JP2003245946A - Optical element, mold for molding optical element and optical element molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably obtain an optical element having optical characteristics excellent in axisymmetric properties in a high yield. <P>SOLUTION: The optical element is obtained by kneading and melting a molding compound under heating and injecting the molten compound in a cavity through a gate to fill the cavity. When the outer diameter of the optical element is set to ϕG, the diameter of the optical effective surface of the optical element is set to ϕLY, the center thickness of the optical element is set to LT, the edge thickness thereof is set to LK, the width in the circumferential direction of the gate connected to the outer periphery of the optical element is set to GH and the thickness of the gate is set to GT to obtain formulae x=LT/LK and y=GT/LK, formulae (1), (2) and (3), that is, 0.8>ϕLY/ϕG, 0.1<GH/ϕG<0.35 and y≥0.0977x+0.47 are satisfied at the same time. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-precision optical element such as a lens, a prism or a mirror used in an optical device, an optical element molding die for forming the optical element, and a molding method of the optical element. .

[0002]

2. Description of the Related Art As a conventional method for molding an optical element, for example, as described in JP-A-5-177725,
An injection molding method is known in which pellets are heated, kneaded, melted, and injection-filled into a cavity of a mold having an insert member for molding an optically effective portion of an optical element.

The conventional molding method and the resulting optical element will be briefly described below with reference to the drawings.

FIG. 4 is a schematic sectional view of an injection molding machine used in the injection molding method. In FIG. 4, 7 is a hopper,
8 is a molding material, 9 is an injection cylinder, 10 is a heating cylinder, 11 is a screw, 12 is a nozzle, 13 is a fixed die plate, 14 is a movable die plate, 15 is a mold clamping cylinder, 5 is an optical element molding die (fixed side). ), 6 is an optical element molding die (movable side), 4 is a sprue, 3 is a runner, 2 is a gate,
Reference numeral 1 is an optical element.

FIG. 3 is a schematic view of a molded product obtained by the above-mentioned injection molding method. FIG. 3 (A) is a top view and FIG. 3 (B) is a line 3B-3B in FIG. 3 (A). FIG. In the figure, 4 is a sprue, 3 is a runner, 2 is a gate, and 1 is an optical element.

A molding material 8 is put into the hopper 7. The molding material 8 moves toward the nozzle 12 as the screw 11 rotates. The molding material 8 is heated and melted and kneaded by the screw 11 and the heating cylinder 10. And nozzle 1
2 through the sprue 4, the runner 3, and the gate 2 in the optical element molding dies 5 and 6 in order, and then injected and filled into a cavity having a desired optical element shape. The optical element molding dies 5 and 6 are set to a predetermined temperature, for example, near the deflection temperature of the molding material 8 under load. When the optical element 1 is cooled to a state where it can be taken out, the optical element molding die 6 is opened, gate cutting is performed, and the sprue 4, runner 3, and gate 2 are formed.
Then, the optical element 1 is taken out.

[0007]

In the above-described conventional optical element molding die, molding method, and optical element, the occurrence of sink marks, jetting, welds, etc. is sufficiently suppressed no matter how the injection molding conditions are controlled. Was difficult.

Further, the obtained optical element has good transferability,
That is, if it has optical characteristics with excellent axial symmetry,
When assembling the optical element into the optical device, it is not necessary to consider the assembling direction of the optical element, so that the working efficiency is improved. Therefore, it is desired to stably obtain an optical element having excellent axial symmetry of optical characteristics with a high yield.

Objects of the present invention include sinking, jetting,
Molding method of optical element, molding method, and optical element capable of stably obtaining an optical element having good transferability, that is, optical characteristics having excellent axial symmetry with a high yield while suppressing occurrence of welds and the like. It is to provide an element.

[0010]

To achieve the above object, the present invention comprises the following items.

The optical element of the present invention is an optical element obtained by heating, kneading and melting a molding material and injecting and filling it into a cavity through a gate. The outer diameter of the optical element is φG, and the optical element ΦLY is the effective optical surface diameter and L is the center thickness of the optical element.
T, the edge thickness of the optical element is LK, the circumferential width of the gate connected to the outer periphery of the optical element is GH, and the thickness of the gate is G.
T, the ratio of the center thickness LT of the optical element to the edge thickness LK is x
(= LT / LK), when the ratio of the gate thickness GT to the edge thickness LK of the optical element is y (= GT / LK), the following formulas (1) to (3) are satisfied. To do.

[0012] 0.8> φLY / φG (1) 0.1 <GH / φG <0.35 (2) y ≧ 0.0977x + 0.47 (3)

Further, the optical element molding die of the present invention comprises a cavity for molding an optical element by injection-filling a molding resin which is kneaded and melted by heating, and constitutes a part of the cavity. An optical element molding die comprising an insert member for forming an optically effective surface and a gate for introducing the molding resin into the cavity, wherein an outer diameter of the optical element to be molded is φG, The optical effective surface diameter of the element is φLY, the center thickness of the optical element is LT, the edge thickness of the optical element is LK, the circumferential width of the gate connected to the outer periphery of the optical element is GH, the gate thickness is GT, The ratio of the center thickness LT of the optical element to the edge thickness LK is x (= LT
/ LK), gate thickness GT and optical element edge thickness LK
When the ratio with is y (= GT / LK), the following formula (1)
~ It is characterized by satisfying the expression (3).

[0014] 0.8> φLY / φG (1) 0.1 <GH / φG <0.35 (2) y ≧ 0.0977x + 0.47 (3)

The optical element molding method of the present invention is a method of molding an optical element by injecting and filling a molding resin melted by heating, kneading and melting into a cavity through a gate of an optical element molding die. The optical element molding die includes an insert member for forming an optically effective surface of the optical element, an outer diameter of the optical element to be molded is φG, an optically effective surface diameter of the optical element is φLY, and a center of the optical element. The thickness is LT, the edge thickness of the optical element is LK, the circumferential width of the gate connected to the outer periphery of the optical element is GH, the gate thickness is GT, the center thickness LT of the optical element and the edge thickness LK are ratios. X (= LT
/ LK), gate thickness GT and optical element edge thickness LK
When the ratio with is y (= GT / LK), the following formula (1)
~ It is characterized by satisfying the expression (3).

[0016] 0.8> φLY / φG (1) 0.1 <GH / φG <0.35 (2) y ≧ 0.0977x + 0.47 (3)

According to the above-described optical element, optical element molding die and optical element molding method of the present invention, the generation of sink marks, jetting, welds, etc. is suppressed, and the gate does not affect the optically effective surface. It is possible to stably obtain an optical element having excellent transferability (axial symmetry).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be obtained by the difference in the shape of a gate provided at the outer peripheral end for filling a molding material and holding pressure when molding an optical element in a molding die. The present invention has been completed, focusing on the fact that the optical performance of optical elements is different.

The problem that the optical element obtained by molding does not have the desired optical performance is that the molding material cannot be filled smoothly in the molding material filling step, or the proper holding pressure of the molding material is not maintained in the cooling step. The surface shape of the insert member that forms the optical effective surface of the optical element cannot be satisfactorily transferred to the optical element due to failure to do so, or stress distortion that occurs in the vicinity of the gate because the molding conditions must be selected unreasonably. Is caused by the fact that a phenomenon such as that affects the optically effective surface occurs, and as a result of these, the optical element has a large astigmatism, which is the optical performance in which the axial symmetry is impaired with respect to the optical axis. There is.

Therefore, according to the present invention, the distance between the outer diameter of the optical element and the optically effective surface of the optical element is adjusted so that the gate does not affect the optically effective surface, that is, the optical performance of the optical element is not affected. The above problem has been solved by using a technical means of controlling the shape of the gate provided on the outer peripheral edge of the optical element.

Embodiments of an optical element, an optical element molding die, and an optical element molding method of the present invention will be described below together with specific examples with reference to the drawings and tables.

FIG. 1 is a schematic view showing the shapes of an optical element and a gate according to an embodiment of the present invention.
Is a top view, and FIG. 1B is a cross-sectional view taken along the line 1B-1B in FIG. FIG. 2 is a schematic view showing the shape of the optical element molding die, and FIG. 2 (A) is a schematic sectional view.
FIG. 2B is a front view of the movable mold as seen from the parting surface, and FIG. 2C is a front view of the fixed mold as seen from the parting surface. In these figures, 1 is an optical element,
Reference numeral 1a is an edge formed around the optical element 1, 2 is a gate connected to the edge 1a of the optical element 1, 3 is a runner connected to the gate 2, 4 is a sprue radially provided with runners 3 Is a fixed-side optical element molding die, 6 is a movable-side optical element molding die, 5a is an insert member incorporated in the fixed-side optical element molding die 5, 6a is an insert member incorporated in the movable-side optical element molding die, 18 Is a parting surface on which the fixed-side optical element molding die 5 and the movable-side optical element molding die 6 are butted.

As an example, the shape of each part of the optical element 1 shown in FIG. 1, that is, the outer diameter φG (the outermost diameter of the optical element 1), the center thickness LT (the thickness of the optical element 1 in the optical axis direction), the edge Thickness LK (thickness in the optical axis direction of edge 1a), optically effective surface diameter φLY1 of the first surface (one surface) of the optical element, second surface (R2)
Surface) optical effective surface diameter φLY2, first surface processing diameter φLK
1, the machining diameter φLK2 of the second surface, the shape of the gate 2,
That is, an optical element molding die in which the width GH of the gate 2 (dimension in the circumferential direction of the optical element 1) and the thickness GT (dimension of the optical element in the optical axis direction) of the gate 2 are changed is manufactured, and the optical element molding die is manufactured. The optical element was molded with a molding die, and the optical characteristics were evaluated and confirmed. The term “optically effective surface” as used herein refers to an optical action surface that is minimally required to produce optical characteristics required for an optical element, and serves as a path of light rays.

Since the injection molding conditions are different in the shape of each optical element, the shape of the gate, etc., the condition is examined each time, and the optimum condition, that is, the molding condition that gives the best optical characteristics is extracted. It began to.

More specifically, an optical element molding die, an optical element, and an optical element molding method will be described.

In the embodiment, as a material of the optical element 1, a polyolefin resin (glass transition point Tg = 150) is used.
C., heat distortion temperature Tt = 125 ° C.) were used. The optical element molding dies 5 and 6 are pre-hardened steel and stainless steel (S5
5C, HPM (for example, trademark of Hitachi Metals, Ltd.), N
An insert member 5 configured by using AK (trademark of Daido Steel Co., Ltd.) or the like to form an optically effective surface of an optical element.
The materials a and 6a were made of cemented carbide. Needless to say, in the present invention, the optical element molding dies 5 and 6 may be any materials other than the above-mentioned materials as long as they can be used for injection molding. Further, as a material of the insert members 5a and 6a, a material such as stainless steel (for example, STAVAX (trademark of Woodeform Co.)) is used as a base material as long as it is a material capable of obtaining surface properties as an optical element, and the surface thereof is electroless nickel plated There is no problem even if a product obtained by subjecting and processing is used as an insert member. However, in consideration of strength, it is preferable to use cemented carbide as the base material. Further, there is no problem even if a protective film or the like is applied to the surface for improving the mold releasability and for preventing the mold from being oxidized and corroded.

An example of the main shape dimensions of the optical element to be obtained is an outer diameter φG = φ4.8 mm, a first surface (R1 surface) effective surface diameter φLY1 = φ3.6 mm, and a center thickness LT = 1.7 m.
m, edge thickness LK = 0.412 mm, double-sided convex shape, and designed and manufactured so as to obtain optical characteristics with desired optical specifications. An example of the shape of the gate is a gate width GH = 1.0 mm, a gate thickness GT = 0.4 mm, and a molding die is manufactured so as to be connected to the outer peripheral portion of the optical element.
Assembled

Next, a molding process using the above-mentioned optical element molding die will be described. Molding was performed using an injection molding machine having the same configuration as the conventional injection molding machine shown in FIG. First, the molding material 8 was put into the hopper 7. Molding material 8 is screw 11
The rotation of the nozzle moves toward the nozzle 12. The molding material 8 is heated and melted and kneaded to a desired temperature by the screw 11 and the heating cylinder 10. Here, the set temperature of the heating cylinder was set to 260 ° C. And also 2
From the nozzle 12 heated to 60 ° C. to the optical element molding die 5,
After passing through the sprue 4, the runner 3, and the gate 2 in 6 in order, they were injected and filled in the cavity of the desired optical element shape. Then, the pressure was maintained by the injection cylinder. The optical element molding dies 5 and 6 are kept at a predetermined constant temperature (here, set to 130 ° C.), and the molding material is cooled at the same time when the filling into the cavity is started. The desired optical characteristics of the optical element cannot be obtained unless proper injection conditions, filling conditions, pressure holding conditions, and temperature conditions of the optical element molding die are selected. After reaching a state where the optical element 1 can be taken out, the optical element molding die 6 was opened, gate cutting was performed, the optical element 1 was taken out from the sprue 4, the runner 3, and the gate 2, and the optical element 1 was taken out.

The above molding conditions are examples, and the molding material,
Needless to say, it is necessary to optimize various molding conditions according to the shape of the optical element and the shape of the gate.

The optical characteristics of the obtained optical element were evaluated by using an interferometer to measure the transmitted wavefront aberration (measurement wavelength: 632.8 nm).
Was measured to determine astigmatism, and thereby the transferability and the axial symmetry of the effective surface of the optical element were evaluated. The smaller the astigmatism, the more preferable it is, but here the astigmatism is 2
Those having a wavelength of 0 mλ or less were considered to have good optical characteristics. An optical element with astigmatism that exceeds that has poor rotational axis symmetry in the optical characteristics of the effective surface, and when mounted on an optical device,
Unless the direction of astigmatism is grasped, the direction is determined and the astigmatism is mounted on the optical device, desired optical characteristics cannot be obtained as the optical device.

The above-mentioned optical element had an astigmatism of 8 mλ and had very good optical characteristics.

An optical element molding die was manufactured in the same manner by changing the shape of the optical element and the shape of the gate variously, and an optical element was obtained under optimized molding conditions. Tables 1 and 2 show the optical element shape and the gate shape of each sample, and Table 3 shows the optical characteristics (astigmatism) and the quality evaluation results of the obtained optical element.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

In Table 3, "-" is entered in the "Astigmatism" column.
That is, even if various molding conditions were changed, it was not possible to obtain an optical element to the extent that the above evaluation of optical characteristics could be performed.

As can be seen from Tables 1 to 3, it is necessary to satisfy the following three conditions in order to obtain the optical element having the optical characteristics excellent in rotational axis symmetry, which is the object of the present invention. .

First, the outer diameter φG of the optical element 1 provided with the gate 2 and the optical effective diameter φLY of the optical element 1 (the optical effective diameter φLY here is the first surface (R1 surface) optically effective of the optical element). Ratio φLY / φ of the diameter φLY1 and the second surface (R2 surface) which is the larger of the optically effective diameter φLY2)
It is necessary to set the optical effective diameter φLY and the outer diameter φG of the optical element 1 so that G satisfies φLY / φG <0.8. When the ratio φLY / φG does not satisfy the above range, no matter how the shape of the gate 2 or the injection molding condition is changed, the influence of stress distortion in the gate 2 portion may be affected.
To the optically effective surface, resulting in an optical element having a large astigmatism.

Second, the outer diameter φG of the optical element 1 and the gate 2
The ratio GH / φG with the width GH is 0.1 <GH / φG <
It is necessary to satisfy 0.35. If the ratio GH / φG does not satisfy this relationship, the transferability will be asymmetric with respect to the optical axis, no matter how the injection molding conditions are changed.
In other words, when an axially asymmetric optical element is required, it can be said that the gate width GH should be set so as not to satisfy the above relationship.

Thirdly, it is necessary to make the thickness deviation shape of the optical element 1 and the thickness shape of the gate 2 with respect to the edge into appropriate dimensions.
That is, the center thickness of the optical element 1 is LT, the edge thickness of the optical element 1 is LK, the thickness of the gate 2 is GT, and the ratio between the center thickness LT of the optical element 1 and the edge thickness LK is x = LT / LK.
When the ratio between the thickness GT of the gate 2 and the edge thickness LK of the optical element 1 is y = GT / LK, y ≧ 0.0977x +
It is necessary to have a relationship that is 0.47.

As is clear from the above experimental results, when the optical element shape and the optical element molding die satisfy the above three conditions, the optical element has good astigmatism.

That is, when the optical element and the molding die (gate) simultaneously satisfy the above three conditions, an optical element having good optical characteristics can be obtained. Therefore, the optical element and the optical element molding die are tried. There is no need to erroneously manufacture, and the optical element molding die and the optical element can be provided at a lower cost.

Therefore, by designing the optical element and the molding die so as to satisfy the above three conditions, and controlling the injection molding conditions so that sink marks, jetting, weld, etc. do not occur in the actual injection molding, An optical element having optical characteristics with excellent axial symmetry can be stably obtained with a high yield.

Although a polyolefin resin is used as the molding material in the above-mentioned embodiments, the molding material is not limited to this.
It goes without saying that the same applies when other molding materials are used.

Needless to say, the temperature conditions and pressure conditions in molding differ depending on the characteristics such as the glass transition point of the molding material and the deflection temperature under load.

[0046]

As described above, according to the present invention, sink marks,
It is possible to stably obtain an optical element having good transferability (axial symmetry) without the gate affecting the optically effective surface while suppressing the occurrence of jetting, welding, and the like.

[Brief description of drawings]

FIG. 1 is a schematic view showing the shapes of an optical element and a gate according to an embodiment of the present invention, FIG. 1 (A) is a top view,
1B is a sectional view taken along the line 1B-1B in FIG.

FIG. 2 is a schematic view showing a shape of an optical element molding die according to an embodiment of the present invention, FIG. 2 (A) is a schematic sectional view,
FIG. 2 (B) is a front view of the movable mold as seen from the parting surface, and FIG. 2 (C) is a front view of the fixed mold as seen from the parting surface.

FIG. 3 is a schematic view of a molded product obtained by the present invention and a conventional injection molding method, FIG. 3 (A) is a top view and FIG. 3 (B).
FIG. 3B is a sectional view taken along the line 3B-3B in FIG.

FIG. 4 is a schematic cross-sectional view of an injection molding machine used in a method of molding an optical element.

[Explanation of symbols]

1 Optical element 1a Koba 2 gates 3 runners 4 sprue 5 Fixed side optical element molding die 5a Insert member 6 Movable side optical element molding die 6a Insert member 7 hopper 8 molding materials 9 injection cylinder 10 heating cylinder 11 screws 12 nozzles 13 Fixed die plate 14 Moving die plate 15 Clamping cylinder 18 Parting surface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Morimoto             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Akihisa Yamada             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Norio Kirita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 4F202 AH73 CA11 CB01 CK06 CK43                       CK54

Claims (3)

[Claims] 1. An optical element obtained by heat-kneading and melting a molding material, and injection-filling it into a cavity through a gate, wherein an outer diameter of the optical element is φG, and an optically effective surface diameter of the optical element is φL
Y, the center thickness of the optical element is LT, the edge thickness of the optical element is LK, the circumferential width of the gate connected to the outer periphery of the optical element is GH, the thickness of the gate is GT, the center thickness L of the optical element
The ratio between T and the edge thickness LK is x (= LT / LK), and the ratio between the gate thickness GT and the optical element edge thickness LK is y (= G
T / LK), an optical element satisfying the following formulas (1) to (3). 0.8> φLY / φG (1) 0.1 <GH / φG <0.35 (2) y ≧ 0.0977x + 0.47 (3) 2. A cavity for injection-filling a molding resin melted by heating, kneading and melting to mold an optical element, and an insert forming a part of the cavity and forming an optically effective surface of the optical element. An optical element molding die comprising a member and a gate for introducing the molding resin into the cavity, wherein an outer diameter of the optical element to be molded is φG, an optical effective surface diameter of the optical element is φLY, The center thickness of the optical element is LT, the edge thickness of the optical element is LK, the circumferential width of the gate connected to the outer circumference of the optical element is GH, the gate thickness is GT, the center thickness LT of the optical element and the edge thickness. The ratio with LK is x (= L
T / LK), gate thickness GT, and optical element edge thickness L
An optical element molding die characterized by satisfying the following formulas (1) to (3) when the ratio with K is y (= GT / LK). 0.8> φLY / φG (1) 0.1 <GH / φG <0.35 (2) y ≧ 0.0977x + 0.47 (3) 3. A method for molding an optical element by injecting and filling a molding resin melted by heating and kneading into a cavity through a gate of the optical element molding die, wherein the optical element molding die comprises the optical element. Of the optical element to be molded, the outer diameter of the optical element is φG, the optical effective surface diameter of the optical element is φLY, the center thickness of the optical element is LT, and the edge thickness of the optical element is LK, the width in the circumferential direction of the gate connected to the outer periphery of the optical element is GH, the thickness of the gate is GT, and the ratio of the center thickness LT of the optical element to the edge thickness LK is x (= L
T / LK), gate thickness GT, and optical element edge thickness L
A method of molding an optical element, characterized in that the following formulas (1) to (3) are satisfied, where the ratio with K is y (= GT / LK). 0.8> φLY / φG (1) 0.1 <GH / φG <0.35 (2) y ≧ 0.0977x + 0.47 (3)