JP2008150245A - Forming die for optical element and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming die for an optical element where compositional change on the surfaces of the forming die and a glass material and the occurrence of glass fusion can be prevented even in the press-forming of the glass material containing bismuth, which has durability and where optical troubles do not occur in the formed optical element and to provide the optical element produced with the forming die for the optical element. <P>SOLUTION: The forming die 1 for the optical element, used when the optical element is produced by press-forming the glass material containing bismuth, has a die base material 2 and a surface layer 3 formed at least on a forming surface 2a. The surface layer 3 contains bismuth of 1.0 wt.% or more and 30.0 wt.% or less as a first component and contains at least one or more kinds of elements or compounds selected from among platinum, gold, palladium, iridium, osmium, ruthenium, rhenium, rhodium, tungsten, tungsten carbide and silicon carbide as a second component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element molding die used for manufacturing an optical element by press-molding a glass material containing bismuth, and an optical element manufactured by the optical element molding mold.

  One method of manufacturing an optical element from a glass material is a method of press molding using an optical element molding die. In the case of the manufacturing method by press molding, since it is not necessary to perform polishing after molding, there is an advantage that an optical element can be manufactured easily and at low cost. Such an optical element molding die is required to be excellent in hardness, heat resistance, non-fusibility with glass, and mirror finish. For this reason, conventionally, cemented carbide, metal, or ceramics has been used as a mold base material for optical element molding dies, and the precious metal system that has excellent heat resistance and non-fusibility to glass on the molding surface. Those having an alloy layer or compound layer formed thereon are selected.

  Specifically, a cemented carbide base material coated with a compound composed of iridium, rhenium, and carbon has been proposed (see, for example, Patent Document 1). In such an optical element molding die, the coated compound is made of iridium, rhenium, and carbon, so that it has oxidation resistance and good releasability from the glass material, resulting in glass fusing. It is said that it is difficult.

In addition, a processed layer that is in an amorphous state is formed on a cemented carbide or alloy mold base material in close contact with the mold base material, and is further in close contact with the processed layer from noble metal, tungsten, tantalum, or the like. The thing in which the protective layer which becomes is formed is proposed (for example, refer patent document 2). Similarly, in such a mold for molding an optical element, it is said that the formation of the protective layer makes it easy to release from the glass and prevents the glass from fusing.
Japanese Patent Publication No. 6-88803 Japanese Patent Laid-Open No. 7-172849

  However, even when optical element molding dies such as Patent Document 1 and Patent Document 2 are used, when an optical element is manufactured using a glass material containing bismuth, the change in the composition of the mold surface or the glass still remains. There was a problem that fusion occurred, the durability of the molding die was lowered, and optical defects such as fogging occurred on the surface of the molded optical element. More specifically, bismuth has a low melting point, is easily alloyed, and has a property of being easily diffused into a metal, particularly at high temperatures. For this reason, when a glass material containing bismuth is used, bismuth contained in the glass material precipitates on the surface of the glass material through segregation in a high temperature environment. Precipitated bismuth is easily diffused to the surface of the mold by contact with the mold during press molding, and the diffused bismuth is partially reduced to metal bismuth and accumulated on the surface of the mold. And since the deposited bismuth gradually accumulates on the glass material surface and the mold surface, the composition of the mold surface and the glass material surface changes, and glass fusion occurs. . Further, the precipitation of bismuth on the surface of the glass material causes optical defects such as fogging in the optical element.

  The present invention has been made in view of the above-described circumstances, and even in the press molding of a glass material containing bismuth, changes in the composition of the molding die surface and the glass material surface and the occurrence of glass fusing. An optical element molding die that can be prevented, has durability, and does not cause optical defects in the molded optical element, and an optical manufactured by the optical element molding die An element is provided.

In order to solve the above problems, the present invention proposes the following means.
An optical element molding die according to the present invention is an optical element molding die used for producing an optical element by press-molding a glass material containing bismuth. A surface layer formed on a molding surface in a range where the glass material contacts at least during the press molding, and the surface layer has 1.0 weight of bismuth as a first component. At least one selected from platinum, gold, palladium, iridium, osmium, ruthenium, rhenium, rhodium, tungsten, tungsten carbide, or silicon carbide. It is characterized by containing the element or compound of this.

  According to the optical element molding die according to the present invention, the surface layer can ensure the hardness and oxidation resistance required for press molding by including the second component. Moreover, the surface layer contains bismuth as a first component in an amount of 1.0% by weight or more, so that an equilibrium state is maintained between the surface layer and the glass material with respect to bismuth, and is included in the glass material during press molding. The diffusion of bismuth into the surface layer can be prevented. For this reason, the change of the composition of the surface layer and the glass material surface due to the diffusion of bismuth can be prevented, and the occurrence of glass fusion due to the increased affinity with the glass material can be prevented. On the other hand, by setting the bismuth contained as the first component to 30.0% by weight or less, the affinity with the glass material containing bismuth in the initial state becomes too high, and glass fusion occurs. Can be prevented. That is, by setting the concentration of bismuth in the surface layer within the above range, it is possible to prevent deterioration in surface accuracy and surface roughness due to changes in the composition of the surface layer and glass fusion for a long period of time.

  In the above optical element molding die, one or more layers are formed between the mold base and the surface layer, and chromium, titanium, aluminum, tungsten carbide, tungsten, silicon carbide, or chromium, titanium, or aluminum. Of these nitrides, it is more preferable to provide an intermediate layer containing at least one element or compound.

  According to the optical element molding die of the present invention, the adhesion between the mold base material and the surface layer can be improved by forming the intermediate layer between the mold base material and the surface layer. . For this reason, the durability can be further improved, and the occurrence of an optical defect of the molded optical element can be more reliably prevented.

  In the above optical element molding die, at least one of the elements contained in the layer formed in contact with the molding surface is formed on the molding surface side of the mold base material. It is more preferable that an injection layer injected from the surface is formed.

  According to the optical element molding die according to the present invention, as the injection layer, an element contained in a layer formed in contact with the molding surface on the molding surface side of the mold matrix is present, so that the mold matrix and the mold The affinity with the layer formed in contact with the base material, that is, the surface layer or the intermediate layer is increased, and the adhesion can be further improved.

The optical element of the present invention is manufactured by press-molding a glass material containing bismuth using the above-described optical element molding die.
According to the optical element of the present invention, it is possible to suppress or prevent the bismuth contained in the glass material from being precipitated and diffused to the surface layer of the optical element molding die during press molding. For this reason, the composition of the glass material surface is changed and the optical element is not fogged, or the glass is not fused to the surface of the molding die, so that the occurrence of optical defects can be prevented. Further, since the optical element molding die can be used repeatedly, the cost can be reduced.

According to the optical element molding die of the present invention, by providing a surface layer, even in press molding of a glass material containing bismuth, the composition of the molding die surface is prevented from changing and the occurrence of glass fusion, and the surface accuracy and It is possible to prevent the deterioration of the surface roughness for a long period of time and improve the durability, and to prevent optical defects from occurring in the molded optical element.
According to the optical element of the present invention, the optical element can be manufactured by press molding with the optical element molding die at a low cost and free from optical defects.

(First embodiment)
FIG. 1 shows a first embodiment according to the present invention. As shown in FIG. 1, an optical element molding die 1 according to this embodiment has a mold surface 1a formed in a predetermined shape, and a glass material, particularly a glass material containing bismuth (Bi), on the mold surface 1a. The optical element is manufactured by contact and press molding, and includes a mold base material 2 and a surface layer 3 formed on the surface of the mold base material 2. The mold base material 2 is formed of a cemented carbide or the like mainly composed of tungsten carbide. Further, the surface layer 3 is formed on at least the molding surface 2a of the surface of the mold base material 2, which is a range where the glass material comes into contact during press molding. The surface layer 3 contains bismuth (Bi) in an amount of 1.0 wt% or more and 30.0 wt% or less, and as a second component, platinum (Pt), gold (Au), palladium (Pd), iridium (Ir) At least one element selected from osmium (Os), ruthenium (Rt), rhenium (Re), rhodium (Rh), tungsten (W), tungsten carbide (WC), or silicon carbide (SiC), or Contains compounds.

  In such an optical element molding die 1, the hardness and oxidation resistance necessary for press molding can be ensured because the surface layer 3 contains any of the above elements or compounds as the second component. Further, when the surface layer 3 contains 1.0% by weight or more of bismuth (Bi) as the first component, the equilibrium state or quasi-equilibrium state is maintained between the surface layer 3 and the glass material with respect to bismuth (Bi). The bismuth (Bi) contained in the glass material can be suppressed or prevented from diffusing into the surface layer 3 during press molding. For this reason, the change of the composition of the surface layer 3 and the glass material surface due to the diffusion of bismuth (Bi) can be prevented, and the occurrence of glass fusion due to the increased affinity with glass can be prevented. On the other hand, by setting the bismuth (Bi) contained as the first component to 30.0% by weight or less, the affinity with the glass material containing bismuth (Bi) in the initial state becomes too high, and the glass is fused. Can be prevented from occurring. That is, by making the concentration of bismuth (Bi) in the surface layer 3 within the above range, it is possible to prevent deterioration of surface accuracy and surface roughness due to a change in the composition of the surface layer 3 and glass fusion for a long period of time. In addition, the durability can be improved, and the occurrence of optical defects in the molded optical element can be prevented. Further, in the optical element molded with such an optical element molding die 1, the composition of the surface of the glass material changes, or the glass is fused to the mold surface, resulting in an optical failure. In addition, the optical element molding die can be used repeatedly, so that the cost can be reduced.

(Second Embodiment)
FIG. 2 shows a second embodiment according to the present invention. In this embodiment, members that are the same as those used in the above-described embodiment are assigned the same reference numerals, and descriptions thereof are omitted.

  As shown in FIG. 2, the optical element molding die 10 of this embodiment includes a mold base material 2, a surface layer 3, and an intermediate layer 11 formed between the mold base material 2 and the surface layer 3. Prepare. The intermediate layer 11 is made of chromium (Cr), titanium (Ti), aluminum (Al), tungsten carbide (WC), tungsten (W), silicon carbide (SiC), or chromium (Cr), titanium (Ti) or aluminum. Among the nitrides of (Al), at least one element or compound is included.

  Here, since chromium (Cr), titanium (Ti), and aluminum (Al) have high reactivity, the adhesion strength between the mold base material 2 and the surface layer 3 can be obtained by including these or nitrides thereof. Can be increased. Tungsten carbide (WC), tungsten (W), and silicon carbide (SiC) have high heat resistance, and can be aligned in crystal orientation when used as a film to be the intermediate layer 11. For this reason, the adhesion strength between the mold base material 2 and the surface layer 3 is uniform, and problems such as partial peeling can be reduced. That is, the adhesion between the mold base material 2 and the surface layer 3 can be improved by selecting at least one of the above elements or compounds contained in the intermediate layer 11. For this reason, in the optical element molding die 10, the durability can be further improved, and an optical defect occurs in the molded optical element due to the peeling of the surface layer 3. Can be prevented more reliably.

  In the present embodiment, the intermediate layer 11 is provided between the mold base material 2 and the surface layer 3, but the present invention is not limited to this, and a plurality of layers are provided, and the composition is different for each layer. It is good as a thing.

(Third embodiment)
FIG. 3 shows a third embodiment according to the present invention. In this embodiment, members that are the same as those used in the above-described embodiment are assigned the same reference numerals, and descriptions thereof are omitted.

  As shown in FIG. 3, in the optical element molding die 20 of this embodiment, the element contained in the surface layer 3 formed in contact with the molding surface 2a is formed on the molding surface 2a side of the mold base material 2. An injection layer 21 injected from 2a is formed. In other words, the implantation layer 21 of the mold base material 2 is ion-implanted with either the first component or the second component shown in the first embodiment. Thus, the presence of the element contained in the surface layer 3 as the injection layer 21 increases the affinity between the mold base material 2 and the surface layer 3 and improves the adhesion. For this reason, in the optical element molding die 20, the durability can be further improved, and an optical defect occurs in the molded optical element due to the peeling of the surface layer 3. Can be prevented more reliably.

  In the present embodiment, the surface layer 3 is formed directly on the molding surface 2a of the mold base material 2 and the injection layer 21 is injected with the elements contained in the surface layer 3, but this is not restrictive. . That is, the intermediate layer 11 shown in the second embodiment is provided between the mold base material 2 and the surface layer 3, and an element contained in the intermediate layer 11 is formed as an injection layer 21 from the molding surface 2 a of the mold base material 2. It may be injected. A plurality of intermediate layers 11 may be provided. In this case, an element contained in the intermediate layer in contact with the molding surface 2a of the mold base material 2 among the plurality of intermediate layers 11 may be injected.

  Examples of the optical element molding die from the first embodiment to the third embodiment will be described below.

  Table 1 shows the configuration of a total of eight types of optical element molding molds: five types prepared in correspondence with the optical element molding molds 1, 10, and 20 of each embodiment and three types manufactured as comparative examples. ing. The following details will be described.

  In correspondence with the optical element molding die 1 of the first embodiment, NO. 1-NO. 3 was prepared. NO. Reference numeral 1 denotes a mold base material 2 made of a cemented carbide mainly composed of tungsten carbide (WC), a surface layer 3, and bismuth (Bi) as a first component and iridium (Ir) as a second component. A noble metal layer having a composition ratio with platinum (Pt) of 1: 49.5: 49.5 was formed to a thickness of 500 nm by ion beam sputtering using a 1Bi-49.5Ir-49.5Pt alloy target.

  NO. 2 is a noble metal having a composition ratio of bismuth (Bi), iridium (Ir), and platinum (Pt) of 15: 42.5: 42.5 as a surface layer 3 on the same mold base material 2 The layer was formed to a thickness of 500 nm by ion beam sputtering using a 15Bi-42.5Ir-42.5Pt alloy target.

  NO. No. 3 is a noble metal layer having a composition ratio of bismuth (Bi), iridium (Ir), and platinum (Pt) of 30:35:35 on the same mold base material 2 as the surface layer 3. The film was formed with a film thickness of 500 nm by ion beam sputtering using a -35Ir-35Pt alloy target.

  Further, in correspondence with the optical element molding die 10 of the second embodiment, the NO. No. 4 optical element molding die was produced. NO. Reference numeral 4 denotes a surface layer 3 after a chromium (Cr) layer is formed as an intermediate layer 11 with a film thickness of 150 nm on the mold base material 2 made of a cemented carbide mainly composed of tungsten carbide (WC) by ion beam sputtering. As a noble metal layer having a composition ratio of bismuth (Bi), iridium (Ir), and platinum (Pt) of 15: 42.5: 42.5, a 15Bi-42.5Ir-42.5Pt alloy target It was formed with a film thickness of 500 nm by ion beam sputtering using

Further, in correspondence with the optical element molding die 20 of the third embodiment, the NO. 5 was prepared. NO. No. 5 is a mold base material 2 made of a cemented carbide containing tungsten carbide (WC) as a main component, with an injection layer 21 as an injection amount 1 × 10 ¹⁵ ions / cm ² , an acceleration voltage of 100 keV, and an ion current of 50 mA. After forming a layer into which iridium ions are implanted at an implantation depth of 50 nm, the composition ratio of bismuth (Bi), iridium (Ir), and platinum (Pt) as the surface layer 3 is 15: 42.5: A noble metal layer having a thickness of 42.5 was formed to a thickness of 500 nm by ion beam sputtering using a 15Bi-42.5Ir-42.5Pt alloy target.

  In Comparative Example 1, the composition of bismuth (Bi), iridium (Ir), and platinum (Pt) as the outermost layer on the mold base material made of a cemented carbide mainly composed of tungsten carbide (WC). A noble metal layer having a ratio of 0.5: 50.0: 49.5 was formed to a thickness of 500 nm by ion beam sputtering using a 0.5Bi-50Ir-49.5Pt alloy target. In Comparative Example 2, the composition ratio of bismuth (Bi), iridium (Ir), and platinum (Pt) as the outermost layer is formed on a mold base material made of a cemented carbide whose main component is tungsten carbide (WC). , 31: 34.5: 34.5, a noble metal layer having a film thickness of 500 nm was formed by ion beam sputtering using a 31Bi-34.5Ir-34.5Pt alloy target. In Comparative Example 3, a chromium (Cr) layer was formed by ion beam sputtering on a mold base material made of a cemented carbide containing tungsten carbide (WC) as a main component, and then iridium (Ir) and platinum ( A noble metal layer having a composition ratio with Pt) of 50:50 was formed with a film thickness of 500 nm by ion beam sputtering using a 50Ir-50Pt alloy target.

  Next, NO. 1-NO. 5 and a total of 8 types of optical element forming molds of Comparative Examples 1 to 3, the optical elements were press-molded from a bismuth-containing glass material, and the number of moldings until a defect occurred was compared. The results are shown in Table 2. The mold temperature during press molding is 550 ° C.

  As shown in Table 2, NO. 1-NO. The optical element molding die 1 shown in No. 3 could be used without any problems up to 1400 repeated uses. On the other hand, NO. 1 is 1413 repeated use, NO. 2, 2361 times, NO. In No. 3, fine peeling of the surface layer 3 occurred in 1939 times. In order to analyze the cause of the failure, each optical element molding die 1 was observed with an electron microscope. As a result, the surface of the mold such as glass fusion and fine irregularities on the surface layer was not confirmed. On the other hand, it was confirmed that the adhesion between the mold base material 2 and the surface layer 3 was reduced, and the surface layer 3 was peeled off from the mold base material 2.

  In addition, NO. 1-NO. When the composition analysis of each surface layer 3 of 3 was conducted, the bismuth (Bi) density | concentration of the surface layer 3 was 2.2 weight%, 16.3 weight%, and 30.0 weight% in order. That is, NO. 1 and NO. Although the bismuth (Bi) concentration contained in the surface layer 3 of 2 is slightly increased as compared with that before the start of molding, it does not change significantly even after repeated use of 1400 times or more. In other words, since a certain amount of bismuth (Bi) is contained as the first component of the surface layer 3, an equilibrium state is maintained between the glass material and the surface layer 3, so that diffusion of bismuth (Bi) is slight. It was confirmed that there was. In addition, NO. No change was observed with respect to the concentration of bismuth (Bi) contained in the surface layer 3. This is presumably because the bismuth concentration of the surface layer 3 was as high as 30.0% by weight, so that the equilibrium state was maintained and no diffusion of bismuth (Bi) from the glass material to the surface layer 3 occurred.

  From the above results, NO. 1-NO. 3 can be used repeatedly up to at least 1400 times, and even if a problem occurs due to repeated use over 1400 times, the adhesion between the mold base 2 and the surface layer 3 It was confirmed that this was not caused by a change in the composition of the surface layer 3 due to the diffusion of bismuth (Bi) or by a fusing of the glass.

  As shown in Table 2, NO. 4 and the optical element molding die 10 shown in FIG. In any of the optical element molding dies 20 shown in No. 5, no defects were observed even when used repeatedly 3000 times or more. That is, NO. 4 in the middle layer 11 and NO. 5, the injection layer 21 improves the adhesion between the mold base material 2 and the surface layer 3. 1-NO. In FIG. 3, it was confirmed that it was possible to prevent problems that were recognized after repeated use 1400 times or more.

  On the other hand, the optical element molding die of Comparative Example 1 was unusable after 103 moldings because glass was fused to the mold surface and some of the optical elements were clouded. The numerical roughness could not be confirmed from the measurement of the surface shape of the optical element. However, when the surface of the mold for molding the optical element of Comparative Example 1 was observed with an electron microscope, peeling of the outermost layer occurred starting from the fused part of the glass. It was confirmed that fogging occurred from the peeled portion of the outermost layer. In addition, elemental analysis in the depth direction of the optical element surface and elemental analysis of the outermost layer of the molding die around the part where the outermost layer was peeled off were performed by X-ray photoelectron spectroscopy (XPS). Bi) It was confirmed that the concentration was high. That is, peeling of the outermost layer occurs due to the glass being fused to the outermost layer, the mold base material exposed by peeling of the outermost layer is oxidized, and the surface roughness of the mold surface is increased. It is presumed that the fogging of the optical element occurred due to the increase in the bismuth (Bi) concentration on the surface. That is, in Comparative Example 1, the concentration of the outermost bismuth (Bi) is increased by the bismuth (Bi) diffused from the glass material at the time of press molding, and the affinity with the glass material is increased. It is thought that seizure occurred and peeling occurred.

  Further, in the optical element molding die of Comparative Example 2, the glass was fused to the mold surface and fogging was observed on a part of the optical element after 42 moldings, and the optical element molding die became unusable. Regarding glass fusion, it is considered that the bismuth (Bi) concentration in the outermost layer was as high as 31.0% by weight, and the affinity between the glass material and the outermost layer became too high. Further, when the surface of the mold for molding the optical element was observed in detail, peeling of the outermost layer occurred starting from the fused portion of the glass, and further glass fusion and fogging of the optical element were observed. It was confirmed that it was generated from the peeled portion of the surface layer. That is, peeling of the outermost layer occurs due to the glass being fused to the outermost layer, and the mold base material exposed by peeling of the outermost layer is oxidized to increase the surface roughness of the mold surface. It is presumed that clouding of the element occurred.

  Further, in the optical element molding die of Comparative Example 3, the glass was fused to the outermost layer in the first molding, and the outermost layer was peeled off starting from the fused portion of the glass in the second molding. It was confirmed that further glass fusion and fogging of the optical element occurred from the peeled portion of the outermost layer. That is, peeling of the outermost layer occurs due to the glass fusing to the outermost layer, and the roughness of the mold surface increases due to the unevenness due to peeling of the outermost layer and the oxidation of the exposed mold base material. It is presumed that clouding of the element occurred. Further, when elemental analysis of the mold surface was performed, it was confirmed that the bismuth (Bi) concentration in the outermost layer was increased.

  As described above, the NO. 1 corresponding to the optical element molding dies 1, 10, 20 of the first to third embodiments. In the optical element molding molds 1 to 5, by providing the surface layer 3, it is possible to prevent glass fusion and change in the composition of the outermost layer 3 even in repeated molding up to at least 1400 times. The resulting surface accuracy and surface roughness are not deteriorated. Furthermore, NO. In the optical element molding molds 10 and 20 of 4 and 5, by providing the intermediate layer 11 or the injection layer 21, the adhesion between the mold base material 2 and the surface layer 3 is improved, and it is possible to repeatedly mold 3000 times or more. It becomes.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included. For example, in the first to third embodiments, the surface layer is formed over the entire range of the surface of the mold base material. What is necessary is just to form in the range which a glass raw material contacts in the case of press molding.

It is sectional drawing which shows the outline of the optical element shaping | molding die concerning the 1st Embodiment of this invention. It is sectional drawing which shows the outline of the optical element shaping | molding die concerning the 2nd Embodiment of this invention. It is sectional drawing which shows the outline of the optical element shaping | molding die concerning the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10, 20 Optical element shaping | molding die 2 Mold base material 2a Molding surface 3 Surface layer 11 Intermediate | middle layer 21 Injection layer

Claims (4)

An optical element molding die used for producing an optical element by press molding a glass material containing bismuth,
Mold base material,
Of the surface of the mold base material, at least, a surface layer formed on a molding surface that is a range in which the glass material contacts in the press molding,
The surface layer contains bismuth as a first component in an amount of 1.0 wt% to 30.0 wt%, and as a second component, platinum, gold, palladium, iridium, osmium, ruthenium, rhenium, rhodium, tungsten A mold for forming an optical element, comprising at least one element or compound selected from tungsten carbide or silicon carbide. The optical element molding die according to claim 1,
One or more layers are formed between the mold base material and the surface layer, and at least one of chromium, titanium, aluminum, tungsten carbide, tungsten, silicon carbide, or nitride of chromium, titanium, or aluminum is used. An optical element molding die comprising an intermediate layer containing an element or a compound. In the optical element molding die according to claim 1 or 2,
At least on the molding surface side of the mold base material, an injection layer is formed by injecting at least one element from the molding surface among elements contained in the layer formed in contact with the molding surface. An optical element molding die characterized by the above.   An optical element produced by press molding a glass material containing bismuth using the optical element molding die according to claim 1.

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