more than 0% and 2% or less,
Al ₂ O ₃ : more than 0% and 0.5% or less,
Li ₂ O: 25% or more and 35% or less,
Na ₂ O: more than 0% and 10% or less,
K ₂ O: 0% or more and 5% or less,
TiO ₂ : 0% or more and 10% or less, ZrO ₂ : 0% or more and 10% or less, and having a composition in which the total of SiO ₂ and Li ₂ O is 95% or less, and
It is characterized by containing Li ₂ Si ₂ O ₅ crystals. Such crystallized glasses can be formed from the glasses described above, have high strength, and are homogeneous.

The crystallized glass of the present invention preferably has a 3-point bending strength of 200 MPa or more measured according to JIS R1601:2008.

The crystallized glass of the present invention preferably has a compressive stress layer on its surface.

The crystallized glass of the present invention preferably has a compressive stress layer on its surface and preferably has a three-point bending strength of 400 MPa or more measured according to JIS R1601:2008.

According to the present invention, the melt viscosity is sufficiently low, and high-strength and uniform crystallized glass can be formed by crystallization treatment, and the melt can be crystallized as it is (in the state of uncrystallized glass). Even in the state of glass, it is possible to provide glass that effectively exhibits high strength through ion exchange (chemical strengthening). Further, according to the present invention, it is possible to provide homogeneous crystallized glass having high strength, which can be formed from the glass described above.

1 is a scanning electron microscope (SEM) image (5000×) of crystallized glass according to an embodiment of the present invention. FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the external appearance of the crystallized glass which concerns on one Embodiment of this invention. 1 is a microscopic image (50 times) of crystallized glass according to an embodiment of the present invention. FIG. FIG. 10 is a microscopic image (50 times) of crystallized glass according to a comparative example. FIG. 2 shows an X-ray diffraction (XRD) pattern of crystallized glass according to one embodiment of the present invention;

(glass)
Hereinafter, the glass of one embodiment of the present invention (sometimes referred to as "the glass of the present embodiment") will be specifically described. The glass of the present embodiment has, in mol% in terms of oxide,
In mol% of oxide conversion,
SiO ₂ : 50% or more and 70% or less,
B ₂ O ₃ : more than 0% and 15% or less,
P ₂ O ₅ : more than 0% and 2% or less,
Al ₂ O ₃ : more than 0% and 0.5% or less,
Li ₂ O: 25% or more and 35% or less,
Na ₂ O: more than 0% and 10% or less,
K ₂ O: 0% or more and 5% or less,
TiO ₂ : 0% or more and 10% or less, ZrO ₂ : 0% or more and 10% or less, and having a composition in which the total of SiO ₂ and Li ₂ O is 95% or less. In this specification, unless otherwise specified, what is simply referred to as "glass" is "non-crystallized glass" or "non-crystallized glass" as opposed to "crystallized glass" described later. shall point to

Since the glass of the present embodiment has the predetermined composition described above, the viscosity of the melted glass is sufficiently low. Therefore, if the glass of this embodiment is used, a member having a complicated shape can be produced by DP, and cost reduction and mass production become possible. Further, since the glass of the present embodiment has the above-described predetermined composition, it can be converted into high-strength and homogeneous crystallized glass by crystallization treatment. Furthermore, the glass of this embodiment has a high ion-exchangeability due to the predetermined composition described above. Therefore, high strength can be effectively exhibited by ion exchange (chemical strengthening), either as it is (in the state of uncrystallized glass) or in the state of crystallized glass. That is, the glass of this embodiment has high adaptability as a glass material.

In addition, the glass of this embodiment may contain other components (described later) other than the components described above. However, the glass of the present embodiment has a composition (SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ , Li ₂ O and Na ₂ O as essential components, and K ₂ O, TiO ₂ and ZrO ₂ as optional components).
Here, "consisting only of the above-described components" includes cases in which impurity components other than the components are inevitably mixed, specifically, the ratio of the impurity components is 0.2 mol% or less. and

First, the reason for limiting the composition of the glass to the above range in the present embodiment will be described.
In addition, unless otherwise specified, "%" regarding components means mol% in terms of oxides.

< _SiO2 >
In the glass of this embodiment, SiO ₂ is an essential component that enables glass formation, and is an important component that constitutes Li ₂ Si ₂ O ₅ crystals that mainly precipitate when crystallized. However, if the content exceeds 70%, the viscosity of the glass melt may be significantly increased. On the other hand, when the content is less than 50%, there is a possibility that the glass-forming ability may be lowered, or Li ₂ Si ₂ O ₅ crystals may not be precipitated when crystallized. Therefore, in the glass of this embodiment, the content of SiO ₂ is set in the range of 50% or more and 70% or less. From the same point of view, the content of SiO ₂ in the glass of the present embodiment is preferably 52% or more, more preferably 54% or more, and still more preferably 56% or more. % or less, more preferably 66% or less, and even more preferably 64% or less.

< _{B2O3 >}
In the glass of the present embodiment, B ₂ O ₃ is a glass-forming component, lowers the viscosity of the glass melt, and further ion-exchanges in a chemical strengthening treatment (ion exchange treatment) using NaNO ₃ molten salt or the like. It is an important essential component that enhances the properties and promotes uniform crystallization. In addition, in the glass of the present embodiment, B ₂ O ₃ is also a component that suppresses shrinkage (increase in specific gravity) when the glass is crystallized. However, if the content exceeds 15%, there is a risk that homogeneous crystallization will not proceed. On the other hand, if it is not contained, the viscosity of the glass melt cannot be lowered, or homogeneous crystallized glass cannot be obtained. Therefore, in the glass of the present embodiment, the content of B ₂ O ₃ is in the range of more than 0% and 15% or less. From the same viewpoint, the content of B ₂ O ₃ in the glass of the present embodiment is preferably 1% or more, more preferably 3% or more, and preferably 12% or less.

< _{P2O5 >}
In the glass of this embodiment, P ₂ O ₅ is an important essential component that promotes homogeneous crystallization. However, if the content exceeds 2%, there is a possibility that the glass-forming ability may deteriorate. On the other hand, if it is not contained, crystals cannot be homogeneously precipitated when the crystallization treatment is performed. Therefore, in the glass of this embodiment, the content of P ₂ O ₅ is set to more than 0 to 2%. From the same point of view, the content of P ₂ O ₅ in the glass of the present embodiment is preferably 0.5% or more, preferably 1.5% or less, and 1% or less. is more preferred.

< _{Al2O3 >}
In the glass of the present embodiment, Al ₂ O ₃ is an important essential component that enhances the glass-forming ability and further enhances the ion-exchangeability in the chemical strengthening treatment using NaNO ₃ molten salt or the like. However, if the content exceeds 0.5%, there is a risk that the viscosity of the glass melt will be significantly increased, and that homogeneous crystallized glass cannot be obtained. On the other hand, if it is not contained, there is a possibility that the strength cannot be sufficiently improved by the chemical strengthening treatment. Therefore, in the glass of this embodiment, the content of Al ₂ O ₃ is more than 0% and 0.5% or less. From the same viewpoint, the content of Al ₂ O ₃ in the glass of the present embodiment is preferably 0.4% or less, more preferably 0.3% or less, and 0.2% or less. is more preferred.

< _Li2O >
In the glass of the present embodiment, Li ₂ O is an essential component that significantly reduces the viscosity of the glass melt, and constitutes Li ₂ Si ₂ O ₅ crystals that mainly precipitate when crystallized. , NaNO3 is an important component that becomes a source of Li ⁺ ions that are exchanged with Na ⁺ ions in chemical strengthening treatment using molten salts such as NaNO ₃ . However, if the content exceeds 35%, there is a risk that the glass-forming ability will decrease and the degree of deformation during crystallization will increase. On the other hand, if the content is less than 25%, the effect of reducing the viscosity of the glass melt is insufficient, and there is a risk that homogeneous crystallization will not proceed. There is a risk that it will not be possible to plan Therefore, in the glass of this embodiment, the content of Li ₂ O is set to 25% or more and 35% or less. From the same point of view, the content of Li ₂ O in the glass of the present embodiment is preferably 26% or more, more preferably 27% or more, further preferably 28% or more, and It is preferably 34% or less, more preferably 33% or less, even more preferably 32% or less.

<Total of SiO ₂ and Li ₂ O>
Here, in the glass of the present embodiment, when the total content of SiO ₂ and Li ₂ O exceeds 95%, even if the content of each of SiO ₂ and Li ₂ O is within the range described above, the glass is crystallized. There is a risk of an increase in the amount of volume (density) change when the steel is reinforced, a risk that homogeneous crystallization does not proceed, and a risk of a decrease in ion exchangeability in the chemical strengthening treatment. Therefore, in the glass of this embodiment, the total content of SiO ₂ and Li ₂ O is made 95% or less. From the same point of view, the total content of SiO ₂ and Li ₂ O in the glass of the present embodiment is preferably 92% or less, more preferably 90% or less. Further, the total content of SiO ₂ and Li ₂ O in the glass of the present embodiment is preferably 80% or more from the viewpoint of precipitating a sufficient amount of Li ₂ Si ₂ O ₅ crystals when crystallized.

< _Na2O >
In the glass of the present embodiment, Na ₂ O is an essential component that reduces the viscosity of the glass melt and enhances the glass _- forming ability when used in combination with Li ₂ O. It is an important component that enhances ion exchange between Na ⁺ ions and Li ⁺ ions during treatment, and serves as a source of Na ⁺ ions that are exchanged with K ⁺ ions in chemical strengthening treatments using KNO ₃ molten salt and the like. In addition, in the glass of the present embodiment, Na ₂ O is also a component that suppresses shrinkage (increase in specific gravity) when the glass is crystallized. However, if the content exceeds 10%, there is a risk that the glass-forming ability will decrease and the degree of deformation during crystallization will increase. On the other hand, if it is not contained, there is a risk that homogeneous crystallization will not proceed and that strength cannot be improved by chemical strengthening treatment. Therefore, in the glass of this embodiment, the content of Na ₂ O is set to more than 0% and 10% or less. From the same point of view, the content of Na ₂ O in the glass of the present embodiment is preferably 1% or more, preferably 8% or less, and more preferably 6% or less.

< _K2O >
In the glass of the present embodiment, K ₂ O is a component that reduces the viscosity of the glass melt and increases the exchangeability between K ⁺ ions and Na ⁺ ions in chemical strengthening treatment using KNO ₃ molten salt. . However, if the content exceeds 5%, there is a risk that the glass-forming ability will decrease and the degree of deformation during crystallization will increase. Therefore, in the glass of this embodiment, the content of K ₂ O is set to 0% or more and 5% or less. From the same point of view, the K ₂ O content in the glass of the present embodiment is preferably 4% or less, more preferably 3% or less, and even more preferably 2% or less.

< _TiO2 >
In the glass of this embodiment, TiO ₂ is a component that increases the opacity of the crystallized glass. However, if the content exceeds 10%, there is a risk that the ion exchangeability in the chemical strengthening treatment will be lowered, and that the degree of deformation during crystallization will increase. Therefore, in the glass of this embodiment, the content of TiO ₂ is set to 0% or more and 10% or less. From the same point of view, the content of TiO ₂ in the glass of the present embodiment is preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less.

< _ZrO2 >
In the glass of this embodiment, ZrO ₂ is a component that increases the opacity of the crystallized glass. However, if the content exceeds 10%, the viscosity of the glass melt may increase, the ion exchangeability in chemical strengthening treatment may decrease, and the degree of deformation during crystallization may increase. be. Therefore, in the glass of this embodiment, the content of ZrO ₂ is set to 0% or more and 10% or less. From the same point of view, the content of ZrO ₂ in the glass of the present embodiment is preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less.

<Other ingredients>
The glass of the present embodiment may contain other components other than the components described above, such as V ₂ O ₅ , Cr ₂ O ₃ , MnO, MnO ₂ , FeO, Fe ₂ O ₃ , Co ₂ O ₃ , as long as the purpose is not lost. , _Co3O4 , NiO, _CuO , _MoO3 , _{CeO2 , Pr2O3 , Nd2O3 , Sm2O3 , Eu2O3 , Tb2O3 , Dy2O3 , Ho2O3} , Er ₂ O ₃ and Tm ₂ O ₃ may be contained in a small amount (for example, in an amount of 10 mol % or less in terms of external ratio).
It should be noted that the calculation of the composition of each component (SiO ₂ , Li ₂ O, etc.) in the glass of the present embodiment does not consider the above other components.

Next, various characteristics of the glass of this embodiment will be described.

The glass of this embodiment is normally transparent. Therefore, the glass of this embodiment is suitable for producing members that require transparency, such as front displays of mobile devices.
In this specification, “transparent” with respect to glass means that the transmittance of any wavelength in visible light (wavelength 380 to 780 nm) is 80% or more in the glass with a thickness of 2.0 mm. do.

As described above, the glass of this embodiment has a sufficiently low viscosity when melted. More specifically, the glass of this embodiment can have a viscosity of 100 dPa·s or less at 1200°C. Further, the viscosity of the glass of the present embodiment at 1200° C. is more preferably 90 dPa·s or less, and even more preferably 80 dPa·s or less. Also, the viscosity of the glass of the present embodiment at 1200° C. is not particularly limited, but is preferably 5 dPa·s or more from the viewpoint of more reliable pressing in DP or the like.
The viscosity of the glass at 1200° C. can be adjusted, for example, by appropriately adjusting the composition of the glass.

The glass of this embodiment preferably has a compressive stress layer on its surface. As described above, since the glass of the present embodiment has high ion exchangeability, forming a compressive stress layer on the surface of the glass by ion exchange (chemical strengthening) or the like can effectively make the glass exhibit higher strength. can.
Formation of a compressive stress layer on the glass surface can be achieved, for example, by subjecting the glass to chemical strengthening treatment (ion exchange treatment), rapidly cooling the glass to strain the surface, or the like.

When the glass of this embodiment has a compressive stress layer on its surface, the glass can have a three-point bending strength of 400 MPa or more. Further, the three-point bending strength of the glass of the present embodiment is more preferably 420 MPa or more, and even more preferably 440 MPa or more.
In this specification, the three-point bending strength of glass is measured in accordance with JIS R1601:2008 "Room temperature bending strength test method for fine ceramics".

<Glass manufacturing method>
Next, a method for manufacturing glass according to the present embodiment will be described.
Here, the glass of the present embodiment may be manufactured according to a conventional manufacturing method without any particular limitation as long as the composition of each component satisfies the above-described range.
For example, first, as raw materials for each component that can be contained in the glass of the present embodiment, oxides, hydroxides, carbonates, nitrates, phosphates, and the like are weighed in predetermined proportions and thoroughly mixed to prepare a glass. raw material. Next, the raw materials for glass preparation are charged into a melting vessel (for example, a precious metal crucible) that does not react with glass raw materials, etc., heated to 1200 to 1500° C. in an electric furnace to melt, and stirred as appropriate. Next, the glass is clarified and homogenized in an electric furnace, cast into a mold preheated to an appropriate temperature, and then slowly cooled in an electric furnace to remove distortion, thereby obtaining the glass of the present embodiment. can. In addition, a small amount of Sb ₂ O ₃ (for example, an amount of 0.5 mol % or less in terms of outside ratio) can be added to improve the coloration of the glass and deaerate the glass.
Note that the above Sb ₂ O ₃ is not taken into account in the calculation of the composition of each component (SiO ₂ , Li ₂ O, etc.) in the glass of this embodiment.

Alternatively, the glass of this embodiment can also be produced by molding into a member having a predetermined shape by a direct press method (DP). More specifically, the raw materials for glass preparation as described above are heated to 1200 to 1500° C. in an electric furnace and melted. Next, after the obtained glass melt is heated to 1200° C. or lower, it is allowed to flow down to a mold having a predetermined shape through an outflow pipe or the like. Then, the glass melt flow is separated by forming a constricted portion by surface tension by using a shear blade or by rapidly lowering the mold directly below, and a glass melt lump having a desired mass is obtained. After that, the glass melt mass is pressed while being cooled in the mold to obtain a glass member having a predetermined shape (the glass of the present embodiment).
Molding by such DP is particularly suitable for manufacturing members having relatively large and complicated shapes, such as housings of mobile devices.

Moreover, the obtained glass can form a compressive stress layer on the surface by, for example, chemically strengthening treatment. More specifically, by immersing the glass in a heated molten salt of NaNO ₃ or KNO ₃ , Li ⁺ ions and Na ⁺ ions near the surface of the glass are replaced with ions having larger ionic radii, thus forming the glass. A compressive stress layer can be formed on the surface.

From the viewpoint of forming a compressive stress layer with higher strength, the temperature of the molten salt in the chemical strengthening treatment is preferably 360 to 440°C. Moreover, from the viewpoint of forming a compressive stress layer with higher strength, the immersion time in the chemical strengthening treatment is preferably 16 hours or less.

(crystallized glass)
Hereinafter, the crystallized glass of one embodiment of the present invention (sometimes referred to as "the crystallized glass of the present embodiment") will be specifically described. The crystallized glass of the present embodiment has, in terms of mol% of oxide,
SiO ₂ : 50% or more and 70% or less,
B ₂ O ₃ : more than 0% and 15% or less,
P ₂ O ₅ : more than 0% and 2% or less,
Al ₂ O ₃ : more than 0% and 0.5% or less,
Li ₂ O: 25% or more and 35% or less,
Na ₂ O: more than 0% and 10% or less,
K ₂ O: 0% or more and 5% or less,
TiO ₂ : 0% or more and 10% or less, ZrO ₂ : 0% or more and 10% or less, and having a composition in which the total of SiO ₂ and Li ₂ O is 95% or less, and
It is characterized by containing Li ₂ Si ₂ O ₅ crystals.
In this specification, the term "crystallized glass" refers to glass that partially contains crystals, and is generally synonymous with "glass ceramic".

Since the crystallized glass of the present embodiment has the above-described predetermined composition and contains Li ₂ Si ₂ O ₅ crystals, it has high strength and is homogeneous. The crystallized glass of the present embodiment can be obtained, for example, by subjecting the glass described above to a crystallization treatment. Also, it can be judged from the X-ray diffraction (XRD) pattern whether or not the Li ₂ Si ₂ O ₅ crystal is included. Moreover, the crystallized glass of the present embodiment has a high ion-exchangeability due to the predetermined composition described above. Therefore, high strength can be effectively exhibited by ion exchange (chemical strengthening).

A specific description of the composition (in terms of oxide) of the crystallized glass of the present embodiment is the same as the description of the composition of the glass described above, and is therefore omitted.

Examples of glass crystallization treatment include heat treatment and laser annealing.

The crystallized glass of the present embodiment can have a three-point bending strength of 200 MPa or more. Moreover, the three-point bending strength of the crystallized glass of the present embodiment is more preferably 220 MPa or more, and still more preferably 240 MPa or more.
The three-point bending strength of crystallized glass is measured in accordance with JIS R1601:2008 "Room temperature bending strength test method for fine ceramics".

The crystallized glass of the present embodiment preferably has a compressive stress layer on its surface. As described above, since the crystallized glass of the present embodiment has a high ion exchange property, by forming a compressive stress layer on the surface of the crystallized glass by ion exchange (chemical strengthening) or the like, it is possible to effectively crystallize higher strength. It can be expressed in glass.
The formation of a compressive stress layer on the crystallized glass surface can be achieved, for example, by subjecting the crystallized glass to a chemical strengthening treatment (ion exchange treatment), rapidly cooling the crystallized glass to strain the surface, or the like. .

When the crystallized glass of the present embodiment has a compressive stress layer on its surface, the crystallized glass can have a three-point bending strength of 400 MPa or more. Further, when the crystallized glass of the present embodiment has a compressive stress layer on its surface, the three-point bending strength of the crystallized glass is more preferably 420 MPa or more, further preferably 440 MPa or more.

<Method for producing crystallized glass>
The crystallized glass of the present embodiment is not particularly limited as long as the composition of each component satisfies the ranges described above and contains Li ₂ Si ₂ O ₅ crystals. It can be manufactured according to the manufacturing method.
For example, by heat-treating the glass (uncrystallized glass) described above in a temperature range higher than the glass transition temperature and at which the glass does not melt, Li ₂ Si ₂ O ₅ crystals are precipitated, and the crystallized glass of the present embodiment is obtained. Obtainable. The heat treatment temperature is preferably 500 to 800° C. from the viewpoint of obtaining the desired crystallized glass more reliably. Moreover, the heat treatment time is preferably 1 to 10 hours from the viewpoint of more reliably precipitating the desired crystals.

In addition, the crystallized glass of the present embodiment may be obtained by molding by direct pressing (DP) using raw materials for glass preparation. For example, during molding by DP, if the cooling rate in the temperature range of 500 to 800° C. is slow, crystals may precipitate in the glass.

In addition, the obtained crystallized glass can form a compressive stress layer on its surface by, for example, chemically strengthening treatment. A detailed description of the chemical strengthening treatment for crystallized glass is the same as the description for the chemical strengthening treatment for glass, and is therefore omitted.

EXAMPLES The glass of the present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

As raw materials for each component shown in Tables 1 and 2, oxides, hydroxides, carbonates, nitrates, phosphates, etc. corresponding to each are weighed so as to be 100 g after vitrification, and thoroughly mixed. , put into a platinum crucible, and melted in an electric furnace at 1200 to 1500° C. for 1 to 2 hours. After that, it was stirred as needed to homogenize it, clarified it, cast it in a mold preheated to an appropriate temperature, and then slowly cooled in an electric furnace to remove distortion, thereby performing Examples 1 to 10 and Glasses (uncrystallized glasses) of Comparative Examples 1 to 10 were obtained. It was confirmed that at least the glasses of Examples 1 to 10 were transparent.

Further, each glass (uncrystallized glass) was heat-treated in an electric furnace at 800° C. or less for 1 to 10 hours (see Tables 1 and 2) to obtain crystallized glass.

Furthermore, each glass (uncrystallized glass) and crystallized glass is subjected to chemical strengthening treatment, more specifically, immersed in a molten salt of NaNO ₃ or KNO ₃ heated to 360 to 440 ° C. for 16 hours or less. (see Tables 1 and 2) to form a compressive stress layer on the surface.

In each example and comparative example, according to the procedure shown below, the viscosity of the glass at 1200 ° C. was measured, the homogeneity of the crystallized glass was evaluated, and the three-point bending strength (glass with a compressive stress layer formed, compression for crystallized glass in which no stress is formed and crystallized glass in which a compressive stress layer is formed). Furthermore, in the crystallized glass of each example and comparative example, the three-point bending strength increase rate associated with the formation of the compressive stress layer was calculated. Tables 1 and 2 show the results.

The viscosity of the glass at 1200°C was measured by the rotating cylinder method. Specifically, a platinum cylinder was immersed in a glass melt at 1200° C., and the viscosity was determined from the rotational force (torque) received by the cylinder when the cylinder was rotated.

The homogeneity of the crystallized glass was evaluated by observing the appearance of the cross section of the crystallized glass (without compressive stress layer) visually and with a microscope (50x magnification) and according to the following criteria.
A: No bias in crystal precipitation is observed even under a microscope B: No bias is observed visually, but a bias is observed under a microscope C: A bias in crystal precipitation is observed visually, or crystals are For reference, regarding the crystallized glass of Example 1 (without compressive stress layer), an image (5000 times) by a scanning electron microscope (SEM) is shown in FIG. The image (50x magnification) is shown in FIG. Further, FIG. 4 shows a microscopic image (50 times) of the crystallized glass of Comparative Example 8 (without compressive stress layer).
In the image of FIG. 1, relatively dark regions are Li ₂ Si ₂ O ₅ crystals, and relatively bright regions are vitreous.

The three-point bending strength was measured according to JIS R1601:2008 "Room temperature bending strength test method for fine ceramics".

It was confirmed from the XRD patterns that Li ₂ Si ₂ O ₅ crystals were deposited in at least the crystallized glasses of Examples 1 to 10. For reference, the XRD pattern of the crystallized glass of Example 1 is shown in FIG.

Further, the specific gravity of the glass (uncrystallized glass) and the crystallized glass of Example 1 and Comparative Example 7 was measured according to JOGIS05-1975 "Method for measuring specific gravity of optical glass". As a result, the specific gravities of the uncrystallized glass and crystallized glass of Example 1 were 2.405 and 2.424, respectively, and the specific gravities of the uncrystallized glass and crystallized glass of Comparative Example 7 were 2.360, respectively. and 2.479.

From Table 1, it can be seen that the glasses according to Examples 1 to 10 all have sufficiently low viscosities of melts, and are therefore suitable for producing members by DP. Further, from Table 1, it can be seen that the glasses provided with a compressive stress layer on the surface according to Examples 1 to 10 all have a three-point bending strength of 400 MPa or more, indicating high strength.

Further, from Table 1, it can be seen that the crystallized glasses of Examples 1 to 10 obtained by heat treatment all have high homogeneity and high strength, with a three-point bending strength of 200 MPa or more. . In particular, as shown in FIG. 3, the crystal structure (pattern) of the crystallized glass of Example 1 was not confirmed in a 50-fold microscope image, so it is clear that the precipitation of crystals was uniform and uniform. be. Such homogeneity is also evident from FIG. 2 showing the appearance of the crystallized glass of Example 1. FIG.

Further, all the crystallized glasses having a compressive stress layer on the surface according to Examples 1 to 10 had a three-point bending strength of 400 MPa or more, indicating high strength. In particular, in the crystallized glasses of Examples 1 to 10, the rate of increase in three-point bending strength due to the formation of the compressive stress layer was large, indicating that the ion exchange effectively improved the strength.

On the other hand, Table 2 shows that in Comparative Examples 1 to 10, one or both of the viscosity of the glass melt and the homogeneity of the crystallized glass are not good. In addition, in Comparative Example 9, vitrification was not performed. This is probably due to too much _Li2O . In addition, from FIG. 4, the crystal structure (pattern) of the crystallized glass of Comparative Example 8 was confirmed in a 50-fold microscope image, which indicates that the precipitation of crystals is biased and non-uniform.

In addition, in Comparative Examples 1 to 10, many of the glass or crystallized glass do not have sufficiently high three-point bending strength. Furthermore, in the crystallized glasses of Comparative Examples 1 to 10, the three-point bending strength increase rate due to the formation of the compressive stress layer is small, that is, in many cases, effective strength improvement by ion exchange cannot be achieved. I understand.

Furthermore, in Example 1, by crystallizing the glass, the specific gravity changed from 2.405 to 2.424, that is, the rate of change in specific gravity was 0.79%. On the other hand, in Comparative Example 7, by crystallizing the glass, the specific gravity changed from 2.360 to 2.479, that is, the specific gravity change rate was 5.04%. From this, it can be seen that the glass of Example 1 undergoes less dimensional change even after crystallization than the glass of Comparative Example 7, and can easily maintain the shape before crystallization during molding by DP or the like. .

According to the present invention, the melt viscosity is sufficiently low, and high-strength and uniform crystallized glass can be formed by crystallization treatment, and the melt can be crystallized as it is (in the state of uncrystallized glass). Even in the state of glass, it is possible to provide glass that effectively exhibits high strength through ion exchange (chemical strengthening). Further, according to the present invention, it is possible to provide homogeneous crystallized glass having high strength, which can be formed from the glass described above.

Claims (8)

In mol% of oxide conversion,
SiO ₂ : 50% or more and 70% or less,
B ₂ O ₃ : more than 0% and 15% or less,
P ₂ O ₅ : more than 0% and 2% or less,
Al ₂ O ₃ : more than 0% and 0.4 % or less,
Li ₂ O: 25% or more and 35% or less,
Na ₂ O: more than 0% and 10% or less,
K ₂ O: 0% or more and 5% or less,
TiO ₂ : 0% or more and 10% or less ZrO ₂ : 0% or more and 10% or less, and having a composition in which the total of SiO ₂ and Li ₂ O is 95% or less. 2. The glass of claim 1, having a viscosity at 1200[deg.] C. of 100 dPa.s or less. 3. The glass according to claim 1 or 2, comprising a compressive stress layer on its surface. 4. The glass according to claim 3, which has a three-point bending strength of 400 MPa or more as measured according to JIS R1601:2008. In mol% of oxide conversion,
SiO ₂ : 50% or more and 70% or less,
B ₂ O ₃ : more than 0% and 15% or less,
P ₂ O ₅ : more than 0% and 2% or less,
Al ₂ O ₃ : more than 0% and 0.4 % or less,
Li ₂ O: 25% or more and 35% or less,
Na ₂ O: more than 0% and 10% or less,
K ₂ O: 0% or more and 5% or less,
TiO ₂ : 0% or more and 10% or less, ZrO ₂ : 0% or more and 10% or less, and having a composition in which the total of SiO ₂ and Li ₂ O is 95% or less, and
A crystallized glass comprising Li ₂ Si ₂ O ₅ crystals. 6. The crystallized glass according to claim 5, which has a three-point bending strength of 200 MPa or more as measured according to JIS R1601:2008. Crystallized glass according to claim 5 or 6, having a compressive stress layer on its surface. The crystallized glass according to claim 7, which has a three-point bending strength of 400 MPa or more as measured according to JIS R1601:2008.

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