Manufacturing method of glass ceramic blank, glass ceramic blank

Abstract

To provide a manufacturing method of a glass-ceramic blank capable of further easily providing the glass-ceramic blank having a natural color tone change.SOLUTION: A manufacturing method of a glass-ceramic blank includes the steps of: preparing a plurality of types of glass-ceramic powder and laminating and pressure-molding the plurality of types of glass-ceramic powder such that adjacent layers have a same color or approximate colors and have different total light transmittance; heating a laminate obtained by the pressure molding, to 500°C or more and 800°C or less so as to degrease; immersing the laminate in a liquid colorant containing unicolor metal ions so as to soak all body of the laminate after the degreasing; and heat-treating the laminate immersed in the liquid colorant at a temperature higher than 750°C and up to 1000°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to glass-ceramic blanks prior to being processed into dental prostheses, and in particular to colored glass-ceramic blanks. [Background technology]

[0002] Glass ceramic blanks, which are materials used to obtain dental prostheses by cutting, can be manufactured using two methods: melt molding, in which molten glass is poured into a mold, and powder molding, in which molten lithium silicate glass is crushed and the powder is pressed to form a mold. With the recent development of digital dentistry and the growing demand for all-ceramic restorations, there is a demand for dental prostheses that have a more natural color change that is closer to that of natural teeth, and therefore glass ceramic blanks are also required to have a natural color change.

[0003] In melt molding, coloring is achieved by adding a colorant before melting, so the resulting glass ceramic blank has a single color tone.

[0004] On the other hand, with regard to powder molding, Patent Document 1 discloses that color changes can be achieved by layering powders of different colors. With this method, the layers overlap, resulting in a step-like change in color, and a natural transition in color cannot be achieved. Furthermore, Patent Document 2 discloses a method of permeating a solidified powder material with multiple liquids of different colors in a predetermined order. This method requires multiple liquids and is time-consuming to manufacture because it is necessary to control the timing and position of permeation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-68079 [Patent Document 2] Japanese Patent Application Publication No. 2018-15364 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above problems, the present disclosure aims to provide a method for manufacturing a glass ceramic blank that can more easily obtain a glass ceramic blank having a natural color change. [Means for solving the problem]

[0007] A first aspect of the present disclosure is a method for manufacturing a glass ceramic blank having multiple layers stacked together, the method including the steps of: preparing multiple types of glass ceramic powder; stacking and pressure-molding the multiple types of glass ceramic powder so that adjacent layers have the same or similar colors and different total light transmittances; heating the pressure-molded laminate at a temperature of 500°C or higher and 800°C or lower to degrease the laminate; immersing the degreased laminate in a colorant liquid containing metal ions of a single color so that the entire laminate is immersed; and heat-treating the laminate immersed in the colorant liquid at a temperature of more than 750°C and not higher than 1000°C.

[0008] In the pressure molding step of the first embodiment, the color difference between adjacent layers may be 5.5 or less.

[0009] In the pressure molding step of the first embodiment, the difference in total light transmittance between adjacent layers may be 0.1 or more and 8 or less.

[0010] In the first embodiment, the total light transmittance may be 33% or more.

[0011] A second aspect of the present disclosure is a glass ceramic blank having a plurality of laminated layers, in which the colors of the materials constituting adjacent layers are the same or similar, and the total light transmittances of the adjacent layers are different.

[0012] In the second embodiment, the color difference between adjacent layers among the plurality of layers may be 5.5 or less, based on the materials themselves that constitute the layers.

[0013] In the second aspect, the difference in total light transmittance may be 0.1 or more and 8 or less.

[0014] In the second embodiment, the total light transmittance may be 33% or more. [Effects of the Invention]

[0015] According to the present disclosure, a glass ceramic blank having a natural color change can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0016] The method for producing a glass ceramic blank according to the present disclosure is based on powder molding. That is, molten lithium silicate glass is pulverized to obtain a powder, and the powder is then pressed and molded to obtain a glass ceramic blank. This will be described in detail below.

[0017] 1.Material To manufacture the glass ceramic blank of the present disclosure, the following materials and their amounts are prepared. SiO2: 60.0 mass% or more and 80.0 mass% or less Li2O: 10.0 mass% or more and 20.0 mass% or less Al2O3: 3.0 mass% or more and 15.0 mass% or less

[0018] If the SiO2 content is outside this range, it becomes difficult to obtain a homogeneous glass blank, and the content is preferably 65 mass % or more and 75 mass % or less. If the Li2O content is outside this range, it becomes difficult to obtain a homogeneous glass blank. The content is preferably 11 mass % or more and 17 mass % or less. If Al2O3 is less than 3.0% by mass, lithium disilicate will precipitate as the main crystalline phase, which may cause problems with machinability, and if it is more than 15.0% by mass, the main crystalline phase will no longer be lithium disilicate, and there is a risk that the mechanical strength will not be sufficient (for example, lithium aluminosilicate will precipitate).The content is preferably 3.0% by mass or more and 7.0% by mass or less.

[0019] The glass ceramic blank may also contain the following compounds as nucleation materials. The type of nucleation material is not particularly limited, and a wide range of known nucleation materials can be used. This allows for efficient generation of nuclei for lithium disilicate crystals. Examples of nucleation materials include P2O5 and T i Examples include O2, ZrO2, Ta2O5, ZnO, Nb2O5, Y2O3, and La2O3, and these materials can be contained in the range of 0 mass% to 10.0 mass%. As can be seen from the fact that the components shown here include 0 mass%, it means that they do not necessarily have to be included and any of them may be included. The same applies to the following.

[0020] Furthermore, the material of the glass ceramic blank may contain the following components in addition to the above. Each of them can be contained in an amount of 0% by mass or more and 15% by mass, but more preferably as follows. Na2O: 0 mass% or more and 2.8 mass% or less K2O: 0 mass% or more and 10.0 mass% or less CaO: 0 mass% or more and 3.0 mass% or less SrO: 0 mass% or more and 10.0 mass% or less BaO: 0 mass% or more and 10.0 mass% or less MgO: 0 mass% or more and 3.0 mass% or less Rb2O: 0 mass% or more and 2.8 mass% or less Cs2O: 0 mass% or more and 2.8 mass% or less Fr2O: 0 mass% or more and 2.8 mass% or less BeO: 0 mass% or more and 3.0 mass% or less RaO: 0 mass% or more and 10.0 mass% or less

[0021] These components can adjust the melting temperature of the material when preparing a dental prosthesis material. However, even if more of these components are added, the improvement in effect is limited, so even if they are added, it is best to keep the amount at 15% by mass or less, as mentioned above.

[0022] Furthermore, from the viewpoint of adjusting the light transmittance, at least one selected from CeO2, Er2O3, and Tb4O7 may be contained. When contained, the content may be about 1 mass % or less.

[0023] 2. Manufacturing method of glass ceramic blanks A method for manufacturing a glass ceramic blank according to one embodiment will be described below. The method for manufacturing a glass ceramic blank S10 according to this embodiment (hereinafter sometimes referred to as "manufacturing method S10") includes a step of preparing multiple types of powder materials (step S11), a step of producing a pressurized laminate (step S12), a step of degreasing (step S13), a step of immersion in a colorant liquid (step S14), and a step of sintering (step S15). Each step will be described below.

[0024] 2.1. Preparation of multiple types of powder materials (step S11) In step S11, multiple types of powder materials with characteristic colors and optical transparency are prepared based on the above-mentioned materials. Each type of powder material can be obtained by blending the above-mentioned materials, melting them at 1300°C to 1600°C, solidifying them by cooling, and then pulverizing them. The pulverization method and degree are well known, but examples include setting the powder particle size to a range of 10 μm to 60 μm. Here, "particle size" refers to the particle size at 50% cumulative value (D50) in the volume-based particle size distribution measured by laser diffraction / scattering. The color and light transmittance characteristics of the various types of powder materials to be prepared are as follows:

[0025] [About color] The multiple types of powder materials to be prepared have the same or similar colors between the powder materials to be stacked adjacently in step S12. Specifically, it is preferable that the color difference ΔE between the powder materials to be stacked adjacently in step S12 is 5.5 or less among the multiple types of powder materials. Here, the color difference ΔE is * a * b * Color difference ΔE in color space * ab " means that the L * a * b * The color distance in the color space is ΔE, and the colors in the two layers are (L * 1, a * 1, b * 1), (L * 2, a * 2, b * 2), it can be expressed by the following formula: ΔE={(L * 2-L * 1) 2 +(a * 2-a * 1) 2 +(b * 2-b * 1) 2} 0.5

[0026] The color difference ΔE was measured as follows. Each powder used is molded into a cylindrical shape, and then a color tone plate is produced in the same manner as in step S13, degreasing, and step S15, sintering (without coloring in step S14), and the plate is sanded with #1000 waterproof abrasive paper to a thickness of 1.2 mm. In other words, the color difference ΔE referred to here is the color difference in a color tone plate obtained by molding each powder into a cylindrical shape and subjecting it to the same heat treatment as in step S13, degreasing, and sintering in step S15, without coloring, and means the difference in color tone inherent in the powder material itself (this is to be distinguished from the color difference after coloring in step S14, which will be described later). Thereafter, the color was measured using a spectrophotometer (SD7000: manufactured by NIPPON DENSHOKU). The obtained color coordinates (CIE1976L according to JIS Z 8781-4)* a * b * The color difference ΔE was calculated using the above formula as the Euclidean distance between the two colors (color coordinates in the color space).

[0027] [Light transmittance] The prepared multiple types of powder materials have different light transmittances. Specifically, among the multiple types of powder materials, the powder materials stacked adjacent to each other in step S12 have different total light transmittances. The total light transmittance is measured using a haze meter (NDH5000 (manufactured by NIPPON DENSHOKU) according to a method in accordance with JIS K 7361, and is defined as the sum of the diffuse transmittance and linear transmittance for incident light using CIE standard illuminant D65.

[0028] In this disclosure, as in the case of measuring color difference, each powder used was molded into a cylindrical shape, and then a color tone plate was produced in the same manner as in the degreasing step S13 and sintering step S15 (without coloring in step S14), and the total luminous transmittance was measured for a color tone plate 1.2 mm thick cut with #1000 waterproof abrasive paper. In other words, the total luminous transmittance referred to here is the total luminous transmittance of a color tone plate obtained by molding each powder into a cylindrical shape and, without coloring, by subjecting it to the degreasing step S13 and heat treatment similar to the sintering step S15, and is based on the total luminous transmittance of the powder material itself.

[0029] The difference in total light transmittance between the different powder materials in adjacent layers is not particularly limited, but is preferably 0.1 to 8, more preferably 0.1 to 6, and even more preferably 0.1 to 3.

[0030] Furthermore, the magnitude of the total light transmittance of the multiple types of powder materials is not particularly limited, but it is preferable that at least one type has a total light transmittance of 33% or more, and more preferably that all types have a total light transmittance of 33% or more.

[0031] 2.2. Preparation of pressurized laminate (step S12) In step S12, the multiple types of powder materials obtained in step S11 are sequentially stacked in a mold and pressure-molded to obtain a pressurized laminate. More specifically, each powder material is mixed with a resin that serves as a binder, and the mixture is layered in order in a mold, and then pressure is applied. The binder is not particularly limited as long as it is a resin that burns off when heated to 500°C or higher and 800°C or lower, but an acrylic resin is preferred, for example. In this embodiment, Oricox KC-1700P (Kyoeisha Chemical Co., Ltd.) is used. The pressure can be applied by, for example, a uniaxial press at a pressure of about 10 MPa or more and less than 20 MPa, preferably 10 MPa or more and 18 MPa or less.

[0032] 2.3. Degreasing treatment (step S13) In step S13, the pressed laminate obtained in step S12 is heated to remove (degrease) the binder resin contained in the pressed laminate. The heating temperature is not particularly limited, but is preferably about 500°C or higher and 800°C or lower. Among these, since crystallization of lithium metasilicate begins at 680°C, heating to about 700°C is more preferable from the viewpoint of smoothly promoting this crystallization.

[0033] 2.4. Immersion in colorant liquid (step S14) In step S14, the degreased pressure laminate obtained in step S13 is immersed in a colorant liquid to obtain a colored pressure laminate. The colorant liquid may be of a single color, for example, a mixture of a solvent and metal ions as a colorant. The solvent is not particularly limited as long as it can dissolve the colorant, and examples thereof include distilled water and alcohol (methanol, ethanol). The colorant may be any suitable metal ion, including, for example, metal oxides used as colorants in lithium silicate glass ceramics. More specifically, salts containing metals such as Ce, Er, Fe, Mn, Tb, and V, such as erbium acetate and cerium acetate, are included. In addition, polyethylene glycol, polypropylene glycol, or the like may be added as a permeation adjuster to improve permeability into the degreased pressure laminate, as needed. A trace amount of hydrochloric acid may also be added, which makes it easier to dissolve the metal salt in the solvent. The blending ratio is not particularly limited, but may be, for example, 70% by mass or more and 90% by mass or less of solvent, 0.1% by mass or more and 20% by mass or less of colorant, and 0% by mass or more and 15% by mass or less of penetration adjuster.

[0034] The penetration is preferably carried out by immersing the entire degreased pressure laminate in the colorant liquid. The immersion may be carried out at ambient temperature, preferably in the range of 10°C to 40°C. The immersion time is preferably 1 minute or more. There is no particular upper limit to the immersion time, but it is preferably 60 minutes or less, because immersion for a longer time has almost no effect on the results.

[0035] 2.5. Sintering (Step S15) In step S15, the colored pressed laminate obtained in step S14 is heat-treated to be sintered, and then cooled to obtain a glass ceramic blank. The heat treatment is maintained at a temperature higher than 750°C and lower than 1000°C for a predetermined time. This allows lithium disilicate crystals to grow, resulting in a lithium disilicate blank whose main crystalline phase is lithium disilicate. The maintenance time is preferably 1 minute or more, more preferably 3 minutes or more. There is no particular upper limit to the time, but it can be 3 hours or less.

[0036] 3. Glass ceramic blanks The glass ceramic blank obtained by the above manufacturing method S10 is a block-shaped material in the shape of a column such as a rectangular pillar or a cylinder, or a plate such as a square plate or a disk, and can be deformed or cut out by machining such as cutting to produce a dental prosthesis.

[0037] In addition, the color difference between adjacent layers of the obtained glass ceramic blank is preferably 8 or less, and the total light transmittance is also preferably different. As described above, the color difference between adjacent layers of the obtained glass ceramic blank is different from the color difference of the powder material described above. Furthermore, it is preferable that the colorant contained in the glass ceramic blank be of the same type and concentration in every portion.

[0038] 4. Effects etc. According to the method for manufacturing a glass ceramic blank described above, a glass ceramic blank that exhibits natural color changes like those of natural teeth can be efficiently manufactured simply by immersing the blank in a colorant liquid of a single color.

[0039] Furthermore, by using materials that satisfy the above-described color and light transmittance between adjacent layers, a glass ceramic blank can be obtained that exhibits natural color changes like natural teeth.

[0040] By ensuring that the difference in total light transmittance between the powder materials used for adjacent layers is between 0.1 and 8, the color tone change between the layers will appear more natural. Furthermore, by making the total light transmittance of at least one type, and more preferably all types, of the powder materials used 33% or more, the color tone change between layers appears more natural, and this also makes it possible to more smoothly carry out the coloring in step S14.

[0041] 5. Working Example In the examples, several types of powders (powders A to J) with different characteristics were used and combined to prepare glass ceramic blanks for testing.

[0042] 5.1. Powder Preparation The powders prepared in accordance with step S11 are shown in Table 1. Table 1 also shows the color and total light transmittance of each powder measured by the method described above. The components of each powder were varied within the following ranges: SiO2: 69.8% by mass or more and 71.2% by mass or less Li2O: 11.2% by mass or more and 13.5% by mass or less Al2O3: 4.3 mass% or more and 5.3 mass% or less P2O5: 3.0 mass% or more and 7.3 mass% or less Na2O: 1.2 mass% or more and 1.6 mass% or less K2O: 1.8% by mass or more and 2.4% by mass or less SrO: 0 mass% or more and 1.7 mass% or less TiO2: 0 mass% or more and 0.5 mass% or less ZrO2: 1.8% by mass or more and 3.2% by mass or less CeO2: 0.1% by mass or more and 0.2% by mass or less Tb4O7:0.4% by mass Colorant: Powder H, Powder I, and Powder J only: 0.2% by mass

[0043] Each type of powder material was obtained by blending the above-mentioned materials, melting them at 1300°C to 1600°C, cooling them to solidify them, and then pulverizing them. The particle size of the obtained powder was 36.53 μm in D50.

[0044] [Table 1]

[0045] Here, color A1 in powder H, color B1 in powder I, and color A2 in powder J are the names of color samples in the Vita Classical Shade Guide (manufactured by Vita Co., Ltd.).

[0046] 5.2. Preparation of glass ceramic blanks The prepared powders were used to produce glass ceramic blanks in the layer configuration shown in Table 2 (for example, "A+B" means that a layer made of powder A and a layer made of powder B are laminated together), according to steps S12 to S14. The conditions for each step are as follows: In the step based on step S12, Oricox KC-1700P (Kyoeisha Chemical Co., Ltd.) was used as a binder and mixed in an amount of 5 mass % with respect to the powder material, and then pressed in a uniaxial press at a pressure of 15 MPa. In the step based on step S13, the obtained pressed laminate was heated at 700° C. for 10 hours to perform debinding.

[0047] In the step based on step S14, the degreased pressurized laminate was immersed in a colorant liquid for 10 minutes at 23° C. (room temperature). The components of the colorant liquid were as follows. Cerium acetate: 6.5% by mass Erbium acetate: 6.5% by mass Polyethylene glycol: 7.0% by mass Distilled water: 80% by mass

[0048] In the step based on step S15, the pressed laminate immersed in the colorant liquid was heated at 880° C. for 1 hour to be sintered.

[0049] 5.3. Evaluation and Results The evaluation items and results are shown in Table 2. Each item is as follows: [Color difference ΔE] The color difference ΔE between adjacent layers of the prepared powder material was measured using the method described above. [Total light transmittance difference] Based on the total light transmittance of each powder material in Table 1, the difference in total light transmittance between adjacent layers in each combination was calculated. [Sensory evaluation (migration)] A sensory evaluation was conducted to assess the naturalness of the color change. The evaluation was conducted visually by five people, and the number of people who felt that the color change was natural was used as the evaluation standard. Specifically, examples where four or more people felt that the color change was natural were rated "excellent," examples where three people felt that it was natural were rated "good," examples where two people felt that it was natural were rated "fair," and examples where one or less people felt that it was natural were rated "poor."

[0050] [Table 2]

[0051] As can be seen from Table 2, by preparing powder material with a color difference ΔE of 5.5 or less between adjacent layers, a glass ceramic blank with a natural color change can be obtained.

[0052] In addition, when the powder materials prepared had a total light transmittance of less than 33%, as in Example 10, the migration property was slightly reduced. In addition, the coloring took a long time and the coloring efficiency tended to decrease.

Claims

1. 1. A method for manufacturing a glass ceramic blank having a plurality of layers stacked thereon, comprising: preparing a plurality of types of glass ceramic powders, laminating and pressure-molding the plurality of types of glass ceramic powders so that adjacent layers have a color difference of 5.5 or less and different total light transmittances; a step of heating the laminate obtained by pressure molding at 500°C or more and 800°C or less to degrease the laminate; a step of immersing the degreased laminate in a colorant liquid of a single color containing metal ions so that the entire laminate is immersed; and heat-treating the laminate immersed in the colorant liquid at a temperature higher than 750°C and not higher than 1000°C. Method for manufacturing glass ceramic blanks.

2. 2. The method for producing a glass ceramic blank according to claim 1, wherein the difference in total light transmittance between the adjacent layers is 0.1 or more and 8 or less in the pressure molding step.

3. 3. The method for producing a glass ceramic blank according to claim 1, wherein the total light transmittance is 33% or more.

4. A glass ceramic blank having a plurality of layers laminated thereon, the color difference between adjacent layers of the plurality of layers is 5.5 or less and the materials constituting the layers have different total light transmittances; The plurality of layers contain a colorant, and the colorant is of the same type and concentration in each region. Glass ceramic blanks.

5. 5. The glass ceramic blank according to claim 4, wherein the difference in total light transmittance is 0.1 or more and 8 or less.

6. 6. The glass ceramic blank according to claim 4, wherein the total light transmittance is 33% or more.

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