Method for manufacturing optical element and optical element

Abstract

To provide a method for manufacturing an optical element that is more excellent in reduction in material loss and molding of a mold.SOLUTION: A method for manufacturing an optical element includes the steps of: forming a mirror-finished material 25 from a columnar material 20 by performing mirror-finishing of heating and finishing the whole surface as a mirror surface of the columnar material; and then the mirror-finished material being subjected to mold press molding.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing an optical element and the optical element. More specifically, the present disclosure relates to a method for manufacturing an optical element that is at least conducive to light transmission, as well as the optical element obtained thereby. [Background technology]

[0002] 2. Description of the Related Art Optical elements made of resin materials, glass materials, etc. have been used for various purposes, for example, as lenses, prisms, mirrors, optical fibers, etc.

[0003] In recent years, optical elements have also been used in the field of optical sensing, such as optical sensors for monitoring systems for disaster prevention and / or crime prevention, or in-vehicle sensor modules for driving assistance systems. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-14455 A [Patent Document 2] International Publication No. 2020 / 071071 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application realized that there were problems to be overcome in the conventional manufacturing of optical elements, and found it necessary to take measures to address these problems. Specifically, they found the following problems:

[0006] Optical elements are manufactured through molding or by machining methods such as cutting, grinding and / or polishing. When manufacturing optical elements by grinding and / or polishing, a lot of material is wasted because the final shape of the optical element is obtained by cutting it out from the raw material (Figure 13).

[0007] Mold press molding is sometimes used to mold optical elements. In this manufacturing method, pressing force is applied to a material using a mold, so it is difficult to actively use materials made of brittle materials.

[0008] The present disclosure has been made in view of the above problems. That is, a main object of the present disclosure is to provide a method for manufacturing an optical element which is more suitable in terms of reducing material loss and molding. [Means for solving the problem]

[0009] The inventors of the present application attempted to solve the above problems by taking a new approach, rather than simply extending the conventional technology, and as a result arrived at a method for manufacturing an optical element that achieves the above-mentioned main object.

[0010] The present disclosure provides a method for manufacturing an optical element, which comprises performing a mirror finishing process in which the entire surface of a columnar material is mirror-finished by heating the columnar material to form a mirror-finished material, and then subjecting the mirror-finished material to mold press molding.

[0011] The present disclosure also provides an optical element obtained by the above manufacturing method. The optical element of the present disclosure includes a light-transmitting portion and a flange portion extending outward from the light-transmitting portion, and the light-transmitting portion has a peripheral region and an inner region that is located more inward than the peripheral region, and the internal strain of the peripheral region is different from that of the inner region. Effect of the Invention

[0012] The manufacturing method of the present disclosure can provide optical elements that are more suitable in terms of reducing material loss and molding.

[0013] Regarding the reduction of material loss, the method disclosed herein can manufacture optical elements under conditions that reduce the material loss of the material. Since the material used in mold press molding has a columnar shape, it is not necessary to obtain a shape relatively close to the shape of the optical element by grinding or the like prior to the molding. For example, when manufacturing an optical element such as a lens, it is not necessary to obtain a spherical shape or a lens-like shape such as a flattened spherical shape by grinding or the like in advance, and the material loss of the optical element can be reduced.

[0014] In terms of mold forming, the method of the present disclosure can form an optical element without applying excessive pressure to the material. In this regard, in the present disclosure, a mirror surface treatment is performed by heating prior to mold press forming. The mirror surface treatment itself can contribute to the transmittance of the optical element, but in the present disclosure, the mirror surface treatment is performed by heating the entire surface of the columnar material. This mirror surface treatment by heating can make the overall shape of the columnar material closer to the final shape of the optical element compared to the original columnar material, so that it is possible to reduce the excessive pressure applied to the material during mold press forming. Therefore, even if the material is made of a brittle material, it can be used more actively in mold press forming. [Brief description of the drawings]

[0015] [Figure 1] Cross-sectional diagrams showing lenses as optical elements (Fig. 1(A): biconvex lens, Fig. 1(B): biconcave lens, Fig. 1(C): meniscus lens) [Diagram 2] Schematic cross-sectional view for explaining a part of the manufacturing method of the present disclosure. [Diagram 3] A cross-sectional view showing a schematic example of the configuration of a die used in mold press molding. [Figure 4] 1 is a process cross-sectional view illustrating a mold press molding method according to the present disclosure; [Diagram 5] FIG. 1 is a cross-sectional view showing a schematic example of a configuration of a non-sleeve type die used in mold press molding. [Figure 6] FIG. 1 is a cross-sectional view showing a schematic example of mold press molding in the manufacturing method of the present disclosure (using a non-sleeve type mold); [Figure 7] Schematic cross-sectional view for explaining "aspects of mirror finishing treatment using a mold" [Figure 8] Schematic cross-sectional view for explaining "aspects of continuous processing using a mold" [Figure 9] Cross-sectional diagrams showing lenses as optical elements (Fig. 9(A): biconvex lens, Fig. 9(B): biconcave lens, Fig. 9(C): meniscus lens) [Figure 10] 1A and 1B are perspective and plan views illustrating an example embodiment of an optical element according to the present disclosure; [Figure 11] FIG. 1 is a schematic diagram showing an example of internal distortion characteristics in a light-transmitting portion of an optical element according to the present disclosure. [Figure 12] FIG. 1 is a cross-sectional view showing a schematic diagram of a method for mold pressing a meniscus lens according to the present disclosure. [Figure 13] Schematic diagram for explaining an example embodiment of manufacturing a lens by cutting out a raw material by grinding and polishing (prior art) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, a method for manufacturing an optical element according to an embodiment and an optical element obtained by the manufacturing method will be described in more detail. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the explanation and to facilitate understanding by those skilled in the art.

[0017] The applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and does not intend to limit the subject matter described in the claims. Note that the various elements in the drawings are merely shown as schematic and illustrative examples for understanding the manufacturing method and optical element of the present disclosure, and the appearance and dimensional ratios may differ from the actual ones.

[0018] The terms "upward" and "downward" used directly or indirectly in this specification correspond to the upward and downward directions in the drawings, respectively. In a preferred embodiment, the vertical downward direction (i.e., the direction in which gravity acts) corresponds to the "downward direction", and the opposite direction corresponds to the "upward direction".

[0019] In this specification, the term "cross-sectional view" is based on a virtual cross-section obtained by cutting the optical element along the thickness direction. In other words, a sketch of a cross-section cut along the thickness of the optical element corresponds to a "cross-sectional view". Typically, the "thickness direction of the optical element" may correspond to the light transmission direction in the optical element. In addition, the term "plan view" used in this specification is based on a sketch of an object viewed from above or below along the thickness direction.

[0020] Various numerical values ​​and ranges mentioned in this specification are intended to include the lower or upper limit numerical value itself, unless a special term such as "less than" or "more than / greater than" is added. In other words, for example, a numerical range such as 1 to 10 can be interpreted as including the lower limit of "1" and the upper limit of "10".

[0021] [Manufacturing method of the present disclosure] The present disclosure relates to a method for manufacturing an optical element, and in particular, to a method for manufacturing an optical element from a material by mold press molding. Mold press molding is a method for pressing a material using a die to form it, and the present disclosure is characterized in matters related to the molding method.

[0022] Specifically, a mirror-finished material is formed from the columnar material by a mirror-finishing process in which the entire surface of the columnar material is heated to give it a mirror finish, and the material obtained by the mirror-finishing process by heating, i.e., the mirror-finished material, is subjected to mold press molding.

[0023] In this specification, the term "optical element" broadly means a member for transmitting light. Thus, the optical element may be, for example, a lens, a prism, or a mirror. Furthermore, the optical element may be a window product related to light transmission. In the narrow sense, the term "optical element" means a member for converging or diverging light, such as a lens (see FIG. 1). When the optical element 10 is a lens, the "light transmitting portion" of the optical element 10 corresponds to the lens portion (at least the portion of the "R surface" including the optically effective surface).

[0024] In the manufacturing method of the present disclosure, the material used in mold press molding is a mirror-finished material obtained from a columnar material by heating the entire surface of the columnar material. In other words, the material used in mold press molding is a material whose entire surface has been mirror-finished by heating.

[0025] Fig. 2 is a schematic diagram showing an exemplary embodiment of the mirror finish treatment in the present disclosure. As shown in Fig. 2, the material to be subjected to mold press molding is a columnar material 20, and the entire surface of the material is heated to obtain a mirror finish material 25. Next, the mirror finish material 25 is subjected to mold press molding using an appropriate mold.

[0026] The columnar material 20, as its name suggests, is a material having a columnar shape as a whole. In other words, the material to be mirror-finished by heating is a material having a three-dimensional shape in which the cross-sectional shape in a predetermined direction (for example, the cross-sectional shape cut along a direction perpendicular to the thickness direction of the optical element) is substantially constant. Such columnar material 20 may have an overall shape such as a triangular prism, a square prism, a hexagonal prism, or a cylinder.

[0027] The columnar material 20 is preferably a single item. Such a material can be obtained from an ingot. When the columnar material is obtained from an ingot, the material loss is small. In other words, the material 20 used in the manufacturing method of the present disclosure does not need to be ground to obtain a shape relatively close to the final optical element shape, and the material loss is small. For example, when performing mold press molding, it is not necessary to obtain a material having a spherical shape or a lens-like shape such as a flattened spherical shape in advance, and the material loss is accordingly small.

[0028] The columnar material may be polygonal or cylindrical. That is, the material to be subjected to the mirror finish by heating may be a prismatic material or a cylindrical material. The prismatic material has a relatively simple shape and can be easily obtained from an ingot. In addition, the prismatic material is less likely to have an enclosed space between the die surface and the material during molding. Therefore, compared with materials with large R surfaces, the prismatic material is less likely to have so-called "air pockets" during molding. The prismatic material may have a quadrangular or approximately quadrangular shape in plan view. In this specification, a quadrangular shape means a shape such as a square or a rectangle. On the other hand, the cylindrical material may have a circular or approximately circular shape in plan view.

[0029] The columnar material may contain, for example, a glass material. That is, a mirror-finished material may be obtained from a material containing a glass material, and the mirror-finished material may be subjected to mold press molding. Glass materials generally have a large linear expansion coefficient, and the amount of expansion during heating and the amount of contraction during cooling during mold press molding are large, making them difficult to mold. In the manufacturing method of the present disclosure, as described below, the "mirror-finishing process by heating" prevents excessive pressure from being applied to the material, and materials containing glass materials can be more actively used.

[0030] In the manufacturing method of the present disclosure, the heating performed as the mirror finishing process is performed by heating the columnar material from the outside as a whole. In other words, the columnar material is heated as a whole, not as a local heating in which only a part of the surface area of ​​the columnar material is heated. Such heating for the mirror finishing process causes the columnar material to undergo a global plastic deformation, and can bring the overall shape of the material closer to the shape of the optical element compared to the original columnar material, thereby reducing the pressing force applied to the material during mold press molding. Therefore, even if the material is made of a brittle material, it can be used more actively in mold press molding.

[0031] Heating for mirror finishing may be performed from the entire periphery of the columnar material. In other words, the columnar material may be heated from all of the upper, lower, and side directions of the columnar material. This allows the surface of the columnar material to be heated overall, not locally, so that the entire material to be molded by press molding can more easily approximate the shape of the optical element. The "side direction" referred to here corresponds to the direction perpendicular to the material axis along the upper direction of the columnar material and the opposite downward direction.

[0032] In the mirror finishing process, it is preferable to soften the entire surface of the columnar material by heating to make the columnar material mirror-finished. This is because it is easier to make the overall shape of the material closer to the shape of the optical element, and the effect of the present disclosure is more easily manifested. The heating time for such mirror finishing may be relatively short. In other words, it is not necessary to soften the columnar material to the center, and at least the surface portion may be softened, so the heating time may be short. Specifically, in the case of a columnar material containing chalcogenide glass (IRG203 manufactured by Xinhuaguang), the heating time for the mirror finishing process may be within 800 seconds, within 700 seconds, or within 650 seconds at a temperature higher than the glass transition temperature (Tg). For example, the columnar material may be heated for 400 to 800 seconds, 500 to 700 seconds, or 550 to 650 seconds in the mirror finishing process.

[0033] In the manufacturing method of the present disclosure, the mirror-finished material obtained by heat-treating the entire surface of the columnar material preferably has a smooth or glossy surface. In other words, the mirror-finished material can preferably have a smooth or glossy surface as its mirror surface.

[0034] The mirror-finished material has a low surface roughness because of its mirror surface. For example, the mirror-finished material may have a surface roughness of Ra50 nm or less, preferably Ra20 nm or less, by the mirror-finished treatment. In other words, the "mirror surface" of the "mirror-finished treatment" / "mirror-finished material" in this disclosure essentially refers to a mirror surface having a surface roughness of Ra50 nm or less, preferably Ra20 nm or less. There is no particular limit to the lower limit of the surface roughness Ra, and it may be, for example, Ra0 nm (excluding 0). In this disclosure, "Ra" is the so-called arithmetic mean roughness, and its value is measured using a scanning white light interferometer (Zygo NewView) for at least one surface constituting the outer surface of the mirror-finished material.

[0035] In the mirror surface treatment by heating, the columnar material may be heated to a temperature higher than its glass transition temperature Tg. That is, the entire surface of the columnar material may be heated under heating conditions higher than the glass transition temperature Tg of the material of the columnar material. For example, as the mirror surface treatment, the columnar material is heated and softened under heating conditions 50 to 200°C higher than the glass transition temperature Tg of the columnar material, more preferably 100 to 190°C higher. Such heating conditions tend to soften the entire surface of the columnar material more effectively, and the effects of the present disclosure tend to be more evident. For example, when the heating temperature is lower than the lower limit of the above temperature range, it is difficult to obtain a sufficient mirror surface, and mirror surface defects of the material are likely to occur, while when the heating temperature is higher than the upper limit of the above temperature range, phenomena such as material cracking are likely to occur during mold press molding. Here, the "glass transition temperature Tg" in the present disclosure is a value obtained from a thermal expansion curve showing the relationship between temperature and sample elongation. As examples of the material of the columnar material, the glass transition temperature Tg of chalcogenide (IRG203 manufactured by Xinhuaguang Co., Ltd.) is, for example, about 266°C, and the glass transition temperature Tg of chalcohalide is, for example, about 375°C.

[0036] In the manufacturing method of the present disclosure, the mirror-finished material obtained by heat-treating the entire surface is subjected to mold press molding. As a result, an optical element is formed from the mirror-finished material through pressure deformation. In other words, the light-transmitting portion and the flange portion of the optical element can be integrally formed from a single mirror-finished material by mold press molding.

[0037] FIG. 3 shows a mold used in mold press molding. As shown in the figure, the mold 50 used in the manufacturing method of the present disclosure is composed of, for example, a pair of upper and lower dies 51 and 52, which are the main parts of the mold, and a mold sleeve 53. The upper and lower dies 51 and 52 can be driven to move relatively close to each other or apart from each other, and a mold cavity 56 is formed between them. The mirrored material is pressed and deformed between the pair of upper and lower dies 51 and 52, thereby forming at least the light transmitting part of the optical element. When the optical element is a lens, the mirrored material is deformed by the pressing force received from the upper and lower dies 51 and 52, and the shape of the lens part, which is the "main part" of the optical element, is obtained. On the other hand, the mold sleeve 53 has a "cylindrical shape" as can be seen from its name, and is provided on the outer circumferential surface of the main part of the mold. The mold sleeve 53 is a mold member that contributes to the formation of the mold cavity together with the upper die side 51 and the lower die 52, and preferably acts to bound the outer edge of the mold cavity.

[0038] As can be seen from this explanation, the term "main mold part" in this specification means a main mold part that contributes to the formation of most of the mold cavity. On the other hand, the term "mold sleeve" in this specification means a mold part that performs a secondary function and is provided on the outer circumferential surface of the main mold part so as to constitute at least a part of the body part of the mold. When the mold cavity is formed by the space surrounded by the upper mold part, the lower mold part, and the mold sleeve of the main mold part, the mold sleeve is a cylindrical mold part that bounds the outer edge of the mold cavity.

[0039] For example, the mold cavity has a circular or substantially circular shape in plan view. That is, the inner peripheral surface of the mold sleeve that bounds the outer edge of the mold cavity may have a circular or substantially circular shape in plan view. Specifically, for example, the outer peripheral surface of the mold main part may have a cylindrical outer surface, to which a cylindrical mold sleeve is provided, resulting in a mold cavity that is circular or substantially circular in plan view.

[0040] The mold press molding using such a mold may be performed under temperature conditions specific to the mirror-finished material. For example, the mold press molding may be performed under temperature conditions lower than the heating temperature of the mirror-finished treatment. This is because the pressure deformation of the mirror-finished material becomes more suitable, and it becomes easier to obtain an optical element in which the light-transmitting portion and the flange portion are more suitably molded integrally. For example, the mold press molding may be performed under temperature conditions that are preferably 20°C to 130°C lower than the heating temperature conditions of the mirror-finished treatment, for example, 40°C to 90°C lower. From another perspective, the heating of the mirror-finished treatment may be performed under temperature conditions that are preferably 20°C to 130°C higher than the heating conditions during the mold press molding, for example, 40°C to 90°C higher. Such heating of the mirror-finished treatment makes it easier to suitably soften the surface of the columnar material as a whole, and the effects of the present disclosure are more likely to be manifested.

[0041] In terms of the relationship with the glass transition temperature of the columnar material, the mold press molding may be performed at a temperature higher than the glass transition temperature of the columnar material. For example, the mold press molding may be performed under a temperature condition that is preferably 40°C to 150°C higher than the glass transition temperature of the columnar material, for example, 60°C to 100°C higher. This is because the mirror-finished material obtained by the mirror-finishing treatment based on heating can be plastically deformed more suitably.

[0042] In the manufacturing method of the present disclosure, mold press molding may be performed under an inert atmosphere. For example, a nitrogen atmosphere may be used as the atmospheric condition for mold press molding. For example, the nitrogen atmosphere may have an oxygen concentration of 10 ppm or less.

[0043] Next, mold press molding will be described over time with reference to Fig. 4. In mold press molding shown in Fig. 4, the end face of the flange portion of the optical element molded in the mold cavity formed between the upper mold and the lower mold is subjected to mold transfer.

[0044] First, as shown in Fig. 4(A), a state is obtained in which the mirror-finished material 25 is put into a mold 50. That is, as shown in the figure, for example, the mirror-finished material 25 is put into a mold cavity 56 surrounded by an upper mold 51, a lower mold 52, and a mold sleeve 53.

[0045] The mirrored material 25 may be a single piece of material. The mirrored material 25 preferably has a mirror surface on its outer surface that is obtained without using mechanical tools such as grinding or polishing and / or liquid treatment (particularly a process in which a mirror surface is obtained by contacting a material with a chemical liquid, for example, a chemical treatment using a chemical polishing liquid with an adjusted pH, such as an acidic range). In relation to such a mirror surface, the overall shape of the mirrored material 25 may have a shape that is closer to the final shape of the optical element than the original columnar material.

[0046] The mirror-finished material 25 put into the die 50 is subjected to deformation by the pressing force from the heated die 50 in the mold press molding. That is, the mirror-finished material 25 is heated by the heat of the die 50 and deformed by the pressing force from the die 50 as shown in Fig. 4(B) and Fig. 4(C) to be formed into a desired shape. More specifically, the single mirror-finished material 25 is plastically deformed by the pressing force from the die 50, and the inner surface shape of the die 50 (particularly the upper die 51 and the lower die 52) is transferred to the mirror-finished material 25, so that the light-transmitting portion and the flange portion are integrally obtained from the material 25. Note that when the columnar material corresponds to a prismatic material and a biconvex lens is formed from the mirror-finished material obtained by heating the entire surface of the material, the mirror-finished material 25 in the die is likely to have the advantage that it is less likely to cause an undesirable "air pocket" on its upper or lower surface.

[0047] The mirror-finished material 25 undergoes plastic deformation during mold pressing, deforming so as to spread outward, and then comes into contact with the mold sleeve 53 (see FIG. 4(D)). In other words, the material 25 comes into contact with the inner peripheral surface 58 of the mold sleeve 53, which has a circular or nearly circular shape in a plan view. In mold press molding, the mold transfer is performed on the entire periphery of the end face of the mirror-finished material in this manner. When the mold transfer is performed on the entire periphery of the end face, the flange shape of the optical element, i.e., the peripheral contour of the optical element, is easily shaped into the desired shape.

[0048] During mold pressing, the deformation of the mirrored material is brought about by the pressing force received from the mold. In the manufacturing method of the present disclosure, the pressing force that can be applied to the material can be set to a pressure that is not excessively excessive. This is because the mirrored material has an overall shape that is preferably closer to the final optical element than the original columnar material due to the above-mentioned "heating of the entire surface". Therefore, even if the material is made of a brittle material, it can be used more actively in mold pressing. For example, glass materials such as chalcogenide materials and / or chalcohalide materials are lens materials with excellent optical properties, but are brittle to pressing forces and have been generally considered unsuitable for mold pressing. In the manufacturing method of the present disclosure, even such glass materials can be used. Note that the fact that the load applied to the mirrored material during mold pressing is not excessive means that it is not necessary to prepare the material in advance into a shape relatively close to the shape of the optical element (for example, a lens-like shape) by grinding the material prior to mold pressing. In other words, the material loss of the material is reduced as a result, and from this perspective, glass materials such as chalcogenide materials and / or chalcohalide materials are easily adopted in the present disclosure.

[0049] A mirror-finished material comprising a glass material (e.g., a chalcogenide material and / or a chalcohalide material) can be mold-pressed with a pressure that is at least 5% lower than that required for a material obtained by mechanical mirror-finishing treatment. In one embodiment, the mold-pressing pressure applied to a mirror-finished material obtained by heat treatment can be reduced by 5% to 50% or 10% to 40% lower than that required for a material obtained by mechanical mirror-finishing treatment.

[0050] The mirror-finished material 25 that has been transferred to the mold as desired is released from the mold in the final stage of mold pressing. In other words, the mirror-finished material that has been plastically deformed by mold pressing is finally removed from the mold after being unloaded and cooled, and is used as the desired optical element 10 (see FIG. 4(E)).

[0051] The manufacturing methods of the present disclosure may be embodied in a variety of forms.

[0052] (Non-edge aspect) In this embodiment, mold press molding is performed without using a mold sleeve. That is, in mold press molding, the end face of the flange part of the optical element molded in the mold cavity formed between the upper mold and the lower mold is not subjected to mold transfer. As the mold, for example, a non-sleeve type mold 50 as shown in FIG. 5 may be used. As shown in the figure, the non-sleeve type mold 50 is mainly composed of an upper mold 51 and a lower mold 52, and does not include a sleeve member (for example, the mold sleeve 53 shown in FIG. 3).

[0053] In this embodiment, when the mirror-finished material is inserted between the upper and lower dies, the outer periphery of the material that is not in contact with the upper and lower dies is not subjected to mold transfer. For example, as shown in the schematic process diagram of Figure 6, mold press molding is performed without transferring to the die sleeve. This means that mold press molding is performed in the same manner as in the embodiment described in Figure 4, but the entire circumference of the end face of the mirror-finished material is not subjected to mold transfer.

[0054] Specifically, the mirror-finished material 25 (see FIG. 6(A)) put into the mold 50 is heated by the heat of the mold 50 and deformed by the pressing force from the mold 50 (see FIG. 6(B) and FIG. 6(C)). In particular, the mirror-finished material 25 receiving the pressing force from the upper mold 51 and the lower mold 52 of the mold 50 is plastically deformed so as to spread outward. The mirror-finished material 25 (FIG. 6(D)) that is transferred to the mold as desired through such plastic deformation is released at the final stage of mold press molding and is taken out as the optical element 10 (see FIG. 6(E)). In this embodiment, the mirror-finished material 25 that is plastically deformed during mold press molding is not pressed against the mold sleeve 53 (see FIG. 4(D)), and therefore the entire circumference of the end surface of the mirror-finished material is not transferred to the mold. Therefore, the outermost end surface (particularly the end surface of the flange portion) of the obtained optical element 10 may have, for example, a rounded shape (see FIG. 6(E)).

[0055] In the manufacturing method of the present disclosure, the mirror-finished material that is mold-press molded has an overall shape that is closer to the final optical element compared to the original columnar material due to the mirror-finishing process. Therefore, the plastic deformation of the mirror-finished material that deforms toward the outer periphery that is not in contact with the upper and lower dies during mold-press molding is easily uniform, and the material can be pressurized and deformed into the desired lens shape by mold-press molding without using a die sleeve.

[0056] In addition, when the mold sleeve is not used, the close contact between the mold sleeve and the lens edge surface during molding is essentially avoided. In other words, when the mold sleeve and the lens edge surface are in close contact with each other, there may be a concern that cracks may occur due to the difference in the linear expansion coefficient during the cooling process after molding, but this is reduced when the mold sleeve is not used.

[0057] (Mirror finishing process using a mold) In this embodiment, the entire surface of the columnar material is heated and mirror-finished by utilizing a die used in mold press molding. For example, the die cavity of the lower die used in mold press molding may be used to perform the mirror-finish treatment. More specifically, as shown in FIG. 7, the heat of the lower die 52 may be used to perform the mirror-finish treatment of the columnar material 20. This means that the columnar material may be mirror-finished by the molding means prior to mold press molding.

[0058] In this embodiment, the columnar material 20 is heated while being placed in the lower die 52, thereby subjecting the columnar material 20 to a mirror finish treatment (see FIG. 7). For example, the columnar material may be placed in a lower die whose temperature has been raised to the heating temperature condition for the mirror finish treatment or in a lower die which is in the process of being heated to the heating temperature, and the columnar material may be heated using the heat from the lower die. Alternatively, the columnar material may be placed in the lower die, and then the lower die may be raised to the heating temperature condition, and the columnar material may be heated using the heat from the lower die. When the die cavity of the lower die is used for the mirror finish treatment in this manner, the lower die may be in contact with only a part of the bottom surface of the columnar material. The columnar material is supported by the lower die at the contact point, and is heated by the lower die which supports it. Note that if the bottom surface of the columnar material is in full contact with the lower die, the bottom surface of the columnar material may be heated too strongly. However, if only a part of the bottom surface of the columnar material is in contact with the lower die, the entire surface is more likely to be heated evenly due to thermal radiation. The lower mold may be a mold that forms, for example, a convex or concave shape of an optical surface of an optical element. In other words, the cavity forming surface of the lower mold may have a shape that is complementary to the convex or concave shape of such an optical surface.

[0059] When the mirror finishing process is performed by heating using the mold cavity, the mirror finishing material can be subjected to mold press molding more smoothly. In other words, since the mold is shared between the mirror finishing process and mold press molding, the transition from the mirror finishing process to the mold press molding is relatively smooth.

[0060] There is no particular limitation on the method of heating the mold. For example, the mold may be heated using a heating coil built into the mold and / or a heat medium flowing through the heat medium pipe of the mold. The mold may be heated using a heating means provided separately from the mold. For example, as shown in FIG. 7, the lower mold 52 may be heated using a heating means 60 provided outside the lower mold 52 to perform the mirror finish treatment of the columnar material. Furthermore, a heating means 65 provided in place of the upper mold at a position where the upper mold is placed when the mold is used (see FIG. 7) may be used, and the columnar material may be heated to perform the mirror finish treatment.

[0061] (Aspects of continuous processing using a mold) In this embodiment, the columnar material is subjected to a mirror-finishing process and the mirror-finished material obtained thereby is cooled continuously using a mold. For example, as shown in FIG. 8, by using a mold press molding mold 50, the entire surface of the columnar material is heated to perform a mirror-finishing process to obtain a mirror-finished material, and then the mirror-finished material may be cooled using the same mold 50. Since the mirror-finished material is obtained using a mold used for mold press molding and the mirror-finished material can be mold-press molded using the mold, smoother production of optical elements can be achieved. In such a continuous process, for example, the time required for mold press molding may be shorter than the time required for the mirror-finishing process.

[0062] (Lens product characteristics) In this embodiment, a lens is manufactured as the optical element 10. That is, a lens for converging or diverging light is manufactured. The type of lens is not particularly limited, and may be a convex lens or a concave lens. The convex lens may be a biconvex lens (FIG. 1(A)) or a plano-convex lens, and the concave lens may be a biconcave lens (FIG. 1(B)) or a plano-concave lens. Furthermore, the lens may be a meniscus lens as shown in FIG. 1(C). Note that the optical element obtained according to the above-mentioned "non-edge embodiment" may have a unique shape since the entire circumference of the end face of the mirror-finished material is not molded and transferred. Specifically, the outermost edge surface of the optical element 10 may have a rounded shape as a whole. For example, in the case of the lens shown in FIG. 9, the outline of the outermost edge surface may be curved as a whole in a cross-sectional view of a biconvex lens (FIG. 9(A)), a biconcave lens (FIG. 9(B)), a meniscus lens (FIG. 9(C)), etc.

[0063] As described above, in the manufacturing method of the present disclosure, the entire surface is heated and the resulting mirror-finished material is subjected to mold press molding, so excessive pressure is unlikely to be applied to the material during mold press molding, and brittle materials can be actively used. Therefore, in the manufacturing method of the present disclosure, chalcogenide materials and / or chalcohalide materials can be more actively used. Chalcogenide materials have suitable transmission characteristics for the infrared region, and chalcohalide materials can have suitable transmission characteristics for not only the infrared region but also the visible light region, so the manufacturing method of the present disclosure can suitably manufacture lenses for at least the infrared region as optical elements.

[0064] [Optical element of the present disclosure] The optical element of the present disclosure is obtained by the above-mentioned manufacturing method and corresponds to the optical element obtained from the material through the above-mentioned mold press molding. In other words, the optical element of the present disclosure is an optical element obtained by mold press molding of a columnar material that has been subjected to a mirror finish treatment by heating the entire surface.

[0065] The optical element of the present disclosure preferably comprises a light-transmitting portion and a flange portion extending outwardly therefrom. When the optical element is a lens, the optical element of the present disclosure comprises a light-transmitting portion corresponding to the lens portion and a flange portion extending outwardly therefrom. The flange portion corresponds to the outermost edge portion of the optical element that does not contribute to light transmission when the optical element is in use, and is a portion of the optical element that may have, for example, a substantially constant thickness.

[0066] A schematic diagram of the optical element 10 being a lens is shown in Fig. 10. Although this is merely one example of an optical element, Fig. 10 shows a perspective view and a plan view of the appearance of a biconvex lens as the optical element 10.

[0067] In the optical element 10 according to the present disclosure, the light-transmitting portion 11 has different internal strains between the peripheral region (for example, the region including the outermost peripheral portion in the light-transmitting portion) and the inner region inside the peripheral region. That is, as shown in the schematic diagram of FIG. 11, the amount of internal strain may be different between the inner region 11A corresponding to the substantial light-transmitting portion of the light-transmitting portion 11 and the peripheral region 11B. The lower diagram of FIG. 11 illustrates the relative magnitude relationship of the internal strain. In the lower diagram of FIG. 11, the relatively dark colored portion indicates that the internal strain is relatively large, and the relatively light colored portion indicates that the internal strain is relatively small or nonexistent. The characteristics of the internal strain in FIG. 11 are preferably related to the manufacturing method described above. In particular, the internal strain associated with mold press molding, which is performed with little material loss, may be brought about in the optical element. The internal distortion shown in FIG. 11 can be said to be an example of internal distortion characteristic of optical elements obtained by mold press molding a material without obtaining an approximation of a lens shape by grinding or the like prior to mold press molding (preferably by mold press molding a material that has been heat-treated as a mirror-finishing process).

[0068] In the present disclosure, the "peripheral region" may correspond to a region including the outermost peripheral portion in a plan view of the light transmitting portion 11. For example, if the diameter of the circle in a plan view of the light transmitting portion 11 is D (see FIG. 11), a light transmitting region outside the concentric region having a diameter of at least 0.5D may be regarded as the "peripheral region".

[0069] The planar shape of the inner region may be a polygon such as a square with each side curved toward the center or periphery. For example, if the light transmitting portion of the optical element is virtually divided into an inner region having a square shape with each side curved toward the center in a planar view and an outer peripheral region, the amount of internal distortion between them may be different.

[0070] In a preferred embodiment, the outer shape of the inner region corresponds to the outer shape of the columnar material before mold press molding to form the optical element. The distortion-free region of the polygonal columnar material such as a square may be processed by mold press molding into a shape in which each side of the polygonal shape such as a square is curved toward the center or periphery. In this case, the light-transmitting part may have different internal distortions between the region corresponding to the outer shape of the columnar material (hereinafter also referred to as the "material-corresponding region") and the other regions. That is, as shown in FIG. 11 (particularly, an exemplary plan view in which the optical element shown at the bottom is a lens), the amount of internal distortion is different between the lens surface of the area portion corresponding to the dimensions of the material-corresponding region and the lens surface of the other area portion in the light-transmitting part 11.

[0071] In the present disclosure, the internal strain in the light-transmitting portion can be grasped, for example, by measuring the retardation (phase difference). A commercially available measuring device may be used to measure the retardation (phase difference), and the internal strain of the light-transmitting portion (i.e., the distribution of the internal strain as shown in the lower diagram of FIG. 11) can be grasped by using a measuring device (manufactured by Photonic Lattice Co., Ltd., model PA-300-MT-NIR850).

[0072] When the columnar material that has been subjected to the mirror finishing process has a prismatic shape, the material-corresponding region of the light-transmitting portion in plan view may be a quadrilateral such as a square. In such a case, for example, the amount of internal strain may be different between the area corresponding to the dimensions of the square-shaped material-corresponding region in plan view and the area corresponding to the other light-transmitting portion (i.e., the surrounding region). Although this is merely an example, the internal strain in the square region area corresponding to the dimensions of the prismatic shape may be about 8 to 12 nm, while the internal strain in the other region area (i.e., the surrounding region area) may be a maximum of about 30 nm.

[0073] Thus, in the optical element of the present disclosure, the amount of internal distortion may be different between the inner region of the light-transmitting part and the surrounding region of its periphery, but the distortion in the inner region including the central part of the light-transmitting part is small or substantially non-existent. Due to such distortion characteristics, the optical element of the present disclosure may have desired optical characteristics as a whole. For example, the optical element of the present disclosure may have optical characteristics that are substantially comparable to those of an optical element manufactured through mechanical processing such as cutting, grinding, and / or polishing (see FIG. 13) (for example, light transmission characteristics that are substantially equivalent to those of an optical element manufactured through such mechanical processing).

[0074] In a preferred embodiment, the optical element has a stress distribution according to the planar shape of the columnar material. That is, when the optical element is made of a glass material, the above manufacturing method may result in a stress distribution according to the glass material shape being brought about in the optical element after molding. In addition, in the optical element of the present disclosure, when it is desired to change the average value of the internal strain within the optical effective diameter, it can be accommodated by changing the dimensions of the columnar material. That is, when changing the average value of the internal strain within the optical effective diameter, it can be accommodated by arbitrarily changing the dimensions of the columnar material to be mirror-finished. In addition, the material is not limited to a prismatic material (that is, the planar shape of the material-equivalent region of the light-transmitting portion is not limited to a quadrangle such as a square), but may be a polygonal shape such as a triangular prism or a hexagonal prism, or a cylindrical shape. That is, the planar shape of the material-equivalent region of the light-transmitting portion may be a triangle, a hexagon, or a circle. In such a case, a stress distribution according to the triangular prism, hexagonal prism, or cylinder of such a material can be obtained in the light-transmitting portion of the optical element.

[0075] The optical element 10 of the present disclosure has a unique configuration, since it is preferably obtained by mold press molding from a single material 20. Specifically, the optical element 10 of the present disclosure preferably has a light-transmitting portion 11 and a flange portion 12 made of the same material and integrated with each other. In the embodiment shown in Fig. 10, the light-transmitting portion 11 corresponding to the lens portion and the flange portion 12 on the outer side thereof are made of the same material and integrated with each other. When integrated with the same material in this way, the homogeneity is increased compared to when the light-transmitting portion 11 and the flange portion 12 are integrated with different materials, and the structural strength of the optical element 10 can be improved.

[0076] The optical element 10 of the present disclosure is obtained under conditions in which the mirror-finished material is not subjected to excessive load during mold press molding. Therefore, the optical element 10 can be suitably obtained from a chalcogenide material and / or a chalcohalide material through mold press molding. That is, the optical element 10 in a preferred embodiment contains a chalcogenide material and / or a chalcohalide material. It can also be said that the optical element 10 can be made of so-called chalcogenide-based and / or chalcohalide-based glass. In the simplest terms, it can be said that the optical element 10 is preferably made of a chalcogenide glass or a chalcohalide glass.

[0077] In the present specification, the term "chalcogenide material" broadly means a material having at least one chalcogen element selected from the group consisting of S (sulfur), Se (selenium) and Te (tellurium) of group VIb of the periodic table as one of its main components. For example, the chalcogenide material may be a material having a composition in which at least one chalcogen element selected from the group consisting of S (sulfur), Se (selenium) and Te (tellurium) is combined with at least one element selected from the group consisting of Ge (germanium), As (arsenic), Sb (antimony), P (phosphorus), Ga (gallium), In (indium) and Si (silicon). In addition, the term "chalcohalide material" means a material having a composition in which a halogen element (at least one element selected from the group consisting of fluorine, chlorine, bromine and iodine) or a compound thereof is introduced into such a chalcogenide material. Such chalcogenide and / or chalcohalide materials may have suitable transmission properties for the infrared region or for both the infrared region and the visible light region, and therefore the optical element 10 of the present disclosure may be suitably used as a lens for transmitting light rays in at least the infrared region.

[0078] Although the embodiments have been described above, they are merely typical examples. Therefore, it will be easily understood by those skilled in the art that the manufacturing method and optical element of the present disclosure are not limited thereto, and various embodiments are possible.

[0079] For example, in the above description, a preferred embodiment of the manufacturing method of the optical element has been described with reference to the drawings, but this is for the sake of convenience of description only. The manufacturing method of the present disclosure may be one in which the overall process is taken into consideration of actual manufacturing. For example, the manufacturing method of the present disclosure may be one based on continuous processing as a whole, or may be one based on batch processing.

[0080] In the above description with reference to FIG. 7, the columnar material is heated with heat from the lower die to perform the mirror finish treatment, but the present disclosure is not limited thereto. For example, the columnar material may be heated and mirror finished using the upper die of the die in addition to or instead of the upper die. In such a case, the upper die may be heated using a heating coil built into the upper die and / or a heat medium flowing through the heat medium pipe of the upper die to perform the mirror finish treatment of the columnar material. In addition, a heating means provided separately from the upper die may be used, and for example, the upper die may be heated and mirror finished using a heating means arranged outside the upper die.

[0081] Furthermore, in the above description, the embodiment has been described with a focus on mold press molding a biconcave lens or a biconvex lens as a lens, but the present disclosure is not limited thereto. For example, as shown in FIG. 12, the present disclosure can be similarly applied to the case where the optical element 10, which is a meniscus lens, is mold press molded. [Industrial Applicability]

[0082] The optical element according to the present disclosure can be used as various lenses. In particular, the optical element according to the present disclosure can be made of a chalcogenide material and / or a chalcohalide material in a preferred embodiment, and can be used as an infrared lens (which is merely one example, but is a lens intended for at least far infrared rays), a visible light lens, or a broadband transmission lens that transmits both infrared and visible light regions. [Explanation of symbols]

[0083] 10 Optical elements 11 Light transmission part 11A Inner area of ​​light transmitting part 11B Surrounding area of ​​light transmitting portion 12 Flange 20 Columnar Material 25 Mirrored material 50 Mold 51 Upper mold 52 Lower mold 53 Mold sleeve 56 Mold Cavity 58 Inner surface of die sleeve 60 Heating means 65 Heating means

Claims

1. A method for manufacturing an optical element, comprising the steps of: A method for manufacturing an optical element, comprising: subjecting a columnar material to a mirror-finishing treatment in which the entire surface of the columnar material is mirror-finished by heating to form a mirror-finished material from the columnar material; and subjecting the mirror-finished material to mold press molding.

2. 2. The method for manufacturing an optical element according to claim 1, wherein the mirror finishing process comprises heating the columnar material under heating conditions that are 50° C. to 200° C. higher than the glass transition temperature of the columnar material to soften it.

3. The method for manufacturing an optical element according to claim 1 , wherein the heating comprises heating the columnar material from above, below, and to the sides.

4. 4. The method for producing an optical element according to claim 1, wherein the mold press molding is carried out at a temperature condition that is 20° C. to 130° C. lower than that of the mirror finishing treatment.

5. 5. The method for producing an optical element according to claim 1, wherein the mold press molding is performed under a temperature condition that is 40° C. to 150° C. higher than the glass transition temperature of the columnar material.

6. The method for manufacturing an optical element according to any one of claims 1 to 5, wherein the mirror finishing treatment is carried out by utilizing a mold cavity of a lower mold used in the mold press molding.

7. The method for manufacturing an optical element according to claim 6 , wherein the lower mold contacts only a portion of a bottom surface of the columnar material.

8. The method for manufacturing an optical element according to claim 6 or 7, wherein the lower mold forms a convex or concave shape of an optical surface of the optical element.

9. 9. The method for manufacturing an optical element according to claim 1, wherein the mirror-finishing treatment makes the surface roughness of the mirror-finished material Ra 50 nm or less.

10. The method for manufacturing an optical element according to any one of claims 1 to 9, wherein the columnar material has a polygonal columnar shape or a cylindrical shape.

11. The method for manufacturing an optical element according to any one of claims 1 to 10, wherein the columnar material includes a chalcogenide material and / or a chalcohalide material.

12. The method for manufacturing an optical element according to any one of claims 1 to 11, wherein in the mold press molding, an end face of a flange portion of the optical element molded in a mold cavity formed between an upper mold and a lower mold is subjected to mold transfer.

13. The method for manufacturing an optical element according to any one of claims 1 to 11, wherein in the mold press molding, an end face of a flange portion of the optical element molded in a mold cavity formed between an upper mold and a lower mold is not subjected to mold transfer.

14. An optical element, a light transmitting portion and a flange portion extending outwardly from the light transmitting portion; An optical element, wherein the light transmitting portion has a different internal strain between a peripheral region and an inner region located more inward than the peripheral region.

15. The optical element according to claim 14 , wherein the inner region has a polygonal shape in plan view, each side of which is curved toward the center or the periphery.

16. 16. The optical element according to claim 14 or 15, wherein the outer shape of the inner region corresponds to the outer shape of a columnar material prior to mold press forming of the optical element.

17. The optical element according to any one of claims 14 to 16, wherein the optical element comprises a chalcogenide and / or chalcohalide material.

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