JPH0696460B2 - Low expansion transparent crystallized glass - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low expansion transparent crystallized glass, and more particularly to a colorless low expansion transparent crystallized glass having high heat resistance.

[Prior Art] Transparent materials having a small expansion coefficient and excellent heat resistance have been demanded from various fields. Quartz glass, which has a very small expansion coefficient of 5 × 10 ⁻⁷ K ⁻¹ , is one of such materials, but it is difficult to manufacture because of its high melting point and is generally expensive. Further, as a transparent material excellent in heat resistance having an expansion coefficient equal to or less than that of quartz glass, Li ₂ O
-Al ₂ O ₃ -SiO ₂ type crystallized glass is available, and some are commercialized. These are generally colored yellow and are not preferred in appearance. Until now, Fe ₂ O ₃ has been reduced in order to reduce this coloring. That is Fe ₂
It is necessary to use an expensive raw material that requires less O ₃ minutes, which has led to higher costs.

[Problems to be Solved by the Invention] The present invention provides a colorless and inexpensive constant expansion transparent crystallized glass having an extremely small expansion coefficient and excellent heat resistance based on the above-mentioned requirements and the problems of the prior art. The purpose is to

[Means for Solving the Problems] The present invention provides Li ₂ O 2.5 to 6.0 Na ₂ O 0 to 4.0 K ₂ O 0 to 4.0 Na ₂ O + K ₂ O 0 to 4.0 MgO 0 to 4.0 ZnO 0 by weight%. _{~4.0 Al 2 O 3 15.0~30.0 SiO 2} 60.0~75.0 SnO 2 1.0~4.0 consists composition of _{ZrO 2 1.0~4.0 SnO 2 + ZrO 2} 3.5~7.0 P 2 O 5 0~4.0 Fe 2 O 3 0.01~0.1 , Visible light transmittance measured by standard light C light with 5.0 mm thickness at 2 ° field is 86% or more, stimulation purity is 4%
And β-quartz solid solution crystals and / or β-
It is a low expansion transparent crystallized glass containing spodumene solid solution as precipitated crystals.

The crystallized glass is obtained by melting raw materials having these components to obtain a glass body and then holding the glass in a temperature range of 700 ° C to 1000 ° C for 0.5 to 10 hours. Crystallized glass containing β-quartz solid solution crystals as the main precipitated crystals is heat-treated in the temperature range of 700 to 900 ° C. The crystallized glass containing β-spodumene solid solution crystals as the main precipitated crystals is heat-treated at a temperature of 900 to 1000 ° C. Crystallized glass produced by the heat treatment usually has a particle size of 100 nm.
It has a structure in which the following fine crystal particles are uniformly dispersed in the matrix of the glass phase.

The crystallized glass of the present invention is obtained by crystallizing a glass having the above composition range by heat treatment, but it is preferable to appropriately set the heat treatment conditions according to the composition and the target characteristics.
The crystallized glass of the present invention can be heat-treated into either a β-quartz solid solution crystal as a main crystal or a β-spodumene solid solution crystal as a main crystal.

Even if the heating schedule of the crystallization is one step, the desired crystallization product can be obtained. However, if the multi-step treatment (for example, two-step treatment or three-step treatment) is performed, the crystal grain size becomes smaller and the transmission due to scattering occurs. It is preferable because the decrease in the rate is reduced and a crystallized product with higher transmittance can be obtained.

In the present invention, ZrO ₂ and SnO ₂ are added as crystallization accelerators, but the function of the ZrO ₂ + SnO ₂ is not clear. However, by only adding the amounts of ZrO ₂ and SnO ₂ each of which is limited in the present invention, a transparent crystallized glass in which fine crystals were uniformly deposited as desired could not be obtained. .

That is, when only ZrO ₂ was added, crystallization was extremely unlikely to occur, and crystallization did not occur until heat treatment was performed at a relatively high temperature for a long time. The obtained crystallized glass was poorly transparent crystallized glass in which coarse crystal grains were deposited nonuniformly, and in the remarkable case, it was crystallized glass.

Further, when only SnO ₂ was added, fine crystals of only SnO ₂ were generated in the initial stage of the heat treatment, and the glass became cloudy. When the heat treatment was further continued, the crystals developed and became opaque.

Regarding crystallization accelerators such as TiO ₂ and ZrO ₂ that have been widely used in the past, they may be used alone or in the form of a compound with other components in the form of fine crystals with a size of several nm at the initial stage of heat treatment. It is said that the LiO ₂ -Al ₂ O ₃ -SiO ₂ -based crystals are precipitated by precipitating and using them as nuclei.

Of these, TiO ₂ has a strong absorption in the near-ultraviolet region, so a relatively small amount added as a crystallization accelerator, for example,
If the glass contains even 1.5 to 5 wt%, light with a wavelength shorter than about 290 nm will not be transmitted at all even in a composition with a small Fe ₂ O ₃ content. It shifts to the wavelength side by about 50 nm, and light with a wavelength shorter than about 340 nm does not pass at all. Further, when Fe ₂ O ₃ is contained in an amount of 0.01 wt% or more, which is mixed by using a normal glass raw material, the absorption at 600 nm or less becomes strong and the material is colored yellow.

In the glass containing TiO ₂ which is usually added as a crystallization accelerator in an amount of about 1.5 to 5% by weight, the present inventors have used 0.01% by weight to 0.1% by weight of Fe ₂ O mixed using an ordinary glass raw material. _{When 3} is contained, a colorless transparent crystallized glass cannot be obtained. Therefore, the present invention was accomplished by studying a crystallization accelerator instead of TiO ₂ and also studying the entire composition range.

Crystallized glass that does not contain TiO _{2 and} has very fine crystals uniformly deposited and has good transparency is SnO ₂ , ZrO _{2 as described} above.
It was obtained by adding and at the same time. The remarkable effect obtained for the first time by combining this ZrO ₂ and SnO ₂ is that, due to their interaction, SnO ₂ , ZrO ₂ or a compound containing them is finely and in large amounts precipitated as compared with the case of using each alone. As a result, Li that precipitates with these crystals as nuclei
It is thought that this is because the O ₂ -Al ₂ O ₃ -SiO ₂ system crystals also become fine.

Further, ZrO ₂ and SnO ₂ do not have absorption in the ultraviolet region and visible region of a relatively long wavelength region, and further, a large shift of absorption due to crystallization and Fe ₂ O _{3 of} TiO ₂ are 0.0
Since strong absorption in the visible region is not observed when the content is 1 wt% or more, transparent crystallized glass obtained by adding them usually contains TiO ₂ as a crystallization accelerator 1.5 to 5 wt%
It has an excellent visible light transmission that transparent crystallized glass does not contain.

Next, in order to make the crystallized glass according to the present invention sufficiently colorless and transparent, that is, specifically, the standard light C at a thickness of 5.0 mm.
Visible light transmittance measured by 2 ° visual field by light is 86% or more,
The reason why each component is limited so that the stimulation purity is 4% or less will be described.

When it exceeds SiO ₂ : 75.0 wt%, it becomes insoluble.

In addition, it becomes difficult to control crystallization, and a desired crystallization product cannot be obtained. If it is less than 60.0 wt%, the expansion coefficient of the crystallized glass becomes large. In order to obtain crystallized glass with good transparency, it is preferably 63.5 to 72.0 wt%.

If Al ₂ O ₃ : 30.0 wt% is exceeded, it becomes insoluble and the expansion coefficient increases. If it is less than 15.0 wt%, the transparency of the crystallized product will be poor.

In addition, in order to obtain a crystallized product with good transparency, 18.0 to 24.0
It is preferably set to wt%.

If Li ₂ O: 6.0 wt% is exceeded, rapid crystallization occurs during heat treatment, and the desired crystallization product cannot be obtained. If it is less than 2.5 wt%, it becomes insoluble.

In addition, 3.0 to obtain a crystallized product with good transparency.
It is preferably set to 5.0 wt%.

When SnO ₂ : 4.0 wt% is exceeded, the effect of promoting crystallization does not change, and undissolved matter is generated, which makes dissolution difficult. If it is less than 1.0 wt%, it becomes insoluble and the effect of promoting crystallization cannot be sufficiently obtained, so that the intended crystallized glass cannot be obtained.

When ZrO ₂ : 4.0 wt% is exceeded, undissolving is likely to occur and dissolution becomes difficult. If it is less than 1.0 wt%, the effect of promoting crystallization cannot be sufficiently obtained, the crystal grain size becomes large, and the transparency becomes poor.

If SnO ₂ + ZrO ₂ : 7.0 wt% is exceeded, undissolution occurs and it becomes difficult to dissolve. If it is less than 3.5 wt%, the effect of promoting crystallization cannot be sufficiently obtained, and the intended crystallized glass cannot be obtained.

_{Fe 2 O 3: Fe 2 O} 3 here are those to be mixed from impurities of the raw material, to the lower limit or less is required Fe ₂ O ₃ minutes of less pure material, leads to high cost If the upper limit is exceeded, the coloring becomes too dark.

Although not an essential component, the following components can be added to obtain the desired crystallized glass.

Na ₂ O and K ₂ O: The solubility can be improved, the crystallinity can be reduced, and the expansion coefficient can be adjusted. 4.0w each
If it is added in excess of t%, the transparency will deteriorate. In order to obtain a crystallized product with good transparency, the content is preferably 3.0 wt% or less, and is preferably 0.3 to 3.0 wt% in total.

MgO: Improves the solubility and greatly increases the expansion coefficient with a small amount of addition. Therefore, if added excessively, the expansion coefficient will become too large, or cracks will occur during crystallization and impair transparency, so it is preferably 4.0 wt% or less, and more preferably 2.0 wt% or less.

ZnO: Not only effective in improving solubility,
It lowers the crystallization temperature, reduces the crystal grain size, and improves transparency. However, if added excessively, devitrification occurs during gradual cooling of the glass, and control of heat treatment becomes difficult, so it is necessary to make it 4.0 wt% or less, and 2.0 wt% or less is more preferable. In order to make the β-spodumene solid solution as the main crystal, it is preferably 0 to 2.0 wt%.

P ₂ O ₅ : A small amount is effective for dissolving ZrO ₂ , but if it exceeds 4.0 wt%, an undissolved substance is produced.

A refining agent such as As ₂ O ₃ or Sb ₂ O ₃ can be added to the crystallized glass within a range that does not impair the properties of the final product.

As described above, when an ordinary low expansion transparent crystallized glass using TiO ₂ as a crystallization accelerator is manufactured using an inexpensive raw material containing a large amount of Fe ₂ O ₃ , it is colored deep yellow. However, in the present invention, TiO _{2 is} used as a crystallization accelerator.
By using SnO ₂ and ZrO ₂ without using the above and limiting the composition range as described above, a colorless low expansion transparent crystallized glass can be obtained even if the same inexpensive raw material as described above is used.

[Examples] The compositions, heat treatment conditions, and average thermal expansion coefficients (α _{50 to 800 of the} obtained crystallized glass of seven examples and one comparative example in the present invention in the temperature range of 50 to 800 ° C. ), 5.0 mm
Table 1 shows the visible light transmittance (Yc) and the stimulus purity (Pe) measured in the 2 ° visual field with the standard light C light at a thickness, and the results of identifying the crystal phase by X-ray diffraction.

First, Example 1 will be described. It was prepared by using ordinary glass raw materials so as to have the composition shown in Table 1. However
0.043 wt% of Fe ₂ O ₃ is an analytical value, which is a mixture of impurities such as raw materials. The prepared batch was melted at 1550 ° C using a platinum crucible, cast in a mold and slowly cooled to obtain a sample glass. This sample glass was tested at 780 ° C for 1h, 860 as shown in Table 1.
Crystallization was performed under a two-stage heat treatment condition of 1 ° C for 1 hour. The temperature rise at this time is
The treatment was performed at 300 ° C./h, the power was turned off after the treatment, and the mixture was allowed to cool to room temperature in the furnace.

The crystallized glass obtained had an excitation purity of 3.0% and a visible light transmittance of 88.2%, and was colorless and transparent. The precipitated crystal was a β-quartz solid solution and had a low expansion coefficient of 3.2 × 10 ^-7 K ^-1 .

In each of Examples 2 to 5, a sample glass was prepared in the same manner as in Example 1 and crystallized under the two-stage conditions shown in Table 1.
The Fe ₂ O ₃ content was 0.035 to 0.068 wt%, but all of the obtained crystallized glasses had an excitation purity of 4% or less and a visible light transmittance of 86% or more, and were colorless and transparent. The precipitated crystal was a β-quartz solid solution as in Example 1, and had a low expansion coefficient of | 6 | × 10 ⁻⁷ K ⁻¹ .

In each of Examples 6 and 7, a sample glass was prepared in the same manner as in Example 1 and crystallized under the one-stage condition shown in Table 1. The precipitated crystals of the obtained crystallized glass were β-spodumene solid solution, and the expansion coefficient was low as | 6 | × 10 ^-7 K ^-1 .
The content of Fe ₂ O ₃ is 0.035,0.065wt%, but the stimulation purity is 4% or less, and the visible light transmittance is 86%. % Or more, it was colorless and transparent.

The comparative example is a crystallized glass that does not include the present invention and uses TiO ₂ as a crystallization accelerator.

Sample glass was prepared in the same manner as in Example 1, and crystallized under the two-stage conditions shown in Table 1. The precipitated crystals of the obtained crystallized glass were β-quartz solid solution, had a low expansion coefficient of -6.0 × 10 ^-7 K ^-1, and had a visible light transmittance of 8
Although it was transparent at 8.1%, the irritation purity was 8.5% and it was colored yellow.

It is clear from the above results that the crystallized glass of the comparative example is very small in thermal expansion coefficient and high in transmittance, but has high stimulation purity and is colored. On the other hand, the crystallized glass obtained in the present invention has a similar small coefficient of thermal expansion,
It can be seen that it is a colorless crystallized glass having a high transmittance and a low excitation purity.

[Effect of the Invention] As described above, according to the present invention, it is generally used.
By using an inexpensive raw material containing a large amount of Fe ₂ O _3, it is possible to inexpensively obtain a colorless crystallized glass having a very small coefficient of thermal expansion and excellent heat resistance and transparency.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 55-3395 (JP, A) JP 42-9600 (JP, B1) JP 45-28914 (JP, B1)

Claims (1)

[Claims] 1. Li ₂ O 2.5 to 6.0 Na ₂ O 0 to 4.0 K ₂ O 0 to 4.0 Na ₂ O + K ₂ O 0 to 4.0 MgO 0 to 4.0 ZnO 0 to 4.0 Al ₂ O ₃ 15.0 to 1% by weight. _{30.0 SiO 2 60.0~75.0 SnO 2 1.0~4.0 ZrO} 2 1.0~4.0 consists composition of _{SnO 2 + ZrO 2 3.5~7.0 P 2} O 5 0~4.0 Fe 2 O 3 0.01~0.1, β- quartz solid solution crystals and / Or β
-Containing Spodumene solid solution as precipitated crystals, 5.0 mm
A low-expansion transparent crystallized glass having a visible light transmittance of 86% or more and a stimulus purity of 4% or less as measured in a 2 ° visual field with standard light C light at a thickness.