JPH11100230A - Infrared ray transmitting glass ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared ray transmitting glass ceramics free from the fear of environmental pollution and suitable as a top plate of cooking utensils. SOLUTION: This infrared ray transmitting glass ceramics has a composition by weight of 60-72% SiO2 , 14-28% Al2 O3 , 2.5-5.5% Li2 O, 0.1-3% MgO, 0.1-3% ZnO, 0-3% CaO, 0-5% BaO, 0.1-1% Ha2 O, 0-1% K2 O, 3-6% TiO2 , 0-3% ZrO2 , 0-3% P2 O5 , 0.01-0.03% V2 O5 , 0.1-2% SnO2 , 0-1% Cl and is structured by depositing β-quartz solid solution as a main crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared transmitting glass ceramic, and more particularly to an infrared transmitting glass ceramic used as a top plate for a smooth stop cooker.

[0002]

2. Description of the Related Art The top plate of a cooker has a high infrared transmittance, it is difficult to see through the internal heating means so as not to impair the aesthetic appearance, it has high mechanical strength and chemical durability, and it has a thermal shock resistance. And a low-expansion Li ₂ O—Al ₂ O ₃ having a dark brown color and a higher infrared transmittance than before.
-SiO ₂ based glass ceramics is used. As this type of material, for example, _{Li 2 O-Al 2 O 3} -SiO 2 based infrared transmitting glass ceramics which was added V ₂ O ₅ in Japanese Patent Publication No. 60-54896 is disclosed.

[0003] By the way, this kind of glass ceramics is
Requires high temperature melting above 1400 ° C. For this reason, As ₂ O _3, which can generate a large amount of fining gas at the time of melting at a high temperature, is used as a fining agent added to glass.

[0004]

SUMMARY OF THE INVENTION In batch melting,
After As ₂ O ₃ in the raw materials is oxidized to As ₂ O ₅ at 400 to 500 ° C., again As ₂ O ₃ at 1200 to 1800 ° C.
To release oxygen gas. The diffusion of the oxygen gas into the bubbles in the glass causes expansion and promotion of the floating of the bubbles, and the bubbles are removed. Due to this effect, As ₂ O ₃ is widely used as a fining agent for glass, and is particularly effective as a fining agent for Li ₂ O—Al ₂ O ₃ —SiO ₂ glass ceramics that require high-temperature melting. . However, As ₂ O ₃ is highly toxic, and may pollute the environment during the glass manufacturing process, waste glass treatment, and the like.

[0005] An object of the present invention is to provide an infrared-transmissive glass ceramic which has no risk of polluting the environment and is suitable as a top plate of a cooker.

[0006]

As As ₂ O ₃ except refining agents SUMMARY OF THE _{INVENTION, SnO 2, Sb 2 O 3} , CeO 2, various chlorides, and various There are sulfides, among others SnO ₂ or chloride Exhibits a fining effect in a temperature range exceeding 1400 ° C., and thus is suitable as a fining agent for glass that requires high-temperature melting. However, SnO ₂ has a strong reducing property and greatly changes the color tone of glass ceramics. Further, when used as a top plate of a cooker, the transmittance in the infrared region decreases, and the heating efficiency decreases.

The present inventors conducted various experiments and found that S
nO ₂ color change that for color development of the V ₂ O ₅ is intensified upon addition of, and to weaken the color of the V ₂ O ₅ found that it is sufficient to reduce the amount, those proposed as the present invention is there.

That is, the infrared transmitting glass ceramic of the present invention is composed of 60 to 72% of SiO ₂ and Al _{2
O 3 14~28%, Li 2 O} 2.5~5.5%, M
gO 0.1-3%, ZnO 0.1-3%, CaO 0
３3%, BaO 0-5%, Na ₂ O 0.1-1%,
_{K 2 O 0~1%, TiO 2} 3~6%, ZrO 2 0~
_{3%, P 2 O 5 0~3} %, V 2 O 5 0.01~0.
It has a composition of 03%, SnO2 0.1 to ₂ %, and Cl 0 to 1%, and is characterized in that a β-quartz solid solution is precipitated as a main crystal.

[0009]

The infrared transmitting glass ceramic of the present invention contains 0.1 to ₂ % (preferably 0.3%) of SnO2 as a fining agent.
~ 1.8%), Cl is 0 ~ 1% (preferably 0.01 ~
1%). In a high temperature range of 1400 ° C. or higher, SnO ₂ is subjected to a chemical reaction (SnO ₂
A large amount of oxygen gas, which is a fining gas, is released by [tetravalent] → SnO [divalent]). On the other hand, Cl is added as a chloride to the glass raw material and exists in the form of Cl ions in the glass melt. Like the oxygen gas, the Cl ions diffuse into the bubbles as the temperature of the glass increases, and cause the bubbles to expand and to promote floating. In the present invention, SnO ₂ may be used alone, but it is desirable to make Cl coexist in order to obtain higher clarity.

[0010] The glass ceramic of the present invention is a Li ₂ O-Al ₂ O ₃ -SiO ₂ having a β-quartz solid solution as a main crystal.
It is a system glass ceramic. Li ₂ O-Al ₂ O _3-
SiO ₂ -based glass ceramics include β-quartz solid solution and β
-Deposits spodumene and exhibits high mechanical strength and chemical durability, but when the amount of precipitated β-spodumene increases, not only does the glass ceramic become cloudy and there is no problem in appearance, And the infrared transmittance is undesirably reduced. Therefore, the present invention is characterized in that a β-quartz solid solution is used as a main crystal.

Hereinafter, the reasons for limiting the composition range as described above will be described.

When the content of SiO ₂ is less than 60%, the coefficient of thermal expansion becomes too large. On the other hand, if it is more than 72%, glass melting becomes difficult. The preferred range of SiO ₂ is 61-70%
It is.

When the content of Al ₂ O ₃ is less than 14%, the chemical durability is lowered and the glass is apt to be devitrified. Meanwhile, 2
If it is more than 8%, the viscosity of the glass becomes too large, and it becomes difficult to melt the glass. Suitable range of Al ₂ O ₃ is from 16 to 2
5%.

If the content of Li ₂ O is less than 2.5%, the crystal tends to become cloudy, and the coefficient of thermal expansion becomes too large.
On the other hand, if it is more than 5.5%, the glass tends to be cloudy and the glass tends to be devitrified. Suitable range of Li ₂ O is 3 to 5
%.

If the content of each of MgO and ZnO is less than 0.1%, the crystallinity becomes low and crystallization becomes difficult. On the other hand, if each is more than 3%, the crystal becomes cloudy and the thermal expansion coefficient becomes too large. The preferred ranges of MgO and ZnO are both 0.2 to 2.5%.

If the content of CaO is more than 3% and the content of BaO is more than 5%, the crystal becomes cloudy and the thermal expansion coefficient becomes too large.
Suitable ranges for CaO and BaO are 0-2% and 0-4.
%.

If the content of Na ₂ O is less than 0.1%, the crystallinity becomes low. If the content is more than 1%, the crystal becomes cloudy and the thermal expansion coefficient becomes too large. The preferred range of Na ₂ O is 0.1.
1 to 0.8%.

If K ₂ O is more than 1%, the crystal becomes cloudy,
Also, the coefficient of thermal expansion becomes too large. Suitable ranges of K ₂ O is from 0 to 0.8%.

When the content of TiO ₂ is less than 3%, the crystallinity is lowered. When the content of TiO ₂ is more than 6%, the glass is apt to be devitrified, and the color tone becomes too dark, thereby lowering the transmittance of infrared rays. Ti
A preferred range of O ₂ is from 3.4 to 5.5%.

If ZrO ₂ is more than 3%, the glass tends to be devitrified. Suitable range of ZrO ₂ is 0 to 2.5%.

If the content of P ₂ O ₅ is more than 3%, the crystal becomes cloudy and the thermal expansion coefficient becomes too large. Suitable range of P ₂ O ₅ is 0 to 2.5%.

When V ₂ O ₅ is less than 0.01%, the color tone becomes thin, and the transmittance of visible light becomes too high. on the other hand,
If it exceeds 0.03%, the color tone becomes too dark and the infrared transmittance becomes too low. A preferred range for V ₂ O ₅ is 0.01
~ 0.02%.

If SnO ₂ is less than 0.1%, the fining effect is not obtained, and if it is more than 2%, the color tone becomes too deep. In addition, glass melting becomes difficult or devitrification tends to occur. SnO ₂
Is in the range of 0.3 to 1.8%.

When the Cl content is more than 1%, the chemical durability is reduced. The preferred range for Cl is 0.01-1%.

The glass ceramic having the above composition is
It has a plate thickness of 3 mm and has a visible light transmittance of 5% or less at a wavelength of 500 nm and an infrared transmittance of 70% or more at a wavelength of 1500 nm. In addition, the glass ceramic of the present invention has a temperature in the range of 30 to 750 ° C. of −5 to 30 × 10 ^−7.
/ ° C indicates an average linear thermal expansion coefficient.

The infrared transmitting glass ceramic of the present invention can be manufactured as follows.

First, the weight percentage of SiO_Two 60-72
%, Al_Two O_Three 14-28%, Li _Two O 2.5 ~
5.5%, MgO 0.1-3%, ZnO 0.1-3
%, CaO 0-3%, BaO 0-5%, Na_Two O
0.1-1%, K_Two O 0-1%, TiO_Two 3-6
%, ZrO_Two 0-3%, P_Two O_Five 0-3%, V_Two O
_FiveGlass raw material so as to have a composition of 0.01 to 0.03%
To mix. At this time, SnO was used as a fining agent._Two From 0.1 to
2% and chloride are added at 0 to 5% in terms of Cl.

Next, the prepared glass raw materials were mixed with 1550-17
After melting at 00 ° C. for 4 to 20 hours, it is molded.

Subsequently, the glass molded body was held at 700 to 800 ° C. for 2 to 4 hours to form nuclei.
By crystallizing by heat treatment at 0 ° C. for 1 to 3 hours,
An infrared transmitting glass ceramic having the above composition can be obtained.

The obtained glass ceramics are subjected to post-processing such as cutting and polishing, or painted on the surface, and then used for applications such as top plates.

[0031]

EXAMPLES The infrared transmitting glass ceramics of the present invention will be described below based on examples.

Tables 1 to 3 show examples of the present invention (sample No. 1).
10 to 10) and Reference Examples (Sample Nos. 11 and 12).

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Each sample was prepared as follows.

First, raw materials were prepared so as to obtain a glass having the composition shown in the table, uniformly mixed, and then melted at 1550-1650 ° C. for 8-20 hours in an electric furnace using a platinum crucible.
Next, the molten glass was poured on a carbon platen, formed into a thickness of 5 mm using a stainless steel roller, and further cooled to room temperature using a slow cooling furnace. This glass molded body was placed in an electric furnace, and was heated from room temperature to 780 at a rate of 300 ° C./h.
The temperature was raised to 0 ° C. and maintained for 2 hours to form nuclei. Subsequently, the temperature was raised to 850 ° C. at a rate of 80 ° C./h, and the temperature was maintained for 1 hour to perform crystallization, followed by furnace cooling.

Each of the samples of the examples obtained in this way had a dark brown to black appearance without white turbidity, and had a glossy smooth surface. As a result of measurement using an X-ray diffractometer, it was found that β-quartz solid solution was precipitated as a main crystal in each sample. A 3 mm-thick sample piece that had been optically polished to a size of 25 × 30 mm was prepared, and the transmittance at wavelengths of 500 nm and 1500 nm was measured using a spectrophotometer. As a result, each sample was 500 n
m shows a transmittance of 4.1% or less at a wavelength of m and a transmittance of 82.0% or more at a wavelength of 1500 nm, and has a V ₂ O ₅ content of more than 0.03%. An infrared transmittance higher than 12 was obtained. Furthermore, the sample is 50mm x 5mmφ
Was processed into a solid bar of, and the average linear thermal expansion coefficient in a temperature range of 30 to 750 ° C. was measured to be −2 to 14 × 10 ⁻⁷ / ° C.
Met.

Next, the clarity was evaluated. Evaluation is 15
The sample was melted at 50 to 1650 ° C. for 4 to 8 hours, roll-formed to prepare a sample, and the number of bubbles per unit weight in the sample was counted. As a result, N
o. Each sample of 1 to 10 exhibited almost the same clarity as in Reference example using As ₂ O ₃ as a fining agent.

[0040]

As described above, the infrared transmitting glass ceramics of the present invention does not need to use As ₂ O ₃ as a fining agent, so that there is no possibility of polluting the environment.
In addition, it has high infrared transmittance and low visible light transmittance. In addition, since it has excellent properties such as mechanical strength, chemical durability, and thermal shock resistance, it is particularly suitable as a top plate for a smooth stop cooker.

Claims (2)

[Claims] 1. 60% to 72% by weight of SiO ₂ ,
_{Al 2 O 3 14~28%, Li} 2 O 2.5~5.5
%, MgO 0.1-3%, ZnO 0.1-3%, C
aO 0-3%, BaO 0-5%, Na ₂ O 0.1
_{~1%, K 2 O 0~1%} , TiO 2 3~6%, Zr
_{O 2 0~3%, P 2 O} 5 0~3%, V 2 O 5 0.
01 to 0.03%, SnO ₂ 0.1 to ₂ %, Cl 0
An infrared-transmitting glass ceramic having a composition of about 1% and a β-quartz solid solution precipitated as a main crystal. 2. The infrared transmitting glass ceramic according to claim 1, which is used as a top plate of a cooker.