High refractive index, low density glass

Abstract

Glass containing 30.0 mol% or more of SiO2, not containing oxides of iron, lead, antimony, and tantalum, and having a refractive index n of 1.75 or more d , and approximately 65 × 10 -7 / K or less, the coefficient of linear thermal expansion α in the temperature range of 20 to 300°C 200-300 A glass having the formula:

Description

Description of Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. §120 of U.S. Provisional Patent Application No. 62 / 773,729, filed November 30, 2018, the contents of which are relied upon and incorporated herein in their entirety by reference. [Technical field]

[0002] This specification relates generally to glass compositions suitable for use in optical displays, such as displays for augmented or virtual reality devices, optical fibers, and optical lenses. More particularly, this specification relates to high refractive index glasses that can be used in displays for augmented or virtual reality devices. [Background technology]

[0003] In recent decades, high refractive index (i.e., n d The demand for optical glasses having a refractive index of >1.60 has increased with the growth of the market for augmented and virtual reality devices. Other requirements for optical glasses used in augmented or virtual reality devices include good transmittance in the visible range, good glass formability, chemical durability, and relatively low manufacturing costs. The production of glasses having a high refractive index is very different from the production of display glasses that do not require such a high refractive index. Thus, the demands of high refractive index optical glasses are not the same as the demands of display glasses, and high refractive index optical glasses will require different glass compositions than display glasses.

[0004] Another requirement of optical glasses for use in augmented or virtual reality devices is low glass density. Many augmented or virtual reality devices are manufactured as wearable devices, so that the mass of the device is supported by the user. Over long periods of time, even relatively lightweight devices can become cumbersome to wear. Therefore, for use in augmented or virtual reality devices, a glass with a low density (i.e., less than 4.00 g / cm3) and a low weight is required. 3 Glass with a density of 1000 or less is preferred.

[0005] To reduce manufacturing costs, it would be preferable for high refractive index glasses to have good chemical and physical properties and viscosity characteristics that are compatible with conventional manufacturing equipment. However, it is difficult to manufacture high refractive index glasses with the desired combination of chemical and physical properties. For example, attempts to increase the refractive index of glasses often result in an undesirable increase in glass density, making the glass article heavier. Attempts to reduce the melting temperature by reducing the high temperature viscosity have resulted in devitrification of the glass melt when forming the glass article. Devitrification occurs due to high liquidus temperatures. Attempts to reduce the glass transition temperature have resulted in an undesirable increase in the thermal expansion coefficient, and attempts to increase the elastic modulus to above 95 GPa have resulted in an undesirable increase in the glass transition temperature.

[0006] It should be noted that some silica-free phosphate glasses can have high refractive index and low CTE. These are not silicate type glasses. US Pat. No. 5,999,333 discloses glasses containing less than 12% silica and more than 12% B. 2 O 3 Including, n d >1.75 and α<60×10 -7 Borate glasses having a .OMEGA. / K have been disclosed. However, both borate and phosphate glasses are known to have low elastic moduli, i.e., they are not stiff enough for many applications. Also, most borate and phosphate (non-silicate) glasses contain PbO, Sb 2 O 3 , Ta 2 O 5 , Gd 2 O 3 , Bi 2 O 3 These materials contain large amounts of harmful and / or expensive and / or heavy oxides such as ZnO, Fe, and ZnO, which are undesirable in mass production. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 8,691,712 Summary of the Invention [Problem to be solved by the invention]

[0008] Thus, there is a need for a silicate high refractive index glass having the above-mentioned attributes, preferably having an elastic modulus greater than 95 GPa, suitable for use in augmented or virtual reality devices or other optical components. [Means for solving the problem]

[0009] According to some embodiments, the glass composition comprises 30.0 mol% or more of SiO 2 and is free of oxides of iron, lead, antimony, and tantalum, and the glass has a refractive index n of 1.75 or greater. d , and approximately 65 × 10 -7 / K or less, the linear thermal expansion coefficient α in the temperature range of 20 to 300°C 20-300 has.

[0010] According to some embodiments, the glass contains 30.0 mol % or more of SiO 2 The glass has a refractive index n of 1.75 or more. d , about 80×10 -7 / K or less linear thermal expansion coefficient (α 20-300 ), and a Young's modulus (E) of more than 100 GPa.

[0011] According to some embodiments, the glass has a thickness of about 65×10 -7 / K or less, the linear thermal expansion coefficient α in the temperature range of 20 to 300°C 20-300 and a Young's modulus (E) of 110 GPa or greater. According to some embodiments, the linear thermal expansion coefficient is about 60×10 -7 / K or less and a Young's modulus (E) of 115 GPa or more. According to some embodiments, the glass has 30 to 45 mole % SiO 2 , 0 to 15 mol% Al 2 O 3, 10 to 20 mol % TiO 2 , 5 to 20 mol % ZnO, 5 to 10 mol % (La 2 O 3 +Y 2 O 3 ), and 0 to 15 mol % alkaline earth metal oxides. According to some embodiments, the glass is free of oxides of iron, lead, antimony, and tantalum.

[0012] According to some embodiments, a glass composition that is substantially free of PbO has, expressed as mole percent of oxides: (a) SiO 2 of 38.0 mol% or more and less than 45.0 mol% 2 , (b) 4.5 mol % or more and 9.5 mol % or less of rare earth metal oxides; (c) 32.0 mole percent or less of divalent metal oxides, including: 2.0 mol% or more and 23.0 mol% or less of (MgO+CaO+SrO+BaO), and ZnO, from 3.0 mol% to 15.0 mol% (d) 0.0 mol % or more and 6.0 mol % or less of an alkali metal oxide, and (e) 0.0 mol% or more and 4.5 mol% or less of Al 2 O 3 , Including, The glass composition has a refractive index of 1.72 or greater.

[0013] According to some embodiments, the refractive index n d is less than or equal to 1.85.

[0014] According to some embodiments, n d is 1.78 to 1.83, and the density d is 3.7 g / cm 3 ~3.9g / cm 3 According to some embodiments, the glass is about 0.20 cm 3 / g or more ratio (n d -1) / d.

[0015] According to some embodiments, the glass has a Young's modulus of about 95-120 GPa and a melting point of about 60×10 within a temperature range of 20° C. to 300° C. -7 / K to 80 x 10 -7 / K. According to some embodiments, the glass has a Young's modulus of about 10-120 GPa and a linear thermal expansion coefficient (CTE) of about 60×10 within the temperature range of 20° C. to 300° C. -7 / K to -80×10 -7 / K.

[0016] According to some embodiments, the glass has a glass transition temperature T of about 600° C. to about 700° C. g , 25 and 35 GPa cm 3 / g (e.g., 28-32 GPa cm 3 / g, or 29 to 31 GPa cm 3 / g, or approximately 30 GPa cm 3 / g), a melting temperature equal to or less than 1450° C., and a liquidus temperature lower than the melting temperature. According to some embodiments, the liquidus temperature is 1300° C., 1325° C., 1350° C., 1375° C., 1400° C., 1410° C., or 1415° C.

[0017] According to some embodiments, the glass has a refractive index measured at 589.3 nm of 1.66 or greater, for example between 1.66 and 1.83 or between 1.78 and 1.83.

[0018] According to some embodiments, the glass has a viscosity of 3.2 g / cm 3 More than 3.9g / cm 3 It has the following density:

[0019] According to some embodiments, the glass has a liquidus temperature of about 1410°C.

[0020] According to some embodiments, the glass has a glass annealing temperature of 600°C or more and 700°C or less.

[0021] Additional features and advantages are set forth in the following detailed description, and in part will be readily apparent to those skilled in the art from that description, or may be learned by practicing the embodiments described herein, including the following detailed description, the claims, and the accompanying drawings.

[0022] It should be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments described herein and, together with the description, serve to explain the design and advantages of the claimed subject matter. [Brief description of the drawings]

[0023] [Figure 1] Graph showing the linear thermal expansion coefficient (α) versus refractive index (Nd) for several high refractive index glasses containing at least 30 mole % SiO2. [Diagram 2] Graph showing the coefficient of linear thermal expansion (α) versus Young's modulus (E) for several high refractive index glasses containing at least 30 mole % SiO2. [Diagram 3] FIG. 1 is an illustration showing the main effects of compositional variations on glass properties for embodiments of glasses disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] definition As used herein, the term "anneal point" refers to the temperature determined in accordance with ASTM C598-93(2013). For typical glass compositions, the anneal point is the temperature at which the viscosity of the glass of a given glass composition drops to about 10 13.2 The temperature is poise.

[0025] The term "liquidus temperature" refers to the temperature above which a glass composition is completely liquid without any crystallization of the glass components. This property is measured by the gradient method according to ASTM C829-81 "Standard Practices for Measurement of Liquidus Temperature of Glass".

[0026] The term "liquidus viscosity" refers to the viscosity of a glass composition at the liquidus temperature of the glass composition.

[0027] As used herein, the term "α" refers to the average linear thermal expansion coefficient (also referred to as the average coefficient of linear thermal expansion) of a glass composition over the temperature range of 20° C. (room temperature (RT)) to 300° C. This property is measured using a horizontal dilatometer (push-rod dilatometer) according to ASTM E228-11 (i.e., α=α, unless otherwise specified). 20-300 , the coefficient of linear thermal expansion in the temperature range of 20 to 300°C). The numerical scale of α is α = ΔL / L o ΔT′, where L o is the linear size of the sample at a temperature within or near the measured range, and ΔL is the change in linear size L over the measured temperature range ΔT. The linear thermal expansion coefficient for the temperature range 20°C to 100°C is 20-300 It is shown that:

[0028] The term "refractive index", or n d refers to the refractive index of a glass composition for the yellow d line of sodium at about 589.3 nm, measured at room temperature RT.

[0029] Unless otherwise specified, for the glass embodiments disclosed herein, the refractive index was measured using the Becke line method.

[0030] The density of the glass embodiments, as measured, was measured at room temperature using Archimedes' principle according to ASTM C693.

[0031] Elastic modulus is measured using resonant ultrasonic spectroscopy using a Quasar RUSpec 4000 available from the Magnaflux Division of ITW Indiana Private Limited.

[0032] Glass transition temperature (T g ) was measured by differential scanning calorimetry (DSC) at a heating rate of 10 K / min, after which the glasses were cooled to RT in air.

[0033] Exemplary embodiments of glasses according to embodiments of the glass compositions described herein have a high refractive index, n d , glass transition temperature T g Advantageously, they have a low coefficient of linear thermal expansion α at lower temperatures, as well as a high modulus of elasticity E, and a high specific modulus of elasticity (E / d). Such glasses can be utilized in numerous optical systems, for example, consumer glasses, camera lenses, and the like, as well as substrates for information recording media. In addition, exemplary glass embodiments are lightweight and advantageously exhibit high stiffness (low deformation under external forces). Other advantages of these glasses include a comparable low melting temperature, and a moderate glass transition temperature T g (e.g., 600° C. to 700° C.). In some embodiments, the glass has a relatively high elastic modulus (E≧100 GPa), which is advantageous in recording media applications. In some embodiments, the glass has an elastic modulus E greater than 95 GPa and less than 125 GPa. In some embodiments, the elastic modulus E of the glass is between 98 GPa and 120 GPa.

[0034] According to an exemplary embodiment, the glass has a glass transition temperature (T) of around 600° C., making the glass compatible with conventional equipment for molding articles. g );Limits glass warping during forming - e.g. 50 x 10 -7 / K and 110×10 -7 / K, preferably α<80×10 -7 / K, or even α<65×10 -7 / K, low thermal expansion, making the glass compatible with other materials such as steel or alloys; a sufficiently low melting temperature below 1450°C, preferably below 1400°C, making the glass melting process less energy intensive and compatible with conventional refractories (e.g., melting temperatures of 1100°C to 1400°C, or 1200°C to 1400°C); and the ability not to develop high stresses in the article when cooled after molding. This last quantity is primarily due to the T g For example, in some embodiments, the linear thermal expansion coefficient α is greater than or equal to 100×10 -7 / K or less, or 60 to 70 × 10 for information recording media -7 / K or less.

[0035] The glass embodiments described herein provide one or more of the following advantages: (a) Low density d (e.g., d<3.9 g / cm 3 , or d≦3.5g / cm 3 , or d≦3.3g / cm 3 , or d≦3.2g / cm 3 , and between them) while having a high refractive index n of 1.65 or less d (For example, N of 1.66, 1.75, 1.78, 1.80, 1.81, 1.83 d For example, 1.67≦N d ≤ 1.83); (b) Relatively low liquidus temperature T L <1500°C, or (e.g., T L <1450℃, T L ≦1410°C) and therefore lower energy consumption during glass production while avoiding or minimizing crystallization of the glass melt when forming articles; (c) A relatively low coefficient of thermal expansion (i.e., a relatively low value of α) between temperatures of 20°C and 300°C (e.g., α≦90×10 -7 / K, α≦80×10 -7 / K, α≦70×10 -7 / K, α≦65×10 -7 / K, α≦60×10 -7 / K) while having a relatively low glass transition temperature T g (For example, T g ≦700℃, or T g ≦650℃, or T g ≦625℃, or T g ≦600° C., or therebetween), which advantageously minimizes stresses and warpage as the glass article cools after forming; and / or (d) Low linear thermal expansion coefficient (α<80×10 -7 / K, or α<70×10 -7 / K, or α<60×10 -7 / K) while having a high refractive index (n d >1.75, or n d >1.78, or n d >1.81).

[0036] For example, in some embodiments, the density d of the glass is 3.2 g / cm 3 ≦d≦3.9g / cm 3 , or 3.5 g / cm 3 ≦d≦3.95g / cm 3 In some embodiments, the glass transition temperature is 575° C.≦T g ≦700℃, or ≦600℃ g ≦700° C. In some embodiments, the density of the glass, d, is 3.2 g / cm 3 ≦d≦3.9g / cm 3 (For example, 3.5 g / cm 3 ≦d≦3.95g / cm 3 ) and the glass transition temperature is 575°C or less T g ≦700℃ (for example, 600℃≦T g ≦700° C. In some embodiments, 55×10 -7 / K≦α≦90×10 -7 / K, or 55×10 -7 / K≦α≦80×10 -7 / K, or 55×10 -7 / K≦α≦65×10 -7 / K, or 55×10 -7 / K≦α≦60×10 -7 In some embodiments, n d >1.75 and α<80×10 -7 In some embodiments, n d >1.78 and α<70×10 -7 / K, and in some embodiments, n d >1.79 and α<60×10 -7 / K.

[0037] In at least some embodiments, the elastic modulus is greater than 100 GPa, or greater than 110 GPa, or even greater than 115 GPa. This high value prevents glass articles and devices made from these articles, such as lenses, displays, or data storage media, from deforming under load.

[0038] The high elastic modulus E, together with the relatively low density d, allows the lightweight glass article to have high resistance to external mechanical forces, which is particularly important for information recording media. The above-mentioned properties can be achieved with high values, e.g., 30 GPa cm 3 The elastic modulus can be quantitatively described by using characteristics such as the specific elastic modulus (E / d) having a value of 0.1 / g.

[0039] A high modulus of elasticity is also advantageous for glass utilized in virtual or augmented reality systems because it prevents (or minimizes) deformation of the elements of the electronic circuits that generate the images in these systems.

[0040] However, it is also known that a high elastic modulus E in glass may result in high thermal stresses in the glass as it cools during the manufacturing process, which is undesirable if the glass is to be used in optical or consumer applications (such as in devices for virtual or augmented reality, or in high refractive index lenses).

[0041] The tendency of an optical article to develop high thermal stresses can be assessed using the ratio E·α / (1-ν), where E represents Young's modulus, α is the mean coefficient of linear thermal expansion, and ν is Poisson's ratio. Thus, the lower the ratio E·α / (1-ν), the smaller the amount of stress. Therefore, embodiments of the glasses described herein preferably have a ratio E·α / (1-ν) of about 1.0 MPa / K or less.

[0042] In order to have a high elastic modulus E while at the same time maintaining the ratio E·α / (1-ν) at a desired sufficiently low level (≦1.0 MPa / K or less), the glass should have a low CTE value (i.e., low α). However, it is particularly important that the glass contains a significant amount of silica (e.g., 30 mol % or more of SiO 2 ), without significant amounts of environmentally harmful (undesirable) species such as lead, antimony, or tantalum, d And it has proven difficult or impossible to produce glasses with low CTE (low α).

[0043] It does not contain these undesirable species and has a low refractive index (n d <1.75) or have a high CTE (high α, α>65×10 in the temperature range of 20 to 300°C) -7 It has only been possible to have glass compositions with SiO 2 of 30 mol % or more. 2 The available data for these two properties is shown in FIG. 1 for comparative glasses (marked as glasses 1-7 in FIG. 1) that contain 0.01% Cr and are substantially free of undesirable elements such as Fe (colorant), Pb, Sb, and Ta. The comparative glasses shown in FIG. 1 have a refractive index of n d >1.75, and in the temperature range of 20°C to 300°C, it is approximately 67×10 -7 / K and 80×10 -7 / K. FIG. 1 also shows measurement data for some of the glass embodiments described herein (marked as Glass 8 by an asterisk, see e.g., the grey area in FIG. 1). All of the glasses shown in FIG. 1 have an α value between nd ≥ 1.75 and α ≤ 80 × 10 -7 / K.

[0044] As shown in FIG. 1, exemplary embodiments of the glass compositions disclosed herein have high refractive indices, n , of greater than 1.75 or even 1.79. d While having a low CTE value (α<70×10 -7 / K, more preferably α<68×10 -7 / K, preferably α<65×10 -7 / K, or even α<60×10 -7 At least some exemplary embodiments of the glass compositions disclosed herein exhibit a high refractive index, n, for example, between 1.75 and 1.8. d While having a low CTE value (α<70×10 -7 / K, more preferably α<68×10 -7 / K, preferably α<65×10 -7 / K, or even α<60×10 -7 / K).

[0045] Designing a glass composition with a high refractive index and low CTE is particularly difficult when the glass must have a high Young's modulus. 2 (without other compositional restrictions) and the refractive index n d The available data on Young's modulus and CTE values ​​for a series of comparative silicate glasses (indicated by the symbols *, +, and ■ in FIG. 2) having Young's modulus E≧1.75 and Young's modulus E≧90 GPa are shown in FIG. 2. FIG. 2 also shows measured data for some of the embodiments of high index glasses (marked by asterisks in FIG. 2) that have been produced as described herein. The glass embodiments shown in FIG. 2 have n d ≥ 1.75 and α ≤ 80 × 10 -7 / K.

[0046] As is evident from this figure, exemplary embodiments of the high refractive index silicate glass compositions disclosed herein have Young's modulus E>100 GPa, or E>110 GPa, or even E>115 GPa, and low CTE values ​​(α<80×10 -7 / K, α<65×10 -7 / K, or even α<60×10 -7 / K) and has a high refractive index (n d >1.78, or even n d For glasses with very high elastic modulus (E>115GPa) and low CTE (α<60×10 -7 The unique combination of (R / K) enables the high refractive index material to remain very rigid during manufacturing, preventing high thermal stresses therein.

[0047] The glass embodiment shown in FIG. 2 does not contain any environmentally harmful, expensive, and / or heavy species (such as the oxides PbO, Sb 2 O 3 , Ta 2 O 5 , Gd 2 O 3 , Bi 2 O 3 All of the glass embodiments described herein contain silica as the primary network former, which makes them inexpensive to manufacture.

[0048] The glass embodiments described herein include three main components: silica (SiO 2 ), titania (TiO 2 ), and zinc oxide (ZnO). The glass may also contain alkaline earth metal oxides and rare earth metal oxides. The glass may also contain alkali metal oxides and other compatible ingredients in small concentrations (e.g., 5 mole percent or less), if desired.

[0049] Embodiments of the glasses described herein can be utilized, for example, in at least two applications: as optical glasses having a high refractive index (hereinafter, the term "high refractive index glass") and / or as substrates for data storage media. The high refractive index glasses may be used in a variety of applications, such as displays for virtual and augmented reality, high refractive index lenses, lasers, etc.

[0050] FIG. 3 shows the relationship between glass properties of the embodiments described herein and the main glass components mentioned above (SiO 2 , ZnO and TiO 2 ) content. It should be understood that the present disclosure relates to glass compositions having numerous potential applications, where different attributes may be relatively more or less important depending on the desired use or application for a particular glass. Thus, depending on the particular use or application, different amounts of components may be preferred for the different glass embodiments described herein to impart different desirable glass properties for the different glass applications described herein.

[0051] In the embodiments of the glass compositions described herein, the components (e.g., SiO 2 , ZnO, TiO 2 , Al 2 O 3 Concentrations of elements such as fluorine, arsenic, arsenic, fluorine ...

[0052] As described above, the glass composition disclosed herein contains silica SiO as a glass network former. 2The silica increases the viscosity of the glass over the entire temperature range and increases the liquidus viscosity, which allows the glass melt to prevent crystallization in the temperature range near the liquidus temperature. The addition of more silica to the glass composition also reduces the glass density and CTE, which is desirable. However, silica significantly reduces the refractive index of the glass. Adding too much silica to the glass composition would also increase the melting temperature of the glass, which would be undesirable. Applicants have found that the SiO in the glass composition is a good alternative to the SiO in the glass composition. 2 It has been discovered that when the content of SiO in the glass composition is less than about 30 mole percent, the silica-based glass is difficult to mold. 2 If the content is greater than about 45 mole percent, the refractive index of the glass becomes too low.

[0053] Thus, for the embodiments of the high refractive index glasses disclosed herein, it is preferred that the silica content in the glass composition be in the range of about 30 to about 45 mol %. In some embodiments, the glass contains SiO 2 in an amount of about 30 to about 33 mol %. 2 These embodiments have the highest refractive index and lowest CTE, but their glass forming ability is not as good as for glasses with higher amounts of silica. In some other embodiments, the glasses contain SiO in an amount of about 40 to about 45 mole %. 2 These glasses are characterized by better glass forming ability, but also by lower refractive index and higher CTE, which may be favorable for applications such as information storage devices. 2 This concentration range would be preferred for glass compositions for use in applications where these properties are equally important, such as the manufacture of high refractive index lenses. It should therefore be understood that the silica content can vary within the range of 30-45 mole %, depending on the preferred combination of properties, i.e., the relative importance of glass formability, refractive index, and CTE, which depends on the particular application of the glass as discussed above.

[0054] The glass composition also includes zinc oxide, ZnO. Zinc oxide improves the mechanical characteristics of the glass and increases the Young's modulus of the glass without significantly increasing the density or CTE of the glass. Zinc oxide increases the refractive index of the glass (relative to silica) without appreciably increasing the density, d, so that the addition of zinc oxide to silica reduces the ratio (n d -1) / d increases, which is advantageous in high refractive index glasses. Zinc oxide also increases the TiO 2 , ZrO 2 , Nb 2 O 5 Zinc oxide can be used to stabilize high refractive index species such as zinc carbide, zinc carbide, zinc carbide-based sapphire ... 2 O 4 To counteract this effect, it may be desirable to provide additional components in the glass, such as alkali and alkaline earth metal oxides, and / or rare earth metal oxides as described below.

[0055] Thus, the preferred range of ZnO in the glass composition embodiments is determined primarily by the amount of other high refractive index species added to the glass. For glasses with the highest refractive index, as well as glasses with relatively low (but still sufficiently high) Young's modulus, such as 100 GPa, higher concentrations of ZnO are preferred, such as about 20 mol% or more. If the requirements for refractive index are not as high, but high stiffness is more important, the ZnO content may be lower, such as about 15 mol% or less. If these properties are equally important, intermediate contents of ZnO, such as 15-17 mol%, or 17-18 mol%, or 18-20 mol%, would be more preferred.

[0056] As mentioned above, the third major component of the glass embodiment is titania TiO 2Titania significantly increases the refractive index of the glass with an equally low effect on density. Furthermore, the addition of titania to glass increases the elastic modulus and fracture toughness of the glass and lowers the CTE. Therefore, the addition of titania would be favorable to provide highly desirable glass characteristics (see Figure 3). However, peraluminized glasses (quantity (Al 2 O 3 -ΣR 2 When titania is added at a concentration of 0.01 to 0.15, which is characterized by a positive value of 0.01 (mol%), titania may precipitate from the melt in the form of rutile or other minerals. The precipitation of titania then increases the liquidus temperature of the glass, which may be undesirable. In addition, at high concentrations, titania may introduce some coloration into the glass, which may be undesirable for some optical glass applications. Therefore, the content of titania in the glass should be as high as possible (e.g., 10 to 20 mol%) to reach better properties in terms of refractive index, density, CTE and modulus, but the maximum amount in the glass composition is also limited by the negative effects mentioned above, such as devitrification of the melt and / or coloration of the glass.

[0057] According to some embodiments, the glass composition contains a relatively small amount of TiO 2 , i.e., about 10 to about 13 mol % TiO 2 These glasses do not exhibit a tendency to devitrify, but offer a reasonably high refractive index, a higher CTE, and a lower Young's modulus. These glasses would be preferred for use in, for example, lenses where the highest refractive index is not required.

[0058] According to some embodiments, the glass composition comprises about 13 to about 15 mol %, or about 15 to about 18 mol % TiO 2 These glasses have a similarly high refractive index (TiO 2 The higher the content, the higher the refractive index) and does not devitrify when it is quenched, for example when cooled between two metal plates.

[0059] According to some other embodiments, the glass composition comprises about 18 to about 20 mol % TiO 2 These glasses have very high refractive indices (n > 1.81). d They exhibit a tendency towards devitrification and colouration, but may also exhibit a tendency towards devitrification and colouration.

[0060] Therefore, TiO in the glass composition 2 The preferred content of may be about 10 to about 20 mol %, e.g., 10 to 12 mol %, 12 to 14 mol %, or 14 to 16 mol %, or 16 to 18 mol %, or 18 to 20 mol %, etc., depending on the particular application, i.e., the equal importance of mechanical, optical and crystallization properties.

[0061] The glass composition may then optionally contain rare earth metal oxides (also referred to herein as "rare earths"). For colorless glasses, rare earth metal oxides include Ce, 2 O 3 ,Pr 2 O 3 , Nd 2 O 3 , Sm 2 O 3 ,EU 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 or a combination thereof. In cases where color is not required or desired in the glass, then the glass composition may contain lanthanum oxide (La 2 O 3 ), yttrium oxide (Y 2 O 3 ), gadolinium oxide (Gd 2 O 3 ), ytterbium oxide (Yb 2 O 3 ), lutetium oxide (Lu 2 O3 ), or a combination thereof. Furthermore, the glass composition may contain small amounts of these rare earth metal oxides when the presence of some coloring is acceptable, such as in thin lenses for consumer spectacles, or sunglasses with the requisite optical performance. When added to a glass composition, rare earth metal oxides increase the refractive index of the glass, thereby improving the optical performance of the glass. They may also lower the liquidus temperature of the glass and prevent the glass melt from devitrifying. Rare earth metal oxides improve the mechanical properties of the glass, for example imparting a high elastic modulus, which is one of the requirements for information recording media and is also a desirable factor for optical glasses.

[0062] However, rare earth metal oxides can also increase the glass density, which increases the (n d -1) / d ratio will be somewhat reduced. For that reason, the lightest (and least expensive) rare earth metal oxide, La 2 O 3 and Y 2 O 3 When low glass density is relatively more important, the lighter rare earth metal oxide Y is preferably used. 2 O 3 would be preferred. Otherwise, La is the least expensive of the rare earth metal oxides. 2 O 3 The effect of other rare earth oxides on the other properties disclosed herein is similar. Thus, other rare earth oxides may also be used in the glass composition; however, they may not be as effective as La with respect to the combination of properties described herein. 2 O 3 and Y 2 O 3 does not provide any significant advantage over

[0063] In the disclosed exemplary embodiment, the least expensive of the rare earth metal oxides (La) was used to demonstrate that the desired combination of properties of high refractive index glasses can be achieved at a relatively low cost. 2 O3 As described above, in order to increase the refractive index of the optical glass, La was added to the optical glass composition. 2 O 3 However, excessive amounts of La 2 O 3 The addition of to the glass composition increases the density of the glass and can cause the glass melt to devitrify upon cooling.

[0064] The total amount of rare earth metal oxides in the glass composition is preferably 1.5 mol% to 10 mol%. For example, if very high values ​​of refractive index are desired along with the highest mechanical performance (such as highest Young's modulus), it may be preferable to add rare earth metal oxides in relatively high concentrations, such as 6 mol% or more (e.g., 6 to 8 mol%, or 8 to 10 mol%). If the highest refractive index is not required and / or the requirements for mechanical performance are not very high, rare earth metal oxides may be used in lower concentrations (e.g., 4 to 6 mol%, or 2 to 4 mol%) or even smaller concentrations (such as 1-2 mol%), or even not used at all.

[0065] The glass composition may include alkaline earth metal oxides, such as BeO, MgO, CaO, SrO, BaO, or combinations thereof. The alkaline earth metal oxides (hereinafter also referred to as "alkaline earth") may neutralize some excess alumina and maintain the liquidus temperature within an acceptable range, such as not exceeding 1350-1450°C.

[0066] However, beryllium oxide (BeO), the lightest of the alkaline earths, does not work as effectively and, in addition, lowers the refractive index of the glass; therefore, BeO is not a preferred component in these glasses.

[0067] Magnesia MgO is the lightest of the alkaline earth metal oxides (except for BeO, which is environmentally undesirable) and shows the greatest impact on mechanical performance, which increases Young's modulus and other elastic moduli (also known to increase fracture toughness). In addition, MgO (relative to other alkaline earth metal oxides) has the lowest impact on CTE. However, MgO also has the lowest impact on the refractive index of the glass (relative to other alkaline earth metal oxides). Thus, a relatively high content of MgO, such as 6-8 mol %, or even up to 10 mol %, would be beneficial for applications that do not require the highest values ​​of refractive index, but do require low CTE and / or high mechanical performance. In other cases, MgO may be used in small concentrations (such as 2-4 mol %, or 4-6 mol %) or not used at all. In general, the preferred content of MgO may vary from 0 to about 10 mol %.

[0068] Calcium oxide, CaO, essentially behaves similarly to MgO, but has a somewhat greater effect on the refractive index and CTE, and a slightly lesser effect on mechanical properties such as Young's modulus. However, CaO is less sensitive to the effects of ZrO 2 or Nb 2 O 5CaO acts significantly better than MgO as a stabilizing species for high refractive index components such as CrO, Mg ... In general, the preferred CaO content will vary from 0 to about 10 mole %.

[0069] Barium oxide BaO behaves somewhat differently than CaO and MgO. What is most important about BaO is that it not only has the highest effect on the refractive index, but also, in addition, TiO 2 , ZrO 2The main advantage of BaO is that it effectively acts as a stabilizing species for other high refractive index species such as BaO. As a result, the addition of BaO to the glass produces the highest effect on the refractive index, with the possibility of increasing the amount of other high refractive index species. However, among the alkaline earth materials, BaO has the highest effect on CTE, the lowest effect on Young's modulus, and the highest effect on density. Thus, the addition of BaO is beneficial when the highest value of refractive index is required. In this case, the glass composition may contain more than 5 mol % BaO, or even up to 10 mol % BaO. However, when the above properties are required in combination, the highest content of BaO is not beneficial, and the preferred value is intermediate, such as 4-6 mol %. When the highest refractive index is not required, the glass composition may contain a fairly small amount of BaO, such as 1-2 mol % or 2-4 mol %, or may not contain this component at all. In general, the preferred content of BaO may vary from 0 to about 10 mol %.

[0070] Strontium oxide SrO acts at an intermediate level between CaO and BaO and does not offer any particular advantage in the glasses considered here compared to CaO, BaO or their combinations. However, technically it is beneficial to use a single component rather than a mixture of the two. In this respect, the use of SrO can be beneficial as an alternative to a mixture (CaO+BaO) in cases where CaO and BaO would otherwise be desirable in a ratio close to 1:1. Also, in some compositional spaces, the use of several different alkaline earths can lower the liquidus temperature compared to the use of a single species; in this case SrO would also be a useful component. In the previously mentioned cases, the preferred amount of SrO in the glass would be similar to that of CaO and MgO, i.e., it would vary from 0 to about 10 mole %, depending on the property requirements.

[0071] In addition to the above components, optical glasses contain alkali metal oxides, namely Li 2 O, Na 2 OK 2 O, Rb 2 O, Cs 2Alkali metal oxides may contain TiO. Alkali metal oxides may be added to modify various properties of glass compositions, such as, for example, melting temperature, viscosity, mechanical strength, chemical durability, CTE and refractive index. Alkali metal oxides (also referred to herein as "alkali") are very effective inhibitors of alumina precipitation in the form of mullite and / or corundum. This occurs because the alkali in the glass melt reacts with alumina to form aluminosilicates that are not refractory in sufficiently small concentrations and correspondingly do not precipitate from the melt, preventing the formation of other alumina-containing species, such as mullite and corundum mentioned above. Similarly, they are effective inhibitors of alumina precipitation, such as TiO 2 , ZrO 2 , Nb 2 O 5 The alkali oxides effectively act as inhibitors of the crystallization of other refractory species, including high refractive index species such as SiO 2 and SiO 3 . Thus, adding alkali to a glass composition often lowers the liquidus temperature, which is beneficial. However, alkali oxides lower both the refractive index and CTE, and raise the CTE, which is undesirable.

[0072] Among the alkali metal oxides, lithium oxide (Li 2 The use of lithium oxide (NaO) is often preferred over the use of other alkali metal oxides because lithium oxide has a less negative effect on the refractive index and Young's modulus, and raises the CTE less than other alkali metal oxides. However, when the best effect on the liquidus temperature is required, the glass should be made with Na 2 OK 2 O, or other alkalis.

[0073] Therefore, alkali metal oxides may be added to the glass in limited amounts (e.g., up to 5 mol %), if necessary, to lower the liquidus temperature of the glass to a desired level while minimizing the negative effects on the refractive index, Young's modulus, and CTE, or may not be added at all if no lowering of the liquidus temperature is required. When using the maximum amount of alkali, such as more than 3 mol %, Li2 The use of O is beneficial. Otherwise, other alkalis may be used. Thus, the preferred content of alkali oxides in the glass composition may vary between 0 and about 5 mol%, such as 0-1 mol%, or 1-2 mol%, or 2-3 mol%, or 3-4 mol%, or 4-5 mol%, depending on the need to lower the liquidus temperature.

[0074] TiO 2 In addition to ZnO and the rare earth metal oxides mentioned above, the refractive index increasing component is ZrO 2 , MoO 3 , WO 3 They may be used in small amounts, such as 0 to 5 mol %, but the peraluminized glass may contain zirconia (ZrO 2 It should be noted that the addition of Ta can raise the liquidus temperature to 1400-1600°C, which can also cause the melt to devitrify. Other species that increase the refractive index are environmentally unfriendly (e.g., Ta 2 O 5 , Sb 2 O 3 etc.) or are significantly more expensive than the species mentioned above, or both. Therefore, these species may not be used in glasses in some cases, but the use of these components may not be efficient in terms of cost-performance ratio.

[0075] Another type of ingredient that may be utilized in the glass composition is a fining agent. A fining agent is used to remove bubbles from the glass melt and make it more homogeneous. For this purpose, different kinds of fining agents may be used, the most preferred of which are those that also have the desired effect on the properties mentioned above, and above all on the refractive index. For this purpose, the glass may be provided with CeO in the amount required for it. 2 , SnO 2 Typically this is from 0 to about 1 mol %, unless a higher amount is required for other purposes, such as cerium oxide, CeO, as one of the rare earth metal oxides (see above). 2will also lower the liquidus temperature in some glass compositions.

[0076] The glass compositions of the embodiments described herein may also optionally contain additional network formers, such as boron oxide (B 2 O 3 ), phosphorus oxide (P 2 O 5 ) may contain small amounts of other compatible species or ingredients. 2 O 3 and P 2 O 5 are known to effectively reduce the CTE of glass and improve the formability of the glass. However, these species also reduce the refractive index and Young's modulus, which is highly undesirable. Thus, these species may be used in small amounts only when there is no other way to achieve the effect they affect. In other cases, their use is undesirable.

[0077] Finally, as mentioned above, the glass composition may contain different components in various combinations. For this reason, the different components may chemically interact with each other, sometimes in quite complex ways (such as the interaction of three, four or even more components together), and these interactions may affect some of the glass properties. The rare earth metal oxides (REO) mentioned above are also useful for the glass composition. m O n ) is composed of many components, especially alumina (Al 2 O 3 ) and alkali metal oxides (Alk 2O) (which in turn also reacts with alumina). Thus, there are several desirable ratios that are met that optimize the properties of the glass. Thus, as mentioned above, alumina, when present in high concentrations in the glass composition, can increase the liquidus temperature of the glass and therefore decrease its liquidus viscosity, which is undesirable. It was also mentioned that this effect can be minimized or compensated for by adding rare earth metal oxides and / or alkali metal oxides to the glass composition. However, the relative abundance of these three components Al 2 O 3 , R.E. m O n and Alk 2 O is in the following ratio: P = [Al 2 O 3 (mol%)-ΣR 2 O(mol%)-1.5ΣRE m O n It was found that this effect was observed when the amount of ZnO in the mixture was in a ratio that satisfied the formula ΣR 2 O is the total content of alkali metal oxides, and ΣRE m O n is the total content of rare earth metal oxides. In practice, however, an exact zero value is not necessary, but rather it is desirable that the aforementioned quantities will not be large, such as -3 mol%≦P≦+3 mol%, or -5 mol%≦P≦+5 mol%. In some cases, it may be possible to reach acceptable glass characteristics without meeting these ratios; however, when |P|≦5 mol%, the glass composition is favorable and has a better overall combination of properties.

[0078] As disclosed above, the density of the optical glasses may, in one or more embodiments, be relatively low. In at least some embodiments, the density was measured (according to ASTM C693). The density d of the optical glasses described herein is 3.9 g / cm 3 Below 3.5g / cm 3 or less than 3.2g / cm 3 For example, 4.00g / cm 3In one or more embodiments, the density of the optical glass is 3.25 g / cm 3 Above 4.00g / cm 3 , 3.4g / cm 3 Above 4.00g / cm 3 Less than or equal to 3.5g / cm 3 Above 4.00g / cm 3 Less than 3.2g / cm 3 Above 4.00g / cm 3 It may be the following:

[0079] As used herein, liquidus temperature is measured by the gradient furnace method, which conforms to ASTM C829-81, Standard Practices for Measurement of Liquidus Temperature of Glass.

[0080] As noted above, "Young's modulus" is measured by resonant ultrasonic spectroscopy using a Quasar RUSpec 4000 manufactured by Magnaflux. According to exemplary embodiments, the Young's modulus of the optical glass is 100 GPa or greater. For example, in some embodiments, the Young's modulus of the optical glass is 100 GPa or greater and 120.0 GPa or less, such as 105 GPa or greater and 120 GPa or less, 85.0 GPa or greater and 100.0 GPa or less, or 90.0 GPa or greater and 95.0 GPa or less, and all ranges and subranges therebetween.

[0081] The thermal stability of the optical glass composition is T x and T g The difference between (i.e., T x -T g ) can be determined by measuring the T x -T g The T value is measured as described above. In one or more embodiments, the T value of the optical glass x -T g may be from 100°C to 250°C, such as from 130°C to 170°C.

[0082] In some embodiments, the thermal expansion coefficient (α) of the glass composition is about 50×10 -7 / K and 65×10 -7 / K and all ranges and subranges therebetween. The coefficient of thermal expansion (α) is determined by using a push-rod dilatometer in accordance with ASTM E228-11.

[0083] As previously disclosed, the optical glass according to the described embodiments disclosed herein may be used in an augmented reality device, a virtual reality device, or an information storage medium. EXAMPLES

[0084] The embodiments will become more apparent from the following examples.

[0085] Representative glass compositions and properties are summarized in Tables 1A and 1B, respectively. Table 1B lists examples of the disclosed glass compositions.

[0086] One or more of the glass compositions having the components listed in Tables 1A and / or 1B below were prepared by conventional glass forming methods. These glasses were melted in air at 1350° C. to 1500° C. in a Pt crucible with an aluminum cover, e.g., B 2 O 3 , Al 2 O 3 , SiO 2 , CO 3 , Na 2 CO 3 , CaCO 3 , BaCO 3 , ZnO, ZrO 2 , TiO 2 , La 2 O 3 , Nb 2 O 5 , SnO 2The glass compositions are produced from a batch of source or starting material (e.g., 1000 g of glass melt, 100% theoretical yield; typical yields have been 900 g or 90% by weight, e.g., due to mechanical losses) including , , and other common species. More specifically, the components of the glass compositions were melted in a platinum crucible at between 1500 and 1600°C for 5 to 6 hours. The glass was then cooled between two steel plates to obtain a sample several mm thick, which was annealed for 1 to 5 hours near the annealing temperature given in Table 2. Multiple samples of each glass composition were prepared. Each of the glass samples was characterized by a refractive index, n d Some of the example compositions were tested for glass transition temperature (T g ), T g The thermal expansion coefficient (α), viscosity, Young's modulus, Poisson's ratio, and liquidus temperature below and above were also examined.

[0087] In Table 1A, all glass components are expressed in mole percent. (Several glass compositions were modeled having the components listed in Table 1A below. These are indicated by an asterisk ( * ) The glass properties of these compositions are comparable to those modeled and measured from prepared glass samples.

[0088] Various properties of glasses formed according to Tables 1A and 1B are given below in Table 2.

[0089] [Table 1A]

[0090] [Table 1B]

[0091] [Table 2]

[0092] The glass embodiments of Tables 1 and 2 exhibit high refractive indices, relatively low densities, fairly low coefficients of thermal expansion, and high elastic moduli.

[0093] These glasses are advantageously lightweight and resistant to crack formation or mechanical damage under load. They have high optical transmittance in the required wavelength range, e.g., the visible range or a portion of the visible range. In addition, many of these glasses exhibit a high modulus of elasticity, making them suitable for use as substrates for information recording media.

[0094] The refractive index determines how thick a glass article, e.g., a lens, can be for its function. The most frequently used characteristic of the refractive index is n d , that is, the refractive index measured for a wavelength of about 589.3 nm, which corresponds to the yellow d line of the sodium spectrum. Thus, the higher the refractive index, the more compact the optical system can be with the same performance. For high-index glasses, n equal to or higher than 1.70 to 1.80 d The glasses described herein can advantageously provide such high refractive indices.

[0095] For many optical systems, such as consumer eyeglasses, smartphone cameras, etc., it is important to have not only a small size but also a light mass. The mass of an article of a given geometric size and shape is determined by its density, d. For high refractive index glasses, it is about 3.5-4.0 g / cm 3 The glasses described herein preferably have density values ​​of about 3.5 to 4.0 g / cm 3 It may conveniently have the following density values:

[0096] A common numerical measure of optical performance that considers both high refractive index and light weight is the ratio (n d -1) / d. This ratio is often referred to as "refraction". The ratio (n d The higher the (n -1) / d, the lighter the lens will be for the same optical performance. For high index glasses, a (n d-1) / d. At least some of the glass embodiments described herein have a value of at least about 0.2. For example, in the glass embodiments described herein, 3 / g≦(n d -1) / d≦0.25cm 3 / g.

[0097] Another requirement of information recording media is a high elastic modulus, i.e., the ratio of the force applied to the substrate or body to the resulting deformation. A high elastic modulus makes the glass article more rigid and allows it to avoid large deformations under external forces that may occur when recording or reading information. There are several numerical characteristics of elasticity. The most common characterization of the rigidity of a material is the Young's modulus E, i.e., the relationship between stress (force per unit area) and strain (proportional deformation) in an article made from this material. The higher the Young's modulus of the material, the smaller the deformation of the article. For the substrate of information recording media, it is desirable to have a Young's modulus of about 100 GPa or more. The glass embodiments described herein advantageously have a Young's modulus of 100 GPa or more.

[0098] For optical elements, high stiffness of the material results in a stable optical image under certain external (especially variable) forces, which is important for certain optical systems. However, a high value of Young's modulus is often in conflict with the technical requirement of low thermal stresses induced in the article during manufacture (see below), which makes it desirable to have a sufficiently low stiffness. Therefore, for high refractive index glasses, it is preferable to have a Young's modulus that is not very high, such as less than 100 GPa. For glass compositions that may be used for both applications, the preferred value of Young's modulus is around 100 GPa.

[0099] To characterize glasses with high Young's modulus and low weight, it is convenient to use the specific elastic modulus E / d, which is the ratio of Young's modulus E to the glass density d. In some exemplary embodiments, the specific elastic modulus of the glass is 30 GPa cm 3 / g≦(E / d)≦40GPa cm3 In some exemplary embodiments, the specific elastic modulus of the glass is 32 GPa cm 3 / g≦(E / d)≦38GPa cm 3 In some exemplary embodiments, the specific elastic modulus of the glass is 30 to 34 GPa cm 3 In some exemplary embodiments, the specific elastic modulus of the glass is 32 to 34 GPa cm 3 In some exemplary embodiments, the specific elastic modulus of the glass is 32 to 40 GPa cm 3 For glass substrates for information recording media, the value of E / d is preferably at least about 30 GPa cm 3 / g, e.g., at least 32 GPa cm 3 / g, or at least 30 GPa cm 3 / g, or 34 GPa cm 3 / g.

[0100] From a technical point of view, it is necessary for optical glasses to avoid excessive stresses that may be induced in the glass article during its manufacture. These stresses appear when the glass article cools after it has been formed. The value of the induced stresses depends on a number of factors, such as the size and shape of the article and the cooling rate in the sensitive temperature range (roughly the interval between the annealing point and the strain point of the glass). All other factors being equal, the value of the stresses depends on the glass composition. This quantity is evaluated as the ratio R = E·α / (1-ν), where E represents Young's modulus, α is the mean coefficient of linear thermal expansion and ν is the Poisson's ratio; all characteristics are related to the glass transition temperature T g They are measured at lower temperatures (the first two of them at room temperature). Thus, all other factors being equal, the lower the ratio E·α / (1-ν), the smaller the value of the stress in the glass. There are several other more complex indices that consider structural relaxation in some way, but all of them consider the value of the thermal expansion coefficient (α) and one of the elastic moduli, usually the E value. With respect to the ratio R=E·α / (1-ν), it is preferred that the optical glasses described herein have an E·α / (1-ν) ratio of 1.0 MPa / K or less.

[0101] The glass should therefore have a fairly low coefficient of thermal expansion (in the following the abbreviation α will be used).

[0102] As noted above, for optical elements, the value of α contributes to thermal stresses that may arise when cooling the article after hot pressing or other forming techniques, and can be considered in terms of the ratio E·α / (1-ν), with preferred values ​​being 1.2 MPa / K or less, e.g., 1.1 MPa / K or less, or 1.0 MPa / K or less. For example, in some embodiments, the ratio E·α / (1-ν) is 0.3 MPa / K≦E·α / (1-ν)≦1.0 MPa / K, or 0.35 MPa / K≦E·α / (1-ν)≦1.0 MPa / K, or 0.4 MPa / K≦E·α / (1-ν)≦1.0 MPa / K.

[0103] Considering that the optimum values ​​of Young's modulus for the described general-purpose glasses are around 100 GPa (see above) and that the typical values ​​of Poisson's ratio for glasses are equal to ν ≈ 0.25, the preferred value of α for these glasses is 60·10 -7 / K to 80·10 -7 / K, or 60 10 -7 / K to 75·10 -7 / K, more preferably 72·10 -7 / K or less, preferably 70·10 -7 / K or less, e.g., 60·10 -7 / K to 70·10 -7 / K, for example, α ≒ 62 10 -7 / K, α ≈ 65·10 -7 / K, α ≈ 67·10 -7 / K, α ≈ 69·10 -7 / K.

[0104] For glass substrates for information recording media, the value of α determines the potential change in linear size of the substrate caused by temperature changes resulting from information recording and / or changes in external temperature. The smaller the value of α, the smaller the temperature-induced deformation. The requirements for α of substrates for information recording media are similar to the previous case: about (60 to 70) × 10 -7It is desirable to have a value of α less than or equal to / K.

[0105] As mentioned above, from a technical standpoint, it is important that these glasses have a minimum level of viscosity at the liquidus temperature (hereinafter, liquidus viscosity) that minimizes the susceptibility of the glass melt to crystallize during the forming of the article. For example, for optical elements formed by hot pressing or similar methods, the minimum acceptable liquidus viscosity (depending on the size of the article and the equipment) may be several poise or more. According to the embodiments disclosed herein, the glasses of the substrates for information recording media advantageously have a liquidus viscosity of about 100 poise or more.

[0106] Another requirement is the glass transition temperature (T ) which approximately characterizes some intermediate temperature in the range at which a glass article becomes mechanically solid when cooled or begins to soften when heated. g ) is roughly T g has a viscosity of 10 13 corresponds to the temperature at which poise is equal; the exact value depends on the glass composition, heating / cooling rates, and other factors. T g If T is too low, the glass article will not be able to withstand the heat treatments that are often performed when manufacturing and / or using glass articles. g If the glass transition temperature is too high, the glass composition will not be compatible with conventional equipment used in manufacturing. Therefore, it is desirable to have a moderate glass transition temperature (e.g., T g <700°C). In accordance with at least some embodiments described herein, it is preferred that the temperature is 590°C < T g ≦700℃, or 590℃≦T g ≦650℃ or 590℃≦T g ≦625°C.

[0107] Another technical requirement concerns the melting temperature, i.e. the minimum temperature at which the glass can be melted and purified from residual gases (originating from the raw materials) in a reasonable time. For most industrial glasses, the melting temperature is the temperature at which the glass melt has a viscosity equal to about 100-300 poise. The temperature corresponding to a viscosity of 200 poise (hereinafter the term "200P temperature") can be considered as an estimate of the melting temperature. The lower the melting temperature, the lower the energy consumption of glass melting. Also, at lower temperatures the glass manufacturing process is more compatible with conventional refractories, and an increase in temperature would cause corrosion of refractory parts in the furnace. Thus, the lower the 200P temperature, the more favorable a given glass composition is for glass melting (all other factors being equal). Many of the embodiments of the glasses disclosed herein have melting temperatures below 1400°C, or below 1375°C, or even below 1350°C.

[0108] All compositional components, relationships, and ratios described herein are given in mole percent unless otherwise specified. All ranges disclosed herein include any and all ranges and subranges encompassed by the broadly disclosed ranges, whether or not expressly stated before or after the range is disclosed.

[0109] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Therefore, it is intended that this specification cover modifications and variations of the various embodiments described herein, provided such modifications and variations come within the scope of the appended claims and their equivalents.

[0110] Preferred embodiments of the present invention will be described below in detail.

[0111] EMBODIMENT 1 In the glass, 30.0 mol% or more of SiO 2 and does not contain oxides of iron, lead, antimony, or tantalum, and has a refractive index n of 1.75 or greater. d , and approximately 65 × 10-7 / K, the linear thermal expansion coefficient α in the temperature range from 20°C to 300°C 20-300 Glass having

[0112] EMBODIMENT 2 30 to 35 mol% SiO 2 , 10 to 15 mol% Al 2 O 3 , 15 to 20 mol % TiO 2 , 15 to 20 mol% ZnO, 5 to 10 mol% La 2 O 3 and 10 to 15 mol % alkaline earth metal oxide.

[0113] EMBODIMENT 3 In the glass, 30.0 mol% or more of SiO 2 Including, refractive index n ≥ 1.75 d , about 80×10 -7 / K or less linear thermal expansion coefficient (α 20-300 ), and a Young's modulus (E) of 100 GPa or more.

[0114] EMBODIMENT 4 The glass is approximately 65×10 -7 / K, the linear thermal expansion coefficient α in the temperature range from 20°C to 300°C 20-300 and a Young's modulus (E) of 110 GPa or greater.

[0115] EMBODIMENT 5 The glass is about 60×10 -7 / K, the linear thermal expansion coefficient α in the temperature range from 20°C to 300°C 20-300 and a Young's modulus (E) of 115 GPa or greater.

[0116] EMBODIMENT 6 30 to 45 mol% SiO 2 , 0 to 15 mol% Al2 O 3 , 10 to 20 mol % TiO 2 , 5 to 20 mol % ZnO, 5 to 10 mol % (La 2 O 3 +Y 2 O 3 6. The glass of any one of claims 3 to 5, comprising:

[0117] EMBODIMENT 7 7. The glass of any one of claims 3 to 6, wherein the glass is free of oxides of iron, lead, antimony, and tantalum.

[0118] EMBODIMENT 8 In a glass composition substantially free of PbO, expressed as mole percent of oxides: (a) SiO 2 of 38.0 mol% or more and less than 45.0 mol% 2 , (b) 4.5 mol % or more and 9.5 mol % or less of rare earth metal oxides; (c) 32.0 mole percent or less of divalent metal oxides, including: 2.0 mol% or more and 23.0 mol% or less of (MgO+CaO+SrO+BaO), and ZnO, from 3.0 mol% to 15.0 mol% (d) 0.0 mol % or more and 6.0 mol % or less of an alkali metal oxide, and (e) 0.0 mol% or more and 4.5 mol% or less of Al 2 O 3 , Including, A glass composition having a refractive index of 1.72 or greater.

[0119] EMBODIMENT 9 9. The glass composition of embodiment 8, wherein the refractive index is less than or equal to 1.85.

[0120] EMBODIMENT 10 The glass composition contains 20 mol % or less of TiO 2 9. The glass composition of embodiment 8, further comprising:

[0121] EMBODIMENT 11 The glass composition has a density of 4 g / cm 3 9. The glass composition of embodiment 8 having a density:

[0122] EMBODIMENT 12 9. The glass composition of claim 8, wherein the glass composition has a Young's modulus of about 95 GPa or more and about 125 GPa or less.

[0123] EMBODIMENT 13 In the glass composition, 30.0 mol% or more of SiO 2 and being substantially free of compounds of Fe, Pb, Sb, and Ta; Refractive index n ≥ 1.75 d , and 65.0 × 10 in the temperature range 20 °C to 300 °C. -7 3. A glass composition having a thermal expansion coefficient of 0.1 to 1.0 K or less.

[0124] EMBODIMENT 14 The glass composition has a viscosity of 60.0×10 in the temperature range of 20° C. to 300° C. -7 14. The glass composition of embodiment 13 having a thermal expansion coefficient of less than or equal to 1 / K.

[0125] EMBODIMENT 15 The glass composition comprises: SiO 30 mol % or more and 35.0 mol % or less 2 , 10 mol% or more and 20 mol% or less of (MgO+CaO+SrO+BaO); 10 mol% or more and 20 mol% or less of TiO 2 , and 10 mol% or more and 20 mol% or less of ZnO; 15. The glass composition of embodiment 13 or 14, further comprising:

[0126] EMBODIMENT 16 The glass composition comprises: 14 mol% or more and 16 mol% or less of TiO2 , 11 mol% or more and 15 mol% or less of (MgO+CaO+SrO+BaO); and 16 mol% or more and 19 mol% or less of ZnO; 16. The glass composition of any one of claims 13 to 15, comprising:

[0127] EMBODIMENT 17 The glass composition comprises: 15 mol% or less of Al 2 O 3 , 8.5 mol% or less of La 2 O 3 , and Less than 5 mol% (Nb 2 O 5 and ZrO 2 ), 17. The glass composition of any one of claims 13 to 16, further comprising:

[0128] EMBODIMENT 18 18. The glass composition of any one of claims 13 to 17, wherein the glass composition is substantially free of compounds of Pb, Bi, and Ta.

[0129] EMBODIMENT 19 16. An optical system made from the glass article of embodiment 15.

[0130] EMBODIMENT 20 An information recording device made from the glass article described in embodiment 15.

[0131] EMBODIMENT 21 16. An augmented reality device made from the optical glass article of embodiment 15.

Claims

1. In the glass composition, 30 to 35 mol % SiO ２ , 10 to 15 mol % Al 2 O 3 , 15 to 20 mol % TiO ２ , 15 to 20 mol % ZnO, 5 to 10 mol % La ２ O ３ and 10 to 15 mole % alkaline earth metal oxide, free of oxides of iron, lead, antimony, and tantalum, and having a refractive index n of 1.72 or greater. ｄ , and about 80×10 －７ / K or less, the linear thermal expansion coefficient α in the temperature range from 20°C to 300°C ２０－３００ The glass composition has the following structure:

2. The refractive index n ｄ is 1.75 or more, and the linear thermal expansion coefficient (α ２０－３００ ) is about 65 x 10 －７ 2. The glass composition according to claim 1, wherein the glass composition has a Young's modulus (E) of 100 GPa or more and a viscosity of 100 MPa or less.

3. 30 to 35 mol% SiO ２ , 10 to 15 mol % Al ２ O ３ and 5 to 10 mol % of (La ２ O ３ +Y ２ O ３ The glass composition of claim 1 , comprising:

4. The glass composition of claim 1 , wherein the refractive index is less than or equal to 1.

85.

5. 4 g / cm ３ 2. The glass composition of claim 1 having a density:

6. 30 mol % or more and 35.0 mol % or less of SiO ２ , and 10 mol% or more and 20 mol% or less (MgO + CaO + SrO + BaO) The glass composition of claim 1 , comprising:

7. 15 mol% or more and 16 mol% or less of TiO ２ , 11 mol% or more and 15 mol% or less (MgO+CaO+SrO+BaO), and 16 mol% or more and 19 mol% or less of ZnO; The glass composition of claim 1 , comprising:

8. 10 to 15 mol% Al ２ O ３ , 5 to 8.5 mol% La ２ O ３ , and Less than 5 mol% (Nb ２ O ５ and ZrO ２ ), The glass composition of claim 1 , comprising:

9. The glass composition according to claim 1 , which is substantially free of Bi compounds.

10. 30 to 35 mol% SiO ２ , 10 to 15 mol % Al 2 O 3 , 15 to 20 mol % TiO ２ , 15 to 20 mol % ZnO, 5 to 10 mol % La ２ O ３ and 10 to 15 mol % of an alkaline earth metal oxide.

11. 11. The glass composition according to claim 1, comprising 0 to 10 mol% BaO.

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