JP4108195B2 - Plastic molded product and molding method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plastic molded product and a molding method thereof, for example, a plastic molded product applied to an optical scanning system such as a laser type digital copying machine, a laser printer, and a facsimile machine, and an optical device such as a video camera, The present invention relates to a plastic molding product such as a thick-walled or uneven-shaped plastic lens having a highly accurate mirror surface or a plastic mirror that can be molded at low cost and with high accuracy.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, optical elements such as rectangular lenses and mirrors having laser beam imaging and various correction functions are used in optical writing units such as laser-type digital copying machines, printers, and facsimile machines.
In recent years, these optical elements have changed from glass to plastic due to demands for cost reduction of products, and in order to cover multiple functions with minimum elements, their mirror surface shape is not only spherical but also complicated It has come to be formed into a non-spherical shape. Further, in the case of a lens, the lens thickness is often increased, and the lens thickness is often designed to be an uneven shape in which the lens thickness is not constant in the longitudinal direction.
[0003]
Such plastic molded products can be mass-produced at low cost by inserting a resin base material into the mold cavity formed in the molded product shape or injection-filling molten resin, even if it is a special shape. Can do.
[0004]
[Problems to be solved by the invention]
However, in such conventional plastic molding, in the process of cooling and solidifying the molten resin material in the mold cavity, it is desirable to make the plastic pressure and resin temperature uniform in the cavity. However, depending on the shape of the molded product, for example, when the lens is unevenly shaped, the cooling rate of the resin varies depending on the part due to the difference in the lens thickness. Due to the difference, the shape accuracy deteriorates, and sinking may occur at a thick lens thickness. For example, when the thick and uneven plastic lens 10 shown in FIG. 7 is molded, the mirror surface (transfer surface) 11, 12 and the side surface (non-transfer surface) 13 are sinked as shown in FIG. 14 will occur.
[0005]
In order to solve this problem, in the injection molding method in which molten resin is injected and filled into the cavity of the mold, if the injection pressure of the molten resin is increased to increase the injection filling amount, the internal strain of the plastic molded product increases. In particular, in the case of a thick or uneven shape, the internal strain increases at the thin portion, which may adversely affect the optical performance.
[0006]
In other words, if the injection pressure is lowered to reduce the internal strain and the injection filling amount of the molten resin is reduced, sinks may occur in the thick wall portion, etc., while the injection filling amount of the molten resin is increased by increasing the injection pressure of the molten resin. If the number is increased, the internal strain may increase at the thin wall portion.
On the other hand, in the injection molding method, by allowing the nest that constitutes the cavity wall surface to move within the mold, the volume shrinkage due to cooling of the filled resin, for example, there is a deviation in the lens thickness. A so-called injection compression molding method is also performed, in which shape accuracy is ensured by advancing the movable nest so as to follow the difference in volume shrinkage generated in each part in the longitudinal direction and compensating pressure to apply equal pressure. ing.
[0007]
However, even with this injection compression molding method, it is difficult to accurately follow the movable nest, and there is a problem that the shape accuracy may not be ensured due to a sink on a part of the mirror surface.
For this reason, research has been conducted to improve the drawbacks of the injection molding method and injection compression molding method. For example, as disclosed in JP-A-2-175115 and JP-A-6-304973, a transfer surface is disclosed. A molding method that generates sink marks is proposed.
[0008]
However, even if this molding method is applied directly to the manufacture of uneven, thick, large aperture, irregularly shaped plastic lenses, etc., sinking may occur in the thick part adjacent to the transfer surface due to the difference in cooling rate. Thus, the resin internal pressure and internal strain may remain in the thin wall portion, which may deteriorate the shape accuracy and increase the birefringence, leading to a decrease in the optical accuracy of the lens.
[0009]
Therefore, the present invention provides a concave or convex shape formed by incomplete transfer at a position where the occurrence point other than the transfer surface is controlled, thereby eliminating the residual resin internal pressure and internal distortion, and so on. An object of the present invention is to provide a high-precision plastic molded product with a production cost comparable to that of a thin molded product even if it has an uneven thickness.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention forms a transfer surface by generating a resin pressure on a resin in a cavity of a mold having one or more transfer surfaces and transferring the transfer surface. In an unevenly shaped plastic molded product, at least one or two or more resin internal pressures or indentations formed in a concave or convex shape by incomplete transfer of the mold cavity shape to a thin wall portion where internal strain is likely to occur. It has a complete transfer portion.
[0011]
In this case, even if the resin internal pressure or internal strain is likely to occur, the imperfect transfer part becomes concave or convex depending on the resin pressure due to imperfect transfer of the mold cavity shape. And prevents internal distortion. Therefore, only by providing the incomplete transfer portion, it is possible to easily ensure the optical accuracy and the like together with the transfer surface of the portion requiring the shape accuracy.
[0012]
By forming the imperfect transfer part in a part other than the transfer surface, the shape accuracy of the entire transfer surface can be secured, and by forming it on the extended surface of the transfer surface, a part of the surface can be transferred. Even if it is a surface, the shape accuracy can be ensured. Note that an incomplete transfer portion may be provided on a portion of the transfer surface that does not require shape accuracy.
As a reference, the edge shape of this imperfect transfer part is formed so as to follow the flat or curved surface shape of the transfer surface, so that the internal pressure and internal strain of the part extending to constitute the transfer surface can be generated. It can be prevented uniformly, and by forming it along the shape of the transfer surface at the part sandwiched by the transfer surface, it can prevent the occurrence of internal pressure and internal strain of the resin in a large area, The accuracy and optical accuracy can be further improved. Even if two or more imperfect transfer parts are formed on the same surface other than the transfer surface, the internal pressure and internal strain can be prevented uniformly in a large area, Generation | occurrence | production of distortion can be prevented locally and shape accuracy, optical accuracy, etc. can be improved more.
[0013]
Then, by forming one or more of the transfer surfaces on the optical mirror surface, it is possible to produce a plastic molded product of an optical element having excellent shape accuracy and optical accuracy.
This plastic molded product may be molded by, for example, injection-filling a resin into a mold cavity that forms an imperfect transfer portion by an injection molding method. For example, a resin pressure is generated in the resin in the cavity. After transferring the surface to be transferred, the concave shape of the incomplete transfer portion is generated by generating local mold release contraction with respect to the cavity shape, and the incomplete transfer is performed by generating local resin pressure release with respect to the cavity shape. The convex shape of the part can be formed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
1 and 2 are views showing a first embodiment of a plastic molded article and a molding method thereof according to the present invention, FIG. 1 is a perspective view showing the plastic molded article, and FIG. 2 is a molding for carrying out the molding method. It is sectional drawing which shows a metal mold | die .
[0015]
In FIG. 1, reference numeral 10 denotes a plastic lens (optical element). The plastic lens 10 has an optical mirror surface (transfer surface) 11 that is curved so that the center of one surface side is thick, and the other surface facing the one surface. The plastic lens 10 is formed in an uneven shape having a mirror surface 12 having a flat side and a side surface (non-transfer surface) 13 between the mirror surfaces 11 and 12. The incomplete transfer portion 21 having a concave shape or a convex shape is formed on the side surface 13 by molding by an injection molding method using 30.
[0016]
The plastic lens (plastic molded product according to the present invention) 10 is not limited to the injection molding method, and various plastic molding methods such as a compression molding method and a blow molding method can be used. Since the inner layer of the molten resin is solidified immediately after injection and filling, the surface layer portion is solidified. As will be described later, the internal resin can be reduced at any position so as to reduce the internal distortion while forming a highly accurate transfer surface. The incomplete transfer portion can be easily made by separating the resin and the cavity wall surface of the mold, and a thick and uneven molded product can be efficiently produced. Therefore, it is preferable to select an injection molding method as in this embodiment.
[0017]
As shown in FIG. 2, the molding die 30 defines a cavity 31 that can be opened and closed by a pair of upper and lower molds, and the molten resin 100 is injected and filled therein. The transfer surfaces 32 a and 33 a formed on the mirror surfaces of the fixed inserts 32 and 33 are defined by the side wall surfaces 34 and 35, and the incomplete transfer portion 21 of the plastic lens 10 is formed inside the side wall surface 34. A movable insert 36 having a corresponding cross-sectional shape and capable of moving forward and backward toward the inside of the cavity 31 is provided.
[0018]
The molding die 30 is configured to perform the molding method of the plastic lens 10 by the injection molding method by automatically or manually controlling the opening and closing and the movement of the movable insert 36, as shown in FIG. 2 (a). As in the normal injection molding method, after the molten resin 100 is injected and filled into the cavity 31, the cooling and solidification of the molten resin 100 in the cavity 31 proceeds and the resin pressure reaches a predetermined pressure. As shown in b), the movable insert 36 is retracted in a direction away from the resin 100 in the cavity 31 and used to provide a gap S between the side wall surface of the movable insert 36 and the resin 100. it can.
[0019]
As a result, the molten resin 100 injected and filled into the cavity 31 of the molding die 30 generates a resin pressure on the wall surface of the cavity 31 and is brought into close contact with the mirror surfaces 32a and 33a and the side wall surfaces 34 and 35 to be cooled and solidified. However, after a certain period of time has passed, the movable insert 36 moves backward and the side wall surfaces are separated, whereby the corresponding portion is deformed according to the resin pressure. At this time, if the resin pressure remains, the separation portion of the resin 100 has a convex shape whose edge portion is similar to the side wall surface of the movable insert 36 due to local pressure release, and the resin pressure is less than atmospheric pressure. The concave lens shape is similar due to local mold release contraction, and the plastic lens 10 is formed with the incomplete transfer portion 21 formed therein.
[0020]
The separated portion of the resin 100 from which the side wall surface of the movable insert 36 is separated can be easily deformed as a free surface, and the heat of the movable insert 36 is difficult to escape. Since the resin moves and contracts preferentially at a higher temperature than the part in contact with the wall surface, it becomes a concave shape, so it does not necessarily become a convex shape even if it becomes a convex shape immediately after separation. . In particular, the filling pressure of the molten resin 100 into the cavity 31 needs to be low enough so that the internal strain does not affect the optical performance. That is, sink marks occur preferentially.
[0021]
Therefore, the plastic lens 10 only forms the incomplete transfer portion 21 having a convex shape or a concave shape according to the resin pressure in a portion corresponding to the side wall surface of the movable insert 36 by an injection molding method using the molding die 30. Thus, the resin internal pressure and the internal strain do not remain, and the optical accuracy having the mirror surfaces 11 and 12 formed with the required shape accuracy can be obtained.
[0022]
Further, the incomplete transfer portion 21 can be formed with high accuracy as a whole by forming it on a side surface different from the mirror surfaces 11 and 12. Further, by making the inner side of the side wall surface 34 defining the cavity 31 of the molding die 30 the side wall surface of the movable insert 36, the incomplete transfer portion 21 is positioned adjacent to the mirror surfaces 11 and 12 continuously. Therefore, the plastic lens 10 can be obtained with low distortion and good shape accuracy without wrapping around the mirror surfaces 11 and 12.
[0023]
In addition, as resin which produces the plastic lens 10, when transparency is requested | required, amorphous resin whose softening temperature is the glass transition temperature, for example, polymethacryl resin, polycarbonate resin, alicyclic acryl Resin, cyclic polyolefin copolymer (for example, Nippon Zeon Co., Ltd. trade name: ZEONEX) and the like can be used. In addition to the optical element, it is possible to use a crystalline resin whose softening temperature is the melting temperature.
[0024]
As described above, in the present embodiment, the plastic lens 10 has the incomplete transfer portion 21, so that even if the plastic lens 10 is thick or uneven, the resin internal pressure and the internal strain do not remain. It can be manufactured at the same production cost as a thin-walled molded article by an injection molding method that has optical accuracy and the like and is low in manufacturing cost and suitable for mass production.
[0025]
Next, FIG. 3 is a view showing a second embodiment of the plastic molded product and the molding method thereof according to the present invention, and is a perspective view showing the plastic molded product molded by the molding method described in the above embodiment . In the present embodiment, since a plastic molded product is molded in substantially the same manner as in the above-described embodiment, the description of the molding method will be briefly described with reference to FIG. 2 (the same applies to the embodiments described below).
[0026]
In FIG. 3, the plastic lens 10 of the present embodiment has mirror surfaces 11, 12 and a side surface 13, and the side surface 13 has an attachment reference surface (transfer surface) in the center in the longitudinal direction instead of the incomplete transfer portion 21. 15, and concave or convex imperfect transfer portions 22 are formed in the thin portions on both sides of the attachment reference surface 15.
The plastic lens 10 is formed by an injection molding method using a molding die 30 so that a transfer receiving surface of a fixed insert provided inside the side wall surface 34 defining the cavity 31 is closely transferred to the mounting reference surface 15. In addition, the movable inserts disposed on both sides of the fixed insert are retracted by cooling and solidifying the surface layer of the molten resin 100 injected and filled into the cavity 31 and the resin pressure is set at a predetermined pressure, thereby providing the gap S. Thus, an incomplete transfer portion 22 having a convex shape due to local pressure release corresponding to the resin pressure or a concave shape due to local mold release contraction is formed.
[0027]
Therefore, the plastic lens 10 can form the mounting reference surface 15 together with the transfer surfaces 11 and 12 with high shape accuracy by the incomplete transfer portion 22, and in the case of a method of inducing sink marks by a conventional injection molding method. While the entire surface is concave and the shape accuracy has not been achieved, the surface cannot be fixed as an attachment reference.
By providing the mounting reference surface 15 on the same side surface (extension surface) 13 between the incomplete transfer portions 22, mounting accuracy can be ensured.
[0028]
Since the incomplete transfer portion 22 is provided in the thin portion of the plastic lens 10, the internal pressure and internal strain of the resin are not left as a whole, and the thin portion is locally prevented from generating the internal pressure and internal strain of the resin. Can be prevented. Moreover, since the incomplete transfer part 22 is provided in two places, the area which deform | transforms into a convex shape or a concave shape can be earned, and the height and the depth which affect the light transmission area | region can be made small.
[0029]
As described above, in the present embodiment, in addition to the operational effects of the above-described embodiments, the plastic lens 10 is provided with the incomplete transfer portion 22 even when the plastic lens 10 has the mounting reference surface 15 on the side surface 13. While securing the mounting accuracy with the high shape accuracy of 15, it is possible to effectively relieve the resin internal pressure and the internal strain in the thin wall portion, thereby further improving the optical accuracy.
[0030]
Note that, as another aspect of the present embodiment, it is needless to say that the present invention can be applied to the case where it is not necessary to provide the attachment reference surface 15 as shown in FIG.
Next, FIG. 5 is a diagram showing a third embodiment of the plastic molded product and the molding method thereof according to the present invention, and is a perspective view showing the plastic molded product molded by the molding method described in the above embodiment .
[0031]
In FIG. 5, the plastic lens 10 of the present embodiment has mirror surfaces 11 and 12 and a side surface 13, and the side surface 13 has a large circular concave or convex shape in the center in the longitudinal direction instead of the incomplete transfer portion 21. An incomplete transfer portion 23 having a shape and small circular concave or convex incomplete transfer portions 24 are formed on the thin portions on both sides of the incomplete transfer portion 23.
[0032]
The plastic lens 10 is a molten resin 100 in which three movable nests provided inside the side wall surface 34 defining the cavity 31 are injected and filled into the cavity 31 by an injection molding method using a molding die 30. The incomplete transfer portion 23 having a convex shape due to local pressure release corresponding to the resin pressure or a concave shape due to local mold release contraction by retreating at the predetermined pressure of the solidification of the surface layer and the resin pressure and providing a gap S, 24 is formed.
[0033]
Accordingly, the plastic lens 10 gains an area to be deformed into a convex shape or a concave shape by the incomplete transfer portions 23 and 24 and reduces the height and depth that affect the light transmission region, while reducing the internal pressure and internal strain of the resin lens 10 as a whole. Can be prevented locally, and the imperfect transfer portion 23 can locally prevent the thin-walled portion from causing resin stress or internal strain.
[0034]
Further, the incomplete transfer portions 23 and 24 are not particularly limited in shape, but there is an advantage that the processing of the mold becomes easy by forming the edge portion in a circular shape.
As described above, in the present embodiment, in addition to the effects of the above-described embodiment, in addition to the thin imperfect transfer portion 24, the large-diameter imperfect transfer portion 23 is provided, so that the internal pressure of the resin can be more effectively reduced. The internal strain can be relaxed and the optical accuracy can be further improved.
[0035]
Next, FIG. 6 is a diagram showing a fourth embodiment of the plastic molded product and the molding method thereof according to the present invention, and is a perspective view showing the plastic molded product molded by the molding method described in the above embodiment .
In FIG. 6, the plastic lens 10 of the present embodiment has mirror surfaces 11, 12 and side surfaces 13, and the side surfaces 13 sandwiched between the mirror surfaces 11, 12 replace the incomplete transfer portion 21 with the mirror surfaces 11, 12. The imperfect transfer portion 25 having a similar shape is formed by forming an edge so as to be along the curved surface / planar shape adjacent to each other via a gap.
[0036]
In this plastic lens 10, a movable nest having a similar cross-sectional shape provided inside the side wall surface 34 defining the cavity 31 is injected and filled into the cavity 31 by an injection molding method using a molding die 30. When the surface layer of the molten resin 100 is cooled and solidified, the recess S is retracted at a predetermined pressure of the resin pressure to provide a void S, or a concave shape due to local pressure release corresponding to the resin pressure or a concave shape due to local release shrinkage A transfer portion 25 is formed.
[0037]
Therefore, the plastic lens 10 gains an area to be deformed into a convex shape or a concave shape by the incomplete transfer portion 25 and reduces its height and depth that affect the light transmission region, while the resin internal pressure and internal strain remain as a whole. In addition, it is possible to prevent the occurrence of resin stress and internal strain even in the thin portion. As described above, in the present embodiment, in addition to the effects of the above-described embodiment, by providing the imperfect transfer portion 25 having a larger area than the imperfect transfer portions 21 to 24, the resin internal pressure and the internal strain can be more effectively achieved. Can be relaxed, and the optical accuracy can be further improved.
[0038]
Although not shown in the drawings as another aspect of the present embodiment, for example, in the case of manufacturing a large plastic lens 10, incomplete transfer along the curved surface / planar shape of each mirror surface 11, 12 is performed. A portion may be formed (Claim 4), and the imperfect transfer portion may be formed with an edge so as to have an area necessary for preventing the occurrence of resin stress and internal strain. In this case, generation of resin stress and internal strain can be effectively prevented, and the mirror surfaces 11 and 12 uniform in the longitudinal direction can be formed.
[0039]
【The invention's effect】
According to the present invention, the incomplete transfer portion provided in the thin portion where the internal pressure of the resin or internal strain is likely to occur is concave or convex depending on the resin pressure so that the cavity shape of the mold is imperfectly transferred during molding. Therefore, it is possible to prevent the resin internal pressure and internal strain from remaining in the portion, and for example, even in the case of uneven-thickness molded products such as thick wall, large diameter, irregular shape , The resin internal pressure and internal strain of the thin part that could not be reduced can be reduced.
[0040]
Therefore, by setting the incomplete transfer portion at an arbitrary position, it is possible to easily obtain a plastic molded product ensuring shape accuracy and optical accuracy.
If the imperfect transfer portion is formed on a portion other than the transfer surface, the shape accuracy of the entire transfer surface can be ensured. If the imperfect transfer portion is formed on the same surface as an extension of the transfer surface, for example, a part of the surface is assembled. It can be accurately formed as an attached reference surface, and its assembling accuracy can be ensured.
[0041]
Further, the imperfect transfer portion is formed so that its edge shape follows the shape of the transfer surface, is formed in a large area along the shape of the transfer surface, or a plurality of portions are formed on the same surface. Resin internal pressure and internal strain can be effectively relaxed, and the shape accuracy and optical accuracy can be further improved.
Thus, for example, by forming an optical mirror surface as the transfer surface, an optical element that requires a highly accurate shape with low strain can be easily and inexpensively manufactured.
[0042]
The incomplete transfer portion can be formed by an injection molding method that is low in manufacturing cost and suitable for mass production. For example, after the surface to be transferred is transferred by generating resin pressure on the resin in the cavity of the mold The concave shape of the imperfect transfer portion can be formed by generating local mold release contraction to the cavity shape, and the convex shape of the imperfect transfer portion can be formed by generating local resin pressure release to the cavity shape. it can.
[0043]
As a result, a configuration that only forms an incomplete transfer portion can provide a highly accurate plastic molded product at a production cost comparable to that of a thin molded product.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of a plastic molded product and a molding method thereof according to the present invention, and is a perspective view showing the plastic molded product.
FIG. 2 is a cross-sectional view showing a molding die for performing the molding method.
FIG. 3 is a view showing a plastic molded article and a molding method thereof according to a second embodiment of the present invention, and is a perspective view showing the plastic molded article.
FIG. 4 is a perspective view of a plastic molded article showing another embodiment.
FIG. 5 is a view showing a plastic molded article and a molding method thereof according to a third embodiment of the present invention, and is a perspective view showing the plastic molded article.
FIG. 6 is a view showing a plastic molded article and a molding method thereof according to a fourth embodiment of the present invention, and is a perspective view showing the plastic molded article.
FIG. 7 is a perspective view showing a conventional plastic molded product.
FIG. 8 is a perspective view showing a plastic molded article for explaining the problem.
[Explanation of symbols]
10 Plastic lenses (plastic molded products)
11, 12 Mirror surface (transfer surface)
13 Side 15 Reference mounting surface (transfer surface)
21-25 Incomplete transfer portion 30 Mold 31 Cavity 32, 33 Fixed insert 32a, 33a Transfer surface 34, 35 Side wall surface 36 Movable insert

Claims (7)

Both ends from the center having transfer surfaces (11, 12) formed by generating resin pressure on a resin in a cavity of a mold having one or more transfer surfaces and transferring the transfer surfaces In the plastic molded product of uneven thickness that the wall thickness becomes thinner
Incomplete transfer portions formed into a concave shape or a convex shape by incomplete transfer of the cavity shape of the mold , both ends of the same surface other than the transfer surface (11, 12) where internal resin pressure and internal strain are likely to occur. A plastic molded product having a thin-walled portion . 2. The plastic molded product according to claim 1 , further comprising an attachment reference surface (15) which is a transfer surface on the same surface other than the transfer surface (11, 12) . The plastic molded product according to claim 1 , further comprising an incomplete transfer portion other than the incomplete transfer portion on the same surface other than the transfer surface (11, 12) . The plastic molded product according to any one of claims 1 to 3, wherein the plastic molded product is an optical element in which one or more of the transfer surfaces (11, 12) are formed on an optical mirror surface . A method for molding a plastic molded product according to any one of claims 1 to 4,
A molding method for a plastic molded article, wherein molding is performed by an injection molding method in which a resin is injected and filled into a cavity of a mold having one or two or more transferred surfaces . A method for molding a plastic molded product according to any one of claims 1 to 4 ,
After transferring the transfer surface by generating a resin pressure on the resin in the cavity of the mold having one or two or more transfer surfaces , the mold release contraction is generated with respect to the cavity shape to cause the non-transfer. A method for molding a plastic molded product, comprising forming a concave shape of a complete transfer portion . A method for molding a plastic molded product according to any one of claims 1 to 4 ,
After the resin surface is transferred to the resin in the cavity of the mold having one or two or more transferred surfaces, the transferred surface is transferred, and then a local resin pressure release for the cavity shape is generated to cause the non-transfer. A method for molding a plastic molded product, comprising forming a convex shape of a complete transfer portion.

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