JPH07266391A - Manufacture and manufacturing device of plastic lens - Google Patents

Abstract

PURPOSE:To stably mold a high precision plastic lens in a short molding cycle time. CONSTITUTION:Tank type cooling holes 2 are set up in a stationary type insertion piece 1 and movable type insertion piece 5 and radii of the insertion piece 1 and tank type cooling hole are taken respectively as A and B, a number of pieces of the tank type cooling holes 2 are taken as N and a distance from an approximate plane of a curved surface of a lens to be obtained by processing the insertion piece up to the tip of the tank type cooling hole 2 is taken as L. Then in a manufacture and manufacturing device of a plastic lens, a mold which is constituted so that when a ratio between the L and (A-BXN1/2) is taken as K (K=L/(A-BXN1/2), the K is within the following range is used for injection molding. 0,75<=K<=1.25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a highly accurate plastic lens using a thermoplastic resin as a molding material.

[0002]

2. Description of the Related Art In recent years, plastic lenses have come to be used as lenses for optical devices such as optical heads of compact disc players and video cameras.

FIG. 3 shows, for example, Japanese Patent Laid-Open No. 3-21103.
6 is a graph showing a relationship between a mold temperature and a lens shape error when a molding material is a polycarbonate resin, which is related to a conventional plastic lens manufacturing method disclosed in Japanese Patent Laid-Open Publication No. In the above-mentioned conventional example, when the ratio of the maximum wall thickness H _max to the minimum wall thickness H _min of the lens, H _max / H _min is 2.5 or less and the cross-sectional area of the gate is 3 mm ² or more, highly accurate lens molding When the molding material is a polycarbonate resin, by controlling the mold temperature within the range of 132 to 140 ° C., the change in the surface shape of the lens due to the fluctuation of the mold temperature can be reduced. By correcting the surface shape of the insert piece so that the surface shape of the molded lens becomes the designed shape, a highly accurate lens having a surface shape accuracy of ± 2 μm is stably molded.

In the above-mentioned conventional example, in order to clarify the molding factors that contribute to the reproducibility of the surface shape of the lens, the effects of changes in the filling speed, cylinder temperature, holding pressure, and mold temperature on the surface shape of the lens. As a result, the mold temperature contributes most to the reproducibility of the surface shape, and the maximum lens thickness H _max
And the minimum wall thickness H _min , H _max / H _min, and the cross-sectional area of the gate are the factors that determine the ratio of the lens shape change to the mold temperature change, and H _max / H _min is 2.5 or less. Then, when the gate cross-sectional area is 3 mm ² or more, the mold temperature is 132 to 140 ° C. for the polycarbonate resin, 106 to 112 ° C. for the acrylic resin, and generally, from the glass transition temperature of the resin. It is said that the reproducibility of the surface shape of the lens at the time of molding is highest in the temperature range of 9 to 21 ° C. on the low temperature side. Control the mold temperature within the above temperature range,
By correcting the surface shape of the insert piece so that the surface shape of the molded lens becomes the design shape of the lens, and by injection molding,
A highly accurate lens with a shape accuracy of ± 2 μm is stably molded.

[0005]

In the conventional method for producing a plastic lens described above, a highly accurate plastic lens can be stably molded, but since the mold temperature is close to the glass transition temperature of the molding material, the molten resin is cooled. There is a problem that the time is long and therefore the molding cycle time is long and the productivity is poor. In addition, since the temperature of the lens released from the mold is close to the glass transition temperature of the molding material, the deformation of the lens occurs due to the relaxation of the internal strain after the release, and the symmetry of the lens decreases. . Further, in the multi-cavity molding, when the shape accuracy of each lens deteriorates due to the deterioration of the temperature control performance of the mold, etc., there is no means to adjust the shape of each lens individually and instantaneously, so the yield decreases. There was a problem.

The present invention has been made in order to solve the above-mentioned problems, and stably molds a highly accurate plastic lens in a short molding cycle time, and a plastic lens having good symmetry can be obtained. An object of the present invention is to provide a molding method and a manufacturing apparatus that improve the yield by performing molding in a short molding cycle time and by instantaneously adjusting the shape of each lens separately in multi-cavity molding.

[0007]

According to a first aspect of the present invention, there are provided a fixed die and a movable die which are arranged to face each other, and insert pieces inserted into the fixed die and the movable die, respectively. In the lens mold, a tank-type cooling hole is installed in each of the insert pieces, the radius of the insert piece is A, the radius of the tank-type cooling hole is B, the number of tank-type cooling holes installed in each insert piece is N, Let L be the distance from the approximate plane of the lens curved surface processed into the insert piece to the tip of the tank-type cooling hole, and the ratio of L to (A−B × N ^1/2 ) is K (K = L / (A−B ×
N ^1/2 )) is used, a high-precision lens is molded in a short molding cycle time using a mold configured so that K falls within the following range.

0.75 ≦ K ≦ 1.25 The invention according to claim 2 of the present invention is the invention according to claim 1, wherein the mold temperature is lower than the glass transition temperature of the molding resin by 30 to 50 ° C. Control to shorten the molding cycle time and improve the symmetry of the lens.

According to a third aspect of the present invention, in the invention according to the first aspect, the insertion piece inserted into the movable die is connected to the ejector plate, and the protrusion of the lens from the movable die is removed. The molding cycle time is shortened by projecting the insert piece through the.

According to a fourth aspect of the present invention, in the invention according to the third aspect, a portion other than a portion forming the lens curved surface of the insert piece inserted into the movable die is covered with a holder part made of hardened steel, and is inserted. Increases the durability of the piece and shortens the molding cycle time.

According to a fifth aspect of the present invention, in the invention according to the third aspect, a ring made of hardened steel is attached to the outer peripheral sliding portion of the insert piece inserted in the movable die to make the insert piece durable. And improve molding cycle time.

Further, the invention according to claim 6 of the present invention has a fixed die and a movable die which are arranged to face each other, and a plurality of insertion pieces inserted into each of the fixed die and the movable die. , Filling the molten resin in the cavity formed by the fixed mold insert piece and the movable mold insert piece, and compressing the molten resin by pressurizing the insert piece with a pressurizing cylinder to perform shaping. In a multi-cavity lens mold, install a pressure cylinder for each movable mold insert piece,
By controlling the pressing force of each pressurizing cylinder based on the result of measuring the shape of each of the molded multiple lenses, the accuracy of the shape of the lens molded in each insert piece is increased and the yield is improved.

According to a seventh aspect of the present invention, in a lens mold having a fixed mold and a movable mold which are arranged so as to face each other, and a receiving piece inserted into each of the fixed mold and the movable mold, A tank-type cooling hole is installed in each of the insert pieces, the radius of the insert piece is A, the radius of the tank-type cooling hole is B, the number of tank-type cooling holes installed in each insert piece is N,
Let L be the distance from the approximate plane of the curved lens surface processed into the insert piece to the tip of the tank-type cooling hole, and let L and (AB × N
^When the ratio of ^1/2 ) is K (K = L / (A−B × N ^1/2 )), it is possible to obtain a high value by using a mold configured such that K is in the following range. An accurate lens can be molded in a short molding cycle time.

0.75 ≦ K ≦ 1.25 Further, in the invention according to claim 8 of the present invention, in the invention according to claim 7, the insertion piece inserted into the movable die is connected to the ejector plate, Since the protrusion of the lens from the movable mold is performed by ejecting the insertion piece through the ejector plate, the molding cycle time is shortened.

According to a ninth aspect of the present invention, in the invention according to the eighth aspect, the parts other than the lens curved surface of the insert piece inserted into the movable die are covered with a holder part made of hardened steel. As a result, the durability of the insert piece is increased and the molding cycle time is shortened.

Further, the invention according to claim 10 of the present invention is
In the invention according to claim 8, since a ring made of hardened steel is attached to the outer peripheral sliding portion of the insert piece inserted in the movable die, the durability of the insert piece is enhanced and the molding cycle time is shortened.

The invention according to claim 11 of the present invention is
A cavity formed by a fixed mold and a movable mold that are arranged to face each other, and a plurality of insert pieces that are respectively inserted in the fixed mold and the movable mold, and are formed by the fixed mold insert piece and the movable mold insert piece. In a multi-cavity lens mold in which a molten resin is filled, and the molding resin is compressed by pressurizing the insertion piece with a pressure cylinder, a movable mold container that forms the cavity. A pressurizing cylinder is installed for each piece, and based on the shape measurement result of each molded multi-cavity lens, by providing a control device for independently controlling the pressurizing force of each pressurizing cylinder, The shape precision of the lens molded in each insert piece is improved, and the yield is improved.

[0018]

In the inventions according to claims 1 and 7 of the present invention, a tank type cooling hole is provided in the insert piece, the radius of the insert piece is A, the radius of the tank type cooling hole is B, and the tank type installed in each insert piece. Let N be the number of cooling holes and L be the distance from the approximate plane of the lens curved surface processed into the insert piece to the tip of the tank cooling hole.
The ratio of L to (A−B × N ^1/2 ) is K (K = L / (A−B ×
N ^1/2 )) is set so that K falls within the following range, the molten resin injected into the mold is cooled with a uniform temperature distribution in a short time and highly accurate. Mold plastic lenses with short molding cycle times.

0.75 ≦ K ≦ 1.25 Further, in the invention according to claim 2, in the invention according to claim 1, the mold temperature is set to 30 from the glass transition temperature of the molding resin.
By controlling to a temperature lower by -50 ° C, the cooling time of the molten resin is shortened, the molding cycle time is shortened, and
The temperature at the time of releasing the lens is lowered, the deformation due to the relaxation of the internal strain after the releasing is reduced, and the symmetry of the lens is improved.

In the inventions according to claims 3 and 8,
In the invention according to claims 1 and 7, the lens is ejected from the movable mold by ejecting the insertion piece through the ejector plate to disperse the pressure applied to the lens at the time of ejection and before the lens is completely solidified. Allows protrusion without deformation, shortens cooling time and molding cycle time.

In the inventions according to claims 4 and 9,
In the inventions according to claims 3 and 8, by covering a portion other than the lens curved surface of the insert piece with a holder part made of hardened steel to enhance the durability of the insert piece when the lens is projected, the life of the insert piece is increased, and Reduce the molding cycle time.

Further, in the inventions according to claims 5 and 10, in the inventions according to claims 3 and 8, ring-shaped hardened steel is attached to the outer peripheral sliding portion of the insert piece to ensure durability of the insert piece when the lens is projected. By increasing the sex
Increases the life of the insert piece and shortens the molding cycle time.

Further, in the invention according to claims 6 and 11, a fixed type and a movable type which are arranged to face each other,
A plurality of insertion pieces inserted into each of the fixed die and the movable die, and a molten resin is filled in a cavity formed by the fixed die insertion piece and the movable die insertion piece, and the insertion is performed by a pressure cylinder. In the multi-cavity lens mold in which the molten resin is compressed and shaped by pressurizing the bridge, a pressurizing cylinder is installed for each of the movable mold-loading frames, and each multi-cavity lens molded Based on the shape measurement result, the pressing force of each pressurizing cylinder is controlled, the shape of each lens is instantaneously adjusted separately, the shape accuracy of each lens is improved, and the yield is improved.

[0024]

EXAMPLES The present invention will be described below with reference to examples.

[Embodiment 1] FIGS. 1 and 2 are a sectional view and a plan view of a movable die of the invention according to claims 1 and 7, respectively. 1 and 2, 1 is a fixed mold insert piece, 2 is a tank type cooling hole installed in the insert piece, 3 is a baffle plate, 4 is a lens (cavity), 5 is a movable mold insert piece,
6 is an ejector pin, and 7 is an ejector plate. 20 is a fixed type, 21 is a movable type, 22 is a sprue, 23
Is a runner and 24 is a gate.

In the first embodiment of the invention according to claims 1 and 7, the radius of the insert piece is A, the radius of the tank type cooling holes is B, the number of tank type cooling holes installed in each insert piece is N, and the insert piece is When the distance from the approximate plane of the processed lens curved surface to the tip of the tank-type cooling hole is L, A = 35 mm, B = 7.5 mm in the fixed mold insert and the movable mold insert.
With N = 4 and L = 20 mm, the distance L from the approximate plane of the lens curved surface processed into the insert piece to the tip of the tank cooling hole
And K (K = L /), which is defined by the ratio of the parameter (A−B × N ^1/2 ) related to the distance between the tank type cooling holes in the insert piece.
(A−B × N ^1/2 )) was set to 1.0. Here, the approximate plane of the lens curved surface processed into the insert piece is orthogonal to the optical axis of the lens curved surface processed into the insert piece, and the mean square of the distance in the optical axis direction from each point on the lens curved surface is This is the smallest surface.

Using this mold, the lens having the shape shown in FIG. 4 was molded by using acrylic resin Acrypet VH001 manufactured by Mitsubishi Rayon Co., Ltd. as a molding material, and the temperature of the resin was measured by using a water medium mold temperature controller. Molded lens with 250 ° C, mold temperature of 110 ° C, filling time of 10 seconds, holding pressure of 1000 kg / cm ² and holding time of 60 seconds, and the cooling time set to the shortest time to eject the lens without deformation. The surface shape of the fixed mold insert piece 1 and the movable mold insert piece 5 is modified so that the surface shape of the lens becomes the design shape of the lens, and molding is performed. I was able to mold it. Here, the shape accuracy means that when the lens surface to be measured is sandwiched by two design curved surfaces having the same optical axis as the lens surface to be measured within the effective diameter of the lens, the distance between the curved surfaces is the minimum. It is expressed by adding ± to the value of 1/2 of the displacement in the optical axis direction.

Next, the effects of the inventions of claims 1 and 7 will be described. In the lens mold, in order to shorten the cooling time of the molten resin, a tank-type cooling hole is provided in the insertion piece, and the tip of the tank-type cooling hole is brought close to the cavity surface of the insertion piece.
The heat transfer distance from the cavity surface to the tank cooling hole should be shortened.However, if the heat transfer distance is too short, the temperature distribution inside the molded product during cooling will increase and the internal strain of the molded product will increase. However, the shape accuracy is reduced.

Therefore, in order to know the optimum value of the heat transfer distance from the cavity surface to the tank-type cooling hole, the radius A of the inserting piece, the radius B of the tank-type cooling hole, and the tank-type cooling hole of each inserting piece are set. The number N of lenses and the distance L from the approximate plane of the curved surface of the lens processed into the insert piece to the tip of the tank-type cooling hole are changed, and the lens having the shape shown in FIG. 4 is manufactured by Mitsubishi Rayon Co., Ltd. Using VH001 as the molding material and a water medium mold temperature controller, set the resin temperature to 250.
℃, mold temperature 110 ℃, filling time 10 seconds, holding pressure 1
Set the pressure holding time to 000 kg / cm ² and the holding time to 60 seconds, and set the cooling time to the shortest time that the lens can be ejected without deformation in each mold, and put the fixed mold so that the surface shape of the molded lens becomes the design shape of the lens. The surface shapes of the piece 1 and the movable mold insert piece 5 were corrected and molded, and the shapes of the molded lenses were evaluated. The results are shown in Table 1 (Examples 1 to 7 and Comparative Examples 1 to 6). As shown in Table 1, it was found that the shape accuracy of the lens and the molding cycle time change depending on the number and size of the tank cooling holes 2.

From the results shown in Table 1, the shape accuracy of the lens, the distance L from the approximate plane of the lens curved surface processed on the insert piece to the tip of the tank type cooling hole, and the distance between the tank type cooling hole in the insert piece are shown. Parameters related to distance (A−B × N ^1/2 )
5, 6 and 7 show the relationship of K (K = L / (A−B × N ^1/2 )) defined by the ratio.
As shown in FIGS. 5 to 7, the lens shape accuracy is K
It has been found that when K is in the range shown below, a highly accurate lens can be molded in a short cycle time.

0.75.ltoreq.K.ltoreq.1.25 In the first embodiment, A = 35 mm, B = 7.5 mm, N = 4, L = for the fixed mold insert and the movable mold insert.
By setting it to 20 mm and setting K = 1.0, a highly accurate lens can be molded in a short cycle time.

In Table 1, as a comparative example, tank-type cooling holes were installed in the insert piece so that K = 0.5 or K = 1.5, and molding was performed in the same manner as in Example 1, and the shape was changed. The measured results are also shown (Comparative Examples 1 to 6). The shape accuracy of the obtained lens was ± 4.0 to 7.7 μm, and the shape accuracy of the lens was inferior to that of Example 1. In addition, as a comparative example, when the tank type cooling hole is not installed in the insert piece, the result of molding in the same manner as in Example 1 and measuring the shape is also shown in Table 1 (Comparative Example 7). . The obtained lens had a shape accuracy of ± 4.6 μm and a molding cycle time of 312 seconds, which was inferior to the lens shape accuracy of Example 1 and a long molding cycle time.

[Embodiment 2] In Embodiment 2 of the invention according to claims 1 and 7 shown in Table 1, in the fixed mold insert piece and the movable mold insert piece, A = 35 mm, B = 7.5 mm, L
= 25 mm, N = 4, K = 1.25, 283
With a molding cycle time of seconds, a lens with a shape accuracy of ± 2.3 μm could be molded.

[Embodiment 3] In Embodiment 3 of the invention according to claims 1 and 7 shown in Table 1, A = 35 mm, B = 7.5 mm, L in the fixed mold insert piece and the movable mold insert piece.
= 15 mm, N = 4, K = 0.75, 278
With a molding cycle time of seconds, a lens with a shape accuracy of ± 2.7 μm could be molded.

[Embodiment 4] In Embodiment 4 of the invention according to claims 1 and 7 shown in Table 1, in the fixed mold insert piece and the movable mold insert piece, A = 30 mm, B = 5.0 mm, L
= 25 mm, N = 4, K = 1.25, 289
With a molding cycle time of seconds, a lens with a shape accuracy of ± 3.3 μm could be molded.

[Embodiment 5] In Embodiment 5 of the invention according to claims 1 and 7 shown in Table 1, in the fixed mold insert piece and the movable mold insert piece, A = 30 mm, B = 5.0 mm, L
= 20 mm, N = 4, K = 1.0, and a lens having a shape accuracy of ± 2.8 μm could be molded with a molding cycle time of 286 seconds.

[Embodiment 6] In Embodiment 6 of the invention according to claims 1 and 7 shown in Table 1, in the fixed mold insert piece and the movable mold insert piece, A = 30 mm, B = 5.0 mm, L
= 15 mm, N = 4, K = 0.75, and 284
With a molding cycle time of seconds, a lens with a shape accuracy of ± 3.2 μm could be molded.

[Embodiment 7] In Embodiment 7 of the invention according to claims 1 and 7 shown in Table 1, in the fixed mold insert piece and the movable mold insert piece, A = 30 mm, B = 7.5 mm, L
= 18.75 mm, N = 1, K = 1.25,
Shape accuracy of ± 3.7 μm with molding cycle time of 291 seconds
I was able to mold the lens.

[Embodiment 8] In Embodiment 8 of the invention according to claims 1 and 7 shown in Table 1, A = 30 mm, B = 7.5 mm, L in the fixed mold insert piece and the movable mold insert piece.
= 15 mm, N = 1, K = 1.0, and a lens with a shape accuracy of ± 3.9 μm could be molded with a molding cycle time of 289 seconds.

[Embodiment 9] In Embodiment 9 of the invention according to claims 1 and 7 shown in Table 1, A = 30 mm, B = 7.5 mm, L in the fixed mold insert piece and the movable mold insert piece.
= 11.25 mm, N = 1, K = 0.75,
Shape accuracy ± 3.2 μm with molding cycle time of 287 seconds
I was able to mold the lens.

[0041]

[Table 1] In Examples 1 to 9 described above, the fixed insert piece, the movable insert piece, and the tank type cooling hole had a circular cross-sectional shape. However, the fixed insert piece, the movable insert piece and the tank type cooling hole were described. The cross-sectional shape may be any other shape. In this case, the radius A of the fixed die insert piece, the movable die insert piece and the radius B of the tank cooling hole are the radii of circles having the same cross-sectional area. In the above embodiment, the case where the radius of the fixed mold insert piece and the radius of the movable mold insert piece are the same has been described, but the radius of the fixed mold insert piece and the radius of the movable mold insert piece may be different. In that case, the value of K is set within the above range for each of the fixed type and the movable type.
Further, in the above embodiment, the case where the radius of the tank type cooling holes installed in each of the fixed type insert piece and the movable type insert piece is the same is explained, but even if the tank type cooling holes of different radii are combined, Often, in that case, as the radius B of the tank-type cooling holes, the radius of a circle whose cross-sectional area is equal to the average value of the cross-sectional areas of the tank-type cooling holes is used. In the above embodiment, the case where the distance L from the approximate plane of the curved lens surface processed into the insert piece to the tip of the tank-type cooling hole is equal in the fixed insert piece and the movable insert piece has been described.
They may be different, and in that case, the value of K is set within the above range for each of the fixed type and the movable type.

[Embodiment 10] Table 2 shows the experimental results of the embodiment of the invention according to claim 2. In Example 10, the mold of Example 1 of the invention according to claim 1 was used, and the lens having the shape shown in FIG. 4 was used as a molding material of acrylic resin Acrypet VH001 manufactured by Mitsubishi Rayon Co., Ltd. Using a mold temperature controller, the resin temperature is 250 ° C., the filling time is 10 seconds, the holding pressure is 1000 kg / cm ² , and the holding time is 6
The mold temperature was set to 0 ° C. for 75 seconds and the cooling time was set as the minimum time at which the lens can be ejected without deformation at the mold temperature, and the asymmetry of the molded lens was examined. as a result,
Molding cycle time of 147 seconds, asymmetry of 1.5μ
m lenses could be molded. Here, the asymmetry of the lens is the maximum value of the thickness in the optical axis direction of a solid formed by rotating the measured lens surface once around the optical axis.

Next, the effect of the invention of claim 2 will be described. In lens molding, if the mold temperature is high, the cooling rate of the molten resin becomes slower, the molding cycle time becomes longer, and the temperature of the lens released from the mold is high, so that internal strain of Deformation of the lens occurs due to relaxation, and the symmetry of the lens decreases. On the other hand, when the mold temperature is low, the molding cycle time is shortened, but since the molten resin injected into the mold flows while solidifying, the pressure distribution in the lens becomes large and the symmetry of the lens decreases. .

Therefore, in order to mold a lens having good symmetry in a short cycle time, the optimum range of mold temperature was investigated. Using the mold of Example 1 of the invention according to Claims 1 and 7, the lens having the shape shown in FIG. 4 was used as a molding material of acrylic resin Acrypet VH001 manufactured by Mitsubishi Rayon Co., Ltd. Use a controller to adjust the resin temperature to 250
℃, filling time 10 seconds, holding pressure 1000 kg / cm ² ,
Hold time set to 60 seconds, mold temperature 65-115 ℃
Molding was performed by changing the cooling time within the range of, and setting the cooling time as the shortest time at which the lens can be ejected without deformation at each mold temperature, and the asymmetry of the molded lens was investigated. The results are shown in Table 2 (Examples 10 to 12 and Comparative Examples 8 to 10). As shown in Table 2, it was found that a lens having good symmetry can be molded in a short cycle time when the mold temperature is 75 to 95 ° C. The glass transition temperature of acrylic resin Acrypet VH001 manufactured by Mitsubishi Rayon Co., Ltd. was 125 ° C. determined from the temperature dependence of viscoelastic properties, and the mold temperature range was 3 with respect to the glass transition temperature of Acrypet VH001.
It is a temperature range on the low temperature side of 0 to 50 ° C.

In Example 10, the mold of Example 1 of the invention according to Claims 1 and 7 was used, and the mold temperature was set to a temperature lower by 50 ° C. than the glass transition temperature of the molding material. A lens having an asymmetry of 1.5 μm could be molded with a molding cycle time of seconds.

As a comparative example, Table 2 shows a mold temperature of 65.
C., 105.degree. C., 115.degree. C. were set, the results were obtained by molding in the same manner as in Example 10 and measuring the asymmetry (Comparative Examples 8 to 10). In Comparative Example 8, the mold temperature was set to 65.
C., that is, a temperature lower by 60 ° C. than the glass transition temperature 125 ° C. of Acrypet VH001. as a result,
The molding cycle time was 137 seconds and the asymmetry of the lens shape was 3.6 μm. Although the molding cycle time was shorter than that of Example 10, the asymmetry increased. In Comparative Example 9, the mold temperature was set to 105 ° C., that is, a temperature 20 ° C. lower than the glass transition temperature 125 ° C. of Acrypet VH001. As a result, the molding cycle time is 214
Second, the asymmetry of the lens shape was 1.9 μm, the molding cycle time was longer and the asymmetry was increased as compared with Example 10. In Comparative Example 10, the mold temperature was 115.
C., that is, a temperature 10 ° C. lower than the glass transition temperature 125 ° C. of Acrypet VH001. as a result,
The molding cycle time was 295 seconds, and the asymmetry of the lens shape was 4.4 μm, so that the molding cycle time was long and the asymmetry was increased as compared with Example 10.

[Example 11] In Example 11 of the invention according to claim 2 shown in Table 2, the mold temperature was 85 ° C, that is, from the glass transition temperature 125 ° C of Acrypet VH001 to 4 ° C.
By setting the temperature 0 ° C. lower, it was possible to mold a lens having an asymmetry of 0.9 μm with a molding cycle time of 159 seconds.

[Embodiment 12] In Embodiment 12 of the invention according to claim 2 shown in Table 2, the mold temperature is 95 ° C., that is,
By setting the glass transition temperature of Acrypet VH001 at 30 ° C. lower than the glass transition temperature of 125 ° C., a lens having an asymmetry of 0.8 μm could be molded at a molding cycle time of 182 seconds.

[0049]

[Table 2] [Embodiment 13] FIG. 8 is a sectional view of a mold of the invention according to claims 3 and 8 of the present invention. In FIG.
For the same or equivalent members as described in,
The same reference numerals are given and detailed description is omitted. In FIG.
The movable mold insert piece 5 is connected to the ejector plate 7, and the movable mold insert piece 5 is connected via the ejector plate 7.
The lens 4 can be released from the movable mold by protruding.

Using the mold having the configuration shown in FIG. 8, the lens having the shape shown in FIG. 4 was used as a molding material of acrylic resin Acrypet VH001 manufactured by Mitsubishi Rayon Co., Ltd. Use, mold temperature 110 ℃, resin temperature 2
50 ° C, filling time 10 seconds, holding pressure 1000 kg / cm
^{2. The} pressure holding time is set to 60 seconds, the cooling time is set to the shortest time to allow the lens to be projected without deformation, and the fixed mold insert piece 1 and the movable mold insert piece 5 are arranged so that the shape of the formed lens becomes the design shape of the lens. The lens surface shape is corrected, and the protrusion from the movable mold is molded by protruding the movable mold insert piece 5. As a result, a lens with a shape accuracy of ± 2.5 μm is molded with a cooling time of 190 seconds and a molding cycle time of 270 seconds. We were able to. In the case of molding in the same manner by ejecting with an ejector pin, in order to mold a lens of similar shape accuracy, the cooling time is 193 seconds and the molding cycle time is 273 seconds. In this embodiment, the ejector pin is used. The cooling time was shortened by 3 seconds, and the molding cycle time was shortened by 3 seconds, as compared with the case of protruding and molding.

[Embodiment 14] FIG. 9 shows a fourth embodiment of the present invention.
It is sectional drawing of the insertion piece of invention which concerns on 9 and 9. In FIG. 9, 5 is a movable die insert piece, 5a is a plating layer of the movable die insert piece, 8 is a holder component made of hardened steel, 8a is a sliding surface of the holder component, and 9 is a screw for fixing the insert die.

At the joint between the movable mold insert piece 5 and the holder 8, the dimensional difference between the outer diameter of the movable mold insert piece 5 and the inner diameter of the holder 8 is 20 μm or less, that is, in order to prevent burrs from being generated in the lens molded product. , The gap must be 20 μm or less. Usually, the lens curved surface and the outer peripheral portion of the movable mold insert 5 are provided with an amorphous nickel plating layer 5a for mirror-finishing by diamond cutting, and the outer peripheral portion has low durability against sliding. In this embodiment, since the holder part 8 made of hardened steel is covered except the part forming the lens curved surface of the movable mold insert piece, the durability of the sliding part is improved.

Using the mold (FIG. 8) of Embodiment 13 of the invention according to claims 3 and 8 having the movable mold insert having the structure shown in FIG. 9, the lens having the shape shown in FIG. Using acrylic resin Acrypet VH001 manufactured by Rayon Co., Ltd. as a molding material and using a water medium mold temperature controller, the mold temperature is set to 1
10 ° C., resin temperature 250 ° C., filling time 10 seconds, holding pressure 1000 kg / cm ² , holding pressure 60 seconds,
The cooling time is set to the shortest time that the lens can be projected without deformation,
The lens surface shapes of the fixed mold insert piece 1 and the movable mold insert piece 5 were modified so that the shape of the molded lens became the design shape of the lens, and the protrusion from the movable mold was formed by protruding the movable mold insert piece 5. As a result, it was possible to mold a lens having a shape accuracy of ± 2.5 μm with a molding cycle time of 270 seconds. In addition, after molding for 50,000 shots, the outer peripheral portion of the cavity was not damaged.

[Embodiment 15] FIG. 10 is a sectional view of an insert piece of the invention according to claims 5 and 10 of the present invention. Figure 1
In 0, 10 is a ring and 10a is a sliding surface of the ring. The diameter of the curved surface portion of the movable mold insert piece 5 forming the curved surface portion of the lens is made smaller than the diameter of the insert piece slide portion, and the ring 10 is fitted into the reduced cylindrical portion, so that the plating layer 5a becomes the slide portion. Instead, the ring outer peripheral portion 10a becomes the sliding surface. In order to attach the ring 10 to the movable mold insert piece 5, first, the inner diameter of the ring is machined to be smaller than the outer diameter of the insert piece of the ring attachment portion, and then the ring 10 is warmed so that the ring inner diameter portion becomes larger than the outer shape of the ring attachment portion. You just have to make it bigger. Usually, the lens curved surface and the outer peripheral portion of the movable mold insert 5 are provided with an amorphous nickel plating layer 5a for mirror-finishing by diamond cutting, and the outer peripheral portion has low durability against sliding. ,
In this embodiment, since the ring-shaped hardened steel 10 was attached to the outer peripheral sliding portion of the insert piece, the durability of the sliding portion was improved.

Using the mold (FIG. 8) of Embodiment 13 of the invention according to claims 3 and 8 having the movable mold insert having the structure shown in FIG. 10, the lens having the shape shown in FIG. Using acrylic resin Acrypet VH001 manufactured by Rayon Co., Ltd. as a molding material and using a water medium mold temperature controller, the mold temperature is set to 1
10 ° C., resin temperature 250 ° C., filling time 10 seconds, holding pressure 1000 kg / cm ² , holding pressure 60 seconds,
The cooling time is set to the shortest time that the lens can be projected without deformation,
The lens surface shapes of the fixed mold insert piece 1 and the movable mold insert piece 5 were modified so that the shape of the molded lens became the design shape of the lens, and the protrusion from the movable mold was formed by protruding the movable mold insert piece 5. As a result, it was possible to mold a lens having a shape accuracy of ± 2.5 μm with a molding cycle time of 270 seconds. In addition, after molding for 50,000 shots, the outer peripheral portion of the cavity was not damaged.

[Embodiment 16] FIG. 11 is a sectional view of a die of the invention according to claims 6 and 11 of the present invention. Figure 11
In FIG. 1, the same or equivalent members as those described in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted. In FIG. 11, reference numeral 11 denotes a pressurizing cylinder for pressurizing the movable mold insert piece 5. The mold shown in FIG. 11 is a four-cavity mold, and includes a fixed mold insert piece 1 and a movable mold insert piece 5.
There are four pairs of and there are four cavities. A pressure cylinder 11 is installed on each of the four movable mold insert pieces 5. 12 is a control device for the pressurizing cylinder 11,
The pressurizing force of each pressurizing cylinder 11 is independently controlled based on the shape measurement result of each lens molded in each cavity.

In the four-cavity mold according to the present invention, as shown in FIG.
Using the acrylic resin Acrypet VH001 manufactured by Mitsubishi Rayon Co., Ltd. as a molding material, the lens having the shape shown in FIG.
50 ° C, filling time is 10 seconds, cooling time is 100 seconds, holding pressure is 1000 kg / cm ² , holding pressure time is 50 seconds, cooling time is 95 seconds. The insert piece 5 is extruded to melt molten resin at 660 kg /
After compressing at 40 cm ² for 40 seconds, the surface shapes of the fixed mold insert piece 1 and the movable mold insert piece 5 are modified so that the shape of the formed lens approaches the design shape of the lens. Shape accuracy of ± 2.2μm, ±
It was 3.3 μm, ± 3.6 μm, and ± 2.5 μm. When the required accuracy of the lens was ± 4 μm, the yield was 100%.

When molding was continued under the same conditions for about half a year,
If water stains adhere to the cooling holes, the cooling performance of the mold deteriorates,
The shape accuracy of each of the four lenses is ± 2.6μ
m, ± 5.6 μm, ± 3.5 μm, ± 4.8 μm, and the yield was reduced to 50%. In order to increase the yield, it is conventionally necessary to disassemble and clean the mold to improve the cooling performance of the mold, but in this embodiment, it is necessary to adjust the compression pressure by each pressurizing cylinder. Thus, the shape accuracy of each lens was adjusted separately. That is, when the relationship between the compression pressure by the pressurizing cylinder 11 and the shape accuracy of the lens was investigated in advance, as shown in FIG. 12, the compression accuracy was changed by 10 kg / cm ² , and the shape accuracy of the lens was about 1. It was found that the adjustment can be made to 0 μm. Therefore, for the lenses whose shape accuracy was ± 5.6 μm and ± 4.8 μm, the compression pressure by the pressure cylinder of the corresponding insert piece was set to the initial value of 660 kg.
Respect / cm ^2, respectively ± 56kg / cm ² and ±
Was molded 48 kg / cm ² is changed, the former, the compression pressure + 56kg / cm ² shape accuracy when changing is 2.2 .mu.m, the compression pressure for the latter -48
The shape accuracy was 2.4 μm when the kg / cm ^{2 was} changed, and the yield was improved to 100%.

In this embodiment, the shape of the molded lens was measured, and the compression pressure for each insert piece was controlled based on the result. However, the lens shape measuring device and the compression pressure control device were connected, and one shot was taken. The compression pressure may be feedback-controlled based on the measurement result of the lens shape every time or every fixed shot.

In the above description, the present invention has been described for the case where an acrylic resin is used as a lens molding resin, but the present invention is not limited to such molding resins, for example, polycarbonate, polystyrene, various polyolefin transparent resins, norbornene various resins. It is also suitably applicable when using a transparent resin, various fluorine-based transparent resins, styrene-acrylonitrile-based copolymer resin, and the like.

[0061]

As described above, according to the inventions according to claims 1 and 7 of the present invention, the fixed mold and the movable mold which are arranged to face each other, and the container inserted in the fixed mold and the movable mold. In a lens mold having a piece, a tank-type cooling hole is installed in the insertion piece, the radius of the insertion piece is A, the radius of the tank-type cooling hole is B, and the number of tank-type cooling holes installed in each insertion piece is N. , The distance from the approximate plane of the curved lens surface processed into the insert piece to the tip of the tank cooling hole is L, L and (AB
When the ratio of × N ^1/2 ) is K (K = L / (A−B × N ^1/2 )), K is configured so as to fall within the following range. It has the effect of molding at the molding cycle time.

0.75 ≦ K ≦ 1.25 According to the invention of claim 2 of the present invention, claim 1
In the invention according to (1), since the mold temperature is controlled to be 30 to 50 ° C. lower than the glass transition temperature of the molding resin, the molding cycle time can be further shortened and the lens asymmetry can be reduced.

Further, according to the inventions according to claims 3 and 8 of the present invention, in the inventions according to claims 1 and 7, the movable die insert piece is connected to the ejector plate, and the protrusion of the lens from the movable die is Since it is carried out by projecting the movable mold insert piece through the ejector plate, there is an effect of further shortening the molding cycle time.

Further, according to the inventions according to claims 4 and 9 of the present invention, in the invention according to claims 3 and 8, the parts other than the part forming the lens curved surface of the insert piece are covered with a holder part made of hardened steel. Therefore, there is an effect that the durability of the insert piece is increased and the molding cycle time is shortened.

Further, according to the inventions according to claims 5 and 10 of the present invention, in the inventions according to claims 3 and 8,
Since the ring-shaped hardened steel is attached to the outer periphery of the insert piece, the insert piece has the effects of improving the durability and shortening the molding cycle time.

According to the sixth and eleventh aspects of the present invention, the fixed mold and the movable mold are disposed so as to face each other, and the plurality of insertion pieces inserted into the fixed mold and the movable mold, respectively. A molten resin is filled in a cavity formed by the fixed mold insert piece and the movable mold insert piece, and the molten resin is compressed by pressurizing the insert piece with a pressurizing cylinder to form a shape. In the multi-cavity lens mold, a pressure cylinder is installed for each movable mold insert piece that forms the cavity, and based on the shape measurement result of each molded multi-cavity lens, Since the pressing force is controlled, the shape of each lens is instantaneously adjusted separately, the shape accuracy of each lens is improved, and the yield is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold of an embodiment of the invention according to claims 1 and 7 of the present invention.

FIG. 2 is a plan view of a movable mold of an embodiment of the invention according to claims 1 and 7 of the present invention.

FIG. 3 is a graph showing the effect of the conventional example.

FIG. 4 is a cross-sectional view and a plan view showing a lens shape according to an example of the present invention.

FIG. 5 is a graph showing effects of the embodiments of the invention according to claims 1 and 7 of the present invention.

FIG. 6 is a graph showing effects of the embodiments of the invention according to claims 1 and 7 of the present invention.

FIG. 7 is a graph showing effects of the embodiments of the invention according to claims 1 and 7 of the present invention.

FIG. 8 is a cross-sectional view of a mold of an embodiment of the invention according to claims 3 and 8 of the present invention.

FIG. 9 is a sectional view of an insert piece of an embodiment of the invention according to claims 4 and 9 of the present invention.

FIG. 10 is a sectional view of an insert piece of an embodiment of the invention according to claims 5 and 10 of the present invention.

FIG. 11 is a cross-sectional view of a mold of an embodiment of the invention according to claims 6 and 11 of the present invention.

FIG. 12 is a graph showing an effect of the embodiment of the invention according to claim 6 of the present invention.

[Explanation of symbols]

 1 Fixed type insert piece 2 Tank type cooling hole 3 Baffle plate 4 Lens 5 Movable type insert piece 6 Ejector pin 7 Ejector plate 8 Holder parts 9 Screw 10 Ring 11 Pressure cylinder 20 Fixed type 21 Movable type

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshikazu Ukai 8-1-1 Tsukaguchihonmachi, Amagasaki City MITSUBISHI ELECTRIC CO., LTD. (72) Inventor Hitoshi NAGANO Nagaokakyo Baba Institute 1 MITSUBISHI ELECTRIC CORPORATION In-house Kyoto Works (72) Inventor Kazuo Tsukakoshi No. 1 Baba-Zou Nagaokakyo City Mitsubishi Electric Co., Ltd. (72) Inventor Muneaki Mukita 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Electric Corporation Material and Device Research In-house (72) Inventor Wataru Suzuki 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Material Device Research Center

Claims (11)

[Claims] 1. A lens mold having a fixed mold and a movable mold which are arranged to face each other, and a insert piece inserted into each of the fixed mold and the movable die, wherein a tank-type cooling hole is provided in each of the insert pieces. , The radius of the insert piece is A, the radius of the tank type cooling hole is B, the number of the tank type cooling holes installed in each insert piece is N, and the tank type cooling is performed from the approximate plane of the curved lens surface of the insert piece. Let L be the distance to the tip of the hole,
The ratio of L to (A−B × N ^1/2 ) is K (K = L / (A−B ×
N ^1/2 )), a method of manufacturing a plastic lens is characterized by using a mold configured such that K is in the following range and performing injection molding. 0.75 ≦ K ≦ 1.25 2. The method for producing a plastic lens according to claim 1, wherein the mold temperature is controlled at a temperature lower than the glass transition temperature of the molding resin by 30 to 50 ° C. to perform the injection molding. 3. The insertion piece inserted in the movable die is connected to an ejector plate, and the lens is ejected from the movable die by ejecting the insertion piece through the ejector plate. A method for manufacturing the described plastic lens. 4. The method of manufacturing a plastic lens according to claim 3, wherein a portion of the insert piece inserted into the movable die other than the portion forming the lens curved surface is covered with a holder component made of hardened steel. 5. The method of manufacturing a plastic lens according to claim 3, wherein a ring made of hardened steel is attached to the outer peripheral sliding portion of the insert piece inserted in the movable mold. 6. A fixed die insert piece and a movable die insert piece having a fixed die and a movable die arranged to face each other, and a plurality of insert pieces inserted into the fixed die and the movable die, respectively. In the multi-cavity lens mold, the molten resin is filled into the cavity formed by, and the molten resin is compressed by pressurizing the insert piece with a pressurizing cylinder. A manufacturing method of a plastic lens, characterized in that a pressure cylinder is installed for each movable mold insert piece to be formed, and the pressure applied to each pressure cylinder is controlled based on the shape measurement result of each molded multi-cavity lens. Method. 7. A lens mold having a fixed die and a movable die arranged to face each other, and insert pieces inserted into the fixed die and the movable die, respectively, wherein tank type cooling holes are provided in each of the insert pieces. Is installed, the radius of the insert piece is A, the radius of the tank-type cooling hole is B, the number of tank-type cooling holes installed in each insert piece is N, and the tank-type cooling is performed from the approximate plane of the curved lens surface of the insert piece. The distance to the tip of the hole is L, and the ratio of L to (A−B × N ^1/2 ) is K (K = L / (A
-B × N ^1/2 )), the apparatus for producing a plastic lens is configured such that K is in the following range. 0.75 ≦ K ≦ 1.25 8. The insert piece inserted into the movable die is connected to an ejector plate, and the lens is ejected from the movable die by ejecting the insert piece through the ejector plate. The plastic lens manufacturing apparatus according to claim 7, wherein 9. The apparatus for manufacturing a plastic lens according to claim 8, wherein a portion other than a lens curved surface portion of the insert piece inserted into the movable mold is covered with a holder component made of hardened steel. 10. The plastic lens manufacturing apparatus according to claim 8, wherein a ring made of hardened steel is attached to the outer peripheral sliding portion of the insert piece inserted into the movable die. 11. A fixed die insert piece and a movable die insert piece having a fixed die and a movable die arranged to face each other, and a plurality of insert pieces inserted in the fixed die and the movable die, respectively. In the multi-cavity lens mold, the molten resin is filled into the cavity formed by, and the molten resin is compressed by pressurizing the insert piece with a pressurizing cylinder. A pressurizing cylinder is installed for each movable mold insert to be formed, and a control device is provided for independently controlling the pressurizing force of each pressurizing cylinder based on the shape measurement result of each molded multi-cavity lens. An apparatus for manufacturing a plastic lens, which is characterized by: