JP2013245151A - Crystallized glass for housing and method for producing crystallized glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide crystallized glass for a housing which is highly strengthened by performing the ion exchanging of nepheline-based crystallized glass at a low ion exchanging temperature and which has a suitable shielding property for the housing of an electronic device, and to provide a method for producing the crystallized glass.SOLUTION: There is provided crystallized glass for a housing which has transmittance of light at a wavelength of 400 nm of 20% or less and which is obtained by performing the ion exchanging of the crystallized glass including a nepheline solid solution crystal corresponding to formula denoted as NaKAlSiO(wherein, x is changeable in a range of 0-8) as a main crystal phase.

Description

  The present invention relates to a crystallized glass for a casing used as an exterior member of an electronic device such as a communication device or an information device that can be carried and used, and a method for producing the crystallized glass.

  Cases of electronic devices such as mobile phones or smartphones are used by appropriately selecting materials such as resin or metal in consideration of various factors such as decoration, scratch resistance, workability, and cost. . In recent years, attempts have been made to use glass, which has not been used conventionally, as a casing material (Patent Document 1). According to Patent Document 1, in an electronic device such as a mobile phone, it is said that a unique decoration effect with a sense of transparency can be exhibited by forming the casing body from glass.

  The electronic device includes a display device such as a liquid crystal panel on the outer surface of the device. These display devices tend to have high definition and high brightness, and accordingly, backlights serving as light sources also tend to have high brightness. In addition to irradiating the light from the light source on the display device side, the light may reach the back surface of the housing that is multiple-reflected inside the device and is covered.

  Further, even in an organic EL (Electro-Luminescence) display that does not require a light source, there is a concern that light leaks from the light emitting element. When metal is used as the material of the housing, there is no problem, but when glass having transparency as described above is used, light from the light source may pass through the housing and be recognized from the outside of the device.

  Therefore, in a casing of an electronic device such as a mobile phone or a smartphone, light shielding properties are required so that components inside the device cannot be seen. Therefore, when glass is used for the housing, light shielding means such as a coating film is provided on the back surface of the glass to give the glass a shielding property against visible light (hereinafter referred to as a shielding property).

  As described above, with the increase in the brightness of the light source of the display device, in order to form a coating film having sufficient shielding properties on the back surface (device side) of the glass, the coating film can be formed into a thick film or from a plurality of layers. A film to be formed, which increases the number of processes and increases the cost.

  Moreover, when a coating film is not formed uniformly, there exists a possibility of impairing the beauty | look of apparatuses, such as light permeate | transmitting only the location where a coating film is thin, and a housing | casing being recognized brightly locally. For example, in a concave housing, it is necessary to form a uniform film over the entire concave surface. However, the process of uniformly forming a coating film having sufficient shielding properties on the concave surface is complicated, which increases the cost.

  In particular, when obtaining a casing having a white appearance, as described above, there is a method of forming a white coating film layer on at least one surface of the transparent glass. However, the white paint has high translucency, and sufficient shielding properties cannot be obtained even if the white coating layer is thickened.

  For this reason, a black coating layer having a high shielding property is laminated on the white coating layer. In this case, it is necessary to increase the thickness of the white coating layer to such an extent that the black coating layer is not recognized. Thus, there is a problem that it is very expensive to obtain a highly shielding housing that exhibits white using a white paint.

  In addition, in an electronic device such as a mobile phone or a smartphone, high strength is required for the housing in consideration of damage due to a drop impact during use or contact damage due to long-term use. In addition, electronic devices such as mobile phones and smartphones are required to be lightweight and thin in order to be differentiated by thin design or to reduce the burden for movement, and are required to increase strength. Therefore, conventionally, in order to improve the scratch resistance of the glass, the glass is chemically strengthened to form a compressive stress layer on the surface to enhance the scratch resistance of the glass.

JP 2009-61730 A

  Accordingly, an object of the present invention is to provide a crystallized glass for a casing and a method for manufacturing the crystallized glass having a decorative property or shielding property and strength suitable for a casing of an electronic device.

That is, the present invention is as follows.
1. A crystallized glass for a casing obtained by subjecting a crystallized glass having a transmittance at a wavelength of 400 nm of 20% or less and containing a nepheline solid solution crystal to an ion exchange treatment.
2. Ion exchange treatment of crystallized glass having a transmittance of 20% or less at a wavelength of 400 nm and containing crystals of Na _8-x K _x Al ₈ Si ₈ O ₃₂ (where x varies in the range of 0 to 8) Crystallized glass for a casing obtained by doing so.
3. 3. The casing according to item 1 or 2 above, wherein the main crystal phase of the crystallized glass is a nepheline solid solution crystal corresponding to Na ₈ -xK _x Al ₈ Si ₈ O ₃₂ (where x varies in the range of 0 to 8). Crystallized glass for body. Here, the main crystal phase is a crystal in which a peak having the highest intensity is obtained when X-ray diffraction measurement is performed on the crystallized glass.
4). The crystallized glass for a casing according to any one of items 1 to 3, wherein the crystallinity of the crystallized glass is 20 to 70%.
5. 5. The crystallized glass for a casing according to any one of items 1 to 4, wherein the crystallized glass contains Na ₂ O.
6). 6. The crystallized glass for a casing described in any one of 1 to 5 above, wherein the crystallized glass contains SiO ₂ and Al ₂ O ₃ .
7). 7. The crystallized glass for a casing according to 5 or 6 above, wherein the crystallized glass contains at least 1 selected from TiO ₂ and K ₂ O.
8). The SiO ₂ 40 to 70% crystallized glass in mole percentage based on the following oxides, _{Al 2 O 3 8~28%, 10~30} % of Na ₂ O, containing _{K 2} O 0% 8. The crystallized glass for a casing described in any one of 1 to 7 above, which is obtained by heat-treating glass.
Here, for example, K 2 _O and to contain 0 to 10% is, K 2 _O is not essential may be incorporated within a range of 10% or less, a meaning, also, the glass of the present invention Components other than these five components may be contained as long as the purpose is not impaired. In that case, the total content of these components is preferably 10% or less, and typically 5% or less.
Moreover, in this specification, content of a glass component is displayed by mol percentage.
9. 9. The crystallized glass for a casing according to any one of 1 to 8 above, wherein the depth of the compressive stress layer is 10 μm or more.
10. The manufacturing method of the crystallized glass which contains the following processes (1) and (2) sequentially.
(1) Glass containing 40 to 70% of SiO ₂ , 8 to 28% of Al ₂ O ₃ , 10 to 30% of Na ₂ O, and 0 to 10% of K ₂ O in a molar percentage display based on the following oxides. Step 2 of heat treating glass at 950 ° C. or lower for 1 to 10 hours Step 2 of heat treating the glass heat treated in Step (1) at 850 to 1200 ° C. for 1 to 10 hours 11. A method for producing crystallized glass that has been subjected to ion exchange treatment, wherein the crystallized glass produced by the method for producing crystallized glass according to item 10 is subjected to ion exchange treatment at 520 ° C. or lower.

  According to the present invention, the nepheline-based crystallized glass is chemically strengthened by ion exchange treatment, so that the glass has a suitable shielding property for a housing of an electronic device without separately providing light shielding means such as a light shielding film, and High-strength crystallized glass for casings can be obtained at low cost. Alternatively, crystallized glass for a housing having design properties and high strength can be obtained at a low cost.

It is a figure which shows the result (magnification 100,000 times) which confirmed the crystallized glass containing a nepheline solid solution crystal | crystallization by SEM.

  Hereinafter, preferred embodiments of the crystallized glass for a casing of the present invention will be described.

  The crystallized glass for a casing of the present invention is packaged in, for example, an electronic device. As for the outer surface of the mobile phone, a display device made up of a liquid crystal panel or an organic EL display and an operation device made up of buttons or an integrated display device such as a touch panel and an operation device are arranged on one outer surface. The frame material surrounds the periphery. The other outer surface is composed of a panel. And there exists a frame material in the thickness part of the apparatus between one outer surface and the other outer surface. The frame material and the frame material, or the panel and the frame material may be configured integrally.

  The crystallized glass for a casing of the present invention can be used for any of the frame material, the panel, and the frame material. Further, these shapes may be flat, or may be a concave shape or a convex shape in which the frame material and the frame material, or the panel and the frame material are integrated.

  A light source of a display device provided in an electronic device is configured to emit white light such as a light emitting diode, an organic EL, or a CCFL. Some organic EL displays include a light emitting element that emits white light or the like without using the light source. When these white light leaks out of the device through the crystallized glass casing, the appearance is deteriorated. Therefore, the crystallized glass casing needs to have a characteristic of reliably blocking white light. Alternatively, by being translucent, it is possible to exhibit a unique decorative effect that is transparent and soft.

  The reason for using the crystallized glass for a casing of the present invention for the casing is as follows. Crystallized glass is obtained by precipitating fine crystal particles inside glass, has high mechanical strength and hardness, and has excellent heat resistance, electrical characteristics, and chemical durability. Crystallized glass has a white appearance as crystal particles in the glass diffuse and reflect and scatter light at the interface. The crystallized glass for a casing of the present invention makes white light transmitted through the glass difficult to recognize on the surface side of the glass by utilizing light scattering of the crystallized glass, or has a design property.

  The crystallized glass for a casing of the present invention is obtained by ion-exchange treatment of crystallized glass having a transmittance of 20% or less at a wavelength of 400 nm and containing nepheline solid solution crystals.

Crystallized glass containing nepheline solid solution crystals Crystallized glass containing nepheline solid solution crystals can be produced through heat treatment of the precursor as described in US Pat. No. 2,920,971. In the production of crystallized glass containing nepheline solid solution crystals, the following steps (i) to (iii) are included.
(I) Melting a glass-forming batch that usually contains a nucleating agent.
(Ii) At the same time, the melt is cooled to a temperature lower than its transition range to form a glass having a desired shape.
(Iii) The glass is subjected to a prescribed heat treatment method to crystallize the glass.

The step (iii) is divided into the following two steps (iii-1) and (iii-2).
(Iii-1) First, the original glass is heated to a temperature within or slightly higher than the transition range to form nuclei in the glass. As conditions for the heat treatment for generating nuclei in the glass, the temperature is preferably 950 ° C. or lower, and more preferably 900 ° C. or lower. Further, the heat treatment time is preferably 1 to 10 hours, and more preferably 2 to 6 hours.
(Iii-2) The glass is heated to a higher temperature, sometimes higher than its softening point, to grow crystals on the nuclei formed in (iii-1). As conditions for the heat treatment for growing the crystal, the temperature is preferably 850 to 1200 ° C., more preferably 900 to 1150 ° C. Further, the heat treatment time is preferably 1 to 10 hours, and more preferably 2 to 6 hours.

  The crystallized glass containing nepheline solid solution crystals obtained by heat treatment under the conditions within the above range is easy to ion-exchange, and the crystallized glass is ion-exchanged to provide a high light shielding property suitable for the casing. Strength can be obtained.

  In the crystallization mechanism, crystals grow substantially simultaneously on innumerable nuclei formed in advance, so that a fine-structured nepheline solid solution containing relatively uniform sized fine crystals uniformly distributed in the glass matrix Crystallized glass containing crystals is obtained, and these crystals occupy most of the glass.

Nepheline solid solution crystals are crystals represented by the formula _{Na 8-x K x Al 8} Si 8 O 32 ( the formula x varies from 0-8). Nepheline solid solution crystals have high ion exchange efficiency, and high strength can be obtained in addition to light shielding properties that are more suitable for the housing by subjecting the crystallized glass containing the crystals to ion exchange treatment.

  Further, the main crystal phase of the crystallized glass is preferably nepheline solid solution crystal. The main crystal phase of the crystallized glass is nepheline solid solution crystal, so that high ion exchange efficiency can be obtained, and the crystallized glass having the nepheline solid solution crystal as the main crystal phase is ion-exchanged so that it is more suitable for the casing. In addition to light shielding properties, high strength can be obtained.

  Typically, 20-90% of crystallized glass containing nepheline solid solution crystals is crystalline. In the present invention, the crystallinity of the crystallized glass containing nepheline solid solution crystals is preferably 20 to 70%, and more preferably 40 to 65%. By setting the degree of crystallinity to 70% or less, ions diffuse in the glass phase during the ion exchange treatment, and the ions are exchanged in the crystal phase by the diffused ions. Is obtained. Moreover, since it whitens by scattering of a crystal phase, the obtained crystallized glass can have light-shielding property suitable for a housing | casing.

As will be described later in the Examples section, the crystallinity C of the crystallized glass containing nepheline solid solution crystal is measured by X-ray diffraction measurement in addition to the crystallized glass containing nepheline solid solution crystal using a crystal other than nepheline solid solution crystal as a reference sample. To obtain the ratio a of the X-ray diffraction intensities of the reference sample and nepheline solid solution crystal, and calculate from the mass ratio b and a of the reference sample and crystallized glass by the following equation.
C = A × a × (b / 1−b)

  Here, A is a constant referred to as a reference intensity ratio (RIR), which is a database diffraction PD that is databased from the International Center for Diffraction Data (http://www.icdd.com/). -2 Use the value shown in Release 2006.

The crystal phase that appears in nepheline solid solution crystals depends on the composition of the original glass and the heat treatment applied to the glass. “Nephelin” refers to a natural mineral having a crystal structure belonging to the hexagonal system and identified by the general chemical formula Na _8-x K _x Al ₈ Si ₈ O ₃₂ (x is 0 to 8). However, it has been found that the mineral nepheline exists as a wide range of solid solutions, the degree of which is not fully understood by the above formula (Geophical Laboratory, Paper No 1309, 'Nepheline Solid Solutions').

  The same applies to crystallized glass containing nepheline solid solution crystals, and the range of solid solutions is even wider because crystal growth occurs under unbalanced conditions. Therefore, metastable crystal glass can grow. The crystal phase of crystallized glass containing nepheline solid solution crystals may change substantially, and these crystals show a common diffraction peak with nepheline solid solution crystals in X-ray diffraction analysis, but the peak spacing and intensity are the same as those of the crystal phase. It may vary depending on the nature.

The crystallized glass containing nepheline solid solution crystals preferably contains Na ₂ O. When the crystallized glass containing the nepheline solid solution crystal contains Na ₂ O, the strength of the crystallized glass by the subsequent ion exchange treatment can be increased. The content of Na ₂ O in the crystallized glass containing nepheline solid solution crystals is preferably 10 to 30%, more preferably 12 to 24%, and still more preferably 15 to 20%.

SiO ₂ and Al ₂ O ₃ are the main components of nepheline solid solution and are essential. The content of SiO ₂ in the crystallized glass containing nepheline solid solution crystals is preferably 40 to 70%, and more preferably 45 to 64%. The content of Al ₂ O ₃ in the crystallized glass containing nepheline solid solution crystals is preferably 8 to 28%, more preferably 15 to 25%, and still more preferably 20 to 24%.

In crystallized glass containing nepheline solid solution crystals, TiO ₂ is essential as a nucleation material.

The content of TiO ₂ in the crystallized glass containing nepheline solid solution crystals is preferably 4 to 12%, and more preferably 5 to 10%.

The crystallized glass containing nepheline solid solution crystals may contain K ₂ O. K ₂ O is one of the components that form nepheline solid solution crystals, is a component that improves meltability, and is a component that increases the ion exchange rate in chemical strengthening. In order to improve the ion exchange rate, the effect is small at less than 1%. Preferably it is 2% or more. When K ₂ O exceeds 10%, the weather resistance decreases. Preferably it is 8% or less.

  The crystallized glass containing nepheline solid solution crystals is preferably whitened. By forming the crystallized glass for housing of the present invention obtained by ion-exchange treatment of crystallized glass containing nepheline solid solution crystal having whitening and light-shielding properties, it is possible to reduce the light without providing a light-shielding means separately. A highly shielding housing that exhibits a white appearance at a low cost can be obtained. Moreover, the housing | casing provided with the designability is obtained.

  The transmittance of the crystallized glass containing nepheline solid solution crystals is preferably 20% or less at a wavelength of 400 nm and 80% or less at a wavelength of 800 nm. In order to make it semi-transparent in order to have design properties, the transmittance at a wavelength of 800 nm is preferably 10 to 80%. In order to provide shielding properties, the transmittance at a wavelength of 400 nm and the transmittance at a wavelength of 800 nm are preferably 10% or less. More preferably, it is 5% or less, More preferably, it is 1% or less. The transmittance of crystallized glass containing nepheline solid solution crystals can be measured by ordinary transmittance measurement (linear transmittance measurement).

  The transmittance of crystallized glass containing nepheline solid solution crystals can be adjusted by adjusting the glass composition and crystallization treatment conditions.

  In the crystallized glass for casing of the present invention, Co, Mn, Fe, Ni, Cu, Cr, V, Zn, Bi, Er, Tm, Nd, Sm, Sn, Ce, Pr, Eu, Ag are used as coloring components. Alternatively, Au may be added. When added, it is 5% or less in terms of mol% based on oxide.

(2) Ion exchange treatment The crystallized glass for a casing of the present invention is obtained by chemically strengthening the crystallized glass containing the nepheline solid solution crystal by ion exchange treatment. Chemical strengthening is a method of increasing the strength of glass by forming a compressive stress layer on the glass surface. Specifically, alkali metal ions (typically Li ions, Na ions) having a small ion radius on the surface of the glass plate by ion exchange at a temperature below the glass transition point are converted to alkali ions (typically Is a process of exchanging Na ions or K ions for Li ions and K ions for Na ions.

The chemical strengthening method is not particularly limited as long as Li ₂ O or Na ₂ O on the glass surface layer and Na ₂ O or K ₂ O in the molten salt can be ion-exchanged. For example, heated potassium nitrate (KNO ₃ ) A method of immersing glass in molten salt.

  The conditions of the ion exchange treatment for forming a chemically strengthened layer (surface compressive stress layer) having a desired surface compressive stress on the glass vary depending on the thickness of the glass, but the temperature condition is preferably 520 ° C. or lower. 500 ° C. or lower, more preferably 350 ° C. or higher, and more preferably 400 ° C. or higher.

  Silica glass containing nepheline solid solution crystals is ion-exchanged at 520 ° C. or lower to prevent potassium nitrate from decomposing and becoming potassium nitrite, and metal such as stainless steel is not affected by potassium nitrite. There is an advantage that it is not necessary to perform the ion exchange treatment in a container or the like, and the cost for the ion exchange treatment can be suppressed.

The time for the ion exchange treatment is preferably 1 to 72 hours, and more preferably 2 to 24. In order to improve productivity, 12 hours or less is preferable. Examples of the molten salt include KNO ₃ . Specifically, for example, it is typical to immerse the glass in KNO ₃ molten salt at 400 to 500 ° C. for 1 to 72 hours.

  The crystallized glass for a casing of the present invention has a compressive stress layer on the surface by ion exchange treatment. In the production of the crystallized glass for a casing of the present invention, a polishing step may be performed when the glass is flat. In the glass polishing process, the grain size of the abrasive grains used in the final stage of polishing is typically 2 to 6 μm. By such abrasive grains, the surface of the glass finally has a maximum size of 5 μm. It is thought that a crack is formed.

  In order to make the strength improvement effect by chemical strengthening effective, it is preferable that there is a surface compressive stress layer deeper than the microcracks formed on the glass surface, and the depth of the surface compressive stress layer generated by chemical strengthening is 6 μm or more. Is preferred. In addition, if a scratch exceeding the depth of the surface compressive stress layer is caused during use, it leads to glass breakage. Therefore, the surface compressive stress layer is preferably deeper, more preferably 10 μm or more, more preferably 20 μm or more, typically 30 μm or more.

  On the other hand, when the surface compressive stress layer is deep, the internal tensile stress increases and the impact at the time of fracture increases. That is, it is known that when the internal tensile stress is large, the glass tends to break up into pieces when it breaks. In a glass having a thickness of 1 mm or less, when the depth of the surface compressive stress layer exceeds 70 μm, scattering at the time of breaking becomes significant.

  Therefore, in the crystallized glass for a casing of the present invention, the depth of the surface compressive stress layer is preferably 70 μm or less. The crystallized glass for a casing of the present invention depends on the exterior electronic device, but for applications such as panels where the probability of contact scratches on the surface is high, the depth of the surface compressive stress layer is reduced for safety. More preferably, it is 60 μm or less, more preferably 50 μm or less, and typically 40 μm or less.

  The surface compressive stress CS (unit: MPa) and the compressive stress layer thickness DOL (unit: μm) of the crystallized glass for casing of the present invention can be measured by measuring birefringence. The depth of the surface compressive stress layer can be measured using EPMA (electron probe microanalyzer) or the like.

  Further, it is possible to apply surface compressive stress due to a difference in thermal expansion by thinly coating the surface with glass having a smaller thermal expansion coefficient than the crystallized glass for housing of the present invention. If clear glass is used, the effect of improving the aesthetics due to the reflection of the front and back surfaces of the coated glass can be obtained.

  In order to whiten the crystallized glass containing nepheline solid solution crystals, the average particle diameter of the crystals is preferably 50 to 2000 nm, and more preferably 100 to 1000 nm. The average particle diameter of the crystal can be measured by SEM observation.

  The crystallized glass for a casing of the present invention is packaged, for example, on an electronic device. On the outer surface of the mobile phone, a display device made up of a liquid crystal panel or an organic EL display and an operation device made up of buttons, or a display device such as a touch panel integrated with an operation device is arranged on one outer surface. The frame material surrounds the periphery. The other outer surface is composed of a panel. And there exists a frame material in the thickness part of the apparatus between one outer surface and the other outer surface. The frame material and the frame material, or the panel and the frame material may be configured integrally.

  The crystallized glass for a casing of the present invention can be used for any of the above-described frame materials, panels, and frame materials. In addition, these shapes may be flat or curved, and may be a concave shape or a convex shape in which the frame material and the frame material, or the panel and the frame material are integrated. Good.

  A light source of a display device provided in an electronic device is configured to emit white light such as a light emitting diode, an organic EL, or a CCFL. Some organic EL displays include a light emitting element that emits white light or the like without using the light source. If these white light leaks out of the device through the crystallized glass for the casing, the appearance will deteriorate. Therefore, it is preferable that the crystallized glass for a housing has a characteristic of reliably blocking white light.

  Further, the crystallized glass for a casing of the present invention is characterized by excellent mechanical strength. Therefore, it can be preferably used for a crystallized glass casing of a portable electronic device such as a mobile phone that requires high strength to the casing.

  The crystallized glass for a housing of the present invention may be formed not only in a flat plate shape but also in a concave shape or a convex shape. In this case, you may press-form in the state which reheated and melt | dissolved the glass shape | molded in the flat plate or the block. Moreover, you may shape | mold into a desired shape by what is called a direct press method which flows out and press-molds a molten glass directly on a press die. Further, a portion corresponding to a display device or a connector of an electronic device may be processed simultaneously with press molding, or may be subjected to cutting after press molding.

  The crystallized glass for a casing of the present invention can be suitably used for a portable electronic device. A portable electronic device is a concept that encompasses communication devices or information devices that can be carried around.

  Examples of the communication device include a mobile phone, a PHS (Personal Handy-phone System), a smartphone, a PDA (Personal Data Assistance), and a PND (Portable Navigation Device, a portable car navigation system) as a communication terminal. Examples of the device include a portable radio, a portable television, and a one-segment receiver.

  Examples of information devices include digital cameras, video cameras, portable music players, sound recorders, portable DVD players, portable game machines, notebook computers, tablet PCs, electronic dictionaries, electronic notebooks, electronic book readers, portable printers, and mobile phones. For example, a scanner. In addition, it is not limited to these for illustration.

  By using the crystallized glass for a casing of the present invention for these portable electronic devices, a portable electronic device having high strength and aesthetic appearance can be obtained.

  Note that the chemically tempered glass of the present invention having high strength and aesthetics can be applied to desktop personal computers, large television sets, building materials, furniture, home appliances, and the like.

(1) Glass transition point (° C)
The glass transition point (Tg) is measured by preparing a cylindrical glass sample having a diameter of 5 mm and a length of 20 mm, and using a thermal expansion meter TD5010SA manufactured by Bruker AXS, Inc., at a rate of temperature increase of 5 ° C./min. Determined by

(2) Transmittance (%)
The transmittance of the glass is about 20 mm × about 20 mm × thickness about 1 mm, and a sample whose upper and lower surfaces are mirror-finished is prepared using a Perkin-Elmer ultraviolet-visible near-infrared spectrophotometer Lambda950. A spectral transmittance curve with a wavelength of 400 to 800 nm was obtained.

(3) Three-point bending strength (MPa)
The three-point bending strength was measured by a three-point bending test under the conditions of a span of 30 mm and a crosshead speed of 0.5 mm / min. After chemically strengthening a glass plate with a thickness of 1 mm and a size of 5 mm × 40 mm and mirror-polished on both sides with cerium oxide, Vickers hardness is applied at the center of each glass plate at a temperature of 20 to 28 ° C. and a humidity of 40 to 60%. Using a meter, a Vickers indenter was driven with a force of 20 kgf = 196 N to form an indentation, and the bending strength (unit: MPa) was measured.

(4) Surface compressive stress (CS), compressive stress layer depth (DOL)
The surface compressive stress (CS) and the depth (DOL) of the compressive stress layer are obtained by passing light through the chemically strengthened glass chemically strengthened layer with a birefringence imaging system Abrio (manufactured by Tokyo Instruments). Was calculated using the photoelastic constant of the glass.

(5) Crystallinity The crystallinity of the crystallized glass containing nepheline solid solution crystals was measured using a RIGAKU X-ray diffractometer LINT-TTRIII, with an Al ₂ O ₃ (corundum) crystal having a crystallinity of 100%. As a reference sample, X-ray diffraction measurement was performed in addition to the crystallized glass containing nepheline solid solution crystals, and the mass ratio of the reference material and crystallized glass containing nepheline solid solution crystals and the ratio of the respective X-ray diffraction line intensities were calculated.

In this example, after adding 1 g of Al ₂ O ₃ (corundum) crystal powder to crystallized glass containing nepheline solid solution crystals pulverized to 44 μm or less and mixing well, 100 mg is used as an X-ray diffraction measurement sample. The intensity ratio A is 1.1, which is based on the Powder Difference File PDF-2 Release 2006, which is databased from the International Center for Diffraction Data (http://www.icdd.com/).

(Production of crystallized glass containing nepheline solid solution crystals)
Glass raw materials were appropriately selected and weighed and mixed so as to give 300 g as glass. Next, it is placed in a platinum crucible, placed in a resistance heating electric furnace at 1650 ° C., melted for 3 hours, defoamed and homogenized, poured into a mold material, and heated at a temperature about 30 ° C. higher than the glass transition point for 1 hour. After holding, the glass was cooled to room temperature at a cooling rate of 1 ° C. per minute to obtain glasses having the compositions shown in Tables 1 to 3.

  A glass transition point Tg (unit: ° C.) was determined using a part of the obtained glass. Moreover, when the transmittance was measured, the transmittance monotonously decreased from the long wavelength side toward the short wavelength side. In Tables 1 to 3, T400 is the transmittance at a wavelength of 400 nm, and T800 is the transmittance at a wavelength of 800 nm.

  The crystallized glass containing nepheline solid solution crystals is maintained at the heat treatment time t1 (unit: hours) at the nucleation heat treatment temperature T1 shown in Tables 1 to 3, and then the heat treatment time t2 at the crystal growth heat treatment temperature T2 (unit: ° C.). (Unit: time) was maintained, and then cooled to room temperature. Both heating and cooling during the heat treatment were performed at a rate of 10 ° C. per minute.

  Tables 1 to 3 show the crystallinity of crystallized glass containing nepheline solid solution crystals. In Tables 1 to 3, the crystallinities of Examples 1 to 9, 13, 14, 17, 18, and 22 are actually measured values, and the crystallinities of Examples 10 to 12, 15, 16, and 19 to 21 are estimated values. is there. In FIG. 1, the SEM photograph of Example 5 is shown. The crystal grain size was 100-200 nm.

(Ion exchange treatment)
The crystallized glass containing nepheline solid solution crystal was chemically strengthened by immersing it in KNO ₃ molten salt at an ion exchange temperature T (unit: ° C.) for a time t (unit: hour). The result of having measured the surface compressive stress (CS) of the chemically strengthened glass, the depth (DOL) of a compressive-stress layer, and three-point bending strength is shown to Tables 1-3.

  Examples 1 to 20 in Tables 1 and 2 are examples, Examples 21 and 22 in Table 3 are reference examples, and Example 23 is a comparative example.

  From the results shown in Tables 1 and 2, the crystallized glass containing nepheline solid solution crystals is subjected to an ion exchange treatment at 520 ° C. or less to obtain a white glass having low transmittance and an improved strength. I understood it.

  Moreover, although the transmittance | permeability was high in Examples 22 and 23, it turned out that the glass which improved the intensity | strength is obtained by ion-exchange processing at 520 degrees C or less.

  In Example 24, a glass in which crystals were precipitated inhomogeneously and was separated into a transparent portion and various spherical portions was obtained.

Claims (9)

  A crystallized glass for a casing obtained by subjecting a crystallized glass having a transmittance at a wavelength of 400 nm of 20% or less and containing a nepheline solid solution crystal to an ion exchange treatment.   The crystallized glass for a casing according to claim 1, wherein the crystallinity of the crystallized glass is 20 to 70%. The crystallized glass for a casing according to claim 1 or 2, wherein the crystallized glass contains Na ₂ O. The crystallized glass for a casing according to any one of claims 1 to ₃ , wherein the crystallized glass contains SiO ₂ and Al ₂ O ₃ . The crystallized glass for a casing according to claim 3 or 4, wherein the crystallized glass contains at least one selected from TiO ₂ and K ₂ O. The SiO ₂ 40 to 70% crystallized glass in mole percentage based on the following oxides, _{Al 2 O 3 8~28%, 10~30} % of Na ₂ O, containing _{K 2} O 0% The crystallized glass for a casing according to any one of claims 1 to 5, which is obtained by heat-treating glass.   The crystallized glass for a casing according to any one of claims 1 to 6, wherein the depth of the compressive stress layer is 10 µm or more. The manufacturing method of the crystallized glass which contains the following processes (1) and (2) sequentially.
(1) Glass containing 40 to 70% of SiO ₂ , 8 to 28% of Al ₂ O ₃ , 10 to 30% of Na ₂ O, and 0 to 10% of K ₂ O in a molar percentage display based on the following oxides. Step of heat treating glass at 950 ° C. or lower for 1 to 10 hours (2) Step of heat treating glass heated in Step (1) at 850 to 1200 ° C. for 1 to 10 hours   A method for producing crystallized glass that has been subjected to ion exchange treatment, wherein the crystallized glass produced by the method for producing crystallized glass according to claim 8 is subjected to ion exchange treatment at 520 ° C or lower.