KR20180102711A - Method for preparing glass-ceramics, capable of adjusting machinability or translucency through change in temperature of heat treatment - Google Patents

Abstract

The present invention relates to a method for manufacturing lithium disilicate crystallized glass containing a silicate as a main component. More particularly, the present invention relates to a method for manufacturing crystallized glass capable of controlling workability or light transmittance according to the size of a crystal by using a primary heat treatment or a secondary heat treatment. The method for manufacturing crystallized glass including the silica crystalline of the present invention comprises the steps of: performing a primary heat treatment at 400-850°C, wherein a lithium disilicate crystalline and silica crystalline of 5-2000 nm are formed; and performing a secondary heat treatment at 780-880°C after the first heat treatment, wherein the light transmittance is controlled by the temperature of the second heat treatment.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a crystallized glass capable of controlling workability or light transmittance by changing a heat treatment temperature,

The present invention relates to a process for producing a crystallized glass of lithium disilicate having a silicate as a main component, and more particularly, to a process for producing a crystallized glass capable of controlling the crystal size, light transmittance and workability by using a primary heat treatment or a secondary heat treatment .

As the economy develops and the national income grows, interest in the appearance increases, and interest in the esthetics of the dental prosthesis is also rising in response to this interest. Accordingly, many kinds of esthetic restorative materials have been introduced. Among them, non-metallic crown materials that do not use metals are being developed in various ways.

The crown material refers to a prosthetic material that restores dentin and enamel of a damaged tooth, and can be divided into inlay, onlay, veneer, and crown depending on the application site. Since the crown material is restored to the outer surface of the teeth, aesthetic characteristics are greatly required, and high strength is required due to abrasion, chipping, and the like of the crown material. Conventionally, materials used as crown materials are leucite glass-ceramics, reinforced porcelain or fluorapatite (Ca ₅ (PO ₄ ) ₃ F) crystallized glass, which have excellent aesthetic properties, It is low at 80 ~ 120 MPa, and there is a disadvantage that the possibility of fracture is high. Accordingly, research is underway to develop high-strength crown materials of various materials at present.

Lithium silicate crystallized glasses were prepared by the method described in Marcus P. Borom and Anna M. Turkalo (Glass division, No. 3-G-73P) in 1973, San Francisco, CA, October 31, 1973 .

Crystalline phases and strengths of various crystal nucleation and growth heat treatments were studied using Li ₂ O-Al ₂ O ₃ -SiO ₂ -Li ₂ OK ₂ OB ₂ O ₃ -P ₂ O ₅ glass. When referring to a high temperature lithium disilicate crystal phase from the lithium metasilicate of low temperature 30 ~ 35 Kpsc (kilogram per square centimeter; Kg / ㎠) showed a strength of, this base glass, the parent _{glass, Li 2 SiO 5, Li 2} SiO 3 Due to the residual stress due to the difference in thermal expansion coefficient of the phases.

Materials and methods for making artificial teeth using glass containing lithium disilicate crystals (monolithic dental crowns) are already known in various patents. However, the known techniques are difficult to machine the crystal phase immediately after the crystal phase is coarsened. For machining, a lithium metal silicate crystalline phase is first formed and processed, and then a second heat treatment is performed to form a high- The accuracy of dimensions is reduced due to shrinkage due to the heat treatment process, and there is a problem that a heat treatment process is added. In general, the CAD / CAM process must be started directly at the hospital and started as quickly as possible to the patient (one-day appointment), which adds time and cost to the patient and the user.

In addition, conventional lithium disilicate crystallized glass materials have a limitation in realizing high light transmittance and opalescence similar to natural ones due to coarse crystal phase.

Particularly, the conventional lithium disilicate crystallized glass material is produced by forming lithium metasilicate crystallized glass having good processability for processing, forming lithium disilicate through the secondary crystallization heat treatment after processing, At this time, the crystal phase size was about 3 ㎛ or more. In this state, the workability was remarkably decreased and only the strength portion could be realized.

EP 1534169B

A problem to be solved by the present invention is to propose a method of manufacturing a crystallized glass including a lithium disilicate crystal phase, a silicate crystal phase and a silica crystal phase having excellent processability by controlling crystal size (nano size) by a first heat treatment temperature change.

Another problem to be solved by the present invention is to provide a method of manufacturing a crystallized glass capable of adjusting light transmittance by controlling the size of a lithium disilicate crystal phase, a silicate crystal phase and a silica crystal phase having a nanocrystal phase.

To this end, the glass composition of the present invention comprises 60 to 83% by weight of SiO ₂ , 10 to 15% by weight of Li ₂ O, 2 to 6% by weight of P ₂ O ₅ serving as a nucleating agent and increases the glass transition temperature and softening point, 1 to 5% by weight of Al ₂ O ₃ improving the chemical durability of the glass, 0.1 to 3% by weight of SrO, 0.1 to 2% by weight of ZnO and 1 to 5% by weight of colorant to increase the glass softening point; And a mixture of alkali and alkaline-earth _{(Na 2 O + K 2 O} ) of increasing the coefficient of thermal expansion of the glass 2.5 to 6 wt%.

To this end, the method for producing a crystallized glass including the silica crystal phase of the present invention is characterized in that the glass composition is subjected to a first heat treatment at 400 to 850 ° C, and a lithium disilicate crystal phase and a silica crystal phase are generated by 5 to 2000 nm by a first heat treatment .

To this end, the method for producing a crystallized glass including the silica crystal phase of the present invention is characterized in that the second heat treatment is performed at 780 to 880 ° C after the first heat treatment, and the light transmittance is controlled by the temperature of the second heat treatment.

The processability and transparency of the glass proposed in the present invention can be variously controlled by one heat treatment or a second heat treatment. Generally, the crystal size in the crystallized glass can be controlled according to the temperature. In the present invention, the lithium disilicate crystal phase and the silica crystal phase are produced through the first heat treatment, and in particular, the crystal phase produced through the first heat treatment At 480 to 800 ° C, and the size of the crystal phase produced at this time is 30 to 500 nm.

In addition, when the final prosthetic prosthesis is completed, a variety of translucent products are required in clinical practice. The present invention proposes a product having a transmittance of 55 to 27% (at a wavelength of 550 nm) through a secondary heat treatment.

As described above, the present invention proposes a method of manufacturing a crystallized glass in which processability and transparency are controlled so that it can be practically used in clinical practice through a first heat treatment condition and a second heat treatment condition.

FIG. 1 is a diagram showing a microstructure observed with a scanning electron microscope in a state where a starting material is subjected to a first heat treatment. FIG.
Fig. 2 is a diagram of a crystalline phase measured by X-ray diffraction analysis in a state where the starting material is subjected to the first heat treatment.
FIG. 3 shows the results of measuring the size of the lithium disilicate crystal phase and the processing resistance (cutting force) according to the first heat treatment temperature.
4 is a light transmission spectrum result data according to a second heat treatment temperature.
5 shows the results of measurement of the size and light transmittance of the lithium disilicate crystal phase according to the second heat treatment temperature.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and further aspects of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

The present invention relates to a glass material capable of controlling the size of crystals at a heat treatment temperature and a method for producing crystallized glass for dental use. In the present invention, a glass composition capable of controlling the size and distribution of crystals according to the heat treatment temperature is developed to solve the esthetics required for the dental materials and the processability of the dental materials. do.

The high-strength crystallized glass for teeth proposed in the present invention includes a silica crystal phase, lithium disilicate crystals and vitreous, and exhibits a very similar color to teeth as a whole, and thus has a high aesthetic property and is suitable for use as a dental material.

Aesthetics In particular, light transmittance greatly affects the degree of scattering of light due to the difference in refractive index of the heterogeneous crystal phase in a compact bulk body. The refractive index of the silica crystal phase is 1.48, and as the content thereof increases, the interface between the glass or the lithium disilicate crystal phase is increased, so that light scattering becomes worse and the transmittance becomes lower. Therefore, it is possible to manufacture a prosthetic material having various translucency by forming only an appropriate amount of silica crystal phase in the glass in order to exhibit the light transmittance that can be used in dentistry.

Conventional lithium disilicate crystallized glass is formed by first forming a lithium metasilicate crystallized glass having a strength of 220 MPa or less and performing secondary crystallization heat treatment to a strength of about 350 MPa To make the prosthesis. At this time, since the transmittance of these materials has already been determined in terms of composition in the block state, various products and amounts are required as many as the required number of light transmittance, and the number of transmissive properties that can be implemented is limited.

The present invention proposes a material capable of being processed in a lithium disilicate state rather than a conventional lithium metasilicate crystal phase by forming a nano-sized lithium disilicate crystal phase and a silica crystal phase, and at the same time, processability and transmittance can be controlled according to the crystallization temperature. Accordingly, it is possible to produce a product having a desired transmittance with a different temperature even with one product, and to produce a product having various light transmittance. Also, the mechanical properties are increased due to the crystals grown after the second heat treatment, and especially the biaxial flexural strength of 490 MPa or more is exhibited.

It can meet the needs of customers who want various light transmittance, and the physical properties are also improved compared to the existing products.

The silica of the present invention The glass containing the crystal phase contains 60 to 83% by weight of SiO ₂ , 10 to 15% by weight of Li ₂ O, 2 to 6% by weight of P ₂ O ₅ serving as nucleating agent, increases the glass transition temperature and softening point, 1 to 5% by weight of Al ₂ O ₃ improving chemical durability, 0.1 to 3% by weight of SrO, 0.1 to 2% by weight of ZnO and 1 to 5% by weight of colorant to increase softening point of glass, And 2.5 to 6 wt% of an alkali and alkaline earth mixture (Na ₂ O + K ₂ O) that increases the coefficient of thermal expansion of the substrate.

The high-strength crystallized glass for teeth according to a preferred embodiment of the present invention may further comprise 1 to 5% by weight of a colorant as described above to impart the same or similar color to teeth. The coloring agent is for imparting the same or similar color and fluorescence as that of the teeth. The coloring agent includes red iron oxide (Fe ₂ O ₃ ), ceria (CeO ₂ ) showing yellow, vanadium pentoxide (V ₂ O ₅ ) showing orange color, Vanadium (V ₂ O ₃ ), Er ₂ O ₃ , Tb ₂ O ₃ , Pr ₂ O ₃ , TaO ₂ , MnO _2, or mixtures thereof. For example, red iron oxide (Fe ₂ O ₃ ), ceria (CeO ₂ ), or vanadium pentoxide (V ₂ O ₅ ) is added together with the starting material and melted to give a yellow color similar to the color of teeth, Titanium oxide (TiO ₂ ) is white and gives a color very similar to the color of teeth.

Li ₂ CO ₃ may be added in place of Li ₂ O, and carbon dioxide (CO ₂ ), which is a carbon (C) component of Li ₂ CO ₃ , may be added to the glass as a gas And discharged. Further, K ₂ CO ₃ and Na ₂ CO ₃ may be added instead of K ₂ O and Na ₂ O in the alkali oxide, and carbon dioxide (CO ₂ ) of K ₂ CO ₃ and Na ₂ CO ₃ , ) Is discharged into the gas in the melting process of the glass and then escapes.

The mixing may be performed using a dry mixing process, and a ball milling process may be used as a dry mixing process. Specifically, the starting material is charged into a ball milling machine, and the ball milling machine is rotated at a constant speed to mechanically pulverize the starting material and mix it uniformly. The ball used for the ball milling machine may be a ball made of a ceramic material such as zirconia or alumina. The balls may have the same size or at least two sizes. Considering the size of the target particle, adjust the size of the ball, the milling time, and the rotation speed per minute of the ball miller. For example, the size of the balls may be set in the range of about 1 mm to 30 mm in consideration of the size of the particles, and the rotation speed of the ball miller may be set in the range of about 50 to 500 rpm. The ball milling is preferably performed for 1 to 48 hours in consideration of the target particle size and the like. By ball milling, the starting material is pulverized into fine sized particles, having a uniform particle size and being uniformly mixed at the same time.

The mixed starting material is placed in a melting furnace, and the starting material is melted by heating the melting furnace containing the starting material. Here, melting means that the starting material is changed into a liquid state viscous material state, not a solid state. The melting furnace is preferably made of a material having a low contact angle in order to suppress the phenomenon that the molten material has a high melting point and a high strength and that the melt adheres to the material. For this purpose, platinum (Pt), diamond-like carbon (DLC), chamotte Or a melting furnace having a surface coated with a material such as platinum (Pt) or diamond-like-carbon (DLC).

The melting is preferably carried out at 1400 to 2000 ° C at normal pressure for 1 to 12 hours. When the melting temperature is less than 1400 ° C, the starting material may not melt, and when the melting temperature exceeds 2000 ° C, excessive energy consumption is required and it is not economical. Therefore, it is preferable to melt at a temperature within the above range Do. If the melting time is too short, the starting material may not be sufficiently melted, and if the melting time is too long, excessive consumption of energy is required, which is not economical. If the heating rate of the melting furnace is too slow, it takes a long time to lower the productivity. If the rate of temperature rise of the melting furnace is too fast, the temperature of the melting furnace is increased by a rapid temperature rise. The volatilization amount becomes large and the physical properties of the crystallized glass may be poor. Therefore, it is preferable to raise the temperature of the melting furnace at the temperature raising rate within the above-mentioned range. The melting is preferably carried out in an oxidizing atmosphere such as oxygen (O ₂ ) and air.

The melt is cast into a defined mold to obtain crystallized glass for a tooth of the desired shape and size. The mold is preferably made of a material having a low contact angle in order to suppress the phenomenon that the glass melt has a high melting point and a high melting point, and the mold is made of a material such as graphite or carbon, It is preferable to preheat the melt to 200 to 300 DEG C and pour the melt into a molding mold.

When the melt contained in the molding mold is cooled to 60-100 ° C, it is transferred to a crystallization heat treatment furnace to nucleate and crystallize the glass to produce a crystallized glass. The reason why the glass proposed in the present invention can be variously controlled in the formability and transparency through the first and second heat treatments is that the crystal size in the crystallized glass can be controlled according to the temperature. The crystal phase produced after the first heat treatment includes a lithium disilicate crystal phase and a silica crystal phase, and a crystal phase of 5 to 2000 nm is generated at a temperature range of 400 to 850 캜, respectively. Of these, the machining force is within a range of 30 to 500 nm (lithium disilicate, silica) having a temperature range of 480 to 800 ° C.

When the final artificial prosthesis is completed through the secondary heat treatment, a variety of light transmittance products are required in the clinic, and generally, the light transmittance is 20 to 55% (550 nm wavelength). The light transmittance was 55 to 18% (550 nm wavelength) when the second heat treatment was performed at 780 to 900 ° C., and the light transmittance after 880 ° C. was lowered to 780 ° C. to 880 ° C., where the size of the crystalline phase (lithium disilicate crystalline phase or silica crystalline phase) corresponds to 0.3-5.5 μm and the light transmittance is 55-18% (550 nm wavelength).

Accordingly, the present invention proposes glass manufacturing methods and heat treatment conditions that can be used in clinics through first and second heat treatments, respectively, in which processability and transparency are controlled.

FIG. 1 is a diagram showing a microstructure observed with a scanning electron microscope in a state where the starting material is subjected to a first heat treatment, and particularly, a first heat treatment temperature is 750 ° C. Referring to FIG. 1, when heat treatment is performed at 750 ° C., it is found that a spherical SiO ₂ crystal phase having a size similar to that of lithium disilicate having a size of about 100 to 2000 nm of an acicular shape exists. That is, normally to the the starting materials to a primary heat treatment, when the other hand of the spherical crystal phase of SiO ₂ does not exist, the starting materials proposed in the present invention, primary heat treatment is seen that the present crystal phase of SiO ₂ spherical .

FIG. 2 is a graph showing the crystal phase of the starting material in the first heat-treated state measured by X-ray diffraction analysis, in particular, the first heat treatment temperature is 750 ° C. Referring to FIG. ₂ , it can be seen from the X-ray diffraction analysis that the crystals shown in FIG. 1 are the crystals of lithium disilicate and SiO ₂ , respectively.

FIG. 3 shows the results of measuring the size of the lithium disilicate crystal phase and the processing resistance (cutting force) according to the first heat treatment temperature. According to Fig. 3, the black graph shows the size of the lithium disilicate crystal phase, and the red graph shows the cutting force. According to the graph, it can be seen that the larger the size of the crystal phase, the greater the cutting force. When the cutting force is increased, a high load is applied to the cutting burr. Therefore, it can be seen that the crystalline phase of 30 to 500 nm, which corresponds to the temperature range of 480 to 800 ° C, is excellent in workability.

4 is a light transmission spectrum result data according to a second heat treatment temperature.

The high translucency (HT) of the lithium disilicate crystalline phase and the silica crystal phase is from 780 to 820 ° C, the medium translucency is from 821 to 840 ° C and the low translucency is from 841 to 840 ° C. 860 ° C and medium opacity (medium transparency: MO) is 861 to 880 ° C, and the holding time is 1 minute to 2 hours. As shown in FIG. 4, as the temperature increases, the translucency decreases and appears as medium opacity at high translucency.

5 shows the results of measurement of the size and light transmittance of the lithium disilicate crystal phase according to the second heat treatment temperature. The present invention is characterized in that the transmittance can be adjusted according to the heat treatment temperature of the crystallized glass. In the case of Fig. 5, the black graph is the size of the lithium disilicate crystal phase, and the red graph is the transmittance. FIG. 5 is a graph showing that the crystal phase size increases when the second heat treatment temperature is increased, and the transmittance decreases as the crystal phase size increases. As the size of the crystal phase increases, the ratio of light absorption and reflection, rather than transmission, becomes higher, thus the transmittance decreases. As a result, it can be seen that the crystallized glass having one composition can be manufactured with various transmittance as the second heat treatment temperature is changed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention .

Claims (7)

60 to 83% by weight of SiO ₂ ,
10 to 15% by weight of Li ₂ O,
2 to 6% by weight of P ₂ O ₅ serving as nucleating agent,
1 to 5% by weight of Al ₂ O ₃ for increasing the glass transition temperature and softening point and improving the chemical durability of the glass,
0.1 to 3% by weight of SrO which increases the softening point of the glass,
0.1 to 2% by weight of ZnO,
1 to 5% by weight of colorant; And
Alkali and alkaline earth mixtures of increasing the thermal expansion coefficient of glass _{(Na 2 O + K 2 O} ) a glass composition containing 2.5 to 6 wt%.
The glass composition of claim 1 is subjected to a first heat treatment at 400 to 850 占 폚,
And a silica crystal phase is produced by the primary heat treatment to produce lithium disilicate and silica crystal phase of 5 to 2000 nm.
The method according to claim 2, wherein the glass composition is subjected to a first heat treatment at 480 to 800 ° C,
And a silica crystal phase is produced by the primary heat treatment to produce a lithium disilicate and a siliceous crystal phase of 30 to 500 nm.
3. The method of claim 2,
After the first heat treatment,
A second heat treatment is performed at 780 to 880 캜,
Wherein the light transmittance is controlled by the temperature of the second heat treatment.
5. The method of claim 4, wherein the lithium disilicate crystal phase and the silica crystal phase have a size of 0.3 to 5.5 占 퐉.
5. The method of claim 4, wherein the high translucency of the lithium disilicate crystal phase and the silica crystal phase is 780 to 820 DEG C, the medium translucency is 821 to 840 DEG C, and the low translucency is 841 ~ 860 ° C and medium opacity of 861 ~ 880 ° C,
And the retention time is from 1 minute to 2 hours.
7. The method according to claim 6, wherein the light transmittance of the lithium disilicate crystal phase and the silica crystal phase is 55% to 27% at 550 nm.

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