JP2021183549A - Glass ceramics - Google Patents

Abstract

To provide a machinable glass ceramics that has a high reflectance to ultraviolet having a wavelength of 400 nm compared to conventional technique.SOLUTION: A glass ceramics is provided, containing by mass%, SiO2: 35 to 60%, Al2O3: 10 to 21%, MgO: 10 to 21%, K2O: 5 to 14%, B2O3: 3 to 11%, ZrO2: 1 to 7% and F: 1 to 7%, the number of fluorine phlogopite crystals present in the matrix of borosilicate glass being 0.30 to 0.45 pieces/μm2.SELECTED DRAWING: Figure 2

Description

The present invention relates to glass ceramics.

Ceramics that can be finely machined are called machinable ceramics. As a kind of free-cutting ceramics, borosilicate glass with excellent thermal and electrical properties, high strength and low thermal expansion is used as a matrix, and fine mica is deposited in the matrix. There are Nable glass ceramics. Since the fine crystals of mica with strong cleavage are dispersed in the vitreous matrix, the mica crystals alleviate the crack growth in the glass, which has the advantage of being easy to machine.

In Patent Document 1, in mass% based on oxide conversion except for fluorine, SiO ₂ : 35 to 60%, Al ₂ O ₃ : 5 to 20%, MgO: 10 to 35%, K ₂ O: 5 to 20. %, B ₂ O ₃ : 2 to 10%, ZrO ₂ : 0 to 10%, and F: 1 to 15%. Free-cutting glass including a step and a crystallization heat treatment step of heat-treating the glass body obtained in the above step by a hot isotropic pressing method to precipitate fluorine mica crystals or fluorine mica crystals and zirconia in the glass. The invention relating to the manufacturing method of ceramics is disclosed.

On the other hand, ceramics having a high reflectance may be used as a package for a light emitting element or a reflector. For example, alumina is inexpensive, has a high whiteness, and has a high reflectance, so that it is used in many light emitting device packages and the like.

JP-A-2007-246297

Although alumina has a high reflectance in visible light, it cannot always be said that the reflectance of ultraviolet rays having a wavelength of 400 nm or less is high. Further, depending on the type of alumina, yellowing may occur due to ultraviolet rays. Further, alumina has poor processability, and it is not easy to process a complicated shape.

On the other hand, Patent Document 1 does not study the reflectance of free-cutting glass-ceramics. In particular, Patent Document 1 cites an example in which pottery stone is used as a specific example, and since a considerable amount of Fe is contained as an impurity, there is a limit to increasing the reflectance.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a machinable glass ceramic having a high reflectance.

The present inventors have conducted diligent research to achieve the above object, and have not deteriorated the free-cutting property of the mica-based machinable glass ceramics in which mica is precipitated on the matrix of borosilicate glass, and the ultraviolet region (specifically). In order to improve the reflectance at a wavelength of 400 nm or less), diligent studies were conducted.

(A) Industrially important mica includes mascovite (hard mica, muscovite) containing potassium as a main component and progopite (soft mica, phlogopite) containing magnesium as a main component. Synthetic mica (fluorine phlogopite) is artificially generated mica (KMg ₃ (AlSi ₃ ) O ₁₀ F ₂ ), which is whiter and slightly harder than muscovite and phlogopite. Be prepared. Mica-based machinable glass ceramics in which white-colored phlogopite fluorine is deposited on a matrix of borosilicate glass have high reflectance in the visible light region. However, the reflectance in the ultraviolet region changes greatly depending on the dispersed state of the fluorine phlogopite crystals. That is, when the number of fluorine phlogopite crystals per unit area is small, the reflectance in the ultraviolet region is extremely lowered. Therefore, it is important to disperse the fluorine phlogopite crystals in the matrix as much as possible.

(B) Fe present in the glass-ceramics lowers the reflectance in the ultraviolet region, and therefore the amount thereof is preferably reduced as much as possible.

(C) When bubbles are present at the interface between the borosilicate glass of the matrix and the phlogopite crystal of fluorine, the reflectance is improved. For this reason, it is preferable to perform crystallization under normal pressure rather than obtaining a glass body that contains essentially no bubbles by a hot isotropic press method.

The present invention has been made based on the above findings, and the following glass ceramics are the gist of the present invention.

By mass%,
SiO ₂ : 35-60%,
Al ₂ O ₃ : 10-21%,
MgO: 10-21%,
K ₂ O: 5-14%,
B ₂ O ₃ : 3-11%,
Includes ZrO ₂ : 1-7% and F: 1-7%
The number of phlogopite crystals present in the matrix of borosilicate glass is 0.30 to 0.45 / μm ² .
Glass ceramics.

According to the present invention, machinable glass ceramics having high reflectance can be obtained. This glass-ceramic has a particularly high reflectance in the ultraviolet region (specifically, a wavelength of 400 nm or less). Therefore, it is useful for, for example, a package of a deep ultraviolet LED lamp, a reflector of a YAG laser, and the like.

FIG. 1 is a photomicrograph (1000 times) of the glass ceramics of Example 1. FIG. 2 is a photomicrograph (5000 times) of the glass ceramics of Example 1. FIG. 3 is a photomicrograph (1000 times) of the glass ceramics of Comparative Example 1. FIG. 4 is a photomicrograph (5000 times) of the glass ceramics of Comparative Example 1.

1. 1. Composition of Glass Ceramics The glass ceramic according to the present invention contains K, Mg, Al, Si and F in a vitreous matrix containing _{SiO 2} , Al ₂ O ₃ , MgO, K ₂ O and B ₂ O _3. It is a glass ceramic in which fluorine gold mica crystals are dispersed. In the glass ceramics according to the present invention, in order to disperse a sufficient amount of fluorine gold mica crystals in the vitreous matrix, SiO ₂ : 35 to 60%, Al ₂ O ₃ : 10 to 21%, MgO: 10 to 21%. , K ₂ O: 5-14%, B ₂ O ₃ : 3-11%, ZrO ₂ : 1-7% and F: 1-7%. In the following description,% with respect to the content of each component means mass%. Further, the content of components other than F and Fe means the content in terms of oxide.

Glass containing SiO ₂ , Al ₂ O ₃ , MgO, K ₂ O and B ₂ O ₃ has a low coefficient of thermal expansion, excellent thermal properties such as heat resistance and heat insulating properties, and electrical properties such as insulating properties. It is a glass belonging to borosilicate glass, which is known to have good and high mechanical strength. When the amount of these components is within the above range, a glass matrix satisfying in terms of the above performance can be formed, and a sufficient amount of fluorine gold mica crystals can be precipitated during the crystallization heat treatment. It is possible to obtain glass ceramics having excellent machinability, mechanical strength, and thermal and electrical properties.

At _{least a part of ZrO 2} (zirconia) precipitates from the glass during heat treatment to generate fine zirconia particles, which has the effect of suppressing crystal growth of phlogopite crystals and improving machinability and mechanical strength. be. Therefore, the above amount of ZrO ₂ is contained.

When the Fe content in the glass ceramics is excessive, the reflectance in the ultraviolet region is lowered, so that the Fe content is preferably 30 ppm or less. It is more preferably 25 ppm or less.

2. 2. About the number of phlogopite crystals of fluorine in the matrix The glass ceramics according to the present invention are glass ceramics in which phlogopite crystals of fluorine are dispersed in a matrix of borosilicate glass. It is important that the number of phlogopite crystals present in the matrix of borosilicate glass is 0.30 to 0.45 / μm ^2. When the number of phlogopite crystals ^{is less than 0.30 / μm 2} , the particle size of the phlogopite crystals becomes relatively large, and it becomes difficult to set the reflectance at a wavelength of 400 nm to 90% or more. On the other hand, if the number of phlogopite crystals of fluorine ^{exceeds 0.45 / μm 2} , the crack growth of the glass cannot be stopped, and there arises a problem that the machinability is deteriorated. Therefore, the number of phlogopite crystals of fluorine is 0.30 to 0.45 / μm ² . The preferred lower limit is 0.35 pieces / μm ² , and the preferred upper limit is 0.40 pieces / μm ² .

The number of fluorine phlogopite crystals in the matrix can be measured by the method described in Examples.

3. 3. In the glass ceramic in the amount of bubbles, it is preferable bubble diameter 0.2~0.4mm is 0.008 to 0.0390 atoms / cm ³ or more. The diameter of the bubble means the diameter equivalent to a circle.

Here, it is the bubbles having a diameter of 0.4 mm or less that affect the reflectance in the ultraviolet region, but the bubbles having a diameter of less than 0.2 mm are difficult to measure, so the diameter is 0.2 to 0.4 mm. It was decided to specify the number by paying attention to the bubbles in. In addition, bubbles having a diameter of more than 0.4 mm become a source of destruction of glass ceramics and may cause a decrease in strength. Therefore, it is preferable that the number of bubbles is 0.4 mm or less in diameter, which is effective for increasing the reflectance in the ultraviolet region, and the intensity is not extremely reduced.

When the bubble diameter 0.2~0.4mm is small, it the reflectance in the ultraviolet region becomes inadequate, bubbles diameter 0.2~0.4mm is 0.008 pieces / cm ³ or more Is preferable. There is no particular limitation on the upper limit, but if the number of bubbles of this size increases, the number of bubbles with a diameter of more than 0.4 mm also increases, which adversely affects the strength, so 0.0390 cells / cm ³ is a practical upper limit. The number of bubbles having a diameter of more than 0.4 mm ^{is preferably 0.0058 cells / cm 3} or less.

The number of bubbles in the glass ceramics can be measured by the method described in Examples.

4. About the manufacturing method of glass ceramics (adjustment of raw materials)
If the compound form of each metal component (component other than fluorine) in the raw material formulation changes to an oxide before melting or during heating of the melt (that is, an oxide precursor), the compound form is other than the oxide. It may be in the form. Preferred compound forms are single oxides, composite oxides, acids, carbonates, fluorides and the like. Fluorine can be supplied as a fluoride of other metal components.

For SiO ₂ , Al ₂ O ₃ and K ₂ O, porcelain stone, which is an inexpensive mineral containing these as a main component, is usually used as a raw material, but is not used in the present invention. This is because such pottery stones often contain a large amount of Fe. Amorphous silica or the like may be used as the SiO ₂ supply source, alumina, aluminum hydroxide or the like may be used as _{the Al 2} O ₃ supply source, and potassium carbonate, potassium borate or the like may be used as the _{K 2 O supply source.} can.

As the zirconium compound, for example, zirconia or zircon (ZrSiO ₄ ) can be used, but since zircon tends to increase the particle size at the time of reprecipitation and causes a decrease in reflectance, zirconia is used and the particles are used. It is desirable to reduce the size.

It is desirable to use magnesium fluoride (MgF _{2) as the fluorine compound.} As the boron compound, boric acid is preferably used because _{boron oxide (B 2} O _{3) is also difficult to melt.} Composite oxides with other components, such as potassium borate, can also be used.

MgO is also supplied from magnesium fluoride, but if it is insufficient, magnesium oxide, magnesium carbonate and the like can be used.

The free-cutting glass-ceramics of the present invention may contain components other than the above as the case may be. Zinc oxide (ZnO) can be mentioned as such a component. ZnO can be blended in an amount of up to 30%.

(Slurry)
The powder of the above raw material is mixed by a known method such as a ball mill. That is, each powder is dry-mixed with a dispersant and a ceramic ball in a container and solidified to obtain a molded product.

(Temporary firing)
The obtained molded product is calcined in an air oven at a temperature of 1000 to 1050 ° C. for 60 to 600 minutes.

(Vitrification)
The calcined material is melted in a melting furnace at a temperature of 1300 to 1400 ° C. for 1 to 10 hours, and slowly cooled to 650 ° C. outside the furnace to vitrify to obtain a glass body.

(Crystallization)
The slowly cooled glass body is heated to a temperature of 800 to 900 ° C. and held for 1 to 10 hours to form crystal nuclei of phlogopite fluorine. Then, the crystal nuclei of phlogopite fluorine are grown and crystallized by holding at a temperature of 1080 to 1110 ° C. for 5 hours. The temperature of this crystallization determines the dispersed state of the fluorine phlogopite crystal. That is, when the crystallization temperature exceeds 1110 ° C., the crystal nuclei of the fluorine phlogopite grow too much, and it becomes difficult to secure a sufficient number. On the other hand, when the crystallization temperature is less than 1080 ° C., the crystal nuclei of phlogopite fluorine are formed but do not grow, so that the number of phlogopite fluorine is too large. The temperature rise rate during heat treatment is treated in the range of 0.2 to 0.8 ° C./min so that abnormal crystal growth does not occur during crystallization. In addition, the glass body placed in the furnace is surrounded by carbon or the like in order to homogenize the heat. It is important that crystallization is carried out at normal pressure in order to leave some bubbles. For example, when crystallization is performed by HIP treatment, almost no bubbles are formed, which is disadvantageous in terms of improving the reflectance in the ultraviolet region. In addition, the number of crystallization by HIP treatment is too large in order to suppress the growth of crystal nuclei of phlogopite fluorine. Therefore, crystallization is performed under normal pressure.

In order to confirm the effect of the present invention, various powder raw materials were dry-mixed together with a dispersant and ceramic balls to obtain a mixed powder. The obtained mixed powder was solidified and calcined at 1030 ° C. for 300 minutes, and then vitrified and crystallized under predetermined conditions to obtain various ceramics. Some ceramics were crystallized by HIP treatment.

Test pieces were collected from the obtained ceramics and various tests were performed.

<Elemental analysis>
Elemental analysis of the above-mentioned test sintered body was carried out by the GDMS method, and the contents of components other than F and Fe in terms of oxide were measured.

<Number of fluorine phlogopite crystals>
The number of fluorine phlogopite crystals in the matrix was obtained by polishing the observation surface of the ceramics and coating it with platinum (Pt) because it was an insulator. The observation surface of the sample was photographed with a scanning electron microscope (JSM-IT500 manufactured by JEOL Ltd.) at a magnification of 8000 (observation field of view: 16 μm × 12 μm = 192 μm ^2). Fluorophlogopite crystals observed in the obtained micrographs are counted, and the number of phlogopite crystals in the obtained observation field ^{is divided by the area of the observation field (192 μm 2} ) to obtain fluorine gold per unit area. The number of mica crystals (pieces / μm ² ) was calculated. The number of phlogopite crystals in contact with the boundary of the observation field was counted as 1/2.

<Number of bubbles>
The number of bubbles in the ceramics is measured by surface-grinding the upper and lower surfaces of the ceramic block with a surface grinding machine and measuring the ceramic block with an ultrasonic flaw detector (SDS-Win3850). bottom. As an example, a ceramic block having a size of 320 mm × 230 mm × 35 mm is scanned, and the obtained data is analyzed to obtain the number of bubbles of φ0.4 mm or more, φ0.2 mm or more and less than φ0.4 mm, and φ0.2 mm or less. The obtained number of bubbles was divided by the volume of the block to obtain the number of bubbles per unit volume.

<Evaluation of workability>
The obtained ceramics were drilled with a drilling machine using a commercially available cemented carbide tool (φ10 mm), and the one that could be drilled was the best (○), but the drilling was possible, but a small chip (=) around the hole. Those with chipping) were defined as good (Δ), and those that could not be drilled were defined as defective (×).

<Evaluation of reflectance>
Using a SolidSpec-3700 manufactured by Shimadzu Corporation, the relative reflectance using an integrating sphere with a standard white plate was measured. A relative reflectance of less than 90% was evaluated as defective (x), 90% or more was evaluated as good (〇), and 94% or more was evaluated as best (⊚).

As shown in Tables 1 to 3, Test Nos. 1, 4, 9, 12 and 28 to 30, which satisfy all the conditions of the present invention, have an excellent reflectance of 90% or more at a wavelength of 400 nm, and are processed. The sex was also good. In particular, Test No. 1, which also satisfies the conditions of the amount of Fe and the number of bubbles, has a particularly excellent reflectance at a wavelength of 400 nm of 94% or more, and is particularly excellent in processability.

On the other hand, test numbers 2, 3, 5 to 8, 10 to 11, 13 to 27, 31 and 32, which do not satisfy the conditions of the present invention, are inferior in the performance of one or both of the reflectance and processability at a wavelength of 400 nm. rice field.

According to the present invention, machinable glass ceramics having high reflectance can be obtained. This glass-ceramic has a particularly high reflectance in the ultraviolet region (specifically, a wavelength of 400 nm or less). Therefore, it is useful for, for example, a package of a deep ultraviolet LED lamp, a reflector of a YAG laser, and the like.

Claims (4)

By mass%,
SiO ₂ : 35-60%,
Al ₂ O ₃ : 10-21%,
MgO: 10-21%,
K ₂ O: 5-14%,
B ₂ O ₃ : 3-11%,
Includes ZrO ₂ : 1-7% and F: 1-7%
The number of phlogopite crystals present in the matrix of borosilicate glass is 0.30 to 0.45 / μm ² .
Glass ceramics. The Fe content in the glass ceramics is 30 ppm or less.
The glass ceramic according to claim 1. In the glass ceramics, the number of bubbles having a diameter of 0.2 to ^{0.4 mm is 0.008 to 0.0390 cells / cm 3} , and the number of bubbles having a diameter of more than 0.4 mm is 0.006 cells / cm ³ or less. The glass ceramic according to claim 1 or 2. The reflectance at a wavelength of 400 nm is 90% or more.
The glass ceramic according to any one of claims 1 to 3.

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