JP2002234742A - Forming die for optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming die for an optical element which is high in productivity which forms optical glass material forming an optical element used for optical pickup and optical communication, etc., by heating and pressing. SOLUTION: This forming die for optical element is constituted in such a manner that a cylindrical frame die 6 which is positioned on an inner peripheral surface of body mold 1 between a static die 2 and a sliding die 4 in the forming die and forms a side surface of the optical element 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for an optical element for heating and pressing an optical glass material for forming an optical element used for an optical pickup or optical communication.

[0002]

2. Description of the Related Art Conventionally, as a molding die for forming an optical element used for an optical pickup, an optical communication or the like, a stationary mold 2 is inserted and fixed at a lower end side of a cylindrical body mold 1 as shown in FIG. An optical glass material 3 for forming an optical element is arranged on a stationary mold 2,
The sliding die 4 was inserted from the upper end side of the body die 1 and slid vertically.

[0003]

However, when such a molding die is used, when the stationary die 2 or the sliding die 4 is inserted into the body die 1, the clearance between them is 0.0.
Since it is about 06 mm to 0.01 mm, the outer peripheral portion of the upper end surface of the stationary mold 2 and particularly the outer peripheral portion of the lower end surface of the sliding die 4 surrounded by a broken line may come into contact with the upper and lower end surfaces of the body die 1 and be damaged. There is a need to be careful with its handling,
In particular, the sliding mold 4 which is removed from the barrel mold 1 when disposing the optical glass material 3 before molding or taking out the optical element after molding has a very large number of opportunities to insert it into the barrel mold 1, thereby increasing the productivity of optical elements. Had a significant impact.

Therefore, the present invention solves such a problem,
An object of the present invention is to provide a molding die for an optical element having high productivity.

[0005]

In order to achieve this object, the invention according to the first aspect of the present invention is particularly directed to an optical element which is positioned between a stationary type and a sliding type on the inner peripheral surface of a barrel type. The outer peripheral end portions of the stationary mold and the sliding mold become non-molded portions of the optical element, and the productivity of the optical element can be improved.

According to a second aspect of the present invention, a predetermined space is provided between the lower surface of the sliding die and the upper end surface of the frame die when the sliding die is lowered to form a predetermined molding space. Therefore, it is possible to suppress the generation of bubbles generated at the time of molding the optical element.

According to a third aspect of the present invention, the thermal expansion coefficient of the body type is set smaller than the thermal expansion coefficients of the stationary type, the sliding type and the frame type. Due to the difference, the adhesion between the stationary mold, the sliding mold and the frame mold and the body mold into which these are inserted during molding is increased, and the displacement of the molding space due to the molding pressure can be suppressed.

According to a fourth aspect of the present invention, in particular, the body is formed of a glass ceramic, and the same effects as those of the third aspect can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. It is to be noted that the same configuration as the above-described conventional one is denoted by the same reference numeral and described.

FIG. 1 shows an optical element 5 used for an optical communication device, an optical pickup, or the like, which is formed by molding glass, resin, or the like. The optical element 5 has a lens portion 5a for processing an optical signal with its upper and lower surfaces curved outward at a central portion. It has a structure in which a flange portion 5b to be used is formed.

Next, when the optical element 5 is molded, it is heated and pressed using a molding die as shown in FIG. The molding die is basically a cylindrical die 1 made of a super steel, and a stationary die 2 made of a cylindrical super steel and inserted from the lower end of the die 1 and fixed to the die 1. And a sliding die 4 which is also made of a columnar super steel and is slidably inserted from the upper end side of the trunk die 1.

As shown in FIG. 3, the optical glass material 3 is placed on the molding surface of the stationary mold 2 inserted and fixed to the lower end side of the barrel mold 1 and heat is applied to the mold so that the temperature range in which the optical glass material 3 can be molded is determined. At this point, the sliding mold 4 is lowered as shown in FIG.
Is formed into a predetermined shape by pressure, and after cooling to the transition point of the optical glass material 3, the sliding mold 4 is raised to take out the molded optical element 5 from the inside of the molding die.

In this molding die, as shown in FIG. 3, a cylindrical frame die 6 made of super steel is provided on the stationary die 2, and the outer peripheral surface of the frame die 6 is a trunk die. 1 is positioned by abutting the inner peripheral surface of the first.

As shown in FIG. 4, the frame mold 6 forms the side surface of the optical element 5 on the inner peripheral surface thereof.
Further, the productivity of the molding die is improved.

That is, by arranging the frame mold 6 in the body mold 1 and molding the side surface of the optical element 5, the stationary mold 2 and the sliding mold 4 outside the molding space of the optical element 5 shown in FIG. The outer peripheral end of the molding surface of the stationary mold 2 or the sliding die 4 becomes a non-molded portion of the optical element 5 as described above. Even if the outer peripheral edge of the upper surface of the stationary die 2 or the outer peripheral edge of the lower surface of the sliding die 4 is damaged when the dies are inserted into the body die 1, the damage affects the molding of the optical element 5. Not,
As a result, the stationary mold 2 and the sliding mold 4 can be easily inserted into the body mold 1, and the productivity of the optical element 5 can be improved.

As shown in FIG. 4, the sliding die 4 is lowered, and the lower surface of the large-diameter portion 4a provided at the upper end of the sliding die 4 comes into contact with the upper end surface of the barrel die 1 so that the predetermined optical element 5 When the molding space is formed, that is, when the sliding die 4 reaches the lowest point in the molding die, a minute space is formed between the molding surface which is the lower end surface of the sliding die 4 and the upper end surface of the frame die 6. Frame 6
By setting the thickness of the sliding die 4, when the sliding die 4 is set at the lowest point as described above, the sliding die 4 and the frame die 6 are not in contact with each other, so that breakage of the molding die during molding can be suppressed, and This gap 7
Is present, unnecessary gas in the molding space can be released from the gap 7 to the outside of the molding die, and generation of bubbles in the optical element 5 can be suppressed.

The thickness of the gap 7 is 0.050 mm
By setting the thickness to about 0.250 mm, even if the optical glass material 3 penetrates into the gap 7 during molding and burrs occur on the optical element 5, if the burrs have such a thickness, the burrs are extremely small in strength and after molding. When the optical element 5 is taken out, the optical element 5 is naturally taken out and does not hinder production.

Further, in such a molding die, at the time of molding, a trunk die 1 and a stationary die 2 and a sliding die 4 inserted therein.
In order to enhance the integrity of the frame mold 6, it is desirable to set the thermal expansion coefficient of the body mold 1 to be smaller than the thermal expansion coefficients of the stationary mold 2, the sliding mold 4 and the frame mold 6. At the time of molding, the adhesion between the stationary mold 2, the sliding mold 4, and the frame mold 6 and the body mold 1 into which these are inserted is enhanced, and the displacement of the molding space due to molding pressure can be suppressed.

In practice, the stationary mold 2, the sliding mold 4 and the frame mold 6 are made of tungsten carbide having a thermal expansion coefficient of about 50 × 10 ^-7, which is a kind of the same steel so that the thermal expansion coefficients are equal. And the body mold 1 has a thermal expansion coefficient of about -1 × 10 ⁻⁷ to 30 × 10 ^{−7, which} is smaller than tungsten carbide.
A glass ceramic containing TiO ₂ as a main component and about 3% to 10% of TiO ₂ is used.

This is because tungsten carbide does not easily adhere to glass or plastic used as the optical glass material 3, has a high atomic density, has a high shape accuracy and a high surface finish accuracy, and is suitable for molding the optical element 5. And that the glass ceramic has the same strength and shape accuracy as super steel, has a thermal expansion coefficient higher than that of tungsten carbide, and has a low thermal expansion, so that the displacement of the sliding shaft of the sliding mold 4 can be reduced. It can be suppressed.

When it is desired to increase the degree of parallelism between the upper and lower surfaces of the optical element 5 shown in FIG. 1, the sliding mold 4 is brought into contact with the barrel mold 1 as shown in FIG. By using the constant stroke pressing method, the displacement of the sliding mold 4 due to cooling can be suppressed because the thermal expansion coefficient of the body mold 1 is low, and the parallelism of the optical element 5 can be increased. When it is desired to improve the transferability of the molding surface of the lens, the pressing force on the optical glass material 3 is made constant instead of using the constant stroke press method in which the lowermost point of the sliding die 4 is determined by the contact with the barrel die 1. By using the constant pressure press method, the molding surface of the sliding die 4 is kept in close contact with the optical glass material 3 in the cooling stage, so that the transferability of the molding surface can be improved.

[0022]

As is apparent from the above description, according to the present invention, in particular, a cylindrical frame which is positioned between the stationary mold and the sliding mold on the inner peripheral surface of the body mold and forms the side surface of the optical element. A mold is provided, and the outer peripheral end portions of the stationary mold and the sliding mold become non-molded portions of the optical element, so that the productivity of the optical element can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical element according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a molding die of the optical element.

FIG. 3 is a sectional view of the molding die.

FIG. 4 is a sectional view showing a molding state of the molding die.

FIG. 5 is a sectional view of a conventional molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body type 2 Static type 3 Optical glass material 4 Sliding type 5 Optical element 6 Frame type

Claims (4)

[Claims] 1. A molding die for molding an optical element by heating and pressing an optical glass material, wherein the molding die is inserted into and fixed to a lower end of the cylindrical die. A columnar stationary mold for molding the lower surface of the optical element, and a columnar sliding mold for molding the upper surface of the optical element while being slidably inserted vertically from the upper end of the body mold, A molding die for an optical element, wherein a cylindrical frame for molding a side surface of the optical element is provided between the stationary die and the sliding die and is positioned on an inner peripheral surface of the barrel die. 2. The optical element according to claim 1, wherein when the sliding die is lowered to form a predetermined molding space, a predetermined interval is provided between the lower surface of the sliding die and the upper end surface of the frame die. Molding mold. 3. The thermal expansion coefficients of the stationary mold, the sliding mold and the frame mold are substantially matched, and the thermal expansion coefficient of the body mold is set smaller than the thermal expansion coefficients of the stationary mold, the sliding mold and the frame mold. A molding die for the optical element according to claim 1. 4. The molding die for an optical element according to claim 3, wherein the stationary mold, the sliding mold and the frame mold are formed of tungsten carbide, and the body mold is formed of glass ceramic.