Method for manufacturing optical glass lens, and optical glass lens

Abstract

To provide an optical glass lens having high shape accuracy, having at least one aspherical curved surface and having a large aperture, and a method for manufacturing the same.SOLUTION: A method, etc., for manufacturing optical glass lens comprises: a heating and molding step of heating a glass material to be molded used as a raw material and press-molding the glass material to be molded by a die to obtain a glass molding material having at least one aspherical curved surface and having an aperture of φ30 or more and φ150 or less; a first cooling step of controlling the temperature of the glass molding material so as to have a cooling gradient of 0.1-5.0°C / min and continuously cooling the glass molding material until the viscosity logfη[dPa sec] of the glass molding material is more than 10 and less than 15 while supplying a load of 1-1500 kgf / cm2 to the glass molding material; and a second cooling step of controlling the temperature of the cooled glass molding material so as to have a cooling gradient larger than that of the first cooling step from a temperature equal to or less than the temperature of the glass molding material when completing the first cooling step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an optical glass lens, and to an optical glass lens. [Background technology]

[0002] Optical glass lenses with aspherical curved surfaces are difficult to manufacture using processing methods such as grinding and polishing, and are therefore usually manufactured using mold press molding. This mold press molding method generally involves press-molding a glass material or glass melt, etc., held at a temperature above which it would deform when force is applied, into a specified mold, followed by a cooling step.

[0003] Furthermore, with regard to this mold press molding method, even when using a phosphate-based glass material, technology is being developed that allows optical glass with a good pressed surface to be obtained even when hot press molding is performed. For example, Patent Document 1 discloses, as the above technology, a method for producing optical elements by hot pressing a phosphate-based glass containing 10 to 30 wt% of Bi2O3 in a mold and then cooling it, in which the glass is brought into contact with the press surface of the mold at a glass viscosity logη = 9 to 10 [dPa·sec], and then a pressure equal to or greater than the critical pressure of oxygen and equal to or less than the glass strength is continuously applied to the glass until the glass viscosity logη increases to 12 [dPa·sec] upon cooling. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-253001 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is room for further improvement in terms of increasing the shape precision (shape precision of the pressed surface) of optical glass lenses obtained by mold press molding. This improvement is particularly required for large-diameter optical glass lenses, at least one of which has an aspherical curved surface, because it is extremely difficult to increase the shape precision when produced by mold press molding.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical glass lens having a high degree of shape precision, at least one surface of which is an aspherical curved surface, and a large diameter, and a method for manufacturing the same. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors have conducted extensive research and have discovered a method for producing a glass molding material having a lens shape, at least one of which has an aspherical curved surface and a diameter of 30 to 150 mm, by heating and molding a glass material as a raw material and then press-molding the material in a mold. The method also involves controlling the temperature of the molded glass material so that the cooling rate is 0.1 to 5.0°C / min and applying a load of 1 to 1500 kgf / cm. 2 The inventors have found that the above-mentioned problems can be solved by a method for producing an optical glass lens, comprising: a first cooling step in which the formed glass compound is continuously cooled while applying a pressure of 0.05 to 0.15, until the viscosity logη [dPa·sec] of the formed glass compound becomes more than 10 and less than 15; and a second cooling step in which the formed glass compound cooled in the first cooling step is cooled from a temperature equal to or lower than the temperature of the formed glass compound at the end of the first cooling step by controlling the temperature so that the cooling gradient is greater than the cooling gradient of the first cooling step. The inventors have also found that this manufacturing method can produce an optical glass lens having at least one aspherical curved surface and a diameter of φ30 to φ150, in which surface shape variations are measured by scanning the same length on this curved surface in two directions passing through the center of the curved surface and perpendicular to each other, and the maximum sag difference when the measured values ​​in the two directions are superimposed is defined as Y (μm) and the diameter is defined as X (mm), where these satisfy a predetermined relationship, and thus the present invention has been completed.

[0008] That is, the present invention provides the following: <1> ~ <13> This includes embodiments of the present invention. <1> A method for manufacturing an optical glass lens having at least one aspherical curved surface and an aperture of φ30 to φ150, comprising the steps of: a heating and molding step of heating a raw glass material to be molded and press-molding it in a mold to obtain a lens-shaped glass material having at least one aspherical curved surface and a diameter of φ30 to φ150; The formed glass material is subjected to temperature control so as to have a cooling gradient of 0.1 to 5.0°C / min and a load of 1 to 1500 kgf / cm. 2 a first cooling step of continuously cooling the formed glass material while applying a pressure of 10 to 15, the viscosity of the formed glass material being greater than 10 and less than 15; a second cooling step of cooling the formed glass material cooled in the first cooling step from a temperature equal to or lower than the temperature of the formed glass material at the end of the first cooling step, by controlling the temperature so that the cooling gradient is greater than the cooling gradient of the first cooling step. A method for manufacturing optical glass lenses. <2> The optical glass lens is a concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens. <1> A method for producing an optical glass lens according to claim 1. <3> The optical glass lens has a center thickness greater than its edge thickness and a thickness deviation ratio (center thickness / edge thickness) of 1.1 or more and 7.0 or less. <1> or <2> A method for producing an optical glass lens according to claim 1. <4> The optical glass lens has an edge thickness greater than a center thickness and a thickness deviation ratio (edge ​​thickness / center thickness) of 1.1 or more and 7.0 or less. <1> or <2> A method for producing an optical glass lens according to claim 1. <5> The optical glass lens has at least one curved surface with an open angle of 25 degrees or more and 75 degrees or less. <1> ~ <4> 1. A method for producing an optical glass lens according to any one of the preceding claims. <6> The optical glass lens is an optical glass lens made of fluorophosphate glass, lanthanum borate glass, or silica gel barium glass. <1> ~ <5> 1. A method for producing an optical glass lens according to any one of the preceding claims. <7> The temperature-raising and forming step is a step of continuously raising the temperatures of both the glass material to be formed and the mold, controlling the temperature so that the temperature rise gradient is 0.1 to 100°C / min within the temperature range from the strain point to the softening point of the glass material to be formed, and then press-forming the glass material using the mold. <1> ~ <6> 1. A method for producing an optical glass lens according to any one of the preceding claims. <8> An optical glass lens having at least one surface that is an aspherical curved surface and an aperture of φ30 or more and φ150 or less, The same length on the curved surface is scanned in two directions that pass through the center of the curved surface and are orthogonal to each other, and the surface shape variation is measured. When the maximum value of the sag difference when the measured values ​​in the two directions are superimposed is Y (μm) and the diameter is X (mm), the relational expression of the following formula (1) is satisfied: Optical glass lens. (1) Y≦0.01X-0.1 <9> a concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens; <8> The optical glass lens according to claim 1. <10> The center thickness is greater than the edge thickness, and the thickness deviation ratio (center thickness / edge thickness) is 1.1 or more and 7.0 or less. <8> or <9> The optical glass lens according to claim 1. <11> The edge thickness is greater than the center thickness, and the thickness deviation ratio (edge ​​thickness / center thickness) is 1.1 or more and 7.0 or less. <8> or <9> The optical glass lens according to claim 1. <12> At least one of the curved surfaces has an open angle of 25 degrees or more and 75 degrees or less. <8> ~ <11> 10. An optical glass lens according to any one of claims 1 to 9. <13> An optical glass lens made of fluorophosphate glass, lanthanum borate glass, or silica gel barium glass. <8> ~ <12> 10. An optical glass lens according to any one of claims 1 to 9. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an optical glass lens having a high degree of shape precision, at least one surface of which is an aspherical curved surface, and a large diameter, as well as a method for manufacturing the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing an embodiment of press molding in a manufacturing method of an optical glass lens according to the present invention. FIG. [Figure 2] 1 is a schematic diagram showing a cross section of an embodiment of a concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens produced by a method for producing an optical glass lens according to the present invention. FIG. [Figure 3] FIG. 1 is a schematic cross-sectional view showing the center thickness, edge thickness, and open angle of an embodiment of a concave meniscus lens or a biconvex lens manufactured by a manufacturing method for an optical glass lens according to the present invention. [Figure 4] FIG. 1 is a schematic diagram showing an example of measuring the surface shape variation of an aspherical curved surface of an optical glass lens according to the present invention. [Figure 5] 2 is a graph showing the sag difference on the concave curved surface of the optical glass lens of Example 1. [Figure 6] 2 is a graph showing the sag difference on the concave curved surface of the optical glass lens of Comparative Example 1. [Figure 7] 1 is a graph showing the relationship between the maximum value Y (μm) of the sag difference and the lens diameter X (mm) for the optical glass lenses of Examples (◯) and Comparative Examples (×). DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will now be described. The present invention is a method for producing an optical glass lens having at least one aspherical curved surface and a diameter of 30 to 150 mm, comprising the steps of: heating a raw material glass material to be molded; and press-molding the raw material glass material using a mold to obtain a lens-shaped formed glass material having at least one aspherical curved surface and a diameter of 30 to 150 mm; and controlling the temperature of the formed glass material to a cooling gradient of 0.1 to 5.0°C / min and applying a load of 1 to 1500 kgf / cm. 2and a second cooling step in which the glass molding compound cooled in the first cooling step is cooled from a temperature equal to or lower than the temperature of the glass molding compound at the end of the first cooling step by controlling the temperature so that the cooling gradient is greater than the cooling gradient in the first cooling step. Furthermore, the present invention also encompasses an optical glass lens having at least one surface that is an aspherical curved surface and has a diameter of 30 to 150 mm, wherein the surface shape variation is measured by scanning the same length on this curved surface in two directions that pass through the center of the curved surface and are orthogonal to each other, and when the measured values ​​in the two directions are superimposed, the maximum sag difference is defined as Y (μm) and the diameter is defined as X (mm), and the optical glass lens satisfies the relational expression (1) below. (1) Y≦0.01X-0.1 Hereinafter, these may also be referred to as "the method for manufacturing an optical glass lens according to the present invention" or "the optical glass lens according to the present invention."

[0012] First, each step of the method for manufacturing an optical glass lens according to the present invention will be described in detail with reference to the drawings. Note that the dimensional ratios shown in the drawings may differ from the actual dimensional ratios in order to facilitate understanding of the invention. Also, some reference numerals are omitted from the drawings. The method for manufacturing an optical glass lens according to the present invention is a method for manufacturing a predetermined optical glass lens by mold press molding, and comprises at least the following heating and molding steps, a first cooling step, and a second cooling step.

[0013] <Heating and molding process> In the method for manufacturing an optical glass lens according to the present invention, the raw glass material to be molded is heated in the heating and molding steps and press-molded in a mold (see, for example, FIG. 1) to obtain a molded glass material of a predetermined lens shape. This glass material to be formed is a raw material to be formed obtained by heating and melting a glass raw material (batch raw material or cullet) containing one or more selected from inorganic oxides, inorganic complex oxides, inorganic fluorides, inorganic hydroxides, inorganic carbonates, inorganic nitrates, inorganic complex salts, organometallic compounds, etc., followed by vitrification, and is in a state before being formed into a lens shape. Therefore, as long as it is not formed into a lens shape, its shape, etc. are not particularly limited.

[0014] Furthermore, there are no particular limitations on the specific components contained in this glass material to be formed, and it may contain any known component (for example, silicon compounds, phosphorus compounds, fluorine compounds, etc.) used in the manufacture of glass such as fluorophosphate glass, silica borate glass, silica bandgap glass, titanium silica glass, lanthanum borate glass, niobium silica glass, niobium phosphate glass, etc., but the method for manufacturing an optical glass lens according to the present invention is characterized in that it is also effective in the manufacture of optical glass lenses made of fluorophosphate glass, lanthanum borate glass, or silica bandgap glass, which have a high linear expansion coefficient and are therefore more difficult to mold by mold press molding. This "fluorophosphate glass" refers to P 5+ as the main cation component (the most abundant of the cation components, for example, 20% or more, or even more than 30% in terms of cation % (mol %)), and F -The glass raw material for forming the glass material described above contains a large amount of boric acid compounds (e.g., borates) and lanthanum compounds (e.g., lanthanum oxide). Therefore, in this case, the glass raw materials for forming the glass material described above should contain a large amount of phosphorus compounds (e.g., phosphates) and fluorine compounds (e.g., inorganic fluorides). Furthermore, "lanthanum borate glass" refers to glass whose oxide-equivalent composition (mass %) is composed primarily of B2O3 and La2O3 (the total amount of these compounds is the largest, e.g., 20% or more, or even more than 30%). Therefore, in this case, the glass raw materials for forming the glass material described above should contain a large amount of boric acid compounds (e.g., borates) and lanthanum compounds (e.g., lanthanum oxide). Furthermore, "silica boride glass" refers to glass whose oxide-equivalent composition (mass %) is composed primarily of SiO2 and BaO (the total amount of these compounds is the largest, e.g., 20% or more, or even more than 30%). In this case, therefore, the glass raw material for obtaining the glass material to be formed should contain a large amount of silicon compounds (such as silicates) and barium compounds (such as barium oxide). Here, "cation % (mol %)" and "anion % (mol %)" refer to the percentage of each component contained in an optical glass lens, with the glass constituent components of the optical glass lens separated into cationic and anionic components, and the total percentage of each being 100 mol %. Also, "oxide equivalent composition (mass %)" refers to the composition of each component contained in glass, assuming that the oxides, complex salts, metal fluorides, etc. used as raw materials for the glass constituent components are all decomposed and converted into oxides during melting, with the total mass of the oxides produced being 100 mass %.

[0015] In this temperature-raising and forming step, the glass material to be formed as described above is heated to a temperature at which it can be press-formed, and then press-formed using a mold, but it is more preferable that this temperature rise be controlled so that the temperature rise gradient is within a certain range and the temperature is raised continuously. At this time, it is also more preferable that the mold be heated in the same way (more preferably, the temperatures of the glass material to be formed and the mold are made substantially equal to each other, that is, press-forming is performed isothermally). Here, "continuously increasing the temperature" means that there is no state during the temperature increase where the temperature rise gradient falls outside the range of a predetermined temperature rise gradient. The same applies hereinafter. Furthermore, "making the temperatures of the glass material to be formed and the mold "substantially equal" means that the temperature difference between them is less than 1°C.

[0016] In particular, the effects of the present invention are more readily achieved by combining this with the first and second cooling steps described below. Furthermore, clouding of the resulting optical glass lens is suppressed, improving the appearance quality. Therefore, the heating and molding step is preferably a step in which the temperature of both the glass material to be molded and the mold are continuously increased, and the temperature is controlled to achieve a temperature increase gradient of 0.1 to 100°C / min (a temperature increase gradient of 0.1 to 100°C per minute) within the temperature range from the strain point to the softening point of the glass material to be molded, and the glass material is press-molded into a predetermined lens shape using this mold. Furthermore, it is more preferable to continuously increase the temperature by controlling the temperature so that the above temperature increase gradient is achieved throughout the entire process from the start to the end of the temperature increase. Note that a higher temperature increase gradient can further shorten the time required for molding, thereby improving productivity. Therefore, the lower limit of the temperature increase gradient is more preferably 0.3°C / min or more, even more preferably 0.7°C / min or more, and even more preferably 1°C / min or more. Furthermore, if this temperature rise gradient is low, volatile components in the glass material being formed can be more easily released, thereby further improving the appearance quality of the resulting optical glass lens. Therefore, the upper limit of the temperature rise gradient is preferably 80°C / min or less, more preferably 60°C / min or less, even more preferably 40°C / min or less, and even more preferably 20°C / min. Here, the strain point is the temperature below which no distortion occurs even when rapidly cooled, and corresponds to the upper limit temperature at which viscous flow of glass does not actually occur (the temperature at which viscosity cannot be measured by the platinum sphere pulling method described later), and is the temperature at which viscosity is 10 14.5The softening point is the temperature at which the viscosity of a glass is 10 dPa·sec. The strain point can be measured by the fiber elongation method based on JIS R 3103-2. The softening point is the lowest temperature at which glass can be molded, hot processed, and pressed. 7.65 This refers to the temperature equivalent to dPa·Sec. The softening point can be measured using the fiber elongation method based on JIS R 3103-1.

[0017] The mold (e.g., reference numeral 51 in FIG. 1) used for press molding in the heating and molding steps is not limited as long as the press surface and mold size are designed so that the heated glass material to be molded can be press-molded using a press mechanism (e.g., reference numeral 53 in FIG. 1) to mold a glass material having a predetermined lens shape with at least one aspherical curved surface and a diameter of φ30 to φ150 (φ30 mm to φ150 mm). The material is also not particularly limited, and the mold may be made of any known material (e.g., alloy) that can be used to form a mold having thermal conductivity and heat resistance during press molding. The lower limit of the diameter of the glass material may be φ40 or more (φ40 mm or more). The upper limit of the diameter of the formed glass compound is more preferably φ100 or less (φ100 mm or less), even more preferably φ80 or less (φ80 mm or less), even more preferably φ70 or less (φ70 mm or less), and even more preferably φ65 or less (φ65 mm or less). Furthermore, the pressing mechanism is not particularly limited, but preferably has a heat source (heating and cooling source) that can control the heating gradient described above and the cooling gradient described below and can heat and cool the mold uniformly (so that the temperature variation range throughout the mold is preferably within 10°C, more preferably within 3°C, and even more preferably within 1°C), and more preferably has one or more pairs of such heat sources arranged to sandwich the glass material to be formed and the mold in the load direction (two or more heat sources arranged to sandwich the glass material to be formed and the mold). By preparing and arranging such a device with a heat source and a mold to match the size and capacity appropriate for the diameter of the desired glass molding material, it becomes possible to press-mold lens-shaped glass moldings with a diameter of φ30 to φ150. Here, "aspheric" means that the entire surface is not a spherical surface with a constant curvature, i.e., a curved surface with two or more curvatures on a single glass surface. Furthermore, "aperture" refers to the maximum outer diameter (mm) of the lens-shaped glass molding (i.e., the finished optical glass lens) when incorporated into a mirror body, and is also the largest diameter (linear diameter, mm) of the optical glass lens measured so as to pass through the center of the glass surface of the optical glass lens (the position on the glass surface that passes through the center of a circle circumscribing the outer periphery of the edge of the glass surface and intersects with a straight line (center line) perpendicular to this circle).

[0018] The load (pressing pressure) applied to the glass material to be formed during the heating and pressing steps is not limited as long as it is possible to form the formed glass material into the above-described shape. For example, the load may be 1 to 1500 kgf / cm. 2 The pressure may be a pressure of 1000 psi or less. The magnitude of the load that can be applied depends on the size of the load generator disposed in the press mechanism and the diameter of the desired lens-shaped formed glass material (i.e., the desired optical glass lens). Therefore, one common approach in glass mold press molding technology is to provide a load generator that is necessary and sufficient for the diameter of the lens-shaped formed glass material and perform press molding. It is preferable that this load be applied during press molding, and not during the temperature rise below the glass transition point.

[0019] The method for producing an optical glass lens according to the present invention is characterized in that the effects of the present invention are fully exhibited even when the mold is designed to obtain a concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens (all of which are shown in FIG. 2, for example) as the final optical glass lens. In other words, the effects of the present invention are fully exhibited even when the optical glass lens to be produced is a large-diameter concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens, which are more difficult to form by press molding. The peripheral shape of the glass side surface (edge ​​of the glass surface) of these optical glass lenses may be circular (substantially circular). The same applies to the optical glass lenses described below.

[0020] The method for producing an optical glass lens according to the present invention is also characterized in that the effects of the present invention are fully exhibited even when the mold is designed to produce an optical glass lens having a center thickness greater than its edge thickness (for example, a convex meniscus lens or a biconvex lens) and a thickness deviation ratio (center thickness / edge thickness) of 1.1 or more and 7.0 or when the mold is designed to produce an optical glass lens having a center thickness greater than its edge thickness (for example, a concave meniscus lens or a biconcave lens) and a thickness deviation ratio (edge ​​thickness / center thickness) of 1.1 or more and 7.0 or less. In other words, the effects of the present invention are fully exhibited even when the optical glass lens produced using the method for producing an optical glass lens according to the present invention is a large-diameter optical glass lens having a center thickness greater than its edge thickness and a thickness deviation ratio of 1.1 or more and 7.0 or a large-diameter optical glass lens having an edge thickness greater than the center thickness and a thickness deviation ratio of 1.1 or more and 7.0 or when the edge thickness is greater than the center thickness and a thickness deviation ratio of 1.1 or more and 7.0 or when the edge thickness is greater than the center thickness and a thickness deviation ratio of 1.1 or more and 7.0 or less (for example, FIG. 3 ), which are more difficult to form by mold press molding. The smaller the thickness deviation ratio, the easier it is to press-mold an optical glass lens, and the easier it is to produce high-quality press-molded optical glass lenses in the method for manufacturing an optical glass lens according to the present invention. However, taking into consideration comparison with general-purpose manufacturing methods, the method for manufacturing an optical glass lens according to the present invention can be said to be particularly effective when the lower limit of the thickness deviation ratio is 2.0 or more, preferably 2.5 or more, or even 3.0 or more. Furthermore, the higher the thickness deviation ratio, the greater the difference in shrinkage between the center thickness and edge thickness of the press-molded optical glass lens, making the optical glass lens more susceptible to cracking. Therefore, the upper limit of the thickness deviation ratio is preferably 6.0 or less, more preferably 5.0 or less, even more preferably 4.5 or less, and even more preferably 4.0 or less. Here, the "center thickness" refers to the lens thickness at the center of the glass surface of the optical glass lens (reference numeral 21 in Figure 3), and the "edge thickness" refers to the lens thickness at the edge of the glass surface of the optical glass lens (reference numeral 23 in Figure 3).

[0021] Furthermore, the method for producing an optical glass lens according to the present invention is characterized in that the effects of the present invention are fully exhibited even when the mold is designed to produce an optical glass lens in which the final optical glass lens has at least one aspherical curved surface (that curved surface if only one surface is aspherical, or at least one of the curved surfaces if both surfaces are aspherical) with an open angle of 25 degrees or more and 75 degrees or less. In other words, the effects of the present invention are fully exhibited even when the optical glass lens produced using the method for producing an optical glass lens according to the present invention is a large-diameter optical glass lens in which at least one aspherical curved surface has an open angle of 25 degrees or more and 75 degrees or less, which also presents a higher degree of difficulty in molding by mold press molding. When this open angle is less than 25 degrees, the molding depth is shallow, and this is a range in which the difficulty of transferring the mold shape to the glass material to be molded is relatively low and molding is possible even without the method for producing an optical glass lens according to the present invention. However, the effects of the method for producing an optical glass lens according to the present invention are fully exhibited even when the lower limit of the open angle is, for example, 30 degrees or more. Furthermore, the larger this open angle, the deeper the molding depth, which increases the difficulty of transferring the mold shape to the glass material to be molded, and tends to make it difficult to achieve the full effect of the present invention. Therefore, the upper limit of the open angle is more preferably 70 degrees or less, even more preferably 60 degrees or less, even more preferably 55 degrees or less, and even more preferably 50 degrees or less. Here, the "open angle" refers to the smaller of the angles formed by the tangent line that touches the glass surface at the center of the glass surface of the optical glass lens and the tangent line that touches the glass surface at the edge of the glass surface of the optical glass lens, which is on the same plane as the center line (reference number 11 in Figure 3) that passes through the tangent line and the center of the glass surface (reference number 25 in Figure 3).

[0022] <First cooling process> Next, in the method for producing an optical glass lens according to the present invention, the formed glass material obtained in the above-mentioned heating and molding step (formed formed glass material in a high-temperature state) is subjected to a first cooling step in which the temperature is precisely controlled to a cooling rate of 0.1 to 5.0°C / min (a cooling rate of 0.1 to 5.0°C per minute) and a load of 1 to 1500 kgf / cm2 While applying a pressure of 1000 MPa, the formed glass compound is continuously cooled until the viscosity logη [dPa sec] of the formed glass compound becomes greater than 10 and less than 15 (press continuous cooling). This cooling and load application can be performed using the same mold and press mechanism as used in the heating and forming steps, but is not limited to this. Here, "continuously cooling" means that there is no state during this cooling that falls outside the range of the cooling gradient. The same applies hereinafter.

[0023] The method for producing an optical glass lens according to the present invention is characterized in that the formed glass material obtained in the heating and molding steps described above is cooled in at least two cooling steps, the first cooling step and the second cooling step described below, which have different cooling gradient conditions, based on the viscosity of the formed glass material to be cooled. The cooling gradient in the first cooling step is precisely controlled within a predetermined range, while the cooling gradient in the second cooling step described below is even greater. These features suppress mold release due to glass shrinkage during cooling and cracking caused by internal stress distribution, enabling the mass production of large-diameter optical glass lenses with high accuracy of aspherical curved surface shape. Furthermore, even when the cooling is performed using the mold as is, the mold releasability after cooling is maintained. The viscosity logη of the formed glass material during the transition from the first cooling step to the second cooling step described below is particularly important. A viscosity logη of 10 or less tends to reduce the accuracy of transfer of the designed mold shape, while a viscosity logη of 15 or more tends to increase the likelihood of surface cracking and defects due to sag differences described below.

[0024] The lower limit of the cooling gradient in this first cooling step is more preferably 0.5°C / min or more, even more preferably 1.0°C / min or more, even more preferably 1.5°C / min or more, and even more preferably 2.0°C / min or more. The upper limit of the cooling gradient in this first cooling step is more preferably 4.5°C / min or less, even more preferably 4.0°C / min or less, even more preferably 3.5°C / min or less, even more preferably 3.0°C / min or less, and even more preferably 2.5°C / min or less. Furthermore, from the viewpoint of improving the shape accuracy of the press when the forming depth is deep, the lower limit of the load is 5 kgf / cm. 2 More preferably, it is 10 kgf / cm or more. 2 More preferably, it is 20 kgf / cm or more. 2 The magnitude of the load that can be applied depends on the size of the load generating device disposed in the press mechanism and the diameter of the target lens-shaped formed glass material, but the upper limit of the load is 1000 kgf / cm. 2 More preferably, it is 800 kgf / cm or less. 2 More preferably, it is 500 kgf / cm or less. 2 More preferably, it is 200 kgf / cm or less. 2 More preferably, it is 150 kgf / cm or less. 2 It is more preferable that the viscosity logη [dPa·sec] of the formed glass compound is cooled until it is more than 11 and less than 14.8, even more preferably more than 12 and less than 14.6, and even more preferably 12.5 or more and 14.5 or less. The load applied to the formed glass compound in this first cooling step may be higher or lower than the load applied in the heating and forming steps described above, but from the viewpoint of improving quality, it is preferable that the load be the same (substantially the same) as or higher than the load applied in the heating and forming steps described above. Here, the "viscosity logη" of this formed glass compound is a value measured by the platinum sphere pulling method, but it is also possible to measure the viscosity logη at multiple temperatures by the above-mentioned method, such as by heating and cooling the glass material to be formed in advance, and then confirm the temperature range within which the viscosity logη falls using a viscosity curve created from these measurements, and then confirm the temperature range in this first cooling step. Alternatively, since the viscosity values ​​corresponding to the strain point, annealing point, and transition point of the formed glass compound are all within the above-mentioned ranges, confirmation may be made using any of these methods for compositions for which these are known in advance. Furthermore, "substantially the same" as the load applied in the heating and forming steps means that the difference from the load applied in the heating and forming steps is ±0.5 kgf / cm. 2 The annealing point is the temperature at which the internal strain of the glass is substantially removed in 15 minutes, and corresponds to the upper limit temperature in the annealing range. 13 This refers to the temperature equivalent to dPa·sec, and can be measured using the fiber elongation method with reference to JIS R 3103-2. Furthermore, the transition point is the temperature at which glass transitions from an amorphous solid to a supercooled liquid, and can be measured as the temperature corresponding to the intersection of the extensions of two straight lines before and after the slope of the curve changes significantly, as determined by JOGIS-08, obtained by heating glass at a constant rate of 4 K per minute.

[0025] <Second cooling process> In the method for producing an optical glass lens according to the present invention, the formed glass material having a predetermined viscosity logη after being cooled in the first cooling step is cooled in the second cooling step from a temperature below the temperature of the formed glass material at the end of the first cooling step, preferably below that temperature and where the viscosity logη of the formed glass material falls within the aforementioned range (a temperature within this range), to a temperature below the glass transition point of the formed glass material, or even below 300°C, or even below 250°C, at a cooling rate greater than that of the first cooling step, preferably greater than 5.0°C / min (a cooling rate of more than 5.0°C per minute). In other words, the formed glass material is cooled at a cooling rate greater than that of the first cooling step (i.e., a higher cooling rate) to obtain a predetermined cooled optical glass lens. From the viewpoint of simplifying and shortening the production process, the end temperature of the second cooling step is preferably 100°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher. It is more preferable that the second cooling step is also a continuous cooling step similar to the first cooling step described above. This cooling step may also be performed using the above-mentioned mold and press mechanism, but is not limited to this.

[0026] Unlike the first cooling step described above, the second cooling step does not require the application of a load to the formed glass compound during cooling. From the standpoint of shape accuracy, etc., in the method for producing an optical glass lens according to the present invention, it is more preferable to perform the predetermined cooling without applying a load to the formed glass compound in the second cooling step. However, in the second cooling step, a load may also be applied to the formed glass compound under the same conditions as in the first cooling step described above.

[0027] <Other processes, etc.> The method for producing an optical glass lens according to the present invention may further include any other steps than those described above, provided that they do not significantly affect the effects of the present invention. For example, after the second cooling step, the method may include a third cooling step in which the formed glass compound is cooled from a temperature below the glass transition point of the formed glass compound (e.g., 100 to 300°C) to a temperature below 50°C, or even to room temperature of 35°C or below (a temperature at which the formed glass can be manually recovered), or a temperature holding step (e.g., room temperature holding step), or may further include a processing step in which the cooled formed glass compound is partially processed (a processing step in which partial processing is performed without substantially changing the glass surface shape, etc.).

[0028] By using the method for manufacturing an optical glass lens according to the present invention as described above, it is possible to obtain optical glass lenses with high shape accuracy (high transfer accuracy of the design mold shape and little surface cracking) and large diameters using mold press molding, without subjecting the glass material to any special pretreatment (such as prior surface treatment such as grinding or polishing). Furthermore, mass production with a high rate of non-defective molding is possible without significantly extending the manufacturing time.

[0029] Next, the optical glass lens according to the present invention will be described in detail with reference to the drawings.

[0030] The optical glass lens according to the present invention is an optical glass usable as a lens for an optical element, having at least one surface that is an aspherical curved surface and has a diameter of φ30 to φ150, and measuring surface shape variation by scanning the same length on this curved surface in two directions that pass through the center of the curved surface and are orthogonal (two orthogonal directions in terms of orientation), and when the maximum sag difference when the measured values ​​in the two directions are superimposed is Y (μm) and the diameter of the optical glass lens is X (mm), these satisfy the relationship shown in formula (1) below. In other words, the optical glass lens according to the present invention is a large-diameter optical glass lens that has an aspherical curved surface and exhibits high shape precision of the aspherical curved surface. This optical glass lens according to the present invention can be manufactured by the method for manufacturing an optical glass lens according to the present invention described above. (1) Y≦0.01X-0.1

[0031] Here, "aspherical surface" and "aperture" have the same meanings as above. The aperture may be φ40 or more, as above, and is preferably φ100 or less, more preferably φ80 or less, more preferably φ70 or less, and more preferably φ65 or less. The "center of the curved surface" is the center of the glass surface of the curved surface. Furthermore, the "sag difference (μm)" is the difference (difference in variation) between the two measurements of the surface shape variation in the above-mentioned two directions when they are superimposed (when the same measurement length range is superimposed on a graph with the center of the curved surface as the reference).

[0032] The method for manufacturing an optical glass lens according to the present invention described above can also produce an optical glass lens in which X and Y satisfy the relation Y≦0.01X−0.11, or even Y≦0.01X−0.12, or even Y≦0.01X−0.14. In other words, the optical glass lens according to the present invention can be one in which the above formula (1) satisfies Y≦0.01X−0.11, or even Y≦0.01X−0.12, or even Y≦0.01X−0.14.

[0033] This measurement of surface shape variation by scanning can be performed using an ultra-high-precision CMM (such as the Panasonic UA3P). Specifically, the ultra-high-precision CMM (for example, as in the example of Figure 4, using a micro air slider 73 equipped with an ultra-high-precision CMM stylus 71) is used to scan the same length of the aspherical curved surface in each of the above two directions to measure the surface shape variation (in the example of Figure 4, surface shape variation measurement portions 13 and 15 in the P direction and the Q direction, which is perpendicular to P direction), and the shape error is graphed in each case from the lens design value (design R). These graphs are then overlaid to confirm the sag difference.

[0034] And, like the optical glass lenses produced by the optical glass lens production method according to the present invention described above, the effects of the present invention can be fully exhibited whether the optical glass lens according to the present invention is a concave meniscus lens, a convex meniscus lens, a biconcave lens or a biconvex lens.

[0035] Furthermore, similar to the optical glass lenses manufactured by the method for manufacturing an optical glass lens according to the present invention described above, the effects of the present invention can be fully achieved even if the optical glass lens according to the present invention is an optical glass lens in which the center thickness is greater than the edge thickness and the thickness deviation ratio (center thickness / edge thickness) is 1.1 or greater and 7.0 or less, or an optical glass lens in which the edge thickness is greater than the center thickness and the thickness deviation ratio (edge ​​thickness / center thickness) is 1.1 or greater and 7.0 or less. Note that the thickness deviation ratio may be the same as the lower limit or upper limit described above.

[0036] Furthermore, the optical glass lens of the present invention can fully exhibit the effects of the present invention even if the mold used for the optical glass lens is one in which the open angle of at least one of the curved surfaces is between 25 and 75 degrees, just like the optical glass lens produced by the method for producing an optical glass lens of the present invention described above. Note that the open angle may also be the lower or upper limit as described above.

[0037] Furthermore, the optical glass lens according to the present invention, like the optical glass lens manufactured by the method for manufacturing an optical glass lens according to the present invention described above, can also be an optical glass lens made of fluorophosphate glass, lanthanum borate glass, or silica gel barium glass, and still exhibit the effects of the present invention to a sufficient extent.

[0038] The optical glass lenses according to the present invention are characterized in that they are effective for large diameter lenses with a wide range of refractive indexes or dispersions, and therefore the method for manufacturing an optical glass lens according to the present invention described above can also be applied to the manufacture of large diameter optical glass lenses with a wide range of refractive indexes or dispersions. The specific refractive index (n d The upper limit of the refractive index (n d The lower limit of the Abbe number (ν ) may be 1.35 or more, 1.40 or more, or 1.49 or more. d The upper limit of the Abbe number (ν ) may be 95 or less, 90 or less, 85 or less, or 82 or less. d The lower limit of ) may be 20 or more, 25 or more, 30 or more, or 35 or more.

[0039] The optical glass lens according to the present invention as described above has high shape precision even though it is an optical glass lens having at least one aspherical curved surface and a large diameter, and the same applies to optical glass lenses having both aspherical curved surfaces and a large diameter.

[0040] The embodiment described above is merely an example for facilitating understanding of the present invention, and is not intended to limit the present invention. In other words, the steps described above may be changed or improved without departing from the spirit of the present invention, and the present invention naturally includes equivalents thereof.

[0041] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples, and various modifications are possible within the technical concept of the present invention. [Example]

[0042] Optical glass lenses (concave meniscus lenses, convex meniscus lenses, biconcave lenses, or biconvex lenses) were manufactured from the glass materials to be molded by the following method.

[0043] The glass materials to be molded were prepared by blending the required amounts of materials containing Si, B, P, Ca, Ba, La, Al, and F for each glass type, melting and vitrifying them. The manufacturing methods for each example and comparative example shown in Table 1 below are explained below. As shown in Table 1 below, Example 1 and Comparative Examples 1-2 had the same composition as Ohara Inc.'s optical glass product S-FPL51 for lenses; Examples 2-3 and 7 and Comparative Examples 3-6 had the same composition as Ohara Inc.'s optical glass product L-LAH84 for lenses; Examples 4, 10-13 and Comparative Examples 8-9 had the same composition as Ohara Inc.'s optical glass product L-LAL13 for lenses; and Examples 5-6, 8-9 and Comparative Example 7 had the same composition as Ohara Inc.'s optical glass product L-BAL42 for lenses.

[0044] As shown in Table 1 below, in the examples, first, in the heating and forming process, a predetermined press mechanism and mold are used to continuously heat the glass material to be formed and the mold at a temperature control rate (1 to 60°C / min) appropriate for the glass type, from the strain point to the softening point of the glass material to be formed. 2The optical glass lenses were manufactured by the following steps: a heating and molding step in which the formed glass compound is press-molded (isothermal molding) under a pressure of 1000 kJ / min to obtain a glass compound having a predetermined lens shape with aspherical curved surfaces on both sides and with a lens diameter, thickness deviation ratio, and open angle as shown in Table 1 below; a first cooling step in which the glass compound is continuously cooled while controlling the temperature to obtain the cooling gradient (first cooling rate) shown in Table 1 below and applying the load shown in Table 1 below, until the viscosity logη of the glass compound reaches the value shown in Table 1 below (the viscosity at the end of pressing logη, i.e., the viscosity at the end of the first cooling step logη); a second cooling step in which the glass compound cooled in the first cooling step is cooled from the temperature of the glass compound at the end of the first cooling step to 200 to 250°C depending on the conditions and the thermal properties of the glass compound, without applying a load, and controlling the temperature to obtain a cooling gradient of more than 5.0°C / min; and a third cooling step in which the glass compound is cooled from the temperature at the end of the second cooling step to room temperature.

[0045] On the other hand, in the comparative examples, an optical glass lens was manufactured by the following steps: first, in a heating and molding step, the glass material to be molded and the mold were both heated and press-molded in the same manner as in the examples using a predetermined press mechanism and mold to obtain a glass molding compound of a predetermined lens shape with aspherical curved surfaces on both sides and with the lens diameter, thickness deviation ratio, and open angle shown in Table 1 below; then, in a first cooling step, the glass molding compound was continuously cooled at a temperature controlled to obtain a higher cooling gradient (first cooling rate) than in the examples shown in Table 1 below and while applying a load shown in Table 1 below until the viscosity logη of the glass molding compound reached the value shown in Table 1 below (pressure termination viscosity logη); then, in a second cooling step, the glass molding compound cooled in the first cooling step was cooled from the temperature of the glass molding compound at the end of the first cooling step to 200 to 250°C depending on the conditions and the thermal properties of the glass molding compound, without applying a load, while controlling the temperature to obtain a cooling gradient of more than 10.0°C / min; and then, in a third cooling step, the glass molding compound was cooled from the temperature of the glass molding compound at the end of the second cooling step to room temperature.

[0046] Then, using a Panasonic UA3P, the same length of each curved surface was scanned on both curved surfaces (concave or convex) of these optical glass lenses in two orthogonal directions passing through the center of each curved surface, as shown in FIG. 4, to measure the surface shape variation. The shape error was then graphed, and the measured values ​​(graphs) in the two directions were then superimposed. Examples of the results are shown in FIG. 5 (the concave curved surface of the concave meniscus lens of Example 1) and FIG. 6 (the concave curved surface of the concave meniscus lens of Comparative Example 1). The quality (appearance, sag difference) evaluation results and the maximum sag difference Y (μm) for each Example and Comparative Example are also shown in Table 1 below. Regarding the quality of appearance of each Example and Comparative Example, those without any visual defects were rated as ◯, and those with visual cracks in the glass were rated as cracks. Regarding the quality of sag difference, those with a relatively small sag difference value overall were rated as ◯, and those with a relatively large sag difference value overall or containing clearly discontinuous points as surface shape variation were rated as ×.

[0047] As a result, the optical glass lenses of the Examples satisfied the relationship of formula (1) Y≦0.01X−0.1, where Y (μm) is the maximum sag difference and X (mm) is the aperture, and were of good quality, including in terms of appearance. On the other hand, the optical glass lenses of the Comparative Examples did not satisfy the relationship of formula (1) Y≦0.01X−0.1, where Y (μm) is the maximum sag difference and X (mm) is the aperture. In particular, the optical glass lenses of Comparative Examples 8 and 9 had noticeable cracks, making it impossible to measure the variation in surface shape. FIG. 7 shows a graph showing the relationship between the maximum sag difference Y (μm) and the aperture X (mm) for each Example and Comparative Example (excluding Comparative Examples 8 and 9). Furthermore, when a large number of optical glass lenses of Example 1 were manufactured, the yield rate of acceptable molding was approximately 100%, whereas when a large number of optical glass lenses of Comparative Example 1 were manufactured, the yield rate of acceptable molding was approximately 50%. Therefore, it was confirmed that the optical glass lenses of the examples have improved shape precision of the lens surface by the above manufacturing method, and that mass production is also possible. The refractive index (n d ) is 1.50, and the Abbe number (ν d) is 81.5, and the refractive index (n d ) is 1.81, and the Abbe number (ν d ) is 40.1, and the refractive index (n d ) is 1.70, and the Abbe number (ν d ) is 53.2, and the refractive index (n d ) is 1.58, and the Abbe number (ν d ) was 59.4.

[0048] [Table 1] [Explanation of symbols]

[0049] 100 optical glass lenses 11 Center of optical glass lens (center line) 13 Measurement of surface shape variation in the P direction of the curved surface of an optical glass lens 15 Measurement of surface shape variation in the Q direction of the curved surface of an optical glass lens 21 Center thickness 23 Edge Thickness 25 opening angle 51 Mold 51-1 Upper Core 51-3 Lower Core 53 Press mechanism 53-1 Heat source plate (heating or cooling plate) 53-3 cylinder 55 Glass material to be formed or glass forming material 71 Stylus 73 Micro Slider

Claims

1. A method for manufacturing an optical glass lens having at least one aspherical curved surface and an aperture of φ30 to φ150, comprising the steps of: a heating and molding step of heating a raw glass material to be molded and press-molding it in a mold to obtain a lens-shaped glass material having at least one aspherical curved surface and a diameter of φ30 to φ150; The formed glass material is subjected to temperature control so as to have a cooling gradient of 0.1 to 5.0°C / min and a load of 1 to 1500 kgf / cm. 2 a first cooling step of continuously cooling the formed glass material while applying a pressure of 1000 kJ / s to the formed glass material until the viscosity of the formed glass material becomes log η [dPa sec] of more than 10 and less than 15; a second cooling step of cooling the formed glass material cooled in the first cooling step from a temperature equal to or lower than the temperature of the formed glass material at the end of the first cooling step, by controlling the temperature so that the cooling gradient is greater than the cooling gradient of the first cooling step. A method for manufacturing optical glass lenses.

2. 2. The method for producing an optical glass lens according to claim 1, wherein the optical glass lens is a concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens.

3. 3. The method for manufacturing an optical glass lens according to claim 1, wherein the optical glass lens has a center thickness greater than its edge thickness and a thickness deviation ratio (center thickness / edge thickness) of 1.1 or more and 7 or less.

4. 3. The method for manufacturing an optical glass lens according to claim 1, wherein the optical glass lens has an edge thickness greater than its center thickness and a thickness deviation ratio (edge ​​thickness / center thickness) of 1.1 or more and 7 or less.

5. 3. The method for manufacturing an optical glass lens according to claim 1, wherein the open angle of at least one of the curved surfaces of the optical glass lens is between 25 degrees and 75 degrees.

6. 3. The method for manufacturing an optical glass lens according to claim 1, wherein the optical glass lens is an optical glass lens made of fluorophosphate glass, lanthanum borate glass, or silica gel boride glass.

7. 3. The method for producing an optical glass lens according to claim 1 or 2, wherein the heating and molding step is a step of continuously raising the temperatures of both the glass material to be molded and the mold, controlling the temperatures so that the temperature rise gradient is 0.1 to 100°C / min within the temperature range from the strain point to the softening point of the glass material to be molded, and then press-molding the glass material using the mold.

8. An optical glass lens having at least one surface that is an aspherical curved surface and an aperture diameter of φ30 or more and φ150 or less, The same length on the curved surface is scanned in two directions passing through the center of the curved surface and perpendicular to each other to measure the variation in surface shape, and when the measured values ​​in the two directions are superimposed, the maximum value of the sag difference is Y (μm) and the diameter is X (mm), the relational expression of the following formula (1) is satisfied: Optical glass lens. (1) Y≦0.01X-0.1

9. 9. The optical glass lens of claim 8, which is a concave meniscus lens, a convex meniscus lens, a biconcave lens, or a biconvex lens.

10. 10. An optical glass lens as defined in claim 8, wherein the center thickness is greater than the edge thickness and the thickness deviation ratio (center thickness / edge thickness) is 1.1 or more and 7.0 or less.

11. 10. An optical glass lens as defined in claim 8, wherein the edge thickness is greater than the center thickness and the thickness deviation ratio (edge ​​thickness / center thickness) is 1.1 or greater and 7.0 or less.

12. 10. An optical glass lens according to claim 8, wherein the open angle of at least one of said curved surfaces is between 25 degrees and 75 degrees.

13. 10. The optical glass lens according to claim 8, which is an optical glass lens made of fluorophosphate glass, lanthanum borate glass, or silica gel barium glass.

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