JP4425071B2 - Glass material for mold press, manufacturing method thereof, and manufacturing method of optical element - Google Patents

Description

  The present invention relates to a glass material for mold press, a method for producing the same, and a method for producing an optical element. More specifically, the present invention relates to a glass material for mold press suitable for manufacturing an optical element having high optical performance, in which fusion with a mold member or uneven thickness is suppressed by a precision mold press. The present invention relates to a method and a method for producing an optical element having the above-described characteristics using the glass material.

  There is known a method of obtaining a glass optical element by softening and press molding a glass material obtained by preforming optical glass into a predetermined shape. According to this method, high-precision optical elements such as lenses and prisms can be obtained with extremely high productivity by press molding using a precision-molded mold based on the desired optical element shape. .

  As a method for manufacturing an optical element in which fusion with a mold is suppressed, for example, (1) a carbon-containing film is formed on the surface of a glass preform by pyrolysis of a hydrocarbon gas, and then the glass preform is molded. Method (for example, refer to Patent Document 1), (2) A glass blank used by press molding is immersed in an acid to reduce the alkali component content of the surface layer and to form a hydrocarbon coating layer on the surface. By forming a reactive glass layer at the interface between the mold and the glass blank to reduce adhesion (for example, see Patent Document 2), and (3) removing the surface alteration layer of the preform by etching with acid or alkali. And the method (for example, refer patent document 3) which prevents a melt | fusion by making uniform a surface layer part and an internal composition is known.

JP-A-8-217468 JP-A-4-321525 JP-A-8-333122

As a result of studying the methods (1) to (3), the present inventors have obtained knowledge as follows.
In the method of (1) described in Patent Document 1, a carbon-containing film is formed on the surface of a glass material with relatively simple equipment, thereby preventing the fusion between mold preforms to some extent. Is obtained. However, effective film formation cannot always be performed depending on the composition of the glass material or the surface state. For this reason, during press molding, there are cases where fusion cannot be prevented at the interface between the molding surface and the glass. The inventors have found that this problem is particularly remarkable when the glass material contains a considerable amount of phosphate.

  In general, a glass material used for a precision glass mold is prepared by preforming into a predetermined volume and a predetermined shape. That is, based on the volume of the optical element to be obtained by press molding, the volume of the glass material and its volume accuracy are determined. The shape to be preformed is determined based on the shape of the optical element to be obtained and / or the preformability derived from the composition of the glass to be used. For example, it can be preformed into a spherical or biconvex curved shape by dropping or flowing molten glass. When these glass materials are used for press molding, they are generally conveyed by a robot and placed on the lower mold forming surface. Further, as a method for supplying the glass material, it can be dropped and supplied onto the lower mold forming surface. In particular, when the glass material is supplied into the mold in a preheated and softened state in advance, the surface of the glass material is floated by airflow to prevent defects on the glass material surface due to contact with the conveying jig. An optical element with very high productivity and high accuracy can be obtained by transporting while maintaining the state, and dropping and supplying the state as it is onto the lower mold surface.

  When a uniform carbon-containing film with a predetermined film thickness is formed on a glass material, the glass material placed on or dropped from the lower mold forming surface has an arrangement position if the lower mold forming surface is a concave curved surface. Even if it is slightly off-center, the glass material can be automatically centered by rolling or sliding to the center. Alternatively, centering using a jig is also possible. That is, if the friction between the surface and the lower mold molding surface is sufficiently small, the glass material moves to the center of the lower mold, and a good optical element (lens or the like) can be molded by the subsequent press molding process. However, if the carbon-containing film is inhomogeneous and partially missing or the film thickness is insufficient, the glass material is placed on the lower mold with insufficient surface slipping, or the dropped glass material is It stops at a position deviated from the center, and is pressed as it is, resulting in an optical element with uneven thickness, or in some cases, the mold is damaged. In particular, when the glass material has a biconvex curved surface and / or when the shape of the lower mold forming surface is a concave curved surface with a gentle curvature, the glass material does not roll and move on the lower mold forming surface. This effect is significant because it is only.

When optical glass containing a specific glass material, especially phosphate, is used, the action of the carbon-containing film formed on the surface cannot be obtained sufficiently, and the movement of the glass material on the lower mold surface is insufficient. It was found by the present inventors that the slipperiness is poor. This effect correlates with the amount of phosphate contained, and in particular, in the case of optical glass containing 25 mol% or more in terms of P ₂ O ₅ , uneven thickness due to the above cause was noticeable.

  Insufficient surface slipperiness also affects moldability during pressing. That is, if the softened glass is insufficiently slidable with the molding surface when it is stretched by the molding surface, the extending direction becomes non-uniform, so that shape defects such as asses and habits are likely to occur.

  By the way, as a material for producing a high-precision optical element by a mold press, a material having a low refractive index and low dispersion (for example, nd is about 1.5 and νd is about 70) is used effectively. These are particularly useful for correcting chromatic aberration in an optical system for imaging equipment, and are highly evaluated as high-value-added glass. In general, as a glass material having such an optical constant, a glass material containing fluorine as a low refractive index and low dispersion component is known. However, when glass containing a considerable amount of fluorine is used in a mold press, the following problems occur. In other words, fluorine, which is a volatile component, adheres and accumulates on the molding surface of the mold, and pollutes the mirror surface of the molding surface that has been subjected to precision machining. For this reason, if the number of press shots is increased, the surface of the optical element to be molded becomes rough, and harmful effects such as spiders occur. To avoid this, the molding surface must be regenerated frequently. That is, it is not suitable for precision mold presses that do not require polishing after molding. When a glass material containing fluorine is preformed by the above-described method, there is also a disadvantage of preformability that striae easily occur on the surface of the glass material.

On the other hand, there are fluorine-containing low refractive index glass materials mainly composed of SiO ₂ , but since the softening temperature is not necessarily low enough, the glass viscosity is set to an appropriate range for mold pressing. In order to achieve this, press molding is performed at a considerably high temperature, which has a problem of deteriorating the mold and the release film formed on the molding surface. Therefore, it has been found that it is effective to use a considerable amount of P ₂ O ₅ in order to obtain low refractive index glass, which is a high value-added glass material, without containing SiO ₂ and fluorine. Therefore, it has been demanded to obtain a glass material that prevents fusion and has a sufficient surface slipperiness with a glass material made of such optical glass.

The method of (2) disclosed in Patent Document 2 does not consider the above-mentioned problem due to the glass containing phosphate, and according to the study by the inventors, the above-mentioned glass material treated with acid is sufficient. The effect was not obtained.
Further, the method (3) disclosed in Patent Document 3 does not take into consideration the fusing property which varies depending on the glass composition.

  Under such circumstances, the present invention is suitable for producing an optical element having high optical performance, in which fusion with a mold member or uneven thickness is suppressed by a precision mold press. It is an object of the present invention to provide a glass material, a method for producing the same, and a method for producing an optical element having the above characteristics using the glass material.

As a result of intensive studies to achieve the above object, the inventors of the present invention include a glass material containing phosphate glass, particularly preferably containing 25 mol% or more as P ₂ O ₅ , and fluorine. It has been found that a material containing a carbon-containing film formed by subjecting the surface of the pre-processed glass material to an alkali treatment using a material that does not substantially contain the material can be suitable for the purpose as a mold press. Based on this finding, the present invention has been completed.

That is, the present invention
(1) A glass material for a mold press, characterized by forming a carbon-containing film after subjecting the surface of a glass material containing phosphate and pre-processed to a predetermined shape to an alkali treatment,
(2) The glass material for mold press according to the above (1), wherein the glass material contains 25 mol% or more of phosphate as P ₂ O ₅ and substantially does not contain fluorine,
(3) The glass material for mold press according to the above (1) or (2), wherein the carbon-containing film is formed by thermally decomposing an unsaturated hydrocarbon compound,
(4) The glass material for a mold press according to the above (1), (2) or (3), wherein the glass material formed with the carbon-containing film has a surface free energy dispersion term ratio of 80% or more. ,
(5) A method for producing a glass material for mold press, comprising forming a carbon-containing film after subjecting the surface of a glass material containing phosphate and pre-processed to a predetermined shape to an alkali treatment,
(6) A method for producing an optical element, wherein the glass material for mold press according to any one of (1) to (4) above is press-molded in a state of being softened by heating,
(7) The heated glass material is dropped and supplied onto a lower mold forming surface of a mold having an upper mold and a lower mold, and the glass material is softened and press-molded with the upper mold and the lower mold (6 The method for producing an optical element according to item (8), and (8) The method for producing an optical element according to item (7), wherein the molding surfaces of the upper mold and the lower mold have carbon-containing release films,
Is to provide.

  According to the present invention, by a precision mold press, fusion with a mold member, uneven thickness, and the like are suppressed, and a glass material for mold press suitable for manufacturing an optical element with high optical performance and a method for manufacturing the same, In addition, a method for producing an optical element having the above characteristics using the glass material can be provided.

The glass raw material used for the glass raw material for mold presses of the present invention contains a phosphate, and the effect of the present invention is remarkable particularly when 25 mol% or more is included as P ₂ O ₅ . Also preferably, contains substantially no fluorine, further, it is preferable not to contain SiO _2.

  The glass material of the present invention preferably contains substantially no lead and arsenic. When these components are applied to a precision glass mold, they contaminate and damage the molding surface of a mirror-finished mold, and cause environmental load problems due to toxicity.

Phosphate-containing glass has a high bondability with H ₂ O, so it is easy to form a hydrated layer on the surface. The surface of phosphate glass has a higher phosphoric acid concentration than the inside (phosphate rich layer). It is thought that is formed. The present inventors considered that such a surface composition causes a different behavior from other glass materials in the pressing process.

Examples of preferable glass material of the present invention include the following glass material 1 and glass material 2. It is very useful as a low dispersion glass having an optical constant having a refractive index nd of about 1.5 and an Abbe number of about 70. Examples thereof include those having a refractive index nd of 1.4 to 1.75 and an Abbe number νd of 55 to 80. Particularly preferably, nd is 1.45 to 1.60 and νd is 55 or more. Examples are given below.
[Glass material 1]
In terms of mol%, an optical glass having P ₂ O ₅ of 40 to 70%, Al ₂ O ₃ of 8% or more, and MgO of 5% or more is preferable. Among these, P ₂ O ₅ is 45% or more, Al ₂ It is more preferable that O ₃ is 8 to 19%, MgO is 5 to 30%, nd is 1.4 to 1.6, and νd is 60 or more. Specifically, by _{mol%, 1~ P 2 O 5 45~65%} , Al 2 O 3 8~19%, 5~30% MgO, the Li ₂ O, Na ₂ O and _{K 2} O in total 25%, B ₂ O ₃ 0-16%, ZnO 0-25%, CaO 0-25%, SrO 0-25%, BaO 0-30%, La ₂ O ₃ 0-10%, Gd ₂ O ₃ 0 _{~10%, Y 2 O 3 0~10} %, Yb 2 O 3 0~10%, include 2 O 3 0~10% _Lu, and the total content of the component is 95% or more, F, As and An optical glass characterized by not containing SiO ₂ can be mentioned.
[Glass material 2]
In terms of mol%, an optical glass of P ₂ O ₅ 25% or more and BaO 20% or more is preferable, and more preferably, the total amount of P ₂ O ₅ and BaO is 65% or more, and Li ₂ O, Na ₂ The total amount of O and K ₂ O is 3% or more.

Further, it is preferable that P ₂ O ₅ is 25 to 55%, BaO is 20 to 50%, nd is 1.5 to 1.75, and νd is 55 to 70. Specifically, in terms of mol%, P ₂ O ₅ 28-50%, BaO more than 20% 50% or less, MgO 1-20%, Li ₂ O, Na ₂ O and K ₂ O in a total amount of 3% Super (however, Li ₂ O 0 to 25%, Na ₂ O 0% or more and less than 10%, K ₂ O 0 to 12%), ZnO more than 0% to 15% or less, B ₂ O ₃ 0 to 25%, Al ₂ O ₃ 0-5%, Gd ₂ O ₃ 0-8%, CaO 0-20%, SrO 0-15%, Sb ₂ O ₃ 0-1%, the total content of the above components is 98% or more An optical glass, further comprising the optical glass, wherein the BaO content is more than 42% by weight, or the BaO content is 42% by weight or less, and the amount of P ₂ O _{5 and} the amount of BaO. optical glass and the like, wherein the weight ratio of _{(P 2} O 5 / BaO) is less than 1.0

The optical glass preferably has a Dw of tertiary or higher as water resistance. More preferably, it is grade 2 or higher. This grade is determined as follows. Such water resistance makes it easy to obtain a uniform carbon-containing film while suppressing surface burns.
<Water resistance (D _W ) of powder method>
Powder glass (particle size: 420 to 590 μm) having a weight corresponding to a specific gravity of gram is put in a platinum basket and immersed in a quartz glass round bottom flask containing 80 mL of pure water (pH = 6.5 to 7.5). Treated in a boiling water bath for 60 minutes and classified into the grades in Table 1 according to the weight loss rate (wt%).

また、耐酸性Ｄ_Ａは、４級以上、より好ましくは、３級以上であることが好ましい。この特級は以下のようにして定められる。
〈粉末法耐酸性（Ｄ_Ａ）
比重グラムに相当する重量の粉末ガラス（粒度４２０〜５９０μｍ）を白金かごに入れ、それを０．０１ｍｏｌ／Ｌ硝酸水溶液８０ｍＬの入った石英ガラス製丸底フラスコ内に浸漬し、沸騰水浴中で６０分間処理し、その減量率（ｗｔ％）によって表２の級に分類。

Also, acid resistance D _A is quaternary or higher, more preferably, is preferably tertiary or higher. This special grade is determined as follows.
<Powder method acid resistance (D _A )
Powder glass (particle size: 420 to 590 μm) having a weight corresponding to a specific gravity of gram is placed in a platinum basket, immersed in a quartz glass round bottom flask containing 80 mL of 0.01 mol / L nitric acid aqueous solution, and heated in a boiling water bath. Treated for 1 minute and classified into the grades in Table 2 according to the weight loss rate (wt%).

なお、光学ガラスの耐候性は、以下の指標により評価することができる。
〈耐候性試験〉
６５℃−９０％湿度下で２平面研磨したガラスを２４０ｈｒ放置し終了後、表面状態を目視観察し、表面の白濁、またはガラス成分による液ジミ状の溶出の有無を評価する。
上記耐候性試験において、白濁、溶出が見られる光学ガラスは、常温、常湿下において放置した場合にも、表面にリン酸イオンのリッチな層が生成しやすく、後述するように、炭素含有膜の成膜に際して、均一な成膜がされにくい傾向にある。

The weather resistance of the optical glass can be evaluated by the following index.
<Weather resistance test>
The glass polished on two planes at 65 ° C.-90% humidity is allowed to stand for 240 hours, and then the surface state is visually observed to evaluate the presence of white turbidity on the surface or elution of liquid spots due to glass components.
In the above weather resistance test, the optical glass showing white turbidity and elution is likely to form a phosphate ion-rich layer on the surface even when left at room temperature and humidity. During the film formation, uniform film formation tends to be difficult.

  The glass material used in the present invention can be the above-mentioned optical glass that has been shaped into a flat plate shape, a columnar shape, a spherical shape, a biconvex curved shape, or the like and has a predetermined volume. Glass can be obtained by processing such as cold cutting and polishing, or can be obtained by hot forming by dropping or flowing molten glass into a mold. In particular, a glass material with a spherical or biconvex curved surface shape by hot forming is highly productive, and when a smooth free surface free of surface defects is obtained and supplied to the lower mold forming surface as described later. It is preferable that it can move (centering) to the center of the molding surface by rolling or sliding with its own weight or with a jig.

  FIG. 1 is an explanatory diagram showing the ease of movement in the case of barium borate-based glass or lanthanum borate-based glass having a carbon-containing film when dropped onto the molding surface, and in this case, the final width It is completely centered by the shifting operation. On the other hand, FIG. 2 is an explanatory view showing the difficulty of movement in the case of a phosphate glass having a conventional carbon-containing film (no alkali treatment) when dropped onto the molding surface. In this case, it does not slip and stops halfway, and does not move even in the final width adjustment operation.

In particular, the preforming of the biconvex curved glass material can be widely performed according to various compositions and volumes. However, the biconvex curved glass material is difficult to move to the center due to its own weight when supplied onto the molding surface. For this reason, the position correction of the glass raw material supplied on the molding surface can be performed using a jig. In particular, when a glass material is supplied by dropping, the position correction by the jig is very useful because the dropping position and the posture at the time of dropping are not constant. At this time, as in the conventional case, if the slipperiness between the molding surface and the glass material is not very good, as shown in FIG. 2, the glass material does not slide to the center even if it is moved to the center by a jig. When the jig is retracted, it is returned to the biased position in the form applied by the jig. Therefore, the present invention shows a remarkable effect when using a glass material having a biconvex curved surface shape or when supplying a molding material by dropping.
In the glass material for mold press of the present invention, the surface of the glass material 1 or glass material 2 containing phosphate and pre-processed into a predetermined shape, preferably pre-processed into a predetermined shape, is as follows. To give an alkali treatment.

[Alkali treatment]
The alkali treatment can be performed by immersing the glass material pre-processed into a predetermined shape in an aqueous solution containing NaOH and / or KOH. Preferably, a solution having a pH of 10 to 12 is used. If the pH is smaller than this, the treatment speed is decreased, which is not preferable. Within this range, the effect of selectively removing the phosphate-rich layer can be obtained. The treatment temperature is preferably 20 to 50 ° C., and the time is about 30 seconds to 5 minutes.
After immersion, a cleaning process is performed. Although there is no limitation in the cleaning treatment process, for example, the following processes: (1) ultrasonic cleaning with city water (for example, about 180 seconds), (2) ultrasonic cleaning with pure water (for example, about 120 seconds), The cleaning process can be performed by sequentially performing (3) ultrasonic cleaning with isopropyl alcohol (for example, about 120 seconds) and (4) drying with CFC vapor.
In the glass material for mold presses of the present invention, after the alkali treatment is performed on the surface in this way, a carbon-containing film is formed as follows.

[Deposition of carbon-containing film]
The carbon-containing film is formed on the surface of the glass material by using a hydrocarbon compound thermal decomposition method, a hydrocarbon compound plasma decomposition method, a vapor deposition method, an ion plating method, a sputtering method, a self-organized film formation method, or the like. However, it is preferable to form the film by thermal decomposition of an unsaturated hydrocarbon compound. Here, the unsaturated hydrocarbon compound refers to a hydrocarbon compound having one or more ethylenically unsaturated bonds or acetylenic triple bonds in the molecule. The reason why film formation by thermal decomposition of the unsaturated hydrocarbon compound is preferable is that it does not require a large-scale film formation apparatus and can form a very thin and substantially uniform film. Acetylene, which has a relatively low thermal decomposition temperature, can be suitably used. The film thickness is preferably 1 to 10 nm, and more preferably 2 to 5 nm.
The film formation can be performed as follows. A film forming container containing a glass material to be formed is evacuated to about 67 Pa or less, and an unsaturated compound gas at a predetermined flow rate is introduced in a state of being heated to a temperature equal to or higher than the thermal decomposition temperature of the unsaturated hydrocarbon compound to be used. When the predetermined pressure is reached, the heating is stopped, the introduction of gas is stopped, and the exhaust is performed. After the temperature has dropped sufficiently, the glass material is taken out.
The glass material used in the present invention contains phosphate, and particularly when a considerable amount of phosphate is contained, it has been found that imparting slipperiness by forming a carbon-containing film is insufficient. It was. Furthermore, the effect of preventing fusion was insufficient. This is thought to be because the phosphate-rich layer is formed on the surface of the glass material, which inhibits the film-forming property of the carbon-containing film.
If the carbon-containing film is repeatedly formed, or the amount of unsaturated compound to be introduced is increased to promote the formation of the carbon-containing film on the glass surface, and the thick film is formed, the glass surface becomes the carbon-containing film. Almost completely covered by. However, when the film thickness is excessively increased, the slipperiness is improved, but an optical element obtained by press molding has a spider or scratch-like appearance defect. This is presumably because the surface of the glass on which the agglomerated carbon or the carbon-containing film having a non-uniform thickness is transferred has irregularities. In the present invention, sufficient slipping and fusion prevention effects can be obtained without excessively increasing the thickness of the carbon-containing film.
The carbon-containing film according to the present invention can be removed by heat treatment after press molding of the optical element.
The carbon-containing film formed on the surface of the glass material for mold press of the present invention can be evaluated by the following method by calculating the surface free energy using a contact angle meter.

[Evaluation of carbon-containing films]
If the surface free energy of a solid or liquid is γ, it is expressed by the following equation.

γ = γ ^d + γ ^p (1)
Here, γ ^d is a solid or liquid dispersion force, and γ ^p is a solid or liquid polar interaction force. That is, in the formula (1), the surface free energy of a solid or liquid can be expressed by the sum of its dispersion force and polar interaction force. Considering the equation (1) with the surface free energy of solid: γ _s γ _s = γ _s ^d + γ _s ^p (2)
(The subscript s represents Solid). Similarly, for liquids, γ _L = γ _L ^d + γ _L ^p (3)
(The subscript L represents Liquid).

  Using two or more types of liquids (for example, two types of water and diiodomethane), the same amount is dropped on the solid, and the contact angle is measured. Next, the surface free energy is calculated from the contact angle. The calculation formula for calculation was based on the Owens-Wendt-Kaelble method.

２種類の液体のγ_Ｌ ^ｄ及びγ_Ｌ ^ｐは文献値を用いる。また、（３）式より２種類の液体それぞれのγ_Ｌを求める。
なお、水およびヨードメタンのγ_Ｌ ^ｄ、γ_Ｌ ^ｐ、γ_Ｌの文献値は、以下の通りである。

Literature values are used for γ _L ^d and γ _L ^p of the two types of liquids. Further, γ _L of each of the two types of liquids is obtained from the equation (3).
The literature values of γ _L ^d , γ _L ^p , and γ _L for water and iodomethane are as follows.

γ _L ^d γ _L ^p γ _L
Water 21.8 51 72.8
Diiodomethane 50.8 0 50.8
For example, the contact angle was determined for a carbon-containing film formed on optical glass.
As a result of the measurement, the contact angle of water was 104.9 °, and this was put into θ in the equation (4), and the other energy values were the values in the above water column.

となる。また、ジヨードメタンの接触角は７２．０°であり、これを同様に計算すると

It becomes. In addition, the contact angle of diiodomethane is 72.0 °.

上式（６）によって得られた分散項γ_ｓ ^ｄを（５）式に代入すると

Substituting the dispersion term γ _s ^d obtained by equation (6) above into equation (5)

となる。これら（６）及び（７）式の値を（２）式に代入することにより
γ_Ｓ＝２１．７６＋０．５９＝２２．３５
固体の表面自由エネルギーγ_ｓが求められ、分散項比は
γ_Ｓ ^ｄ×１００／γ_Ｓ
で求められる。

It becomes. By substituting the values of the equations (6) and (7) into the equation (2), γ _S = 21.76 + 0.59 = 2.35
The surface free energy γ _{s of the} solid is obtained, and the dispersion term ratio is γ _S ^d × 100 / γ _S
Is required.

  The dispersion term ratio means the proportion of nonpolar components constituting the surface. When the surface free energy of the glass material on which the carbon-containing film is formed is calculated, the dispersion term ratio is considered to have a substantially positive correlation with the nonpolar component, that is, the coverage of carbon. The present inventors have found that this dispersion term ratio is an index of the likelihood of occurrence of fusion and uneven thickness during press molding. As shown in Examples to be described later, when the dispersion term ratio is 80 or more, good fusing deterrence and slipperiness were obtained.

  The present invention also includes a method for producing a glass material for mold press, characterized by forming a carbon-containing film after subjecting the surface of a glass material containing phosphate and pre-processed to a predetermined shape to an alkali treatment, and There is also provided a method for producing an optical element, characterized in that the above-described glass material for mold press according to the present invention is press-molded while being softened by heating.

In the method for producing an optical element of the present invention, as described above, a glass material formed by pre-processing into a predetermined shape and subjecting the surface to an alkali treatment and then forming a carbon-containing film is produced by a known press molding apparatus. Supply and place between upper and lower molds. The temperature of the glass material at the start of press molding is preferably a temperature at which the viscosity is 10 ⁹ Pa · s or less. More preferably, it is the range of ^105.5-10 < ⁹ > Pa * s. On the other hand, the mold temperature of the upper and lower molds is preferably in a temperature range in which the viscosity of the glass material is 10 ⁷ Pa · s or more.

  The glass material may be supplied into the mold by a robot at room temperature and both may be heated at the same time, or the glass material preheated outside the mold before supply may be supplied to the preheated mold. Moreover, you may heat a shaping | molding die and a glass raw material after supply.

When supplying glass material preheated outside the mold to the preheated mold, the preheating temperature of the glass material should be higher than the preheating temperature of the mold, and press molding can be started immediately after supply. This is advantageous for shortening the molding cycle time. In this case, the preheating temperature of the mold is equivalent to 10 ⁷ to 10 ¹² Pa · s, and the preheating temperature of the glass material is preferably equivalent to 10 ^5.5 to 10 ^8.5 Pa · s. A difference may be provided. It can be determined according to the lens shape to be press-molded and the glass material.

  When preheating the glass material outside the mold, it is preferable to heat the glass material by placing it in a heating furnace for a predetermined time in a state of being floated by an inert gas. Thereafter, the softened glass material is transferred to the lower mold while being placed on the floating jig, and the floating jig is divided, whereby the glass material can be dropped and supplied onto the lower mold.

  The glass material supplied to the lower mold surface can be corrected to the center position by a jig serving as a position correction means. 3 and 4 are drawings showing an example of a positioning arm for positioning the preform with respect to the lower mold of the press molding apparatus, FIG. 3 is a front view, and FIG. 4 is an enlarged view.

  In FIG. 3, the positioning arm 300 has a long shape, and can be divided into two arm divided bodies 302 and 304 around the center line N in the width direction. The positioning arm 300 further includes six positioning blocks 310 for positioning the preform along the longitudinal direction thereof. Each positioning block 310 can be divided into two parts 312 and 314 on the center line N of the positioning arm 300. By opening and closing in parallel with the opening and closing of the arm divided bodies 302 and 304, the inner periphery of the rhomboid opening 316 is obtained. Touch the outer periphery of the preform at the surface. The arm divided bodies 302 and 304 of the positioning arm 300 are respectively attached to a pair of slide bodies 306 and 308 at one end in the longitudinal direction (left end in the figure). The slide bodies 306 and 308 are moved toward and away from each other by a driving mechanism (not shown) (in the direction indicated by the arrow in the figure), and the slide bodies 306 and 308 are opened and closed while keeping parallel to each other.

  The positioning arm 300 is preferably used by preheating, and the preheating temperature is set to a humidity that does not cause a surface defect of the preform even when it comes into contact with the preform when correcting the position of the preform as the molding target. . For example, the preheating temperature is about Tg−200 to Tg + 100 ° C., preferably about Tg−100 to Tg with respect to Tg and Ts of the glass constituting the preform.

  Moreover, as a raw material of the positioning arm 300, it is preferable that it is a thing with high heat resistance, excellent mechanical strength, and low wettability with glass, for example, a carbonaceous material is mentioned.

  FIG. 4 shows an enlarged view (a) and a closed state (b) of the arm divided bodies 302 and 304 of the positioning arm 300. In FIG. 4, the facing surfaces of the arm divided bodies 302 and 304 are defined as butt surfaces S. Positioning surfaces 402 and 404 that are in contact with the outer periphery of the preform (indicated by symbol P in FIG. 4) are formed on the side of the abutting surface S of the arm divided bodies 302 and 304, respectively. As shown in FIG. 4A, when the arm divided bodies 302 and 304 are opened, the positioning surfaces 402 and 404 face the outer periphery of the preform P that is dropped and supplied onto the molding surface of the lower mold. ing. As shown in FIG. 4B, when the arm divided bodies 302 and 304 are closed, the positioning surfaces 402 and 404 come into contact with the outer circumferences of the respective preforms P to position them. Since the positioning surfaces 402 and 404 are inclined with respect to the opening / closing direction (the width direction of the positioning arm 300), each preform P can be positioned in the longitudinal direction and the width direction of the positioning arm 300. By this positioning, the center of the preform P and the center of the molding surface of the lower mold are substantially matched.

  The positioning arm 300 is configured to wait for the preform to be dropped while the arm divided bodies 302 and 304 are opened at the operating position (that is, the position where the positioning block 310 corresponds to each molding surface of the lower mold). ing. When the preform is dropped and supplied from a transfer arm (not shown), the arm divided bodies 302 and 304 are opened and closed in parallel one to several times, and the positioning surface 402 or the positioning surface 404 (or both surfaces) is moved to each preform P. The center of the plurality of preforms P can be substantially coincided with the center of the molding surface of the lower mold at the same time.

  After the positioning of the preform is completed, the positioning arm 300 is retracted from the lower mold. After that, press molding of the preform is performed by the press molding apparatus. That is, the press molding apparatus moves the upper mold or the lower mold (or both), presses the preform on these molding surfaces, and molds an optical element having a desired shape.

A load is applied to the glass material supplied into the molding die by the approach of the upper die and the lower die, and the glass material is greatly deformed to be formed into a desired optical element shape. Simultaneously with the application of the load, cooling is started at a predetermined time point thereafter, and when the glass viscosity becomes 10 ¹¹ Pa · s or more, the upper and lower molds are separated and released. During the cooling, further load application may be performed. Preferably, the mold release temperature corresponds to a viscosity of 10 ¹² to 10 ¹³ Pa · s.

  In the present invention, when adopting a method of dropping and supplying preheated glass material to a preheated mold, it is possible to perform centering satisfactorily even using phosphate glass and to prevent fusion. Thus, a remarkable effect can be obtained.

  The mold used here can be made of, for example, silicon carbide, silicon nitride, cemented carbide or the like as a base material. Moreover, it is preferable that a mold release film is formed on the molding surface of the mold so as to promote mold release and provide slipperiness with the glass material. As the release film, a release film containing carbon is preferable, and friction with the glass material can be reduced. The carbon-containing film can be formed by using, for example, carbon or an organic material as a raw material by a sputtering method, a vacuum deposition method, an ion plating method, a plasma CVD method, or the like.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Experimental example 1
Glass materials were preformed using five types of optical glasses A to E having the compositions shown in Table 3 and the physical properties shown in Table 4, and optical elements (lenses) were obtained by press molding using these.

すなわち、上記５つの硝材を、溶融状態から滴下することによって得られた、両凸曲面形状のガラス素材に、アセチレンの熱分解による炭素含有層を成膜した。

That is, a carbon-containing layer formed by pyrolysis of acetylene was formed on a biconvex curved glass material obtained by dropping the five glass materials from a molten state.

Specifically, the inside of the reaction vessel (Bergger) was evacuated to 67 Pa or less and then heated and maintained at 480 ° C. By evacuating with a vacuum pump while flowing nitrogen gas from the gas pipe, it was kept at 21.3 kPa and purged for 30 minutes. Thereafter, the introduction of gas was stopped, and the exhaust was performed to 67 Pa. Thereafter, acetylene was continuously introduced for 100 minutes at a flow rate of 65 cm ³ / min until the pressure reached 16 kPa. After reaching a predetermined pressure, the heating was stopped, the introduction of acetylene was stopped, and vacuuming was performed. After the temperature dropped, the glass to be formed was taken out. In Table 5 below, this process was repeated twice for “2 times”.

  A biconvex lens having a diameter of 18 mm was press-molded using the glass material thus obtained. That is, the glass material is preheated to 580 to 630 ° C. outside the mold, is transported onto the lower mold forming surface using a floating jig in a softened state, and the glass material is lowered by dividing the floating dish. Drop-fed onto the mold surface. Next, the glass material was pressed between the upper and lower molding surfaces with a load of 2940 N, and when it was pushed, cooling was performed at a cooling rate of 100 ° C./min. When the temperature became equal to or lower than the glass Tg, the mold was released and the molded optical element was taken out. The mold used was a precision-worked silicon carbide base material formed by CVD, and a carbon-containing film formed by ion plating as the release film.

Glass A and glass B not containing P ₂ O ₅ had no problem in dropping supply in standard film formation. Glass C, D, and Glass E containing P ₂ O ₅ are all formed into a standard film, and the transfer jig is fused when dropped, or the lower mold surface is fused and fused after dropping. Since the lens could not be centered well even if it was shifted and pressed in a state of being shifted from the center, the obtained lens was uneven.

Since C, D and E glasses contain a large amount of P ₂ O ₅ , the weather resistance is weak, and a hydrate layer containing a large amount of phosphoric acid is eluted on the surface (results of a 65 ° C.-90% weather resistance test). For this reason, a phosphoric acid rich layer is formed on the surface at the time of storage after preforming the glass material, and this layer is considered to be insufficiently removed only by the washing step, and the coating of the carbon-containing film is insufficient.
When the film formation was doubled, the problem of poor drop supply was solved, but due to the aggregation of carbon, a poor appearance occurred in the lens after pressing.

For glass C, D, glass E glass materials immersed in a pH 11.5 solution at room temperature for 1 minute and then a carbon-containing film is formed, there is no problem with both the drop supply and the appearance after pressing even with standard film formation. A quality lens was obtained. This is presumably because the P ₂ O ₅ rich layer was removed by alkali treatment and the carbon-containing film was thin and formed uniformly.

  For the glass material after film formation, a drop of water and diiodomethane was dropped on the preform surface as a guideline for determining whether or not to supply a drop, and from the contact angle, the dispersion term ratio indicating the homogeneity of the film on the surface was calculated. It became like Table 5. It has been found that when the dispersion term ratio exceeds 80%, no problem occurs in the drop supply, and press molding is performed without any problem. These results are shown in Table 5.

なお、表５中の落下供給および外観の評価基準は、以下のとおりである。
落下供給：１０回の落下供給中、治具への融着、又は下型成形面への融着、偏肉のいずれかが１回以上発生した場合に×とした。
外観：下記のいずれかが認められた場合に×とした。
キズ・よごれ×は
・レンズ径Ｄに対して幅３０μｍ以上、Ｄ／１０以上長さのキズ状の外観不良があること
・レンズ径Ｄに対して幅３０μｍ以上 Ｄ／２０〜Ｄ／１０未満の長さのキズ状の外観不良が２本以上あること
クモリ×は
・６０Ｗの電球の前に目から１０ｃｍ離した状態でレンズを手で持ち目視でクモリが確認されること。

In addition, the evaluation criteria of the fall supply and appearance in Table 5 are as follows.
Drop supply: x is indicated when any one of fusing to the jig, fusing to the lower mold forming surface, or uneven thickness occurs at least once during the ten times of drop supply.
Appearance: x was marked when any of the following was observed.
Scratches / stains are: • There is a scratch-like appearance defect with a width of 30 μm or more and a length of D / 10 or more with respect to the lens diameter D. • With a width of 30 μm or more with respect to the lens diameter D There must be at least two scratch-like appearance defects in length. Spider X is: • The spider should be visually confirmed by holding the lens with your hand 10cm away from the front of the 60W bulb.

  The glass material for a mold press of the present invention can provide an optical element with high optical performance by suppressing fusion with a mold member or uneven thickness by a precision mold press.

It is explanatory drawing which shows the ease of the movement at the time of dropping and supplying to a shaping | molding surface about the case of the barium borate-type glass or lanthanum borate-type glass which has a carbon containing film | membrane. It is explanatory drawing which shows the difficulty of a movement at the time of dropping and supplying to the shaping | molding surface about the case of the phosphate type glass which has the conventional carbon containing film | membrane (no alkali treatment). It is a front view which shows the planar shape of the positioning arm which positions a preform with respect to the lower mold | type of a press molding apparatus. FIG. 4 is an enlarged view of the positioning arm shown in FIG. 3.

Explanation of symbols

300 Positioning arm 302, 304 Arm divided body 306, 308 Slide body 310 Positioning block 316 Opening 402, 404 Positioning surface

Claims (8)

  A glass material for a mold press comprising a carbon-containing film after an alkali treatment is performed on a surface of a glass material that includes phosphate and is pre-processed into a predetermined shape. The glass material for mold press according to claim 1, wherein the glass material contains 25 mol% or more of phosphate as P ₂ O ₅ and substantially does not contain fluorine.   The glass material for mold press according to claim 1 or 2, wherein the carbon-containing film is formed by thermally decomposing an unsaturated hydrocarbon compound.   The glass material for a mold press according to claim 1, 2 or 3, wherein the glass material formed with the carbon-containing film has a surface free energy dispersion term ratio of 80% or more.   A method for producing a glass material for a mold press, comprising: forming a carbon-containing film after subjecting a surface of a glass material containing a phosphate and pre-processed to a predetermined shape to an alkali treatment.   A method for producing an optical element, wherein the glass material for mold press according to any one of claims 1 to 4 is press-molded while being softened by heating.   The heated glass material is dropped and supplied onto a lower mold forming surface of a mold having an upper mold and a lower mold, and press molding is performed with the upper mold and the lower mold in a state where the glass material is softened. A method for manufacturing an optical element.   The manufacturing method of the optical element of Claim 7 which has a carbon containing release film on the molding surface of an upper mold | type and a lower mold | type.

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