JP3485275B2 - Mass production method of glass lens - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to an optical measuring instrument, video equipment, audio equipment, office equipment, to mass production method of an aspheric lens or a diffractive optical element which glass lens of the optical equipment parts used in the optical communication equipment .

[0002]

2. Description of the Related Art Since an aspherical lens has a characteristic that aberration can be eliminated by a single lens and a compact and high-performance lens system can be constructed, downsizing of optical equipment can be achieved. It is an essential component for higher performance. The aspherical lens manufacturing method was previously limited to the grinding and polishing method, but this method has limitations in workability and mass productivity, and increases the cost. Therefore, this method is practically used only in a limited range. There wasn't. Therefore, the appearance of an aspherical lens obtained by a press molding method which is excellent in workability and mass productivity has been strongly desired.

Further, the diffractive optical element utilizes the property of diffracting light, whereas a normal lens utilizes the property of refracting light, and Fresnel zone plates, diffraction gratings, holograms, etc. have long been known. ing. In particular, recently, it has become possible to form patterns designed by computers on quartz or glass by so-called microfabrication technology such as lithography and ion beam etching, and it is possible to realize designs with a higher degree of freedom than before. It has become. The diffractive optical element manufactured by the microfabrication technique may be particularly referred to as a binary optical element. The diffractive optical element makes it easy to correct various aberrations in a complicated optical system. For example, a collimator lens for an optical pickup of a compact disc (CD) or a mini disc (MD) drive, a lens for a laser scanner, a laser pointer, etc. The collimator lens, the microlens array, the objective lens of the optical disk head, the optical waveguide lens, the compound function lens for optical path conversion and light collection, etc. have been proposed, prototyped, or put into practical use. The pattern size of the diffractive optical element ranges from several hundreds of microns to submicrons, but micron to submicron order processing is only possible by directly processing quartz glass by microfabrication technology, so mass production at low cost is possible. The current situation is difficult. There is also a method of press-molding an optical plastic with a molding die on which an inverted image of a diffraction pattern is formed, but since the optical characteristics of plastic have a large temperature dependence, there are many problems in producing a highly accurate element. Therefore, development of a diffractive optical element obtained by press-molding glass having excellent stability is strongly desired.

In a hard disk device, which is an external storage device of a computer, the data capacity handled by a personal computer and the like is rapidly increasing, and further improvement in recording density is strongly desired. However, in the conventional magnetic recording / reproducing system, the recording density is approaching the limit, and various new magnetic recording systems have been studied and proposed. Among them, a discreet track system has recently been drawing attention. This is, for example, Nikkei Electronics magazine, No. 586 (19
(Published 93.7.19) This is described in detail in a paper entitled "Development of Technology for Increasing Hard Disk Drive Capacity to that of Optical Disks" on pages 169 to 182. However, in a conventional flat substrate, leakage that occurs from the side of the head gap. Although there was a limit to the track pitch due to extra recording in the track-to-track area due to the magnetic field, by providing a groove between the recording tracks of the hard disk, the influence of the leakage magnetic field is prevented and the track pitch is increased. It is to increase the recording density. This system requires a magnetic recording medium in which grooves are regularly engraved by repeating about 1 to several μm, that is, a substrate of the magnetic recording medium with grooves.
There are various possible methods for producing such a grooved substrate, but if it is possible to press a glass flat plate with a molding die (male mold) that is precisely processed into a predetermined shape and has excellent durability, it will lead to industrial productivity. It is expected to be an excellent method for manufacturing a grooved magnetic recording medium substrate, and its realization is strongly desired.

As described above, it seems certain that the press molding method will continue to be used as an important technique for molding glass products. Glass lenses are currently used on the industrial scale by the press molding method. Molding of glass lenses by the press molding method is performed by press molding glass heated to a temperature showing an appropriate viscosity with a molding mold that has been precisely processed into a female mold of a predetermined shape, that is, the lens shape of the product. Then, the molding surface of the molding mold is transferred. Since the state of the molding surface is transferred to the glass lens, the material of the molding mold must be thermally stable at the glass molding temperature, yet have sufficient rigidity at that temperature so that it will not be deformed by the molding pressure. In addition, the molding surface must be capable of being processed to optical surface accuracy, and the surface state must not change even by repeated pressure molding. In order to satisfy such requirements, it is necessary to configure the mold with a material having excellent heat resistance, a dense structure, and low reactivity with the molding atmosphere gas and glass. Various hard films made of alloys, various high temperature heat resistant ceramics or the like or hard films formed on a substrate have been proposed. For example, Japanese Patent Laid-Open No. 3-
In 12331, a mold made of a ceramic sintered body containing chromium oxide and zirconium oxide as main components is disclosed. In JP-A-2-199036, an i-carbon film is formed on the surface of a SiC substrate by an ion plating method. A formed mold is disclosed.

[0006] These existing molds have excellent durability under the condition that the molding temperature is less than 600 ° C in glass lens molding, and the surface condition thereof hardly changes even after repeated molding for several thousand times or more. Shows. However, for example, in molding a barium-containing borosilicate optical glass having a high refractive index and a low dispersion such that the molding temperature exceeds 600 ° C., the surface of the mold is rapidly deteriorated with these existing mold materials. Problems such as roughness and adhesion of glass and mold occur. The situation is the same when submicron processing is required, such as a diffractive optical element or a substrate of a discrete track type magnetic recording medium. No matter which mold material is used, the material forming the surface of the mold is There is a problem of deterioration, and it cannot withstand repeated molding of tens of thousands of times. In particular, in a mold having a groove of micron to submicron, the mold surface is damaged and worn around the corner portion of the groove, and the mold is less deteriorated than in the case of press molding of an article having a smooth surface like a lens. It tends to progress rapidly.
For this reason, there is a problem that the life of the mold becomes a bottleneck and the manufacturing cost cannot be reduced.

A molding die having a molding surface made of an alloy of a noble metal may be difficult to be fused with glass, but it is insufficient as a long-life mold because of its low hardness and low yield stress.

[0008] The present invention has been made to solve the problems of the production method of an aspheric lens or diffractive optical element which glass lens as described above, the purpose is the properties required for the particular application owned by, and excellent in mass production, Ru near to provide a production method of inexpensive glass lenses.

[0009]

SUMMARY OF THE INVENTION The present inventors
As a result of conducting studies to achieve the objective, the present invention has been achieved.
It was

[0010] An object of the present invention is to pressure molding by mold a glass preform heated softened
Is a method of mass-producing glass lenses by repeating
Thus, the pressure molding is a hydroxyl group contained in the glass structure.
And the total amount of water molecules is 55 ppm or less in terms of water molecules.
Using a glass preform, precisely shape this into the lens shape
The above-mentioned molding is performed by putting it in a processed mold and applying pressure.
Characterized by transferring the molding surface of the mold
It was achieved by the method of mass producing glass lenses .

First, the process leading to the completion of the present invention will be described.

Since the damage to the mold is directly caused by the fusion between the glass surface and the molding die at the time of molding, the present inventors have examined the fusion mechanism between the glass and the mold. As a result, (1) water is released from the glass structure near the pressing temperature, and (2) this water oxidizes the non-oxide mold surface,
(3) Further, the glass modifying component in the glass, particularly the cations of the alkali metal and the alkaline earth metal, move to the glass-type interface, and (4) as a result, the glass modifying component It was found that a new glass forming reaction occurs between the oxidized mold surface and the forming glass due to the action of cations and water, and the glass phase at the interface fuses the mold and the forming glass.

The fusing mechanism will be further described. Generally, glass contains hydroxyl groups and water on both the surface and the inside thereof. The desorption behavior of water from glass is traced by heating BaCD5 glass (softening temperature of about 600 ° C), which is a typical barium-containing borosilicate glass, and mass spectrometric analysis of gas components desorbing at each temperature. Then, there is an initial desorption peak at around 120 to 200 ° C, then a small amount of continuous desorption continues to around 500 ° C, and a rapid and large amount of desorption from around the softening temperature of 600 ° C. To be observed. It is presumed that desorption of water adsorbed on the surface at around 120 to 200 ° C is due to condensation dehydration of hydroxyl groups on the surface (mostly hydroxyl groups bonded to Si, that is, silanol groups) up to around 550 ° C. On the other hand, a large amount of desorption from around the softening temperature occurs at a temperature at which the glass structure becomes soft and ions and molecules easily move, so that the hydroxyl groups fixed in the glass structure and the incorporated water molecules are It is thought to be due to movement to the surface and desorption. Such rapid desorption of water from around the glass softening temperature is not limited to BaCD5 glass,
It is also observed in other borosilicate glasses, lanthanum glasses, phosphate glasses, etc., and is considered to be a very general phenomenon in oxide glasses. When the amount of desorbed water was quantified for the BaCD5 glass by the Karl Fischer method, it was 10 ppm (weight) or less in the low to medium temperature range, which is considered to be due to the adsorbed water and surface hydroxyl groups, whereas the glass at 650 ° C. It was found that the desorbed water from the structure reached 80 to 100 ppm.

The press molding of ordinary glass is carried out in an inert atmosphere such as nitrogen gas or a weak reducing atmosphere such as forming gas in order to prevent oxidation of the molding die. In particular, at high temperatures, the oxidizing effect is strong, so that the effect of the antioxidant atmosphere during press molding is offset. In particular, the amount of water desorbed near the softening temperature increases the oxygen partial pressure on the surface of the mold due to its large amount, and since the temperature is high, it is believed that the function of oxidizing the mold is particularly strong. In order to confirm this, BaCD5 glass and various mold materials were laminated in a plate shape, heat-treated at 600 ° C. in nitrogen gas having a residual water content of 3 ppm or less, and cooled, and then the contact interface was analyzed by an analytical electron microscope. . As a result, CVD
On the surface of the high-purity SiC mold by the method, a new amorphous layer, which was not observed in the sample before the heat treatment, was considered to be an oxide, and a reaction layer was formed at the interface between this amorphous layer and BaCD5 glass. It was found that another amorphous layer that seems to be formed was formed. Further, as a result of elemental analysis, only silicon and oxygen were detected from the oxide layer on the mold surface, while the main modifying components of BaCD5 glass such as barium and lithium were detected from the reaction layer, and the concentration thereof was BaCD5 glass. The concentration was higher than in the bulk. ESCA analysis of a sample obtained by similarly heat-treating BaCD5 glass alone revealed that the concentrations of Ba and Li on the glass surface were higher than those in the glass bulk. However, when the heat treatment was performed at 500 ° C. or lower, no concentration of Ba or Li on the mold surface was observed.

From the above results, the above-mentioned fusion bonding mechanism was recalled. In actual press molding, since the glass is pressed against the mold by the pressure of the glass, it is considered that the fusion between the glass and the mold is further promoted. Therefore, if fusion of the mold and glass would occur by such a mechanism, it may be possible to prevent fusion of both by eliminating the desorption of water from the glass, and further research was conducted.

As a result, in the glass lens obtained by press molding the heat-softened glass preform with a molding die, the total amount of hydroxyl groups and water molecules contained in the structure of the glass lens is When converted to 50 ppm or less, (1) the glass lens has a higher light transmittance in the infrared region than conventional products, and is suitably used as an aspherical lens or a diffractive optical element , (2) The present inventors have found that the glass lens has excellent mass productivity and is inexpensive.

Further, in the method of mass- molding a glass lens by press-molding a heat-softened glass preform with a molding die, the total amount of hydroxyl groups and water molecules contained in the glass structure is 55 ppm or less in terms of water molecules. The present inventors have found that by using a reform, a glass lens having the characteristics suitable for each use as described above can be mass-produced and obtained at a low cost.

By the mass production method of the glass lens of the present invention
In the obtained glass lens , the total amount of hydroxyl groups and water molecules contained in the structure of the glass lens is preferably 50 ppm or less in terms of water molecules. The reason is that if it exceeds 50 ppm, not only the absorption due to the hydroxyl group and water near the wavelength of 1400 nm becomes large, the light transmittance in the infrared region becomes low, and the corrosiveness with respect to metal becomes high, but also glass mold and is easily fused, while the mold is damaged by the few press molding times, if it is 50ppm or less, without the above problems, suitable for non-spherical lens or a diffractive optical element which the particular application This is because a glass lens having the above characteristics can be mass-produced and provided at a low cost. The total amount of hydroxyl groups and water molecules contained in the glass lens structure is 10 pp in terms of water molecules.
It is particularly preferably m or less.

Meanwhile, in the production method of the glass lens of the present invention, the hydroxyl group is to produce a glass lens by press molding by mold a glass preform heated softened, contained in the structure of the glass preform and The total amount of water molecules is limited to 55 ppm or less in terms of water molecules. The reason is that if it exceeds 55 ppm, not only the glass and the mold are easily fused and the mold is broken by a small number of press moldings, but also the obtained glass lens contains a large amount of hydroxyl groups and water, become light transmittance is low in, and since corrosive increased to metals, to crack suitability loss of an aspherical lens or a diffractive optical element with respect to, is not more than 55 ppm, no above problems The reason is that the optical products suitable for the above-mentioned individual applications can be mass-produced at low cost. The total amount of hydroxyl groups and water molecules contained in the structure of the glass preform is particularly preferably 15 ppm or less in terms of water molecules.

In the glass lens mass production method of the present invention, as a glass preform, a gas is circulated and bubbled through the glass melt during glass melting to evaporate water molecules together with the gas to reduce the amount of water. It is preferable to use a glass preform. Gases that are distributed or bubbled include fluorine gas, chlorine gas, C
Halogen atom-containing gases such as Cl ₄ and SOCl ₂ are particularly effective. By passing these gases through the glass melt heated to a low viscosity of about 10 ² poise for a predetermined time, the total amount of residual hydroxyl groups and water molecules is increased. Can be 55 ppm or less. As gas, oxygen gas, carbon dioxide gas,
When an inert gas (nitrogen gas, argon gas, etc.) is used, the effect of dehydration is inferior to that of the halogen atom-containing gas, but the total amount of residual hydroxyl groups and water molecules can be reduced to 15 ppm or less.

An example of the effect of reducing the amount of water in the glass due to gas flow and bubbling during glass melting will be described below.

At the time of melting the glass, a BaCD5 glass plate dehydrated by flowing and bubbling a halogen gas and a high-purity SiC plate by the CVD method were superposed on each other, and the residual water content was 3 pp.
heat treatment at 600 ° C in a nitrogen atmosphere of m or less, cooling,
ESCA analysis was performed on the collected sample. As a result, in the case of dehydrated BaCD5 glass, normal undehydrated BaC
It was found that unlike the case of D5 glass, almost no oxidation of the SiC surface occurred. Ordinary non-dehydrated Ba
In CD5 glass, the glass and SiC were often fused even after heating and cooling, but in the case of dehydrated BaCD5 glass, fusion with SiC was not observed at all, and water in the glass structure was not recognized. Alternatively, it has been shown that glass and mold fusion can be significantly reduced by reducing the amount of hydroxyl groups. The amount of water desorbed from the dehydrated BaCD5 glass at 600 ° C. was measured by the Karl Fischer method,
It was 2 ppm or less. This result shows that by using dehydrated glass, fusion between the mold and the glass in press molding can be reduced, and thereby damage to the mold can also be reduced.

If water is present in the atmosphere during press molding, even if dehydration from the glass is suppressed, the mold surface is oxidized by the water in the atmosphere, resulting in fusion between the mold and the glass. In order to prevent this, in the glass lens mass production method of the present invention, it is preferable to suppress the residual water content in the atmosphere during press molding to 50 ppm or less. The reason is that when the content is 50 ppm or less, the airtightness of the press molding apparatus and the atmosphere gas supply system is improved, and the residual water content of the atmosphere gas can be reduced.

As the glass lens of the present invention, in addition to various aspherical lenses, a Fresnel zone plate, a diffraction grating, a hologram, a collimator lens for an optical pickup of a compact disc (CD) or a mini disc (MD) drive, and a laser scanner. lens, a collimator lens, such as a laser pointer, a microlens array, an objective lens of an optical disk head, the optical waveguide lens, etc. diffractive optical element such as an optical path conversion and multi-functional lens for collecting light Ru mentioned.

In the production of a diffractive optical element that requires the transfer of a fine pattern, a substrate such as quartz glass or various heat-resistant alloys, which has been processed in advance as a mold, is coated with a thin film of various materials. Things are available. A wide variety of materials can be selected for the coating layer. Typical examples are MgO, Al ₂ O ₃ , TiO ₂ , and Cr.
₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , In ₂ O ₃ , SnO ₂ ,
Oxides such as HfO ₂ , Si ₃ N ₄ , SiC, and transition metals, particularly nitrides, carbides, borides, etc. of elements of Groups 4 and 5 of the Periodic Table.

[0026]

EXAMPLES The present invention will be described in more detail with reference to examples. Example 1, Comparative Example 1 About 10 kg of BaCD5 glass, which is a kind of optical barium-containing borosilicate glass with low dispersion and high refractive index, was melted in a platinum crucible at 1300 ° C. for 30 minutes, and carbon tetrachloride was used with oxygen gas as a carrier. The dehydrated glass was produced by circulating and bubbling through a quartz pipe into the glass melt. Carbon tetrachloride is stored as a liquid in a container at room temperature, and oxygen gas is flowed into the glass melt at a rate of 1 liter per minute to send it into the glass melt. A glass preform was produced from the cooled glass. 68 this preform
The glass preform was heated to 0 ° C. at a temperature rising rate of 10 ° C./min and the water content in the glass preform was measured by the Karl Fischer method (here, “water content” means the total amount of hydroxyl groups and water molecules).
The same applies below. ) Was determined to be 7 ppm (Example 1). For comparison, a glass preform was prepared from normal BaCD5 glass having a water content of 95 ppm which was not dehydrated (Comparative Example 1).

These glass preforms were prepared as described in JP-A-3-
The lens was repeatedly molded under the following conditions by placing it in a mold made of a chromium oxide sintered body in which zirconium oxide described in 12331 was dispersed. Molding conditions: Molding temperature 650 ° C. Molding pressure 10 MPa Pressurization time 20 seconds Atmosphere Nitrogen (residual water content 7 ppm)

When the glass preform of Example 1 was used, no roughening of the mold surface was observed after repeated molding over 20,000 times. On the other hand, when the glass preform of Comparative Example 1 was used, the glass adhered to the molding die in the first press and the surface of the molding die after peeling the glass was the sintered body particles forming the molding die. The surface of the mold was roughened due to the falling off, and molding was impossible. The water content of the glass lens molded in Example 1 was measured and found to be 5 ppm.

Further, these glass lenses were processed into a flat plate having a thickness of 10 mm, and the spectral transmittance in the wavelength range of 200 to 2500 nm was measured. The results are shown in FIG. 1. Although the glass of Example 1 has no absorption around 1400 nm, the conventional glass of Comparative Example 1 shows a decrease in transmittance of about 2% near 1420 nm and around 2000 nm. Therefore, the decrease in the transmittance on the long wavelength side was larger than that of the glass of Example 1.

Examples 2 to 11 and Comparative Examples 2 to 3 Various kinds of dehydrated BaCD5 glass obtained by dehydrating BaCD5 glass at various melting temperatures, gas species and gas circulation times shown in Table 1 were obtained. A preform was produced and repeatedly molded under the same molding conditions as in Example 1. In the dehydration treatment, SOCl ₂ was held in a container at room temperature as a liquid, and oxygen gas as a carrier gas was allowed to flow therethrough at a predetermined flow rate and sent into the glass melt.
The state of the mold surface was observed every 100 presses, and when a small chip was found on the mold surface, it was considered that the mold was broken,
The number of presses at the time of observation before that was taken as the number of presses in which the mold was broken. As is clear from Table 1, the life of the mold exceeds 28,000 times when the residual water content in the preform is 10 ppm or less (Examples 3, 4, 5, 10 and 1).
1), 50pp even if the residual water content exceeds 10ppm
If m or less, a mold life of 10,000 times or more was obtained (Examples 1, 6, 7, 8, 9). On the other hand, in Comparative Examples 2 and 3 in which the residual water content exceeded 70 ppm, in both cases, the mold and glass were fused at an extremely early stage and the mold was broken. Further, the water contents of the glass lenses obtained in Examples 2 to 11 are 11, 7, 5, 3, 35, 36, 40, respectively.
It was 40,6,5 ppm.

[0031]

[Table 1]

Examples 12-15, Comparative Examples 4-5 Using the same glass preforms used in Example 1,
A molding die in which an i-carbon film is formed on the surface of a SiC base material by an ion plating method described in JP-A-2-199036 is used, and the molding atmosphere is the same as in Example 1 except for the molding atmosphere. The press forming was repeated as described above.

As shown in Table 2, the life of the mold is 600 when the residual water content in the molding atmosphere is 50 ppm or less.
It is as long as 0 times or more (Examples 12 to 15), while 50p
It has become clear that when it exceeds pm, the life of the mold is significantly shortened (Comparative Examples 4 and 5). Examples 12 to 15
The water content of the glass product obtained in
It was 13 ppm.

[0034]

[Table 2]

Example 16, Comparative Example 6 A metal chrome disk having a diameter of 2.5 inches (63.5 mm) and a thickness of 10 nm, which was flat-processed to have a flatness of 5 μm and a surface roughness (Rmax) of 0.1 μm, and had a width of 10 nm. 1.4 μm, height 0.
Grooves of 2 μm were formed by etching in a concentric pattern with a pitch of 2 μm. This was heat-treated in air at 650 ° C. for 30 minutes to form a film of chromium oxide on the surface to obtain a molding die.

A disk (diameter: 2.5 inches, polished from an aluminosilicate glass treated under the same dehydration conditions as in Example 1 except that the glass melting temperature was 1500 ° C. was polished to a surface roughness (Rmax) of 0.05 μm. A thickness of 1 mm) was produced (Example 16). The residual water content of this glass is 9 pp
It was m. For comparison, a disk having the same surface roughness and dimensions as in Example 16 was prepared from a normal aluminosilicate glass that had not been dehydrated (Comparative Example 6).

A mold having a chromium oxide film was backed up with a silicon nitride sintered body, and the glass disk was press-molded under the following conditions. Molding conditions: Molding temperature 850 ° C. Molding pressure 20 MPa Pressurization time 20 seconds Atmosphere Nitrogen (residual water content 7 ppm)

In Example 16 in which dehydrated glass was molded, surface roughness of the molding die and adhesion of glass were not observed even after molding was repeated 20,000 times or more. Further, when the glass surface formed after repeating 20,000 times was observed with a scanning electron microscope, a width of 0.6
grooves with a depth of 0.2 μm and a pitch of 2 μ are formed,
It was confirmed that there were no defects such as chipping and defective depth. The water content of the glass product obtained in Example 16 was 8 ppm.
Met. On the other hand, Comparative Example 6 using glass not dehydrated
In the third molding, adhesion of the mold and glass over the entire surface occurred, and also in the molded glass, the surface was minutely chipped from the first molding.

Example 17, Comparative Example 7 Flatness was 5 μm, surface roughness (Rmax) was 0.1 μm, and the surface was polished and polished, and metal chromium was vapor-deposited on SiC formed by a CVD method with a diameter of 25 mm and a thickness of 10 nm to form a positive type. A resist was applied, and an inverted pattern of micro Fresnel lenses was formed on the SiC surface by the steps of EB exposure, development, chromium etching, resist stripping, and SiC etching by RIE. The pattern depth is 1 μm, and the pitch is 10 μm at the minimum. An i-carbon film having a thickness of 70 nm was formed on this surface by an ion plating method to obtain a molding die.

The same dehydrated BaC used in Example 1.
D5 glass (Example 17) and the same non-dehydrated BaCD5 glass (Comparative Example 7) as in Comparative Example 1 were prepared, and this was repeatedly molded under the following pressing conditions using the above-mentioned molding die. Molding conditions: Molding temperature 650 ° C. Molding pressure 20 MPa Pressurizing time 20 seconds Atmosphere Nitrogen (residual water content 7 ppm)

In Example 17 in which dehydrated glass was molded, surface roughness of the molding die and adhesion of glass were not observed even after molding was repeated 20,000 times or more. Further, when the glass surface formed after repeating 20,000 times was observed with a scanning electron microscope, it was confirmed that the pattern was satisfactorily transferred over the entire surface of the glass and that there were no defects such as chipping and defective depth. . The water content of the glass product obtained in Example 17 was 7 ppm. On the other hand, in Comparative Example 7 using the glass that had not been dehydrated, the mold and the glass were entirely attached to each other in the sixth molding, and the molded glass also had fine chipping on the surface from the first molding. Was.

Further, a Cr underlayer, C
Sputter coat the oCrPt magnetic layer at room temperature to 250 ° C
The stability of the coat layer was examined by applying the heat cycle of 5 times. No alteration was observed in the sample using the substrate of Example 17, but small swells of several tens nm in size were observed on the film surface in the sample using the substrate of Comparative Example 7.

[0043]

The effects of the present invention will be described below.

That is, according to the present invention, an aspheric lens
Mass production method of glass lenses with excellent effects in terms of mass productivity and price, which enables production of glass lenses having characteristics suitable for individual applications such as lenses and diffractive optical elements without damaging the molding die for a long period of time. Was provided.

[Brief description of drawings]

FIG. 1 is a spectral transmittance curve diagram of glass lenses obtained in Example 1 and Comparative Example 1.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuaki Hashimoto 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Hoya Co., Ltd. (56) References JP-A-6-67198 (JP, A) Kai 59-199546 (JP, A) JP 64-28245 (JP, A) JP 61-132526 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C03B 11 / 00,11 / 16 C03C 3/00

Claims (4)

(57) [Claims] 1. A glass is prepared by repeatedly press-molding a heat-softened glass preform with a molding die.
A method for mass-producing lenses , wherein the pressure molding uses a glass preform in which the total amount of hydroxyl groups and water molecules contained in the glass structure is 55 ppm or less in terms of water molecules ,
Put this in a mold that has been precisely processed into the shape of the lens, and add
Transferring the molding surface of the mold by pressing
Characterized in that it is carried out by mass production <br/> method of a glass lens. 2. The mass production method for a glass lens according to claim 1 , wherein a glass preform having a total amount of hydroxyl groups and water molecules contained in the structure of 15 ppm or less in terms of water molecules is used. The 3. A pressure molding and performing in the following non-oxidizing atmosphere water content 50ppm claim 1 or
2. A method for mass producing glass lenses according to 2 . 4. As the glass for the glass preform, a glass in which a halogen atom-containing gas, an oxygen gas, a carbon dioxide gas, or an inert gas is circulated in the melted glass melt at the time of melting the glass preform. The method for mass-producing glass lenses according to any one of claims 1 to 3 , which is characterized in that.