JPH0540984Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection mold device for molding lenses, and particularly to an injection mold device suitable for molding plastic lenses.

[Conventional technology]

Plastic lenses require high dimensional accuracy and have essentially different thickness distributions. Therefore, when molding plastic materials into molds, there may be variations in molding pressure and temperature over time and location. This results in a large degree of difficulty in molding compared to molding other plastic parts other than plastic lenses.

Currently, injection compression molding is considered to have the best molding precision as a method for molding plastic lenses.

The mold equipment used for this type of injection compression molding injects molten plastic material into the cavity of the mold, which is formed into a shape corresponding to the lens shape. By controlling the injection pressure of the plastic material injected into the cavity and cavity compression according to the temporal and spatial temperature distribution within the cavity, distortion on the lens surface and overall warping can be kept to a minimum, and the resin density and dimensions can be reduced. It is believed that it is possible to mold plastic lenses with good precision.

However, in recent years, as devices using plastic lenses have become smaller and thinner, the so-called non-effective diameter, which is the outer dimension of the lens surface of plastic lenses minus the effective dimension, has tended to become smaller. Even plastic cleansers that do not have the necessary properties are now in demand.

Furthermore, the flanges formed around the outer periphery of plastic lenses are currently becoming more complex, taking advantage of the fact that plastic lens molded products can have a free outer shape depending on the cavity shape of the mold.

[The problem that the idea attempts to solve]

However, such plastic lenses with a small non-effective diameter or no non-effective diameter,
When manufacturing plastic lenses with complex-shaped flanges by injection molding, the temperature inside the mold cavity tends to become even more uneven, making it extremely difficult to control the injection of plastic material into the cavity and compress the cavity. becomes.

Therefore, the dimensional accuracy near the outer periphery of the plastic lens deteriorates, and the wavefront accuracy of the plastic lens tends to deviate from the generally required intersection of ±5 μm.

Furthermore, the shape of the wavefront near the gate where the plastic material is injected into the mold cavity tends to be different from the shape of the wavefront at a portion away from the gate, and as the lens shape becomes more complex, warping and deformation become larger.

As a result of intensive experimental observations of injection molding molds, the inventor of the present invention focused on the fact that the uneven temperature balance that occurs in the mold during molding has an extremely large effect on the dimensional accuracy of the plastic lens, and completed the present invention. .

This invention was made to solve the above-mentioned conventional drawbacks, and it is easy to maintain a good heat balance during molding in injection molding, which is said to be relatively suitable for molding plastic lenses. An object of the present invention is to provide an injection molding device which can easily mold a plastic lens having a small or non-effective diameter or a plastic lens having a flange with high precision.

[Means to solve the problem]

In order to solve such problems, the present invention has a cylindrical electrical heating member which is arranged in an annular manner distributed along the circumferential direction inside the column, and an annular cooling hole along the circumferential direction of the electric heating member. 1 inner mold;
The electric heating member is formed into a cylindrical shape and has annularly distributed distribution along the circumferential direction inside the electric heating member, and an annular cooling hole along the circumferential direction of the electric heating member. a first mold having a first outer mold; a first mold having a cylindrical shape and having electric heating members distributed in an annular manner along the circumferential direction inside the first mold; and annular cooling holes along the circumferential direction of the first mold; a second inner mold having a cylindrical shape and having electrical heating members distributed in an annular manner along the circumferential direction inside the mold and annular cooling holes along the circumferential direction; It is configured by combining a second outer mold that is fitted onto the outer periphery of the mold and a second mold that has a second outer mold.

The first and second inner molds are configured to form a molding cavity at least between the tips of the first and second inner molds when their ends abut against each other.

[Effect]

In the injection mold device of the present invention equipped with such a means, the first and second molds are columnar or cylindrical as a whole, and the electric heating member is annularly shaped along the circumferential direction in these molds. Since the cooling holes are arranged in a distributed manner and the cooling holes are also arranged annularly along the circumferential direction, the temperature balance of the entire first and second molds tends to be good and uniform.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 are a longitudinal sectional view and a transverse sectional view showing an embodiment of an injection mold apparatus for molding lenses according to the present invention.

In the figure, two cylindrical steel optical inserts 3 and 5 are fixed to a base 1 on the fixed side so as to hang down at a distance from each other.

In each of the optical inserts 3 and 5, blind holes 7 formed from the base 1 side toward the tip thereof are formed in an annular manner distributed at equal intervals along the circumferential direction.
A heat generating member 9 such as a nichrome wire is housed inside in an insulated state, and is connected to a suitable control power source (not shown) on the base 1 side.

In each optical insert 3, 5, an annular water hole 11 is formed inside the annularly arranged blind hole 7 at approximately the same position as the tip of the blind hole 7, and the base 1
A suitable control water source (not shown) led to the side allows cooling water to flow down through the optical inserts 3,5. The broken lines in the figure are virtual representations of water flow, and are not strictly accurate.

A cylindrical steel cavity bush 13, 15 is provided on the outer periphery of each optical insert 3, 5.
is fitted into the base 1, the optical insert 3, and the cavity bush 13, or the base 1, the optical insert 5, and the cavity bush 15.
19 is formed.

Each cavity bush 13, 15 has a base 1
Blind holes 21 formed from the side toward the tip are distributed annularly at equal intervals along the circumferential direction, and a heat generating member 23 similar to the heat generating member 9 is housed in each blind hole 21, and the base 1 side to a suitable control power source (not shown).

Inside the blind hole 21 arranged in an annular manner in each cavity bush 13, 15, a water hole 25 is arranged in an annular manner so as to surround the cavity bush 13, 15 at a position below the tip of the blind hole 21. Formed base 1
and is connected to a suitable control water source (not shown).

The peripheral edge of the tip of each optical insert 3, 5 and the tip of the cavity bush 13, 15 are in the same position, and the optical insert 3,
The portion surrounded by the peripheral edge of the tip 5 is a protruding portion 27.

Similar to the optical inserts 3 and 5, two steel optical inserts 31 and 33 are erected from the base 29 on the movable side at a distance from each other.

Each optical insert 31, 33 also has a base 2.
Blind holes 35 formed from the 9 side toward the tip thereof are distributed annularly at equal intervals along the circumferential direction, and a heat generating member 37 is housed in each blind hole 35, and the base 1
It is connected to a suitable control power source (not shown) at the side.

A water hole 39 is formed inside the blind hole 35 of each optical insert 31, 33 at approximately the same position as the tip of the blind hole 35, and is led out to the base 29 side and connected to an appropriate control water source (not shown). is connected to.

Cavity bushes 41 and 43 similar to the cavity bushes 13 and 15 are fitted into the outer periphery of each optical insert 31 and 33, and the base 29, the optical insert 31 and the cavity bush 41 or the base 29 , the optical insert 33 and the cavity bush 43 form second molds 45 and 47 which are movable molds.

Each cavity bush 41, 43 has a base 2.
Blind holes 49 formed from the 9 side toward the tip are distributed in an annular manner at equal intervals along the circumferential direction, and a heat generating member 51 such as the heat generating member 9 is accommodated in each blind hole 49. Connected to a control power source (not shown).

In each cavity bush 41, 43, the blind hole 49 is located inside the annularly arranged blind hole 7.
A water hole 53 is formed in an annular shape to a position higher than the tip of the water hole 53, and is led out to the base 29 and connected to an appropriate control water source (not shown) on the base 29 side.

An annular gap 54 is formed at the inner periphery of the tips of the cavity bushes 41 and 43, and the tips of the optical inserts 31 and 33 form a recess 55 that is continuously recessed from the inner wall forming the gap 54. ing.

Therefore, the tip of the first mold 17, 19 and the second mold
With the tips of the molds 45 and 47 in contact with each other, the first
Optical inserts 3 and 5 of molds 17 and 19
and optical inserts 31, 33 of cavity bushes 13, 15 and second molds 45, 47.
and between the cavity bushes 41 and 43,
Cavities 57 and 59 are formed to correspond to the external shape of the plastic lens to be molded.

Symbols 61 and 63 in the figure represent cavities 57 and 59 respectively.
These are a runner and an injection gate for injecting molten resin into the tank.

As shown in FIG. 3, the injection mold device of the present invention configured in this manner has a first mold 17, 19 on a fixed side and a second mold 45, 4 on a movable side.
7 is raised to bring their tips into contact with each other, and current is passed through the heat generating members 9, 23, 37, 51 to heat the first and second molds 17, 19, 45, 47 to a predetermined temperature, and approximately Molten plastic material at 220 DEG C. is injected into cavities 57, 59 through injection gate 63 under predetermined pressure control.

Note that polymethyl methacrymate (PMMA), polyvinyl chloride (PVC), polystyrene (PS), polycarbonate (PC), etc. are suitable as the plastic material.

Thereafter, water is poured into the water holes 11, 25, 39, and 53 to solidify while cooling, thereby forming a plastic lens 65 as shown in FIGS. 4 and 5.

Reference numeral 67 in FIG. 5 is a plastic lens 65.
is a flange integrally formed on the outer periphery of the plastic lens 65, and symbol A is the effective diameter of the plastic lens 65, and symbol B is the effective diameter of the plastic lens 65.
is a measurement diameter, which will be described later, and symbol Z is the height dimension between the center part of the plastic lens 65 and a surface part separated by B from the center part.

In the injection mold device of the present invention, each heat generating member 9, 23, 37, 51 and water hole 11, 25, 3
It is preferable to independently control the water flowing through the cavities 13, 15, 4.
1 and 43 are preferably formed with a certain degree of thickness from the viewpoint of ensuring mechanical strength.

In this way, the injection mold device for lens molding of the present invention has a first mold 17 having a cylindrical shape as a whole,
Since the plastic lens 65 is molded using the mold 19 and the second molds 45, 47, the heat generating members 9, 23, 37, 51 and the water holes 11, 2
If the water flowing through 5, 39, and 53 is appropriately controlled, the heat balance of the mold will be uniform, and fine adjustment will be easy.

Therefore, even in the case of a plastic lens with a small non-effective diameter or no non-effective diameter, or a plastic lens with a complicated flange, the wavefront precision of the lens is accurate and warping and deformation can be suppressed.

In the plastic lens 65 shown in FIGS. 4 and 5, the present inventor proposed that A=120 mm and B=59 mm.
For 100 samples, the tolerance between the measured value Z and the design value was measured in the +X, -X, +Y, and -Y directions, and the results were as shown in FIGS. 6 to 9.
Note that the two-dot chain line in the figure indicates the tolerance range of ±5 μm.

According to this, in the -X direction, there were some items that were slightly out of tolerance, but they were within a generally satisfactory range, and in the +X direction, although the dimensions were closer to the lower limit side, there were no items that were outside of the tolerance. Furthermore, good results were obtained in the Y direction.

On the other hand, if a plastic lens as shown in Fig. 5 is molded using a mold having a cavity bush with a square outer shape or a mold with a square template placed outside the cavity bush, for example, 10th
The results were as shown in Figures 1-13.

In other words, it can be seen that in the -X and +X directions, the surface of the plastic lens is out of tolerance, and there is a large inclination on the surface of the plastic lens, and in the Y direction, there is something out of tolerance, but the width of the variation is large and it is out of tolerance. Something existed.

The large deviation from the tolerance in the X direction is thought to be because the injection gate for the molten resin is located in the X direction.

In the embodiment of the present invention described above, the first mold 17
and the second mold 45 or the first mold 19 and the second mold 47 as one set, but in the present invention, the first mold 17 and the second mold 45 or 1st
It goes without saying that the configuration may be made of only one of the mold 19 and the second mold 47.

Furthermore, in the present invention, the molding cavity 5
7, 59 are the first and second molds 17, 19, 4
5,47 optical inserts 3,5,31,
33 and cavity bushes 13, 15, 4
1.43, but the present invention is not limited thereto.

For example, optical inserts 3, 5, 31,
The cavity may be formed only by the space between the first and second molds 17, 19, 45, 4, and one of the optical inserts 3, 5 may be flat.
7, at least those optical inserts 3, 5, when their tips abut;
It is also possible to form a molding cavity between the tips of 31 and 33. However, as mentioned above, the cavity bushes 13, 15, 41,
43, it is easier to manufacture a mold, and it is also easier to mold a plastic lens having a flange.

Note that FIG. 1 and FIG. 3 described above show an example in which the first and second molds are arranged in the vertical direction.
However, although not shown in the drawings, the present invention can also be implemented in a horizontally arranged configuration.

[Effect of idea]

The injection molding mold device of the present invention described above has electrical heating members distributed in an annular manner along the circumferential direction and cooling holes also arranged in an annular manner along the circumferential direction, and a first mold having a circular outer shape. and a second mold, and a molding cavity is formed between the tips of the first and second molds, resulting in a good heat balance during molding in a circular injection mold. It is easy to keep the plastic lens in a clean state, and it is possible to easily mold a plastic lens with a small non-effective diameter or no non-effective diameter, or a plastic lens with a flange with high precision.

[Brief explanation of drawings]

1 and 2 are a longitudinal sectional view and a transverse sectional view (-cross section) showing an embodiment of an injection molding mold device for lens molding according to the present invention, and FIG.
4 and 5 are longitudinal cross-sectional views showing the process of molding a plastic lens using the injection molding device shown in FIG. 1. FIGS. 6 to 9 are diagrams showing the tolerance variation measurement results when plastic lenses are molded using the injection molding device shown in FIG. 1, and FIGS. 10 to 13 are FIG. 2 is a diagram showing the results of measuring tolerance variations when a plastic lens is molded using a conventional injection molding device. 1, 29... Base, 3, 5... First inner mold (optical insert), 7, 21, 35, 49
... Blind hole, 9, 23, 37, 51 ... Heat generating member,
11, 25, 39...Cooling hole (water hole), 13, 1
5...First outer mold (cavity bush), 1
7, 19...first mold, 27...protrusion, 3
1, 33... Second inner mold (optical insert), 41, 43... Second outer mold (cavity bush), 45, 47... Second mold, 53...
... recess, 57, 59 ... cavity, 63 ... injection gate, 65 ... plastic lens, 67 ...
...Flange.

Claims (1)

[Claims for Utility Model Registration] A first inner mold having a cylindrical shape and having electric heating members distributed in an annular manner along the circumferential direction inside the mold and annular cooling holes along the circumferential direction. The first inner mold has a cylindrical shape and has electrical heating members distributed in an annular manner along the circumferential direction inside the mold, and annular cooling holes along the circumferential direction, and is fitted into the outer periphery of the first inner mold. a first outer mold having a first outer mold;
a second inner mold formed in a cylindrical shape and having electric heating members distributed in an annular manner along the circumferential direction inside the mold and annular cooling holes along the circumferential direction; A second mold, which is formed into a shape and has electrical heating members distributed in an annular manner along the circumferential direction inside the mold, and annular cooling holes along the circumferential direction, and is fitted on the outer periphery of the second inner mold. A second mold having an outer mold of
a mold, and a molding cavity formed between at least the tips of the first and second inner molds when the tips of the first and second molds abut each other. An injection mold device for lens molding featuring: