JPH04198060A - Light-transmitting ceramics and production thereof - Google Patents

Abstract

PURPOSE:To obtain the light-transmitting ceramics having improved light transmittance in the visible light region by adding a specific acrylic resin and a binder to a mixture of MgO, Y2O3., and Al2O3, injection-molding the mixture, removing the acrylic resin and the binder from the molded product, and subsequently sintering the remaining molded product. CONSTITUTION:A mixture of 0.01-0.2wt.% of Mg0 powder, 0.01-0.2wt.% of Y2O3, and the remaining amount of Al2O3, each having an average particle size of <=0.8mum, is mixed with 1-10wt.% of an acrylic resin having a glass transition point of <=100 deg.C, and spray-dried to obtain granular powder. The granular powder is kneaded with a binder so that the sum of the acrylic resin and the binder is 35-70vol.%, and subsequently injection-molded. The molded product is heated at 400-600 deg.C in the atmosphere or in an inert gas atmosphere to remove the acrylic resin and the binder, followed by sintering the remaining molded product at 1600-2000 deg.C in a hydrogen gas atmosphere or in vacuo to obtain a light-transmitting ceramics having an in-line transmittance (1mm thick) of >=70%. The binder is a 4:1-1:4 mixture of a thermoplastic resin (e.g. PE having a melt flow rate of 100-300g/10min) and contributing to the shape retention of the molded product with a thermoplastic resin (e.g. paraffin wax having a Vicat softening point of 50-90 deg.C) and contributing to the flowability of the kneaded product on the injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic exhibiting transparency in the visible light region and a method for manufacturing the same.

(Prior Art) Translucent ceramics are generally manufactured by press-molding ceramic powder and then sintering it. However, with this method, it is difficult to manufacture products with three-dimensionally complex shapes or products with thin-walled parts. In addition, in order to obtain products with complex shapes,
After sintering, the sintered body was polished by mechanical polishing, but depending on the conditions of the mechanical polishing, fine racks called hair cracks were formed on the surface of the sintered body, which affected the mechanical strength and toughness of the product. In addition, there is a problem in that mechanical polishing requires a considerable amount of time, resulting in an increase in product price.

In order to eliminate these drawbacks of conventional methods, a mixture of a mixed powder of aluminum oxide powder, magnesium oxide powder, and yttrium oxide powder mixed with an organic binder was injection molded into a mold of a predetermined shape. Attempts have been made to heat the injection molded body to remove the binder and then perform a sintering treatment to produce a translucent ceramic product. According to this method, it is possible to manufacture products with complex shapes.

(Problem to be Solved by the Invention) However, in the above injection molding method, since an organic binder is used in addition to the metal oxide mixed powder, magnesium oxide powder and yttrium oxide powder, which are used in small quantities, are used. It is extremely difficult to uniformly disperse aluminum oxide powder into the aluminum oxide powder, resulting in uneven composition distribution of the resulting sintered body, and as a result, satisfactory translucency cannot be obtained. There's a problem.

Therefore, an object of the present invention is to provide ceramics with excellent translucency, and to provide a method capable of manufacturing a ceramic molded article with excellent translucency and a complicated shape.

(Means for achieving the object) According to the present invention, magnesium oxide 0.01 to 0.2
There is provided a translucent ceramic comprising 0.01 to 0.2 wt% yttrium oxide and the balance aluminum oxide, and having an in-line transmittance of 70% or more at a thickness of 1 mm.

According to the present invention, the composition further includes (a) 0.01 to 0.2% by weight of magnesium oxide powder, 0.01 to 0.2% by weight of aluminum oxide powder, and the remainder being aluminum oxide powder. A step of preparing a mixed powder such that (bl) an acrylic resin having a glass transition temperature of 100° C. or less is mixed with the mixed powder in an amount of 1 to 10% by weight of the total, and magnesium oxide powder and yttrium oxide are mixed. (c) adding a binder material to the mixed powder in which the magnesium oxide powder and yttrium oxide powder are uniformly dispersed; the total amount of the binder material and the acrylic resin; or the whole 3
(d) injection molding the kneaded product into a molded body of a predetermined shape; (el) removing the acrylic resin and binder material from the molded body; (f) The molded article from which the acrylic resin and binder material have been removed is heated for 160 minutes in a hydrogen atmosphere or in a vacuum.
A method for manufacturing translucent ceramics is provided, which comprises a step of firing at 0 to 2000°C.

In the conventional injection molding method, the metal oxide powders of magnesium oxide, yttrium oxide, and aluminum oxide were mixed with the binder material at the same time. Uniform dispersion could not be achieved, and as a result, ceramics with excellent translucency could not be obtained.

However, according to the present invention, magnesium oxide and yttrium oxide are uniformly dispersed by adding acrylic resin to the metal oxide mixed powder in advance, and then a binder material is added to the mixture for injection molding, firing, etc. By performing this process, it became possible to obtain ceramics with excellent translucency.

Manufacturing method The translucent ceramics of the present invention is produced by the above steps (a) to (
Each of these steps will be explained below.

Step (a): In the present invention, first, a mixed powder of magnesium oxide, yttrium oxide, and aluminum oxide is prepared, and this mixed powder is used as a starting material.

The composition of this mixed powder is magnesium oxide powder or 0.0
1 to 0.2% by weight, and yttrium oxide powder or 0,0
It is important that the amount is 1 to 0.2% by weight, and that the remainder be aluminum oxide powder.If the composition is outside this range, satisfactory translucency cannot be obtained.

That is, in order to exhibit translucency, it is necessary that the relative density of the sintered body obtained by sintering, which will be described later, be at least 99%. Magnesium oxide suppresses the growth of crystal grains in the final stage of sintering, thereby promoting the disappearance of bores inside the grain boundaries and improving the sintered density, and also helps to make the grain sizes uniform. It acts on Therefore, magnesium oxide plays a major role in improving translucency. For example, if the magnesium oxide content is less than 0.01% by weight, it is insufficient to exhibit such an effect, the density of the sintered body is not high enough, and satisfactory translucency cannot be obtained. . Also, if it is more than 0.2% by weight,
Magnesium oxide or a composite oxide of magnesium oxide and other metal oxides is formed at the grain boundaries of the sintered body, causing light scattering and resulting in an inconvenience such as a decrease in translucency. Furthermore, yttrium oxide has the effect of significantly increasing the effect of magnesium oxide as a sintering aid;
If the content is less than 0.01% by weight, such effects will not be fully exhibited and the density of the sintered body will not be sufficiently high, making it difficult to obtain, for example, in-line transmittance or translucency of 70% or more. I can't do it. If the amount exceeds 0.2% by weight, yttrium oxide or a composite oxide of yttrium oxide and other metal oxides will be formed at the grain boundaries of the sintered body, resulting in a decrease in translucency as described above. invite.

In the present invention, commercially available metal oxide powders can be used to prepare the mixed powder, but in order to achieve translucency, it is preferable to use highly purified metal oxide powders. It is. Further, in order to improve the sintered density and exhibit good translucency, it is desirable that the average particle size of these particles be in the submicron order, for example, in the range of 0.8 μm or less.

Step (b): In the present invention, next, an acrylic resin is mixed into the mixed powder. This acrylic resin has a surfactant-like effect, and by using it,
Magnesium oxide powder and yttrium oxide powder are uniformly dispersed in the aluminum oxide powder.

This acrylic resin may be added from 1 to 10% per total mixture obtained.
It is used in proportions by weight of IO, in particular from 2 to 6% by weight. The amount of acrylic resin used is less than 1% by weight or 10% by weight
When the magnesium oxide and yttrium oxide are not uniformly dispersed, the final product (
The translucency of the sintered body differs depending on the part.

In addition, this acrylic resin has a glass transition temperature (T
g) having a temperature of 100°C or less is used. If an acrylic resin with a glass transition temperature higher than 100° C. is used, the molded product obtained by injection molding, which will be described later, will be hard and brittle, causing problems in its handling. Specific examples of acrylic resins include methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate,
Cyclohexyl acrylate, 2-ethylcyclohexyl acrylate, propyl acrylate, hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate,
Examples include polymers such as butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, and lauryl methacrylate. They can be used alone or in a blend of two or more, and two or more of the above monomers can also be copolymerized and used.

The above-mentioned acrylic resin and the mixture prepared in step (a) can be mixed by various methods known per se, or by a method of producing granular powder using a spray dryer, which is often used in fine ceramics. is the most suitable.

Step (c): In this step (c), a binder material is added to the mixed powder in which magnesium oxide and yttrium oxide obtained in step (b) are uniformly dispersed, and crosstalk is performed.

The binder material used in this process is used to effectively perform injection molding, which will be described later, and is usually a thermoplastic plastic that contributes to the shape retention of the molded product after injection molding and a binder material that is used to maintain the shape of the molded product after injection molding. used in combination with thermoplastics that contribute to its properties.

Thermoplastics that contribute to this shape retention include melt flow rate (MF, R, ASTM D 12
Examples of thermoplastic resins having a temperature (36° to 230° C.) of 100 to 300 g/10 minutes include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, and polystyrene. If the MFR is lower than 100g/10min,
Injection moldability is unsatisfactory, and 300g/10
If it is higher than 100%, the strength and shape retention of the injection molded article will decrease.

In addition, as a thermoplastic plastic that contributes to fluidity during injection molding, Vicat softening point (JIS K 7206)
For example, waxes such as paraffin wax, microcrystalline wax, low molecular weight polyethylene wax, modified wax, and atactic polypropylene can be mentioned. If the softening point is lower than 50° C., the cycle time of injection molding becomes longer, and the resin is easily softened, resulting in disadvantages such as poor workability during molding. Furthermore, the softening point is 90
When the temperature is higher than 0.degree. C., the fluidity decreases and the thermal decomposition point increases, resulting in a decrease in binder removal properties.

Thermoplastic plastics that contribute to these shape retention and thermoplastic plastics that contribute to fluidity during injection molding differ depending on the type, or generally have a weight of 4.
:I to 1:4, particularly preferably 3:1 to 1:3.

In the present invention, the above-mentioned binder material, in total amount with the above-mentioned acrylic resin, is 35 to 70% per kneaded material.
It is necessary that it be used in the proportion of % by volume. If it is less than 35% by volume, the fluidity of the kneaded product will decrease and injection molding will be difficult, and if it exceeds 75% by volume, it will be very difficult to remove the binder, resulting in a decrease in the translucency of the final product, etc. cause inconvenience.

Further, kneading with the binder material can be easily carried out using a kneading device such as a kneader 1 or various mixers.

Step (d): Next, the kneaded material prepared in step (c) is injected into a mold having a desired shape to obtain a molded product having the desired shape.

This injection molding can be carried out using the equipment and equipment used for ordinary injection molding of plastics as they are. In general, the injection conditions are preferably heating temperature of 80 to 200° C., injection pressure of 500 to 2000 kg/a.

Step (e): Next, the molded body is debindered to remove the acrylic resin and binder material contained in the molded body.

This debinding is usually carried out by heating in the air or in an inert atmosphere such as nitrogen gas.

The heating temperature ranges numerically from 400 to 600°C.

Step (f); Following the binder removal described above, a firing treatment is performed.

In the present invention, it is necessary to perform this firing in a hydrogen atmosphere or in a vacuum. Generally, in the final stage of firing, small bores are usually present within the crystal grains, and eliminating these bores is important for improving translucency. In other words, if firing is performed in hydrogen, hydrogen will remain in the bore, or because hydrogen has excellent diffusivity, it will easily pass through the bore through the grain boundaries and be discharged from the fired body. be done. As a result of this, the bore easily disappears due to ion diffusion. Furthermore, since there is almost no gas inside the bore in a vacuum, the bore is similarly easily annihilated by the diffusion of ions. Therefore,
Ceramics with excellent translucency can be obtained by firing in a hydrogen atmosphere or in a vacuum.

The firing temperature is 1,600 to 2,000℃, especially 1,700℃.
1850'c range. At temperatures lower than 1600°C, the relative density of the resulting fired body will not be sufficiently improved,
As a result, the light transmittance decreases, and if firing is performed at a temperature higher than 2000°C, magnesium evaporates from the surface of the fired body, and as a result, the relative density of the surface of the fired body does not improve, and the light transmittance decreases. This will result in whitening.

Such firing is performed to such an extent that the relative density of the fired body is 99% or more.

Translucent Ceramics The thus obtained ceramics of the present invention has a composition of 0.01 to 0.2% by weight of magnesium oxide, 0.01 to 0.2% by weight of yttrium oxide, and the balance aluminum oxide. , it has extremely good transparency in the visible light range. For example, as is clear from the examples described later, the in-line transmittance is in the range of 70% or more. This in-line transmittance indicates the ratio of the intensity of transmitted light incident within a certain angle to the intensity of incident light when a parallel light beam of a certain intensity is incident on a sample of a certain thickness.

(Example) Example 1 Magnesium oxide powder was prepared by using magnesium oxide powder with an average particle size of 0.15 μm, yttrium oxide powder with an average particle size of 0.15 μm, and aluminum oxide powder with an average particle size of 0.15 μm. A mixed powder containing 0.05% by weight of yttrium oxide and yttrium oxide was prepared.

Next, as an acrylic resin, polybutyl methacrylate (glass transition temperature: 20°C) was added to the above mixed powder in various amounts as shown in Table 1, and the mixture was dried using a centrifugal spray dryer. Granulation was performed to prepare a homogeneous dispersion. The median particle size of the prepared uniform dispersion (granules) is approximately 40 μm.

Various thermoplastic plastics were added as binder materials to each of these uniform dispersions, and kneaded products were prepared using a planetary mixer. The types of thermoplastic plastics used and the amounts added are as shown in Table 1. In addition, the volume % of the total amount of this thermoplastic plastic and the acrylic resin (polybutyl methacrylate) is also the first
Shown in the table.

This kneaded material was injection molded using an injection molding machine at an injection temperature of 90''C and an injection pressure of 600 kg/cnr to obtain a disc-shaped molded product with a diameter of 10 plates and a thickness of 2 mm.

Next, the molded body was removed from the binder while being heated in an air stream (heating temperature: 500'C), and then fired for 6 hours at a temperature of I800'C in a hydrogen stream.

The surface of the obtained sintered body was polished with diamond to a thickness of 1
After aligning the cabinet, use an absorbance meter to measure the visible light range (300 nm).
m~11l100n Tin line transmittance was measured.

The measurement results are shown in Table 1.

The physical properties of the thermoplastic plastic used as the binder material are as follows.

Polyethylene; Polystyrene: Polybropylene; Ethylene-vinyl acetate copolymer; Paraffin wax; Atactic polypropylene: Modified wax; Examples 2 to 7 The magnesium oxide content and yttrium oxide content in the mixed powder of metal oxides are as shown in Table 1. Various changes were made to
Further, a disk-shaped injection molded article was prepared in the same manner as in Example 1, except that the type and amount of the thermoplastic plastic used were changed as shown in Table 1.

Furthermore, a sintered body was obtained in the same manner as in the example except that the firing was performed in a hydrogen stream.

Table 1 shows the in-line transmittance of the obtained sintered body.

Comparative Examples 1 to 7 Same as Examples 2 to 6 above, except that the amounts of magnesium oxide powder, yttrium oxide powder, polybutyl methacrylate, and thermoplastic plastic as a binder material were varied for comparison. A sintered body was prepared using the same method, and its in-line transmittance was measured. The measurement results are shown in Table 2.

In Comparative Examples 1 to 3, the amounts of magnesium oxide and yttrium oxide used were outside the scope of the present invention, and in Comparative Examples 4 and 5, the amounts of polybutyl methacrylate used were outside the scope of the present invention. Examples 6 and 7 are examples in which the total amount of polybutyl methacrylate and thermoplastic plastic is outside the scope of the present invention.

(Effects of the Invention) The ceramics of the present invention have extremely excellent translucency in the visible light region, and according to the manufacturing method of the present invention, three-dimensionally complex shapes can be manufactured using the injection molding method. It becomes possible to effectively produce a ceramic molded product that has the following properties and has excellent translucency.

Claims (2)

[Claims] (1) Consisting of 0.01 to 0.2% by weight of magnesium oxide, 0.01 to 0.2% by weight of yttrium oxide, and the balance being aluminum oxide, and having an in-line transmittance of 70% or more at a thickness of 1 mm. Translucent ceramics. (2) (a) Prepare a mixed powder so that it has a composition of 0.01 to 0.2 wt% magnesium oxide powder, 0.01 to 0.2 wt% yttrium oxide powder, and the balance aluminum oxide powder. Step (b) Mixing an acrylic resin with a glass transition temperature of 100°C or less into the mixed powder in an amount of 1 to 10% by weight of the total, and adding magnesium oxide powder and yttrium oxide powder to aluminum oxide powder. (c) A binder material is added to the mixed powder in which magnesium oxide powder and yttrium oxide powder are uniformly dispersed, and the total amount of the binder material and the acrylic resin is 3% of the total amount.
(d) injection molding the kneaded product into a molded body of a predetermined shape; (e) removing the acrylic resin and binder material from the molded body; and (f) the molded body from which the acrylic resin and binder material have been removed is heated for 160 minutes in a hydrogen atmosphere or in a vacuum.
A method for producing translucent ceramics, comprising the steps of firing at 0 to 2000°C.