High refractive index silicate glass composition with reduced devitrification rate

Abstract

Provided is a glass composition comprising 25 to 40 mass% SiO2, 2.5 to 10 mass% B2O3, 0 to 10 mass% Al2O3, 0 to 15 mass% Li2O, 0 to 16 mass% Li2O, Na2O, and K2O in total, 10 to 25 mass% CaO, 0 to 15 mass% BaO, 0 to 5 mass% MgO, 0 to 5 mass% SrO, 10 to 30 mass% CaO, BaO, MgO, and SrO in total, 0 to 7 mass% ZnO, 2 to 10 mass% ZrO, 2 to 15 mass% TiO2, 5 to 25 mass% Nb2O5, 0 to 5 mass% Ta2O5, 5 to 25 mass% La2O3, and 0 to 5 mass% Y2O3. The glass composition has a refractive index of about 1.74 to about 1.80 and a viscosity of about 3.5 g / cm 3 ~About 4.0g / cm 3 , a critical cooling rate of about 1°C / min to about 50°C / min, and a liquidus viscosity of more than 25 poise.

Description

Cross - Reference to Related Applications

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 772,728, filed on November 29, 2018, the content of which is relied upon and incorporated herein by reference in its entirety.

Technical Field

[0002] The present invention relates to a high - refractive - index silicate glass composition, and more particularly, to a silicate glass composition with a reduced devitrification rate.

Background Art

[0003] High - refractive - index (n D ) and low - density glasses have long been recognized as particularly desirable in a variety of optical devices, including microscopes, glasses, displays, virtual reality devices, and augmented reality devices that require high correction and minimum weight. Currently known low - density and very high - refractive - index glasses exhibit high dispersivity, or put another way, have a low Abbe number (ν), i.e., often an Abbe number (ν) less than 30, resulting in rainbow colors appearing on the sides of lenses. In addition, these same high - refractive - index glasses also exhibit insufficient thermal stability.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Accordingly, there is a need for an improved high - refractive - index glass composition that provides improved optical performance, reliability, and an improved material that can lead to reduced manufacturing costs for producing optical devices.

Means for Solving the Problems

[0005] According to some aspects of the present disclosure, a glass composition is provided. The glass composition comprises 25 to 40% by mass of SiO2; 2.5 to 10% by mass of B2O3; 0 to 10% by mass of Al2O3; 0 to 15% by mass of Li2O; a total of 0 to 16% by mass of Li2O, Na2O, and K2O; 10 to 25% by mass of CaO; 0 to 15% by mass of BaO; 0 to 5% by mass of MgO; 0 to 5% by mass of SrO; a total of 10 to 30% by mass of CaO, BaO, MgO, and SrO; 0 to 7% by mass of ZnO; 2 to 10% by mass of ZrO; 2 to 15% by mass of TiO2; 5 to 25% by mass of Nb2O5; 0 to 5% by mass of Ta2O5; 5 to 25% by mass of La2O3; and 0 to 5% by mass of Y2O3. The glass composition has a refractive index of about 1.74 to about 1.80, a density of about 3.5 g / cm 3 ~ about 4.0 g / cm 3 and a critical cooling rate of about 1 °C / min to about 50 °C / min, and a liquid phase viscosity exceeding 25 poises.

[0006] According to some aspects of the present disclosure, a method of forming a glass is provided. The method includes providing a mixture of glass components, the mixture comprising 25 to 40% by mass of SiO2; 2.5 to 10% by mass of B2O3; 0 to 10% by mass of Al2O3; 0 to 15% by mass of Li2O; 10 to 25% by mass of CaO; 0 to 15% by mass of BaO; 0 to 5% by mass of MgO; 0 to 5% by mass of SrO; 0 to 7% by mass of ZnO; 2 to 10% by mass of ZrO; 2 to 15% by mass of TiO2; 5 to 25% by mass of Nb2O5; 0 to 5% by mass of Ta2O5; 5 to 25% by mass of La2O3; and 0 to 5% by mass of Y2O3; heating the mixture to a temperature of at least 1,350 °C to form a molten glass; and cooling the molten glass at a critical cooling rate of about 1 °C / min to about 50 °C / min to form a glass. The glass does not contain visible microcrystals (e.g., stones or crystals) observable by the naked eye or under an optical microscope and has a refractive index of about 1.74 to about 1.80, a density of about 3.5 g / cm 3 ~ about 4.0 g / cm 3 and a critical cooling rate of about 1 °C / min to about 50 °C / min, and a liquid phase viscosity exceeding 25 poises.

[0007] According to another aspect of the present disclosure, a glass composition is provided. The glass composition comprises 25-30 wt% SiO2; 2.5-6 wt% B2O3; 0-10 wt% Li2O; 15-20 wt% CaO; 0-10 wt% BaO; 10-25 wt% La2O3; 2-10 wt% ZrO2; 5-20 wt% Nb2O5; and 2-10 wt% TiO2. The glass composition has a critical cooling rate of about 1 °C / min to about 50 °C / min and a liquid phase viscosity exceeding 25 poises.

[0008] Additional features and advantages will be described in the following detailed description, some of which will be readily apparent to those skilled in the art from that description, or may be recognized by practicing the embodiments described herein, including the following detailed description, the claims, and the accompanying drawings.

[0009] It should be understood that both the foregoing summary and the following detailed description are merely illustrative and are intended to provide an overview or framework for understanding the nature and characteristics of the claims. The accompanying drawings are included to provide a further understanding and are incorporated herein and constitute a part thereof. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operations of the various embodiments.

[0010] The following is a description of the figures of the accompanying drawings. The figures are not necessarily to scale, and certain features and specific figures within the drawings may be shown exaggerated in scale or in schematic form for clarity and brevity.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0012] Additional features and advantages are described in the following detailed description, will be apparent to those skilled in the art from that description, or will be recognized by practicing the embodiments described in the following description together with the claims and the accompanying drawings.

[0013] As used herein, the term "and / or" when used in a list of two or more items means that any one of the listed items can be used alone or any combination of two or more of the listed items can be used. For example, if a composition is described as including components A, B, and / or C, the composition can include A only; B only; C only; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0014] In this specification, relational terms such as first and second, upper and lower are used merely to distinguish one existence or operation from another existence or operation, and do not necessarily require or imply such an actual relationship or order between such existences or operations.

[0015] Modifications of the present disclosure will occur to those skilled in the art and those who make or use the present disclosure. Accordingly, the embodiments shown in the drawings and described above are for illustrative purposes only and are not intended to limit the scope of the present disclosure as defined by the following claims, including the doctrine of equivalents, to be construed in accordance with the principles of patent law.

[0016] For the purposes of the present disclosure, the term "coupled" (in all its forms: couple, coupling, coupled, etc.) generally means the direct or indirect connection of two components to each other. Such connection may be essentially fixed or essentially movable. Such connection may be achieved by the two components and an additional intermediate member integrally formed therewith as a single unitary body or as a single unitary body having the two components. Such connection may be essentially permanent or essentially removable or releasable, unless otherwise specified.

[0017] As used herein, the term "about" means that quantities, sizes, formulations, parameters, and other quantities and characteristics are not exact and need not be exact, reflecting tolerances, conversion factors, rounding, measurement errors, etc., and other factors known to those skilled in the art, and may be approximated and / or may be larger or smaller as necessary. When the term "about" is used in describing a value or endpoint of a range, the present disclosure is to be understood as including the particular value or endpoint recited. Whether or not the numerical values or endpoints of a range in the specification are described with "about", the numerical values or endpoints of the range are intended to include two embodiments, one modified by "about" and one not modified. Further, it will be understood that each endpoint of a range is important in relation to, and independent of, the other endpoint.

[0018] As used herein, the terms "substantial", "substantially", and their variants are intended to indicate that the recited feature is equal to or approximately equal to a value or description. For example, a "substantially flat" surface is intended to indicate a flat or approximately flat surface. Further, "substantially" is intended to indicate that two values are equal or approximately equal. In some embodiments, "substantially" may mean values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0019] The directional terms used in this specification (e.g., up, down, right, left, front, back, top, bottom) are made only with reference to the drawn figures and are not intended to mean absolute directions.

[0020] As used in this specification, the terms "the", "a", or "an" mean "at least one" and should not be limited to "only one" unless expressly indicated to the contrary. Thus, for example, a reference to "a component" includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0021] This disclosure teaches a class of high refractive index silicate glass compositions that can provide a high refractive index (>1.75), high transmittance, low density (<3.8 g / cm 3 ), high thermal stability, and chemical durability. These glasses provided can be highly transparent, resistant to crystallization, chemically resistant, and highly refractive. The glass composition can include 25 - 40 wt% SiO2; 2.5 - 10 wt% B2O3; 0 - 10 wt% Al2O3; 0 - 15 wt% Li2O; a total of 0 - 16 wt% Li2O, Na2O, and K2O; 10 - 25 wt% CaO; 0 - 15 wt% BaO; 0 - 5 wt% MgO; 0 - 5 wt% SrO; a total of 10 - 30 wt% CaO, BaO, MgO, and SrO; 0 - 7 wt% ZnO; 2 - 10 wt% ZrO2; 2 - 15 wt% TiO2; 5 - 25 wt% Nb2O5; 0 - 5 wt% Ta2O5; 5 - 25 wt% La2O3; and 0 - 5 wt% Y2O3. In various aspects of the disclosure, the glass composition can include other components in the range of about 0 wt% to about 5 wt%. In some aspects, the glass composition has a refractive index of about 1.74 to about 1.80, about 3.5 g / cm 3 ~ about 4.0 g / cm 3It has a density, a critical cooling rate of about 1 °C / min to about 50 °C / min, and a liquid-phase viscosity (P) exceeding 25 poises. In various examples, the liquid-phase viscosity can be greater than 25 poises, greater than 50 poises, or greater than 75 poises. The main components used to form these compositions are SiO2; B2O3; alkali and alkaline earth oxides including, for example, Al2O3, Li2O, Na2O, CaO, BaO, SrO; and high refractive index components: ZnO, ZrO2, TiO2, La2O3, Nb2O5. The glass compositions disclosed herein may not contain components suspected of being harmful to human health and / or the environment. Specifically, in some embodiments, the glass compositions herein can be designed to not contain arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), thallium (Tl), or vanadium (V). In other embodiments, no clarifying agent needs to be added to obtain bubble-free glass.

[0022] In some embodiments, the glass composition can contain 25 to 30% by weight of SiO2; 2.5 to 6% by weight of B2O3; 0 to 10% by weight of Li2O; 15 to 20% by weight of CaO; 0 to 10% by weight of BaO; 10 to 25% by weight of La2O3; 2 to 10% by weight of ZrO2; 5 to 20% by weight of Nb2O5; and 2 to 10% by weight of TiO2, where 40 to 55% by weight is the total of BaO, La2O3, ZrO2, Nb2O5, and TiO2. In other embodiments, the glass composition can also contain about 28% by weight of SiO2; about 3% by weight of B2O3; about 16% by weight of CaO; about 8% by weight of BaO; about 16% by weight of La2O3; about 3% by weight of ZrO2; about 18% by weight of Nb2O5; and about 8% by weight of TiO2, where the total in mass % of BaO, La2O3, ZrO2, Nb2O5, and TiO2 is about 53% by weight.

[0023] The glass compositions disclosed herein have a critical cooling rate (Q cIt is possible to provide several improved properties, including the devitrification resistance (kinetics) measured by . The critical cooling rate of the glass is kinetically driven and provides the rate necessary to cool each amorphous molten glass composition to avoid crystallization. For example, a critical constant cooling rate of the glass of 55 °C / min means that the corresponding molten glass needs to be cooled at a rate of at least 55 °C / min to prevent crystallization of the glass. Crystallization of the glass can also result in non-uniform optical properties or visible defects. Cooling the molten glass at a uniform and rapid rate (e.g., 50 °C / min or more) across the entire sample can be costly and / or problematic. Conversely, a glass having a critical cooling rate of 5 °C / min means that it only requires each molten glass to be cooled at 5 °C / min to prevent crystallization. In such an example, even if the sample is cooled faster than the critical cooling rate of 5 °C / min, it will not cause adverse effects such as crystallization, which may offer flexibility to manufacturers in preparing glass samples with consistent and uniformly dispersed optical properties. For example, a glass composition with a low critical cooling rate can be used to form thin objects such as sheets or tubes using various glass forming techniques (e.g., casting, pressing, rolling, drawing, etc.). In some embodiments, the glass composition can have a critical cooling rate of less than about 30 °C / min, less than about 25 °C / min, less than about 20 °C / min, less than about 17.5 °C / min, less than about 15 °C / min, less than about 12.5 °C / min, less than about 10 °C / min, less than about 7.5 °C / min, less than about 5 °C / min, or less than about 2.5 °C / min. In some embodiments, the glass composition can have a critical cooling rate of about 30 °C / min, about 25 °C / min, about 20 °C / min, about 17.5 °C / min, about 15 °C / min, about 12.5 °C / min, about 10 °C / min, about 7.5 °C / min, about 5 °C / min, or about 2.5 °C / min. In some embodiments, the glass composition can have a critical cooling rate of about 1 °C / min to about 50 °C / min, about 1 °C / min to about 45 °C / min, about 1 °C / min to about 40 °C / min, about 1 °C / min to about 35 °C / min, about 1 °C / min to about 30 °C / min, about 1 °C / min to about 25 °C / min, about 1 °C / min to about 20 °C / min, about 1 °C / min to about 15 °C / min, about 1 °C / min to about 10 °C / min, or about 1 °C / min to about 5 °C / min.

[0024] Conventionally, the liquid-phase viscosity (η liq )(P) of a glass sample has been provided to explain the workability of the glass. The liquid-phase viscosity of a glass is a thermodynamically driven property at which crystallization begins to occur at a given viscosity of the glass. Comparing the liquid-phase viscosity values of various molten glass samples would help manufacturers recognize how viscous or liquid the sample needs to be before crystallization starts. As discussed above for the critical cooling rate, crystallization that occurs when the glass is being cooled can lead to non-uniform optical properties or visible defects. The higher the value of the liquid-phase viscosity, the higher the viscosity of the glass needs to be for crystal defects to start forming in the lattice. Glass manufacturers have conventionally considered the liquid-phase viscosity in processing considerations, but it is necessary to monitor both the critical cooling rate and the liquid-phase viscosity to match the processing conditions to the desired application. In some embodiments, the glass composition can have a liquid-phase viscosity greater than 15, greater than 25, greater than 50, greater than 75, greater than 100, greater than 125, greater than 150, greater than 175, or greater than 200. In some embodiments, the glass composition can have a liquid-phase viscosity of about 15, about 25, about 50, about 75, about 100, about 125, about 150, about 175, or about 200.

[0025] In forming processes (e.g., stretching, thin rolling) used to manufacture large structures (e.g., with a diameter greater than 150 mm) and / or small structures (e.g., a glass wafer with a thickness less than 0.5 mm) using glass with a refractive index greater than 1.75, a very fluid glass (forming viscosity < 50 poise) is required to achieve the desired shape ratio. The glass liquid-phase viscosity, while important to consider, is not a factor that limits the formation of each structure. Rather, it appears as devitrification kinetics that controls the time available for glass formation before the problem of devitrification occurs. As described above, by considering and balancing both the critical cooling rate and the liquid-phase viscosity, the parameters required for the formation of a given structure are determined.

[0026] The KA of the glass is related to the dynamic thermal stability of the glass or the resistance to devitrification during heating or cooling, where KA defines the difference (Δ) between the glass transition temperature (Tg) and the temperature onset of the first crystallization peak measured by DSC. The KA measured by DSC depends on the particle size distribution and the heating rate. In various aspects of the present disclosure, the particle size for KA measurement can be at least about 15 μm, at least about 20 μm, at least about 25 μm, at least about 30 μm, at least about 35 μm, at least about 40 μm, at least about 45 μm, and / or combinations or ranges thereof. In some aspects of the present disclosure, the heating rate can be at least about 5 °C, at least about 10 °C, at least about 15 °C, at least about 20 °C, and / or combinations or ranges thereof. The higher the KA temperature, the more resistant the glass is to devitrification or crystallization. In some aspects, KA is greater than about 175 °C, greater than about 180 °C, greater than about 185 °C, greater than about 190 °C, greater than about 195 °C, greater than about 200 °C, or greater than about 205 °C. In other aspects, KA is about 175 °C, about 180 °C, about 185 °C, about 190 °C, about 195 °C, about 200 °C, or about 205 °C. The measurement of the KA value and the Q c value is not governed by standardized techniques for both, but is defined in the Examples section.

[0027] In some aspects, the refractive index for the various glass embodiments disclosed herein can range from about 1.74 to about 1.80 and have a visible total transmittance (T vis ) of greater than about 80% at a 10 mm optical path length. In some aspects, the refractive index of the glass can be greater than about 1.74, greater than about 1.75, greater than about 1.76, greater than about 1.77, greater than about 1.78, greater than about 1.79, or greater than about 1.80. In other aspects, the refractive index can be about 1.74, about 1.75, about 1.76, about 1.77, about 1.78, about 1.79, or about 1.80. In some aspects, the visible total transmittance (T vis ) of the glass can be about 80% at a 10 mm optical path length, about 82.5% at a 10 mm optical path length, about 85% at a 10 mm optical path length, about 87.5% at a 10 mm optical path length, or about 90% at a 10 mm optical path length.

[0028] In some embodiments, the density of the various glass embodiments disclosed herein is from about 3.25 g / cm 3 to about 4.0 g / cm 3 ; from about 3.4 g / cm 3 to about 3.8 g / cm 3 ; from about 3.5 g / cm 3 to about 3.75 g / cm 3 ; or from about 3.6 g / cm 3 to about 3.7 g / cm 3 and may be in the range of. In some embodiments, the glass density is about 3.25 g / cm 3 ; about 3.30 g / cm 3 ; about 3.35 g / cm 3 ; about 3.40 g / cm 3 ; about 3.45 g / cm 3 ; about 3.50 g / cm 3 ; about 3.55 g / cm 3 ; about 3.60 g / cm 3 ; about 3.65 g / cm 3 ; about 3.70 g / cm 3 ; or about 3.75 g / cm 3 and may be.

[0029] In some embodiments, the various glass embodiments disclosed herein have an Abbe number (ν) of less than about 50, less than about 45, less than about 40, less than about 35, less than about 30, or less than about 25.

[0030] Next, referring to FIG. 1, provided is a plot of differential scanning calorimetry (DSC) of Example 1 described below, taken at a heating rate of 10° C. / min, according to some aspects of the present disclosure. The first endotherm suggesting the glass transition temperature was observed at 615° C., followed by a large exothermic peak corresponding to the glass crystallization event. The large exothermic peak associated with the glass crystallization event is the tallest and sharpest peak in the DSC plot. The large exothermic peak associated with the glass crystallization event is also the most energetic event recorded by the DSC plot. The peak onset of the glass crystallization event is recorded at 808° C. The KA value, defined as the Δ between the glass transition temperature (Tg) and the onset temperature of the first crystallization peak, is 808° C. - 615° C. = 193° C. A composite endothermic peak was observed at approximately 980° C. The composite endothermic peak is induced by the crystal melting event of the previously formed crystals.

[0031] Next, referring to FIGS. 2, 3, and 4, presented are several photographs corresponding to the composition of Example 4 detailed below, in which the glass was cooled from 1150° C. to 600° C. at rates of 5° C. / min, 10° C. / min, and 30° C. / min. The photograph of FIG. 2 shows the crystals formed throughout the glass pate, particularly the crystals scattered in the veined central portion. The photographs of FIGS. 3 and 4 demonstrate and show that no crystals were formed even when cooled at rates of 10° C. / min and 30° C. / min. Thus, the critical cooling rate (Q c ) is between 10° C. / min and 10° C. / min for the glass of Example 4.

Example

[0032] Material The glass compositions disclosed herein were formed using commercially available materials. Each component was used as received.

[0033] Measurement of differential scanning calorimetry (DSC) The glass transition temperature (T g ) and the melting transition temperature (T x) The start was measured using a differential scanning calorimeter (PYRIS PERKIN ELMER) at a heating rate of 10 °C / min. The glass samples were measured as glass powders (25 - 38 μm) with a controlled particle size distribution. Approximately 30 mg of glass powder was used for each measurement.

[0034] Measurement of density The density of each glass sample was measured using a Helium Pycnometer Accupy 1330 Micromeritic.

[0035] Measurement of transmittance (T%) The glass transmittance was measured on polished glass samples (2.0 mm) using a UV - VIS - NIR spectrophotometer CARY500 scan that included a Labsphere DRA - CA - 5500 for collecting diffused light. The transmittance % was measured at 1 - nanometer intervals from 380 mm to 800 nm.

[0036] Measurement of high-temperature viscosity The glass melt viscosity was measured using a rotational spindle viscometer in accordance with Procedure A of ASTM C - 965. This technique measures the viscosity at a specific temperature using the constant angular velocity method to generate the viscosity / temperature curve of the molten glass.

[0037] Measurement of liquidus temperature The liquidus temperature was measured using small glass pieces placed in a small platinum cup. Next, the glass was heat - treated at a given temperature for 17 hours and then air - quenched to room temperature. An optical microscope with a magnification (1,000 - 4,000 times) was used to detect the presence of crystals on the glass / air side and the platinum / glass side of the glass sample. The liquidus temperature was confirmed when the formation of crystals was observed with respect to the treatment temperature.

[0038] Measurement of refractive index and Abbe number The measurement of refractive index and Abbe number was carried out at a laser wavelength of 587 nm using a Metricon Model 2010 PrismCoupler. The refractive index of the material was measured using a refractometer with the critical reflection angle. If a material with refractive index n is coupled to a prism using refractive index np, the laser light directed towards the base of the prism will be completely reflected until the angle of incidence is less than the critical angle (θ c ). The formula for θ c is “θc = arcsin(n / n p )”.

[0039] Measurement of critical cooling rate Q c or R c is defined as the critical cooling rate and is the value of the threshold of a certain cooling rate of a glass melt at which devitrification occurs during a constant cooling. The critical cooling rate is often determined from a TTT diagram (see below), where the glass is heated isothermally at a given temperature and the volume percentage (volume %) of crystals is determined as a function of time. A line showing an example of the temperature - time conditions where the crystal volume fraction is 0.1 is plotted. In this specification, a non - isothermal method was adopted. In this test, a glass of a given volume (1.0 cm 3 ) is placed in a platinum dish. Next, the glass is preheated in an electric furnace at T Liq + 50 °C for 30 minutes and then cooled to room temperature at a constant cooling rate (i.e., 60 °C / min) (accurately by contacting a thermocouple with the glass). Finally, the glass is then inspected with an optical microscope (1,000 times magnification) to check whether crystals are confirmed on the side of the glass / platinum interface.

[0040] Examples 1 to 5 Examples 1 to 5 were prepared by placing 1000 g (total weight) of raw materials (i.e., quartz, boric acid, calcium carbonate, niobium oxide, etc.) in a pure platinum crucible, mixing them, and introducing the filled crucible into a Globar furnace preheated to 1350°C. Next, the furnace was raised to a temperature of 1500°C and held at this temperature for 4 hours. Next, each melt was poured onto a cooled stainless steel table and made into a sheet pate with a thickness of 6 mm. Next, the corresponding sheet pates were annealed at 650°C. The individual components used in the production of Examples 1 to 6 are presented in Table 1 below:

[0041] [Table 1]

[0042] The refractive index, Abbe number, density, glass transition temperature (T g ), T x onset of exothermic peak, KA, liquid phase, Q c , liquid phase viscosity (P), and transmittance at 10 mm for Examples 1 to 6 are presented in Table 2 below:

[0043] [Table 2]

[0044] When the boron content increases and / or the lithium content decreases (see Examples 1 and 4, Examples 1 and 5, and Examples 1 and 6), the liquid phase temperature does not decrease significantly, but the critical cooling rate Q c measured in the glass of Example 1 is improved to 1°C / min < Q c < 5°C / min relative to Q c > 55°C / min. The substitution of lithium with barium in Example 6 showed a significant increase in the liquid phase viscosity and Q c . In addition, the glass of Example 6 has a high liquid phase viscosity and Q cSince it is shown that it is more resistant to devitrification than Example 1 due to its low value, the specific refractive index of Example 6 is inferior to that of Example 1. It should also be noted that as the content of ΣBaO+La2O3+ZrO2+Nb2O5+TiO2 increases, the refractive index and density also increase.

[0045] Those skilled in the art will appreciate that the construction of the described devices and other components may not be limited to specific materials. Other exemplary embodiments of the devices disclosed herein can be formed from a variety of materials unless otherwise specified herein.

[0046] For the purposes of this disclosure, the term "coupled" (in all its forms, coupling, being coupled, coupled, etc.) generally means the direct or indirect connection of two components (electrical or mechanical) to each other. Such a connection may be either essentially fixed or essentially movable. Such a connection can be achieved by the two components (electrical or mechanical) and an additional intermediate member integrally formed therewith either with each other or with the two components as a single unitary body. Such a connection may be essentially permanent or essentially removable or releasable unless otherwise specified.

[0047] It is also important to note that the structure and arrangement of the elements of the device as shown in the exemplary embodiments are merely exemplary. In this disclosure, only some embodiments of the present invention are described in detail. However, those skilled in the art who consider this disclosure will be able to make many modifications (for example, variations in the size, dimensions, structure, shape, and ratio of various elements, values of parameters, mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel and non-obvious teachings and advantages of the recited subject matter. For example, elements shown as integrally formed may be composed of multiple parts, or elements shown as multiple parts may be integrally formed. The operation of the interface can be reversed or otherwise changed. The length or width of the structure, and / or members, or connectors, or other elements of the system can be changed, and the nature or number of adjustment positions provided between elements may be changed. Note that the elements and / or assemblies of the system can be constructed from any of a variety of materials that provide sufficient strength or durability in any of a variety of colors, textures, and combinations. Therefore, all such changes are intended to be included within the scope of the present invention. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions, and arrangement of the desired and other exemplary embodiments without departing from the spirit of the present invention.

[0048] It will be understood that any of the processes described or steps within the described processes can be combined with other disclosed processes or steps to form structures within the scope of this device. The exemplary structures and processes disclosed herein are for purposes of illustration and should not be construed as limiting.

[0049] It should also be understood that changes and modifications can be made to the foregoing structure without departing from the concept of the present invention. Furthermore, such a concept is intended to be covered by the following claims, unless the claims explicitly provide otherwise by their language.

[0050] The above description should be regarded as merely an illustration of the exemplary embodiments. Modifications to the device will occur to those skilled in the art or those who manufacture or use the device. Therefore, the embodiments shown in the drawings and described above are for illustrative purposes only, and it should be understood that it is not intended to limit the scope of the present device as defined by the following claims, including the doctrine of equivalents, and as construed in accordance with the principles of the patent law.

[0051] Hereinafter, preferred embodiments of the present invention will be described item by item.

[0052] Embodiment 1 A glass composition comprising: 25 to 40% by mass of SiO2; 2.5 to 10% by mass of B2O3; 0 to 10% by mass of Al2O3; 0 to 15% by mass of Li2O; 10 to 25% by mass of CaO; 0 to 15% by mass of BaO; 0 to 5% by mass of MgO; 0 to 5% by mass of SrO; 0 to 7% by mass of ZnO; 2 to 10% by mass of ZrO; 2 to 15% by mass of TiO2; 5 to 25% by mass of Nb2O5; 0 to 5% by mass of Ta2O5; 5 to 25% by mass of La2O3; and 0 to 5% by mass of Y2O3 and having, the glass having a refractive index of about 1.74 to about 1.80, a density of about 3.5 g / cm 3 to about 4.0 g / cm 3 a critical cooling rate of about 1 °C / min to about 50 °C / min, and a liquid-phase viscosity of more than 25 poises. A glass composition.

[0053] Embodiment 2 The glass composition according to Embodiment 1, wherein the critical cooling rate is about 1 °C / min to about 25 °C / min.

[0054] Embodiment 3 The glass composition according to Embodiment 1, wherein the critical cooling rate is from about 1 °C / min to about 10 °C / min.

[0055] Embodiment 4 The glass composition according to Embodiment 1, wherein the critical cooling rate is from about 1 °C / min to about 5 °C / min.

[0056] Embodiment 5 The glass composition according to any one of Embodiments 1 to 4, wherein the contents of Li2O, Na2O, and K2O are from 0% by mass to about 16% by mass.

[0057] Embodiment 6 The glass composition according to any one of Embodiments 1 to 5, wherein the contents of CaO, BaO, MgO, and SrO are from about 10% by mass to about 30% by mass.

[0058] Embodiment 7 The glass composition according to any one of Embodiments 1 to 6, wherein the transmittance of the glass at 385 nm is from about 80% to about 90%.

[0059] Embodiment 8 The glass composition according to any one of Embodiments 1 to 7, wherein the glass does not contain arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), thallium (Tl), or vanadium (V).

[0060] Embodiment 9 In a method for forming glass, the method comprises Providing a mixture of glass components, comprising a mixture of glass components containing 25 to 40% by mass of SiO2; 2.5 to 10% by mass of B2O3; 0 to 10% by mass of Al2O3; 0 to 15% by mass of Li2O; 10 to 25% by mass of CaO; 0 to 15% by mass of BaO; 0 to 5% by mass of MgO; 0 to 5% by mass of SrO; 0 to 7% by mass of ZnO; 2 to 10% by mass of ZrO; 2 to 15% by mass of TiO2; 5 to 25% by mass of Nb2O5; 0 to 5% by mass of Ta2O5; 5 to 25% by mass of La2O3; and 0 to 5% by mass of Y2O3; Heating the mixture to a temperature of at least 1,350 °C to form a molten glass; and Cooling the molten glass at a critical cooling rate of about 1 °C / min to about 50 °C / min to form a glass comprising the glass being free of visible microcrystals A method for forming a glass.

[0061] Embodiment 10 The method according to embodiment 9, wherein the molten glass is cooled at a critical cooling rate of about 1 °C / min to about 25 °C / min.

[0062] Embodiment 11 The method according to embodiment 9, wherein the molten glass is cooled at a critical cooling rate of about 1 °C / min to about 10 °C / min.

[0063] Embodiment 12 The method according to any one of embodiments 9 to 11, wherein the glass has a refractive index of about 1.74 to about 1.80, a density of about 3.5 g / cm 3 to about 4.0 g / cm 3 and a liquid phase viscosity exceeding 75P.

[0064] Embodiment 13 The method according to any one of embodiments 9 to 12, wherein the glass has an Abbe number of about 30 to about 35.

[0065] Embodiment 14 The method according to any one of Embodiments 9 to 13, wherein the mixture of the glass components contains about 28% by mass of SiO2; about 3% by mass of B2O3; about 16% by mass of CaO; about 8% by mass of BaO; about 16% by mass of La2O3; about 3% by mass of ZrO2; about 18% by mass of Nb2O5; and about 8% by mass of TiO2.

[0066] Embodiment 15 A glass composition, 25 to 30% by mass of SiO2; 2.5 to 6% by mass of B2O3; 0 to 10% by mass of Li2O; 15 to 20% by mass of CaO; 0 to 10% by mass of BaO; 10 to 25% by mass of La2O3; 2 to 10% by mass of ZrO2; 5 to 20% by mass of Nb2O5; and 2 to 10% by mass of TiO2 containing wherein the glass composition has a critical cooling rate of about 1 °C / min to about 50 °C / min and a liquid-phase viscosity exceeding 25 poises. Glass composition.

[0067] Embodiment 16 The glass composition according to Embodiment 15, wherein the BaO, La2O3, ZrO2, Nb2O5, and TiO2 contents are about 40% by mass to about 55% by mass.

[0068] Embodiment 17 The glass composition according to Embodiment 15 or 16, wherein the critical cooling rate is about 1 °C / min to about 5 °C / min.

[0069] Embodiment 18 The glass composition according to any one of Embodiments 15 to 17, wherein the transmittance of the glass at 385 nm is about 80% to about 90%.

[0070] Embodiment 19 The glass composition has a refractive index of about 1.74 to about 1.80 and about 3.5 g / cm 3 ~ about 4.0 g / cm3 A glass composition according to any one of Embodiments 15 to 18, having the density of

[0071] Embodiment 20 A glass composition according to any one of Embodiments 15 to 19, wherein the glass composition comprises about 28% by mass of SiO2; about 3% by mass of B2O3; about 16% by mass of CaO; about 8% by mass of BaO; about 16% by mass of La2O3; about 3% by mass of ZrO2; about 18% by mass of Nb2O5; and about 8% by mass of TiO2.

Claims

1. A glass composition comprising: 25 to 40 mass% of SiO ２ ; 2.5 to 10 mass% of B ２ O ３ ; 0 to 10 mass% of Al ２ O ３ ; 0 to 15 mass% of Li ２ O; 15 to 20% by mass of CaO; 0 to 15% by mass of BaO; 0 to 5% by mass of MgO; 0 to 5% by mass of SrO; 0 to 7% by mass of ZnO; 2 to 10 mass% of ZrO ２ ; 2 to 15% by mass of TiO ２ ; 17.7 to 25 mass% of Nb ２ O ５ ; 0 to 5 mass% Ta ２ O ５ ; 5 to 16 mass% of La ２ O ３ ; and 0 to 5 mass% of Y ２ O ３ , and contains The glass has a refractive index of 1.74 to 1.80, a density of 3.5 g / cm ３ to 4.0 g / cm ３ and a critical cooling rate of 1 °C / min to 50 °C / min, a glass composition.

2. The glass composition according to Claim 1, wherein the critical cooling rate is from 1 °C / min to 25 °C / min.

3. (i) The Li ２ O, Na ２ O, and K ２ The content of O is 0% by mass to 16% by mass, or (ii) the content of CaO, BaO, MgO, and SrO is 10% by mass to 30% by mass, and at least one of them The glass composition according to Claim 1 or 2.

4. The glass composition according to any one of Claims 1 to 3, wherein the transmittance of the glass at 385 nm is from 80% to 90%.

5. The glass composition according to any one of Claims 1 to 4, wherein the glass does not contain arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), thallium (Tl), or vanadium (V).

6. A method of forming a glass, the method comprising: A step of providing a mixture of glass components, comprising 25 to 40% by mass of SiO ２ ; 2.5 to 10% by mass of B ２ O ３ ; 0 to 10% by mass of Al ２ O ３ ; 0 to 15% by mass of Li ２ O; 15 to 20% by mass of CaO; 0 to 15% by mass of BaO; 0 to 5% by mass of MgO; 0 to 5% by mass of SrO; 0 to 7% by mass of ZnO; 2 to 10% by mass of ZrO ２ ; 2 to 15% by mass of TiO ２ ; 17.7 to 25 mass% of Nb ２ O ５ ; 0 to 5 mass% of Ta ２ O ５ ; 5 to 16 mass% of La ２ O ３ ; and 0 to 5% by mass of Y ２ O ３ , providing a mixture of glass components containing; heating the mixture to a temperature of at least 1,350 °C to form a molten glass; and cooling the molten glass at a critical cooling rate of from 1 °C / min to 50 °C / min to form a glass, wherein the glass does not contain visible microcrystals. A method of forming a glass.

7. The method according to Claim 6, wherein the molten glass is cooled at a critical cooling rate of from 1 °C / min to 25 °C / min.

8. The glass has at least one of a refractive index of 1.74 to 1.80, a density of 3.5 g / cm ３ to 4.0 g / cm ３ and an Abbe number of 30 to 35, the method according to claim 6 or 7.

9. A glass composition comprising: 25 to 30 mass% of SiO ２ ; 2.5 to 6% by mass of B ２ O ３ ; 0 to 10 mass% of Li ２ O; 15 to 20% by mass of CaO; 0 to 10% by mass of BaO; 10 to 16 mass% of La ２ O ３ ; 2 to 10 mass% of ZrO ２ ; 17.7 to 20 mass% of Nb ２ O ５ ; and 2 to 10 mass% of TiO ２ and the glass composition has a critical cooling rate of from 1 °C / min to 50 °C / min. A glass composition.

10. The above-mentioned BaO, La ２ O ３ , ZrO ２ , Nb ２ O ５ , and TiO ２ The glass composition according to any one of claims 1 to 5 and 9, wherein the total content thereof is 40% by mass to 55% by mass.

11. The glass has at least one of a transmittance of 80% to 90% at 385 nm, a refractive index of 1.74 to 1.80, and a density of 3.5 g / cm ３ to 4.0 g / cm ３ The glass composition according to claim 9 or 10.

12. The glass composition contains 28% by mass of SiO ２ ; 3% by mass of B ２ O ３ ; 16% by mass of CaO; 8% by mass of BaO; 16% by mass of La ２ O ３ ; 3% by mass of ZrO ２ ; 18% by mass of Nb ２ O ５ ; and 8% by mass of TiO ２ The glass composition according to any one of claims 1 to 5 and 9 to 11, containing the same.

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