JP3424749B2 - Crystallized glass articles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystallized glass article manufactured by using crystallizable glass which can be redrawn.

[0002]

2. Description of the Related Art Crystallized glass is a material exhibiting unique properties that glass does not have, due to various crystals precipitated in the glass. For example, when crystals such as β-quartz solid solution and β-spodumene are precipitated, crystallized glass exhibiting extremely low expansion or negative expansion can be obtained. Moreover, crystallized glass generally has higher mechanical strength than glass due to the presence of these crystals.

In recent years, a crystallized glass having such excellent characteristics is precision processed into a thin rod shape, a thin tube shape, a thin plate shape or the like to produce a product requiring precise dimensional accuracy such as electronic parts and precision machine parts. Attempts have been made to apply it to the field.

[0004]

A forming method called a redraw forming method is known as a method for precisely processing glass. This method is to stretch-form a glass molded body that has been preformed to have an appropriate precision while heating it to a temperature equal to or higher than the softening point of glass, and continuously produce glass products that require high precision. It is widely used as a manufacturing method.

However, in the case of the conventional crystallized glass, it is difficult to perform the redraw molding like the glass for the following reasons. That is, the conventional crystallized glass has a problem that the heat resistance is too high, devitrification occurs during heating, stretching is difficult, and the amount of crystal changes due to heating, resulting in a large change in physical properties. This is because Therefore, it was also considered to redraw the glass before becoming crystallized glass, so-called raw glass, but since this kind of glass is designed to be easily crystallized by heating, the raw glass for redraw molding is used. When heated, devitrification inevitably occurs, making it impossible to control not only the dimensions but also the physical properties.

Therefore, in the case of precision processing of crystallized glass, the same mechanical processing as ceramics is inevitably required, resulting in an extremely high cost at present.

The present invention has been made in view of such circumstances, and an object thereof is to provide a crystallized glass article produced by using crystallized glass capable of redraw molding.

[0008]

As a result of many studies, the present inventor has found that the crystallized glass can be redraw-molded, that it can be softened and stretched when heated, and that it can be drawn even when heated. Based on the knowledge that two points that the crystal phase is stable are important, the essential conditions for the crystallized glass that can be redraw-molded were specified.

That is, the crystallized glass article of the present invention has a precipitated crystal grain of 10 μm or less and a glass phase ratio of 10 to 85.
Volume%, while having a softening point lower than the melting point of the main precipitated crystals, a preformed body of crystallized glass having the property that crystallization does not substantially progress even when heated to a temperature above the softening point, It is characterized by being stretch-formed.

[0010]

The crystallized glass used for producing the crystallized glass article of the present invention has precipitated crystal particles of 10 μm or less, preferably 5 μm or less. If the crystal size exceeds 10 μm, the elongation during redraw molding is significantly reduced, and the crystal sticks out to the surface, causing devitrification, and significantly deteriorating the dimensions and physical properties of the material.

The crystallized glass is characterized in that the proportion of the glass phase is 10 to 85% by volume, preferably 20 to 65% by volume. If the glass phase is less than 10% by volume, it is difficult to obtain sufficient softening property for lidro-molding, and 85% by volume.
If the amount is larger than the above, the amount of crystals decreases, and the characteristics of the crystallized glass tend to deteriorate.

The crystallized glass is characterized in that the softening point of the crystallized glass is lower than the melting point of the mainly precipitated crystals. If the softening point is lower than the melting point, redraw molding can be performed at a temperature lower than the melting point, and crystals remain after molding, so molding can be performed while maintaining the properties as crystallized glass. . The softening point and melting point of crystallized glass can be measured by differential thermal analysis (DTA). The crystallized glass whose softening point cannot be detected by differential thermal analysis is a crystallized glass in which crystals are remarkably precipitated when heated, or the proportion of the glass phase is too small to be softened, which is impossible to redraw.

An even more important factor is the fact that crystallization does not substantially progress even when heated to a temperature above the softening point. In other words, since the surface newly generated by redraw molding has a higher free energy than the inside, in the case of crystallized glass where crystallization is easy to proceed, coarse crystals (devitrified substances) are concentrated and deposited on the surface. It is difficult to do so, and the dimensions and physical properties of the molded product are significantly deteriorated. In the present invention, the property that crystallization does not substantially progress means that the crystal phase does not increase by 15% by volume or more, preferably 10% by volume or more, even if it is heated and held at a temperature of the softening point or higher. Means that.

The crystallized glass used in the present invention is not particularly limited in its precipitated crystal and glass composition as long as it has the above-mentioned characteristics. The type of precipitated crystals should be selected according to the purpose and application, and the composition system of glass is also determined accordingly. For example, when the desired crystallized glass of low expansion, beta-quartz solid solution Li ₂ precipitated the or beta-spodumene solid solution as the predominant crystalline O-Al ₂ O
₃ -SiO ₂ based crystallized glass is preferred. The crystallized glass of this system will be described below.

In the case of the Li ₂ O--Al ₂ O ₃ --SiO ₂ system crystallized glass, the SiO ₂ 55 to 72% (preferably 62 to 68.5%) SiO ₂ is expressed in weight percentage in developing the above-mentioned characteristics. , Al ₂ O ₃ 14 to 30% (preferably 16 to 24.5%), Li ₂ O 1.5 to 3%
(Preferably 1.8 to 2.8%), K ₂ O 1 to 10%
It is preferable to use one having a composition (preferably 2.5 to 7%).

The reason for limiting the ratio of each component in this way is as follows.

SiO ₂ is a main constituent component of glass and a crystal component. If SiO ₂ is less than 55%, a crystallized glass having a uniform structure cannot be obtained, and if it is more than 72%, the softening point of the crystallized glass becomes high and the meltability at the time of melting the glass deteriorates, resulting in unevenness. Because it will be in a state,
Partial devitrification is likely to occur and redraw moldability is significantly reduced.

Al ₂ O ₃ is also a crystal constituent component, and 14%
If the amount is less than the above range, the crystals become coarse and redraw formability is significantly deteriorated. On the other hand, if it exceeds 30%, devitrification tends to occur during redrawing.

Li ₂ O is indispensable as a constituent component of crystals, and if it is less than 1.5%, it is difficult to obtain a uniform crystallized glass, and if it exceeds 3%, the crystallinity becomes too strong, and the ratio of the glass phase. Is insufficient, and crystallization is likely to proceed in the process of redraw molding.

K ₂ O is an essential component for controlling the crystallinity and has an important influence on the proportion of the glass phase and the softening point. That is, if K ₂ O is less than 1%, the crystallinity becomes too strong, the proportion of the glass phase becomes insufficient, and the softening point of the crystallized glass becomes high. On the other hand, if it exceeds 10%, it becomes difficult to form crystallized glass.

In this composition system, in addition to the above components, T
₁ to 4.5% of iO ₂ (preferably 1.5 to 3.5)
%) And 0 to 4% ZrO ₂ (preferably 1.5 to 2.5
%), But the total amount of TiO ₂ and ZrO ₂ is 2.5 to 7%
(Preferably 3 to 6%), ZnO is 0 to 10% (preferably 1.5 to 5%), MgO is 0 to 2.5% (preferably 0.5 to 1.5%), and CaO is 0. ~ 2.5% (preferably 0 to 1%), BaO 0 to 3% (preferably 0 to 2)
%), 0 to 7% of B ₂ O ₃ (preferably 0 to 5%), N
It is desirable to add 0 to 2% (preferably 0 to 1%) of a ₂ O and 0 to 0.8% (preferably 0 to 0.5%) of P ₂ O ₅ . The reasons for limiting each component are as follows.

TiO ₂ and ZrO ₂ are substances that act as nuclei during crystal precipitation and have a function of making crystals fine. If the total of both is less than 2.5%, it becomes difficult to obtain a dense crystal. If the total amount of both exceeds 7%, or if each exceeds the upper limit of the above range alone, the glass tends to become non-uniform.

ZnO, MgO, CaO, BaO, B ₂ O
_{Both 3} and Na ₂ O are effective components for lowering the softening point of the crystallized glass, and can be added within the respective ranges, but if they exceed these ranges, heterogeneous crystals tend to precipitate. The devitrification becomes stronger.

P ₂ O ₅ has a function of making crystals finer, but if it exceeds 0.8%, devitrification becomes strong.

In addition to the above, the total amount of As ₂ O ₃ , Sb ₂ O ₃ , SnO, and Pb should not exceed 5%.
O, Bi ₂ O ₃ and the like can also be added.

Next, a method for producing the crystallized glass article of the present invention will be described.

First, the crystallized glass is preformed into a desired shape.

Subsequently, the crystallized glass preform is stretch-molded while being heated to a temperature equal to or higher than the softening point, and cut into a desired length to obtain a redraw-molded crystallized glass article of the present invention. be able to.

[0029]

EXAMPLES The present invention will be described below based on examples.

Table 1 shows examples of the present invention (Sample Nos. 1 to 1).
5) and Table 2 show comparative examples (Sample Nos. 6 to 8), respectively.

[0031]

[Table 1]

[0032]

[Table 2]

Glass raw materials prepared so as to have the composition shown in the table were put into a glass melting furnace, melted at 1650 ° C. for 24 hours, and then cast into a cylindrical shape having a diameter of 50 mm and a length of 500 mm. These glasses were then heated in an electric furnace to crystallize. The crystallization was performed by heating each at the nucleation temperature and the crystal growth temperature shown in Tables 1 and 2 for 4 hours.

With respect to the crystallized glass molded body thus obtained, the type and particle size of precipitated crystal particles, the proportion of the glass phase, the melting point of the main crystal, and the softening point of the crystallized glass were measured. Moreover, after heating for 1 hour at a temperature 70 ° C. higher than the softening point or 50 to 150 ° C. lower than the melting point of the main crystal, the proportion occupied by the glass phase was measured again. The results are shown in Tables 3 and 4.

[0035]

[Table 3]

[0036]

[Table 4]

Next, the outer circumference of the crystallized glass molding was ground with a diamond tool to adjust the roundness, and the diameter was 400 mm.
Of the preform. Subsequently, as shown in FIG. 1, the preform G is continuously fed from the upper portion of the annular electric furnace 1 at a speed of 5 mm / min, and the lower end of the compact that is softened and deformed and extends downward is sandwiched by the roller 2. Then, it was stretched at a speed of 1280 mm / min so as to be a thin rod having a diameter of 2.5 mm, and the formability was evaluated. In the figure, g indicates a molded crystallized glass article. Redraw molding was performed at the temperatures shown in Tables 3 and 4. The evaluation results of each sample are shown in Tables 3 and 4.

As is apparent from the table, No. 1 which is an embodiment of the present invention. In each of the samples 1 to 5, the crystal grain size was 2.5 μm or less, the ratio of the glass phase was 20 to 65% by volume, and the softening point was lower than the melting point of the main crystal. Further, it was found that the glass phase increased by 5 to 25% by volume after heating, and crystallization did not proceed at all. When the redraw moldability of these samples was evaluated, they all showed good moldability.

On the other hand, in Comparative Example No. It was found that the sample of Sample No. 6 had a glass phase ratio reduced by 25% by volume when heated, and crystallization significantly proceeded. Further, the softening point could not be measured because crystallization remarkably progressed when heated. When the moldability of this sample was evaluated, the glass was cut during stretching, and many devitrified substances were observed on the surface. Sample No. In No. 7, the softening point could not be measured because the proportion of the glass phase was extremely small. When the moldability of this sample was evaluated, the softening deformation was insufficient and the sample could not be stretched. Sample No. No. 8 had coarse crystal grains. When the moldability was evaluated, the glass was cut during the drawing and the devitrification was remarkable.

The types of the main precipitated crystals were specified by X-ray diffraction (XRD), and the particle size of the precipitated crystal particles and the proportion of the glass phase were measured using a scanning electron microscope (SEM). The melting point of the main crystal and the softening point of the crystallized glass were measured by differential thermal analysis (DTA) using a powdered sample of 150 mesh or less. Redraw moldability (elongation, presence of devitrified matter) was evaluated as follows. Regarding the elongation, those in which cutting did not occur during redraw molding were evaluated as good, and those in which cutting and no elongation occurred were regarded as defective. With respect to the devitrified material, the surface of the sample after molding was visually observed, and those in which the devitrified material was not observed were classified as none and those in which the devitrified material was recognized.

[0041]

As described above, the crystallized glass article of the present invention does not need to be machined because it is produced by redraw molding. Therefore, it can be provided with high accuracy and at low cost, and can be applied to fields such as electronic parts and precision machine parts.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing redraw molding.

[Explanation of symbols]

G Crystallized glass preform g Redraw molded crystallized glass article 1 ring electric furnace Two rollers

Claims (3)

(57) [Claims] 1. Precipitated crystal grains are 10 μm or less, the proportion of glass phase is 10 to 85% by volume, and they have a softening point lower than the melting point of the main precipitated crystals, and even when heated to a temperature above the softening point. A crystallized glass article, which is obtained by stretch-molding a preformed body of crystallized glass having a property that crystallization does not substantially progress. 2. The crystallized glass article according to claim 1, wherein the mainly precipitated crystals are β-quartz solid solution or β-spodumene solid solution. 3. SiO as a main component₂ , Al₂ O₃ , L
i₂ O, K₂ Contains O, and the content of each of these components is by weight
SiO in percentage₂   55-72%, Al₂ O ₃   14 ~
30%, Li₂ O 1.5-3%, K₂ O 1-10%
2. The crystallized glass according to claim 1, characterized in that
Goods.