JP2003089136A - Molding method for plastic molded article and mold therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for a plastic molded article for manufacturing an optical element made of plastics such as the lens, mirror or the like of a scanning optical system with a high accuracy, and a mold therefor. SOLUTION: The mold 1 has at least one transfer surface 3 among surfaces for forming a cavity 2 and at least one surface among surfaces other than the transfer surface 3 is formed of a slidable cavity insert 4. A molten resin 10 is injected in the cavity 2 of the mold 1 heated to < a softening temperature to fill the cavity and brought into close contact with the transfer surface 3 and subsequently cooled and solidified to mold the plastic molded article. In this case, the cavity insert 4 is separated from the resin 10 to form a gap 6 between the cavity insert 4 and the resin and all of surfaces other than the contact surface with the gap 6 are heated to a predetermined temperature. Accordingly, the non-uniform temperature distribution in the molded article generated when the cavity insert 4 is separated from the resin 10 can be suppressed and the molded article low in strain and having a high accuracy can be molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding a plastic molded product and a mold, and more particularly, to a plastic optical element such as a lens and a mirror used in an electrophotographic scanning optical system and a mold therefor. The present invention relates to a molding method and a mold for a plastic molded product manufactured with high accuracy.

[0002]

2. Description of the Related Art Optical elements such as a rectangular lens or a mirror having a laser beam image forming and various correcting devices are used in an optical writing optical system such as a laser type digital copying machine, a laser printer or a facsimile machine. ing.

In recent years, in order to reduce the cost of products, these optical elements have changed their materials from glass to plastic, and their shapes have lens thicknesses that are thick, thin, or thin depending on the required optical performance. , A uniform thickness shape in the longitudinal direction or an uneven thickness shape, which is not constant, are diversified.

As a method of manufacturing an optical element, an injection molding method is generally used because it is low in manufacturing cost and suitable for mass production. When manufacturing an optical element by an injection molding method, it is desirable that the resin pressure and the resin temperature in the mold become uniform in the step of injecting and filling the resin material heated and melted into the mold and cooling and solidifying. It is desirable to secure the shape accuracy.

However, when the lens thickness is uneven, the cooling rate of the filled resin is different in each part in the longitudinal direction due to the deviation of the lens thickness, and the volume shrinkage amount is different, so that the shape accuracy is deteriorated. However, there is a problem that sink marks are generated in a place where the lens thickness is large. Also,
In the case of thick wall, volume shrinkage is large in the process of cooling the resin, so sink marks are likely to occur, and if the injection pressure is increased to prevent sink marks (when the resin filling amount is increased),
There is a problem that the internal distortion becomes large and the optical performance is adversely affected.

To solve this problem, the mold temperature is set higher than the glass transition temperature (Tg point) of the resin so that the cooling rate of the filled resin is as constant as possible in each part in the longitudinal direction. The problem can be solved by using the method of gradually cooling until the glass transition temperature Tg point or lower.

However, there is a problem that the cooling time (molding time) becomes long and the cost becomes high.

[0008] Therefore, the present applicant has previously proposed that at least one
A pair of golds having one or more transfer surfaces, at least one or more cavity pieces being slidably provided on the surface other than the transfer surfaces, and at least one or more cavities being defined by the transfer surface and the cavity pieces. A mold is prepared, the mold is heated and maintained below the softening temperature of the resin, the molten resin heated above the softening temperature is injected and filled in the cavity, and then resin pressure is generated on the transfer surface to cause the resin In the method for molding a plastic molded article, in which the resin is cooled to a softening temperature or lower, and then the mold is opened and taken out, when the molten resin is cooled to a temperature lower than the softening temperature. A plastic molded product in which at least one of the cavity pieces is slid so as to be separated from the resin to forcibly define a gap between the resin and the cavity piece Proposes a molding method (see Japanese Patent Laid-Open No. 11-28745).

That is, in this method for molding a plastic molded article, a molten resin is injected and filled in a mold, and then a slidable cavity provided on a non-transfer surface is provided while cooling to below the softening temperature of the resin. This is a molding method in which the piece is moved in a direction away from the resin to forcibly define a gap between the cavity piece and the resin. At this time, in the part in contact with the void, the resin does not easily move because the adhesive force with the mold wall surface does not work, and the sink mark (concave shape or convex shape or both of them is preferentially applied to this part. Yes) can be generated. As a result, sink marks can be prevented from occurring on the transfer surface, and a molded product with high shape accuracy can be obtained. Further, by molding at low pressure, it is possible to obtain a molded product having very good internal strain.

[0010]

However, in such a conventional method for molding a plastic molded article,
There were the following problems.

That is, as shown in FIG. 12, in the conventional method for molding a plastic molded article, the molten resin 1 is placed in the cavity 102 of the mold 100 having the transfer surface 101.
After injection filling 03, while cooling to below the softening temperature of the resin 103, the slidable cavity piece 104 on the non-transfer surface is moved in a direction away from the resin 103 as indicated by an arrow in FIG. Then, as shown in FIG. 14, sink marks 106 are preferentially generated in the portion where the resin 103 is cooled and is in contact with the air layer 105. afterwards,
After the resin 103 is cooled in the mold 100 until the temperature of the resin 103 becomes uniform, the molded product is taken out of the mold 100. At this time, the void 105 is formed in the mold cavity 102.
It is very difficult for heat to move as compared with the metal material constituting the. Therefore, the resin 103 is used in the mold cavity 10
As shown in FIGS. 15 and 16, there is a difference in the progress of the resin cooling between the portion in contact with the wall surface of 2 and the portion in contact with the void 105, and as shown in FIG.
Cooling proceeds with an asymmetrical temperature distribution inside, resulting in a decrease in shape accuracy. Further, when the molded product 110 is an optical lens, the cooling rate of the resin increases at the portion in contact with the wall surface of the mold, so that the internal strain also decreases. Therefore, in order to obtain the molded product 110 with higher accuracy, it is necessary to improve the molding method.

Therefore, the invention according to claim 1 has at least one transfer surface among the surfaces forming the cavity, and at least one surface other than the transfer surface is slidable. When molding a plastic molded product by injection-filling a molten resin into the cavity of the mold that is formed by a piece and is heated below the softening temperature, and bringing the resin into close contact with the transfer surface, and then cooling and solidifying the resin. When the cavity piece is separated from the resin by separating the cavity piece from the resin to form a gap between the cavity piece and the resin and heating at least one surface other than the surface in contact with the gap to a predetermined temperature. A plastic molded product that suppresses the uneven temperature distribution in the molded product that is generated by heating the surface other than the surface that is in contact with the voids, has a low distortion, and can mold a highly accurate molded product. And its object is to provide a molding method.

According to the second aspect of the present invention, the surface to be heated in the heating step is heated to a temperature substantially the same as the resin temperature of the surface in contact with the void, so that the temperature distribution in the molded product is made more uniform, It is an object of the present invention to provide a method for molding a plastic molded product which has a low distortion and can mold a molded product with higher accuracy.

According to a third aspect of the present invention, the surface of the mold which is in contact with the void and faces the surface of the mold is heated in a heating step.
An object of the present invention is to provide a method for molding a plastic molded product, which has a simple structure and can be molded at a low cost and with high accuracy by reducing the heating means provided in the mold.

According to a fourth aspect of the present invention, there is provided a cavity piece having at least one transfer surface among surfaces forming a cavity, and at least one surface other than the transfer surface is slidable. Molten resin is injected and filled into the cavity that is formed and heated below the softening temperature, and after the resin is brought into close contact with the transfer surface, the cavity piece is separated from the resin and a gap is formed between the cavity piece and the resin. The cavity is formed by heating at least one mold surface of the mold surface other than the surface contacting the voids of the mold formed and solidified by cooling the resin to mold the plastic molded article, by the heating means. The uneven temperature distribution inside the molded product that occurs when the bridge is separated from the resin is suppressed by heating the surfaces other than the surface that contacts the voids, and the molded product with low distortion and high precision is formed. Can do Is an object of the present invention to provide a mold.

According to the invention of claim 5, as the heating means,
It is an object of the present invention to provide a die which is inexpensive and capable of molding a highly accurate molded product by using a general-purpose heater by using a heater.

In a sixth aspect of the present invention, as the heating means,
By using a planar heat generating member that is approximately the same size as the surface of the mold to be heated, it efficiently heats, simplifies and facilitates the layout of the mold, is cheaper, and has a higher accuracy. The object is to provide a mold capable of molding a molded product.

According to the invention of claim 7, as a heating means,
An object of the present invention is to provide a mold that can heat a mold more efficiently and mold a molded product with higher accuracy by using a thin film electric resistor.

According to the invention of claim 8, as a heating means,
By using a fluid heating medium and a fluid passage through which the heating medium flows, the effects of overshoot and hunting can be prevented, temperature control can be performed accurately and easily, and a highly accurate molded product can be obtained. It is an object of the present invention to provide a mold capable of molding.

According to a ninth aspect of the present invention, there is provided a cavity piece having at least one transfer surface among the surfaces forming a cavity, and at least one surface other than the transfer surface is slidable. Molten resin is injected and filled in the cavity that is formed and heated below the softening temperature, and after the resin is brought into close contact with the transfer surface, the cavity piece is separated from the resin and a gap is formed between the cavity resin and the resin. Then, at least one mold surface of the mold surface other than the surface in contact with the void of the mold for cooling and solidifying the resin to mold the plastic molded product is lower in heat than the other mold surface for forming the cavity. By forming the mold with a low thermal conductivity material having conductivity, it is possible to prevent uneven temperature distribution in the molded product that occurs when the cavity piece is separated from the resin, without providing a heating means in the mold. Structure of Simple, and, together with the inexpensive, and its object is to provide a mold capable of molding a high-precision molded products.

According to the tenth aspect of the present invention, by using a ceramic material as the low thermal conductivity material, the mold has a strength that can sufficiently withstand the resin pressure during molding, and the structure of the mold is simple. And while making it cheap,
It is an object of the present invention to provide a mold capable of molding a highly accurate molded product.

According to an eleventh aspect of the present invention, a molded article is provided by disposing a high heat conductive material having higher heat conductivity than other mold surfaces forming the cavity on the cavity side of the low heat conductive material. It is an object of the present invention to provide a mold capable of making the resin temperature inside the resin uniform according to the time change and molding a molded product with higher accuracy at low cost.

According to a twelfth aspect of the present invention, the heating means according to any one of the fourth to eighth aspects is provided in the mold according to any one of the ninth to eleventh aspects, More efficiently equalize the resin temperature in the molded product,
It is an object of the present invention to provide a mold capable of molding a molded product with higher accuracy.

[0024]

According to a first aspect of the present invention, there is provided a method for molding a plastic molded article, which has at least one transfer surface among surfaces forming a cavity, and at least one surface other than the transfer surface. After injecting and filling a molten resin into the cavity of the mold, which has one or more surfaces formed of slidable cavity pieces and is heated below the softening temperature, and closely adheres the resin to the transfer surface. In the method of molding a plastic molded product, which is cooled and solidified to mold a plastic molded product, a cavity forming step of separating the cavity piece from the resin to form a void between the resin and a surface other than a surface in contact with the cavity. The above object is achieved by performing a heating step of heating at least one of the surfaces to a predetermined temperature.

According to the above construction, at least one transfer surface among the surfaces forming the cavity is formed, and at least one surface other than the transfer surface is formed of a slidable cavity piece. Injecting a molten resin into the cavity of the mold heated below the softening temperature, bringing the resin into close contact with the transfer surface, and then allowing it to cool and solidify to form a plastic molded product. Since a space is formed between the resin and the resin and at least one surface other than the surface in contact with the space is heated to a predetermined temperature, the inside of the molded product generated when the cavity piece is separated from the resin Non-uniform temperature distribution can be suppressed by heating the surface other than the surface in contact with the void, with low distortion,
In addition, it is possible to mold a highly accurate molded product.

In this case, for example, as described in claim 2, in the method of molding a plastic molded article, the surface to be heated in the heating step is heated to substantially the same temperature as the resin temperature of the surface in contact with the void. May be.

According to the above construction, the surface to be heated in the heating process is heated to substantially the same temperature as the resin temperature of the surface in contact with the void, so that the temperature distribution in the molded product can be made more uniform, It is possible to mold a molded product with lower distortion and higher accuracy.

Further, for example, as described in claim 3, in the molding method of the plastic molded product, a surface facing the surface of the mold in contact with the void may be heated in the heating step.

According to the above structure, the surface of the mold facing the cavity and the surface facing the mold are heated in the heating process. Therefore, the heating means provided in the mold is reduced and the mold has a simple structure. Therefore, the molded product can be molded at low cost and with high accuracy.

The mold of the invention according to claim 4 has at least one transfer surface among the surfaces forming the cavity, and at least one surface other than the transfer surface is slidable. A molten resin is injected and filled into the cavity formed by the cavity piece and heated below the softening temperature, and the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin to cause the resin In the mold for forming a plastic molded product by forming a void between the resin and the resin, the at least one mold surface other than the surface in contact with the void is heated to a predetermined temperature. By providing the heating means, the above object is achieved.

According to the above construction, at least one transfer surface among the surfaces forming the cavity is formed, and at least one of the surfaces other than the transfer surface is formed of a slidable cavity piece. , Molten resin is injected and filled into the cavity heated below the softening temperature, and the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin to form a gap with the resin. Since the resin is cooled and solidified, at least one mold surface other than the surface in contact with the voids of the mold for molding the plastic molded product is heated to a predetermined temperature by the heating means. The uneven temperature distribution in the molded product that occurs when the resin is separated from the resin can be suppressed by heating the surface other than the surface in contact with the voids, low distortion, and highly accurate molded product Molding It can be.

In this case, for example, as described in claim 5, the heating means may be a heater.

According to the above construction, since the heater is used as the heating means, a general-purpose heater can be used to form an inexpensive and highly accurate molded product.

Further, for example, as described in claim 6, the heating means may be a planar heating member having substantially the same size as the surface of the mold to be heated.

According to the above construction, since the sheet heating member having substantially the same size as the surface of the die to be heated is used as the heating means, the heating is performed efficiently and the die layout is simple and easy. Therefore, it is possible to mold a molded product that is inexpensive and has a higher precision.

Further, for example, as described in claim 7, the heating means may be a thin film electric resistor.

According to the above construction, since the thin film electric resistor is used as the heating means, it is possible to heat more efficiently, and it is possible to mold a molded article with higher accuracy.

Further, for example, as described in claim 8, the heating means may be formed of a fluid heating medium and a fluid passage through which the heating medium flows.

According to the above construction, since the heating means is formed of the fluid heating medium and the fluid passage through which the heating medium flows, the influence of overshooting or hunting is prevented, and the temperature control is performed. Can be performed accurately and easily, and a molded product with higher accuracy can be molded.

The mold of the invention according to claim 9 has at least one transfer surface among the surfaces forming the cavity, and at least one surface other than the transfer surface is slidable. A molten resin is injected and filled into the cavity formed by the cavity piece and heated below the softening temperature, and the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin to cause the resin In a mold for forming a plastic molded article by forming a void between the resin and the resin, the at least one mold surface other than the surface in contact with the void forms the cavity. The object is achieved by being formed of a low heat conductive material having a lower heat conductivity than other mold surfaces.

According to the above construction, at least one transfer surface among the surfaces forming the cavity is formed, and at least one surface other than the transfer surface is formed of a slidable cavity piece. , Molten resin is injected and filled into the cavity heated below the softening temperature, and the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin to form a void between the resin and the cavity piece. , At least one mold surface of the mold surface other than the surface of the mold for cooling and solidifying the resin to mold the plastic molded article has a lower thermal conductivity than the other mold surface for forming the cavity. Since it is formed of a low heat conductive material having, it is possible to prevent uneven temperature distribution in the molded product that occurs when the cavity piece is separated from the resin, without providing a heating means in the mold, Mold Structure is a simple and it is possible to inexpensive, can be formed with high precision moldings.

In this case, for example, the low thermal conductivity material may be a ceramic material.

According to the above construction, since the ceramic material is used as the low thermal conductivity material, it is possible to obtain a mold having a strength sufficient to withstand the resin pressure at the time of molding, and the structure of the mold is obtained. The molding can be simple and inexpensive, and a highly accurate molded product can be molded.

Further, for example, as described in claim 11, the mold has a higher thermal conductivity on the cavity side than the low thermal conductivity material than on another mold surface forming the cavity. A high thermal conductivity material may be provided.

According to the above structure, since the high thermal conductivity material having higher thermal conductivity than the other mold surfaces forming the cavity is disposed on the cavity side of the low thermal conductivity material, the inside of the molded product is improved. The resin temperature can be made uniform according to the time change, and a more highly accurate molded product can be molded at low cost.

Furthermore, for example, as described in claim 12, the heating means according to any one of claims 4 to 8 may be provided.

According to the above configuration, the ninth to the first aspects are provided.
Since the heating means according to any one of claims 4 to 8 is arranged in the mold according to any one of items 1 to 6, the resin temperature in the molded product can be made more uniform. Therefore, it is possible to mold a molded product with higher accuracy.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiments described below are preferred embodiments of the present invention, and therefore have various technically preferable limitations. However, the scope of the present invention refers to the present invention particularly in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

1 to 3 are views showing a first embodiment of a molding method and a mold of a plastic molded product of the present invention, and FIG. 1 is a molding method and a mold of a plastic molded product of the present invention. FIG. 3 is a front cross-sectional view of a mold 1 for molding a plastic molded product to which the first embodiment of is applied.

In FIG. 1, a mold 1 has at least one transfer surface 3 in a cavity 2, and at least one surface other than the transfer surface 3 is covered by a slidable cavity piece 4. It is configured. Slidable cavity piece 4
Other members of the mold 1 are provided with a heater (heating means) 5, and the mold 1 of the present embodiment is provided with three heaters 5. As this heater 5, a general-purpose heater can be used.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 1 of the present embodiment, first, the molten resin 10 is placed in the cavity 2 of the mold 1.
After injection filling inside, the resin 10 is cooled to below its softening temperature. In this cooling process, the cavity forming process is performed in which the slidable cavity piece 4 is moved in a direction away from the resin 10 to form the cavity 6. In order to prevent an asymmetrical temperature distribution from occurring in the molded product at this time, a heating step treatment is performed in which the surface other than the surface in contact with the void 6 is heated by the heater 5. As a result, as shown in FIG. 3, the asymmetric temperature distribution generated on the surface of the resin 10 in contact with the mold 1 (point A in FIG. 2) and the surface in contact with the void 6 (point B in FIG. 2) is shown in FIG. In addition, it is possible to improve and obtain a highly accurate molded product. Further, when the molded product is an optical lens, a molded product having good internal distortion can be obtained.

As shown in the temperature analysis value in the molded product in FIG. 3, the temperature for heating the member of the mold 1 is set so that the molding surface to be heated is substantially equal to the temperature of the surface in contact with the void 6. The more it does, the more accurate the molded product can be obtained.

As described above, the molding method of the mold 1 and the plastic molded article of the present embodiment has at least one transfer surface 3 among the surfaces forming the cavity 2, and the transfer surface 3 other than the transfer surface 3 is formed. At least one of the surfaces is formed by a slidable cavity piece 4, and a molten resin 10 is injected and filled into a cavity 2 of a mold 1 that is heated below a softening temperature, and the resin 10 is transferred. After closely contacting with the surface 3, when cooling and solidifying to mold a plastic molded article, the cavity piece 4 is separated from the resin 10 to form a void 6 between the resin 10 and the surface other than the surface in contact with the void 6. All the surfaces are heated to a predetermined temperature.

Therefore, the uneven temperature distribution in the molded product, which occurs when the cavity piece 4 is separated from the resin 10, can be suppressed by heating the surface other than the surface in contact with the voids 6, and the low temperature distribution can be suppressed. It is possible to mold a molded product with high accuracy and with distortion.

Further, in the molding method of the mold 1 and the plastic molded product of the present embodiment, the surface of the mold 1 heated in the heating process is heated to substantially the same temperature as the temperature of the resin 10 on the surface in contact with the void 6. is doing.

Therefore, the temperature distribution in the molded product can be made more uniform, and the molded product can be molded with lower distortion and higher accuracy.

Further, in the molding method of the mold 1 and the plastic molded product of the present embodiment, the heater 5 is used as the heating means.

Therefore, by using the general-purpose heater 5, an inexpensive and highly accurate molded product can be molded.

FIG. 4 is a front sectional view of a mold 20 for molding a plastic molded product to which the method for molding a plastic molded product and the second embodiment of the mold of the present invention are applied.

In FIG. 4, the mold 20 has a cavity 2
1 has at least one or more transfer surfaces 22, and the transfer surface 2
At least one of the surfaces other than 2 is constituted by the cavity piece 23 which is slidable. A heater (heating means) 24 is provided on the member of the mold 20 facing the slidable cavity piece 23.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 20 of the present embodiment, first, the molten resin 25 is injected and filled into the cavity 21 of the mold 20, and then the resin 25 is cooled to a temperature below its softness temperature. . In this cooling process, the slidable cavity piece 23 is moved in the direction away from the resin 25 to form the gap 26. In order to prevent an asymmetrical temperature distribution in the molded product generated at this time, the surface facing the surface contacting the void 26 is heated by the heater 24.

In this case, the mold 1 of the first embodiment described above
Compared with, the resin temperature distribution in the molded product becomes asymmetrical, so there is a drawback that the accuracy of the molded product is slightly reduced.
It is possible to reduce the number of heating heaters 24 provided at 0, and to simplify the structure of the mold 20. Therefore,
By adopting the configuration of the present embodiment in accordance with the required accuracy of the molded product, the plastic molded product can be molded at low cost and with high accuracy.

As described above, in the molding method of the mold 20 and the plastic molded product of the present embodiment, the surface facing the surface of the mold 20 in contact with the space 26 is heated in the heating process.

Therefore, the heating means provided on the mold 20 can be reduced and the mold 20 can be made to have a simple structure, and the molded product can be molded at low cost and with high precision.

FIG. 5 is a front sectional view of a mold 30 for molding a plastic molded product according to the third embodiment of the method for molding a plastic molded product of the present invention and the mold of the present embodiment.

In FIG. 5, the mold 30 has a cavity 3
1 has at least one or more transfer surfaces 32, and the transfer surface 3
At least one of the surfaces other than 2 is constituted by the cavity piece 33 which is slidable. A planar heater (heating means, planar heating member) 34 is provided on the member of the mold 30 that faces the slidable cavity piece 33.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 30 of the present embodiment, first, the molten resin 35 is injected and filled into the cavity 31 of the mold 30, and then the resin 35 is cooled to a temperature below its softness temperature. . During this cooling process, the slidable cavity piece 33 is moved in a direction away from the resin 35 to form a gap 36. In order to prevent an asymmetric temperature distribution from occurring in the molded product at this time, the surface facing the surface in contact with the void 36 is heated by the flat heater 34.

In this case, the mold 1 of the first embodiment described above
Compared with the above, since the heating heater 34 is planar, the resin 35 can be uniformly and efficiently heated, a highly accurate molded product can be molded, and the planar heating heater 34 is attached to the mold 30. Can be laid out easily and easily. As a result, the structure of the mold 30 can be simplified. Therefore, by adopting the configuration of the present embodiment in accordance with the required accuracy of the molded product, the plastic molded product can be molded at low cost and with high accuracy.

FIG. 6 is a front sectional view of a mold 40 for molding a plastic molded product to which the method for molding a plastic molded product of the present invention and the mold of the fourth embodiment of the present embodiment are applied.

In FIG. 6, the mold 40 has a cavity 4
1 has at least one transfer surface 42, and the transfer surface 4
At least one of the surfaces other than 2 is constituted by a slidable cavity piece 43. Members of the mold 40 other than the slidable cavity piece 43 are provided with thin-film electric resistors 44 that generate heat when energized as a heat generating means. Two thin film electrical resistors 44 are provided.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 40 of the present embodiment, first, the molten resin 45 is injected and filled into the cavity 41 of the mold 40, and then the resin 45 is cooled to a temperature below its softness temperature. . In this cooling process, the slidable cavity piece 43 is moved in a direction away from the resin 45 to form a gap 46. In order to prevent an asymmetrical temperature distribution from occurring in the molded product at this time, the thin film electric resistor 44 provided on a member of the mold 40 other than the cavity piece 43 is energized to clean the surface of the mold 40. To heat.

In this case, the mold 3 of the third embodiment described above
Compared with the planar heating heater 34 of 0, the resin 45 can be heated more responsively, uniformly and efficiently,
In addition to being able to mold more accurate molded products,
The thin film electric resistor 44 can be easily and easily laid out on the mold 40. As a result, the structure of the mold 40 can be simplified. Therefore, by adopting the configuration of the present embodiment in accordance with the required accuracy of the molded product, the plastic molded product can be molded at low cost and with high accuracy.

FIG. 7 is a front sectional view of a mold 50 for molding a plastic molded product to which the method for molding a plastic molded product and the mold of the fifth embodiment of the present invention are applied.

In FIG. 7, the mold 50 has a cavity 5
1 has at least one transfer surface 52, and the transfer surface 5
At least one of the surfaces other than 2 is constituted by the cavity piece 53 which is slidable. A heat pipe 54 is provided on a member of the mold 50 which faces the slidable cavity piece 53. A heat medium such as heated oil or water is caused to flow through the heat pipe 54 as a heat source to heat the resin 55 in the cavity 51 described later.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 50 of the present embodiment, first, the molten resin 55 is injected and filled into the cavity 51 of the mold 50, and then the resin 55 is cooled to a temperature below its softness temperature. . In this cooling process, the slidable cavity piece 53 is moved in the direction away from the resin 55 to form the void 56. In order to prevent an asymmetrical temperature distribution from occurring in the molded product at this time, a heated heat medium such as oil or water is made to flow through the heat pipe 54 to heat the surface opposite to the surface in contact with the void 56.

In this case, as in the case of using the heaters 5, 24, 34 and the thin-film electric resistor 44 used in the above-mentioned embodiment, overshoot (a phenomenon in which the temperature rises above the set value) ) Or hatching (a phenomenon in which the temperature fluctuates with respect to a set value), temperature control can be performed easily and appropriately, and a plastic molded product can be molded with higher accuracy.

FIG. 8 is a front sectional view of a mold 60 for molding a plastic molded product to which the method for molding a plastic molded product of the present invention and the sixth embodiment of the mold are applied.

In FIG. 8, the mold 60 is a cavity 6
1 has at least one or more transfer surfaces 62, and the transfer surface 6
At least one of the surfaces other than 2 is constituted by a slidable cavity piece 63. The portion of the mold 60 facing the cavity 61 other than the slidable cavity piece 63 is formed of a low thermal conductive material 64 having a lower thermal conductivity than that of the forming member of the mold 60. This low thermal conductivity material 6
For example, a ceramic material (alumina, zirconia) or the like can be used as 4.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 60 of the present embodiment, first, the molten resin 65 is injected and filled into the cavity 61 of the mold 60, and then the resin 65 is cooled to a temperature below its softness temperature. . During this cooling process, the slidable cavity piece 63 is moved in a direction away from the resin 65 to form a gap 66. An asymmetric temperature distribution tends to occur in the molded product generated at this time, but since the surfaces other than the surface in contact with the void 65 are formed of the low thermal conductive material 64 having lower thermal conductivity than the mold 60, It is possible to prevent an asymmetric temperature distribution from occurring in the molded product. Therefore, it is possible to obtain a highly accurate molded product and to configure the mold 60 having sufficient strength to withstand the resin pressure during molding. Further, when the molded product is an optical lens, a molded product having good internal distortion can be obtained.

Further, it is not necessary to provide heating means in the mold 60, the structure of the mold 60 can be simplified, and the cost can be reduced.

9 to 11 are front sectional views of a mold 70 for molding a plastic molded product to which the method for molding a plastic molded product and the seventh embodiment of the mold of the present invention are applied.

In FIG. 9, the mold 70 has a cavity 7
1 has at least one transfer surface 72, and the transfer surface 7
At least one of the surfaces other than 2 is constituted by a freely movable cavity piece 73. A member of a portion of the mold 70 facing the slidable cavity piece 73 is provided with a planar high thermal conductivity material 74 having high thermal conductivity on the cavity 71 side, and further, this high thermal conductivity material. A planar low-thermal-conductivity material 75 having low thermal conductivity is provided in a state of being in contact with the surface of 74 on the side opposite to the cavity 71. For example, a metal material or the like is used as the high thermal conductivity material 74, and a ceramic material or the like is used as the low thermal conductivity material 75.

Next, the operation of this embodiment will be described. When molding a plastic molded product using the mold 70 of the present embodiment, first, the molten resin 76 is injected and filled into the cavity 71 of the mold 70, and then the resin 76 is cooled to a temperature below its softness temperature. . In this cooling process, the slidable cavity piece 73 is moved in a direction away from the resin 76 to form the gap 77.

Although an asymmetric temperature distribution tends to occur in the molded product generated at this time, the mold 70 constituting the surface to be heated is formed.
Since the high heat conductive material 74 and the low heat conductive material 75 are sequentially laminated in the member (1), the temperature distribution in the molded product can be made uniform. That is, as shown in FIG. 12 showing the temperature change with time passage of points A and B in FIG. 11, immediately after the resin 76 is filled, the heat of the molded product is accumulated in the high thermal conductive material 74, and the temperature rises. Since it becomes difficult for heat to transfer with time, the resin temperature in the molded product becomes uniform according to the change of time. As a result, a highly accurate molded product can be formed with a very simple structure of the mold 70.

Although the invention made by the present inventor has been specifically described based on the preferred embodiments, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

[0086]

According to the method of molding a plastic molded article of the invention described in claim 1, at least one of the surfaces forming the cavity has a transfer surface, and at least one of the surfaces other than the transfer surface. The above surface is formed by a slideable cavity piece, and the molten resin is injected and filled into the cavity of the mold heated below the softening temperature, and the resin is brought into close contact with the transfer surface and then cooled and solidified. At the time of molding a plastic molded product by molding, the cavity piece is separated from the resin to form a gap between the cavity piece and the resin, and at least one surface other than the surface in contact with the gap is heated to a predetermined temperature. The uneven temperature distribution in the molded product that occurs when the resin is separated from the resin can be suppressed by heating the surface other than the surface in contact with the voids, low distortion, and highly accurate molded product Formed It can be.

According to the method of molding a plastic molded article of the second aspect of the present invention, the surface to be heated in the heating step is heated to substantially the same temperature as the resin temperature of the surface in contact with the void, so that the temperature distribution in the molded article is Can be made even more uniform, and a molded product with even lower distortion and higher accuracy can be formed.

According to the method for molding a plastic molded article of the third aspect of the present invention, the surface facing the surface of the mold which is in contact with the void is heated in the heating step, so that the heating means provided in the mold is reduced. The mold can have a simple structure, and the molded product can be molded inexpensively and with high accuracy.

According to the mold of the fourth aspect of the present invention, at least one transfer surface among the surfaces forming the cavity has a transfer surface, and at least one surface other than the transfer surface slides. A molten resin is injected and filled into a cavity formed by a possible cavity piece and heated below the softening temperature, and the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin and A space is formed between the mold and at least one mold surface of the mold surface other than the surface in contact with the space of the mold for cooling and solidifying the resin to mold the plastic molded product is heated to a predetermined temperature by the heating means. Therefore, the uneven temperature distribution in the molded product that occurs when the cavity piece is separated from the resin can be suppressed by heating the surface other than the surface in contact with the void, with low distortion, And high precision molding It can be molded.

According to the mold of the fifth aspect of the present invention, since the heater is used as the heating means, a general-purpose heater can be used to form an inexpensive and highly accurate molded product. it can.

According to the die of the invention described in claim 6, since the sheet heating member having substantially the same size as the surface of the die to be heated is used as the heating means, the heating is performed efficiently and
The layout of the mold can be made simple and easy, and it is possible to mold an inexpensive molded product with higher accuracy.

According to the die of the invention as set forth in claim 7, since the thin film electric resistor is used as the heating means, it is possible to heat more efficiently and to form a molded article with higher precision. can do.

According to the die of the invention described in claim 8, since the heating means is formed of the fluid heating medium and the fluid passage through which the heating medium flows, the influence of overshoot or hunting is exerted. The temperature control can be performed accurately and easily, and a molded product with higher accuracy can be molded.

According to the die of the invention described in claim 9, at least one transfer surface among the surfaces forming the cavity is provided, and at least one surface other than the transfer surface slides. A molten resin is injected and filled in the cavity formed by a possible cavity piece and heated below the softening temperature, and the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin and At least one mold surface of the mold other than the surface in contact with the void of the mold in which the resin is cooled and solidified by forming a void between the resin and another metal for forming the cavity. Since it is made of a low thermal conductivity material that has a lower thermal conductivity than the mold surface, the uneven temperature distribution in the molded product that occurs when the cavity piece is separated from the resin without providing heating means in the mold Prevent Bets can be, a simple structure of the mold, and it is possible to inexpensive, it can be formed with high precision moldings.

According to the mold of the tenth aspect of the present invention, since the ceramic material is used as the low thermal conductivity material, the mold can be made sufficiently strong to withstand the resin pressure during molding. Therefore, the structure of the mold can be simple and inexpensive, and a highly accurate molded product can be molded.

According to the mold of the eleventh aspect of the present invention, the high heat conductive material having higher heat conductivity than the other mold surface forming the cavity is disposed on the cavity side of the low heat conductive material. Therefore, the resin temperature in the molded product can be made uniform according to the time change, and the molded product with higher accuracy can be molded at low cost.

According to the mold of the invention described in claim 12, the heating means described in any one of claims 4 to 8 is arranged on the mold described in any one of claims 9 to 11. Since it is provided, the resin temperature in the molded product can be made more uniform, and the molded product with higher accuracy can be molded.

[Brief description of drawings]

FIG. 1 is a front sectional view of an essential part of a mold to which a method for molding a plastic molded product and a mold according to a first embodiment of the present invention are applied.

FIG. 2 is a front cross-sectional view of an essential part showing detection points of temperature distribution of a resin molded product of the mold of FIG.

FIG. 3 is a diagram showing a relationship between temperature and time at a temperature detection point of the mold shown in FIG.

FIG. 4 is a front sectional view of an essential part of a mold to which a molding method for a plastic molded product and a mold according to a second embodiment of the present invention are applied.

FIG. 5 is a front sectional view of an essential part of a mold to which a molding method for a plastic molded product and a third embodiment of the mold according to the present invention are applied.

FIG. 6 is a front sectional view of a main part of a mold to which a molding method for a plastic molded product and a mold according to a fourth embodiment of the present invention are applied.

FIG. 7 is a front sectional view of a main part of a mold to which a molding method of a plastic molded product and a mold according to a fifth embodiment of the present invention are applied.

FIG. 8 is a front sectional view of an essential part of a mold to which a molding method for a plastic molded product and a mold according to a sixth embodiment of the present invention are applied.

FIG. 9 is a front sectional view of a main part of a mold to which a molding method for a plastic molded product and a mold according to a seventh embodiment of the present invention are applied.

10 is a front cross-sectional view of the main parts showing the detection points of the temperature distribution of the resin molded product of the mold of FIG.

11 is a diagram showing a relationship between temperature and time at a temperature detection point of the mold shown in FIG.

FIG. 12 is a front cross-sectional view of a main portion of a conventional mold in which a molten resin is filled in a cavity.

13 is a front cross-sectional view of a main part of a state where the cavity piece of the mold in FIG. 12 is moved in a direction in which it is separated from the resin.

14 is a front sectional view of a main part of a mold in which sink marks are generated in the resin as the cavity piece of FIG. 13 is moved.

FIG. 15 is a front cross-sectional view of the main parts showing the detection points of the temperature distribution of the resin molded product of the mold of FIG.

16 is a diagram showing a relationship between temperature and time at a temperature detection point of the mold shown in FIG.

FIG. 17 is a front view of a molded product that is molded by a conventional mold and has distortion.

[Explanation of symbols]

1 mold 2 cavities 3 Transfer surface 4 cavity pieces 5 heater 6 void 10 resin 20 mold 21 cavity 22 Transfer surface 23 Cavity pieces 24 heating heater 25 resin 26 void 30 molds 31 cavity 32 Transfer surface 33 cavity pieces 34 Heater 35 resin 36 void 40 mold 41 cavity 42 Transfer surface 43 Cavity piece 44 Thin film resistor 45 resin 46 void 50 mold 51 cavity 52 transcription 53 cavity pieces 54 heat pipe 55 resin 56 void 60 mold 61 cavity 62 Transfer surface 63 cavity pieces 64 Low thermal conductivity material 65 resin 66 void 70 mold 71 cavity 72 Transfer surface 73 cavity pieces 74 High thermal conductivity material 75 Low thermal conductivity material 76 resin 77 Void

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F202 AM34 CA11 CB01 CD02 CK54                       CN01 CN18                 4F206 JA07 JN34 JN43 JQ81

Claims (12)

[Claims] 1. A surface having at least one transfer surface among the surfaces forming a cavity, and at least one surface other than the transfer surface is formed of a slidable cavity piece and is less than a softening temperature. In a molding method of a plastic molded article, in which the molten resin is injected and filled in the cavity of the mold heated to, and after the resin is brought into close contact with the transfer surface, the plastic molded article is molded by cooling and solidifying, Performing a void forming step of separating the cavity piece from the resin to form a void between the resin and the resin, and a heating step of heating at least one surface other than the surface in contact with the void to a predetermined temperature. A method for molding a plastic molded article, which is characterized by: 2. The method for molding a plastic molded article comprises heating the surface to be heated in the heating step to substantially the same temperature as the resin temperature of the surface in contact with the void.
A method for molding a plastic molded product as described above. 3. The plastic according to claim 1, wherein in the method for molding the plastic molded product, a surface facing the surface of the mold in contact with the void is heated in the heating step. Molding method for molded products. 4. A surface for forming a cavity having at least one transfer surface, and at least one surface other than the transfer surface is formed of a slidable cavity piece and has a temperature lower than a softening temperature. A molten resin is injected and filled into the cavity that is heated to, the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin to form a gap between the resin and the cavity piece. A mold for molding a plastic molded product by cooling and solidifying the resin, further comprising heating means for heating at least one mold surface of a mold surface other than a surface in contact with the void to a predetermined temperature. And the mold. 5. The mold according to claim 4, wherein the heating means is a heater. 6. The mold according to claim 4, wherein the heating means is a planar heat generating member having substantially the same size as the surface of the mold to be heated. 7. The mold according to claim 4, wherein the heating means is a thin film electric resistor. 8. The mold according to claim 4, wherein the heating means is formed of a fluid heating medium and a fluid passage through which the heating medium flows. 9. A surface having at least one transfer surface among the surfaces forming a cavity, and at least one surface other than the transfer surface is formed of a slidable cavity piece and is less than a softening temperature. A molten resin is injected and filled into the cavity that is heated to, the resin is brought into close contact with the transfer surface, and then the cavity piece is separated from the resin to form a gap between the resin and the cavity piece. In the mold for molding the plastic molded product by cooling and solidifying the resin, at least one mold surface of the mold surfaces other than the surface in contact with the void has lower heat than the other mold surface forming the cavity. A metal mold formed of a low thermal conductive material having conductivity. 10. The mold according to claim 9, wherein the low thermal conductivity material is a ceramic material. 11. The mold is provided with a high thermal conductivity material having higher thermal conductivity than other mold surfaces forming the cavity, closer to the cavity than the low thermal conductivity material. The mold according to claim 9 or 10, characterized in that. 12. The mold according to any one of claims 9 to 11, wherein the heating means according to any one of claims 4 to 8 is provided.