TWI697461B - Method for processing lithium disilicate glass ceramics - Google Patents

Abstract

This invention provides a method for processing lithium disilicate glass ceramics, which comprises steps of t subjecting a thermal treatment to a lithium disilicate glass so as to form a lithium disilicate glass ceramics containing a crystal phase that is greater than 50% crystallinity and define the lithium disilicate glass ceramics having a desired- processing portion; and processing the lithium disilicate glass ceramics by a pulsed-laser having a pulse width no more than 10 ^-9second so as to remove the desired-processing portion of the lithium disilicate glass ceramics.

Description

Processing method of lithium disilicate glass ceramic

The present invention relates to a lithium disilicate glass ceramics (lithium disilicate glass ceramics), in particular to a processing method of lithium disilicate glass ceramics.

The use of lithium disilicate glass ceramics as a heavy building material for dental crowns has been one of the trends in the past two decades. However, the process of making porcelain blocks from lithium disilicate is limited due to its low crystallinity. Lithium silicate glass ceramics are prone to surface melting, chipping and poor material removal efficiency under the action of external forces. Therefore, the existing lithium disilicate glass ceramics have not been able to make breakthroughs to meet the mainstream laser engraving and milling process methods in the market. , And only suitable for CNC turning and milling.

Referring to Figure 1, an existing method for forming lithium disilicate glass ceramics includes the following steps: (A) a mixing step 11, mixing a powder containing silicon dioxide (SiO ₂ ) and lithium oxide (Li ₂ O) A mixture of powders to form a batch of powders; (B) a molding step 12 is to fill the batch of powders in a forming mold (not shown) to form a preliminarily crystal-free body; (C) ) Two-stage heat treatment step 13 is to apply a two-stage heat treatment to the non-crystalline phase body to crystallize the non-crystalline phase body into a lithium disilicate containing a crystallinity between 20% and 40% The main crystal phase of the lithium disilicate glass ceramic body; (D) a turning-milling precision forming step 14 is to grind the lithium disilicate glass-ceramic body by CNC turning and milling to precisely form a high precision The lithium disilicate glass-ceramic body; and (E) a post-forming heat treatment step 15, which is to subject the high-precision lithium disilicate glass-ceramic body to a heat treatment at 850°C to become a body containing more than 70% Lithium disilicate glass ceramics with the main crystal phase of lithium disilicate.

According to the above, the existing lithium disilicate glass ceramics are only suitable for mechanical processing and grinding due to their low crystallinity (20% to 40%), and cannot achieve good material removal effects through laser engraving and milling. Difficulties in shaping dental crown products.

In view of this, solving the aforementioned problems is a subject to be broken through by relevant technicians in the technical field.

Therefore, the purpose of the present invention is to provide a method for processing lithium disilicate glass ceramics that is suitable for laser engraving and milling and has a better material removal rate.

Therefore, the processing method of lithium disilicate glass ceramics of the present invention includes the following steps: a heat treatment is applied to an amorphous lithium disilicate glass (amorphous) to form a lithium disilicate with a crystallinity greater than or equal to 50% Glass ceramics, and define that the lithium disilicate glass ceramic has an area to be processed; and processing the lithium disilicate glass ceramic with a pulsed laser to remove the area of the lithium disilicate glass ceramic to be processed Material, and the pulse width of the pulsed laser is less than or equal to 10 ^-9 seconds.

The effect of the present invention is to use a pulsed laser to process the lithium disilicate glass ceramics with a crystallinity greater than or equal to 50%, which can avoid the absorption of lithium disilicate glass ceramics with low thermal conductivity. The thermal energy of the laser causes the heat to be broken, and this improves the removal rate of the lithium disilicate glass ceramic.

21: Grinding step

22: Calcination step

23: melting step

24: forming steps

25: At least two-stage heat treatment steps

26: Laser processing steps

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, in which: FIG. 1 is a flow chart illustrating a conventional method for forming lithium disilicate glass ceramics; FIG. 2 is a flow chart The figure illustrates an embodiment of the method for processing lithium disilicate glass ceramics of the present invention; Figure 3 is an image diagram illustrating the appearance and morphology of the lithium disilicate glass prepared by a comparative example 1 of the processing method of the present invention Figure 4 is an image diagram illustrating the appearance of a lithium disilicate glass ceramic body prepared by Comparative Example 2 of one of the processing methods of the present invention; Figure 5 is an image diagram illustrating the processing method of the present invention The appearance and morphology of the lithium disilicate glass ceramic prepared in Example 1; and FIG. 6 is an image diagram illustrating the appearance and morphology of lithium disilicate glass ceramics prepared by a specific example 2 of the processing method of the present invention.

Referring to FIG. 2, an embodiment of the method for processing a lithium disilicate glass ceramic body of the present invention includes the following steps: (a) a grinding step 21, (b) a calcining step 22, (c) a melting step 23. (d) a forming step 24, (e) at least a two-stage heat treatment step 25, and (f) a laser processing step 26.

The grinding step 21 is to grind a mixture containing silicon oxide powder and lithium oxide powder; wherein the molar ratio of silicon oxide to lithium oxide is greater than 2.

In the calcination step 22, the mixture is calcined for 0.5 hours to 4 hours in two stages at a temperature of 300°C to 800°C to form a batch of stable powder.

The melting step 23 is to set the batch of stable powders in a high temperature furnace to melt into a molten soup.

The forming step 24 is to pour the molten broth into a mold that has been preheated to a temperature between 300° C. and 700° C. to form a lithium disilicate glass without bubbles, cracks, and crystal phases.

The at least two-stage heat treatment step 25 is to sequentially nucleating and grain growing the lithium disilicate glass without crystal phase to form a lithium disilicate glass ceramic with a crystallinity greater than or equal to 50%, And define the lithium disilicate glass ceramic Porcelain has an area to be processed. Specifically, the first heat treatment temperature in the at least two-stage heat treatment step 25 is between 300°C and 700°C, and the purpose is to generate crystal nuclei in the lithium disilicate glass without crystal phase; The second heat treatment temperature in step 25 of step heat treatment is between 700°C and 950°C, and its purpose is to make the crystal nuclei in the lithium disilicate glass continue to produce grain growth so that the glass phase is transformed into a crystalline phase. , Thereby improving the crystallinity of lithium disilicate glass ceramics. It should be supplemented here that the driving force for crystal grain growth (crystallization) comes from thermal energy, so the temperature, time and frequency of heat treatment are important keys for determining the crystal phase transition of the lithium disilicate glass ceramic.

The laser processing step 26 is to process the lithium disilicate glass ceramic with a pulsed laser to remove the material in the region to be processed of the lithium disilicate glass ceramic and form a silicon dioxide with a final appearance. Lithium oxide glass ceramics, and the pulse width of the pulsed laser is less than or equal to 10 ^-9 seconds. The final appearance of the lithium disilicate glass ceramic depends on its final application. For example, when the lithium disilicate glass ceramic is used for dental crown reconstruction, the final appearance is the appearance of a dental crown.

Preferably, the molar ratio of silicon oxide to lithium oxide in the grinding step 21 is between 2.1 and 2.5. More preferably, the mixture in the grinding step 21 also contains at least one oxide powder selected from the group consisting of: zirconia (SiO ₂ ), alumina (Al ₂ O ₃ ), magnesium oxide (MgO), Potassium oxide (K ₂ O) and phosphorus oxide (P ₂ O ₅ ).

It should be noted here that based on the lithium disilicate glass ceramic is a material with extremely low heat transfer rate, once the lithium disilicate glass ceramic cannot be quickly removed due to the absorption of heat energy It is extremely easy to cause the lithium disilicate glass ceramic to break. In addition, when the crystallinity of lithium disilicate glass ceramics is lower [that is, the phase ratio of amorphous glass is higher], the laser light is more likely to be reflected on the surface of lithium disilicate glass ceramics, and also A large amount of penetration produces refraction, so that the laser light cannot be focused on the material removal part of the lithium disilicate glass ceramic to be processed, and the material removal part of the material to be processed area can absorb relatively little laser light energy, and ultimately cannot Effectively remove materials; on the contrary, when the crystallinity of lithium disilicate glass ceramics is higher (that is, the phase ratio of amorphous glass is lower), the laser light is less likely to be reflected and refracted, so that the laser light can be completely Focus on the material removal part of the lithium disilicate glass ceramic to be processed, so that the material can be effectively removed by a large amount of laser light to achieve the purpose of laser engraving and milling.

It can be seen from the detailed description in the previous paragraph that the high crystallinity lithium disilicate glass ceramic has better laser light energy absorption. In order to avoid the present invention performing the laser processing step S26, the high crystallinity disilicate glass Lithium glass ceramics instantly absorb a large amount of laser light energy and heat storage to cause material fragmentation. It is better to choose pulsed laser for processing, especially selected from nanosecond laser, picosecond laser, or femtosecond laser; in the present invention Among them, the crystallinity of the lithium disilicate glass ceramic formed in the at least two-stage heat treatment step 25 is preferably between 50% and 95%.

More preferably, the scanning speed of the pulsed laser in the laser processing step S26 is between 600mm/sec and 1000mm/sec; the pulsed laser in the laser processing step S26 has an effect on the lithium disilicate glass ceramic The amount of removal per unit time is between 11.8 mm ³ /min to 60 mm ³ /min.

Preferably, the processing method of this embodiment of the present invention further includes a post-processing heat treatment step after the laser processing step S26. The post-processing heat treatment step is to subject the lithium disilicate glass ceramic to a heat treatment between 500° C. and 800° C. for 0.1 hour to 2 hours. The purpose is to eliminate the lithium disilicate glass ceramic during the laser application. Thermal stress accumulated in the processing step S26.

Referring to FIG. 3, it is the appearance and morphology of a lithium disilicate glass of Comparative Example 1 formed by the processing method of the above-mentioned embodiment of the present invention. This comparative example 1 is lithium disilicate glass (amorphous; that is, 100% glass phase), and its laser processing step S26 is to use a picosecond laser with a frequency of 1183kHz and an output power of 50W, and the scanning speed is 1000mm/sec. As shown in FIG. 3, it can be seen that the lithium disilicate glass (amorphous) can only have a processing depth of 0.38 mm, and cracks occur after the laser processing step S26 is performed.

Referring to FIG. 4, it is the appearance of a lithium disilicate glass ceramic of Comparative Example 2 formed by the processing method of the foregoing embodiment of the present invention. The parameters performed in the laser processing step S26 are the same as those of the Comparative Example. 1. The difference is that the lithium disilicate glass ceramic of Comparative Example 2 has 70% glass phase (amorphous) and 30% lithium disilicate ceramic phase (crystalline phase). As shown in FIG. 4, it can be seen that the processing depth of the lithium disilicate glass ceramic is about 0.49 mm, and cracks are generated after performing the laser processing step S26.

Referring to FIG. 5, it is the appearance of a lithium disilicate glass ceramic of specific example 1 formed by the processing method of the above-mentioned embodiment of the present invention, and its laser processing steps The parameters executed by S26 are the same as those of Comparative Example 1, except that the lithium disilicate glass ceramic of this specific example 1 has 50% glass phase (amorphous) and 50% lithium disilicate ceramic phase. (Crystal phase). As shown in FIG. 5, it can be seen that the processing depth of the lithium disilicate glass ceramic can be increased to 0.57 mm, and after the laser processing step S26 is performed, only micro cracks are generated.

Referring to FIG. 6, the appearance and morphology of a lithium disilicate glass ceramic of specific example 2 formed by the processing method of the above-mentioned embodiment of the present invention, the parameters executed in the laser processing step S26 are the same as those of the comparative example 1. The difference is that the lithium disilicate glass ceramic of this specific example 2 has 30% glass phase (amorphous) and 70% lithium disilicate ceramic phase (crystalline phase). As shown in FIG. 6, the processing depth of the lithium disilicate glass ceramic can be further increased to 0.68 mm, and the appearance of the laser processing step S26 is complete without microcracks.

In summary, the method for processing lithium disilicate glass ceramics of the present invention improves the laser light by increasing the crystallinity of lithium disilicate glass ceramics to greater than or equal to 50%, and with the discontinuous action of pulsed lasers. Energy absorption rate while avoiding the continuous accumulation of a large amount of heat energy; in this way, when the pulse laser is used to focus on the material removal part of the lithium disilicate glass ceramic to be processed, in addition to preventing the processing process due to thermal continuity In addition to the problem of fragmentation caused by the accumulation of lithium disilicate glass ceramics, the high crystallinity of the lithium disilicate glass ceramic can focus the laser light energy, thereby achieving a better effect of material removal and achieving the purpose of the present invention.

However, the above are only examples of the present invention. To limit the scope of implementation of the present invention, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the patent of the present invention.

21: Grinding step

22: Calcination step

23: melting step

24: forming steps

25: At least two-stage heat treatment steps

26: Laser processing steps

Claims (7)

A method for processing lithium disilicate glass ceramics, comprising the following steps: applying a heat treatment to a lithium disilicate glass without crystalline phase to form a lithium disilicate glass ceramic with a crystallinity greater than or equal to 50%, and defining the The lithium disilicate glass ceramic has a region to be processed; and the lithium disilicate glass ceramic is processed by a pulsed laser to remove the material in the region to be processed of the lithium disilicate glass ceramic, and the pulse type The pulse width of the laser is less than or equal to ^10-9 seconds; wherein, the scanning speed of the pulsed laser is between 600mm/sec and 1000mm/sec, and the processing depth is greater than or equal to 0.57mm. The method for processing lithium disilicate glass ceramics according to claim 1, wherein the heat treatment is carried out at least two-stage heat treatment, and the at least two-stage heat treatment is to sequentially nucleate and crystallize the lithium disilicate glass, and the The crystallinity of the lithium disilicate glass ceramic formed by at least two-stage heat treatment is between 50% and 95%. The method for processing lithium disilicate glass ceramics according to claim 2, wherein the pulsed laser is selected from nanosecond laser, picosecond laser, or femtosecond laser. The processing method of the lithium disilicate glass ceramic according to a request, wherein the pulsed laser removal amount per unit time of the lithium disilicate glass ceramic is between 11.8mm ³ / min to 60mm ³ / min. The method for processing lithium disilicate glass ceramics according to claim 1, further comprising the following steps before performing the heat treatment: grinding a mixture containing silicon oxide powder and lithium oxide powder; calcining the mixture to form a batch of stable powder body; Melting the batch of stable powders into a molten soup; and pouring the molten soup into a preheated mold to form the crystalline phase-free lithium disilicate glass. The method for processing lithium disilicate glass ceramics according to claim 5, wherein the molar ratio of silicon oxide to lithium oxide of the mixture is between 2.1 and 2.5. The method for processing lithium disilicate glass ceramics according to claim 1, further comprising a post-processing heat treatment step after the pulse laser processing.

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