Precision press-molding preform, process for the production thereof, optical element and process for the production of the optical element

a technology of press-molding and preforms, which is applied in the direction of manufacturing tools, instruments, lenses, etc., can solve the problems of inability to produce high-quality production, inability to achieve excellent image reproduction, and reddish image obtained, etc., to achieve stable production of optical elements, excellent near infrared absorbing function, and excellent press-molding durability

Inactive Publication Date: 2005-03-10
HOYA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0029] According to the present invention, there can be provided a precision press-molding preform which is excellent in precision press-moldability and durability and which enables the stable production of an optical element having an excellent near infrared absorbing function, etc., and a process for the production thereof.
[0030] According to the present invention, further, there can be provided an optical element that is a precision press-molded product from the above preform and a process for the production of the optical element.
[0031] There can be therefore obtained various optical elements such as

Problems solved by technology

Otherwise, an image obtained comes to be reddish, and no excellent image reproduction can be attained.
However, the above low-pass filter and the above aspherical lens have a problem that they cannot be produced highly productively when an infrared-light-absorbing glass is mechanically processed.
Since, however, a conventional near-infrared-absorbing glass contains arsenic, a large amount of P2O5 or fluorine for attaining a high transmittance at and around 400 nm, such a glass is not suitable as a glass for precision press-molding.
Arsenic involves environmental problems due to its toxicity.
Further, it exhibits very high oxidizability, so that it may damage the molding surface of a press mold used for the precision press-molding and may make it impossible

Method used

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  • Precision press-molding preform, process for the production thereof, optical element and process for the production of the optical element

Examples

Experimental program
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Effect test

example 1

[0120] Oxides, carbonates, sulfates, nitrates, phosphates, fluorides, hydroxides, etc., as raw materials for a glass were weighed in an amount of 250 to 300 g so as to obtain a glass composition having a predetermined amount ratio shown in Table 1, and these materials were fully mixed to obtain a formulated batch. The formulated batch was placed in a platinum crucible and melted in air with stirring at a temperature of 900 to 1,100° C. for 1 to 4 hours. After melted, a clarified and homogenized molten glass was cast into a 40×70×15 mm carbon mold and gradually cooled to a temperature around the glass transition temperature thereof, and immediately thereafter, the glass is placed in an annealing furnace and annealed around the glass transition temperature for about 1 hour to allow the glass to be cooled to room temperature. The thus-obtained optical glass was observed through an optical microscope to show no precipitation of a crystal.

[0121] Table 2 shows external transmittances (T4...

example 2

[0133]FIG. 2 shows a schematic cross-sectional view of a precision press-molding apparatus. A preform 4 that was obtained in the same manner as in Example 1 was placed between a lower mold member 2 and an upper mold member 1 of the precision press-molding apparatus shown in FIG. 2, and the atmosphere in a quartz tube 11 was replaced with a nitrogen atmosphere. A heater 12 was electrically powered to heat the quartz tube 11 internally. The temperature of the heater 12 was set such that the temperature inside a press mold was higher than the sag temperature of the glass by 20 to 60° C., and while the temperature was maintained, a pressing rod 13 was caused to move downward to press the upper mold member 1, so that the preform in the mold was precision press-molded. The molding pressure was adjusted to 8 MPa, and the molding time period was adjusted to 30 seconds. After the pressing, the molding pressure was decreased, and while the mold product was in a state where it was in contact i...

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Abstract

A precision press-molding preform for producing an optical element for use in an imaging device using a CCD type or MOS type solid image-sensing device, which is formed of a glass composition containing, by mol %, 25 to 45% of P205, 0.5 to 10% of CuO, 0 to 10% of B203, 0 to 10% of Al203, 2 to 30% of Li2O, 0 to 25% of Na2O, 0 to 15% of K2O, the total content of Li2O, Na2O and K2O being 3 to 40%, 3 to 45% of BaO, 0 to 30% of ZnO, 0 to 20% of MgO, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 10% of Bi2O3, 0 to 5% of La2O3, 0 to 5% of Gd2O3 and 0 to 5% of Y2O3, the total content of these components being at least 98%, and a precision press-molding preform, which is formed of a phosphate glass containing CuO, an alkali metal oxide, BaO and ZnO and having a BaO content/ZnO content molar ratio (BaO/ZnO) of greater than 1.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a precision press-molding preform (a preform for precision press-molding) and a process for the production thereof and also relates to an optical element and a process for the production thereof. More specifically, the present invention relates to a precision press-molding preform, the preform being formed of a phosphate glass and being for an optical element to be encased in an imaging device of a color VTR or digital camera using a solid image sensing device of a CCD (Charge-Coupled Device) type or MOS (Metal-Oxide-Semiconductor) type, and a process for the production thereof. And, it also relates to various optical elements formed from such preforms by precision press-molding, particularly, an optical element having a near infrared absorbing function, and a process for the production thereof. TECHNICAL BACKGROUND [0002] Conventionally, most of imaging devices of digital cameras and digital VTR cameras use CCD and MOS ...

Claims

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Application Information

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IPC IPC(8): G02B1/00C03B7/12C03B11/12C03C3/16C03C3/17C03C3/19C03C4/08G02B3/00
CPCC03B7/12C03C3/17C03B11/122Y02P40/57
Inventor FUJIWARA, YASUHIROZOU, XUELU
Owner HOYA CORP
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